• 한국정보과학회논문지:시스템및이론
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• 제32권2호
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• pp.75-84
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• 2005

이 연구는 공간적/시간적 지역성의 효과론 이용하기 위하여 SRAM 버퍼를 사용하는 고성능 NAND-Type 플래쉬 메모리 패키지의 설계에 관한 것이다. 제안된 SRAM 버퍼를 내장한 새로운 NAND형 플래쉬 메모리 패키지 구조는 크게 세 부분으로 구성되어 있다. 즉, 작은 블록 크기의 완전 연관 희생 버퍼(victim buffer)와 큰 블록 크기를 지원하는 완전 연관 공간 버퍼(spatial buffer), 그리고 동적 페칭 유닛(dynamic fetching unit)으로 구성되어 있다. 제안하는 새로운 NAND 형 플래쉬 메모리 패키지는 기존의 NAND형 플래쉬 메모리 구조와 비교할 때 매우 뛰어난 성능 향상 및 저 전력 소비를 이끌어낼 수 있다. 시뮬레이션 결과에 따르면 제안된 NAND 플래쉬 메모리 패키지는 기존의 NAND 플래쉬 메모리와 비교하여 접근 실패율에서는 70%, 평균 메모리 접근 시간에서는 67%의 감소 효과를 보여준다. 더욱이 주어진 크기(e.g., 3KB)의 SRAM 버퍼를 이용한 제안된 패키지는 여덟 배 크기의 직접 사상 버퍼(e.g., 32KB)를 이용한 패키지 및 두 배 크기의 완전 연관 버퍼(e.g., 8KB)를 이용한 패키지보다도 평균 접근 실패율 및 평균 메모리 접근 시간에서 더욱 우수한 성능 향상을 이끌어낼 수 있다.

• Earthquakes and Structures
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• 제12권5호
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• pp.479-487
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• 2017

Frictional dampers are used in structural engineering as means of passive control. Meanwhile, frictional damper shave a disadvantage compared to viscous rivals since the slippage force must be exceeded to activate the device, and cannot be ideal full range of possible events. The concept of semi-active control is utilized to overcome this shortcoming. In this paper, a new semi-active frictional damper called Smart Adjustable Frictional (SAF) damper is introduced. SAF damper consists of hydraulic, electronic units and sensors which are all linked with an active control discipline. SAF acts as a smart damper which can adapt its slippage threshold during a dynamic excitation by measuring and controlling the structural response. The novelty of this damper is, while it controls the response of the structure in real time with acceptable time delay. The paper also reports on the results of a series of experiments which have been performed on SAF dampers to obtain their prescribed hysteretic behavior for various control algorithms. The results show that SAF can produce the desired slippage load of various algorithms in real time. Numerical models incorporating control simulations are also made to obtain the hysteretic response of the system which agrees closely with test results.

• Smart Structures and Systems
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• 제18권4호
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• pp.787-800
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• 2016

The aim of the paper is to analyze nonlinear transverse vibration of an embedded piezoelectric plate reinforced with single walled carbon nanotubes (SWCNTs). The system in rested in a Pasternak foundation. The micro-electro-mechanical model is employed to calculate mechanical and electrical properties of nanocomposite. Using nonlinear strain-displacement relations and considering charge equation for coupling between electrical and mechanical fields, the motion equations are derived based on energy method and Hamilton's principle. These equations can't be solved analytically due to their nonlinear terms. Hence, differential quadrature method (DQM) is employed to solve the governing differential equations for the case when all four ends are clamped supported and free electrical boundary condition. The influences of the elastic medium, volume fraction and orientation angle of the SWCNTs reinforcement and aspect ratio are shown on frequency of structure. The results indicate that with increasing volume fraction of SWCNTs, the frequency increases. This study might be useful for the design and smart control of nano/micro devices such as MEMS and NEMS.

• 한국정밀공학회지
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• 제10권1호
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• pp.134-141
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• 1993

Electro-Rheological(ER) fluids undergo a phase-change when subjected to an external electic field, and this phase-change typically manifests itself as a many-order-of-magnitude change in the rheological behavior. This phenomenon permits the global stiffness and energy- dissipation properties of the beam structures to be tuned in order to synthesize the desired vibration characteristics. This paper reports on a proof-of-concept experimental investigation focussed on evaluation the vibration properties of hollow cantilevered beams filled with an ER fluid. and consequently deriving an empirical model for predicting field-dependent vibration characteristics. A hydrous-based ER fluid consisting of corn starch and silicone oil is employed. The beams are considered to be uniform viscoelastic materials and modelled as a viscously-damped harmonic oscillator. Natural frequency, damping ratio and elastic modulus are evaluated with respect to the electric field and compared among three different beams: two types of different volume fraction of ER fluid and one type of different particle concentration of ER fluid by weight. Transient and forced vibration responses are examined in time domain to demonstrate the validity of the proposed empirical model and to evaluate the feasibility of using the ERfluid as an actuator in a closed-loop control system.

• Ocean Systems Engineering
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• 제7권2호
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• pp.107-120
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• 2017

Spud-can is used for fixing jack-up rig on seabed. It needs to be inserted up to the required depth during the installation process to secure enough soil reaction and prevent overturning accidents. On the other hand, it should be extracted from seabed soils as fast as possible during the extraction process to minimize the corresponding operational cost. To achieve such goals, spud-can may be equipped with water-jetting system including monitoring and control. To develop such a smart spud-can, a reliable numerical simulation tool is essential and it has also to be validated against physical model tests. In this regard, authors developed a numerical simulation tool by using a commercial program ANSYS with extended Drucker-Prager (EDP) formula. Authors also conducted small-scale (1/100) physical model tests for verification and calibration purpose. By using the numerical model, a systematic parametric study is conducted both for sand and K(kaolin)-clay with varying important soil parameters and the best estimated soil properties of the physical test are deduced. Then, by using the selected soil properties, the numerical and experimental results for a sand/K-clay multi-layer case are cross-checked to show reasonably good agreement. The validated numerical model will be useful in the next-stage study which includes controllable water-jetting.

• 스마트미디어저널
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• 제8권1호
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• pp.35-42
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• 2019

IoT 디바이스 기술의 발전으로 디바이스가 주변 환경을 인식하고 동작하게 되면서, 막대한 양의 IoT 디바이스 데이터를 효율적으로 처리하기 위한 방안이 요구되고 있다. 기존에 사용되던 클라우드 컴퓨팅은 부하와 거리에 따른 전송 지연 문제가 발생한다. 이러한 문제를 해결하기 위해 포그 컴퓨팅이 등장하였다. 포그 컴퓨팅은 IoT 디바이스를 제어하기 위한 환경으로, 클라우드의 단점을 해결하기 위해 IoT 디바이스를 가까이 두어 근거리 통신을 수행한다. 그러나 IoT를 위한 포그 컴퓨팅 관련 연구들은 포그컴퓨팅의 구조와 프레임워크에 대한 연구가 주를 이룬다. 따라서 본 논문에서는 포그컴퓨팅을 수행하기 위한 플랫폼을 제안한다. 제안하는 플랫폼은 포그 컴퓨팅 환경에서 IoT 디바이스를 모니터링 및 분석, 제어할 수 있는 통합 플랫폼이다.

• Smart Structures and Systems
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• 제28권6호
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• pp.737-744
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• 2021

In this study, structural health monitoring (SHM) methods of carbon fiber reinforced plastics (CFRPs) were investigated using electrical resistance. The developed sensing technique monitored electrical resistance in accordance with the impact damage of a CFRP. The changes in electrical resistances with multiple electrode sets enabled SHM without extra sensors so that this technique can be called self-sensing. Moreover, this study proposed electrodes only at peripheral side of a structure to minimize the number of electrodes compared to those in an array which has square number of sensors as the sensing area increases. For the intensive investigation, electromechanical sensitivity in terms of electrode distance was analyzed and optimized under drop weight impact testing. Then, SHM methods with electrodes in an array and electrodes in peripheral edges were comparatively investigated. The developed methods successfully localized impact damages into 2D coordinates. Furthermore, damage severity can be shown with a damage map by calculating electrical resistance change ratio. Therefore, structural health self-sensing system using electrical resistance was successfully developed with the minimum number of electrodes.

• 한국전자통신학회논문지
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• 제11권1호
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• pp.53-58
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• 2016

지구 온난화, 고유가 그리고 심각한 전력난 문제를 해소하기 위해, 가정용 전기요금 누진제 적용과 함께 산업용 전기요금의 지속적인 상승이 이루어지고 있어 에너지 이용 효율을 크게 개선할 수 있는 에너지 저장 시스템을 스마트 그리드에 적용하기 위한 노력들이 새롭게 시도되고 있다. 본 연구에서는 에너지 저장 장치로 활용될 수 있는 리튬이온 전지의 구성 및 동작원리, 에너지 저장 시스템의 전력계통 적용 분야, 배터리 에너지 컨버터 기술, 그리고 적용사례를 연구함으로서 에너지 저장 시스템을 전력계통에 적용하는 데 필요한 기반 기술을 확립한다.

• Smart Structures and Systems
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• 제15권3호
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• pp.897-911
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• 2015

This study presents a novel approach based on advancements in Evolutionary Computation for data-driven modeling of complex multi-dimensional memory-dependent systems. The investigated example is a benchmark coupled three-dimensional system that incorporates 6 Bouc-Wen elements, and is subjected to external excitations at three points. The proposed technique of this research adapts Genetic Programming for discovering the optimum structure of the differential equation of an auxiliary variable associated with every specific degree-of-freedom of this system that integrates the imposed effect of vibrations at all other degrees-of-freedom. After the termination of the first phase of the optimization process, a system of differential equations is formed that represent the multi-dimensional hysteretic system. Then, the parameters of this system of differential equations are optimized in the second phase using Genetic Algorithms to yield accurate response estimates globally, because the separately obtained differential equations are coupled essentially, and their true performance can be assessed only when the entire system of coupled differential equations is solved. The resultant model after the second phase of optimization is a low-order low-complexity surrogate computational model that represents the investigated three-dimensional memory-dependent system. Hence, this research presents a promising data-driven modeling technique for obtaining optimized representative models for multi-dimensional hysteretic systems that yield reasonably accurate results, and can be generalized to many problems, in various fields, ranging from engineering to economics as well as biology.

• 한국멀티미디어학회논문지
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• 제22권3호
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• pp.366-373
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• 2019

The development of monitoring and analysis systems to increase productivity while saving energy is needed as a method to reduce huge amount of energy consumed in the process of producing large forged products. In this paper, we propose a system to monitor and analyze energy usage in real-time collected from gas-meter, wattmeter, and thermometer based on IoT installed in forging factories. The system consists of a data collection server for collecting and processing data from IoT- based platform and existing SCADA equipment and ERP/MES system in forging factories, and an application server for providing services to users. To develop the system, the overall system structure is logically diagrammed, and the databases configuration and implementation modules to efficiently store and manage data are presented. In the future, the system will be utilized to reduce energy consumption by analyzing energy usage pattern and optimizing process works with real-time energy usage and production process data for each facility.