Structural engineerStructural engineers analyze, design, plan, and research structural components and structural systems to achieve design goals and ensure the safety and comfort of users or occupants. Their work takes account mainly of safety, technical, economic, and environmental concerns, but they may also consider aesthetic and social factors. Structural engineering is usually considered a specialty discipline within civil engineering, but it can also be studied in its own right.
Road surfaceA road surface (English), or pavement (American), is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, macadam, hoggin, cobblestone and granite setts were extensively used, but these have mostly been replaced by asphalt or concrete laid on a compacted base course. Asphalt mixtures have been used in pavement construction since the beginning of the 20th century and are of two types: metalled (hard-surfaced) and unmetalled roads.
Ordre totalEn mathématiques, on appelle relation d'ordre total sur un ensemble E toute relation d'ordre ≤ pour laquelle deux éléments de E sont toujours comparables, c'est-à-dire que On dit alors que E est totalement ordonné par ≤. Une relation binaire ≤ sur un ensemble E est un ordre total si (pour tous éléments x, y et z de E) : x ≤ x (réflexivité) ; si x ≤ y et y ≤ x, alors x = y (antisymétrie) ; si x ≤ y et y ≤ z, alors x ≤ z (transitivité) ; x ≤ y ou y ≤ x (totalité). Les trois premières propriétés sont celles faisant de ≤ une relation d'ordre.
Ordre lexicographiqueEn mathématiques, un ordre lexicographique est un ordre que l'on définit sur les suites finies d'éléments d'un ensemble ordonné (ou, de façon équivalente, les mots construits sur un ensemble ordonné). Sa définition est une généralisation de l'ordre du dictionnaire : l'ensemble ordonné est l'alphabet, les mots sont bien des suites finies de lettres de l'alphabet. La principale propriété de l'ordre lexicographique est de conserver la totalité de l'ordre initial.
Structural loadA structural load or structural action is a force, deformation, or acceleration applied to structural elements. A load causes stress, deformation, and displacement in a structure. Structural analysis, a discipline in engineering, analyzes the effects of loads on structures and structural elements. Excess load may cause structural failure, so this should be considered and controlled during the design of a structure. Particular mechanical structures—such as aircraft, satellites, rockets, space stations, ships, and submarines—are subject to their own particular structural loads and actions.
Order isomorphismIn the mathematical field of order theory, an order isomorphism is a special kind of monotone function that constitutes a suitable notion of isomorphism for partially ordered sets (posets). Whenever two posets are order isomorphic, they can be considered to be "essentially the same" in the sense that either of the orders can be obtained from the other just by renaming of elements. Two strictly weaker notions that relate to order isomorphisms are order embeddings and Galois connections.
Sensibilité climatiquevignette|redresse=1.5|Diagramme des facteurs qui déterminent la sensibilité du climat. L'augmentation des niveaux de entraîne un réchauffement initial. Ce réchauffement est amplifié par l'effet net des rétroactions. Parmi les rétroactions qui se renforcent d'elles-mêmes, on peut citer la fonte des glaces qui réfléchissent la lumière du soleil et l'augmentation de l'évaporation, qui accroît la quantité moyenne de vapeur d'eau dans l'atmosphère, laquelle est un gaz à effet de serre.
Environmental issuesEnvironmental issues are disruptions in the usual function of ecosystems. Further, these issues can be caused by humans (human impact on the environment) or they can be natural. These issues are considered serious when the ecosystem cannot recover in the present situation, and catastrophic if the ecosystem is projected to certainly collapse. Environmental protection is the practice of protecting the natural environment on the individual, organizational or governmental levels, for the benefit of both the environment and humans.
Ligne de partage des eauxLa ligne de partage des eaux est une limite géographique qui divise hydrographiquement en plusieurs bassins versants. Plus précisément, de chaque côté de cette ligne, les eaux de pluie s’écoulent vers des exutoires différents. Le plus souvent, cette ligne, longue et sinueuse, correspond à une ligne de crêtes topographiques parcourant des hauteurs composées de montagnes, de collines, voire de simples ondulations de terrain.
StructureA structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as biological organisms, minerals and chemicals. Abstract structures include data structures in computer science and musical form. Types of structure include a hierarchy (a cascade of one-to-many relationships), a network featuring many-to-many links, or a lattice featuring connections between components that are neighbors in space.
