• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2003.06a
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• pp.292-295
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• 2003

블루투스 전송 기술은 2.4㎓ 의 ISM(Industrial Scientific Medicine)밴드에서 주파수 호핑 방식을 사용한다. 주파수 호핑율은 연결 상태에서 초당 1600회, 조회 또는 호출 상태에서 초당 3200회의 호핑을 한다. Hop 채널 선택은 블루투스 표준안에서 제시한 5개의 호핑 시퀸스 중 하나를 선택하고 호핑 주파수에 따라 이를 매핑 함으로써 이루어진다. 본 논문에서는 6개의 상태에 따라 다르게 실행되는 채널 계산을 효율적으로 제어하고 필요한 연산모듈의 수를 줄이기 위해 9비트 프로세서를 이용해 Hop 선택 모듈을 설계하고 구현한다. 설계된 모듈은 레지스터 파일, 마이크로프로그램 제어장치, 가산, 치환(permutation), Modulo 계산을 위한 3개의 연산장치로 구성된다. Hop 채널 계산 중 가장 클럭 소요가 큰 Modulo 연산은 SRT나눗셈 알고리즘을 사용하여 음수 값 계산 및 연산 속도 향상을 꾀하였다. 제시된 Hop 선택 모듈은 하드웨어 묘사언어인 VHDL로 설계하고 시뮬레이션 및 테스트는 Xilinx FPGA를 이용해 검증하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.9
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• pp.718-726
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• 1998

J-E 특성 AC 임피더스 분석 그리고 주파수- 전도 특성들을 실험하여 임펄스 전류 서지가 ZnO 바리스터의 열화(degradation)에 미치는 영향을 고찰하였다. ZnO 바리스터 시편에 임펄스 전류(300A/$cm^24, 8/50$\mu s$)를 인가시킨 결과, 입계(grain boundary) 특성을 나타내는 비선형계수 $\alpha$와 E\ulcorner\ulcorner의 값은 크게 감소하였으나, 입자 특성을 나타내는 E_{100A}, E_{300A}$ 값에서는 큰 변화가 없었다. 이러한 열화 현상은 입계의 위치한 부성 전하 밀도, $N_s$의 감소에 한 쇼트키 장벽의 변화에 기인한 것으로 나타났다. 임펄스 서지에 의해 열화된 ZnO 바리스터는 AC 임피더스 분석에서 현저한 non-Debye 특성을 보이며, 이는 병렬 RC 네트워크로 모델링한 Cole-Cole 완화 관계식으로 입계의 열화 특성을 잘 설명할 수 있었다. 주파수-전도도 관계를 검토한 결과 Zno 바리스터는 호핑 전도(hopping conduction),\$sigma(\omega)\varpropto\omega^{\eta}$ 특성을 나타내면, 임펄스 서지가 인가된 이후 n 값이 감소하였다. 이는 임펄스 서지에 의해 입RP 결합 상태(defect states)가 호핑 전도가 발생하기 쉽고 다중(multiple)호핑에 의한 전도 메커니즘을 갖는 것으로 고찰되었다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.46-55
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• 2009

In RFID field, when the neighboring readers try to occupy the same or adjacent channel simultaneously, there exists reader-to-reader interference; it calls reader collision. From the reader collision, the tags cannot response correctly query from the reader. Reader anti-collision schemes have been developed, and particularly, the Listen-Before-Talk(LBT) scheme is proposed to avoid reader collision in ETSI in multi channel environment. However, in ETSI, there is a drawback that the reader collision does not decreases effectively because the reader selects randomly a channel without considering the channel environment and readers try to occupy the channel concurrently. In this paper, we propose a algorithm based on LBT scheme considering multi channel environment as well as made up for the drawbacks of LBT The proposed algorithm applies random backoff, the collision avoidance mechanism. And it can reduce delay because of our proposed estimation mechanism Simulation using OPNET shows that the proposed algorithm achieves higher superiority than that of the simple algorithms in sparse and dense reader mode.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.839-847
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• 2000

This paper presents modal analysis and mean conveying velocity (M.C.V.) control of bowl parts feeder activated by piezoactuators. Bowl parts feeders are being widely used in many industry fields for automatic assembly line. In general, the electromagnet has been and being used as exciting actuator of these vibratory bowl feeders. However, because of complexity of its mechanism and limited capability of the electromagnet actuator, there exist various impending problems such as severe noise, nonlinear motion of parts, passive characteristics and so forth. As one of solutions for these problems, piezoelectric actuators as new actuating technology have been proposed recently to excite the bowl parts feeder. In this paper, modal analysis of the proposed model has been performed to examine the modal characteristics of the model by using commercial FEM software and modeling with respects to MCV is constructed. Finally, MCV of the parts is to be controlled to track the desired one with PID controller.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.11
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• pp.53-60
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• 2005

In this paper, we analyze the performance of UWB MC-CDMA system and compareit with DS-CDMA and OFDM systems, which have been drafting in standardization even now. Too many Rake Fingers are needed in the DS-CDMA system to separate multi-path signals, which results in highsystem complexity. OFDM radio power fails to qualify for FCC certification unless frequency hopping. From this reason, MC-CDMA system considered is proposed in this paper. It has lower complexity compared with DS-CDMA and shows good performance against frequency selective fading. In addition, for a wide-band communication, less radio power per spectrum is allowed in the MC-CDMA system than in an OFDM system. Simulation result show that the DS-CDMA system has better performance with single user, but MC-CDMA system shows best performance in case of multi user environment.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.112-117
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• 1999

The pulsed field gradient NMR method has been used to determine self-diffusion coefficients in ternary N-alkyl-N, N-dimethylamine oxide/hydrocarbon/$D_2O$ system. For n = 12, 14, 16 and n' = 8, 10, 12, 14, 16, in the micellar phase, diffusion is chiefly governed by the hydrodynamic transport of micelles, supplemented by an exchange of solubilized hydrocarbon upon micellar collisions. This investgation is performed by variations in both the surfactant alkyl chain length and in the size of the hydrocarbon molecules. In cubic phases, the solvent still exhibits values of the diffusion coefficients which are typical for motion in a continuous water phase, with the microemulsion droplets acting as obstacle. Mobilities of the surfactant in the gel state were low and have been determined only for the surfactant($C_{12}DMAO$) with the shortest alkyl chain length. Exchange of hydrocarbon between micellar entities in the gel was found to be occured by a hopping process, the associated rate decreased with alkyl chain length of the surfactant.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.130-133
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• 2002

As a society advances, an aging phenomenon and many diseases which did not exist in old times are happening. Especially, in case of the aged patient, because we cant know the time the condition of the patients health become worse, the study of the Tele-information system has been actively carried out by the necessity of a persistent observation. A ECG signal a kind of a vital signals has been widely used to the medical information system as an usual clinical diagnosis for the patients who possess heart diseases. BlueTooth is a close range wireless communication technology which uses a wireless frequency 2.4GHz and has a high trust and self - error correction technology according to a low power consumption quality and a high-speed frequency hopping. This makes get a high trust concerning a data transmission than an existing modem. In addition, though wireless modem is restricted by a minimal of a wireless terminal, It will be possible to coincide with the function of the portable with the low power consumption quality by using Bluetooth. And as the system on a chip of module progresses, the possibility of the small size is present According to this, Bluetooth module transmits the medical information, which is input from the outside among the operations that use the Bluetooth to the Bluetooth module that is connected the host PC. And the system that the host PC transmits the medical information from the connected Bluetooth module to the Internet has once embedded. this study let the host PC embedded in advance of the existing system and transmit the medical information by the addition of the Tcp/Ip protocol stark under all embedded environments to internet.