941 resultados para Road Geometrics.


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Scientific studies on the materials management systems and practices actually followed in various organizations in India are rather limited. This is particularly true with respect to service industries. In this context ,the present study on the “materials management in state transport undertakings in India, with special reference to kerala state road corporation” assumes particular significance . This study, examines critically, the prevailing set up, procedures and practices of materials management in the Kerala state road transport corporation and compares them with the prevailing practices in other similar state transport undertakings. It indicates several areas for improvement with respect to the organization, materials planning, purchasing, store keeping and other aspects. It also seeks to develop a comprehensive inventory control system for KSRTC.

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An efficient passenger road transport system is a boon to any city and an inefficient one its bane. Passenger bus transport operation involves various aspects like passenger convenience, profitability of operation and social, technological and environmental factors. The author’s interest in this area was aroused when he conducted a traffic survey of Trivandrum City in 1979. While some studies on the performance of the Kerala State Road Transport Corporation in specific areas like finance, inventory control etc. have already been made, no study has been made from the operational point of view. The study is also the first one of its kind in dealing with the transportation problems for a second order city like Trivandrum. The objective of this research study is to develop a scientific basis for analysing and understanding the various operational aspects of urban bus transport management like assessing travel demand, depot location, fleet allocation, vehicle scheduling, maintenance etc. The operation of public road transportation in Trivandrum City is analysed on the basis of this theoretical background. The studies made have relevance to any medium sized city in India or even abroad. If not properly managed, deterioration of any public utility system is a natural process and it adversely affects the consumers, the economy and the nation. Making any system more efficient requires careful analysis, judicious decision making and proper implementation. It is hoped that this study will throw some light into the various operational aspects of urban passenger road transport management which can be of some help to make it perform more efficiently

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Presenta algunas de las diferentes máquinas utilizadas en la construcción de carreteras, como excavadoras, camiones volquetes, campactadoras, asfaltadoras. Un glosario ilustrado proporciona una primera herramienta de referencia para las máquinas que aparecen en la publicación. Para niños hasta siete años.

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Grassland bird species continue to decline steeply across North America. Road-based surveys such as the North American Breeding Bird Survey (BBS) are often used to estimate trends and population sizes and to build species distribution models for grassland birds, although roadside survey counts may introduce bias in estimates because of differences in habitats along roadsides and in off-road surveys. We tested for differences in land cover composition and in the avian community on 21 roadside-based survey routes and in an equal number of adjacent off-road walking routes in the grasslands of southern Alberta, Canada. Off-road routes (n = 225 point counts) had more native grassland and short shrubs and less fallow land and road area than the roadside routes (n = 225 point counts). Consequently, 17 of the 39 bird species differed between the two route types in frequency of occurrence and relative abundance, measured using an indicator species analysis. Six species, including five obligate grassland species, were more prevalent at off-road sites; they included four species listed under the Canadian federal Species At Risk Act or listed by the Committee on the Status of Endangered Wildlife in Canada: Sprague’s Pipit (Anthus spragueii), Baird’s Sparrow (Ammodramus bairdii), the Chestnut-collared Longspur (Calcarius ornatus), and McCown’s Longspur (Rhynchophanes mccownii). The six species were as much as four times more abundant on off-road sites. Species more prevalent along roadside routes included common species and those typical of farmland and other human-modified habitats, e.g., the European Starling (Sturnus vulgaris), the Black-billed Magpie (Pica hudsonia), and the House Sparrow (Passer domesticus). Differences in avian community composition between roadside and off-road surveys suggest that the use of BBS data when generating population estimates or distribution models may overestimate certain common species and underestimate others of conservation concern. Our results highlight the need to develop appropriate corrections for bias in estimates derived from roadside sampling, and the need to design surveys that sample bird communities across a more representative cross-section of the landscape, both near and far from roads. 

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Aerosols and their precursors are emitted abundantly by transport activities. Transportation constitutes one of the fastest growing activities and its growth is predicted to increase significantly in the future. Previous studies have estimated the aerosol direct radiative forcing from one transport sub-sector, but only one study to our knowledge estimated the range of radiative forcing from the main aerosol components (sulphate, black carbon (BC) and organic carbon) for the whole transportation sector. In this study, we compare results from two different chemical transport models and three radiation codes under different hypothesis of mixing: internal and external mixing using emission inventories for the year 2000. The main results from this study consist of a positive direct radiative forcing for aerosols emitted by road traffic of +20±11 mW m−2 for an externally mixed aerosol, and of +32±13 mW m−2 when BC is internally mixed. These direct radiative forcings are much higher than the previously published estimate of +3±11 mW m−2. For transport activities from shipping, the net direct aerosol radiative forcing is negative. This forcing is dominated by the contribution of the sulphate. For both an external and an internal mixture, the radiative forcing from shipping is estimated at −26±4 mW m−2. These estimates are in very good agreement with the range of a previously published one (from −46 to −13 mW m−2) but with a much narrower range. By contrast, the direct aerosol forcing from aviation is estimated to be small, and in the range −0.9 to +0.3 mW m−2.

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In the UK, public expenditure on transport infrastructure is nearly £6 billion for the past few years. Over £500 million per year were spent on bridge assessment and strengthening and reducing the backlog of road requiring maintenance. A further £200 million a year will be spent on keeping the safe operation of the network and efficiently through day to day maintenance, lighting and signing . The Department of Transport is planning to extend private sector experience in road management and operation by introducing Design, Build, Finance and Operate (DBFO) This paper investigates the different ways of financing road transport infrastructure including road pricing, private finance in transport infrastructure, the role of the private sector, Design, Build, Finance and Operate (DBFO) schemes, the benefits and problems of such schemes. The paper considers planning gain as a means of financing transport infrastructure with examples of developers to fund link road building and improvements to the local planning system

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The eukaryotic genome is a mosaic of eubacterial and archaeal genes in addition to those unique to itself. The mosaic may have arisen as the result of two prokaryotes merging their genomes, or from genes acquired from an endosymbiont of eubacterial origin. A third possibility is that the eukaryotic genome arose from successive events of lateral gene transfer over long periods of time. This theory does not exclude the endosymbiont, but questions whether it is necessary to explain the peculiar set of eukaryotic genes. We use phylogenetic studies and reconstructions of ancestral first appearances of genes on the prokaryotic phylogeny to assess evidence for the lateral gene transfer scenario. We find that phylogenies advanced to support fusion can also arise from a succession of lateral gene transfer events. Our reconstructions of ancestral first appearances of genes reveal that the various genes that make up the eukaryotic mosaic arose at different times and in diverse lineages on the prokaryotic tree, and were not available in a single lineage. Successive events of lateral gene transfer can explain the unusual mosaic structure of the eukaryotic genome, with its content linked to the immediate adaptive value of the genes its acquired. Progress in understanding eukaryotes may come from identifying ancestral features such as the eukaryotic splicesome that could explain why this lineage invaded, or created, the eukaryoticniche.