• The KSFM Journal of Fluid Machinery
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• v.13 no.1
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• pp.23-28
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• 2010

A draft tube which has impeller to elevate bottom water and spread it over surface of lake water, induces convective circulation of lake water, a Long-Distance Circulation (LDC). Circulation of lake water make stratified water mixed and enhance DO (Dissolved Oxygen) of bottom water. Circulation rate of water is determined by draft rate of the tube, which is dependent on design parameters of the draft tube system, i. e. dimension of impeller and diffuser, inclined angle of impeller, impeller shape, and rotational speed. In this study, change in draft rate and power consumption of circulation equipment was investigated numerically with changing impeller dimension, angle and rotational speed. It was found that flowrate of draft water was increased as the dimensions of draft tube and impeller, and rotational speed and inclined angle of impeller increased. The power consumption was also elevated with increasing parameter values, and final selection of parameter values was made to satisfy target flowrates and power consumption.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.3
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• pp.290-301
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• 2006

A push pull hood system is frequently applied to control contaminants evaporated from an open surface tank. Efficiency of push pull hood system is affected by various parameters, such as, cross draft, vessel shapes, tank surface area, liquid temperature. A previous work assisted by flow visualization technique qualitatively showed that a strong cross draft blown from the pull hood to push slot could destroy a stable wall-jet on the surface of tank, resulting in the abrupt escape of smoke from the surface. In this study, the tracer gas method was applied to determine the effect of cross-draft on the capture efficiency qualitatively. A new concept of capture efficiency was introduced, that is, linear efficiency. This can be determined by measuring the mass of tracer gas in the duct of pull hood while the linear tracer source is in between push slot and pull hood. By traversing the linear tracer source from the push slot to the pull hood, it can be found where the contaminant is escaped from the tank. Total capture efficiency can be determined by averaging the linear efficiencies. Under the condition of cross-draft velocities of 0, 0.4, 0.75, 1.05 and 1.47m/s, total capture efficiencies were measured as 97.6, 95.4, 94.6, 92.7 and 70.5% respectively. The abrupt reduction of efficiency with cross-draft velocity of 1.47m/s was due to the destruction of tank surface wall-jet by the counter-current cross-draft. The same phenomenon was observed in the previous flow visualization study. As an alternative to overcome this abrupt efficiency drop, the 20% increase of hood flow rates was tested, resulting in 20% efficiency increase.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.88-94
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• 2009

In this paper, vibration characteristics after applying variable speed control to fans with a rated speed used in a power plant are studied by performing experiments and analyzing finite element models. Then the campbell diagram is presented to verify the reason of the abnormal vibration measured from fan structure during variable operation of Forced Draft Fan & Induced Draft Fan. According to results, it is found that amplitude of acceleration increases abruptly when a 2X harmonic component meets the natural frequency of fan rotor. Therefore it is very important thing that investigate exactly dynamic characteristics for the rotor at variable speed zone before applying variable speed control to a rotor with a rated speed.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.307-315
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• 1993

A direct draft measurement system was developed based on the swingle tree- the rear component of the single-animal harnessing (or yoking) system . The prototype was made from a tube, on which four strain gages were attached. The pull of the draft animal through the flexible pull chains or ropes causes the beam to bend, The bending strain is sensed by the strain gages and the bridge converts this to a voltage signal. Counterweights keep the tube correctly oriented if the angle of pull changes , while end bearing follow the variations in the angle of pull. Hence, the voltage output is proportional to the draft. the device has highly linear response, acceptable sensitivity negligible error and hysteresis. It is suitable for electronic data acquisition, non-intrusive , easy to attach and detach and is reasonably priced.

• Journal of the Korean Data and Information Science Society
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• v.19 no.4
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• pp.1081-1089
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• 2008

Beginning in the 2007-2008 season, the men's pro-basketball league changed a foreigner selection method by introducing a draft system which leads to a tryout from the free agency system. Also in the same season, the woman's pro-basketball league changed its system from one that permitted foreign players to one that doesn't allow foreign player participation. The reason for this change is thought to be financial problems. However this institutional change brings about the reduction in the quality of basketball and it will affect spectators in a negative way. The empirical study attempted to analyze the effects which follows an institutional change in Korean men's pro-basketball. The research showed that the men's pro-basketball league wasn't affected at all due to foreigner selection method by a draft system that led to a tryout from the free agency system.

• Journal of Biosystems Engineering
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• v.22 no.2
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• pp.117-126
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• 1997

A series of soil bin experiment was carried out on sandy loam to investigate if it is possible to predict implement draft by some analog tool. Chisel configuration resembling a cone penetrometer section was used as an analog tool. The angle of cone was 30 degree. Three types of tillage implement, or oriental janggi, moldboard plow and chisel plow were chosen for this study. Experimental tillage speed was 0.22, 0.33, 0.49 m/s ad tillage depth was 8, 12, 16cm. For the experimental tillage speed range, the increase of tillage speed did not affect the tillage draft for the three types of implement and analog tool, but as the tillage depth increased, tillage draft of the three types of implement and analog tool increased linearly. The linear relationship was found between the tillage draft of analog tool and that of three types of tillage implement for the experimental tillage depth and speed range with high value of $R^2$ Thus it was concluded from the above results that an analog tool can be used to predict the tillage draft of oriental janggi, moldboard plow and chisel plow. But more experiment for various soil types and theoretical verification are needed for more generallization.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.469-475
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• 2010

The operation scenarios, types of ice, draft and propulsion system are important design point on the beginning stage of the ice breaking vessel. The concept of hull form in ice breaking vessel has to compromise the performance according to the operation route especially if ship is operating in ice and ice free water. The several hull forms were proposed to optimize the capability of the vessel in this paper. The effect of hull form according to type of ice is also discussing and explaining the ice resistance in each ice type as like pack ice, brash ice, level ice, rubble ice and ice ridge. The draft effect was examined and propulsion system for example FPP(Fixed pitch propeller), CPP(Controllable pitch propeller) and POD system was compared focusing on the propulsion efficiency.

• Journal of Biosystems Engineering
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• v.17 no.3
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• pp.223-228
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• 1992

This study was conducted to develop an electro-hydraulic three-point hitch control system using an electro-hydraulic servo valve and microcomputer and to investigate the performance of the three-point hitch control system through indoor and field experiments. 1. The results from indoor experiments coincided with those from computer simulation reported in the previous paper. However, the draft control with the value 4 of Kd showed a slight sustained oscillation after it reached the draft set. 2. From the field experiments, it appeared that the RMS errors increased with the ground speed of tractor. In position control, the three-point hitch control system with electro-hydraulic servo valve showed better performance than that with on-off electro-magnetic valve in the ground speed less than 1.6 m/s. In draft control, however, there was no significant differece in performance between those two systems. 3. In depth control, the both types of electro-hydraulic three-point hitch control system showed better performance than the conventional mechanical-hydraulic three-point hitch control system.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.569-581
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• 1996

A microcomputer -based data acquistion system was designed and developed at Michigan State University , USA to conduct field data studies. The system designed for the research carried out used an Apple IIe microcomputer for collecting data on-board the tractor. An AII3 Analog to Digital (A/D_ convertor was chosen to interface each analog signal to the microcomputer. A commercially available Dj TPM II was employed to display information such as an engine speed, ground speed, percent drive wheel slip , distance travelled and area covered per hour. The frequency output from the radar unit was channeled through a frequency to voltage (F/V) convertor , so that AII3 Analog to Digital (A/D) convertor could read it. The fuel consumption was measured using on EMCO pdp-1 fuel flow meter attached to the engine fuel line. The draft of the tillage and other drag equipment was determined using strain gages attached to the drawbar of the tractor. The system was developed to collect the draft and fuel requirements for various farm equipment different kind of soils.

• International Journal of Fluid Machinery and Systems
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• v.2 no.3
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• pp.260-268
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• 2009

The effects of acoustic modes in the penstock on the self-excited oscillation in hydraulic power system were studied by assuming a finite sound velocity in the penstock. The flow in the draft tube is considered to be incompressible assuming that the length of the draft tube is smaller than the wavelength of the oscillation. It was found that various acoustic modes in the penstock can become unstable (amplified) by the diffuser effect of the draft tube or the effect of swirl flow from the runner. Their effects on each mode are discussed.