• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.11
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• pp.1265-1270
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• 2015

For the sensor node or collection node operating with a battery in a wireless sensor network, MAC protocols with improved energy efficiency are important performance factors. In this paper, in order to improve the restrictive capability in accordance with the fixed activity period of the duty cycle technology in the MAC protocol for wireless sensor networks, we propose a periodic adaptive wakeup technique based on receive prediction. The proposed technique is through a performance evaluation using the CC2500 RF transceiver and C8051F330 microcontroller based wireless node, to analyze the minimum active period. As a result, it was confirmed that it is possible to improve energy efficiency by adaptively changing the sleep period in accordance with the change of period.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.728-731
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• 2008

Recently demands in construction of the stand-alone networks and interconnection between convergence devices have led an increase in research on IETF MANET working group, Bluetooth, and HomeRF working group and much attention has been paid to the application of MANET as a Ubiquitous network which is growing fast. With performance both as hosts and routers, easy network configuration, and fast response, mobile nodes participating in MANET are suitable for Embedded computing, but have vulnerable points, such as lack of network scalability and dynamic network topology due to mobility, passive attacks, active attacks, which make continuous security service impossible. For perfect MANET setting, routing is required which can guarantee security and efficiency through secure routing. In routing in this study, hashed AODV is used to protect from counterfeiting messages by malicious nodes in the course of path 'finding and setting, and disguising misrouted messages as different mobile nodes and inputting them into the network.

• Applied Biological Chemistry
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• v.34 no.2
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• pp.180-186
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• 1991

A water soluble antifungal antibiotic, Solumycin, was separated from the culture broth of Streptomyces sp. LAM-593, isolated from soil, by butanol extraction, alumina-, 1st and 2nd Sephadex LH-20 column chromatography. The substance was pale yellow crystal which gave a single spot at Rf value 0.24 with ethanol-ammonia water-water (8:1:1), 0.46 with butanol-ethanol-water (5:1:4), 0.84 with 50% methanol on silica gel TLC. It was dissolved well in water, methanol and acidic aq. butanol but not in ethanol, acetone, ethyl acetate, chloroform. acetic acid etc., and gave positive Fehling and Molish reaction. The UV spectrum in methanol showed absorption at 342, 361, 380, and 404 nm. The antibiotic was active against fungi such as Candide, Cryptococcus, Saccharomyces, Trichophyton and Trichosporon, but not to bacteria such as Bacillus, Escherichia and Staphylococcus.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.170-170
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• 2011

태양전지와 박막 트랜지스터를 위한 유망한 재료로서 수소화된 비정질 실리콘과 나노결정 실리콘 박막이 관심을 받아 왔다. 특히, 수소화된 나노결정 실리콘 박막은 비정질 대비 높은 방향성과 조밀한 구조 덕에 박막 태양전지나 TFT(Thin film transistor) 소자의 성능 향상에 기여할 수 있는 물질로 연구되고 있다. 이러한 박막들은 보통 $SiH_4$같은 Si을 포함한 가스에 다량의 $H_2$를 희석시켜 플라즈마 화학 증착법(PECVD, Plasma Enhanced Chemical Vapor Deposition)에 의해 성장된다. 이러한 CVD증착 방식을 이용하여 결정화된 박막을 얻기 위해서는 대개 높은 수소 희석비를 이용하는 것이 일반적이나, 이러한 공정 방식은 실리콘이 결합되어야 할 결합위치에 bonding energy가 더 높은 수소의 결합을 촉진하게 된다. 이러한 특성은 박막 태양전지에서 효율을 떨어뜨리는 주요 요소로 작용하고 있다.(1) 본 연구에서는 수소의 결합 확률을 낮춘 결정화된 박막을 성장시키기 위해 수소를 대신하여 헬륨을 희석가스로 사용하여 박막을 증착하고 그 특성을 분석해 보았다. 박막의 구조적 특성, 결정화도(Xc), 플라즈마 내 활성 라디칼(Active radical in plasma), Si-H결합 특성, 전도도(Conductivity)와 같은 박막 특성을 알아보기 위해 주사전자현미경(SEM, Scanning Electron Microscopy), 라만 분광기(Raman spectroscopy), 광 방출 분광기(OES, Optical Emission Spectrocopy), 적외선 분광기(FT-IR, Fourier Transform-Infrared Spectroscopy), Keithley measurement kit이 사용되었다. 수소를 대신하여 헬륨을 사용함으로써 동일 결정화도 대비 10%이상 낮은 microstructure factor 값을 얻을 수 있었으며 인가되는 RF 전력을 140W까지 증가시켰을 때 약 80%의 결정화도를 관찰할 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.334-334
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• 2012

Transparent oxide semiconductors have recently attracted much attention as channel layer materials due to advantageous electrical and optical characteristics such as high mobility, high stability, and good transparency. In addition, transparent oxide semiconductor can be fabricated at low temperature with a low production cost and it permits highly uniform devices such as large area displays. A variety of thin film transistors (TFTs) have been studied including ZnO, InZnO, and InGaZnO as the channel layer. Recently, there are many studies for substitution of Ga in InGaZnO TFTs due to their problem, such as stability of devices. In this work, new quaternary compound materials, tantalum-indium-tin oxide (TaInSnO) thin films were fabricated by using co-sputtering and used for the active channel layer in thin film transistors (TFTs). We deposited TaInSnO films in a mixed gas (O2+Ar) atmosphere by co-sputtering from Ta and ITO targets, respectively. The electric characteristics of TaInSnO TFTs and thin films were investigated according to the RF power applied to the $Ta_2O_5$ target. The addition of Ta elements could suppress the formation of oxygen vacancies because of the stronger oxidation tendency of Ta relative to that of In or Sn. Therefore the free carrier density decreased with increasing RF power of $Ta_2O_5$ in TaInSnO thin film. The optimized characteristics of TaInSnO TFT showed an on/off current ratio of $1.4{\times}108$, a threshold voltage of 2.91 V, a field-effect mobility of 2.37 cm2/Vs, and a subthreshold swing of 0.48 V/dec.

• Korean Journal of Food Science and Technology
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• v.27 no.6
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• pp.972-977
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• 1995

The induction of phase II enzymes including quinone reductase [NAD(P)H dehydrogenase(quinone): NAD(P)H : (quinone acceptor) oxidoreductase, EC 1.6.99.2] is a major mechanism of whereby a large group of heterogeneous compounds prevent the toxic, mutagenic, and neoplastic effects of carcinogen. Using murine hepatoma cells(Hepalclc7 cells), quinone reductase(QR) inducers as the possible chemopreventive agents were screened from rice bran, wheat bran, soymilk residue, defatted soybean cake, defatted sesame and perilla residues. The 80% methanol extracts of defatted sesame and perilla residues induced quinone reductase significantly while the others did have little effect on the enzyme induction. Thin layer chromatography of the extracts showed that the fastest moving band(Rf=0.70) in the developing solvent of n-butanol : n-propanol : 2N ammonia(10 : 60 : 30) was responsible for the enzyme induction by the 80% methanol extracts of defatted sesame and perilla residues. Further identification of active component(s) is in progress.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.889-891
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• 2017

Visible light communication technology, which is a communication using LED lighting, is defined by IEEE 802.15.7 WG and active research is under way. Visible light communication is advantageous not only to avoid interference with existing RF communication but also to provide location based service through accurate positioning by utilizing LOS (Line of Sight) characteristic. Therefore, it is very easy and efficient to locate and track the user's location. In this paper, we implemented a visible light communication transceiver using USB interface for easy application to portable devices. It supports the mobility of mobile devices through internet protocol and showed BER performance of less than $10^{-3}dBm$ at over 1m, which is the height of lighting and smart device during walking.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.569-577
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• 1999

A wideband RF receiver for satellite mobile communications system was fabricated and evaluated of performance in low noise amplifier and high gain amplifier. The low noise amplifier used to the resistive decoupling and self-bias circuits. The low noise amplifier is fabricated with both the RF circuits and the self-bias circuits. Using a INA-03184, the high gain amplifier consists of matched amplifier type. The active bias circuitry can be used to provide temperature stability without requiring the large voltage drop or relatively high-dissipated power needed with a bias stabilized resistor. The bandpass filter was used to reduce a spurious level. As a result, the characteristics of the receiver implemented here show more than 55 dB in gain, 50.83 dBc in a spurious level and less than 1.8 : 1 in input and output voltage standing wave ratio(VSWR), especially the carrier to noise ratio is a 43.15 dB/Hz at a 1 KHz from 1537.5 MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.199-207
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• 2011

A Ku-band low noise amplifier has been designed and fabricated by using 0.25 um SiGe BiCMOS process. The developed Ku-band LNA RFIC which has been designed with hetero-junction bipolar transistor(HBT) in the BiCMOS process have noise figure about 2.0 dB and linear gain over 19 dB in the frequency range from 9 GHz to 14 GHz. Optimization technique for p-tap value and electro-magnetic(EM) simulation technique had been used to overcome the inaccuracy in the PDK provided from the foundry service company and to supply the insufficient inductor library. The finally fabricated low noise amplifier of two fabrication runs has been implemented with the size of $0.65\;mm{\times}0.55\;mm$. The pure amplifier circuit layout with the reduced size of $0.4\;mm{\times}0.4\;mm$ without the input and output RF pads and DC bais pads has been incorporated as low noise amplication stages in the multi-function RFIC for the active phased array antenna of Ku-band satellite VSAT.

• The Journal of Korean Institute of Next Generation Computing
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• v.13 no.4
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• pp.112-123
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• 2017

Research for the inverse estimation of RF threats and the efficient electronic attack based on the parameters of the electronic information has been active in the electronic warfare (EW) situations. In this paper, an EW transmission simulator is constructed from the modeling of radar threats, EW receivers, and propagation environments with the collected electronic information in order to verify the performance of the inverse estimation algorithm in various and practical EW situations. In simulation results, we show that the range tracking error and angle tracking error are produced within ten meters and one degree, respectively. And also, we show that the changing relations between the angle tracking error and the parameters of the monopulse angle tracking radar such as the beamwidth and squint angle in simulation results correspond with those in the theoretical modeling. Accordingly, the constructed EW simulator can be used to observe the modifying characteristics of the electronic information in transmission environments, and then, to evaluate the performance of the inverse estimation system in various EW situations.