• Journal of Sensor Science and Technology
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• v.9 no.5
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• pp.365-372
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• 2000

In this study, a multichannel taste sensor using the evanescent field absorption in fiber optic was developed, and evaluated its characteristics for several basic taste substances. This sensor is based on the change of evanescent field absorption at the surface of optical fiber core layer. The sensor device was made of a plastic-clad-silica fiber (3M Co., FP-400-UHT, core diameter $400\;{\mu}m$) and a middle portion of cladding layer was removed and the surface of stripped fiber core was dip-coated with a sensing membrane. And then, it was determined the difference of evanescent field absorption into the sensing membrane, according to various taste substances and its concentrations variance. The sensing membranes were prepared with six kinds of dyes, were known as potential sensitive dye together with silicone polymer the same refractive index of cladding. Each output patterns were obtained from the sensor devices could be distinguished not only five kinds of basic taste substances such as sweetness, saltiness, sourness, bitterness and umami, but also various mixed taste substances.

• Journal of Biomedical Engineering Research
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• v.30 no.1
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• pp.18-22
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• 2009

Laser has been widely used in various fields of medicine. Recently, noninvasive low-level laser therapeutic medical devices have been introduced in market. However, low-level laser cannot deliver enough photon density to expect positive therapeutic results in deep tissue layer due to the light scattering property in tissue. In order to overcome the limitation, this study was aimed to develop a negative pressure applied low-level laser probe to optimize laser transmission pattern and therefore, to improve photon density in soft tissue. In order to evaluate the possibility of clinical application of the developed laser probe, ex-vivo experiments were performed with porcine skin samples and laser transmissions were quantitatively measured as a function of tissue compression. The laser probe has an air suction hole to apply negative pressure to skin, a transparent plastic body to observe variations of tissue, and a small metallic optical fiber guide to support the optical fiber when negative pressure was applied. By applying negative pressure to the laser probe, the porcine skin under the metallic optical fiber guide is compressed down and, at the same time, low-level laser is emitted into the skin. Finally, the diffusion images of laser in the sample were acquired by a CCD camera and analyzed. Compared to the peak intensity without the compression, the peak intensity of laser increased about $2{\sim}2.5$ times and FWHM decreased about $1.67{\sim}2.85$ times. In addition, the laser peak intensity was positively and linearly increased as a function of compression. In conclusion, we verified that the developed low-level laser probe can control the photon density in tissue by applying compression, and therefore, its potential for clinical applications.

• Journal of the Korean Chemical Society
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• v.33 no.4
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• pp.431-435
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• 1989

The refractive index, refractive-index distribution, birefringence, and the attenuation of the plastic fiber prepared from the transparent PMMA prerod were measured in accordance with continuous heat drawing temperature($T_d$). The refractive indices were decreased with $T_d$ elevation but the refractive-index distribution from the center of fiber to periphery was higher at lower $T_d$. The steep decrease of gradient index was only at the periphery of higher $T_d$. Birefringence was observed only below $220^{\circ}C$ and ranged $5{\times}10^{-4}$ to $6{\times}10^{-4}$. No birefringence was observed above $220^{\circ}C$. An elevation of $T_d$ brought about a monotonous decrease in the attenuation of the fiber.

• Polymer(Korea)
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• v.30 no.4
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• pp.326-331
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• 2006

MMA(methyl methacrylate)/IPMI(N-isopropyl maleimide) copolymers are one of the well known heat resistant materials for POF(plastic optical fiber). However, because of the large difference in the reactivity ratio between MMA and IPMI$(r_1/r_2=1.72:0.17)$, the compositional drift occurs during the polymerization process which causes the deterioration of the physical properties of these copolymers. In this paper, we report that the compositional drift of the copolymer could be reduced by the addition of styrene (St) which increased the reactivity of IPMI in the MMA/IPMI copolymerization system and conversion was also increased by 1.5 or 2 times. The MMA/IPMI/St terpolymer had higher refractive index than the MMA/IPMI copolymer which depended on the contents of sytrene.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3018-3025
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• 2021

The authors developed a volumetric dosimetry detector system using in-house 3D-printable plastic scintillator resins. Three tumor model scintillators (TMSs) were developed using magnetic resonance images of a tumor. The detector system consisted of a TMS, an optical fiber, a photomultiplier tube, and an electrometer. The background signal, including the Cherenkov lights generated in the optical fiber, was subtracted from the output signal. The system showed 2.1% instability when the TMS was reassembled. The system efficiencies in collecting lights for a given absorbed energy were determined by calibration at a secondary standard dosimetry laboratory (k_SSDL) or by calibration using Monte Carlo simulations (k_sim). The TMSs were irradiated in a Gamma Knife® Icon^TM (Elekta AB, Stockholm, Sweden) following a treatment plan. The energies absorbed to the TMSs were measured and compared with a calculated value. While the measured energy determined with k_SSDL was (5.84 ± 3.56) % lower than the calculated value, the energy with k_sim was (2.00 ± 0.76) % higher. Although the TMS detector system worked reasonably well in measuring the absorbed energy to a tumor, further improvements in the calibration procedure and system stability are needed for the system to be accepted as a quality assurance tool.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.2891-2898
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• 2000

The objective of this paper is to develop a fiber-optic acoustic emission(AE) sensor applicable to on-line monitoring systems which is suitable for long-distance signal transmission. An AE sensor was developed by use of a fiber-optic cantilever and an extrinsic Fabry-Perot interferometer(EEPI). The efficiency of signal processing was improved by driving the high frequency AE signals into the low frequency ones. In order to verify the developed sensor, the tensile and the pencil lead fracture(PLF) tests were performed including the experiment showing the Kaiser effect. Form tests, AE signals were successfully detected in the elastic-plastic deformation range, especially higher signals at the crack propagation. The developed sensor was expected to be used for an on-line monitoring of crack propagation in mechanical system.

• Journal of Sensor Science and Technology
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• v.20 no.2
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• pp.96-101
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• 2011

In this study, we fabricated a fiber-optic phantom dosimeter by arraying square type of plastic optical fibers in a PMMA phantom for measuring relative depth doses of therapeutic photon beams. To minimize the cross-talk between fiber-optic dosimeters, we selected appropriate septum by measuring leaked scintillating lights according to the various kinds of septa. In addition, we measured percentage depth doses of 6, 15 MV photon beams using a fiber-optic phantom dosimeter.

• Macromolecular Research
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• v.12 no.6
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• pp.564-572
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• 2004

Modem applications could benefit from multifunctional materials having anisotropic optical, electrical, thermal, or mechanical properties, especially when coupled with locally controlled distribution of the directional response. Such materials are difficult to engineer by conventional methods, but the electric field-aided technology presented herein is able to locally tailor electroactive composites. Applying an electric field to a polymer in its liquid state allows the orientation of chain- or fiber-like inclusions or phases from what was originally an isotropic material. Such composites can be formed from liquid solutions, melts, or mixtures of pre-polymers and cross-linking agents. Upon curing, a 'created composite' results; it consists of these 'pseudofibers' embedded in a matrix. One can also create oriented composites from embedded spheres, flakes, or fiber-like shapes in a liquid plastic. Orientation of the externally applied electric field defines the orientation of the field-aided self-assembled composites. The strength and duration of exposure of the electric field control the degree of anisotropy created. Results of electromechanical testing of these modified materials, which are relevant to sensing and actuation applications, are presented. The materials' micro/nanostructures were analyzed using microscopy and X-ray diffraction techniques.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.5
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• pp.429-438
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• 2003

The effects of fiber orientation on acoustic emission(AE) characteristics have been studied for the unidirectional and satin-weave, continuous glass-fiber reinforced plastic(UD-GFRP and SW-GFRP) tensile specimens. Reflection and transmission optical microscopy was used for investigation of the damage zone of specimens. AE signals were classified as different types by using short time fourier transform(STFT) : AE signals with high intensity and high frequency band were due to fiber fracture, while weak AE signals with low frequency band were due to matrix and interfacial cracking. The feature in the rate of hit-events having high amplitudes showed a process of fiber breakages, which expressed the characteristic fracture processes of individual fiber-reinforced plastics with different fiber orientations and with different notching directions. As a consequence, the fracture behavior of the continuous GFRP could be monitored as nondestructive evaluation(NDE) through the AE technique.

• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.233-237
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• 2000

In general. fiber-optic medical endoscopes are made from glass step index (SI) fibers. These endoscopes have limitations in both image quality and mechanical properties. In particular. the image resolution of the SI endoscopes is limited to about 5$\mu$m. In this study the image resolution of plastic graded index (GRIN) super-resolution image guides with pixel sizes from 7 to 2.5 $\mu$m were measured and compared with those of 91ass SI image guides. There is an improvement in resolution of the plastic GRIN image guides as the microfiber diameter is reduced from 7 $\mu$m to 2.5 $\mu$m. The measured resolution of plastic GRIN image guide with 2.5 $\mu$m microfibers is more than a factor of two higher than that of g1ass SI image guide with 5$\mu$m microfibers. This new design of optical systems could have a major impact on a wide array of future optical systems used in defense. industrial, and medical applications.