• Steel and Composite Structures
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• v.36 no.6
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• pp.671-687
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• 2020

The aim of this research is to analyze buckling and bending behavior of a sandwich Reddy beam with porous core and composite face sheets reinforced by boron nitride nanotubes (BNNTs) and shape memory alloy (SMA) wires resting on Vlasov's foundation. To this end, first, displacement field's equations are written based on the higher-order shear deformation theory (HSDT). And also, to model the SMA wire properties, constitutive equation of Brinson is used. Then, by utilizing the principle of minimum potential energy, the governing equations are derived and also, Navier's analytical solution is applied to solve the governing equations of the sandwich beam. The effect of some important parameters such as SMA temperature, the volume fraction of SMA, the coefficient of porosity, different patterns of BNNTs and porous distributions on the behavior of buckling and bending of the sandwich beam are investigated. The obtained results show that when SMA wires are in martensite phase, the maximum deflection of the sandwich beam decreases and the critical buckling load increases significantly. Furthermore, the porosity coefficient plays an important role in the maximum deflection and the critical buckling load. It is concluded that increasing porosity coefficient, regardless of porous distribution, leads to an increase in the critical buckling load and a decrease in the maximum deflection of the sandwich beam.

• Steel and Composite Structures
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• v.29 no.3
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• pp.319-332
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• 2018

This paper investigates the free vibration of geometrically imperfect functionally graded car-bon nanotube-reinforced composite (FG-CNTRC) beams that are integrated with two sur-face-bonded piezoelectric layers and subjected to a combined action of a uniform temperature rise, a constant actuator voltage and an in-plane force. The material properties of FG-CNTRCs are assumed to be temperature-dependent and vary continuously across the thick-ness. A generic imperfection function is employed to simulate various possible imperfections with different shapes and locations in the beam. The governing equations that account for the influence of initial geometric imperfection are derived based on the first-order shear deformation theory. The postbuckling configurations of FG-CNTRC hybrid beams are determined by the differential quadrature method combined with the modified Newton-Raphson technique, after which the fundamental frequencies of hybrid beams in the postbuckled state are obtained by a standard eigenvalue algorithm. The effects of CNT distribution pattern and volume fraction, geometric imperfection, thermo-electro-mechanical load, as well as boundary condition are examined in detail through parametric studies. The results show that the fundamental frequency of an imperfect beam is higher than that of its perfect counterpart. The influence of geometric imperfection tends to be much more pronounced around the critical buckling temperature.

• The Korean Journal of Air & Space Law and Policy
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• v.12
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• pp.246-274
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• 2000

This paper discusses the qualification criteria for international hub airport and suggests the strategies for Inchon International Airport (IIA) to be the hub airport in the East Asia. Recently, many East and Southeast Asia countries have invested on large scale international airports like Chap Lak Kok airport, Pudong airport etc.. as Korea have done on IIA. IIA to be open in 2001 will face a serious competition with these airport. Being a hub airport requires geographic proximity. sufficient volume of local traffic. uncongested infrastructure, a good accessibility to surrounding industrial centers. high quality of service to the airline. In order to promote airlines to land at IIA. Korea Government need to establish Open Sky Policy to many countries and national flag carriers of Korea need to be involved in a global alliance. Developing vicinity of IIA as free trade zone will generated more local traffic which makes IIA as more attractive candidate for airlines. The Korea airspace is one of the most restricted area in the world becuase of the national security. which limits civil aircraft maneuvers. The airspace need to be re-structured to exploit the full capacity of IIA.

• Journal of computational fluids engineering
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• v.6 no.1
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• pp.1-13
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• 2001

The natural convection heat transfer and solidification in a stratified pool are studied. The flow and heat transfer characteristics in a heat generating pool are compared between single-layered and double-layered pools. And local Nusselt number distributions on outer walls are obtained to consider thermal loads on a vessel wall. The cooling and solidification of Al₂O₃/Fe melt in a hemispherical vessel are simulated to study the mechanism of heat transfer and temperature distribution. A unstructured mesh is chosen for this study because of the non-orthogonality originated from the boundaries of double-layered pool. Interface between the layers is modeled to be fixed. With this assumption mass flux across the interface is neglected, but shear force and heat flux are considered by boundary conditions. The colocated cell-centered finite volume method is used with the Rhie-Chow interpolation to compute cell face velocity. To prevent non-physical solutions near walls in case body force is large the wall pressure is extrapolated by the way to include body force. The numerical solutions calculated by current method show that averaged downward heat flux of the double-layered pool increases compared to single-layered pool and maximum temperature occurs right below the interface of the layers.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2261-2267
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• 1992

The equations are derived for the evaluation of the axial contact force. The contact forces for rubber seals are analyzed as a function of the ratio of real contact length, the thickness of seal lip, the inclined angle of seal lip, and the interference between the edge of seal lip and the rotating inner ring. The design data for rubber seals are presented in terms of the ratio of real contact length, initial inclined lip angle, lip thickness and the interference. The calculated results show that the deflected interference and the circumferential stress cause considerable change of contcat forces for the low sealed pressure.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.515-518
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• 2006

This paper presents the friction and wear characteristics of contact type sealing unit for a water turbine of a small hydro-power generation, which Is to stop a leakage of a circulating water from a outside of an impeller to an inside of a rolling bearing. The surface wear strongly affect to the seal life of a mechanical face seal. In this study, the hardness of a stainless steel in which is a heat-treated is 892.8 in Vickers hardness and the hardness of silicone carbide of SiC is 714.1 in Vickers hardness. The surface hardness of a heat-treated stainless steel is 25% high compared with that of a ceramic material of SiC. The contact modes of rubbing surfaces aye a dry friction a water film friction and a mixed friction that is contaminated by a dust, silt and moistures, etc. These two factors of a contact rubbing modes and a material property are very important parameters on the tribological performance such as a friction and wear between a seal ring and a seal seat. The experimental result shows that the surface hardness of a seal material is very important on the friction coefficient and a wear volume. Thus, the results recommend higher hardness of a seal material, which may reduce a friction loss and increase a wear life of primary seal components

• Korean Journal of Human Ecology
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• v.15 no.1
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• pp.129-139
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• 2006

The purpose of this study is to compare the hairstyles between Korean and Australian women, who have different individual hair characteristics, social backgrounds, and culture from each other. Data were collected through a survey of 208 Australian females and 392 Koreans. Frequency analysis, t-test, and two-way ANOVA were used to analyze the data. The results are as follows: Korean and Australian women maintain a hairstyle for six months or less in most of the cases. They preferred a hairstyle with bang, and the elderly especially a shorter hair length. Choosing their hairstyles depended on such factors as hair length, dyeing, form of face, harmony with clothing, and social status. There was no difference, however, in a preferred hair length. Korean women possessed brown and black hair colors in a descending order, whereas Australians light blonde and brown in a descending order as well. There was a big difference in the preference for a permanent wave. Korean women preferred to give a volume or curl to their hair, while Australians wanted to have a straight hair. According to the study on a hairstyle behavior, it was found that there were differences in fashion and individuality between two countries and also in dependency among age groups, whereas no differences existed in beauty.

• The Journal of Korea Robotics Society
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• v.5 no.1
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• pp.7-13
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• 2010

This paper presents the sound-based emotion estimation method and the growing HRI (human-robot interaction) system for a Mon-E robot. The method of emotion estimation uses the musical element based on the law of harmony and counterpoint. The emotion is estimated from sound using the information of musical elements which include chord, tempo, volume, harmonic and compass. In this paper, the estimated emotions display the standard 12 emotions including Eckman's 6 emotions (anger, disgust, fear, happiness, sadness, surprise) and the opposite 6 emotions (calmness, love, confidence, unhappiness, gladness, comfortableness) of those. The growing HRI system analyzes sensing information, estimated emotion and service log in an edutainment robot. So, it commands the behavior of the robot. The growing HRI system consists of the emotion client and the emotion server. The emotion client estimates the emotion from sound. This client not only transmits the estimated emotion and sensing information to the emotion server but also delivers response coming from the emotion server to the main program of the robot. The emotion server not only updates the rule table of HRI using information transmitted from the emotion client and but also transmits the response of the HRI to the emotion client. The proposed system was applied to a Mon-E robot and can supply friendly HRI service to users.

• Proceedings of the KSRS Conference
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• v.1
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• pp.417-420
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• 2006

In these days, mobile application dealing with information contents on mobile or handheld devices such as mobile communicator, PDA or WAP device face the most important industrial needs. The motivation of this study is the design and implementation of mobile application using high resolution satellite imagery, large-sized image data set. Although major advantages of mobile devices are portability and mobility to users, limited system resources such as small-sized memory, slow CPU, low power and small screen size are the main obstacles to developers who should handle a large volume of geo-based 3D model. Related to this, the previous works have been concentrated on GIS-based location awareness services on mobile; however, the mobile 3D terrain model, which aims at this study, with the source data of DEM (Digital Elevation Model) and high resolution satellite imagery is not considered yet, in the other mobile systems. The main functions of 3D graphic processing or pixel pipeline in this prototype are implemented with OpenGL|ES (Embedded System) standard API (Application Programming Interface) released by Khronos group. In the developing stage, experiments to investigate optimal operation environment and good performance are carried out: TIN-based vertex generation with regular elevation data, image tiling, and image-vertex texturing, text processing of Unicode type and ASCII type.

• Journal of the Korean Wood Science and Technology
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• v.20 no.3
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• pp.29-37
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• 1992

This research was carried out to investigate the effects of cyclic humidification on the dimensional stability of particleboard manufactured according the three specific gravity levels and com-ply fabricated with a core of particleboard and veneer or plywood as the face and back materials. Both the particleboard and com-ply were subjected to four cycles of 50-90-50% relative humidity. The results are summarized as follows: Particleboard and com-ply followed a clear pattern of increasing dimensions and weight on the adsorption cycle and decreasing dimensions and weight on the humidification cycle. After the fourth cycle, the dimensions and weight of both particleboard and com-ply were greater than those originally measured. The greater part of increase in occurred during the first humidification cycle. The specific gravity of particleboard has a significant effect thickness and volume change. The dimensional stability of com-ply was better than that of particleboard. In addition, the dimensional stability of com-ply bonded with plywood was better than that of com-ply bonded with veneer.