Coasting in gear is a common driving mode for the conventional vehicle equipped with the internal combustion engine(ICE), and the assistant braking function of ICE is utilized to decelerate the vehicle in this mode. H...Coasting in gear is a common driving mode for the conventional vehicle equipped with the internal combustion engine(ICE), and the assistant braking function of ICE is utilized to decelerate the vehicle in this mode. However, the electric vehicle(EV) does not have this feature in the coasting mode due to the relatively small inertia of the driving motor, so it will cause the driver cannot obtain the similar driving feeling to that of the conventional vehicle, and even a traffic accident may occur if the driver cannot immediately adapt to the changes. In this paper, the coasting control for EV is researched based on the driving feeling. A conventional vehicle equipped with continuously variable transmission(CVT) is taken as the reference vehicle, and the combined simulation model of EV is established based on AVL CRUISE and MATLAB/Simulink. The torque characteristic of the CVT output shaft is measured in coasting mode, and the data are smoothed and fitted to a polynomial curve. For the EV in coasting mode, if the state of charge(SOC) of the battery is below 95%, the polynomial curve is used as the control target for the torque characteristic of the driving motor, otherwise, the required torque is replaced by hydraulic braking torque to keep the same deceleration. The co-simulation of Matlab/Simulink/Stateflow and AVL CRUISE, as well as the hardware-in-loop experiment combined with d SPACE are carried out to verify the effectiveness and the real-time performance of the control algorithm. The results show that the EV with coasting braking control system has similar driving feeling to that of the reference vehicle, meanwhile, the battery SOC can be increased by 0.036% and 0.021% in the initial speed of 100 km/h and 50 km/h, respectively. The proposed control algorithm for EV is beneficial to improve the driving feeling in coasting mode, and it also makes the EV has the assistant braking function.展开更多
The lubricating characteristics of CVTF(continuously variable transmission fluid) mixed with a multi-functional complex additive were studied. The said complex additive contained an organic borate ester and a new type...The lubricating characteristics of CVTF(continuously variable transmission fluid) mixed with a multi-functional complex additive were studied. The said complex additive contained an organic borate ester and a new type of friction improver comprising phosphorus element and poly-methylmethacrylate(PMMA), and a viscosity index improver. The viscosity-pressure characteristics were evaluated by a high-pressure quartz viscometer, and the anti-wear property was investigated by a four-ball friction tester. The mechanism of lubrication by the CVTF was studied using X-ray photoelectron spectroscopy(XPS). The results showed that CVTF T10, which contained a multi-functional complex additive, exhibited excellent properties, featuring greater solidification pressure and pressure-viscosity coefficient, improved oil film strength, and low wear value. These attributes meet the special CVTF requirements for "high friction and low wear" that make it possible to provide both traction and lubrication. The lubricating mechanism was varied using different functional elements, such as inert and active elements. Sulfur and phosphorus are active extreme pressure elements that can react on the metal friction surface and produce an extreme pressure lubrication film. Boron is an inert functional element and does not react upon the metal surface; boron is only adsorbed onto the metal surface to act as a lubricant for adsorption film and fillers.展开更多
Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipmen...Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipment is necessary. But it is difficult to evaluate it reasonably and comprehensively due to its complexity. A "holistic" approach was discussed to evaluate the energy performance of central air-conditioning system for an extra-large commercial building in a subtropical city. All procedures were described in detail, including field investigation method, field measurement instruments, data processing and data analyzing. The main factors affecting energy consumption of air-conditioning system were analyzed and the annual cooling-energy use intensity of this building was calculated and also compared with other shopping malls and other types of buildings in Guangzhou. And COP(coefficient of performance) of chiller, water transfer factor of chilled water system and cooling water system were taken into consideration. At last, the thermal comfort and indoor air quality issues were addressed. The results show that the chilled water pumps are over-sized and the indoor environmental quality should be improved. The purpose of this work is to provide reference for energy performance assessment method for air-conditioning system.展开更多
A mathematical model of gear tooth profiles using the ellipse curve, whose curvature is convenient to control by changing the mathematical parameters as its line of action, was built based on the meshing theory. The e...A mathematical model of gear tooth profiles using the ellipse curve, whose curvature is convenient to control by changing the mathematical parameters as its line of action, was built based on the meshing theory. The equation of undercutting condition was derived from the model. A special epicycloidal tooth profile was also presented. An example gear drive with variation of the ellipse parameters was taken to illustrate the proposed method. The contact ratio of the gear drive designed by the proposed method was analyzed. A comparison of the property of the gear drive designed with the involute gear drive was also carried out. The results confirm that the proposed gear drive has higher contact ratio in comparison with the involute gear drive.展开更多
A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by disc...A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by discrete points and the cutter figuration determined by analytic function was built for their geometrical relationship and conjugate motion during the machining process. Conjugate points in the cutter section corresponding to the discrete points on the cosine gear tooth surface and the conjugate movements were solved. By using the flexible control of the CNC procedure, the active control of the cutting trace of the slotting cutter was accomplished and the envelop forming of the cosine gear was obtained. Based on the software C++ and Matlab, the computer aided manufacturing(CAM) system of the cosine gear was developed, and the simulation of the slotting process was accomplished. Several examples were provided to illustrate the approach. The result of the simulation demonstrates that the proposed slotting method is feasible.展开更多
We studied the energetic behaviors of interstitial and substitution carbon(C)/nitrogen(N) impurities as well as their interactions with the vacancy in vanadium by first-principles simulations. Both C and N impurities ...We studied the energetic behaviors of interstitial and substitution carbon(C)/nitrogen(N) impurities as well as their interactions with the vacancy in vanadium by first-principles simulations. Both C and N impurities prefer the octahedral site(O-site). N exhibits a lower formation energy than C. Due to the hybridization between vanadium-d and N/C-p, the N-p states are located at the energy from-6.00 e V to-5.00 e V, which is much deeper than that from-5.00 e V to-3.00 e V for the C-p states. Two impurities in bulk vanadium, C–C, C–N, and N–N can be paired up at the two neighboring Osites along the 111 direction and the binding energies of the pairs are 0.227 e V, 0.162 e V, and 0.201 e V, respectively.Further, we find that both C and N do not prefer to stay at the vacancy center and its vicinity, but occupy the O-site off the vacancy in the interstitial lattice in vanadium. The possible physical mechanism is that C/N in the O-site tends to form a carbide/nitride-like structure with its neighboring vanadium atoms, leading to the formation of the strong C/N–vanadium bonding containing a covalent component.展开更多
Electrical conductivity and pH sensitivity of nano-PANI membrane was studied. In this work,an ordered porous nano-polyaniline/acrylate gel polymer( PAGP) membrane was prepared from methyl methacrylate( MMA)/acrylic ac...Electrical conductivity and pH sensitivity of nano-PANI membrane was studied. In this work,an ordered porous nano-polyaniline/acrylate gel polymer( PAGP) membrane was prepared from methyl methacrylate( MMA)/acrylic acid( AA)/nano-PANI bicontinuous microemulsions. The morphology,electric conductivity and p H sensitivity of the composite membrane were studied using scanning electronic microscopy,atomic force microscopy,and electrochemical impedance spectroscopy. It was found that the polymer matrix comprises of two types of proton migrating tunnels: interconnect hydrophilic trench( IHT) and continuous amphiphilic matrix( CAM). The increase of doped nano-PANI particles in those channels leads to a formation of three dimension grain-boundary network. It contributes to the short response time and good reversibility of the sensors. Impedance changes in the low-frequency region reveal an inductive behavior to PANI membrane,which maybe the contribution of faradaic pseudocapacitance of the polymer materials.展开更多
In view of the large energy loss problem in the traditional full hydraulic steering system,a scheme of replacing the ordinary pump with the priority valve with the load sensitive variable pump is proposed to make the ...In view of the large energy loss problem in the traditional full hydraulic steering system,a scheme of replacing the ordinary pump with the priority valve with the load sensitive variable pump is proposed to make the variable pump provide the corresponding flow rate according to the needs of the steering system to achieve the purpose of energy saving.Through the establishment of the system AMESim simulation model,the data comparison shows that the energy loss of the load sensitive variable steering system is significantly reduced relative to the traditional full hydraulic steering system.展开更多
The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct ...The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct to the thermal comfort or thermal sensation of occupants, even to the relationship between thermal conditions and thermal sensation. In this paper, a series of experiments were designed and conducted for understanding the non-uniform conditions and the occupant's thermal responses in vehicle cabin during the heating period. To accurately assess the transient temperature distribution in cabin in common daily condition, the air temperature at a number of positions is measured in a full size vehicle cabin under natural winter environment in South China by using a discrete thermocouples network. The occupant body is divided into nine segments, the skin temperature at each segment and the occupant's local thermal sensation at the head, body, upper limb and lower limb are monitored continuously. The skin temperature is observed by using a discrete thermocouples network, and the local thermal sensation is evaluated by using a seven-point thermal comfort survey questionnaire proposed by American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc(ASHRAE) Standard. The relationship between the skin temperature and the thermal sensation is discussed and regressed by statistics method. The results show that the interior air temperature is highly non-uniform over the vehicle cabin. The locations where the occupants sit have a significant effect on the occupant's thermal responses, including the skin temperature and the thermal sensation. The skin temperature and thermal sensation are quite different between body segments due to the effect of non-uniform conditions, clothing resistance, and the human thermal regulating system. A quantitative relationship between the thermal sensation and the skin temperature at each body segment of occupant in real life traffic is presented. The investigation result indicates that the skin temperature is a robust index to evaluate the thermal sensation. Applying the skin temperature to designing and controlling parameters of the heating, ventilation and air conditioning(HVAC) system may benefit the thermal comfort and reducing energy consumption.展开更多
The structure and working principle of a kind of permanent-magnet adsorption tracked wall-climbing ro-bot used in ship was analyzed in this paper. The robot can complete vertical climbing wall function when perma-nent...The structure and working principle of a kind of permanent-magnet adsorption tracked wall-climbing ro-bot used in ship was analyzed in this paper. The robot can complete vertical climbing wall function when perma-nent-magnet adsorption tracked was driven by ac servo motor. In order to improve the load capacity and obstaclesurmounting ability of robot, a new permanent-magnet auxiliary caster adsorption mechanism and driven wheelfloating mechanism were used for the design of structure. In thispaper, the mechanical state of the permanent-mag-netic adsorption tracked climbing mechanism was analyzed. Through the magnetic simulation and experimental a-nalysis of magnetic adsorption system, the adsorption unit structure and electric drive system parameters of thepermanent-magnet tracked wall-climbing robot were reasonably designed.展开更多
The deformation behavior of BMC, machining in difference cutting depth were investigated using SEMand cutting force measurement system. Then new fracture and shear band information extraction method based onindependen...The deformation behavior of BMC, machining in difference cutting depth were investigated using SEMand cutting force measurement system. Then new fracture and shear band information extraction method based onindependent component analysis （ICA） and fast Fourier transform （FFT） were used to analyze the original forcesignals. The main cutting force signals were extracted from the original signals by ICA method. The energy spec-trum of those main signals is processed by FFT. The analysis results show that the high frequency contents of cut-ting force increasing with the cutting depth. The fracture and shear band generation behavior in BMG chip resultin strong high frequency cutting force signals and the high frequency contents of cutting force increasing with thecutting depth. Besides, the frequency of Fz is 115 Hz and its amplitude also increases with the increasing ofdepth.展开更多
The transmission systems of the differential velocity vane pumps(DVVP) have periodic vibrations under loads. And it is not easy to find the reason. In order to optimize the performance of the pump, the authors propose...The transmission systems of the differential velocity vane pumps(DVVP) have periodic vibrations under loads. And it is not easy to find the reason. In order to optimize the performance of the pump, the authors proposed DVVP driven by the hybrid Higher-order Fourier non-circular gears and tested it. There were also similar periodic vibrations and noises under loads. Taking into account this phenomenon, the paper proposes fluid mechanics and solid mechanics simulation methodology to analyze the coupling dynamics between fluid and transmission system and reveals the reason. The results show that the pump has the reverse drive phenomenon, which is that the blades drive the non-circular gears when the suction and discharge is alternating. The reverse drive phenomenon leads the sign of the shaft torque to be changed in positive and negative way. So the transmission system produces torsional vibrations. In order to confirm the simulation results, micro strains of the input shaft of the pump impeller are measured by the Wheatstone bridge and wireless sensor technology. The relationships between strain and torque are obtained by experimental calibration, and then the true torque of input shaft is calculated indirectly. The experimental results are consistent to the simulation results. It is proven that the periodic vibrations are mainly caused by fluid solid coupling, which leads to periodic torsional vibration of the transmission system.展开更多
The current work is concerned with modelling and analysis for a pilot relief valve, thus successfully bringing a systematic method for designing and analyzing similar valves. The essence of the work is to solve two im...The current work is concerned with modelling and analysis for a pilot relief valve, thus successfully bringing a systematic method for designing and analyzing similar valves. The essence of the work is to solve two important problems, one for positions of the pilot valve influenced by flow force and the other is for the opening of the relief valve governed by a thin annular plate. The computational fluid dynamics(CFD) method is used to present the flow force. Using a series of experiments, the flow rate versus pressure drop shows the rationality of the CFD results. In order to obtain the opening of relief valve with higher accuracy, the large deflection theory of thin plates is adopted. An equivalent method for replacing the concentrated force is innovatively proposed so that all of the loads of the plates can be given by a unified expression, which reduces the number of the governing equations and intermediate boundary conditions. For presenting a very simple and reliable method for solving the governing equation, an unconstrained nonlinear optimization is innovatively introduced to solve the deflection of the thin annular plate. Being verified by finite-element method(FEM) of the relief valve, the equivalent method and optimization can solve deflection of thin plates rapidly and accurately. Reflected through a complete model for the pilot relief valve, the theoretical flow rate of the pilot relief valve is consistent with experimental conclusion. Once again, the comparisons bring us insight into the accuracy of the method adopted in the current work.展开更多
We propose a new laser preparation technique to solder Sn-Ag3.5-Cu0.7 on a copper clad laminate(CCL).The experiment is conducted by selective laser heating and melting the thin solder layer and then preprinting it on ...We propose a new laser preparation technique to solder Sn-Ag3.5-Cu0.7 on a copper clad laminate(CCL).The experiment is conducted by selective laser heating and melting the thin solder layer and then preprinting it on CCL in order to form the matrix with solder pads.Through the analysis of macro morphology of the matrix with solder pads and microstructure of single pads,this technique is proved to be suitable for preparing solder pads and that the solder pads are of good mechanical properties.The results also reveal that high frequency laser pulse is beneficial to the formation of better solder pad,and that the 12-W fiber laser with a beam diameter of 0.030 mm can solder Sn-Ag3.5-Cu0.7 successfully on CCL at 500-kHz pulse frequency.The optimized parameters of laser soldering on CCL are as follows:the laser power is 12 W,the scanning speed is 1.0 mm/s,the beam diameter is 0.030 mm,the lead-free solder is Sn-Ag3.5-Cu0.7,and the laser pulse frequency is 500 kHz.展开更多
Phosphors Ca4(PO4)2O:Ce3+/Li+,Eu2+ were prepared by solid state reaction successfully, and characterized by X-ray diffraction, UV-Vis spectrometer and photoluminescence spectrometry. The as-prepared phosphors exhibite...Phosphors Ca4(PO4)2O:Ce3+/Li+,Eu2+ were prepared by solid state reaction successfully, and characterized by X-ray diffraction, UV-Vis spectrometer and photoluminescence spectrometry. The as-prepared phosphors exhibited strong absorption in the UV-visible region and dual-emission bands centered at approximately 460 and 630 nm. Energy transfer from Ce3+ to Eu2+ was also observed. By varying the excitation wavelength, these new phosphors exhibited tunable emissions from blue to white and then to yellow, making them potential candidates as UV-convertible phosphors for white light emitting diodes.展开更多
Based on the Magneto-Hydro-Dynamic(MHD)theory,a united three-dimensional(3D)transient numerical model is developed to investigate the dynamic behaviors of arc plasma for a magnesium alloy AZ61A gas tungsten arc weldin...Based on the Magneto-Hydro-Dynamic(MHD)theory,a united three-dimensional(3D)transient numerical model is developed to investigate the dynamic behaviors of arc plasma for a magnesium alloy AZ61A gas tungsten arc welding(GTAW)arc.The arc,electrode and workpiece are integrated into one calculation domain to avoid both presumed distribution of the current density at the electrode tip and the assumption of constant conditions of interface between welding arc and workpiece.The distributions of electric potential,current density,magnetic flux density,electromagnetic force,velocity,temperature,and pressure of the arc plasma in the 3D space are analyzed by using the numerical model.Results indicate that the maximum gradient of the electric potential in the whole arc space exists around the electrode tip,where the electric current density,electromagnetic force,and temperature are also the maximum.However,maximum pressure is found at the velocity stagnation,which is above the workpiece.Comparison between predicted temperature and measured one in arc region shows a good agreement.展开更多
In this paper, we investigate the learning issue in the adaptive neural network (NN) output feedback control of nonlinear systems in Brunovsky canonical form with unknown affine term. With only output measurements, a ...In this paper, we investigate the learning issue in the adaptive neural network (NN) output feedback control of nonlinear systems in Brunovsky canonical form with unknown affine term. With only output measurements, a high-gain observer (HGO) is employed to estimate the derivatives of the system output which may be associated with the generation of peaking phenomenon. The adverse effect of peaking on learning and its elimination strategies are analyzed. When the gain of HGO is chosen too high, it may cause the failure of learning from the unknown closed-loop system dynamics. Hence, the gain of HGO is not chosen too high to relieve peaking and guarantee the accuracy of the estimated system states. Then, learning from the unknown closed-loop system dynamics can be achieved. When repeating the same or similar control tasks, a neural learning controller is presented which can effectively recall and reuse the learned knowledge to guarantee the output tracking performance. Finally, simulation results demonstrate the effectiveness of the proposed scheme.展开更多
Fractal networks are widely applied in the field of heat and mass transfer. As one of the important parts of the fractal network, Y-shaped structure definitely has a significant impact on the performance of the whole ...Fractal networks are widely applied in the field of heat and mass transfer. As one of the important parts of the fractal network, Y-shaped structure definitely has a significant impact on the performance of the whole network. In this paper, the analytical relationship between Y-shaped microchannel geometry and its capillary flow time is established through theoretical analysis with mass continuity equation and Navier-Stokes(N-S) equations.The result reveals that the capillary flow time increases with the increase of the topology length and bifurcation angle of the Y-shaped microchannel, but decreases with the increase of the channel width.展开更多
基金Supported by Guangdong Provincial Science and Technology Planning Project of China(Grant Nos.2013B010402006,2013B010405007,2013B090600024)
文摘Coasting in gear is a common driving mode for the conventional vehicle equipped with the internal combustion engine(ICE), and the assistant braking function of ICE is utilized to decelerate the vehicle in this mode. However, the electric vehicle(EV) does not have this feature in the coasting mode due to the relatively small inertia of the driving motor, so it will cause the driver cannot obtain the similar driving feeling to that of the conventional vehicle, and even a traffic accident may occur if the driver cannot immediately adapt to the changes. In this paper, the coasting control for EV is researched based on the driving feeling. A conventional vehicle equipped with continuously variable transmission(CVT) is taken as the reference vehicle, and the combined simulation model of EV is established based on AVL CRUISE and MATLAB/Simulink. The torque characteristic of the CVT output shaft is measured in coasting mode, and the data are smoothed and fitted to a polynomial curve. For the EV in coasting mode, if the state of charge(SOC) of the battery is below 95%, the polynomial curve is used as the control target for the torque characteristic of the driving motor, otherwise, the required torque is replaced by hydraulic braking torque to keep the same deceleration. The co-simulation of Matlab/Simulink/Stateflow and AVL CRUISE, as well as the hardware-in-loop experiment combined with d SPACE are carried out to verify the effectiveness and the real-time performance of the control algorithm. The results show that the EV with coasting braking control system has similar driving feeling to that of the reference vehicle, meanwhile, the battery SOC can be increased by 0.036% and 0.021% in the initial speed of 100 km/h and 50 km/h, respectively. The proposed control algorithm for EV is beneficial to improve the driving feeling in coasting mode, and it also makes the EV has the assistant braking function.
基金financially supported by the China National Machinery Industry Corporation Science & Technology Development Fund (SINOMACH12 No.180)
文摘The lubricating characteristics of CVTF(continuously variable transmission fluid) mixed with a multi-functional complex additive were studied. The said complex additive contained an organic borate ester and a new type of friction improver comprising phosphorus element and poly-methylmethacrylate(PMMA), and a viscosity index improver. The viscosity-pressure characteristics were evaluated by a high-pressure quartz viscometer, and the anti-wear property was investigated by a four-ball friction tester. The mechanism of lubrication by the CVTF was studied using X-ray photoelectron spectroscopy(XPS). The results showed that CVTF T10, which contained a multi-functional complex additive, exhibited excellent properties, featuring greater solidification pressure and pressure-viscosity coefficient, improved oil film strength, and low wear value. These attributes meet the special CVTF requirements for "high friction and low wear" that make it possible to provide both traction and lubrication. The lubricating mechanism was varied using different functional elements, such as inert and active elements. Sulfur and phosphorus are active extreme pressure elements that can react on the metal friction surface and produce an extreme pressure lubrication film. Boron is an inert functional element and does not react upon the metal surface; boron is only adsorbed onto the metal surface to act as a lubricant for adsorption film and fillers.
基金Project(2011B061200043)supported by the Guangdong Provincial Department of Science and Technology,China
文摘Energy performance assessment on central air-conditioning system is essential to optimize operating, reduce operating costs, improve indoor environmental quality, and determine whether the retrofitting of the equipment is necessary. But it is difficult to evaluate it reasonably and comprehensively due to its complexity. A "holistic" approach was discussed to evaluate the energy performance of central air-conditioning system for an extra-large commercial building in a subtropical city. All procedures were described in detail, including field investigation method, field measurement instruments, data processing and data analyzing. The main factors affecting energy consumption of air-conditioning system were analyzed and the annual cooling-energy use intensity of this building was calculated and also compared with other shopping malls and other types of buildings in Guangzhou. And COP(coefficient of performance) of chiller, water transfer factor of chilled water system and cooling water system were taken into consideration. At last, the thermal comfort and indoor air quality issues were addressed. The results show that the chilled water pumps are over-sized and the indoor environmental quality should be improved. The purpose of this work is to provide reference for energy performance assessment method for air-conditioning system.
基金Projects(51205335,51375411)supported by the National Natural Science Foundation of ChinaProjects(2013J01209,2012J01237)supported by the Natural Science Foundation of Fujian Province,China+2 种基金Project(2014H0049)supported by the Major S&T Program of Fujian Province,ChinaProject(E201400800)supported by the International Cooperation and Exchange Research Plan of Xiamen University of Technology,ChinaProject(YKJ14008R)supported by the Scientific Research for the High Level Talent of Xiamen University of Technology,China
文摘A mathematical model of gear tooth profiles using the ellipse curve, whose curvature is convenient to control by changing the mathematical parameters as its line of action, was built based on the meshing theory. The equation of undercutting condition was derived from the model. A special epicycloidal tooth profile was also presented. An example gear drive with variation of the ellipse parameters was taken to illustrate the proposed method. The contact ratio of the gear drive designed by the proposed method was analyzed. A comparison of the property of the gear drive designed with the involute gear drive was also carried out. The results confirm that the proposed gear drive has higher contact ratio in comparison with the involute gear drive.
基金Projects(51205335,50975242,51375411) supported by the National Natural Science Foundation of ChinaProject(2013J01209) supported by the Natural Science Foundation of Fujian Province,China
文摘A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by discrete points and the cutter figuration determined by analytic function was built for their geometrical relationship and conjugate motion during the machining process. Conjugate points in the cutter section corresponding to the discrete points on the cosine gear tooth surface and the conjugate movements were solved. By using the flexible control of the CNC procedure, the active control of the cutting trace of the slotting cutter was accomplished and the envelop forming of the cosine gear was obtained. Based on the software C++ and Matlab, the computer aided manufacturing(CAM) system of the cosine gear was developed, and the simulation of the slotting process was accomplished. Several examples were provided to illustrate the approach. The result of the simulation demonstrates that the proposed slotting method is feasible.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11575153 and 11375108)
文摘We studied the energetic behaviors of interstitial and substitution carbon(C)/nitrogen(N) impurities as well as their interactions with the vacancy in vanadium by first-principles simulations. Both C and N impurities prefer the octahedral site(O-site). N exhibits a lower formation energy than C. Due to the hybridization between vanadium-d and N/C-p, the N-p states are located at the energy from-6.00 e V to-5.00 e V, which is much deeper than that from-5.00 e V to-3.00 e V for the C-p states. Two impurities in bulk vanadium, C–C, C–N, and N–N can be paired up at the two neighboring Osites along the 111 direction and the binding energies of the pairs are 0.227 e V, 0.162 e V, and 0.201 e V, respectively.Further, we find that both C and N do not prefer to stay at the vacancy center and its vicinity, but occupy the O-site off the vacancy in the interstitial lattice in vanadium. The possible physical mechanism is that C/N in the O-site tends to form a carbide/nitride-like structure with its neighboring vanadium atoms, leading to the formation of the strong C/N–vanadium bonding containing a covalent component.
基金This work was supported by National Natural Science Foundation of China （No. 50875088 ） and Foundation for Distinguished Young Teachers＇ Training of Guangdong（Yq2013106）.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51571093)the Fundamental Research Funds for the Central Universities(Grant No.2015ZM094)
文摘Electrical conductivity and pH sensitivity of nano-PANI membrane was studied. In this work,an ordered porous nano-polyaniline/acrylate gel polymer( PAGP) membrane was prepared from methyl methacrylate( MMA)/acrylic acid( AA)/nano-PANI bicontinuous microemulsions. The morphology,electric conductivity and p H sensitivity of the composite membrane were studied using scanning electronic microscopy,atomic force microscopy,and electrochemical impedance spectroscopy. It was found that the polymer matrix comprises of two types of proton migrating tunnels: interconnect hydrophilic trench( IHT) and continuous amphiphilic matrix( CAM). The increase of doped nano-PANI particles in those channels leads to a formation of three dimension grain-boundary network. It contributes to the short response time and good reversibility of the sensors. Impedance changes in the low-frequency region reveal an inductive behavior to PANI membrane,which maybe the contribution of faradaic pseudocapacitance of the polymer materials.
基金Key R&D Plan of Shandong Province(2015GGX105005)。
文摘In view of the large energy loss problem in the traditional full hydraulic steering system,a scheme of replacing the ordinary pump with the priority valve with the load sensitive variable pump is proposed to make the variable pump provide the corresponding flow rate according to the needs of the steering system to achieve the purpose of energy saving.Through the establishment of the system AMESim simulation model,the data comparison shows that the energy loss of the load sensitive variable steering system is significantly reduced relative to the traditional full hydraulic steering system.
基金supported by National Natural Science Foundation of China(Grant No.51375170)Open Fund of State Key Lab of Environmental Adaptability for Industrial Products of China
文摘The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct to the thermal comfort or thermal sensation of occupants, even to the relationship between thermal conditions and thermal sensation. In this paper, a series of experiments were designed and conducted for understanding the non-uniform conditions and the occupant's thermal responses in vehicle cabin during the heating period. To accurately assess the transient temperature distribution in cabin in common daily condition, the air temperature at a number of positions is measured in a full size vehicle cabin under natural winter environment in South China by using a discrete thermocouples network. The occupant body is divided into nine segments, the skin temperature at each segment and the occupant's local thermal sensation at the head, body, upper limb and lower limb are monitored continuously. The skin temperature is observed by using a discrete thermocouples network, and the local thermal sensation is evaluated by using a seven-point thermal comfort survey questionnaire proposed by American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc(ASHRAE) Standard. The relationship between the skin temperature and the thermal sensation is discussed and regressed by statistics method. The results show that the interior air temperature is highly non-uniform over the vehicle cabin. The locations where the occupants sit have a significant effect on the occupant's thermal responses, including the skin temperature and the thermal sensation. The skin temperature and thermal sensation are quite different between body segments due to the effect of non-uniform conditions, clothing resistance, and the human thermal regulating system. A quantitative relationship between the thermal sensation and the skin temperature at each body segment of occupant in real life traffic is presented. The investigation result indicates that the skin temperature is a robust index to evaluate the thermal sensation. Applying the skin temperature to designing and controlling parameters of the heating, ventilation and air conditioning(HVAC) system may benefit the thermal comfort and reducing energy consumption.
基金supported by the National Natural Science Foundation of China ( 11272122 )Guangdong Province section of major research projects (2012A090 300011)Science and Technology Project of Shaoguan (2014CXY-C312)
文摘The structure and working principle of a kind of permanent-magnet adsorption tracked wall-climbing ro-bot used in ship was analyzed in this paper. The robot can complete vertical climbing wall function when perma-nent-magnet adsorption tracked was driven by ac servo motor. In order to improve the load capacity and obstaclesurmounting ability of robot, a new permanent-magnet auxiliary caster adsorption mechanism and driven wheelfloating mechanism were used for the design of structure. In thispaper, the mechanical state of the permanent-mag-netic adsorption tracked climbing mechanism was analyzed. Through the magnetic simulation and experimental a-nalysis of magnetic adsorption system, the adsorption unit structure and electric drive system parameters of thepermanent-magnet tracked wall-climbing robot were reasonably designed.
基金This investigation is supported by National Natural Science Foundation of China （51375173） and Guangdong Provincial Science and Technology Project （2012B091000009, 2012A032300007）.
基金supported by Hubeil Natural Science Foundation,P. R. China ( No2014CFB637)
文摘The deformation behavior of BMC, machining in difference cutting depth were investigated using SEMand cutting force measurement system. Then new fracture and shear band information extraction method based onindependent component analysis （ICA） and fast Fourier transform （FFT） were used to analyze the original forcesignals. The main cutting force signals were extracted from the original signals by ICA method. The energy spec-trum of those main signals is processed by FFT. The analysis results show that the high frequency contents of cut-ting force increasing with the cutting depth. The fracture and shear band generation behavior in BMG chip resultin strong high frequency cutting force signals and the high frequency contents of cutting force increasing with thecutting depth. Besides, the frequency of Fz is 115 Hz and its amplitude also increases with the increasing ofdepth.
基金financially supported by the Project of fundamental Commonweal Research of Zhejiang Province(Grant No.LGG18E050004)the National Natural Science Foundation of China(Grant No.51305403 and No.51675486)
文摘The transmission systems of the differential velocity vane pumps(DVVP) have periodic vibrations under loads. And it is not easy to find the reason. In order to optimize the performance of the pump, the authors proposed DVVP driven by the hybrid Higher-order Fourier non-circular gears and tested it. There were also similar periodic vibrations and noises under loads. Taking into account this phenomenon, the paper proposes fluid mechanics and solid mechanics simulation methodology to analyze the coupling dynamics between fluid and transmission system and reveals the reason. The results show that the pump has the reverse drive phenomenon, which is that the blades drive the non-circular gears when the suction and discharge is alternating. The reverse drive phenomenon leads the sign of the shaft torque to be changed in positive and negative way. So the transmission system produces torsional vibrations. In order to confirm the simulation results, micro strains of the input shaft of the pump impeller are measured by the Wheatstone bridge and wireless sensor technology. The relationships between strain and torque are obtained by experimental calibration, and then the true torque of input shaft is calculated indirectly. The experimental results are consistent to the simulation results. It is proven that the periodic vibrations are mainly caused by fluid solid coupling, which leads to periodic torsional vibration of the transmission system.
文摘The current work is concerned with modelling and analysis for a pilot relief valve, thus successfully bringing a systematic method for designing and analyzing similar valves. The essence of the work is to solve two important problems, one for positions of the pilot valve influenced by flow force and the other is for the opening of the relief valve governed by a thin annular plate. The computational fluid dynamics(CFD) method is used to present the flow force. Using a series of experiments, the flow rate versus pressure drop shows the rationality of the CFD results. In order to obtain the opening of relief valve with higher accuracy, the large deflection theory of thin plates is adopted. An equivalent method for replacing the concentrated force is innovatively proposed so that all of the loads of the plates can be given by a unified expression, which reduces the number of the governing equations and intermediate boundary conditions. For presenting a very simple and reliable method for solving the governing equation, an unconstrained nonlinear optimization is innovatively introduced to solve the deflection of the thin annular plate. Being verified by finite-element method(FEM) of the relief valve, the equivalent method and optimization can solve deflection of thin plates rapidly and accurately. Reflected through a complete model for the pilot relief valve, the theoretical flow rate of the pilot relief valve is consistent with experimental conclusion. Once again, the comparisons bring us insight into the accuracy of the method adopted in the current work.
文摘We propose a new laser preparation technique to solder Sn-Ag3.5-Cu0.7 on a copper clad laminate(CCL).The experiment is conducted by selective laser heating and melting the thin solder layer and then preprinting it on CCL in order to form the matrix with solder pads.Through the analysis of macro morphology of the matrix with solder pads and microstructure of single pads,this technique is proved to be suitable for preparing solder pads and that the solder pads are of good mechanical properties.The results also reveal that high frequency laser pulse is beneficial to the formation of better solder pad,and that the 12-W fiber laser with a beam diameter of 0.030 mm can solder Sn-Ag3.5-Cu0.7 successfully on CCL at 500-kHz pulse frequency.The optimized parameters of laser soldering on CCL are as follows:the laser power is 12 W,the scanning speed is 1.0 mm/s,the beam diameter is 0.030 mm,the lead-free solder is Sn-Ag3.5-Cu0.7,and the laser pulse frequency is 500 kHz.
基金supported by the National Natural Science Foundation of China(5127224361370049)+4 种基金Natural Science Foundation of Zhejiang Province(LY14E020008LZ14F050001LR14A040002LQ13E020003LR14A04002)
文摘Phosphors Ca4(PO4)2O:Ce3+/Li+,Eu2+ were prepared by solid state reaction successfully, and characterized by X-ray diffraction, UV-Vis spectrometer and photoluminescence spectrometry. The as-prepared phosphors exhibited strong absorption in the UV-visible region and dual-emission bands centered at approximately 460 and 630 nm. Energy transfer from Ce3+ to Eu2+ was also observed. By varying the excitation wavelength, these new phosphors exhibited tunable emissions from blue to white and then to yellow, making them potential candidates as UV-convertible phosphors for white light emitting diodes.
基金supported by the Fundamental Research Funds for the Central Universities (No. 2012ZZ0059)the National Natural Science Foundation of China (No. E51375173)+1 种基金the Open Fund of State Key Laboratory of Materials Processing and Die & Mould Technology (No. 2011-P02)a project of Shandong Province Higher Educational Science and Technology Program (No. J12LA16)
文摘Based on the Magneto-Hydro-Dynamic(MHD)theory,a united three-dimensional(3D)transient numerical model is developed to investigate the dynamic behaviors of arc plasma for a magnesium alloy AZ61A gas tungsten arc welding(GTAW)arc.The arc,electrode and workpiece are integrated into one calculation domain to avoid both presumed distribution of the current density at the electrode tip and the assumption of constant conditions of interface between welding arc and workpiece.The distributions of electric potential,current density,magnetic flux density,electromagnetic force,velocity,temperature,and pressure of the arc plasma in the 3D space are analyzed by using the numerical model.Results indicate that the maximum gradient of the electric potential in the whole arc space exists around the electrode tip,where the electric current density,electromagnetic force,and temperature are also the maximum.However,maximum pressure is found at the velocity stagnation,which is above the workpiece.Comparison between predicted temperature and measured one in arc region shows a good agreement.
文摘In this paper, we investigate the learning issue in the adaptive neural network (NN) output feedback control of nonlinear systems in Brunovsky canonical form with unknown affine term. With only output measurements, a high-gain observer (HGO) is employed to estimate the derivatives of the system output which may be associated with the generation of peaking phenomenon. The adverse effect of peaking on learning and its elimination strategies are analyzed. When the gain of HGO is chosen too high, it may cause the failure of learning from the unknown closed-loop system dynamics. Hence, the gain of HGO is not chosen too high to relieve peaking and guarantee the accuracy of the estimated system states. Then, learning from the unknown closed-loop system dynamics can be achieved. When repeating the same or similar control tasks, a neural learning controller is presented which can effectively recall and reuse the learned knowledge to guarantee the output tracking performance. Finally, simulation results demonstrate the effectiveness of the proposed scheme.
基金the National Natural Science Foundation of China(No.51375169)
文摘Fractal networks are widely applied in the field of heat and mass transfer. As one of the important parts of the fractal network, Y-shaped structure definitely has a significant impact on the performance of the whole network. In this paper, the analytical relationship between Y-shaped microchannel geometry and its capillary flow time is established through theoretical analysis with mass continuity equation and Navier-Stokes(N-S) equations.The result reveals that the capillary flow time increases with the increase of the topology length and bifurcation angle of the Y-shaped microchannel, but decreases with the increase of the channel width.
