检索结果-南通市图书馆

维普期刊数据库博看期刊

Response of Pinus taiwanensis growth to climate changes at its southern limit of Daiyun Mountain, China's Mainland Fujian Province

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2016年第2期59卷 328-336页

作者： CHEN Dan FANG KeYan LI YingJun dong zhipeng ZHANG Yu ZHOU FeiFei Institute of Geography Key Laboratory of Humid Subtropical Eco-geographical Process (Ministry of Education)College of Geographical Sciences Fujian Normal University Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of Sciences Research Center for Scientific Development in Fenhe River Valley Taiyuan Normal University

The Pinus taiwanensis trees of a Chinese endemic species form pure forests at infertile sites in humid subtropical China, which can aid soil reservation and ecological resiliency at such sites. Herein, we used dendrochronological methods to investigate the growth patterns and their relationship with climate by analyzing 158 cores of 79 P. taiwanensis trees at 4 sites in their southernmost distribution in China's Mainland at Daiyun Mountain in Fujian Province. Tree growths at sites with favor- able conditions generally showed an age-related growth trend, which decreased from approximately 5 mm to 0.5 mm in about a century. Trees in moderately stressed environments established high growth in their juvenile periods but were highly suscep- tible to environmental stresses such as a sharp growth decline in the 1990s. The temperature in February and the moisture in July are the major limiting factors for most of the tree growths, except for a few extremely stressed P. taiwanensis trees. The growth of the dwarf P. taiwanensis trees, with all ring diameters of the first 20 years less than 4 ram, is mainly limited by the dry climate in May. Under the potential future warming trend, drought stress can be particularly threatening to these dwarf P. taiwanensis trees, which are likely to be the germplasm resources for this species in this region.

关键词： Daiyun Mountain Pinus taiwanensis Climate-growth relationships Drought Global warming

Earth Observation Brain(EOB):an intelligent earth observation system

在线全文

学校读者我要写书评

暂无评论

Geo-Spatial Information Science 2017年第2期20卷 134-140页

作者： Deren Li Mi Wang zhipeng dong Xin Shen Lite Shi State Key Laboratory of Information Engineering in Surveying Mapping and Remote Sensing(LIESMARS)Wuhan UniversityWuhanChina Collaborative Innovation Center of Geospatial Technology Wuhan UniversityWuhanChina

Since the twenty-first century,with the rapid development of high-resolution earth observation satellites,the earth observation satellite system has developed from the initial single satellite observation model to the current satellite constellation formed by light and small satellites observation ***-weather and all-directional fine earth observation can now be *** the future,the satellite constellation,communication satellites,navigation satellites,and aircrafts are linked through dynamic linking network to form an air-space information network to realize real-time services of intelligent air-space *** further enhance the perception,cognition,and quick response ability of the network,we propose the concept and model of the Earth Observation Brain(EOB)−the intelligent earth system based on events perception in this ***,some key technologies needed to be solved in the EOB are also *** application example is illustrated to show the process of perception and cognition in the primary stage of the *** the future,EOB can observe what change of what object,the when and where to push these right information to mobile terminal of right people at the right time and right *** users can obtain any data,information,and knowledge in real-time through the EOB.

关键词： Earth Observation Brain(EOB) intelligent earth observation system space-air-ground co-observation spatial perception and cognition emergency response ability

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

圆锥滚子轴承内圈大挡边碎裂失效分析

哈尔滨轴承 2024年第2期45卷 39-41页

作者：仪欣申明月董智鹏王宇瓦房店轴承集团国家轴承工程技术研究中心有限公司辽宁瓦房店116300 瓦房店轴承集团传动机械轴承研究所辽宁瓦房店116300 瓦房店轴承集团制造工艺及设备研发中心辽宁瓦房店116300 瓦房店轴承集团特种精密轴承制造有限公司辽宁瓦房店116300

针对某型圆锥滚子轴承内圈大挡边碎裂的问题,采用化学成分分析、金相组织检验及洛氏硬度检验等技术对失效原因进行了分析。结果表明:内圈大挡边油沟表面加工质量较差导致该处应力集中因素增大,该处表面的氧化和脱碳使其强度降低、缺口... 详细信息

针对某型圆锥滚子轴承内圈大挡边碎裂的问题,采用化学成分分析、金相组织检验及洛氏硬度检验等技术对失效原因进行了分析。结果表明:内圈大挡边油沟表面加工质量较差导致该处应力集中因素增大,该处表面的氧化和脱碳使其强度降低、缺口敏感性增加,最终导致内圈大挡边碎裂。

关键词：氧化脱碳层表面加工质量化学成分金相组织

A benchmark-based method for evaluating hyperparameter optimization techniques of neural networks for surface water quality prediction

在线全文

学校读者我要写书评

暂无评论

Frontiers of Environmental Science & Engineering 2024年第5期18卷 13-27页

作者： Xuan Wang Yan dong Jing Yang zhipeng Liu Jinsuo Lu School of Environmental and Municipal Engineering Xi’an University of Architecture and TechnologyXi’an710055China Shaanxi Key Laboratory of Environmental Engineering Xi’an University of Architecture and TechnologyXi’an710055China State Key Laboratory of Green Building in West China Xi’an University of Architecture and TechnologyXi’an710055China

Neural networks(NNs)have been used extensively in surface water prediction tasks due to computing algorithm improvements and data *** essential step in developing an NN is the hyperparameter *** practice,it is common to manually determine hyperparameters in the studies of NNs in water resources *** may result in considerable randomness and require significant computation time;therefore,hyperparameter optimization(HPO)is *** study adopted five representatives of the HPO techniques in the surface water quality prediction tasks,including the grid sampling(GS),random search(RS),genetic algorithm(GA),Bayesian optimization(BO)based on the Gaussian process(GP),and the tree Parzen estimator(TPE).For the evaluation of these techniques,this study proposed a method:first,the optimal hyperparameter value sets achieved by GS were regarded as the benchmark;then,the other HPO techniques were evaluated and compared with the benchmark in convergence,optimization orientation,and consistency of the optimized *** results indicated that the TPE-based BO algorithm was recommended because it yielded stable convergence,reasonable optimization orientation,and the highest consistency rates with the benchmark *** optimization consistency rates via TPE for the hyperparameters hidden layers,hidden dimension,learning rate,and batch size were 86.7%,73.3%,73.3%,and 80.0%,*** the evaluation of HPO techniques directly based on the prediction performance of the optimized NN in a single HPO test,the proposed benchmark-based HPO evaluation approach is feasible and robust.

关键词： Neural networks Hyperparameter optimization Surface water quality prediction Bayes optimization Genetic algorithm

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

萃取装备在烯草酮连续化生产中的应用

世界农药 2024年第2期46卷 41-46页

作者：许东兵董志鹏郭庆春许峰王勇中国科学院过程工程研究所北京100190 河北兰升生物科技有限公司河北晋州052260

连续化是化工生产发展方向,以烯草酮生产中涉及的液-液萃取分离过程为对象,针对液-液萃取分离体系中杂质种类、含量及分离特性,详细探究两相流动及传质特性,开发了高效萃取塔、管式萃取器和油水聚结分离材料等,并成功应用于烯草酮生产... 详细信息

连续化是化工生产发展方向,以烯草酮生产中涉及的液-液萃取分离过程为对象,针对液-液萃取分离体系中杂质种类、含量及分离特性,详细探究两相流动及传质特性,开发了高效萃取塔、管式萃取器和油水聚结分离材料等,并成功应用于烯草酮生产萃取分离工段,实现了其连续自动化生产。基于高效萃取装备解决了传统釜式生产存在的密闭性差、产品质量不稳定、废水量大、能耗高、安全性差等问题,推动了我国农药化工生产技术水平持续提升。

关键词：烯草酮萃取塔管式萃取器聚结分离材料连续化

在线全文

学校读者我要写书评

暂无评论

QC小组活动在铸造企业开展情况总结及展望

中国铸造装备与技术 2024年第2期59卷 72-76页

作者：时晓鞠欣宝张凯董志鹏綦宗超潍柴重机股份有限公司山东潍坊261001

立足大缸径材料成型中心质量管理小组活动实际,结合潍柴WOS管理模式的推进要求,介绍铸造企业质量管理小组的开展情况、活动推进的典型经验及常见的推进问题,阐述质量管理小组对质量管理和质量改进的重要贡献并对铸造业质量管理小组未来... 详细信息

立足大缸径材料成型中心质量管理小组活动实际,结合潍柴WOS管理模式的推进要求,介绍铸造企业质量管理小组的开展情况、活动推进的典型经验及常见的推进问题,阐述质量管理小组对质量管理和质量改进的重要贡献并对铸造业质量管理小组未来发展进行展望。

关键词： QC小组铸造质量管理

General radical difluoromethylation using difluoroacetic anhydride via photoredox catalysis

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2024年第8期67卷 2637-2646页

作者： Meng He Yankai Yang Heng Zhang zhipeng Guan Zhi-Bing dong Hong Yi Aiwen Lei School of Chemistry and Environmental Engineering Wuhan Institute of TechnologyWuhan 430205China College of Chemistry and Molecular Sciences and Institute for Advanced Studies(IAS) Wuhan UniversityWuhan 430072China

CF_(2)H-containing molecules play pivotal roles in diverse fields from medicinal chemistry to materials science. However, the application of existing CF_(2)H reagents as a source of CF_(2)H radical is limited by their reactivity and preparation. Herein, we develop a simple and general visible-light-catalyzed radical difluoromethylation reaction of alkenes, dienes, and heteroaromatics using commercially available, easy-to-handle, and low-cost difluoroacetic anhydride as the CF_(2)H reagent. This scalable protocol enables the convenient synthesis of a range of CF_(2)H-containing compounds under mild conditions, exhibiting a broad substrate scope and functional group tolerance. Potential applications are further demonstrated by gram-scale synthesis, sunlight experiments, derivatization experiments as well as the synthesis of bioactive molecules.

关键词： radical difluoromethylation alkenes/dienes/heteroaromatics difluoroacetic anhydride photoredox

Evaluation of the Relative Tectonic Activity from the Faults in the Gengma-Lancang-Menghai Seismic Belt(Southwestern China)

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2024年第1期35卷 131-143页

作者： Dan Wang Youpu dong zhipeng Xi dongyue Zhang Jiaxin Duan Huayu Yu Liang Yu Faculty of Land Resource Engineering Kunming University of Science and TechnologyKunming 650093China

The Gengma-Lancang-Menghai seismic belt,the southernmost part of the North-South seismic belt,is controlled by four active faults:the Nantinghe fault(NTHF),the Sanjianshan fault(SJSF),the Hanmuba-Lancang fault(HMB-LCF),and the Heihe fault(HHF),from northwest to ***,the tectonic activity of the faults in the Gengma-Lancang-Menghai seismic belt has not been fully studied *** the present work,we conducted tectonic geomorphic indices to analyze the relative tectonic activity along the faults in the seismic belt based on the digital elevation *** interpreted asymmetric factor,index of drainage basin shape,hypsometric integral,normalized streamlength gradient,valley floor-to-width to height ratio,and longitudinal profiles to show that the relative tectonic activity is higher in the north and lower in the south,and is strong in the region from Shanjia to Huimin in the center of the seismic belt.

关键词： Gengma-Lancang-Menghai seismic belt southeastern Tibetan Plateau geomorphic indices longitudinal profile

Direct generation of 3.17 mJ green pulses in a cavity-dumped Ho^(3+)-doped fiber laser at 543 nm

在线全文

学校读者我要写书评

暂无评论

Photonics Research 2023年第3期11卷 413-419页

作者： TIANRAN LI ZIYU WANG JINHAI ZOU JINFEN HONG QIUJUN RUAN HANG WANG zhipeng dong ZHENGQIAN LUO Fujian Key Laboratory of Ultrafast Laser Technology and Applications Xiamen UniversityXiamen 361005China Department of Electronic Engineering Xiamen UniversityXiamen 361005China Shenzhen Research Institute of Xiamen University Shenzhen 518129China Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(IKKEM) Xiamen 361005China

High-energy pulsed lasers in the green spectral region are of tremendous interest for applications in space laser ranging,underwater detection,precise processing,and scientific *** pulsed lasers currently are difficult to access to the so-called“green gap,”and high-energy green pulsed lasers still heavily rely on the nonlinear frequency conversion of near-IR lasers,precluding compact and low-cost green laser ***,we address this challenge by demonstrating,for the first time to the best of our knowledge,millijoule-level green pulses generated directly from a fiber *** green pulsed fiber laser consists of a 450 nm pump laser diode,a Ho^(3+)-doped ZBLAN fiber,and a cavity-dumping module based on a visible wavelength acousto-optic *** pulse operation in the cavity-dumping regime at 543 nm is observed with a tunable repetition rate in a large range of 100 Hz–3 MHz and a pulse duration of 72–116 *** maximum pulse energy of 3.17 mJ at 100 Hz is successfully achieved,which is three orders of magnitude higher than those of the rare-earth-doped fiber green lasers previously *** work provides a model for compact,high-efficiency,and high-energy visible fiber pulsed lasers.

关键词： fiber laser pump