Zr 합금의 석출물 및 부식특성에 미치는 Fe 와 Mn 첨가 영향

김현길,위명용,정용환,이명호,박상윤 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.11

In order to Investigate the effects of Fe and Mn on the precipitate and corrosion characteristics of Zr based alloys for nuclear fuel cladding, autoclave corrosion tests on the ternary(Zr-0.8Sn-X) alloys have been carried out at 360℃. The corrosion behavior of Zr-Sn-Fe alloy showed the cubic corrosion rate in the pre-transition region and the linear corrosion rate in the post-transition region. The good corrosion resistance in Zr-Sn-Fe alloy system was observed in Fe contents more than 0.2 wt%. The corrosion behavior of Zr-Sn-Mn alloy was significantly accelerated from the early stage. The lowest weight gain was observed in 0.2 wt% Mn. Based on the precipitate anallysis by TEM, it is thought that the corrosion of Zr-alloys would be related to the size of precipitate.

수평방향의 정현파 가진을 받는 강체 블록의 비선형 로킹진동특성

김지훈,김정호,양인영,정낙규,정만용 한국산업안전학회 1999 한국안전학회지 Vol.14 No.4

This research concentrates on the influence of non-linearities associated with impact for the nonlinear rocking behavior of rigid block subjected to one dimensional sinusoidal excitation of horizontal direction. The transition of two governing rocking equations, the abrupt reduction in the kinetic energy associated with impact, and sliding motion of block. In this study, two type of rocking vibration system are considered. One is the undamped rocking vibration system, disregarding energy dissipation at impact and the other is the damped rocking system, including energy dissipation and sliding motion. The response analysis using non-dimensional rocking equation is carried out for the change of excitation parameters and friction coefficient. The chaos responses were discovered in the wide response region, particularly, for the case of high excitation amplitude and their chaos characteristics were examined by the time history, Poincare map, power spectra and Lyapunov Exponent of rocking responses. The complex behavior of chaos response, in the phase space, were illustrated by Poincare map. The bifurcation diagram and Poincare map were shown to be effective in order to understand chaos of rocking system.

화재완화를 위한 소듐 루프 건물의 구획화

김병호,권상운,정경채,김광락,황성태 한국산업안전학회 1998 한국안전학회지 Vol.13 No.3

Analysis on the study for the sodium fire mitigation was carried out using the CONTAIN-LMR code. Sodium loop building was partitioned into the many cells, in which the safety venting systems were installed for the purpose of improving the sodium fire safety and minimizing its effect on the sodium loop building. The effects of sodium fire on sodium loop building partitioned into the many cells and not partitioned were investigated. The peak pressure and temperature of each cell accompanied by sodium fire in sodium loop building partitioned were lower than those of sodium loop building not partitioned. In the case of partitioning sodium loop building, the pressures, temperatures and aerosols into cells were transferred through propagation path of CONTAIN-LMR sodium fire model simulated by this study, and the effect of sodium spray fire on sodium loop building was mitigated by partitioning building. In addition, the excessive rise of pressure into cells was prevented by installing the over-pressure exhaust valve and under-pressure exhaust valve on the flow path between cells.

2 차원 정현파 가진을 받는 강체블록의 록킹진동에 있어서의 카오스 : 미끄럼이 없는 경우에 대하여 In the Case of No Sliding Occurrence

김지훈,김정호,양인영,정만용,양광영 한국산업안전학회 1999 한국안전학회지 Vol.14 No.2

This research deals with the non-linearities associated with impact and sliding for the rocking behavior of rigid block subjected to two dimensional excitation of horizontal and vertical direction. The non-linearities examined of impact between block and base: The transition of two governing rocking equations, the abrupt reduction in kinetic energy associated with impact. In this study, the rocking vibration system of two types are considered for several friction condition. One is the undamped rocking vibration system, disregarding energy dissipation at impact and the other is the damped rocking system, including energy dissipation at impact. The response analysis by non-dimensional rocking equation is carried out for the change of excitation amplitude. The chaos responses were discovered in the wide response region, particularly, in the case of high vertical excitation and their chaos characteristics are examined by Poincare map, power spectra and Lyapunov Exponent. The complex behavior of chaos response, in the phase space, were illustrated by Poincare map. Therefore, Poincare map will be a significant material in order to understand chaos of rocking system.

핵연료 피복관용 Zr 합금의 열처리에 다른 미세조직 및 부식특성

정용환,이명호,박상윤,김환철 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.12

The effects of final annealing temperature on microstructure and corrosion behavior of Zr-based alloys were investigated. Four kinds of Zr alleys were used for microstructural study and corrosion teat. Corrosion tests were carried out in static mini autoclave under 400℃ steam condition. Microstructures were analyzed by using TEM/EDS and image analyzer. The grain size and precipitate size of Zircaloy-4 increased with increasing the annealing temperature. As the annealing temperature increased, the corrosion resistance of Zircaloy-4 also increased due to the increase of precipitate size and grain size. Therefore, the precipitate size and grain size play an important role on the control of corrosion resistance of Zircaloy-4. However, it was considered from this study that the corrosion resistance of Nb-containing alloys would be controlled by the characteristics of beta phase rather than precipitate size.

다공질 박막을 이용한 FET 형 용존 산소 센서의 유속 의존성 개선

김영진,손병기,이영철,정훈 경북대학교 전자기술연구소 2001 電子技術硏究誌 Vol.22 No.2

FET type dissolved oxygen sensor was proposed to overcome the disadvantages of the amperometric Clark sensor. The inherent problem of the proposed sensor, however, is the flow dependence of the sensor performances since the proposed sensor detects the pH change in close proximity to the working electrode. In this study, a hydrodynamic porous thin film which can reduce the flow dependence were proposed the suggested porous thin film were formed onto sensing area and working electrode with mixed polymer matrix of TEOS and DEDMS.

Zr-xNb 2원계 합금의 미세조직과 부식특성에 미치는 Nb 의 영향

김현길,임윤수,위명용,정용환 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.5

To develop the advanced Zr alloy for nuclear fuel cladding, the microstructure and corrosion characteristics of Zr-xNb binary alloys were studied of Nb addition. Microstructural observation and corrosion behavior of Zr-xNb alloys with niobium content were carried to develop an advanced nuclear fuel cladding materials. Niobium addition results in refining the final grain size, increasing precipitation in matrix and reducing corrosion resistance of the alloy in 360℃, 18.9㎫ water. The alloy with 0.2 wt.% Nb, especially, showed the highest corrosion resistance in this study which was related to columnar structure of the oxide and relatively high content of tetra-ZrO₂. This supports that the corrosion behavior of the Zr-Nb alloy significantly depended on the microstructure and composition of the oxide. mom the XRD analysis, SEM study and TEM observation on the oxide having equal oxide thickness, the 0.2 wt.% Nb alloy showing the best corrosion resistance had higher fraction of tetra-ZrO₂ and columnar structure than other alloys. Therefore, it is considered that the corrosion of Zr-xNb binary alloy would be controlled by the oxide characteristics like tetra-ZrO₂ and equiaxed structure.

위장관 간질종양의 임상 및 병리학적 고찰

김영호,장우영,이순진,손희정,최규완,도재혁,백승운,이준행,이풍렬,이종철,박철근,임윤정,김갑철,김재준,임효근 대한소화기학회 2001 대한소화기학회지 Vol.37 No.3

Background & Aims: Gastrointestinal stromal tumor (GIST) constitutes primary nonepithelial neoplasms of the gastrointestinal tract and includes most tumors previously designated as leiomyomas/leiomyosarcomas. GIST is pathologically divided into benign, borderline and malignanct tumor. This study was carried out to delineate the clinical and pathologic features of GIST and to establish the features predicting malignancy. Methods: Clinicopathologic data of 84 patients who had GIST from 1995 to 1999 were reviewed. Results: The subjects were 42 men and 42 women, and their mean age was 59.3±13.2 years. We located fifty-two tumors in the stomach, 28 tumors in the small intestine and 4 tumors in the colorectum years. Histopathology revealed benign tumors in 23 of the 84 patients, borderline tumors in 22, malignant tumors in 39. The average size of tumors was 6.23 cm in diameter (range, 0.6-26 cm). Metastasis was noted in 15.5% of the patients at diagnosis. On endoscopy, ulceration was more common in malignancy. Endsonographic findings except size were not significant statistically. On contrast enhanced computed tomography, malignancy showed more irregular shape and variable attenuation than benign lesions, which seemed to be valuable factor. Conclusions: The variables predicting malignancy were large tumor size (≥5 cm), location of the colorectum, palpable abdominal mass, ulceration on endoscopy, and less uniformity in shape and variable attenuation on computed tomography.

Nb 첨가 Zr 합금의 열처리 조건에 따른 LiOH 용액에서의 부식특성 연구

김현길,정용환,김도훈 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.5

In order to develop the new zirconium alloys for cladding materials, the effects of Nb addition and the final heat treatment on the microstructure and corrosion characteristics of Zr-xNb(x = 0.2, 1.0 wt.%) alloys were investigated. The 1.0Nb alloy showed higher corrosion resistance than 0.2Nb alloy at 360℃, 70 ppm LiOH solution. The microstructure of oxide films that having equal oxide thickness has been characterized by TEM. The oxide of 1.0Nb alloy was mainly composed of columnar grains but the oxide of 0.2Nb alloys was mainly composed of equiaxed grains. From the XRD analysis of equal oxide thickness, the oxide of 1.0Nb alloy has higher tetra-ZrO₂ volume fraction than 0.2Nb alloys. Also when hydrogen pick-up content and fraction were measured with the corroded specimens of 0.2, 1.0Nb alloy at pre and post transition region, the hydrogen pick-up content and fraction were lower in 1.0Nb than 0.2Nb alloy. From the final heat treatment effect, the 1.0Nb alloy was affected annealing temperature but the 0.2Nb alloy was not.

차량 하중을 받는 노출 가스배관의 진동특성 연구

김준호,홍성경,정석영 한국산업안전학회 1999 한국안전학회지 Vol.14 No.4

Exposed gas pipeline in underground, especially subway construction site, has been continuously vibrated by vehicle above ground. Because this vibration can cause unexpected damages to pipeline, we had measured and analyzed the vibration. This paper presents results of the vibration analysis of exposed gas pipeline and the results are as follows. The major vertical vibration frequency of pipeline was about 13 Hz and the other frequency components disappeared when the vibration transmitted to I-beam and wire rope. Existence of wooden casement had not affect vibration of exposed gas pipeline. The results of modal analysis by experimental and analytical methods have good agreement and it is also shown that exposed pipeline has possibility of resonance at second mode.