• Composites Research
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• v.28 no.4
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• pp.219-225
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• 2015

Air spoiler, which can reduce the drag during operation, can be considered as a possible means to reduce carbon dioxide emission and to increase fuel efficiency. In this study, a composite air spoiler was designed and tested by static and repeated loads. The Green Water Pressure of 0.1 MPa a ship experiences during operation was perpendicularly applied to the air spoiler. Air spoiler was manufactured with sandwich panel which has glass fabric face and balsa core. Multiple sandwich panels were assembled to steel frame by bolt joint. The joint was designed to have bearing failure and examined by static and fatigue tests. Tests showed that the designed joint has enough margin of safety to endure joint failure. The developed sandwich panel to air spoiler is planned to be applied to a large scale commercial ship.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.3
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• pp.260-272
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• 2001

All-ceramic restorations have had a more limited life expectancy than metal ceramic restorations because of their low strength. Their relatively lower strength and resistance to fracture have restricted the use of all-ceramic crowns to anterior applications where occlusal loads are lower. But there has been increasing interest in all-ceramic restorations because patients are primarily concerned with improved esthetics. Many efforts have been made to in prove the mechanical properties of dental ceramics. This study was designed to elucidate the influence of the luting agent on the strength of the Empress 2 crown (staining technique) cemented on human teeth. Seventy extracted human permanent molar teeth were chosen. Teeth were prepared for Empress 2 crowns with milling machine on a surveyor. A dental bur was placed in the mandrel that was positioned so that the long axis of the bur was perpendicular to the surveyor base. Dimensions of the Empress 2 crown preparation were $6^{\circ}$ taper on each side, $1.5{\pm}0.1mm$ shoulder margin, and 4mm crown height. The luting cements used in this study were as follow: 1. Uncemented 2. Zinc phosphate cements (Confi-Dental) 3. Conventional glass ionomer cement : Fuji 1 (GC) 4. Resin-modified glass ionomer cements : Fuji plus (GC) 5. Adhesive cements : Panavia F (Kuralay), Variolink II (Vivadent), Choice (Bisco). Fracture test using Instron. The crowns were loaded in compressive force to evaluate the effect of these cements on the breaking strength of these all-ceramic crowns. A steel ball with a diameter of 4mm was placed on the occlusal surface and load was applied to the steel ball by a cylindrical bolt with a crosshead speed of 0.5mm per minute until fracture occurred. The fractured surface was examined using Scanning Electron Microscopic Image (SEM) to discover the correlation between fracture strength and bonding capacity. Within the limitation of this in vitro study design, the results were as follows : 1. fomentations significantly increased the fracture resistance of Empress ceramic crowns compared to control. Uncemented (206.9 N): ZPC (812.9 N): Fuji 1 (879.5 N): Fuji Plus (937.7 N): Choice (1105.4 N): Variolink II (1221.1 N): Panavia F (1445.2 N). 2. Resin luting agent, treated by a silane bond enhancing agents, yielded a significant increase in fracture resistance. In some of the Panavia F group, a fracture extended into dentin. 3. According to SEM images of fractured Empress crowns, the stronger the bond at both interfaces(crown and die), the more fracture strength was acquired.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.635-642
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• 2014

In this paper, an efficient technique is developed to predict failure probability of three failure modes(case rupture, fracture and bolt breakage) related to solid rocket motor case due to the inner pressure during the mission flight. The overall procedure consists of the steps: 1) design parameters affecting the case failure are identified and their uncertainties are modelled by probability distribution, 2) combustion analysis in the interior of the case is carried out to obtain maximum expected operating pressure(MEOP), 3) stress and other structural performances are evaluated by finite element analysis(FEA), and 4) failure probabilities are calculated for the above mentioned failure modes. Axi-symmetric assumption for FEA is employed for simplification while contact between bolted joint is accounted for. Efficient procedure is developed to evaluate failure probability which consists of finding first an Most Probable Failure Point(MPP) using First-Order Reliability Method(FORM), next making a response surface model around the MPP using Latin Hypercube Sampling(LHS), and finally calculating failure probability by employing Importance Sampling.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.18 no.1
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• pp.64-80
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• 1992

Considerable interest has been generated in age-related non-enzymatic glycosylation and crosslinking of collagen in view of its extracellular nature, and its long biological half-life. The effects of UVA, which penetrates deep in dermis, and reactive oxygen species (ROS) on age- related changes of dermal collagen were studied. The amount of nonenzymatic glycosylation, fragmentation, and crosslinking of collagen were monitored from the mixtures of Type I collagen from calf skin and glucose, irradiated by UVA, with or without scavengers of ROS. At both high and low glucose dosages, non-enzymatic glycosylation was not affected by UVA irradiation. At high glucose dosage, however, glycosylation was reduced by the scavengers of superoxide radical and singlet oxygen, bolt not by hydroxyl radical scavengers. Fragmentation was increased by UVA and decreased by all ROS scavengers. Crosslinking was also enhanced by UVA, and effectively blocked crosslinking. Superoxide radical and singlet oxygen, which were produced by autoxidation of glucose independently to UVA, may encounter the initial phase of glycation. ROS generated from Amadory compounds by UVA enhanced fragmentation and crosslinking Hydroxyl radical was thought to be a major ROS affecting crosslinking. These results suggest that UVA and ROS are able to enhance age-related structural changes of collagen, as affecting many other tissue and cellular components.

• The Korea Journal of Herbology
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• v.35 no.4
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• pp.17-23
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• 2020

Objectives : In this study, we investigated the protective effects of Charybdis japonica (C. japonica) water extract on the acute reflux esophagitis in rat models. Methods : Twenty rats were divided into four groups for examination: normal control group (n=6), the reflux esophagitis group (n=6), reflux esophagitis treated with positive control group (ranitidine 40 mg/kg, n=6), reflux esophagitis treated with C. japonica group (100 mg/kg, n=6). All rats fasted for 18 hr and then were induced with reflux esophagitis by a pylorus and forestomach ligation operation. After 4 hr, the rats were sacrificed. The proinflammatory cytokine and proteins expression measured by western bolt assay, and the histopathological analysis of the esophageal mucosa measured by hematoxylin and eosin staining. Results : C. japonica administration significantly was protecting esophageal mucosal damage upon histological analysis of reflux esophagitis in rats. The C. japonica treatment confirmed the protection of the reduction of claudin-5, an evaluation index of the damage of tight junctions in the reflux esophagitis. C. japonica was also found to inhibit the expression of proteins such as COX-2 and TNF-α in the rat esophagus. C. japonica markedly attenuated the activation of NF-κB and phosphorylation of IκBα at the same time. Conclusion : These results indicated that C. japonica suppressed the development of esophagitis through the modulation of inflammation by regulating NF-κB activation. Based on these findings, we concluded that C. japonica can prevent reflux esophagitis.

• Journal of the Korean Magnetics Society
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• v.14 no.4
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• pp.143-148
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• 2004

Effects of residual flux density M$_{res}$ and number of inspection on the detection voltage and flux density B of the gas pipeline were investigated in MFL inspection, which is widely used for the non-destructive inspection in a gas pipeline. A simulation equipment composed of the magnetizer and iron ring attached on an aluminum disc was constructed instead of a huge gas pipeline facility. With this system. the iron ring could be perfectly demagnetized and signals from the bolt screw stuck on the disc could be clearly detected so that the effects of M$_{res}$S and the inspection number on the detection voltage and B of iron ring were effectively investigated. With increasing the number of inspection, M$_{res}$, B of the iron ring and the detection voltage decreased and then kept at constant values while final M$_{res}$ increased with increasing initial M$_{res}$. If inspection condition were kept unchanged, the detection voltage was proportional to the last M$_{res}$ of the iron ring instead of B. This was probably due to magnetic hysteresis of the iron ring inherited from magnetic domain so that consideration on the magnetic hysteresis was inevitable in the analysis of MFL signal from defects of a gas pipeline. A new inspection scheme using the magnetizer with reversed magnetization in the subsequent inspection was proposed from the result that a high detection voltage could be obtained in the first inspection of gas pipeline with positive M$_{res}$.

• Fire Science and Engineering
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• v.34 no.3
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• pp.67-75
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• 2020

In this study, the risk of heat generation due to normal and overload currents that vary with the abnormal loosening angle of wire-connecting bolts were identified. The risks were analyzed based on the thermal characteristics to minimize the carbonization accidents of terminal blocks inside distribution panels typically used in industrial sites. We applied a method for measuring the heating temperature and temperature variations in the terminal blocks in real-time by installing a resistance temperature detector sensor board in the terminal block. The experimental results showed that the terminal block model with a low-rated current exhibited a higher heating temperature, thus, confirming the need to select the terminal block capacity based on load currents. Additionally, the higher the rated current of the terminal block with a high-rated current and the higher the degree of loosening, the faster the carbonization point. Such heating temperature monitoring enabled real-time thermal temperature measurement and a step-by-step risk level setting through thermal analysis. The results of the measurement and analysis of carbonization risks can provide a theoretical basis for further research regarding the risk of fire due to carbonization. Furthermore, the deterioration measurement method using the temperature sensor board developed in this study is widely applicable to prevent fires caused by poor electrical contact as well as risk-level management.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.2
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• pp.379-385
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• 2017

In general, distribution board, panel board and motor control center can be installed over a wide area such as residence of group, building, schools, factories, ports, airports, water service and sewerage, substation and heavy industries that are used to supply converts the voltages extra high voltage into optimal voltage. There are electrical accidents due to rise of contact temperature, loose contact between busbar, deterioration of the contact resistance, over temperature of the busbars. In this paper, we designed and implemented the busbar joint and temperature measurement system, which can measure the joint resistance of busbar and loose connection between busbar using potentiometer and non-contact infrared sensor. The experimental results show that tightening the bolt and nut is fully engaged, resistance was decreased and maximum error range was 0.1mm. Also, the experimental result showed that the temperature at the contact area is increased from $27.3^{\circ}C$ to $69.3^{\circ}C$by the contact resistance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.475-481
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• 2018

In this study, the safety and effectiveness of ope cutter, developed to prevent frequent accident propeller windingness at sea. First, we calculated the bolt strength of the three types of rope cutting devices used in the experiment and the torsional stresses on the shafting system theoretical equation and the finite element method. As a result, the bolts used in the rope cutter confirmed from the viewpoint of safety life design and fail safe design. Also, safety satisfactory because of the small effect on the shaft system when locking up. Experiments were carried out to cut ropes and fishing nets from the sea using the ships equipped with three types of rope cutters verified to be safe. As a result, ropes of 20 to 50 mm in thickness were generally cut. It was found that the cutting efficiency of a rope cutter attached to shafting decreased when cutting thick ropes.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.699-714
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• 2022

The objective of this study is to suggest a safe and economical pillar reinforcement method when very near-twin tunnels with a minimum interval of 1 m passes through a soft zone such as weathered soil or weathered rock. A standard cross-sectional view of a two-lane road tunnel was applied to suggest a pillar reinforcement method for the very near-twin tunnels. The thickness of the pillar was 1 m. The ground condition around the tunnel was weathered soil or weathered rock. There were four reinforcement methods for pillar stability evaluation. These were rock bolt reinforcement, pre-stressed steel strand reinforcement, horizontal steel pipe grouting reinforcement, horizontal steel pipe grouting + prestressed steel strand reinforcement. When the ground condition was weathered soil, only the pillar reinforced the horizontal steel pipe grouting + prestressed steel strand did not failed. When the ground condition was weathered rock, there were no failure of the pillar reinforced the horizontal steel pipe grouting or the horizontal steel pipe grouting + prestressed steel strand. It is considered that the horizontal steel pipe grouting reinforcement played a role in increasing the stability of the upper part of the pillar by supporting the upper load applied to the upper part of the pillar.