检索结果-南通市图书馆

Exploring differentiated improvement strategies of cultivated land quality in China

在线全文

学校读者我要写书评

暂无评论

Frontiers of Agricultural Science and Engineering 2024年第2期11卷 282-291页

作者： Wenguang CHEN xiangbin KONG Yubo LIAO College of Land Science and Technology China Agricultural University

Quality is the core feature of cultivated land. In the face of deteriorating cultivated land quality and growing food demand, improving cultivated land quality is a top priority for guaranteeing the sustainable use of resources and national food security. Cultivated land quality in the new era can be considered in four dimensions: suitability, contiguity, resistance and ecological stress. Cultivated land suitability in China shows a decreasing trend from east to west, cultivated land contiguity is high in the north-east and low in the south-west. In terms of cultivated land resistance, the number of strongly and weakly resistant cropping fields is small and spatially clustered. Cultivated land with ecological stress is mainly located in the northern region. Based on the current situation of cultivated land quality and the strategic needs of national high-quality development, China's future goals for improving cultivated land quality include four aspects: promoting the sustainable use of resources,improving the economic benefits of farming, coping with extreme meteorological disasters and meeting the transition of the food system.Against the backdrop of a volatile international environment and high domestic demand for food, China should guarantee a safe supply of staples, a stable supply of animal feed and a moderate supply of high-nutrient food. In the future, China should create three major food production spaces: highstandard, low-to medium-yield, and marginal cultivated land. China urgently needs to construct three paths to implement the goal of improving cultivated land quality, namely the development of high-standard cultivated land with the core of spatial optimization, resilience enhancement and scale coupling,the transformation of low-to medium-yield cultivated land with the core of obstacle elimination, tenure adjustment, ecological sustainable, and the conservation development of marginal cultivated land with a focus on sustainable use.

关键词： China cultivated land quality differentiated improvement food security

Stress distribution and surrounding rock control of mining near to the overlying coal pillar in the working face

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2019年第6期29卷 881-887页

作者： Rui Gao Bin Yu xiangbin meng Key Laboratory of Deep Coal Resource Mining School of MinesMinistry of Education of ChinaChina University of Mining&TechnologyXuzhou 221116China Datong Coal Mine Group Co.Ltd. Datong 037000China

The occurrence of overlying coal pillar(OCP)exerts a strong effect on the stress and strain distribution of the surrounding rock in the stope.In this paper,the stress distribution characteristics are analyzed via the numerical calculation with the account of OCP presence or absence.In addition,this study revealed the joint effect of side pressure relief area of the goaf and stress concentration in OCP on the final stress distribution.Furthermore,the rules of abutment stress distribution affected by three influencing factors,namely horizontal-vertical distances between OCP and working face and buried depth of OCP,are analyzed.The functional model linking the peak stress of surrounding rock with the above influencing factors is developed.The field application of the above results proved that the rib spalling and deformation of a 2.95 m-high and 5.66 m-wide roadway could be efficiently controlled by rationally adjusting working states of the support,and adopting the hydraulic prop coordinated with the p type metal beam and anchor cable to strengthen the surrounding rock of working face and roadway,respectively.The proposed measures are considered appropriate to satisfy the safe operation requirements.

关键词： Overlying coal pillar(OCP) Stress distribution Influencing factors Surrounding rock control

Performance Analysis of Spatial Modulation Aided UAV Communication Systems in Cooperative Relay Networks

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Electronics 2024年

作者： xiangbin YU Mingfeng XIE Ning LI Cuimin PAN College of Electronic and Information Engineering Nanjing University of Aeronautics and Astronautics State Key Laboratory of Millimeter Waves Southeast University

In this paper, by introducing the spatial modulation(SM) scheme into the unmanned aerial vehicle(UAV) relaying system, a SM-aided UAV(SM-UAV) cooperative relay network is presented. The performance of the SM-UAV relay network is investigated over Nakagami-m fading channels, where the UAV remains stationary over a given area. According to the performance analysis, using the amplify-and-forward(AF) protocol, the effective signalto-noise ratio(SNR) and the corresponding probability density function and moment generating function are, respectively, derived. With these results, the average bit error rate(BER) is further deduced, and resultant approximate closed-form expression is achieved. Based on the approximate BER, we derive the asymptotic BER to characterize the error performance of the system at high SNR. With this asymptotic BER, the diversity gain of the system is derived, and the resulting diversity order is attained. Simulation results illustrate the effectiveness of the performance analysis. Namely, approximate BER has the value close to the simulated one, and asymptotic BER can match the corresponding simulation well at high SNR. Thus, the BER performance of the system can be effectively assessed in theory, and conventional simulation will be avoided. Besides, the impacts of the antenna number, modulation order,fading parameter and UAV position on the system performance are also analyzed. The results indicate that the BER performance is increased with the increases of Nakagami parameter m and/or receive antenna and/or the decrease of modulation order.

关键词：

Evolution of Grain Selection in Spiral Selector during Directional Solidification of Nickel-base Superalloys

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 Materials Science & Technology 2011年第2期27卷 118-126页

作者： xiangbin meng Jinguo Li Tao Jin Xiaofeng Sun Changbo Sun Zhuangqi Hu Institute of Metal Research Chinese Academy of SciencesShenyang 00China Graduate School of Chinese Academy of Sciences Beijing 000China Shenyang Liming Aero-engine(Group) Corporation Ltd. Aviation Industry Corporation of China(AVIC)Shenyang 110043China

The process of grain selection in the spiral selector was investigated by both a ProCAST simulation based on a cellular automaton finite element（CAFE） model and experimental confirmation.The results show that the height of starter block,the spiral diameter and initial angle play an important role in grain selection.The dimension of selector should be maintained in a stable range to optimize the grain orientation and select a single crystal efficiently.A selector which can efficiently select a single crystal had been successfully designed.Grain orientation fluctuation in the spiral part was also studied by means of the variation of thermal condition.

关键词： Ni-base single crystal superalloys Grain selection Directional solidification

硬件损伤下多窃听器NOMA系统平均保密容量分析

在线全文

学校读者我要写书评

暂无评论

Transactions of Nanjing University of Aeronautics and Astronautics 2024年第2期41卷 244-252页

作者：何安苏虞湘宾周玥南京航空航天大学电子信息工程学院中国南京211106 中国科学院无线传感器网络与通信重点实验室中国上海200050

研究了非正交多址(Non‑orthogonal‑multiple‑access,NOMA)接入通信系统的物理层安全性能。当基站采用下行NOMA方案发送信息时,由于信道的开放性,信息容易被窃听,而当存在多个随机分布的窃听者时,安全性能会进一步降低。为了增强存在硬... 详细信息

研究了非正交多址(Non‑orthogonal‑multiple‑access,NOMA)接入通信系统的物理层安全性能。当基站采用下行NOMA方案发送信息时,由于信道的开放性,信息容易被窃听,而当存在多个随机分布的窃听者时,安全性能会进一步降低。为了增强存在硬件损伤系统的物理层安全性能,本文考虑保护区的方法,针对地面用户与基站之间存在直连链路的情况,采用莱斯衰落来建模小尺度衰落。本文还假设多个窃听者的位置遵循齐次泊松点过程(Homogeneous Poisson point process,HPPP),借助高斯切比雪夫积分公式,推导了平均保密容量的闭式表达式,并给出了在高信噪比情况下的渐近表达式来获得进一步见解。仿真结果验证了保护区方法在增强安全性能方面的有效性,并说明了不同参数对系统保密性能的影响。

关键词：平均保密容量非正交多址硬件损伤莱斯衰落物理层安全

Modes of Grain Selection in Spiral Selector during Directional Solidification of Nickel-base Superalloys

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2012年第3期28卷 214-220页

作者： xiangbin meng Qi Lu Jinguo Li Tao Jin Xiaofeng Sun Jun Zhang ZhongqiangChen Yanhui Wang Zhuangqi Hu Institute of Metal Research Chinese Academy of SciencesShenyang 110016China Graduate School of Chinese Academy of Sciences Beijing 100049China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China Aviation Industry Corporation of China(AVIC)Shenyang Liming Aero-engine(Group)Corporation LTD. Shenyang 110043China

The modes of grain selection in spiral selector were investigated by both a ProCAST simulation and experimental confirmation. The results show that the efficiency of grain selection in starter block is associated with the geometry shape. At the early stage of grain selection, the optimization of grain orientation is dominated by competitive grain growth, but the optimization of grain orientation in starter block is gradually dominated by geometry shape at the later stage of grain selection. Besides, the spiral part could also optimize the orientation of the selected single crystal when the initial angle is large enough, and the single crystal selection in spiral parts with different pitch lengths and initial angles is dominated by different modes. The simulation results agree well with experimental ones.

关键词： Ni-base single crystal superalloys Competitive grain growth Geometry shape Directional solidification Spiral selector

在线全文

学校读者我要写书评

暂无评论

贝叶斯统计中共轭先验分布的教学研究

吉林省教育学院学报 2024年第1期40卷 127-136页

作者：孟祥斌陈丽东北师范大学长春大学

先验分布在贝叶斯统计中扮演着关键角色,而共轭先验则是其中最为重要的一种。学生对共轭先验分布的理解和掌握程度直接影响他们对贝叶斯统计方法的学习效果。目前的大多数教材通常是先介绍一些常见分布的共轭先验,然后再证明其共轭性质... 详细信息

先验分布在贝叶斯统计中扮演着关键角色,而共轭先验则是其中最为重要的一种。学生对共轭先验分布的理解和掌握程度直接影响他们对贝叶斯统计方法的学习效果。目前的大多数教材通常是先介绍一些常见分布的共轭先验,然后再证明其共轭性质。然而,这种教学方法缺乏深度和灵活性。为了解决这个问题,本文提出在更广泛的指数族分布下,给出参数共轭先验的一般表达形式。接着,针对一些常见分布,通过从指数分布族结构推导出其待估参数的共轭先验,使得学生不仅能深刻理解共轭先验的本质,还能学到一种更为灵活的共轭先验选择策略。这种从一般到具体的教学方法有助于提高学生对贝叶斯统计的理解深度,并培养学生灵活运用共轭先验的能力。

关键词：贝叶斯统计共轭先验分布指数分布族

In vitro bench testing using patient-specific 3D models for percutaneous pulmonary valve implantation with Venus P-valve

在线全文

学校读者我要写书评

暂无评论

中华医学杂志(英文版) 2024年第8期137卷 2023 Aug 22页

作者： Han Yu Shao Zehua Sun Zirui Han Yan Xu Hongdang Song Shubo Pan xiangbin de Jaegere Peter P. T. Fan Taibing Zhang Gejun Department of Cardiology Erasmus MC Rotterdam 3015 GD Netherlands Department of Structure Heart Disease Central China Fuwai Hospital of Zhengzhou University Zhengzhou Henan 451460 China Children’s Heart Center Department of Anesthesiology Fuwai Hospital Chinese Academy of Medical Sciences Beijing 100037

Background: Due to the wide variety of morphology, size, and dynamics, selecting an optimal valve size and location poses great difficulty in percutaneous pulmonary valve implantation (PPVI). This study aimed to report our experience within vitro bench testing using patient-specific three-dimensional (3D)-printed models for planning PPVI with the Venus P-valve.Methods: Patient-specific 3D soft models were generated using PolyJet printing with a compliant synthetic material in 15 patients scheduled to undergo PPVI between July 2018 and July 2020 in Central China Fuwai Hospital of Zhengzhou University.Results: 3D model bench testing altered treatment strategy in all patients (100%). One patient was referred for surgery because testing revealed that even the largest Venus P-valve would not anchor properly. In the remaining 14 patients, valve size and/or implantation location was altered to avoid valve migration and/or compression coronary artery. In four patients, it was decided to change the point anchoring because of inverted cone-shaped right ventricular outflow tract (RVOT) (n = 2) or risk of compression coronary artery (n = 2). Concerning sizing, we found that an oversize of 2-5 mm suffices. Anchoring of the valve was dictated by the flaring of the in- and outflow portion in the pulmonary artery. PPVI was successful in all 14 patients (absence of valve migration, no coronary compression, and none-to-mild residual pulmonary regurgitation [PR]). The diameter of the Venus P-valve in the 3D simulation group was significantly smaller than that of the conventional planning group (36 [2]vs. 32 [4],Z = -3.77,P <0.001).Conclusions: In vitro testing indicated no need to oversize the Venus P-valve to the degree recommended by the balloon-sizing technique, as 2-5 mm sufficed.

关键词： Heart valve prosthesis implantation Percutaneous pulmonary valve intervention Pulmonary regurgitation In vitro bench testing 3D printing Venus P-valve

Status and trends in the stability of the three largest ice shelves in Antarctica

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2024年第8期 2615-2632页

作者： Rongxing LI Guojun LI Lu AN menglian XIA Da LV Yuan CHENG Aiguo ZHAO Tian CHANG xiangbin CUI Shengkai ZHANG Shijie LIU Yixiang TIAN Weian WANG Center for Spatial Information Science and Sustainable Development Applications Tongji University College of Surveying and Geo-informatics Tongji University Postdoctoral Research Station of Shanghai Surveying and Mapping Institute Key Laboratory of Spatial-temporal Big Data Analysis and Application of Natural Resources in Megacities Institute for Conservation of Cultural Heritage School of Cultural Heritage and Information Management Shanghai University Polar Research Institute of China Chinese Antarctic Center of Surveying and Mapping Wuhan University

The Ross, Filchner-Ronne, and Amery ice shelves are the three largest ice shelves in Antarctica, playing a crucial role in supporting the Antarctic ice sheet. However, current studies on the stability of the three largest ice shelves primarily focus on singular or limited factors, lacking a comprehensive assessment of multiple parameters. To systematically and in-depth study the stability and trend of the three largest ice shelves, we comprehensively collected and analyzed key parameters, including elevation changes, basal melting, surface meltwater, major rifts propagation rate, suture zones, ice front area change rate,grounding lines, ice velocity, and mass balance. Additionally, we selected the collapsed Larsen B Ice Shelf(LBIS), the rapidly changing and structurally weakened Pine Island Ice Shelf(PIIS), and the accelerating Totten Ice Shelf(TIS) as reference ice shelves. By comparing and analyzing the key parameters between these reference ice shelves and the three largest ice shelves, we find the status and trends in the stability of the latter. Our findings reveal that most key parameters of the three largest ice shelves present relatively minor variations compared to those of the reference ice shelves. Specifically, 50% of the parameters are smaller than those of the accelerating TIS, 88% are smaller than those of the rapidly changing PIIS, and all parameters are smaller than those of the collapsed LBIS. Furthermore, after analyzing parameters that are not smaller than those of the TIS, it is observed that they remain in a stable state. Hence, the three largest ice shelves are currently undergoing natural changes that do not threaten their stability in the short term. Nevertheless, the evolution of the ice shelves under global climate change remains uncertain,making long-term observation and monitoring essential to assess their impact on sea level rise.

关键词：