• 한국전자파학회논문지
• /
• 제11권2호
• /
• pp.294-301
• /
• 2000

RF(radio frequency) 시스템의 송신탄을 설계할 때 고려해야 할 중요한 요소 중의 하나인 EMI(Electro magnetic interference)의 규격시험에서 항상 문제시되는 것이 송신기의 출력 스펙트럼에서 나타나는 불요 신호(Spurious interference) 이다. 이 불요 성분들 중 특히 문제가 되고 있는 것이 국부발진기(LO; Local oscillator)로부터 누설되는 LOL(Local oscillator leakage) 성분이다. 이 LOL성분은 국부발진기에서 누설(leakage)되어 RF단의 증폭기를 통하여 증폭되어 최종 출력에서 매우 높은 선호의 크기로 나타난다. 일반적으로 LOL을 제거하기 위해 서 너치필터(Notch filter) 또는 대역통과필터 (Band pass filter)를 사용해왔다. 본 논문에서는 국부발진기로부터 누설되는 불요 성분, 즉 LOL성분을 제거하는 방법으로 LOL과 동일한 크기를 가지고 위상 차이가 $180^{\circ}$인 신호를 국부발전기의 출력에서 만들어 믹서( Mixer)의 출력단에 더함으로써 LOL성분을 효과적으로 제거한다. 본 방 식을 무선랜(WLAN; Wireless 1$\infty$al area network) 시스템에 적용한 결과. 기존의 방식보다 30 dB 이상 LO 누설선호플 감쇄시킬 수 있었다 또한 본 방식은 RF 시스댐을 소형화 및 MMIC(Monolithic microwave integrated C circuit)화 할 경우 종전의 방법보다 효과적일 것으로 기대된다.

• Bulletin of the Korean Chemical Society
• /
• 제32권5호
• /
• pp.1640-1644
• /
• 2011

Water-soluble mutant of intrinsically insoluble protein, crambin, was produced by mutagenesis based on the sequence analysis with homologous proteins. Thr1, Phe13, and Lys33 of crambin were substituted for Lys, Tyr, and Lys, respectively. The resultant mutant was soluble in aqueous buffer as well as in dodecylphosphocholine (DPC) micelle solution. The $^1H-^{15}N$ spectrum of the mutant crambin showed spectral similarity to that of the wild-type protein except for local regions proximal to the sites of mutation. Solution structure of water-soluble mutant crambin was determined in aqueous buffer by NMR spectroscopy. The structure was almost identical to the wild-type structure determined in non-aqueous solvent. Subtle difference in structure was very local and related to the change of the intra- and inter-protein hydrophobic interaction of crambin. The structural details for the enhanced solubility of crambin in aqueous solvent by the mutation were provided and discussed.

• 물과 미래
• /
• 제22권2호
• /
• pp.201-211
• /
• 1989

인접계측지점의 상관성을 이용하여 결측지점의 자료를 보완한 다음, 다중상관 기법에 의하여 총강우량의 호우곡면을 구성한다. 구성된 호우 곡면에서 주기성분을 분리하여 호우잔차를 발생시키는데, 이중 프리에 해석을 이용했다. 각 강우에 잔차성분들은 균질등방성이라고 가정하여 이에 대응하는 자기 상관 함수를 조사하엿다. 실용성을 보완하기 위해서 경험치와 비교하였다. 모든 강우에 대한 정규상관 함수의 계수는 비슷한 양상을 보였다. 위의 결과를 사용하여 한강유역에 내린 강우의 공간분포를 나타내는 환상스펙트럼 분포함수를 추정하였다.

• Current Optics and Photonics
• /
• 제1권4호
• /
• pp.372-377
• /
• 2017

We demonstrate that the local resonance of metamaterials can be tuned by the effects of organic thin films under photoexcitation. Tris (8-hydroxyquinolinato) aluminum ($Alq_3$) layers are deposited on metamaterial/silicon hybrid structures. By varying the thickness of the $Alq_3$ layer on the subwavelength scale, the resonant peak of the metamaterial becomes very adjustable, due to the effect of a thin dielectric substrate. In addition, under photoexcitation all the spectral peaks of the resonance shift to higher frequencies. This originates from the reduction of the capacitive response generated inside the gaps of split-ring resonators. The adjustability of the electromagnetic spectrum may be useful for developing optical systems requiring refractive-index engineering and active optical devices.

• 한국자기공명학회논문지
• /
• 제10권2호
• /
• pp.197-202
• /
• 2006

[ $^{11}B$ ] nuclear magnetic resonance (NMR) measurements were performed on the single crystals of $TbB_4$ to investigate local electronic structure and 4f spin dynamics. $^{11}B$ NMR spectrum, Knight shift, spin-lattice and spin-spin relaxation rates were measured down to 4K at 8T. $^{11}B$ NMR shift and linewidth are huge and strongly temperature dependent due to the 4f moments. In addition, both are proportional to magnetic susceptibility, indicating that the hyperfine field at the boron site originates from the 4f spins of Tb. Below $T_N$, the single broad resonance peak of $^{11}B$ NMR splits into several peaks reflecting the local magnetic fields due to antiferromagnetic spin arrangements. The longitudinal and the transverse relaxation rates, $1/T_1\;and\;1/T_2$, independent of temperature above $T_N$, decreases tremendously confirming huge suppression of spin fluctuation below $T_N$.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권8호
• /
• pp.3965-3983
• /
• 2017

We propose a novel eye tracking method that can estimate 3D world coordinates using an infrared (IR) stereo camera for indoor and outdoor environments. This method first detects dark evidences such as eyes, eyebrows and mouths by fast multi-level thresholding. Among these evidences, eye pair evidences are detected by evidential reasoning and geometrical rules. For robust accuracy, two classifiers based on multiple layer perceptron (MLP) using gradient local binary patterns (GLBPs) verify whether the detected evidences are real eye pairs or not. Finally, the 3D world coordinates of detected eyes are calculated by region-based stereo matching. Compared with other eye detection methods, the proposed method can detect the eyes of people wearing sunglasses due to the use of the IR spectrum. Especially, when people are in dark environments such as driving at nighttime, driving in an indoor carpark, or passing through a tunnel, human eyes can be robustly detected because we use active IR illuminators. In the experimental results, it is shown that the proposed method can detect eye pairs with high performance in real-time under variable illumination conditions. Therefore, the proposed method can contribute to human-computer interactions (HCIs) and intelligent transportation systems (ITSs) applications such as gaze tracking, windshield head-up display and drowsiness detection.

• Bulletin of the Korean Chemical Society
• /
• 제18권7호
• /
• pp.743-749
• /
• 1997

Local structure refinement of the BaFe1-xSnxO3-y system (x=0.00-0.50) has been carried out with Fe K-edge x-ray absorpion spectroscopic studies. It is found out that the Fe ions are placed in two different symmetric sites such as tetrahedral and octahedral sites in the compounds by comparison with Fe K-edge x-ray absorption near edge structure (XANES) spectrum of the γ-Fe2O3 compound as a reference. Small absorption peaks of dipole-forbiden transitions appear at a pre-edge region of 7111 eV due to the existence of Fe ions in the tetrahedral and octahedral sites. The peak intensity decreases with the substitution amount of Sn ion. Three different absorption peaks of 1s→4p dipole-allowed transition appear on the energy region between 7123 and 7131 eV. The peaks correspond to 1s→4p main transition of Fe ions in tetrahedral and octahedral sites and 1s→4p transition followed by the shakedown process of ligand to metal charge transfer. The bond distances between Fe ions in the tetrahedral site and nearest neighboring oxygen atom (Fe-4O), and those in octahedral site (Fe-6O) are determined with the extended x-ray absorption fine structure (EXAFS) analysis. Two different interatomic distances increase with the substitution amount of Sn ion and also the bond lengths of Fe-4O are shorter than those of Fe-6O in all compounds.

• Nuclear Engineering and Technology
• /
• 제51권3호
• /
• pp.719-722
• /
• 2019

Gamma-ray images generally suffer from a lot of noise because of low photon detection in the gamma camera system. The purpose of this study is to improve the image quality in gamma-ray images using a gamma camera system with a fast nonlocal means (FNLM) noise reduction algorithm with an acceleration function. The designed FNLM algorithm is based on local region considerations, including the Euclidean distance in the gamma-ray image and use of the encoded information. To evaluate the noise characteristics, the normalized noise power spectrum (NNPS), contrast-to-noise ratio (CNR), and coefficient of variation (COV) were used. According to the NNPS result, the lowest values can be obtained using the FNLM noise reduction algorithm. In addition, when the conventional methods and the FNLM noise reduction algorithm were compared, the average CNR and COV using the proposed algorithm were approximately 2.23 and 7.95 times better than those of the noisy image, respectively. In particular, the image-processing time of the FNLM noise reduction algorithm can achieve the fastest time compared with conventional noise reduction methods. The results of the image qualities related to noise characteristics demonstrated the superiority of the proposed FNLM noise reduction algorithm in a gamma camera system.

• 자원환경지질
• /
• 제55권3호
• /
• pp.231-239
• /
• 2022

The irregular shape of the disturbances is a fundamental issue for mining engineers at the Sidi Chennane phosphate deposit in Morocco. A precise classification of disturbed areas is therefore necessary to understand their part in the overall volume of phosphate. In this paper, we investigate the theoretical and practical aspects of studying and measuring multifractal spectrums as a defining and representative parameter for distinguishing between the phosphate deposit of a low rate of disturbances and the deposit of a high rate. An empirical multifractal approach was used by analyzing the disturbed areas through the geoelectric images of an area located in the Sidi Chennane phosphate deposit. The Generalized fractal dimension, D(q), the Singularities of strength, α(q), the local dimension, f(α) and their conjugate parameter the mass exponent, τ(q) as well as f(α)-α spectrum were the common multifractal parameters used. The results reported show wide variations of the analyzed images, indicating that the multifractal analysis is an indicator for evaluate and characterize the disturbed areas within the phosphates deposits through the studied geoelectric images. This could be the starting point for future work aimed at improving phosphate exploration planning.

• 대한기계학회논문집A
• /
• 제38권7호
• /
• pp.817-822
• /
• 2014

경춘 복선의 일반 전동열차와 준 고속 열차인 ITX-청춘이 개통된 이래, 서울과 춘천을 오가는 유동인구가 급증하고 있다. 이는 대용량성과 저렴한 요금, 운행의 정시성 및 안전성 측면에서 다른 교통수단에 비해 철도 운송의 경쟁력이 높기 때문이다. 그러나 실내소음 측면에서는 전동 열차에 대한 승객들의 불만이 상당하다. 특히 터널 구간에서 실내소음은 급격히 높아져 대화에도 지장을 줄 정도이다. 본 연구에서는 경춘선 일반 전동 열차와 ITX-청춘 열차를 대상으로 정상 주행 중의 실내소음 특성을 비교 분석한다. 개활지, 터널 및 교량에서의 소음 레벨, 주파수 특성과 음질 지수를 분석하고, 실내 위치에 따른 소음레벨의 차이를 비교하여 소음의 전달 경로를 파악함으로써 향후 전동 열차의 실내소음 향상을 위한 기초 정보를 제공하고자 한다.