• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.211.2-211.2
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• 2014

Epitaxial complex oxide thin film heterostructures have attracted a great attention for their multifunctional properties, such as ferroelectricity, and ferromagnetism. Two dimensional electron gas (2DEG) confined at the interface between two insulating perovskite oxides such as LaAlO3/SrTiO3 interface, provides opportunities to expand various electronic and memory devices in nano-scale. Recently, it was reported that the conductivity of 2DEG could be controlled by external electric field. However, the switched conductivity of 2DEG was not stable with time, resulting in relaxation due to the reaction between charged surface on LaAlO3 layer and atmospheric conditions. In this report, we demonstrated a way to control the conductivity of 2DEG in non-volatile way integrating ferroelectric materials into LAO/STO heterostructure. We fabricated epitaxial Pb(Zr0.2Ti0.8)O3 films on LAO/STO heterostructure by pulsed laser deposition. The conductivity of 2DEG was reproducibly controlled with 3-order magnitude by switching the spontaneous polarization of PZT layer. The controlled conductivity was stable with time without relaxation over 60 hours. This is also consistent with robust polarization state of PZT layer confirmed by piezoresponse force microscopy. This work demonstrates a model system to combine ferroelectric material and 2DEG, which guides a way to realize novel multifunctional electronic devices.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(4)
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• pp.21-24
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• 2001

In this paper, we present a fast face detection algorithm by estimating the eye region using neural network. To implement a real time face detection system, it is necessary to reduce search space. We limit the search space just to a few pairs of eye candidates. For the selection of them, we first isolate possible eye regions in the fast and robust way by modified histogram equalization. The eye candidates are paired to form an eye pair and each of the eye pair is estimated how close it is to a true eye pair in two aspects : One is how similar the two eye candidates are in shape and the other is how close each of them is to a true eye image A multi-layer perceptron neural network is used to find the eye candidate region's closeness to the true eye image. Just a few best candidates are then verified by eigenfaces. The experimental results show that this approach is fast and reliable. We achieved 94% detection rate with average 0.1 sec Processing time in Pentium III PC in the experiment on 424 gray scale images from MIT, Yale, and Yonsei databases.

• 대한기계학회논문집A
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• 제28권10호
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• pp.1541-1548
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• 2004

A nano-stage simulation tool is developed for an advanced E-beam lithography system. Even if piezo-actuators are believed to be compatible fer the E-beam lithograpy system it is difficult to predict their characteristics due to their nonlinearities such as hysteresis and creep. In this paper, the nonlinear properties are modeled for a piezo-actuator by considering the voltage range and speed variations. The hysteresis is described as the first order differential equation with 24 sets of parameters and the creep is modeled as a time-dependent logarithmic function with 2 sets of a parameter. A two-axis nano stage with piezo-actuators are investigated for realizing nano scale motions. The characteristics of flexure guide mechanisms are analyzed based on the finite element method using the ANSYS software. The simulation tool for the nano stage is constructed by using the RecurDyn software. The dynamic response of the nano stage is obtained in simulations and compared with the experimental data.

• 한국전문물리치료학회지
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• 제28권2호
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• pp.101-107
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• 2021

Background: Studies suggest that induced emotional changes can affect the sensory-motor system involved in the practice of muscle activity and movement in physical aspects. Previous studies have shown focused on effects just feedback on muscle activity associated with emotions but rarely have focused induced emotional change on gross motor function such as muscle activity. Objects: The purpose of this study was to compare biceps activity and emotion that before and after viewing a video was induced positive or negative emotion. Methods: The study enrolled 34 healthy male and female who scored at normal points on the Center for Epidermiological Studies-Depression Scale. The study measured over two weeks, showing subjects pleasant and sad videos one by one in a week. We performed to measure the biceps brachii activity which is maximal voluntary isometric contraction (MVIC) and the visual analog mood scale (VAMS) scores before and after one week. The significance level was set to α = 0.05. Results: There was no significant difference in muscle activity of the biceps brachii before and after each video was viewed (p > 0.05). However, the visual analogue mood scale showed an increase in VAMS after viewing each video (p < 0.05). Conclusion: We figured out induced emotional changes are cause actual emotional changes but there are no differences in muscle activity. In this research, watching the video with a short time looks like insufficient to change muscle activity. Nevertheless, there might be different when we check various muscles with sufficient time for viewing the video. Further study is needed to measure a variety of muscles with more time for viewing the video.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권8호
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• pp.2993-3010
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• 2021

The job shop scheduling problem (JSSP) plays a critical role in smart manufacturing, an effective JSSP scheduler could save time cost and increase productivity. Conventional methods are very time-consumption and cannot deal with complicated JSSP instances as it uses one optimal algorithm to solve JSSP. This paper proposes an effective scheduler based on deep learning technology named self-supervised long-short term memory (SS-LSTM) to handle complex JSSP accurately. First, using the optimal method to generate sufficient training samples in small-scale JSSP. SS-LSTM is then applied to extract rich feature representations from generated training samples and decide the next action. In the proposed SS-LSTM, two channels are employed to reflect the full production statues. Specifically, the detailed-level channel records 18 detailed product information while the system-level channel reflects the type of whole system states identified by the k-means algorithm. Moreover, adopting a self-supervised mechanism with LSTM autoencoder to keep high feature extraction capacity simultaneously ensuring the reliable feature representative ability. The authors implemented, trained, and compared the proposed method with the other leading learning-based methods on some complicated JSSP instances. The experimental results have confirmed the effectiveness and priority of the proposed method for solving complex JSSP instances in terms of make-span.

• Advances in aircraft and spacecraft science
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• 제8권1호
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• pp.69-85
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• 2021

A modified fuzzy mechanical control of large-scale multiple time delayed dynamic systems in states is considered in this paper. To do this, at the first level, a two-step strategy is proposed to divide a large system into several interconnected subsystems. As a modified fuzzy control command, the next was received as feedback theory based on the energetic function and the LMI optimal stability criteria which allow researchers to solve this problem and have the whole system in asymptotically stability. Modeling the Fisher equation and the temperature gauge for high-speed aircraft and spacecraft shows that the calculation method is efficient.

• 제어로봇시스템학회논문지
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• 제21권1호
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• pp.1-6
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• 2015

This paper investigates the longitudinal flight dynamics and stability of flapping-wing micro air vehicles. Periodic external forces and moments due to the flapping motion characterize the dynamics of this system as NLTP (Non Linear Time Periodic). However, the averaging theorem can be applied to an NLTP system to obtain an NLTI (Non Linear Time Invariant) system which allows us to use a standard eigen value analysis to assess the stability of the system with linearization around a reference point. In this paper, we investigate the dynamics and stability of a hawkmoth-scale flapping-wing air vehicle by establishing an LTI (Linear Time Invariant) system model around a hovering condition. Also, a direct time integration of full nonlinear equations of motion of the flapping-wing micro air vehicle is conducted to see how the longitudinal flight dynamics appear in the time domain beyond the reference point, i.e. hovering condition. In the study, the flapping-wing air vehicle exhibited three distinct dynamic modes of motion in the longitudinal plane of motion: two stable subsidence modes and one unstable oscillatory mode. The unstable oscillatory mode is found to be a combination of a pitching velocity state and a forward/backward velocity state.

• 전자공학회논문지SC
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• 제46권1호
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• pp.28-33
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• 2009

음성 인식 연구에서 잡음이 존재하는 음성 발음의 처음과 끝을 찾아내는 것은 매우 중요하다. 음성 종점 탐지를 위한 기존의 방식으로는 2개의 간단한 시간 영역 측정법인 단시간 에너지와 단시간 영점교차 비율 방법이 있다. 위의 방법들은 낮은 신호 대 잡음비의 환경에서는 정확한 결과를 보장 할 수 없기 때문에 본 논문에서는 시간 영역 파형의 리아프노프 지수를 이용하여 음성의 시작과 종점을 구별하는 새로운 접근법을 제시하였다. 제안한 방법은 Mel-Scale특징 방법에서 요구되는 종점 탐지 과정을 위한 주파수 영역 매개변수를 얻는 과정이 필요 없기 때문에 보다 간단하다. 제안한 방법의 성능 검증을 위해 아라비아 숫자의 음성단어 분석에 적용해 보았으며, 결과를 통하여 제안한 방법이 인식률을 현저히 증가시킴을 확인하였다.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제8권2호
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• pp.35-40
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• 2019

기존 악성코드 탐지는 다형성 또는 난독화 기법이 적용된 변종 악성코드 탐지에 취약하다. 기계학습 알고리즘은 악성코드에 내재된 패턴을 학습시켜 유사 행위 탐지가 가능해 기존 탐지 방법을 대체할 수 있다. 시간에 따라 변화하는 악성코드 패턴을 학습시키기 위해 지속적으로 데이터를 수집해야한다. 그러나 대용량 악성코드 파일의 저장 및 처리 과정은 높은 공간과 시간 복잡도가 수반된다. 이 논문에서는 공간 복잡도를 완화하고 처리 시간을 가속화하기 위해 HDFS 기반 분산 처리 시스템을 설계한다. 분산 처리 시스템을 이용해 2-gram 특징과 필터링 기준에 따른 API 특징 2개, APICFG 특징을 추출하고 앙상블 학습 모델의 일반화 성능을 비교했다. 실험 결과로 특징 추출의 시간 복잡도는 컴퓨터 한 대의 처리 시간과 비교했을 때 약 3.75배 속도가 개선되었으며, 공간 복잡도는 약 5배의 효율성을 보였다. 특징 별 분류 성능을 비교했을 때 2-gram 특징이 가장 우수했으나 훈련 데이터 차원이 높아 학습 시간이 오래 소요되었다.

• KSBB Journal
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• 제6권2호
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• pp.135-141
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• 1991

This study thus looks into two treatment processess : i) Anaerobic digester coupled with hollow fibre membrane unit. Treatment of starch waste with anaerobic digester-membrane system was studied. $0.17\m^2$ area of hollow fibre membrane unit of known pore size was immersed into laboratory-scale anaerobic digestion system. The pore size of membrane was varied from 0.03 to $\0.15mu$m. The hydraulic retention time of anaerobic digester was varied from 1.5 to 10 days. The effect of hydraulic retention time on treatment efficiency was significant while effect of membrane size was not significant. The gas production was about 0.74㎥/kg COD treated. The COD removal efficient was about 80-95% depending on the hydraulic retention time. ii ) Crossflow ultrafiltration as post treatment to anaerobic filter. The effluent from anaerobic filter, which had a total COD in the range of 4,500-5,200 mg/L was treated by crossflow ultrafiltration units. The study conducted with different membrane pore size indicated that membrace with 1,000,000 molecular weight cut-off size gave a higher COD removal efficiency in the range of 83-87% while giving a study flux of $120-130 L/\m^2$.h. A study was conducted to see the long term clogging effect of membrane also.