• 조명전기설비학회논문지
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• 제30권1호
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• pp.72-78
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• 2016

In terms of power components which use environmentally-friendly dry air that can substitute SF6, there have been studies on the electrical properties of the solid insulation "spacer" for the purpose of securing dielectric strength as they become smaller. This study laminated solid insulation to keep the creeping distance the same in the dry air and investigated vertical surface discharge characteristics by shape. The three sheets of disk-type solid insulation(Bakelite) were laminated in a manner to keep the creeping distance the same. The lamination was categorized as follows: "Type A" in which the insulations with the same disk diameter were laminated; "Type B" in which the insulations whose middle disk diameter was large were laminated; and "Type C" in which the ones whose middle disk diameter was small were laminated. For a vertical surface discharge experiment, dry air was injected into the test chamber depending on the shape of the laminated solid insulation, and chamber pressure was adjusted in a range of 0.1-0.6MPa. As volume decreased, surface discharging voltage by unit volume increased. This was because of dielectric polarization according to the structural characteristics of the shape of lamination. The highest surface discharging voltage was found in "Type C."

• 한국산학기술학회논문지
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• 제19권11호
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• pp.481-487
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• 2018

땅밀림 피해지에서 피해지점 및 균열 탐지, 피해규모를 효율적으로 분석하기 위해서 무인기를 활용한 피해지 탐지 및 모니터링 방안에 대해 본 연구에서 제시하였다. 땅밀림 피해지에서 무인기를 촬영하고 분석한 결과, 정사영상을 구축하면 피해지의 균열 탐지 및 규모를 파악할 수 있기 때문에 현장조사 전에 조사자 안전을 확보하고, 조사계획 수립에 효율적 활용이 가능하였다. 또한, 정사영상에서 지형정보를 추출하면 땅밀림 피해지 균열에 대한 정량적 분석이 가능하였다. 본 연구에서 시범적으로 적용한 대상지에서는 전체 균열 면적 1.01ha, 길이 1.07km, 평균 폭 10m, 단차범위 1~10m로 땅밀림 피해가 발생한 것으로 나타났다. 땅밀림 피해지에서는 정기적인 무인기 촬영을 통하여 지형변위를 탐지하고 피해 확산 방향, 규모 등에 대한 모니터링이 가능하기 때문에 복구계획 수립에 효율적으로 활용할 수 있다. 무인기를 이용하여 땅밀림 피해지에 시험 적용한 결과, 지형이 험준하고 위험한 산지에서 빠르고 쉽게 정성적 정량적 결과를 획득할 수 있는 장점이 있었다. 산사태, 토석류, 땅밀림과 같은 산지토사재해 현장에서 무인기 활용가치가 높기 때문에 관련 산업분야 발전에 기여할 수 있을 것으로 기대된다.

• Journal of Welding and Joining
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• 제18권1호
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• pp.46-51
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• 2000

Ultrasonic nondestructive evaluation (UNDE) technique is commonly used for detecting inner defects in the materials. Recently, new methods are trying to apply for detecting surface and subsurface flaws using Rayleigh wave or creeping wave. These techniques, however, have following problems. Echo amplitude is remarkably affected by the surface conditions and discrimination of echo pattern is usually difficult because shear wave propagate in the material at the same time. We can apply surface SH-wave(which is horizontally polarized shear wave traveling along near surface layer) technique to detect surface flaws. In this paper, directivity, distance amplitude characteristics and detectability of surface flaws at fillet weld hills of the 5 MHz and 2 MHz surface flaws at fillet weld hills of the 5 MHz and 2 MHz surface Sh-wave are experimentally investigated. As a result of the study, it was found out that these techniques are valuable for the detection of fatigue cracks at fillet weld heels which can not be detected by other ultrasonic techniques such as angle beam technique and which are inaccessible for non-destructive testings e.g. MT(magnetic particle testing) or PT(liquid penetrant testing).

• 대한심미치과학회지
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• 제10권1호
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• pp.30-45
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• 2001

In recent years, clinicians' and dentists' esthetic demands in dentistry have increased rapidly. The ultimate goal in modern restorative dentistry is to achieve "white" and "pink" esthetics in the esthetically important zones. Therefore, modern esthetic dentistry involves not only the restoration of lost teeth and their associated hard tissues, but increasingly the management and reconstruction of the encasing gingiva with adequate surgical techniques. Interdental space are filled by interdental papilla in the healthy gingiva, preventing plaque deposition and protecting periodontal tissue from infection. This also inhibits impaction of food remnants and whistling through the teeth during speech. These functional aspects are obviously important, but esthetic aspects are important as well. Complete and predictable restoration of lost interdental papillae remains one of the biggest challenges in periodontal reconstructive surgery. One of the most challenging and least predictable problems is the reconstruction of the lost interdental papilla. The interdental papilla, as a structure with minor blood supply, was left more or less untouched by clinicians. Most of the reconstructive techniques to rebuild lost interdental papillae focus on the maxillary anterior region, where esthetic defects appear interproximally as "black triangle". Causes for interdental tissue loss are, for example, commom periodontal diseases, tooth extraction, excessive surgical periodontal treatment, and localized progressive gingiva and periodontal diseases. If an interdental papilla is absent because of a diastema, orthodontic closure is the treatment of choice. "Creeping" papilla formation has been described by closing the interdental space and creating a contact area. In certain cases this formation can also be achieved with appropriate restorative techniques and alteration of the mesial contours of the adjacent teeth. The presence of an interdental papilla depends on the distance between the crest of bone and the interproximal contact point, allowing it to fill interdental spaces with soft tissue by altering the mesial contours of the adjacent teeth and positioning the contact point more apically. The interdental tissue can also be conditioned with the use of provisional crowns prior to the definitive restoration. If all other procedures are contraindicated or fail, prosthetic solutions have to be considered as the last possibility to rebuild lost interdental papillae. Interdental spaces can be filled using pink-colored resin or porcelain, and the use of a removable gingival mask might be the last opportunity to hide severe tissue defects.

• Geomechanics and Engineering
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• 제4권1호
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• pp.67-78
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• 2012

Soil foundations exhibit significant creeping deformation, which may result in excessive settlement and failure of superstructures. Based on the theory of viscoelasticity and fractional calculus, a fractional Kelvin-Voigt model is proposed to account for the time-dependent behavior of soil foundation under vertical line load. Analytical solution of settlements in the foundation was derived using Laplace transforms. The influence of the model parameters on the time-dependent settlement is studied through a parametric study. Results indicate that the settlement-time relationship can be accurately captured by varying values of the fractional order of differential operator and the coefficient of viscosity. In comparison with the classical Kelvin-Voigt model, the fractional model can provide a more accurate prediction of long-term settlements of soil foundation. The determination of influential distance also affects the calculation of settlements.

• Geomechanics and Engineering
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• 제18권2호
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• pp.215-224
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• 2019

Excavation of long tunnels by shielded TBMs is a safe, fast, and efficient method of tunneling that mitigates many risks related to ground conditions. However, long-distance tunneling in great depth through adverse geological conditions brings about limitations in the application of TBMs. Among various harsh geological conditions, squeezing ground as a consequence of tunnel wall and face convergence could lead to cluttered blocking, shield jamming and in some cases failure in the support system. These issues or a combination of them could seriously hinder the performance of TBMs. The technique of excavation has a strong influence on the tunnel response when it is excavated under squeezing conditions. The Golab water conveyance tunnel was excavated by a double-shield TBM. This tunnel passes mainly through metamorphic weak rocks with up to 650 m overburden. These metamorphic rocks (Shales, Slates, Phyllites and Schists) together with some fault zones are incapable of sustaining high tangential stresses. Prediction of the convergence, estimation of the creeping effects and presenting strategies to overcome the squeezing ground are regarded as challenging tasks for the tunneling engineer. In this paper, the squeezing potential of the rock mass is investigated in specific regions by dint of numerical and analytical methods. Subsequently, several operational solutions which were conducted to counteract the challenges are explained in detail.

• 아시안잔디학회지
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• 제20권1호
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• pp.11-23
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• 2006

본 연구는 골프 코스 관리자가 관리 방법에 따른 그린 스피드를 쉽게 예측할 수 있는 정보를 제공하기 위해 롤링, 이슬제거, 그리고 롤링+이슬 제거를 각각 1회 작업 후 깎기 높이의 변화($4.0{\sim}2.5mm$)와 시간 경과($0{\sim}8hr$)에 따른 4가지 유형의 그린스피드 예측 모형을 통한 빠른 그린 관리 방법을 제시하고자 수행하였다. 공 구름 거리 측정 값은 레이크사이드 컨트리 클럽 동코스 연습용 퍼팅 그린[(Creeping bentgrass (Agrosis palustris Huds. 'Penncross')]에서 2001년 10월 18일과 2002년 5월 25일에 하였다. 자료는 SPSS for window Rel. 10.0(SPSS Inc, 2000) 통계 패키지를 이용하여 다중 회귀 분석하였다. 4가지 유형의 그린스피드 예측 모형중, 빠른 그린 관리 방법의 기준을 설명해 줄 수 있는 회귀식은 식4[($Y_4=4.171-0.225{\cdot}X_1-0.038{\cdot}X_2$(여기서 $Y_4$ : 1회 이슬 제거+1회 롤링시 그린 스피드(m), $X_1$ : 깎기 높이($4.0{\sim}2.5mm,\;X_2$) : 시간 경과($0{\sim}8hr$)]이었다. 이 식은 1회 이슬 제거(스펀지 롤러) $\rightarrow$ 3.0mm 이하의 깎기 높이(21인치 11날 보행식 그린모아, 토너먼트 밑날 장착) $\rightarrow$ 1회 롤링(경량 롤러)의 관리 작업을 할 경우 라운드 종료까지도 3.2m이상의 빠른 그린을 얻을 수 있는 것을 예측하였다. 따라서 이런 관리 시스템은 공식 골프 대회를 위한 빠른 그린의 관리의 기준이 될 것으로 기대되어 진다.

• Journal of Plant Biotechnology
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• 제49권3호
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• pp.163-170
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• 2022

전 세계적으로 LMO (Living Modified Organisms)의 이용과 상업화는 지속적으로 증가하는 추세이다. 국내에서 LM 식물의 상업적 재배는 아직 이뤄지고 있지 않으나 연구개발 및 수입, 연구시설의 신고 등은 활발히 진행되고 있는 실정이다. LM 식물은 개발 및 환경위해성 평가 단계에서 온실과 야외 포장에서의 실험이 요구되나 개발 중인 단계에서는 아직 환경에 대한 안전성이 입증되지 않아 환경방출에 대한 안전관리가 요구된다. LM 식물의 개발 연구는 일반적으로 실험실, 격리온실, 격리포장에서 수행되며 각 연구 구역마다 LMO법 통합고시 등에서 안전관리 규정이 마련되어 있다. LM 식물 연구 사고사례 중 일본의 LM 페튜니아 유출 사고는 LM 식물 연구 도중 교잡 가능 거리에 있는 일반 식물은 LM 식물로 간주하여 취급되어야 함을 시사하고 있으며, 미국의 LM creeping bentgrass 유출 사례는 바람 등에 의해 종자의 산포가 용이한 LM 식물의 경우 종자 비산에 대한 강력한 방지 대책 수립의 필요성을 시사한다. 또한 국내 LM 들잔디 유출과 LM 면화 유출 사례는 빗물 등에 의한 식물 영양번식체 유출 및 LM 종자 혼입에 대한 안전 대책 수립의 필요성을 제시한다. 미승인된 LM 식물의 환경방출에 따른 확산은 제거와 복구에 많은 시간과 비용, 노력이 요구된다. 따라서 최근 생명공학기술을 적용하는 LM 식물들이 다양화됨에 따라 개발자 및 연구자는 환경생태계에 미치는 영향을 사전에 파악하고 환경방출 방지 등 철저한 안전관리가 요구되는 바이다.

• 한국조경학회지
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• 제31권1호
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• pp.66-77
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• 2003

The purpose of this study is to propose a standard putting green management program to prepare fast green suitable for international golf tournaments, and to conform whether the reported green speed model can be applied to the real field situations. The west course of Lakeside Country Club was selected for the case study. This study was initiated on August 1st, 2001 and continued through October 4th, 2001. The results are summarized as follows: 1. Following the long-term schedule, 'penncross' creeping bentgrass turf was mowed at 5.0mm(37days), 4.5mm(8days), 4.0mm(4days), 3.5mm(2days), 3.2mm(2days), 3.0mm(2days), 2.8mm(2days) and the mowing direction was changed daily. Variation of mowing height was reduced to a minimum range. Core aerification with deep tines was applied 19 days prior to the first practice round. Dry sand maintenance was top-dressed 2 times at 1.5mm/$m^2$ on the 17th day and 1.0mm/$m^2$ on the 10th day. Minimum irrigation was applied to keep the turf alive. During the tournament preparation week, dew on the putting greens was removed by using a sponge roller. Following the dew removal, the greens were cut once each morning at a height of 2.8mm. The mower used was the 21 inch working behind mower equipped with a tournament bedknife and 11 reel blades. Following the mowing, the peens were rolled with a light-weight roller in one direction in the morning. Rolling was used as a finishing technique to ensure that the surface was as smooth as possible, and to provide true ball roll and maximum green speed. In conclusion these management practices satisfied the daily green stimpmeter readings required for USGA championship play. 2. During the period of tournament preparation, no damage was observed on the green, but scalping in green edge appeared in about 0.39% of the total area of 18 greens in the west course.

• The Korean Journal of Ecology
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• 제27권5호
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• pp.257-261
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• 2004

눈향나무(Juniperus chinensis var. sargentii Henry)는 사할린, 일본 등의 동북아시아와 한반도에서는 전국의 고산지대에서 자라는 상록성 소관목으로서 희귀 및 멸종 위기 식물(산림청)로 지정되어 있다. 본 연구에서는 한라산에 서식하는 눈향나무 집단의 분포형태 및 특성, 유전적 다양성과 공간적 유전구조를 파악하였다. 조사구(40m × 60m)에는 총 131개의 눈향나무 clump가 자생하고 있었으며 이들 전체 본수를 대상으로 군집지수를 계산한 바, 임의분포하고 있음을 확인하였다 모든 개체들에 대하여 ISSR 유전자형을 비교한 결과, 15개체는 클론으로, 나머지는 각기 서로 다른 genet으로 구성 되 어 있었다. 21개 의 ISSR 표지자를 바탕으로 계산한 Shannon의 다양성지수(I=0.463)는 적은 개체수와 제한적 분포에도 불구하고 유전적 다양성이 다른 수종에 비해 비교적 높은 편으로 나타났다. 공간적 자기상관 분석방법을 이용하여 공간적 유전구조를 파악한 결과, 조사지역내의 눈향나무 집단은 8m 이내에서 유전적으로 유사한 군락구조를 갖고 있는 것으로 나타났으며, 클론 번식이 공간적 유전 구조에 미치는 영향은 거의 없는 것으로 판단되었다.