检索结果-南通市图书馆

Causes, effects and control of seasonal frost action in railways

Research in Cold and Arid Regions 2013年第4期5卷 363-367页

作者： Antti Nurmikolu Mika Silvast Railway Track Structures Tampere University of TechnologyTampere Finland Professor Railway Division Roadscanners OyTampere Finland Director

Seasonally cold climate and resulting frost action set great demands to railway track substructure in order to maintain Irack geomelry. Chal- lenges culminate on high-speed lines, where the tolerances for roughness are the tightest. Problems may result in highly increased Irack maintenance and need for temporary speed reslrictions. The causes of frost action can be associated with subsoil, subballast or ballast. The major concern in frost protection is to avoid the freezing of frost susceptible subsoil by using sufficient thickness of subballast and relying on non-fi＇ost-susctible subballast material. This paper provides an overview of the main research findings on the role of ballast, subballast and subsoil in frost acedon. In new comlruclion the material specificalions, design procedures and construction methods have been developed to ensure adequate performance of Irack subscatt, but special challenges exist in managing existing Wacks that were not designed for modem requirements. In order to perform cost-effective and sustainable track maintenance, it is necessary to recognize the problem areas and define the root-causes of problems. For locating the problem sections and defining the causes of defects, a sophisticated analysis based on integration of track geometry and ground penetrating radar （GPR） data has been developed and is summarized in this paper,

关键词： frost action railway Irack ballast subballast subsoil frost susceptibility ground peneWating radar, track geometry Irackmaintenance

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Simulation on Sequential Construction Process and Structure of the Pisa Tower

引用

Journal of Building Construction and Planning Research 2020年第1期8卷 30-41页

作者： Jun Geng Zuping Meng Bangxun Yin Liufei Zhu Jilin University Jilin China National Chiao Tung University Taiwan China University of Manchester Manchester UK The Experimental High School Attached to Beijing Normal University Beijing China

The leaning of structures happens all around the world and generates impacts on different extents;thus, it is important to learn about the causes behind. In this report, the sequential construction of a typical leaning structure, the Tower of Pisa, is discussed and simulated by using a finite element code, PLAXIS. The simulation is performed on a two-dimensional plane with simplifications taken into consideration in making modeling feasible under limitations. Three distinct models are built with one as a control variable, while the other two models are set up with exact eccentricity. Data are obtained from the analysis and are plotted in a graph to clearly show the relationship between the tilting angle and construction phases. With reasonable and completed simulation, the study is able to show the significant role compressible subsoil plays in impacting the tilting performance of a tall building.

关键词： The Leaning Tower of Pisa Tilting Angle Sequential Construction subsoil Tilting Performance PLAXIS

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Effects of Continuous Vertical Soil Pores on Root and Shoot Growth of Winter Wheat: A Microcosm Study

引用

Agricultural Sciences 2018年第6期9卷 750-764页

作者： Tim Dresemann Miriam Athmann Lukas Heringer Timo Kautz INRES-Agroecology and Organic Farming University of Bonn Bonn Germany Experimental Farm Wiesengut Hennef Germany INRES Soil Science University of Bonn Bonn Germany

Round shaped, continuous vertical pores (CVPs) in the soil are typically created by roots and earthworms. CVPs with diameters > 2 mm are abundant in many agricultural soils. We hypothesized that potential effects of CVPs on shoot growth of winter wheat (Triticum aestivum L.) increase with: 1) decreasing availability of water and 2) decreasing availability of nutrients in the topsoil. We conducted a microcosm experiment with different irrigation regimes (Irr+/Irr-) and P concentrations (P+/P-), with or without artificially created continuous vertical pores (CVP+/CVP-). Winter wheat was cultivated for 16 weeks. In the bulk soil, presence of CVPs resulted in decreased root length in 20 - 40 cm but increased root length in 40 - 60 cm soil depth. In general, total root length of winter wheat in 20 - 60 cm soil depth was higher when CVPs were present or when P concentrations in the topsoil were elevated. Presence of CVPs generally had a positive effect on shoot dry matter and N uptake of wheat. In columns with high phosphorous concentrations but low soil moisture in the topsoil, presence of CVPs increased shoot dry matter by 66%;in contrast, the beneficial effect of CVPs on shoot dry matter was only 39% in columns with high nutrient concentrations and high soil moisture in the topsoil. In total numbers, however, the effect of CVPs on P uptake into the shoot was more pronounced when P concentrations in the topsoil were elevated. We conclude that CVPs can promote the exploration of the solid soil phase by high root-length densities, but adequate nutrient supply in the topsoil is essential.

关键词： subsoil Mechanical Resistance Drought Stress P Supply Nutrient Acquisition

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plough pan impacts maize(Zea mays L.)grain yield,carbon assimilation,leaf senescence and nitrogen uptake in northeast of China

Plough pan impacts maize(Zea mays L.)grain yield,carbon assi...

引用

2016年全国青年作物栽培与生理学术研讨会

作者： Qing-Jun Cao Fen-Tuan Yang Xiaoli Jiang LamineDiallo Xi-Feng Chen Gang Li Jilin Academy of Agriculture Science/Key Laboratory of Northeast crop physiology ecology and cultivation Ministry of Agriculture in People’s Republic of China

【Research Background】 subsoil compaction,which caused by ever increasing wheel loads in agricultural machinery for agricultural land,has becoming a global problem and presents in increasing risk in many of development and developing *** Northeast of China,plough pan formation is considered to be a consequence of conventional tillage practices,which had negatively effects on soil physical and chemical ***,the restricted maize growths may reduce the maintenance of photosynthetic capability or N supply during the grain filling *** are in turn may influence N balance and reduction of leaf stay-green degree during maize growth stage due to limited water together with nutrient availabilityThus,the purpose of this study by pot experiment is to examine:(1) the effect of plough pan on photosynthetic capability,carbon assimilation,and leaf stay-green rate during post-anthesis;(2)the effect of plough pan on N accumulation,remobilization and distribution in Jilin province,Northeast of China.【Materials and methods】The study was carried out at the experimental field of Jilin Academy of Agricultural Sciences,Changchun city,Jilin province(43°49′7″N,125°23′47″E).The site is located in north temperate continental monsoon climate zoneThe typical hybrid maize variety "Zhengdan 958" was investigated with simulated plow pan(SP) and simulated subsoiling(SS,control) in potted condition.【Results and Analysis】 Plant height and,stem diameter and post-anthesis leaf stay-green degree were significant reduced by plough pan in both *** with SS,SP highly reduced net photosynthetic rate(Pn) during growth stage,thereby lead to a decrease of dry matter accumulation(DMA) and grain yield(GY) in three consecutive *** root weight and nodal roots number were observed reduced;plow pan significantly affected total roots weight in the plow layer and in the subsoil layer,but had no significant effect on the top soil *** regression of root-shoot we

关键词： plough pan subsoil leaf stay-green N remobilization N uptake

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Engineering Geological Problems of Levee Along Middle and Lower Reaches of Yangtze River

引用

人民长江 2002年第Z1期33卷 74-77页

作者： MA Gui-shengSenior Engineer, Comprehensive Reconnaissance Bureau, Changjiang Water Resources Commission, Wuhan 430010, China Senior Engineer Comprehensive Reconnaissance Bureau Changjiang Water Resources Commission Wuhan 430010 China

The levee along middle and lower reaches of Yangtze, about 3 600 km long, was built mostly on loose quaternary deposit with changeful complicated formation and geologic defects. Hence, during flood season, dangerous events occur frequently, which imperil the levee’s safety and pose great threats to life and property of people behind the levee. According to the exploration and investigation results, a classification of subsoil profile is made. And then the analysis on main engineering geologic problems, i.e seepage failure of dyke and bank slope instability, is conducted. The internal relations between main engineering geologic problems and subsoil profile are found out, which provides a scientific basis for the design of strengthening dykes.

关键词： subsoil profile seepage failure bank slope instability

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：