期刊文献+
共找到7,352篇文章
< 1 2 250 >
每页显示 20 50 100
Satellite monitoring of land-use and land-cover changes in northern Togo protected areas 被引量:2
1
作者 Fousseni Folega Chun-yu Zhang +5 位作者 Xiu-hai Zhao Kperkouma Wala Komlan Batawila Hua-guo Huang Marra Dourma Koffi Akpagana 《Journal of Forestry Research》 SCIE CAS CSCD 2014年第2期385-392,共8页
Remote-sensing data for protected areas in northern Togo, obtained in three different years (2007, 2000, and 1987), were used to assess and map changes in land cover and land use for this drought prone zone. The nor... Remote-sensing data for protected areas in northern Togo, obtained in three different years (2007, 2000, and 1987), were used to assess and map changes in land cover and land use for this drought prone zone. The normalized difference vegetation index (NDVI) was applied to the images to map changes in vegetation. An unsupervised classification, followed by classes recoding, filtering, identifications, area computing and post-classification process were applied to the composite of the three years of NDVI images. Maximum likelihood classification was applied to the 2007 image (ETM+2007) using a supervised classification process. Seven vegetation classes were defined from training data sets. The seven classes included the following biomes: riparian forest, dry forest, flooded vegetation, wooded savanna, fallows, parkland, and water. For these classes, the overall accuracy and the overall kappa statistic for the classi- fied map were 72.5% and 0.67, respectively. Data analyses indicated a great change in land resources; especially between 1987 and 2000 proba- bly due to the impact of democratization process social, economic, and political disorder from 1990. Wide-scale loss of vegetation occurred during this period. However, areas of vegetation clearing and regrowth were more visible between 2000 and 2007. The main source of confusion in the contingency matrix was due to heterogeneity within certain classes. It could also be due to spectral homogeneity among the classes. This research provides a baseline for future ecological landscape research and for the next management program in the area. 展开更多
关键词 land change NDVI land cover protected areas Northern Togo
在线阅读 下载PDF
Effect of land-use changes on chemical and physical properties of soil in western Iran(Zagros oak forests) 被引量:5
2
作者 Kyumars Mohmmadi Samani Narges Pordel +1 位作者 Vahid Hosseini Zahed Shakeri 《Journal of Forestry Research》 SCIE CAS CSCD 2020年第2期637-647,共11页
The consequence of land-use change from forest to agriculture and other uses has become one of the world’s greatest concerns.The soil,one of the most important components of forests and containing all the required pl... The consequence of land-use change from forest to agriculture and other uses has become one of the world’s greatest concerns.The soil,one of the most important components of forests and containing all the required plant nutrients as soluble ions,is highly impacted by these changes.Because vast areas of the Zagros forests in western Iran have changed in use during the last few decades,the present study investigated the effects of landuse changes of forest area to agriculture,orchard,and agroforestry on soil chemical and physical properties.Soil was sampled at four land-use areas:less-disturbed forest areas(control)and agricultural,orchard,and agroforestry areas.Among each of the two forest-use areas(agroforestry and orchard),we selected five trees with similar-sized crowns and sampled under each tree crown at 0-15 and>15-30 cm depths.Five soil samples also were taken in agriculture area at each depth.The findings indicated that during land-use changes,soil sand particles decreased,and clay and silt particles of soil increased,resulting in a fine soil texture.Moreover,the amount of nitrogen(N),phosphorus(P),organic carbon(OC),and electrical conductivity(EC)of soil decreased at both depths due to the decrease in organic matter.Soil pH and magnesium(Mg)level rose during land-use change at both depths except at agricultural sites.Soil potassium(K)content decreased during agricultural use due to the elimination of tree cover.The level of K decreased only at the depth of 0-15 cm because of K dependency on parent materials.Generally,most soil nutrients were affected by plant removal in the conversion.Forest and agricultural soil are distinguishable by their properties,while land-uses such as agroforestry-orchard separated from the others.Soil nutrients were severely affected by the decrease and elimination of tree cover,plowing,and continuous harvesting,resulting in a decline in soil quality and fertility. 展开更多
关键词 Chemical soil properties land-use change AGROFORESTRY AGRICULTURE Zagros Oak forest
在线阅读 下载PDF
Effects of different land-use systems (grazing and understory cultivation) on growth and yield of semi-arid oak coppices 被引量:2
3
作者 Ali Soltani Hamdollah Sadeghi Kaji Saleh Kahyani 《Journal of Forestry Research》 SCIE CAS CSCD 2020年第6期2235-2244,共10页
The present study examines the extent of negative eff ects of traditional multiple land-use systems on oak coppices,from a forest management point of view.The study area was located in approximately 10,000 ha of hilly... The present study examines the extent of negative eff ects of traditional multiple land-use systems on oak coppices,from a forest management point of view.The study area was located in approximately 10,000 ha of hilly Brant’s oak(Quercus brantii Lindl.)woodlands in the central Zagros Mountains.In the same site-quality class,three land-use systems were compared:simple coppice(Co),coppice in conjunction with small ruminant grazing(CoG),and coppice with understory rain-fed wheat cultivation plus grazing(CoCG).Data on total wood volume of trunk and major branches,and annual ring growth,were collected and analyzed from 74 stands in 15 coppiced woodland patches.The results showed the advantage of Co over CoG and CoCG land-uses by 43 and 60 m 3 of mean accumulated wood volume per hectare,respectively.The diameter growth analysis also revealed an annual increase in wood production of trees in Co land-uses over 43 years,with an exception of the recent decade,when growth coincided with a severe drought.Using a back-extrapolation method,the minimum rotation age of woodlands in Co land-use was found to be 23.6 years,5 and 7 years shorter than those of CoG and CoCG land-uses,respectively.Unlike CoCG,woodlands located in Co and CoG land-use systems demonstrated a high level of agreement with self-thinning rule of−3/2.Values for the stand density index for coppiced oak woodlands were between more than 1000 for the least disturbed(Co)and less than 400 for the most disturbed woodlands(CoCG).The structure and growth rate of the coppiced oak woodlands were irreversibly disrupted by understory tillage plus grazing and in less extent by grazing alone.It was concluded that ending undergrowth cultivation in semi-arid oak coppices should be addressed as a priority by adopting minimum regulations. 展开更多
关键词 COPPICING land-use impact assessment Diameter growth Multi-purpose land-use Self-thinning rule Stand density index
在线阅读 下载PDF
Evaluation of Land-Use Efficiency Based on Regional Scale——A Case Study in Zhanjiang,Guangdong Province 被引量:8
4
作者 CHEN Shi-yin LIU Yao-lin CHEN Cui-fang 《Journal of China University of Mining and Technology》 EI 2007年第2期215-219,共5页
Evaluating land use efficiency is critical to the revision of general land use planning. An assessment indicator system for regional land use efficiency was established in this paper from the aspects of society,econom... Evaluating land use efficiency is critical to the revision of general land use planning. An assessment indicator system for regional land use efficiency was established in this paper from the aspects of society,economy,ecology and environment. The weight of each indicator was defined by an analytical hierarchy process (AHP) and the entropy method (EM). Then,a case study in Zhanjiang was carried out to analyze the regional land use efficiency from 1996 to 2004 and its development by using the method of multifactor composite evaluation and an analytical model of the de-gree of coordination. The results indicate that land use efficiency with respect to society and the economy improved,whereas the ecological and environmental efficiencies were found to decrease. The degree of coordination in Zhanjiang is still at the status of basic coordination. Finally,measures for enhancing the ecological and environmental establish-ment are suggested in order to improve the regulations of land use structure and patterns,establish ecological forests for the public good and green corridors and prevent the soil erosion. 展开更多
关键词 regional scale land-use efficiency degree of coordination EVALUATION
在线阅读 下载PDF
Evaluation of land-use pattern change in West Bhanugach Reserved Forest,Bangladesh,using remote sensing and GIS techniques 被引量:2
5
作者 Md. Abdul Halim Abdus Shahid +5 位作者 Mohammad Shaheed Hossain Chowdhury Mst. Nazmun Nahar Md. Shawkat Islam Sohel Nuruddin Md. Jahangir Masao Koike 《Journal of Forestry Research》 SCIE CAS CSCD 2008年第3期193-198,共6页
A study was conducted to investigate the land-use pattern change over a period of 18 years (1988-2006) by using remote sens- ing and Geographical Information System (GIS) technologies, in the West Bhanugach Reserv... A study was conducted to investigate the land-use pattern change over a period of 18 years (1988-2006) by using remote sens- ing and Geographical Information System (GIS) technologies, in the West Bhanugach Reserved Forest, a hill forest, in Sylhet Forest Divi- sion of Bangladesh, The images were processed using ERDAS Imagine software. Both supervised and unsupervised approaches were ap- plied and ground control points were collected using a GPS. Maps were prepared using GIS software. Results showed that vegetation cover drastically decreased from the year 1988 to 1996 (l 826 ha to l 714.85 ha), but increased gradually from the year 1996 to 2006 (l 714.85 ha to l 847.83 ha) due to the initiation of co-management practice involving local communities. Change in bare land was inversely proportionate to the amount of vegetation cover changes unless any other land-uses were converted into bare land. The area of water bodies increased from the year 1988 to 1996 (307.67 ha to 379.53 ha), but decreased from the year 1996 to 1997, then remained invariabile from the year 1997 to 2006. Some recommendations were also made for applying the RS and GIS techniques to study the land-use pattern change in the Bhanugach Reserved Forest and to create a GIS data base for the study area. 展开更多
关键词 land-use remote sensing Geographical Information System West Bhanugach Reserved Forest BANGLADESH
在线阅读 下载PDF
Land-use changes in the small watershed of the Loess Plateau,hilly-gully region, China 被引量:2
6
作者 Yini Han Jianzhi Niu Feizhou Wu 《Journal of Forestry Research》 SCIE CAS CSCD 2015年第1期91-99,共9页
As more and more farmland is converted to forestry, the need for effective decision support regarding the use of land in the fragile ecological environment of the Loess Plateau hilly-gully area. The Luoyugou watershed... As more and more farmland is converted to forestry, the need for effective decision support regarding the use of land in the fragile ecological environment of the Loess Plateau hilly-gully area. The Luoyugou watershed was chosen as the study area to calculate the single dynamic degree, integrated dynamic degree, and change indexes of land use, as well as the land-use type transition matrix. This was done by interpreting the TM and SPOT images of the Luoyugou watershed in 1986, 1995, and2004 and making statistical analysis. The results of ou statistical analysis show that the conversion of slope farm land to terrace and forest land plays a dominant role in land-use changes in the Luoyugou watershed from 1986 to2004. The land-use changes are mainly driven by popula tion growth, socio-economic development, consume spending, and investment in forest ecology. 展开更多
关键词 Loess Plateau hilly-gully region Luoyugou watershed Land use and cover changes Driving force
在线阅读 下载PDF
Characteristics of soil organic carbon andtotal nitrogen storages for differentland-use types in Central Yunnan Plateau 被引量:1
7
作者 SHEN Fangyuan TUO Yunfei +4 位作者 WANG Qian WANG Fei ZHENG Yang DU Wenjuan XIANG Ping 《排灌机械工程学报》 CSCD 北大核心 2022年第5期519-528,共10页
Two-factor analysis of variance and redundancy analysis were used to analyze the characte-ristics of soil organic carbon total nitrogen storage in garden land,forestland,grassland,farmland,and bare land in the Dachunh... Two-factor analysis of variance and redundancy analysis were used to analyze the characte-ristics of soil organic carbon total nitrogen storage in garden land,forestland,grassland,farmland,and bare land in the Dachunhe watershed of Jinning District,Kunming City,Yunnan Province,China.The effects of the soil organic carbon,total nitrogen stratification ratio,soil physical and chemical factors on the storage characteristics of organic carbon and total nitrogen of different land-use types were analyzed.The results show that the rates of carbon and nitrogen stratification in soil from 0-20 cm and 40-60 cm of the same land-use types differed are statistically significant(P<0.05).The organic carbon and total nitrogen stratification ratio SR1 of garden land soil are 38.5%and 25.3%,respectively,which are higher than SR^(2).The soil organic carbon and total nitrogen stratification ratio SR^(2) of different land-use types are greater than SR1.There are statistically significant differences in the SR^(2) soil organic carbon and total nitrogen stratification ratios(P<0.05).Soil organic carbon and total nitrogen storage of diffe-rent land-use types gradually decrease with increasing soil depth,with the maximum soil organic carbon and total nitrogen storage in the 0-20 cm soil layer.Soil organic carbon and total nitrogen sto-rage at the same soil depth are significantly different(P<0.05).Soil organic carbon and total nitrogen storage in the garden land are greater than those in the other land-use types.Soil organic carbon and total nitrogen storage in 0-20 cm garden land are 4.96 and 3.19 times than those in bare land,respectively;soil organic carbon and total nitrogen storage are explained by 93.66%and 1.53%in redundancy analysis RDA1 and RDA2,respectively.All physicochemical factors except Available Phosphorus and pH are statistically significance with carbon and nitrogen storage(P<0.05).Soil cationic exchange capacity,Available Phosphorus,C/N ratio,and Moisture Content are positively correlated with organic carbon and total nitrogen storage.In contrast,soil Bulk Density is negatively correlated with organic carbon storage and total nitrogen storage.Available Phosphorus,C/N ratio,and Moisture Content are the main factors promoting soil organic carbon and total nitrogen accumulation. 展开更多
关键词 soil organic carbon storage soil total nitrogen storage stratification ratio land-use types Central Yunnan Plateau
在线阅读 下载PDF
Using classification assignment rules to assess land-use change impacts on forest biodiversity at local-to-national scales 被引量:1
8
作者 Kathrin Affeld Susan K. Wiser +1 位作者 Ian J. Payton Miquel DeCaceres 《Forest Ecosystems》 SCIE CSCD 2018年第2期162-176,共15页
Background: Ecosystem representation is one key component in assessing the biodiversity impacts of land-use changes that will irrevocably alter natural ecosystems. We show how detailed vegetation plot data can be use... Background: Ecosystem representation is one key component in assessing the biodiversity impacts of land-use changes that will irrevocably alter natural ecosystems. We show how detailed vegetation plot data can be used to assess the potential impact of inundation by a proposed hydroelectricity dam in the Mokihinui gorge, New Zealand, on representation of natural forests. Specifically we ask: 1) How well are the types of forest represented Locally, regionally, and nationally; and 2) How does the number of distinct communities (i.e. beta diversity) in the target catchment compare with other catchments nationally? Methods: For local and regional comparisons plant species composition was recorded on 45 objectively located 400 m2 vegetation plots established in each of three gorges, with one being the proposed inundation area of the Mokihinui lower gorge. The fuzzy classification framework of noise clustering was used to assign these plots to a specific alliance and association of a pre-existing national-scale classification. NationaLly, we examined the relationship between the number of alliances and associations in a catchment and either catchment size or the number of plots per catchment by fitting Generalised Additive Models. Results: The four alliances and five associations that were observed in the Mokihinui lower gorge arepresent in the region but limited locally. One association was narrowly distributed nationally, but is the mostfrequent association in the Mokihinui lower gorge; inundation may have consequences of national importance to its long-term persistence. That the Mokihinui lower gorge area had nearly twice as many plots that could not be assigned to pre- existing alliances and associations than either the Mokihinui upper or the Karamea lower gorges and proportionally more than the national dataset emphasises the compositional distinctiveness of this gorge. These outlier plots in the Mokihinui lower gorge may be unsorted assemblages of species or reflect sampling bias or that native- dominated woody riparian vegetation is rare on the landscape. At a national scale, the Mokihinui catchment has a higher diversity of forest alliances and associations (i.e. beta-diversity) than predicted based on catchment size and sampling intensity. Conclusions: Our analytical approach demonstrates one transparent solution to a common conservation planning problem: assessing how well ecosystems that will be destroyed by a proposed land-use change are represented using a multi-scale spatial and compositional framework. We provide a useful tool for assessing potential consequences of land-use change that can help guide decision making. 展开更多
关键词 BETA-DIVERSITY Biodiversity conservation Environmental impacts Ecosystem representation Hydroelectricity dams land-use change National vegetation classification Noise clustering New Zealand NVS databank Plant community composition
在线阅读 下载PDF
Expansion of traditional land-use and deforestation:a case study of an adat forest in the Kandilo Subwatershed,East Kalimantan,Indonesia
9
作者 Hunggul Y.S.H.Nugroho Anne van der Veen +1 位作者 Andrew K.Skidmore Yousif A.Hussin 《Journal of Forestry Research》 SCIE CAS CSCD 2018年第2期488-506,共19页
Deforestation issues are more problematic when indigenous(adat) communities,living within a forest,have lived there for many generations.These adat communities,who employ traditional land-use,are frequently accused of... Deforestation issues are more problematic when indigenous(adat) communities,living within a forest,have lived there for many generations.These adat communities,who employ traditional land-use,are frequently accused of encroaching on the forest.To understand existing and future trends in the spatial patterns of the expansion of traditional land-use and deforestation,we conducted a case study in the Kandilo Subwatershed using mixed methods with image interpretation,spatial modelling and sociocultural surveys to examine the interrelationships between physical conditions,community characteristics and traditional land-use expansion.We investigated community characteristics through household interviews,communication with key informants,and discussions with focusgroups.By using an area production model,we were able to analyze the effect of improved farming systems,policy intervention and law enforcement on traditional land-use expansion and deforestation.Based on our examination of a 20-year period of traditional land-use activities in adat forests,the evidence indicated that the steeper the slope of the land and the farther the distance from the village,the lower the rate of deforestation.Our study found that customary law,regulating traditional land-use,played an important role in controlling deforestation and land degradation.We conclude that the integration of land allocation,improved farming practices and enforcement of customary law are effective measures to improve traditional land productivity while avoiding deforestation and land degradation. 展开更多
关键词 Adat people Agriculture expansion Area production model(APM) Customary law DEFORESTATION Traditional land-use
在线阅读 下载PDF
Information System for Land-Use Planning and Management
10
作者 俞晓 苗放 《Journal of Southwest Jiaotong University(English Edition)》 2008年第4期372-379,共8页
In order to maintain the overall social interest in land use and improve the level of land administration, an information system for land-use planning and management (ISLUPM) was established, which is composed of pr... In order to maintain the overall social interest in land use and improve the level of land administration, an information system for land-use planning and management (ISLUPM) was established, which is composed of presentation layer, business logic layer and data layer in the general structure. The application support platform of the ISLUPM, built based on COM, COM + and .NET standard components, includes data engine, data management, assemblies, components management, operation management, and interface. Then, an elaboration was made on major functions of the ISLUPM, such as planning revision scheme, planning operation flow, digital processing, thematic analysis and inquiry, and preparation of the chart of reserved land resources. The developed system has been successfully applied to the land-use planning and management work of Longquanyi District, Chengdu, China. It may provide a reference for development of geographic information system (GIS) for land and resources. 展开更多
关键词 land-use planning Planning management Information system Revision scheme Digital processing (3IS
在线阅读 下载PDF
基于遥感指数的我国西部矿区生态质量监测——以彬长矿区为例 被引量:1
11
作者 姚顽强 李悠 +4 位作者 郑俊良 蔺小虎 相里海龙 惠伯辰 李文欣 《金属矿山》 北大核心 2025年第1期259-266,共8页
我国西部矿区是煤炭资源开采的主要地区,也是最具代表性的生态脆弱区,探讨西部矿区自然生态环境的演变趋势及影响机制,对于矿区自然环境保护与有序恢复有着重要意义。以彬长矿区为例,通过遥感和GIS技术,利用Sentinel-2和Landsat 8遥感... 我国西部矿区是煤炭资源开采的主要地区,也是最具代表性的生态脆弱区,探讨西部矿区自然生态环境的演变趋势及影响机制,对于矿区自然环境保护与有序恢复有着重要意义。以彬长矿区为例,通过遥感和GIS技术,利用Sentinel-2和Landsat 8遥感影像数据,基于遥感生态指数(Remote Sensing Ecological Index,RSEI)模型,在深入剖析该矿区土地利用/覆被变化(Land Use/Cover Change,LUCC)和生态环境时空演变的基础上,分析了该矿区LUCC的生态质量。结果表明:①2017—2022年矿区LUCC结构上出现明显的转移特征,形成以林地、耕地和建设用地为主的新LUCC格局,并伴随着林地大范围转出为耕地和建设用地的情况,转移量约191.04 km^(2)。②5 a中,矿区生态环境质量呈下降趋势,RSEI由0.54降至0.47,研究发现矿区生态环境质量主要受绿度和干度指标因子影响。③2017—2022年矿区生态环境质量改善的面积占总面积的9%,生态环境质量恶化的面积占总面积的22%,分析结果可为西部矿区生态环境保护和修复提供参考。 展开更多
关键词 生态修复 遥感 GIS 遥感生态指数 土地利用/覆被变化 生态质量
在线阅读 下载PDF
三江平原不同季节植被覆盖变化及其对气候变化的响应
12
作者 李海燕 曾星雨 +6 位作者 何璞 张弘强 崔玲 周博奇 任卓群 罗春雨 曲艺 《安徽农业科学》 2025年第6期195-200,共6页
应用遥感和GIS技术,结合统计和相关分析等方法,基于MODIS NDVI和气象(气温、降水)数据,探讨2000—2020年三江平原植被各季节NDVI变化趋势、空间分布格局及其对气候变化的响应。结果表明:在时间尺度上,近21年三江平原春季、夏季、秋季植... 应用遥感和GIS技术,结合统计和相关分析等方法,基于MODIS NDVI和气象(气温、降水)数据,探讨2000—2020年三江平原植被各季节NDVI变化趋势、空间分布格局及其对气候变化的响应。结果表明:在时间尺度上,近21年三江平原春季、夏季、秋季植被NDVI呈上升趋势,春季升幅最大(0.156/10 a),秋季升幅最小(0.075/10 a)。在空间分布上,春季NDVI较低,约70.10%区域处于低覆盖植被区(NDVI≤0.4),中覆盖植被区(0.4<NDVI<0.6)占29.10%;夏季植被生长较好,NDVI迅速增加,高覆盖植被区(NDVI≥0.6)几乎占三江平原整个区域,占比为97.53%;秋季植被NDVI空间分布与春季相似,但数值与春季相比,低覆盖植被区有所减少,中、高覆盖植被区均有所增加。在相关性分析中,春季94.18%植被NDVI与气温呈正相关,夏季(91.21%)和秋季(63.46%)大部分区域植被NDVI与气温呈负相关,说明春季气温的升高对大多数植被生长主要起促进作用,夏季气温的下降对植被生长主要起促进作用,秋季气温的升高对植被生长主要起抑制作用;夏季(88.90%)和秋季(80.81%)大部分区域植被NDVI与降水量呈正相关,春季82.46%区域与降水量呈负相关,说明夏季和秋季降水量的增多对三江平原植被生长主要具有促进作用,而春季降水量的增多对大多数植被生长具有抑制作用。 展开更多
关键词 归一化植被指数(NDVI) 植被覆盖 季节变化 气候变化 三江平原
在线阅读 下载PDF
原初引力波望远镜环境保护罩高度轴系结构方案及控制策略
13
作者 乐中宇 蒋粲奕 +3 位作者 徐进 邓壮壮 郑波 陈亮 《红外与激光工程》 北大核心 2025年第1期187-198,共12页
阿里原初引力波项目为保护望远镜提出了独特的环境保护罩方案,该研究针对该方案的高度轴系结构及控制策略展开。首先,根据望远镜运行模式对高度轴系进行运动及结构方案设计,建立系统的接触和摩擦模型,并进行动力学仿真。基于仿真结果提... 阿里原初引力波项目为保护望远镜提出了独特的环境保护罩方案,该研究针对该方案的高度轴系结构及控制策略展开。首先,根据望远镜运行模式对高度轴系进行运动及结构方案设计,建立系统的接触和摩擦模型,并进行动力学仿真。基于仿真结果提出基于目标位置的力矩补偿双电机控制策略,并为主动电机设计了基于SAPSO-BP策略的PID控制器。控制系统仿真结果表明,基于SAPSOBP的PID控制器在1°/s阶跃信号下,相对于调节时间相同的PSO-BP策略超调量减少了6%,且在一定扰动下能够更好地抑制峰值误差。通过对高度轴系统验证,该控制策略在1°/s及2°/s阶跃信号、梯形信号以及正弦信号下表现出了良好的跟随性能,并可以实现主从电机的协调分配与稳定运行,其速度跟踪误差均满足设计要求。 展开更多
关键词 环境保护罩高度轴系 多体动力学 双电机控制策略 BP-PID控制器 SAPSO优化算法
在线阅读 下载PDF
基于贝叶斯修正的锈蚀RC结构保护层开裂时间预测
14
作者 黄天立 李群 +3 位作者 陈龙 陈华鹏 阳波 何益斌 《中南大学学报(自然科学版)》 北大核心 2025年第2期575-585,共11页
腐蚀电流密度的测量存在误差,且物理模型预测腐蚀电流密度时具有较大的不确定性。为了量化物理模型的不确定性,准确预测钢筋非均匀锈蚀引起的钢筋混凝土(RC)结构保护层开裂时间,提出一种基于贝叶斯修正的锈蚀RC结构保护层开裂时间预测... 腐蚀电流密度的测量存在误差,且物理模型预测腐蚀电流密度时具有较大的不确定性。为了量化物理模型的不确定性,准确预测钢筋非均匀锈蚀引起的钢筋混凝土(RC)结构保护层开裂时间,提出一种基于贝叶斯修正的锈蚀RC结构保护层开裂时间预测方法。首先,采用贝叶斯方法结合实测数据推断RC结构腐蚀开裂过程中的腐蚀电流密度物理模型中的参数,采用马尔科夫蒙特卡罗方法中的Metropolis-Hastings算法进行采样,得到参数的后验分布;然后,利用后验分布传递参数的不确定性,得到腐蚀电流密度预测模型;最后,利用锈蚀产物质量相等将非均匀腐蚀的钢筋锈蚀椭圆模型转换成均匀腐蚀的厚壁圆筒模型来计算混凝土保护层中的应力,通过钢筋损失量与腐蚀电流密度预测值之间的关系,预测混凝土保护层开裂时间。通过2个试验试件验证所提方法预测锈蚀RC结构保护层开裂时间的有效性。研究结果表明:基于贝叶斯修正后的腐蚀电流密度预测模型能准确地预测腐蚀电流密度,且能够有效地预测锈蚀RC结构保护层开裂时间,开裂时间的预测值与实测值之间的相对误差小于5%。 展开更多
关键词 锈蚀钢筋混凝土结构 保护层开裂 开裂时间 非均匀锈蚀 贝叶斯方法
在线阅读 下载PDF
基于YOLOv5的井盖隐患智能识别研究
15
作者 黄健 向思怡 《现代信息科技》 2025年第3期68-72,78,共6页
作为城市地下管网系统的关键防护构件,井盖的安全状态直接影响市政设施运维效率与公共安全。针对传统井盖安全隐患检测方法存在效率低、误报率高等问题,文章提出基于改进YOLOv5的智能检测方法。通过构建多尺度特征融合机制,文章结合五... 作为城市地下管网系统的关键防护构件,井盖的安全状态直接影响市政设施运维效率与公共安全。针对传统井盖安全隐患检测方法存在效率低、误报率高等问题,文章提出基于改进YOLOv5的智能检测方法。通过构建多尺度特征融合机制,文章结合五折交叉验证法对标注数据集进行模型训练,实现了对破损、移位、缺失等典型安全隐患的精准识别。实验结果表明,改进模型在自建井盖数据集上的平均精度(mAP)达95.2%,相比于YOLOv4模型,精度和检测速度均有所提升。该算法通过优化特征金字塔结构与损失函数,有效增强了复杂路面场景下的目标表征能力,为城市基础设施智能化运维提供了可靠的技术支持。 展开更多
关键词 井盖隐患 YOLOv5 目标检测 激活函数
在线阅读 下载PDF
城市道路检查井井盖问题分析及优化措施研究
16
作者 徐林 《市政技术》 2025年第2期138-144,189,共8页
近年来道路空间内各类专业管线的检查井井盖频繁出现问题,对居民的交通出行和生命安全造成了严重影响,已引起社会的广泛关注。通过现场踏勘、专业调研以及案例借鉴,系统梳理了当前检查井井盖存在的主要问题,并针对检查井井盖数量过多、... 近年来道路空间内各类专业管线的检查井井盖频繁出现问题,对居民的交通出行和生命安全造成了严重影响,已引起社会的广泛关注。通过现场踏勘、专业调研以及案例借鉴,系统梳理了当前检查井井盖存在的主要问题,并针对检查井井盖数量过多、空间位置不合理、施工不规范以及运维管理不到位等关键问题深入分析了其成因,同时从规划设计角度提出了道路空间检查井井盖优化与提升的具体策略以及规划实施建议。此外,针对不同区域和项目的规划与治理需求,提供了切实可行的实施路径与方法,旨在为后续更大范围的推广与应用提供实践参考。 展开更多
关键词 检查井井盖 城市道路空间 综合统筹 精细化设计 优化提升策略
在线阅读 下载PDF
Flange Cover装置在海洋油气储运设施上的应用分析 被引量:1
17
作者 刘焰明 刘吉飞 +2 位作者 程久欢 朱汉华 范世东 《船海工程》 北大核心 2017年第5期111-114,共4页
针对Flange Cover的安装空间及形式需求;在设计中采用经验公式对Flange Cover的尺寸及结构强度进行计算,采用ANSYS及CFD等数值分析辅助工具进行模拟及核算,得出满足安装、强度及J-60防火要求的Flange Cover形式。
关键词 立管 FLANGE cover J60 ANSYS FLUENT
在线阅读 下载PDF
电驱式单行水稻育秧盘摆盘覆土机设计与试验 被引量:1
18
作者 刘俊兵 王鑫淼 +3 位作者 张正 尹博 董晓威 陈长海 《农机化研究》 北大核心 2025年第1期61-66,共6页
为实现水稻育秧棚内机械化,针对现有育秧模式中秧盘摆放与底表土铺覆环节劳动强度大、生产效率低、作业时间长,以及现有秧盘摆放装置大多不适用于塑料软盘等问题,结合水稻育秧农艺要求,设计了一种电驱式单行水稻育秧盘摆盘覆土一体机。... 为实现水稻育秧棚内机械化,针对现有育秧模式中秧盘摆放与底表土铺覆环节劳动强度大、生产效率低、作业时间长,以及现有秧盘摆放装置大多不适用于塑料软盘等问题,结合水稻育秧农艺要求,设计了一种电驱式单行水稻育秧盘摆盘覆土一体机。阐述了整机结构与摆盘覆土的基本原理,对覆土皮带与横向导轨进行了仿真分析,并验证了设计的合理性。以覆土量均匀性变异系数、覆土表面平整度、秧盘纵向整齐度和秧盘横向整齐度为试验指标进行田间试验,结果表明:电驱式单行水稻育秧盘摆盘覆土机作业效果较好,覆土量均匀性变异系数<3%,覆土表面平整度<2 mm,秧盘纵向横向整齐度均≤2 mm,满足水稻育秧农艺要求和水稻工厂化技术要求中对秧盘摆放与覆土的技术规范要求。 展开更多
关键词 水稻育秧 电驱 摆盘机构 覆土装置
在线阅读 下载PDF
鲜食玉米收获机果穗箱盖设计
19
作者 赵伟 张鑫 +6 位作者 叶彤 兰海涛 聂美玲 常建国 刘兴博 杨金砖 李志博 《农机化研究》 北大核心 2025年第3期56-62,共7页
鲜食玉米收获作业初期,玉米直接砸在果穗箱底部将产生严重机械损伤,为减小此阶段的损伤,设计了一款减损果穗箱盖。该箱盖主要由减损板、四杆驱动机构、缓冲弹簧组成,可降低鲜食玉米落至箱底前的速度,从而减少其跌落损伤,实现减损目的。... 鲜食玉米收获作业初期,玉米直接砸在果穗箱底部将产生严重机械损伤,为减小此阶段的损伤,设计了一款减损果穗箱盖。该箱盖主要由减损板、四杆驱动机构、缓冲弹簧组成,可降低鲜食玉米落至箱底前的速度,从而减少其跌落损伤,实现减损目的。通过对鲜食玉米收获机无盖作业时单个玉米的动能分析,得到单个玉米最小损伤变形能。设计果穗箱盖四杆动力机构,使其满足作业效果;对缓冲弹簧进行受力分析,得到缓冲弹簧的最大载荷,以此确定缓冲弹簧参数。分析有盖作业时鲜食玉米下落碰撞运动,计算得到鲜食玉米接触箱底时的理论变形能,此时的变形能远小于无盖作业,证明了鲜食玉米收获过程中有盖作业减损的可能性。对设计的鲜食玉米果穗箱盖进行田间验证试验,结果表明:果穗箱盖对收获初期鲜食玉米有明显保护作用,通过对果穗箱底进行分区采样,发现箱底中间位置损伤程度低于边缘位置,满足预期果穗箱盖减损要求。 展开更多
关键词 鲜食玉米 果穗箱盖 变形能 四杆机构 损伤
在线阅读 下载PDF
基于T.Cover模型的网格资源分配策略研究
20
作者 郑晓薇 刘海君 张建强 《微电子学与计算机》 CSCD 北大核心 2012年第6期33-36,共4页
针对网格环境中资源分布性、异构性等特点,提出了一种基于T.cover最优投资决策模型的网格资源分配策略.采用Gridsim进行模拟实验,并将该算法与随机算法进行了对比,结果表明该分配策略在任务完成时间及费用方面具有一定的优越性,能够提... 针对网格环境中资源分布性、异构性等特点,提出了一种基于T.cover最优投资决策模型的网格资源分配策略.采用Gridsim进行模拟实验,并将该算法与随机算法进行了对比,结果表明该分配策略在任务完成时间及费用方面具有一定的优越性,能够提高资源分配效率,对动态、异构的网格环境具有较好的适应性,实现了网格资源的平衡分配. 展开更多
关键词 T.cover模型 资源分配 GRIDSIM
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部