• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.1
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• pp.117-129
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• 2009

The bullwhip effect is known as the significant factor which causes unnecessary inventory, lost sales or cost increase in supply chains. Therefore, the causes of the bullwhip effect must be examined and removed. In this paper, we develop two analytical tools for the bullwhip effect control in supply chains. First, we develop the quantitative models for computing the bullwhip effect in a three-stage supply chain consisted of a single retailer, a single distributor and a single manufacturer when the fixed-interval replenishment policy is applied at each stage. The quantitative models are developed under the different conditions for the demand forecasting and share of customer demand information. They are validated through the computational experiments. Second, we develop a simulation-based decision support system for the bullwhip effect control in a more diverse dynamic supply chain environment. The system includes a what-if analysis function to examine the effects of varying input parameters such as operating policies and costs on the bullwhip effect.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.851-856
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• 2003

A cross-flow fan consists of an impeller, a stabilizer and a rearguider. When it applied for an air conditioner, an evaporator should be added. It relatively makes high dynamic pressure at low speed because a working fluid passes through an impeller blade twice and blades have a forward curved shape. Therefore, the performance of a cross-flow fan is influenced 25% by the impeller, 60% by the rearguider and the stabilizer, 15% by the heat exchanger. At the low flow rate, there are a rapid pressure head reduction, a noise increase and an unsteady flow against a stabilizer and a rearguider. Moreover, the reciprocal relation between the impeller and the flow passage is the important factor for performance improvement of the cross-flow tan because each parameter is independent. The performance characteristics in the cross-flow fan are graphically depicted with various impeller outlet angles and rearguiders.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.208-209
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• 2018

In this study, the tensile properties of hybrid fiber reinforced cementitious composites under the high strain rate was evaluated. Experimental results, the HSF1.5PVA0.5 shown the highest tensile strength because the PVA fiber suppressed the micro cracks in the matrix around the hooked steel fiber and improved the pull-out resistance of hooked steel fiber. Thus, DIF of strain capacity and fracture toughness of HSF1.5PVA were greatly improved. Also, the fracture toughness was greatly improved because the tensile stress was slowly decreased after the peak stress by improvement of the pull-out resistance performance of hooked steel fiber at strain rate 10¹/s.

• Earthquakes and Structures
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• v.3 no.5
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• pp.749-766
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• 2012

Structural control through integration of passive damping devices within the building structure has been increasingly implemented internationally in the last years and has proven to be a most promising strategy for earthquake safety. In the present paper an alternative configuration of an innovative energy dissipation mechanism that consists of slender tension only bracing members with closed loop and a hysteretic damper is investigated in its dynamic behavior. The implementation of the adaptable dual control system, ADCS, in frame structures enables a dual function of the component members, leading to two practically uncoupled systems, i.e., the primary frame, responsible for the normal vertical and horizontal forces and the closed bracing-damper mechanism, for the earthquake forces and the necessary energy dissipation. Three representative international earthquake motions of differing frequency contents, duration and peak ground acceleration have been considered for the numerical verification of the effectiveness and properties of the SDOF systems with the proposed ADCS-configuration. The control mechanism may result in significant energy dissipation, when the geometrical and mechanical properties, i.e., stiffness and yield force of the integrated damper, are predefined. An optimum damper ratio, DR, defined as the ratio of the stiffness to the yield force of the hysteretic damper, is proposed to be used along with the stiffness factor of the damper's- to the primary frame's stiffness, in order for the control mechanism to achieve high energy dissipation and at the same time to prevent any increase of the system's maximum base shear and relative displacements. The results are summarized in a preliminary design methodology for ADCS.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.147-148
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• 2017

In this study, the tensile properties of mono and hybrid fiber reinforced cement-based composite according to fiber blending ratio under the high strain rate was evaluated. Experimental results, the HSF1.5PVA0.5 shown the highest tensile strength because the PVA fiber suppressed the micro cracks in the matrix around the hooked steel fiber and improved the pull-out resistance of hooked steel fiber. Thus, DIF of strain capacity and fracture toughness of HSF1.5PVA were greatly improved. Also, the fracture toughness was greatly improved because the tensile stress was slowly decreased after the peak stress by improvement of the pull-out resistance of hooked steel fiber at strain rate 101/s.

• Journal of Korea Trade
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• v.26 no.6
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• pp.61-82
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• 2022

Purpose - This study analyzed the effect of obtaining international products and qualification certification on exports according to the suitability evaluation system. Recently, non-tariff barriers have emerged as technical barriers, and the Biden administration is trying to achieve export growth and economic growth by utilizing the demand for conformity assessment following the Fourth Industrial Revolution and the free trade system from the perspective of Korea. Design/methodology - This study analyzed the effect of a manufacturer's product certification acquisition on a company's export performance using Resource-Based View-based multiple regression analysis. To this end, concentration validity was confirmed through Factor analysis and Cronbach's alpha, and correlation analysis was performed to verify discriminant validity. Findings - Product certification and qualification have a positive impact on the company's export performance. In particular, technological dynamism and relationship control have had a significant impact. Originality/value - Considering that the Conformity Assessment Management Act will take effect in earnest in 2022, this study is believed to suggest that companies that have been certified to meet international standards may improve their export performance and increase their value in the future. International market.

• International Journal of Advanced Culture Technology
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• v.11 no.2
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• pp.10-29
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• 2023

Grit or perseverance as a factor for student success and life has gained increasing attention. Statistical methods have been the norm in analyzing various aspects of grit, but they do not address the transient and dynamic behavior well. We, for the first time, developed two linear dynamical models that specifically address the feedback structure of a child's desire to achieve a high grade point average (GPA) and the necessary effort that will increase stress between parents and a child. We call the dynamical model as GSES (Goal, Status, Effort & Stress). The two dynamical models incorporate the positive (i.e., achieving a high GPA) and the negative sides (i.e., effort and elevated stress and thus unhappiness) for being gritty or perseverant. Different types of parenting style and a child's characteristics were simulated whether parents and a child are empathetic or stubborn to their expectations and stress (i.e., willing or unwilling to change). Simulations show that when both parents and a child are empathetic to each other's expectation and stress, the most stable situations with minimal stress and effort occur. When a stubborn parent's and a stubborn child were studied together, this resulted in the highest elevation of stress and effort. Stubborn parents and a complying or empathetic child resulted in considerably high stress to a child. Interference from parents may unexpectedly result in a situation in which a child's stress is seriously elevated. The GSES model shows the U-shaped happiness curve (i.e., reciprocal of stress) caused by the increasing and then decreasing goal

• Wind and Structures
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• v.36 no.1
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• pp.1-14
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• 2023

To evaluate the wind shielding effect of bridge towers with multiple limbs on high-speed trains, a wind tunnel test was conducted to investigate the aerodynamic characteristics of vehicles traversing multi-limb towers, which represented a combination of the steady aerodynamic coefficient of the vehicle-bridge system and wind environment around the tower. Subsequently, the analysis model of wind-vehicle-bridge (WVB) system considering the additional moments caused by lift and drag forces under nonuniform wind was proposed, and the reliability and accuracy of the proposed model of WVB system were verified using another model. Finally, the factors influencing the wind shielding effect of multi-limb towers were analyzed. The results indicate that the wind speed distributions along the span exhibit two sudden changes, and the wind speed generally decreases with increasing wind direction angle. The pitching and yawing accelerations of vehicles under nonuniform wind loads significantly increase due to the additional pitching and yawing moments. The sudden change values of the lateral and yawing accelerations caused by the wind shielding effect of multi-limb tower are 0.43 m/s² and 0.11 rad/s² within 0.4 s, respectively. The results indicate that the wind shielding effect of a multi-limb tower is the controlling factor in WVB systems.

• Journal of Soil and Groundwater Environment
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• v.11 no.2
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• pp.45-55
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• 2006

A 2-D unconfined flow model is developed to analyze annual variations of groundwater level and bank filtration rate (BFR) for an experimental riverbank filtration site in Koryeong, Korea. Two types of boundary conditions are examined for the river boundary in the conceptual model: the static head condition that uses the average water level of the river and the dynamic cyclic condition that incorporates annual fluctuation of water level. Simulations show that the estimated BFR ranges $74.3{\sim}87.0%$ annually with the mean of 82.4% for the static head boundary condition and $52.7{\sim}98.1%$ with the mean of 78.5% for the dynamic cyclic condition. The results illustrate that the dynamic cyclic condition should be used for accurate evaluation of BFR. Simulations also show that increase of the distance between the river and the pumping wells slightly decreases BFR up to 4%, and thereby indicate that it is not a critical factor to be accounted for in designing BFR of the bank filtration system. A sensitivity analysis is performed to examine the effects of model parameters such as hydraulic conductivity and specific yield of the aquifer, recharge rate, and pumping rate. The results demonstrate that the average groundwater level and BFR are most sensitive to both the pumping rate and the recharge rate, while the water level of the pumping wells is sensitive to the hydraulic conductivity and the pumping rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.391-400
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• 2009

Recently, cellular communication networks are migrating from 2G to 3G. Spectrum utilization tends to be inefficient during the transition. Cognitive radio (CR) technology can be a key solution to increase spectrum efficiency by allowing secondary networks to utilize frequency resource of primary networks. However, conventional CR approaches which do not utilize the frequency reuse factor of primary networks may incur degradation of whole network performance. In this paper, we propose a mechanism that a secondary network senses pilot signals of a primary network and select optimum frequency bands. In order to maximize whole network performance, we formulate an optimization problem subject to interference constraints for a primary network and present algorithms. Simulation results compare the proposed method with the conventional method. Our proposed method shows performance gain over the conventional method if channel variation of a primary network is dynamic and the frequency reuse factor of a primary network is high.