• 제목/요약/키워드: 복합다양체

검색결과 360건 처리시간 0.023초

Characterization of Transgenic Tall Fescue Plants Expressing Two Antioxidant Genes in Response to Environmental Stresses (두 가지 항산화유전자를 동시에 발현시킨 형질전환 톨 페스큐 식물체의 환경스트레스에 대한 내성 특성 해명)

  • Lee, Sang-Hoon;Lee, Ki-Won;Kim, Ki-Yong;Choi, Gi-Jun;Seo, Sung;Kwak, Sang-Soo;Kwon, Suk-Yoon;Yun, Dae-Jin;Lee, Byung-Hyun
    • Journal of The Korean Society of Grassland and Forage Science
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    • 제27권2호
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    • pp.109-116
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    • 2007
  • Environmental stress is the major limiting factor in plant productivity. As an effort to solve the global food and environmental problems using the plant biotechnology, we have developed transgenic tall fescue (Festuca arundinacea Schreb.) plants via Agrobacterium-mediated gene transfer method. To develop transgenic tall fescue plants with enhanced tolerance to the environmental stresses, both CuZn superoxide dismutase (CuZnSOD) and ascorbate peroxidase (APX) genes were incorporated in a pIG121 binary vector and the both of the genes were controlled separately by an oxidative stress-inducible sweet potato peroxidase 2 (SWPA2) premoter expressed in chloroplasts. Leaf discs of transgenic plants showed 10-30% less damage compared to the wild-type when they exposed to a wide range of environmental stresses including methyl viologen (MV), $H_2O_2$ and heavy metals. In addition, when $200{\mu}M$ MV was sprayed onto the whole plants, transgenic plants showed a significant reduction of visible damage compared to wild-type plants that were almost damaged. These results suggest that over expression of CuZnSOD and APX genes in transgenic plants might be a useful strategy to protect the crops against a wide range of environmental stresses.

Improvement of Indoor Positioning Accuracy using Smart LED System Implementation (스마트 LED 시스템을 이용한 실내위치인식 정밀도 개선)

  • Lee, Dong Su;Huh, Hyeong Seok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • 제22권1호
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    • pp.786-791
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    • 2021
  • In this paper, in order to minimize limitations such as signal interference and positioning errors in existing indoor positioning systems, a smart LED-based positioning system for excellent line-of-sight radio environments and precise location tracking is proposed to improve accuracy. An IEEE 802.4 Zigbee module is mounted on the SMPS board of a smart LED; RSSI and LQI signals are received from a moving tag, and the system is configured to transmit the measured data to the positioning server through a gateway. For the experiment, the necessary hardware, such as the gateway and the smart LED module, were separately designed, and the experiment was conducted after configuring the system in an external field office. The positioning error was within 70cm as a result of performing complex calculations in the positioning server after transmitting a vector value of the moving object obtained from the direction sensor, together with a signal from the moving object received by the smart LED. The result is a significantly improved positioning error, compared to an existing short-range wireless communications-based system, and shows the level at which commercial products can be implemented.

Dispersion Characteristics of Magnetic Particle/Graphene Hybrid Based on Dispersant and Electromagnetic Interference Shielding Characteristics of Composites (분산제에 따른 자성금속 무전해도금 기반 그래핀 분산 특성 및 복합재의 전자파 차폐 특성 연구)

  • Lee, Kyunbae;Lee, Junsik;Jung, Byung Mun;Lee, Sang Bok;Kim, Taehoon
    • Composites Research
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    • 제31권3호
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    • pp.111-116
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    • 2018
  • In this paper, magnetic FeCoNi particles have been grown through electroless plating on the surface of graphene, and then this hybrid material has been dispersed by various surfactants to prepare films. The pyridine surfactant shows the highest dispersability and low surface resistance value (351 Ohm/sq) and the electromagnetic shielding ability at the frequency of 10 GHz. Specially, the evaporation of the pyridine during the drying process could be able to form the internal conductive network and high dispersion of FeCoNi on the surface of graphene.

Reliability and Sensitivity Analysis for Laminated Composite Plate Using Response Surface Method (반응면 기법을 이용한 복합재 평판의 신뢰도 및 민감도해석)

  • Lee, Seokje;Jang, Moon-Ho;Kim, Jae-Ki;Moon, Jung-Won;Kim, In-Gul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • 제37권4호
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    • pp.461-466
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    • 2013
  • Advanced fiber-reinforced laminated composites are widely used in various fields of engineering to reduce weight. The material property of each ply is well known; specifically, it is known that ply is less reliable than metallic materials and very sensitive to the loading direction. Therefore, it is important to consider this uncertainty in the design of laminated composites. In this study, reliability analysis is conducted using COMSOL and MATLAB interactions for a laminated composite plate for the case in which the tip deflection is the design requirement and the material property is a random variable. Furthermore, the efficiency and accuracy of the approximation method is identified, and a probabilistic sensitivity analysis is conducted. As a result, we can prove the applicability of the advanced design method for the stabilizer of an underwater vehicle.

Technique Status of Carbon Fibers-reinforced Composites for Aircrafts (항공기용 탄소섬유강화 복합재료의 기술동향)

  • Kim, Ki-Seok;Park, Soo-Jin
    • Elastomers and Composites
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    • 제46권2호
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    • pp.118-124
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    • 2011
  • Recently, the need of new materials which have excellent physical properties and functional characteristics has been increased in all industries. In particular, body weight reduction via new materials in aerospace industry was significantly emphasized by the requirement of environmental protection through the fuel savings and reduction of greenhouse gas, i.e., carbon dioxide($CO_2$). Also, for various applications, the development of high performance custom materials with excellent physical properties was the current primary goal of materials science and technology. In this respect, carbon fiber-reinforced composites were the most candidates among the various materials. Indeed, carbon fiber-reinforced composites have been lately used as essential materials for the weight reduction of aircraft and the demand has increased remarkably. Therefore, in this paper, we focused on the need of carbon fiber composites in the fields of aircraft and technique status.

Preparation of poly(vinyl alcohol)-coated Composite Nanofiltration Membranes on Various Support Membranes (다양한 지지체 분리막 위에 poly(vinyl alcohol)이 코팅된 나노복합막의 제조)

  • Lee Kew-Ho;Kim In-Chul
    • Membrane Journal
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    • 제15권1호
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    • pp.34-43
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    • 2005
  • The poly(vinyl alcohol) (PVA)-based thin film composite nanofiltration (NF) membranes were prepared by coating polysulfone ultrafiltration membranes, sulfonated polyethersulfone and polyamide NF membranes with aqueous PVA solution by a pressurizing method. The PVA was cross-linked with aqueous glutaraldehyde solution. The NF membranes coated with a very low concentration of PVA on all the support membranes was successfully prepared. With increasing the hydrophilicity of the support membranes, the water flux increased. Especially, ζ-potential of negatively charged polyamide NF membrane was reduced by coating the membrane with PVA. A fouling experiment was carried out with positively charged surfactant, humic acid, complex of humic acid and calcium ion and bovine serum albumin. A non-coated polyamide NF membrane was significantly fouled by various foulants. The fouling process when using humic acid and protein occurred at the isoelectric point. There was severe fouling when using humic acid and adding bivalent cations. By coating the polyamide NF membrane with aqueous PVA solution, fouling was reduced. The polyamide NF membrane coated with PVA was resistant to the acidic and basic solution.

Evaluation of Composite Laminates for Aircraft Primary-Structure Applications Using Non-Linear Parameter of Ultrasonic Guided Wave (유도초음파의 비선형 파라미터를 이용한 항공기 구조체의 복합재료 적층판 열화 평가)

  • Cho, Youn-Ho;Kim, Do-Youn;Choi, Heung-Soap;Lee, Joon-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • 제30권2호
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    • pp.126-131
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    • 2010
  • The purpose of this study is to assess the condition of composites used in aircraft under varying temperature environment with ultrasound guided wave technique. Investigation of crucial influential factor on the composite health monitoring related to aircraft operational environments such as the number of thermal cycles and temperature deviation between ground level and flight altitude has been of a great concern for aircraft safety issue. In this study, ultrasonic guided wave health monitoring scheme is proposed to evaluate composite specimens damaged with the thermal fatigue simulating aircraft operational condition. Guided wave dispersion curves are used to select right modes which show a promising sensitivity to each different thermal fatigue damage level. The present approach can be also implemented as one of on-lines health monitoring tools for aircraft.

Characteristics and Development Trends of Heat-Resistant Composites for Flight Propulsion System (비행체 추진기관용 내열 복합재의 특성 및 개발 동향)

  • Hwang, Ki-Young;Park, Jong Kyoo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • 제47권9호
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    • pp.629-641
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    • 2019
  • In order to limit the temperature rise of the structure to a certain level or less while maintaining the aerodynamic shape of solid rocket nozzle by effectively blocking a large amount of heat introduced by the combustion gas of high temperature and high pressure, the heat-resistant materials such as C/C composite having excellent ablation resistance are applied to a position in contact with the combustion gas, and the heat-insulating materials having a low thermal diffusivity are applied to the backside thereof. SiC/SiC composite, which has excellent oxidation resistance, is applied to gas turbine engines and contributes to increase engine performance due to light weight and heat-resistant improvement. Scramjet, flying at hypersonic speed, has been studying the development of C/SiC structures using the endothermic fuel as a coolant because the intake air temperature is very high. In this paper, characteristics, application examples, and development trends of various heat-resistant composites used in solid rocket nozzles, gas turbine engines, and ramjet/scramjet propulsions were discussed.

Development of Al-SiC Metal Matrix Composites by using Hot Press Forming Technologies (열간가압성형기술을 이용한 Ai-SiC 금속기 복합재료 개발)

  • Jeon, Ho-Jin;Kim, Tae-Won
    • Composites Research
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    • 제20권4호
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    • pp.9-17
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    • 2007
  • Powder metallurgy has been employed for the development of SiC particle reinforced aluminum metal matrix composites by means of hot isotropic pressing and vacuum hot pressing. A material model based on micro-mechanical approach then has been presented for the processes. Densification occurs by the inelastic flow of matrix materials during the consolidation, and consequently it depends on many process conditions such as applied pressure, temperature and volume fraction of reinforcement. The model is implemented into finite element software so that the process simulation can be performed enabling the predicted relative density to be compared with experimental data. In order to determine the performance of finished products, further tensile test has been conducted using the developed specimens. The effect of internal void of the materials on mechanical properties therefore can be investigated.

Effect of Nitrogen Compounds and Organic Carbon Concentrations on $N_2O$ Emission during Denitrification (탈질에서 질소성분 및 유기탄소 농도가 $N_2O$ 배출에 미치는 영향)

  • Kim, Dong-Jin;Kim, Heon-Ki;Kim, Yu-Ri
    • Clean Technology
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    • 제17권2호
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    • pp.134-141
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    • 2011
  • The effects of the compounds and concentrations of nitrogenous electron acceptor, the ratio of electron donor/electron acceptor (C/N), and the complexity of electron donor on the emission of $N_2O$ during wastewater denitrification were quantitatively investigated in this study. The higher ${NO_3}^-$ and ${NO_2}^-$ concentrations, the more $N_2O$ emission was observed. ${NO_2}^-$ has strong effect on $N_2O$ emission as it emitted morc $N_2O$ than ${NO_3}^-$, 50 mg/L of ${NO_2}^-$-N gave the highest conversion (9.3%) and yield (9.8%) of $N_2O$ while ${NO_3}^-$-N (50 mg/L) gave 5.6% conversion and 11.0% yield. Lower C/N ratio decreases nitrogen removal efficiency, but it increases the conversion of $N_2O$ because of the incomplete denitrification by the limited organic carbon. When real domestic wastewater is used as the electron donor of the denitrification, $N_2O$ emission is reduced to 1/10 of the emission when single carbon (acetate) is used. It is thought that multiple carbon source utilizes many denitrification pathways and it seems to be helpful for the reduction of $N_2O$ emission.