• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1381-1384
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• 2005

In these days, the piezoresistive material has been applied to various sensors in order to measure the change of physical quantities. But the relationship between the sensitivity of a sensor and the position and size of piezoresistor has rarely been studied. Therefore, this paper was focused on the distribution of the resistance change ratio on the diaphragm and bridge surface where piezoresistor would be formed, and proposed the proper size and position of piezoresistor with which the sensitivity of sensor was increased. As the width of mass and boss was increased, the distance between piezoresistors was closed and the maximum value of resistance change ratio was decreased by the increase of the structure stiffness. And according to the increment of seismic mass size, the value of resistance change ratio is decreased by increase of the structure stiffness. Y directional piezoresistor is formed in the position of $100\mu{m}\;apart\;from\;cantilever\;edge\;and\;length\;of\;that\;is\;800\mu{m}$.

• Journal of Korean Society of Transportation
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• v.34 no.3
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• pp.248-262
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• 2016

The study documents the analysis on characters and symbols shown in the pavement markings in the perspective of mathematics educators. The purpose of this study is to propose a pavement marking method that can enhance readability from the driver's eye position. To this end, this study analyzed the figure of the pavement markings that can be actually recognized by the projective geometry perspective. As a result, it proposed alternatives to the current pavement markings by introducing the concept of the compression ratio. Results of the study are as follows. First, the rule was established to obtain the compression ratio. If the observation of two viewing angles are x and y, then the compression ratio S is ${\sin}y/{\cos}\(\frac{x-y}{2}\)$. Second, we presented two alternatives to the pavement marking method for the displayed information. One is a method for improving the pavement markings in terms of the compression ratio, the other is a method by varying vertical length of the pavement markings while holding its width constant. Based on the outcomes from this study, a mathematical analysis can be further studied for the perception of speed according to the types of pavement marking line.

• Journal of Biosystems Engineering
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• v.35 no.4
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• pp.215-223
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• 2010

In order to develop an precision aerial pesticide application system to be attached to an unmanned helicopter which can be applied to small lots of land, this study analyzed the flowing and spraying characteristics of the spray droplets by the main rotor downwash by setting the application conditions at the flight altitude of 3 m, the diameter of main rotor of 3.1 m, the boom length of around 2.8 m, and the spraying rate of 8 L/ha. The results of this study are summarized below. Through analysis of the covering area ratio of the spray droplets by main rotor downwash by nozzle type, boom with tilt angle and height, it was found that the covering area ratio of the twin flat-fan nozzle of around 25% was more uniform than other types of nozzle, also boom with $10^{\circ}$ tilt angle and spraying height of 3 m was shown to be the appropriate conditions for aerial application of pesticides. It was found that the nozzle position to minimize the scattering loss of spray droplets due to vortex phenomenon at both ends of the main rotor was around 10 cm from the end of the main rotor. An application test for the aerial pesticide application system attached to the HUA-ACEI unmanned helicopter developed by the Rural Development Administration showed that the range of covering area ratio of the spray droplets was 10-25%, and the spraying width was approximately 7 m when over 10% of covering area ratio was considered for valid spraying.

• Structural Engineering and Mechanics
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• v.47 no.6
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• pp.819-838
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• 2013

This paper summarises the results of an experimental study to investigate the flexural behaviour of reinforced concrete beams strengthened using carbon-fibre reinforced polymer (CFRP) laminate in four-point bending. The experimental parameters included are the reinforcing bar ratio ${\rho}_s$ and preload level. Four bar ratios were selected (${\rho}_s=0.13$ to 0.86%), representing the section of two longitudinal tensile reinforcements, with diameters of 8, 14, 16, and 20 mm in order to reveal the effect of bar ratio on failure load and failure mode. Eight beams that could be considered "full-scale" in size, measuring 200 mm in width, 400 mm in total height and 2300 mm in length, were tested. Three beams were selected with different bar ratios (${\rho}_1$, ${\rho}_2$, ${\rho}_3$), and considered as control specimens (without ), while three other beams identical to the control beams with the same CFRP laminates ratio and a seventh beam with ${\rho}_{min}$ (the lowest bar ratio) were also used. In the second part of the study, two beams with the bar ratio ${\rho}_2$ were preloaded at two levels, 50 and 100% of their ultimate loads, and then repaired. This experimental investigation was consolidated using an analytical model. The experimental and analytical results indicate that the flexional capacity and stiffness of strengthened and repaired beams using CFRP laminate were increased compared to those of control beams, and the behaviour of repaired beams was nearly similar to the undamaged and strengthened beams; unlike the ductility of strengthened beams, which was greatly reduced compared to the control.

• The Journal of the Korean dental association
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• v.47 no.7
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• pp.444-454
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• 2009

The purpose of this study was to compare the shaping abilities of LightSpeed, ProTaper-Universal, and hybrid technique using S-series of ProTaper-Universal and LigthSpeed. The 72 simulated root canals of J-shape were used and classified as flowing 3 groups according to the instrumentation methods; Group P of 24 canal blocks were prepared with ProTaper-Universal, Group L was prepared with LightSpeed, and Group H was prepared with hybrid technique (initial shaping with ProTaper-Universal SI and S2 and apical shaping with LightSpeed from #25 to #50). A second-year resident of Endodontic department prepared the resin block canals to apical size #50 (F5 in Group P). The time lapses for instrumentation and the reduction of root canal curvature after shaping were measured. The pre- and post-instrumented root canals were scanned and superimposed to evaluate and calculate the increased canal width and apical centering ratio. The results were as followings: Group Land H showed significant less instrumentation time than Group P (p < 0.05). The ProTaper system showed greater reduction of root canal curvature and working length diminishment than other methods (p < 0.05). LightSpeed system showed best canal curvature preserving characteristics. The Group P had greater instrumented widths at all levels examined (p < 0.05). Group L and Group H showed lower centering ratio (ability to preserve the canal center; the lower ratio means the better canal center preservation) than Group P (p < 0.05). Group H had the lowest centering ratio at the 1 mm level.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.2
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• pp.318-327
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• 2002

In this paper, heat transfer and pressure oscillation characteristics on oscillating capillary tube heat pipe(OCHP) according to input heat flux, mixture ratio of working fluid and inclination angle were investigated and were compared single working fluid(R-142b) with binary mixture working fluid(R-142b-Ethano1). OCHP was made to serpentine structure of loop type with 10 turns by drilling the channels of length 220mm, width 1.5mm, and depth 1.5mm on the surface of brass plate. In this study, R-l42b and R-l42b-Ethanol were used as working fluids, the charging ratio of working fluids was 40(vol.%), the input heat flux to evaporating section was changed from 0.3W/㎠ to 1.8W/㎠, and mixture ratio of working fluid was R(100%), R(95%)-E(5%), R(90%)-E(10%), and R(85%)-E(15%). From the experimental results, it was found that the effective thermal conductivity of single working fluid was better than that of binary mixture working fluid. But, in case of binary mixture working fluid, critical heat flux was higher than that of single working fluid. And, the higher the mixture ratios of working fluid, the lower heat transfer performance. In case of pressure oscillation, as the inclination angle was lower, pressure wave was more irregular. These phenomena were more serious when the working fluid was binary mixture. Besides, when mixture ratio was higher, saturated pressure was increased, more irregular wave was observed and the mean amplitude was increased. For the same input heat flux, inclination angle and charging ratio, when pressure oscillation has sinusoidal wave, mean amplitude was small, and saturated pressure was low value, the heat transfer was excellent.

• Journal of The Korean Society of Grassland and Forage Science
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• v.12 no.1
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• pp.49-58
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• 1992

The purpose of the experiment was to determine the effect of plant density and pattern on growth characteristics, total dry matter yield. protein yield and palatability of sorghum-sudangrass hybrid (Sordan 79). The main treatment was three levels of plant density (Skg, 15kg. 30kg/ha) and the sub treatment was two plant patterns of square and rectangular planting.The experiment was arranged as a split plot design and conducted on the Experimental Livestock Farm of Kon-Kuk Univ. in Chungju, 1989. The results obtained are summarized as follows :1. As the plant density was increased, plant length, leaf length, leaf width(P<0.05) and leaf number were gradually decreased, but in the same plant density, plant length, leaf length, leaf width and leaf number were generally increased in the rectangular plot. 2. In the first cutting time, the ratio of leaf was the highest at the rectangular plot of high density (30kg/ha, 25cm$\times$4cm), but in the second cutting time, the ratio of leaf was the highest at the square plot of medium density (15kg/ha, 14cm$\times$ 14cm). 3. The ratio of dead stubble after cutting was generally increased by increasing the plant density. Also, in the same planting density, the ratio of dead stubble was generally increased in the square plot. 4. The tiller number per plant tended to decreased by increasing thc plant density, and the tiller number was increased in the rectangular plot. In the same plant density. 5. Total fresh and dry matter yield were the highest at the rectangular plot of medium density (IS kg/ha, 33cm$\times$6cm) wholly, but the low density was shown the lowest.6. The crude protein content was increased by increasing the plant density per unit area(P<0.05) and the protein yield was also increased by increasing the planting density. 7. According to the increase of plant density, the stem was thinned, but NDF, ADF did not show different. The palatability was in the order of high (30kg/ha))medium (15kg/ha))low density(5kgiha) at the first cutting time, but it was in the order of high)low)medium density at the second cutting time.

• Journal of The Korean Society of Grassland and Forage Science
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• v.12 no.1
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• pp.19.2-19.2
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• 1992

The purpose of the experiment was to determine the effect of plant density and pattern on growthcharacteristics, total dry matter yield. protein yield and palatability of sorghum-sudangrass hybrid(Sordan 79). The main treatment was three levels of plant density (Skg, 15kg. 30kg/ha) and the subtreatment was two plant patterns of square and rectangular planting.The experiment was arranged as a split plot design and conducted on the Experimental Livestock Farm of Kon-Kuk Univ. in Chungju, 1989.The results obtained are summarized as follows :1. As the plant density was increased, plant length, leaf length, leaf width(P<0.05) and leaf number were gradually decreased, but in the same plant density, plant length, leaf length, leaf width and leaf number were generally increased in the rectangular plot.2. In the first cutting time, the ratio of leaf was the highest at the rectangular plot of high density(30kg/ha, 25cm$\times$4cm), but in the second cutting time, the ratio of leaf was the highest at the square plot of medium density (15kg/ha, 14cm$\times$ 14cm). 3. The ratio of dead stubble after cutting was generally increased by increasing the plant density. Also, in the same planting density, the ratio of dead stubble was generally increased in the square plot. 4. The tiller number per plant tended to decreased by increasing thc plant density, and the tiller number was increased in the rectangular plot. In the same plant density. 5. Total fresh and dry matter yield were the highest at the rectangular plot of medium density (ISkg/ha, 33cm$\times$6cm) wholly, but the low density was shown the lowest.6. The crude protein content was increased by increasing the plant density per unit area(P<0.05) and the protein yield was also increased by increasing the planting density. 7. According to the increase of plant density, the stem was thinned, but NDF, ADF did not show different. The palatability was in the order of high (30kg/ha))medium (15kg/ha))low density(5kgiha)at the first cutting time, but it was in the order of high)low)medium density at the second cutting time.

• Journal of the Korean Wood Science and Technology
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• v.46 no.5
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• pp.486-496
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• 2018

This study was conducted to confirm an effect of span length on bending properties of larch dimensional lumber in the four point bending test. The size of specimen in this study was 38 (width) ${\times}$ 89 (depth) ${\times}$ 3,600 (length) $mm^3$, and average air-dry density and moisture content of the specimens was $543.5kg/m^3$ and 10.5%, respectively. Visually graded No. 1 dimensional lumbers of 248 were divided by two groups to compare modulus of rupture (MOR) and modulus of elasticity (MOE). One group was tested in the four point bending test with span length of 1,650 mm, and other was tested with span length of 3,000 mm. While MOE was not different according to span length in 5% significance level, MOR was different in accordance with span lengths and was in inverse proportion to change of span length. Fifth percentiles of MOR in span length of 1,650 and 3,000 mm were 28.65 and 25.70 MPa, respectively. It was confirmed that the difference between MORs in each case increased as normalized rank increased. This is because of size effect in Weibull weakest link failure theory. Therefore, KS F 2150, in which there is only regulation about span to depth ratio of 15 or more, is needed to be revised to contain a method considering size effect for MOR. From the method, various results of bending test with different size of lumber could be used to determine design value of lumber.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.5
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• pp.425-430
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• 1992

This experiment was carried out to collect the Korean red rices and to evaluate them as useful germplasm, 1,113 lines of weedy red rices were collected from farmer's field of the Korean peninsula from 1988 to 1991. The collected red rices were classified into two groups : One was long grain type with length /width ratio of 3.01$\pm$0.11 in paddy rice and the other was short grain type with length /width ratio of 2.28$\pm$0.12. Among the collected red rices 289 lines were long grain type and 824 lines were short. The red rices of long grain type were distributed in Nagdong and Seomjin river vallies of the southern part of the Korean peninsula, and the short ones were distributed all around of the peninsula. Among the collected long grain type red rices, 90.8% was red and 9.2% was white, and among the short grain type 88.8% was red, 10.6% was brown and 0.6% was white in pericarp color. 9.3% of the long grain type and 30.7% of the short grain type of the Korean red rices reacted to phenol solution. In the short grain type, 4.3% was waxy grained, but no waxy line was found in the long grain type. All the long grained Korean red rice showed easy shattering and no awn, however in the short grained red rices, 85.2% showed easy shattering and 49.6% was awned.