• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.39-44
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• 2003

The welded specimens were made by butt welding of the 2 wires of 50mm length using the pulsed YAG laser. The laser welded wires were tested for investigating the shape memory effect and the ability of super elasticity. The fatigue properties of the welded wires were investigated using the rotary bending fatigue tester specially designed for wires. Moreover, the effect of defocusing distance during laser welding on the static and fatigue properties was Investigated. The shape memory effect and super elasticity of the laser welded wires were approximately identical with that of base metal at the test temperature below 353K. However, the welded wires were broken within elastic limit at the test temperature above 353k. Under the cyclic bending loading conditions, the welded wires could be useful only below the elastic limit, while the base metal had sufficient fatigue life even the stress induced M-phase region. The fatigue strength of the welded wires was about half of that of the base metal. The deterioration of the static and fatigue properties in the welded wires was proven to be from the large difference of the transformation behavior between the base metal and welded part that is caused by vaporization of Ni-content at the welded part during the welding process. The defocusing distance below 3mm acted more largely on lowering the strength of the welded wires than that of 6mm or 8mm.

• Korean Journal of Pharmacognosy
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• v.54 no.1
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• pp.38-43
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• 2023

A simple and accurate assay was developed for the quantitative analysis of 1-deoxynojirimycin (1-DNJ) derived from the silkworm (Bombyx mori). Normal-phase high-performance liquid chromatography coupled with an evaporative light scattering detector (HPLC-ELSD) and a hydrophilic interaction liquid chromatography column was used. Various parameters were applied to optimize the analysis method. The limits of detection and quantification of 1-DNJ were 2.97 × 10^-3 and 9.00 × 10^-3 mg/mL, respectively. The calibration curve showed good linearity results. The concentration range and the r² value were 0.0625-1.0 mg/mL and 0.9997, respectively. The accuracy test demonstrated a significantly high recovery rate (89.95-103.22%). The relative standard deviation was ≤ 1.00%. Thus, a method for the accurate identification and quantitative analysis of 1-DNJ in silkworms was developed. Moreover, in this procedure, the process of derivatization of 1-DNJ, which was required in previous experiments, could be eliminated. This technique may be actively utilized for the development of pharmaceuticals and health functional foods using 1-DNJ.

• Mass Spectrometry Letters
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• v.15 no.1
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• pp.49-53
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• 2024

Ceramide is a lipid in which sphingoid bases and fatty acids are linked by amide bonds. As a marker of skin disease in the human stratum corneum, its disease-causing and therapeutic effects have been partially confirmed, and it is therefore an important element in commercially available cosmetic formulations. However, structural diversity caused by differences in the chain length, number, and location of hydroxyl groups makes quality control difficult. In this study, a method was established to separate different ceramide species using reversed-phase LC-MS/MS and thus enable qualitative evaluation. Separation of four standards was achieved within a short retention time, and the accuracy and sensitivity of the method were demonstrated by the low limit of detection (LOD) calculated based on the calibration curve showing linearity, with R² > 0.994. After verification of reproducibility and reliability through intra- and inter-day analyses, the efficiency of the method was confirmed through analysis of commercial cosmetic raw materials.

• Earthquakes and Structures
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• v.26 no.5
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• pp.327-336
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• 2024

Evaluation of tunnel performance in seismic-prone areas demands efficient means of estimating performance at different hazard levels. The present study introduces an innovative push-over analysis approach which employs the standard earthquake spectrum to simulate the performance of a tunnel. The numerical simulation has taken into account the lining and surrounding rock to calculate the rock-tunnel interaction subjected to a static push-over displacement regime. Elastic perfectly plastic models for the lining and hardening strain rock medium were used to portray the development of plastic hinges, nonlinear deformation, and performance of the tunnel structure. Separately using a computational algorithm, the non-linear response spectrum was approximated from the average shear strain of the rock model. A NATM tunnel in Turkey was chosen for parametric study. A seismic performance curve and two performance thresholds are introduced that are based on the proposed nonlinear seismic static loading approach and the formation of plastic hinges. The tunnel model was also subjected to a harmonic excitation with a smooth response spectrum and different amplitudes in the fully-dynamic phase to assess the accuracy of the approach. The parametric study investigated the effects of the lining stiffness and capacity and soil stiffness on the seismic performance of the tunnel.

• Annals of Hepato-Biliary-Pancreatic Surgery
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• v.27 no.4
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• pp.428-432
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• 2023

Minimally invasive pancreatoduodenectomy (MIS PD) is a well reported technique with several advantages over conventional open pancreatoduodenectomy. In comparison to distal pancreatectomy, the adoption of MIS PD has been slow due to the technical challenges involved, particularly in the reconstruction phase of the pancreatojejunostomy (PJ) anastomosis. Hence, we introduce a lowcost model for PJ anastomosis simulation in MIS PD. We fashioned a model of a cut pancreas and limb of jejunum using economical and easily accessible materials comprising felt fabric and the modelling compound, Play-Doh. Surgeons can practice MIS PJ suturing using this model to help mount their individual learning curve for PJ creation. Our video demonstrates that this model can be utilized in simulation practice mimicking steps during live surgery. Our model is a cost-effective and easily replicable tool for surgeons looking to simulate MIS PJ creation in preparation for MIS PD.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.67-72
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• 2023

A simple and accurate method was developed for the quantitative analysis of oleanonic acid (OA) from mastic gum. The analysis was carried out using reverse-phase high-performance liquid chromatography combined with a photodiode array detector (HPLC/PDA). Our optimized method was validated by measuring various parameters, using an INNO C18 column fitted with a gradient elution system. The results revealed limits of detection and quantification of 0.34 and 1.042 ㎍/mL, respectively. The OA calibration curve exhibited excellent linearity over the concentration range of 0.0625 to 2.0 mg/mL, with r² =0.9996. Accuracy tests revealed a high recovery rate of 99.44-103.66%, with precision values below 0.15%. These results suggest that the present analytical method can identify and quantify OA in mastic gum with high precision. The HPLC approach developed in this study might be applied to routine analyses and large-scale extraction procedures for OA content quantification.

• Journal of Ceramic Processing Research
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• v.23 no.4
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• pp.436-442
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• 2022

Gallium nitride (GaN) substrates were ground in two different grinding wheel abrasive sizes of 270 and 800-mesh, and thechange in surface morphologies of the substrates and the depth of subsurface damage (SSD) were observed. With the 800-meshgrinding wheel, the surface roughness (SR) and the depth of SSD of the sample tended to decrease, which was not the casewith the 270-mesh grinding wheel. In the X-ray rocking curve, the sample exhibited some compressive stress with the 270-meshgrinding wheel, but with the 800-mesh grinding wheel, it demonstrated the occurrence of tensile stresses in the sample and adecrease in full width at half maximum (FWHM), which confirms an improvement in the crystallinity. In the Raman spectra,the compressive stress of the 270-mesh grinding wheel and the tensile stress of the 800-mesh grinding wheel were confirmedthrough peak shifts. Photoluminescence (PL) spectra confirmed that the intensity ratio of the yellow luminescence increasedat the 800-mesh grinding wheel, and a blue shift occurred further. These results indicate that the SR and the depth of SSDwere proportional to the abrasive grain size of the grinding wheel. At the same time, the increase in PL intensity at specificpeak positions indicates that the stress stemming from the grinding process was concentrated at the crystal surface. The abovemechanism is illustrated in a schematic diagram, which confirms the possibility of improving the grinding efficiency andsubsequent polishing processes in future applications.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.171-179
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• 1997

During the day time in summer, peak of air conditing load, and electric power management system lies under overloaded condition. The reason is the enlarged peak load value of electric power caused by increased air-cooling load in summer. To prevent load concentration during day time and overloaded condition of power management system, some energy storage methods are suggested. One of these methods is ice storage system. Water has some good properties as P.C.M.(Phase Chang Material) : Its melting point is the range of required operation temperature. It has large specific latent heat and is chemically stable compared to other organic or inorganic substances. It is cheap and easy to treat. This study represents experimental results of heat transfer characteristics of P.C.M. under the outward melting process in a vertical cylinder. We experimented with twelve combinations of conditions, i.e., three different inlet temperatures($7^{\circ}C,\;4^{\circ}C\;and\;1^{\circ}C$), two working fluid directions(upward and downward), and two aspect ratios, H/R(4 and 2). At the inlet temperature of $7^{\circ}C$ and $4^{\circ}C$, there was temperature stagnation region where the temperature of P.C.M. remains constant at $4^{\circ}C$ regardless of aspect ratio and direction of working fluid. This temperature stagnation occurs as the water, at its maximum density, flows down to the lower region. The phase change interface formed bell-shaped curve as the melting process continued. With a new set of conditions(4H/R, inlet temperature $4^{\circ}C$ and $1^{\circ}C$, downward/upwerd inlet direction), the movement of phase change interface was faster when the working flued inlet direction was downward. With the same set of conditions, melting rate and total melting energy were larger when the working fluid inlet direction was downward. The results were reversed when the other sets of conditions were applied.

• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.191-197
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• 2017

The safety nature of construction industry differs from that of manufacturing sector. For instance, accident risk level dramatically varies at each phase of construction process. Korean Occupational and Health Safety Act has been regulated OHS expense and it contributed reducing accident risk and enhancing safety culture for many years. However, although current regulation guides to use OHS expense proportionate to construction progress, it still allows late use of the expense. This study was conducted for the purpose of presenting methods of estimating a step-by-step OHS expense rate required at each construction phase. In order to do provide proper OHS expense schedule, it analysed accident risk of each construction phase by sorting out 1439 cases of construction site fatality reports, and proposed a method of generating appropriate OHS expense scheme according to its construction work progress characteristics. Both linear and sigmoidal S-curve model were used for the analysis, and the latter generally requires earlier use of OHS expense. By comparing the estimated OHS expense use schedule with current criteria, more than 27%p early use of OHS expense is required for the prevention of accident.

• Journal of Life Science
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• v.18 no.7
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• pp.980-985
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• 2008

This study was carried out to develope an alcoholic drink by fermentation of onion extract using Saccharomyces cerevisiae. The optimal conditions for ethanol production were obtained by standing culture at $25^{\circ}C$ for 5 days with 5% inoculum volume. At the results by flask culture, the growth curve of used S. cerevisiae reached to the stantionary phase at 48 hr and the death phase at 90 hr, whereas ethanol production reached maximum at 114 hr. Under the above conditions, a large scale production was carried out. A standing culture in 5 l fermenter showed the similar results to its flask culture, but progressed 24 hr rapidly more than that of the flask culture. A fed-batch culture was performed by addition of the onionic medium supplemented with 10% (v/v) sucrose after 72 hr from the fermenting start. The fed-batch culture could prevent S. cerevisiae from entering into the death phase and maintain constant level of alcohol production. A continuous culture was able to carry out by adding per every 24 hr the onionic medium supplemented with 10% (v/v) sucrose after 72 hr from the fermenting start. Although S. cerevisiae used showed a little decreased growth, alcohol production maintained roughly the constant level at the maximum yield. To enhance the quality of this alcoholic drink, $2-O-{\alpha}-D-glucopyranosyl$ L-ascorbic acid (AA-2G) was supplemented into the onion extract of the substrate for fermentation. As resulted at this study, this alcoholic drink containing AA-2G should be used as a functional fermented alcohol drink strengthened with vitamin C.