• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.597-602
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• 2015

CrMo alloy steel was nitrided using two types of processing methods, ion-nitriding processing and nitrocarburizing. Both processes were conducted for a duration of 30 min. To compare the surface hardness of the alloys created by the different processes, microhardness tests were conducted, and fatigue tests of each material were performed by a cantilever rotary bending fatigue test machine (Yamamoto, YRB 200) in the very high cycle regime ($N>10^7cycle$). Fractography of the fractured surfaces was conducted by scanning electron microscopy - to observe the fracture mechanisms of very high cycle fatigue and the effect of the nitriding process on the fatigue characteristics.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.387-395
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• 2000

The purpose of this research is to evaluate the capacity of strength and plastic deformation of those members, and provide experimental data on the seismic behavior of these members as a basis for developing guidelines for designing seismically resistant concrete-filled steel tubular columns. Eighteen cantilever-type specimens were tested under constant axial load and cyclically lateral load as models of bottom columns in high-rise building. The parameters studied in the test program included, are width-thickness ratio of steel tube, slenderness ratio (Lo/D) and axial force ratio. From the test results, the effects of parameters on the strength, the deformation capacity, energy absorption capacity are discussed. The specimen flexural capacity under combined axial and lateral loading was found to be almost accurately predicted by criteria AIJ and AISC-LRFD providing conservative results. Therefore KSSC for encased composite column can be applied to the concrete filled column if composite section and elastic modulus are modified according to AIJ and AISC-LRFD. Finally, the proposed flexural capacity considering confinement effects is a food agreement on the tests results.

• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.613-625
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• 2002

This paper aimed to investigate the damage process of steel parts experiencing failure under strong repeated loading. Likewise, a damage index using various factors related to the damage was proposed. An analysis method for evaluating the damage state was also developed. The damage assessment method focused on the local strain history at the cross-section of the heaviest concentration of deformation. Cantilever-type steel parts were analyzed under uniaxial load combined with a constant axial load, considering horizontal displacement history, Loading patterns and steel types were considered as the main parameters in analyzing the models. The effects of the parameters on the failure modes, deformation capacity, and damage process as seen from the analysis results were also discussed. Each failure process was compared as steel types. In addition, the failure of steel parts under strong repeated loading was determined according to loading. Results revealed that the state of the failure is closely related to the local plastic strain.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.10
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• pp.941-946
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• 2013

In this paper, an enhanced method for attitude determination is proposed for systems using an IMU (Inertial Measurement Unit). In attitude determination with IMU, it is generally assumed that the IMU can be located in the center of gravity on the vehicle. If the IMU is not located in the center of gravity, the accelerometers of the IMU are disturbed from additive accelerations such as centripetal acceleration and tangential acceleration. Additive accelerations are derived from the lever arm which is the distance between the center of gravity and the position of the IMU. The performance of estimation errors can be maintained in system with a non-zero lever arm, if the lever arm is estimated to remove the additive accelerations from the accelerometer's measurements. In this paper, an estimation using Kalman filter is proposed to include the lever arm in the state variables of the state space equation. For the Kalman filter, the process model and the measurement model for attitude determination are made up by using quaternion. In order to evaluate the proposed algorithm, both of the simulations and the experiments are performed for the simplified scenario of motion.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.111-120
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• 2016

PCAOB conducts the direct supervision for the PCAOB registered accounting firm. Therefore, if an accounting firm is registered with the PCAOB, it will thoroughly manage for their quality management systems. The registered auditor can be expected to have better quality of the audit. This study carried out the analysis using the audit fee which proxies for audit quality. The results of analysis are as follows. After controlling for foreign accounting firms affiliated status, company size, risky assets, leverage, ROA, and market-related variables, PCAOB is a significant explanatory variable for the audit fees. The results of this study support the hypothesis that PCAOB-registered auditors will provide a good audit quality.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.137-140
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• 2008

Minimizing the girder number and appling the long span deck of plate girder bridge is the main factors in the practical and economic design of the Twin Steel Girder Bridge. Therefore, it is important to verify the ability of the long span concrete deck. In this paper, to improve the problem, the precast concrete full depth deck has been used instead of cast-in-place concrete deck. The precast concrete full depth deck having longitudinal and transverse prestress is efficient to design of the long span concrete slabs. This paper introduces the design concept of Twin Steel Bridge using the precast concrete full depth deck and applied design case.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.65-75
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• 2006

Nonlinear pushover analysis is used to evaluate the earthquake response of building structures. To accurately predict the inelastic response of a structure, the prescribed story load profile should be able to describe the earthquake force profile which actually occurs during the time-history response of the structure. In the present study, a new modal combination method was developed to predict the earthquake load profiles of building structures. In the proposed method, multiple story load profiles are predicted by combining the modal spectrum responses multiplied by the modal combination factors. Parametric studies were performed far moment-resisting frames and walls. Based on the results. the modal combination factors were determined according to the hierarchy of each mode affecting the dynamic responses of structures. The proposed modal combination method was applied to prototype buildings with and without vertical irregularity. The results showed that the proposed method predicts the actual story load profiles which occur during the time-history responses of the structures.

• Journal of the Korea Concrete Institute
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• v.13 no.2
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• pp.153-160
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• 2001

In this study, the size effect on axial compressive strength for concrete members was experimentally investigated. Experiment of mode I failure, which is one of the two representative compressive failure modes, was carried out by using double cantilever beam specimens. By varying the eccentricity of applied loads with respect to the axis on each cantilever and the initial crack length, the size effect of axial compressive strength of concrete was investigated, and new parameters for the modified size effect law (MSEL) were suggested using least square method (LSM). The test results show that size effect appears for axial compressive strength of cracked specimens. For the eccentricity of loads, the influence of tensile and compressive stress at the crack tip are significant and so that the size effect is present. In other words, if the influence of tensile stress at the crack tip grows up, the size effect of concrete increases. And the effect of initial crack length on axial compressive strength is present, however, the differences with crack length are not apparent because the size of fracture process zone (FPZ) of all specimens in the high-strength concrete is similar regardless of differences of specimen slenderness.

• The Korean Journal of Financial Management
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• v.21 no.2
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• pp.65-98
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• 2004

This paper analyzes the foreign exchange exposure and the influence of determinants on the significant exposure under various return horizons of US dollar and the Japanese yen. Also this research is extended to the existence of asymmetric exposures to foreign exchange risk. The exchange rate exposures exhibit significant time variations that are very large to represent changes in cash flow sensitivities, but the relation of the significant exposures and time variations is not monotonically increasing. The extent to which a firm is exposed to exchange rate fluctuations can be explained by the level of the growth potential, nm size and leverage. For the various return horizons, firms with a higher growth potential tend to have higher exposures. And the larger firms' exposures tend to be smaller. The influences of the level of export ratio and leverage vary with return horizons and each periods. It is found that the exposures of fins are asymmetric. The asymmetry is mainly explained by the market share hypothesis. The level of export ratio commonly influences the asymmetric exposures to the US dollar and the Japanese yen.

• Journal of the Korean Institute of Gas
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• v.8 no.4 s.25
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• pp.30-35
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• 2004

In this paper, the metal seal for a pressure vessel has been analyzed using the Daguchi method. This method may efficiently optimize the design parameters for a cantilever sealing device of a pressure vessel in terms of dimensions and angles. The computed results indicate that the optimized design parameters can only be drawn by sixteen experimental numbers of iterations when the Daguchi design technique has been employed. This means that the Daguchi design method is very useful for the optimization design of the curved design of the structure. Based on the computed results by the Daguchi design technique, the dimension and angle of the metal seal structure are given as $d_1=50mm,\;d_2=60mm,\;a_1=20^{\circ},\;a_2=8^{\circ},\;a_3=5^{\circ}$.