Journal of Electrical Engineering and Technology, 2012
In this paper, a high-performance optical gating in a junction device based on a vanadium dioxide... more In this paper, a high-performance optical gating in a junction device based on a vanadium dioxide dioxide (VO 2) thin film grown by a sol-gel method was experimentally demonstrated by directly illuminating the VO 2 film of the device with an infrared light at ~1554.6 nm. The threshold voltage of the fabricated device could be tuned by ~76.8 % at an illumination power of ~39.8 mW resulting in a tuning efficiency of ~1.930 %/mW, which was ~4.9 times as large as that obtained in the previous device fabricated using the VO 2 thin film deposited by a pulsed laser deposition method. The rising and falling times of the optical gating operation were measured as ~50 ms and ~200 ms, respectively, which were ~20 times as rapid as those obtained in the previous device.
This paper demonstrates the development of optical temperature sensor based on the etched silica-... more This paper demonstrates the development of optical temperature sensor based on the etched silica-based planar waveguide Bragg grating. Topics include design and fabrication of the etched planar waveguide Bragg grating optical temperature sensor. The typical bandwidth and reflectivity of the surface etched grating has been-0.2 nm and-9 %, respectively, at a wavelength of-1552 nm. The temperature-induced wavelength change is found to be slightly non-linear over-2oo•C temperature range. Typically, the temperature-induced fractional Bragg wavelength shift measured in this experiment is 0.0132 nmj"C with linear curve fit. Theoretical models with nonlinear temperature effect for the grating response based on waveguide and plate deformation theories agree with experiments to within acceptable tolerance.
A new approach for manufacturing hollow polyimide (PI) microspheres is presented. The method is b... more A new approach for manufacturing hollow polyimide (PI) microspheres is presented. The method is based on cavitation bubbles and small CO 2 gas bubble which can generate uniform microspheres. When liquid PI was irradiated by a 355-nm nanosecond pulsed laser in a gas pressure chamber, microspheres ranging from 25 to 35 lm and smaller spheres attached to the microspheres ranging from 5 lm to submicron dimensions were generated in the liquid. Microspheres ranging from 25 to 35 lm were fabricated by laser-induced formation. The spheres' morphology was influenced by the pressure in the chamber. When the pressure is high in the chamber, non-uniform microspheres are produced due to flow caused by the laserinduced shockwave and change of the carbon dioxide concentration in the liquid. Smaller spheres with 5 lm to submicron dimensions attached onto the microspheres were fabricated by a gas bubble template method and laser-induced formation. The resulting shell of hollow PI microspheres was about 4 lm, and the sphere inside has a porous structure. Our results indicate that the proposed laser-induced formation technology in a gas pressure chamber can be used to prepare polymer spheres by controlling the gas pressure.
In this paper, we show that the fiber Bragg grating sensor can be used to detect and differentiat... more In this paper, we show that the fiber Bragg grating sensor can be used to detect and differentiate the number of layers that are deposited on the fiber surface. A theory was developed for calculating the wavelength change as thin films of biological and chemical layers are immobilized on the surface of the fiber in the presence of a surrounding
21st International Conference on Optical Fiber Sensors, 2011
ABSTRACT We demonstrate an etched-core fiber Bragg grating sensor for detection of bio-chemical a... more ABSTRACT We demonstrate an etched-core fiber Bragg grating sensor for detection of bio-chemical agents. The fiber Bragg grating of the sensor is etched to a diameter of 7 mum. The transition between the etched and the unetched core consists of an asymmetric taper resulting in excitation of multiple modes. The different excited modes respond differently to change in refractive index, temperature and strain. This allows for measurements for changes in these three parameters in a single measurement by simultaneous measurement of reflections in Bragg wavelengths for different modes. This parametric discrimination is confirmed experimentally by measuring the refractive index of water as temperature is increased. The sensor is then integrated in a micro-fluidic channel fabricated using Polydimethylsiloxane (PDMS) substrate and tested by introducing different chemicals. The sensitivity of the sensor to refractive index change is 92 nm/riu close to the refractive index of water. Assuming a wavelength resolution of 1 pm, index resolution of 1x10-5, a strain resolution of 1 microstrain, and a temperature resolution of 0.032 ºC is achieved by the sensor.
Using asymmetrical non-adiabatic tapers we excite 3 modes in an etched-core-fiber-Bragg-grating s... more Using asymmetrical non-adiabatic tapers we excite 3 modes in an etched-core-fiber-Bragg-grating sensor and show that the refractive index, temperature and strain can be measured simultaneously in bio-chemical sensing experiments.
Engineering Plasticity and Its Applications from Nanoscale to Macroscale - Proceedings of the 9th AEPA2008, 2009
ABSTRACT Semi-solid forging process has many advantages such as long die life, good mechanical pr... more ABSTRACT Semi-solid forging process has many advantages such as long die life, good mechanical properties and energy savings. But rheology material has complex characteristics, i.e., thixotropic behavior. Also, difference of the particle velocity between solid and liquid phase in the semi-solid state material causes a liquid segregation and specific stress variation. A number of simulation tools have been attempted for analyzing these behaviors of rheology material. However, general plastic or fluid dynamic analysis is not suitable. Therefore, we set up the stress equation to include viscosity, in order for investigating on how the moving behavior the solid particle in the rheology material during forging process is affected by viscosity, temperature, and solid fraction. In this study, a dynamics simulation was performed for the control of liquid segregation and the prediction of stresses on particles by changing forming velocity and viscosity in a compression experiment as part of a study on the analysis of the rheology aluminum forming process.
Interest in the rheology forming technology for fabrication of light weight materials and for res... more Interest in the rheology forming technology for fabrication of light weight materials and for resolving environmental issues has been growing in industrial and academic society. In this study, the helical shape stirrer was designed to produce rheological material. The experimental variables, which were stirring time 0-1200 sec, stirring velocity 0-100 rpm and melt temperatures for semisolid states, were established. The rheological materials were produced under established experiment conditions, and then mechanical properties were measured. Sequence-production equipments were appended to fabrication system of rheology material to make rheology materials continuously. Therefore, the development of sequence-production system equipped with a specially designed mechanical stirrer in spiral shape was necessary for fabricating fine grains and their uniform globular rheology materials. The thixoforging was experimented with rheological A6061 wrought aluminum alloy fabricated by the spiral ...
Journal of Electrical Engineering and Technology, 2012
In this paper, a high-performance optical gating in a junction device based on a vanadium dioxide... more In this paper, a high-performance optical gating in a junction device based on a vanadium dioxide dioxide (VO 2) thin film grown by a sol-gel method was experimentally demonstrated by directly illuminating the VO 2 film of the device with an infrared light at ~1554.6 nm. The threshold voltage of the fabricated device could be tuned by ~76.8 % at an illumination power of ~39.8 mW resulting in a tuning efficiency of ~1.930 %/mW, which was ~4.9 times as large as that obtained in the previous device fabricated using the VO 2 thin film deposited by a pulsed laser deposition method. The rising and falling times of the optical gating operation were measured as ~50 ms and ~200 ms, respectively, which were ~20 times as rapid as those obtained in the previous device.
This paper demonstrates the development of optical temperature sensor based on the etched silica-... more This paper demonstrates the development of optical temperature sensor based on the etched silica-based planar waveguide Bragg grating. Topics include design and fabrication of the etched planar waveguide Bragg grating optical temperature sensor. The typical bandwidth and reflectivity of the surface etched grating has been-0.2 nm and-9 %, respectively, at a wavelength of-1552 nm. The temperature-induced wavelength change is found to be slightly non-linear over-2oo•C temperature range. Typically, the temperature-induced fractional Bragg wavelength shift measured in this experiment is 0.0132 nmj"C with linear curve fit. Theoretical models with nonlinear temperature effect for the grating response based on waveguide and plate deformation theories agree with experiments to within acceptable tolerance.
A new approach for manufacturing hollow polyimide (PI) microspheres is presented. The method is b... more A new approach for manufacturing hollow polyimide (PI) microspheres is presented. The method is based on cavitation bubbles and small CO 2 gas bubble which can generate uniform microspheres. When liquid PI was irradiated by a 355-nm nanosecond pulsed laser in a gas pressure chamber, microspheres ranging from 25 to 35 lm and smaller spheres attached to the microspheres ranging from 5 lm to submicron dimensions were generated in the liquid. Microspheres ranging from 25 to 35 lm were fabricated by laser-induced formation. The spheres' morphology was influenced by the pressure in the chamber. When the pressure is high in the chamber, non-uniform microspheres are produced due to flow caused by the laserinduced shockwave and change of the carbon dioxide concentration in the liquid. Smaller spheres with 5 lm to submicron dimensions attached onto the microspheres were fabricated by a gas bubble template method and laser-induced formation. The resulting shell of hollow PI microspheres was about 4 lm, and the sphere inside has a porous structure. Our results indicate that the proposed laser-induced formation technology in a gas pressure chamber can be used to prepare polymer spheres by controlling the gas pressure.
In this paper, we show that the fiber Bragg grating sensor can be used to detect and differentiat... more In this paper, we show that the fiber Bragg grating sensor can be used to detect and differentiate the number of layers that are deposited on the fiber surface. A theory was developed for calculating the wavelength change as thin films of biological and chemical layers are immobilized on the surface of the fiber in the presence of a surrounding
21st International Conference on Optical Fiber Sensors, 2011
ABSTRACT We demonstrate an etched-core fiber Bragg grating sensor for detection of bio-chemical a... more ABSTRACT We demonstrate an etched-core fiber Bragg grating sensor for detection of bio-chemical agents. The fiber Bragg grating of the sensor is etched to a diameter of 7 mum. The transition between the etched and the unetched core consists of an asymmetric taper resulting in excitation of multiple modes. The different excited modes respond differently to change in refractive index, temperature and strain. This allows for measurements for changes in these three parameters in a single measurement by simultaneous measurement of reflections in Bragg wavelengths for different modes. This parametric discrimination is confirmed experimentally by measuring the refractive index of water as temperature is increased. The sensor is then integrated in a micro-fluidic channel fabricated using Polydimethylsiloxane (PDMS) substrate and tested by introducing different chemicals. The sensitivity of the sensor to refractive index change is 92 nm/riu close to the refractive index of water. Assuming a wavelength resolution of 1 pm, index resolution of 1x10-5, a strain resolution of 1 microstrain, and a temperature resolution of 0.032 ºC is achieved by the sensor.
Using asymmetrical non-adiabatic tapers we excite 3 modes in an etched-core-fiber-Bragg-grating s... more Using asymmetrical non-adiabatic tapers we excite 3 modes in an etched-core-fiber-Bragg-grating sensor and show that the refractive index, temperature and strain can be measured simultaneously in bio-chemical sensing experiments.
Engineering Plasticity and Its Applications from Nanoscale to Macroscale - Proceedings of the 9th AEPA2008, 2009
ABSTRACT Semi-solid forging process has many advantages such as long die life, good mechanical pr... more ABSTRACT Semi-solid forging process has many advantages such as long die life, good mechanical properties and energy savings. But rheology material has complex characteristics, i.e., thixotropic behavior. Also, difference of the particle velocity between solid and liquid phase in the semi-solid state material causes a liquid segregation and specific stress variation. A number of simulation tools have been attempted for analyzing these behaviors of rheology material. However, general plastic or fluid dynamic analysis is not suitable. Therefore, we set up the stress equation to include viscosity, in order for investigating on how the moving behavior the solid particle in the rheology material during forging process is affected by viscosity, temperature, and solid fraction. In this study, a dynamics simulation was performed for the control of liquid segregation and the prediction of stresses on particles by changing forming velocity and viscosity in a compression experiment as part of a study on the analysis of the rheology aluminum forming process.
Interest in the rheology forming technology for fabrication of light weight materials and for res... more Interest in the rheology forming technology for fabrication of light weight materials and for resolving environmental issues has been growing in industrial and academic society. In this study, the helical shape stirrer was designed to produce rheological material. The experimental variables, which were stirring time 0-1200 sec, stirring velocity 0-100 rpm and melt temperatures for semisolid states, were established. The rheological materials were produced under established experiment conditions, and then mechanical properties were measured. Sequence-production equipments were appended to fabrication system of rheology material to make rheology materials continuously. Therefore, the development of sequence-production system equipped with a specially designed mechanical stirrer in spiral shape was necessary for fabricating fine grains and their uniform globular rheology materials. The thixoforging was experimented with rheological A6061 wrought aluminum alloy fabricated by the spiral ...
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