• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.25-31
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• 2008

Cp-Ti and Ti-6Al-4V alloys commonly used dental implant materials, particularly for orthopaedic and osteosynthesis because of its suitable mechanical properties and excellent biocompatibility. This alloys have excellent corrosion behavior in the clinical environment. The first factor to decide the success of dental implantation is sufficient osseointegration and high corrosion resistance between on implant fixture and its surrounding bone tissue. In this study, in order to increase corrosion resistance and biocompatibility of Cp-Ti and Ti-6Al-4V alloy that surface of manufactured alloy was coated with TiN by RF-magnetron sputtering method. The electrochemical behavior of TiN coated Cp-Ti and Ti-6Al-4V alloy were investigated using potentiodynamic (EG&G Co, PARSTAT 2273. USA) and potentiostatic test (250mV) in 0.9% NaCl solution at 36.5 $\pm$ 1$^{\circ}C$. These results are as follows : 1. From the microstructure analysis, Cp-Ti showed the acicular structure of $\alpha$-phase and Ti-6Al-4V showed the micro-acicular structure of ${\alpha}+{\beta}$ phase. 2. From the potentiodynamic test, Ecorr value of Cp-Ti and Ti-6Al-4V alloys showed -702.48mV and -319.87mV, respectively. Ti-6Al-4V alloy value was higher than Cp-Ti alloy. 3. From the analysis of TiN and coated layer, TIN coated surface showed columnar structure with 800 nm thickness. 4. The corrosion resistance of TiN coated Cp-Ti and Ti-6Al-4V alloys were higher than those of the non-coated Ti alloys in 0.9% NaCl solution from potentiodynamic test, indicating better protective effect. 5. The passivation current density of TiN coated Cp-Ti and Ti-6Al-4V alloys were smaller than that of the noncoated implant fixture in 0.9% NaCl solution, indicating the good protective effect resulting from more compact and homogeneous layer formation.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.1
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• pp.5-17
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• 2000

To evaluate the possible therapeutic effects of growth hormone and vitamin C on multiorgan failure, a rat model was developed for LPS-induced sepsis. Using this model, the effects of growth hormone and vitamin C on tissue damages, catalase and i-NOS activities, and MDA levels were examined in the lung and liver. The level of TNF- in plasm was also examined. Male, Sprague-Dawley rats were injected with LPS intraperitoneally then divided into 3 groups : positive controls injected with LPS only, the ones injected with growth hormone or vitamin C immediately after the LPS injections. The lung and the liver were then isolated, blood samples were collected at 24 or 48 hours after the LPS injection, then examined for histopathological and biochemical changes. The results obtained were as follows. 1. LPS induced sinusoid vasodilation and mild destruction of lobular structure in the liver. In the lung, alveolar structure appeared to be thickened and interstitial edema was observed. The levels of MDA in the liver and the lung was increased by LPS, while the activity of catalase was decreased. The activity of i-NOS of those tissues was also increased, which was more pronounced at 24 hr. The level of TNF- in plasm was increased by LPS 2. In the lung, vitamin C suppressed lymphocyte and neutrophil infiltration, alveolar wall thickening and interstitial edema. In the liver, vitamin C protected against the destruction of the lobular structure. The activity of catalase reduced by LPS was reversed partly by vitamin C. The activity of i-NOS enhanced by LPS was also reversed by vitamin C. The level of TNF- in plasm reduced in some animals by vitamin C, which however was not significant statistically(p<0.05). 3. Growth hormone showed similar protective effects against inflammation and damages in the liver and lung tissues. Growth hormone reversed partly the LPS effects on the level of MDA, the activity of catalase and i-NOS induction in the liver and the lung. Growth hormone reduced plasma level of TNF-${\alpha}$ substantially, which contrasted from vitamin C. Besides this, overall protective effects of growth hormone against LPS-induced experimental sepsis were similar to those of vitamin C. From this results, the mechanism of growth hormone on suppression of LPS-induced tissue damage might be associated with production of antioxidative enzyme and suppression of plasma TNF- level.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.557-564
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• 2009

In recent years, there have been numerous explosion-related accidents due to military and terrorist activities. Such incidents caused not only damages to structures but also human casualties, especially in urban areas. To protect structures and save human lives against explosion accidents, better understanding of the explosion effect on structures is needed. In an explosion, the blast overpressure is applied to concrete structures as an impulsive load of extremely short duration with very high pressure and heat. Generally, concrete is known to have a relatively high blast resistance compared to other construction materials. However, information and test results related to the blast experiment of internal and external have been limited due to military and national security reasons. Therefore, in this paper, to evaluate blast effect on reinforced have concrete structure and its protective performance, blast tests are carried out with $1.0m{\times}1.0m{\times}150mm$ reinforce concrete slab structure at the Agency for Defence Development. The standoff blast distance is 1.5 m and the preliminary tests consists with TNT 9 lbs and TNT 35 lbs and the main tests used ANFO 35 lbs. It is the first ever blast experiment for nonmilitary purposes domestically. In this paper, based on the basic experiment procedure and measurement details for acquiring structural behavior data, the blast experimental measurement system and procedure are established details. The procedure of blast experiments are based on the established measurement system which consists of sensor, signal conditioner, DAQ system, software. It can be used as basic research references for related research areas, which include protective design and effective behavior measurements of structure under blast loading.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2383-2389
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• 2002

This paper describes an experimental study on fatigue life extension by using cold working process in fastener hole of aircraft structure. Cold working process was applied for A12024-7351 specimens by considering the effect of edge margin on fatigue life. It is generally recognized that cold working process offers a protective zone around fastener hole of aluminum aircraft structure due to the residual compressive stresses which lead to retardation of crack growth. Thus this process provides the beneficial effect of increasing the fatigue life of the component. there by decreasing maintenance costs. It has also been successfully incorporated into damage tolerance and structural integrity programs. Cold working specimens were tested at constant amplitude peak cyclic stresses. Fatigue life of cold working specimen compared with that of specimen fabricated with base material. The increase of fatigue life for cold working specimen is discussed by both considering the effect of residual compressive stresses measured by X-ray diffraction technique and quantitative effect of edge margin.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.5
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• pp.485-491
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• 2015

In this study, the experimental and analytical investigation on structural integrity evaluation of spline shaft of self propelled artillery' generator were carried out. For this work, macro and microstructure fractography of spline shaft were observed. According to the results of the structure analysis and simulation, the shaft was redesigned and optimized. To improve the stiffness and shear stress, the material was changed from the SNCM220 to SNCM439 and surface roughness and protective coating treatment are changed to increase the stress relaxation, respectively. From the result of the torsion test of shaft and accelerated life test of generator, the shaft of a SNCM439 with heat-treatment(Q/T) and electroless nickel plating was superior quality reliability and durability than the others. Therefore, modeling and simulation corresponded well with the experimental result and structural safety was confirmed by generator performing.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.4
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• pp.1-14
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• 1991

In PECVD(Plasma-Enhanced Chemical Vapor Deposition) process, titanium nitride is thin and its adhesion is poor for the protective coatings. Therefore it has been studied that intermediate layer forms between substrate and TiN thin film. Using R.F. plasma nitriding, nitride layer was first formed, then TiN thin film coated by PECVD. The chemical composition of the coatings has been characterized using AES, EDS and their crystallographic structure by means of XRD. Mechanical properties such as microhardness and film adhesion have also been determined by vickers hardness test, scratch test and indentation test. As a result, there was no difference in chemical composition and structure between the TiN deposition only and the composite of TiN deposition on nitrided steel. It was found that nitrided substrate increased the hardness of TiN coatings and was beneficial in preventing the plastic deformation in the substrate. Therefore the effective load bearing capacity of the TiN coatings on nitrided steel was increased and their adhesion was improved as well. According to the results of this study, the processes that lead to the formation of composite layers characterized by good working properties, i.e., high microhardness, adhesion and resistance to deformation.

• Journal of Microbiology and Biotechnology
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• v.28 no.9
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• pp.1457-1466
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• 2018

In the present study, the stabilizing effect of four different biological osmolytes on Bacillus licheniformis ${\gamma}$-glutamyl transpeptidase (BlGGT) was investigated. BlGGT appeared to be stable under temperatures below $40^{\circ}C$, but the enzyme retained less than 10% of its activity at $60^{\circ}C$. The tested osmolytes exhibited different degrees of effectiveness against temperature inactivation of BlGGT, and sucrose was found to be the most effective among these. The use of circular dichroism spectroscopy for studying the secondary structure of BlGGT revealed that the temperature-induced conformational change of the protein molecule could be prevented by the osmolytes. Consistently, the molecular structure of the enzyme was essentially conserved by the osmolytes at elevated temperatures as monitored by fluorescence spectroscopy. Sucrose was further observed to counteract guanidine hydrochloride (GdnHCl)-and urea-induced denaturation of BlGGT. Taken together, we observed evidently that some well-known biological osmolytes, especially sucrose, make a dominant contribution to the structural stabilization of BlGTT.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.580-584
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• 2007

The ZrC layer instead of SiC layer is a critical and essential layer in TRISO coated fuel particles since it is a protective layer against diffusion of fission products and provides mechanical strength for the fuel particle. In this study, we carried out computational simulation before actual experiment. With these simulation results, Zirconium carbide (ZrC) films were chemically vapor deposited on $ZrO_2$ substrate using zirconium tetrachloride $(ZrCl_4),\;CH_4$ as a source and $H_2$ dilution gas, respectively. The change of input gas ratio was correlated with growth rate and morphology of deposited ZrC films. The growth rate of ZrC films increased as the input gas ratio decreased. The microstructure of ZrC films was changed with input gas ratio; small granular type grain structure was exhibited at the low input gas ratio. Angular type structure of increased grain size was observed at the high input gas ratio.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.3
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• pp.41-48
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• 2019

The industrial safety helmets are personal protective equipment (PPE), used to protect the head against falls from a height. This study indicated the necessity of wearing a safety helmet while working at heights below 4 m, through analysis of fall accidents occurring in the industrial field. The stress, displacement, and strain of the safety helmet shell structure have been analyzed using the finite element method with various thicknesses, engineering plastics, and designs. It was preferred that the safety helmet shell structure had a reinforcement frame of uniform thickness in terms of increased impact strength and strain energy absorption rate. The thickness can be reduced to lighten the total weight for workers wearing safety helmets.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.451-457
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• 2014

Recently, as a means of resolving the issue of legal liability in the event of an accident or a disaster, a wide variety of simulation techniques, such as structural and structure-fluid interaction analysis, have been used in the field of forensic engineering. The plate girder bridge discussed in this paper was being constructed between a pier and an abutment to expand an existing bridge, but an accident whereby the bridge overturned occurred at the end of the concrete laying process for a protective wall. This accident was caused by additional loads not being considered at the time of the design as well as the actual construction being different from the design. The additional loads ultimately generated a negative support force. In this study, we determined the cause of the accident by comparing the structural stability of the original design with that of the additional, non-conforming construction using MIDAS structural analysis.