• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.197-202
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• 2008

In this paper, a hybrid vibration-impedance approaches is newly proposed to detect the occurrence of damage, the location of damage, and extent of damage in steel plate-girder bridges. The hybrid scheme mainly consists of three sequential phases: 1) to alarm the occurrence of damage, 2) to classify the alarmed damage, and 3) to estimate the classified damage in detail. Damage types of interest include flexural stiffness-loss in girder and bolts-loose in supports. In the first phase, the global occurrence of damage is alarmed by monitoring changes in acceleration features. In the second phase, the alarmed damage is classified into subsystems by recognizing patterns of impedance features. In the final phase, the location and the extent of damage are estimated by using modal strain energy-based damage index method and root mean square deviation method. The feasibility of the proposed system is evaluated on a laboratory-scaled steel plate-girder bridge model for which hybrid vibration-impedance signatures were measured for several damage scenarios.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 추계 학술논문 발표대회
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• pp.141-148
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• 2009

The purpose of this paper is to propose a standard test methods of resistance to root penetration for waterproofing and rootproofing membrane using green roof system. Green roof system is considered to be an important subject in construction industry for green growth project. At the same time, we have to consider the counterplan for protection the damage of waterproofing layer and concrete substrate from the penetration of plant root. But many kinds of materials for protection from root penetration are using in construction field. But the performance of those materials is not clear, and there is not test methods for the evaluation of performance. So in this paper, based on the research results of 4 institutes during four years and foreign cases, we made a standard test methods of resistance to root penetration for waterproofing and rootproofing membrane using green roof system. This test method deals with about environmental condition of laboratory, experimental facilities, kinds of plant, specimen of test, management methods, evaluation duration and documents, etc.

• 대한안전경영과학회지
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• 제12권2호
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• pp.75-82
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• 2010

Gas turbines for power generating operate in a very high temperature condition and use natural gas for fuel. For this reason, many cases of damage happen at hot gas parts which are severely affected by high temperature gas and many cases of explosion occur by fuel gas. So a lot of efforts should be made to prevent hot gas parts damage and gas explosion accidents. Though there are many damage cases and explosion accidents, it is very difficult to find out the root causes of hot gas parts damage caused by gas explosion due to gas leakage in the heat exchanger for air cooling and gas heating. To prevent gas turbine from damage caused by gas explosion, removal of leakage gas from gas turbine is inevitably required before firing the gas turbine and installing alarm systems is also required for detecting gas leakage at stop valve to turbine while shut down.

• 한국작물학회지
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• 제66권3호
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• pp.183-189
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• 2021

볍씨 종자의 최아정도 및 최아 손상정도에 따른 출현율 및 초기생육변화를 분석한 결과는 다음과 같다. 1. 볍씨 최아 길이가 길수록 출현율은 다소 감소하였으며 생육온도가 18℃ 이상으로 높을수록 차이가 큰 것으로 나타났다. 2. 최아 길이가 길수록 초장신장 속도가 감소하였으며 생육온도가 21℃ 이상으로 높을 시 최아길이 3 mm에서 초장이 크게 감소하였다. 3. 최아길이에 따른 엽수변화는 없었으나 줄기 두께 및 줄기 건물중, 뿌리 건물중은 최아길이가 길수록 유의하게 감소하였다. 4. 최아 손상정도가 증가할수록 출현율은 유의하게 감소하였으며 생육온도가 높을수록 감소폭은 증가하으며 엽수변화는 없었으나 줄기 두께 및 줄기 건물중, 뿌리 건물중은 최아 손상도가 길수록 유의하게 감소하였다. 최아 길이 및 종자 손상정도별 뿌리 건물중과 줄기 건물 중 변화는 유의한 정의 상관관계를 보였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.240-247
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• 2006

Piezoelectric sensor-based health monitoring technique using a two-step support vector machine (SYM) classifier is discussed for damage identification of a railroad track. An active sensing system composed of two PZT patches was investigated in conjunction with both impedance and guided wave propagation methods to detect two kinds of damage of the railroad track (one is a hole damage of 0.5cm in diameter at web section and the other is a transverse cut damage of 7.5cm in length and 0.5cm in depth at head section). Two damage-sensitive features were extracted one by one from each method; a) feature I: root mean square deviations (RMSD) of impedance signatures and b) feature II: wavelet coefficients for $A_0$ mode of guided waves. By defining damage indices from those damage-sensitive features, a two-dimensional damage feature (2-D DF) space was made. In order to minimize a false-positive indication of the current active sensing system, a two-step SYM classifier was applied to the 2-D DF space. As a result, optimal separable hyper-planes were successfully established by the two-step SYM classifier: Damage detection was accomplished by the first step-SYM, and damage classification was also carried out by the second step-SYM. Finally, the applicability of the proposed two-step SYM classifier has been verified by thirty test patterns.

• Wind and Structures
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• 제16권3호
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• pp.263-278
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• 2013

The fatigue load of a turbine blade has become more important because the size of commercial wind turbines has increased dramatically in the past 30 years. The reduction of the fatigue load can result in an increase in operational efficiency. This paper numerically investigates the load reduction of large wind turbine blades using active aerodynamic load control devices, namely trailing edge flaps. The PD and LQG controllers are used to determine the trailing edge flap angle; the difference between the root bending moment and its mean value during turbulent wind conditions is used as the error signal of the controllers. By numerically analyzing the effect of the trailing edge flaps on the wind turbines, a reduction of 30-50% in the standard deviation of the root bending moment was achieved. This result implies a reduction in the fatigue damage on the wind turbines, which allows the turbine blade lengths to be increased without exceeding the designed fatigue damage limit.

• 한국환경농학회지
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• 제1권2호
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• pp.99-104
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• 1982

Hop근부(根腐)로 인(因)한 폐원(廢園)의 원인(原因)이 heptachlor잔류독성(殘留毒性)에 의한 피해(被害)인가를 구명(究明)하기 위하여 1980년(年)부터 1981년(年)까지 3개지역(個地域) 9개(個) 농가(農家) 피해포장(被害圃場)의 현장조사(現場調査)와 heptachlor약해(藥害) 시험(試驗)을 실시(實施)하였던바 그 결과(結果)를 요약(要約)하면 다음과 같다. 1) 농가포장(農家圃場)에서 발생(發生)된 hop근부(根腐) 양상(樣相)과 heptachlor 약해(藥害) 시험(試驗)에서 나타난 근부(根腐) 양상(樣相)이 일치(一致)되어 hop근부(根腐)에 의한 폐원(廢園)의 원인(原因)은 heptacholor 잔류독성(殘留毒性)의 피해(被害)임이 입증(立證)되었다. 2) 근부(根腐) 양상(樣相)은 heptachlor의 토양잔류량(土壤殘留量)이 적은 곳에서는 갈색반점(褐色斑點)으로 시작(始作)되어 부패(腐敗)되고, 잔류량(殘留量)이 많은 곳에서는 근수(根數)가 적고 비대(肥大)가 되지 않으며 갈변(褐變)하면서 고사(枯死)되었다. 3) 피해(被害) 만(蔓)의 생육(生育) 상태(狀態)는 만장(蔓長)이 짧아지고 측지수(側枝數)가 감소(減少)되며 만(蔓)의 유연성(柔軟性)이 없어 쉽게 절단(切斷)되었다. 4) Hop근부(根腐) 피해(被害)의 주물질(主物質)은 heptacholor epoxide로 추정(推定)되었으며, 토양중(土壤中) 잔류농도(殘留濃度)가 0.009 ppm에서도 피해(被害)가 심(甚)하였다. 5) heptacholor피해(被害)는 시용후(施用後) 10년(年)이 경과(經過)되어도 나타났다.

• Restorative Dentistry and Endodontics
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• 제37권4호
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• pp.228-231
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• 2012

Invasive cervical resorption is a relatively uncommon form of external root resorption. It is characterized by invasion of cervical region of the root by fibrovascular tissue derived from the periodontal ligament. This case presents an invasive cervical resorption occurring in maxillary lateral incisor, following damage in cervical cementum from avulsion and intracoronal bleaching procedure. Flap reflection, debridement and restoration with glass ionomer cement were performed in an attempt to repair the defect. But after 2 mon, more resorption extended apically. Considering root stability and recurrence potential, we decided to extract the tooth. Invasive cervical resorption in advanced stages may present great challenges for clinicians. Therefore, prevention and early detection must be stressed when dealing with patients presenting history of potential predisposing factors.

• 대한소아치과학회지
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• 제23권4호
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• pp.968-974
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• 1996

Intra-alveolar transverse crown & root fx. provokes many problems in treatment. Conventionally, extraction of the injured tooth and its prosthodontic restoration has been the treatment of choice. Though orthodontic extrusion could be an alternative treatment, there would be a situation it's inadequate to apply. Loss of natural tooth would be a psychological damage to the patient, of course. This report describes a replantation method of tooth in case of intra-alveolar transverse crown & root fracture. The fractured tooth was extracted, rotated, then replanted. Fixation and esthetic restoration was done. And then endodontic treatment was followed. Continuing follow-up of its function and endodontic status is required.

• 대한치과의사협회지
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• 제52권2호
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• pp.85-95
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• 2014

Completely avulsed tooth caused by a traumatic injury needs replantation for treatment choice. But, replantated tooth usually comes with inflammatory root resorption, replacement resorption and ankylosis, moreover ankylosis cause severe functional and esthetic problems. The outcome of replantated tooth depends on the following factors; minimal damage to pulp and periodontal tissue, the length of extraoral time, the medium of the tooth stored, the level of root formation and so on. The purpose of this case report is to describe the variable resorption pattern and to discuss types that influence the occurrence of resorption.