Papers by Keyword: Calculation

Abstract: In this paper, we studied the electronic density of states (DOS) and optical properties ZnO using first-principles method. We find that the electronic density of states was different in bulk ZnO and ZnO nanotube. The DOS of bulk ZnO spread at wide energy while the DOS of ZnO nanotube concentrated in a narrow energy range. The peak around-18 eV moved to a higher energy. The peaks more than Fermi level concentrated to the Fermi level, which meant the conductivity of ZnO nanotube was better than that of bulk ZnO. We also calculated the optical properties of ZnO nanotube. The optical properties showed that there were peaks around 8 eV, which may come from electrons transition between Zn 3d and O 2p states. Our calculation provided a reference for the application of ZnO nanotube in optical devices.

Abstract: This paper is devoted to the comparison of theoretically defined solidus and liquidus temperatures based on above mentioned theoretical methods with the results of high-temperature thermal analysis carried out on two devices (Netzsch STA 449 F3 Jupiter; Setaram SETSYS 18_TM). On large samples (23 g), the method of direct thermal analysis was applied. On small samples (200 mg), the experiments using differential thermal analysis were realized. It was found out that the solidus and liquidus temperatures for the studied steel grade can vary in dependence on the used determination method. The used methodology of thermal analysis is fully reproducible, and the these thermo-analytical results can be considered as necessary for the correct setting of critical parameters in applied research on the process of steel casting.

Abstract: The flow pattern is unique in a certain range of pore size divided by the Knudsen number. In order to characterize permeability of nanopore in shale gas reservoir more accurately, the formulas of nanopore permeability are put forward considering the influence of adsorption gas and flow patterns. After the calculated results were compared and analyzed, the conclusions are obtained as follows: (1) Pore size is the main factor to determine the flow pattern; (2) There are three main flow pattern in the nanopore of Longmaxi formation shale reservoirs, slip flow, Fick diffusion and transition diffusion, meanwhile Darcy percolation and Knudsen diffusion do not exist; (3) Flow pattern has great influence on apparent permeability and adsorption has a greater impact in a high pressure condition (greater than 20MPa).

Abstract: Based on introducing engineering background and characteristics of river, the Yellow River in lanzhou section of the hydrological and sediment characteristics and characteristics of riverbed evolution are analyzed. On this basis, determine the once-in-a-century flow, and calculate the once-in-a-century flow when the bridge was analyzed and local scour of general erosion depth, scope of backwater height, etc.On the bridge of the embedment depth, clearance under the bridge, such as the check, and the bridge construction impact on the stability of river regime is analyzed.

Abstract: It is noticed that introduction of frequency convertors has an adverse effect on the reliability indexes of the critical equipment of the thermal power station. The paper considers the method for calculation reliability based on the logical-and-probabilistic method with the following expert estimation of the entity technical state. Examples of the developed structural models of the power station’s reliability and its separate units as fault trees are provided. Based on the results of expert evaluation of the equipment fault occurrence intervals before and after introduction of the frequency convertors, average times to failure have been calculated. The paper also gives recommendations for providing reliability of the essential auxiliaries’ electric drives at the introduction of the frequency convertors.

Abstract: Live working (LW) is performed to provide high reliability of transmission lines (TL). Only “bare hand” method of LW is used at voltage systems more than 200 kV. Live working (LW) is possible if the minimum approaching distances are in working place. This requirement provides the safety of LW excluding flashover of insulating gaps under the switching overvoltage impact. In some cases it is impossible to provide the required gaps in LW zone. In order to protect it against possible flashover, special arresters were designed. Their effect on overvoltage magnitude was checked in calculations.

Abstract: The multipoint steam injection string of the horizontal well is a commonly used downhole component for high efficiency steam injection of the thermal recovery horizontal well. A reasonable layout of the valves to ensure an even steam output of each point is still not well designed. At present, a general design method which is urgently necessary isn’t applied by each factory. According to the balance relationship of the momentum, the energy and the mass of the fluid flowing in the string, the pressure distribution equation of the fluid flowing in the multipoint steam injection string is built. On the basis of this equation, the design calculation method of the multipoint steam injection string is come up with. A specific example is given in the paper. Study shows that, with the equation built in this paper, the string can be designed with each axial valve having the same output, so that the technical demand of an even steam injection of the horizontal well section can be met.

Abstract: Modulus of elasticity of steel wire rope (elastic modulus) is a characteristic value, which is important not only for users of the steel rope, but also for designers of machines and machinery that are equipped with the steel wire rope. Values of the elastic modulus depends predominately on the elastic modulus of the material, which the rope is manufactured from as well as it depends on the various other factors. The most important influencing factors are as follows: rope construction, type of core, angle and way of wire stranding, angle and way of rope lay as well as kind of lubricant. The real value of the elastic modulus has also impact on prolongation of the steel wire rope and on intensity of its dynamical loading. The rope elastic modulus value can be determined by means of the various methods. There are analysed in this article such methods for determination of the rope elastic modulus, which can be applied for a computer simulation.

Abstract: Screw conveyors are continuously operating transport mechanisms designated for conveying bulk materials that involve the use of a spiral screw rotating inside a stable trough moving the material along the trough. They are used for specific needs of transportation of bulk materials for shorter distances with lower transportation performance. These are conveyors without traction components. The present paper is concerned with the use of screw conveyors in practice and the risks associated with their operation.

Abstract: Each object has its own specific properties, objects can be uniquely identified by its properties. "Properties" are properties of all the main features of the concept only, property values ​​are often given a certain amount of semantics, in the calculation of similarity among the different attributes if only to consider the type of calculation is obviously not complete [1]. For example: blue and blue, the similarity calculation in the property type, we can not determine its degree of similarity, but it is the same type of semantic expression under the different languages. Another example: domperidone and domperidone, which is the same type of drugs. Therefore, we attribute value in the calculation of the time, but also taking into account the semantic similarity.