• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.13-19
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• 2003

Giving teachers and students the clean visual environment, the classroom lighting is an important part that prevents the decrease of the visual acuity and improves the studying environment. In order to improve the classroom lighting, a proper blackboard luminaire is to be developed. This paper explains how to design the optical form of the high efficient reflector which offers the uniform illuminance at the vertical surface of the blackboard and, after all, the problem of a large source in reflector design process is explained.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.8
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• pp.563-569
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• 2008

Radiative, heating is suitable for outdoor heating system in windy and cold seasons. Optimal design of the reflector is very important to maximize heat transfer to a specific target area in the open space. The geometrical optical theory can be applied to analyze efficiency of the reflector. Commercial ray tracing computer programs are available only for limited geometries of the reflector. Alternatively, it may be designed and analyzed through an approximated simple lens theory. Two types of reflectors are analyzed using either of these methods. The key issue in this paper is to propose a new illumination experimental method for determination of the radiative efficiency. Optical light source and illuminometer are employed. The calculated efficiency of the reflector is compared with experimental one for checking the reliability. The relative errors between the experimental and analytical results are less than 5%, which proves the validity of this method. Based on these methodologies, a practical reflector and heating lamp unit is developed.

• Composites Research
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• v.37 no.3
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• pp.219-225
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• 2024

It is essential to develop a light-weight, high-performance structure for the deployable reflector antenna, which is the payload of a reconnaissance satellite, considering launch and orbital operation performance. Among them, the composite main reflector is a key component that constitutes a deployable reflector antenna. In particular, the development of a high-performance main reflector is required to acquire high-quality satellite images after agile attitude control maneuvers during satellite missions. To develop main reflector, the initial design of the main reflector was confirmed considering the structural performance according to the laminate stacking design and material properties of the composite main reflector that constitutes the deployable reflector antenna. Based on the initial design, four types of composite main reflectors were manufactured with the variable for manufacturing process. As variables for manufacturing process, the curing process of the composite structure, the application of adhesive film between the carbon fiber composite sheet and the honeycomb core, and the venting path inside the sandwich composite were selected. After manufacture main reflector, weight measurement, non-destructive testing(NDT), surface error measurement, and modal test were performed on the four types of main reflectors produced. By selecting a manufacturing process that does not apply adhesive film and includes venting path, for a composite main reflector with light weight and structural performance, we developed and verified a main reflector that can be applied to the SAR(Synthetic Aperture Rader) satellite.

• Composites Research
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• v.36 no.3
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• pp.230-240
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• 2023

The deployable reflector antenna consists of 24 unit main reflectors, and is mounted on a launch vehicle in a folded state. This satellite reaches the operating orbit and the antenna of satellite is deployed, and performs a mission. The deployable reflector antenna has the advantage of reduce the storage volume of payload of launch vehicle, allowing large space structures to be mounted in the limited storage space of the launch vehicle. In this paper, structural analysis was performed on the main reflector constituting the deployable reflector antenna, and through this, the initial conceptual design was performed. Lightweight composite main reflector was designed by applying a carbon fiber composite and honeycomb core. The laminate pattern and shape were selected as design variables and a design that satisfies the operation conditions was derived. Then, the performance of the lightweight composite reflector antenna was analyzed by performing detailed structural analysis on modal analysis, quasi-static, thermal gradient, and dynamic behavior.

• Journal of Navigation and Port Research
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• v.27 no.3
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• pp.267-272
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• 2003

This paper describes design method of Passive-type Radar Reflector (PRR) which is to provide the requirement of newly revised 2000 SOLAS regulations on the Radar Reflector. The main target of this work is to find the optimum shape of a radar target having large Radar Cross Section (RCS). Through the RCS analysis based on the theoretical approach, two kinds of PRR models, RRR-F model for use in fisheries and PRR-S model for use in small sized ship, are designed and discussed their RCS performance. RCS measurement tests for the various sized samples are carried out in an anechoic chamber. As evaluation results it was clearly shown that the conventional sphere-type shows optimum shape in case of PRR-S, while the cylinder-type which consists of large sized corner clusters or zig-zag flat plats gives best performance in case of PRR-F.

• KIEAE Journal
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• v.2 no.3
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• pp.33-38
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• 2002

The intermediate range of temperatures($100{\sim}300^{\circ}C$) which can be achieved with CPCs(Compound Parabolic Concentrators) without tracking device provides both economic and thermal advantages for solar collector design. The present paper summarizes critical design considerations for CPC with cylindrical absorber and its optical performance using ray tracing program. Concentration ratios vary as acceptance half angle, ratio of reflector height to aperture width and ratio of reflector area to aperture area. This effects showed that the concentration ratio was increased as acceptance angle but optimum ratio of reflector height to aperture width existed at critical value. As a result of ray tracing, solar ray losses was maximized at acceptance half angle and this problem was solved by increasing absorber tube diameter. The concentrating flux distribution on the absorber surface was uniform but peak flux existed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.826-831
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• 2008

This paper presents hybrid antenna(HA) design based on shaped reflector for mobile satellite communication. HA is composed of a shaped reflector and a feeder having $1{\times}8$ linear phased array, and reflector shaping method is applied for the performance optimization with minimum aperture size. And, in the feeder design, HA has another merit to minimize the manufacturing cost by optimizing the number of element. Proposed HA is designed at Ka-band and can electrically control a beam pattern within ${\pm}3^{\circ}$ in the basic angle of $+45^{\circ}$ in elevation. This antenna is designed to meet ITU-R S.465-5 for beam pattern including side-lobe level.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.9
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• pp.1-5
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• 2013

We developed high-efficient 6W-LED package with simple structure by applying Heat Slug and silicone-reflector. LED package was manufactured in $8.5{\times}8.5mm$ sized multi-chip structure having thickness of $500{\mu}m$ achieved by bonding silicon-reflector with prepreg on top of the plate after implementing the reflector placed on copper substrate Half Etching by thickness of $200{\mu}m$. The luminous flux, luminous efficacy, correlated color temperature, color rendering index and thermal resistance of developed LED was evaluated, and it verified the application of products by applying it to 120W-LED road luminaires through simulation. The luminous efficacy of LED package reached over 130lm/W, and it is possible to be manufactured into 120W-LED road luminaires using 18 packages. In addition, the simulation results showed average of horizontal illuminance and overall illuminance uniformity that is suitable for three-lane road.

• Structural Engineering and Mechanics
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• v.8 no.4
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• pp.401-410
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• 1999

A method of optimum design based on reliability for antenna structures is presented in this paper. By constructing the equivalent event, the formula is derived for calculating the reliability of reflector accuracy of antenna under the action of random wind load. The optimal model is developed, in which the cross sectional areas of member are treated as design variables, the structure weight as objective function, the reliability of reflector accuracy and the strength or stability of structural elements as constraints. The improved accelerated convergence gradient algorithm developed by the author is used. The design results show that the method in this paper is feasible and effective.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.5
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• pp.411-416
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• 2014

In this research we present design optimization methods for a vehicle-mounted satellite antenna positioner. Our initial antenna positioner was conservatively designed to satisfy a worst case scenario where wind blew across the positioner at the speed of 120 km/h. Investigating stresses and safety based on Finite Element Methods (FEM), we find reflector support frames can be optimized to significantly reduce the weight of the positioner system. Thus, we optimize the reflector support frame from the given initial design while considering weight, maximum stress, maximum allowable deflection, cross section, and thickness. As a result, Shape C and the thickness of 2 mm are determined for the cross section of the reflector support frame. Applying this result, the weight of the new antenna positioner is 57.343 kg, which is decreased by 10.74% compared to the initial conservative design.