一种智能的最短航线构建方法   总被引：2，自引：0，他引：2  

张立华  朱庆  张安民  刘雁春  韩元利 《测绘学报》2008,37(1):0-113

航线的优化设计是舰船安全、经济航行的基础。本文提出一种智能的最短航线构建方法。通过追踪安全等深线,获取障碍区,然后测试线段与障碍区的空间关系来智能地搜索最短路径。实验表明,与传统方法相比,新方法在效率、准确性和可靠性上都具有明显的优势。  相似文献   

一种利用凸包思想顾及障碍物的聚类分析     

ZHANG Xiao-peng  WU Fang  MENG Yan-bin  ZHANG Jing-hui 《测绘学院学报》2008,(2)

提出了利用凸包思想求取障碍距离的方法,并对该方法进行了理论与实践上的探讨。然后以所求得的障碍距离为依据,利用改进后的k-中心点法进行实验。实验表明,其结果不仅可以得到两点之间的障碍距离与障碍路径,而且可以实现顾及障碍物聚类的要求。最后对实验结果做出了总结与展望。  相似文献   

基于光流的旋翼无人机障碍物检测方法     

张小东  孙国鹏 《测绘与空间地理信息》2017,40(5)

针对传统光流法检测障碍物准确性不高、适应性差的问题,提出了一种基于金字塔LK光流的旋翼无人机单目视觉自主障碍物检测方法。该方法通过金字塔LK光流法获取光流信息,结合光流大小和拍摄间距与物距的关系设定自适应阈值,比较光流与阈值的大小并对障碍物进行检测与判定。实验证明:该方法可以有效地检测到障碍物,能满足无人机在多种条件下的避障需求,具有较高的准确性、鲁棒性和适应性。  相似文献   

中国普通高中教育均等化及障碍因素分析   总被引：1，自引：1，他引：0  

苏飞  莫潇杭  魏敏  李博 《地理科学》2017,37(10):1478-1485

以中国31个省级行政单元为研究对象,从教育背景、教育投入、教育过程和教育结果4个方面构建指标体系,采用集对分析模型测度各省份普通高中教育均等化水平,运用障碍度分析法揭示阻碍各省份普通高中教育均等化水平提升的主要因素。研究表明：从综合均等度来看,普通高中教育均等化水平较高的省份集中在环渤海地区和江浙沪地区,其中北京市最高,河南省最低。从空间格局来看,各省份普通高中教育均等化水平有显著差异,总体上呈现“东-西-中”递减趋势。分析表明,P1（高中阶段毛入学率）、S3（高级职称专任教师比例）、S2（本科学历及以上专任教师比例）、P2（学校数量/万名学生）是影响各省份普通高中教育均等化水平提升的主要因素。  相似文献   

新疆和田地区旅游经济系统脆弱性研究     

卢有斌  李晓东  孜比布拉&#;司马义  赵学鹏 《地域研究与开发》2017,36(1)

以新疆和田地区为例,利用2000—2014年和田地区相关统计数据,运用集对分析法分析和田地区的旅游经济系统的脆弱性特征。结果表明:和田地区旅游经济系统的脆弱性除2009年为高水平外,其余年份脆弱性均为中度水平;从脆弱性整体发展趋势来看,和田地区旅游经济系统脆弱性以2009年为拐点,呈现先升后降趋势;由障碍度因素分析得出,旅游从业人员占总从业人员比重、地区内部各县市生产总值变异系数等敏感性因子,旅游劳动生产率、人均GDP等应对性因子是制约和田地区旅游经济系统脆弱性下降的重要因素。  相似文献   

Effects of intercropping on rhizosphere soil microorganisms and root exudates of Lanzhou lily(Lilium davidii var. unicolor)     

CuiPing Hua  YaJun Wang  ZhongKui Xie  ZhiHong Guo  YuBao Zhang  Yang Qiu  Le Wang 《寒旱区科学》2018,10(2):159-168

Both yield and quality of Lanzhou lily(Lilium davidii var. unicolor) are seriously affected by continuous cropping. We attempted to understand the effects of intercropping on the obstacles associated with continuous cropping of Lanzhou lily(Lilium davidii var. unicolor). The changes of rhizosphere microbial biomass and diversity in interplanting and monoculturing systems were studied by using the Illumina Hi Seq sequencing technique. The contents and composition of lily root exudates were measured by gas chromatography–mass spectrometer(GC–MS). The intercropping results of Lanzhou lily showed:(1) There was no difference in the composition of the rhizosphere soil microbes at the phylum level, but the relative abundance of the microbes decreased; and the relative abundance of harmful fungi such as Fusarium sp. increased. The relative abundance of Pleosporales sp. and other beneficial bacteria were reduced. After OTU(operational taxonomic unit)clustering, there were some beneficial bacteria, such as Chaetomium sp., in the lily rhizosphere soil in the interplanting system that had not existed in the single-cropping system. We did not find harmful bacteria that had existed in the single-cropping systm in the rhizosphere soil of interplanting system. The above results indicated that the changes of relative abundance of soil fungi and bacteria in lily rhizosphere soil was not conducive to improving the ecological structure of rhizosphere soil microbes. At the same time, the microbial composition change is very complex—beneficial and yet inadequate at the same time.(2) Root exudates provide a matrix for the growth of microorganisms. Combined with the detection of root exudates, the decrease in the composition of the root exudates of the lily was probably the reason for the decrease of the relative abundance of microbes after intercropping. At the same time, the decrease of the relative content of phenolic compounds, which inhibit the growth of microorganisms, did not increase the relative content of rhizosphere soil microorganisms. Changes in amino acids and total sugars may be responsible for the growth of Fusarium sp.. The results showed that the intercropping pattern did not noticeably alleviate the obstacle to continuous cropping of Lanzhou lily, and the change of microbial biomass and diversity was even unfavorable. However, the emergence of some beneficial bacteria, the disappearance of harmful fungi, and other changes with intercropping are in favor of alleviation of obstacles to continuous cropping of Lanzhou lily.  相似文献   

东北老工业基地绿色发展评价及障碍因素分析   总被引：3，自引：1，他引：2  

任嘉敏  马延吉 《地理科学》2018,38(7):1042-1050

以东北老工业基地11个典型城市为研究对象,从资源利用、产业绿色化、经济发展质量、环境保护、绿色人居5方面构建指标体系,分析东北老工业基地绿色发展水平时空演变特征,运用障碍度模型揭示其绿色发展水平提升的障碍因子。研究表明：东北老工业基地城市间绿色发展水平差异显著,高值区始终分布在沈阳、长春、大连、哈尔滨。研究期内,高水平类型城市数量增加,中高、低水平城市数量减少,以四大城市为核心的绿色发展水平空间格局更加明显。科学技术支出占GDP比重、政府财政自给率、环境保护支出占GDP比重、人均GDP、规模以上工业企业成本费用利润率是影响东北老工业基地绿色发展水平提升的主要障碍因子。  相似文献   

Modelling of Random Waves over Submerged Breakwaters and Its Application to Reflection Estimation     

石瑞祥  周宗仁尹彰 《中国海洋工程》2006,20(2):243-258

1.IntroductionGreat efforts have been devoted to the protection of coastal areas over many years by erectingdikes,seawalls,groin systems,and detached breakwaters.The sea walls,jetties,detached breakwa-ters,etc.are traditionally adopted as absorbingfacilit…  相似文献   

Probabilistic Model for Concentration Fluctuations in Compact-Source Plumes in an Urban Environment     

Eugene Yee  Bing-Chen Wang  Fue-Sang Lien 《Boundary-Layer Meteorology》2009,130(2):169-208

A comprehensive model for the prediction of concentration fluctuations in plumes dispersing in the complex and highly disturbed wind flows in an urban environment is formulated. The mean flow and turbulence fields in the urban area are obtained using a Reynolds-averaged Navier-Stokes (RANS) flow model, while the standard k-ϵ turbulence model (k is the turbulence kinetic energy and ϵ is the viscous dissipation rate) is used to close the model. The RANS model provides a specification of the velocity statistics of the highly disturbed wind flow in the urban area, required for the solution of the transport equations for the mean concentration and concentration variance (both of which are formulated in the Eulerian framework). A physically-based formulation for the scalar dissipation time scale t _d , required for the closure of the transport equation for , is presented. This formulation relates t _d to an inner time scale corresponding to “internal” concentration fluctuation associated with relative dispersion, rather than an outer time scale associated with the entire portion of the fluctuation spectrum. The two lowest-order moments of concentration ( and ) are used to determine the parameters of a pre-chosen functional form for the concentration probability density function (clipped-gamma distribution). Results of detailed comparisons between a water-channel experiment of flow and dispersion in an idealized obstacle array and the model predictions for mean flow, turbulence kinetic energy, mean concentration, concentration variance, and concentration probability density function are presented.  相似文献   

青海南部环境质量与可持续发展的障碍因素分析   总被引：1，自引：1，他引：0  

赵名茶 《地理科学进展》1998,17(4):27-34

青海南部由玉树州和果洛州组成,为纯牧区,本文从可持续发展的观点出发,研究了本区的环境质量问题,对障碍生态环境可持续发展的要素－低氧含量、低温与草场退化进行了深入的分析,提出低氧含量存在的自然地理原理,而草场退化的产生除自然条件外,鼠害与人类活动致使过牧、过载也是重要的原因。  相似文献