• International Journal of Fluid Machinery and Systems
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• v.9 no.1
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• pp.28-38
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• 2016

The flexible control system for hydraulic pile hammer using main control valve is present to the requirement of rapidly reversing with high frequency. To ensure the working reliability of hydraulic pile hammer, the reversing performance of the main control valve should commutate robustness to various interfere factors. Through simulation model built in Simulink/Stateflow and experiment, the effects of relative parameters to reverse performance of main control are analyzed and the main interfere factors for reversing performance are acquired. Treating reverse required time as design objects, some structure parameters as control factors, control pressure, input flow and gaps between spool and valve body as interfere factors, the robust design of the main control valve is done. The combination of factors with the strongest anti-jamming capability is acquired which ensured the reliability and anti-jamming capability of the main control valve. It also provides guidance on design and application of the main control valve used in large flow control with interferes.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.162-172
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• 2016

The placement of the complete baseband processing in a centralized pool results in high data rate requirement and inflexibility of the fronthaul network, which challenges the energy and cost effectiveness of the cloud radio access network (C-RAN). Recently, redesign of the C-RAN through functional split in the baseband processing chain has been proposed to overcome these challenges. This paper evaluates, by mathematical and simulation methods, different splits with respect to network level energy and cost efficiency having in the mind the expected quality of service. The proposed mathematical model quantifies the multiplexing gains and the trade-offs between centralization and decentralization concerning the cost of the pool, fronthaul network capacity and resource utilization. The event-based simulation captures the influence of the traffic load dynamics and traffic type variation on designing an efficient fronthaul network. Based on the obtained results, we derive a principle for fronthaul dimensioning based on the traffic profile. This principle allows for efficient radio access network with respect to multiplexing gains while achieving the expected users' quality of service.

• The Transactions of the Korea Information Processing Society
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• v.4 no.7
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• pp.1706-1718
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• 1997

The rapid increase in the use of many commercial software products has necessitated a systematic and objective method of their evaluation and selection. Our study focuses on the assignment of weights and choice of proper models. First, the weights of attributes are assigned consistently by using the analytic hierarchy process. Second, many models, which can be suitable for the structure of evaluation and selection for software product, are collected, categorized into two types of model, and compared in terms of their strength and weakness. The models involved are four compensatory models and seven noncompensatory models. Finally, they are analyzed through the application of specific software products(database data modelers) in terms of their attributes. Our study enhances the applicability of models to a variety of user requirement utilizing the evaluating procedure and applications.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.5
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• pp.1323-1333
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• 2016

According to spreading of smart devices and development of communication technology, the security issues come to the fore in the modern factory. Especially, the smart facpry should be considered the risk management plan how to identify and evaluate, control the risks. In this paper, we suggest the minimum security requirements applying SFRPN(Smart Factory Risk Priority Number) model to domestic smart factory on the basis of the results inspecting factories.

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.351-359
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• 2016

The Korean Prototype Gen-IV sodium-cooled fast reactor (PGSFR) is supposed to be loaded with a relatively-costly low-enriched U fuel, while its envisaged transuranic fuels are not available for transmutation. In this work, the U-enrichment reduction by improving the neutron economy is pursued to save the fuel cost. To improve the neutron economy of the core, a new reflector material, PbO, has been introduced to replace the conventional HT9 reflector in the current PGSFR core. Two types of PbO reflectors are considered: one is the conventional pin-type and the other one is an inverted configuration. The inverted PbO reflector design is intended to maximize the PbO volume fraction in the reflector assembly. In addition, the core radial configuration is also modified to maximize the performance of the PbO reflector. For the baseline PGSFR core with several reflector options, the U enrichment requirement has been analyzed and the fuel depletion analysis is performed to derive the equilibrium cycle parameters. The linear reactivity model is used to determine the equilibrium cycle performances of the core. Impacts of the new PbO reflectors are characterized in terms of the cycle length, neutron leakage, radial power distribution, and operational fuel cost.

• Proceedings of the Korean Society for Quality Management Conference
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• 2006.04a
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• pp.355-358
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• 2006

The emotional quality of the product have become an important factor in purchasing decision. Classical approach of product design has focused on providing proper functions of the product. However, as the life-cycle of products become shorter and the customer's needs get more diversified, it is now necessary to accommodate the customer's emotional requirement in product design. This study aims to analyze and interpret the emotional characteristics based customer preference survey. This study consisted of two part. First part was to search the optimal combination of design variables through DOE of predetermined 5 design variables. In the second part, we developed customer preference index model to measure the customer preferences about 16 different wood flooring product.

• Transactions of Materials Processing
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• v.13 no.6 s.70
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• pp.497-502
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• 2004

The shape of cold rolled steel sheets is defined as the degree of flatness, and the flatter, the better. Because undesirable strip shapes of cold rolled steel sheets can affect not only visible problem but also automatic working process in customer's lines, the requirement of the customers is more and more stringent. So we usually used the tension leveler to make high quality of strip flatness. For the improvement of the quality of strip flatness, this report developed three- dimensional FEM (Finite Element Method) simulation model, and analysis about the strain and stress distribution of strip in the tension leveling process. The numerical study can be summarized as follows. (1) If we pass the edge wave material (steepness: $1.0\%$) that the stress-difference between the strip center and the edge is 5.2kgf through tension leveler. the stress-difference is decreased 0.45kgf and the steepness is improved to $0.29\%$. (2) If the Intermesh is increased from 6mm to 7mm, the steepness is improved from $0.294\%$ to $0.268\%$. (3) If the initial steepness is decreased form $1.0\%$ to $0.75\%$, the final steepness is improved from $0.294\%$ to $0.263\%$. We know that more increased intermesh and lower initial steepness make the final steepness improved.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.543-548
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• 2013

This paper presents a design of magnetorheological (MR) damper for control vibration of washing machine. This design is based on the requirements such as small dimensions with high damping force, and minimal consumed energy. The MR damper is designed using the shear mode of MR fluid, and Bingham plastic model is used for optimization process. In this design, a multi-coil design is adopted for damper to enhance damping force and reduce optimally structural parts. In optimization process, ADPL (Ansys Parametric Design Language) program is applied. Base on the optimal parameters, MR damper is manufactured and tested. In evaluation of MR damper, a modified sliding mode control is formulated and applied in both simulation and experiment. Results of experiment show that the MR damper satisfy the requirement of damping force for vibration control of washing machine.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.347-355
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• 2001

A heat transfer analysis in a ventilation chamber of Plasma Display Panel(PDP) has been conducted. The process requirement is to precisely follow prescribed temperature trajectory while maintaining temperature uniformity for each panel. Firstly, experiment in a test chamber has been carried out and the results are compared with the unsteady 3D numerical data. Reasonable agreement was found, which suggested that the employed numerical model had its credibility in actual PDP ventilation processes. On this ground, a tact-type heating/cooling system was analyzed. The panel temperature in the 40$^{\circ}C$ tact-type system was more uniform than that in the 80$^{\circ}C$ one. For improving the uniformity of panel temperature, relocation of ventilation head to the rear part and inlet flow control are required. Comparison of full simulation of a cart and simplified simulation of one panel indicates the optimized panel pitch can also be predicted.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.486-489
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• 2004

The active magnetic bearing (AMB) systems mounted in moving vehicles are exposed to the disturbances due to the base motion, often leading to malfunction or damage as well as inaccurate positioning of the systems. Thus, in the controller design of such AMB systems, robustness to base disturbances becomes an essential requirement. In this study, effective control schemes are proposed for the homo-polar AMB system, which uses permanent magnets for generation of bias magnetic flux, when it is subject to base motion, and its control performance is experimentally evaluated. The base motion of AMB system is modeled as the dynamic disturbances in the gravity and base excitation forces. To effectively compensate for the disturbances, the angle feed-forward controller based on the inverse dynamic model and the acceleration feed-forward controller based on the normalized filtered-X LMS algorithm are proposed. The performance test of the prototype AMB system is carried out, when the system is mounted on rate table. The experimental results show that the performance of the proposed controllers for the AMB system is satisfactory in compensating for the disturbances due to the base motion.