• 방송공학회논문지
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• 제17권5호
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• pp.864-875
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• 2012

본 논문에서는 단일 반송파 MIMO 시스템 기반의 PN 부호열을 이용한 반송파 주파수 오차 추정 방법을 제안한다. 제안하는 방법은 송신되는 각각의 PN 부호열들의 위상을 회전시켜 전송하여, 일부 PN 부호열들이 서로 상쇄되어 버리는 것을 방지한다. 수신한 PN 부호열과 수신기에서 자체 생성한 PN 부호열의 공액곱셈 연산을 통해 변조를 제거한 뒤, 다수의 자기 상관기를 이용한 ML (Maximum Likelihood) 알고리듬을 이용하여 반송파 주파수 오차를 추정한다. 또한 시변채널에서의 정확한 주파수 오차 추정을 위해 채널 정보를 이용한 주파수 오차 추정 구조를 제안하였다. 컴퓨터 모의실험을 통해, 송신 및 수신 안테나가 두 개인 $2{\times}2$ MIMO 시스템에 제안하는 기법을 적용하고 L&R 알고리듬을 이용하여 AWGN (Additive White Gaussian Noise) 환경 및 시변 Rayleigh 채널에서의 MSE (Mean Square Error) 성능을 측정하였다. 그 결과 AWGN 환경 상에서 MIMO 시스템에 적용한 제안된 기법의 MSE 성능이 SISO 시스템에서의 성능과 거의 동일함을 보였다. 또한 시변 Rayleigh 채널에서 제안된 채널 정보를 이용한 추정 기법의 MSE 성능이 기존 방법 및 SISO 시스템에 비해 높음을 보였다.

• Biomolecules & Therapeutics
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• 제24권6호
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• pp.572-580
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• 2016

3-Deoxysappanchalcone (3-DSC) has been reported to possess anti-allergic, antiviral, anti-inflammatory and antioxidant activities. In the present study, we investigated the effects of 3-DSC on the proliferation of human hair follicle dermal papilla cells (HDPCs) and mouse hair growth in vivo. A real-time cell analyzer system, luciferase assay, Western blot and real-time polymerase chain reaction (PCR) were employed to measure the biochemical changes occurring in HDPCs in response to 3-DSC treatment. The effect of 3-DSC on hair growth in C57BL/6 mice was also examined. 3-DSC promoted the proliferation of HDPCs, similar to Tofacitinib, an inhibitor of janus-activated kinase (JAK). 3-DSC promoted phosphorylation of ${\beta}$-catenin and transcriptional activation of the T-cell factor. In addition, 3-DSC potentiated interleukin-6 (IL-6)-induced phosphorylation and subsequent transactivation of signal transducer and activator of transcription-3 (STAT3), thereby increasing the expression of cyclin-dependent kinase-4 (Cdk4), fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF). On the contrary, 3-DSC attenuated STAT6 mRNA expression and IL4-induced STAT6 phosphorylation in HDPCs. Finally, we observed that topical application of 3-DSC promoted the anagen phase of hair growth in C57BL/6 mice. 3-DSC stimulates hair growth possibly by inducing proliferation of follicular dermal papilla cells via modulation of $WNT/{\beta}$-catenin and STAT signaling.

• 한국항행학회논문지
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• 제22권5호
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• pp.420-428
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• 2018

본 논문은 태양광 발전시스템을 승압쵸퍼와 단상 펄스폭변조 전압형인버터를 사용하여 전원차단 경우나 전압변동 및 부하변동에 의한 출력전류 변화에도 일정한 출력전압을 유지하는 무정전 전원 공급장치(UPS)를 구성하였다. 본 시스템은 전압형인버터를 교류전원과 동기 시켜서 운전하고 정상상태에서는 전원으로부터 운전하고 정상상태에서는 전원으로부터 직류 측에 연결된 축전지를 태양전지를 이용한 광기전력효과와 함께 일정전압을 충전하며, 전원의 차단, 전원의 전압변동 및 부하전류의 변화에도 일정한 전압을 유지하도록 하였다. 에너지 저장장치 (ESS; energy storage system)를 상시 운영하여 공항의 기상 변화에 따른 파장별 LED 항공 유도신호 등을 효율적으로 운용하는 시스템을 구성 하였고, 전력절감효과를 얻을 수 있는 에너지절약 전원복합형 전력변환장치로 구성되어 있다. 출력은 PWM방식에 의하여 양호한 파형이 되도록 하고 전원차단과 부하의 상태의 변화 및 전원 전압 변동에도 일정한 전압으로 출력됨을 실험을 통하여 확인 할 수 있었다.

• 한국재료학회지
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• 제23권4호
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• pp.215-218
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• 2013

Vanadium dioxide ($VO_2$) is an attractive material for smart window applications where the transmittance of light can be automatically modulated from a transparent state to an opaque state at the critical temperature of ${\sim}68^{\circ}C$. Meanwhile, F : $SnO_2$ (F-doped $SnO_2$, FTO) glass is a transparent conductive oxide material that is widely used in solar-energy-related applications because of its excellent optical and electrical properties. Relatively high transmittance and low emissivity have been obtained for FTO-coated glasses. Tunable transmittance corresponding to ambient temperature and low emissivity can be expected from $VO_2$ films deposited onto FTO glasses. In this study, FTO glasses were applied for the deposition of $VO_2$ thin films by pulsed DC magnetron sputtering. $VO_2$ thin films were also deposited on a Pyrex substrate for comparison. To decrease the phase transition temperature of $VO_2$, tungsten-doped $VO_2$ films were also deposited onto FTO glasses. The visible transmittance of $VO_2$/FTO was higher than that of $VO_2$/pyrex due to the increased crystallinity of the $VO_2$ thin film deposited on FTO and decreased interface reflection. Although the solar transmittance modulation of $VO_2$/FTO was lower than that of $VO_2$/pyrex, room temperature solar transmittance of $VO_2$/FTO was lower than that of $VO_2$/pyrex, which is advantageous for reflecting solar heat energy in summer.

• Journal of Power Electronics
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• 제18권3호
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• pp.702-713
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• 2018

Power loss reduction and total harmonic distortion(THD) minimization are two important goals of improving three-level inverters. In this paper, an optimized pulse width modulation (PWM) strategy that can reduce switching losses and balance the neutral point with an optional THD of three-level neutral-point-clamped inverters is proposed. An analysis of the two-level discontinuous PWM (DPWM) strategy indicates that the optimal goal of the proposed PWM strategy is to reduce switching losses to a minimum without increasing the THD compared to that of traditional SVPWMs. Thus, the analysis of the two-level DPWM strategy is introduced. Through the rational allocation of the zero vector, only two-phase switching devices are active in each sector, and their switching losses can be reduced by one-third compared with those of traditional PWM strategies. A detailed analysis of the impact of small vectors, which correspond to different zero vectors, on the neutral-point potential is conducted, and a hysteresis control method is proposed to balance the neutral point. This method is simple, does not judge the direction of midpoint currents, and can adjust the switching times of devices and the fluctuation of the neutral-point potential by changing the hysteresis loop width. Simulation and experimental results prove the effectiveness and feasibility of the proposed strategy.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.152-152
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• 2017

Titanium and its alloys have been widely used for biomedical applications. However, the use of the Ti-6Al-4V alloy in biomaterial is then a subject of controversy because aluminum ions and vanadium oxide have potential detrimental influence on the human body due to vanadium and aluminum. Hence, recent works showed that the synthesis of new Ti-based alloys for implant application involves more biocompatible metallic alloying element,such as, Nb, Hf, Zr and Mo. In particular, Nb and Hf are one of the most effective Ti ${\beta}$-stabilizer and reducing the elastic modulus. Plasma electrolyte oxidation (PEO) is known as excellent method in the biocompatibility of biomaterial due to quickly coating time and controlled coating condition. The anodized oxide layer and diameter modulation of Ti alloys can be obtained function of improvement of cell adhesion. Silicon (Si) and magnesium (Mg) has a beneficial effect on bone. Si in particular has been found to be essential for normal bone and cartilage growth and development. In vitro studies have shown that Mg plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. Therefore, in this study, Si and Mg coatings on the hydroxyapatite film formed Ti-29Nb-xHf alloys by plasma electrolyte oxidation has been investigated using several experimental techniques. Ti-29Nb-xHf (x= 0, 3, 7 and 15wt%, mass fraction) alloys were prepared Ti-29Nb-xHf alloys of containing Hf up from 0 wt% to 15 wt% were melted by using a vacuum furnace. Ti-29Nb-xHf alloys were homogenized for 2 hr at $1050^{\circ}C$. The electrolyte was Si and Mg ions containing calcium acetate monohydrate + calcium glycerophosphate at room temperature. The microstructure, phase and composition of Si and Mg coated oxide surface of Ti-29Nb-xHf alloys were examined by FE-SEM, EDS, and XRD.

• The Korean Journal of Pain
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• 제19권2호
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• pp.137-141
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• 2006

Background: It has been known that melatonin is involved in the modulation of nociceptive transmission. However, the effect of melatonin administered spinally has not been examined. Therefore, we examined the effect of melatonin on the formalin-induced or thermal-induced nociception at the spinal level. Methods: Intrathecal catheter was inserted into the subarachnoid space of male Sprague-Dawley rats. Pain was assessed by formalin test (induced by injection of $50{\mu}l$ of a 5% formalin solution to the hindpaw) or Hot-Box test (induced by radiant heat application to the hindpaw). The effect of intrathecal melatonin was examined on flinching behavior in the formalin test or withdrawal response in Hot-Box test. Results: Intrathecal melatonin produced a limited, but dose-dependent reduction of the flinching response during phase 1 and 2 in the formalin test. In addition, melatonin delivered at evening also decreased the flinching response in both phases of the formalin test. Melatonin restrictively increased the withdrawal latency in Hot-Box test. Conclusions: These results suggest that melatonin is active against the formalin- and thermal-induced nocicpetion at the spinal level, but the effect is limited.

• Biomolecules & Therapeutics
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• 제19권1호
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• pp.126-133
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• 2011

The fruit of Actinidia arguta (AA) has been used mainly for the treatment of skin diseases, diuresis, diabetes mellitus and osteoporosis in Korean traditional medicine. It is known that AA (hardy kiwi) fruit extract has an effect on 2-chloro-1,3,5-trinitrobenzene-induced atopic dermatitis-like skin lesions in NC/Nga mice. Mode of action for it is associated with the modulation of biphasic Th1/Th2 cytokines. Furthermore, DA9102 containing AA is a herbal medicine currently under phase II clinical trial for atopic dermatitis in Korea. However, no active principles of AA on the decrease of Th2 cytokines including IL-4 and IL-10 have been identified. In this study, bioactivity-guided fractionation of an alcohol extract from the dried fruits of AA using ELISA assay for IL-4 production led to the isolation of $\alpha$-linolenic acid (I), linoleic acid (II), ethyl linolenate (III), ethyl linoleate (IV) and ethyl stearate (V) as the major active components. These compounds showed the down-regulatory effects of IL-4 production in A23187-stimulated RBL-2H3 cells without cytotoxicity.

• 한국통신학회논문지
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• 제29권9A호
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• pp.991-997
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• 2004

본 논문은 HomePNA 2.0 모뎀 칩을 위한 모뎀 수신부의 구조를 제안한다. HomePNA 2.0 전송 채널은 브릿지 탭과 HAM 대역의 영향 등으로 매우 열악하다. 이러한 채널을 통해 전송을 가능하게 하기 위해 HomePNA 2.0 은 훈련신호를 사용하여 매 프레임 마다 채널을 등화하고 FD-QAM 전송 방식을 선택적으로 사용한다. 따라서 모뎀 수신부는 일반적 QAM 방식 신호의 북조 기능과 함께 이러한 전송 방식의 특정을 최대한 상려 모뎀 수신 성 능을 극대화 히는 구조가 필요하다 연구 결과 모뎀 수신부의 가능을 송수신 상태에 따라 정상 수신 모드와 충돌 감지 오드의 2 가지로 정의 하였다 본 논문은 특히, 모뎀 수신부를 구성하는 핵심 블록인 등화기와 위상 동기부, 프레임 동기부에 대해서 사용된 알고리즘을 밝혔으며, 버스트 방식 모뎀의 채널 등화 성능을 높이고 안정적으로 동작 시키기 위한 구조를 제얀 하였다 마지막으로 제안된 모뎀 수신부의 성능을 분석하기 위해서 SPW 모델을 사용하여 채널 별 전송 가능 속도를 예측 하였다.

• 한국진공학회지
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• 제16권5호
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• pp.343-347
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• 2007

Glass disk상에 대향 타겟식 스퍼터링(Facing Target Sputtering) 방식을 이용하여 $0.1\;{\AA}/s$의 낮은 증착속도로 증착시킬 경우 b.c.c. (100)면 우선배향성을 확인하였으며, 그 위에 Pt박막을 증착시킨 경우 hetero-epitaxial 성장에 의해 Pt박막이(111)의 조밀면이 아닌 (100)면이 우선배향 되었다. 이렇게 형성된 Fe (100)/Pt (100) 이층막(두께 각 3 nm)을 $600\;^{\circ}C$ 수소분위기에서 열처리함에 의해 막전체에 걸쳐서 f.c.t. (00n)면을 형성시키는 데 성공하고, 또한 Fe (100)면 상에 Pt 박막을 증착시키는 동안 열처리를 하고 증착 이후 수소분위기에서 열처리함에 의해 열처리 시간 및 온도를 크게 낮출 수 있음을 확인하였다.