• Journal of Power Electronics
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• v.18 no.2
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• pp.332-342
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• 2018

This paper proposes a parameter design method for multi-element resonant converters (MERCs) with a unique resonant zero point (RZP). This method is mainly composed of four steps. These steps include program filtration, loss comparison, 3D figure fine-tuning and priority compromise. It features easy implementation, effectiveness and universal applicability for almost all of the existing RZP-MERCs. Meanwhile, other design methods are always exclusive for a specific topology. In addition, a novel dual-CTL converter is also proposed here. It belongs to the RZP-MERC family and is designed in detail to explain the process of parameter selection. The performance of the proposed method is verified experimentally on a 500W prototype. The obtained results indicate that with the selected parameters, an extensive dc voltage gain is obtained. It also possesses over-current protection and minimal switching loss. The designed converter achieves high efficiencies among wide load ranges, and the peak efficiency reaches 96.9%.

• International Commerce and Information Review
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• v.8 no.3
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• pp.193-206
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• 2006

The United States demands that the Korean Government include in the WTO GPA the privately invested projects of the BOT contract. Controversy surrounding BOT contract will continue. As of result of opening up of private investment market including BOT contracts, inflow of foreign capital will be expanded, and it will provide an opportunity for rectifying any unreasonable policies or regulations. With active penetration of foreign companies, there is a possibility for deepening of competition in the private investment market, and if a foreign administrative company is selected, possibility of assigning high value works such as design to foreign companies leaving labor intensive work such as construction to domestic companies exists, and also, difficulties resulting from agreement between the employer and the foreign administrative company exists. Large-scale construction companies must put forth their efficiency and creativity, and through revolutionary constructions by private sectors, reduction in construction cost should be made possible, and must also increase efficiency in maintenance, repair, and management of the facility. On the other hand, in order for Korean construction companies of BOT businesses to be able to enter the foreign BOT industry, the government needs to conduct studies in information and policies of various nations.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.4
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• pp.59-74
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• 1987

In this dissertation, a complete model of commutatorless static Kramer type slip power recovery system of 3.phi. induction motor has been designed and tested in the laboratory, and the experimental results are compared with the numerical values. The main results of this study are summerized as follows. (1) Maintenance and repair of the mechanical commutator is obviated by adopting a thyristor commutator in place of the mechanical commutator in the conventional Kramer system. (2) The experimental results of developed torque, and stator current are generally coincided with the numerical values obtained by the derived equation, proving their validity. (3) This system is simulated and the following operational characteristics are obtained with suitable design values : (a) The speed control range of 7:1 is obtained when the turn ratio of induction motor is lowered to about 3:1 to 4:1 and the generating constant of auxiliary synchronous motor is increased to 120-175 range. (b) Its efficiency can be increased to 75-85%, the range for static Scherbius system and its power factor takes values in the range of 65-85%, which is twice of the range for static Scherbius system.

• Journal of Korea Multimedia Society
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• v.21 no.4
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• pp.499-512
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• 2018

The application of analytical techniques for the rational determination of problems arising from management science and corporate management. In a way that is the opposite of the repair plan that can predict accurate results is increasing utilization of the complex-based analysis methodology. In this study, we examined the application of physical space and the methodological utilization of the pedestrian model analysis that applied the simulation to the Health Checkup Center. The conclusions are as follows. First, the spatial analysis and measurement for empirical research has confirmed that the efficiency assessment through the pedestrian model simulation can lead to an objective evaluation. Second, it seems to be able to reduce the queue through a change in the number of services of the low-pressure and the hearing laboratory, the recovery room with a high proportion of male disturbances and relatively long use time. The third, the spatial density analysis and the time required to reduce the density change in comparative analysis, and the spatial layout changes, the increase in the capacity of 80 people, approximately 16 minutes to shorten the process duration.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.6
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• pp.153-158
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• 2017

Reducer is a device to transmit and change torque and speed from drive shaft to driven shaft with excellent transmission efficiency, and it is widely used in many areas today. Reduction gear consists of two axes, gear, bearing supporting axes, and housing. The simplest method to transmit rotation or power to multiple axes is to attach circular plates to two axes and contact each other. However, in this case, if increasing number of rotations or if contact pressure is small, because of slipping, it cannot transmit power. For problems for the current reducer case, it is heavy and its assembling and repair is difficult. In addition, there are few studies about manufacturing and performance testing of worm gear reducer, causing lack of the foundation to improve the product competition and the performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.61-69
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• 2020

This paper examined the operational efficiency of the new rice variety "Sindongjin" farmed by the Rural Development Administration. Thirty farmers were surveyed in the survey area--Jeonbuk-do Province. The operational efficiency was analyzed by studying the data of these 30 farmers. The operational efficiency of the farmers was analyzed through a survey using the DEA model for analysis. DEA analysis was performed to obtain the technical efficiency of the farmers. The results showed that the DEA technical efficiencies of 12 farmers were efficient, and 18 farmers were inefficient. Farmers No. 13 and No. 25 were representative of inefficiency, and the results show that the cost of input elements was high. An analysis of the determinants of efficiency through the Tobit model found that the operating efficiency increased with decreasing variable costs (Seed costs, By-product fertilizer costs, General fertilizer cost, Pesticides cost, Cost of water, electricity, gas, and Cost of small farm implements) and fixed costs (Repair cost and Other costs). There is a problem of excess input from farmers, and these input costs need to be reduced.

• Journal of the Korea Safety Management & Science
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• v.6 no.1
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• pp.49-60
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• 2004

Industrial facilities are becoming more complex and various with rapidly developing technologies. A number of installations and equipments are increased to improve productivity, and they are operated under the condition of high temperature and pressure. They are continuously repaired, replaced or abolished because of the deterioration with time, but their repair and replacement are not easy for economical and environmental concerns. If possible, the deteriorating equipments should be inspected and repaired effectively considering the state of maintenance and preservation, economic efficiency, and safety. That's where RBI(Risk Based Inspection) fits in. Even if RBI technology has been known among specialists, there were no tools readily available and it was hard to practice and apply RBI in industrial inspection and safety management. In the development of the qualitative RBI, the overall algorithm adopted API-581 BRD. The qualitative RBI program was developed to search the appling process.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2129-2134
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• 2011

This research increases efficiency of track-maintenance repair and cuts maintenance cost with relocating Continuous Welded Rail how to set up install criteria by comprehension analysis through an on-the-spot survey and track measurement about installing place at expansion joint of Continuous Welded Rail. This scope of this research is 427 places installed at Line No.1~4, Seoulmetro. We take a field study and select two spots. So we survey wheel-load, cross-load and railbed cross-resistance and suggest install criteria of expansion joint of Continuous Welded Rail through investigation and analysis of track facilities about neighboring section of expansion joint.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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• pp.496-503
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• 1999

In this paper, the improvement of cap tilting system in heavy truck and the development of program for automatic design are discussed. Cab tilting system takes some important roles in heavy truck, absorbing discomfort vibration from load, increasing repair efficiency and making sure of safety. Common manual cab tilting system cannot be easily tilt up in sloped road, giving difficulty to driver as cal tilting up/down. So recently hydraulic cab tilting system is in wide use. But some problem such as tilting up/down speed is not constant and sudden swing of cab has brought discredit from user. Therefore, this paper presents advanced cab tilting system which prevents sudden swing of cab and development of program for selecting design parameters automatically.

• Journal of the Korea Institute of Building Construction
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• v.5 no.4 s.18
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• pp.91-98
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• 2005

This paper illustrates a comparative analysis on the economic efficiency of remodeling method that is one of major factors in totting more desirable standards and proposes to utilize LCC calculation techniques in generating a required budget for more effective quantity-based analysis that is both objective and effect. Rather than comparing only the initial lost of two different methods, it seems through to compare their entire life cycle cost that includes any repair and reconstruction/ remodeling expenses, thus generate overall quantitative analysis in objective perspective