检索结果-南通市图书馆

Vision-Based Adaptive Prescribed-Time Control of UAV for Uncooperative Target Tracking with Performance Constraint

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2024年第5期37卷 1956-1977页

作者： SHE xuehua MA Hui REN Hongru li Hongyi School of Automation and the Guangdong Provincial Key Laboratory of Intelligent Decision and Cooperative Control Guangdong University of Technology School of Mathematics and Statistics Guangdong University of Technology College of Electronic and Information Engineering and Chongqing Key Laboratory of Generic Technology and System of Service Robots Southwest University

This paper discusses the uncooperative target tracking control problem for the unmanned aerial vehicle(UAV) under the performance constraint and scaled relative velocity constraint, in which the states of the uncooperative target can only be estimated through a vision sensor. Considering the limited detection range, a prescribed performance function is designed to ensure the transient and steady-state performances of the tracking system. Meanwhile, the scaled relative velocity constraint in the dynamic phase is taken into account, and a time-varying nonlinear transformation is used to solve the constraint problem, which not only overcomes the feasibility condition but also fails to violate the constraint boundaries. Finally, the practically prescribed-time stability technique is incorporated into the controller design procedure to guarantee that all signals within the closed-loop system are *** is proved that the UAV can follow the uncooperative target at the desired relative position within a prescribed time, thereby improving the applicability of the vision-based tracking approach. Simulation results have been presented to prove the validity of the proposed control strategy.

关键词： Nonlinear transformation performance constraint prescribed-time tracking uncooperative target vision-based measurement

Spatial heterogeneity of plant species on the windward slope of active sand dunes in a semi-arid region of China

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Arid Land 2013年第1期5卷 80-88页

作者： DeMing JIANG ChunPing MIAO xuehua li XiaoLan li ALAMUSA QuanLai ZHOU Institute of Applied Ecology Chinese Academy of Sciences Shenyang 110016 China Graduate University of Chinese Academy of Sciences Beijing 100049 China Xinjiang Academy of Agricultural and Reclamation Sciences Shihezi 832000 China

Species richness and abundance are two important species diversity variables that have attracted particular attention because of their significance in determining present and future species composition conditions. This paper aims to explain the qualitative and quantitative relationships between species diversity pattern and grain size （i.e. size of the sampling unit）, and species diversity pattern and sampling area, and to analyze species diversity variability on active sand dunes in the Horqin Sandy Land, northeastern Inner Mongolia, China. A 50 mx50 m sampling plot was selected on the windward slope, where the dominant species was annual herb Agriophyllum squarrosum. Species composition and abundance at five grain sizes were recorded, and the species-area curves were produced for thirteen grain sizes. The range of values for species abundance tended to increase with in- creasing grain size in the study area, whereas, generally, species richness did not follow this rule because of poor species richness on the windward slope of active sand dunes. However, the homogeneity of species richness in- creased significantly. With the increase in sampling area, species abundance increased linearly, but richness in- creased logarithmically. Furthermore, variograms showed that species diversity on the windward slope of active sand dunes was weakly anisotropic and the distribution pattern was random, according to the Moran Coefficient. The results also showed that species richness was low, with a random distribution pattern. This conflicts with the results of previous studies that showed spatial aggregation in lower richness in a sampling area within a community and inferred that the physical processes play a more important role in species diversity than distribution pattern on active sand dunes. Further research into different diversity patterns and mechanisms between active sand dunes and interdune lowlands should be conducted to better understand biodiversity conservation in

关键词： abundance richness grain size species-area curve variogram Horqin Sandy Land

Facile preparation and efficient MnxCoy porous nanosheets for the sustainable catalytic process of soot

在线全文

学校读者我要写书评

暂无评论

Green Energy & Environment 2024年第3期9卷 516-528页

作者： Miaomiao Hu Kun Zhou Tingyi Zhao Zheng li Xianhai Zeng Di Yu xuehua Yu Mingqin Zhao Zhihui Shao Qixiang Xu Bing Cui Flavors and Fragrance Engineering&Technology Research Center of Henan Province College of Tobacco ScienceHenan Agricultural UniversityZhengzhou450002China School of Ecology and Environment Zhengzhou UniversityZhengzhou450001China College of Energy Xiamen UniversityXiamen361102China College of Chemistry and Chemical Engineering Shenyang Normal UniversityShenyang110034China

The pursuit of high-performance is worth considerable effort in catalysis for energy efficiency and environmental sustainability. To develop redox catalysts with superior performance for soot combustion, a series of Mn_(x)Co_(y) oxides were synthesized using MgO template *** method greatly improves the preparation and catalytic efficiency and is more in line with the current theme of green catalysts and sustainable development. The resulting Mn_(1)Co_(2.3) has a strong activation capability of gaseous oxygen due to a high concentration of Co^(3+) and Mn^(3+). The Mn doping enhanced the intrinsic activity by prompting oxygen vacancy formation and gaseous oxygen adsorption. The nanosheet morphology with abundant mesoporous significantly increased the solid–solid contact efficiency and improved the adsorption capability of gaseous reactants. The novel design of Mn_(1)Co_(2.3)oxide enhanced its catalytic performance through a synergistic effect of Mn doping and the porous nanosheet morphology, showing significant potential for the preparation of high-performance soot combustion catalysts.

关键词： Soot combustion Intrinsic activity Contact efficiency Mn doping DFT

Prediction of rock-burst-threatened areas in an island coal face and its prevention:A case study

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2016年第6期26卷 1125-1133页

作者： li xuehua Pan Fan li Huaizhen Zhao Min Ding lingxiao Zhang Wenxi School of Mines China University of Mining and Technology State Key Laboratory of Deep Coal Resource Mining China University of Mining and TechnologyXuzhou School of Energy Science and Engineering Henan Polytechnic University

The island coal face arises in coal mines with the purpose of preventing gas explosion or maintaining the balance between mining and tunneling. However, its particular stress conditions in the surrounding rock may increase the difficulty of stress control in the coal face and in its mining roadways, especially when the coal seam, the roof, and the floor have rock-burst propensities. The high energy accumulated in the island coal face and in its roof and floor will intensify rock-burst propensity or even induce rock burst,which further result in great casualties and financial losses. Taking island coal face 2321 in Jinqiao coal mine as a case, we propose a method for the prediction of rock-burst-threatened areas in an island coal face with weak rock-burst propensity. Based on the analysis of the movement of the overlying roof and characteristics of stress distribution, this method combined numerical simulation with drilling bits to ensure the prediction accuracy. The effects of coal pillars with different widths on the mitigation of stress concentration in the coal face and on the prevention of rock burst are analyzed together with the mechanism behind. Finally, corresponding measures against the rock burst in the island coal face are proposed.

关键词：孤岛工作面采煤工作面危险区预测岩爆实例防治数值模拟方法瓦斯爆炸

Spatial structure and species composition of soil seed banks in moving sand dune systems of northeast China

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2016年第1期27卷 75-80页

作者： Chunping Miao xuehua li Meiyu Jia Xu Han Deming Jiang Institute of Applied Ecology Chinese Academy of SciencesShenyang 110016 People's Republic of China University of Chinese Academy of Sciences Beijing 100049People's Republic of China

Soil seed banks can provide a mechanistic for understanding the recruitment dynamics and can inform conservation management of ecosystems. To investigate the contribution of soil seed banks to vegetation restoration in moving sand dune systems, we compared seed structure and species similarity between soil seed banks and standing vegetation among moving sand dunes, ecotones and dune slacks in northeast China. Average seed density in dune slacks was greater than in ecotones or moving sand dunes. Seed density in the soil layer of 0-10 cm was greater than at 10-20 cm both in the moving sand dunes and the eco- tones, but seed densities were similar at depths of 10-20 and 20-30 cm in moving sand dunes. Moreover, the spatial autocorrelation of seed density on moving sand dunes was weak but was strong on the ecotones and dune slacks. The species in the soil seed bank of moving sand dune systems were nearly all annuals, and the low similarity was mainly due to the lack of perennial species that were common in standing vegetation. Consequently, vegetation restoration cannot mainly rely on the soil seed banks in the movingsand dunes and more attention should be paid to protection of the dune slacks because they are the main source of seed disperse and seedling recruitment in moving sand dune systems.

关键词： Compositional similarity Seed density Seedling recruitment Species composition Horqin sandyland

在线全文

学校读者我要写书评

暂无评论

赤水河威信段鱼类多样性及动态特征研究

昆明学院学报 2024年第3期46卷 57-67页

作者：洪梓晋吴程黄显杰裴莹李继业李柏樵申亮常梅秀邓缘媛李宛莹曾明胡永杰付彦琪李涛赵祖权陈文善李学华昆明学院农学与生命科学学院云南昆明650214 昆明学院昆明滇池(湖泊)污染防治合作研究中心云南昆明650214 长江上游珍稀特有鱼类国家级自然保护区云南管护局云南昭通657099 中交一公局集团有限公司北京100024 云南森捷环境工程有限公司云南昆明650034

近年来,赤水河鱼类资源经历了受损、保护、恢复的过程.目前研究与实践集中于赤水河云南段,而对威信境内鱼类多样性研究未见报道.因此,结合历史相关资料及近年调查数据,研究了赤水河威信段鱼类多样性动态特征.结果表明,赤水河威信段鱼类... 详细信息

近年来,赤水河鱼类资源经历了受损、保护、恢复的过程.目前研究与实践集中于赤水河云南段,而对威信境内鱼类多样性研究未见报道.因此,结合历史相关资料及近年调查数据,研究了赤水河威信段鱼类多样性动态特征.结果表明,赤水河威信段鱼类有5目10科46属51种,其干支流鱼类多样性相似度高,不同空间尺度鱼类优势种组成有所差异,且近年鱼类物种恢复成效明显,其中干流鱼类2023年物种数是2019年的2.72倍.

关键词：赤水河水生态鱼类生物多样性

Carbonate formation and water level changes in a paleo-lake and its implication for carbon cycle and climate change, arid China

在线全文

学校读者我要写书评

暂无评论

Frontiers of Earth Science 2013年第4期7卷 487-500页

作者： Yu li Nai'ang WANG Zhuolun li xuehua ZHOU Chengqi ZHANG Yue WANG College of Earth and Environmental Sciences Center for Hydrologic Cycle and Water Resources in Arid Region Lanzhou University Lanzhou 730000 China

碳酸盐免职是在湖的一个主要的无机的碳水池，它变化取决于气候变化和内部湖动力学。关于在湖碳酸盐和气候之间的关系的研究将帮助在湖的系统理解碳周期的机制。这研究的途径是明确地在 paleo 湖(宰埃·莱克) 与 Holocene 长期的气候变... 详细信息

碳酸盐免职是在湖的一个主要的无机的碳水池，它变化取决于气候变化和内部湖动力学。关于在湖碳酸盐和气候之间的关系的研究将帮助在湖的系统理解碳周期的机制。这研究的途径是明确地在 paleo 湖(宰埃·莱克) 与 Holocene 长期的气候变化和湖进化连接碳酸盐形成，它是在干旱中国的典型内陆排水盆的一个终端湖。这篇论文从宰埃·莱克的不同地点在谷物尺寸，碳酸盐内容和沉积样品的矿物学的作文上论述分析。方解石和霰石是为湖碳酸盐的二个主要部件的结果表演，和碳酸盐丰富与湖扩大被联系在期间对中间的 Holocene 晚冰川、早。在中国的干旱区域的 Holocene 湖扩大通常与能在终端湖加强盆宽的表面碳酸盐累积的高盆宽的降水被连接。为这个原因，宰埃·莱克在 Holocene 的湿时期期间起碳水池的一个作用。

关键词：碳酸盐沉积气候变化干旱地区古湖泊水位变化中国全新世中期环和

Applicability of different indices for delineating the boundary of arid region: A case study in northwestern China

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2024年

作者： Xue Peng Xiang li Yingyibing Shen xuehua Che Shipei Dong Zhuolun li Key Laboratory of Western China's Environmental Systems (Ministry of Education) College of Earth and Environmental Sciences Center for Glacier and Desert Research Lanzhou University

Arid regions are vital components of Earth's land surface. Clarifying the area/boundary of arid region is crucial for comprehending area changes and potential mechanisms. However， the accuracy and applicability of arid region boundary delineated by different indices remain unclear. In this study， the annual precipitation （AP）， humidity index （H）， and aridity index （K） were calculated for delineating arid region of China using 106 meteorological stations during 1990–2019. The results suggest that AP and H can accurately delineate arid region， because they are consistent with the distribution of typical soil and vegetation in arid region， whereas K is not. Moreover， AP is the best index for delineating arid region in regions with limited meteorological data， especially in studying long-term patterns and mechanisms of area changes. The accuracy of delineating arid region using H is enhanced in regions with abundant meteorological data. Over the past 30 years， influenced by the increase of atmospheric moisture influx and precipitation， the area in arid region of northwestern China decreased by 70×103–90×103km2， resulting in the present area of approximately 1.55×106km2. This study provides appropriate indices for delineating arid region， contributing to improving our knowledge of regional responses difference to climate change.

关键词：

Comparison of seed germination of four Artemisia species (Asteraceae) in northeastern Inner Mongolia,China

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Arid Land 2012年第1期4卷 36-42页

作者： xuehua li DeMing JIANG Alamusa QuanLai ZHOU Toshio OSHIDA Institute of Applied Ecology Chinese Academy of Sciences Azabu University Sagamihara 252-5201Japan

Two psammophile-dominated Artemisia semi-shrubs （A. wudanica and A. halodendron） and two annual Artemisia forbs （A. sieversiana and A. scoparia） bear significant ecological functions in Horqin Sandy Land, but systematical information on their achenes＇ germination is very limited. A set of studies were conducted to evaluate seed germination responses to storage periods and methods, different temperatures, lights conditions and sand burial depths, in order to determine inter-specific germination variation in the same genus and to explain how the species adapt to its microhabitat. Fresh achenes of A. wudanica, A. halodendron and A. sieversiana showed high germination capacities, but those of A. scoparia had obvious innate dormancy, which could be broken by chilling and dry storage, especially long-term dry storage. Achene germination of the two semi-shrubs preferred lower temperature fluctuation （10 to 22℃） and was not sensitive to light. But the two annuals preferred higher temperature fluctuation （34 to 22℃） and strong light for their achene germination. These four Artemisia species showed similar responses to sand burial, i.e. soil surface was most favorable for seedling emergence, and the deeper the sand burial, the fewer the seedling emergence. For the two semi-shrubs, their microhabitats are sand dunes with high temperature and intense light, which are not favorable for germination and seedling survival. Only rainfall contributes to temporary decrease of temperature and then triggers germination. We deduced that germination is not the main but a supplementary repro- ductive mode for the two semi-shrubs in sand dunes. For the two annuals, achene germination is the only reproductive mode, but different responses have been developed for microhabitat adaptation. For A. sieversiana, high germination capacities in wide temperature ranges and all light conditions could improve its competition and advancement in the wettest microhabitats. For A. scoparia, obvious innate

关键词： annuals semi-shrubs Artemisia species germination chilling and dry storage light temperature sand burial