• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.423-430
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• 1994

We designed and fabricated the single mode fiber pigtailed DFB-LD module for 2.5 Gbps optical communication system. In the design of the DFB-LD module, we made the module divided into two parts of inner sub-module and outer 14-pin butterfly package and cylindrical shaped sub-module contain quasi confocal 2 lens system including optical isolator and electrical connection between these parts via hybrid substrate of bias T circuit. Laser welding was used to assemble the sub-module which requires accurate fixing between optical elements. The fabricated DFB-LD module showed optical coupling efficiency of 20% and - 3 dB small signal response of more than 2.6 GHz. We confirmed mechanical reliability of the module by temperature cycle test where the tested module exhibit optical power fluctuation of less than 10%. Finally we evaluated the performance of the fabricated DFB-LD module as light source of 2.5 Gbps optical communication system, sensitivity of - 30.2 dBm was obtained through 47 km optical fiber transmission under the criterion of $1\times10^{-10}$ BER and transmission penalties were 1.5 dB caused by extinction ratio and 1.0 dB caused by chromatic dispersion of normal single mode fiber. fiber.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.317-329
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• 2014

In vision measurement systems based on structured light, the key point of detection precision is to determine accurately the central position of the projected laser line in the image. The purpose of this research is to extract laser line centers based on a decision function generated to distinguish the real centers from candidate points with a high recognition rate. First, preprocessing of an image adopting a difference image method is conducted to realize image segmentation of the laser line. Second, the feature points in an integral pixel level are selected as the initiating light line centers by the eigenvalues of the Hessian matrix. Third, according to the light intensity distribution of a laser line obeying a Gaussian distribution in transverse section and a constant distribution in longitudinal section, a normalized model of Hessian matrix eigenvalues for the candidate centers of the laser line is presented to balance reasonably the two eigenvalues that indicate the variation tendencies of the second-order partial derivatives of the Gaussian function and constant function, respectively. The proposed model integrates a Gaussian recognition function and a sinusoidal recognition function. The Gaussian recognition function estimates the characteristic that one eigenvalue approaches zero, and enhances the sensitivity of the decision function to that characteristic, which corresponds to the longitudinal direction of the laser line. The sinusoidal recognition function evaluates the feature that the other eigenvalue is negative with a large absolute value, making the decision function more sensitive to that feature, which is related to the transverse direction of the laser line. In the proposed model the decision function is weighted for higher values to the real centers synthetically, considering the properties in the longitudinal and transverse directions of the laser line. Moreover, this method provides a decision value from 0 to 1 for arbitrary candidate centers, which yields a normalized measure for different laser lines in different images. The normalized results of pixels close to 1 are determined to be the real centers by progressive scanning of the image columns. Finally, the zero point of a second-order Taylor expansion in the eigenvector's direction is employed to refine further the extraction results of the central points at the subpixel level. The experimental results show that the method based on this normalization model accurately extracts the coordinates of laser line centers and obtains a higher recognition rate in two group experiments.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.358-373
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• 1997

Resin modified glass ionomers were introduced in 1988 to overcome the problems of moisture sensitivity and low early mechanical strength of conventional glass ionomers and to maintain their clinical advantages. The purpose of this study was to evaluate the color stability of four resin modified glass ionomers(Fuji II LC, Vitremer, Dyract and VariGlass), one resin composite material(Z-100), and one conventional glass ionomer(GC Fuji II) under several conditions. These conditions were as follows: 1) before curing, 2) after curing, 3) after polishing, 4) after 500 thermocycling, 5) after 1,000 thermocycling, 6) after 1,500 thermocycling and 7) after 2,000 thermocycling. Three specimens of each material/shade combination were made. Materials were condensed into metal mold with a diameter of 10 mm and a thickness of 2.0 mm, and were pressed between glass plates. The material was polymerized using a light polymerizing unit(Visilux II, 3M, USA). After removal of excess, the surface was polished sequentially on wet sandpapers. A reflection spectrophotometer(Model TC-6FX, Tokyo Denshoku Co., Japan) was used to determine CIELAB coordinates($L^*,a^*$ and $b^*$) of each specimen. CIE standard illumination C was used as the light source. The results were as follows : 1. In comparing different shades of same material, CIELAB color difference(${\Delta}E^*$) value was not significantly different from each other(p>0.05). 2. CIELAB color difference(${\Delta}E^*$) values between after-curing and after-polishing were ranged from 5.53 to 27.08. These values were higher than those of other condition combinations. 3. CIELAB color difference(${\Delta}E^*$) values between before-thermocycling and after-thermocycling were ranged from 1.40 to 7.81. Despite the number of thermocycling increased, CIELAB color difference(${\Delta}E^*$) value was low. 4. The color stability of resin modified glass ionomers was more stable than that of conventional glass ionomers but less stable than that of Z100.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.27-33
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• 2017

The determination of disulfide bonds is important for comprehensive understanding of the chemical structure of protein. So far, many strategies for the disulfide bond analysis have been suggested in terms of speed and sensitivity. However, most of these strategies have not considered free thiol residues in the target protein in the process of determining the disulfide bond. We suggested the strategy which was composed of four steps for the identification of disulfide bonds; the first step was the prediction of possible disulfide bonds, the second step was the determination of free cysteine residues, the third step was the analysis of disulfide bond using a high-resolution mass spectrometry, and the final step was the determination of disulfide bonds based on the comprehensive verification. In this study, we performed the characterization of disulfide bonds for the recombinant protein (HRPE1), where 1 and 5 inter- and intra-chain disulfide bonds were identified, respectively.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.52.2-52.2
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• 2014

The Immersion Grating Infrared Spectrometer (IGRINS) is an unprecedentedly minimized infrared cross-dispersed echelle spectrograph with a high-resolution and high-sensitivity optical performance. A silicon immersion grating features the instrument for the first time in this field. IGRINS will cover the entire portion of the wavelength range between 1.45 and $2.45{\mu}m$ accessible from the ground in a single exposure with spectral resolution of 40,000. Individual volume phase holographic (VPH) gratings serve as cross-dispersing elements for separate spectrograph arms covering the H and K bands. On the 2.7m Harlan J. Smith telescope at the McDonald Observatory, the slit size is $1^{\prime\prime}{\times}15^{\prime\prime}$. IGRINS has a $0.27^{\prime\prime}$ pixel-1 plate scale on a $2048{\times}2048$ pixel Teledyne Scientific & Imaging HAWAII-2RG detector with SIDECAR ASIC cryogenic controller. The instrument includes four subsystems; a calibration unit, an input relay optics module, a slit-viewing camera, and nearly identical H and K spectrograph modules. The use of a silicon immersion grating and a compact white pupil design allows the spectrograph collimated beam size to be 25mm, which permits the entire cryogenic system to be contained in a moderately sized rectangular vacuum chamber. The fabrication and assembly of the optical and mechanical hardware components were completed in 2013. In this presentation, we describe the major design characteristics of the instrument and the early performance estimated from the first light commissioning at the McDonald Observatory.

• Journal of the Ergonomics Society of Korea
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• v.30 no.1
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• pp.99-108
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• 2011

Almost all companies have paid much attention to the safety management ranging from maintenance to operation even at the stage of designing in order to prevent accidents, but fatal accidents continue to increase throughout the world. In particular, it is essential to systematically prevent such fatal accidents as fire, explosion or leakage of toxic gas at factories in order to not only protect the workers and neighbors but also prevent economic losses and environmental pollution. Though it is well known that accident probability is very low in NPP(Nuclear Power Plants), the reason why many researches are still being performed about the accidents is the results may be so severe. HRA is the main process to make preparation for possibility of human error in designing of the NPP. But those techniques have some problems and limitation as follows; the evaluation sensitivity of those techniques are out of date. And the evaluation of human error is not coupled with the design process. Additionally, the scope of the human error which has to be included in reliability assessment should be expanded. This work focuses on the coincidence of human error and mechanical failure for some important performance shaping factors to propose a method for improving safety effectively of the process industries. In order to apply in these purposes into the thesis, I found 63 critical Performance Shaping Factors of the eight dimensions throughout studies that I executed earlier. In this study, various analysis of opinion of specialists(Personal Factors, Training, Knowledge or Experience, Procedures and Documentation, Information, Communications, HMI, Workplace Design, Quality of Environment, Team Factors) and the guideline for construction of PSF were accomplished. The selected method was AHP which simplifies objective conclusions by maintaining consistency. This research focused on the implementation process of PSF to evaluate the process of PSF at each phase. As a result, we propose an evaluation model of PSF as a tool to find critical problem at each phase and improve on how to resolve the problems found at each phase. This evaluation model makes it possible to extraction of PSF succesfully by presenting the basis of assessment which will be used by enterprises to minimize the trial and error of construction process of PSF.

• Membrane Journal
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• v.31 no.2
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• pp.87-100
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• 2021

With a striking increase in the level of contamination and subsequent degradations in the environment, detection and monitoring of contaminants in various sites has become a crucial mission in current society. In this review, we have summarized the current research areas in membrane-based colorimetric sensors for trace detection of various molecules. The researches covered in this summary utilize membranes composed of cellulose fibers as sensing platforms and metal nanoparticles or fluorophores as optical reagents. Displaying decent or excellent sensitivity, most of the developed sensors achieve a significant selectivity in the presence of interfering ions. The physical and chemical properties of cellulose membrane platforms can be customized by changing the synthesis method or type of optical reagent used, allowing a wide range of applications possible. Membrane-based sensors are also portable and have great mechanical properties, which enable on-site detection of contaminants. With such superior qualities, membrane-based sensors examined in the researches were used for versatile purposes including quantification of heavy metals in drinking water, trace detection of toxic antibiotics and heavy metals in environmental water samples. Some of the sensors exhibited additional features like antimicrobial ability and recyclability. Lastly, while most of the sensors aimed for a detection enabled by naked eyes through rapid colour change, many of them investigated further detection methods like fluorescence, UV-vis spectroscopy, and RGB colour intensity.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.1-14
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• 2019

A full scale hydrodynamic simulation that requires an accurate reproduction of shock-induced detonation was conducted for design of an energetic component system. A detailed hydrodynamic analysis SW was developed to validate the reactive flow model for predicting the shock propagation in a train configuration and to quantify the shock sensitivity of the energetic materials. The pyrotechnic device is composed of four main components, namely a donor unit (HNS+HMX), a bulkhead (STS), an acceptor explosive (RDX), and a propellant (BPN) for gas generation. The pressurized gases generated from the burning propellant were purged into a 10 cc release chamber for study of the inherent oscillatory flow induced by the interferences between shock and rarefaction waves. The pressure fluctuations measured from experiment and calculation were investigated to further validate the peculiar peak at specific characteristic frequency (${\omega}_c=8.3kHz$). In this paper, a step-by-step numerical description of detonation of high explosive components, deflagration of propellant component, and deformation of metal component is given in order to facilitate the proper implementation of the outlined formulation into a shock physics code for a full scale hydrodynamic simulation of the energetic component system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.557-564
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• 2019

The characteristics of the torque and torque ripple of Interior Permanent Magnet Synchronous Motor(IPMSM) are influenced by the size and position of the rotor magnet and the size of the stator slot. This paper deals with the optimal design method for improving torque and torque ripplerate for IPMSM using Response Surface Methodology(RSM). Two objective functions of torque output and torque ripple were derived from the sensitivity analysis by Plackett-Burmann(PB) for the characteristic variables affecting torque and torque ripple. Secondary characteristic variables were selected from the derived objective function and RSM secondary regression model function was estimated by the experiment schedule and analysis results according to the Central Composite Design (CCD). The reliability of the secondary regression model was verified using ANOVA table. The analysis according to the experimental schedule was verified by JMAG(Ver. 18.0) which is Finite Element Method(FEM) software. The torque output of IPMSM applied with final characteristic variables was increased torque output by 11.5 % and the torque ripplerate was reduced by 9.1 %.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.148-158
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• 2022

The electrochemical CO₂ reduction (ECR) to produce value-added fuels and chemicals using clean energy sources (like solar and wind) is a promising technology to neutralize the carbon cycle and reproduce the fuels. Presently, the ECR has been the most attractive route to produce carbon-building blocks that have growing global production and high market demand. The electrochemical CO₂ reduction could be extensively implemented if it produces valuable products at those costs which are financially competitive with the present market prices. Herein, the electrochemical conversion of CO₂ obtained from flue gases of a power plant to produce diesel and formic acid using a consistent techno-economic approach is presented. The first scenario analyzed the production of diesel fuel which was formed through Fischer-Tropsch processing of CO (obtained through electroreduction of CO₂) and hydrogen, while in the second scenario, direct electrochemical CO₂ reduction to formic acid was considered. As per the base case assumptions extracted from the previous outstanding research studies, both processes weren't competitive with the existing fuel prices, indicating that high electrochemical (EC) cell capital cost was the main limiting component. The diesel fuel production was predicted as the best route for the cost-effective production of fuels under conceivable optimistic case assumptions, and the formic acid was found to be costly in terms of stored energy contents and has a facile production mechanism at those costs which are financially competitive with its bulk market price. In both processes, the liquid product cost was greatly affected by the parameters affecting the EC cell capital expenses, such as cost concerning the electrode area, faradaic efficiency, and current density.