• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.50-64
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• 2013

In clustered sensor networks, since a CH (Cluster Head) collects data from its members and delivers the collected data to the sink, it is very important to prevent compromised nodes from joining a CH election and manipulating and fabricating the election result. In order to protect CH elections from compromised nodes, unpredictability, non-manipulability, and agreement property should be guaranteed in CH elections. However, existing CH election schemes cannot prevent intelligent compromised nodes from skilfully violating those properties via their cooperation. In this paper, we propose a scheme which protects the CH election process by detecting intelligent compromised nodes and excluding them. For every CH election round, each member gives a direct trust value to other members according to their behavior. Then a real reputation value is given to each member by combining the direct trust value and indirect trust values provided by other members. Then, each node evaluates the real reputation values of members in its cluster and excludes some untrustable nodes from CH candidates. The scheme greatly improves the non-manipulability and agreement property of CH election results compared to other rival schemes. Furthermore, the scheme preserves the high non-manipulability and the high agreement property even in an environment where message losses can happen.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.5
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• pp.529-541
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• 2020

Although TBM's cutterhead requires design review for fatigue failure due to wear-induced section loss as well as heavy load during excavation, it is difficult to find a case of fatigue analysis for TBM cutterhead at present. In this study, a stress-life design review was conducted on cutter heads with a diameter of 8.2 m using S-N curves as a safety life design concept. Also, we introduced the fatigue design method of construction equipment and the method of assessing fatigue damage and explained the results of the fatigue analysis on the TBM cutter head with a diameter of 8.2 m. The S-N curve has been shown to play a key role in fatigue design and can also be used to assess how much fatigue damage a structure is suffering from at this point in time. In the future, it is necessary to find out when fatigue problems occur during using the equipment and when it is good to conduct safety inspections of the equipment.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.2
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• pp.167-181
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• 2019

Currently, the development of evaluation technology for vibration and shock load characteristics and spent nuclear fuel structural integrity under normal conditions of transport is being conducted in the Republic of Korea. This is the first such research conducted in the Republic of Korea and, thus, previous international studies need to be investigated and will be referred to in the ongoing project. Before 2000, several studies related to measurement of vibration and shock loads on spent nuclear fuel were conducted in the US. US national research institutes conducted uniaxial fuel assembly shaker tests, concrete block tests, and multi-axis fuel assembly tests between 2009 and 2016. In 2017, multi-modal transportation tests including road, sea, and rail transport were also performed by research institutes from the US, Spain and the Republic of Korea. Therefore, test preparation procedures, acceleration and strain measurement results, and finite-element and multi-body dynamics analysis were investigated. Based on the measured strain data, the preliminary conclusion was obtained that the measured strain was too small to cause damage to spent nuclear fuel rods. However, this conclusion is a preliminary conclusion that only reviews part of the results; a detailed review is being conducted in the US. The investigation of international studies on spent nuclear fuel structural integrity tests considering vibration and shock loads under normal conditions of transport in the US will be useful data for the project being conducted in the Republic of Korea.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.103-110
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• 2019

Damage to the pavement system due to various causes will be required rapid repair work for reopening the vehicle traffic. The magnesium oxide phosphate composite(MPC) has a short curing time and is capable of early compressive strength development, is suitable for rapid repair materials. The aim of this study was to evaluate the hardening and compressive strength characteristics of MPC according to the water-binder (W / B) ratio and magnesium-phosphate(M / P) ratio in order to develop repair materials consisted with light burned magnesia and potassium dihydrogen phosphate. In order to ensure the workability in the field application, the difference of mechanical properties according to standard sand and ordinary sand and performance of retards were evaluated. The mix proportion with W/B ratio was about 35% and the M/P ratio was about 1.0 ~ 1.2 has a superior perfomance with strength and hardening condition. Especially, the strength of composite at only 1 day curing with W/B ratio of 0.35 and the M/P ratio of 1.2 was shown the higher than 25.0 MPa. Boric acid as a retarder was found to be suitable for ensuring the working time, and the purity of magnesium oxide was about 90 ~ 95%, which is effective for ensuring curing time and strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.135-142
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• 2022

In this study, lap spliced ultra-high strength reinforced concrete beams were tested and the code criteria for calculating the lap splice length which was affected by the transverse reinforcement and concrete covering performance were reviewed. The main variables for test were set as fiber volume fraction and transverse reinforcing bar arrangement to improve the confining performance of the concrete cover. The change of the confining performance of concrete cover according to the increase in the fiber mixing amount at 1% and 2% volume ratio was examined, and D10 stirrups with a spacing of 100 mm were placed in the lap spliced region. As a result of the test, the specimens confined by the stirrups showed a sudden drop of load bearing capacity with horizontal cracking at the position of tensile longitudinal reinforcement. However, horizontal cracks were not appeared at the location of longitudinal reinforcement for the specimens with steel fiber. And these specimens showed gradual decrease of load bearing capacity after experiencing peak load. In particular, it was found that the strain at the position of the tensile longitudinal reinforcements of the specimens to which the mixing ratio of 2% was applied exceeds the yield strain. As a result of measuring the strain on the concrete surface, it was found that the fiber was more effective in preventing damage to the concrete surface than the stirrups for short lap spliced region.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.71-80
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• 2010

Bridge deck is directly influenced by environment and vehicle load, it is easily damaged so that it requires an appropriate repair and retrofit. Therefore, developing a bridge deck with high durability is necessary in order to minimize the maintenance of bridge deck and use it to its design life. In this study, static test was carried out to evaluate a fatigue capacity of steel-concrete composite deck, which was newly developed by supplementing problems of existing reinforced concrete deck. Based on results from the static test, fatigue load was decided, and fatigue test was conducted under the constant amplitude repeated load. From the fatigue tests, the S-N curve regarding principle structural details of composite deck was made, and characteristics of fatigue behavior was estimated by comparing and evaluating it with fatigue design criteria. In addition, fatigue design guideline was presented. As a result, it is found that each structural details of composite deck proposed by this study, such as upper flange of corrugated steel plate and middle section of it, shear connector and lower flange of corrugated steel plate, is satisfying the fatigue strength.

• Korean Journal of Culture and Social Issue
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• v.19 no.2
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• pp.203-234
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• 2013

This study was performed to clarify 'jajonshim' which is different from self-esteem in its social representation and concept in Korean society. In order to refine the notion of 'jajonshim', we first referred to literature and short essay on jajonshim and analyzed its cultural meaning and social representation in Korea. As a result, jajonshim was considered necessary condition for human beings in Korean culture. Although jajonshim was not well recognized normally, it became critical when it was threatened by others and considered to be what one must save as well. Furthermore, the ground theory designed by Strauss and Corbin was utilized in order to analyze Korean interviewees' experience of jajonshim. Koreans believed that their jajonshim was injured when others disrespected their values, which consequently produced negative emotions. When their jajonshim was damaged, people also used 3 coping strategies to recover it. Based on the results, jajonshim was distinguished from self-esteem. First, jajonshim is a type of self-awareness people experience when they are disrespected; thus, it is different from self-esteem which is maintained stable regardless of any events or situations. Second, unlike self-esteem which is solely evaluated by oneself, jajonshim is evaluated by other people's point of view. This study shows that jajonshim exists in the context of Korean culture and has significance in clarifying the cognitive structure and experience process of jajonshim.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.182-192
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• 2023

In this study, the efficacy of Engineered Cementitious Composite(ECC) jacket for masonry fences subjected to lateral dynamic load was experimentally verified through a shaking table test, comparing it with the performance of an unreinforced masonry(URM) fence. Firstly, dominant frequencies, modal damping ratios and deformed shapes were identified through an impact hammer test. URM and ECC-strengthened fences with heights of 940mm and 970mm had natural frequencies of 6.4 and 35.3Hz, and first modal damping ratios of 7.0 and 5.3%, respectively. Secondly, a shaking table test was conducted in the out-of-plane direction, applying a historical earthquake, El Centro(1940) scaled from 25 to 300%. For the URM fence, flexural cracking occurred at the interface of brick and mortar joint(i.e., bed joint) at the ground motion scaled to 50%, and out-of-plane overturning failure followed during the subsequent test conducted at the ground motion scaled to 30%. On the other hand, the ECC-jacketed fence showed a robust performance without any crack or damage until the ground motion scaled to 300%. Finally, the base shear forces exerted upon the URM and ECC-jacketed fences by the ground motions scaled to 25~300% were evaluated and compared with the ones calculated according to the design code. In contrast to the collapse risk of the URM fence at the ground motion of 1,000-year return period, the ECC-jacketed fence was estimated to remain safe up to the 4,800-year return period ground motion.

• Journal of Chest Surgery
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• v.34 no.3
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• pp.212-223
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• 2001

배경: 이식폐의 보존 및 재관류 동안 cyclic adenosine monophosphate(cAMP)와 nitric oxide(NO)는 폐혈관 내 순환조절을 유지하는데 있어 중심적인 역할을 한다. 그러나 내치세포내의 cAMP와 NO 모두 허혈-재관류 과정 동안에 현저하게 감소한다. 이에 저자는 low potassium dextran(LPD) 폐조본액에 cAMP의 유사체인 dibutyry1 cAMP(db-cAMP)와 NO의 공여물질인 nitroglycerin(NTG)을 첨가하여 이들의 폐보존 효과를 알아보고, 이들은 첨가한 폐보존액 들의 효과를 비교하였다. 대상 및 방법: 토끼 폐장 분리관류 모형에 실험군은 각각 6마리씩 4개군으로 단순 LPD 페보존액만 사용한 경우(I군), LPD 용액에 NTG 만 참가한 경우(II군), cAMP 만 첨가한 겨우(III군) 그리고 두가지 모두를 첨가한 경우는 IV군으로 분류하였으며, 폐보존액이 주입된 심폐블록은 영상 1$0^{\circ}C$에서 24시간 동안 보관한 다음 100% 산소농도에서 기계호흡을 하면서 신선 정맥혈로 30분 동안 재관류를 시행하였다. 재관류폐의 평가를 위해 폐기능 및 폐부종 정도를 정량 측정하였으며, 유출로 혈액으로부터 tumor necrosis factor $\alpha$(TNF-$\alpha$)와 간접적인 NO의 총량을 알기 위해 nitrite/nitrate의 양을 측정하였다. 또한 재관류가 끝난 후 광학 및 전자현미경학적 소견을 관찰하였다. 결과: 모든 실험군 중 제 IV군 의 폐보존 능력이 가장 우수하였으나, 제 II, III, IV군 사이는 통RP적으로 유의한 차이가 없었다. 제 I군은 제 II, III, IV군들에 비해 유의하게 폐기능이 가장 나쁘고 폐부종 정도가 가장 심했다(p<0.05). 제 II군은 제 III군에 비해 더 좋은 폐기능을 보였고, 폐부종 정도가 덜 하였으나 통계적은 유의성은 없었다. TNF-$\alpha$ 는 제 IV 군이 Irns에 비해 유의하게 분비량이 적었다. (p<0.05). 총 NO의 양은 제 II군과 IV 군이 제 I 군과 III군보다 유의하게 높았으나(p<0.001), 제 II군과 IV군, 제 I군과 III군 사이 비교에서 유의한 차이는 없었다. 또한 제 I 군과 III군에서는 시간이 지남에 따라 유의하게 NO의 양이 점차 감소하였다. (p<0.05). 광학 및 전자현민경 소견상 폐포 및 폐혈관 구조가 제 II, III, IV 군이 I 군에 비해 더 잘 보존되어있었다. 결론: LPD 폐보존액에 db-cAMP 및 NTG의 첨가는 폐보존 효과가 모두 우수함을 확인하였고 이들의 폐보존 효과 차이는 거의 없음을 알수 있었다. 그렇지만 이들의 병합사용이 폐혈관 항상성을 더 잘 유지시킬 수 있고 허혈-재관류 손상을 줄여 폐보존 효과를 높일 수 있을 것이라고 기대된다.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.421-431
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• 2007

The main purpose of this study is to develop a sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing one of the carbon or glass chopped fibers and one of the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In order to investigate the material property of the sprayed FRP, this study carried out tensile tests of the material specimens, which were changed with the combinations of various variables including the length of chopped fiber and the mixture ratio of chopped fiber and resin. These variables were set to have the equal material strength, compared with that of one layer of the FRP sheet. As a result, the optimal length of glass and carbon chopped fibers was fumed out to be 38 mm, and the optimal mixture ratio between chopped fiber and resin was also turned out to be 1 : 2 from each variable. And also, the thickness of the sprayed FRP to have the equal strength to one layer of the FRP sheet was finally calculated. In is study, a series of experiments were carried out to evaluate the strengthening effects of flexural beams, shear beams and damaged beams strengthened with the sprayed FRP method, respectively. The results revealed that the strengthening effects of the flexural and shear specimens were reasonably similar to those of the FRP sheet, and the developed Sprayed FRP technique is able to be used as a strengthening scheme of existing RC building.