• Journal of the Korean Institute of Gas
• /
• v.24 no.6
• /
• pp.61-69
• /
• 2020

This paper is a study of the behavior characteristics that occur in the hydrogen storage vessel TYPE 1 according to pressure and temperature conditions by FEM(Finite element method). Von Mises stress (VMS) generated at the highest pressure was compared with Yield strength (YS) of the material for structural safety assessment of the container, and the results of plastic strain energy density (PSED) were analyzed as basic data for life expectancy. According to the analysis results, the safety of the hydrogen gas storage vessel is not ensured due to the occurrence of VMS higher than the yield strength on the bottom of the storage container at a gas pressure of 40 Mpa or higher. In addition, the results of VMS caused by temperature conditions are very low and the behavior by temperature can be ignored. The maximum pressure of VMS/YS below 1 is calculated to be about 30 Mpa, indicating that the hydrogen storage container subject to this paper should be managed with a gas charging pressure of less than 30 Mpa.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.12
• /
• pp.619-628
• /
• 2020

This study examined the experiences of users regarding their use of electronic informed consent in hospital. A qualitative descriptive study was conducted using focus groups and in-depth interviews with 30 Korean nurses and 27 patients. Data were collected from one university hospital. The responses were analyzed by qualitative content analysis. Most participants perceived the use of electronic informed consent as convenient and straightforward, as well as saving space and money. On the other hand, the participants stated that the system was unsatisfactory in part because of the occasional unexpected machinery error or malfunction. Some patients wished for function improvements related to the e-signature, making it more comparable to a handwritten signature, and the adjustability of the font size. The nurses wanted a wider implementation of electronic informed consent because it was not being used for all informed consent cases, resulting in confusion and an additional workload. For the use of an electronic informed consent system, it is important to minimize the inconvenience and to maximize the satisfaction of the users, including nurses and patients.

• Journal of the Korean Institute of Gas
• /
• v.25 no.6
• /
• pp.92-97
• /
• 2021

In accordance with the revision of the Enforcement Regulations of the High-Pressure Gas Safety Management Act in February 2021, from August 27, 2021, the operation status of safety devices such as gas leak detection and alarm devices, emergency shut-off devices and flame detectors installed at hydrogen vehicle charging stations can be monitored in real time. It is transmitted and operated by the computer system managed by Korea Gas Safety Corporations. We intend to share the results of statistical analysis of abnormal signals that have occurred along with the results of the monitoring system construction so that they can be used for the safety management of hydrogen refueling stations, and to seek future safety management directions.

• The Journal of the Convergence on Culture Technology
• /
• v.9 no.3
• /
• pp.701-706
• /
• 2023

The Korean government and industry have presented a roadmap for the commercialization of UAM services and are promoting it in earnest. In order to introduce full-scale UAM services, there are various issues to be solved, such as the development of high-performance aircraft, the design of network bases and corridors, the optimization of operation management, and the establishment of related laws and systems. In this study, in terms of optimizing operation management, we will examine research trends by field, focusing on Korea, and derive research topics that need to be solved in the future. Korean researchers have suggested that research is centered on UAM service usage fees, usage intentions and acceptance models, and vertiport location selection, but operational optimization studies such as service order acceptance, aircraft repositioning, and battery charging and maintenance scheduling are needed in the future.

• Restorative Dentistry and Endodontics
• /
• v.30 no.2
• /
• pp.112-120
• /
• 2005

This study was done to evaluate whether there were any differences in microleakage of class V composite restorations according to restoration site and cavity size. Total sixty-four restorations were made in molar teeth using Esthet-X. Small ($2\;{\times}\;2\;{\times}\;1.5\;mm$) and large ($4{\times}2{\times}1.5\;mm$) restorations were made at the buccal/lingual surface and the proximal surface each. After 1,000 times of thermocycling ($5^{\circ}\;-\;55^{\circ}C$), resin replica was made and the percentage of marginal gap to the whole periphery of the restoration was estimated from SEM evaluation. Thermocycled tooth was dye penetrated with $50\%$ silver nitrate solution. After imbedding in an auto-curing resin, it was serially ground with a thickness of 0.25 mm. Volumetric microleakage was estimated after reconstructing three dimensionally. Two-way ANOVA and independent T-test for dye volume, Mann-Whitney U test for the percentage of marginal gap, Spearman's rho test for the relationship between two techniques were used, The results were as follows : 1. The site and size of the restoration affected on the microleakage of restoration. Namely, much more leakage was seen in the proximal and the large restorations rather than the buccal/lingual and the small restorations. 2. Close relationship was found between two techniques (Correlation coefficient = 0.614/ P = 0.000). Within the limits of this study, it was noted that proximal and the large restorations leaked more than buccal/lingual and the small restorations. Therefore, it should be strictly recommended large exposure of margins should be avoided by reducing unnecessary tooth reduction.

• Journal of the Korean Electrochemical Society
• /
• v.23 no.4
• /
• pp.105-112
• /
• 2020

Transition metal oxide, which undergoes a conversion reaction in the negative electrode material for a lithium-ion batteries, has a high specific capacity, but still has several critical problems. In this study, manganese pyrophosphate (Mn₂P₂O₇), nickel pyrophosphate (Ni₂P₂O₇), and carbon composite materials with pyrophosphates as novel negative electrode materials instead of transition metal oxide, are synthesized through simple solid-state reaction. The initial reversible capacity of Mn₂P₂O₇ and Ni₂P₂O₇ are 333 and 340 mAh g^-1, and when the composite materials are composed with carbon, the reversible capacity increases to 433 and 387 mAh g^-1, respectively. The initial Coulombic efficiency is also improved by about 10%. The Mn₂P₂O₇ and carbon composite material has the highest initial capacity and efficiency, and has the best cycle performance. Mn₂P₂O₇ containing polyanion, has a lower specific capacity due to the large mass of polyanion compared to MnO (manganese oxide). However, since Mn₂P₂O₇ shows a voltage curve with a slope, the charging (lithiation) voltage increases from 0.51 to 0.57 V (vs. Li/Li⁺), and the discharge (delithiation) voltage decreases from 1.15 to 1.01 V (vs. Li/Li⁺). Therefore, the voltage efficiency of the cell is improved because the voltage difference between charging and discharging is greatly reduced from 0.64 to 0.44 V, and the operating voltage of the full cell increases because the negative electrode potential is lowered during the discharging process.

• Restorative Dentistry and Endodontics
• /
• v.29 no.2
• /
• pp.170-176
• /
• 2004

Objectives : In the unique metal iris method. the developing interfacial gap at the cavity floor resulting from the cavity wall property during polymerizing composite resin might affect the nominal shear bond strength values. The aim of this study is to evaluate that the iris method reduces the cohesive failure in the substrates and the cavity wall property effects on the shear bond strength tests using iris method. Materials and Methods : The occlusal dentin of 64 extracted human molars were randomly divided into 4 groups to simulate two different levels of cavity wall property (metal and dentin iris) and two different materials ($ONE-STEP^{\circledR}$ and $ALL-BOND^{\circledR}$ 2) for each wall property. After positioning the iris on the dentin surface. composite resin was packed and light-cured. After 24 hours the shear bond strength was measured at a crosshead speed of 0.5 mm/min. Fracture analysis was performed using a microscope and SEM. The data was analyzed statistically by a two-way ANOV A and t-test. Results : The shear bond strength with metal iris was significant higher than those with dentin iris (p＝0.034). Using $ONE-STEP^{\circledR}$, the shear bond strength with metal iris was significant higher than those with dentin iris (p＝0.005), but not in $ALL-BOND^{\circledR}$ 2 (p＝0.774). The incidence of cohesive failure was very lower than other shear bond strength tests that did not use iris method. Conclusions：The iris method may significantly reduce the cohesive failures in the substrates. According to the bonding agent systems. the shear bond strength was affected by the cavity wall property.

• The Journal of Engineering Geology
• /
• v.23 no.1
• /
• pp.29-36
• /
• 2013

The application of appropriate rehabilitation methods can improve the efficiency of clogged wells and extend their life. In this paper, we study the feasibility of well cleaning using high-voltage pulsed discharge, in which electrical energy is used to produce impulsive pressure in water, in contrast to conventional methods that employ chemical or pneumatic energy sources. This technique utilizes the compressive shock wave generated by the expansive force of hot, dense plasma that is produced during a pulsed discharge in the gap between electrodes immersed in water. Compared with conventional techniques, this method is simple, and easy to handle and control. Using a capacitive pulsed power system with an electrical energy of 200 J, an impulsive pressure of 10.7 MPa is achieved at the position 6 cm away from the discharge gap. The amplitude of the impulsive pressure was easily controlled by adjusting the charging voltage of the capacitor and was almost linearly proportional to peak discharge current. The technique achieved good results in cleaning feasibility tests with mock-up specimens similar to clogged well screens.

• Restorative Dentistry and Endodontics
• /
• v.31 no.2
• /
• pp.133-139
• /
• 2006

The purposes of this study were firstly to identify the microbial species on gutta-percha (GP) cones exposed at outpatient clinics using polymerase chain reaction, and secondly to evaluate the rapid sterilization effect of two chemical disinfectants at chair side. It also evaluated the alteration of surface texture of GP cones after 5-min soaking into two chemical disinfectants. A total of 100 GP cones from two endodontic departments were randomly selected for microbial detection using PCR assay with universal primer. After inoculation on the sterilized GP cones with the same microorganism identified by PCR assay, they were soaked in two chemical disinfectants: 5% NaOCl and 2% chlorhexidine for 1, 3, 5, and 10 minutes. The sterilization effect was evaluated by turbidity and subculture. The change of surface textures using a scanning electron microscope was also examined after 5 min-soaking in two chemical disinfectants. Results showed that four bacterial species were detected in 17 GP cones, and all the species belonged to the genus Staphylococcus. Two chemical disinfectants were effective in sterilization with just 1 minute soaking. On the SEM picture of NaOCl-soaked GP cone, a cluster of cuboidal crystals was seen on the cone surface. Present data demonstrate that two chemical disinfectants are useful for rapid sterilization of GP cone just before obturation at chair side, while CHX-soaked GP cone has cleaner surface without crystal precipitation than that of NaOCl-treated cone.

• Korean Journal of Food Science and Technology
• /
• v.39 no.2
• /
• pp.122-127
• /
• 2007

In this study, an analytical method was optimized for detecting dioxin-like PCBs in fish and shellfish. Here, homogenized samples were extracted using an accelerated solvent extraction (ASE) system with 33 mL cell size. Multilayer column chromatography, which consisted of acidic, basic and neutral silica gels, was used for the clean up of the extracts. The instrumental analysis was executed by HRGC/HRMS to a resolution of 10,000 using 4 window multiple ion detection (MID) mode. For the results, the average recoveries ranged from 94.1 to 104.1% (${\pm}8.4$) and the limit of detection was approximately 0.1 pg/g at S/N ratio >3. Finally, the detected concentrations of dioxin-like PCBs for fish and shellfish were in the range of 0.030-1.836 pg TEQ/g.