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        검색결과 212

        61.
        2018.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 생물다양성이 매우 중요하게 여겨지고 있는 백두대간 일대인 단목령-구룡령 구간의 산림식생을 보다 더 생태적이고 체계적인 보전 및 관리 계획 수립을 위한 기초자료를 제공하고자 수행하였다. 총 조사구 142개소에 대해 Z.-M. 학파의 식물사회학적인 방법을 사용하였고 식생조사 및 입지 환경 특성을 조사하였다. 산림식생의 유형은 1개 군락군, 2개 군락, 4개 군, 4개 소군의 단위체계를 가진 것으로 분석되었는데 상재도급 Ⅴ형에 해당하는 신갈나무와 당단풍나무는 대체적으로 향존중으로 나타났으며, 조사 지역의 산림생태계 관리 계획에 있어 중점관리대상종이 될 것으로 판단되었다. 그리고 종다양성에 대한 결과를 살펴보면 VT3형에서 우점종들이 균일하게 분포되어 있었고 VT4 형의 종들은 다양하게 분포하고 있었을 뿐만 아니라 종들이 제일 풍부하게 나타났다. 또한, 단목령-구룡령 구간에서는 희귀식물이 다소 분포하였는데 멸종위기종인 벌깨풀과 위기종인 구실바위취, 취약종인 백작약, 두메대극, 금강초롱꽃, 어리병풍, 약관심종인 등칡, 도깨비부채, 참배암차즈기, 미치광이풀, 병풍쌈 등 총 24종의 희귀식물이 나타났다.
        4,000원
        62.
        2018.04 구독 인증기관·개인회원 무료
        Panax quinquefolius (PQ)은 미국 지역에서 주로 재배하는 삼이며, 피로 회복과 면역 증진, 혈압 및 콜레스테롤 조절에 효능이 있는 것으로 알려져 있다. 이러한 효과들을 나타내는 것은 인삼의 특유한 사포닌(saponin) 성분인 진세노사이드(ginsenoside)에 기인하는 것으로 알려져 있다. 식품의 가공방법 중의 하나인 팽화는 압력과 온도를 가하여 식품 중에 존재하는 녹말의 호화, 단백질의 변성 및 조직화, 저장 중 지질의 산화에 의한 변패 등을 유발시키는 효소의 불활성화, 수분이 제거 및 다공성 구조를 야기한다. 따라서 본 실험의 목적은 팽화 압력에 따른 PQ의 추출수율, 조사포닌 함량 및 항산화능의 변화를 분석하여 한국인삼(Panax ginseng, PG)과의 차이점을 구명하는 것이다. 시료는 건조된 미국산과 캐나다산 PQ를 쌀과 배합하여 사용하였다. PQ를 686, 784, 882, 980kPa로 팽화한 후 70% 발효 주정으로 추출하였다. 추출액을 농축하여 증류수에 녹인 후, 이들의 추출수율, 조사포닌 함량 및 항산화능의 변화를 분석하였다. 팽화압력과 상관없이 팽화 캐나다삼이 팽화 미국삼보다 부피와 크기가 컸다. 두 인삼 모두 압력 조건이 높아질수록 갈변화가 더 진행되었으며, 784kPa부터 표면이 바스러지고 882kPa부터 내부와 분리되는 현상이 발생하였다. 팽화 전 캐나다삼의 추출수율과 조사포닌, DPPH 라디칼 소거능 모두 미국삼보다 높은 값을 나타내었다. 팽화 후 두 인삼 모두 control에 비하여 추출수율, 조사포닌, DPPH 라디칼 소거능이 증가하였다. 추출수율과 조사포닌의 함량의 경우, 캐나다삼은 압력에 따라 증가하였고, 미국삼은 감소하다 증가하는 경향을 나타내었다. 추출수율은 팽화 전후 압력에 상관없이 미국삼보다 캐나다삼이 높았으며, 조사포닌 및 DPPH 라디칼 소거능의 경우 특정한 경향을 나타내지 않았다. 본 실험에 사용한 팽화 미국삼 및 캐나다삼은 팽화 한국삼보다 추출수율과 항산화능은 낮지만, 조사포닌의 함량이 높았다. 따라서 팽화로 인한 미국삼 및 캐나다삼 조사포닌 함량 증가가 팽화 한국삼보다 더 크게 유의적으로 증가하여 이들을 활용한 다양한 제품들의 개발이 가능하고 국제시장에서 이들이 중요한 역할을 할 것으로 기대된다.
        63.
        2018.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this paper, the performance of the Refrigerator is improved by controlling the fan speed on the condenser side or subcooling/superheating degree by superimposing the refrigerant on the inlet side of the compressor to the outlet side pipe. However, these methods may have the effect of lowering the performance due to operation of the severe condition of the main parts and may not achieve the intended performance. The Peltier Module was used to improve the performance of the refrigerator and increase the durability of the main parts through an artificial subcooling device.
        4,000원
        64.
        2018.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Since the encoder and resolver are expensive, it is difficult to apply it as a position sensor of a motor in a real industrial field. Optical position sensors, such as encoders and resolvers, are also difficult to mount because of their size and durability. Therefore, in order to solve these problems, we propose a system that uses a linear motor as a stator and a magnet plate as a mover, and a system that excludes a separate linear scale and uses two linear Hall sensors and permanent magnets to generate a conventional sine wave, A linear motor capable of detecting an absolute position and a movement position of a magnet, a control method thereof, and a technology development that can reduce a production cost by developing a position control system using a magnet mover that can improve stability and reliability.
        4,000원
        67.
        2017.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, we analyzed the radiant heat performance of ballast fin when the aspect ratio of the fin of ballast was changed. The minimum size of the mesh was 0.02 mm, and the grid number was about more than 11 thousand. In order to analyze the radiant heat performance of ballast fin, the aspect ratio of fin was 1.00(2 mm:2 mm), 1.80(1.5 mm:2.7 mm), and 0.56(2.7 mm:1.5 mm) respectively; that the heat transfer area was constantly 0.4 mm 2 . The numerical condition was that heat flux was constantly 1×10 5 W/m 2 , and measuring times were 0.1 second, 0.2 second, 0.5 second, 2 seconds, 5 seconds and 10 seconds respectively. The temperature values of fin at the 1.00 and 1.80 of aspect ratios were extremely large when heat flux time was 10 seconds. As a result, the maximum value of radiant heat performance of ballast fin appeared to the aspect ratio of 1.80.
        4,000원
        68.
        2017.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        To increase the productivity of in vitro development, the antioxidants have been used for culture system of bovine oocytes and embryos. However, comparative studies on these molecules are rare and direct beneficial effects on blastocyst production cannot be discriminated for best results. The study was conducted to determine the influence of N-acetyl-L-cysteine (NAC), N-acetyl-L-cysteine amide (NACA), glutathione (GSH) and cysteamime (CYS) on maturation competence of COCs from GV to MII stage and productivity of blastocyst formation during in vitro fertilization and culture. There was no difference among maturation rates of oocytes to metaphase II with polar body with antioxidants for any of the treatment groups (p>0.05). However, the significant improvement on the rate of blastocysts (32.3±5.0%) was found in 0.1 mM CYS treatment than 0.3 mM NAC, 0.2 mM NACA or 0.5mM GSH (p<0.05). The addition of NAC (18.8±3.7%) or NACA (21.2±3.9%) did not improve development competence to morula and blastocysts than control (24.4±4.1%) and GSH (26.5±5.0%) (p>0.05). Our study showed that medium supplementation with CYS during IVM and IVC improved the rate of bovine embryo development but not with NAC, NACA and GSH addition.
        4,000원
        69.
        2017.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The elevated temperature and high humidity has been known as main reason for heat stress on animals and cause detrimental effects on productivity of organisms and physiological conditions of normal bioactivities. The aims of this study were to evaluate the relationship between time of heat shock simulation during in vitro maturation and developmental competence of subsequent embryo after in vitro fertilization. Heat shocked cumulus-oocyte complexes (COCs) of Korean native cattle were subjected to normal conditions for 22, 21, 18 and 12 h respectively and transferred to heat stress inducing condition at 40.5 °C in other incubator for 0 (control), 1 and 4 h. After maturation for 22 h, the oocytes were fertilized and cultured in mSOF media for 8 d and examined the developmental capacity of embryos. There were no differences in maturation and cleavage rates between 0, 1 and 4 h heat socked oocytes, but blastocysts formation were lower in the 4 h heat stressed oocytes. The apoptotic cells of developed blastocysts were also increased in at day 8 with 4 h heat shocked oocytes. These results indicate that heat shock on oocytes during maturation could cause negative effects on the developmental competence of embryos.
        4,000원
        70.
        2017.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This paper presents a vibration mitigation method for a railroad station using dual layer TMD (Tuned Mass Damper) technology. The proposed technology can be applied to a platform by installing a spring-damper system between the platform and the railroad station structure. Especially, considering passenger comfort, the technology is developed for not just reducing the vibration of the railroad station structure but minimizing the vibration of the platform. The technology consists of two serially connected masses, and the vibration of the top mass is designed to be minimized, while the bottom mass serves as the platform TMD. The design parameters such as the spring constant and damping coefficient of the dual layer TMD system are optimized using the acceleration response of the structure, at which the platform is installed. The feasibility and performance of the vibration mitigation method is verified via a numerical example of a simple beam structure subjected to a moving load, which can be analogized as a railroad station with a moving train on top. The result of the numerical study shows that the proposed method can effectively reduces the vibration of the top mass as well as the beam structure at the design speed of the moving load.
        4,000원
        71.
        2017.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Recently, measures for reducing noise and vibration of a railroad station are actively being developed to enhance its property value and comfort level of passengers. In this paper, the applicability of the recently developed vibration mitigation method utilizing a platform TMD (Tuned Mass Damper) by installing a spring-damper system beneath the platform is experimentally verified using a bench scale structure. The two-story bench scale structure is built to simulate a real railroad station, and vibration reduction effect is verified by comparing acceleration before and after applying the platform TMD at the 2nd floor of the structure. The design parameters of the platform TMD system is determined based on vibration analysis result and the MTMD (Multiple TMD) theory recently developed to enhance the effectiveness of the platform TMD method. The vibration is excited to the bench-scale structure using a vibrator. The performance test result for a spring-damper system is also presented. The result of the experiment reveals that the platform TMD method can reduce the vibration of the bench-scale structure by greater than 5dB(V).
        4,000원
        72.
        2017.04 구독 인증기관 무료, 개인회원 유료
        최근 도심지에서 지중매설관의 구조적 결함에 의한 토사 유실로 인해 지하 공동이 빈번하게 발생하고 있다. 본 연구에서는 이러한 지하 공동을 파악하는데 있어 현장 실험 수행 결과 전기비저항 탐사와 공압콘관입시험이 지반 조건의 이상 징후를 탐지하는데 효율적임을 확인하였다. 또한, 이미지 분석을 통한 전기비저항 실험 측정값을 정량화 하여 평균 비저항 값을 산정하는 방법을 제안하였다. 실대형 실험 결과, 평균 비저항 값이 감소할수록 위험도가 증가하였고, 공압콘관입시험 결과, N치가 작을수록 위험도가 높다는 것을 확인하였으며, 제한적인 측정 데이터 수를 토대로 평균 비저항 값과 공압콘관입시험의 결과를 토대로 상관관계를 나타내었을 때, 지반의 지하공동 발생과 관련된 위험 수준을 제한적으로 평가할 수 있을 것으로 판단된다.
        3,000원
        73.
        2017.04 구독 인증기관·개인회원 무료
        The study presents technology which can decrease the vibration of railroad station via adopting a friction bearing system beneath a platform. The platform itself then constitutes a tuned mass damper system (TMD) as the bearing provides stiffness and damping of the TMD system. To increase the robustness of the TMD system, the bearing system with adjustable stiffness is utilized. The vibration reduction performance of the TMD system is verified via numerical analysis on an elevated railroad station known as having a structural type with highest noise and vibration level. The numerical analysis is performed using a commercial program, ABAQUS. The vibration analysis is performed considering vehicle-track-structure interaction. The result of the numerical analysis shows that the TMD technology can reduce significant amount of vibration of a railroad station.
        75.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this paper, a study on noise reduction characteristics of the precast floating track system, being developed as measures to mitigate noise and vibration of existing as well as constructing elevated railroad stations, is presented using numerical analysis. One of the most prominent sound analysis program, Virtual Lab., is utilized in investigating noise reduction performance of the precast floating track system, and structural velocity data, obtained from vibration analysis on a model-updated elevated railroad station considering vehicle-track-structure interaction, are used for the input of the sound analysis. The sound analysis is performed using the finite element method, and noise reduction performance before and after installing the precast floating track system is compared at three enclosed areas in the Daecheon Station, selected as a representative of elevated railroad stations in this nation. From the comparison result, it is seen that the precast floating track system can decrease noise by average of 5dB∼8dB when the Saemaeul train passing through the station and 10dB∼15dB when the KTX train passing through. Also, the noise reduction characteristics is different depending on the type of train and the distance from the track.
        4,000원
        76.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Cryopreservation of germ cells from genetically proven animals could be a source of restoration tools from the risk of extinction or disappearance of wanted characteristics. Using frozen semen, the genetic gains of Korean native cattle have been increased greatly for 70 years. The preservation of genetic resources as a form of frozen semen straw has limited availability due to the numbers. To circumvent this weakness of frozen semen, we tested two re-freezing methods with different initial thawing temperatures using frozen Korean proven semen and rare breed semen from albino, black and chikso breeders. It has been known that human sperm could resist to cryo-damages by repeated freeze-thaw cycles, but not for Korean proven bulls number (KPN) or for rare breeds. Total 7 frozen semem from brindled(2), black(1), Korean Albino(2) and KPN(1) bulls were used for our research. After thawing straws under 5°C/2min or 37°C/40sec with low temperature water bath and thermo jug, spermatozoa were re-diluted with triladyl diluents after first thawing and re-frozen. Sperm motilities were compared between animals and treated groups after re-thawing. Mean values of motility and viability of refrozen/thawed sperm for expansion of the number of straws were significantly higher in 5°C than in 37°C (P< < 0.05). However, the activity of viable sperm thawed at 5°C was significantly decreased after first and second thawing. It is estimated that re-freezing of frozen semen from rare Korean native cattle is possible with resistant properties of survived spermatozoa.
        4,000원
        77.
        2017.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was to develop the products that the Lamp and Ballast are combined for the purpose of easy installation to complement the difficulty of the installation process due to the structure of existing product which the lamp and the Ballast are separated, and that have 8-wavelengths dual-lamp structure such as solar, an advantage of more than 3 times longer life than fluorescent lamp and immediately lighting. This study developed the commercialized products that can prevent the environmental pollution caused by low efficiency and short life time of existing Lamps, and can replace the LED Lighting products which has high Glare index with high price, has also developed the variety of application for industrial, commercial, indoor and military. The applied product are Street lights, Security lights, Flood lights, Indoor lights and lights for fishing. This study solved the optimum distribution and placement of components considering the lightest weight first and thermal interference caused by combination of lamp and ballast by thermal release through applying the double bulkhead design of ballast box, and implemented the high efficiency Eco-friendly products with excellent visibility which can be applied and used for indoor and outdoor both place through high temperature and high humidity test, which has an advantage of 8-wavelengths of same spectrum of solar through the initial trial production.
        4,000원
        78.
        2017.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study describes the effects of polyurethane/loess powder (PU/LP) nanofiber thin films composite produced from electrospun for absorption volatile organic compounds (VOCs) from air. Environmental issue has become a focus with improving people's living quality. The VOCs are one of the factors that affect the environmental safety. So, in order to improve the environment and safety for people, many air cleaning techniques have been investigated. One of the methods is nanofiber filtration technology. In this study, the PU nanofiber thin film has been studied that it has the adsorption of VOCs capacity, and LP nanoparticles (NPs) can be used as an additive to load into PU nanofiber thin film by electrospinning. For studying PU/LP nanofiber thin films's absorption of VOCs capacity, 4 samples (0, 10, 30, and 50 wt% LP with respect to PU) were manufactured, respectively. The results show that PU composite mats containing 30 wt% LP NPs has the highest VOCs absorption capacity, and the adsorption capacity for toluene was the highest compared to benzene and chloroform.
        4,000원
        79.
        2016.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, we designed the 3-dimensional tire mold according to the A automobile company’s tire model, and analysed the distribution of temperature of mold using the numerical method when the heat flux and heat transfer time at the surface of tire mold were changed. A analysis region of mold was the 1/16 of entire mold, and the grid number was about more than 880 thousand. In order to analyze the temperature change of mold, the thinnest part of the mold was chosen as the research object, and then the temperature of 6 points on the vertical downward direction of the thinnest part was analyzed with the time change. While the numerical condition was that heat flux was 321,200 W/m2, 440,000 W/m2 and 880,000 W/m2, and measuring time was 0.1 second, 0.2 second, 0.5 second and 1 second, respectively. As a result, the temperature difference between the surface temperature and the lowest temperature of mold was 7.3℃ when the heat transfer time was 0.1 second. Also, the minimum temperature difference was almost 0.11℃ when the heat transfer increased to 1 second. It can be explained that the main material of tire mold was aluminum and its thermal conductivity was high (k=140 W/m·K). In addition, when the heat transfer time was more than 1 second, the heat flux of mold surface will be transmitted at the inside of the thinnest part, and the heat transfer will be a marked difference according to the shape of the thinnest part.
        4,000원
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