• Economic and Environmental Geology
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• v.46 no.5
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• pp.445-453
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• 2013

The Uiseong Tapriri Five-Storied Stone Pagoda (National Treasure No. 77) is typical stone cultural heritage in Unified Silla Dynasty, Korea. The pagoda has been occurred black, brown discoloration and microcrack, exfoliation, granularity decomposition with white discoloration because of continuous weathering. As the results of analysis for the contaminants, chemical weatherings are generated that black contaminant by manganese oxide, brown contaminant by iron oxide, white contaminants by gypsum and taranakite. And physical weatherings, such as microcrack, exfoliation, are occurred by salt(gypsum) crystallization. Therefore, these need to remove the contaminants according to the conservation treatment manual, and regular monitoring using P-XRF to preserve long-term the Five-Storied Stone Pagoda at Tapri-ri, Uiseong.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.5
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• pp.443-451
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• 2013

Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect any further growth or expansion of preexisting defects or to characterize failure mechanisms. Recently, this kind of technique, that is an in-situ monitoring of inside damages of materials or structures, becomes increasingly popular for monitoring the integrity of large structures like a huge wind turbine blade. In this study, the activities of AE signals generated from external artificial sources was evaluated and located by new developed signal mapping source location method and this test is conducted by 750 kW full-scale blade. And a new source location method was applied to assess the damage in the wind turbine blade during step-by-step static load test. In this static loading test, we have used a full scale blade of 100 kW in capacity. The results show that the acoustic emission activities give a good agreement with the stress distribution and damage location in the blade. Finally, the applicability of the new source location method was confirmed by comparison of the result of source location and experimental damage location.

• Journal of Life Science
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• v.33 no.7
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• pp.586-592
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• 2023

Oxidative stress is a critical factor affecting the quality and viability of sperm during boar semen storage. Oxidative stress is also a significant concern during the process of freezing semen. The process of semen storage involves exposing the sperm to various stressors, including temperature changes, cryoprotectants, and extended periods of incubation. In addition, oxidative stress can lead to the production of reactive oxygen species (ROS) within the sperm, resulting in oxidative damage to cellular components, such as lipids, proteins, and DNA. Striking a balance between ROS production and the antioxidant defense system is crucial for maintaining sperm viability and functionality during semen storage. Moreover, the prolonged storage of boar semen leads to an increase in ROS levels, which can impair sperm motility, membrane integrity, and DNA integrity. ROS-induced lipid peroxidation affects the fluidity and stability of sperm membranes, leading to decreased sperm motility. Moreover, oxidative damage to the DNA can result in DNA fragmentation, compromising the genetic integrity of the sperm. In conclusion, oxidative stress is a significant challenge in maintaining sperm quality during boar semen storage. Understanding the mechanisms underlying oxidative stress and their impacts on sperm function is crucial for developing effective strategies to minimize oxidative damage and improve sperm storage outcomes.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.482-482
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• 2012

대기압 플라즈마 소스는 미생물을 살균하는 효과를 가지고 있으나 그 메커니즘에 대해서는 여전히 많은 연구가 필요한 실정이다. 우리는 본 연구에서 메커니즘 규명을 위한 시작단계로 플라즈마에 대한 미생물의 반응을 생물학적 및 물리적 분석을 통해 보고자 하였다. 연구에 사용한 미생물은 yeast인 Saccharomyces cerevisiae 이며 Ar Gas 플라즈마를 사용하였다. Yeast에 일정한 시간 동안 플라즈마를 조사한 후 세포의 생존, 모양 변화 관찰 및 DNA에 대한 영향이 분석되었고 r-FIB 장비를 이용하여 세포표면의 이차전자 방출계수를 측정하였다. 플라즈마 조사 시간에 따라 Yeast active cell의 수가 감소하며, water에 넣고 조사할때에는 YPD media에 넣고 조사한 것에 비해 급격히 감소함을 볼 수 있다. 셀의 모양 관찰 결과도 water에 넣고 조사할 때, YPD media보다 더 찌그러듬을 볼 수 있다. 플라즈마 조사량에 따라서 Water의 PH 값은 YPD에 비해 급격히 낮아짐을 보인다. pH의 값을 달리하고 SNP와 H2O2가 첨가된 water에 Yeast를 배양시킬 때, pH의 값이 낮아질수록 yeast의 생존도 감소함을 볼 수 있다. 그리고 DNA gel electrophoresis를 통해 플라즈마 처리를 하게되면 Yeast의 DNA 양이 감소하는 것을 관찰할 수 있다. 또한 플라즈마 처리를 3분 하였을 때의 Yeast 세포막으로부터 방출되는 이차전자방출계수는 다른 처리시간에 대한 값에 비하여 확연히 증가하는 것을 볼 수 있다. 이들 사실로부터 플라즈마의 효과로 인해 외부의 전자를 흡수 및 차단할 수 있는 기능을 갖고 있는 Yeast 세포막의 구조가 변형되어 손상되었음을 의미한다.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.49-55
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• 2018

In this study, we investigated the cellular protective effects and mechanisms of nicotiflorin and its aglycone kaempferol isolated from Annona muricata. The protective effect of these components against $^1O_2$-induced cell damage was also studied by using L-ascorbic acid and (+)-${\alpha}$-tocopherol as controls. Kaempferol exhibited the most potent protective effect, followed by (+)-${\alpha}$-tocopherol and nicotiflorin. L-Ascorbic acid did not exhibit any cellular protective effects. To elucidate the mechanism underlying protective effects, the quenching rate constant of the singlet oxygen, free radical-scavenging activity, ROS-scavenging activity, and uptake ratio of the erythrocyte membrane were measured. The results showed that the cell membrane penetration is a key factor determining the cellular protective effect of kaempferol and its glycoside nicotiflorin. The result from L-ascorbic acid demonstrated that the cellular protective effect of a compound depends on its ability to penetrate the cell membrane and is independent of its antioxidant capacity. In addition, it is suggested that cellular protective effects of kaempferol and (+)-${\alpha}$-tocopherol depend not only on the cell permeability, but also on free radical- and ROS-scavenging activities. These results indicate that the cell permeability and free radical- and ROS- scavenging activities of antioxidants are major factors affecting the protection of cell membranes against the oxidative damage induced by photosensitization reaction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.188-196
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• 2021

For the tactical vehicles operated by the Korean army, the hub-reduction portal axle was applied considering Korea's topographical characteristics. Hub-reduction was applied to a Korean military vehicle to increase the vehicle body to secure ground clearance and improve the driving capability on rough roads, such as unpaved and field land by increasing the torque. The Korean military is operating tactical vehicles after various performance tests, including durability driving, but wheel damage occurred in one of the vehicles operating in the front units. Failure analysis revealed many damaged parts, including the hub, making it difficult to determine the cause. Therefore, an analysis of the failure occurrence mechanism for each damaged part was conducted, which confirmed that the cause of wheel breakage was a hub. Furthermore, the root cause of the hub breakage was a crack due to internal pores and foreign matters. In addition, a realistic improvement plan that can be applied throughout the design, manufacture, and shipping stages was presented using the fishbone diagram analysis. The derived improvement plan was verified through unit performance tests, including CAE and actual vehicle tests, and by reflecting this, the driving safety of Korean tactical vehicles was improved. Finally, it is expected that the proposed method for analyzing the failure occurrence mechanism will be used as reference material when analyzing the quality problems of similar military vehicles in the future.

• Journal of Food Hygiene and Safety
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• v.39 no.3
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• pp.273-280
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• 2024

In this study, the antibacterial activity and mechanisms of bitter orange extract, a natural antibacterial agent, were investigated, with a focus on its potential application in washing water for controlling Salmonella Typhimurium contamination of salad, a ready-to-eat food. The minimum inhibitory concentration (MIC) of bitter orange extract against S. Typhimurium was determined using the broth dilution method. Subsequently, S. Typhimurium was exposed to various concentrations of bitter orange extract (1/16 MIC-2 MIC) and growth curves were measured. Following treatment with bitter orange extract, we investigated its antibacterial mechanism by measuring intracellular reactive oxygen species (ROS) levels, alterations in membrane potential and integrity, and nucleic acid leakage in S. Typhimurium. Additionally, salads artificially contaminated with S. Typhimurium were treated with different concentrations of bitter orange extract using the dipping method for various durations to assess the reduction effect. The MIC of bitter orange extract against S. Typhimurium was 195.313 mg/L, and bacterial growth was completely inhibited at a concentration of 1 MIC. Furthermore, an increase in bitter orange extract concentration correlated with elevated intracellular ROS levels, membrane potential disruption, membrane damage, and nucleic acid release. Importantly, salads treated with bitter orange extract exhibited a significant reduction in S. Typhimurium counts compared to the control, and prolonged treatment times resulted in further reductions in bacterial counts. Bitter orange extract was more effective than sodium hypochlorite and can be used as a safer salad wash. These findings indicate the potential treatment of salads to prevent foodborne illnesses.

• Journal of IKEEE
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• v.16 no.4
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• pp.389-394
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• 2012

Most current systems have ignored security vulnerability concerned with boot firmware. It is highly likely that boot firmware may cause serious system errors, such as hardware manipulations by malicious programs or code, the operating system corruption caused by malicious code and software piracy under a condition of no consideration of security mechanism because boot firmware has an authority over external devices as well as hardware controls. This paper proposed a structural security mechanism based on software equipped with encrypted bootstrap patterns different from pre-existing bootstrap methods in terms of securely loading an operating system, searching for malicious codes and preventing software piracy so as to provide reliability of boot firmware. Moreover, through experiments, it proved its superiority in detection capability and overhead ranging between 1.5 % ~ 3 % lower than other software security mechanisms.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.7
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• pp.333-340
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• 2005

One of the most important core technologies required for the design of the ITS (Intrusion Tolerance System) that performs continuously minimal essential services even when the network-based computer system is partially compromised because of the external or internal intrusions is the quantitative dependability analysis of the ITS. In this paper, we applied self-healing mechanism, the core technology of autonomic computing to secure the protection power of the ITS. We analyzed a state transition diagram of the ITS composed of a Primary server and a backup server utilizing two factors of self-healing mechanism (fault model and system response) and calculated the availability of ITS through simulation experiments and also performed studies on two cases of vulnerability attack.

• Explosives and Blasting
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• v.23 no.4
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• pp.31-44
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• 2005

In highly stressed conditions, the excavation damage zone induced by stress redistribution and disturbance must be evaluated after tunnel excavation. Therefore, the investigation of stress-induced deformation and fracture in rock is indispensable. In this study, fracture and damage mechanisms of rock induced by the accumulation of microcracks were investigated by the moving point regression technique as well as acoustic emission measured during uniaxial compression tests. Especially, the modified procedures to determine damage thresholds more systematically were newly proposed, and successfully applied to rock. From experiments, crack initiation and track damage stress levels were estimated to be $33{\~}36\%$ and $84{\~}89\%$ of uniaxial compressive strength respectively, for both of Hwangdeung granite and Yeosan marble. However, the normalized crack closure stress level for Yeosan marble was much higher than for Hwangdeung granite. In addition, the largest proportion of total axial strain in Hwangdeung granite was attributable to elastic deformation and initial microcracking. However, the greatest part of axial deformation in Yeosan marble arose from initial crack closure and unstable cracking. Finally, it was seen that unstable cracking after the crack damage stress level played a key part in the lateral deformation in rocks under uniaxial compression.