• 한국통신학회논문지
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• 제36권10B호
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• pp.1200-1209
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• 2011

본 논문에서는 수중환경에서의 거리에 따른 전파 손실 특성을 이용한 직교 주파수 분할 다중 접속 방식(Orthogonal Frequency Division Multiple Access, OFDMA) 기반의 새로운 에너지 효율적인 매체 접속 제어(Medium Access Control, MAC) 프로토콜을 제안한다. 제안하는 방식은 센서 노드들을 싱크 노드를 중심으로 싱크 노드와의 거리에 따라 그룹을 나눈 후, 그룹에 서로 다른 주파수 대역을 각각 할당하여 사용하도록 한다. 이러한 방식으로 네트워크 전체의 전송 전력 소모를 줄이고 각 센서 노드에게 최소 허용 신호 대 잡음비 (Accepted Minimum SNR, AMS)를 보장한다. 추가적으로 싱크 노드는 동적 인 부채널 할당 (dynamic sub-channel allocation)으로 데이터 전송률을 향상한다. 모의실험을 통해 제안하는 매체 접속 제어 프로토콜의 수중 센서 네트워크에서의 성능을 확인할 수 있었다.

• 방사선산업학회지
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• 제17권4호
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• pp.397-403
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• 2023

The purpose of this study is to obtain brain MRI images through Heavenly T₂ FLAIR and DWI techniques to find out strengths and weaknesses of each image. Data were analyzed on 13 normal people and 17 brain tumor patients. Philips Ingenia 3.0TCX was used as the equipment used for the inspection, and 32 Channel Head Coil was used to acquire data. Using Image J and Infinity PACS Data, 3mm² of gray matter, white matter, cerebellum, basal ganglia, and tumor areas were set and measured. Quantitative analysis measured SNR and CNR as an analysis method, and qualitative analysis evaluated overall image quality, lesion conspicuity, image distortion, susceptibility artifact and ghost artifact on a 5-point scale. The statistical significance of data analysis was that Wilcox-on Signed Rank Test and Paired t-test were executed, and the statistical program used was SPSS ver.22.0 and the p value was less than 0.05. In quantitative analysis, the SNR of gray matter, white matter, cerebellum, basal ganglia, and tumor of Heavily T₂ FLAIR is 41.45±0.13, 40.52±0.45, 41.44±0.51, 40.96±0.09, 35.28±0.46 and the CNR is 15.24±0.13, 16.75±0.23, 16.28±0.41, 15.83±0.17, 16.63±0.51. In DWI, SNR is 32.58±0.22, 36.75±0.17, 30.21±0.19, 35.83±0.11, 43.29±0.08, and CNR is 13.14±0.63, 14.21±0.31, 12.95±0.32, 11.73±0.09, 17.56±0.52. In normal tissues, Heavenly T₂ FLAIR obtained high results, but in disease evaluation, high results were obtained at DWI, b=1000 (p<0.05). In addition, in the qualitative analysis, overall image quality, lesion conspicuity, image distortion, susceptibility artifact and ghost artifact aspects of the Heavily T₂ FLAIR were evaluated, and 3.75±0.28, 2.29±0.24, 3.86±0.23, 4.08±0.21, 3.79±0.22 values were found, respectively, and 2.53±0.39, 4.13±0.29, 1.90±0.20, 1.81±0.21, 1.52±0.45 in DWI. As a result of qualitative analysis, overall image quality, image distortion, susceptibility artifact and ghost artifact were rated higher than DWI. However, DWI was evaluated higher in lesion conspicuity (p<0.05). In normal tissues, the level of Heavenly T₂ FLAIR was higher, but the DWI technique was higher in the evaluation of the disease (tumor). The two results were necessary techniques depending on the normal site and the location of the disease. In conclusion, statistically significant results were obtained from the two techniques. In quantitative and qualitative analysis, the two techniques had advantages and disadvantages, and in normal and disease evaluation, the two techniques produced useful results. These results are believed to be educational data for clinical basic evaluation and MRI in the future.

• 한국전자파학회논문지
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• 제19권6호
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• pp.669-676
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• 2008

MIMO-OFDMA 시스템에서 자원 할당의 최적화 문제가 거론되고 있다. 본 논문은 SFC 방식 아래 채널에 대한 정보를 가지고 적응 변조 및 부호 기법과 전력 제어 기법을 적용하여 전체 시스템 처리량의 최대화에 목표를 두었다. 첫 번째로 수신 받은 채널에 대한 정보를 기반으로 각 서브 채널의 전력 레벨이 결정된다. 그 다음으로는 변조 타입에 맞게 서브캐리어가 할당되어진다. 시뮬레이션 결과는 실제로 전송되어진 데이터 용량 측면에서 기존의 알고리즘보다 제안한 알고리즘이 더 나은 성능을 보인다.

• Molecules and Cells
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• 제22권2호
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• pp.198-202
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• 2006

The $P2X_7$ receptor, an ATP-gated cation channel, induces cell death in immune cells and is involved in neurodegenerative diseases. Although the receptor plays various roles in these diseases, the cellular mechanisms involved are poorly understood and antagonists are limited. Here, the development of a cell-based assay for human $P2X_7$ receptor is reported. We established permanent lines of HEK 293 cells expressing a high level of $hP2X_7$ receptor. Functional activity of the $hP2X_7$ receptor was confirmed by whole-cell patch recording of ATP-induced ion currents. Prolonged exposure to ATP resulted in death of the $hP2X_7$-expressing HEK 293 cells and this cell death could be quantified. Two known $P2X_7$ antagonists, PPADS and KN-62, blocked ATP-induced death in a concentration-dependent manner. Thus, this assay can be used to screen for new antagonists of $hP2X_7$ receptors.

• 대한전자공학회논문지SD
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• 제41권10호
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• pp.17-22
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• 2004

본 논문에서는 진폭 변조와 펄스 폭 변조를 모두 사용하는 새로운 AMOLED 디스플레이 구동 방식을 개발하였다. 펄스 폭 변조를 위해서 다섯 개의 서브 프레임으로 화상 프레임을 나누었고 진폭 변조를 위해 TFT 게이트 전압에 의해 제어되는 3가지의 OLED 휘도(전류) 레벨을 사용하였다. 이 두 종류의 변조를 조합하여 35(=243) 계조를 얻었다. 그리고 DAC를 사용하지 않고 2개의 쉬프트 레지스터를 갖는 새로운 데이터 전극 구동 회로를 설계하였다. 회로 동작은 6㎛ 채널 길이 다결정 TFT의 전류-전압 특성에서 추출된 TFT 파라미터를 이용한 HSpice 시뮬레이션을 통하여 검증하였다. 시뮬레이션 결과로부터 320×240, 이중 스캔, 243 계조 AMOLED 디스플레이를 구현할 수 있음을 확인하였다.

• Natural Product Sciences
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• 제19권2호
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• pp.179-185
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• 2013

Polygalae radix (PR) has traditionally been used as a sedative and anti-stress agent in oriental countries for a long time. PR which contains many ingredients is especially rich in saponins. This study was performed to investigate whether ethanol extract of PR enhances pentobarbital-induced sleep behaviors. In addition, possible mechanisms also were investigated. PR inhibited locomotor activity in mice. PR increased sleep rate and sleep time by concomitant administration with sub-hypnotic dose of pentobarbital (28 mg/kg). PR prolonged total sleeping time, and shortened sleep latency induced by pentobarbital (42 mg/kg). In addition, PR increased intracellular chloride concentration in primary cultured neuronal cells. The expression level of glutamic acid decarboxylase (GAD) were increased, and ${\gamma}$-aminobutyric acid $(GABA)_A$ receptors subunits were modulated by PR, especially increasing ${\gamma}$-subunit expression. In conclusion, PR augments penobarbital-induced sleep behaviors through activation of $GABA_A$ receptors and chloride channel complex.

• ETRI Journal
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• 제39권2호
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• pp.255-263
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• 2017

This paper proposes a graph-theatrical approach to optimize spatial reuse by adopting a technique that quantizes the channel information into single bit sub-messages. First, we introduce an interference graph to model the network topology. Based on the interference graph, the computational requirements of the algorithm that computes the optimal spatial reuse factor of each user are reduced to quasilinear time complexity, ideal for practical implementation. We perform a resource allocation procedure that can maximize the efficiency of spatial reuse. The proposed spatial reuse scheme provides advantages in beamforming systems, where in the interference with neighbor nodes can be mitigated by using directional beams. Based on results of system level measurements performed to illustrate the physical interference from practical millimeter wave wireless links, we conclude that the potential of the proposed algorithm is both feasible and promising.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.389-393
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• 2003

This paper describes the design of enhanced TSSI RF Power Detector which has wide dynamic range using switch and Log amp. This Power Detector consists of low and high gain loops, and they adaptively switched by output DC voltage which is proportioned to input power level. Because Power Detector needs to separate the channel, so architecture is heterodyne system having 70MHz intermediate frequency. This proposed RF Power Detector is settle to the satisfaction of Closed loop power control system for W-CDMA optic repeater, and the obtained dynamic range cover the higher than 50dB.

• 한국전기전자재료학회논문지
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• 제28권5호
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• pp.291-294
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• 2015

Recently, ZnO based oxide TFTs used in the flexible and transparent display devices are widely studied. To apply to OLED display switching devices, electrical performance and stability are important issues. In this study, to improve these electrical properties, we fabricated TFTs having Al doped Zinc Oxide (AZO) layer inserted between the gate insulator and ZnO layer. The AZO and ZnO layers are deposited by Atomic layer deposition (ALD) method. I-V transfer characteristics and stability of the suggested devices are investigated under the positive gate bias condition while the channel defects are also analyzed by the photoluminescence spectrum. The TFTs with AZO layer show lower threshold voltage ($V_{th}$) and superior sub-threshold slop. In the case of $V_{th}$ shift after positive gate bias stress, the stability is also better than that of ZnO channel TFTs. This improvement is thought to be caused by the reduced defect density in AZO/ZnO stack devices, which can be confirmed by the photoluminescence spectrum analysis results where the defect related deep level emission of AZO is lower than that of ZnO layer.

• 대한의용생체공학회:의공학회지
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• 제36권3호
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• pp.61-68
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• 2015

In this paper, we studied the effects of intersection angles of the flow-foucusing type droplet generation device inlet channel on droplet diameter using numerical simulation modeling. We modeled different intersection angles with a fixed continuous channel width, dispersed channels width, orifices width, and expansion channels width. Numerical simulations were performed using COMSOL Multiphysics$^{(R)}$ to solve the incompressible Navier-Stokes equations for a two-phase flow in various flow-focusing geometries. Modeling results showed that an increase of the intersection angle causes an increase in the modification of the dispersed flow rate ($v^{\prime}{_d}$), and the increase of the modification of the continuous flow rate ($v^{\prime}{_c}$) obstructs the dispersed phase fluid flow, thereby reducing the droplet diameter. However, the droplet diameter did not decrease, even when the intersection angle increased. The droplet diameter decreased when the intersection angle was less than $90^{\circ}$, increased at an intersection angle of $90^{\circ}$, and decreased when the intersection angle was more than $90^{\circ}$. Furthermore, when the intermediate energy deceased, there was a decrease in the droplet diameter when the intersection angle increased. Therefore, variations in the droplet diameter can be used to change the intersection angle and fluid flow rate.