• Journal of Biosystems Engineering
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• v.43 no.1
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• pp.1-13
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• 2018

Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission's power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission's gear, bearing, and oil seal. The motor's power was input in the transmission's input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.

• Fisheries and Aquatic Sciences
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• v.11 no.4
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• pp.195-204
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• 2008

Viral diseases are major emerging problems of shrimp that have affected the production, and even complete losses for shrimp farms. In this study, we developed a sensitive TaqMan real-time PCR method to quantify white spot syndrome virus (WSSV) and hepatopancreatic parvovirus (HPV) in the shrimp and pond water in which fleshy shrimp, Fenneropenaeus chinensis, and Pacific white shrimp, Litopenaeus vannamei, are reared. WSSV and HPV in pond seawaters ranged from $1.65{\times}10^3$ to $2.43{\times}10^9$ and from 0 to $4.43{\times}10^5$ copies/L of seawater, respectively. Of 20 ponds analyzed, all pond water and shrimp were positive for WSSv. L. vannamei showed higher susceptibility to WSSV than F chinensis. HPV was detected only in the pond water for F chinensis. In shrimp tissue, however, HPV was found in both species, with 23-times higher infection rate in F chinensis than L. vannamei. The total bacterial counts in the pond water ranged from $2.23{\times}l0^3$ to $1.98{\times}l0^5\;CFU/mL$. The variations in total bacterial count for each pond appeared to correlate to the variations of the WSSV load. Statistical analysis indicated that there was no significant difference (P>0.05) between the WSSV load in pond water and shrimp, and there was no relationship between total bacterial load and viral load in the pond water. However, a significant difference (P<0.01) was found between HPV load and L. vannamei and F chinensis pond water.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.3
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• pp.3878-3884
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• 1975

This study was carried out to develop the throw-in type thresher with its size as small as possible. Developing the smallest possible size of the throw-in type thresher has been very important to increase mobility and to reduce the machine price. The thresher that developed for this purpose was tested as to threshing and separation performance for the samples collected in eight catch boxes under the concave while threshing. The amount of grain collected in each compartments was measured and the threshing and separating pattern along the total span of the threshing drum was determined. The performance of separating and threshing units of the test thresher and threshing loss was evaluated by use of the developed grain separating apparatus and the method for measuring the grain separating performance of threshers. The results are summarized as follows; 1. The unthreshed grain (drum losses) and semi-threshed grain did not appeared at all throughout the treatments. 2. When threshed by making use of the developed throw-in type thresher, the threshing grain loss at about 25 per cent grain moisture was about one-half when threshed at about 18 per cent grain moisture. 3. And its grain separating loss in higher feed rate was decreased in comparison with that of lower feed rate. These results suggests that the throw-in type thresher may be suitable for wet threshing and for higher feed rate of threshing. 4. Above 60 per cent of total grain passing through concave fell through the screen within a scant 30 cm from the feeding inlet. This threshing pattern may suggest that major threshing action may be finished before about one third of cylinder length. The required separating load extended over the whole drum span is so defferent that separating elements should be redesigned so as to accomodate this variable pattern of separation load. 5. It was apparent from the experiment that the length of the threshing drum of the throw-in type thresher could be reduced from 1285mm to about 1050mm without increasing grain separation loss greatly.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.602-607
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• 2006

In this paper, the distributed network synthesis, which is useful to the design of wireless power amplifiers, is proposed, and a RF power amplifier is designed using the technique. The transfer function of distributed matching circuits is derived by Chebyshev approximation, and network element values for a specified topology are given as a function of minimum insertion losses and ripples. As an example, after a power transistor is modeled by load-pull data, the synthesis for distributed matching networks is applied to a power amplifier design, which has the electrical performance of 17dB gain and less IM3 than -43dBc at the 20W output power between 800 to 900MHz frequency range. Experimental results from a fabricated amplifier are shown to approach the design performance in the operating frequency range. The design of impedance matching networks by the transfer function synthesis is a useful method for the design of RF power amplifiers.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1066-1071
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• 2005

This paper presents the two lossless auxiliary inductors-assisted voltage source type half bridge (single ended push pull: SEPP) series resonant high frequency inverter for induction heated fixing roller in copy and printing machines. The simple high-frequency inverter treated here can completely achieve stable zero current soft switching (ZCS) commutation for wide its output power regulation ranges and load variations under its constant high frequency pulse density modulation (PDM) scheme. Its transient and steady state operating principle is originally described and discussed for a constant high-frequency PDM control strategy under a stable ZCS operation commutation, together with its output effective power regulation characteristics-based on the high frequency PDM strategy. The experimental operating performances of this voltage source SEPP ZCS-PDM series resonant high frequency inverter using IGBTs are illustrated as compared with computer simulation results and experimental ones. Its power losses analysis and actual efficiency are evaluated and discussed on the basis of simulation and experimental results. The feasible effectiveness of this high frequency inverter appliance implemented here is proved from the practical point of view.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.6 s.261
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• pp.574-580
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• 2007

The objective of this article is to present an analysis of all heat transfer paths through the energy nose under closed door conditions when refrigeration system of household refrigerator-freezer is operating on. Both experimental and numerical methods are suggested as a means of determining the overall energy nose load amount as well as the load due to each pathway such as mullion section and F and R sides of the household refrigerator-freezer. In other words, all loads determined in this article are just energy nose and not the loads seen by the refrigeration system. We suggest good ideas for improving the heat transfer losses such as conduction and convection through the energy nose. As we can be known from the experimental test results, it is effective to prevent the heat loss of a mullion section. And energy efficiency is also decreased approximately 6% compared to that of a baseline sample test result. As we can be known from the Ansys 8.1 analysis, it is shown the steady state temperature distribution in figures from 6 to 8. And the direction of the heat flow through the energy nose section is also easily seen from that In conclusion, the article is focused on an energy nose section in household refrigerator-freezer for practical proposes which is the energy saving in a household refrigerator-freezer. And the method suggested may be applied to any make or model to aid in the search for high efficient energy nose section of household side by side refrigerator-freezer as well as top mounted refrigerator-freezer, commercial refrigerator and so on.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.185-190
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• 2016

The high-power 6.6 kV XLPE (or CV) cables at Korean electric power stations have been in operation for the last 40 years. Most of the XLPE cables starts deteriorating in 6-8 years from the operating instant of time, some cables may be breakdown at any moment even though they were installed in recent years, causing, huge socioeconomic losses. In order to prevent unexpected cable accident, the operating status of power cables should be monitored in regularly, timely bases. We have invented a device in order to systematically monitor and prevent an abrupt accidents of high-power cables in operation at power station. It has been installed at Korean Western Power Co. Ltd. at Taean, and operating normally for the last 4 years. In this paper, we introduce the functions and operating principles of the measuring device, and present the relationship between humidity and insulation status of XLPE cables for the load of electric turbine generator.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.213-218
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• 2017

High-voltage power systems operate in order to generate and transmit electric power at power stations. Compared to low-power systems, high-power systems are complex in structure, large-scale, and expensive. When high-power cable accidents occur, most facilities are incapacitated-including low-power systems-causing huge economic losses. Great care must therefore be taken in designing, installing and managing power systems. Although dependent on installation circumstances and usage conditions, in some cases the cross-sectional areas of cables fall short of the critical area due to the expansion of and improper design and installation of power facilities. In this situation, the exceeded ampacity (allowable current) above the critical value caused by the operating current initiates the deterioration processes of power cables. In order to systematically monitor power cables operating at power stations, we have developed the first device of its kind in Korea. In this paper, we present the analyzed characteristics of expected temperatures of cables based on the load current of high-voltage cables operating at Korean Western Power Co. Ltd. We can predict the lifetime of cables by analyzing the temperature obtained from our device.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.3
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• pp.137-145
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• 2015

In this study, the actual energy consumption of the secondary side of District Heating System (DHS) with different hot water supply temperature control methods are compared. Three methods are Set-point Control, Outdoor Temperature Reset Control and Outdoor Temperature Prediction Control. While Outdoor Temperature Reset Control has been widely used for energy savings of the secondary side of the system, the results show that Outdoor Temperature Prediction Control method saves more energy. In general, Outdoor Temperature Prediction Control method lowers the supply temperature of hot water, and it reduces standby losses and increases overall heat transfer value of heated spaces due to more flow into the space. During actual energy consumption monitoring, Outdoor Temperature Prediction Control method saves about 7.1% in comparison to Outdoor Temperature Reset Control method and about 15.7% in comparison to Set-point Control method. Also, it is found that at when partial load condition, such as daytime, the fluctuation of hot water supply temperature with Set-point Control is more severe than Outdoor Temperature Prediction Control. Therefore, it proves that Outdoor Temperature Prediction Control is more stable even at the partial load conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2737-2743
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• 2015

The wind power plant must be able to produce reactive power at the POI bus of a wind farm connected to power system to keep or control the voltage of POI bus. But, the reactive power capability of wind turbines may not be sufficient to control the voltage of POI bus due to the reactive power losses in connection lines between wind farm and POI bus. The solution of this problem is to install an external STATCOM. The proposed cooperative control method of STATCOM and conventional reactive power compensators such as Switched-shunt and tap changing transformer can control the voltage of POI bus more efficiently. The simulation results are shown that the voltage drop of POI Bus of Test System with the arbitrary load change rate to initial loads is improved more than 60% and the voltage of load bus is maintained more than 95% of rated voltage.