• Journal of Mechanical Science and Technology
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• 제16권5호
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• pp.633-638
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• 2002

An approach to enhance dimensional accuracy of the grinding process has been presented, and grinding of a glass material with a metal-bonded diamond wheel has been studied. In this study, a grinding tool is suspended flexibly and controlled by an electromagnetic actuator. During grinding, profile error of a ground surface is indirectly measured and fed back to a control system. A model of grinding error has been suggested on which the indirect measurement has been based. An optimal PID control is adopted and effectiveness of the in-process feedback control has been verified experimentally.

• 한국컴퓨터그래픽스학회논문지
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• 제9권1호
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• pp.19-27
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• 2003

Most interaction schemes in virtual environment are indirect in one way or another. ln particular, without a haptic device (which introduces its own problems due to its cumbersomeness), users must rely on visual (or/and aural) feedback, and can not directly appreciate the 3Dness of the interaction object even with stereoscopy. This causes a drop in object presence because people are used to, for instance, observing objects in one's hand, rotating and manipulating them with physical contact. To alleviate this problem, this paper proposes a hand-held cubic screen, named TangibleScreen, on which the appearance of the target interaction object is projected. We choose the Relief Texture Mapping as the rendering method to correctly generate the viewer dependent textures to be projected on the non-planar surfaces of the TangibleScreen.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제6권1호
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• pp.52-57
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• 2006

In this paper, we have proposed a new adaptive fuzzy control algorithm based on Takagi-Sugeno fuzzy model. The regulation problem for the uncertain SISO nonlinear system is solved by the proposed algorithm. Using the advanced stability theory, the stability of the state, the control gain and the parameter approximation error is proved. Unlike the existing feedback linearization based methods, the proposed algorithm can guarantee the global stability in the presence of the singularity in the inverse dynamics of the plant. The performance of the proposed algorithm is demonstrated through the problem of balancing and swing-up of an inverted pendulum on a cart.

• 한국소프트웨어감정평가학회 논문지
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• 제15권2호
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• pp.129-140
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• 2019

In the IoT environment, there is a huge amount of heterogeneous devices with limited capacity. Existing trust evaluation methods are not adequate to accommodate this requirement due to the limited storage space and computational resources. In addition, since IoT devices are mainly human operated devices, the trust evaluation should reflect the social relations among device owners. There is also a need for a mechanism that reflects the tendency of the trustor and environmental factors. In this paper, we propose an adaptable trust evaluation method for SOA-based IoT system to deal with these issues. The proposed model is designed to minimize the confidence bias and to dynamically respond to environmental changes by combining direct evaluation and indirect evaluation. It is expected that it will be possible to secure trust through quantitative evaluation by providing feedback based on social relationships.

• 한국지구과학회지
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• 제44권6호
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• pp.578-593
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• 2023

2017년 7월 15일 서울과 수도권에 집중호우를 발생시킨 깊은 대류운과 강수 발달에 대한 종관 기상 메커니즘을 규명하고 중국 동부지역으로부터의 PM_2.5 에어로졸의 간접효과를 WRF-Chem 실험을 통해 분석하였다. WRF-Chem 모델에 에어로졸과 복사의 피드백, 구름 화학 과정, 습식 세정을 모두 포함한 ARI (Aerosol Radiation Interaction) 실험과 에어로졸과 복사의 피드백을 제외하고 구름 화학 과정, 습식 세정만을 포함한 ACR (Aerosol Cloud Radiation interaction) 실험 결과의 차이로부터 PM_2.5 에어로졸 간접효과를 산출하였다. 2017년 7월 15일 새벽에 황해와 한반도에서는 동아시아 대륙에서 저기압-북서 태평양의 고기압 분포로 인해 중국 남동 지역과 동중국해로부터 덥고 습한 기류가 수렴하고 있었다. 이러한 황해의 종관 기상에 의해 발달하는 대류운은 높이 12 km 이상이며 고체 수상체를 형성하고 있었는데, 이는 주로 대륙 위에서 발달하는 한랭운(많은 빙정을 형성하며 운정고도가 8 km 이상)의 특성을 나타내고 있었다. 특히, WRF-Chem 모델 실험을 통해 중국 동부지역으로부터 확산하는 PM_2.5 에어로졸이 구름물 형성에 5.7%, 고체 수상체 형성에 10.4%, 그리고 액체 수상체 형성에 10.8%로 대류운이 한랭운으로 발달하는 데 기여하고 있었다. 본 연구는 황해 위에서 깊은 대류운이 발달하는 과정에 대한 기상적 메커니즘과 더불어 중국 동부지역으로부터 에어로졸에 의한 간접효과의 영향을 제시하였다.

• Restorative Dentistry and Endodontics
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• 제26권2호
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• pp.134-140
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• 2001

The polymerization shrinkage of composite resins is an important drawback although the composites have many advantages-more esthetic and conservative than metallic restoratives etc. The purposes of this research were to develop a new measurement method and to manufacture an instrument that can measure the initial dynamic volumetric shrinkage of composite resins during polymerization. The instrument was basically an electromagnetic balance that constructed with a force transducer using position sensitive photo detector(PSPD) and a negative feedback servo amplifier of proportional-derivative(PD) controller. The volumetric change of composites during polymerization was detected continuously as buoyancy change in distilled water by means of Archimedes's principle. It was converted to continuous electrical voltage signal in real time. The signal was properly conditioned and filtered and then it was stored in computer by a data acquisition(DAQ) board. By using this electronic instrument. the dynamic patterns of the polymerization shrinkage of eight commercial(Z-100, DenFil, AeliteFil, Z-250, P-60, SureFil, Synergy compact, and Tetric ceram) composite resins were measured and compared. The results were as follows. 1. From this project of developing instrument, the ability has been achieved that can acquire and process data of electrical signal transformed from various physical phenomenon by using temperature, displacement. photo. and force transducer. As a consequence, the instrumentation and measurement system used to analyze the physical characteristics of various dental materials in dental research field can be designed, manufactured and implemented in lab. 2. This instrument has some advantages. It was insensible to temperature change and could measure true dynamic volumetric shrinkage in real time without complicated process. It showed accuracy and high precision results with small standard deviation. 3. The polymerization shrinkage of composites was significantly different between brands and ranged from 2.47％ to 3.89％, The order of polymerization shrinkage was as follows, in order of increasing shrinkage, SureFil, P60, Z250, Z100, Synergy compact. DenFil, Tetric ceram, and AeliteFil. 4. The polymerization shrinkage rate per unit time, dVol％/dt, showed that the instrument can provide an indirect research method for polymerization reaction kinetics.

• 디지털융복합연구
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• 제18권9호
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• pp.49-56
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• 2020

본 연구의 목적은 플립러닝 모형을 적용한 영어수업에서의 글쓰기 과제에 대한 오류수정 피드백이 학습자의 영어 성취도에 어떠한 영향을 미치는지를 파악하고, 수업 만족도에 영향을 미치는 요인이 무엇인지를 규명하는 것이다. 본 연구를 위해 수업 만족도를 예측하는 요인으로 오류수정 피드백에 대한 반응과 감정을 선정하고, 이들의 예측력을 규명하였다. 연구 참여자들은 94명의 대학생으로 두 개의 집단인 플립러닝을 적용한 실험집단 48명과 전통적 교수법을 적용한 통제집단 46명으로 나누어 평가시험과 글쓰기 과제를 사전·사후로 실시하고, 수업 처치 후 실험집단을 대상으로 설문조사를 진행하였다. 연구 결과를 살펴보면, 플립러닝을 기반으로 한 수업 방법이 학습자의 영어 성취도 향상에 유의미한 영향을 미치는 것으로 나타났으며, 오류수정 피드백에 대한 반응과 감정 모두 수업 만족도를 유의미하게 예측하는 것으로 나타났다. 이러한 결과를 근거로, 본 연구에서는 플립러닝형 수업의 효율적인 운영을 위한 방안을 제안하고자 한다.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.169-178
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• 2021

본 연구는 간호대학생의 정신간호학실습에 대한 교내실습 경험을 탐색하기 위한 질적 연구이다. 연구대상자는 강원도 소재 일 대학교에서 정신간호를 실습하는 3학년 학생 62명으로, 자료수집 기간은 2020.08.03.~08.20까지였다. 수집된 자료는 Colaizzi의 방법을 적용하여 분석하였다. 연구 결과 1) 현장경험에 대한 아쉬움 2) 배움을 통한 성취 3) 미래 간호사 역할에 대한 두려움 4) 과제 작성에 대한 부담감 5) 임상 긴장감으로부터 자유로움 6) 타 부서와의 협력의 중요성의 6가지 범주가 도출되었다. 교내실습 평가에서는 즉각적 피드백과 자세한 설명, 간접 체험의 내용이 긍정적으로 평가되었다. 이를 바탕으로 향후 교내실습의 효과적 운영을 위해서는 시뮬레이션 실습을 포함하여, 간접 체험실습, 온라인/비대면 실습, 대면실습 등의 다양한 콘텐츠가 적절히 활용되어 임상실습과의 격차를 줄이는 효율적 프로그램의 개발이 필요하다. 더불어 정신간호학 실습 교육에서는 치료적 의사소통 및 환청 중재와 같은 실무의 격차를 줄이기 위한 다각적 노력이 더욱 필요함을 제언하는 바이다.

• Journal of Ship and Ocean Technology
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• 제11권1호
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• pp.36-46
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• 2007

The maintenance of a ship is essential for safe navigation and hence regular surveys are prescribed according to the rule of classification societies. A hull inspection is generally performed by professional divers, but it takes a long time and the efficiency is low in terms of time and cost. In this research, a ROV(Remotely Operated Vehicle) named as SNU-ROV(Seoul National University-ROV) is developed to replace the conventional inspection method. In this system, the ROV is intended to be used for inspecting ship and harbor because harbor inspection is merging as a safety measure against any possible terror actions. In order to increase the efficiency of inspection, the ROV must be able to measure the exact position of damages. SNU-ROV has a positioning system based on LBL(Long Base Line). In shallow water such as harbor, however, LBL has bad DOP(Dilution of Precision) in the depth direction due to the limited depth. Thus LBL only can not locate the exact depth position. To solve the DOP problem, a pressure sensor is introduced to LBL and a complementary filter is attached by using indirect feedback Kalman filter. Thus developed positioning system is verified by simulation and experiment in towing tank.

• Journal of Power Electronics
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• 제4권4호
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• pp.217-227
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• 2004

A robust controller that combines the merits of the feed-back, feed-forward and model-following control for induction motor drives utilizing field orientation control is designed in this paper. The proposed controller is a two-degrees-of­freedom (2DOF) integral plus proportional & rate feedback (I-PD) speed controller combined with a model-following (2DOF I-PD MFC) speed controller. A systematic mathematical procedure is derived to find the parameters of the 2DOF I-PD MFC speed controller according to certain specifications for the drive system. Initially, we start with the I-PD feed­back controller design, then we add the feed-forward controller. These two controllers combine to form the 2DOF I-PD speed controller. To realize high dynamic performance for disturbance rejection and set point tracking characterisitics, a MFC controller is designed and added to the 2DOF I-PD controller. This combination is called a 2DOF I-PD MFC speed controller. We then study the effect of the 2DOF I-PD MFC speed controller on the performance of the drive system under different operating conditions. A computer simulation is also run to demonstrate the effectiveness of the proposed controller. The results verify that the proposed 2DOF I-PD MFC controller is more accurate and more reliable in the presence of load disturbance and motor parameter variations than a 2DOF I-PD controller without a MFC. Also, the proposed controller grants rapid and accurate responses to the reference model, regardless of whether a load disturbance is imposed or the induction machine parameters vary.