• Advances in nano research
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• v.7 no.4
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• pp.223-231
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• 2019

In this article the frequency response of magneto-flexo-electric rotary porous (MFERP) nanobeams subjected to thermal loads has been investigated through nonlocal strain gradient elasticity theory. A quasi-3D beam model beam theory is used for the expositions of the displacement components. With the aid of Hamilton's principle, the governing equations of MFERP nanobeams are obtained. Further, administrating an analytical solution the frequency problem of MFERP nanobeams are solved. In addition the numerical examples are also provided to evaluate the effect of nonlocal strain gradient parameter, hygro thermo environment, flexoelectric effect, in-plane magnet field, volume fraction of porosity and angular velocity on the dimensionless eigen frequency.

• International Journal of Aerospace System Engineering
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• v.5 no.2
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• pp.8-15
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• 2018

For small earth observation satellites, alignment between the optical components is important for precise observation. However, satellite cameras are structurally subject to misalignment in the launch environment where vibration excitations and impacts apply, and in space environments where zero gravity, vacuum, radiant heat and degassing occur. All of these variables can cause misalignment among the optical components. The misalignment among optical components results in degradation of image quality, and a re-alignment process is needed to compensate for the misalignment. This process of re-alignment between optical components is referred to as a refocusing process. In this paper, we proposed a 3 - axis focusing mechanism to perform the refocusing process. This mechanism is attached to the back of the secondary mirror and consists of three piezoelectric inertia-friction actuators to compensate the x-axis, y-axis tilt, and de-space through three-axis motion. The fabricated focus mechanism demonstrated excellent servo performance by experimenting with PD servo control.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.426-427
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• 2019

본 논문에서는 다양한 양극 활물질을 가지는 리튬이온 배터리를 이용하여 전기 자동차의 구동 전원으로 사용되는 리튬 이차전지의 성능, 신뢰성 및 안전성을 위한 시험 절차 중 하나인 복합 진동 시험을 진행하였다. 고출력과 고용량의 특성을 가지는 배터리를 복합진동 실험에 기반을 두어 배터리 내부의 전기적 특성 파라미터 변화를 분석한다.

• International Journal of High-Rise Buildings
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• v.10 no.2
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• pp.123-135
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• 2021

Solid Viscoelastic Coupling Dampers (VCDs) provide distributed damping that improves the dynamic performance of tall buildings for both wind-storms and earthquakes for all amplitudes of vibration. They are configured in place of typical structural members in tall buildings and therefore do not occupy any architectural space. This paper summarizes the research and development at the University of Toronto in collaboration with Nippon Steel Engineering, 3M and Kinetica over the past two decades. In addition, impact studies on buildings incorporating the VCDs are presented, consisting of a wind sensitive 66-story building in Toronto, a dual-wind and seismic performance-based design of a 4-tower development in Manila and finally a 630 meter Megatall building in Southeast Asia in a severe seismic environment. In all applications the VCDs are shown to provide significant benefits in the dynamic performance under both wind and earthquake loading in a cost-effective manner.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.705-714
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• 2022

The aim of this paper is to investigate nonlinear dynamic responses of functionally graded composite beam resting on the nonlinear viscoelastic foundation subjected to moving mass with temperature rising. The non-linear strain-displacement relationship is considered in the finite strain theory and the governing nonlinear dynamic equation is obtained by using the Hamilton's principle. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then the governing equation is solved by using of multiple time scale method. The influences of temperature rising, material distribution parameter, nonlinear viscoelastic foundation parameters, magnitude and velocity of the moving mass on the nonlinear dynamic responses are investigated. Also, the buckling temperatures of the functionally graded beams based on the finite strain theory are obtained.

• Structural Engineering and Mechanics
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• v.85 no.6
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• pp.709-716
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• 2023

In this paper, the shape factors of cellular meta-material plates (MMPs) having diverse cell arrays have been determined as the first attempt to finally examine their stability and vibrational frequencies. The MMPs are actually constructed from cylindrical or cubic cellular cores and two face sheets. Sandwich-like MMPs with circular and square holes in the face sheets have been selected in such a way that the effective material properties depend on the cellular architectures. For verifying the frequency results, finite element (FE) simulations are done in Abaqus software. Several graphical results have been represented to explore the effects of cellular architectures on vibrational frequencies and dynamic responses of the MMPs. Also, the deflection-frequency and stability curves in the case of forced vibrations have been plotted for diverse cell arrays.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.293-296
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• 2022

본 논문에서는 실제 주행하는 철도가 지나가는 터널에서 유발되는 안전사고 및 주변에 거주하는 주민들과, 서식하는 야생동물들에게 피해를 입힐 수 있는 소음과 진동을 감지하고, 철도가 터널을 운행하는 상황을 구현하여, 너털에서의 위험 요소들에 대한 상황 데이이터들을 센서를 통해 데이터 수집을 진행하고 다양한 위험 상황으로부터 실시간 감지를 통해 데이터들을 분석하고 적절한 상황 지원을 위한 실시간 인지시스템 모델을 설계하고 지원한다.

• Structural Engineering and Mechanics
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• v.88 no.6
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• pp.569-581
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• 2023

This paper introduces a system to detect and diagnose anomalies in pumped storage hydropower plants. We collect data from various types of sensors, including those monitoring temperature, vibration, and power. The data are classified according to the operation modes (pump and turbine operation modes) and normalized to remove the influence of the external environment. To detect anomalies and diagnose their types, we adopt a multivariate normal distribution analysis by learning the distribution of the normal data. The feasibility of the proposed system is evaluated using actual monitoring data of a pumped storage hydropower plant. The proposed system can be used to implement condition monitoring systems for other plants through modifications.

• Structural Engineering and Mechanics
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• v.90 no.6
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• pp.531-542
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• 2024

This study proposes a ground anchor using electromagnetic induction and utilizes an extended structure using hinges and links and mounting and sensing using electromagnets. The aim is to secure the anchor force, excluding grout, and to secure various sensing capabilities, including ground behavior. We propose a design based on the drilling diameter of 150 mm, and the materials used were STS304 and Aluminum 6061-T6. Computerized analysis was performed to confirm structural safety and functional implementation. The pull-out experiment was conducted by simulating the bedrock environment on a model earthwork as an experiment to check whether anchor force was generated by the insertion and tension of the anchor. The environmental pollution of grout, the difficulty of removing strands, and the inability to check whether the anchor is seated, which were pointed out as disadvantages of the existing ground anchor, were solved. Therefore, this study suggest that it can be effectively utilized as a secure and monitored anchoring solution in eco-friendly construction practices, including the installation of landslide prevention barriers.

• Journal of Ocean Engineering and Technology
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• v.29 no.1
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• pp.34-44
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• 2015

A hydraulic tensile test machine (HSTM) is one of the devices used to obtain the flow stress of a material during high-speed elongation. This paper first describes some features of a newly built HSTM. The improvement histories of the upper and lower jigs, which are the most vital parts of the HSTM, are also presented. We have frequently witnessed test failures with 1st generation jigs and specimens due to slip between the jig and specimen. 2nd generation jigs provide more stable test results, but the use of a longer upper jig induces excessive vibration and consequently makes it difficult to attach an environment chamber. 3rd generation jigs have some advances in terms of the symmetric fastening between the upper jig and specimen, as well as an exemption from direct contact between the lower jig and specimen. The performance of an environment chamber is verified by high and low temperature tests. A high-speed displacement measurement system is introduced based on a high-speed camera and motion-tracking software with aid of a surface grid device for the specimen.