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Effect of shrub-grass vegetation coverage and slope gradient on runoff and sediment yield under simulated rainfall 认领
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作者 Dandan Han Jingcheng Deng +3 位作者 Chaojun Gu Xingmin Mu Peng Gao Jianjian Gao 《国际泥沙研究:英文版》 SCIE 2021年第1期29-37,共9页
Evaluating the benefits of sediment and runoff reduction in different vegetation types is essential for studying the mechanisms of soil and water conservation on the Loess Plateau.The experiment was conducted in shrub... Evaluating the benefits of sediment and runoff reduction in different vegetation types is essential for studying the mechanisms of soil and water conservation on the Loess Plateau.The experiment was conducted in shrub-grass plots with nine levels of mixed vegetation coverage from 0%to 70%,three slopes(10,15,and 20)and two rainfall intensities(1.0 and 2.5 mm/min).The results showed that the vegetation coverage and slope gradient significantly affect runoff and sediment yield.Shrub-grass vegetation coverage had a significant effect on the runoff start-time,runoff flow velocity,runoff rate,and soil erosion rate on hillslopes.Mixed vegetation coverage could effectively delay the runoff starttime and decrease the runoff flow velocity.However,the effects of the slope gradient on runoff and sediment yield are opposite to those of vegetation coverage.Shrub-grass vegetation coverage could effectively increase runoff and sediment yield reduction benefits,while their benefits were affected by the rainfall intensity.At the 1.0 mm/min rainfall intensity,the reduction in the sediment production rate was greater than that under the 2.5 mm/min intensity.However,when the shrub-grass vegetation coverage exceeded 42%,the runoff reduction benefit was more obvious at higher rainfall intensities.The cumulative sediment yield increased with increasing cumulative runoff,and the rate of increase in the cumulative runoff was greater than that of the cumulative sediment yield with increasing of shrub-grass vegetation coverage.Moreover,there was a power function relationship between cumulative sediment yield and cumulative runoff yield(P<0.05).Our paper is expected to provide a good reference on the ecological environment and vegetation construction on the Loess Plateau. 展开更多
关键词 Simulated rainfall Shrub-grass coverage SLOPE Runoff and sediment yield
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文章速递分层式基站自动规划补盲方法与系统 认领
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作者 涂鸿渐 阮克敏 +1 位作者 全力 吴曙辉 《电信工程技术与标准化》 2021年第1期59-64,共6页
5G移动通信网络的建设优化需要运营商投入大量的资金和人力,可以充分借鉴成熟的4G规划方法、技术和经验,在有限的资源投入条件下,达到较佳的信号覆盖。分层式基站自动化规划方案可以分层并精确定位到盲点盲区等所需建立基站的位置,进一... 5G移动通信网络的建设优化需要运营商投入大量的资金和人力,可以充分借鉴成熟的4G规划方法、技术和经验,在有限的资源投入条件下,达到较佳的信号覆盖。分层式基站自动化规划方案可以分层并精确定位到盲点盲区等所需建立基站的位置,进一步对规划的待建基站进行优化,确保站址和站型合理且网络结构最优,有效避免资源浪费。 展开更多
关键词 分层 覆盖 补盲
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Associated Factors with the Child’s Fully Immunized in the Tambacounda Health District (Senegal) 认领
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作者 Khadim Niang Tidiane Gadiaga +5 位作者 Jean Augustin Tine Omar Bassoum Fatou Bintou Diongue Amadou Ibra Diallo Adama Faye Ndiaye Papa 《流行病学期刊(英文)》 2020年第2期167-178,共12页
To improve vaccination coverage among children under one year of age in the Tambacounda health district, a household survey was carried out among mothers or babysitters. The objective was to study the factors related ... To improve vaccination coverage among children under one year of age in the Tambacounda health district, a household survey was carried out among mothers or babysitters. The objective was to study the factors related to child’s fully immunized in children aged 12 to 23 months. The cross-sectional, descriptive and analytical survey was carried out during the month of April 2019. A multistage cluster survey selected a sample of 657 mothers and babysitters. The data was collected using a questionnaire made from the World Health Organization reference guide. Data entry and analysis were done with Epi Info software and R. Among the women surveyed, biological mothers were the most representative (96.9%). In the series, 74.1% had a good knowledge of the age for initiating vaccination, 78.2% knew the number of contacts. The vaccination record of the children was available in 92.2%, and 71.0% of them had presented an adverse event. The proportion of children fully immunized was 41.0%. Complete childhood vaccination was positively associated with income-generating activity in women (0R = 2.4) and the short distance (<100 m) between home and place of vaccination (OR = 1.5). It was also improved by having a qualified health worker as a vaccinator (OR = 1.4) satisfaction in relation to visit (OR = 2.0), the advice given by the vaccinator (OR = 1.7) and the fixing of the date of the next vaccination appointment (OR = 2.5). The implementation of a good strategy for improving the quality of immunization services is an important element for strengthening immunization coverage in the Tambacounda health district. 展开更多
关键词 VACCINATION CHILD HEALTH IMMUNIZATION COVERAGE Senegal
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海外可再生能源项目融资分析 认领
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作者 卢志强 《风力发电》 2020年第1期1-7,共7页
随着我国能源投资国际化发展日益蓬勃,对境外有限追索权项目融资模式的探索以丰富传统海外投资模式在近年越发引起关注。卢志强先生在本文分享了他二十多年来在银行和新能源行业国内外融资的丰富经验,为我国海外投资方介绍项目融资与企... 随着我国能源投资国际化发展日益蓬勃,对境外有限追索权项目融资模式的探索以丰富传统海外投资模式在近年越发引起关注。卢志强先生在本文分享了他二十多年来在银行和新能源行业国内外融资的丰富经验,为我国海外投资方介绍项目融资与企业贷款的优势和方案对比、从贷方的角度分析银行对项目融资是怎么来评估以及转嫁风险、并为复杂的条款进行解读。借力外部融资除了可减少企业因负债率,更是为海外项目风险把关,确保项目更加可行和完善的。 展开更多
关键词 Environmental Social and Corporate Governance Limited Recourse Financing EPC Agreement Debt Service Coverage Ratio Multi Agencies
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A Method for Deploying the Minimal Number of UAV Base Stations in Cellular Networks 认领
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作者 Hailong Huang Chao Huang Dazhong Ma 《自动化学报:英文版》 EI CSCD 2020年第2期559-567,共9页
In this paper,we consider the scenario of using unmanned aerial vehicles base stations(UAV-BSs)to serve cellular users.In particular,we focus on frnding the minimum number of UAV-BSs as well as their deployment.We pro... In this paper,we consider the scenario of using unmanned aerial vehicles base stations(UAV-BSs)to serve cellular users.In particular,we focus on frnding the minimum number of UAV-BSs as well as their deployment.We propose an optimization model which minimizes the number of UAV-BSs and optimize their positions such that the user equipment(UE)covered ratio is no less than the expectation of network suppliers,the UEs receive acceptable downlink rates,and the UAV-BSs can work in a sustainable manner.We show the NP-hardness of this problem and then propose a method to address it.The method first estimates the range of the number of UAV-BSs and then converts the original problem to one which maximizes the UE served ratio,given the number of UAV-BSs within that range.We present a maximizing algorithm to solve it with the proof of convergence.Extensive simulations based on a realistic dataset have been conducted to demonstrate the effectiveness of the proposed method. 展开更多
关键词 BLANKET COVERAGE cellular networks COVERAGE control PROACTIVE DEPLOYMENT unmanned aerial vehicles(UAV)
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A Fault-Based Testing Approach in Safety Critical Medical Systems 认领
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作者 Xaveria Youh Djam Yisa Henry Kimbi 《软件工程与应用(英文)》 2020年第6期129-142,共14页
<span style="font-family:Verdana;">The advent of technology has opened unprecedented opportunities in health care delivery system as the demand for intelligent and knowledge-based systems has increased... <span style="font-family:Verdana;">The advent of technology has opened unprecedented opportunities in health care delivery system as the demand for intelligent and knowledge-based systems has increased as modern medical practices become more knowledge-intensive. As a result of this, there is greater need to investigate the pervasiveness of software faults in Safety critical medical systems for proper diagnosis. The sheer volume of code in these systems creates significant concerns about the quality of the software. The rate of untimely deaths nowadays is alarming partly due to the medical device used to carry out the diagnosis process. A safety-critical medical (SCM) system is a complex system in which the malfunctioning of software could result in death, injury of the patient or damage to the environment. The malfunctioning of the software could be as a result of the inadequacy in software testing due to test suit problem or oracle problem. Testing a SCM system poses great challenges to software testers. One of these challenges is the need to generate a limited number of test cases of a given regression test suite in a manner that does not compromise its defect detection ability. This paper presents a novel five-stage fault-based testing procedure for SCM, a model-based approach to generate test cases for differential diagnosis of Tuberculosis. We used Prime Path Coverage and Edge-Pair Coverage as coverage criteria to ensure maximum coverage to identify feasible paths. We analyzed the proposed testing procedure with the help of three metrics consisting of Fault Detection Density, Fault Detection Effectiveness and Mutation Adequacy Score. We evaluated the effectiveness of our testing procedure by running the suggested test cases on a sample historical data of tuberculosis patients. The experimental results show that our developed testing procedure has some advantages such as creating mutant graphs and Fuzzy Cognitive Map Engine while resolving the problem of eliminating infeasible test cases for effective decisio 展开更多
关键词 Mutation Testing Software Development Software Testing Test Coverage Mutation Adequacy Score
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Vaccine Coverage of Newly Introduced Vaccines and Factors Influencing among Children Less Than 23 Months in Laikipia North Subcounty 认领
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作者 Donald Mogoi Eric M. Muchiri Alfred M. Mutuma 《预防医学期刊(英文)》 2020年第2期9-43,共35页
The epidemiology of vaccine preventable diseases has been modified by use and implementation of various vaccination programs in many countries. However, because of observed suboptimal vaccination rates, debate has eme... The epidemiology of vaccine preventable diseases has been modified by use and implementation of various vaccination programs in many countries. However, because of observed suboptimal vaccination rates, debate has emerged on the benefits of such vaccines worldwide. Maternal and childhood vaccinations have been evaluated and found extremely effective at preventing illness in pregnant women and new-borns despite low uptake of such vaccines in many areas. The objective of this study was to determine the Vaccination Coverage and factors that influence uptake of newly introduced vaccines among children aged less than 23 months in Laikipia North Sub-County. The study used multistage sampled parents and guardians of children below 23 months of age but residents of Laikipia North Sub-County within Laikipia County. Trained interviewers visited sampled households and administered a standardized pretested questionnaire. Mothers and guardians were interviewed and asked to show the interviewers Mother-Child Post Natal Booklets for the study enrolled children. Key informant questionnaires were also administered to Health facility staff. Data entry and analysis were performed using SPSS and Microsoft Excel. Chi-Square for Proportion and Student T-test were used to assess factors influencing uptake of vaccines in the sub-county. The study found that slightly above half (59%) of the care givers indicated that their child had been vaccinated. Majority (61%) of the care givers had their children given rotavirus vaccine while an equal number (61%) had their children given Pneumococcal vaccine. 52% of the care givers indicated that their children were given IPV (Inactivated Polio Vaccine). 53% of the children who were given rotavirus vaccine received the required 2 doses. Among social-cultural factors, the need for permission from mother-in-law (p = 0.003), belief that vaccination makes girls infertile (p = 0.046) and belief that vaccination at a very young age can harm the child (p = 0.021). Migration with animals or nomadic lifesty 展开更多
关键词 INFANT Vaccine VACCINATION COVERAGE Factor
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Forehead Flap in Coverage of Nasal Defects: Our Experience 认领
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作者 Mohamed Elsayed Mohamed Mohamed Ahmed Fathy Mohamed Eldehn 《现代整形外科(英文)》 2020年第1期1-8,共8页
Background: Coverage of post-traumatic or post-oncosurgical nasal defects is a very challenging procedure. Small nasal defects may be covered by skin grafts or small local flaps while larger nasal defects require more... Background: Coverage of post-traumatic or post-oncosurgical nasal defects is a very challenging procedure. Small nasal defects may be covered by skin grafts or small local flaps while larger nasal defects require more complex flap coverage techniques as using tissue expanders, prefabricated flaps or free flaps. The forehead flap has been used for centuries and remains a workhorse flap for reconstruction of large and complex nasal defects. Aim: evaluate the feasibility and versatility of forehead flap for resurfacing nasal defects. Materials and Methods: 12 patients underwent coverage of nasal defects after trauma or tumor excision using forehead flaps. All flaps needed a second stage for flap separation 3 weeks after the time of operation. The size of the harvested flap, the harvesting time, results of transferred flaps, patient satisfaction and flap-related complications were analyzed. Results: 12 patients (10 males and 2 females) underwent reconstruction of different nasal defects using 12 forehead flaps. The overall complications occurred in 2 patients. The remaining 10 patients showed no complications and passed an uneventful follow-up period. 7 Patients were very satisfied, 4 were satisfied and only one patient was not satisfied as she was 23 years old young female and was subjected to human bite. Follow-up periods ranged from 6 to 12 months. Conclusion: Nasal defects can successfully be managed with the forehead flap. Probably, the flap provides the best result due to the good matching of the skin in terms of color, texture, and thickness. Also, despite the increasing use of free flaps, the forehead flap is still a valid and safe option for nasal defects coverage that allows good aesthetics and functional outcomes. 展开更多
关键词 NASAL DEFECTS FOREHEAD FLAP FLAP COVERAGE NASAL Reconstruction
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文章速递Interval Estimation in a Two Parameter Weibull Distribution Based on Type-2 Censored Data 认领
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作者 Raphael Masila Mweleli Luke Akong’o Orawo +1 位作者 Cox Lwaka Tamba Justin Obwoge Okenye 《统计学期刊(英文)》 2020年第6期1039-1056,共18页
In this paper, we consider the construction of the approximate profile-</span><span style="font-family:""> </span><span style="font-family:Verdana;">likelihood confiden... In this paper, we consider the construction of the approximate profile-</span><span style="font-family:""> </span><span style="font-family:Verdana;">likelihood confidence intervals for parameters of the 2-parameter Weibull distribution based on small type-2 censored samples. In previous research works, the traditional Wald method has been used to construct approximate confidence intervals for the 2-parameter Weibull distribution</span><span style="font-family:""> </span><span style="font-family:Verdana;">under type-2 censoring scheme. However, the Wald technique is based on normality assumption and thus may not produce accurate interval estimates for small samples. The profile-likelihood and Wald confidence intervals are constructed for the shape and scale parameters of the 2-parameter Weibull distribution based on simulated and real type-2 censored data, and are hence compared using confidence length and coverage probability. 展开更多
关键词 Two-Parameter Weibull Distribution Interval Estimation Relative Likelihood Function Maximum Relative Likelihood Function Profile-Likelihood Interval Coverage Probability
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文章速递Analysis of Transit Network Design Using GIS and Honeybee Algorithm in the City of Sanandaj, Iran 认领
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作者 Armin Ahmadi 《地理信息系统(英文)》 2020年第6期716-731,共16页
Public transit planning is a user-oriented problem, respectful of financial issues and involves different stakeholders such as the general public, the transportation provider and the local government. One of the main ... Public transit planning is a user-oriented problem, respectful of financial issues and involves different stakeholders such as the general public, the transportation provider and the local government. One of the main components of public transit planning is the transit network design (TND) problem. This research is an attempt to perform transit network design and analysis in the city of Sanandaj, Iran using the capabilities of GIS and Honeybee algorithm. Objectives of this study are formulating a multi-objective model of the TND problem, developing a GIS-based procedure for solving the TND problem and examination of the solutions using artificial metaheuristic methods such as honeybee algorithm. The transit network design approach in this research, aims to reduce the walking distance, the total travel distance and the total number of stops needed for a suitable transit service in Sanandaj, Iran. One of the contributions of this research is developing a transit network design with utilizing a spectrum of GIS software modelling functionalities and using the abilities of the artificial intelligence in modelling and assessment of the transit network. 展开更多
关键词 Transit Network Design (TND) GIS Honeybee Algorithm Coverage Planning
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基于回声探测监测沉水植物盖度的插值方法研究:以杭州西湖沉水植物盖度监测为例 认领
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作者 彭雪 张璐 +4 位作者 黄素珍 蔺庆伟 刘碧云 张义 吴振斌 《湖泊科学》 EI CAS CSCD 北大核心 2020年第2期472-482,共11页
沉水植物作为水生态系统的重要组成成分,在水生态系统物质循环和能量流动中发挥着重要作用,其覆盖度和生物量是评价湖泊等浅水水体系统稳定性的关键参数.随着高效和无损伤监测的回声探测仪在沉水植物盖度监测中的应用,其精确度算法也受... 沉水植物作为水生态系统的重要组成成分,在水生态系统物质循环和能量流动中发挥着重要作用,其覆盖度和生物量是评价湖泊等浅水水体系统稳定性的关键参数.随着高效和无损伤监测的回声探测仪在沉水植物盖度监测中的应用,其精确度算法也受到了越来越多的关注.本研究以成功恢复沉水植物的浅水湖泊杭州西湖为研究对象,利用BioSonics便携型回声探测仪——MX采集沉水植物回声样本.同时结合人工样方设置,采集与回声探测对应位点的沉水植物样本,验证回声探测结果的精确性.通过建立回归模型分析回声探测得到的沉水植物体积百分比(PVI)与人工样方获得的对应平均鲜重关系,结果表明二者具有较好的相关性.分别采用普通克里金法、反距离权重法、径向基函数法3种插值方法对同一季节的不同湖泊和同一湖泊的不同季节未采集区域沉水植物的盖度数据进行插值分析,并对插值结果进行交叉验证,以确定方法的精确度.交叉验证结果表明,插值精确度反距离权重法>径向基函数法>普通克里金法.研究结果为回声探测与插值分析方法结合在大尺度浅水水体中沉水植物监测应用提供了技术支撑. 展开更多
关键词 沉水植物 盖度 回声探测 GIS 空间插值 杭州西湖
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浙江高校在线开放课程学分互认的一体化建设 认领
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作者 厉毅 邵阳博 吕长生 《教育理论与实践》 北大核心 2020年第24期40-43,共4页
学分互认作为高校在线开放课程建设的核心环节,决定着高校在线开放课程建设的可持续性。在宏观政策要落地、互认标准体系要打通、双重目标要实现的推动下,浙江省进行了学分互认一体化的特色建设,搭建了以“三驾马车”为协同推进学分互... 学分互认作为高校在线开放课程建设的核心环节,决定着高校在线开放课程建设的可持续性。在宏观政策要落地、互认标准体系要打通、双重目标要实现的推动下,浙江省进行了学分互认一体化的特色建设,搭建了以“三驾马车”为协同推进学分互认的平台,实现了以“课程转学分”为思路的动态发展的资源整合。审视未来,后续的工作还需进一步完善和强化学分互认的制度建设、动力机制和覆盖范围。 展开更多
关键词 浙江高校 在线开放课程 学分互认 一体化建设 资源整合 制度建设 动力机制 覆盖范围
青藏高原共玉公路沿线取弃土场修复效果可持续性评估 认领
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作者 郭淑梅 郑天立 +2 位作者 黄文博 宋珊珊 唐玲 《草业科学》 CAS CSCD 2020年第11期2243-2250,共8页
青藏高原地区因公路建设遗留的大量取弃土场虽被及时修复,但草地生态系统修复效果是否具有可持续性还存在较大的不确定性。本研究以共和至玉树高速公路(以下简称共玉公路)沿线的取弃土场修复草地为研究对象,比较了低海拔(3个样点)和高海... 青藏高原地区因公路建设遗留的大量取弃土场虽被及时修复,但草地生态系统修复效果是否具有可持续性还存在较大的不确定性。本研究以共和至玉树高速公路(以下简称共玉公路)沿线的取弃土场修复草地为研究对象,比较了低海拔(3个样点)和高海拔(3个样点)样地取弃土场草地与相对应的天然草地之间的植被群落高度、盖度、物种丰富度、香农–威纳指数、辛普森多样性指数以及草地植物群落结构的差异。结果显示:取弃土场与天然草地之间的植被群落盖度、物种丰富度、香农–威纳指数、辛普森多样性指数以及群落结构均存在显著差异(P<0.05)。低海拔取弃土场草地的植被群落高度显著低于天然草地的高度(P<0.05),而高海拔样地取弃土场的植被群落高度与天然草地的高度无显著差异(P>0.05)。综上,取弃土场在种草修复4年后草地盖度有所增加,但其整体修复效果与天然草地仍存在较大差距,取弃土场草地修复效果并不具有可持续性。 展开更多
关键词 共玉公路 天然草地 盖度 植物多样性 群落结构 青藏高原
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亚龙湾西岸造礁石珊瑚种类多样性及恢复潜力分析 认领
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作者 黄丁勇 李元超 +1 位作者 王建佳 郑新庆 《海洋与湖沼》 CAS CSCD 北大核心 2020年第3期444-455,共12页
基于2018年12月在亚龙湾沿岸进行的13个站位的珊瑚礁调查,本文分析了该区域造礁石珊瑚的多样性、分布、覆盖率、死亡率和补充量。结果表明,亚龙湾西岸8个站位共发现造礁石珊瑚12科27属55种和11个未定种,其中蜂巢珊瑚科的种类最多,包括9... 基于2018年12月在亚龙湾沿岸进行的13个站位的珊瑚礁调查,本文分析了该区域造礁石珊瑚的多样性、分布、覆盖率、死亡率和补充量。结果表明,亚龙湾西岸8个站位共发现造礁石珊瑚12科27属55种和11个未定种,其中蜂巢珊瑚科的种类最多,包括9属25种,其次为鹿角珊瑚科,包括3属17种。亚龙湾西岸各站位造礁石珊瑚种类数为12—33种,平均27种;覆盖率为2.8%—22.9%,平均12.9%;以丛生盔形珊瑚(Galaxea fascicularis)、同双星珊瑚(Diploastrea heliopora)和澄黄滨珊瑚(Poriteslutea)等团块状珊瑚为主要优势种;种类多样性和空间分布异质性都较高。与2010—2011年相比,亚龙湾西岸造礁石珊瑚平均覆盖率显著下降,优势种也有较大的变化,表明该海域的珊瑚礁已大幅衰退,这可能与偏高的悬浮物含量和沉积速率有关。不过,亚龙湾西岸造礁石珊瑚的补充量为1.6ind./m2,与周边海区相比,有相对较高的自然恢复潜力。 展开更多
关键词 三亚 亚龙湾 造礁石珊瑚 多样性 覆盖率 补充量
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清代中俄三大边贸区的差异性及历史启示 认领
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作者 张喜琴 李阳 《江西师范大学学报:哲学社会科学版》 CSSCI 北大核心 2020年第3期102-108,共7页
本文在总结和梳理清代中俄贸易总体概貌的同时,针对中俄恰克图贸易、新疆贸易和东北贸易此消彼长的经济关系,重点比较分析三大贸易区域的贸易动因、商人主体、商品结构、消费结构、交易方式及运输路线等方面的差异,进而探讨和总结其作... 本文在总结和梳理清代中俄贸易总体概貌的同时,针对中俄恰克图贸易、新疆贸易和东北贸易此消彼长的经济关系,重点比较分析三大贸易区域的贸易动因、商人主体、商品结构、消费结构、交易方式及运输路线等方面的差异,进而探讨和总结其作用影响及历史启示。 展开更多
关键词 中俄边贸区 交易方式 商人主体 辐射范围
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基于小结构体的无线传感器网络部署算法 认领
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作者 史佳琦 谭励 +2 位作者 唐小江 连晓峰 王浩宇 《计算机应用》 CSCD 北大核心 2020年第7期2033-2037,共5页
目前无线传感器网络中节点的部署主要采用基于Voronoi图的算法,在使用Voronoi算法进行部署的过程中由于参与部署的节点数量多,算法的复杂度高,导致算法的迭代时间较长。为解决节点部署中算法迭代时间较长的问题,提出一种基于小结构体的... 目前无线传感器网络中节点的部署主要采用基于Voronoi图的算法,在使用Voronoi算法进行部署的过程中由于参与部署的节点数量多,算法的复杂度高,导致算法的迭代时间较长。为解决节点部署中算法迭代时间较长的问题,提出一种基于小结构体的部署算法(DABA)。首先,将节点组合成小结构体;然后,计算小结构体的中心位置坐标;最后,利用Voronoi图进行节点部署。所提算法对于部署区域存在障碍的情况仍然能有效进行部署。实验结果表明,DABA在部署时间方面能够比基于Voronoi图的算法减少三分之二。所提算法可明显减少算法的迭代时间,同时降低算法的复杂性。 展开更多
关键词 小结构体 VORONOI图 覆盖率 移动距离 迭代时间
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面向物联网业务绿色接入的异构蜂窝网络优化 认领 被引量:1
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作者 刘娅汐 皇甫伟 《工程科学学报》 EI CSCD 北大核心 2020年第4期483-489,共7页
物联网是未来赛博使能业务的重要支撑平台.蜂窝网络则被认为是广泛分布在部署区域中的物联网终端数据接入的主要渠道,尤其在广域覆盖方面具有难以替代的价值.在满足覆盖要求的条件下,降低蜂窝网络基站的下行发射功率在绿色通信方面具有... 物联网是未来赛博使能业务的重要支撑平台.蜂窝网络则被认为是广泛分布在部署区域中的物联网终端数据接入的主要渠道,尤其在广域覆盖方面具有难以替代的价值.在满足覆盖要求的条件下,降低蜂窝网络基站的下行发射功率在绿色通信方面具有重要的研究意义.由此提出了一种基于优化目标平滑近似和均方根传播策略的梯度下降算法,在满足物联网业务覆盖率的条件下最小化基站的总下行发射功率.首先,使用罚函数方法将复杂约束条件的异构蜂窝网络优化问题转化为简单约束形式的优化问题;其次,将不可导的目标函数通过平滑近似转化为可导形式,并给出其对天线下倾角和下行功率参数的梯度解析形式;最后,使用均方根传播梯度下降算法进行转化后的目标函数优化.仿真实验结果表明该算法可以在满足覆盖率指标的条件下最小化基站的总下行发射功率,与现有元启发算法和普通梯度下降算法相比,具有良好的收敛速度,并能更好地抑制优化过程中振荡. 展开更多
关键词 物联网 覆盖率 总下行功率损耗 天线下倾角 梯度下降法
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1984—2014年北京地区不透水地表的时空变化及其温度效应研究 认领
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作者 张稼乐 潘志华 +6 位作者 匡文慧 潘宇鹰 韩国琳 王佳琳 黄娜 张子源 尹文娟 《气候变化研究进展》 CSCD 北大核心 2020年第3期296-305,共10页
研究城市地表覆盖与地表温度(LST)的关系对改善城市生态环境具有重要科学意义。在Landsat TM数据支持下,利用线性光谱混合分析模型提取不透水地表信息,结合LST和地表热通量,分析不透水地表覆盖度(ISA)和LST的时空变化特征及其相互关系,... 研究城市地表覆盖与地表温度(LST)的关系对改善城市生态环境具有重要科学意义。在Landsat TM数据支持下,利用线性光谱混合分析模型提取不透水地表信息,结合LST和地表热通量,分析不透水地表覆盖度(ISA)和LST的时空变化特征及其相互关系,探讨不透水地表对LST的影响机理。结果表明:1984—2014年北京不透水地表面积迅速增长,中覆盖度比例下降,高覆盖度比例增加;LST从市中心向郊区递减,高温区向外扩张;LST和ISA呈显著正相关,但不是简单的线性关系;ISA处于0.6~0.9时LST上升速率最快,减少ISA在此范围内的不透水地表集中分布可缓解高温区集中的现象。 展开更多
关键词 不透水地表 覆盖度 地表温度(LST) 时空特征 北京
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大功率皮基站应用探讨 认领
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作者 黄大九 韩飞 李佳 《现代传输》 2020年第6期50-55,共6页
经过多年的4G网络建设,城区及农村住户相对集中区域电信4G网络覆盖较好,但小区地下停车场、电梯、偏远农村等局部区域4G覆盖还需完善。本文通过大功率皮基站在农村、地下停车场、电梯等场景的试点测试,论证大功率皮基站在上述场景的可... 经过多年的4G网络建设,城区及农村住户相对集中区域电信4G网络覆盖较好,但小区地下停车场、电梯、偏远农村等局部区域4G覆盖还需完善。本文通过大功率皮基站在农村、地下停车场、电梯等场景的试点测试,论证大功率皮基站在上述场景的可适用性,是一种以低成本解决低流量区域的行之有效的手段。 展开更多
关键词 大功率皮基站 覆盖 低成本
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利用无人机遥感技术提取农作物植被覆盖度方法研究 认领
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作者 王猛 隋学艳 +2 位作者 梁守真 侯学会 梁永全 《作物杂志》 CAS 北大核心 2020年第3期177-183,共7页
基于无人机的遥感信息获取技术已广泛应用在农业领域。无人机遥感平台获取农作物信息技术具有高时效、高分辨率、低成本、快速、准确等特点,是目前精准农业中农田信息获取的重要手段之一。利用无人机遥感技术获取可见光影像,以棉花、花... 基于无人机的遥感信息获取技术已广泛应用在农业领域。无人机遥感平台获取农作物信息技术具有高时效、高分辨率、低成本、快速、准确等特点,是目前精准农业中农田信息获取的重要手段之一。利用无人机遥感技术获取可见光影像,以棉花、花生和玉米为研究对象,选取不同的植被指数进行可见光图像阈值分割,结合研究区域可见光影像监督分类结果,确定3种作物提取植被覆盖度方法。试验结果表明,利用无人机可见光图像植被指数阈值分类方法,可以有效提取作物植被覆盖度。该方法对于棉花、花生和玉米3种作物植被覆盖信息的提取精度较高。 展开更多
关键词 无人机 农作物 覆盖度 提取 植被指数
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