• 한국화재소방학회논문지
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• 제21권4호
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• pp.52-58
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• 2007

본 연구는 숲 가꾸기 실행지와 미실행지의 임분 특성이 산불에 미치는 영향에 관한 연구이다. 조사지역은 강원도 양양군, 인제군 그리고 경기도 가평군 등 3개 군에서 14개소를 선정하였으며, 이중 숲 가꾸기 실행지 9개소, 미실행지의 5개소에 대한 현장조사를 실시하였다. 현장조사를 통해 임목의 수고, 흉고직경, 지하고, 죽은 가지 고사율, 임목밀도, 울폐도, 관목층 및 초본층 피도를 조사하였으며 이 자료를 통해 숲 가꾸기 실행 및 미실행지의 임내특성분석을 실시하였다. 또한 임내특성 분석으로부터 산불발생 및 확산 위험성과의 관계를 분석하였다. 숲 가꾸기 실행지역과 미실행지역의 임분 특성조사 결과 숲 가꾸기 실행지역이 미실행지역에 비해 상대적으로 평균 지하고는 높았고, 임목본수는 적었으며, 죽은 가지 고사율은 적었고, 초본층 피도는 높게 나타나고 있어 숲 가꾸기 실행지역의 산불위험도는 미실행지역보다 낮아질 것으로 판단되었다.

• Corrosion Science and Technology
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• 제19권3호
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• pp.131-137
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• 2020

A number of piping components in the secondary system of nuclear power plants (NPPs) are exposed to aging mechanisms, such as flow-accelerated corrosion (FAC), cavitation, flashing, solid particle erosion, and liquid droplet impingement erosion. Those mechanisms may lead to thinning, leaking, or rupture of the components. Due to the pipe ruptures caused by wall thinning in Surry unit 2 in the USA in 1986 and Mihama unit 3 in Japan in 1994, pipe wall thinning management has emerged as one of the most important issues in the nuclear industry. To manage pipe wall thinning, a foreign program has been utilized for NPPs in Korea since 1996. As our experience and knowledge of pipe wall thinning management have accumulated, our program needs to reflect our experience, requests from users, and the result of recent experiments using Flow Accelerated Corrosion Testing System (FACTS). FACTS is the empirical experimental facility developed by Korea Atomic Energy Research Institute (KAERI) for tests. Accordingly, KEPCO-E&C developed a 3D-based pipe wall thinning management program called ToSPACE in 2016. This paper describes a comparison between the FAC analysis results using ToSPACE and the experimental results using FACTS to verify their applicability to pipe wall thinning management in NPPs.

• Journal of Magnetics
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• 제18권3호
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• pp.342-347
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• 2013

Local wall thinning in pipelines affects the structural integrity of industries, such as nuclear power plants (NPPs). In the present study, a development of pulsed eddy current (PEC) technology that detects the wall thinning of pipelines covered with insulation is reviewed. The methods and experimental results, which have two kinds of probe with a single and double core, were compared. For this purpose, the single and double core probes having one and two excitation coils have been devised, and the differential probe with two Hall sensors has been fabricated to measure the wall thinning in insulated pipelines. The test sample is a stainless steel having different thickness, laminated by plastic insulation to simulate the pipelines in NPPs. The excitation coils in the probe is driven by a rectangular current pulse, the difference of two Hall sensors has been measured as a resultant PEC signal. The peak value of the detected signal is used to describe the wall thinning. The double core probe has better performance to detect the wall thinning covered with insulation; the single core probe can detect the wall thinning up to an insulation thickness of 18 mm, whereas the double probe can detect up to 25 mm. The results show that the double core PEC probe has the potential to detect the wall thinning in an insulated pipeline of the NPPs.

• Journal of the Korean Wood Science and Technology
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• 제31권2호
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• pp.16-23
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• 2003

간벌이 국산 잣나무 조림목의 용재품질에 미치는 영향을 구명함으로써 잣나무 인공조림목의 양질재 생산과 효율적 이용을 위한 기초자료를 제공하고자 수행된 본 연구에서 다음과 같은 결과를 얻었다. 강도의 간벌을 실시한 곳에서는 원목의 단위 m당 표면옹이 출현수가 감소하였고, 죽은 옹이의 비율도 감소하였으나 옹이의 크기는 커졌으며, 옹이의 상향각은 죽은옹이가 산옹이보다 컸다. 굽은 원목은 간벌을 하지 않은 곳보다 강도간벌을 실시한 곳에서 적게 출현하였고, 원주형질률은 강도간벌을 실시한 곳에서 높게 나타났으며 지상고 3.2 m 이하 부위의 원목에서 더욱 향상되었다. 무결점재면률은 무간벌구에 비해 강도간벌구에서 향상되었으며, 원목품등은 간벌을 강하게 실시한 경우일수록 높게 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제51권2호
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• pp.109-132
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• 2023

The objective of this study was to reveal the impact of thinning and pruning regimes on the physical and mechanical properties of clonal teak wood planted in Java. In this study, a 15-year-old clonal teak plantation was carried out and the obtained data were evaluated with analysis of variance (ANOVA). The results showed that different thinning intensities had a significant impact on the alteration of heartwood volume development (F = 25.63; p < 0.0001). Meanwhile, the impact of different thinning treatments in several physical properties depends on the pruning treatment levels [moisture content (F= 12.18, p < 0.0001); tangential shrinkage (F = 15.60, p < 0.0001); T/R ratio (F = 7.17, p < 0.0001); and volumetric shrinkage (F = 10.81, p < 0.0001)]. However, different thinning intensities had no significant impact on wood basic density alteration (F = 0.72, p = 0.486), while pruning intensities affect the differences between radial (F = 3.52, p = 0.030) and volumetric shrinkage (F = 3.13, p = 0.044). In mechanical properties, thinning intensity levels did not promote any significant differences [modulus of elasticity (F = 1.41, p = 0.248); modulus of rupture (F = 0.94, p = 0.392); compressive strength parallel to grain (F = 0.21, p = 0.813); and compressive strength perpendicular to the grain (F = 0.41, p = 0.669)]. Meanwhile, different pruning treatments and combination treatments were not significantly altered all mechanical properties. These results indicated that the thinning and pruning regimes can enhance the mechanical properties without having a serious alteration in the physical properties of clonal teak wood.

• 한국환경생태학회지
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• 제32권3호
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• pp.303-312
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• 2018

본 연구는 숲가꾸기가 시행된 부산대학교 제1학술림을 대상으로 간벌 전 후의 산림생물량 및 온도를 실측하여 천연림에서 간벌에 따른 산림생물량 감소와 산림 내부 온도변화의 관계를 확인하고자 하였다. 산림생물량은 간벌 전 후 동일 조사구에 흉고단면적, 수관단면적, 수관체적을 각각 동일한 도출식을 적용하여 도출하였으며, 산림 온도와의 관계성을 파악하고자 하였다. 온도측정은 간벌 이전인 2016년 04월 20일~28일, 간벌 전후인 2016년 07월 26일~11월 04일, 간벌 이듬해인 2017년 04월 15일~05월 08일에 각각 실시하였으며 온도데이터로거를 방형구 내 중앙에 위치한 수목의 지상 2.0m 높이에 북향으로 설치하여 동일기간동안 각 10분마다 데이터가 기록되도록 설치하였다. 간벌이 산림 전역에 진행되어 산림 내 대조구 설정이 어려워 인근 도시에 위치한 동래구 지역별상세관측자료(AWS)를 대조구로 활용하였다. 산림생물량의 변화와 온도와의 관계성을 분석한 결과, 산림 내부 온도 변화는 한낮 시간대(PM12:00~15:00)에 가장 큰 변화를 보였으며, 산림생물량 중 수관체적과 깊은 관계성을 가지고 있었다. 간벌 직후(평균 $0.74^{\circ}C$)보다 간벌 후 1년이 경과한 시점(평균$1.91^{\circ}C$)에서 훨씬 높은 온도 상승을 보였다. 조사구별 수관체적 감소비율과 온도 상승정도를 비교한 결과, 수관체적 감소량이 15.4%로 가장 높았던 리기다소나무군락에서 간벌 직후와 1년 후 분석에서 각각 $1.06^{\circ}C$, $2.49^{\circ}C$로 가장 높은 온도 상승을 나타냈다. 수관체적 감소비율이 5.0%로 가장 적었던 리기다소나무-소나무군락에서 간벌 직후는 그 차이가 없었으며 1년 후 분석에서는 $0.92^{\circ}C$가 상승하였다. 천연림에서 간벌로 인한 산림생물량 감소는 산림내부 온도를 급격히 상승시키는 것을 확인할 수 있었으며 특히, 간벌 직후보다는 이듬해에 더 극심하게 나타나고 있어 제거된 산림생물량에 의한 미기후 변화는 단기간에 회복될 수 없음을 확인할 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2977-2982
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• 2007

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle - installed downstream of the high pressure turbine extraction steam line - inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical analysis results using the FLUENT code and the down scale experimental data which effect on disclosing of the shell wall thinning of the high pressure feedwater heaters by porous plate.

• Nuclear Medicine and Molecular Imaging
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• 제41권3호
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• pp.260-262
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• 2007

A 68-year-old man with small cell carcinoma of the lung and adenocarcinoma of the prostate underwent Tc-99m MDP bone scintigraphy for the evaluation of skeletal metastases. Bilateral symmetrical photon defects in both parietal bones of the skull were observed. The radiographs of the skull demonstrates biparietal thinning in the same area of the abnormality identified on bone scintigraphy. Although these findings in cancer patients can be mistaken for skeletal metastases, the symmetry and location of the photon defects are generally indicative of biparietal thinning.

• 대한기계학회논문집A
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• 제29권5호
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• pp.734-742
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• 2005

The present study proposes the integrity evaluation model for a straight pipe with local wall thinning defect, which reflects the characteristics of training shape and loading condition in the Piping of nuclear power plant. For this purpose, a series of finite element analyses are performed under various defect geometries and loading conditions, and real pipe experiment data performed previously is employed. The model includes the effect of thinning length as well as thinning depth and width, and also it considers the combined loading effect between internal pressure and bending moment. The proposed model has been validated using the results of finite element analysis and pipe experiment data. The results indicate that the proposed model provides more reliable predictions of pipe failure than the current existing model, in terms of accuracy, consistency, and conservativeness of results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.156-162
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• 2006

Pipe thinning is one of the major issues for the structural fracture of pipes of nuclear power plants. Therefore a method to inspect a large area of piping systems quickly and accurately is needed. In this paper, we proposed the method for monitoring pipe thinning. Our basic idea come from that a group velocity of impact wave is different as wall thickness. If the group velocity is measured, wall thickness can be estimated. To obtain the group velocity, time-frequency analysis is used. This is because an arrival time difference can be measured easily in time-frequency domain rather than time domain. To test the performance of this technique, experiments have been performed for a plate and U type pipe. Results show that the proposed technique is quite powerful in the monitoring pipe thinning.