• Journal of the Korean earth science society
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• v.36 no.1
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• pp.109-124
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• 2015

A novel approach, hybrid surface rainfall (KNU-HSR) technique developed by Kyungpook Natinal University, was utilized for improving the radar rainfall estimation. The KNU-HSR technique estimates radar rainfall at a 2D hybrid surface consistings of the lowest radar bins that is immune to ground clutter contaminations and significant beam blockage. Two HSR techniques, static and dynamic HSRs, were compared and evaluated in this study. Static HSR technique utilizes beam blockage map and ground clutter map to yield the hybrid surface whereas dynamic HSR technique additionally applies quality index map that are derived from the fuzzy logic algorithm for a quality control in real time. The performances of two HSRs were evaluated by correlation coefficient (CORR), total ratio (RATIO), mean bias (BIAS), normalized standard deviation (NSD), and mean relative error (MRE) for ten rain cases. Dynamic HSR (CORR=0.88, BIAS= $-0.24mm\;hr^{-1}$, NSD=0.41, MRE=37.6%) shows better performances than static HSR without correction of reflectivity calibration bias (CORR=0.87, BIAS= $-2.94mm\;hr^{-1}$, NSD=0.76, MRE=58.4%) for all skill scores. Dynamic HSR technique overestimates surface rainfall at near range whereas it underestimates rainfall at far ranges due to the effects of beam broadening and increasing the radar beam height. In terms of NSD and MRE, dynamic HSR shows the best results regardless of the distance from radar. Static HSR significantly overestimates a surface rainfall at weaker rainfall intensity. However, RATIO of dynamic HSR remains almost 1.0 for all ranges of rainfall intensity. After correcting system bias of reflectivity, NSD and MRE of dynamic HSR are improved by about 20 and 15%, respectively.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.675-681
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• 2008

This study introduced a new steel-jacketing method to retrofit RC columns. It also estimated the performance of steel-jacketed concrete cylinders. Twelve concrete cylinders were fabricated with varying steel jacket thicknesses of 1.0, 1.5, and 2.0 mm. Lateral confining pressure was applied with three clamps and the performance of plain concrete cylinders was compared with that of steel-jacketed cylinders. Steel jacket proved to be effective in increasing the strength of the cylinder. Finally, Li's constitutive model was compared with that of the experimentalresults. However, Li's model showed incongruity in Region II, which indicates the region after the yield of steel jackets. Therefore, the modified value of n was used for the region and the model showed a good agreement.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.153-166
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• 1999

Since the reliability of results by the existing analyzing method is low, in the case of for excavation performed in urban area whose stability is of great importance, construction control based on field monitoring is always necessary. But the field monitoring reflects only the behavior of construction process that has already been carried out, and it has limitations in predicting the behavior of the expected construction process, which is practically more important for construction control. In this study, construction control system for excavation which can predict the behavior of the expected processes during construction with high degree of accuracy, is developed by adopting inverse analysis. The inverse analied applied field monitoring results to excavation analysis can improve the reliability of predicted results. The developed system uses an elasto-plastic soil spring model for the excavation analysis and the minimization of least squared errors between measured displacements and calculated displacements for the inverse analysis. All the required processes for construction control can be performed as an integrated work within the system reflecting real time application and user's convenience. Their applicabilitis are confirmed by two case studies.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.545-552
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• 2015

Process modeling and simulation is a powerful methodology to quantitatively predict the change of process variables when operating and design conditions are changed. In this study, considering drawbacks of currently used process simulator for combined cycle plants, we developed process modeling system equipped with an ease of use and flexibility for model development. For this purpose, the analysis of combined cycle processes was carried out and consequently, mathematical models and libraries were developed. Furthermore, in view of the fact that the level of the abstraction of process models depends on the purpose of simulation as well as the available data, simple and rigorous models were also developed for some important units. In use of reference combined plant, we executed process simulation using the developed modeling system and the comparison was made between the results of simulation and the reference data. Less than 1% marginal error was identified and we concluded that the modeling system can be applied for commercial combined cycle processes.

• The Journal of the Acoustical Society of Korea
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• v.33 no.4
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• pp.255-261
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• 2014

This paper presents an underwater acoustic communication with nonlinear chirp modulation. The information is carried by the carrier amplitude, frequency or phase in the most common underwater acoustic communications. However, the proposed method includes the information within frequency variation of carrier wave for a symbol. Especially, as carrier wave the hyperbolic frequency modulated signal, one of the nonlinear chirp signal, is used and it is robust in the Doppler channel. The proposed method was analyzed and compared to conventional method by simulation. When the doppler shift existed, the error probability of the proposed method is reduced by 5~12 % than conventional method with linear frequency modulated signal. Sea trial was performed to analyze the performance of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1172-1182
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• 1993

In orthogonal machining a quantitative model for burr formation process and fracture when tool exits workpiece is proposed. When no fracture during burr formation burr formation process is divided by three parts; Initiation, Development and Final burr formation. According to the properties of workpiece fracture will happen or not after initiation of burr formation. Considering the fact that fracture depends on the ductility of workpiece, the fracture strain obtained from ductile fracture criterion is used for prediction. It is verified that the fracture strain from tension test can be used as fracture criterion in burr formation without large error. For detailed observation of burr formation an experimental stage for micro orthogonal cutting inside SEM (Scanning Electron Microscope) is built. Through the comparison between model prediction and experimental result from orthogonal machining in milling machine the model is verified.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.2
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• pp.34-34
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• 1987

Friction welding has emerged as a reliable process for high-production commercial application with significant economic and technical advantages. But nondestructive test in friction weld was not clearly developed. Therefore the experimental verification is necessary in order to understand the characteristics of the pulse echo effects according to various change in welding conditions. This paper presents a new attempt to detect the bond strength of friction welds by ultrasonic. Instead of looking for a flaw or cracks at the interface, the new approach evaluates the coefficient by reflection which provides a single quantitative indicator involving the acoustic energy reflected at the interface. The objective of this study is to find the relationship between the reflection coefficients and the weld strength. Results of the bar-to-bar friction welding of aluminum to copper and stainless steel and such relationship investigation are presented and interpreted.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.2
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• pp.80-85
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• 1987

Friction welding has emerged as a reliable process for high-production commercial application with significant economic and technical advantages. But nondestructive test in friction weld was not clearly developed. Therefore the experimental verification is necessary in order to understand the characteristics of the pulse echo effects according to various change in welding conditions. This paper presents a new attempt to detect the bond strength of friction welds by ultrasonic. Instead of looking for a flaw or cracks at the interface, the new approach evaluates the coefficient by reflection which provides a single quantitative indicator involving the acoustic energy reflected at the interface. The objective of this study is to find the relationship between the reflection coefficients and the weld strength. Results of the bar-to-bar friction welding of aluminum to copper and stainless steel and such relationship investigation are presented and interpreted.

• Journal of Korean Society of Forest Science
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• v.89 no.4
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• pp.463-469
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• 2000

Douglas-fir (Pseudotsuga menziesd Mirb. Franco) is highly regarded as a commercial timber species throughout the world in part due to its fast growth relative to many other species. In this study, basal area per hectare equation for Douglas-fir plantations in Southland of New Zealand has been developed based on medium measurement cycles of permanent sample plots data set. The function was developed using the algebraic difference equation method, and various sigmoid-shaped projection equations were used. Parameter estimation was obtained by non-linear routine of the SAS. As a result, of the functions tested a variant of the Schumacher polymorphic function including site index and thinning term as predictor variables showed the higher precision of the fitting. The results indicate that site index is positively correlated with basal area growth. And the thinning term was found to be useful to increase precision of the model.

• Journal of the Korean Society of Costume
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• v.57 no.5 s.114
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• pp.1-11
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• 2007

The purpose of this study was to analyze and minimize structural error between sample knitting and actual knitting in weft knitting apparel. Basic stitches used in this study were plain stitch, $0{\times}0$ rib stitch, $1{\times}1$ rib stitch, $2{\times}2$ rib stitch, Milan rib stitch. They were knitted into two different gauges(7 and 12 gauge) and 6 different sample sizes by computer program. The weight, length and width of these 5 basic knitting stitches were measured and their changes according to gauge, stitch and knitting were calculated and analyzed. The results were as follows; The weight of $0{\times}0$ rib stitch was the largest, followed by Milan rib stitch, $2{\times}2$ rib stitch, plain stitch and $1{\times}1$ rib stitch. As the density of stitch per unit area increases, the weight increases. The length of $0{\times}0$ rib stitch was the largest, followed by plain stitch, $2{\times}2$ rib stitch, $1{\times}1$ rib stitch and Milan stitch in both 7 and 12 gauge. As the number of course increases, the length increases accordingly. However, its increase ratio shows higher than that of number of course. It means that the reduction in number of course is needed to get aimed length. The width of Milan rib stitch was the largest, followed by $0{\times}0$ rib stitch, plain stitch, $2{\times}2$ rib stitch, $1{\times}1$ rib stitch in 7 gauge. In 12 gauge, Milan stitch, plain stitch and $0{\times}0$ rib stitch were the highest, followed by $2{\times}2$ rib stitch and $1{\times}1$ rib stitch. It showed that the change in shape of stitch influenced on the width more than the length of stitch.