• Journal of Biosystems Engineering
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• v.36 no.4
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• pp.243-251
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• 2011

Purpose of this study was to analyze power requirement of an agricultural tractor for baler operation. First, a power measurement system was developed and installed in a 75 kW agricultural tractor. Strain-gages with a telemetry system were used to measure torques of transmission and PTO input shafts. An engine tachometer was used to measure rotational speed of transmission and PTO input shafts. The measurement system also included pressure sensors to measure pressure of hydraulic pumps, an I/O interface to acquire the sensor signals, and an embedded system to determine power requirements. Second, field experiments were conducted at two PTO speed levels, and proportion of utilization ratio of rated engine power and power consumption of major parts (transmission input shaft, PTO input shaft, main hydraulic pump, and auxiliary hydraulic pump) were analyzed. Results of usage proportion of engine power for PTO speed level 1 and 2 were 4.1 and 2.2%, 31.5 and 16.3%, 49.6 and 59.7%, 14.4 and 20.8%, and 0.4 and 1.0%, respectively, for ratio of measured engine power to rated engine power of less than 25%, 25 ~ 50%, 50 ~ 75%, 75 ~ 100%, and greater than 100%. The results showed that the usage proportion increased in the range with the ratio of power requirement to rated engine power of over than 50% when the PTO gear was shifted from P1 to P2. Averaged engine power requirement for baling operation, tying and discharging operation, and total operation were 43.3, 37.3, and 42.0 kW and 49.0, 37.0, and 47.4 kW, respectively, for PTO speed level 1 and 2. Paired t-test showed significant difference in power consumption of engine, transmission input shaft, and PTO input shaft for different PTO speed levels. Therefore, the power consumption of engine for baler operation increased when the PTO gear was shifted from P1 to P2. It was indicated that the power requirement of tractor was affected by the PTO rotational speed for baler operation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.2
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• pp.87-100
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• 2007

This study was carried out to offer fundamental data for improving the fishing efficiency of the Danish seine. The net height and the shape in the water was measured to analyze the efficiency of the existing Danish seine. And then, an improved fishing gear was developed based on the results and was tested in the field. Measuring devices were attached on center of a ground rope and a head rope. The net height is the spread distance between the ground rope and the head rope, which was measured on the different ratio of buoyancy. The results are obtained as follows. The net height estimated from the design plan of horizontal hanging ratio 0.40 in the existing Danish seine A and B estimated both 4.94m. The net height of the existing Danish seine A and B was respectively 1.8m and 2.3m, which form 36.4% and 46.2% of the net height estimated from the design plan. Buoyancy was changed as 79.5% and 96.2% relative to the sinking force in the existing Danish seine. The net height of 79.5% was 3.95m which increased to 80% of the estimated net height. The other shows the same result with the first case. It is not necessarily that the high buoyancy/sinking force ratio make the high net height, 80% is adequate as the buoyancy/sinking force ratio. In case of the improved Danish seine, the mean net height was about 5.0m, means 58.3% of estimated net height 8.58m.

• Journal of Wetlands Research
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• v.23 no.3
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• pp.234-241
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• 2021

This paper contributes to the understanding of the effect of pulley on the performance of the vortex turbine in free water surface. The experimental work was to analyze the rotation, voltage and current of the turbine due to physical factors (vortex height, velocity, effective head, etc.) at flow rates ranging from 0.0069 to 0.0077 m³/s in the inlet channel. As a result, the experimental values showed that voltage, current and rotational speed of the vortex turbine decreased with increasing the pulley ratio regardless of the blade type. The efficiency of straight blade and twisted blade was 52 % at the gear ratio of 0.45, whereas the efficiency of small twisted blade was 54 % at the pulley ratio of 0.21. The highest amount of the energy generated by the water free vortex turbine occurred within a pulley ratio of 0.5. The efficiency of this vortex turbine was observed at 0.2 ~ 58 % depending on the pulley ratio.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.3
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• pp.223-230
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• 2002

Investigations were made on catch composition, sex ratio, relationships between carapace length, body weight and fecundity and spawning season of major target shrimps (Acetes chinensis, A. japonicus) in the shrimp fishing areas of south-western coastal waters, accounting for about $45\%$ of annual shrimp landings in Korea. Catches were collected monthly in the fishing areas from March 2000 to February 2001, using single pocket-walled fishing gear, Total 59 species (shrimps 14, fishes 34, other crustaceans 8 and cephalopods 3 species) occurred. During the study period the bycatch-to-shrimp ratio of shrimp fishery was 2.42 in April 2000 and less than 1 for all months except for August 2000 and Febuary 2001. Compared with shrimp fishery of other areas and nations, these results indicate that effect of the fishing gear on catches of other species is minor, suggesting higher gear selectivity for shrimps. Of shrimps, there were two dominant species (A. chinensis, A. japonirus). Average sex ratio was 1.44 $\pm$ 0.42 for A. japonicus and 1,44 $\pm$ 0.43 for A. chinensis, which are dominant females in August. Average fecundity was 4,812 $\pm$ 1,511 for A. japonicus and 5,561 $\pm$ 1,900 for A. chinensis. In the two species mature females were found in the period from May to August. Similarly, the gonadosomatic index (GSI) was higher in July and August, with a peak in July, These results indicate that their main spawning season was summer.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.7-13
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• 2005

In the case of fabricating micro pole structures such as column, square-pole and gear shaft by the micro end-milling process, it can be useful in the fields of industry, for example, micro parts, electrode for electrical discharge machining and micro mold for injection molding. In this study, machining factors and the process were analyzed. Machining experiments of various micro pole configurations were performed. Analysis of the change and effect of the cutting force according to the machining conditions was carried out. An analytical study of the deformation of the micro pole caused cutting conditions and cutting force through the finite element method and ANSYS program was carried out. As a result, this research presented a method of fabricating the column pole of below $100{\mu}m$ diameter with high aspect ratio by using micro end-milling process, and based on that, a method of fabricating a variety of applicable structures. Also the minimum size of the pole capable of fabricating through theory and experiment were demonstrated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.234-239
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• 2013

There are many types of speed reducer for industrial uses. However the cycloid speed reducer is widely used in manipulators based on excellent performance of low backlash, high reduction ratio and compact size. It is essential to use precision speed reducer for accuracy of position controls on robot systems and electric vehicles. The cycloid speed reducer has a eccentric rotating motion and offset to avoid some problem of assembly, so it has a disadvantage for vibration. In this paper, a multi-body dynamic model is developed for a cycloid speed reducer and the dynamic behaviors of the reducer are investigated. The cycloid speed reducer consists of cycloidal plate gears, housing gear, input shaft, output pin and shaft, and eccentric bearings. Using a CAD program, each component of cycloid reducer is modeled based on the offset and eccentric. Multi-body simulations using Recurdyn and test using a rig tester are performed. As a result, the pin reaction force and the amplitude of housing displacement are increased by the larger offset and smaller eccentric value of cycloid reducer.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.162-169
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• 2000

This study was carried out to develop a continuously variable-speed transmission(CVT) for agricultural tractor. A full-toroidal CVT mechanism with four discs and six rollers was selected as a device for changing speed ratio continuously. In the step of system layout design, the sizes of roller cylinders and end-load cylinder, which were critical factors for controlling the variator, were designed. Also the control pressure range was designed to limit the contact pressure of variator. In order to make the maximum speed of vehicle as 30km/h, the planetary gear and the six pairs of gears were designed. Also the hydraulic clutch, silent chain, hydraulic manifold and electronic controller were designed. After the design, a prototype with CVT controller was developed and tested. The speed of vehicle was changed continuously to the speed set by driver and the settling time was about 0.52 second at the step-response test (reduction ratio of variator 2.0 to 1.0), which was acceptable as a response time for working with tractor.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.118-124
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• 2007

The efficiency of the hybrid systems which are composed of compound planetary gear sets depend on the amount of the recirculating energy among the motors and battery. This paper studies the analysis of the system efficiency with the parameters, ${\alpha},\;{\beta},\;{\gamma_a},\;{\gamma_b}$ and $\gamma_s$. The efficiency of the systems and the relative torque, speed and power of the power resources are represented by these parameters. The recuperating parameter $\kappa$ which makes the systems generalized is introduced, so the efficiencies of the modes such as the hybrid mode, the engine mode, the motoring mode and the recuperating mode are analyzed with simple equations. The tendency of the system efficiency according to the variations of the $\gamma_s$ and $\kappa$ are studied, by which it can be possible to reduce the loss of the power because the strategies for avoiding the singular speed ratio $\gamma_s$ are helpful for the system efficiency and specific value of $\kappa$ can increase the efficiency of the systems.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.4
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• pp.355-358
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• 2001

This paper presents case studies on the multi-species fisheries in Korean waters. Multi-species fisheries were divided into two types, that is, multi-species by a single fishery and single species by multiple fisheries. For the case of the multi-species by a single fishery, a multi-species yield-per-recruit model was applied to the Korean pair trawl fishery, which exploits demersal fishes such as, hairtail (Trichiurus lepturus), small yellow croaker (Pseudosciaena polyactis), white croaker (Argyrosomus argentatus) and pomfret (Pampus echinogaster). The overall fishing mortality ($F_x$) values for the multi-species was estimated and compared to the spawning potential ratio ($F_{x\%}$) val ues estimated from the spawning biomass-per-recruit model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.11
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• pp.837-847
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• 2020

A velocity profile for flapping flight is optimized to increase the power efficiency of 20g weighted flapping wing micro air vehicle in hover. The experimental optimization of flapping velocity profile is carried out with a real sized flapper, and various velocity profiles are realized by non-circular gear. Kriging with noise is adopted as a meta model of the profile optimization to reflect the data noise by uncertainty. The optimization results confirm that the flapping efficiency (thrust-to-power ratio) is substantially improved (11.3%) through the elastic deformation that carries the angular kinetic energy from previous stroke.