• Journal of the Korean Solar Energy Society
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• v.24 no.1
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• pp.39-45
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• 2004

The thermal performance of glass evacuated tube solar collectors with finned tubes is numerically modelled with code and investigated to see the effect of toe inner tube diameter and incidence angle. The solar collector consists of a two-layered glass tube and an inner tube. Finned tubes are used as the inner tube of the collector in order to improve the performance of the solar collector. Two strip-type fins are attached on the opposite sides of the inner tube surface. The fin is wide enough to be tightly fatted inside the glass tube. The results show that if the incidence angle is small, the effect of the tube diameters is not significant on the thermal performance and the outlet air temperature. If the incidence angle is large, however, the outlet air temperature and the performance increases as the inner tube diameter increases.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.9
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• pp.938-943
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• 2014

The scattered field by a gap/crack on the PEC surface of a large object having low-observable RCS cannot be negligible, but may not be analyzed by the known high-frequency technique. If the electrical width of the crack is very small, the crack can be modeled by an impedance strip, whose scattering formulation can be analytically obtained based on a low-frequency approximation. The scattering solution is formulated for the 2D strip and TE(Transverse Electric) or TM(Transverse Magnetic) wave incidence, from which a 3D ILDC(Incremental Length Diffraction Coefficients) can be extracted. Using the ILDC formulation, the scattering by any arbitrary shaped crack can be estimated. In this paper, an improved ILDC equations are proposed, which combine the known TE and TM solutions. The improved accuracy of the proposed solution is numerically verified.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.3
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• pp.97-104
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• 2010

The purpose of this study is to evaluate sediment yield reduction under various field slope conditions with rice straw mat. The Vegetative Filter Strip Model-W (VFSMOD-W) and Soil and Water Assessment Tool (SWAT) were used for simulation of sediment yield reduction effect of rice straw mat. The Universe Soil Loss Equation Practice factor (USLE P factor), being able to reflect simulation of rice straw mat in the agricultural field, were estimated for each slope with VFSMOD-W and measured soil erosion values under 5, 10, and 20 % slopes. Then with the regression equation for slopes, USLE P factor was derived and used as input data for each Hydrological Response Unit (HRU) in the SWAT model. The SWAT Spatially Distributed-HRU (SD-HRU) pre-processor module was utilized, moreover, in order to consider spatial location and topographic features (measured topographic features by field survey) of all HRU within each subwatershed in the study watershed. Result of monthly sediment yield without rice straw mat (Jan. 2000 - Aug. 2007) was 814.72 ton/month, and with rice straw mat (Jan. 2000 - Aug. 2007) was 526.75 ton/month, which was reduced as 35.35 % compared without it. Also, during the rainy season (from Jun. to Sep. 2000 - 2007), when without vs. with rice straw mat, monthly sediment indicated 2,109.54 ton and 1,358.61 ton respectively. It showed about 35.60 % was reduced depending on rice straw mat. As shown in this study, if rice straw mat is used as a Best Management Practice (BMP) in the sloping fields, rainfall-driven sediment yield will be reduced effectively.

• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1410-1417
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• 2006

The metal processing system usually consists of various components such like motors, work rolls, backup rolls, idle rolls, sensors, etc. Even a simple fault in a single component in the system may cause a serious damage on the final product. It is therefore necessary to diagnose the faults of the components to detect and prevent system failure. Especially, the defects in a work roll are critical to the quality of strip. It is especially difficult to detect faults of a roll by using the existing frequency analysis method if the speed of the roll is changing. In this study, a new diagnosis method for roll eccentricity under the roll speed changes was developed. The new method was induced from analyzing the rolling mechanism by using rolling force models, radius-speed relationship, and measured rolling force, etc. Simulation results by using the field data show that the proposed method is very useful.

• ETRI Journal
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• v.30 no.5
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• pp.729-734
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• 2008

Wireless communication systems, such as WLAN or Bluetooth receivers, employ preamble data to estimate the channel characteristics, introducing stringent settling-time constraints. This makes the use of traditional closed-loop feedback automatic gain control (AGC) circuits impractical for these applications. In this paper, a compact feedforward AGC circuit is proposed to obtain a fast-settling response. The AGC has been implemented in a 0.35 ${\mu}m$ standard CMOS technology. Supplied at 1.8 V, it operates with a power consumption of 1.6 mW at frequencies as high as 100 MHz, while its gain ranges from 0 dB to 21 dB in 3 dB steps through a digital word. The settling time of the circuit is below 0.25 ${\mu}s$.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.413-416
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• 2007

If obstacle in GIS(Gas Insulted Switchgear), its affects are great are on the community and it is consequently demanded lots of difficulities to recover and repair. Accordingly, diagnosis techniques, that are able to prevent from accidents before they happen by providing more stable and highly reliable power effectively and finding sign of the accidents is very important. The strip-senser measured impedance bandwidth of the proposed antenna is from 0.5[GHz] to 2.5[GHz] with the stop band from 0.5[GHz] to 1.7[GHz] for VSWR<2. The antenna is will play an important role for the senser for insulation diagnosis system by UHF method of real site GIS and power equipment using $SF_6$ gas.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.04a
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• pp.117-120
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• 2009

The rolling of flat slabs or sheet metal is probably the most advanced technique of metalworking technology. In spite of this very intensive activity, the problem if edge cracking has not been resolved. Although edge cracking is a major industrial problem, relatively little well-documented experimental work has been published on subject. Despite the paucity of exact experiments, it is reasonably certain from published data that three causes contribute to its occurrence; (1) limited ductility of the rolled material (2) uneven deformation at the edges and (3) variations in stresses along the width of the rolled material, particular near the edge. The present study was carried out to show the generation of edge cracking using ductile fracture criteria and FE-simulation. The validity of simulated results was verified by rolling experiments of steel strip.

• Wind and Structures
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• v.3 no.1
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• pp.23-40
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• 2000

In the early morning hours of February 23rd, 1998, seven large tornadoes ravaged central Florida. A total of 42 people were killed and millions of dollars of damage was done. A strip mall and other commercial structures sustained considerable damage and several residential areas were completely destroyed. Based on field observations, the paper examines the causes and sequence of structural failure for the masonry single family homes. Wind speeds are estimated based on the observed damage, and compared to the meteorological data. Finally, recommendations are given that could help to eliminate or reduce similar failures in the future. It was found that with simple, cost effective measures, most if not all of the damage could have been prevented.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.1 no.2
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• pp.16-22
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• 1983

The method of least squares is an adequate method of adjustment in various fields of engineering where redundant observations are necessary to obtain accurate values. The Consideration of weight of each Observation can improve the accuracy if the reliabilities of observations vary. The strip coordinates were weighted as inversely proportionate to the rotations $\kappa, \varphi, \omega$ which occur in the computation of model coordinates. The resulting errors in absolute coordinates were compared with the errors unweighted case to investigate the influence of orientation elements on absolute coordinates.

• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.97-101
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• 2009

In the modem semiconductor industry, the progress that consumes the most capital and labor is cleansing process. Cleansing process is to remove impurities that can affect the operation of the device and deteriorate its function. Especially, Photoresist (PR) progress that etches the device always requires cleansing at the end of the progress. Also, HDI-PR (High-Dose Ion-implanted Photoresist) created from PR progress is difficult to remove. Thus, in modem IC cleansing, many steps of cleansing are used, including dry and wet cleansing. In this paper, we suggested to combine existing dry-cleansing and wet-cleansing, each represented by plasma cleansing and stripper solution, as Plasma Liquid-Vapor Activation (PLVA). This PLVA method enhances the effect of existing cleansing solution, and decreases the amount of solution and time required to strip. We stripped HDI-PR by activated solution and measured surface hardness and Young's modulus by Nano-indenter. Nano-indenter is the equipment that determines the hardness and the modulus of elasticity by indenting nano-sized tip with specific shape into the surface and measuring weight and z-axis displacement. We measured the change of surface hardness and Young's modulus before and after the cleansing. As a result, we found out that the surface hardness of the sample sharply decreased after the cleansing by plasma-activated PR stripper solution. It can be considered that if physical surface-cleansing process is inserted after this, more effective elimination of HDI-PR is possible.