Papers by Keyword: Theory

Abstract: Near-field acoustic holography (NAH) is a powerful technique for identifying noise sources and visualizing acoustic field.The theory and algorithm of NAH techniques are introduced , and it is proved by experiment and simulation. The researches on near field acoustical holography (NAH) are reviewed，including the sound field separation technique and Patch NAH technique arisen in recent years.The difficulties in NAH and research on current situations are discussed , Finally,some engineering applications are introduced by detailed examples.

Abstract: There is a confused and contradictory literature on the role of small concentrationsof niobium on the development of the so-called local brittle zones in steels. These zones consistof a mixture of martensite and austenite and hence, their formation should be predictable usingmodern microstructure calculation methods. Following an assessment of the most relevant literature,a mathematical model is presented which enables three quantities to be calculated, the fractionof martensite, the carbon concentration of the martensite, and its ability to influence toughness.Examples are presented for particular linepipe steels, and then the generic effect of alloying elementsother than niobium, on the development of local zones.

Abstract: When the depth-sensing (nano)indentation is applied to sintered samples, measured properties, which are expected to represent the material of an individual grain, seem to depend on the overall porosity of the macroscopic sample. To understand such a result, it is assumed that while the nanoindenter penetrates into the surface grain and probes the properties of its material, the grain itself serves as another, larger indenter indenting the rest of sample and probing the properties that represent the bulk of material rather than individual grains. Load vs. displacement curve reflects the synergetic response of these two “indenters” and so it contains information about the sample’s mechanical properties at both microscopic and macroscopic scales. Obtained theoretical results agree qualitatively with the experimental data (the dependence of the indentation modulus on the porosity of sample; the indentation size effect).

Abstract: Diffusion filtration combustion attains widely attention as its small volume, compact structure, large power range and less emissions which is very important for saving energy in recent years. It is the combustion that fuel and oxidant are separated before burning in porous media. The researches about diffusion filtration combustion are summarized the theory, experiment and numerical simulation in this paper. There is still much knowledge unknown which should be worked on.

Abstract: Rough set theory has found an increasingly wide utilization since it was promoted in 1980s.And study on the application of rough set theory in every field has a great development in recent years. Application of rough set theory in attribute reduction, continuous attributes discretization, and uncertainty measuring, as well as application of information entropy in rough set theory are reviewed in this paper. What we will do next is to probe further into the application of information entropy in rough set theory.

Abstract: It is important to study theoretical and practical significance on strategic environmental assessment of municipal waste management system. This paper analyzes the research situation of strategic environmental assessment in China and put forward the theoretical basis of strategic environmental assessment on municipal waste management system, including strategic theory, low-carbon theory, cyclic economy theory and sustainable development theory. In the theoretical views, strategic environmental assessment of municipal waste management policies, plans and programs system can be studied for a better and More sustainable management mode of household waste. At the same time, the article gives a research frame of strategic environmental assessment on municipal waste management system in China.

Abstract: The paper introduces the importance of stability and current reseach status on prestressed concrete cable-beam structure system.It demonstrates the basic relative theory on stability in concretely research and applies this theory into the prestressed concrete cable-beam structure system,the formula of stability on this system is come true to make the analyze prestressed concrete cable-beam structure system precisely.

Abstract: The author carefully analyzed the theoretical basis and means with reading articles and books about the quantitative forecast for mineral resources evaluation.And completely summarizes the new theoretical frontiers, such as metallogenic series, metallogenic system, the origin of the model and so on, as well as about the methodology, gis, geochemical blocks and so on.

Abstract: The development of rail transit and the construction above subway station (CASS) will have profound influence on city. This paper tries to take Tianjin’s practical situation into consideration, and after analyzing the theories and CASS in and abroad, attempts to find objective law between rail transit and urban development in Tianjin from the interaction of M1 (Metro 1 of Tianjin subway system) construction and urban development. Base on the existing problems and experience, this paper puts forward the methods of exploitation above subway station and the qualitative indicators. Then take an under construction station’s exploitation as an example, raising qualitative principles and quantitative indicators to the site construction nearby. By doing this, aim at leading the future CASS and realizing the harmonious interaction between the development of urban rail transit and land use above it.

Abstract: Optical tools such as infra-red absorption, photoluminescence, or Raman spectroscopy have been used for decades to observe the localized vibrational modes associated with impurities in semiconductors. The frequencies of these modes slightly shift with the isotope of the impurity while host-atom isotopes often show up as shoulders in the spectra. These shifts and shoulders are precious indicators of the nature of the defect. But sometimes, very small isotope-related frequency shifts cause very large changes in vibrational lifetimes. Impurity-isotope effects have now been predicted to impact the thermal conductivity of semiconductors containing a few atomic percent of impurities. Impurity isotope effects can be surprisingly large.