• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.230-237
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• 2022

It is essential that service life of reinforced concrete structures in economic and safety aspects should be secured. It is well-known that chloride attack is a typical deterioration mechanism in field concrete structures. To prevent serious accidents like collapse, many studies have been conducted to increase resistance of chloride ingress using concrete mixed with GGBS. The usage of GGBS concrete is nowadays mandatory. Since most concretes in the field are unsaturated, study regarding chloride absorption is necessary, but many studies have focused on the chloride diffusion phenomenon. Methods for evaluating chloride absorption are cost and improper in the field. It is necessary to develop a simple method for evaluating chloride absorption in practice. This study evaluated resistance of chloride ingress in GGBS concretes with impedance measurement and absorption test. From the results, it was confirmed that the contents of absorbed chloride were linearly correlated with the measured electrical resistivities (or conductivities) in the concrete. At the end of the test, the electrical conductivities were 250.8 S/m (w/b=0.4) and 303.1 S/m (w/b=0.6) for PC concretes, and 2.6 S/m (w/b=0.4) and 64.4 S/m (w/b=0.6) for GGBS concretes, respectively. Considering influencing factors for chloride absorption and impedance measurement, chloride ingress into concrete is mainly affected by pore structures due to replacement of GGBS. Especially, formations of pore structure are different with binder, thereby binders should be considered in building reinforced concrete structures exposed to chloride environments.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.395-406
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• 2023

The first technological advance to improve the output and efficiency of the latest steam turbines operating in co-generation plants in Korea can be said to be progress in the field of materials that can use high-temperature, high-pressures steam. As a result of design efforts to improve the internal efficiency of steam turbines along with the development of materials, only a few manufacturers of steam turbine have produced high efficiency steam turbines. The internal efficiency of a steam turbine on the steam path operating for a long period of time is gradually lost owing to the limit of mechanical life, and efficiency and output decrease. Therefore, this study aims to develop a model that can analyze the steam flow path performance of HP (High Pressure) and IP (Intermediate Pressure) steam turbine for a co-generation plant using a commercial program and propose a performance calculation method. Owing to the complex performance calculation method of steam turbines, major variables are presented to serve as practically useful references for steam turbine practitioners. In addition, the thermal dynamic analysis(such as heat balance diagram calculation) and the the thermal dynamic calculation required for steam turbine performance calculation and the suitability of the steam turbine performance calculation results were compared with the performance test results.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.325-330
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• 2004

Several kinds of low voltage cables have been used in nuclear power plants for the supply of electric power, supervision, and the propagation of control signals. These low voltage tables must be inspected for safe and stable operation of nuclear power plants. In particular, the degradation diagnosis to estimate the integrity of low voltage rabies has recently been emphasized according to the long use of nuclear power plants. In order to evaluate their degradation, the surrounding temperature, hardness of insulation material, elongation at breaking point (EAB), etc. have been used. However, the measurement of temperature or hardness is not useful because of the absence of quantitative criteria; the inspection of a sample requires turning off of the power plant power; and, the electrical inspection method is not sufficiently sensitive from the initial through the middle stage of degradation. In this research, based on the theory that the ultrasonic velocity changes with relation to the degradation of the material, we measured the ultrasonic velocity as low voltage cables were degraded. To this end, an ultrasonic degradation diagnosis device was developed and used to measure the ultrasonic velocity with the clothing on the cable, and it was confirmed that the ultrasonic velocity changes according to the degradation of low voltage cables. The low voltage cables used in nuclear power plants were degraded at an accelerated rate, and EAB was measured in a tensile test conducted after the measurement of ultrasonic velocity. With the increasing degradation degree, the ultrasonic velocity decreased, whose potential as a useful parameter for the quantitative degradation evaluation was thus confirmed.

• Journal of Korean Society of Forest Science
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• v.85 no.3
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• pp.439-442
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• 1996

In this study, we tried to figure out the ecology of Masakimyia pustulae Yukawa et Sunose which attacts evergreen euonymus and results in scenic damage caused by early falling of leaves and may increase the susceptibility for anthrocnose. In addition, we tried to develope a method for the control of the insect to prevent spreading of the damage by use of insecticide. The results obtained from the study were as follows : 1. Masakimyia pustulae emerged from late April to late May at Chuncheon area. Average length of the adult insects was $1.88{\pm}0.43mm$, and the life span of them reached about 11 hours. The sex ratio of the insect was 56 : 44(female : male), and they ovipositied $90{\pm}28$ eggs. The shape of eggs was oval with average length $0.32{\pm}0.013mm$. The length of larvae averaged $1.64{\pm}0.25mm$ and started pupation from mid-March, which took about 40~50 days, although there was variance due to temperature variation in each spring. 2. The 3% powder of carbofuran treatment by burying $200g/m^3$ of the insecticide around the damaged tree during mid-March with additional burying about a week after pupation showed good result for the control of the insect, which resulted in more than 96.2% removal of the insects.

• Journal of the Korean Electrochemical Society
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• v.18 no.2
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• pp.68-74
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• 2015

To compare the microstructure and electrochemical properties between two binary alloys (Cr-Si, Ni-Si), two composition of binary alloys with the same capacity were selected using phase-diagram and prepared by matrix-stabilization method to suppress the volume expansion of Si by inactive-matrix. Master alloys were made by Arc-melting followed by fine structured ribbon sample preparation by Rapid Solidification Process (RSP, Melt-spinning method) under the same conditions. Also powder samples were produced by wet grinding for X-Ray Diffraction (XRD) and electrochemical measurements. As predicted from the phase diagram, only active-Si and inactive-matrix ($CrSi_2$, $NiSi_2$) were detected. The results of Scanning Electron Microscope (SEM) and Transmission Electron Microscopy - Energy Dispersive X-ray Spectroscopy (TEM-EDS) show that Cr-Si alloy has finer microstructure than Ni-Si alloy, which was also predictable through phase diagram. The electrochemical properties related to microstructure were evaluated by coin type full- and half-cells. Separately, self-designed test-cells were used to measure the volume expansion of Si during reaction. Volume expansion of Cr-Si alloy electrode with finer microstructure was suppressed significantly and improved in cycle capability, in comparison Ni-Si alloy with coarse microstructure. From these, we could infer the correlation of microstructure, volume expansion and electrochemical degradation and these properties might be predicted by phase diagram.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.1
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• pp.61-67
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• 2015

Recently, the initiation of outside diameter stress corrosion cracking (ODSCC) at the tube support plate region of domestic steam generators (SG) with Alloy600 HTMA tubes has been increasing. As a result, SGs with Alloy600 HTMA tubes must be replaced early or are scheduled to be replaced prior to their designed lifetime. ODSCC is one of the biggest threats to the integrity of SG tubes. Therefore, the accurate evaluation of tube integrity to determine ODSCC is needed. Eddy current testing (ECT) is conducted periodically, and its results could be input as parameters for evaluating the integrity of SG tubes. The reliability of an ECT inspection system depends on the performance of the inspection technique and abilty of the analyst. The detection probability and ECT sizing error of degradation are considered to be the performance indices of a nondestructive evaluation (NDE) system. This paper introduces an optimized evaluation method for ECT, as well as the sizing error, including the analyst performance. This study was based on the results of a round robin program in which 10 inspection analysts from 5 different companies participated. The analysis of ECT sizing results was performed using a linear regression model relating the true defect size data to the measured ECT size data.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.3
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• pp.25-29
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• 2014

Plasma organic thin film for PCB surface finish is a potential replacement of the conventional PCB finishes because of environment-friendly process, high corrosion-resistance and long shelf life over 1 year. In this study, solder joint properties of the plasma organic surface finish were estimated and compared with OSP surface finish. The plasma surface finish was deposited by chemical vapor deposition from fluorine-based precursors. The thickness of the plasma organic coating was 20 nm. Sn-3.0Ag-0.5Cu (SAC305) solder was used as solder joint materials. From a salt spray test, the plasma organic coating had higher corrosion resistance than the OSP surface finish. The spreadability of SAC305 on plasma organic coating was higher than that on OSP surface finish. SEM and TEM micrographs showed that the interfacial microstructure of the plasma surface finish sample were similar to that of the OSP sample. Solder joint strength of the plasma finish sample was also similar to that of the OSP finished sample.

• Journal of Preventive Medicine and Public Health
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• v.22 no.1 s.25
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• pp.14-24
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• 1989

현재 중국에는 55개의 소수민족이 있으며, 그 인구총수는 6,700만을 초과한다. 중국정부는 특히 70년대 후반서부터 소수민족에 대한 일연의 보호정책을 쓰고 있으며 다수민족인 한족에 대하여 엄격히 실시하는 1가구 1자녀 정책에서도 소수민족을 제외하고 있다. 이에 따라 소수민족의 증가는 현저하게 늘었다. 그러나 전반적인 인구학적특성으로 보면 소수민족은 아직 후진성을 면하지 못하고 있다. 조선족이라고 일컫는 재중 우리교포는 한족을 포함하여 중국내 어느 민족과 비교하여도 인구학적으로 독특한 위치를 차지하는 경우가 많다. 예를 들어 인구증가율은 가장 낮으며 어느민족보다 앞서서 1970년대 중반에 이미 대치수준 이하의 출생률에 도달한 것으로 믿어지고 있다(Han 등, 1988). 문맹률은 최하이며 대학수업율은 최고로 높다(장(張), 1984). 사망률은 전소수민족중 가장 낮고 평균 수명은 가장 길다(Dowdle, 1984). 이렇게 재중 조선족은 인구학적으로 가장 선진적이기 때문에 1자녀 정책에 대한 수용 준비가 다른 민족보다 앞서 있다고 할 수 있겠다. 물론 조선족은 소수민족에 속하기 때문에 1자녀정책에 구애될 필요가 전혀 없다. 따라서 조선족 가정에서 1자녀만을 낳겠다는 서약을 하여 이른바 '독생자녀증'을 영수하면 이것은 한족의 경우와 달리 자율의사에 따른 것이라 할 수 있을 것이다. 이 논문에서는 다음 두가지를 다루기로 하겠다. 즉, 조선족이 인구학적으로 보아 딴 민족에 비하여 어떤 위치에 있으며, 또 중국의 중요인구정책인 1가정 1자녀제에 어떻게 반응하고 독생자녀증을 어떻게 수용하느냐 하는 것이다. 이 밖에 중국의 대소수민족 인구정책의 앞날에 대하여도 약간의 전망을 하여볼까 한다.스와 여기에 사용되는 신호 방식을 논의하고 있다. 그 외에도 전광 통신망 운용에 필요한 라우팅 및 파장할당 방법과 OXC를 이용한 그물형 망에서의 보호 및 복구에 대한 연구도 활발히 진행되고 있다.rotene 보충군에 비하여 유의적으로 높았으며 retinyl acetat와 B-carotene 보충군 사이에는 유의적인 차이가 없었다.3.17%로 가장 양호하였으나, 양파망과 염화비닐판을 수직으로 놓은 것은 각각 1.52%와 1.61%로 비교적 저조하였다. 수정 후 40일째부터 90일째까지 측정한 부착치패의 경과 일수에 따른 각장의 성장은 $SL=184.44e^{0.0335X}(r^2=0.9861)$의 회귀직선식으로서 나타났다. 중간육성 시험에서 수심별 성장을 분석한 결과, 비단가리비 치패는 저층보다 표층이 각장 5.92mm, 전중량 6.07g 정도 더 빨리 성장하였다. 시간으로 하여 l 주 44 시간을 기준으로 측정하면 통상질환관리 18.56시간, 지역사회 보건관리 5.67 시간, 모자보건 및 가족계획 5.52 시간, 사업 운영관리 및 지도 4.10시간, 지역사회 조직 및 개발 3.05 시간, 보건정보체계 개발 및 수집 2.94 시간, 사업계획 수립 2.89시간의 순으로 나타났다. 5) 보건진료원의 업무영역별 수행 소요시간의 상판판계를 살펴보면 지역사펴 조직 및 개발을 위 해 소요한 시간은 사엽계획 수립 소요시간 및 보건정 보체계 관리 소요시간과 순상관관계를, 사업 계획 수립 소요시간은 지역사회 보건관리, 모자보건 및 가족계획 관리 소요시간 및 보건정보체제 관리 소요시간과 순상관관계를 나타냈다. 또한 통상질환관리 소요시간은 지역 사회 조직 및 개발, 사업계획 수립, 지역사회 보건관리와 모자보건

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.459-467
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• 2019

The landing gear is a component that requires a high degree of safety to protect the lives of rotary-wing aircraft and boarding personnel, absorbing the impact on transfer/landing and supporting the fuselage during taxiing and mooring on the ground. In particular, the wheel landing gear supporting the aircraft fuselage absorbs most of the shock from the ground through the shock absorber and tires. This ensures the safety of the pilot on board the aircraft and satisfies the operational capability of the soldiers between missions. During the operation of a rotary-wing aircraft, a number of piston pins, which are a component of the right main wheel landing gear, were found to be broken. Therefore, this study examined the root cause of the piston pin crack phenomenon found in the main wheel landing gear. For this purpose, various causes were identified from fracture surface analysis of a flight test. In particular, the possibility of cracking was analyzed based on the influence on the fastening torque with the drag beam component applied to the piston pin at the time of development. This ensures the fatigue life and structural integrity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.7-12
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• 2019

The naval surface vessels, which were often exposed to harsh marine environment, tended to be corrosive due to military operations on various sea-areas and courses. Although R.O.K Navy applied various methods to protect further corrosion, the hull corrosion occurred due to cavitation were found on the naval surface vessels at regular and occasional docking. Hull corrosion was a critical factor directly to affect the lifetime of ships and their operational capabilities adversely. In this paper, EH 2350, which was the main anticorrosion paint used by R.O.K. Navy, was compared with DuraTough DL by used by the U.S Navy to collect materials related to anti-corrosion paint. In addition, the paint compatibility verification was conducted through wear abrasion test. Assuming that it was exposed to sea-environment various both abrasion cycle and weight for objective verification. by varying both the abrasion cycles and weights. In this study, the reliability of the EH 2350 conformity, which was used in Naval surface vessels, was secured.