• The Journal of the Korea institute of electronic communication sciences
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• 제3권2호
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• pp.93-100
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• 2008

In this paper, Low Noise Block down converter(LNB) is designed for a Ka-band satellite television receiver only(TVRO) using commercially available MMIC. Designed Low Noise Block down-converter is composed of three stage amplifiers involving input noise matched at first amplification stage, image reject band pass filter, frequency mixer and intermediate frequency amplification. Through LNB Module power budget to obtain gain and attenuation, Optimum LNB devices satisfying Ka-band LNB technical specification are selected. Experimental results of designed Ka-band LNB yields conversion gain of over $58{\pm}1dB$, noise figure of less than 1.5dB and phase noise of -94.6dBc @10KHz.

• Journal of the Institute of Electronics Engineers of Korea SD
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• 제45권2호
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• pp.125-129
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• 2008

A low-voltage active CMOS inductor approach, which can improve the quality-factor(Q), is proposed in this paper. A low-voltage active inductor circuit topology with a feedback resistance is proposed, which can substantially improve its equivalent inductance and quality-factor(Q). This proposed low-voltage active inductor with a feedback resistance was simulated by ADS(Agilent) using 0.18um standard CMOS technology. Simulation showed that the designed active inductor had a maximum quality-factor(Q) of 3000 with a 1.5nH inductance at 4GHz

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 한국지능시스템학회 2008년도 춘계학술대회 학술발표회 논문집
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• pp.251-254
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• 2008

유비쿼터스 네트워크의 실현을 위한 4세대 통신방식의 유력한 후보로 부상하는 OFDM (Orthogonal Frequency Division Multiplexing) 통신방식이 육상에 주목받고 있으며, 고속 데이터 전송을 위한 무선랜의 표준기술로 확정되어 있다. 해상 통신의 경우에서도 OFDM 통신방식은 단파대역을 이용한 데이터 전송방식으로 제안되고 있으며, ITU (International Telecommunication Union)는 해상통신에서 32-point FFT를 사용하도록 권고하고 있다. 해상 통신에서는 해양사고 및 조난 시에도 통신이 이루어져야 하는 한계상황을 고려하면, OFDM 통신방식의 중요 디바이스인 FFT는 저전력으로 동작되어야 한다. 따라서 본 논문에서는 OFDM 방식의 중요 디바이스인 32-point FFT를 저전력으로 동작시키기 위해 radix-2와 radix-4를 이용하여 저전력 32-point FFT 알고리즘을 제안한다. 최적화된 설계로 32-point FFT를 저전력 동작이 가능하도록 설계하였으며, 제안한 알고리즘은 VHDL로 구현하고 FPGA Spartan3 board에 장착하여 Matlab의 이론값과 비교, 검증하였다. 제안된 32-point FFT는 해상통신에서의 OFDM 적용을 위한 선도기술로 유용할 것이다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국정보통신학회 2016년도 춘계학술대회
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• pp.691-692
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• 2016

본 논문은 802.11a 무선 랜용 5.25-GHz BiCMOS 저 잡음 증폭기를 제안한다. 이러한 회로는 1볼트 전원에서 동작하며, 저 전압 전원 공급에서도 높은 전압 이득을 가지도록 설계하였다. 제안한 회로는 $0.18{\mu}m$ SiGe HBT BiCMOS로 설계되어 있다. 저 전압 및 저 전력 동작을 위해 바이어스 회로는 밴드 갭 참조 (band-gap reference circuit) 바이어스 회로를 사용하였다. 제안한 회로는 최근 발표된 연구결과에 비해 높은 전압이득, 낮은 잡음지수 및 작은 칩 크기 특성을 보였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제2권3호
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• pp.353-358
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• 1998

This paper presents development of a LNA operating at 1.71 ∼ 1.18 GHz used for a receiver of KOREA PCS base station and transponder. Using resistive decoupling circuits, a signal at low frequency is dissipated by a resistor. This design method increases the stability of the LNA and suitable for input stage matching. The LNA consists of low noise GaAs FET ATF-10136 and internally matched VNA-25. The LNA is fabricated with both the RF circuit and the self-bias circuits in aluminum housing. As a result, the characteristics of the LNA implemented here shows 30 dB in gain and 0.85 dB in noise figure.

• The Journal of the Korea institute of electronic communication sciences
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• 제14권2호
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• pp.283-288
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• 2019

LPWA (Low Power Wide Area) networks have been considered as one of the technologies which can be implemented in IoT (Internet of Things) applications by providing less power and longer communication range compared with existing wireless technologies. In this paper, we investigate LoRa which is one of representative technologies for LPWA networks. First, we present general properties and several technologies of LPWA networks. Then, the technical specification, properties, and pros/cons of LoRa are studied. Finally, we discuss analysis of LoRa's performance and its ehancement technologies by focusing on physical layer and MAC (Medium Access Control) layer.

• The Korean Journal of Food And Nutrition
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• 제25권4호
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• pp.878-887
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• 2012

This study investigated the fermentative characteristics and immunomodulating activity in Kimchi added with various salts (salt replacement and herb-salt with Acanthopanax senticosus and Glycyrrhizae uralensis) for the reduction of Na concentration in Kimchi. Kimchi using a salt replacement and herb-salt showed a higher level of acidity (0.8~0.84%) than that of the control (0.7%) at 7-day fermentation. Kimchi using a salt replacement and herb-salt showed a lower level of salinity (1.72~1.98%) than that of control (2.3~2.57%) during fermentation. The growth of Lactobacillus spp. and Leuconostoc spp. recorded the highest level ($2.3{\times}10^8$ and $2.8{\times}10^6cfu/g$, respectively) in control at 6 day-fermentation. However, those levels in Kimchi prepared with salt replacement and herb-salt were $3.5{\sim}5.4{\times}10^8$ and $6.1{\times}10^6cfu/g$, respectively. It is assumed that the high level of acidity of Kimchi prepared with salt replacement and herb-salt was caused by the increase in the growth of Lactobacillus spp. and Leuconostoc spp.. When the macrophage stimulating activity of salt replacement kimchi (Salt-R kimchi) supplemented with hot-water extract from Acanthopanax sentisus (AS) or Glycyrrhiza uralensis (GU) was investigated on aging period, Salt-RA kimchi with AS 5% at 6 days (2.78-fold of saline control at $100{\mu}g/m{\ell}$) and Salt-RG kimchi with GU 5% at 9 days (2.02-fold) significantly increased compared to the Salt-RA kimchi without AS or GU. In addition, Salt-RAG kimchi with AS 3% and GU 3% improved the bitter taste of Salt-RA and potently stimulated the macrophage at 6 days (1.28-fold of Salt-R kimchi) even though its activity was lower than Salt-RA (5%, 1.39-fold).

• Journal of Chest Surgery
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• 제42권5호
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• pp.588-596
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• 2009

Background: To clarify the effect of hypoxia on vascular contractility, we tried to show whether hypoxia induced the release of endothelium-derived relaxing factor (EDRF) and the nature of the underlying mechanism for this release. Material and Method: Isometric contractions were observed in rabbit aorta, and the released EDRF from the rabbit aorta was bioassayed by using rabbit denuded carotid artery. The intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) in the cultured rabbit aortic endothelial cells was recorded by a microfluorimeter with using Fura-2/AM. Hypoxia was evoked to the blood vessels or endothelial cells by eliminating the $O_2$ in the aerating gases in the external solution. Chemical hypoxia was evoked by applying deoxyglucose or $CN^-$. Result: Hypoxia relaxed the precontracted rabbit thoracic aorta that had its endothelium, and the magnitude of the relaxation was gradually increased by repetitive bouts of hypoxia. In contrast, hypoxia-induced relaxation was not evoked in the aorta that was denuded of endothelium. In a bioassay experiment, hypoxia released endothelium-derived relaxing factor (EDRF) and the release was inhibited by L-NAME or the $K^+$ channel blocker tetraethylammonium (TEA). In the cultured endothelial cells, hypoxia augmented the ATP-induced increase of the intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) and this increase was inhibited by TEA. Furthermore, chemical hypoxia also increased the $Ca^{2+}$ influx. Conclusion: From these results, it can be concluded that hypoxia might induce the release of NO from rabbit aortic endothelial cells by increasing $[[Ca^{2+}]_i$.

• Journal of Aquaculture
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• 제14권4호
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• pp.213-220
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• 2001

To study the effect of salinity on maturation and spawning, two series of experiments were carried out during November, 1998- July, 1999 and January, 1999- March 2000. In the first series, the control group (C) was reared at 14.3$^{\circ}C$ and 35.1$\textperthousand$ S, but the experimental group was reared at 33.8$\textperthousand$ S. In the second series, they were also exposed to approximately the same temperature but the experimental group was reared at still lowered salinity of 2p.6$\textperthousand$. Survival, food intake and growth of the experimental groups in either series reared at lower salinities were higher than those of their respective control groups. At lower salinity, larger number of females attained spontaneous sexual maturity and successfully spawned. Hatching success of the eggs spawned by the experimental females reared at lower salinities was also higher (54-56$\textperthousand$) than that (~19%) of the control group reared at higher salinity.

• Clinical and Experimental Pediatrics
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• 제45권12호
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• pp.1503-1511
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• 2002

Purpose : Although the short- and long-term outcomes of low birth weight(LBW) neonatal intensive care unit(NICU) survivors have been extensively studied, much less information is available for normal birth weight(NBW) infants(greater than 2,500 gm) who require NICU care. Methods : We retrospectively examined the neonatal hospitalizations and one year health status of 302 NBW and 131 LBW admissions to our NICU. Information on the neonatal hospitalization was obtained from a review of medical records. Postdischarge health status was collected by using telephone surveys and medical records. Results : After initial discharge, 21.2% of the NBW infants and 23% of the LBW infants required rehospitalization during the first year of life and there was no significant difference between the two groups. The reasons for rehospitalization of the NBW infants included respiratory disorders (32.1%), G-I problems(26.2%), genitourinary problems(11.9%), surgery(10.7%), cardiac problems(7.1%), and congenital/developmental problems(1.2%). For the LBW infants, the order of frequency was the same, with the percentages slightly different. Neonatal risk factors related to the rehospitalization of the NBW infants included mechanical ventilation, duration of mechanical ventilation, and congenital anomaly. But no positive significant correlation of neonatal risk factors with rehospitalization of LBW infants was found. Conclusion : Low and normal birthweight NICU survivors were rehospitalized at similar rates. The most common cause of rehospitalization was respiratory problems. Neonatal risk factors related to rehospitalization of NBW infants were mechanical ventilation, duration of mechanical ventilation, and congenital anomaly. However, no positive significant correlation of neonatal risk factors with rehospitalization of LBW infants was found. The data suggests that NBW infant survivors, as well as LBW infant NICU survivors, require close follow up.