• The Korean Journal of Pesticide Science
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• v.17 no.2
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• pp.126-132
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• 2013

The objectives of this study were to provide the basic data of the residue of deltamethrin in the stream water. Deltamethrin was treated on side of Ban-Suk stream and Juk-Dong ditch for hygienic purpose by air spray. The drift concentration of deltamethrin was investigated with different wind speed condition on Ban-Suk stream (A), and the change of residue with time course on Juck-dong ford (B). Also we found the residual change of deltamethrin until 48 hour in Yu-Seong stream confluence (C) where two streams join. Maximum residues of A were $0.17{\mu}g/L$ (5 min, 200 m) at strong wind speed and $4.42{\mu}g/L$ (0 min, 25 m) at moderate wind speed according to different wind velocity. Residues of B were $0.15{\sim}0.26{\mu}g/L$ (0~480 min) after spraying, and decreased to a non-detected level after 720 min. Residues of C were $0.15{\mu}g/L$ (0 min), $0.11{\mu}g/L$ (1 min) and $0.10{\mu}g/L$ (12 hr) after spraying, and no residues were detected in any other samples. From these results, it is concluded that deltamethrin residues in water should be rapidly diluted into stream water and affected negligible toxic effect to stream ecosystem.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.436-447
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• 2004

Wetland plants have evolved specialized adaptations to survive in the low-oxygen conditions associated with prolonged flooding. The development of internal gas space by means of aerenchyma is crucial for wetland plants to transport $O_2$ from the atmosphere into the roots and rhizome. The formation of tissue with high porosity depends on the species and environmental condition, which can control the depth of root penetration and the duration of root tolerance in the flooded sediments. The oxygen in the internal gas space of plants can be delivered from the atmosphere to the root and rhizome by both passive molecular diffusion and convective throughflow. The release of $O_2$ from the roots supplies oxygen demand for root respiration, microbial respiration, and chemical oxidation processes and stimulates aerobic decomposition of organic matter. Another essential mechanism of wetland plants is downward water movement across the root zone induced by water uptake. Natural and constructed wetlands sediments have low hydraulic conductivity due to the relatively fine particle sizes in the litter layer and, therefore, negligible water movement. Under such condition, the water uptake by wetland plants creates a water potential difference in the rhizosphere which acts as a driving force to draw water and dissolved solutes into the sediments. A large number of anatomical, morphological and physiological studies have been conducted to investigate the specialized adaptations of wetland plants that enable them to tolerate water saturated environment and to support their biochemical activities. Despite this, there is little knowledge regarding how the combined effects of wetland plants influence the biogeochemistry of wetland sediments. A further investigation of how the Presence of plants and their growth cycle affects the biogeochemistry of sediments will be of particular importance to understand the role of wetland in the ecological environment.

• Journal of the Korean Electrochemical Society
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• v.18 no.3
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• pp.121-129
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• 2015

The platinum anode for the electrolytic reduction process is generally surrounded by a nonporous ceramic shroud with an open bottom to offer a path for $O_2$ gas produced on the anode surface and prevent the corrosion of the electrolytic reducer. However, the $O^{2-}$ ions generated from the cathode are transported only in a limited fashion through the open bottom of the anode shroud because the nonporous shroud hinders the transport of the $O^{2-}$ ions to the anode surface, which leads to a decrease in the current density and an increase in the operation time of the process. In the present study, we demonstrate the electrolytic reduction of 1 kg-uranium oxide ($UO_2$) using the porous shroud to investigate its long-term stability. The $UO_2$ with the size of 1~4mm and the density of $10.30{\sim}10.41g/cm^3$ was used for the cathode. The platinum and 5-layer STS mesh were used for the anode and its shroud, respectively. After the termination of the electrolytic reduction run in 1.5 wt.% $Li_2O-LiCl$ molten salt, it was revealed that the U metal was successfully converted from the $UO_2$ and the anode and its shroud were used without any significant damage.

• Journal of Radiation Protection and Research
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• v.40 no.4
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• pp.194-201
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• 2015

We have investigated the EPR signal properties in 12 components of two mobile phones (LCD, OLED) using electron paramagnetic resonance (EPR) spectrometer in this study.EPR measurements were performed at normal atmospheric conditions using Bruker EXEXSYS-II E500 spectrometer with X-band bridge, and samples were irradiated by $^{137}Cs$ gamma-ray source. To identify the presence of radiation-induced signal (RIS), the EPR spectra of each sample were measured unirradiated and irradiated at 50 Gy. Then, dose-response curve and signal intensity variating by time after irradiation were measured. As a result, the signal intensity increased after irradiation in all samples except the USIM plastic and IC chip. Among the samples, cover glass(CG), lens, light guide plate(LGP) and diffusion sheet have shown fine linearity ($R^2$ > 0.99). Especially, the LGP had ideal characteristics for dosimetry because there were no signal in 0 Gy and high rate of increase in RIS. However, this sample showed weakness in fading. Signal intensity of LGP and Diffusion Sheet decreased by 50% within 72 hours after irradiation, while signals of Cover Glass and Lens were stably preserved during the short period of time. In order to apply rapidly EPR dosimetry using mobile phone components in large-scale radiation accidents, further studies on signal differences for same components of the different mobile phone, fading, pretreatment of samples and processing of background signal are needed. However, it will be possible to do dosimetry by dose-additive method or comparative method using unirradiated same product in small-scale accident.

• Journal of Bio-Environment Control
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• v.24 no.2
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• pp.51-56
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• 2015

The objective of this study was to evaluate the effect of silicate fertilizer on growth, physiology and abiotic stress tolerance of Chinese cabbage seedlings. Five silicate concentrations (8, 16, 32, 64, and 128mM) and control (non-treatment) were applied to Chinese cabbage seedlings twice a week. Three weeks after application of silicate treatment, seedlings were used for treating abiotic stresses and were assessed for growth and physiological characteristics. Growth parameters significantly increased in 8, 16, and 32mM treatments except 64 and 128mM. Total root surface area, total root length, and number of root tips increased in 8, 16 and 32mM treatments, but they decreased in treated seedlings with 64 and 128mM of silicate. The highest growth parameters and root morphology were observed in 8mM treatment. As for the effect on the seedling physiology, transpiration rates decreased while stomatal diffusive resistance increased to increasing silicate concentration. The application of silicate reduced the electrical conductivity, heating and chilling injury index at high and low temperatures. Silicate enhanced drought tolerance of Chinese seedlings by delaying the starting time of wilting point. The starting time of wilting point in the control was 3 days after discontinuation of irrigation, while in the 8, 64 and 128mM of silicate treatments were 4 days, and the 16 and 32mM treatments were 5 days. All plants were wilted after 5 days in control without irrigation whereas it showed in 8mM treatment after 6 days, in 16, 32, 64, 128mM treatments after 7 days.

• Communications of Mathematical Education
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• v.16
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• pp.217-218
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• 2003

제7차 교육과정의 기본방향인 '21세기의 세계화 정보화 시대를 주도할 자율적이고 창의적인 한국인 육성'에서 볼 수 있듯이, 새로운 교육과정에서는 학생들의 창의력을 신장시키기 위한 방안으로 교과별 교육과정이나 재량활동 운영 등을 제시한 바 있다. 수학교육에서도 이러한 시대적 흐름에 발맞추어 수학적 창의력의 신장이 강조되고 있는 상황이다. 그동안 이론적인 측면과 실제적인 측면에서 수학적 창의성에 대한 성과가 축적되었다. 이론적인 측면에서 볼 때, Haylock(1987)등에 의해 창의력과 수학적 창의력의 구분되었으며, 특히 '수학적' 창의력에 대한 다양한 정의가 제안되었다. 실제적인 측면에서도 수학적 창의력을 측정하려는 평가 도구들이 그 동안 여러 가지로 개발하였다. 그러나, 이러한 수학적 창의력에 관한 전반적인 연구는 종국적으로 교실 수학수업에 반영되어야 함에도 불구하고, 그리 만족스럽지 못한 상황이다. 특히, 교실에서 수학수업을 실제로 담당하는 교사들이 수학적 창의력을 위한 수업을 하고자 하더라도 당장 가까이에서 구할 수 있는 교수 학습 자료가 여전히 부족한 상황이다. 물론 그 동안 교실 수학수업에서 사용할 수 있는 창의력 개발 프로그램이 전무한 것은 아니다. 그런데 그들 대부분은 게임이나 퍼즐을 이용한 것으로 그 수준이 단순 흥미유발에 그치고 있거나 소수의 영재아를 위한 소재를 중심으로, 특히 수학적 사고 과정을 따르기보다는, 시행착오를 거쳐 원하는 결과를 얻을 가능성이 많으며, 수학과의 연계성이 불분명한 채로 단순놀이에 그치는 경우가 적지 않아, 수업과 연관되어 창의력의 신장이라는 측면에서 볼 때, 적용하기 어려운 사례가 많다. 이러한 상황을 개선하는 데 기여하고자, 현재 교과교육공동연구 지원사업의 하나로 한국 학술 진흥재단의 지원을 받아, '개방형 문제(open-ended problems)'를 중심 소재로 한 '수학적 창의성'을 신장하기 위한 교수학습 프로그램을 개발하여, 중학교 1학년을 대상으로 연구를 진행하고 있다. 개방형 문제라 함은 명백한 정의가 어렵지만 Pehkeon(1995)는 개방형문제의 정의를 명백히 하기위한 시도로서 그 반대로 닫힌 문제에 대한 정의로부터 시작하여, 어떤 문제가 닫혀있다고 하는 것은 그 문제의 출발 상황과 목표 상황이 닫혀 있는 것, 즉 명백히 설명되어있을 때라면 개방형 문제는 이와 반대의 개념임을 시사하였다. Silver(1995)는 개방형 문제를 문제 자체가 다른 해석이 가능하거나 서로 다를 인정할만한 답을 가질 수 있는 문제 또는 풀이과정이 다양한 문제, 자연스럽게 다른 문제들을 제안하거나 일반화를 제시할 수 있는 문제라고 정의하였다. 따라서 개방형 문제란 출발상황이나 목표 상황의 일부가 닫혀있지 않을 때를 말하고 문제의 조건을 만족하는 해답이 여러 가지로 존재하는 문제를 뜻한다. 수학적 창의력을 개발하는 데, 다른 문제 유형보다도, 개방형 문제가 유리하다는 점은 이미 여러 학자들에 의해 주장되어왔다. 미국 국립영재교육센터(NRCG/T)는 기존의 사지선다형이나 단답형 문제와 질문들은 학생들의 사고 능력에 관한 정보를 거의 알려주지 못하기 때문에 한 가지 이상의 답을 요구하는 ‘open-ended' 또는 ’open-response' 문제와 질문을 가지고 수학 분야에서의 창의적 사고 능력과 표현능력을 측정해야 한다고 하였고, 개방형 문제가 일반적으로 정답이 하나인 문제보다 고차원적인 사고를 요구하게 하는 문제 형태라고 하였다. 본 연구에서는 이러한 근거를 바탕으로 개방형 문제의 유형을 다양한 답이 존재하는 문제, 다양한 해결 전략이 가능한 문제, 답이 없는 문제, 문제 만들기, 일반화가 가능한 문제 등으로 보고, 수학적 창의성 중 특히 확산적 사고에 초점을 맞추어 개방형 문제가 확산적 사고의 요소인 유창성, 독창성, 유연성 등에 각각 어떤 영향을 미치는지 20주의 프로그램을 개발, 진행하여 그 효과를 검증하고자 한다. 개방형 문제를 활용한 수학적 창의력 신장 프로그램을 개발하고 현장 학교에 실험 적용하여 그 효과를 분석하고자 하는 본 연구는 창의력 신장에 비중을 두는 수학과 교수-학습 과정에 실제적인 교수 학습 자료를 제공하는 것뿐만 아니라 교사들에게는 수학교실에서 사용 가능한 실제적인 활용방안을, 학생들에게는 주어진 문제를 여러 가지 각도에서 생각하면서 다양한 사고를 경험하는 기회를 가질 수 있어, 수학을 보는 학생들의 태도에도 긍정적인 변화를 가져올 수 있을 것이라 기대한다.

• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.369-376
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• 2008

The aim of this study was to compare the compositions and cytotoxicity of white ProRoot MTA (white mineral trioxide aggregate) and 3 kinds of Portland cements. The elements, simple oxides and phase compositions of white MTA (WMTA), gray Portland cement (GPC), white Portland cement (WPC) and fast setting cement (FSC) were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray fluorescence spectrometry (XRF) and X-ray diffractometry (XRD). Agar diffusion test was carried out to evaluate the cytotoxicity of WMTA and 3 kinds of Portland cements. The results showed that WMTA and WPC contained far less magnesium (Mg), iron (Fe), manganese (Mn), and zinc (Zn) than GPC and FSC. FSC contained far more aluminum oxide ($Al_2O_3$) than WMTA, GPC, and WPC. WMTA, GPC, WPC and FSC were composed of main phases. such as tricalcicium silicate ($3CaO{\cdot}SiO_2$), dicalcium silicate ($2CaO{\cdot}SiO_2$), tricalcium aluminate ($3CaO{\cdot}Al_2O_3$), and tetracalcium aluminoferrite ($4CaO{\cdot}Al_2O_3{\cdot}Fe_2O_3$). The significance of the differences in cellular response between WMTA, GPC, WPC and FSC was statistically analyzed by Kruskal-Wallis Exact test with Bonferroni' s correction. The result showed no statistically significant difference (p > 0.05). WMTA, GPC, WPC and FSC showed similar compositions. However there were notable differences in the content of minor elements. such as aluminum (Al), magnesium, iron, manganese, and zinc. These differences might influence the physical properties of cements.

• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.405-412
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• 2008

This study was aimed to investigate whether an oxygen inhibition layer (OIL) is essential for the interfacial bonding between resin composite layers or not. A composite (Z-250, 3M ESPE) was filled in two layers using two aluminum plate molds with a hole of 3.7 mm diameter. The surface of first layer of cured composite was prepared by one of five methods as followings, thereafter second layer of composite was filled and cured: Group 1 - OIL is allowed to remain on the surface of cured composite; Group 2 - OIL was removed by rubbing with acetone-soaked cotton; Group 3 - formation of the OIL was inhibited using a Mylar strip; Group 4 - OIL was covered with glycerin and light-cured; Group 5 (control) - composite was bulk-filled in a layer. The interfacial shear bond strength between two layers was tested and the fracture modes were observed. To investigate the propagation of polymerization reaction from active area having a photo-initiator to inactive area without the initiator, a flowable composite (Aelite Flow) or an adhesive resin (Adhesive of ScotchBond Multipurpose) was placed over an experimental composite (Exp_Com) which does not include a photoinitiator and light-cured. After sectioning the specimen, the cured thickness of the Exp_Com was measured. The bond strength of group 2, 3 and 4 did not show statistically significant difference with group 1. Groups 3 and 4 were not statistically significant different with control group 5. The cured thicknesses of Exp_Com under the flowable resin and adhesive resin were 20.95 (0.90) urn and 42.13 (2.09), respectively.

• Fire Science and Engineering
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• v.31 no.5
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• pp.53-62
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• 2017

Electric power which is the energy source of economy and industries requires long distance transportation due to regional difference between its production and consumption, and it is supplied through the multi-loop transmission and distribution system. Prior to its actual use, electric power flows through several transformations by voltage transformers in substations depending on the characteristics of each usage, and a transformer has the structure consisting of the main body, winding wire, insulating oil and bushings. A transformer fire that breaks out in substations entails the primary damage that interrupts the power supply to houses and commercial facilities and causes various safety accidents as well as the secondary economic losses. It is considered that causes of such fire include the leak of insulating oil resulting from the destruction of bottom part of bushings, and the chain reaction of fire due to insulating oil that reaches its ignition point within 1 second. The smoke detector and automatic fire extinguishing system are established in order to minimize fire damage, but a difficulty in securing golden time for extinguishing fire due to delay in the operation of detector and release of gas from the extinguishing system has become a problem. Accordingly, this study was carried out according to needs of active mechanism to prevent the spread of fire and block the leak of insulating oil, in accordance with the importance of securing golden time in extinguishing a fire in its early stage. A bushings fireproof structure was developed by applying the high temperature shape retention materials, which are expanded by flame, and mechanical flame cutoff devices. The bushings fireproof structure was installed on the transformer model produced by applying the actual standards of bushings and flange, and the full scale fire test was carried out. It was confirmed that the bushings fireproof structure operated at accurate position and height within 3 seconds from the flame initiation. It is considered that it could block the spread of flame effectively in the event of actual transformer fire.

• Journal of Korea Water Resources Association
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• v.50 no.7
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• pp.455-465
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• 2017

Understanding of the two-dimensional velocity field is crucial in terms of analyzing various hydrodynamic and fluvial processes in the riverine environments. Until recently, many numerical models have played major roles of providing such velocity field instead of in-situ flow measurements, because there were limitations in instruments and methodologies suitable for efficiently measuring in the broad range of river reaches. In the last decades, however, the advent of modernized instrumentations started to revolutionize the flow measurements. Among others, acoustic Doppler current profilers (ADCPs) became very promising especially for accurately assessing streamflow discharge, and they are also able to provide the detailed velocity field very efficiently. Thus it became possible to capture the velocity field only with field observations. Since most of ADCPs measurements have been mostly conducted in the cross-sectional lines despite their capabilities, it is still required to apply appropriate interpolation methods to obtain dense velocity field as likely as results from numerical simulations. However, anisotropic nature of the meandering river channel could have brought in the difficulties for applying simple spatial interpolation methods for handling dynamic flow velocity vector, since the flow direction continuously changes over the curvature of the channel shape. Without considering anisotropic characteristics in terms of the meandering, therefore, conventional interpolation methods such as IDW and Kriging possibly lead to erroneous results, when they dealt with velocity vectors in the meandering channel. Based on the consecutive ADCP cross-sectional measurements in the meandering river channel. For this purpose, the geographic coordinate with the measured ADCP velocity was converted from the conventional Cartesian coordinate (x, y) to a curvilinear coordinate (s, n). The results from application of A-VIM showed significant improvement in accuracy as much as 41.5% in RMSE.