• The Korean Journal of Pesticide Science
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• v.19 no.3
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• pp.317-322
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• 2015

This study was conducted to obtain basic data for deriving the appropriate application amount of insecticide for effective pest control. We have investigated the correlation among the application amount of insecticide, the adhesion amount of active ingredient and the pest control effect. The linear standard curve of acetamiprid was $R^2=0.9994$, and the scope of the recovery factor was between 71% and 93% with less than 6% of the coefficient of variation. During the test conducted in 2015, the application amount was reduced to 302 L/10a which was 70 L less than the previous year and the spraying pressure was reduced as well. After analyzing the adhesion amount of active ingredient, it was found that a correlation coefficient of adhesion amount of the active ingredients became lower from 82% to 69%, that indicated insecticide liquid was evenly distributed compared to 2014. Also more than 95% of control effect was displayed, thereby indicating that there is a close relation with the correlation coefficient of the adhesion amount of active ingredient. It also presented that the adhesion amount of active ingredient on the ground was 2.2 times more than that on the leaves of apple trees.

• Journal of Korea Water Resources Association
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• v.36 no.6
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• pp.1013-1023
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• 2003

This study was performed to improve water quality of stream by applying hydraulic structures (weir and river bed material) made of porous concrete. The physical and chemical characteristics of porous concrete were measured to estimate application possibility of it in hydraulic structures and it was considered as a proper material for the hydraulic structures. In the results of comparison for the component of matters attached on the hydraulic structures made of porous and ordinary concrete, DW (dry weight) amount attached on porous concrete was 1.6 times higher than that on ordinary concrete under the condition of the same flow rate but influence by flow rate (difference of 10 times) was not shown. Therefore, we could understand that the material of media was more important in DW amount than flow rate. The rate of AFDM (ash free dry mass) to DW also was more at porous concrete than at ordinary concrete. Especially, the high rates of nitrogen and phosphorous in matters attached on porous concrete verify that they were removed by assimilation, adsorption and metabolism of periphyton. The removal percentage of SS, BOD, COD, T-N and T-P by hydraulic structures applying porous concrete compared with ordinary concrete was increased by 34.6%, 36.9%, 33.9%, 18.3% and 21.6%, respectively. Therefore, applying porous concrete to hydraulic structure is expected to contribute to improvement of stream water quality.

• Korean Journal of Agricultural Science
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• v.29 no.2
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• pp.67-77
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• 2002

This study aims at investigating the realities of tractor rotary tilling and paving operations performed by farm families in the central part of the country, measuring the power requirement so as to find the energy-saving factors for tractor rotary tilling, and designing a device to prevent soil adherence to the inside of the rotary cover-this part is the most subject to soil adherence and affects the power requirement. As a result of rotary tilling tests using rotaries equipped with a soil adherence preventer, the power requirement values were measured to be 52.18, 52.44, 49.01 and 46.34 PS for general, stainless steel, rubber and PE rotaries, and as a results of measurement of the quantities of the soil adhered to rotaries after their tilling tests, on the average, the quantities were measured to be 5.6, 5.7, 3.1 and 2.7kg for general, stainless steel, rubber and PE rotaries, respectively. The PE rotary cover reduced the power requirement and soil adherence by 11 and 52%, respectively.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.489-499
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• 2009

It is quite difficult to predict the flexural strength of post-tensioned members with unbonded tendons (unbonded posttensioned members, UPT members) because of debonding behavior between concrete and prestressing tendons, which is different from that with bonded tendons. Despite many previous researches, our understanding on the flexural strength of UPT members is still insufficient, and thus, national codes use different methods to calculate the strength, which quite often give very different results. Therefore, this paper reviews various existing methods, and aims at proposing an improved rational strength model for UPT flexural members having better accuracy. Additionally, a database containing a large number of test data on UPT flexural members has been established and used for verification of the proposed flexural strength model. The analysis results show that the proposed method provides much better accuracy than many existing methods including the rigid-body model that utilizes the assumption of concentrated deformation and plastic hinge length, and that it also gives proper consideration on the effects of primary parameters such as reinforcement ratio, loading pattern, concrete strength, etc. Especially, the proposed method also well predicts the ultimate stress of unbonded tendons of over-reinforced members, which are often possible in construction fields, and high strength concrete members.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.678-685
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• 2006

A certain width of attached gingiva is required to maintain gingival health The purpose of this study was to examine the dimensional changes in the width of attached gingiva and the depth of gingival sulcus among the deciduous, mixed and permanent dentitions and establish baseline information on the width of attached gingiva in Korean children. Eighty-eight children aged 4 to 14, who visited the Department of Pediatric Dentistry at Samsung Medical Center, were selected and divided into 3 groups according to the periods of dentition: deciduous, mixed and permanent dentitions. The width of keratinized gingiva and the depth of gingival sulcus were measured in each group with a periodontal probe and the width of attached gingiva was determined. The width of attached gingiva in maxillary and mandibular first molars increased significantly with age after eruption in the permanent dentition (p<0.05). The sulcus depth significantly increased in newly erupted permanent teeth with narrower width of attached gingiva (p<0.05) in all of the experimented teeth with the exception of the mandibular central incisor during the transition period. The results suggest that the mean width of attached gingiva does not increase steadily from the deciduous to the permanent dentition.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.24 no.1
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• pp.22-29
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• 1988

In order to investigate the shearing efficiency of the Danish sein net using in the sea area of korea, the autors carried out a models of prototype net, and the nets on which the canvas attached to the rear part of the square and to the extension wing of the prototype net, respectively. The model net is made of scale of 1/35 according to Tauti's Law of similarity on fishing gear. The result obtained are as follows: 1. The hydrodynamic resistance increased the maximum 30% in case of the canvas attached to the square, and decreased the maximum 35% in case of the canvas attached to the extension wing in comparison with prototype net. 2. The height of net mouth increased the maximum 12% in case of the canvas attached to the square, and decreased the maximum 5.8% in case of the canvas attached to the extension wing in comparison with prototype net. 3. The width of net mouth decreased the maximum 4% in case of the canvas attached to the square, and increased the maximum 8.4% in case of the canvas attached to the extension wing in comparison with prototype net. 4. The projective area of net mouth increased the maximum 13.6% in case of the canvas attached to the square and increased the maximum 11.8% in case of the canvas attached to she extension wing in comparison prototype net.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.3
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• pp.427-436
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• 2005

Topical application of APF gel can increase the surface roughness of resin composites and the roughened surfaces may allow increased bacterial accumulation and surface staining. Resin specimens of two proprietary resin composites, Filtek Z250(FZ) and Filtek Supreme Universal(FS), and experimental resin composites containing 0%, 3%, 6% nanofillers(E0, E3, E6) were fabricated and divided into two groups of the same number; APF treatment group and no treatment group. The amount of S. mutans adhered to specimens and the mean surface roughness(Ra) were measured. The results were as follows; 1. In no treatment group, the amount of S. mutans adhered to FS was the smallest. It was significantly different from those of FZ, E3, E6(p<0.05) although it was not significantly different from that of E0(p>0.05). 2. For all resin composites used, the amount of S. mutans adhesion in APF treatment group was significantly greater than that in no treatment group(p<0.05). 3. In APF treatment group, the amount of S. mutans adhesion was significantly different between materials(p<0.05), and increased in order of FS, FZ, E0, E3 and E6. 4. Difference of the surface roughness(Ra) between materials was not statistically significant in both no treatment group and APF treatment group(p>0.05)

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.859-862
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• 2008

The objective of this study offer the equation of the development length for GFRP reinforcement. Pullout test carried out to propose the development length for GFRP reinforcement. Test variables included embedment length (L=15, 30 and 45d$_b$ ), pure cover thickness(C=0.5, 1.0, 1.5, and 2.0d$_b$ ), diameter of reforcement(D10, D13 and D16), and three types, (domestic : K2KR, K3KR, foreign : AsUS) of GFRP reinforcement. The method of test were introduced pure pullout and tests lasted until the GFRP reinforcements were reached final failure. Based on the results through the pullout test, the bond characteristics and average bond stress for GFRP reinforcement were investigated. The equation of development length was proposed based on the regression analysis selected specimens having splitting failure. The equation gained from this study compared with the design equation provided by ACI committee 440.1R-06. The results through this study are capable of the flexural member design with GFRP reinforcement having lab spliced.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.585-593
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• 2003

This study deals with literature review, developing a predicting equation for the ultimate stress of prestressing steel, and experimental test with the parameters affecting the ultimate stress of prestressing steel in reinforced concrete beams strengthened by external prestressing. The ACI predicting equation for the ultimate stress of unbonded prestressing steel is analyzed to develop a new integrated predicting equation. The proposed predicting equation takes rationally the effect of internal reinforcing bars into consideration as a function of prestressing steel depth to neutral depth ratio. In the experimental study, steel reinforced concrete beams strengthened using external prestressing steel are tested with the test parameters having a large effect on the ultimate stress of prestressing steel. The test parameters includes reinforcing bar and external prestressing steel reinforcement ratios, and span to depth ratio. The test results are analyzed to confirm the rationality and applicability of the proposed equation for predicting the ultimate stress of external prestressing steel.

• Journal of the Korea Institute of Building Construction
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• v.9 no.6
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• pp.141-149
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• 2009

The objective of this study was to propose a development length equation for bottom and top GFRP bars. Including the bottom and top GRPP bars, a total of 104 modified pullout tests were completed. The test variables were embedment length (15, 30, 45db), net cover thickness (0.5~2.0db), different GFRP bar types, and bar diameters (10, 13, 16mm). The average bond stresses were determined based on the modified pullout test results. Two variable linear regression analyses were performed on the results of the average bond stresses. Utilizing the 5% fractile concept, a conservative development length design equation was derived. The design equation of the development length for bottom and top GFRP bars was proposed and the design equation derived in this study was compared to the ACI 440.1R-06 committee equation.