• Journal of the Korean Applied Science and Technology
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• v.32 no.3
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• pp.405-411
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• 2015

Carbon composites for flexible fiber heating element were examined to improve the electrical conductivity in this study. Carbon composites using carbon black, denka black, super-c, super-p with/without CNF or dispersant such as BCS03 and Sikament-nn were prepared. Carbon composite slurry was coated on plane film and yarns(cotton, polyester) and the performances of prepared heating materials were investigated by checking electrical surface resistance, adhesion strength. The plane heating element using carbon black under natural drying condition($25^{\circ}C$) had better physical properties such as surface resistance(185.3 Ohm/sq) and adhesion strength(above 90%) than those of other carbon composite heating elements. From these results, polyester heating element coated by carbon black showed better electrical line resistance(33.2 kOhm/cm) than cotton heating element. Then, it was found that polyester heating element coated by carbon black with CNF(3 wt%) and BCS03(1 wt%) appeared best properties(0.604 kOhm/cm).

• Steel and Composite Structures
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• v.15 no.2
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• pp.175-202
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• 2013

The super convergent laminated composite beam element is newly derived for the lateral stability analysis. For this, a theoretical model of the laminated composite beams is developed based on the first-order shear deformation beam theory. The present laminated beam takes into account the transverse shear and the restrained warping induced shear deformation. The second-order coupling torque resulting from the geometric nonlinearity is rigorously derived. From the principle of minimum total potential energy, the stability equations and force-displacement relationships are derived and the explicit expressions for the displacement parameters are presented by applying the power series expansions of displacement components to simultaneous ordinary differential equations. Finally, the member stiffness matrix is determined using the force-displacement relationships. In order to show accuracy and superiority of the beam element developed by this study, the critical lateral buckling moments for bisymmetric and monosymmetric I-beams are presented and compared with other results available in the literature, the isoparametric beam elements, and shell elements from ABAQUS.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.6
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• pp.173-179
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• 2009

Recently, the super capacitor(EDLC) which has drawn attention as a new energy storage element has a lot of advantage such as no maintenance, long lifetime and quick charge/discharge characteristics with large current. The objective of this paper is propose a parameter measurement method to detect the changes in equivalent series resistor (ESR) and the capacitance value of a super capacitor in order to analysis the internal characteristic and worn-out state of a super capacitor. For proposed method, only the capacitor voltage measurement using simple analog switch is required. In addition, experimental results of voltage sag compensation system in order to compensate the input voltage drop during short-term power interruption adopted super capacitor are presented.

• Journal of the Korean Institute of Landscape Architecture
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• v.20 no.4
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• pp.54-75
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• 1993

The purpose of this thesis is to suggest objective basic data for the super graphics in the urban landscape through the quantitative visual quality analysis. For this, the image structure of super graphics have been measured mainly by questionnaries and semantic differential scle method and analyzed by the method of factor analysis, means and multiple regression. Degree of visual preference have been measured mainly by questionnaries and likert attitude scale method and finaly these data have been analyzed by using the stepwise method. The data were collected by presenting 12 super graphics photographs-4 each sample pictures from the 3 each selected districts representing typical urban landscape style(central business district, shopping district, apartment complex). Observer groups were categorized as professionals, students, the others. Result of this thesis can be summarized as fallows: 1. From all 12(3${\times}$4) sample super graphics, the value of each semantic differential scale among the observer groups were presented significant group difference. But no significant difference of the S.D. scale value were observed among central business district, shopping district and apartment complex super graphics. 2. For all experimental points, 4 types of factor have been observed. Factors covering the image of super graphics were found to be the evaluation, the intimacy, the potentiality and the tidiness. 3. Main factors of the super graphics image and factors indicating the group variations yielded high significance between areas. 4. The harmony with surrounding environment, the proper selection of super graphics subject yielded high values for all groups. Especially, the good color sense with building was the most important variable determining the degree of visual preference. 5. The urban C.B.D. super graphics obtained 5∼12 ranks of regional visual preference and the shopping district super graphics obtained 2∼11 ranks, and apartment complex super graphics obtained 1∼7 ranks.

• The Journal of the Acoustical Society of Korea
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• v.33 no.3
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• pp.191-199
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• 2014

Wave reflection and transmission characteristics in waveguides are an important issue in many engineering applications. A combined spectral element and finite element (SE/FE) method is used to investigate the effects of local non-uniformities but limited at relatively low frequencies because the SE is formulated by using a beam theory. For higher frequency applications, a method named a combined spectral super element and finite element (SSE/FE) method was presented recently, replacing spectral elements with spectral super elements. This SSE/FE approach requires a long computing time due to the coupling of SSE and FE matrices. If a local non-uniformity has a uniform cross-section along its short length, the FE part could be further replaced by SSE, which improves performance of the combined SSE/FE method in terms of the modeling effort and computing time. In this paper SSEs are combined to investigate the characteristics of waves propagating along waveguides possessing geometric non-uniformities. Two models are regarded: a rail with a local defect and a periodically ribbed plate. In the case of the rail example, firstly, the results predicted by a combined SSE/FE method are compared with those from the combined SSEs in order to justify that the combined SSEs work properly. Then the SSEs are applied to a ribbed plate which has periodically repeated non-uniformities along its length. For the ribbed plate, the propagation characteristics are investigated in terms of the propagation constant.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.1
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• pp.39-44
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• 2010

Recently underwater systems moving at high speed such as a super-cavitating torpedo have been studied for their practical advantage of the dramatic drag reduction. In this study we are focusing our attention on super-cavitating flows around axisymmetric cavitators. A numerical method based on inviscid flow is developed and the results for several shapes of the cavitator are presented. First using a potential based boundary element method, we find the shape of the cavtiator yielding a sufficiently large enough cavity to surround the body. Second, numerical predictions of supercavity are validated by comparing, with experimental observations carried out in a high speed cavitation tunnel at Chungnam National University (CNU CT).

• Geomechanics and Engineering
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• v.2 no.4
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• pp.281-302
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• 2010

An extended model for the response of a rigid footing on a reinforced foundation bed on super soft soil is proposed by incorporating the rough membrane element into the granular bed. The super soft soil, the granular bed and the reinforcement are modeled as non-linear Winkler springs, non-linear Pasternak layer and rough membrane respectively. The hyperbolic stress-displacement response of the super soft soil and the hyperbolic shear stress-shear strain response of the granular fill are considered. The finite deformation theory is used since large settlements are expected to develop due to deformation of the super-soft soil. Parametric studies quantify the effect of each parameter on the stress-settlement response of the reinforced foundation bed, the settlement and tension profiles.

• International Journal of Railway
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• v.2 no.4
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• pp.170-174
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• 2009

Super speed tube train is introduced to increase the speed of ground transportation. The super speed tube train levitates magnetically and runs in a partial vacuum tube, which can reduce the air resistance significantly. However, the strong magnetic force enough to propel the massive train can affect to the tube infrastructure. In this paper, authors have analyzed the leakage flux patterns and induced eddy current on the tube by using 3-dimensional Finite Element Method. These effects are investigated, especially by varying the materials and diameters of the tube. From the simulation results, the aluminum tube with the diameter of 3[m] is needed to be concerned because the induced eddy current produces joule heat, raises the inside temperature of the tube, and might be able to lead to electro-chemical corrosion on the tube, consequently reduce the durability.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.89-96
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• 2009

In recent years, there has been a considerable interest in the application of super plastic forming in the aircraft and automotive industries. This requires a detailed design of the technological process in order to exploit its peculiar potentialities better. Nowadays, the finite element method is used to plan the sheet metal forming processes whose simulation requires determination of material constants for super plastic materials. The present work is aimed to show a simple method to characterize super plastic materials duplex stainless steel which was formed by a constant gaspressure to hemispheres with and without back pressure. The forming operation was performed using an in-house designed and built biaxial forming apparatus. The temporal change of dome heights of hemispheres were measured for applying the pressures. The flow stresses and strain rates developed at the top of the dome during the forming step were shown to follow closely the flow stress - strain rate relationship obtained from the strain rate change tests performed at the same temperature.

• KIEAE Journal
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• v.10 no.5
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• pp.151-157
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• 2010

This study is connected with evaluation of the progressive collapse resisting capacity for sustainable RC super tall building design. As the progressive collapse is not considered in current design codes in Korea, differences between linear static and dynamic analysis based on the GSA guidelines was analyzed for better evaluation, and the analysis model of flat plate system was determined. Finally, the progressive collapse resisting capacity was evaluated for structural system of super tall building. According to this study, the results by linear dynamic analysis were underestimated than the results by linear static analysis. Thus, the dynamic coefficient value of 2 provides conservative approach. The Effective Beam Width's model, currently used in field, is useful for the analysis about lateral force, but this model does not consider the effect of load redistribution by the slab. Hence, finite element analysis considering slab element will be needed for progressive collapse resisting capacity of the flat plate system. Finally, analysis model of 80-story building designed based on KBC(Korea Building Code) shows the weakness against progressive collapse because the DCR value is over 2. Thus, the countermeasure for alternative loading path such as installment of spandrel beam and reinforcements around slab is required to prevent the progressive collapse.