Applied Mechanics and Materials Vols. 66-68

Abstract: This paper investigates characteristics of heat transfer in Fe micrometer and nanometer powder. The understanding for thermal properties of the powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. Nanosized particles possess characteristic physical and chemical properties different from those of bulk materials due to the confinement of electrons, excitons, and photons into small volumes. Therefore it is valuable to discuss the thermal behaviours of powders constituted by nanometer-sized particles. The powder is wrapped up in the slender tube. One end of the slender tube filled with powder is connected to the low constant-temperature reservoir and the other end is kept at room temperature. The temperature histories at the 1cm location of the slender tube from the low constant-temperature reservoir are recorded using thermalcouples. Powders of particles with the diameter sizes 20nm and 5000nm are employed in this experiment. The results show that the thermal diffusion in the 20nm Fe powder is faster than that in the 5000nm Fe powder.

Abstract: This paper elaborates on the development of elastic combined packing and an integrated device for treating domestic sewage aboard ships, analyzes the growth of combined packing microorganisms, the speed of membrane forming as well as the impact of raw water quality on membrane forming, and conducts a simulation experiment of treating domestic sewage by membrane bio-reactors. Researches show that elastic combined packing features high specific surface area and high speed of membrane forming and that this integrated domestic sewage treatment device performs well and can be widely applied.

Abstract: The compressed air vibration in air slide table of ultra precision machines is an obstacle for gaining Nano-metric level of accuracies in the products created by these machines. In this article, the vibration behavior of air slide table due to compressed air layer is analyzed. The air slide table fluid and dynamic analytical model has been derived. In order to have air exit velocity from clearance gap, the finite element software FLUENT was applied. Finally, in order to calculate the displacements of table due to vibration and drawing its curves via time at the presence of varieties of air pressure, the second order differential equation was solved by MATLAB. In solving differential equation the Rang-Kutta method was used.

Abstract: Starting from the establishment of generalized predictive model based on neural network, LM optimization algorithm is applied to the perdictive control model for study in order to solve these problems that the training speed of the BP network is slow and it is easy to trap into the local minimum.Generalized predictive control and neural network which has the capability of approaching any nonlinear function are combined to forecast the future outputs of the system.LM algorithm is used instead of gradient descent method to optimize controller parameters and it makes full use of Jacobian matrix information identified by neural network.The result of Matlab simulation indicates that the neural network using LM algorithm has the feature of fast convergence rate,model of high precision and good robustness,which is more suitable for real-time nonlinear control.

Abstract: Permanent magnet synchronous generator (PMSG) are commonly used in direct-drive wind power generation systems, which produce high efficiency, high reliability and low cost in wind power generation. This paper presents a new and simple control scheme using predictive control, which is used in PMSGs and grid-connected inverters. The controller uses the models of PMSGs and grid-connected inverters to predict on each sampling interval. A cost function defines the desired behavior of the system. The switching state that minimizes the cost function is selected and applied during the next sampling interval. At any wind speed within the operating range, the PMSG rotor speed can optimally controlled to extract maximum wind power. The simulated results show that the proposed control scheme can provide the direct-drive wind power generation system with the maximum efficiency and high dynamic performance.

Abstract: The technique to suppress regenerative chatter is to regulate the spindle speed around the mean speed to disturb the regenerative mechanism. According to the technique, it builds a platform to collect, process the machine working information and output control instruction. On the platform, some advanced algorithms are applied to analyze and finish the control task.

Abstract: The system goal is fixed as the choice and optimization of passenger travel-transfer station. Then the inquire method of all kinds of travel schedules is proposed and Railway Passenger Travel Aided Decision System(RPTADS) is developed with WEBGIS. The aim of the system is to provide the query result to passengers, and the optimal route will be displayed on the map intuitively, which make the synchronous connection reality between the text inquiry result and the map specific display. In addition, the timetable database of railway passenger transportation could be renewed timely by background decision software according to line conditions.

Abstract: This paper designs a dual topological structure of grid-connected inverter for high-power wind turbine, and introduces PWM converter's operational state. It establishes mathematical model of grid-side converter for wind turbine, then it puts forward the dual closed-loop vector control strategy of grid-side converter based on dq coordinate. The combination of the dual topological structure and decoupling control realize the functioning of high-power factor and two-way transmission of energy. Grid-side converter can stabilize DC side voltage during rapidly changed wind velocity which led to changes of output power in generator. Active or reactive output current can be adjusted independently. The hardware experiments and simulation results verify the feasibility of the proposed control scheme in both the high stability accuracy and excellent property of grid-connected.

Abstract: Thispaperdealswithcomparisonsoffiniteelementmodelsofadhesivelybondedjoints. Inordertoincreasetheaccuracyoftheresults,fivelayersofsolidelementswereusedacrossthe adhesivelayerwhichwasonly0.05mminthickness.Thefiniteelementswererefinedgraduallyin steps from adherends to adhesive layer. In these models, most regions of the adherends and adhesiveweremodelledusingsolidbrickelementsbutsomesolidtriangularprismelementswere usedforasmoothtransition.Insomeofthemodels,linearinterpolationelementsoffullorreduced integrationandofhybridformulationwereused.Inothermodels,quadraticinterpolationelements of full or reduced integration and of hybrid formulation were used. Comparisons are performed betweenmodelswithdifferentmodellingapproachinordertofindasuitablemodeltopredictthe mechanicalbehaviourofadhesivelybondedjoints.

Abstract: Tribometer is an instrument that offers precise and repeatable wear/friction measurement of a surface. The coefficient of friction is a dimensionless scalar value which describes the ratio of the force of friction between two bodies. It is an empirical measurement; it has to be measured experimentally, and cannot be found through calculations. This tribometer measures coefficient of friction between any two materials in dry test scenario using flat bed approach; moreover it measures both kinetic and dynamic coefficient of friction. As emphasized in the title it is first of its kind being fabricated in Pakistan, which is a huge achievement considering the fact that not much research work is being done in this field in Pakistan. This tribometer is designed to prioritize accuracy and manufacturing cost.