• Korean Journal of Soil Science and Fertilizer
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• v.15 no.1
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• pp.49-50
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• 1982

The objective of this paper is to review the changes in fertilizer use pattern and to discuss some aspects of the fertilizer development in Korea. Fertilizer consumption in Korea have steadily increased to triple the application rates of N, P and K during the 15 years from 1965 to 1980, and Korea became one of the countries which apply fertilizers at the highest rate. The ratio of N: $P_2O_5$: $K_2O$ in fertilizer consumption changed from 55.4 : 31.4 : 13.1 in 1965 to 54.0 : 23.8 : 22.2 in 1980. It can be said that Korean farmers practise a balanced fertilization at least in view of fertilizer consumption as compared to other developing countries. However, differences in soil properties, crops, and climate varying as region were not reflected on fertilization. In the technological development of fertilizer, the chemical form and composition of the fertilizer as well as the suitability to the specific crops must be taken into consideration for the efficient use of fertilizers. Although organic fertilizers and manure are accepted as minor element suppliers, it is necessary to add minor elements into chemical fertilizers on the industrial process. Industrial waste may be used for the agricultural production as a measure of pollution control providing careful study on the waste.

• Journal of Forest and Environmental Science
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• v.24 no.1
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• pp.47-51
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• 2008

The first pruning works of planted trees on forest area carry out when tree height reached at 6 meters. And the second works carry out when it grow to 12~13 meters of tree height. Pruning works are necessary for producing straight log without knar by tool or machine. Generally, the mechanized pruning works Self-propelled pruning machine, chain pruning saw and other tools are used in mechanized pruning works. However, manual pruning saw which is usually using pruning tool was for this study. To investigate the pruning works efficiency, Pinus densiflora, Pinus koraiensis and Pinus rigida which were distributed in Kangwon-Do was surveyed. Height of surveyed the trees were 10~16 meters and its pruning works range were 6.2~6.7 meters of tree height. As results, pruning works efficiency of Pinus densiflora, Pinus koraiensis and Pinus rigida were 3.14 min/tree, 5.06 min/tree and 4.44 min/tree, respectively. Also, possible pruning works of man-day for Pinus densiflora, Pinus koraiensis and Pinus rigida was 104, 64, and 81 trees, respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.642-648
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• 2015

Recently, there have been many studies pertaining to reducing energy consumption on ships. As part of those studies, the energy consumption of ships can be reduced by understanding and controlling the varying loads, excluding fixed loads. In existing ships, engine room fans are usually operated based on the actual experience of the crew without any special guidelines. To realize energy reduction, we investigate the characteristics of engine-room fans, and we propose an energy-management system called the engine room fan control system (ERFCS) and the ERFCS algorithm. The ERFCS controls the fan speed depending on the temperature and pressure, where one to four fans are operated depending on changes in the load. In addition, the minimum rotation speed of the engine-room fan was limited to 50% to prevent the surging phenomenon, which is due to fan damage or low pressure resulting from mechanical friction or heating at low fan speeds. We develop a fan control system simulation model using LabVIEW that is based on the proposed algorithm and ISO 8861. Finally, we perform simulations to confirm that operation of the proposed fan control system is possible using only 46.4% of the power required by the existing method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8700-8706
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• 2015

The first driving device of the power bogies for the Korean high-speed railway vehicle consists of the traction motor (TM) and the motor reduction gears unit (MRU). Although TM and MRU are the mechanically integrated structures, their time between overhauls (TBO) have two separate intervals due to different technical requirements(i.e. TBO of MRU: $1.8{\times}10^6km$, TBO of TM: $2.5{\times}10^6km$). Therefore, to reduce the unnecessary number of preventive maintenances, it is important to evaluate the optimal TBO with a viewpoint of reliability-center maintenance towards cost-effective solution. In this study, derived from the field data in maintenance, fault tree analysis and failure rate of the subsystem considering criticality of the components are evaluated respectively. To minimize the conventional total maintenance cost, the same optimal TBO of the components is derived from genetic algorithm considering target reliability and improvement factor. In this algorithm, a chromosome which comprised of each individual is the minimum preventive maintenance interval. The fitness function of the individual in generation is acquired through the formulation using an inverse number of the total maintenance cost. Whereas the lowest common multiple method produces only a four percent reduction compared to what the existing method did, the optimal TBO of them using genetic algorithm is $2.25{\times}10^6$km, which is reduced to about 14% comparing the conventional method.

• Journal of Biosystems Engineering
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• v.36 no.2
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• pp.79-88
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• 2011

The purpose of this study was to analyze power requirement of an agricultural tractor by major field operations. First a survey was conducted to obtain annual usage ratio of agricultural tractor by field operation. Plowing, rotary tillage, and loader operations were selected as major field operations of agricultural tractor. Second, a power measurement system was constructed with strain-gauge sensors to measure torque of four driving axles and a PTO axle, speed sensors to measure rotational speed of the driving axles and an engine shaft, pressure sensors to measure pressure of hydraulic pumps, an I/O interface to acquire the sensor signals, and an embedded system to calculate power requirement. Third, the major field operations were experimented under fields with different soil conditions following planned operation paths. Power requirement was analyzed during the total operation period consisted of actual operation period (plowing, rotary tillage, and loader operations) and period before and after the actual operation (3-point hitch operating, forward and reverse driving, braking, and steering). Power requirement of tractor major components such as driving axle part, PTO part, main hydraulic part, and auxiliary hydraulic part were measured and calculated to determine usage ratio of agricultural tractor power. Results of averaged power requirement for actual field operation and total operation were 23.1 and 17.5 kW, 24.6 and 19.1 kW, and 14.9 and 8.9 kW, respectively, for plowing, rotary tillage, and loader operations. The results showed that rotary tillage required the greatest power among the operations. Averaged power requirement of driving axles, PTO axle, main hydraulic part, and auxiliary part during the actual field operation were 8.1, 7.8, 3.4, and 1.5 kW, respectively, and the total requirement power was about 70 % (20.8 kW) of the rated power. Averaged power requirement of driving axles, PTO axle, main hydraulic, and auxiliary hydraulic for the total operation period were 6.5, 6.0, 2.1, 0.9 kW, respectively, and total requirement power was about 52 % (15.5 kW) of the rated power. Driving axles required the greatest amount of power among the components.

• 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 Biosystems Engineering
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• v.5 no.2
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• pp.58-66
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• 1980

A survey was conducted to investigate the power tiller accidents. Eight provinces were covered for this study, and 278 power tiller owners were selected randomly by computer random generator. The results are summarized as follows : A. Frequency of accident. (1) Each power tiller had an accident 0.98 times a year and once every 361 hours of use. Higher frequency of accident was found during the miscellaneous operations including the preparation for farming operation, and there was one accident for every 92 hours of use. (2) The power tiller, which are more than six years old, met an accident 1.19 times a year , or one every 311 hours of use. This value was the highest one compared with any other group. (3) Kerosene engine power tillers met an accident 0.97 times a year, or one every 389 hours of use. It was one tie a year, or once every 329 hours of use for diesel engine power tillers. (4) Among diesel-engine power tillers, 10 horse-power group showed a higher frequency tillers. B. Cause of accident (1) The accidents of power tiller were mainly of sefety , which occurred due to the lack of attention during the operation and 47.4% of the total accidents. The next was of accidental, which represented 26.3% of the total accidents. (2) High percentage of safety accidents occurred during the preparation for farming operation including adjustment. Most of the accidental accidents occurred during the transportation. (3) Lower frequency of accident was found in the power tiller group which were operated by the 21-40 years old operator in comparison with that of the power tiller which was operated by other age group. Power tillers which were operated by high school graduates experienced less accidents compared to other education levels. C. Damage by accident (1) Eighty seven pescents of the total accidents caused damage to the power tiller operator , and 13 % of the total accidents caused property damage only. (2) With regard to the damage to the power tiller operator, 73.8% of the total accidents caused light injury but 26.3% caused heavy injury. (3) Accidents which occurred during machine preparation , and farming operations caused minor injury to the operator, but the accidents during transportation caused heavy injury which cost more than 15 days for recovery. (4) Among the 39 accidents , which caused property damage 18 accidents were from the transportation . Among the total property damage accidents 53.8% were light one which cost only less than 1,000 won. (5) The property damage from each accident cost 1,017 won, on the average, with regard to the kinds of operation, the highest property damage occurred during transportation work, with the value of 2, 965won.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.29-36
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• 2017

In this study, acombined cogeneration power plant produced two types of thermal energy and electric or mechanical power in a single process. The performance of each component of the gas turbine-combined cogeneration system was expressed as a function of the fuel consumption of the entire system, and the heat and electricity performance of each component. The entire system consisted of two gas turbines in the upper system, and two heat recovery steam generators (HRSG), a steam turbine, and two district heat exchangers in the lower system. In the gas turbine combined cogeneration system, the performance test after 10,000 hours of operation time, which is subject to an ASME PTC 46 performance test, was carried out by the installation of various experimental facilities. The performance of the overall output and power plant efficiency was also analyzed. Based on the performance test data, the test results were compared to confirm the change in performance. This study performed thermodynamic system analysis of gas turbines, heat recovery steam generators, and steam turbines to obtain the theoretical results. A comparison was made between the theoretical and actual values of the total heat generation value of the entire system and the heat released to the atmosphere, as well as the theoretical and actual efficiencies of the electrical output and thermal output. The test results for the performance characteristics of the gas turbine combined cogeneration power plant were compared with the thermodynamic efficiency characteristics and an error of 0.3% was found.

• Current Industrial and Technological Trends in Aerospace
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• v.6 no.1
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• pp.90-98
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• 2008

Nanotechnology(NT) refers to a field of advanced micro-technology covering the creation and manufacturing of materials on the atomic and molecular scale and requires interdisciplinary study with various fields including materials science, physics, chemistry, electronics and others. Whileas nanotechnology is a kind of micro and small scaled science, space technology(ST) is one of the larger and system technologies utilizing broad fields of mechanical, materials, electronics and communication technologies. It is necessary to select and concentrate the functional items of nanotechnology for efficient application to be utilized in space technology, due to the cross-sectional characteristics of nanotechnology within nanomaterials, nanoelectronics, and nanomanufacturing. This paper provides the current state of art of nanotechnology in space technology by evaluating NASA's activities and the 9th frame of the project ANTARES(Analysis of Nanotechnology Applications in Space Developments and Systems) with the support of the German Aerospace Center (DLR), Space Flight Management, Division Technology for Space Systems and Robotics. It has shown that it is necessary to apply nanotechnology to space technology in order to achieve international competitiveness, for the nanotechnology can bring the previously impossible things to reality. Since KARI plans to send an unmanned probe to the moon's orbit and land a probe on the moon's surface in 2025, it is urgently needed to incorporate nanotechnology to national space development plan.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.4
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• pp.362-367
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• 2017

This study was conducted to compare the particulate removal efficiency of the developed diesel particulate filter using various measurement methods in a high-speed marine diesel engine. A four-stroke mechanical marine diesel engine is used for the test, which has a maximum output of 403 kW and is coupled to an AC dynamometer to control engine speed and load. The test was conducted based on four steady-state engine operating conditions of E3 engine test cycle for the measurement of PM and soot removal efficiency using partial dilution method considered as gravimetric method and filter smoke number method as light absorption method, respectively. As a result of the removal efficiency measurement according to the application of diesel particulate filter, particulate matter was reduced from 76% to 91% and the soot was reduced by more than 90% while meeting the permissible engine back pressure. From these results, the applicability of diesel particulate filter adopted in high-speed marine diesel engines could be confirmed. In addition, based on the result that the particulate removal efficiency varies with different measurement methods, the necessity of unification of these methods could be identified.