• Journal of Welding and Joining
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• v.25 no.3
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• pp.85-91
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• 2007

The conventional study on the laser surface transformation hardening has been carried out with a beam of the specified shape and uniform power-intensity distribution in order to ensure the uniformity of the hardening depth. Two types of beams - the circular gaussian beam and rectangular beam of the uniform power-intensity distribution were used in this study. we were supposed to optimize the process parameters and to compare the hardening results with two optics respectively. As a result, the hardness distribution of the hardened zone was similar in both cases and the hardened phase by the rectangular beam was denser than that by the circular gaussian beam.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.255-262
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• 2002

In this paper, an improved multi-objective optimmum design method is proposed. And it is applied to steel frames under seismic loads. The multi-objective optimization problem is formulated with three optimality criteria, namely, minimum structural weight and maximum strain energy and stability. The Pareto curve can be obtained by performing the multi-objective optimization for multistory shear buildings. In order to efficiently solve the multi-objective optimization problem the decomposition method that separates both system-level and element-level is used. In addition, various techniques such as effective reanalysis technique with respect to intermediate variables and sensitivity analysis using an automatic differentiation (AD) we incorporated. Moreover, the relationship function among section properties induced from the profile is used in order to link system-level and element level. From the results of numerical investigation, it may be stated that the proposed method will lead to the more rational design compared with the conventional one.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.756-757
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• 2006

P/M enables the economical production of components for many kinds of gears. Functionally, the sub gear requires high tooth accuracy and bending fatigue strength. The whole tooth profile was sized after sintering to satisfy the gear tooth accuracy specification. The part was redesigned to reduce machining requirements. The required bending fatigue strength was achieved through appropriate material choice and induction of compressive residual stress by shotpeening after carburizing. The P/M sub gear replaced a forged steel gear, satisfied performance requirements, expanded the use of P/M applications and provided over 30% cost reduction.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.181-184
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• 2005

When concrete structures are exposed under marine condition for a long time, the steel in concrete is corroded due to the ingression of chlorides in the seawater. Because the damages of corrosion resulting from the chloride ion are very serious, many researches have been performed. However evaluation on chloride attack of concrete structures are not fully examined, recently. Therefore, the objective of this paper is to study the applicability of colormetric method. For the purpose of this, reaction mechanism of colormetric method were investigated, and the colormetric method is applied for marine concrete structures. According to the test results, the diffusion coefficient by colormetric method is not so different to the value of chloride concentration profile test. It is confirmed that the colormetric method is useful tool for estimating the chloride of concrete structures in situ. The average chloride amount of colored parts indicates 0.9kg/$m^{3}$ per concrete unit weight.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.767-774
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• 2008

The spot where bottom foundation of a marine bridge is constructed is deep in depth of water and a bedrock, bearing stratum, is very deeply distributed. So, I analyzed material of soil profile and then evaluate bearing capacity and safety of settlement when a stake of site construction is designed using a projection cast in place concrete pile and a sacrifice steel cast in place pile. Also, I analyzed and researched pratical affairs like a slime processing and plumbing maintenance in supervision of execution.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.892-894
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• 1995

This paper deals with developmeant and application of coating thickness control system in hot dip galvanizing process. According to the line conditions, such as line speed, strip size and target coating weight, a predictive preset model sets the initial oprating conditions. Referring the zine coating informations from the gauge, mean coating value controller adjusts the chamber pressure and horizontal distance between strip and air knife, while coating deviation controller adjusts the lip gap profile of the air knife. All adaptive gains are interactively calculated by numeric models based on the theoretical analysis. The operating result with this system effectively reduces the coating deviation in transverse direction as well as in longitudinal direction.

• Structural Engineering and Mechanics
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• v.74 no.2
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• pp.255-266
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• 2020

The main requirements of modern welded metal structures are the load-carrying capacity (safety), fitness for production, and economy. The primary objective of attaching longitudinal stiffeners is to improve the buckling strength of relatively thin compression panels. This paper gives several comparisons for stiffened plates with different loadings (static, dynamic), different shape of stiffeners (flat, L-shape, trapezoidal), different steel grades, and different welding technologies (SMAW, GMAW, SAW), different costs to show the necessity of a combination of design, fabrication and economic aspects. Safety and fitness for production are guaranteed by fulfilling the design and fabrication constraints. The economy is achieved by minimizing the cost function. It is shown that the optimum sizes depend on the welding technology, the material yield stress, the profile of the stiffeners, the load cycles and the place of the production.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.1
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• pp.84-95
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• 1991

This paper deals with crater wear when the SUS304 steel which forms the saw- toothed chip was cut by carbide tools. When the saw-toothed chip was formed, and optical creater wear measuring technique was used which provides complete information, both qualitatively and quantitatively, on the crater development. In this optical contour mapping technique an profile projector was used, making it possible to draw the depth contours of the crater directly. 98 contour maps of crater wear representing twelve different cutting conditions were presented. Also, the rake angles changed to have ${\alpha}$ =$6^{\circ}$, ${\alpha}$ =$-6^{\circ}$

• Proceedings of the KACD Conference
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• 2003.11a
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• pp.589-590
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• 2003

Mesiobuccal or distobuccal canals of maxillary molars and mesiobuccal or mesiolingual canals of mandibular malars were selected. Forty specimens were divided into four groups according to the instruments used : stainless steel K-files($MANI^{\circledR}$, Matsutani Seisakusho Co. Takanezawa, Japan), nickel-titanium K-files (Naviflex $NT^{TM}$, Brassler, Savannah, U.S.A.), $Profile^{\circledR}$, and $ProTaper^{TM}$ (Dentsply-Maillefer, Ballaigues, Switzerland). Occlusal surface of each tooth and root apex were flattened by using diamond burs and sandpaper. Before instrumentation, a rubber stop was fixed with glue to the ＃10 K-files of initial working length in each tooth.(omitted)

• Journal of Surface Science and Engineering
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• v.32 no.3
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• pp.249-252
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• 1999

Boriding is one of the chemical method to increase surface hardness as well as carburizing, and nitriding. Gas boriding and boron paste boriding methods were investigated to replace salt bath boriding. Boron paste boriding method is selected due to safety, small waste and low cost. And then boriding is also carried out micro-pulsed PECVD in order to increase efficiency of boriding. Mechanical properties, microstructure, surface concentration, and depth profile of borided layer is investigated by micro-vickers hardness tester, SEM, XRD, and AES.