• Restorative Dentistry and Endodontics
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• 제29권3호
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• pp.267-272
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• 2004

The purpose of this in vitro study was to evaluate the effect of surface defects and cross-sectional configuration of NiTi rotary files on the fatigue life under cyclic loading. Three NiTi rotary files ($K3^{TM},{\;}ProFile^{\circledR},{\;}and{\;}HERO{\;}642^{\circledR}$) with ＃30/.04 taper were evaluated. Each rotary file was divided into 2 subgroups : control (no surface defects) and experimental group (artificial surface defects), A total of six groups of each 10 were tested. The NiTi rotary files were rotated at 300rpm using the apparatus which simulated curved canal (40 degree of curvature) until they fracture. The number of cycles to fracture was calculated and the fractured surfaces were observed with a scanning electron microscope. The data were analyzed statistically. The results showed that experimental groups with surface defects had lower number of cycles to fracture than control group but there was only a statistical significance between control and experimental group in the $K3^{TM}$ (p<0.05), There was no strong correlation between the cross-sectional configuration area and fracture resistance under experimental conditions. Several of fractured files demonstrated characteristic patterns of brittle fracture consistent with the propagation of pre-existing cracks. This data indicate that surface defects of NiTi rotary files may significantly decrease fatigue life and it may be one possible factor for early fracture of NiTi rotary files in clinical practice.

• 생명과학회지
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• 제12권3호
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• pp.325-331
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• 2002

달맞이꽃 추출물로써 항산화활성을 알아보기 위하여 사람 low densty lipoprotein(LDL)에 대하여 실험하였다. 사람 LDL에 CuSO$_4$를 첨가한 후 배양하면서 달맞이꽃 추출을 일정 농도씩 증가시키면서 첨가하여 배양하였다. 달맞이꽃 추출물로서 LDL의 산화에 대한 개시와 연쇄 반응에서 thiobarbituric acid reactivy substances (TBARS)와 전기 영동 및 공액 2중 결합으로 측정하였다. 달맞이꽃 추출물을 LDL에 첨가한 후 macrophage J774로써 배양한 결과 TBARS값은 용량 의존형의 항산화 활성을 나타내었으며 전기 영동 이동상에서도 대조구에 비하여 각 시험구에서 LDL의 산화를 억제하였다. 또 공액 2중 결합에 대한 실험에서 용량 의존형산화 억제 효과를 나타내었다. 달맞이꽃 추출물의 항산화 활성은 40 $\mu\textrm{g}$/ml의 농도에서도 항산화 효과가 있었으나 80$\mu\textrm{g}$/mL의 농도에서는 거의 완전한 억제효과가 있었다. 그리고 비타민 C 및 $\alpha$-dl-tocopherol과 비교한 결과 달맞이들 추출물이 약간 높은 항산화 활성을 나타내었다.

• 원예과학기술지
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• 제33권1호
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• pp.11-17
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• 2015

The study was conducted to investigate the effect of rootstock on growth and early yield of stenting-propagated cut roses (Rosa hybrida Hort.) 'Pink Aurora' and 'Yellow King'. The scions, prepared as single-node cuttings, each with a five-leaflet leaf, were grafted onto cuttings of Rosa indica 'Major', Rosa multiflora 'Chille Wonye No. 1', Rosa multiflora 'K-1', or Rosa multiflora 'Burr' as the rootstock. The rootstock cuttings were removed of all leaves and buds before grafting. The base of scion and the top of rootstock were held together and simultaneously cut at a $45^{\circ}$ angle for ease of grafting. Scion-rootstock unions were stuck in rockwool cubes and placed on a misted glasshouse bench for rooting before being transplanted into a rockwool slabs for cultivation. Rooting was the greatest in the 'Pink Aurora' and 'Yellow King' grafted on the rootstock Rosa indica 'Major'. In 'Pink Aurora', stem length, stem diameter, five-leaflet leaves per stem, and stem fresh weight of the harvested cut flowers were not affected by the rootstock. The greatest total yield of 'Pink Aurora' was obtained in plants grafted onto the Rosa indica 'Major' rootstock. Overall growth of 'Yellow King' was the greatest in plants grafted onto Rosa multiflora 'Burr' rootstock, although total yield was not affected by the rootstock. These results suggest that Rosa indica 'Major' is the most effective rootstock not only for rooting, but also for early yield and growth for stenting propagation of these cut roses.

• 농업생명과학연구
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• 제43권6호
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• pp.29-33
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• 2009

솔나리의 무병균주 획득과 기내 대량증식을 위해 식물생장조절물질이 인편의 재분화에 미치는 영향을 알아보기 위해 본 연구를 수행한 결과 인편은 캘러스가 유기된 2주 후 분화가 관찰되었고, 배양 4주 후에는 잎, 뿌리, 소인편이 생성되었다. TDZ 0.1 mg/L + NAA 0.01 mg/L를 첨가한 처리구에서 잎의 분화율이 87.5%로 가장 높았으며, 뿌리 분화율은 BA 0.2 mg/L 첨가구가 81.8%로 가장 높은 분화율을 보였다. 캘러스 형성률은 TDZ를 포함한 배지에서 형성 되었다. 한 인편당 생성된 잎과 인편의 수는 TDZ 0.1 mg/L가 5.7개로 가장 많은 수가 분화 되었으며 식물체의 전체 길이와 잎 길이 그리고 뿌리 길이는 Zeatin 1.0 mg/L + NAA 0.1 mg/L가 10.5 cm로 가장 길었고, 인편의 길이는 TDZ 0.1 mg/L 처리구에서 1.4 cm로 가장 길었다.

• Plant Resources
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• 제7권1호
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• pp.29-35
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• 2004

Root chicory (Cichorium intybus L. var. sativus) is potential alternative medicinal and sugar crop which accumulates a high amount of linear polyfructan, inulin in its roots. A problem in root production is that over-wintered stock plants often flower. Once the plant becomes reproductive, stem elongation and root growth slows and floral buds arise from every node, rendering the plants useless for propagation. The objectives of this research was to examine the effectiveness of manipulating environmental factors containing photoperiod, temperature and number of leaf states. The experiment was performed in growth chamber to create two photoperiods (8 h, and 16 h) with three temperature regimes (5$^{\circ}C$/3$^{\circ}C$, 1$0^{\circ}C$/8$^{\circ}C$ and 15$^{\circ}C$/13$^{\circ}C$ day/night temperature) for a total of six treatments on three type of true-leaf stage of plant. Data of bolting rate, shoot and root length, shoot and fresh weight was invetigated in each treatments. This is the first report on changes in bolting rate and shoots and roots production during a whole growing season and differences in the effect of cold and photoperiod treatment depending on the true-leaf stage of plant.

• 한국재난정보학회 논문집
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• 제15권2호
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• pp.282-291
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• 2019

연구목적: 최근 모바일 기술은 우리의 일상생활과 경제활동 및 재난안전관리에 이르기까지 4차산업 패러다임의 축으로서 확장되고 있다. 하지만 모바일 기기를 통한 위치정보 서비스 체계가 미흡하여 재난안전 위급상황에서 신속한 대응이 어렵다. 본 연구에서는 사고 및 재난으로 인한 응급상황 발생 시 요구조자의 정확한 위치 파악과 위치체계를 일원화 하여 대국민 재난안전 서비스를 하는데 목적이 있다. 연구방법: 본 연구의 방법은 국가지점번호 NFC 활용 앱 개발을 위하여 기존 문헌 및 안전관련 앱의 조사와 비교 분석을 한다. 또한 요구조자의 필요기능 분석을 통한 시스템 구성과 요소기술을 통한 설계 방법으로 진행하였다. 연구결과: 본 연구의 결과는 모바일에서 긴급상황 시 또는 재난 시 신고를 위하여 위치를 알릴 수 있는 기능과 양방향으로 구현할 수 있도록 설계 및 시스템으로 개발 하였다. 결론: 주소체계를 일원화하고 NFC를 활용한 위치정보전달 통합시스템을 개발하여 위기 시 국민이 쉽게 활용할 수 있는 재난안전 위치서비스를 제공 할 수 있다.

• Journal of Welding and Joining
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• 제26권3호
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• pp.67-73
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• 2008

Fatigue life evaluation of welded structures in a range of high cycles is one of the most difficult problems since extremely small plastic deformation and damage occur during the loading cycles. Moreover, it is very difficult to identify the strong non-linearities of welding, inducing residual stress. In this paper, numerical fatigue test method for welded structures was developed using continuum damage mechanics with inherent strain. Recently, continuum damage mechanics, which can simulate both crack initiation at the micro-scale level and crack propagation at the meso-scale level, has been adopted in the fracture related problem. In order to consider the residual stresses in the welded strictures, damage calculation in conjunction with welding, inducing inherent strain, was proposed. The numerical results obtained from the damage calculation were compared to experimental results.

• Current Research on Agriculture and Life Sciences
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• 제18권
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• pp.1-7
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• 2000

본 실험은 식물조직배양 기법을 통하여 한란과 심비디움의 효율적인 증식을 위한 식물 생장조절물질의 적정 처리방법을 구명하고자 수행하였다. 한란의 rhizome 형성은 무처리 및 10 ppm kinetin + 2 ppm NAA, 심비디움의 protocorm 형성은 무처리 및 10 ppm kinetin + 0.05 ppm NAA에서 아주 양호하였다. Callus 유도의 적정 식물 생장조절물질의 농도는 구명하지 못했다. 한란 rhizome으로부터의 shoot 분화에는 10 ppm BA + 2 ppm NAA, 5 ppm BA + 2ppm NAA, 심비디움 protocorm으로부터의 shoot 분화는 10 ppm Kinetin + 0.05 ppm NAA, 1 ppm Kinetin + 2 ppm NAA에서 비교적 효과적인 것으로 나타났다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.95-98
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• 1996

Universal Learning Network(U.L.N.), which can model and control the large scale complicated systems naturally, consists of nonlinearly operated nodes and multi-branches that may have arbitrary time delays including zero or minus ones. Therefore, U.L.N. can be applied to many kinds of systems which are difficult to be expressed by ordinary first order difference equations with one sampling time delay. It has been already reported that learning algorithm of parameter variables in U.L.N. by forward and backward propagation is useful for modeling, managing and controlling of the large scale complicated systems such as industrial plants, economic, social and life phenomena. But, in the previous learning algorithm of U.L.N., time delays between the nodes were fixed, in other words, criterion function of U.L.N. was improved by adjusting only parameter variables. In this paper, a new learning algorithm is proposed, where not only parameter variables but also time delays between the nodes can be adjusted. Because time delays are integral numbers, adjustment of time delays can be carried out by a kind of random search procedure which executes intensified and diversified search in a single framework.

• Structural Engineering and Mechanics
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• 제63권6호
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• pp.703-712
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• 2017

The composite blades of offshore wind turbines accumulate structural damage such as fatigue cracking due to harsh operation environments during their service time, leading to premature structural failures. This paper investigates various fatigue crack models for reproducing crack development in composite blades and proposes a stochastic approach to predict fatigue crack evolution and to analyse failure probability for the composite blades. Three typical fatigue models for the propagation of fatigue cracks, i.e., Miner model, Paris model and Reifsnider model, are discussed to reproduce the fatigue crack evolution in composite blades subjected to cyclical loadings. The lifetime probability of fatigue failure of the composite blades is estimated by stochastic deterioration modelling such as gamma process. Based on time-dependent reliability analysis and lifecycle cost analysis, an optimised maintenance policy is determined to make the optimal decision for the composite blades during the service time. A numerical example is employed to investigate the effectiveness of predicting fatigue crack growth, estimating the probability of fatigue failure and evaluating an optimal maintenance policy. The results from the numerical study show that the stochastic gamma process together with the proper fatigue models can provide a useful tool for remaining useful life predictions and optimum maintenance strategies of the composite blades of offshore wind turbines.