Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved b...Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved by using a quantitative method. In this work, volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers. Laser deposition experiments with FV520B, one of martensitic stainless steels, were designed by using the Taguchi method. Four process variables, namely, laser power （P）, scanning speed （Vs）, wire feed rate （Vf）, and wire current （/）, were optimized based on the analysis of signal-to-noise （S/N） ratio. Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method. A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks, which resulted in a good metallurgical bonding interface.展开更多
Stray magnetic fields with a fixed frequency of 50/60 Hz are ubiquitous in buildings,factories,and power system equipment.Researchers are increasingly focusing on har-vesting electrical energy from stray magnetic fiel...Stray magnetic fields with a fixed frequency of 50/60 Hz are ubiquitous in buildings,factories,and power system equipment.Researchers are increasingly focusing on har-vesting electrical energy from stray magnetic fields to provide sustainable energy for the Internet of Things(IoT)devices.Magneto‐mechano‐electric energy conversion is the most efficient way to convert low‐frequency stray magnetic fields into electricity.In this study,we proposed a hybrid piezo/triboelectric nanogenerator(HP/TENG)on the basis of a cantilever beam to use stray magnetic fields from the surrounding environment.The hybrid nanogenerator provided high output voltage/current and power of∼176 V/375μA and 4.7 mW(matched impedance of 20 kΩ)in a magnetic field environment of 4 Oe.The device provided a stable 3.6 V direct current output by incorporating energy management circuitry to sustainably drive power to commercial wireless temperature/humidity sensors.The HP/TENG has a significant application potential in IoT,which can use stray magnetic energy and a power wireless sensor system.展开更多
Si/Gesuperlattices are promising thermoelec- tric materials to convert thermal energy into electric power. The nanoscale thermal transport in Si/Gesuperlattices is investigated via molecular dynamics （MD） simulation...Si/Gesuperlattices are promising thermoelec- tric materials to convert thermal energy into electric power. The nanoscale thermal transport in Si/Gesuperlattices is investigated via molecular dynamics （MD） simulation in this short communication. The impact of Si and Ge interface on the cross-plane thermal conductivity reduction in the Si/Gesuperlattices is studied by designing cone- structured interface and aperiodicity between the Si and Ge layers. The temperature difference between the left and right sides of the Si/Gesuperlattices is set up for none- quilibrium MD simulation. The spatial distribution of temperature is recorded to examine whether the steady- state has been reached. As a crucial factor to quantify thermal transport, the temporal evolution of heat flux flowing through Si/Gesuperlattices is calculated. Com- pared with the even interface, the cone-structured interface contributes remarkable resistance to the thermal transport, whereas the aperiodic arrangement of Si and Ge layers with unequal thicknesses has a marginal influence on the reduction of effective thermal conductivity. The interface with divergent cone-structure shows the most excellent performance of all the simulated cases, which brings a 33% reduction of the average thermal conductivity to the other Si/Gesuperlattices with even, convergent cone-structured interfaces and aperiodic arrangements. The design of divergent cone-structured interface sheds promising lighton enhancing the thermoelectric efficiency of Si/Ge based materials.展开更多
文摘Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved by using a quantitative method. In this work, volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers. Laser deposition experiments with FV520B, one of martensitic stainless steels, were designed by using the Taguchi method. Four process variables, namely, laser power （P）, scanning speed （Vs）, wire feed rate （Vf）, and wire current （/）, were optimized based on the analysis of signal-to-noise （S/N） ratio. Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method. A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks, which resulted in a good metallurgical bonding interface.
基金supported by the State Grid Corporation of China through the Science and Technology Project under Grant 52094020006Z。
文摘Stray magnetic fields with a fixed frequency of 50/60 Hz are ubiquitous in buildings,factories,and power system equipment.Researchers are increasingly focusing on har-vesting electrical energy from stray magnetic fields to provide sustainable energy for the Internet of Things(IoT)devices.Magneto‐mechano‐electric energy conversion is the most efficient way to convert low‐frequency stray magnetic fields into electricity.In this study,we proposed a hybrid piezo/triboelectric nanogenerator(HP/TENG)on the basis of a cantilever beam to use stray magnetic fields from the surrounding environment.The hybrid nanogenerator provided high output voltage/current and power of∼176 V/375μA and 4.7 mW(matched impedance of 20 kΩ)in a magnetic field environment of 4 Oe.The device provided a stable 3.6 V direct current output by incorporating energy management circuitry to sustainably drive power to commercial wireless temperature/humidity sensors.The HP/TENG has a significant application potential in IoT,which can use stray magnetic energy and a power wireless sensor system.
文摘Si/Gesuperlattices are promising thermoelec- tric materials to convert thermal energy into electric power. The nanoscale thermal transport in Si/Gesuperlattices is investigated via molecular dynamics （MD） simulation in this short communication. The impact of Si and Ge interface on the cross-plane thermal conductivity reduction in the Si/Gesuperlattices is studied by designing cone- structured interface and aperiodicity between the Si and Ge layers. The temperature difference between the left and right sides of the Si/Gesuperlattices is set up for none- quilibrium MD simulation. The spatial distribution of temperature is recorded to examine whether the steady- state has been reached. As a crucial factor to quantify thermal transport, the temporal evolution of heat flux flowing through Si/Gesuperlattices is calculated. Com- pared with the even interface, the cone-structured interface contributes remarkable resistance to the thermal transport, whereas the aperiodic arrangement of Si and Ge layers with unequal thicknesses has a marginal influence on the reduction of effective thermal conductivity. The interface with divergent cone-structure shows the most excellent performance of all the simulated cases, which brings a 33% reduction of the average thermal conductivity to the other Si/Gesuperlattices with even, convergent cone-structured interfaces and aperiodic arrangements. The design of divergent cone-structured interface sheds promising lighton enhancing the thermoelectric efficiency of Si/Ge based materials.
