Abstract:Based on present research status of quasicrystal, the classification with structural symmetry, the construction of quasi-periodic model and the correlation between quasicrystal and its approximants were introduced briefly. The preparation technology of bulk single grian quasicrystal, defect evolution during plastic deformation, surface structure, surface property and other physical properties were summarized. Theoretical research such as continuum mechanics, atomistic simulation, Monte Carlo simulation and Finite Element Method were also discussed. The application of quasicrystal was prospected according to its physical properties including low surface energy, low friction coefficient and wear rate, excellent dispersion strengthening, high hardness and Young's Modulus, plasticity at high temperature, high thermal resistance and corrosion resistance, etc. Current limitations such as brittleness and bulk volume were pointed out, and issues which remain to be solved for further engineering applications were listed.

Abstract:An adaptive active disturbance rejection control is proposed for flexible manipulators with uncertain payload. The two-time scale model of the multiple-flexible-link manipulator is derived via singular perturbation technique. For the fast subsystem, a linear quadratic regulator controller is designed. It depresses the oscillation of flexible links and drives the states to the slow manifold quickly. For the slow subsystem, an adaptive active disturbance rejection controller is proposed to track the desired angular position. A recursive least-squares algorithm is utilized to estimate the payload mass and compensate for the uncertainty. Simulation results show that the mean squire error is less than 0.08 rad even when the payload uncertainty up to 200% of the pre-estimation of the payload mass, which is superior to the case without compensation for the payload uncertain. Thus, the proposed control scheme guarantees a robust performance in presence of uncertain payload and under different maneuver speeds.

Abstract:According to the created robot theatre script, a big turtle robotic system was developed for performance at digital stage. This robot includes mechanics system and control system, and the mechanics system is composed of four 3-DOF modularized light weight legs a flexible neck with continuous curvature, a shell opening and closing device and a carbon fiber torso frame. All the mechanotronics devices, including motors, circuit board et al, are installed in the main body. Through the synchronous belt, the motion of the motor is transferred to the outer end, largely reducing the size and weight of the cantilever, then reducing the load of the motor. The control system consists of a PC and an embedded controller, respectively provides the functions of human-computer interaction at high level and the realtime control of each joint at low level. According to the requirement of performance at the stage, a COG self-adjusting gait planning method was presented, assuring the stability during the movement of multiple legs. Finally, the robotic prototype was developed which had beautiful appearance. After the verification based on certain experiments, the robot was used to conduct a number of public performances. The results showed that the developed robot perfectly played the role of the drama performance and provoked audience to love it.

Abstract:Studying the dynamic regulation of the landing impact forces and influence factors for landing impact is the basis of analysis of the dynamic stability of robots. Considering that the rubber mat in landing phase is in large deformation during the landing process of robot, the dynamic model and simulation model of the landing impact process that consists of the dynamic models of robot's leg and body, the viscoelastic model of rubber floor in large deformation and the thermodynamics model of gas in cylinder chambers are built. In addition, the simulation results show that the change of foundation elastic reaction and damping force in the compression phase makes impact force increase quickly, reach a maximum and then decrease, that the maximum impact increases as the falling height and the storage module of rubber increase, decreases as the thickness of the rubber increases, and that the larger ratio, the smaller maximum impact when the ratio of the dissipative energy scale factor to the vibration frequency is less than 0.01, and the larger ratio, the larger maximum impact when the ratio is more than 0.01. The maximum relative error of simulation results and experiment results of the robot for 0.1 m free fall is less than 7.6%, which verifies the simulation results.

Abstract:To investigate the influence of fluid characteristics on the polishing properties during sono-assisted polishing and analyze the affecting pattern of ultrasonic wave on the material removal rate(MRR)at the workpiece surface, for smooth polishing pad and pad with small holes, simulation models for ultrasonic vibration assisted polishing under different film-thickness are built and analyzed with FLUENT software. The influence of different process parameter on the value and distribution pattern of pressure, velocity and air phase are obtained. Simulation results show that the ultrasonic wave can cause strong shear flow and high pressure at the workpiece surface, and the shear flow and pressure grow stronger with the decrease of film thickness. Pores at the pad break the continuous fluid flow under workpiece, which makes velocity and pressure of fluid change abruptly and creates more ultrasonic cavitation, which increases the MRR.

Abstract:The conventional electro-hydraulic load simulator is subjected to motion disturbance of the tested equipment. To eliminate the disturbance, a novel friction electro-hydraulic loading system for testing actuators or servo drive systems is proposed to improve the accuracy of load simulation in the laboratory environment. The motion disturbance of the test equipment on conventional electro-hydraulic load simulator is analyzed. And an active electro hydraulic torque servo loading system based on friction loading is designed. According to the principle of loading, the mathematical model of the friction loading system is established. It shows that the friction loading scheme is not affected by motion of tested equipment. In view of the fact that there are many variable parameters in the actual process, especially time-varying and uncertain friction, simulations are made to analyze the loading performance of the friction electro-hydraulic loading system. Simulation results show that the conventional electro-hydraulic load simulator may be disturbed by motion of the tested equipment so greatly that Its loading performance is hard to be further promoted. Although the friction coefficient may be influenced by the relative motion, load pressure, temperature and other factors. the friction electro-hydraulic loading system can keep high precision torque simulation.

Abstract:A new type two-stage proportional electro-hydraulic regulator valve using piezoelectric ceramics is promoted to cancel the requirement of pressure sensor. The piezoelectric ceramics controls the openness of pilot valve. The pressure drops across the fixed damping hole in the pilot supplier, and the throttling orifice of the pilot valve change accordingly. Thus the output pressure of pilot stage is controlled by the piezoelectric actuator and it serves as the command pressure to the main stage. The detailed structure and working principle have been given, and mathematical models and simulation models have been established. The influences of structural parameters over static and dynamic performances have been studied by Simulink simulation. A tuning spring has been employed to extend the lower bound of output pressure to 0. A three-land main spool has been employed to reduce the flow force and increase the precision, which is verified by flow field analysis. Proper feedback damping hole has been chosen according to dynamic simulation to ensure dynamic performance of pressure reducing valve. The new type valve proved to be able to work as a pressure reducing vavle without empoying a pressure sensor, and it has good output pressure range, pressure precision and fast and steady dynamic response.

Abstract:The conventional finite element method is over-reliance on the mesh dimension, specifically, the mesh distortion is usually serious in the contact area of the abrasive particle and workpiece which makes it more difficult to simulate the formation process of internal cracks in brittle materials. To simulate the lapping process of fused silica optics, FE/SPH model of the machining process for a single abrasive particle was established. Then a new way to simulate the cutting process of brittle materials was provided. The formation process of subsurface crack and the influence of cutting parameters on subsurface damage depths were analyzed. Simulation results show that the brittle material is in the elastic-plastic deformation stage when abrasive particle is just beginning to cut into the workpiece, further amounts of microcracks arise under the extrusion and tear effects of the abrasive particle. The combination and extension of microcracks produced transverse and longitudinal cracks, which are parallel and perpendicular to the workpiece surface, respectively. Consequently, brittle-fracture removal of the workpiece material is completed.

Abstract:To reduce the energy loss of high-lift low pressure turbine (LPT) and improve the aerodynamic performance, numerical simulation method was used to study the effects of trailing edge shapes on the aerodynamic performance of high-lift LPT L2F cascades. The effects of three trailing edge shapes, deflected trailing edge, increasing trailing edge thickness and the Gurney flap on the energy loss and flow were studied. It is shown that the three trailing edge shapes all can increase flow turning angle, decrease energy loss coefficient at low Reynolds number (Re) and increase the energy loss at high Re, however the deflected trailing edge is more effective than the others to improve the aerodynamic performance of the LPT cascades. Deflected trailing edge decrease energy loss by 16.5% at Re of 20 000 and free-stream turbulence intensities (FSTI) of 3.3%. The three trailing edge shapes deflected the main flow, accelerate boundary layer flow on the suction side, and suppress the flow separation, which tend to decrease the energy loss. However the three trailing edge shapes enhance the mixing flow behind the trailing edge, which tend to increase the energy loss.

Abstract:To have good ignition performance of lean premixed swirling combustor (LPSC) at ultralow equivalence ratios, this paper researched experimentally the combustion characteristics of ignition processes for LPSC at the ultralow equivalence ratio conditions of 0.013~0.502 based on different conditions of ignition fuel ratio (F_n). The results indicate that, when F₂=10 %, F₃=15 % and F₄=20 %, LPSC can ignite successfully at the equivalence ratio intervals of 0.063-0.251, 0.042-0.377 and 0.05-0.502 respectively, and the minimum values of equivalence ratio for ignition process are respectively 0.063, 0.039 and 0.011 by the fitting calculations of experimental results, but LPSC fails to ignite at F₁=5 %. With decreasing equivalence ratio, the outlet temperature rise has a drop due to the increase of air massflow, which can lead to the rising of CH₄ and CO concentrations and the deceasing of combustion efficiency simultaneously. LPSC can ignite successfully at relatively low equivalence ratio for high F_n, but in which combustion efficiency deceases and pollutant emissions rise because of too much air massflow. Thus, keeping a certain massflow of ignition fuel is beneficial for high-efficiency and rapid startup of LPSC at ultralow equivalence ratio.

Abstract:AAEM species, such as inorganic and organic states, are distributed in the pyrolysis biochar, which affect the reactivity of biochar. The speciation of AAEM species in biochar was determined by chemical analysis fractionation and ICP-AES. The effect of AAEM species on the reactivity of biochar was analyzed by the thermal gravimetric analysis. The results show that the Na and K elements are mainly water-soluble, while the Ca and Mg elements are mainly in the insoluble state. At 370 ℃, NH₄Ac-soluble AAEM species are responsible for the middle and late stage in the reaction. Washed by H₂O, NH₄Ac and HCl successively, the reactivity of biochar decreases. When the carbon conversion rate is relatively small, the water-soluble AAEM species play an important role in promoting the reactivity of biochar. When the carbon conversion rate is higher than a certain value, the reactivity of original biochar is lower than that of the H₂O-washed biochar. The catalytic effect of NH₄Ac-soluble AAEM species on the reactivity of biochar is relatively stable, and the effect of HCl-soluble AAEM species is the most.

Abstract:To study the effect of volatile-char interaction on biochar functional groups, the one-stage fluidized bed/fixed bed reactor and Py were used in the experiment, and the biochar structure was analyzed by Fourier transform infrared spectrometer in the qualitative and semi-quantitative aspects. The results show that with the increase of temperature, the influence of interaction on biochar structure is more intense. The characteristic peaks of biochar functional groups are reduced and the species of peaks are reduced due to the volatile-char interaction which has a destructive effect on the alkyl side chain and accelerates its detachment from aromatic ring. Without the volatile-char interaction or with the interaction but at low temperature, the maturity of organic matter of biochar increases with the increasing of temperature. However at high temperature, the parameters decrease and the free radicals generated by the volatile splitting can cause the condensation of aromatic ring, which leads to the increase of C_ar content.

Abstract:To quickly and efficiently calculate the cooling characteristics of double wall composite cooling structure used in turbine blades, a set of pipeline network coupling algorithm which is enforceable for air-cooled blade simulation has been applied to the designed double wall cooling blade. Combining with one-dimensional pipeline network method and interpolation process between blade wall unit and corresponding outflow field grid, HIT3D-Coolnet pipeline network coupling procedure is composed, and the simulation validity of this algorithm has been verified by turbine blade test data. For the new-style cooling technology of double wall cooling structure, three compound cooling schemes have been preliminarily constructed. The HIT3D-Coolnet quickly gets blade outer wall temperature information to select the initial scheme. With the flow characteristics analysis of double wall structure of the primary scheme by full three-dimensional numerical simulation, measures have been taken to improve the initial design. Flow field analysis shows that the cooling air introduced into the narrow cavity impacts the chamber wall, forms specific vortex structures which can effectively enhance the internal convective heat transfer. Under the reasonable cooling distribution, the double wall cooling technology can obtain relatively good cooling effect.

Abstract:To promote the development of electric vehicle technologies in China, a comparative analysis on the development of electric vehicle technologies in China and USA is made based on all published electric-vehicle-related patent data. The number of new patents, the main patentee and the technical field are indicated to analyze the technology development process, research hot spots, and innovation subject from the view of both industry and technologies. The cases of typical enterprises are also checked, and the findings show that though starting to develop electric vehicle technologies is late, China has paid more attention to developing electric vehicle technologies than USA since 2001, and is catching up fast. The battery and its synergistic control with internal combustion engine are the core technologies. There is a clear gap between China and USA in terms of joint control of vehicle subsystems and digital data processing. Our government should keep supporting the development of electric vehicle, and enterprises should seize the opportunities for both promoting production and sales, and enhancing their technical capabilities.

Abstract:Taking CNC (computerized numerical control) lathe as research object, this paper aims at drawbacks of the allocation model based on traditional failure independence hypothesis, and a multi-factor reliability allocation is proposed considering failure correlation among subsystems. Copula theory was applied to failure correlation analysis, and reliability function of CNC lathe was established. According to the failure mode effects and criticality analysis (FMECA), traditional computational formula of criticality was modified. Allocation matrix was established considering several allocation factors to get allocation vector, and allocation vector and reliability function of CNC lathe was combined to get failure rates of all the subsystems. The allocation method was applied to a specific example of a CNC lathe, and results were analyzed and compared considering different situations of failure correlation. It can be concluded that the allocation results of failure rate considering failure correlation are better than those based on failure independence hypothesis. Therefore, the allocation method proposed in this paper is of great significance in reducing the costs for design and manufacture of subsystems of CNC lathe.

Abstract:For the purpose of improving the driving range and the applicability of electric vehicle, a range-extended electric vehicle using a micro gas turbine as the range-extender is designed. Firstly, the powertrain and main parts of a certain model of electric vehicle are analyzed. Then the vehicle specifications and main parts are determined according to the analyzing and calculating results. Finally the vehicle model is built in Advisor and the feasibility and fuel consumption are simulated. According to the simulating results, Gas turbine range-extended electric vehicle presented in this paper can meet the demand of most users in pure electrical mode. In range-extended mode, the equivalent fuel consumption is 2.02 L/100 km. This scheme makes vehicle adaptive to multiple kind of fuel, and compared with conventional vehicles, the energy from power grid is fully used and the fuel economy is greatly improved.

Abstract:The engine cannot exert the peak torque if the parameters of motors are not match well in a power split hybrid vehicle. In such a case, the engine is working at a speed so that it has the ability to exert its peak torque while the motor limits the torque of engine due to the working points of motors. To solve this problem, a novel strategy is proposed for the parameter matching of the dual-mode power split transmission with the optimum of the power output characteristics as objective. The motors' maximum speed and torque are matched on the basis of the analysis on the characteristics of the dual-mode hybrid transmission. The relation ship between the motors' rated speed and the engine working points is studied with the help of analysis on the characteristics of electric power split, and the method for the motors' rated speed matching is put forward. The validity of the matching method is validated by matching examples. Finally, the motors and the engine performance are analyzed and the results show that the power split transmission can exert the peak torque of the engine and motors at the same time by coordinating the working points of them.

Abstract:As for the vehicle surface water pollution problem during the car wading, this paper combined the traditional automotive aerodynamics expertise and multiphase theory to research the water film distribution with the image processing technology. Through modifying the wheel plate, the influence of the number of holes and the opening area on the distribution of water film was analyzed and compared. After the experiment, T7 model had the most perfect wading performance of the four different wheel plate opening holes number in this paper. The water film distribution ratio decreased by 20.67% compared with the original value. We can know that the spoke structure is conductive to improve the wading performance and the less number of spoke has the smaller water phase attachment on the vehicle body surface. When the opening area increase under the same number of wheel plate the water phase attachment area will also increase.

Abstract:To deal with the difference of heating strategy resulted from the different conditions of the slabs, a kind of entropy weight-TOPSIS method is proposed, which takes a single furnace zone as the research object and combines with the intermediate process of entropy weight and TOPSIS. A concept of special steel grade level is introduced to quantify steel grade, which is taken as the evaluation indexes with the slab temperature difference, slab location and thickness. This model combines the requirements for the difference of evaluation index in the entropy weight method and the weighted method of TOPSIS. The objective entropy weight is used as the closeness degree of the TOPSIS method, and by normalizing it the final weight of the slab is obtained and the temperature of control zone can be set. The simulation results show that, compared with the fixed weight model, the average and maximum temperature difference are decreased by 5.05 ℃ and 7.77 ℃, and the fluctuation value of furnace temperature is reduced by 8.98 ℃.

Abstract:To resolve the regeneration problem of non-thermal plasma (NTP) reactor, the oxidation behaviors of particulate matter (PM) sampled at different engine loads were investigated using thermogravimetric analyzer. The results showed that the content of volatile organic compounds (VOC) differed great at different engine loads in raw PM but little in PM aggregation, and the percentage of the high volatile organic compounds (HVOC) in VOC increased with engine load. Little difference was observed for the oxidation behaviors of raw PM collected at different engine loads while the profiles of oxidation activity of PM aggregation moved toward left when increasing engine load. Longer time was needed to oxidize PM aggregation than raw PM. At isothermal condition, the activation energy was similar for raw PM and PM aggregation, however, the activation energy of the PM escaping from non-thermal plasma reactor was higher than that of raw PM and PM aggregation.

Abstract:To explore the interaction mechanism between femtosecond laser and K24 Nickel-based superalloy, Planck equation and Fresnel's formula are employed to derivate variation curve of pulse width dependent reflectivity and absorption coefficient of K24 superalloy. Linear hypothesis taken from solid mechanics is utilized to derivate lattice heat capacity and electronic specific heat coefficient of K24 superalloy. Temperature variation of electron and lattice during single pulse femtosecond laser ablation process is theoretically described by a simplified one dimensional two temperature model and finite difference method. Theoretical single pulse femtosecond laser ablation depth is calculated referring to vaporization temperature of K24 superalloy. Corresponding experiments are carried out to verify the accuracy of simulation results using low pulse frequency. Orthogonal experiments are carried out to investigate the influence rules of several technological parameters on the morphology features of micro holes. Results show that the scanning velocity is of the most significant effect, followed by feed distance, while scanning time and average power have relatively small effects on morphology of micro holes. This work provides theoretical and experimental foundation for the application of femtosecond laser drilling of superalloy.

Abstract:To improve the accuracy and efficiency of the using of static surrogate model for nonlinear structure optimization, the adaptive iteration least square support vector regression(LSSVR)is introduced to research the optimal solution of load path in the T-shape tube hydroforming process. The maximum contact area of the tube and counter punch and the minimum thinning ratio of the thickness are take as the optimization objective, and those the contact area is greater than the simulation value, the maximum thinning ratio of the thickness is smaller than the experimental value and the protrusion height is greater than test values, are select as constraint conditions. The Latin hypercube design is employed to construct the initial support vector regression model, and some extra sampling points are added to reconstruct the support vector regression model to obtain the Pareto optimal solution set during each iteration. Finally the ideal point is used to obtain a compromise solution from the Pareto optimal solution set for the engineers. The contact area of the most satisfactory solution increases 32.42% and the minimum thickness increases 14.97% compared with the experimental results when the protrusion height is not changing worse. The results show that the adaptive iteration LSSVR model can ensure the accuracy and efficiency of the optimization design in a small amount of samples.

Abstract:To improve the efficiency of Kriging based structural reliability analysis, a new adaptive learning function VF is proposed after analyzing the weakness of existing learning functions. The learning function VF combines variance and joint probability density function both of which can affect the accuracy of estimated failure probability. This method can avoid wasting samples caused by sampling in the area where the value of joint probability density function is low, and increase learning efficiency. Firstly, a large number of candidate sample points are generated by Monte Carlo method, and the point that maximizes the proposed learning function value is defined as the best one. Secondly, a suitable stopping condition is proposed, which can not only ensure the accuracy of failure probability but also reduce iterations dramatically. Finally, two numerical examples are analyzed to show that the proposed method requires fewer calls to the performance function than other methods and it has high convergence speed, good accuracy and stability. And the method can be used in engineering problems with implicit and high nonlinear performance function.

Abstract:To reasonably and timely solve the quality problem lacking of correlation detection information, a case-based reasoning method was proposed based on extension knowledge representation by taking the limitations of formal representation and reasoning method into consideration. Firstly, the knowledge representations of matter-element characteristic items and instance model in quality problem domain were put forward based on the matter-element model. Secondly, the problems of feature adjustment in the process of case retrieving, reusing, revising and retaining were solved by extension transformation. And then, combining with hierarchical organization form for cases based on domain knowledge and nearest neighbor strategy, the case retrieval algorithm was adapted for quality problems in the production process. With the application in vibration problem of 608-2RS ball bearing, the result indicates that the method has good practicability and feasibility.

Abstract:To efficiently address the multi-order-per-job (MOPJ) scheduling problem of a single machine with multiple preprocess constraints in wafer fabrications, including setup time, uncertain allocation of front opening unified pods(FOUPs), machine parameter adjustment, a scheduling problem domain was described and a mathematical programming model was set up with an objective of minimizing total completion time, and several theorems were established to obtain superior feasible solutions, in addition, a hybrid invasive weed optimization algorithm combined with differential evolution and adopted a two-level encoding mechanism was developed, in which the learning mechanism was introduced to enhance the quality of the solution. Moreover, adaptive process was applied to the mutation and neighborhood search to effectively improve the algorithm convergence. Finally, simulation results verify the validness and feasibility of the proposed algorithm and show that a 10% improvement is made on the performance by the scheduling approach.

Abstract:Abstract: A down-load control strategy for supercharged boiler installation is put forward, which can increase the boiler's down-load speed and improve maneuverability of power system. By the simulation platform named SimuWorks, the down-load characteristic is analyzed based on the mechanistic models of marine supercharged boiler installation. The simulation result shows that the model has a high credibility, the error between simulation model and actual equipment is under 0.3%. The max valve-closed speed is 1.85 (°)/s, and it takes boiler 172 s to return stable. Down-load by steps will shorten elapsed time at least 43.78% to return stable, and the more steps, the less time spends.

Abstract:To explore the hunting behavior of the thermostatic-expansion-valve (TEV), dynamic characteristics of the TEV (TEX2 externally balanced type) control-loop ranged from stability to vibration were studied under the selected 7 sets of water mal-distribution experimentally. Results showed that as F₂ dropped from 36.9% to 27.0%, the TEV control-loop was stable and the overall evaporator capacity decreased by only 3.4%. As F₂ dropped from 27.0% to 9.1%, evaporator overall outlet temperature changed from stability to vibration. Its vibration amplitude increased gradually with the phase transformation from vapor to mist, indicating that hunting behavior of TEV control-loop occurred, and the overall evaporator capacity decreased by 14.1%. The superheated refrigerant gas from Circuit 1 outlet only provided sensible heat and couldn't evaporate the liquid refrigerant out of Circuit 2 into superheated steam. Consequently, refrigerant in the evaporator overall outlet was of a smaller superheat than the necessary minimal stable signal (MSS) of the TEV, even at two-phase state, and would inevitably give rise to the hunting of the TEV -controlled system according to the MSS theory. These experimental results might provide references for the design of the heat exchanger of multi-circuit refrigerating system.

Abstract:To explore the unsteady characteristics of two-phase flows and hydrodynamic force, the experiment with micro-hole array on a streamlined cylinder had been conducted by applying the high speed camera system and six-component balance system. Reynolds numbers and air entrainment coefficient are defined. Some conclusions can be drawn as follows: Elastic body area flow field is evenly distributed water and gas two-phase hybrid state, flow stability, non steadiness is not obvious; Tail areas flow field is more disordered, the unsteady characteristic is obvious, and the tail periodic shedding causes a cyclical fluctuation phenomenon of vortex cavitation resistance coefficient. The unsteady characteristic of ventilated two-phase flow around a streamlined cylinder relates to the Reynolds number and air entrainment coefficient. The fluctuating range of drag coefficient decreases and the vortex shedding frequency remains unchanged as the air entrainment coefficient increases, and they all increase as the Reynolds numbers increases.

Abstract:The existing research of process similarity mostly focuses on process structure but neglects the business semantic, and the similarity calculation on process structure is somehow deficient on computation complexity. To solve this problem, this paper proposes a business process representation with synthetical feature extraction, and a corresponding similarity calculation method is given at the same time. Weight notation of edges is used to extend the process structure for structure feature extraction based on the analysis of basic process control patterns, and high level business semantic is also involved for constructing business process semantic model for semantic feature extraction. The classic similarity metrics of node and edge are heuristically adapted to form a new structure similarity metric, and the similarity of business semantic is computed on vector space model and set theory. The total similarity is deduced by the weighted sum of structure and semantic similarity, and the computation model is self-adaptive to other existing methods by the adjustment of weight assignment. Finally, experiments are carried out to verify the performance of similarity computation, and the results show that the model of this paper is more adaptive and higher in computation efficiency when comparing to other methods in the literatures.