• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.4
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• pp.255-259
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• 2006

For the intruder detection, a buried fiber-optic sensor based on fiber-optic Mach-Zehnder interferometer is demonstrated. We buried the sensor arm in a styrene board and exerted pressure on it. The pressure-induced deformation speed has almost linear relationship with the output frequencies of the interference signals, and about 4.25 Hz frequency change per 0.01m/s was obtained. Also it has been shown that the amplitude of frequency component increases according to the weight of mass.

• Clinical and Molecular Hepatology
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• v.24 no.4
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• pp.417-423
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• 2018

Anemia appears frequently in patients with alcoholic liver disease (ALD) but has never been linked to bilateral nonarteritic anterior ischemic optic neuropathy (NAION). A 65-year-old woman with a medical history of alcoholic cirrhosis was admitted for bilateral NAION. On admission, she was found to have a low arterial pressure and severe normocytic anemia (48 g/L). The anemia was related to chronic bleeding due to antral gastritis along with other factors associated with ALD. The applied treatment consisted of urgent transfusion followed by high doses of proton-pump inhibitors, iron and vitamin supplementation, and support in lifestyle measures. Her hemoglobin levels remained stable after 2 years but the patient still suffered from visual loss. This case highlights the link between anemia and bilateral NAION in ALD patients. The optic nerve head is prone to infarction in this context due to the vascularization characteristics of ALD. Hemoglobin levels should be monitored in ALD patients to avoid the severe complication of NAION.

• Current Optics and Photonics
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• v.6 no.3
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• pp.323-331
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• 2022

Electro-optic modulator (EOM) takes a vital role in connecting the electric and optical fields. Here, we present a heterogeneously integrated EOM based on the lithium niobate-on-insulator (LNOI) platform. The key modulation waveguide structure is a field-enhanced slot waveguide formed by embedding silicon nanowires in a thin-film lithium niobate (LN), which is different from the previously reported LN ridge or etchless LN waveguides. Based on such slot structure, optical mode field area is reduced and enhanced electric field in the slot region can interact well with LN material with high Electro-optic (EO) coefficient. Therefore, the improvements in both aspects have positive effects on enhancing the modulation performance. From results, the corresponding EOM by adding such modulation waveguide structure achieves better performance, where the key half-wave-voltage-length product (V_𝜋L) and 3 dB EO bandwidth are 1.78 V·cm and 40 GHz under the electrode gap width of only 6 ㎛, respectively. Moreover, Lower V_𝜋L can also be achieved. With these characteristics, such field-enhanced waveguide structure could further promote the development of LNOI-based EOM.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.2
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• pp.209-229
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• 2022

This work provided a review of three techniques-(1) spectrochemical, (2) electrochemical, and (3) spectroelectrochemical-for molten salt medias. A spectroelectrochemical system was designed by utilizing this information. Here, we designed a spectroelectrochemical cell (SEC) and calibrated temperature controllers, and performed initial tests to explore the system's capability limit. There were several issues and a redesign of the cell was accomplished. The modification of the design allowed us to assemble, align the system with the light sources, and successfully transferred the setup inside a controlled environment. A preliminary run was executed to obtain transmission and absorption background of NaCl-CaCl₂ salt at 600℃. It shows that the quartz cuvette has high transmittance effects across all wavelengths and there were lower transmittance effects at the lower wavelength in the molten salt media. Despite a successful initial run, the quartz vessel was mated to the inner cavity of the SEC body. Moreover, there was shearing in the patch cord which resulted in damage to the fiber optic cable, deterioration of the SEC, corrosion in the connection of the cell body, and fiber optic damage. The next generation of the SEC should attach a high temperature fiber optic patch cords without introducing internal mechanical stress to the patch cord body. In addition, MACOR should be used as the cell body materials to prevent corrosion of the surface and avoid the mating issue and a use of an adapter from a manufacturer that combines the free beam to a fiber optic cable should be incorporated in the future design.

• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.75-81
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• 2013

We fabricated translucent opal glass to replace the polycarbonate diffuser in LED lighting systems in order to solve the durability problem. Batch materials of opal glass with a composition of calcium phosphate were created and melted at $1550^{\circ}C$, and the effect of opaqueness was identified by an addition of 1~7% calcium phosphate as an opacifier raw material. As a result, translucent opal glass was obtained by the melting of the mixed batch materials with a composition of more than 5% calcium phosphate glass at $1550^{\circ}C$ for 2 hrs, which had excellent optical properties for the diffuser of a LED lighting system with no dazzling from direct light by a high haze value exceeding 90% and a low parallel transmittance value of about 5%. For the thermal properties, the thermal expansion coefficient was found to be $5.6{\sim}5.9{\times}10^{-6}/^{\circ}C$ and the softening point was $874{\sim}884^{\circ}C$. In addition, good thermal properties such as good thermal shock resistance and feasibility for use with a general manufacturing process during the forming of glass tubes and bulbs were noted. Therefore, it is concluded that this translucent opal glass can be used as a glass diffuser material for LED lighting due to its high heat resistance and high durability as a replacement for a polycarbonate diffuser.

• Smart Structures and Systems
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• v.12 no.1
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• pp.41-54
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• 2013

Concrete is known as a heterogeneous product which is composed of complex chemical composition and reaction. The development of concrete thermal effect during early age is critical on its future structural health and long term durability. When cement is mixed with water, the exothermic chemical reaction generates hydration heat, which raises the temperature within the concrete. Consequently, cracking may occur if the concrete temperature rises too high or if there is a large temperature difference between the interior and the exterior of concrete structures during early age hydration. This paper describes the contribution of novel Fabry-Perot (FP) fiber optic temperature sensors to investigate the thermal effects of concrete hydration process. Concrete specimens were manufactured under various water-to-cement (w/c) ratios from 0.40 to 0.60. During the first 24 hours of concreting, two FP fiber optic temperature sensors were inserted into concrete specimens with the protection of copper tubing to monitor the surface and core temperature change. The experimental results revealed effects of w/c ratios on surface and core temperature developments during early age hydration, as well as demonstrating that FP fiber optic sensors are capable of capturing temperature variation in the concrete with reliable performance. Temperature profiles are used for calculating the apparent activation energy ($E_a$) and the heat of hydration (H(t)) of concrete, which can help us to better understand cement hydration.

• Journal of Sensor Science and Technology
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• v.6 no.3
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• pp.172-179
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• 1997

This paper describes a multiplexed-multivariate fiber-optic interferometric sensor system with remote sensing capability. Signal processor of the implemented sensor system is designed as a digital fringe counter that is well adapted to the signal processing of the remote fiber-optic Fabry-Perot interferometric sensor array. By summing up the reported optical data of the optical fiber, a guideline for choosing the optical effect suitable for a specific measurand is presented. As an example, a pressure sensing device that utilizes the strain-optic effect of the optical fiber by attaching it onto a stainless steel diaphragm of which diameter is 4.3 cm, is built and attached to the sensor system. The changes in optical phase difference of the fiber-optic Fabry-Perot interferometric press ure sensor while filling a water tank 2 meters high, was counted by the half-fringe counting signal processor. Test results showed that the measurement error is less than ${\pm}3.6\;cm$ over the measured range of 2 meters.

• Journal of Sensor Science and Technology
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• v.21 no.4
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• pp.287-292
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• 2012

A fiber-optic radiation sensor was fabricated using a sensing probe, a plastic optical fiber, a photomultiplier tube, and a multichannel analyzer for gamma-ray spectroscopy. As an inorganic scintillator of the sensing probe, a LYSO crystal was used. In this study, we obtained the relationship between the photon counts of the fiber-optic radiation sensor and the activity of the radioactive isotope. In addition, the gamma-ray energy spectra were also measured using a fiber-optic radiation sensor to discriminate species of gamma-ray emitters.

• Korean Journal of Materials Research
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• v.24 no.12
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• pp.715-719
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• 2014

(PDDA/$SiO_2$) thin films that consisted of positively charged poly (diallyldimethylammonium chloride) (PDDA) and negatively charged $SiO_2$ nanoparticles were fabricated on a glass substrate by an applying voltage layer-by-layer (LBL) self-assembly method. In this study, the microstructure and optical properties of the (PDDA/$SiO_2$) thin films coated on glass substrate were measured as a function of the applied voltage on the Pt electrodes. When 1.0 V was applied to a Pt electrode in a PDDA and $SiO_2$ solution, the thickness of the $(PDDA/SiO_2)_{10}$ thin film increased from 79 nm to 166 nm. The surface roughness also increased from 15.21 nm to 33.25 nm because the adsorption volume of the oppositely charged PDDA and $SiO_2$ solution increased. Especially, when the voltage was applied to the Pt electrode in the $SiO_2$ solution, the thickness increase of the (PDDA/$SiO_2$) thin film was larger than that obtained when using the PDDA solution. The refractive index of the fabricated (PDDA/$SiO_2$) thin film was ca. n = 1.31~1.32. The transmittance of the glass substrate coated by (PDDA/$SiO_2$)6 thin film with a thickness of 106 nm increased from ca. 91.37 to 95.74% in the visible range.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.5
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• pp.373-379
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• 2020

In this study, TiN-coated cBN (cubic-structure boron nitride) powders were successfully synthesized by a sol-gel method using titanium (IV) isopropoxide (TTIP) and by controlling the heat treatment conditions. After the sol-gel process, amorphous nano-sized TiO_x was uniformly coated on the surface of cBN powder particles. The obtained TiO_x-coated cBN powders were heated at 1,000~1,300℃ for 1 or 6 h in a flow of 95%N₂-5%H₂ mixed gas. With increasing temperature, the chemical composition of the TiO_x coating layer changed in the order of TiO₂→Ti₆O₁₁→Ti₄O₇→TiN due to reduction of the Ti ions. The TiN coating layer was observable in the samples heated at 1,200℃ and appeared as the main phase in the sample heated at 1,300℃. The resulting thickness of the TiN coating layer of the sample heated at 1,300℃ was approximately 45~50 nm.