• Journal of The Korean Society of Grassland and Forage Science
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• v.37 no.2
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• pp.183-188
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• 2017

This study investigated the comparative growth characteristics, yield, chemical compositions, and nutritive yield of Italian ryegrass cultivars harvested in a paddy field. The experimental design was a randomized block design with three replicates. The treatments consisted of seven Italian ryegrass cultivars (Kogreen, Kowinmaster, Hwasan 101, Kowinnearly, Kospeed, Sahalie select, and Strike). The planting date was October 21, 2009 and the sample harvest was occurred on May 21, 2010. Dry matter yield was higher in Kowinnerary and Kogreen than in the other varieties (p<0.05). Crude protein and ether extract contents were highest in Hwasan 101 and lowest in Kospeed. The content of total digestible nutrients did not differ among the Italian ryegrass varieties. The amino acid contents were in the order Hwasan 101 > Strike > Kowinnearly > Kogreen > Sahalie select > Kospeed > Kowinnearly (p<0.05). Fructose content was highest in Kospeed, while glucose and sucrose contents were highest in Hwasan 101. The results of this study indicate that Kowinnearly, in terms of dry matter yield, and Hwasan 101, in terms of feed value (chemical composition and free sugar content), may be recommended for forage production in a paddy field.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.5
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• pp.598-607
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• 2016

This study was conducted to evaluate the amount of nitrogen (N) top dressing based on the normalized difference vegetation indices (NDVI) by ground based sensors for leaf perilla under the polyethylene house. Experimental design was the randomized complete block design for five N fertilization levels and conventional fertilization with 3 and 4 replications in Gumsan-gun and Milyang-si field, respectively. Dry weight (DW), concentration of N, and amount of N uptake by leaf perilla as well as NDVIs from sensors were measured monthly. Difference of growth characteristics among treatments in Gumsan field was wider than Milyang. SPAD-502 chlorophyll meter reading explained 43.4% of the variability in N content of leaves in Gumsan field at $150^{th}$ day after seedling (DAS) and 45.9% in Milyang at $239^{th}$ DAS. Indexes of red sensor (RNDVI) and amber sensor (ANDVI) at $172^{th}$ day after seedling (DAS) in Gumsan explained 50% and 57% of the variability in N content of leaves. RNDVI and ANDVI at $31^{th}$ DAS in Milyang explained 60% and 65% of the variability in DW of leaves. Based on the relationship between ANDVI and N application rate, ANDVI at $172^{th}$ DAS in Gumsan explained 57% of the variability in N application rate but non significant relationship in Milyang field. Average sufficiency index (SI) calculated from ratio of each measurement index per maximum index of ANDVI at $172^{th}$ DAS in Gumsan explained 73% of the variability in N application rate. Although the relationship between NDVIs and growth characteristics was various upon growing season, SI by NDVIs of ground based remote sensors at top dressing season was thought to be useful index for recommendation of N top dressing rate of leaf perilla.

• Journal of Biosystems Engineering
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• v.37 no.4
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• pp.225-232
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• 2012

Purpose: Accurate monitoring of information from various agricultural vehicles is one of the most important factors for appropriate management strategy of field operations. While there has been a number of study and design on applications of sensors and actuators for data acquisition and control system in tractor, incompatibility between various customized hardware and software has become a major obstacle to the universal deployment in real field operation. International standard for implementation of electronic control unit (ECU) in agricultural vehicles has becoming a mandatory requirement for inter-operation compatibility in the international trade of agricultural vehicle industries. The ISO 11783 standard is basically based upon well known communication technology designated using the controller area network (CAN) bus. While CAN bus could provide 1.0 Mbps of communication speed, the standard only recommended 250 kbps. Methods: This study presents the implementation and evaluation of ISO 11783 for tractor electronic control units (TECU)with a higher transmission rate from multiple ECU than 250 kbps. Throughput and loss rate of the developed prototype were calculated across manipulated bus load for laboratory experimental tests, and the maximum requirement of transmission rate by ISO 11873 was satisfied with lower than 60% of bus load. Results: Field tests with a TECU implemented to process messages from global positioning system (GPS) receiver resulted that the root mean square error of position information was lower than 4 m with 0.5 m/s as a travelling speed. Conclusions: Results of this study represent the utilization of the international standard ISO 11783 to providepractical developments in terms with the inter-operability of TECU.

• Journal of the Korean Society for Library and Information Science
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• v.19
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• pp.189-241
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• 1990

This study identified cognitive styles of online searchers in terms of Field Dependence (FD) and Field Independence (FI) dimension and determined whether searching performance was affected by FD / FI cognitive differences between online searchers and the extent to which searching performance was affected by the FD / FI dimension of cognitive style. This study used a quasi experimental design with 41 student subjects using the Lockheed DIALOG system and ERIC ONT AP database. Cognitive styles of student subjects were measured by using GEFT (Group Embedded Figure Test) and the subjects were divided into two cognitive groups- FD and FI based on the GEFT scores. Each subject was assigned two predetermined searches which had different search goals-a 'high precision search' and a 'high recall search.' Search performance of the two cognitive groups on the two problems was compared in order to see how these two groups responded to achieving different search goals in terms of search strategy, search inputs, and resulting search outputs. The major findings of this study were: 1. The pattern of approaching a search problem regardless of whether it was a high precision search or a high recall search was not significantly different between the two cognitive groups. 2. The FI group tended to use significantly more terms for the high recall search than the FD group but slightly less time than the FD group. However, significant differences in connect time between the two groups were not revealed. 3. For both search problems the FI group achieved a significantly higher success rate than the FD group. The FI group were significantly more successful searchers than the FD group. As for unit / cost, although the FI group were more cost effective than those of the FD group for both searches, these differences were too small to be statistically significant. 4. Mean differences of the search performance variables between the FD / FI groups were consistent across the two types of search questions. The FI group seemed to be equally effective for both types of search questions. In conclusion, the differences found in number of terms used and success rate between the two cognitive groups apparently resulted from different cognitive styles.

• Journal of the Korean Geosynthetics Society
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• v.13 no.1
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• pp.53-61
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• 2014

Sea gives us a lot of benefits and one of them is a role of transporting goods easily by ship. Accordingly the industrial area or the container yard is constructed either on the low sea or near the sea. Sea dredging ground is made by pumping them using dredge pump to the inside of embankment after dredging undersea soils. The dredging ground after pumping is in the slurry state but as time goes, consolidation by the own weight happens and evaporation happens at the surface of dredging ground. The evaporation causes the crest layer in the upper side of dredging ground. Under the crest layer there is still a soil of slurry state which has just little bearing resistance. This kind of characteristics makes it difficult to get a exact bearing capacity using the equations proposed until now. In this study we have performed simultaneously both the field loading tests and the cone penetration tests on the sea dredging ground. From the result of field tests, new experimental equation for the ultimate bearing capacity has been proposed. If we use the new equation, it is believed that some design of sea dredging ground could be more accurate.

• International Journal of Automotive Technology
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• v.7 no.7
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• pp.847-852
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• 2006

A fitting process carried out in the automobile transmission assembly line is classified into three classes; heat fitting, press fitting, and their combined fitting. Heat fitting is a method that applies heat in the outer diameter of a gear to a suitable range under the tempering temperature and assembles the gear and the shaft made larger than the inner radius of the gear. Its stress depends on the yield strength of a gear. Press fitting is a method that generally squeezes gear toward that of a shaft at room temperature by a press. Another method heats warmly gear and safely squeezes it toward that of a shaft. A warm shrink fitting process for an automobile transmission part is now gradually increased, but the parts (shaft/gear) assembled by the process produced dimensional change in both outer diameter and profile of the gear so that it may cause noise and vibration between gears. In order to solve these problems, we need an analysis of a warm shrink fitting process in which design parameters such as contact pressure according to fitting interference between outer diameter of a shaft and inner diameter of a gear, fitting temperature, and profile tolerance of gear are involved. In this study, an closed form equation to predict the contact pressure and fitting load was proposed in order to develop an optimization technique of a warm shrink fitting process and verified its reliability through the experimental results measured in the field and FEM, thermal-structural coupled field analysis. Actual loads measured in the field have a good agreement with the results obtained from theoretical and finite element analysis and also the expanded amounts of the outer diameters of the gears have a good agreement with the results.

• Tunnel and Underground Space
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• v.13 no.4
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• pp.287-293
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• 2003

A long vertical duct is an essential installation for extracting smoke to the ground level when a fire occurs in an underground space. Due to the limitations of its basic assumptions, the existing two-layer zone model is unsuitable to model smoke dispersion through a long vertical duct. Therefore, an assessment was made to investigate the applicability of the field model, which is based on the computational fluid dynamics (CFD). A similar configuration to the published experimental work was modeled to test the validity. It is clear that under a consistent decision criterion based on the mass fraction, the field model (CFD) is able to predict that the diffusion front progresses up the shaft with exactly the same rate as that in the empirical correlation equation. This result is for better than the mathematically obtained equations in previously published research. Therefore, it can be said that the field model is an excellent option to predict the smoke dispersion through the long vertical shaft.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.603-609
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• 2015

Dry air is an excellent alternative to $SF_6$ gas and is used as an insulation gas in Eco-friendly Gas Insulated Switchgears (EGISs), which has gained popularity in industry. Solid insulators in EGIS play an important role in electrical insulation. On the other hand, surface discharge can occur easily when solid insulators are used. This paper explored the surface discharge characteristics on the structure of three-layered laminated solid insulators to elevate the flashover voltage. A laminated solid insulator was inserted after the quasi-uniform electric field was formed in the test chamber. Dry air was then injected to set the internal pressure to 1 ~ 6 atm, and the AC voltage was applied. When identical solid insulators were stacked, the surface discharge characteristics were similar to those of a single solid insulator. On the other hand, the flashover voltage rose when the middle part was thicker and had lower permittivity than the top and bottom parts in the laminated solid insulator. Based on experimental results, when stacking a solid insulator in three layers, the middle part of the solid insulator should be at least four times as thick as the top and bottom parts and have lower permittivity than the others. In addition, the flashover voltage increased with increasing gas pressure on the surface of the laminated solid insulator due to the gas effect. This study may allow insulation design engineers to have useful information when using dry air for the insulation gas where the surface discharge can occur.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.466-471
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• 2014

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. This paper presents a numerical analysis method for a simplified vehicle model. The internal air cavity including trim component are included in the simulation. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using PowerFlow. The second step consists in the computation of the vibro-acoustic transmission through the window using the finite element vibro-acoustic solver Actran. Additionally in order to validate the numerical process, an experimental set-up has been created based on the simplified vehicle. The vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.2
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• pp.85-93
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• 2018

This study investigated the structural behavior and field applicability of sandwich type GFRP arches with polymer mortar in core. As a result, in case of crack loading and failure loading, total strains at crown were the highest; the fracture strain at crown was 0.01690, which is 4.2 times greater than the fracture strain (0.004) of cement concrete. The 3 % deflection load was 17.42 kN, the flexural strength was $163.98{\times}10^{-3}GPa$, and the flexural elastic modulus was 11.884 GPa. From load-deflection relationship up to 3.5 % deflection, 3D analysis results and experimental values were observed to be almost identical. It was considered reasonable to set a deflection rate limit to be 3 % for structural safety purpose. The standard external flexural strength of semicircular arch used in this study was approximately 2.64 times higher than that of hume pipe (2 type standard) and tripled composite pipe. The external pressure strength at fracture was approximately 1.57 times higher than that of hume pipe. It was confirmed that the implementing semicircular arch had mechanically more advantage than the circular pipe. Optimum member thickness was 8~53 mm according to arch radius of 450~1,800 mm and cover depth of 2~10 m. It was found that the larger strength could be obtained even if the thickness of member was smaller than that of concrete structure. In field application study, figures and equations were derived for obtaining applicable cover depth and optimum member thickness according to loading conditions. These would be useful data for design and manufacture of sandwich type semicircular arch.