.
Fig.3. Surface finisher
1- side stop-боковой ограничитель
2- bin-бункер (расходного запаса материала)
Road construction. In modern road construction, there is much greater recognition of the importance of the subsoil beneath a road. It is regarded as an integral part of the road. In case of mechanical stabilization granular or cohesive materials are added to the subsoil
Fig.4. Typical cross-section of a bituminous road
1- grass verge-обочина (травяная обочина) дороги
2- crossfall-поперечный уклон
3- asphalt surface (bituminous layer, bituminous coating)
4- base-щснова, основная (базовая) подложка
5- gravel sub-base course (hardcore sub-base course, Telford base),
an anti-frost layer-подложка гравия, морозостойкая подложка
6- sub-drainage-дренажный подслой (дренаж)
7- perforated cement pipe-перфорированная цементная труба
8- drainage ditch-дренажный сток (канава)
9- soil covering-грунтовое покрытие (насыпной грунт)
Fig.5. Three-wheeled rolled, a road roller
1- roller-каток, 2- all-weather roof – всепогодная
Nanotechnology
Nanotechnology is a field of applied science and technology covering a broad range of topics. The main unifying theme is the control of matter on a scale smaller than 1 micrometre, normally between 1-100 nanometers, as well as the fabrication of devices on this same length scale. It is a highly multidisciplinary field, drawing from fields such as colloidal science, device physics, and supramolecular chemistry.
Much speculation exists as to what new science and technology might result from these lines of research. Some view nanotechnology as a marketing term that describes pre-existing lines of research applied to the sub-micron size scale.
Nanotechnology could variously be seen as an extension of existing sciences into the nanoscale, or as recasting of existing sciences using a newer, more modern term. Two main approaches are used in nanotechnology: one is a "bottom-up" approach where materials and devices are built from molecular components which assemble themselves chemically using principles of molecular recognition; the other being a «top-down» approach where nano-objects are constructed from larger entities without atomic-level control.
The first distinguishing concepts in nanotechnology were made by physicist Richard Feynman at an American Physical Society meeting at Caltech in 1959. Feynman described a process by which the ability to manipulate individual atoms and molecules might be developed, using one set of precise tools to build and operate another proportionally smaller set, and so on down to the needed scale.
The term "nanotechnology" was defined by Tokyo Science University Professor Norio Taniguchi in a 1974 paper as follows: "Nanotechnology" mainly consists of the processing, separation, consolidation, and deformation, of materials by one atom or by one molecule. » In the 1980s the basic idea of this definition was explored in much more depth by Dr. K. Eric Drexler, who promoted the technological significance of nano-scale phenomena.
Nanotechnology and nanoscience got started in the early 1980s with two major developments: the birth of cluster science and the invention of the scanning tunneling microscope (STM). This development led to the discovery of fullerenes in 1986 and carbon nanotubes a few years later. In another development, the synthesis and properties of semiconductor nanocrystals were studied. This led to a fast increasing number of metal oxide nanoparticles of quantum dots. 1
A unique aspect of nanotechnology is the vastly increased ratio of surface area to volume present in many nanoscale materials, which opens new possibilities in surface-based science, such as catalysis. A number of physical phenomena become noticeably pronounced as the size of the system decreases. These include statistical mechanical effects, as well as quantum mechanical effects, for example the "quantum size effect" where the electronic properties of solids are altered with great reductions in particle size. This effect does not come into play by going from macro to micro dimensions. •
However, it becomes dominant when the nanometer size range is reached. Additionally, a number of physical properties change when compared to macroscopic systems. One example is the increase in surface area to volume of materials. This catalytic activity also opens potential risks in their interaction with biomaterials.
Materials reduced to the nanoscale can suddenly show very different properties compared to what they exhibit on a macroscale, enabling unique applications. For instance, opaque substances become transparent (copper); inert materials become catalysts (platinum); stable materials turn combustible (aluminum); solids turn into liquids at room temperature (gold); insulators become conductors (silicon). A material such as gold, which is chemically inert at normal scales, can serve as a potent chemical catalyst at nanoscales.
Much of the fascination with nanotechnology stems from these unique quantum and surface phenomena that matter exhibits at the nanoscale. Molecular nanotechnology, sometimes called molecular manufacturing, is a term given to the concept of engineered nanosystems (nanoscale machines) operating on the molecular scale. It is especially associated with the concept of a molecular assembler, a machine that can produce a desired structure or device atom-by-atom using the principles of mechanosynthesis.
Manufacturing in the context of productive nanosystems is not related to, and should be clearly distinguished from, the conventional technologies used to manufacture nanomaterials such as carbon nanotubes and nanoparticles.
As nanotechnology is a very broad term, there are many disparate but sometimes overlapping subfields that could fall under its umbrella. Note that these are fairly nebulous and a single subfield may overlap many of them, especially as the field of nanotechnology continues to mature.