A novel way to design arbitrarily shaped retro-reflectors by optics surface transformation is proposed. The entire design process consists of filling an optic-null medium between the input and output surfaces of the r...A novel way to design arbitrarily shaped retro-reflectors by optics surface transformation is proposed. The entire design process consists of filling an optic-null medium between the input and output surfaces of the retroreflector, on which the points have 180 deg reverse corresponding relations. The retro-reflector can be designed to be very thin(a planar structure) with high efficiency. The effective working angles of our retro-reflector are very large(from-80 deg to +80 deg), which can, in principle, be further extended. Layered metal plates and zero refractive index materials are designed to realize the proposed retro-reflector for a TM polarized beam.展开更多
A new method of collision-free path plan integrated in virtual processing is developed to improve the efficiency of laser surface hardening on dies. The path plan is based on the premise of no collision and the optimi...A new method of collision-free path plan integrated in virtual processing is developed to improve the efficiency of laser surface hardening on dies. The path plan is based on the premise of no collision and the optimization object is the shortest path. The optimization model of collision-free path is built from traveling salesman problem （TSP）. Collision-free path between two machining points is calculated in configuration space （C-Space）. Ant colony optimization （ACO） algorithm is applied to TSP of all the machining points to find the shortest path, which is simulated in virtual environment set up by IGRIP software. Virtual machining time, no-collision report, etc, are put out atter the simulation. An example on autobody die is processed in the virtual platform, the simulation results display that ACO has perfect optimization effect, and the method of virtual processing with integration of collision-free optimal path is practical.展开更多
Laser surface transformation hardening becomes one of the most effective processes used to improve wear and fatigue resistance of mechanical parts. In this process, the material physicochemical properties and the heat...Laser surface transformation hardening becomes one of the most effective processes used to improve wear and fatigue resistance of mechanical parts. In this process, the material physicochemical properties and the heating system parameters have significant effects on the characteristics of the hardened surface. To appropriately exploit the benefits presented by the laser surface hardening, it is necessary to develop a comprehensive strategy to control the process variables in order to produce desired hardened surface attributes without being forced to use the traditional and fastidious trial and error procedures. The paper presents a study of hardness profile predictive modeling and experimental validation for spline shafts using a 3D model. The proposed approach is based on thermal and metallurgical simulations, experimental investigations and statistical analysis to build the prediction model. The simulation of the hardening process is carried out using 3D finite element model on commercial software. The model is used to estimate the temperature distribution and the hardness profile attributes for various hardening parameters, such as laser power, shaft rotation speed and scanning speed. The experimental calibration and validation of the model are performed on a 3 kW Nd:Yag laser system using a structured experimental design and confirmed statistical analysis tools. The results reveal that the model can provide not only a consistent and accurate prediction of temperature distribution and hardness profile characteristics under variable hardening parameters and conditions but also a comprehensive and quantitative analysis of process parameters effects. The modelling results show a great concordance between predicted and measured values for the dimensions of hardened zones.展开更多
This study investigates the dielectric and thermal properties of transformer oil-based nanofluids incorporating Fe_(3)O_(4)-coated SiO_(2) core-shell nanoparticles as nanofillers.The nanoparticles were synthesised wit...This study investigates the dielectric and thermal properties of transformer oil-based nanofluids incorporating Fe_(3)O_(4)-coated SiO_(2) core-shell nanoparticles as nanofillers.The nanoparticles were synthesised with varying shell thicknesses,and two samples underwent surface treatment.Fourier transform infrared spectroscopy was used to characterise the nanoparticles.The spectra for unmodified and modified nanoparticles detected Fe-O bond,Si-O-Si bond and oleic acid existence.The nanofluids were prepared using a two-step method:nanoparticles were first prepared at concentrations of 0.04,0.07 and 0.10 g/L,and then mixed with the base oil and dispersed using ultrasonication.AC breakdown strength was measured for samples at these concentrations to determine the optimum concentration for each type of nanoparticle.The optimum concentration,which provided the best performance for AC breakdown voltage across all nanoparticle types,was found to be 0.07 g/L.Thermal conductivity testing was then conducted at this optimum concentration.The addition of nanofillers resulted in increased AC breakdown strength and thermal conductivity.Particle size and zeta size measurements were carried out to assess the dispersion behaviour of the nanofluid samples.The physical discussion examined potential reasons for improvements in AC breakdown voltage and thermal conductivity.Trapping and de-trapping processes,shell thickness and surface modifications were analysed in relation to improved dielectric performance.Ballistic phonon transport and Brownian motion mechanisms were employed to explain the observed enhancements in thermal conductivity.These findings indicate the potential for developing a new class of liquid dielectrics suitable for use in power transformers.展开更多
基金supported in part by the National Natural Science Foundation of China (Nos. 61971300 and 61905208)the Scientific and Technological Innovation Programs (STIP) of Higher Education Institutions in Shanxi (Nos. 2019L0159 and 2019L0146)the National Key Research and Development Program of China (No. 2017YFA0205700)
文摘A novel way to design arbitrarily shaped retro-reflectors by optics surface transformation is proposed. The entire design process consists of filling an optic-null medium between the input and output surfaces of the retroreflector, on which the points have 180 deg reverse corresponding relations. The retro-reflector can be designed to be very thin(a planar structure) with high efficiency. The effective working angles of our retro-reflector are very large(from-80 deg to +80 deg), which can, in principle, be further extended. Layered metal plates and zero refractive index materials are designed to realize the proposed retro-reflector for a TM polarized beam.
基金This project is supported by Great Device Development Project of Chinese Academy of Sciences, China(No.[1997]167)Knowledge Innovation Great Project of Chinese Academy of Sciences, China, in 2000-2003(No. KGCX1-11).
文摘A new method of collision-free path plan integrated in virtual processing is developed to improve the efficiency of laser surface hardening on dies. The path plan is based on the premise of no collision and the optimization object is the shortest path. The optimization model of collision-free path is built from traveling salesman problem （TSP）. Collision-free path between two machining points is calculated in configuration space （C-Space）. Ant colony optimization （ACO） algorithm is applied to TSP of all the machining points to find the shortest path, which is simulated in virtual environment set up by IGRIP software. Virtual machining time, no-collision report, etc, are put out atter the simulation. An example on autobody die is processed in the virtual platform, the simulation results display that ACO has perfect optimization effect, and the method of virtual processing with integration of collision-free optimal path is practical.
文摘Laser surface transformation hardening becomes one of the most effective processes used to improve wear and fatigue resistance of mechanical parts. In this process, the material physicochemical properties and the heating system parameters have significant effects on the characteristics of the hardened surface. To appropriately exploit the benefits presented by the laser surface hardening, it is necessary to develop a comprehensive strategy to control the process variables in order to produce desired hardened surface attributes without being forced to use the traditional and fastidious trial and error procedures. The paper presents a study of hardness profile predictive modeling and experimental validation for spline shafts using a 3D model. The proposed approach is based on thermal and metallurgical simulations, experimental investigations and statistical analysis to build the prediction model. The simulation of the hardening process is carried out using 3D finite element model on commercial software. The model is used to estimate the temperature distribution and the hardness profile attributes for various hardening parameters, such as laser power, shaft rotation speed and scanning speed. The experimental calibration and validation of the model are performed on a 3 kW Nd:Yag laser system using a structured experimental design and confirmed statistical analysis tools. The results reveal that the model can provide not only a consistent and accurate prediction of temperature distribution and hardness profile characteristics under variable hardening parameters and conditions but also a comprehensive and quantitative analysis of process parameters effects. The modelling results show a great concordance between predicted and measured values for the dimensions of hardened zones.
文摘This study investigates the dielectric and thermal properties of transformer oil-based nanofluids incorporating Fe_(3)O_(4)-coated SiO_(2) core-shell nanoparticles as nanofillers.The nanoparticles were synthesised with varying shell thicknesses,and two samples underwent surface treatment.Fourier transform infrared spectroscopy was used to characterise the nanoparticles.The spectra for unmodified and modified nanoparticles detected Fe-O bond,Si-O-Si bond and oleic acid existence.The nanofluids were prepared using a two-step method:nanoparticles were first prepared at concentrations of 0.04,0.07 and 0.10 g/L,and then mixed with the base oil and dispersed using ultrasonication.AC breakdown strength was measured for samples at these concentrations to determine the optimum concentration for each type of nanoparticle.The optimum concentration,which provided the best performance for AC breakdown voltage across all nanoparticle types,was found to be 0.07 g/L.Thermal conductivity testing was then conducted at this optimum concentration.The addition of nanofillers resulted in increased AC breakdown strength and thermal conductivity.Particle size and zeta size measurements were carried out to assess the dispersion behaviour of the nanofluid samples.The physical discussion examined potential reasons for improvements in AC breakdown voltage and thermal conductivity.Trapping and de-trapping processes,shell thickness and surface modifications were analysed in relation to improved dielectric performance.Ballistic phonon transport and Brownian motion mechanisms were employed to explain the observed enhancements in thermal conductivity.These findings indicate the potential for developing a new class of liquid dielectrics suitable for use in power transformers.
