• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.215.2-215.2
• /
• 2013

본 연구에서는 흑연(graphite)과 티타늄(titanum; Ti) 타겟이 양쪽에 부착되어 있는 비대칭 마그네트론 스퍼터링 장치를 이용하여 Ti이 도핑되어진 다이아몬드상 탄소박막(Ti doped Diamond-like carbon, DLC:Ti)을 증착하였다. 흑연과 티타늄 타겟의 파워는 고정하고 기판에 음의 DC 바이어스를 인가하여 DC 바이어스 변화에 따른 DLC:Ti 박막을 증착하였다. 증착되어진 박막의 음의 DC 바이어스의 변화에 따라 변화되어지는 경도와 마찰계수, 표면의 거칠기, 접촉각 등의 트라이볼로지 특성들을 분석하였으며, XPS와 라만등의 분석법을 이용하여 박막의 구조적 특성과 트라이볼로지 특성과의 관계를 고찰하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.79-83
• /
• 2005

SEA is a useful tool to predict noise and vibration response in high frequency region but has a weak point not to be able to express modal behavior in low frequency region. For a structure with middle subsystem having relatively higher modal density than excited subsystem and receiving subsystem, we studied the possibility that the modal behavior of receiving subsystem can express by considering finite mobility of excited subsystem. For a simply three-coupled beams which is chosen for feasibility study, the response of receiving beam was investigated with varying the length & area moment of inertia of middle beam. In case that the middle beam has relatively higher modal density than exciting beam, the application to finite mobility of excited beam led to express modal behavior of receiving beam relatively well.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.11a
• /
• pp.291-300
• /
• 2000

This paper proposes the new hybrid analysis of vibration in the medium to high frequency ranges including PFA and SEA concept. The core part of this method is the applications of coupling loss factor(CLF) instead of power transmission, reflection coefficients in boundary condition. This method shows very promising compared to the classical PFA for the various damping loss factors and wide ranges of frequencies. Besides this paper presents the applicable method in Power Flow Finite Element Method by forming the joint element matrix with CLF. These hybrid concepts are expected to improve SEA and PFA methods in vibration analysis.

• Journal of Navigation and Port Research
• /
• v.38 no.1
• /
• pp.65-71
• /
• 2014

Gyeongbu and Namhae expressways in the country, are the major arterial highways which are connected with the Busan port in the north-south and east-west directions, respectively, and required to study the traffic characteristics about the hourly volume factors(K-factor) by concentrated midium-size and large-size cargo trucks of 20% or higher in expressways. We therefore attempted to predict the K-factor in expressways through the correlation analysis between K-factor and K-factor estimates on the basis of the short-term VDS data collected at the basic segments of the above major expressways. As a result, power model appeared to be appropriate in predicting K-factor by the K-factor estimate based on VDS data for 7 days with a high explanatory power and validity.

• Journal of Sensor Science and Technology
• /
• v.3 no.3
• /
• pp.36-44
• /
• 1994

A fiber-optic temperature sensor utilizing InP as a sensing medium was implemented and tested to determine the dependance of the optical characteristics of InP on physical parameters for the use as design parameters in this type of sensors. The optical absorption coefficient of InP has been determined through the experimental measurement of the fundamental optical absorption characteristics at various temperature points. The transmission characteristics of light source at three temperature points($249^{\circ}K$, $298^{\circ}K$, $369^{\circ}K$) are computed from the optical absorption coefficient for a fixed length of InP. A series of measurement concluded that optical absorption edge moves to longer wavelength region at a speed of 0.42 nm / $^{\circ}K$ as the specimen gets hotter, and that increasing the thickness of the InP sensing layer shifts power density curve to lower temperature region.

• Journal of Korea Society of Industrial Information Systems
• /
• v.25 no.2
• /
• pp.39-47
• /
• 2020

This paper introduces a novel system-level framework that derives energy efficient electric vehicle (EV) driving speed profile to extend EV driving range without additional cost. This paper first implements an EV power train model considering forces acting on a driving vehicle and motor efficiency. Then, it derivate the minimum-energy driving speed profile for a given driving mission defined by the route. This framework first formulates an optimization problem and uses the dynamic programming algorithm with a weighting factor to derive a speed profile minimizing both of energy consumption and driving time. This paper introduces various weighting factor tracking methods to satisfy the driving time constraint. Simulation results show that runtime of the proposed scaling algorithm is 34% and 50% smaller than those of the binary search algorithm and greedy algorithm, respectively.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2017.04a
• /
• pp.166-166
• /
• 2017

모돈의 건강 상태를 정량 지수화 하기 위한 연구를 수행 중이다. 지제이상, 섭식 불량, 수면 패턴 등의 운동 특성 분석을 위하여 복수의 초음파 센서를 이용하였다. 시계열 계측 신호를 분석하여 정량 지수화를 수행하는 과정에서 주파수 도메인 분석을 시도하였다. 이 과정에서 주파수 도메인의 분해능에 따른 편차 극복을 위한 비선형 모델링을 수행하였다. 또한 인접한 시계열 데이터 구간 간의 상관성 분석이 가능하면 대용량 데이터의 실시간 처리로 인한 지연 시간 극복 및 기대되는 예후에 대한 조기 진단이 가능할 것이다. 본 연구에서는 구글에서 제공하는 Tensorflow와 NVIDIA에서 제공하는 CUDA 엔진을 동시 적용한 심층 학습 시스템을 이용하였다. 전 처리를 위하여 주파수 분해능 (2분, 3분, 5분, 7분, 11분, 13분, 17분, 19분)에 따른 데이터 집합을 1단계로 두고, 상위 10 순위 안에 드는 파워 스펙트럼 밀도의 크기를 2단계로 하여, 총 2~10개의 입력 노드를 순차적으로 선정하였고, 동일한 방식으로 인접한 시계열의 파워 스펙터럼 밀도를 순위를 변화시켜 지정하였다. 대표적인 심층학습 모델인 Softmax regression with a multilayer convolutional network를 이용하여 Recursive feature selection 경우의 수를 $8{\times}9{\times}9$로 총 648 가지 선정하고, Epoch는 10,000회로 지정하였다. Calibration 모델링의 경우 Cost function이 10% 이하인 경우 해당 경우의 학습을 중단하였으며, 모델 간 상호 교차 검증을 수행하기 위하여 $_8C_2{\times}_8C_2{\times}_8C_2$ 경우의 수에 대한 Verification test를 수행하였다. Calibration 과정 상 모든 경우에 대하여 10% 이하의 Cost function 값을 보였으나, 검증 테스트 과정에서 모든 경우에 대하여 $r^2$ < 0.5 인 결정 계수 값이 나타났다. 단적으로 심층학습 모델의 과도한 적합(Over fitting) 방식의 한계를 보인 것이라 판단할 수 있다. 적합한 Feature selection 및 심층 학습 모델에 대한 지속적이고 추가적인 고려를 통해 과도적합을 해소함과 동시에 실효적이고 활용 가능한 Classification을 위한 입, 출력 노드 단의 전후 Indexing, Quantization에 대한 고려가 필요할 것이다. 이를 통해 모돈 생체 정보 정량화를 위한 지능형 현장 진단 기술 연구를 지속할 것이다.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.15 no.3
• /
• pp.527-532
• /
• 2020

In this paper, we presented the results of analysis through EEG measurement for the purpose of checking the frequency band of EEG signals that can be used for personal authentication. The measurement status was divided into the open-eye state and the closed-eye state depending on the presence or absence of an optical task. The data measured in the EEG experiments was divided into seven frequency bands : delta waves, theta waves, alpha waves, SMR waves, mid-beta waves, beta waves and gamma waves to identify the frequency band with the smallest power fluctuation over time. In our results, there was no significant difference between the open-eye state and the closed-eye state, and the SMR waves and mid-beta waves related to human concentration had the smallest fluctuation in power over time, and were a highly reproducible frequency band.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.2
• /
• pp.82-92
• /
• 2008

Recently, many digital signal processing(DSP) applications such as H.264, CDMA and MP3 are predominant tasks for modern high-performance portable devices. These applications are generally computation-intensive, and therefore, require quite complicated accelerator units to improve performance. Designing such specialized, yet fixed DSP accelerators takes lots of effort. Therefore, DSPs with multiple accelerators often have a very poor time-to-market and an unacceptable area overhead. To avoid such long time-to-market and high-area overhead, dynamically reconfigurable DSP architectures have attracted a lot of attention lately. Dynamically reconfigurable DSPs typically employ a multi-functional DSP accelerator which executes similar, yet different multiple kinds of computations for DSP applications. With this type of dynamically reconfigurable DSP accelerators, the time to market reduces significantly. However, integrating multiple functionalities into a single IP often results in excessive control and area overhead. Therefore, delay and power consumption often turn out to be quite excessive. In this thesis, to reduce power consumption of dynamically reconfigurable IPs, we propose a novel fine-grained clock gating scheme, and to reduce size of dynamically reconfigurable IPs, we propose a compact multiplier-less multiplication unit where shifters and adders carry out constant multiplications.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.9
• /
• pp.15-22
• /
• 2000

The effects of carrier transport and input power on the extinction ratio was theoretically analyzed in a 1.55${\mu}m$ InGaAsP/InGaAsP multiple-quantum-well(MQW) electroabsorption(EA) modulator. Poisson's equation, current continuity equations for electrons and holes, and optical field distribution were self-consistently solved by considering electric field dependent absorption coefficients. The field screening effect due to the carrier accumulation in heterointerface and the space-charge region occurred more seriously at the input side of modulator as input optical intensity increased. It was revealed that extinction ratio could be steeply degraded for modulator with the length of 200${\mu}m$ when an input power exceeds 10mW. A degradation of extinction ratio due to the field screening effect would be more significantly at high-performance devices such as a 1.55${\mu}m$DFB-LD/EA-modulator integrated source where optical coupling efficiency is almost complete or a very high-speed modulator with its length as short as a few tens ${\mu}m$.