• ETRI Journal
• /
• 제44권3호
• /
• pp.379-388
• /
• 2022

This study proposes a novel low-complexity algorithm for computing inverse fast Fourier transform (IFFT)/fast Fourier transform (FFT) operations in binary phase shift keying-modulated orthogonal frequency division multiplexing (OFDM) communication systems without requiring any twiddle factor multiplications. The peak-to-average power ratio (PAPR) reduction capacity of an efficient PAPR reduction technique, that is, H-SLM method, is evaluated using the proposed IFFT algorithm without any complex multiplications, and the impact of oversampling factor for the accurate calculation of PAPR is analyzed. The power spectral density of an OFDM signal generated using the proposed multiplierless IFFT algorithm is also examined. Moreover, the bit-error-rate performance of the H-SLM technique with the proposed IFFT/FFT algorithm is compared with the classical methods. Simulation results show that the proposed IFFT/FFT algorithm used in the H-SLM method requires no complex multiplications, thereby minimizing power consumption as well as the area of IFFT/FFT processors used in OFDM communication systems.

• 대한의용생체공학회:의공학회지
• /
• 제8권1호
• /
• pp.41-48
• /
• 1987

In estimating the freguency-dependent attenuation coefficient, we analyzed the range-dependent ultrasonic beam and proposed the method of calculating the experimental equation of beam pattern in order to reduce the error on the influence of beam pattern. These experimental equations are divided into the spectral centroid and the spec ural standard deviation slope according to axial propagation length. These are repnesented by the first-order equation in the near field of the beam and the second- order eqLlatlon In the far field. In order to prove the validity of this method, the attenuation coefficients of the non-corrected ease and the corrected case are compared. Using the reflected signal from acryle plate, the attenuation coefficients were estimated by the spectral shift method ann the spectral difference method. The result shows attenuation coeffi talents after correction are better than attenuation coefficients before correction. And this method can be applied In vivo measurement.

• Journal of Oral Medicine and Pain
• /
• 제22권1호
• /
• pp.145-155
• /
• 1997

The purpose of this study was to compare differences in endurance time and EMG power spectral characteristics of the masticatory muscles during sustained isometric contraction between patients and controls. 15 CMD patients{8 women and 7 men, aged 15 to 38 years(24.1$\pm$7.5)}, and 15 healthy volunteers{8 women and 7 men, aged 15 to 30 years(24.7$\pm$3.4)} without past history or present symptoms of CMD were included in this study. Sustained isometric contractions of masticatory muscles were perfomeed as long as possible at 50% level of maximum voluntary contraction(MVC) of EMG activity via visual feedback, and the duration of sustained isometric contraction(endurance time) was examined. The author perfomed EMG power spectral analysis in the myoelectric signals of masseter and anterior temporal muscle during sustained isometric contraction in CMD patients with chronic muscle pain and healthy controls. The author came to following conclusions from the results. 1. The endurance time of the patient group was shorter than the control group in sustained isometric contraction of masticatory muscles(p<0.01). 2. MF values of masticatory muscles with sustained isometric contraction during endurance time were decreased following regression line in both groups(p<0.01, r>0.9). 3. The amount of MF shift to lower frequency range exhibited no significant differences between the patients and the control group in sustained isometric contraction during endurance time. 4. SMF to lower frequency range of the patient group was steeper than the control group in sustained isometric contraction during endurance time(p<0.05).

• Current Optics and Photonics
• /
• 제4권6호
• /
• pp.477-482
• /
• 2020

Recently, one of the authors has been reported an optically tunable fiber Bragg grating (FBG) with a photomechanical polymer. It was based on a typical FBG with a downsized diameter of 60 ㎛, coated with azobenzene-containing polymer material. Azobenzene is a well-known reversibly photomechanical stretchable material under ultraviolet (UV) light. The small part of the functional-coating region on the FBG absorbed UV light, which pulled the UV-exposed part of the grating. It was selectable as tunable FBG or tunable chirped FBG, by adjusting the position of UV exposure on the grating. As proof of concept for the tunable FBG device, the characteristics just including UV-induced center-wavelength shift and spectral-width changes of the device were reported. In this paper, we report for the first time that the microactuator makes it possible to control the spectral shape of the FBG reflection, according to the specifications (shape and intensity) of the UV beam that reaches the FBG coated with the azobenzene polymer. In addition, we provide the group-delay profiles for the chirped FBG, so that the sign of its dispersion (normal or anomalous) can be tailored by simply selecting the moving direction of the UV light's displacement in the experiment.

• Journal of Platform Technology
• /
• 제11권1호
• /
• pp.3-10
• /
• 2023

최근 Unmanned Aerial Vehicles (UAVs)은 높은 유동성 및 낮은 하드웨어 비용으로 5G, 6G 무선 통신에서 큰 관심을 받고 있다. 여전히 Blockage와 에너지 문제가 존재하지만 이러한 문제들은 Reconfigurable Intelligent Surface (RIS)를 활용하여 해결할 수 있다. 또한 RIS를 UAV 통신에 이용함으로써 신호를 받지 못하는 사용자에게 신호를 전송하여 Spectral Efficiency를 향상시키며, 에너지 소비를 줄일 수 있다. 현재 대부분의 연구들은 송신 전력과 RIS 위상을 교대로 최적화하여 Power Consumption 최소화 및 데이터 전송 Delay 최소화 등의 목적을 달성하였다. 본 논문에서는 대역폭 최적화를 포함하여 합산 정보 전달율을 최대화하는 알고리즘을 제안한다. 이에 대한 성능평가를 진행하였고, 시뮬레이션을 통해 제안한 알고리즘의 우수성을 보였다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 춘계학술대회논문집
• /
• pp.843-846
• /
• 2004

Cavity tone is generated due to the feedback between flow and acoustic wave. It is recognized that the period is determined by the time required for the flow convection in one direction, the time required for the acoustic propagation in the other direction and the time for phase shift depending on the flows and mode. Most of the phenomena have been investigated by experiments and a simple but fundamental theory. But the cause of the phase shift and the correctness of the theory have not been clearly explained so far. In this paper, the phenomena are calculated numerically to obtain detail information of flow and acoustic wave to explain the mechanism including the phase. High order high resolution scheme of optimized high order compact is used to resolve the small acoustic quantities and large flow quantities at the same time. The data are reduced using cross correlation function in space and time and cross spectral density function which has phase information. Abrupt change in pressure near corner in cavity is observed and is relate to phase variation. The time required for the feedback between the flow and acoustic wave is calculated after the numerical simulation f3r various modes. The periods based on the time calculated using the above method and direct observation from the acoustic waves generated and propagated in the numerical simulation are compared. It is found that no phase shift is required if we examine the time required carefully. Rossiter's formula for the cavity tone used for quick estimation needs to be modified far some modes.

• 한국측량학회지
• /
• 제34권2호
• /
• pp.133-142
• /
• 2016

KOMPSAT-3A (KOrea Multi-Purpose SATellite-3A) was launched in March 25 2015 with specification of 0.5 meters resolution panchromatic and four 2.2 meters resolution multi spectral sensors in 12km swath width at nadir. To better understand KOMPSAT-3A positional accuracy, this paper reports a test result on the accuracy of recently released KOMPSAT-3A beta test images. A number of ground points were acquired from 1:1,000 digital topographic maps over the target area for the accuracy validation. First, the original RPCs (Rational Polynomial Coefficients) were validated without any GCPs (Ground Control Points). Then we continued the test by modeling the errors in the image space using shift-only, shift and drift, and the affine model. Ground restitution accuracy was also analyzed even though the across track image pairs do not have optimal convergence angle. The experimental results showed that the shift and drift-based RPCs correction was optimal showing comparable accuracy of less than 1.5 pixels with less GCPs compared to the affine model.

• 대한전자공학회논문지TC
• /
• 제44권6호
• /
• pp.18-23
• /
• 2007

본 논문에서는 높은 스펙트럼 효율 및 우수한 용량을 제공할 수 있는 다중안테나 기반의 Feher-patented quadrature phase shift keying(FQPSK) 시스템을 고려한다. 매 비트 구간마다 샘플링된 복소 기저 대역 신호가 여덟 개의 위상 값만을 가진다는 사실을 이용하여 maximum likelihood sequence estimation 기법을 이용하여 FQPSK 복조를 수행하고 이를 다중 안테나 시스템으로 확장한다. 다중 안테나 FQPSK 수신기의 성능을 모의실험을 통해 분석하고, zero-forcing 수신기 및 minimum-mean-square-error 수신기에 대한 union upper bound를 구하도록 한다.

• 한국자기공명학회논문지
• /
• 제28권2호
• /
• pp.6-9
• /
• 2024

HscA is a Hsp70-type chaperone protein that plays an essential role to mediate the iron-sulfur (Fe-S) cluster biogenesis mechanism in Escherichia coli. Like other Hsp70 chaperones, HscA is composed of two domains: the nucleotide binding domain (NBD), which can hydrolyze ATP and use its chemical energy to facilitate the Fe-S cluster transfer process, and the substrate binding domain (SBD), which directly interacts with the substrate, IscU, the scaffold protein of an Fe-S cluster. In the present work, we prepared the isolated SBD construct of HscA (HscA(SBD)) and conducted the solution-state nuclear magnetic resonance (NMR) experiments to have its backbone chemical shift assignment information. Due to low spectral quality of HscA(SBD), we obtained all the NMR data from the sample containing the peptide LPPVKIHC, the HscA-interaction motif of IscU, from which the chemical shift assignment could be done successfully. We expect that this information provides an important basis to execute detailed structural characterization of HscA and appreciate its interaction with IscU.

• Advances in nano research
• /
• 제2권1호
• /
• pp.69-76
• /
• 2014

We have obtained opal-like photonic crystals based on opals and inverted opals exhibiting a shift of the selective reflection band toward longer and shorter wavelengths with respect to the diffraction band of the initial opal consisting of $SiO_2$ spheres. The contribution of frames forming three-dimensional periodic structures and that of fillers to the spectral arrangement of the diffraction bands has been determined.