Numerical studies on transient heat transfer characteristics of air-array-jet impingement with a small jet-to-plate distance and a large temperature difference between nozzles and plate were presented.The dimensionles...Numerical studies on transient heat transfer characteristics of air-array-jet impingement with a small jet-to-plate distance and a large temperature difference between nozzles and plate were presented.The dimensionless jet-to-plate distance(H/D)was 0.2,and non-dimensional nozzle-to-nozzle spacing(S/D)was 3,4,5 and 6,respectively.It is found that the quenching time is shortened at a constant total mass flow at air jet inlet m·(m·=218.21 kg/h),and the heat transfer uniformity is deterio-rated as S/D increases.However,the adding reversed-flow nozzles can shorten the quenching time of the glass plate considerably with a modest change in the heat transfer uniformity.The results at variable m·are the same as those at a fixed m·.Furthermore,the parity and arrangement of nozzles are also discussed,It is found that an odd number of nozzles is more beneficial for transient heat transfer.Based on these results,an appropriate proposal for ultra-thin glass tempering process is presented.展开更多
To further extend knowledge about the detailed knowledge on the crossflow characteristics in a multi-jets system under a confined space,particle image velocimetry (PIV) was employed to investigate the flow structures ...To further extend knowledge about the detailed knowledge on the crossflow characteristics in a multi-jets system under a confined space,particle image velocimetry (PIV) was employed to investigate the flow structures together with the distributions of the mean velocity components for Reynolds numbers (Re) ranging from 6 213 to 13 418,nozzle-to-plate spacing (H/D) varying from 0. 20 to1. 25,respectively. Results show that the crossflow configuration is significantly different from those of large nozzle-to-plate spacing. In addition,a turning point H/D=0.50 is revealed in the profile of the normalized maximum radial velocity which is associated with the heat transfer distribution on the impingement plate.展开更多
The validity of a novel, direct and convenient method for micromechanical property measurements by beam bending using a nanoindenter is demonstrated. This method combines a very high load resolution with a nanometric ...The validity of a novel, direct and convenient method for micromechanical property measurements by beam bending using a nanoindenter is demonstrated. This method combines a very high load resolution with a nanometric precision in the determination of the microcantilever beam deflection. The method is described clearly. In the deflection of microbeams, the influence of the indenter tip pushing into the top of the microbeams and the curvature across its width must be considered. The measurements were made on single-layer, micro-thick, several kinds of width and length polysilicon beams that were fabricated using conventional integrated circuit (IC) fabrication techniques. The elastic of a polysilicon microcantilever beam will vary linearly with the force and the deformation is thought to be elastic. Furthermore, it suggests that Young modulus of the beam can be determined from the slope of this linear relation. From the load deflection data acquired during bending the mechanical properties of the thin films were determined. Measured Young modulus is 137 GPa with approximately a ±2.9%～±6.3% difference in Young modulus.展开更多
The naniondentation fracture of multilayer hard coatings, such as TiN, TiN/Ti(C, N)/TiC, TiN/Ti (C,N)/TiC/Ti (C, N)/TiC and TiN/Ti (C, N)/TiC/Ti (C,N)/TiC/Ti(C,N)/TiC coating, deposited on cemented carbide using a CVD...The naniondentation fracture of multilayer hard coatings, such as TiN, TiN/Ti(C, N)/TiC, TiN/Ti (C,N)/TiC/Ti (C, N)/TiC and TiN/Ti (C, N)/TiC/Ti (C,N)/TiC/Ti(C,N)/TiC coating, deposited on cemented carbide using a CVD technique are studied. It is found that these coatings have high hardness. Based on the analysis of the energy release in cracking, the fracture toughness of these coatings are calculated. The observations clearly establish a step occurs in the force-displacement curves at the onset of coating fracture and a straight line segment in the load-penetration depth squared curves to idenntify the interfacial failure of coatings. The hardness, fracture toughness and anti-wearability of these coatings are clearly compared. The results show that with the layers increasing, the fracture toughness and anti-wearbility are getting larger.展开更多
The rapid increase in the aging population prompts the development of wearable devices and sophisticated robots. With their ability to collect complex information about their surroundings via e-skins, robots could per...The rapid increase in the aging population prompts the development of wearable devices and sophisticated robots. With their ability to collect complex information about their surroundings via e-skins, robots could perform more dynamic and variable tasks such as rescue missions or caring for the elderly. In this paper, we present a new concept of utilizing a very simple, highly flexible and stretchable capacitor sensor array, that can be attached on the surface of a retractable robot hand to realize three functions: determining the location, shape, and pressure of an object. This adaptive sensing system is accomplished using capacitors connected by aligned carbon nanotube(CNT) films constructed on an elastomer dielectric material, which can reduce the requirement on the accuracy of the machine vision system. This study has a very broad application in the manufacture of intelligent software robots.展开更多
To study the ferroelectric photovoltaic effect based on polycrystalline films,preparation of high-quality polycrystalline films with low leakage and high remnant polarization is essential.Polycrystalline Bi Fe O3(BFO)...To study the ferroelectric photovoltaic effect based on polycrystalline films,preparation of high-quality polycrystalline films with low leakage and high remnant polarization is essential.Polycrystalline Bi Fe O3(BFO)thin films with extremely large remnant polarization(2Pr=180μC/cm2)were successfully deposited on glass substrates coated with indium tin oxide using a modified radio frequency magnetron sputtering method.Symmetric and asymmetric cells were constructed to investigate the ferroelectric photovoltaic effect in order to understand the relationship between polarization and photovoltaic response.All examined cells showed polarization-induced photovoltaic effect.Our findings also showed that the ferroelectric photovoltaic effect is highly dependent on the material used for the top electrode and the thickness of the polycrystalline film.展开更多
0.14 at%Mn-doped 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3(0.95NBT-0.05BT)lead-free single crystals were grown by a top-seeded solution growth method(TSSG).X-ray powder diffraction measurement showed that the as-grown single cr...0.14 at%Mn-doped 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3(0.95NBT-0.05BT)lead-free single crystals were grown by a top-seeded solution growth method(TSSG).X-ray powder diffraction measurement showed that the as-grown single crystals exhibit rhombohedral perovskite structure with apparent distortion.With the increase of temperature,successive structural phase transitions occur in the Mn-doped 0.95NBT-0.05BT single crystals.After poling,apparent dielectric anomaly is induced accompanied by the increase of the character of diffuse phase transition and the decrease of the value of dielectric constant.The Mn-doped0.95NBT-0.05BT single crystals exhibit complex domain structure,in which micro and macro domains coexist with statistically 4mm symmetry.The Mn-doped 0.95NBT-0.05BT lead-free single crystals exhibit excellent piezoelectric and pyroelectric properties,which will lead to promising advance in piezoelectric and pyroelectric applications.The infrared-absorption band occurred around 630.6 cm 1can be assigned to the"stretching"normal vibration of[Na1/2Bi1/2]/Ti-O group.The three diffused Raman bands centered around 300,560 and 800 cm 1can be attributed to F2g[TiO6]bending vibration,A1g[TiO6]stretching vibration and"soft mode"mixed by bending and stretching vibrations.展开更多
Mechanical stability and sticking are the troublesome problems in microfabrication andoperation processes when separations of components in MEMS are in the sub-micrometer regime.Some mechanical effects including quant...Mechanical stability and sticking are the troublesome problems in microfabrication andoperation processes when separations of components in MEMS are in the sub-micrometer regime.Some mechanical effects including quantum mechanical effect should be taken into account forsolving the problems. The influence of capillary forces on sticking of a surface micromachined mi-crocantilever in ambient environment or the rinse liquid and the influence of quantum mechanicaleffect such as the Casimir effect on sticking and stability of a micro membrane strip cavity structurein vacuum were investigated. A factual rough model theory about sticking problem under theCasimir effect was suggested for the first time. The study on the design of anti-sticking structuresunder different forces shows that sticking and stability of microcantilevers and micro membranestrip cavities has something to do with Young’s modulus of materials, surface properties, length ofstructures, thickness of structures and separation between the fixed surface and the deflectingcomponent. But, it is independent of width of structures. The map of the size design of anti-stickingstructures was put forward for the first time. This also provides a way to design a MEMS structurewith high resistance to collapse.展开更多
The application of a p~＋/p configuration in the window layer of hydrogenated amorphous silicon thin film solar cells is simulated and analyzed utilizing an AMPS-ID program.The differences between p~＋-p-i-n configura...The application of a p~＋/p configuration in the window layer of hydrogenated amorphous silicon thin film solar cells is simulated and analyzed utilizing an AMPS-ID program.The differences between p~＋-p-i-n configuration solar cells and p-i-n configuration solar cells are pointed out.The effects of dopant concentration, thickness of p~＋-layer,contact barrier height and defect density on solar cells are analyzed.Our results indicate that solar cells with a p~＋-p-i-n configuration have a better performance.The open circuit voltage and short circuit current were improved by increasing the dopant concentration of the p~＋ layer and lowering the front contact barrier height.The defect density at the p/i interface which exceeds two orders of magnitude in the intrinsic layer will deteriorate the cell property.展开更多
基金Natural Science Foundation of China(51335002,51905049)。
文摘Numerical studies on transient heat transfer characteristics of air-array-jet impingement with a small jet-to-plate distance and a large temperature difference between nozzles and plate were presented.The dimensionless jet-to-plate distance(H/D)was 0.2,and non-dimensional nozzle-to-nozzle spacing(S/D)was 3,4,5 and 6,respectively.It is found that the quenching time is shortened at a constant total mass flow at air jet inlet m·(m·=218.21 kg/h),and the heat transfer uniformity is deterio-rated as S/D increases.However,the adding reversed-flow nozzles can shorten the quenching time of the glass plate considerably with a modest change in the heat transfer uniformity.The results at variable m·are the same as those at a fixed m·.Furthermore,the parity and arrangement of nozzles are also discussed,It is found that an odd number of nozzles is more beneficial for transient heat transfer.Based on these results,an appropriate proposal for ultra-thin glass tempering process is presented.
基金National Natural Science Foundation of China(51335002)
文摘To further extend knowledge about the detailed knowledge on the crossflow characteristics in a multi-jets system under a confined space,particle image velocimetry (PIV) was employed to investigate the flow structures together with the distributions of the mean velocity components for Reynolds numbers (Re) ranging from 6 213 to 13 418,nozzle-to-plate spacing (H/D) varying from 0. 20 to1. 25,respectively. Results show that the crossflow configuration is significantly different from those of large nozzle-to-plate spacing. In addition,a turning point H/D=0.50 is revealed in the profile of the normalized maximum radial velocity which is associated with the heat transfer distribution on the impingement plate.
文摘The validity of a novel, direct and convenient method for micromechanical property measurements by beam bending using a nanoindenter is demonstrated. This method combines a very high load resolution with a nanometric precision in the determination of the microcantilever beam deflection. The method is described clearly. In the deflection of microbeams, the influence of the indenter tip pushing into the top of the microbeams and the curvature across its width must be considered. The measurements were made on single-layer, micro-thick, several kinds of width and length polysilicon beams that were fabricated using conventional integrated circuit (IC) fabrication techniques. The elastic of a polysilicon microcantilever beam will vary linearly with the force and the deformation is thought to be elastic. Furthermore, it suggests that Young modulus of the beam can be determined from the slope of this linear relation. From the load deflection data acquired during bending the mechanical properties of the thin films were determined. Measured Young modulus is 137 GPa with approximately a ±2.9%～±6.3% difference in Young modulus.
文摘The naniondentation fracture of multilayer hard coatings, such as TiN, TiN/Ti(C, N)/TiC, TiN/Ti (C,N)/TiC/Ti (C, N)/TiC and TiN/Ti (C, N)/TiC/Ti (C,N)/TiC/Ti(C,N)/TiC coating, deposited on cemented carbide using a CVD technique are studied. It is found that these coatings have high hardness. Based on the analysis of the energy release in cracking, the fracture toughness of these coatings are calculated. The observations clearly establish a step occurs in the force-displacement curves at the onset of coating fracture and a straight line segment in the load-penetration depth squared curves to idenntify the interfacial failure of coatings. The hardness, fracture toughness and anti-wearability of these coatings are clearly compared. The results show that with the layers increasing, the fracture toughness and anti-wearbility are getting larger.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFB0307000-01)the National Natural Science Foundation of China(Grant No.91648109)the Priority Academic Program Development of Jiangsu Higher Education Institutions,333 Project of Jiangsu Province
文摘The rapid increase in the aging population prompts the development of wearable devices and sophisticated robots. With their ability to collect complex information about their surroundings via e-skins, robots could perform more dynamic and variable tasks such as rescue missions or caring for the elderly. In this paper, we present a new concept of utilizing a very simple, highly flexible and stretchable capacitor sensor array, that can be attached on the surface of a retractable robot hand to realize three functions: determining the location, shape, and pressure of an object. This adaptive sensing system is accomplished using capacitors connected by aligned carbon nanotube(CNT) films constructed on an elastomer dielectric material, which can reduce the requirement on the accuracy of the machine vision system. This study has a very broad application in the manufacture of intelligent software robots.
基金supported by the National High Technology Research and Development Program(Grant No.2011AA050511)Jiangsu"333"Project,the Priority Academic Program Development of Jiangsu Higher Education Institutions and Research and Innovation Project for College Graduates of Jiangsu Province(Grant No.CXLX13_722)
文摘To study the ferroelectric photovoltaic effect based on polycrystalline films,preparation of high-quality polycrystalline films with low leakage and high remnant polarization is essential.Polycrystalline Bi Fe O3(BFO)thin films with extremely large remnant polarization(2Pr=180μC/cm2)were successfully deposited on glass substrates coated with indium tin oxide using a modified radio frequency magnetron sputtering method.Symmetric and asymmetric cells were constructed to investigate the ferroelectric photovoltaic effect in order to understand the relationship between polarization and photovoltaic response.All examined cells showed polarization-induced photovoltaic effect.Our findings also showed that the ferroelectric photovoltaic effect is highly dependent on the material used for the top electrode and the thickness of the polycrystalline film.
基金supported by the National Natural Science Foundation of China(51242006)the Qing Lan Project,the Key Laboratory of Inorganic Function Material and Device,Chinese Academy of Sciences(KLIFMD-2011-02)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘0.14 at%Mn-doped 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3(0.95NBT-0.05BT)lead-free single crystals were grown by a top-seeded solution growth method(TSSG).X-ray powder diffraction measurement showed that the as-grown single crystals exhibit rhombohedral perovskite structure with apparent distortion.With the increase of temperature,successive structural phase transitions occur in the Mn-doped 0.95NBT-0.05BT single crystals.After poling,apparent dielectric anomaly is induced accompanied by the increase of the character of diffuse phase transition and the decrease of the value of dielectric constant.The Mn-doped0.95NBT-0.05BT single crystals exhibit complex domain structure,in which micro and macro domains coexist with statistically 4mm symmetry.The Mn-doped 0.95NBT-0.05BT lead-free single crystals exhibit excellent piezoelectric and pyroelectric properties,which will lead to promising advance in piezoelectric and pyroelectric applications.The infrared-absorption band occurred around 630.6 cm 1can be assigned to the"stretching"normal vibration of[Na1/2Bi1/2]/Ti-O group.The three diffused Raman bands centered around 300,560 and 800 cm 1can be attributed to F2g[TiO6]bending vibration,A1g[TiO6]stretching vibration and"soft mode"mixed by bending and stretching vibrations.
文摘Mechanical stability and sticking are the troublesome problems in microfabrication andoperation processes when separations of components in MEMS are in the sub-micrometer regime.Some mechanical effects including quantum mechanical effect should be taken into account forsolving the problems. The influence of capillary forces on sticking of a surface micromachined mi-crocantilever in ambient environment or the rinse liquid and the influence of quantum mechanicaleffect such as the Casimir effect on sticking and stability of a micro membrane strip cavity structurein vacuum were investigated. A factual rough model theory about sticking problem under theCasimir effect was suggested for the first time. The study on the design of anti-sticking structuresunder different forces shows that sticking and stability of microcantilevers and micro membranestrip cavities has something to do with Young’s modulus of materials, surface properties, length ofstructures, thickness of structures and separation between the fixed surface and the deflectingcomponent. But, it is independent of width of structures. The map of the size design of anti-stickingstructures was put forward for the first time. This also provides a way to design a MEMS structurewith high resistance to collapse.
基金supported by the Key Programs for Science and Technology Development of Jiangsu,China(Nos.BE20080030,BE2009028)the Qing Lan Project,China(No.2008-04)the Jiangsu"333"Project,China(No.201041)
文摘The application of a p~＋/p configuration in the window layer of hydrogenated amorphous silicon thin film solar cells is simulated and analyzed utilizing an AMPS-ID program.The differences between p~＋-p-i-n configuration solar cells and p-i-n configuration solar cells are pointed out.The effects of dopant concentration, thickness of p~＋-layer,contact barrier height and defect density on solar cells are analyzed.Our results indicate that solar cells with a p~＋-p-i-n configuration have a better performance.The open circuit voltage and short circuit current were improved by increasing the dopant concentration of the p~＋ layer and lowering the front contact barrier height.The defect density at the p/i interface which exceeds two orders of magnitude in the intrinsic layer will deteriorate the cell property.
