• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.47-56
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• 2003

Geometric cutting-simulation and verification play an important role in detecting NC machining errors in mold & die manufacturing and thereby reducing correcting time & cost on the shop floor. Current researches in the area may be categorized into view-based, solid-based, and discrete vector-based methods mainly depending on workpiece models. Each methodology has its own strengths and weaknesses in terms of computing speed, representation accuracy, and its ability of numerical inspection. The paper proposes a hybrid modeling scheme for workpiece representation with z-map model and discrete vector model, which performs 3-axis and 5-axis cutting-simulation via tool swept surface construction by connecting a sequence of silhouette curves.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.361-373
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• 2007

In previous work, an approach based on maximizing the efficiency of an internal combustion engine while ignoring the power conversion efficiency of other powertrain components, such as the electric motor and power battery or ultracapacitor, was implemented in the steady-state optimization of an internal combustion engine for hybrid electric vehicles. In this paper, a novel control algorithm was developed and successfully justified as the basis for maximal power conversion efficiency of overall powertrain components. Results indicated that fuel economy improvement by 3.9% compared with the conventional control algorithm under China urban transient-state driving-cycle conditions. In addition, using the view of the novel control algorithm, maximal power generation of the electric motor can be chosen.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.12 no.20
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• pp.39-45
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• 1989

This article is concerned with cost analysis in product warranty policy. The warranty cost can be different according to warranty rate and warranty renewal policy. In this paper the stepdown warranty is used. The warranty renewal policy is considered when the warranty is received upon free replacement period as item failing. Assuming the non repairable item as one item is sold, investigated manufacturer's cost in stepdown warranty policy. Also manufacturer's cost is calculated in the free replacement. pro-rata. hybrid policy. Numerical example is given over Weibull time to failure distribution, comparing stepdown warranty policy with free replacement, pro-rata, hybrid one in the manufacturer's point of view. The sensitivity analysis of warranty cost according to the number of warranty period step is included.

• Journal of the Korean Society for Railway
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• v.9 no.6 s.37
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• pp.635-643
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• 2006

In this paper, a theorectical approach is studied to predict structural performances and weight-reduction rates of hybrid bodyshells in case that the materials of roof structures are substituted. To determine other light-weight materials to be substituted for the original roof materials, bending and twisting deformations are considered under constant stiffness and strength conditions, which derive some new weight-reduction indices from a structural performance point of view. The indices derived to estimate the weight-reduction can be utilized as a good criterion at the conceptual design for material substitution of the roofs.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.198-200
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• 2006

In this paper, three types of power control strategies for controlling a Fuel Cell Hybrid Electric Vehicle(FCHEV) are studied in view of fuel economy. The FCHEV has become one of alternatives for future vehicles since it does emit water only without any exhaust gas while it has a high well-to-wheel efficiency together with an energy saving due to regenerative braking. However, it has also several disadvantages such as the complexity of vehicle system, the increased weight and the extra battery cost. Among various power control strategies, a static power control strategy, a power assist control strategy and a fuzzy logic-based power control strategy are simulated and compared to show the effectiveness of each method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.21-22
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• 2021

Early academic warning is considered as an inherent problem in education data mining. Early and timely concern and guidance can save a student's university career. It is widely assumed as a multi-class classification system in view of machine learning. Therefore, An accurate and precise methodical solution is a complicated task to accomplish. For this issue, we present a hybrid model employing rough set theory with a back-propagation neural network to ameliorate the predictive capability of the system with an illustrative example. The experimental results show that it is an effective early academic warning model with an escalating improvement in predictive accuracy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.6
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• pp.1285-1290
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• 2012

People have been interested in the next generation media and service over 3D by development of 3D industry and generalization of 3D-related content and equipment in recent year. Many researchers predict that a strong candidate is digital hologram. Holographic technology is classified to capture(or generation), processing, and display(or reconstruction). This paper discusses the digital holographic display system using hybrid image pickup system and proposes a new structure of digital holographic display system. Through the proposed method a digital hologram can be scalably serviced according to display equipments with various resolutions, computing power of decoding part, and network bandwidth.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.4
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• pp.927-933
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• 2014

Ship Power Management System(SPMS) based on Communication Network(CN) is one of the most significant factor for a safe voyage. Therefore, most of the vessels are using greater capacity generator than necessary to prevent pulsating load for safety purposes. However, It provokes low-load damage and reduces generator efficiency that using large capacity generator. Accordingly, in this paper propose hybrid power system for prevent damage of pulse load. Simulation using NI's LabVIEW was conducted for the design of the power system based on actual navigation data of the ship. Also, propose applying methods for hybrid power system in connection with the auxiliary power system for safe navigation.

• Smart Structures and Systems
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• v.22 no.5
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• pp.587-609
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• 2018

There is greater significance in identifying the incipient damages in structures at the time of their initiation as timely rectification of these minor incipient cracks can save huge maintenance cost. However, the change in the global dynamic characteristics of a structure due to these subtle damages are insignificant enough to detect using the majority of the current damage diagnostic techniques. Keeping this in view, we propose a hybrid damage diagnostic technique for detection of minor incipient damages in the structures. In the proposed automated hybrid algorithm, the raw dynamic signatures obtained from the structure are decomposed to uni-modal signals and the dynamic signature are reconstructed by identifying and combining only the uni-modal signals altered by the minor incipient damage. We use these reconstructed signals for damage diagnostics using ARMAX model. Numerical simulation studies are carried out to investigate and evaluate the proposed hybrid damage diagnostic algorithm and their capability in identifying minor/incipient damage with noisy measurements. Finally, experimental studies on a beam are also presented to compliment the numerical simulations in order to demonstrate the practical application of the proposed algorithm.

• Structural Engineering and Mechanics
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• v.65 no.6
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• pp.707-719
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• 2018

In this article, a new method is introduced to improve the local search capability of meta-heuristic algorithms using the projection of the path on the border of constraints. In a mathematical point of view, the Gradient Projection Method is applied through a new approach, while the imposed limitations are removed. Accordingly, the gradient vector is replaced with a new meta-heuristic based vector. Besides, the active constraint identification algorithm, and the projection method are changed into less complex approaches. As a result, if a constraint is violated by an agent, a new path will be suggested to correct the direction of the agent's movement. The presented procedure includes three main steps: (1) the identification of the active constraint, (2) the neighboring point determination, and (3) the new direction and step length. Moreover, this method can be applied to some meta-heuristic algorithms. It increases the chance of convergence in the final phase of the search process, especially when the number of the violations of the constraints increases. The method is applied jointly with the authors' newly developed meta-heuristic algorithm, entitled Star Graph. The capability of the resulted hybrid method is examined using the optimal design of truss and frame structures. Eventually, the comparison of the results with other meta-heuristics of the literature shows that the hybrid method is successful in the global as well as local search.