Prediction of rainfall runoff‐induced sediment load from bare land surfaces by generalized regression neural network and empirical model

Based on three rainfall run‐off‐induced sediment transport data for bare surface experimental plots, the generalized regression neural network (GRNN) and empirical models were developed to predict sediment load. Rainfall intensity, slope, rainfall duration, soil particle median diameter, clay content of the soil, rill density and soil particle mass density constituted the input variables of the models while sediment load was the target output. The GRNN model was trained and tested. The GRNN model was found successful in predicting sediment load. Sensitivity analysis by the GRNN model revealed that slope and rainfall duration were the most sensitive parameters. In addition to the GRNN model, two empirical models were proposed: (1) in the first empirical model, all the input variables were related to the sediment load, and (2) in the second empirical model, only rainfall intensity, slope and rainfall duration were related to the sediment load. The empirical models were calibrated and validated. At the calibration stage, the coefficients and the exponents of the empirical models were obtained using the genetic algorithm optimization method. The validated empirical models were also applied to two more experimental data sets: (1) one data set was from a field experiment, and (2) one set was from a laboratory experiment. The results indicated the success of the empirical models in predicting sediment load from bare land surfaces.     

Geosynthetics in erosion control — the principles

The principles of erosion control are basic, but geosynthetic materials manufactured and marketed for erosion control applications have varied significantly in the last decade. The problem of soil retention, protection, revegetation, and turf reinforcement can be solved with many different materials, both organic and synthetic. Specific material properties must, however, be met to achieve proper performance.

This paper provides a review of the primary geosynthetic materials used for erosion control and their basic applications, including blankets for ground cover, geotextiles for filter protection beneath armor, geotextiles for silt control, synthetic mats and blankets used for erosion control/revegetation and turf reinforcement. The paper also includes several generic, physical-property criteria for the materials to be used in the primary applications discussed.     

切坯机使挤出更完美——切坯技术现状

<正>切坯机是挤出机的主要部分,因为它是黏土泥条连续地通过切坯机制作最终产品的唯一方法。同时,切坯机也是切割后坯体全自动托盘处理、码坯、输送设备的一部分。从第一台人工切坯机到现在电子控制自动化切割设备,切坯机已经经历了快速和全面的发展。     

Behaviour of self-centring shear walls——A state of the art review

The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated construction due to the incorporation of prefabricated elements and segmental construction for different materials (e.g., concrete, masonry, and timber), reduced residual drifts, and little damage upon extreme seismic and wind loads. Concrete, masonry, and timber are often used for the construction of unbonded PT structural wall systems. Despite extensive research since the 1980s, there are no well-established design guidelines available on the shear wall configuration with the required energy dissipation system, joint’s locations and acceptance criteria for shear sliding, confinement, seismic performance factors, PT loss, PT force range and residual drifts of shear walls subjected to lateral loads. In this research a comprehensive state-of-the-art literature review was performed on self-centring shear wall system. An extensive study was carried out to collect a database of 100 concrete, masonry, and self-centring shear wall tests from the literature. The established database was then used to review shear walls’ configurations, material, and components to benchmark requirements applicable for design purposes. The behaviour of concrete, masonry and timber shear walls were compared and critically analysed. The general behaviour, force-displacement performance of the walls, ductility, and seismic response factors, were critically reviewed and analysed for different self-centring wall systems to understand the effect of different parameters including configurations of the walls, material used for construction of the wall (concrete, masonry, timber) and axial stress ratio. The outcome of this research can be used to better understand the behaviour of self-centring wall system in order to develop design guidelines for such walls.     

Durability of soil-cement for building purposes — rain erosion resistance test

In this paper, the effects of compaction pressure (moulding pressure), simulated rainfall, and cement content on the durability of soil-cement bricks have been investigated. The results show that the resistance of the bricks to erosion by raindrops was enhanced by increase in compaction pressure and cement content. The bricks stabilised with 5 percent cement and compressed at 8 MN/m², compaction pressure were found durable to rain erosion. Higher cement content and/or higher compaction pressures yielded very negligibly higher weight losses. These later cases are considered uneconomical. The spray pressure (250 Kn/M²), distance from the face of brick (140mm), duration of spray (3 hours), were also found adequate for rainfall durability tests on cement stabilised soils.     

弦支结构体系研究进展

在阐述预应力钢结构发展历程的基础上,根据预应力钢结构中构件类型组成,将预应力钢结构分为刚性、刚柔混合和柔性三种预应力钢结构类型,其中刚柔混合预应力钢结构中的弦支结构是一种典型的预应力钢结构,是目前应用最广泛的结构体系之一。对于预应力钢结构的核心构件——拉索的温度线膨胀系数,建议今后工程设计时采用以理论分析和试验研究为基础的数据,即钢丝绳、钢绞线、半平行钢丝束三种索材的线膨胀系数值分别为1.92×10-5,1.38×10-5,1.87×10-5/℃。在分析弦支结构体系概念的基础上,将其分为平面弦支结构、可分解的空间弦支结构和不可分解的空间弦支结构三类,并对弦支结构体系中拉索的数值模拟理论进行了总结分析。随后分别针对三种弦支结构类型,对其发展历程、结构构成、结构特点以及工程应用进行了分析总结。     

Sewer asset management – state of the art and research needs

ABSTRACT

Sewer asset management gained momentum and importance in recent years due to economic considerations, since infrastructure maintenance and rehabilitation directly represent major investments. Because physical urban water infrastructure has life expectancies of up to 100 years or more, contemporary urban drainage systems are strongly influenced by historical decisions and implementations. The current decisions taken in sewer asset management will, therefore, have a long-lasting impact on the functionality and quality of future services provided by these networks. These decisions can be supported by different approaches ranging from various inspection techniques, deterioration models to assess the probability of failure or the technical service life, to sophisticated decision support systems crossing boundaries to other urban infrastructure. This paper presents the state of the art in sewer asset management in its manifold facets spanning a wide field of research and highlights existing research gaps while giving an outlook on future developments and research areas.     

Landscape photography: from art to now — artists' contemporary concerns

An account of the use of landscape as subject-matter as a basis for the exploration of personal concerns and the search for self by various 20th Century photographers. Particular reference is made to the landscape photography of Eugene Atget, Edward Weston and Bill Brandt.     

Soil erosion susceptibility of Johor River basin

Malaysia is undergoing tremendous environmental changes due to population growth, economic development and urbanization. This has stimulated a rapid land use changes which in turn has increased the rate of soil erosion and river sedimentation. In this study, Universal Soil Loss Equation (USLE) and the Modified Universal Soil Loss Equation (MUSLE) are applied within a geographical information system (GIS) to assess the spatial pattern of soil erosion susceptibility of Johor River basin, Malaysia. Geomorphological, landuse and soil information along with other hydrological data such as, annual peak flow and runoff volumes are used to estimate the parameters required for the calculation of soil erosion susceptibility. The results show that annual erosion rate varies between 0.2 and 248.2 t/ha/year according to USLE, and between 19.2 and 2179.9 thousand tons per event according to MUSLE. The land cover management is found as the major factor responsible for soil erosion in the basin.     

Planning history in Australia: The state of the art

Over the last two decades, planning history in Australia has firmed as both a specific research field and pragmatic endeavour geared to planning practice. The emergence of an identifiable planning history strand across the borders of such disciplines as planning, political science, human geography, and history in the mid‐1970s gained much of its rationale from other developments at this time, including the academic legitimation of urban studies and urban history, an unprecedented level of governmental interest in urban and regional development, reassessment and reaction to traditional land use planning, and the benevolent imprimatur of the British Planning History Group. From the vantage point of the early 1990s, a substantive literature can now be critically surveyed. Diverse if not fragmented, parochial and sometimes quirky, the general nature of this body of work partly reflects the spatial isolationism and parochialism that have been hallmarks of Australian cultural and political development. Beyond the straitlaced general surveys of state, city and metropolitan planning, several established lines of inquiry are evident, notably colonial town layout, civic design, the impact of planning movements, evaluations of metropolitan planning, political conflict, and federal urban policy. The links with cognate fields such as housing, landscape architecture and, increasingly, environmental studies, are close. Alongside these general themes have come more distinctively Antipodean preoccupations like the planning of Adelaide and Canberra as well as the work of Walter Burley Griffin. Future challenges lie in more original research, integration, theory development, and policy relevance.     

Detection of smoke gases by solid state sensors — A focus on research activities

Conventional smoke detection in fire alarm systems is based on a measurement of either physical properties of smoke aerosols (ionization and optical detectors), temperature increase (thermal detectors) or electromagnetic radiation emitted by the fire (radiation detectors). Not much emphasis has been put on smoke gases as signatures of various types of fires. In this paper the most elementary gases produced in CEN-norm fires are qualitatively discussed in order to define levels of gas concentrations reached on time scales typical of early fire warning. Based on that information, various principles and the current state of the research and development of solid state gas sensors are presented and discussed. These are, in particular, the solid state electrolyte, the metal oxide semiconductor, the silicon semiconductor device element and, finally, the microcalorimeter. It is concluded that, with the exception of the last mentioned operating principle, solid state gas detection could provide a viable alternative or additional means for the detection of smouldering or pyrolytic fires at an early stage.     

基于分权状态下的授权艺术

授权与分权是现代组织中权力分散的两条基本途径,两者既相互区别又相互联系。分权是一条组织工作原则,授权是一门领导艺术。在新的历史时期,面对复杂多变、竞争激励的外部环境,组织内部决策的复杂性和时效性已空前提高,此时,作为管理组织的领导者,已不可能事必躬亲、事无巨细,必须正确地认识授权的重要性、掌握授权的艺术。敢于授权又善于授权已成为现代领导活动的重要特征及目标追求。在现代组织中,权力的分散一般可以通过两条基本途径来实现:一是组织层级化设计中的分权(即制度分权);二是作为管理组织的领导者在工作过程中的授权。尽管授…     

铝合金空间网格结构研究现状及关键问题

相比于钢结构,铝合金结构由于其自重轻、耐腐蚀和易加工等优点,在结构工程中备受关注,其应用也日益增多。从铝合金作为建筑结构用材与钢材的特性对比出发,列举了国内外大量具有代表性的铝合金空间网格结构,综述了国内外对于铝合金单、双层网壳和网架等铝合金空间网格结构及节点体系的研究现状,并指出目前试验研究、理论研究和设计应用的主要不足之处;通过进一步探讨,提出铝合金空间网格结构的研究与应用中需解决的若干关键技术问题,这些问题集中在节点刚度和杆件初始缺陷对铝合金单层网壳结构整体稳定性的影响、新型节点形式的研究以及铝合金空间网格结构的抗震、抗火性能研究等方面。     

视频火灾探测系统现状分析

介绍了国内外目前在视频火灾探测领域的几种典型产品以及视频探测算法的研究现状,分析了各个系统及算法的特点,并对此领域的发展前景进行了讨论和展望。     

浅谈升降脚手架技术发展现状和安全管理

介绍了升降脚手架技术的发展现状,针对升降脚手架施工中易出现的薄弱环节,提出了升降脚手架安全生产管理的重点。     

锈蚀钢筋与混凝土粘结性能研究进展

粘结性能退化是锈蚀钢筋混凝土构件力学性能下降的主要原因之一.锈蚀对钢筋与混凝土粘结性能的影响已成为混凝土结构耐久性研究的重要内容.文章全面地介绍了钢筋锈蚀及粘结性能测试的试验方法;系统地回顾与评述了锈蚀引起的粘结强度演化规律、粘结滑移本构关系以及粘结退化对结构承载力的影响等方面的研究进展.