• 자원리싸이클링
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• 제21권3호
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• pp.48-55
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• 2012

최근 친환경적이며 고효율적인 폐동선의 재활용을 위하여 다양한 방안이 모색되고 있는 실정이다. 본 연구에서는 폐동선의 고주파 유도가열을 이용하여 폐동선의 피복제거의 실험을 수행하여 폐동선의 친환경적이며 고효율의 재활용방안을 모색하고자 다양한 공정조건하에 최적화된 방안을 도출하였다. FT-IR 분석결과, 폐동선에 코팅된 물질은 polyester임이 나타났으며, 와전류의 전산모사결과, 최적화 과정을 도출하고 이에 대하여 논의하였다. 폐동선의 피복을 효과적으로 단시간에 분리하기 위하여 폐동선을 고주파 유도코일에 수직으로 장입하고 $950^{\circ}C$이상의 온도에서 유지해야 함을 알 수 있다.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권2호
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• pp.68-71
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• 2006

Active thermography has been used for several years in the field of remote non-destructive testing. It provides thermal images for remote detection and imaging of damages. Also, it is based on propagation and reflection of thermal waves which are launched from the surface into the inspected component by absorption of modulated radiation. For energy deposition, it use external heat sources (e.g., halogen lamp or convective heating) or internal heat generation (e.g., microwaves, eddy current, or elastic wave). Among the external heat sources, the ultrasound is generally used for energy deposition because of defect selective heating up. The heat source generating a thermal wave is provided by the defect itself due to the attenuation of amplitude modulated ultrasound. A defect causes locally enhanced losses and consequently selective heating up. Therefore amplitude modulation of the injected ultrasonic wave turns a defect into a thermal wave transmitter whose signal is detected at the surface by thermal infrared camera. This way ultrasound thermography(UT) allows for selective defect detection which enhances the probability of defect detection in the presence of complicated intact structures. In this paper the applicability of UT for fast defect detection is described. Examples are presented showing the detection of defects in PCB material. Measurements are performed on various kinds of typical defects in PCB materials (both Cu metal and non-metal epoxy). The obtained thermal image reveals area of defect in row of thick epoxy material and PCB.

• 수산해양기술연구
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• 제24권4호
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• pp.150-157
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• 1988

여수연해 정치망 어장의 6월, 7월, 8월의 해황변화에 따른 어황관계를 조사하고 분석한 결과는 다음과 같다. 1) 하천수의 유입이 많은 내해와 돌산연안의 정치망 어장에서는 고온.저염분수가 분포하고 외해에는 저온 고염분수가 분포한다. 2) 정치망 어장부근에는 6월의 와류형성과 8월의 수온약층 형성으로 어류가 군집을 하는데 영향을 미쳐 좋은 어획량을 보여 주고 있다. 3) 정치망 어장에서 어획수온범위는 11$^{\circ}C$~28$^{\circ}C$이며 좋은 어획량을 나타내는 범위는 21$^{\circ}C$~27$^{\circ}C$였다. 또한 염분의 범위는 31.60$\textperthousand$~34.80$\textperthousand$이고 어획이 가장 좋은 범위는 33.80$\textperthousand$~33.99$\textperthousand$였다. 4) 어획대상물의 어획순위는 삼치, 전갱이, 삼치, 정어리, 고등어, 갈치의 순으로 나타났다.

• 비파괴검사학회지
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• 제30권1호
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• pp.13-19
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• 2010

본 논문에서는 원전SG세관 결함 크기 추정을 위한 새로운 구조의 추정시스템에 대한 연구를 수행한다. 기존의 연구에서는 결함 크기를 추정하기 위하여 각각의 결함 형태별로 결함크기추정시스템을 설계하였다. 이와 같은 경우, 추정시스템의 구조가 복잡해지고 결함 크기 추정 이전에 수행하는 결함형태분류기의 정확성이 떨어질 경우 결함 크기 추정 성능도 결과적으로 악화될 수밖에 없다. 이에 본 논문에서는 결함 형태 분류 과정을 필요로 하지 않는 결함크기추정시스템의 성능을 분석하고 이를 향상시키기 위한 방안을 연구하였다. 기존의 추정시스템은 각각의 결함 형태별로 특화된 추정기를 사용하기 때문에 추정 성능이 훨씬 뛰어날 것으로 예상되었지만, 실험 결과 두 추정시스템의 성능 차이는 그리 크지 않다는 것을 알 수 있었다. 따라서 결함형태분류기의 정확성이 완벽하지 않을 경우, 본 논문에서 제안한 구조의 추정기가 효과적으로 사용될 수 있을 것으로 기대된다.

• Corrosion Science and Technology
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• 제15권2호
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• pp.84-91
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• 2016

The transport and deposition of corrosion products in pressurized water nuclear reactor (PWR) steam generators have led to corrosion (SCC, denting etc.) problems. Lancing, mechanical cleaning and chemical cleaning have been used to reduce these problems. The methods of lancing and mechanical cleaning have limitations in removing corrosion products due to the structure of steam generator tubes. But high temperature chemical cleaning (HTCC) with EDTA is the most effective method to remove corrosion products regardless of the structure. However, EDTA in chemical cleaning aqueous solution and chemical cleaning environments affects the integrity of materials used in steam generators. The nuclear power plants have to perform the pre-test (also called as qualification test (QT)) that confirms the effect on the integrity of materials after HTCC. This is one of the series studies that assess the effect, and this study determines the effects of 20 % EDTA aqueous solution on defective tubes in high temperature chemical cleaning environments. The depth and magnitude of defects in steam generator (SG) tubes were measured by eddy current test (ECT) signals. Surface analysis and magnitude of defects were performed by using SEM/EDS. Corrosion rate was assessed by weight loss of specimens. The ECT signals (potential and depth %) of defective tubes increased marginally. But the lengths of defects, oxides on the surface and weights of specimens did not change. The average corrosion rate of standard corrosion specimens was negligible. But the surfaces on specimens showed traces of etching. The depth of etching showed a range on the nanometer. After comprehensive evaluation of all the results, it is concluded that 20 % EDTA aqueous solution in high temperature chemical cleaning environments does not have a negative effect on defective tubes.

• 한국압력기기공학회 논문집
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• 제7권3호
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• pp.61-66
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• 2011

The integrity of the SG(Steam Generator) tubes has been challenged by numerous factors such as flaws, operation, atmosphere, inherently degraded materials, loose parts and even human errors. Of the factors, loose parts(or foreign materials) on the secondary side of the tubes can bring about volumetric defects and even leakage from the primary to the secondary side in a short period of time. More serious concerns about the loose parts are their unknown influx path and rapid growth rate of the defects affected by the loose parts. Therefore it is imperative to detect and characterize the foreign materials and the defects. As a part of the measures for loose part detection, TTS(Top of Tubesheet) MRPC(Motorized Rotating Pancake Coils) ECT has been carried out especially to the restricted high probability area of the loose part. However, in the presence of loose parts in the other areas, wide range loose part detection techniques are required. In this study, loose part standard tube was presented as a way to accurately detect and characterize loose part signals. And the SG tube ECT bobbin coil and MRPC ISI(In-service Inspection) data of domestic OPR-1000 and Westinghouse Model F(W_F) were reviewed and consequently, comprehensive loose part detection technique is derived especially by applying bobbin coil signals

• 전기학회논문지P
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• 제61권4호
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• pp.220-224
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• 2012

The analysis on the bus bar effect is conducted to develop a cost effective 24kV/2,000A switchgear. The temperature enclosures and bus bars could rise due to several heat sources such as eddy current losses and copper losses. Therefore, a study on the characteristics of the electric field intensity and electromagnetic loss according to the bus bar size in a bus bar compartment is essential to design a electrically reliable high voltage switchgear. It is investigated that the electromagnetic influence to the temperature rising and the dielectric stability according to various bus bar sizes by using finite element method(FEM). The electric field intensity and electromagnetic loss according to various bus bar sizes are calculated to design a reliable and a high voltage switchgear. As results, it is found that the electromagnetic loss and the dielectric stability of bus bar could be determined by a bus bar size. It means that a cost effective 24kV/2,000A high voltage switchgear could be developed by selecting the proper size of a bus bar. Also, it is recognized that the electromagnetic characteristics according to various bus bar sizes in order to design an electrically stable high voltage switchgear when the enclosure size is determined as a fixed value. Futhermore, studies on the various nominal voltage class and bus bar sizes will be conducted to develop a cost effective high voltage switchgear.

• Wind and Structures
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• 제30권4호
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• pp.339-366
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• 2020

This study aims at modeling boundary layers (BLs) encountered in sparse and built environments (i.e. open, suburban and urban) at the subsonic Wind Tunnel (WT) at Ryerson University (RU). This WT has an insignificant turbulence intensity and requires a flow-conditioning system consisting of turbulence generating elements (i.e., spires, roughness blocks, barriers) to achieve proper turbulent characteristics. This system was developed and validated in the current study in three phases. In phase I, several Computational Fluid Dynamic (CFD) simulations of the tunnel with generating elements were conducted to understand the effect of each element on the flow. This led to a preliminary design of the system, in which horizontal barriers (slats) are added to the spires to introduce turbulence at higher levels of the tunnel. This design was revisited in phase II, to specify slat dimensions leading to target BLs encountered by tall buildings. It was found that rougher BLs require deeper slats and, therefore, two-layer slats (one fixed and one movable) were implemented to provide the required range of slat depth to model most BLs. This system only involves slat movement to change the BL, which is very useful for automatic wind tunnel testing of tall buildings. The system was validated in phase III by conducting experimental wind tunnel testingof the system and comparing the resulting flow field with the target BL fields considering two length scales typically used for wind tunnel testing. A very good match was obtained for all wind field characteristics which confirms accuracy of the system.

• 전산구조공학
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• 제9권2호
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• pp.143-151
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• 1996

구조 및 전기적 제약조건을 고려한 전자력 발사기의 최적설계에 대해 연구하였다. 펄스형 대전류가 흐르는 발사기의 단면적이 최소화되었으며 각 요소(레일, 측면벽, 세라믹 및 강철)의 허용응력과 예하중을 고려하였다. 전기적 제약조건은 발사기의 성능을 저하시키는 와전류 효과를 방지하기 위한 세라믹의 두께로 정하였다. 90mm발사기의 설계에서 응력해석과 최적화는 ANSYS코드를 사용하여 수행되었다. 예하중을 받는 최적설계에서는 예하중을 받지 않는 최적설계보다 53%의 단면적이 감소되었다. 레일의 원호각이 45.deg.일때 발사기의 성능이 가장 양호하다. 레일의 원호각이 45.deg.일때 Fahrenthold 연구결과와 비교하여 9%의 변형량 감소와 10.4%의 변형량 감소를 얻었고, 예하중도 186Mpa에서 59.8Mpa로 감소되었다. 연구결과는 설계 요구조건을 충분히 만족시켜 주고 있음을 보여 주었다.

• 한국자기학회지
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• 제8권5호
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• pp.255-260
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• 1998

두께 10$\mu\textrm{m}$ 이하의 코발트계 극박형 비정질합금의 진공중 용탕급냉방법에 의한 제조조건과 자기적 특성에 대해 연구되었다. 구리 냉각롤의 회전 선속도를 55 m/s로 하였을 때, 0.05 kgf/cm2 이하의 용탕분사압 조건에서 극박형 리본이 얻어졌다. 합금 두께는 용탕분사 가스압력의 감소에 비례하여 직선적으로 감소하였으며, 이와 동시에 폭의 감소도 함께 일어났다. 이는 극박형 합금을 만들기 위해 용탕분사압을 극단적으로 감소시키면 노즐구의 양단부에서 용융금속과 노즐 사이의 마찰효과가 크게 나타나 유효분사압이 현저히 감소하는 데에 기인하는 것으로 해석되었다. 저주파(1 kHz) 실효투자율은 대략 2차 함수의 관계로 리본 두께의 감소에 따라 저하되었다. 반면 보자력은 두께의 감소에 반비례하여 증가하였는데, 이들 현상은 거의 전적으로 표면효과의 증대에 의한 자벽이동의 억제에 그 원인이 있는 것으로 판단되었다. 그러나 고주파(1 MHz) 실효투자율은 두께의 감소에 따라 증가하였는바 이는 와전류 발생이 억제되어 자기장 방향으로의 자화회전이 보다 용이해지기 때문으로 생각되었으며, 결과적으로 극박화에 의해 MHz 대역에서 우수한 저손실 성질을 나타내는 자심 특성의 실현이 가능하였다.