• Journal of Information Technology Applications and Management
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• v.12 no.1
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• pp.49-68
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• 2005

It is one of the crucial components of electronic logistics systems to manage logistics information of cargos and transportation companies and to mediate appropriate brokerage between them. Due to the advance of e-Commerce technologies many kinds of logistics transactions can be handled by means of EDI or XML/EDI applications. but the brokering processing relies mostly on the traditional processes and the research in this field is still at the initial stage. In this paper we study a logistics brokering system for ships and cargos and describe the design and implementation of the system. We analyze the brokering constraints for logistics of cargos and ships and construct an optimization model for their brokering. We also suggest a brokering procedure and a simple heuristic algorithm with respect to the proposed matching criteria. The experimental result shows that the proposed greedy-based heuristic algorithm performs very well. In its response time the proposed algorithm executed within a couple of seconds independently of the number of cargos and the container capacities of ships. The output of the algorithm is very close to that of the optimal solution. showing higher than 95% of approximation. The proposed system is implemented for the Web environment using JSP and PL/SQL.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2076-2082
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• 2003

A cross-flow fan is widely used on many industrial fields: mining industry, automobile and home appliances, etc. The design point of the cross-flow fan is generally based on the region within low static pressure and high flow rate. It relatively makes high dynamic pressure at low speed because a working fluid passes through an impeller blade twice. However, it has low static pressure efficiency between 30% and 40% because of relative high impact loss. Recently, in the air-conditioning systems, the operating behaviors at the off-design points are highly regarded to broaden the application area for various air-cooling loads. Especially, at the lower flow rate, there exists a rapid pressure head reduction, a noise increase and an irregular flow field against a rearguider as a scroll of centrifugal fan. Numerical analyses are carried out for investigating the flow characteristics in a cross-flow fan including the impeller, the rearguider and the stabilizer. Especially, various types of rearguiders are estimated by numerical and experimental methods to insure the stable operation in the region of lower flow rate. Numerical domains are discretized by hexahedral cells. Three-dimensional, unsteady governing equations are solved using FVM, PISO algorithm, sliding grid system and standard ${\kappa}-{\varepsilon}$ turbulence model. ASHRAE standard fan tester is also used to estimate the performance of the modeled crossflow fan.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.299-303
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• 2001

In this paper, we introduce the Partial Half-Through Type Plate Girder Bridge proposed by Hyundai Development Co. and KRTC Consortium in Turn-Key Based design last year, and this type of bridge may be adapted to the railway bridge under similar conditions. This bridge across the North Han River was to be concerned its find view and the protection of water source. For its location is inside the dam, it required the long span and the clearance for the flood also. Its new composite section was able to diminish the deflection and vibration. Its shop-fabrication could control its quality easily, and might to be launched. This structural type have satisfied its functions, construction situations, and overall safeties, so this is the field-oriented type. However the composition and connections of the proposed members are different to the recent forms, and difficult to be applied to present specifications. Therefore it requires a certification on the application for more safety by not only analytical verifications but also experimental studies. Nevertheless, this type of bridge may have some more applications from now on.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1327-1332
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• 2014

This paper presents information about the examples of the design on Illumination of Structures(LED Light Pipe for lighthouse) in Korea. We have applied illumination by flood-lighting or facade-lighting in place of the 57 lighthouses (offshore structures) and 4 beacons. The ways of illumination of structures are using direct illumination with LED, halogen lamps and metal halide lamps, and indirect illumination with LED non-neon lamps. The illumination of structures helps a observer to identify the Aids to Navigation and w aterway. The fabricated LED Light Pipe is a transparent acrylic round bar and easy to install. The Light Pipe is arranged in two rows of L ED (78ea). It can be connected in series. It has 4 colours(Red, Green, Yellow, White). We analyzed and the horizontal divergence angle of the LED light pipe is defined as the range with 50% of maximum luminous intensity. Also, we evaluated the conspicuity on the origin al lantern and LED Light pipe for lighthouse. The field experiment was conducted in 'Yeosuguhang lighthouse' in Yeosu-city (Korea). F rom the experimental results, it was confirmed that the fabricated LED Light Pipe is clearly distinguished.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.486-491
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• 2013

Creak noise is kind of scratching noise which is usually generated in drum brake system on the vehicle. When driver brakes vehicle or applies parking lever, drum brake shoe moves to the drum side to stop the vehicle. And at that time, moving shoe scratches backing plate ledge surface, and that makes scratching noise in special condition. This study presents how we can generate creak noise in the laboratory and how we can reduce it by experimental approach. Through several and various type of tests, we could generate creak noise with damage on ledge area of the backing plate in the lab and we verified tab type shoe design can reduce this scratching noise. As a result of this study, we notified how creak noise happens in the vehicle, and that tab type design shoe has good performance of ledge area damage based on lab test(rig & dynamometer equipment), and that this can reduce potential risk of creak noise in the field.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.5 s.98
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• pp.604-611
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• 2005

The relationship between floor impact sound and vibration has been studied by field measurements, and the vibration modal characteristics have been analyzed. Vibration levels impacted by a standard heavy-weight impact source have been predicted according to the main design parameters using finite element method. Experimental results show that the dominant frequencies of the heavy impact sounds range below 100 Hz and that they are coincident with natural frequencies of the concrete slab. In addition, simple 2-dimensional finite element models are proposed to substitute 2 types of 3-dimensional models of complicated floor structural slabs those by The analytical result shows that the natural frequencies from first to fifth mode well correspond to those by experiments with an error of less than $12\%$, and acceleration peak value iscoincident with an error of less than $2\%$. Using the finite element model. vibration levels areestimated according to the design Parameters, slab thickness, compressive strength, and as a result, the thickness is revealed as effective to increase natural frequencies by $20\~30\%$ and to reduce the vibration level by 3$\~$4 dB per 30 mm of extra thickness.

• International Journal of Railway
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• v.4 no.4
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• pp.109-115
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• 2011

An analysis and design method for reducing aerodynamic noise in high-speed trains based on biomimetics of noiseless flight of owl is proposed. Five factors related to the morphology of the flight feather have been selected, and the candidate optimal shape of the flight feather is determined. The turbulent flow field analysis demonstrates that the optimal shape leads to diminished vortex formation by causing separation of the flow as well as allowing the fluid to climb up along the surface of the flight feather. To determine the effect of scaling of the owl's flight feather on the noise reduction, a two-fold and a four-fold scaled up model of the feather are constructed, and the numerical simulations are carried out to obtain the aerodynamic noise levels for each scale. Original model is found to reduce the noise level by 10 dBA, while two-fold increase in length dimensions reduces the noise by 12 dBA. Validation of numerical solution using wind tunnel experimental measurements is presented as well.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.412-419
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• 2020

In this study, a 70 W buck converter using GaN metal-oxide-semiconductor field-effect transistor (MOSFET) is developed. This converter exhibits over 97 % efficiency, high power density, and 48 V-to-12 V/1.2 V/1 V (triple output). Three gate drivers and six GaN MOSFETs are placed in a 1 ㎠ area to enhance power density and heat dissipation capacity. The theoretical switching and conduction losses of the GaN MOSFETs are calculated. Inductances, capacitances, and resistances for the output filters of the three buck converters are determined to achieve the desired current, voltage ripples, and efficiency. An equivalent circuit model for the thermal analysis of the proposed triple-output buck converter is presented. The junction temperatures of the GaN MOSFETs are estimated using the thermal model. Circuit operation and temperature analysis are evaluated using a circuit simulation tool and the finite element analysis results. An experimental test bed is built to evaluate the proposed design. The estimated switch and heat sink temperatures coincide well with the measured results. The designed buck converter has 130 W/in³ power density and 97.6 % efficiency.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.3
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• pp.82-89
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• 2009

The purpose of this study is to investigate the actual field application of the linear piston pump for the solid transferring driven by the hydraulic power unit. In this paper, the numerical analysis and performance evaluating experiments were performed. CFX program has been used to obtain the solutions for the problems of three-dimensional, turbulent water flow in the linear piston pump. The velocity and the pressure distributions are obtained using the turbulent $k-\varepsilon$ model. To evaluate the performance of the linear piston pump, the performance test stand and data acquisition system were manufactured. The numerical predictions agree favorably with experimental results within 7% error. Speed of the piston which is satisfied the flow rate 3,000l/min which considers from basic design became 0.33m/s. This paper could be applied to the design of the linear piston pump for the fish transferring.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.3
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• pp.275-284
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• 2022

Linear Shaped Charge(LSC) is widely used as a separation system in the field of weapon system. However, there are some disadvantages that are charging lots of explosives due to lack of uniformity and having difficulties of the design of liner and explosives because of manufacturing process. In order to solve these problems, Precision Linear Shaped Charge(PLSC) that can design a liner independently and charge explosives uniformly has been developed. In this study, PLSC was designed to have a proper liner shape and amount of explosives, and the penetration test of PLSC with different stand-off distance from liner to target was conducted. On the basis of the penetration test results of PLSC, the numerical analysis method using AUTODYN was established and verified. The penetrative mechanism and characteristics of PLSC with targets of different materials was analyzed from experimental and numerical results.