• Journal of Electrical Engineering and Technology
• /
• v.10 no.6
• /
• pp.2376-2383
• /
• 2015

Assistance of the operator’s walking ability while carrying a load is a challenging area in lower limb exoskeletons. We implement an exoskeleton called the Unmanned Technology Research Center Exoskeleton (UTRCEXO), which enables the operator to walk with a load more comfortably. The UTRCEXO makes use of two types of DC motor to assist the hip and knee joints. The UTRCEXO detects the operator’s walking intention including step initiation with insole-type FSRs faster without using any bio-signals and precedes the operator’s step with a reference torque. It not only reduces interaction forces between the operator and the UTRCEXO, but also allows the operator to walk with a load more comfortably. In this paper, we present the UTRCEXO implementing the walking assistance mechanism with interaction force reduction during walking.

• Ocean Systems Engineering
• /
• v.6 no.4
• /
• pp.345-362
• /
• 2016

This study aims to develop the numerical method to estimate level ice impact load and investigate the dynamic interaction between an arctic Spar with sloped surface and drifting level ice. When the level ice approaches the downward sloped structure, the interaction can be decomposed into three sequential phases: the breaking phase, when ice contacts the structure and is bent by bending moment; the rotating phase, when the broken ice is submerged and rotated underneath the structure; and the sliding phase, when the submerged broken ice becomes parallel to the sloping surface causing buoyancy-induced fictional forces. In each phase, the analytical formulas are constructed to account for the relevant physics and the results are compared to other existing methods or standards. The time-dependent ice load is coupled with hull-riser-mooring coupled dynamic analysis program. Then, the fully coupled program is applied to a moored arctic Spar with sloped surface with drifting level ice. The occurrence of dynamic resonance between ice load and spar motion causing large mooring tension is demonstrated.

• Journal of the Korean Geotechnical Society
• /
• v.17 no.3
• /
• pp.95-102
• /
• 2001

본 연구에서는 말뚝-지반, 말뚝-캡 상호작용을 고려한 군말뚝 거동을 해석하는 효율적인 알고리즘을 제안하였다. 단독말뚝의 말뚝-지반 상호작용은 하중전이법을 사용하여 비선형적인 특성을 갖는 지반스프링(p-y, t-z, q-z 곡선등)을 이용하여 모델링하였으며 Beam-column 방법을 이용하여 말뚝-지반 시스템을 수치적으로 모델링하였다. 좀 더 실제적인 군말뚝의 해석을 위해서 지반-말뚝-지반 상호작용에 의한 그룹효과와 더불어 군말뚝 내에서 말뚝의 위치 및 말뚝과 말뚝캡의 결합조건에 따른 말뚝-캡 상호작용에 의한 효과를 고려하였다. 본 연구에서는 말뚝-캡의 상호작용에 중점을 두었으며 Beam-column 방법을 이용하여 이를 해석할 수 있는 타당한 수치해석적 방법을 개발하고자 하였다. 개발된 알고리즘을 수치해석 예제를 통해 비교, 검증하였다.

• Journal of Ocean Engineering and Technology
• /
• v.7 no.2
• /
• pp.162-172
• /
• 1993

In the present paper, the overall state of the arts of ice mechanics which is the most typical research topic of the artic engineering field was studied. And also, ice loads genrated by ice-structure interaction were estimated using numerical approach. The effects of viscous property of ice sheets to the ice load were investigated. The time dependent deformation behaviors of ice was modeled by visco-plastic problem using the finite element formalism. Constitutive model representing the material properties of ice was idealized by comblned rheological model with Maxwell and Voigt models. Numerical calculations for the bending and crushing behavior of ice sheet which are the most typical interaction modes between ice sheets and structures were carried out. The time dependent viscous behaviors of ice sheets interaction forces acting on structures were analyzed and the results were studied in detail.

• Fire Science and Engineering
• /
• v.22 no.2
• /
• pp.84-90
• /
• 2008

This paper aims to experimentally investigate the in-fire performance of composite beams with respect to the effects of load ratio and shear interaction. Under a Standard ISO834 fire, the development of temperature and deflection of simply supported composite beams were recorded. In particular, the transition of temperature distribution across the cross-section. The fire resistance of composite beam was interpreted regarding the level of shear interaction.

• Asia pacific journal of information systems
• /
• v.25 no.1
• /
• pp.25-60
• /
• 2015

Use cases are commonly used to represent customer requirements during systems development. In a large software development environment, finding relevant use cases from a library of past or related projects is a complex, error-prone and expensive task. This study proposes an ontological methodology to support use case retrieval in an interactive manner. The architecture of a prototype system that implements this methodology is presented. To evaluate whether the proposed approach can provide satisfactory results to users, this study develops a research model and hypotheses based on interaction theory. These hypotheses are empirically tested using a laboratory experiment which controls information filtering and perceived interaction. Our study suggests that a system which interacts with a user intelligently reduces cognitive load and increases self-efficacy and satisfaction.

• Journal of the Korean Society of Visualization
• /
• v.17 no.2
• /
• pp.17-24
• /
• 2019

The purpose of this study is to study the fluid-dynamic and structural characteristics of the conventional greenhouse and to find possible improvement on the current greenhouse. The greenhouse is required to have enough rigidity of the structure while the installation and reinforcement should be as easy as possible. In this study, the structural stability to the snow load was tested through the computational structure analysis based on the building structure standard, and the wind load was computed by computational fluid-structure interaction analysis. The current analysis can be used as a reference data for a new greenhouse and it will be economically viable by reducing installation and maintenance costs.

• Journal of Wind Energy
• /
• v.4 no.1
• /
• pp.68-74
• /
• 2013

Offshore wind farm is being increased since there are much trouble to develop onshore wind farm. But in the offshore, wind turbine wake does not dissipate less than onshore wind turbine because of low turbulence level. Thus this remained wake interacted to other wind turbine. This interaction reduces energy production in wind farm and have a bad influence on fatigue load of wind turbine. In this research, CFD model was constructed to analyze wake effect in offshore wind farm. A method that wind turbine rotor region was modelled in porous media was devised to reduce computation load and validated by comparison with Horns Rev measurement. Then wake interaction between two wind turbine was analyzed by devised porous model.

• Computers and Concrete
• /
• v.6 no.6
• /
• pp.473-490
• /
• 2009

This paper presents a new methodology to evaluate the load carrying capacity of deteriorated non-slender concrete bridge pier columns by construction of the full P-M interaction diagrams. The proposed method incorporates the actual material properties of deteriorated columns, and accounts for amount of corrosion and exposed corroded bar length, concrete loss, loss of concrete confinement and strength due to stirrup deterioration, bond failure, and type of stresses in the corroded reinforcement. The developed structural model and the damaged material models are integrated in a spreadsheet for evaluating the load carrying capacity for different deterioration stages and/or corrosion amounts. Available experimental and analytical data for the effects of corrosion on short columns subject to axial loads combined with moments (eccentricity induced) are used to verify the accuracy of proposed model. It was observed that, for the limited available experimental data, the proposed model is conservative and is capable of predicting the load carrying capacity of deteriorated reinforced concrete columns with reasonable accuracy. The proposed analytical method will improve the understanding of effects of deterioration on structural members, and allow engineers to qualitatively assess load carrying capacity of deteriorated reinforced concrete bridge pier columns.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.6
• /
• pp.3423-3428
• /
• 2014

Numerical studies were performed to evaluate the structural safety of a greenhouse under both snow and wind loads. In the case of a wind load, fluid-structure interaction (FSI) method was used to consider the local pressure distributions on the greenhouse-induced by aerodynamic characteristics. The results showed that the maximum stress and deformation occur near the junction of pipe supports and rafters of the roof, where connecting clips are installed. Moreover, the wind load is a more severe condition than a snow load. Overall, these results will be used to design a prefabricated connecting clip with easy installation and low maintenance.