Papers by Keyword: Theory

Abstract: The technique and results of experimental studies of creep deformations of compressed elements made of foam concrete at constant compressive stresses in the 0.15-0.75 range of R_b are presented. The nature of the relationship between stresses and the corresponding deformations, the degree of reversibility of creep deformations during unloading of samples and the tendency of concrete to aging have been established. From the standpoint of the hereditary theory of aging, analytical expressions have been selected to approximate the curves of specific creep deformations depending on the average density of foam concrete and the magnitude of compression stresses. The largest deviations of the specific creep deformations of foam concrete between theoretical and experimental values are 11.4%, and the standard deviations for the entire observation period are 2.0%

Abstract: A novel study of interdiffusion analysis in multicomponent alloys is presented. A custom written Matlab fitting program (MFP) is used as the main tool for the present study. The interdiffusion matrices are obtained using a newly developed mathematical approach based on the fitting into the closed form solution for the composition profiles. Overall, the new fitting method gives very good outcomes and allows the probing of multiple solutions (validated by back tests) that exist when a single diffusion couple is used in a multicomponent system. An important finding of the present investigations is that small differences in composition profiles may lead to large differences in the interdiffusion coefficients.

Abstract: A novel study of analysis interdiffusion in multicomponent alloys is investigated by means of closed form solutions and numerical simulations. Quaternary as well as selected CoCrFeMnNi (HEAs) quinary metallic systems are analysed using one, two and three diffusion couples with the full set of interdiffusion coefficients being calculated. A custom written Matlab fitting program (MFP) is used as the main tool for the simultaneous fitting into multiple composition profiles in both systems. The retrieved interdiffusion matrices are obtained using a newly developed approach that is interlinked with composition vectors, eigenvalues and eigenvector. On average, it can be concluded that the accuracy of the obtained matrices steadily improves with the increase of the number of couples used in the analysis.

Abstract: Elastic fields, generating by defects of the structure, influence the diffusion processes. It leads to the alteration of the phase transformation kinetic. One of the chief aims of our work is to obtain general equations for the diffusion fluxes under strain that give the possibility for using these equations at low temperatures, as in this case the strain influence on the diffusion fluxes is manifested in maximal degree. Our approach takes into consideration, that the strains can alter the surrounding atom configuration near the jumping one and consequently the local magnitude of the activation barrier and a rate of atom jump. The rates of atom jumps in different directions define the flux density of the vacancies. Now we take into account, that strain values are different in the saddle point and in the rest atom position, in differ from our consideration that was done by us earlier. As a result in the development of our approach the general equations for the vacancy fluxes are obtained for fcc and bcc metals. In our paper we discuss the main features of the theory of diffusion under stress and its applications. In particular we examine how elastic stress, arising from nanovoids, influence the diffusion vacancy fluxes and the growth rate of voids in metals.

Abstract: A theory for mathematical framework is developed with axioms for fatigue damage, quantification and relativity concept, boundary conditions, and compatibility, allowing us to evaluate the validity of candidate damage equations/quantities on S-N plane for prediction of fatigue life. Manifestation points for accumulated damage were defined for boundary conditions by differentiating between damage accumulated before failure, and failure caused by damage at quantised fatigue loading cycles. A selected damage equation leading to a theoretical S-N curve was validated as an example.

Abstract: Based on the full understanding of the current status of the reactive power optimization study, we propose an improved type of immune algorithm to solve the reactive power optimization problem by introducing the immune clonal selection algorithm (ICSA) genetic manipulation, affinity of mature, cloning and memory mechanism, and use the appropriate operator to ensure that the algorithm can quickly converge to the global optimal solution to improve the efficiency of the algorithm solving and solution accuracy, avoiding the "curse of dimensionality" and precocious problems. ICSA algorithm is proposed to improve the convergence speed simultaneously. Better maintain the diversity of the population. Effectively overcome the premature convergence of evolutionary computation itself is difficult to solve the problem. Four different examples of calculation results show that this method has superior computational efficiency and convergence capability, high quality and are solved, very suitable for solving large-scale power system reactive power optimization problem, with a strong practical value.

Abstract: Materials testing technology is the summary of the experience in the long-term practice of material testing process. However, it is so serious that the theoretical teaching is divorced from experimental teaching. In order to improve the teaching quality, the reason of the problem are analyzed, and the following solutions are proposed, such as refining and reforming the contents of theory teaching, focusing on its application in practice and experiment, timely updating knowledge of testing software applications, employing modern technical means for assist theory teaching, attaching great importance to experiment teaching, and arising the students' learning interests through the use of comprehensive experiments week, and so on.

Abstract: The graduation design of engineering course is an important practice teaching link of the preliminary scientific research trained for students in university, and is also an effective way of high-quality innovative applied talents. In accordance with the requirements of materials science and engineering course, the undergraduate graduation design of the materials professional is implemented. The professional theoretical knowledge applied to practical production and the studies of material properties are emphasized, and combined with scientific research. The students' initiative and creativity is stimulated, and their comprehensive quality is improved by adopting the heuristic teaching. Through a series of graduation design practice, the best way of thinking summed up is that the students' ability is cultivated by the teachers' scientific research project combination of actual production plan of the enterprise for adapting to the needs of society at present.

Abstract: Architectural engineering, also known as building engineering, is the application of engineering principles and technology to building design and construction. Definitions of an architectural engineer may refer to an engineer in the structural, mechanical, electrical, construction or other engineering fields of building design and construction; a licensed engineering professional in parts of the United States; in informal contexts, and formally in some places, a professional synonymous with or similar to an architect. Structural engineering involves the analysis and design of physical objects (buildings, bridges, equipment supports, towers and walls). Those concentrating on buildings are responsible for the structural performance of a large part of the built environment and are, sometimes, informally referred to as “building engineers”.

Abstract: This paper in view of the northern city produce large amounts of carbon dioxide in winter for heating and cause increasingly serious air pollution when burns coal, puts forward supply theory of combined heat and power (CHP) systems to provide housing and shops daily hot water supply, electricity, heating, cooling energy and designed a validation to test process and verify the formula of Combined Heat and Power systems , traditional heating system and air conditioning system in carbon dioxide discharge. Demonstrate the theory basis and validation method for using new type of heating mode when heating season in north.