• Smart Structures and Systems
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• v.9 no.4
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• pp.335-353
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• 2012

This study suggests a simple two-step method for structural vibration-based health monitoring for beam-like structures which only utilizes mode shape curvature and few natural frequencies of the structures in order to detect and localize cracks. The method is firstly based on the application of wavelet transform to detect crack locations from mode shape curvature. Then particle swarm optimization is applied to evaluate crack depth. As the Rayleigh quotient is introduced to estimate natural frequencies of cracked beams, the relationship of natural frequencies and crack depths can be easily obtained with only a simple formula. The method is demonstrated and validated numerically, using the numerical examples (cantilever beam and simply supported shaft) in the literature, and experimentally for a cantilever beam. Our results show that mode shape curvature and few estimated natural frequencies can be used to detect crack locations and depths precisely even under a certain level of noise. The method can be extended for health monitoring of other more complicated structures.

• Journal of the Korea Furniture Society
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• v.23 no.4
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• pp.407-414
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• 2012

In order to develop the end use of cylindrical laminated veneer lumber (LVL) such as wooden crafts, the light resistance properties of natural dye-colored and finished cylindrical LVL was investigated. The study results were as follows; The cross section of LVL showed the higher light resistance than its tangential section, and the light resistance also increased with surface coated. On the other hand, LVL specimen were colored by 9 natural dyes of amur cork-tree etc., and the natural and apparent hue harmonized with wood was found after coating and light resistance test. Particularly, The dyes extracted from amur cork-tree, persimon and sappan wood showed orange color, reddish brown and red color respectively, giving an accenting effect to original wood color.

• Korean Institute of Interior Design Journal
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• v.18 no.1
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• pp.108-116
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• 2009

As an aging society accelerates its pace for the present, providing a pleasant environment to nursing homes is such an environmental requirement with which elderly people could improve their quality of life and even acquire the effects of healing. As an optimal element of ensuring amenity, nature is a general hospital that heals human beings physically and mentally. In this vein, the investigator drew out the frame of analysis, namely emotional/healing/relating amenity, by means of theoretical examination of such natural elements as water, light, soil/stone, and plant. And on the basis of the drawn amenity, the investigator examined the application of natural elements to study subjects in order to analyze the ensured amenity. Study findings show that the existing nursing homes have ensured healing amenity sufficiently, but they are unsatisfactory in ensuring emotional and relating amenity. Based on interview survey, the investigator suggests that the introduction of natural elements into nursing homes such public space as mediation space, interaction space, and rest places to ensure emotional/healing/relating amenity must be ideally equipped with the formation of outdoor forest in which water, light, soil/stone, and plant get joined together, rather than Introducing a single element respectively. In addition, the plan of construction of nursing homes must take residing elderly people's emotional/healing/relating amenity into account on the basis of physical amenity.

• The KIPS Transactions:PartD
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• v.15D no.5
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• pp.647-658
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• 2008

Customers' requirements written in a natural language are rewritten to modeling language in development phases. In many cases, those who participate in development cannot understand requirements written in modeling language. This paper proposes the translation technique from the requirement model which is written by REED(REquirement EDitor) tool into a natural language in order to help for the customer understanding requirement model. This technique consists of three phases: $1^{st}$ phase is generating the IORT(Input-Output Relation Tree), $2^{nd}$ phase is generating the RTT(Requirement Translation Tree), $3^{rd}$ phase is translating into a natural language.

• Biomolecules & Therapeutics
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• v.14 no.4
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• pp.216-219
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• 2006

In order to establish the anti-inflammatory cellular mechanism of the paeony root(Paeonia lactiflora, Pall, Paeoniaceae), the constituents including paeoniflorin, albiflorin, (+)-catechin, paeonol, benzoic acid and methyl gallate were evaluated for their effects on arachidonate and NO metabolism. Among the compounds tested, only paeonol weakly inhibited cyclooxygenase-2-mediated $PGE_2$ production from LPS-treated RAW 264.7 cells. (+)-Catechin and methyl gallate weakly inhibited inducible nitric oxide synthase-mediated NO production from the same cell line. In particular, methyl gallate significantly inhibited 5-lipoxygenase from RBL-l cells with an $IC_{50}$ of 8.4 ${\mu}M$. These results suggest that the inhibition of these components on arachidonate and NO metabolism may contribute at least in part to anti-inflammatory mechanism of the paeony root.

• Journal of the Korean Solar Energy Society
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• v.30 no.2
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• pp.87-95
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• 2010

This study analyzed the performance of solar chimney system for natural ventilation in underground space. A mathematical model of the solar chimney was proposed in order to predict its performance under varying parameters and Korea climatic condition. Steady state heat transfer equations were set up using a energy balanced equations and solved using a inverse matrix method. Numerical simulation program to analyze system was developed by using MATLAB. As the results, the ventilation performance of the solar chimney was determined by the temperature difference of air channel and inlet, and the temperature difference was influenced by insolation, stack height and distance of air gab. Also the solar chimney system can provide $262.9m^3/h$ of annual average ventilation rate. Because seasonal differences of ventilation rate was calculated within 25%, the solar chimney system can be used for every season in Korea climatic condition. Through this study, performance of solar chimney system for natural ventilation was verified by numerical method. Consequently, the solar chimney system is proved to be effective device for natural ventilation utilizing at all times, and the additional studies should be made through the experimental method for imagineering and commercialization.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.897-902
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• 2006

Natural ventilation is an effective method for improving IAQ(Indoor Air Quality) and removing heats in buildings. In oder to use natural ventilation, many factors such as wind pressure around the buildings and possibility of air intake on different shapes need to be known. On this paper, the natural ventilation performance in multi-housing units of tower-type buildings was investigated. Tower-type multi-housing buildings are recently more and more constructed for they may change urban landscape and get more openness in multi-housing site. However, such housing buildings have problems with natural ventilation because of the various directions of the building units. The purpose of this paper is to find the proper building direction regarding to wind direction in order to optimize air intake in every units in the building.

• Steel and Composite Structures
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• v.31 no.6
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• pp.591-600
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• 2019

Based on the energy-variational principle, a coupling vibration analysis model of high-speed railway simply supported beam bridge-track structure system (HSRBTS) was established by considering the effect of shear deformation. The vibration differential equation and natural boundary conditions of HSRBTS were derived by considering the interlayer slip effect. Then, an analytic calculation method for the natural vibration frequency of this system was obtained. By taking two simply supported beam bridges of high-speed railway of 24 m and 32 m in span as examples, ANSYS and MIDAS finite-element numerical calculation methods were compared with the analytic method established in this paper. The calculation results show that two of them agree well with each other, validating the analytic method reported in this paper. The analytic method established in this study was used to evaluate the natural vibration characteristics of HSRBTS under different interlayer stiffness and length of rails at different subgrade sections. The results show that the vertical interlayer compressive stiffness had a great influence on the high-order natural vibration frequency of HSRBTS, and the effect of longitudinal interlayer slip stiffness on the natural vibration frequency of HSRBTS could be ignored. Under different vertical interlayer stiffness conditions, the subgrade section of HSRBTS has a critical rail length, and the critical length of rail at subgrade section decreases with the increase in vertical interlayer compressive stiffness.

• Journal of Ocean Engineering and Technology
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• v.34 no.6
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• pp.481-488
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• 2020

Composite materialsuch as glass-fiber reinforced plastic and carbon-fiber reinforced plastic (CFRP) shows anisotropic property and have been widely used for structural members and outfitings of ships. The structural safety of composite structures has been generally evaluated via finite element analysis. This paper presents a technique for updating the finite element model of anisotropic beams or plates via natural frequencies. The finite element model updates involved a compensation process of anisotropic material properties, such as the elastic and shear moduli of orthotropic structural members. The technique adopted was based on a discrete genetic algorithm, which is an optimization technique. The cost function was adopted to assess the optimization problem, which consisted of the calculated and referenced low-order natural frequencies for the target structure. The optimization process was implemented with MATLAB, which includes the finite element updates and the corresponding natural frequency calculations with MSC/NASTRAN. Material properties of a virtual cantilevered orthotropic beam were estimated to verify the presented method and the results obtained were compared with the reference values. Furthermore, the technique was applied to a cantilevered CFRP beam to successfully estimate the unknown material properties.

• Smart Structures and Systems
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• v.30 no.2
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• pp.173-181
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• 2022

The current paper presents a technique to detect crack in non-uniform cantilever-type pipe beams, that have step changes in the properties of their cross sections, restrained by a translational and rotational spring with a tip mass at the free end. An equation for estimating the natural frequencies for the non-uniform beams is derived using the boundary and continuity conditions, and an equivalent bending stiffness for cracked beam is applied to calculate the natural frequencies of the cracked beam. An experimental study for a step-changed non-uniform cantilever-type pipe beam restrained by bolts with a tip mass is carried out to verify the proposed method. The translational and rotational spring constants are updated using the neural network technique to the results of the experiment for intact case in order to establish a baseline model for the subsequent crack detection. Then, several numerical simulations for the specimen are carried out using the derived equation for estimating the natural frequencies of the cracked beam to construct a set of training patterns of a neural network. The crack locations and sizes are identified using the trained neural network for the 5 damage cases. It is found that the crack locations and sizes are reasonably well estimated from a practical point of view. And it is considered that the usefulness of the proposed method for structural health monitoring of the step-changed non-uniform cantilever-type pipe beam-like structures elastically restrained in the ground and have a tip mass at the free end could be verified.