• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.214-214
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• 2000

This paper deals with the non contact optical sensor to measure the shape of transparent plates such as glass panel of LCD(Liquid Crystal Display). The conventional methods to obtain the shape or thickness of a transparent plates are contact type sensor such as LVOT(Linear Variable Differential Transformer). Due to the contact between the tip of the sensor and the surface of objects, the tip is abraded. In addition, the high temperature glass casting makes the size of sensor body changed. These reasons makes the sensor degraded. In this paper, to overcome these problem, we proposed a low cost noncontact optical sensor this is composed of the Hologram laser unit of a CD-Pickup and a plastic lens. To evaluate the performance of the proposed optical sensor, a series of experiments were performed for various measurement condition. Based upon observation of the experimental result, the developed sensor shows good result for measuring the shape of transparent plates.

• Coupled systems mechanics
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• 제4권1호
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• pp.1-18
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• 2015

The state-based peridynamics is considered a nonlocal method in which the equations of motion utilize integral form as opposed to the partial differential equations in the classical continuum mechanics. As a result, the enforcement of boundary conditions in solid mechanics analyses cannot follow the standard way as in a classical continuum theory. In this paper, a new approach for the boundary condition enforcement in the state-based peridynamic formulation is presented. The new method is first formulated based on a convex kernel approximation to restore the Kronecker-delta property on the boundary in 1-D case. The convex kernel approximation is further localized near the boundary to meet the condition that recovers the correct boundary particle forces. The new formulation is extended to the two-dimensional problem and is shown to reserve the conservation of linear momentum and angular momentum. Three numerical benchmarks are provided to demonstrate the effectiveness and accuracy of the proposed approach.

• Smart Structures and Systems
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• 제25권6호
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• pp.643-655
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• 2020

Active control of nonlinear vibration of stiffened functionally graded (SFG) cylindrical shell is studied in this paper. The system is subjected to axial and transverse periodic loads in the presence of thermal uncertainty. The material composition is considered to be continuously graded in the thickness direction, also these properties depend on temperature. The relations of strain-displacement are derived based on the classical shell theory and the von Kármán equations. For modeling the stiffeners on the cylindrical shell surface, the smeared stiffener technique is used. The Galerkin method is used to discretize the partial differential equations of motion. Some comparisons are made to validate the SFG model. For suppression of the nonlinear vibration, the linear and nonlinear control strategies are applied. For control objectives, the piezoelectric actuator is attached to the external surface of the shell and the thin ring piezoelectric sensor is attached to the middle internal surface of shell. The effect of PID, feedback linearization and sliding mode control on the suppression of vibration for SFG cylindrical shell is presented.

• Smart Structures and Systems
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• 제26권3호
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• pp.361-371
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• 2020

Exact solution for nonlinear behavior of clamped-clamped functionally graded (FG) buckled beams is presented. The effective material properties are considered to vary along the thickness direction according to exponential-law form. The in-plane inertia and damping are neglected, and hence the governing equations are reduced to a single nonlinear fourth-order partial-integral-differential equation. The von Kármán geometric nonlinearity has been considered in the formulation. Galerkin procedure is used to obtain a second order nonlinear ordinary equation with quadratic and cubic nonlinear terms. Based on the mode of the corresponding linear problem, which readily satisfy the boundary conditions, the frequencies for the nonlinear problem are obtained using the Jacobi elliptic functions. The effects of various parameters such as the Young's modulus ratio, the beam slenderness ratio, the vibration amplitude and the magnitude of axial load on the nonlinear behavior are examined.

• 설비공학논문집
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• 제25권2호
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• pp.109-118
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• 2013

The absence of a simple and general analytical model has been a problem in the design and analysis of desiccant-assisted air-conditioning systems. In this study, such an analytical model has been developed based on the approximate integral solution of the coupled transient ordinary differential equations for the heat and mass transfer processes in a desiccant wheel. It turned out that the initial conditions should be determined by the solution of four linear algebraic equations including the heat and mass transfer equations for the air flow as well as the energy and mass conservation equations for the desiccant bed. It is also shown that time-averaged exit air temperature and humidity relations could be given in terms of the heat and mass transfer effectiveness.

• Coupled systems mechanics
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• 제8권2호
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• pp.147-168
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• 2019

This work aims to simulate three-dimensional heavy oil flow in a reservoir with heater-wells. Mass, momentum and energy balances, as well as correlations for rock and fluid properties, are used to obtain non-linear partial differential equations for the fluid pressure and temperature, and for the rock temperature. Heat transfer is simulated using a two-equation model that is more appropriate when fluid and rock have very different thermal properties, and we also perform comparisons between one- and two-equation models. The governing equations are discretized using the Finite Volume Method. For the numerical solution, we apply a linearization and an operator splitting. As a consequence, three algebraic subsystems of linearized equations are solved using the Conjugate Gradient Method. The results obtained show the suitability of the numerical method and the technical feasibility of heating the reservoir with static equipment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권12호
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• pp.3398-3415
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• 2023

Internet-of-Things (IoT) is an emerging technology that interconnects millions of small devices to enable communication between the devices. It is heavily deployed across small scale to large scale industries because of its wide range of applications. These devices are very capable of transferring data over the internet including critical data in few applications. Such data is exposed to various security threats and thereby raises privacy-related concerns. Even devices can be compromised by the attacker. Modern cryptographic algorithms running on traditional machines provide authentication, confidentiality, integrity, and non-repudiation in an easy manner. IoT devices have numerous constraints related to memory, storage, processors, operating systems and power. Researchers have proposed several hardware and software implementations for addressing security attacks in lightweight encryption mechanism. Several works have made on lightweight block ciphers for improving the confidentiality by means of providing security level against cryptanalysis techniques. With the advances in the cipher breaking techniques, it is important to increase the security level to much higher. This paper, focuses on securing the critical data that is being transmitted over the internet by PRESENT using key-based dynamic S-Box. Security analysis of the proposed algorithm against other lightweight block cipher shows a significant improvement against linear and differential attacks, biclique attack and avalanche effect. A novel key-based dynamic S-Box approach for PRESENT strongly withstands cryptanalytic attacks in the IoT Network.

• 한국정보처리학회논문지
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• 제2권4호
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• pp.535-542
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• 1995

이 논문에서 우리는 CM-5와 같은 초대형병렬컴퓨터에서 대형 이산선형체제를 풀기 위한 준비행렬로써 두 가지를 소개한다. 대다수의 초대형병렬컴퓨터들은 프로세서간의 통신을 메세지패씽(messagepassing)에 의존하는데 현재의 기술수준하에서는 이 통신속 도가 실수계산속도에 비해 매우 느리므로 종래의 메모리공유컴퓨터에서와는 달리 데이 터통신량을 최소화하는 알고리듬이 요구된다. 블록 SOR에 다중색채기법을 가미한 알고 리듬이 그 한 예로써 우리는 이를 CM-5에서 구현한 결과 N=512x512 행렬에서 프로세서 의 수가 16에서 512의 범위 하에서 50%의 효율을 실현하였다. 반면 종래의 효율적인 병렬 준비행렬로 알려진 AKI알고리듬은 방대한 량의 데이터통신 때문에 매우 열등한 결과를 보여준다.

• 한국지진공학회논문집
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• 제9권3호
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• pp.33-42
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• 2005

비선형 함수로 모델링되는 동적 시스템의 비선형 파라미터를 결정하기 위하여 주파수 영역 볼테라 모델을 적용하는 연구를 수행하였다. 시간영역의 1차, 2차, 3차 전달함수에 해당하는 주파수 영역의 볼테라 핵함수를 비선형 파라미터 산정 과정에 3차 비선형 항까지 포함시켰다. Schetzen의 방법으로 시스템의 비선형 미분방정식에 적합한 볼테라 급수 표현식을 정하고, 이로부터 유도되는 비선형 전달함수를 입력 출력 관계식에 사용하였다. 관찰된 입력을 비선형 주파수 영역 모델에 대입하여 계산한 출력과 관찰된 출력의 차이로 오차를 정의한 후 오차를 최소화 시키는 시스템 파라미터의 값을 구하였다. 예제를 통하여 선형 주파수 구간 뿐만 아니라 2차 혹은 3차 비선형이 지배적인 주파수 범위 대에서 볼테라 모델이 충분한 정확성과 수렴성을 가지며 인식된 파라미터는 실제 값과 잘 일치함을 확인할 수 있었다.

• 대한전자공학회논문지SD
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• 제44권8호
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• pp.16-21
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• 2007

본 논문은 구조물 모니터링을 위한 광섬유 센서 시스템의 수신단 응용을 위한 CMOS 기반의 가변 이득 증폭기 집적회로 설계에 초점을 두고 있다. 차동증폭기와 선형 linear-in-dB 제어기를 사용한 3단 가변 이득 증폭기를 제시하였다. 제안된 가변이득 증폭기는 전류의 비에 의해 증폭기의 이득이 linear-in-dB 하게 조절되는 일반적인 가변 이득 증폭기의 변형된 형태이다. 본 논문에서 제안된 가변 이득 증폭기는 1.5 dB의 간격으로 77 dB의 다이내믹 영역을 가졌다. 이득오차는 77 dB 다이내믹 영역에서 1.5 dB 이하를 얻었다. 동작범위는 10 MHz를 얻었으며, 단일 1.8 V 전압에서 13.8 mW의 전력소모 특성을 보였다. 이 가변 이득 증폭기는 Magnachip 사의 $0.18{\mu}m$ CMOS 공정을 사용하여 구현되었으며, 유효면적은 $430{\mu}m{\times}350{\mu}m$ 이었다. 제안된 가변 이득 증폭기는 구조물 모니터링을 위한 광섬유 센서 시스템의 수신단에 적용이 가능하였다 측정 결과에 따라 제안된 방법은 다이내믹 영역의 증대와 좋은 linear-in-dB 특성 관점에서 유효하였다.