• Journal of Yeungnam Medical Science
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• 제30권1호
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• pp.10-16
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• 2013

Background: Toll-like receptors (TLRs) are well-known pattern recognition receptors. Among the 13 TLRs, TLR2 is the most known receptor for immune response. It activates mitogen-activated protein kinases (MAPKs), which are counterbalanced by MAPK phosphatases [MKPs or dual-specificity phosphatases (DUSPs)]. However, the regulatory mechanism of DUSPs is still unclear. In this study, the effect of a TLR2 ligand (TLR2L, Pam3CSK4) on DUSP4 expression in Raw264.7 cells was demonstrated. Methods: A Raw264.7 mouse macrophage cell line was cultured in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum and 1% antibiotics (100 U/mL penicillin and 100 g/mL streptomycin) at $37^{\circ}C$ in 5% $CO_2$. TLR2L (Pam3CSK4)-mediated DUSP4 expressions were confirmed with RT-PCR and western blot analysis. In addition, the detection of reactive oxygen species (ROS) was measured with lucigenin assay. Results: Pam3CSK4 induced the expression of DUSP1, 2, 4, 5 and 16. The DUSP4 expression was also increased by TLR4 and 9 agonists (lipopolysaccharide and CpG ODN, respectively). Pam3CSK4 also induced ERK1/2 phosphorylation and ROS production, and the Pam3CSK4-induced DUSP4 expression was decreased by ERK1/2 (U0126) and ROS (DPI) inhibitors. U0126 suppressed the ROS production by Pam3CSK4. Conclusion: Pam3CSK4-mediated DUSP4 expression is regulated by ERK1/2 and ROS. This finding suggests the physiological importance of DUSP4 in TLR2-mediated immune response.

• ETRI Journal
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• 제36권1호
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• pp.42-50
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• 2014

Orthogonal frequency division multiplexing (OFDM) is a modulation technique that allows the transmission of high data rates over wideband radio channels subject to frequency selective fading by dividing the data into several narrowband and flat fading channels. OFDM has high spectral efficiency and channel robustness. However, a major drawback of OFDM is that the peak-to-average power ratio (PAPR) of the transmitted signals is high, which causes nonlinear distortion in the received data and reduces the efficiency of the high power amplifier in the transmitter. The most straightforward method to solve this problem is to use a nonlinear mapping algorithm to transform the signal into a new signal that has a smaller PAPR. One of the latest nonlinear methods proposed to reduce the PAPR is the $L_2$-by-3 algorithm, which is based on the discrete sliding norm transform. In this paper, a new algorithm based on the $L_2$-by-3 method is proposed. The proposed method is very simple and has a low complexity analysis. Simulation results show that the proposed method performs better, has better power spectral density, and is less sensitive to the modulation type and number of subcarriers than $L_2$-by-3.

• KSBB Journal
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• 제5권1호
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• pp.49-58
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• 1990

대장균으로부터 alpha interferon의 생산과 분비를 유도하기 위해 대장균의 lipoprotein promoter, lactose promoter 및 operator와 lipoprotein의 signal seqquence를 가지는 vector에 alpha-IFN유전자를 cloning하여 발현 vector pIF-III-B와 vector pIF-III-C를 제작하였다.

• 대한전자공학회논문지TC
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• 제41권2호
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• pp.65-70
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• 2004

본 논문에서는 비선형 RF(Radio Frequency) 증폭기의 선형화를 위한 새로운 구조의 전치왜곡 선형화기를 제안한다. 전치 왜곡에 이용되는 3차 비선형 성분은 RF 신호의 포락선(envelope) 전력을 이용하여 발생시킨다. 3차 왜곡 성분 발생기(3rd order distortion generator)는 FET로 구성되었고, 왜곡 신호 발생 후 남아 있는 주 신호 성분 제거를 위해 평형 결합 구조를 제시하였다. 발생된 3차 혼변조 신호는 RF 대역에서 진폭과 위상을 조절함으로써 최적의 선형화 조건을 만족시킨다. 2-tone 실험결과 증폭기의3차 흔변조특성이 30～40㏈ 개선되었다. IS-95 CDMA 신호 실험 결과 인접 채널 전력 비(ACPR)가 약 l0㏈이상 개선됨을 확인하였다.

• 제어로봇시스템학회논문지
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• 제19권2호
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• pp.113-118
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• 2013

In this paper, spoofing effects on a GNSS receiver were analyzed. The spoofer (spoofing device) was classified to two categories. One is an active spoofer and the other is a passive spoofer. The active spoofer was considered for analysis. For the analysis of spoofing effects on a GNSS receiver, a real-time GNSS spoofing simulator was developed. The simulator was consisted with two parts which are a baseband signal generation part and a RF up-conversion part. The first GNSS baseband signal was generated according to spoofing parameters such as range, range rate, GNSS navigation data, spoofing to GNSS signal ratio, and etc. The generated baseband signal was up-converted to GNSS L1 band. Then the signal transmitted to a GNSS signal. For a perfect spoofing, a spoofer knew an accurate position and velocity of a spoofing target. But, in real world, that is not nearly possible. Although uncertainty of position and velocity of the target was existed, the spoofer was operated as an efficient jammer.

• 대한전자공학회논문지TC
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• 제41권11호
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• pp.17-23
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• 2004

본 논문에서는 전 디지털 모뎀의 기저 대역 전송 신호를 IF 출력 신호로 주파수 변환하는 모듈에서 발생하는 국부발진 누설 신호를 역 위상 기법을 사용하여 제거하고, aperture 개방형 루프 공진기로 구성되는 광대역 필터를 구성하여 낮은 군지연과 높은 대역 제한 특성을 갖는 광대역 IF 인터페이스 모듈을 설계하고 제작하였다. 45 Mbps 및 155 Mbps 전 디지털 모뎀을 위한 광대역 IFIU는 전송 대역과 밀접하여 간섭 신호로 작용하는 국부발진 신호의 누설 신호를 -60 dBc 이하로 억압하였으며, 각각의 전송율에 대한 IFIU의 군 지연은 15 ns와 8 ns의 낮은 특성으로 구현하였다. L-대역 중심 주파수와 150 MHz 대역통과 특성을 갖는 모듈의 이득 평탄도는 2 dB 이내의 특성으로 광대역 위성통신 시스템 전송에 필요한 요구 조건을 만족하였다.

• ETRI Journal
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• 제42권5호
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• pp.781-789
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• 2020

In this study, an E-band low-noise amplifier (LNA) monolithic microwave integrated circuit (MMIC) has been designed using silicon-germanium 130-nm bipolar complementary metal-oxide-semiconductor technology to suppress unwanted signal gain outside operating frequencies and improve the signal gain and noise figures at operating frequencies. The proposed impedance-controllable filter has series (R_s) and parallel (R_p) resistors instead of a conventional inductor-capacitor (L-C) filter without any resistor in an interstage matching circuit. Using the impedance-controllable filter instead of the conventional L-C filter, the unwanted high signal gains of the designed E-band LNA at frequencies of 54 GHz to 57 GHz are suppressed by 8 dB to 12 dB from 24 dB to 26 dB to 12 dB to 18 dB. The small-signal gain S₂₁ at the operating frequencies of 70 GHz to 95 GHz are only decreased by 1.4 dB to 2.4 dB from 21.6 dB to 25.4 dB to 19.2 dB to 24.0 dB. The fabricated E-band LNA MMIC with the proposed filter has a measured S₂₁ of 16 dB to 21 dB, input matching (S₁₁) of -14 dB to -5 dB, and output matching (S₂₂) of -19 dB to -4 dB at E-band operating frequencies of 70 GHz to 95 GHz.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.235-240
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• 2006

Ionospheric scintillation induces a rapid change in the amplitude and phase of radio wave signals. This is due to irregularities of electron density in the F-region of the ionosphere. It reduces the accuracy of both pseudorange and carrier phase measurements in GPS/satellite based Augmentation system (SBAS) receivers, and can cause loss of lock on the satellite signal. Scintillation is not as strong at mid-latitude regions such that positioning is not affected as much. Severe effects of scintillation occur mainly in a band approximately 20 degrees on either side of the magnetic equator and sometimes in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. This paper focuses on estimation of the effects of ionospheric scintillation on GPS and SBAS signals using a software receiver. Software receivers have the advantage of flexibility over conventional receivers in examining performance. PC based receivers are especially effective in studying errors such as multipath and ionospheric scintillation. This is because it is possible to analyze IF signal data stored in host PC by the various processing algorithms. A L1 C/A software GPS receiver was developed consisting of a RF front-end module and a signal processing program on the PC. The RF front-end module consists of a down converter and a general purpose device for acquiring data. The signal processing program written in MATLAB implements signal acquisition, tracking, and pseudorange measurements. The receiver achieves standalone positioning with accuracy between 5 and 10 meters in 2drms. Typical phase locked loop (PLL) designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. So the effects of ionospheric scintillation was estimated on the performance of GPS L1 C/A and SBAS receivers in terms of degradation of PLL accuracy considering the effect of various noise sources such as thermal noise jitter, ionospheric phase jitter and dynamic stress error.

• 조명전기설비학회논문지
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• 제18권2호
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• pp.36-43
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• 2004

본 연구에서는 운전중인 직류전동기의 브러시를 임의로 회전하여 브러시와 정류자편에 불꽃을 발생시켰을 때, 초음파센서와 AE센서를 이용하여 각각의 기계적 노이즈 신호를 검출하였으며, 이를 주파수 스펙트럼으로 분석하였다. 또한 직류전동기의 브러시가 중성축에 정상적으로 위치하여 운전하고 있을 때, 초음파센서와 AE센서를 이용하여 각각의 자기적 노이즈 신호를 검출하였으며, 이를 주파수 스펙트럼으로 분석하였다. 그리고 직류전동기의 브러시를 임의로 회전한 경우의 기계적 노이즈 신호 및 브러시가 중성축에 위치한 경우의 자기적 노이즈 신호를 비교ㆍ분석하였다. 실험 결과, 운전중인 직류전동기의 브러시를 회전방향으로 임의로 회전하여 검출한 초음파의 기계적 노이즈 신호는 브러시가 중성축에 정상적으로 위치하여 검출한 초음파의 자기적 노이즈 신호보다 대략 2.5∼3.0배 증가되었다. 또한 운전중인 직류전동기의 브러시를 회전방향으로 임의로 회전하여 불꽃을 발생시켰을 때, AE의 기계적 노이즈 신호를 검출하여 주파수 스펙트럼으로 분석한 결과 주된 주파수 영역이 대략 1.3[MHz]∼l.5[MHz]인 것으로 나타났다

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3654-3658
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• 2013

The synthesis of a DO3A conjugate of [(p-aniline benzothiazole)methyl]pyridine ($L^2H_3$) and its gadolinium complex of the type [$Gd(L^2)(H_2O)$] ($GdL^2$) is described. The $R_1$ relaxivity ($=4.50mM^{-1}sec^{-1}$) and kinetic inertness of $GdL^2$ compares well with those of structurally analogous Dotarem$^{(R)}$ ($R_1=3.70mM^{-1}sec^{-1}$), a typical extracellular (ECF) MRI contrast agent (CA). Yet, by comparison with Dotarem$^{(R)}$, $GdL^2$ exhibits non-covalent interactions with human serum albumin (HSA) as evidenced by the ${\varepsilon}^*$ titration curve along with in vivo MR signal enhancement in both aorta and heart. Liver-specific nature of $GdL^2$ is also observed as excretion is made through gallbladder. Most notably, $GdL^2$ further demonstrates specificity toward the MDA-MB-231 breast cancer.