• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.99-106
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• 2007

This paper deals with the static and dynamic optimal shapes of both clamped columns with constant volume. The parabolic taper with the regular polygon cross-section is considered, whose material volume and column length are held constant. Numerical methods are developed for solving natural frequencies and buckling loads of columns subjected to an axial compressive load. Differential equations governing the free vibrations of such column are derived. The Runge-Kutta method is used to integrate the differential equations, and the Regula-Falsi method is used to determine natural frequencies and buckling loads, respectively. From the numerical results, dynamic stability regions, dynamic optimal shapes and configurations of strongest columns are presented in figures and tables.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.363-374
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• 2000

An accurate method is presented for vibrations of rhombic plates having three different combinations of clamped, simply supported, and free edge conditions. A specific feature here is that the analysis explicitly considers the moment singularities that occur in the two opposite corners having obtuse angles of the rhombic plates. Stationary conditions of single-field Lagrangian functional are derived using the Ritz method. Convergence studies of frequencies show that the corner functions accelerate the convergence rate of solutions. In this paper, accurate frequencies and normalized contours of the vibratory transverse displacement are presented for highly skewed rhombic plates, so that a significant effect of corner stress singularities nay be understood.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.417-428
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• 2000

In recent years, composite materials have been used in civil engineering as well as architecture, automobile, aerospace, shipping industries. Composite materials are composed of two or more different materials to produce desirable properties for structural strength. The shell structures have the advantage of more efficient load resistance due to its curved shape as compared to the plate structures. And the shell structures with composite materials have many advantages in strength, corrosion resistance, and weight reduction. The objective of this study is to analyze circular conical shells with shear deformation effects and to prove the advantage of composite materials. To solve differential equations of conical shells, this paper used finite difference method.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.1
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• pp.19-26
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• 1996

Melt-quenching of steels leads to various metallographic effects such as refinement of grain size, extension of the solid solubility of carbon and alloying elements, and is expected to improve the mechanical properties of conventional steels. Furthermore, this technique is a useful method for producing sheet directly from liquid state. And it will lend itself to development as a continuous cast process which offers significant savings in energy and product costs. The purpose of this study is to present the microstructures of melt-quenched austenitic stainless steels. As the results of this study, the morphology of melt-quenched microstructure show that the roll contact area is columnar structure, and the free surface area is dendrite structure. As the line speed increases, the ratio of $d_{colunnar}/d_{total}$ increases from 0.12 to 0.60, but the ribbon thickness decreases from $150{\mu}m$ to $30{\mu}m$.

• Journal of the Semiconductor & Display Technology
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• v.19 no.3
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• pp.1-6
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• 2020

In this paper, a method for improving the defect classification performance in steel plate surface has been studied, based on DWT(discrete wavelet transform) and SVM(support vector machine). Surface images of the steel plate have low contrast, uneven, and featureless, so that the contrast between defect and defect-free regions is not discriminated. These characteristics make it difficult to extract the feature of the surface defect image. In order to improve the characteristics of these images, a synthetic images based on discrete wavelet transform are modeled. Using the synthetic images, edge-based features are extracted and also geometrical features are computed. SVM was configured in order to classify defect images using extracted features. As results of the experiment, the support vector machine based classifier showed good classification performance of 94.3%. The proposed classifier is expected to contribute to the key element of inspection process in smart factory.

• International Journal of High-Rise Buildings
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• v.6 no.1
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• pp.33-47
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• 2017

This mixed-use Raffles City (RCH) development is located near the Qiantang River in Hangzhou, the capital of Zhejiang province, located southwest of Shanghai, China. The project incorporates retail, offices, housing, and hotel facilities and marks the site of a cultural landscape within the Quianjiang New Town Area. The project is composed of two 250-meter-tall twisting towers with a form of vibrant waves, along with a commercial podium and three stories of basement car parking. It reaches a height of 60 stories, presenting views both to and from the Qiantang River and West Lake areas, with a total floor area of almost 400,000 square meters. A composite moment frame plus concrete core structural system was adopted for the tower structures. Concrete filled steel tubular (CFT) columns together with steel reinforced concrete (SRC) beams form the outer moment frame of the towers' structure. The internal slabs and floor beams are of reinforced concrete. This paper presents the engineering design and construction of this highly complex project. Through comprehensive discussion and careful elaboration, some conclusions are reached, which serve as a reference guide for the design and construction of similar free-form, hybrid, mix-use buildings.

• Corrosion Science and Technology
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• v.9 no.5
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• pp.175-186
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• 2010

The auto industry is demanding more ductile high-strength steel grades to build lighter and stronger car bodies. The hot-dip galvanizing problems of these new steel grades are creating a demand for an improved method to control zinc wettability. The simplest way to improve zinc wettability on industrial hot-dip galvanizing lines is to increase the strip immersion temperature at zinc bath entry for enhancing the aluminothermic reaction. However, this practice increases the reactivity due to overheating the zinc in the snout which induces the formation of brittle Fe-Zn compounds at the strip/coating interface with the formation of higher amounts of dross in the zinc bath and snout contamination. Thus, this simple practice can only be utilized for short production periods of one to two hours without deteriorating coating quality. This problem has been solved by employing a technique that allows the use of a higher and attuned strip immersion temperature at zinc bath entry while still maintaining a constantly low zinc bath temperature. This has been proven to provide the solution for both the improved wettability and a significant reduction in the amounts of dross in the zinc bath.

• Current Photovoltaic Research
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• v.2 no.3
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• pp.79-83
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• 2014

Dye-sensitized solar cells (DSSCs) are applied in the emerging fields of building integrated photovoltaic and electronics integrated photovoltaic like small portable power sources as demands are increased with characteristic advantages. Highly flexible dye-sensitized solar cells (DSSCs) prepared on single stainless steel mesh were proposed in this paper. Single mesh DSSCs structure utilizing the spraying the chopped glass paper on the surface treated stainless steel mesh for integrating the space element and the electrode components, counter electrode component and photoelectrode component were coated on each side of the single mesh. The fabricated single mesh DSSCs showed the energy-conversion efficiency 0.50% which show highly bendable ability. The new single mesh DSSCs may have potential applications as highly bendable solar cells to overcome the limitations of TCO-based DSSCs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1300-1305
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• 2007

Plastic board drain is one of the methods to reinforce weak soil, and it has been widely used because of economical efficiency, convenience of construction, and ease of quality control. The weight of PBD equipment which places PBD perpendicularly underground in the depth of 40m has to be minimized to obtain convenience installation and movement while standing against press drawing load. In this study, the performance of stability was evaluated with stress distribution at the steel construction of former equipment by structural analysis: And the steel construction which can increase strength while reducing the weight was also presented. As a result of this study, presented construction can obtain more stability by use of the weight 700kg lighter than the former one.

• Journal of Korean Society of Steel Construction
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• v.23 no.2
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• pp.189-198
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• 2011

Many new structural systems have been developed to build free-form structures, which is the new architectural trend for aesthetic beauty. The diagrid system resists both gravity and later loads, with its perimeter-diagonal columns. In the current seismic-design provisions, however, a seismic-performance factor for a new structural system has not yet been provided. ATC-63 provides a new methodology for defining various seismic-performance factors, including the response modification factor. In this paper, nonlinear static and dynamic analyses were conducted for the 3D diagrid frame, with each load applied at $0-180^{\circ}$ degrees. Through these analyses, the seismic performance of the diagrid system was evaluated.