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Journal articles on the topic "Acier rail"
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Gao, Yu-Fu, Li-Ping Rong, Dong-Hui Zhao, Jia-Qi Zhang, and Jia-Shuo Chen. "Effects of simulated acid rain on the photosynthetic physiology of Acer ginnala seedlings." Canadian Journal of Forest Research 51, no. 1 (January 2021): 18–24. http://dx.doi.org/10.1139/cjfr-2020-0091.
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Extensive areas in China have been receiving high levels of acid rain. Acid rain affects plant growth by reducing the chlorophyll content, destroying leaf structure, and hindering photosynthesis. Acer ginnala Maxim. has a high economic, ornamental, and medicinal value. To clarify the acid rain resistance mechanism of maple trees, the chlorophyll content, gas exchange parameters, and chlorophyll fluorescence parameters were measured in the leaves of 2-year-old Acer ginnala seedlings 0, 15, and 30 days after simulated acid rain at pH 5.6, 5.0, 4.5, 4.0, 3.5, and 2.5. The results showed that the relative content of chlorophyll gradually decreased with the increasing acidity. The net photosynthetic rate (Pn) decreased with the increasing acidity, and the difference among the treatments was significant except for between pH 5.0 and the control. The stomatal conductance at pH < 5.0 was significantly lower than that of the control, and the intercellular carbon dioxide (CO2) concentration of the leaves with the pH < 4.5 treatments was significantly lower than that of the control. As the acidity increased, both Fv/Fm and Fv/F0 (Fv, variable fluorescence; Fm, maximum fluorescence; F0, initial fluorescence) decreased. The difference in the photosynthetic performance index based on the absorbed light energy (PIabs) between the pH 5.0 treatment and the control was not significant during the three periods after the simulated acid rain stress, whereas in the other treatments, this index was significantly lower than that of the control. Our results indicated that under mild acid rain (pH > 4.0) stress, the chlorophyll content, gas exchange parameters, and chlorophyll fluorescence parameters of Acer ginnala changed little, whereas in the other treatments, especially the severe acid rain (pH < 3.0) treatment, these indices showed significant changes that had a severe impact on plant growth and development.
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Zhang, Yuyang, Tao Yu, Wenbao Ma, Buddhi Dayananda, Kenji Iwasaki, and Junqing Li. "Morphological, Physiological and Photophysiological Responses of Critically Endangered Acer catalpifolium to Acid Stress." Plants 10, no. 9 (September 19, 2021): 1958. http://dx.doi.org/10.3390/plants10091958.
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Acid rain deposition (AR) has long-lasting implications for the community stability and biodiversity conservation in southwest China. Acer catalpifolium is a critically endangered species in the rain zone of Western China where AR occurs frequently. To understand the effects of AR on the morphology and physiology of A. catalpifolium, we conducted an acid stress simulation experiment for 1.5 years. The morphological, physiological, and photosynthetic responses of A. catalpifolium to the acidity, composition, and deposition pattern of acid stress was observed. The results showed that simulated acid stress can promote the growth of A. catalpifolium via the soil application mode. The growth improvement of A. catalpifolium under nitric-balanced acid rain via the soil application mode was greater than that of sulfuric-dominated acid rain via the soil application mode. On the contrary, the growth of A. catalpifolium was significantly inhibited by acid stress and the inhibition increased with the acidity of acid stress applied via leaf spraying. The inhibitory impacts of nitric-balanced acid rain via the leaf spraying of A. catalpifolium were greater than that of sulfur-dominant acid rain via leaf spraying. The observations presented in this work can be utilized for considering potential population restoration plans for A. catalpifolium, as well as the forests in southwest China.
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Kim, Y. T., and R. H. Leech. "Effects of Climatic Conditions on Sap Flow in Sugar Maple." Forestry Chronicle 61, no. 4 (August 1, 1985): 303–7. http://dx.doi.org/10.5558/tfc61303-4.
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Temperature, sunlight and precipitation were studied to examine their influence on sugar maple (Acer saccharum Marsh) sap flow over a five-year period. Temperature was the most important climatic factor influencing the amount of sap flow. Sunlight also increased the sap flow, but rain one day before the sap collection reduced it.
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Roberts, Mark R., and Norman L. Christensen. "Vegetation variation among mesic successional forest stands in northern lower Michigan." Canadian Journal of Botany 66, no. 6 (June 1, 1988): 1080–90. http://dx.doi.org/10.1139/b88-154.
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Vegetation composition of the shrub–tree and herb layers was sampled in 70 successional aspen (Populus tremuloides and Populus grandidentata) stands of different ages (1–90 years) on a variety of sites in northern lower Michigan. Physical and chemical characteristics of soil profiles were also measured at each site. Three stand groupings were identified based on site conditions and detrended correspondence analysis (DCA) ordination of the vegetation. Sandy dry-mesic soils support forests of Acer rubrum, Quercus rubra, Pinus resinosa, and Pinus strobus. On lowland sandy soils with a fluctuating water table, Pinus strobus, Abies balsamea, Viburnum lentago, and Viburnum cassinoides are important. Mesic soils with stratified calcareous layers or clay till substrates support Acer saccharum, Fagus grandifolia, Tilia americana, Fraxinus americana, Ostrya virginiana, and Acer pensylvanicum. Canonical correlation analysis (CCA) was used to compare DCA scores with soil variables; first-axis DCA scores were correlated with a suite of soil variables and stand age was correlated with second or third DCA axis scores. Separate DCA ordinations of the dry-mesic and mesic groups revealed successional relations on these sites. On dry-mesic sites, Pinus resinosa and Pinus strobus increase in importance with stand age, while Prunus serotina, Prunus virginiana, Prunus pensylvanica, and the aspens decrease. On mesic sites, early successional species include the aspens, Corylus cornuta, Prunus serotina, and Prunus pensylvanica. Fagus grandifolia, Acer pensylvanicum, Quercus rubra, Viburnum acerifolium, Betula papyrifera, Acer rubrum, and Tilia americana are more abundant in mature mesic-site stands. Ordinations of the herb data were remarkably similar to those for trees and shrubs except on dry-mesic sites. Much of the residual variability in vegetation not accounted for by site conditions and stand age is probably related to historical factors such as the nature of disturbance and variations in seed rain.
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Yan, Qiaoling, Qun Gang, and Jiaojun Zhu. "Size-Dependent Patterns of Seed Rain in Gaps in Temperate Secondary Forests, Northeast China." Forests 10, no. 2 (February 4, 2019): 123. http://dx.doi.org/10.3390/f10020123.
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Secondary forests have become the major forest type worldwide, and are experiencing various disturbances and exhibiting obvious vegetation degradation (e.g., reduced biodiversity and decreased productivity) compared with primary forests. Forest gap is a common small-scale disturbance in secondary forests. Promoting natural regeneration under gap disturbance is an important approach to recover biodiversity and ecosystem services for temperate secondary forests. The gap size is the crucial characteristic controlling natural regeneration of many tree species. However, little is known about the spatiotemporal pattern of seed rain for gravity-dispersed and wind-dispersed tree species in gaps of varying sizes. The objectives of this study were to determine how seed rain of dominant tree species depend on gap size, and consequently, to explore some gap-based silviculture solutions for restoring secondary forests from the view of seed dispersal. The spatial distribution of seed rain in gaps with three sizes (large gaps of 250–350 m2, medium gaps of 150–250 m2, and small gaps of < 150 m2), the temporal dynamics of seed rain over three years, and the relationship between seed rain and soil seed banks were explored in temperate secondary forests. The results showed that more than 90% of the seeds in seed rain were wind-dispersed, and their seed rain density and the contribution of seed rain to soil seed bank in medium gaps reached the highest (p = 0.03). The results suggest that establishing medium-sized gaps (i.e., gap size with 150–250 m2) in the secondary forests is more favorable for improving the natural regeneration potential (arrival of seeds and forming soil seed bank) of gap-dependent and wind-dispersed species (e.g., Acer mono) in gaps.
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Gaber, B. A., and T. C. Hutchinson. "The neutralisation of acid rain by the leaves of four boreal forest species." Canadian Journal of Botany 66, no. 9 (September 1, 1988): 1877–82. http://dx.doi.org/10.1139/b88-256.
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A field study was carried out in the boreal forest of Ontario to measure the neutralisation response of the leaves of Cornus canadensis, Aralia nudicaulis, Maianthemum canadense, and Acer spicatum to simulated acid rain. Plots of each species were sprayed with pH 5.6, 3.8, or 3.2 rain, and the pH of the raindrops on the leaves and on Parafilm (control) was measured with a microelectrode at 15-min intervals until the leaves dried. Species differed in their ability to neutralise the rain, with C. canadensis consistently neutralising acidic raindrops the most. The neutralisation response varied greatly between pH treatments, with greatest neutralisation occurring at the most acidic pH treatment. Raindrop neutralisation primarily took place within the first few minutes following the spray. For this reason, the dissolution of basic particulates on the leaf surface was probably responsible for the rapid changes in raindrop pH, while slower changes may reflect cation exchange processes with the cell walls. Weather conditions determined the rate of evaporation of the raindrops, and this affected their acidity. High rates of evaporation reduced the time available for leaf surface – raindrop interactions and are probably responsible for the acidification observed in some plots.
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Beckage, Brian, James S. Clark, Barton D. Clinton, and Bruce L. Haines. "A long-term study of tree seedling recruitment in southern Appalachian forests: the effects of canopy gaps and shrub understories." Canadian Journal of Forest Research 30, no. 10 (October 1, 2000): 1617–31. http://dx.doi.org/10.1139/x00-075.
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We examined the importance of intermediate-sized gaps and a dense shrub layer on tree seedling recruitment in a southern Appalachian deciduous forest. We created 12 canopy gaps under two contrasting understory conditions: 6 gaps were dominated by the dense, shade-producing shrub, Rhododendron maximum L., while the remaining gaps were relatively open. Density of first-year and >first-year seedlings was monitored for 5 years in transects extending from adjacent undisturbed forest through the experimental gaps. We concurrently measured the understory light environment, soil moisture, litter biomass, and seed rain. Neither species diversity nor richness consistently increased following gap formation. Acer rubrum L. responded consistently to canopy gaps with increased seedling densities while most other species, including both shade-tolerant and shade-intolerant species, did not. Seedling densities were especially low and unresponsive to gap formation in areas dominated by R. maximum. Understory light levels were consistently low beneath R. maximum and did not increase with canopy gap formation. Our results suggest that dense shrub cover can neutralize recruitment opportunities in canopy gaps, that seed rain often limits recruitment in gaps, and that canopy gaps that are larger or include understory disturbance are needed to maintain diversity in these forests.
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Zhang, Yuyang, Cheng Tian, Tao Yu, Buddhi Dayananda, Brendan Fu, Samiddhi L. Senaratne, Cuiyun Wu, and Junqing Li. "Differential effects of acid rain on photosynthetic performance and pigment composition of the critically endangered Acer amplum subsp. catalpifolium." Global Ecology and Conservation 30 (October 2021): e01773. http://dx.doi.org/10.1016/j.gecco.2021.e01773.
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Rodinkova, V. V. "Аеропалінологічний спектр м. Дніпропетровськ як основа профілактики сезонної алергії." Visnyk of Dnipropetrovsk University. Biology, medicine 4, no. 1 (February 21, 2013): 3–9. http://dx.doi.org/10.15421/021314.
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Hay fever is important allergenic complain with number of patients rising year by year. Ukraine holds the leading positions in Europe in accordance with pollinosis morbidity. Therefore, it’s important to determine regional pollen spectrum for all five climatic and geographical zones of the country having certain variety of plants’ allergens. There are just a few cities with a constant pollen monitoring carried out in Ukraine. They are Vinnytsia, Kyiv, Odessa and Lviv. Palynological range of other Ukrainian cities remains unknown or poorly studied. Dnipropetrovsk – Ukrainian city with location in the Central part of the country in the Steppe zone – isn’t exception as well. Thus, the aim of our study was to determine the pattern of airborne pollen distribution and pollen calendar creation for the city of Dnipropetrovsk. Pollen count obtained at Vinnytsia National Pirogov Memorial Medical University (VNMU) by Aerobiology Research Group. Study was held in 2010 from the 17th of March till the 20th of October on daily basis employed volumetric methods using the Burkard trap. It stands on the roof of the Dnipropetrovsk Municipal hospital at 20 meters of a relative height above ground. The air samples were sent by currier mail on weekly basis from Dnipropetrovsk to Vinnytsia for the research term. 51 pollen types were determined during the study period. The aeropalinological research was done for the Dnipropetrovsk at first. Study was conducted in association with the European Aeroallergen Network (EAN). The EAN tools and the software package “Statistica 5.5” were used for data statistical analysis. The study showed prevalence of the airborne herbal pollen types in Dnipropetrovsk. The “weeds : trees” pollen ratio was «88 : 12». Most abundant pollen rain (59% of total annual pollen count) was produced by Ambrosia. The second position with 6% was held by Amaranthus / Chenopodiaceae pollen group and Urtica dioica pollen. Artemisia and other representatives of Asteraceae constituted of 5% each. The most abundant tree pollen rain (4% from total annual count) was produced by the Populus species. Betula pollen was the next having up 2% of annual pollen rain in Dnipropetrovsk. As can be seen, the first arboreal spring-summer pollination wave was not massive in Dnipropetrovsk. It was represented by Populus, Betula, Acer, Fraxinus, Quercus, Ulmus, Pinus, Juglans pollen spread in the end of March, whole April and the first weeks of May mostly. However, the second wave was intensively seen from the mid of July till the mid of October. Important airborne pollen producing taxa were Artemisisia, Ambrosia, Asteraceae, Chenopodiaceae, Urtica, Plantago, Polygonaceae pollen at that time. Important airborne pollen allergens of Poaceae family (grasses) held the 7th position in the total annual pollen rain and were recorded between two pollination waves from the mid of May till the end of June mostly. The worst period for the patients was associated with the Betula, Acer and Quercus pollination from 13th of April till the mid of May and with Ambrosia and Artemisia pollination from 28th of July, till September, 30. The present airborne pollen calendar should be considered while diagnosing the hay fever symptoms in sensitive patients. It’s important to continue the pollen count and control in Dnіpropetrovsk due to constant changing of climatic and anthropogenic conditions impacting the pollen production and release.
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Tauer, Pamela K., and Janet C. Cole. "Effect of Fabric and Plastic Containers on Plant Growth and Root Zone Temperatures of Four Tree Species." Journal of Environmental Horticulture 27, no. 3 (September 1, 2009): 145–48. http://dx.doi.org/10.24266/0738-2898-27.3.145.
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Abstract Live oak (Quercus virginiana Mill.), red maple (Acer rubrum L.), and sweet gum (Liquidambar styraciflua L.) trees were planted in #7 fabric or plastic containers on April 18, 2004, and grown for two growing seasons. Live oak and golden rain tree (Koelreuteria paniculata Laxm.) trees were planted in #10 fabric or plastic containers on May 6, 2005, and harvested the following summer. Plant height, canopy width, and caliper were measured periodically, and root zone temperatures were recorded at 30-min intervals throughout each study. In the 2004 planting, live oak height and canopy width increased more for plants in plastic containers than for those in fabric containers from May to July 2004. In contrast, no difference in live oak height or canopy width growth occurred between container types from July to September 2004, but trunk caliper increased more in plastic than in fabric containers during this time interval. No differences between container treatments were noted for any measured parameter for red maple or sweet gum trees planted in 2004 or for golden rain tree or live oak trees planted in 2005 at any measurement interval during the study. Average monthly high and low substrate temperatures were similar between the two container types throughout the study. Fabric containers appear to be a reasonable alternative to plastic containers for above ground nursery crop production, although small differences in growth occur for some species.
Dissertations / Theses on the topic "Acier rail"
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Oriol, Pierre. "Comportement des aciers à rails vis-à-vis de l'hydrogène : diffusion, perméation et fragilisation." Châtenay-Malabry, Ecole centrale de Paris, 1987. http://www.theses.fr/1987ECAP0041.
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Etude de la diffusion et de la perméation a l'hydrogène dans différentes nuances d'aciers à rail en fonction de la teneur en soufre, du sens de prélèvement des éprouvettes et du taux de corroyage. Étude de la fragilisation différée sur une nuance dure par suivi de l'émission acoustique en fonction du chargement en hydrogène. Examen de l'influence de l'hydrogène sur le comportement en traction des différentes nuances
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Saint-Aimé, Loïc. "Simulation numérique transitoire de la sollicitation cyclique du contact roue-rail." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10227/document.
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Sous l’effet des sollicitations mécaniques répétées induites par les passages des trains, on observe l’apparition de fissures de fatigue de contact dans les rails. Une fois amorcées, celles-ci peuvent se propager et mener à la rupture du rail. Dans un contexte d’intensification du trafic, l’optimisation de la politique de maintenance devient stratégique pour les entreprises du transport ferroviaire. Dans ce contexte, un modèle 3D éléments finis du contact roue/rail en courbe a été développé pour reproduire les mécanismes d’amorçage des fissures "Head Check". Ce modèle permet de simuler la sollicitation répétée du contact roue/rail. Cette modélisation a permis d’analyser l’influence de la plasticité sur la distribution de la pression de contact et sur les champs mécaniques résiduels au sein du rail au cours du chargement cyclique. Il ainsi est montré que l’actualisation du contact au cours des chargements répétés est du premier ordre. Les résultats ont permis d’identifier des zones potentielles d’amorçage de fissures de Head Check correspondant à des points matériels sur lesquels la déformation plastique s’accumule de manière considérable. En effet, on observe une correspondance entre ces orientations « accommodées » de la déformation plastique principale et l’orientation des micro-fissures amorcées sur la surface des rails ayant cumulé un faible tonnage (0-10 MGT). Ceci conforte le fait que la méthode proposée est un outil prometteur pour la simulation 3D de la fatigue du contact roue-railAs a result of repeated loading induced by train passages, rails are subjected to rolling contact fatigue cracks. Once initiated, cracks could propagate and lead to rail failure. In a context of increased traffic, maintenance policy optimization becomes strategic for railway companies. Thus to define an enhanced planning of maintenance, a better understanding of rail fatigue damage mechanisms is crucial. Under the circumstances, a 3D wheel-rail rolling contact finite element model has been developed in order to reproduce « Head Check » cracks initiation mechanisms. This model allows sequential repeated wheel-rail rolling contact loading. Thus this calculation procedure is used to analyze the influence of plasticity on contact pressure distribution and consequently on residual mechanical fields in the rail during cyclic loading. It is shown that contact conditions evolution during repeated loading must be considered in the first order. The results allowed the identification of potential Head Check cracks initiation zones that correspond to material points on which plastic deformation accumulates significantly. Indeed, there is a correspondence between the « accommodated » principal plastic strain directions and orientation of micro-cracks initiated on rails surface subjected to low cumulative tonnage (0-10MGT). This reinforces the fact that our proposed method is a promising tool for 3D wheel-rail rolling contact fatigue simulation
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Nhari, Ahmed. "Etude par diffraction des rayons x des contraintes residuelles induites par le mode de dressage dans les rails : relation avec la tenue en voie." Paris, ENSAM, 1987. http://www.theses.fr/1987ENAM0004.
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Analyse de l'influence du mode de dressage et du roulement sur les caracteristiques du rail, avec une attention plus particuliere portee aux contraintes residuelles et a l'ecrouissage, etudies au moyen de la methode de diffraction x
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Simon, Samuel. "De la dynamique ferroviaire à l’accommodation microstructurale du rail : Contribution des TTS à la réponse tribologique des aciers : Cas du défaut de squat." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0028/document.
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Le squat est un défaut de fatigue de contact apparaissant à la surface du rail et dont le mécanisme d’amorçage est mal compris. Afin de pallier ce manque, une analyse tribologique locale de la bande de roulement du rail est mise en oeuvre à proximité d’un squat naissant. Cette caractérisation révèle une anisotropie importante des couches superficielles du rail associée aux développements de Transformations Tribologiques Superficielles. Ces résultats témoignent de conditions de contact roue/rail particulières dans la zone d’étude, notamment d’un niveau d’efforts de cisaillement inhabituel pour une voie en alignement. Dans le but de valider ces observations, plusieurs essais sont effectués. D’une part les conditions de contact roue/rail dans une zone de squats sont mesurées à partir d’un train instrumenté. D’autre part, la réponse tribologique de l’acier à rail à ces conditions de contact est étudiée à travers le suivi régulier d’une zone d’essais soumise à la circulation ferroviaire. Ces essais permettent d’identifier un déséquilibre important des efforts de traction sur les bogies moteurs et des glissements locaux élevés de la roue sur le rail. Différents mécanismes d’amorçage thermo-mécaniques sont alors proposés au sein d’un schéma global de la réponse tribologique de l’acier à railSquats have recently become recognised as one of the major rolling contact fatigue defects in modern railway networks for which there is currently no solution other than preventive grinding operations or costly rail renewal. To better understand the entire damage mechanism of squat, A tribological and metallurgical analysis of the rolling band and the near surface layer was performed close to an incipient squat. This characterization show a significant anisotropy of the rail surface layer associated with developments of Tribological Transformation of Surface. These results reflect some specific wheel/rail contact conditions in this squat area, including an unusual level of shear forces in a straight track. In order to validate this observations, two tests were performed. On the one hand, the contact conditions in a squat area were measured from an instrumented train. On the other hand, the tribological response of the rail steel was studied through regular monitoring of a test site subjected to railway traffic. These tests allow to identify a high imbalance of the traction forces and the presence of local slips at the wheel/rail interface. Several thermomechanical initiation mechanism of squats are then given in a overall diagram of the tribological response of rail steels
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Oriol, Pierre. "Comportement des aciers à rails vis-à-vis de l'hydrogène diffusion, perméation et fragilisation /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376085569.
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Peters, Anna L. "The Effects of Soil Phosphorus on Acer rubrum Fecundity." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1398164024.
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Sieffert, Yannick Jullien Jean-François Michel Gérard. "L Entretoisement des ponts mixtes multipoutre ferroviaires." Villeurbanne : Doc'INSA, 2005. http://docinsa.insa-lyon.fr/these/pont.php?id=sieffert.
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Sieffert, Yannick. "L' Entretoisement des ponts mixtes multipoutres ferroviaires." Lyon, INSA, 2004. http://theses.insa-lyon.fr/publication/2004ISAL0086/these.pdf.
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L'objectif de ce travail est de rendre plus compétitif les ponts mixtes à poutres pour des petites et moyennes portées. Dans cette optique, des innovations doivent être apportées pour simplifier leur conception et leur réalisation. En particulier, l'entretoisement intermédiaire de ces ponts est coûteux car il nécessite la réalisation de soudure sur le chantier. Or, le rôle de cet entretoisement est mal connu et repose sur des principes empiriques. Ainsi, la pertinence de l'entretoisement est, tout d'abord, analysée. La simulation numérique par la Méthode des éléments Finis est alors utilisée. Cette modélisation nécessite la prise en compte de différents phénomènes physiques : la représentation tridimensionnelle du problème, les lois de comportement des matériaux et les sollicitations. La vitesse des véhicules est aussi considérée afin d'appréhender la réponse dynamique des ouvrages sous le passage d'un convoi ferroviaire de type TGV. La pertinence du modèle numérique développée est confrontée à une expérimentation en laboratoire d'une structure représentant un pont réel à échelle réduite. Enfin, un nouveau type d'entretoisement en béton est développée et valider par des essais en laboratoire et par une simulation numérique.
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Belhadj, Ahmed Abdelwahed. "Contribution à l’amélioration de la rectitude dans l’obtention de produits longs : application aux abouts de rails." Thesis, Paris, ENSAM, 2013. http://www.theses.fr/2013ENAM0066/document.
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Les produits longs se distinguent par une dimension, généralement la longueur plus importante que la hauteur et la largeur, à titre d'exemple les rails de chemin de fer. Ces produits sont obtenus par déformation plastique à chaud puis refroidissement. Au cours du processus de fabrication, l'hétérogénéité du refroidissement et de la déformation plastique induisent un défaut géométrique de rectitude. Pour parachever la rectitude du produit, un redressage à froid est alors nécessaire. Souvent des dresseuses à galets sont utilisées pour corriger la rectitude du centre de produit, cependant, il reste les abouts. Ces derniers sont redressés au moyen d'une presse à partir de l'image de leurs profils obtenus par mesurage optique. La procédure de mesure/redressage est répétée jusqu'à la conformité du produit. Le temps de réalisation est variable, il dépend de l'apprentissage des paramètres clés liés à la géométrie et au matériau du produit à redresser. Compte tenu des exigences de plus en plus sévères sur la rectitude des produits longs d'une part et une volonté d'augmenter la productivité d'autre part, l'objet de ce travail de recherche consiste à optimiser le procédé de redressage des abouts de produits longs. Dans un premier temps, les déformations élastiques générées au cours du mesurage d'un produit long ont été filtrées. Ensuite, les erreurs des moyens de mesure ont été séparées de la mesure du produit au moyen d'une analyse couplée ce qui a permis une meilleure évaluation de la rectitude du produit. Par ailleurs, en se basant sur l'image du profil du produit, une méthodologie de redressage semi-automatique a été mise en place. Cette dernière est essentiellement basée sur une interaction entre la métrologie et la mécanique et représente une contribution à l'automatisation du procédé de redressage des abouts des produits longsLong workpieces are characterized by one dimension, usually length is larger than the height and width, for example, railway rails. These products are obtained by hot rolling and then cooling. During manufacturing process, heterogeneity of cooling and plastic deformation induced straightness error. In order to correct this geometrical error, cold straightening process is necessary. Usually, straightening machines are used to correct the straightness of the workpiece center however; the ends' sides were still not straightened. Based on the optical measurement profile, these ends are straightened by mechanical press. The measuring/straightening closed loop is repeated until the straightness of the product is conformed. The process time depends on the knowledge of key parameters related to geometry and material of workpiece. The objective of this research work is to optimize straightening process of the ends of long workpieces. As a first step, the elastic deformation generated during the measurement of long workpiece has been filtered. Then, a coupled analysis of measurement was used to separate error of machine measurement from workpiece measurement, which allowed a better assessment of workpiece straightness profile. Furthermore, based on straightness profile, a semi-automatic straightening methodology has been developed. It is essentially based on an interaction between metrology and mechanics and it is a contribution to the automation of straightening process for ends parts of long workpieces
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Meyer, Ann-Carolin. "Physiologische Untersuchungen am Stamm und im Kronenraum eines Fichtenaltbestandes nach experimenteller Manipulation des Wasser- und Ionenhaushaltes (Dachprojekt Solling)." Doctoral thesis, [S.l. : s.n.], 2001. http://webdoc.sub.gwdg.de/diss/2002/meyer/meyer.pdf.
Full textBooks on the topic "Acier rail"
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Atkinson, Susan Marguerite. Effects of simulated acid rain on the growth and physiology of "Acer saccherum" Marsh, and "Pinus banksiana" Lamb seedlings. 1987.
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