Search

The turbulent convective heat transfer in a transversely grooved tube of molten salt with natural convection effect has been numerically investigated. In general, the average Nusselt number with and without considering natural convection in transversely grooved tube was almost equal. According to the simulated results, the heat transfer coefficient of transversely grooved tube in upside region was lower than that of downside region. The effect of natural convection on unilateral heat transfer in transversely grooved tube was more obvious with lower Reynolds number and higher inlet temperature, and the effect of natural convection on unilateral heat transfer was lower with bigger groove deep.

Experiments of high-efficiently compound machining (CM) combined by EDM and arc machining of AISI 321 stainless steel at 658mm3/min material removal rate (MRR) using solid electrodes of different materials and different diameters of less than 5mm were conducted. The CM process parameters, including electrode rotation speed, peak current, electrode materials and electrode diameter, were studied to evaluate the effect on MRR, relative electrode wear rate (REWR) and width of overcut (WOC). The re-solidified layer of 321 for CM was also investigated. Faster electrode rotation speed, higher peak current, larger electrode diameter and pure tungsten electrode material are essential to achieve lower REWR and higher MRR. The processing conditions were bad using electrode diameter of 2mm. The re-solidified materials are significantly more densely than base materials.

Aiming at the lack of standard design method and the shortcomings of main functions of the existing drive circuit, a “Element-level Design under Transmission Voltage Switch Theory” is set forth and a smallest circuit structure namely as drive-unit, which contains Superstratum-unit, Substratum-unit and LC-unit, is designed in this paper to achieve the necessary functions. The drive circuit of n×n ignition bridges has been got from the structure expansion formula along with the expected life estimation. The Ebers-Moll Model of transistor and the internal circuit of MOSFET were used to make a theoretical analysis and the conclusion of such analysis was verified by simulation subsequently. Actual measurement has been made and the results show that the circuit in simple structure has provided a strong loading ability and accurate output; some elements of the circuit have been heated when the circuit was working; and the response time of the circuit was of the microsecond-level.

Kind of self-insulation walls which combined silt sintered porous brick with reflective insulation coating to local conditions are introduced in this paper. It not only can reach the effect of composite insulation, but also can eliminate fire safety hidden danger of the self-insulation wall. Exterior wall of the summer and winter thermal performance were analyzed, Through its feasibility experiments and is worth a certain region to promote.

In the downstream of Yangtze River where there is abundant silt resources, perforated brick which fired by sludge, supplemented by reflective insulation coating to replace the widely used polystyrene insulation materials. It can achieve requirement of A-class fire prevention for heat preservation wall. The heat insulation performance of not painted thermal wall and composite thermal insulation wall painted by reflective insulation coating were compared. Data results show that heat insulation performance of the wall painted is much better than that of the not painted wall.

Cold recycle mixture with emulsified asphalt is a material which is economical, environmental and energy saving. Now it is widely applied to road recycling engineering, while there is no unified standard for its molding and curing methods. The orthogonal test shows that cold recycle mix with emulsified asphalt can get the better technical indicators after the molding and curing methods. At first, each side 50 times compaction after mixture putting into mold. Then put specimen side in the 60°C wind drying oven at least 40 hours. Next take the specimen out and compact each side 25 times immediately. Finally put specimen side on the ground at least 12 hours at room temperature, and then take the test-piece from the mold for test.

Soil mechanics has been developed for a long time and its concept system is basically complete. But there are still some concepts not being defined clearly. The unclear concepts of seepage force are stated from three phenomenological characteristics aspects in this paper. The difference between loaded object and calculated range is cleared. The contact rule of solid phase and liquid phase is illustrated. The mathematical meaning of seepage force is clarified. Though judging the critical hydraulic gradient of soil flow on surface of cohesionless soil, the difference and correlation of the soil particle and clod analysis based on the phenomenological characteristics will be illustrated.

The paper studies that temperature and different interlayer contact conditions between ultra-thin wearing course and original pavement have an impact on interlayer shear stress. Calculate parameters of each layer asphalt mixture materials under different temperature through empirical formula. Substitute the parameters into BISAR3.0 software to calculate maximum interlayer shearing stress of ultra-thin wearing course under different temperature and interlayer contact conditions. The results show that interlayer contact conditions and temperature have a great influence on interlayer shearing stress of ultra-thin wearing course.

With the continuous development of network applications, the new network structure emerging. To solve the interconnection of heterogeneous computer networks is essential, real-time network traffic is the current focus of the study of computer network. Articles focus on these two aspects of the problem and put forward a thought of heterogeneous network with the structure, in the network-level and application-level implementation of a heterogeneous network interfaces isomorphism. We discusses the implementation of real-time communication network principle and method based on the client / server model, gives a heterogeneous network to solve the problem of real-time communication process model, programs and implementation framework.

Based on collecting the regional survey data and prospecting the study region of geothermal geology and geothermal fluid characteristics, evaluate the geothermal energy reserves and the recoverable reserves of geothermal water uses geothermal reserve method and analytical method in Julang Pasture, and evaluates the geothermal fluid quality comprehensively. The above evaluation provides a preliminary basis for sustainable development, utilization and protection of geothermal resources in that region.

Trust problem is a key issue for Mobile P2P (MP2P) network security. In MP2P network, terminals addressing mode, communication way and display identifier are different to traditional P2P network. Some security issues such as: malicious slander and collusion, free ride phenomenon, are even more serious compared to traditional P2P network. Aimed at these above issues, a Proxy-based Security-Feedback Trust Model (PSTM) is proposed. Different types of terminals access to different proxy servers to shield the discrepancy between different terminal equipments on MP2P equipment access network layer. Meanwhile, proxy servers can reduce the problem of single point failure with method of trust related tables backup and recovery. Certificate Feedback Raters identification and qualification through security resource-selection protocol then integrate trust information according to similarity of terminal and resource types with weight. Furthermore, set global contribution value and evaluation value in multi-granularity trust computation to motivate mobile peers honest feedbacks. Divide mobile peers direct trust value into peer-oriented and resource-oriented values to make trust feedbacks more authentic. Simulation experiments show that PSTM can reduce malicious slander and collusion effectively. It also can restrain self-ish peers free ride behaviors and increase successful cooperation rate of high-contributed nodes in MP2P network.

According to the requirement for variable-frequency power supply when a liner motor runs in a household appliance, a variable frequency speed regulation system of three-phase SPWM is designed based on ATmega48 Micro-controller. The hardware structure, the SPWM technology of software program and V/f control strategy are analyzed. In the end of this paper, experiment waves are illustrated. The results show that the running of the system is simple and convenient; the reliability of the system is excellent.

Asphalt mixing plant cold recycled materials as the layer below has been widely applied in recent years, It has better performance compared with other structural materials for the prevention and treatment of reflective cracking,for further analysis the stress conditions of the material as a grass-roots-bit suffered upper load transfer.In this paper, useing the ABAQUS software modeling analysis of three different structural pavement layers on top and bottom of the situation by force. The results show that the grassroots cold recycling layer structure has obvious characteristics of flexible it has better controlable to reflective cracking.

By adding Sasobit, DAT and BLT additives to reach the purpose of hot mix asphalt mixture construction temperature decreasing, achieve energy conservation and environmental protection. With an AC-13 SBS modified hot mix asphalt as reference, the high and low temperature performance and water stability of three energy-saving and environment-protecting road materials are evaluated through laboratory tests. The results show that compared with HMA, all the three kinds of energy-saving and environment-protecting road materials exhibited a significant increase by 8%-15% in high temperature stability. While the low temperature cracking resistance and anti-water damage performance of Sasobit mixture were decreased somewhat, little changes in these two aspects of the performance of the other two materials. Finally, analyses the economic benefits, and provide the basis for the choice of asphalt mixture cooling additives.

The theory of vacuum preloading was mainly focused on calculations of settlement and consolidation degree, but not on the bearing capacity improvement under vacuum preloading. Based on the Mohr-Coulombs failure criterion and elastic-plastic theory, the formula of bearing capacity improvement of vacuum preloading foundation was deduced under undrained condition. The consolidation and vacuum attenuation degree were taken into the consideration, and a calculation formula with fewer parameters by using CU total stress strength index was derived. Meanwhile the relation between bearing capacity and undrained shear strength was presented as well as that of bearing capacity and vertical effective stress increment.

As for implementing functions in slope online monitoring system by exploiting data acquired via GPS, good and high efficient stored procedures are essential. More importantly, a good designed stored procedure can simultaneously provide decision services for multiple users. By integrating the Client/Server and Browser/Server subsystems, this system explores a much convenient and automatic way to manages the mining area. 18 database tables are designed to support the database operation, such as the GPSSTATICRESULT table that storeds accurate static data and the STATIONINFO table that records all equipment information. Moreover, the design and implementation of stored procedures is analysed to flexibly support complicated system functions. The results indicate that system working with stored procedures has high performance on applications open-pit mine. The results not only confirmed the applicability and effectiveness of stored procedures, but also revealed system with stored procedures has advantages of conveniently managing mining data, timely sending real-time monitoring information, optimizing security of mine production and making auxiliary decision for enterprise.

In order to control the flow rate in a butterfly valve accurately, the moment, which acts on the rotation axis of valve plate, caused by flowing fluid must be considered. Taking air as the medium, the parameters of internal flow fields, such as the velocity and pressure, are simulated by CFD for a standard butterfly valve. The distribution of velocity and pressure fields that changes with various openings and a curve of aerodynamic moment are obtained. The results show that, as the opening of valve goes larger, the resultant moment on valve plate is monotonically increased. At the opening of 70°, the moment reaches its maximum. After the opening of 70° the moment begins monotonically decreasing and the resultant moment is close to zero at 90°.

In order to consider the influence of water pressure on cohesive soil slope with groundwater, the local and global water pressure methods are proposed. The equivalence and applicability of the two methods based on the simplified Bishop’s method are analyzed. The local water pressure method considers the water pressures on boundaries as components and the global water pressure method considers the water pressures as a resultant force. The physical analysis and numerical verification showed these two methods are completely equivalent. While the global water pressure method is more convenient in hydrostatic condition, the local water pressure method is prior in seepage condition. It is also pointed out that there are significant defects in some regular expressions of simplified Bishop’s method. Because they neglect the moment generated by water pressure on the top boundary of slope or wrongly evaluate of the hydrodynamic failure states with hydrostatic stress parameters.