Abstract:Reverse engineering was used to develop a Q6 child dummy neck geometric model, and then a detailed and high-quality Q6 child dummy neck finite element (FE) model was developed. The material parameters of the neck FE model which should be optimized were determined after the sensitivity analysis of parameter variables. Based on the calibration test results of a real dummy neck, the Curve Mapping algorithm was applied to the multi-objective optimization of the material parameters of the neck FE model in the performance of head angles and moments in both frontal and lateral calibration tests, and optimized solutions were obtained after several iterations by sequential with domain reduction metamodel-based optimization method. The simulation has shown that the Q6 child dummy neck FE model meets the requirements of calibration quite well.

Abstract:The energy absorption characteristics of foam-filled thin-walled columns subjected to oblique loads were analyzed with the finite element simulation technology. The influences of foam density, thickness, and aspect ratio of columns on the bending critical angle and average impact force were investigated. The formulation of the average impact force was developed in terms of design parameters and oblique impact angle. The results show that the critical angle of foam-filled columns is less than that of empty columns, and foam-filler density has a great influence on the critical angle. With the increase of cross section width from 70 mm to 90 mm, the critical angle of empty columns increases from 6° to 9°, while that of foam-filled columns does not change significantly. The critical angle of empty columns is not significantly influenced by the wall thickness, while higher wall thickness of foam-filled columns leads to larger critical angle. The average impact force is an exponential function of the impact angle, and is inversely proportional to the square aspect ratio and proportional to the exponential power of the wall thickness and density.

Abstract:Compared with other cross section shapes of thin-walled tubes, octagon multi-cell thin-walled tubes have the characteristics of compact structure and high specific energy absorption. The energy absorption characteristics of octagon multi-cell thin-walled tubes under quasi-static axial loading were simulated with finite element software Abaqus. The effects of the cross sections shape and structural parameters on energy absorption characteristics of the multi-cell tubes were analyzed. According to the indicator of the energy absorption characteristics, a side to side distribution of the octagon multi-cell tubes (S2S) was optimized by using the non-dominated sorting genetic algorithm. The results show that the energy absorption characteristics of the side to side distribution is better than the corner to corner distribution, and the octagon multi-cell S2S tubes is optimal; and structural parameters significantly influence its energy absorption characteristics; the octagon multi-cell S2S tubes optimized has better energy absorption characteristics, the specific energy absorption is increased by 33.11%, and the peak crushing force is reduced by 3.78%.

Abstract:This paper simulated the heat transfer process of a cabin with air-conditioning cooling under natural exposure, and obtained the steady temperature distribution of the cabin thermal environment and the body. Some experiments were conducted to find out the transient change law of passenger compartment temperature with air-conditioning on/off. The simulation results show that the front cabin is cooler than the rear cabin, but the regional temperature differences on vertical direction is large. Large temperature difference is also observed on the human model. The experiment results agree well with the simulation ones, and it is found out that the air-conditioning cooling model can effectively reduce the temperature unevenness of the front cabin. And in the first 10 minutes of cooling the temperature changes rapidly, and after that only small temperature variation is observed.

Abstract:In order to study the flow field characteristics of a boundary layer on non-smooth car body surface, large eddy simulation and realizable turbulence model were used for the numerical simulation and calculation of external car body flow field in both transient-state and steady-state. Then, the flow field parameters, such as velocity, thickness of viscous sub-layer, wall shear stress, surface friction coefficient, turbulence intensity and turbulence dissipation rate within the boundary layer of both non-smooth and smooth model, were compared and analyzed. The influence of the non-smooth surface upon the flow field characteristics of the car body was analyzed. The results show that the velocity within the boundary layer of the non-smooth model is obviously higher than that of the smooth model, and boundary layer thickness, wall shear stress, local frictional resistance coefficient, turbulence intensity and turbulence dissipation rate are also less than the smooth model. The introduction of non-smooth surface contributes to the mixing effect of the wake flow of the carbody, preventing the ejector effect upon outside high-speed flow to internal low-speed flow, thus reducing the loss of energy of the car body flow field.

Abstract:To improve computational accuracy and efficiency of the energy release rate for piezoelectric body containing a crack and to reduce the workload of program compiling and debugging, a formulation based on the four node piezoelectric element was presented for electromechanical virtual crack closure technique. Based on the proposed formulation, a fracture of piezoelectric element was implemented with ABAQUS user defined subroutine UEL with the idea of dummy nodes. The element can be solved independently with energy release rate component, which is validated by comparing the analytical solution with the theory of a center cracked piezoelectric with different materials, crack length and mesh for energy release rates. Numerical examples show that this new fracture piezoelectric element is easy to use with high precision and is insensitive to the mesh size.

Abstract:TK6920B CNC floor type boring and milling machine is a type of heavy duty machine tool, and it is easy to generate flexural deformation during the extension of its ram due to its weight and the gravitational off-center of the ram and the headstock, which affects the machining accuracy during processing. In order to solve this problem, the prestress flexural deflection machining method and hydraulic rod compensation method were proposed. Ansys WB software was applied to analyze and predict the ram flexural deformation and compensation effect so that it can cut down experiment cost. By comparing the measured flexural deformation of the ram with the finite element method (FEM) simulation results, it shows that deformation error is controlled within 5 μm, the FEM simulation results are reliable and the total ram deformation is about 20 μm. It is proved that proposed compensation methods are also effective and can meet the requirements of machining.

Abstract:Minimal quantity lubrication (MQL) is a green manufacturing technology. Based on thermal coupling theory on machined residual stress formation，there was a turning experiment to understand how MQL affected turning residual stresses，and the experiment materials were 45 steel, 40Cr steels(hardening),40Cr steels（annealing）and 304 stainless steel. In the experiment，the residual stresses, the cutting force and the cutting temperature were obtained in dry cutting, air cooling cutting, wet cutting and MQL. Then, the reasons were analyzed for the different distribution of the residual stress in all lubrication methods，and laws and mechanism were obtained about how MQL affected residual stress. The experiment results have shown that MQL helps to reduce residual tensile stress, MQL has obvious impact on high toughness and strength material, its impact on materials difficult to cut is greater than ordinary carbon steel, and the inhibition of thermal effects by MQL is the main mechanism which affects residual stress.

Abstract:Magnesium Alloy Cartridge Case is a combined revolution body with the feature of variable thickness and curvature. According to its structural characteristics, a scheme of automatic ultrasonic testing was presented, and a corresponding automatic ultrasonic testing system was designed. The kinematics model of 6-DOF testing platform was built to realize the accurate control of the ultrasonic scanning motion path and probe position. An ultrasonic measurement model for case defect was proposed and the defect size characterizing curves were drawn on the basis of defect scattering models and multi-Gaussian ultrasonic beam models inside the case. An ultrasonic scan experiment was conducted by using 6-DOF testing platform, and the validation of the work was verified by the realization of the detection and sizing of artificial defects.

Abstract:To give the specific hydrofoil for tidal turbine, the design optimization method for hydrofoil was investigated. The proposed approach was based on genetic algorithm. The function of lift coefficient, lift-drag ratio, drag coefficient and pressure coefficient were chosen as the objective functions. XFOIL software was employed to evaluate the hydrodynamic efficiency and pressure on the surface. Several typical design objective functions were established under different design requirements, and the corresponding hydrofoil curves were given in the proposed method. Numerical result shows that this approach can deal with the hydrofoil design optimization problem for tidal turbine according to the specific design requirement. The given hydrofoil can not only improve hydrodynamic coefficient but also avoid its cavitation problem. The location of maximum thickness is closer to trailing edge for minimized pressure coefficient, while it approaches the leading edge under maximized lift coefficient condition. The hydrodynamic efficiency and pressure distribution for various attack angles should be considered to achieve the designated objective function.

Abstract:Shock signal filtering method based on the adaptive decomposition level of wavelet transformation approach was proposed to extract weak vibration signals covered with shock vibration signals. This method chose the wavelet base according to the characters of shock signal, and then removed the impact vibration signal with the theory of the adaptive decomposition level of wavelet transformation. In order to get a better result of filtering, a self-adaptive method was proposed to determine the decomposition level. The numerical simulation of standard weak signals and actual measured weak sand vibration signals both under the impacted interference shows that this method can determine wavelet decomposition level and can effectively extract weak vibration information covered with shock vibration signals.

Abstract:1.5% of the nano montmorillonite (M) and palygorskite (P) were separately added to the phenol prepolymer, and phenolic resins were synthesized in in-situ method (called PF/M and PF/P). The TG analysis of the synthetic resins was carried out. The synthetic resins PF/M and PF/P were used as the new resin matrix to prepare semimetal friction material samples. Tribological performance test was carried on an XD-MSM fixed speed type friction-wear the testing machine. The results show that the heat resistance of PF/M by nano-particles for 1.5% and its tribological performance of friction material are better than no nanoparticle composite PF and PF/P. The carbon residue rate of mass fraction of 1.5% synthetic resin PF/M is more than PF/P and PF, separately increased by 4% and 12% at 600 ℃. The temperature thermal recession of the sample prepared by PF/M is increased by 50 ℃ and 100 ℃ more than the sample prepared by PF/P and no nano-particles composite resin, and has stable friction coefficient. Its wear rate is separately reduced by 16.8% and 27% than FP-1.5 and F-0.0 at the high temperature of 350 ℃.

Abstract:In the digital output port of the traditional multi-power system, there are pull-up-drop-down competition and serious asymmetry between positive edge and negative edge, which results in a large delay-power product， while the large voltage fluctuation and spurious triggering result in a high SSN noise. To deal with these problems, this paper proposed a novel output circuit architecture, which employs a quick voltage level transform circuit to reduce the delay-power product and a resistance of ground bounce output structure to reduce the SSN noise. The output circuit was fabricated by SMIC18mmrf process, and the test shows that the delay-power consumption product is reduced by 5%~15% and SNN noise amplitude is lowered by 30%, compared with the traditional circuit, which indicates the high performance of the novel output circuit.

Abstract:A measurement system for the testing of transmission lines was designed and implemented, which greatly reduced the testing time, avoided the arrangement of cables, and hence enhanced the efficiency of the test. The measurement system, consisting of a center station, a current acquisition and transmitting node, a voltage acquisition and transmitting node, etc., is based on wireless communication. A high-speed wireless bridge working at 2.4GHz together with a clock synchronization module based on the IEEE1588 communicating protocol was employed for the communication and time synchronization. The data storage, waveform display, data analysis, automatic report generation and other functions have been achieved in the measurement system. A practical test was done at a 500 kV substation in Jiangsu Province of China, which proves the validity and effectiveness of the measurement system.

Abstract:A distributed generator (Distributed Generator, DG) multi-objective optimization model was established to the distribution network. Minimum power loss cost, distributed power system operating costs and minimum active power loss minimum were taken as the objective functions for the power balance. More restrictions and other constraints, using a weighted linear multi-objective manner, were taken as a single target, and the use of quantum particle swarm optimization helped to achieve the above objectives. IEEE33 node system simulation results show that the optimization of the location and the capacity of DG can effectively reduce the economic costs of the system, improve the distribution network and optimize economic operation.

Abstract:Based on the mathematical model of photovoltaics and the concept of average model, average-state mathematic modeling was done with a Buck circuit. Based on the sliding-mode theory and operating characteristic of photovoltaics, a fixed-frequency-sliding-mode (FFSM) controller was proposed for photovoltaic system MPPT with the existence and the stability proved. Through sufficient theoretical analysis, system simulations and experiments were implemented .The results of simulations and experiments show that the fixed-frequency-sliding-mode controller can achieve photovoltaic system MPPT with tiny buffeting and the control arithmetic works well.

Abstract:The asymmetric heat conduction in one dimensional function graded materials consisting of two segment Frenkel-Kontorova chains was investigated by using nonequilibrium molecular dynamics simulations. The calculated results show that the rectifying direction of the system can be reversed only by adjusting the thermal bias. The rectification reversal is caused directly by the negative differential thermal resistance, and relies on the properties of interface and system size. It is interesting that, for specific materials the rectifying direction can be reversed only by adjusting the thermal bias. Considering the novel asymmetric heat conduction in the system, possible applications to manage the thermal rectification in situ directionally without re-building the structure were discussed.

Abstract:The existing social tag recommending technology has the problems of data sparsity, high time complexity and low interpretability. To solve these problems, this paper proposed a tag recommending approach called TagRec-UPMF, which jointly factorizes the latent feature factor based on PMF. The approach jointly builds the corresponding feature vector in the form of probability, combining latent features of the three different facets of users, resources and tags, and then produces the top-N recommendation according to the linear combination of the inner products between the feature vectors of each pair. The proposed algorithm improves its accuracy in the case of the large size and sparse data, and it can be used for large-scale data due to the linear complexity. Experimental results show that our method has higher accuracy and lower time consuming than TagRec-CF, and Tucker, NMF, etc. Meanwhile, the proposed method has better precision than PITF algorithm when their complexity is of little difference. And our method shows lower complexity compared with TTD algorithm while their precision are nearly the same.

Abstract:To address the problem of performance analysis of sliding-window-accumulation detection (SWA) and order-statistics sliding-window-accumulation detection (OS-SWA) of extended target under space-time correlated K-distributed (C-KD) clutter background, the approximate PDF expressions for the test statistics under null hypothesis were derived on the basis of the theory of generalized K-distribution fitting, moment matching, effective sample size estimation of relevant data and fractional order statistics computing. The relationships between false-alarm probability, CFAR detection threshold and clutter parameters were established. Monte-Carlo test was used to evaluate the precision of the fitted PDF and the false-alarm-rate controlled by the given detection threshold. The effectiveness and reasonableness of the proposed methods has been demonstrated with theoretical analyses and simulation experiments.

Abstract:Increasingly more people are worried about the electromagnetic radiation of the communication network base station. The growing number of complaints has made base station siting difficult. This paper considered base station coverage and costs, while taking into account the impact of electromagnetic radiation on the environment of the base station. An optimized low electromagnetic radiation 3G network base stations site selection scheme was proposed in this paper. With the base station siting principles and an analysis of the electromagnetic radiation of typical base stations, this paper established a base station evaluation model based on multi-objective design optimization algorithm and proposed a 3G network base station site selection method based on improved immune optimization. A simulation area was set up for simulation tests. The results show that the proposed base station optimization program can not only meet the coverage requirements with relatively smaller construction cost, but also reduce the impact of electromagnetic radiation for better social benefits.

Abstract:Classical Gaussian mixture model (GMM) can describe the multimodal state of the video pixels and GMM has certain robustness in dealing with complex scenes, such as slowly changing lighting. However, it still causes false detection because of the change of pixel values in the same position when the background of the scene is re-exposed after being covered. To solve the repetitive background problem, a Gaussian mixture model based on history background (HBGMM) was proposed in this paper. Compared with traditional Gaussian mixture model, this model can quickly adjust the learning rate by marking the historical background and counting the matched times. We also processed differently between the historical and non-historical model weights lower than threshold to update the model weights to reduce the false detection rate. Experiment results show that the proposed HBGMM can realize the function of remembering the scenes and adapt to the changes of scenes more quickly, thus decreasing the false detection rate.

Abstract:In order to improve the security and efficiency of data access control under multi-authority environment, an access-tree based multi-authority ABE (ATB-MAABE) has been proposed in this paper. In ATB-MAABE, CA is only used for public parameters generating and authority verification, which reduces the security risk introduced by CA. Access control policy is defined by the DO(data owner)， and the attribute-based secret key components are generated by DO and different attributes authorities. By using the access tree based control policy, this scheme can prevent the attacks from the user and authority collusion. Furthermore, the user's global identifier (GID) is not required in secret key generating, which can support anonymous data control and sharing. Finally, the security proof is given by using the Decisional Bilinear Diffie-Hellman (DBDH) assumption, and the experiment results show the efficiency of this scheme in encryption/decryption operations.