检索结果-南通市图书馆

A review of space-object collision probability computation methods

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Astrodynamics 2022年第2期6卷 95-120页

作者： jia-sheng li Zhen Yang Ya-Zhong Luo College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073China Hunan Key Laboratory of Intelligent Planning and Simulation for Aerospace Missions Changsha 410073China

The collision probability computation of space objects plays an important role in space situational awareness,particularly for conjunction assessment and collision *** works mainly relied on Monte Carlo simulations to predict collision *** such simulations are accurate when a large number of samples are used,these methods are perceived as computationally intensive,which limits their application in *** overcome this limitation,many approximation methods have been developed over the past three *** paper presents a comprehensive review of existing space-object collision probability computation *** advantages and limitations of different methods are analyzed and a systematic comparison is *** regarding how to select a suitable method for different short-term encounter scenarios is then ***,potential future research avenues are discussed.

关键词： collision probability space situational awareness collision avoidance astrodynamics

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

On Concave Operators

Acta Mathematica Sinica,English Series 2006年第2期22卷 577-582页

作者： Zhan Dong liANG Wen Xia WANG sheng jia li Department of Mathematics Shanxi University Department of Mathematics Zhengzhou University Department of Mathematics Taiyuan Teachers College

We prove that a u0-concave operator can include other concave operators, and derive a sufficient and necessary condition for the existence and uniqueness of the fixed point of a kind of u0-concave operator under a wea... 详细信息

关键词： cone increasing operator Banach space concave operator

On the Strong n-partite Tournaments with Exactly Two Cycles of Length n-1

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2018年第4期34卷 710-717页

作者： Qiao-ping GUO Yu-bao GUO sheng-jia li Chun-fang li School of Mathematical Sciences Shanxi University Taiyuan 030006 China Lehrstuhl C fiir Mathematik RWTH Aachen Templergraben 55 52062 Aachen Germany

Gutin and Rafiey（Australas J. Combin. 34（2006）, 17-21） provided an example of an n-partite tournament with exactly n-m ＋ 1 cycles of length of m for any given m with 4 ≤ m ≤ n, and posed the following question. Let 3 ≤ m ≤n and n ≥ 4. Are there strong n-partite tournaments, which are not themselves tournaments, with exactly n-m ＋ 1 cycles of length m for two values of m？ In the same paper,they showed that this question has a negative answer for two values n-1 and n. In this paper, we prove that a strong n-partite tournament with exactly two cycles of length n-1 must contain some given multipartite tournament as subdigraph. As a corollary, we also show that the above question has a negative answer for two values n-1 and any l with 3 ≤ l ≤ n and l ≠n-1.

关键词： nmltipartite tournaments tournaments cycles

Technological optimization of fully mechanized caving mining face with large mining heights

在线全文

学校读者我要写书评

暂无评论

Journal of Coal Science & Engineering(China) 2013年第3期19卷 290-294页

作者： Lu-jia FAN sheng-li YANG Faculty of Resources and Safety Engineering China University of Mining and Technology (Beijing) Beijing 100083 China

Fully mechanized cave mining with large mining height is a new mining method, due to its large mining thickness and lower roadway excavation, the technology has been widely used in China＇s thick seam mining. In order to improve the top-coal recovery ratio of fully mechanized cave mining with large mining height, a study was conducted on optimizing the caving process, based on the mechanized caving face 1302N in Longgu Coal Mine. This was achieved by improving the PFC numerical calculation methods, and establishing a more accurate model system. On this basis, the recovery ratio of the top coal in different drawing intervals and technologies was investigated in order to achieve a reasonable caving process. The top-coal tracking system was used for practical surveying of the recovery ratio of top coal.

关键词： fully mechanized caving face large mining height caving process optimization numerical calculation by PFC top-coal tracking system

Maximum Principles for a Class of Nonlinear Elliptic Boundary Value Problems

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2005年第3期21卷 373-380页

作者： Jun-tang Ding sheng-jia li jiang-hao Hao School of Mathematical Sciences Shanxi University Taiyuan 030006 China

The Hopf＇s maximum principles are utilized to obtain maximum principles for functions defined on solutions of nonlinear elliptic equations in divergence form （g（u）u,i）,i ＋f（x,u,q）=0（q=｜△↓u｜^2）, subject T... 详细信息

关键词： Nonlinear elliptic equations maximum principles bounds of gradient

A corrosion-resistant and age-hardenable Mg-Al-Mn-Ca-Ce dilute alloy with fine-grained structure processed by controlled rolling

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第32期163卷 223-236页

作者： jia-sheng li Mei-Xuan li Zhen-Ming Hua Yuan-Ting Mo Kai Guan Min Zha Yipeng Gao Hui-Yuan Wang Key Laboratory of Automobile Materials of Ministry of Education&School of Materials Science and Engineering Nanling CampusJilin UniversityChangchun 130025China State Key Laboratory of Automotive Simulation and Control Jilin UniversityChangchun 130012China International Center of Future Science Jilin UniversityChangchun 130012China

Low strength and poor corrosion resistance are two long-standing bottlenecks with dilute Mg ***,we report that the corrosion resistance of Mg-0.6Al-0.5Mn-0.2Ca(wt.%)alloy sheet can be significantly improved by micro-alloying with 0.3 wt.%Ce,and the strength can be considerably augmented after aging *** optimization of strength,ductility,and corrosion resistance is difficult due to the inherent trade-off in Mg ***,our aged Mg-0.6Al-0.5Mn-0.2Ca-0.3Ce alloy features with yield strength(YS)of∼194 MPa,ultimate tensile strength(UTS)of∼265 MPa,elongation to failure(EF)of∼17.2%,and corrosion rate(CR)of 2.2 mm y^(−1),the combination of which exhibits competitive advantage over other comparative dilute Mg *** is found that Ce addition decreases the activity of cathodic phases,inhibits detrimental effects of Fe impurities,and forms a protective Ce-containing surface *** high strength stems from the precipitation of ordered Guinier-Preston(G.P.)zones dispersed in uniform fine grains with an average grain size of∼8.2μ*** atomic-scale *** result in a noticeable age hardening response but do not act as crack initiation and propagation site,so our alloy also performs satisfactory *** work sheds light on the design and fabrication of strong,ductile,and corrosion-resistant dilute magnesium alloys to be used in electronic products and automotive bodies.

关键词： Magnesium alloy Micro-alloying Aging G.P.zones Mechanical property Corrosion

Passive activity enhances residual control ability in patients with complete spinal cord injury

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第8期20卷 2337-2347页

作者： Yanqing Xiao Mingming Gao Zejia He jia Zheng Hongming Bai jia-sheng Rao Guiyun Song Wei Song Xiaoguang li Beijing Key Laboratory for Biomaterials and Neural Regeneration Beijing Advanced Innovation Center for Biomedical EngineeringSchool of Biological Science and Medical EngineeringBeihang UniversityBeijingChina Department of Rehabilitation Evaluation China Rehabilitation Research CenterBeijingChina Cardiac Center Beijing Children’s HospitalCapital Medical UniversityBeijingChina The State Key Laboratory of Virtual Reality Technology and Systems Beihang UniversityBeijingChina Department of Rehabilitation Engineering China Rehabilitation Science InstituteBeijingChina

Patients with complete spinal cord injury retain the potential for volitional muscle activity in muscles located below the spinal injury ***,because of prolonged inactivity,initial attempts to activate these muscles may not effectively engage any of the remaining neurons in the descending pathway.A previous study unexpectedly found that a brief clinical round of passive activity significantly increased volitional muscle activation,as measured by surface *** this study,we further explored the effect of passive activity on surface electromyographic signals during volitional control tasks among individuals with complete spinal cord *** patients with chronic complete thoracic spinal cord injury were *** electromyography data from eight major leg muscles were acquired and compared before and after the passive activity *** results indicated that the passive activity led to an increased number of activated volitional muscles and an increased frequency of *** the cumulative root mean square of surface electromyography amplitude for volitional control of movement showed a slight increase after passive activity,the difference was not statistically *** findings suggest that brief passive activity may enhance the ability to initiate volitional muscle activity during surface electromyography tasks and underscore the potential of passive activity for improving residual motor control among patients with motor complete spinal cord injury.

关键词： complete spinal cord injury cycle training epidural electrical stimulation motor training passive activity physiological state spinal cord circuit surface electromyography volitional control task

Chromosome-level genome assembly of the dotted gizzard shad(Konosirus punctatus) provides insights into its adaptive evolution

在线全文

学校读者我要写书评

暂无评论

Zoological Research 2022年第2期43卷 217-220页

作者： Bing-jian liu Kun Zhang Shu-Fei Zhang Yi-Fan liu jia-sheng li Ying Peng Xun Jin Yun-Peng Wang Si-Xu Zheng li Gong li-Qin liu Zhen-Ming Lu National Engineering Laboratory of Marine Germplasm Resources Exploration and Utilization Zhejiang Ocean UniversityZhoushanZhejiang 316022China Guangdong Provincial Key Laboratory of Fishery Ecology and Environment South China Sea Fisheries Research InstituteChinese Academy of Fisheries SciencesGuangzhouGuangdong 510300China National Engineering Research Center for Facilitated Marine Aquaculture Marine Science and Technology CollegeZhejiang Ocean UniversityZhoushanZhejiang 316022China

Konosirus punctatus is an economically important marine fishery resource and is widely distributed from the Indian to Pacific *** is a good non-model species for genetic studies on salinity and temperature ***,a high-... 详细信息

关键词： salinity Indian evolution

High efficiency solid–liquid hybrid-state quantum dot light-emitting diodes

在线全文

学校读者我要写书评

暂无评论

Photonics Research 2018年第12期6卷 1107-1115页

作者： jia-sheng li YONG TANG ZONG-TAO li LONG-SHI RAO XIN-RUI DING BIN-HAI YU Engineering Research Center of Green Manufacturing for Energy-Saving and New-Energy Technology South China University of TechnologyGuangzhou 510640China Foshan Nationstar Optoelectronics Company Ltd. Foshan 528000China

Quantum dots(QDs) can achieve high quantum yields close to unity in liquid solutions, whereas they exhibit a decreased conversion efficiency after being integrated into solid-state polymer matrices for light-emitting diode(LED) devices, which is called the host matrix effect. In this study, we propose a solid–liquid hybrid-state QD-LED to solve this issue. The ethylene-terminated polydimethylsiloxane (ethylene-PDMS) is used to establish a solid-state cross-linked network, whereas the methyl-terminated PDMS (methyl-PDMS) is used in its liquid state. From a macroscopic level, the cured solid–liquid hybrid-state PDMS (SLHP) composites reach a solid state,which is stable and flexible enough to be used in LED devices. Compared with LEDs using conventional QD/solid PDMS composites at equal color conversion efficiency ranging from 40% to 60%, the luminous flux of LEDs with QD/SLHP composites is increased by 13.0% using an optimized methyl-PDMS concentration of 85 wt. %.As a result, high efficiency QD-LEDs using QDs as the only color convertor with luminous efficacy of 89.6 lm/W (0.19 A) were achieved, which show a working stability comparable with that using conventional solid-state structures at a harsh condition. Consequently, the novel approach shows great potential for achieving high efficiency and high stability QD-LEDs, which is also compatible with current structures used in illumination and display applications.

关键词： devices matrix PDMS LEDs unity after reach flux