• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.571-576
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• 2001

Hydroforming, the new production technology, has been used to manufacture many parts of vehicle in the recent auto industry. When Hydroforming is applied, it is possible to make parts simplification and flexible alteration of section shape in many advantages such as weight reduction, number of parts reduction or performance improvement. This research into shape optimization which reduces number of parts and weight maintaining performance was achieved. In this paper, the COWL CROSS BAA and MT'g BAKT parts of A car STEERING support SYSTEM was introduced by using Hydroforming.

• Journal of the Korean Institute of Gas
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• v.14 no.3
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• pp.41-45
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• 2010

The physical properties of DME(Dimethyl Ether) are very similar to LPG and well-mixed. As cetane number of DME is similar to diesel fuel that can replace diesel fuel and alternative energy. DME is a clean energy source that can be manufactured from various raw materials such as natural gas, CBM(Coal Bed Methane) and biomass. DME has no carbon-carbon bond in its molecular structure and its combustion essentially generates no soot as well as no SOx. The development of DME process in KOGAS have 4 section. First, syngas section can be manufactured various syngas ratio. This completes the tri-reforming process for the synthesis gas ratio of approximately 4.0 to 1.0 range can be adjusted. Second, $CO_2$ is removed from the $CO_2$ removal section of about 92~99%, so the maximum concentration of $CO_2$ entering the DME synthesis reactor should not exceed 8%. Third, in the DME synthesis section, if the temperature of DME reactor increases, the activity of DME catalyst increased. but for the long-term activity is desirable to maintain the proper temperature. Finally, the purity of DME in the DME purification section is over 99.6%.

• Kyungpook Mathematical Journal
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• v.47 no.2
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• pp.165-714
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• 2007

The basis number of a graph G is the least positive integer $k$ such that G has a $k$-fold basis. In this paper, we prove that the basis number of the cartesian product of a path with a circular ladder, a M$\ddot{o}$bius ladder and path with a net is exactly 3. This improves the upper bound of the basis number of these graphs for a general theorem on the cartesian product of graphs obtained by Ali and Marougi, see [2]. Also, by this general result, the cartesian product of a theta graph with a M$\ddot{o}$bius ladder is at most 5. But in section 3 we prove that it is at most 4.

• Journal for History of Mathematics
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• v.13 no.2
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• pp.49-64
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• 2000

Every real number can be expressed as a simple continued fraction. In particular, a number is rational if and only if its simple continued fraction has a finite number of terms. Owing to this property, continued fractions have been a powerful tool which determines a real number to be rational or not. Continued fractions provide not only a series of best estimate for a real number, but also a useful method for finding near commensurabilities between events with different periods. In this paper, we investigate the history and some properties of continued fractions, and then consider their applications in several examples. Also we explain why the Fibonacci numbers and the Golden section appear in nature in terms of continued fractions, with some examples such as the arrangements of petals round a flower, leaves round branches and seeds on seed head.

• Korean Journal of Plant Taxonomy
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• v.38 no.4
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• pp.477-502
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• 2008

Morphological characters of inflorescence, spikelet, rachilla, glume, lemma and palea about 17 taxa of Korean Poa L. were investigated to evaluate their taxonomic significances. The bulbil present or not, inflorescence shape, callus shape of lemma and surface shape of palea were thought to be the subgenus characters. The keels shapes of palea, the number of lower glume, lateral nerve shape of lemma were thought to be the section characters. The number of floret, rachilla present or not, the number of lower glume, nerve shape of glume, surface shape of lemma were thought to be the species characters. Consequently, 17 taxa of the Korean Poa L. is classified into 3 subgenus (Ochlopoa, Stenopoa, Stenopoa), 7 section(Arenariae, Ochlopoa, Homalopoa, Poa, Pandemos, Tichopoa, Stenopoa). 6 taxa, P. ullungdoensis, P. takeshimana and P. matsumurae, P. nipponica, P. radula, P. viridula, not included in the existing classification system, were suggested to their taxonomic category in infragenic rank, and P. nemoralis, had been included in section Stenopoa of subgenus Stenopoa, was proposed to move to section Poa of subgenus Poa. P. ullungdoensis, reported as new species in 1955, was grasped its taxonomic identity.

• Journal of Korean Society of Steel Construction
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• v.26 no.4
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• pp.263-275
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• 2014

In this study, connection of steel reinforced concrete(SRC) column and composite beam which consists of H-section and U-section members were tested under cyclic loading. An essential point of the composite beam is the structural performance of welded joint between the H-section and the U-section members. To improve the structural performance of joint of two beam members, vertical stiffeners, trapezoidal stiffeners, and top bars were used. Five full-scaled specimens were designed to study the effect of a number of parameters on cyclic performance of connections such as H-section beam size($H-500{\times}200{\times}10{\times}16$, $H-600{\times}200{\times}11{\times}17$), the presence of stiffeners and top bars, and the presence of no weld access hole(WAH) method. Based on the test results, deformation capacity of the specimens with H-500 series beam and H-600 series beam were 4% and 3% rotation angle, which is the requirement for the Special Moment Frame and Intermediate Moment Frame(IMF), respectively. Test result showed that deformation capacity of connection with stiffeners and top bars is greater than that of connection without stiffeners and top bars. Finally, energy dissipation capacity and strain profile of specimens were summarized.

• Korean Journal of Optics and Photonics
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• v.17 no.6
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• pp.548-555
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• 2006

We investigate the effect of the reflectivity of both facets and the phase of a phase tuning section on the self-pulsation (SP) characteristics of multisection index-coupled (IC) DFB lasers composed of two index-coupled DFB sections and a phase tuning section between them in terms of yield. In the case of weak coupling strength, as the reflectivity of both facets increases, the effect of reflected fields from both facets and the other DFB section on the mode characteristics of one DFB section increases. Thus the number of mode hoping increases and yield decreases for the variation of phases of both facets. In the case of strong coupling strength, as the reflectivity of both facets increases, the spatial hole burning effect increases, so that the yield decreases. The maximum yield and the range of the phase of a phase tuning section with yield more than 40% decrease as the facet reflectivity increases irrespective of coupling strength. As the coupling strength increases, the variation of yield for the variation of the phase of a phase tuning section increases and the variation of the phase of a phase tuning section with the maximum yield for the variation of the reflectivity of both facets decreases. The yield characteristics of the cases with the coupling strengths of 2 and 3 are better than those with the coupling strengths of 1.2 and 4.

• The Journal of the Acoustical Society of Korea
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• v.19 no.1
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• pp.54-60
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• 2000

There are many works to analyze a simple expansion chamber involving higher order modes. These works are classified to mode matching method, velocity potential method and finite element method. Among these methods, mode matching method has good performance at analyzing a concentric expansion chamber. Generally inlet/outlet pipe cross section area is smaller than middle chamber cross section area. So the number of higher order modes of inlet/outlet pipe can be fewer than that of middle chamber. But mode matching method must use the same number of higher order modes at inlet pipe, middle chamber and outlet pipe. Therefore the redundant modes of inlet/outlet pipe makes the computation time of mode matching method longer. In this paper, the new method, which can select number of each higher order modes of inlet pipe, middle chamber and outlet pipe, was suggested. And this method was compared to conventional mode matching method and finite element method in order to demonstrate the accuracy of the new method and to show that the new method can reduce a calculating time.

• Wind and Structures
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• v.22 no.2
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• pp.253-272
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• 2016

The paper concerns with the method and results of wind tunnel investigations of the Strouhal number (St) of a stationary iced cable model of cable-supported bridges with respect to different angles of wind attack. The investigations were conducted in the Climatic Wind Tunnel Laboratory of the Czech Academy of Sciences in $Tel{\check{c}}$. The methodology leading to the experimental icing of the inclined cable model was prepared in a climatic section of the laboratory. The shape of the ice on the cable was registered by a photogrammetry method. A section of an iced cable model with a smaller scale was reproduced with a 3D printing procedure for subsequent aerodynamic investigations. The St values were determined within the range of the Reynolds number (Re) between $2.4{\cdot}10^4$ and $16.5{\cdot}10^4$, based on the dominant vortex shedding frequencies measured in the wake of the model. The model was oriented at three principal angles of wind attack for each of selected Re values. The flow regimes were distinguished for each model configuration. In order to recognize the tunnel blockage effect the St of a circular smooth cylinder was also tested. Good agreement with the reported values in the subcritical Re range of a circular cylinder was obtained. The knowledge of the flow regimes of the airflow around an iced cable and the associated St values could constitute a basis to formulate a mathematical description of the vortex-induced force acting on the iced cable of a cable-supported bridge and could allow predicting the cable response due to the vortex excitation phenomenon.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.82-96
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• 2019

A semi-submersible structure has been widely used for offshore drilling and production of oil and gas. The small water plane area makes the structure very sensitive to weight increase in terms of payload and stability. Therefore, it is necessary to lighten the substructure from the early design stage. This study aims at an optimization of hull structure based on a sophisticated yield and buckling strength in accordance with classification rules. An in-house strength assessment system is developed to automate the procedure such as a generation of buckling panels, a collection of required panel information, automatic buckling and yield check and so on. The developed system enables an automatic yield and buckling strength check of all panels composing the hull structure at each iteration of the optimization. Design variables are plate thickness and stiffener section profiles. In order to overcome the difficulty of large number of design variables and the computational burden of FE analysis, various methods are proposed. The steepest descent method is selected as the optimization algorithm for an efficient search. For a reduction of the number of design variables and a direct application to practical design, the stiffener section variable is determined by selecting one from a pre-defined standard library. Plate thickness is also discretized at 0.5t interval. The number of FE analysis is reduced by using equations to analytically estimating the stress changes in gradient calculation and line search steps. As an endeavor to robust optimization, the number of design variables to be simultaneously optimized is divided by grouping the scantling variables by the plane. A sequential optimization is performed group by group. As a verification example, a central column of a semi-submersible structure is optimized and compared with a conventional optimization of all design variables at once.