• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.2
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• pp.133-139
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• 1982

One of factors that affect combustion in the cylinder of the engine is to keep a greater energy in the ignition system to minimize pollutant emissions and to increase its performance of the low temperature. This paper reviews theoretically the state and input variables of the ignition system from the state transition equation. Effects on characteristics of the system such as primary current, secondary available voltage and spark duration by reducing the pre-resistance from 3.5 to 0 ohm in 12V system is experimentally investigated when the ignition coil has a primary resistance of 1.5 ohms ad the dwell angle of the breaker point is 43.2 degrees (0.75 radian). Advantages and limitations for using the low resistance of the primary circuit are also presented to optimize the performance of the ignition system with the breaker point.

• Journal of Korean Society on Water Environment
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• v.29 no.4
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• pp.466-475
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• 2013

Non-point source pollution management is one of the most important issues in Korean water quality/watershed management. In recent years, Low Impact Development (LID) has emerged as an effective approach to control stormwater in an urban area. This study illustrates how to design and evaluate the effect of non-point pollutant management using EPA-SWMM LID module and suggests design parameters for modeling LID facilities. In addition, optimal installation locations of LID can be determined by a simple distributed hydrologic model by using SWMM for a long-term.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.9
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• pp.65-70
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• 2015

Minimal line length enables low-cost construction of the transmission lines and low-loss transportation of electric power. This paper presents a derivation to determine the coordinate and length of the straight line that minimally connects two perpendicular lines x-axis and y-axis via a specific point, using the optimization technique. The author shows a formula to obtain the minimal length, which is represented by the cube root of the coordinate given by the specific point. Case studies have been also discussed to prove the optimal solutions derived by the proposed formula.

• Journal of Ship and Ocean Technology
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• v.1 no.2
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• pp.11-18
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• 1997

The leading edge of a low-drag super-cavitating foil has been made to be thick enough by using a point drag which is supposed to be a linear model of the Kirchhoff lamina. In the present paper, the relation between the point drag and the Kirchhoff lamina is made clear by analyzing the cavity drag of both models and the leading edge radius of the point drag model and the lamina thickness of Kirchhoff\`s profile K. The matched asymptotic expansion is effectively made use of in designing a practical super-cavitating fool which is not only of low drag but also structurally sound. Also it has a distinct leading edge cavity separation point. The cavity foil shapes of trans-cavitating propeller blade sections designed by present method are shown.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.629-633
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• 2006

We investigated a new longitudinal acceleration wave decomposition method in time domain. The proposed method separates up- and down-stream waves with an axial strain and axial acceleration measured at a single point on the transmission path. The advantages such as low computation load and easy implementation would be possible by developing time domain under the following assumptions; low frequency range, uniform cross sectional area and elastic wave propagation. We confirmed the feasibility and performance of the method through experiment using Split Hopkinson Pressure Bar (SHPB). The method can be effective in several applications, including active vibration control with wave view point, where real time wave decomposition is necessary.

• Journal of Environmental Health Sciences
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• v.1 no.1
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• pp.36-40
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• 1974

A Study on environmental sanitation on the well in Seoul was made to find the degree of Physio-chemical and Bacterial contamination. For this study 30 wells were located at Nokbundong Hongjaidong and Hongeundong from September 13 to 22 1971. As the results of this study the following conclusions were obtained. 1) Seventy per cent were being utilizing by from 10 to 50 households per well. 2) About 93 per cent of the wells were found to be dug out in Rocks. 3) Eighty-three per cent of the wells surveyed in the slums had a depth of water shorter than 20 cm. 4) The degree of Total Viable Bacteria contamination were high point $15{\times}10^2$ low point 13 and coliform bacteria were high point $79{\times}10^1$ low point 1 organism per ml. 5) Only 4 wells (13.3%) were able to drink but 26 wells (86.7%) were not drinking by physio-chemical and Bacterial contamination.

• International Journal of Highway Engineering
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• v.15 no.5
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• pp.195-202
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• 2013

PURPOSES : This study analyzed the regional dew possibility in road sign using meteorological data. METHODS : Four years of meteorological data such as temperature, humidity, dew point, wind velocity were collected and analyzed. As a result of literature review, dew was frequent in large diurnal range, high humidity and weak wind. So, dew possibility was analyzed by (temperature-dew point ${\leq}1^{\circ}C$ and wind velocity ${\leq}$ 1.5m/s). RESULTS : The possibility was analyzed for each meteorological observation point and the point of Suncheon and Bonghwa were selected as the most likely points of dew in road sign. The area of East Coast, Kyungbuk and Kyungnam were relatively low potential. CONCLUSIONS : Alternative with high effect of preventing dew should be selected in high possibility dew area despite of low economics.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.60
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• pp.11-22
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• 2000

The main objective of this research is to analyze an order point and an order quantity of a distribution center and each branch to attain a target service level in multi-level inventory distribution system. In case of product item, we use the item with low volume of average monthly demand. Under the continuous review method, the distribution center places a particular order quantity to an outside supplier whenever the level of inventory reaches an order point, and receives the order quantity after elapsing a certain lead time. Also, each branch places an order quantity to the distribution center whenever the level of inventory reaches an order point, and receives the quantity after elapsing a particular lead time. When an out of stock condition occurs, we assume that the item is backordered. For considering more realistic situations, we use generic type of probability distribution of lead times. In the variable lead time model, the actually achieved service level is estimated as the expected service level. Therefore, this study focuses on the analysis of deciding the optimal order point and order quantity to achieve a target service level at each depot as a expected service level, while the system-wide inventory level is minimized. In addition, we analyze the order level as a maximum level of inventory to suggest more efficient way to develop the low demand item model.

• Earthquakes and Structures
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• v.23 no.4
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• pp.363-371
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• 2022

Traditional metal dampers have disadvantages such as a higher yield point and inadequate adjustability. The experimental results show that the low yield point steel has superior energy dissipation hysteretic capacity and can be applied to seismic structures. To overcome these deficiencies, a novel compound metal damper comprising both low yield point steel plates and common steel plates is presented. The optimization objectives, including "maximum rigidity" and "full stress state", are proposed to obtain the optimal edge shape of a compound metal damper. The numerical results show that the optimized composite metal damper has the advantages such as full hysteresis curve, uniform stress distribution, more sufficient energy consumption, and it can adjust the yield strength of the damper according to the engineering requirements. In view of the mechanical characteristics of the compound metal damper, the equivalent model of eccentric cross bracing is established, and the approximate analytical solution of the yield strength and the yield displacement is proposed. A nonlinear simulation analysis is carried out for the overall aseismic capacity of three-layer-frame structures with a compound metal damper. It is verified that a compound metal damper has better energy dissipation capacity and superior seismic performance, especially for a damper with double-objective optimized shape.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.133-139
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• 2011

In this paper, Based on Two-dimensional Flow Theory, adopting quasi-orthogonal method and point-by-point integration method to design the impeller of the low specific speed centrifugal pump by code, and using RANS (Reynolds Averaged N-S) Equation with a standard k-${\varepsilon}$ two-equation turbulence model and log-law wall function to solve 3D turbulent flow field in the impeller of the low specific speed pump. An analysis of the influences of the blade profile on velocity distributions, pressure distributions and pump performance and the investigation of the flow regulation pattern in the impeller of the centrifugal pump are presented. And the result shows that this method can be used as a new way in low speed centrifugal pump impeller design.