• Korean Journal of Agricultural Science
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• v.13 no.2
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• pp.265-278
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• 1986

This study was attempted to improve the thermal efficiency of 6 kW water-cooled diesel engine on power tiller. The engine performance tests were conducted to find out the effect of cooling water capacity of 2700cc, 2800cc, 2900cc, 3000cc, 3100cc on power, brake specific fuel consumption (BSFC), torque, temperature of cooling water and lubricating oil and friction losses of the engine with D. C. dynamometer. The results obtained in the study are summarized as follows: 1. The performance of the engine tested was adequated to Korea Industrial Standard but actual economy power was 10% higher than the labeled rated power of the engine. The BSFC of the engine tested 297.8g/kW-h which is belong a little higher level than hreign products. The temperature of cooling water was $101^{\circ}C$ which is higher than SAE standard ($88^{\circ}C$) 2. The friction losses of engine tested was 3.656 kW at 2200 rpm of rated rpm (piston speed 6.97m/sec) and is higher than those of foreign products. 3. When the cooling water capacity was increased from 2700cc to 3100cc the power output of the engine was increased from 6.7 kW to 7.13 kW at the rate of 6.4% and also the torque of the engine was increased from 28.85 N.m to 30.76 N.m at the rate of 6.39%. 4. When the cooling water capacity was increased from 2700cc to 3100cc, the BSFC was decreased 6.9g/kW-h from 310.9g/kW-h to 304.1g/kW-h, and after one half hour operation with full load, the temperature of cooling water was decreased $13^{\circ}C$ from $101^{\circ}C$ to $88^{\circ}C$ and also the temperature of lubricant oil was decreased $6.4^{\circ}C$ from $76.7^{\circ}C$ to $70.4^{\circ}C$. 5. The mechanical efficiency was increased from 70.08% to 71.08% when the cooling water capacity was increased from 2700cc to 3100cc.

• Korean Journal of Remote Sensing
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• v.40 no.4
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• pp.363-375
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• 2024

Waterbody change detection using satellite images has recently been carried out in various regions in South Korea, utilizing multiple types of sensors. This study utilizes optical satellite images from Landsat and Sentinel-2 based on Google Earth Engine (GEE) to analyze long-term surface water area changes in four monitored small and medium-sized water supply dams and agricultural reservoirs in South Korea. The analysis covers 19 years for the water supply dams and 27 years for the agricultural reservoirs. By employing image analysis methods such as normalized difference water index, Canny Edge Detection, and Otsu'sthresholding for waterbody detection, the study reliably extracted water surface areas, allowing for clear annual changes in waterbodies to be observed. When comparing the time series data of surface water areas derived from satellite images to actual measured water levels, a high correlation coefficient above 0.8 was found for the water supply dams. However, the agricultural reservoirs showed a lower correlation, between 0.5 and 0.7, attributed to the characteristics of agricultural reservoir management and the inadequacy of comparative data rather than the satellite image analysis itself. The analysis also revealed several inconsistencies in the results for smaller reservoirs, indicating the need for further studies on these reservoirs. The changes in surface water area, calculated using GEE, provide valuable spatial information on waterbody changes across the entire watershed, which cannot be identified solely by measuring water levels. This highlights the usefulness of efficiently processing extensive long-term satellite imagery data. Based on these findings, it is expected that future research could apply this method to a larger number of dam reservoirs with varying sizes,shapes, and monitoring statuses, potentially yielding additional insights into different reservoir groups.

• Journal of Biosystems Engineering
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• v.8 no.2
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• pp.39-48
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• 1983

This study was performed to obtain the basic data which could be used for the modification of the manual center-burner-type rice-husk furnace into a small scale automatic type for the multi-purpose use in the farm. For this purpose, first, the utilization feasibility of the rice-husk furnace in the farm was analyzed briefly in aspects of available amount of rice-husk for the fuel, annual operation time and replaceble amount of residential heating energy with rice-husk in the farm. For the experiment a prototype furnace geared with an automatic feeding device was fabricated, and feed rate, mold size and chimney height were changed to investigate the combustion efficiency of rice-husk and thermal efficiency of the furnace. Also, optimum and limiting operational factors were observed in each treatments. The results obtained are summarized as follows. 1. If the rice-husk is intensively used for residential heating in the farm for winter season, on an average 51 percent of the total heating energy can be replaced with the rice-husk. Therefore, development of a small scale automatic rice-husk furnace was recognized to be feasible. 2. The operational condition depending on husk-feed rates was very important factor for successive steady burning operation of the given furnace. When the feed-rate was 1.5 kg/hr, the top of the burning zone should be kept at the position about 55 cm from the bottom of the combustion chamber with the periodic removal of ash (termed as steady state position), which was 18 cm above the mold waist. When the feed rates were 2.4 kg/hr and 3.0 kg/hr, the steady state position was at about 4 cm above the mold waist. 3. The mold size affected inflow rate of air into the furnace and consequently CO content in the exhaust gas. The relatively bigger mold gave positive effect on the air-inflow rate. 4. When the husk-feed rates were 1.5 kg/hr, 2.4 kg/hr, 3.0 kg/hr, the combustion efficiencies of the rice-husk were 98.5%, 97.4% and 95.0%, the thermal efficiencies of the furnace were 93.4%, 93.2% and 87.6%, and CO content in the exhaust gas were 1.21%, 1.03%, and 2.43%, respectively. The air-inflow rates were decreased with the increase of feed rates. When the amount of excess air was 30-40%, the CO content in the exhaust gas was at the minimum level. 5. When the chimney height was lowered from 260 cm to 96 cm, the air-inflow rate was slightly decreased, but the average temperature in the combustion chamber, CO content in the exhaust gas and combustion and thermal efficiencies were not changed significantly. 6. The incidental problems associated with the protytype furnace were accumulation of the ash inside the mold, accumulation of the cinder between the outer-drum of the furnace and the combustion chamber wall, and accumulation of the cinder in the chimney.

• Membrane Journal
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• v.17 no.2
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• pp.99-111
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• 2007

It is impossible to remove toxic organic substances that are recognized as a cancer caused suspicious element in drinking water using the conventional water purification method. This study introduces groundwater into a reaction chamber as an effective amount of water to process this water using a mixed method of AOP oxidation and M/F membrane and purifies it as a desirable level by artificially mixing such toxic substances in order to effectively process the water. Based on this fact, this study configures an optimal operation condition. The VOCs existed in toxic substances was investigated as a term of phenol and toluene, and agricultural chemicals were also investigated as a term of parathion, diazinon and carbaryl. The experiment applied in this study was performed using a single and composite soolution. In the operation condition applied to fully dissolve and remove such substances, the amount of $H_2O_2$ injected in the process was 150 mL of a fixed quantity, the value of pH was configured as $5.5{\sim}6.0$, the temperature was controlled as a range of $12{\sim}16^{\circ}C$, the dissolved amount of ozone was applied more than 5.0 mg/L, the reaction time was determined as an optimal condition, such as $30{\sim}40$ minutes, and the segregation membrane in the same reactor was determined for acquire water drinking of large quantity using a pore size of $0.45{\mu}m$ M/F membrane.

• Journal of Bio-Environment Control
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• v.20 no.1
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• pp.1-7
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• 2011

The objective of the present study is to identify the applicability of a low pressure fogging system for cooling commercial tomato greenhouse. In particular, the cooling system in this experiment utilizes low pressure spray nozzles which were developed in Korea recently. The experimental result that the temperature in fog-cooled greenhouse was lower than the non-cooled greenhouse showed the cooling effect by the low pressure fogging system. But because the relative humidity in fog-cooled greenhouse was comparatively low, the satisfactory cooling effect could be acquired by narrowing the space of fog nozzles and extending fogging time to supply more fog spray quantity. The variation of temperature distribution in fog-cooled greenhouse along timelag was insignificant during short time, but that was great during long period of day. This result showed the variation of temperature along timelag was slight by fog cooling but great by other factors like radiation, ventilation, air flow, etc. The advanced operation technology of fog system was required to reduce the variation of temperature along time lag. We plan to suggest the advanced installation and operation technology of low pressure fogging system for cooling commercial tomato greenhouse by further experiments in near future.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.4
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• pp.290-298
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• 2013

A Saemangeum Development Project, which is a national project in South Korea, has started with the objective of developing the reclaimed area mainly agricultural land use since the mid'80s. To develop a model of the global eco-reclamation, constructions of the eco-friendly counter facilities such as sluice gates and inner dikes, as well as environmental preservation measures for an estuary reservoir, have been carried out. However, reasonable measures of the water quality management for the Saemangeum area are required. Thus, the purpose of this study is to rigorously analyze and quantitatively evaluate the environmental problems due to the water level management associated with inner dike constructions. To achieve these objectives, the affecting factors on determination of water level management are described and a series of calibrated transient-state numerical simulations was performed to demonstrate the salinity distribution difference in the estuary before and after the construction of inner dikes. The overall salinity reduced about 2~5 psu, and the seawater intrusion was weakened by a well-regulated waterway after construction of the inner dikes compared to before construction of them.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.1
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• pp.104-111
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• 2011

In order to assess the performance of co-digester using pig slurry and food waste at the farm scale biogas production facility, the anaerobic facility that adopts the one-stage CSTR of 5 $m^3\;day^{-1}$ input scale was designed and installed under the conditions of the OLR of 2.33 kg $m^3\;day^{-1}$ and HRT of 30 days in an pig farmhouse. Several operation parameters were monitored for assessment of the process performance. The anaerobic facility was operated in three stages to compare the performance of the anaerobic co-digester. In the Stage I, that was fed with a mix of pig slurry to food waste ratio of 7:3 in the input volume, where input TS content was 4.7 (${\pm}0.8$) %, and OLR was 0.837-1.668 kg-VS $m^3\;day^{-1}$. An average biogas yield observed was 252 $Nm^3\;day^{-1}$ with methane content 67.9%. This facility was capable of producing an electricity of 626 kWh $day^{-1}$ and a heat recovery of 689 Mcal day-1. In Stage II, that was fed with a mixture of pig slurry and food waste at the ratio of 6:4 in the input volume, where input TS content was 6.9 (${\pm}1.9$) %, and OLR was 1.220-3.524 kg-VS $m^3\;day^{-1}$. The TS content of digestate was increased to 3.0 (${\pm}0.3$) %. In Stage III, that was fed with only pig slurry, input TS content was 3.6 (${\pm}2.0$) %, and OLR was 0.182-2.187 kg-VS $m^3\;day^{-1}$. In stage III, TS and volatile solid contents in the input pig slurry were highly variable, and input VFAs and alkalinity values that affect the performance of anaerobic digester were also more variable and sensitive to the variation of input organic loading during the digester operation. The biogas produced in the stage III, ranged from 11.3 to 170.0 $m^3\;day^{-1}$, which was lower than 222.5-330.2 $m^3\;day^{-1}$ produced in the stage II.

• Journal of agricultural medicine and community health
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• v.16 no.2
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• pp.97-119
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• 1991

Korea has made a rapid economic development since the last three decades. This has helped Korea narrow the gap in health service differences in resource availability and in quality of care. However urban and rural differentials are still remarkable. This study has maintained that health status of rural residents is inferior to that of urban dwellers. Therefore, this study was carried out to develop policy measures for improving health services in rural areas. In order to achieve the objective of this study the authors collaborated closely and made field visits, interviews and conducted an extensive literature review regarding rural health services. The following policy options are recommended as a summary ; First, the quality of rural health personnel is a single most important factor influencing the level of rural health services. An innovative program for public health doctors to the internship and/or residency training program such as specialty board program of family medicine. Second, dissatisfaction regarding employment of public health doctors is problematic. More rational employment and deployment programs are needed to meet their personal desire. One way to do this is to make it wide open and competitive. Third this study shows how to increase physician productivity in the rural public health sector. Incentive system needs to be elaborated for the career development of rural health workers. University linked job opportunity as clinical professor is an example. Fourth, without straightening the function of health centers and subcenters, the future of rural health services is doomed to failure. Straightening primary health care is one way to enrich the program of public health facilities and reactivating the operation of health center/hospital is another. A close linkage of public facilities with private hospitals is a minimum requirement for the operation of health delivery system within a health district. Fifth, some measures are urgently required to enhance hospital services in medically underserved areas. Financial subsidy, tax exemption, long-term public loans and higher priority of health manpower deployment are some of them. Sixth, new health programs should be in tiated to meet changing needs of peoples in rural areas. Home health care program, hospice program, nursing home, residential program for the elderly are recommended.

• Journal of Biosystems Engineering
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• v.3 no.2
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• pp.114-125
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• 1978

The use of petroleum fuels in grain drying causes problems of high cost and management. To solve these problems, it is required to study on soLar energy as an alternative to petroleum fuels for grain drying. The purposes of this study were to find out the optimum received area and air flow rate of a flat-plate solar air collector for grain drying and to assess its effects on grain drying with a small grain bin. The results of this study are summarized as follows ; 1. The calculated optimum tilt angles of the collector in the summer and autumn drying seasons were 20 and 50 degress, respectively, in suwon area. 2. The outlet temperature of the collector was $36^\circ C$ on the daily average with the maximum of $36^\circ C$ at 12:00 o clock. Solar radiation on the collector surface was 1.04 ly( 1 langley = 1 cal/$cm^2$) per minute on the daily average and 1.30 ly per minute on the maximum at 11:00am. The thermal efficiency of the collector was 62.4 percent on the daily average, and the air flow-rate per unit receiving are was 1.03 $m^3$/min/$m^2$.4. The calculated optimum receiving area and the air flow-rate per unit cubic volume for paddy in autumn drying season was 2 $m^2$ and 2$m^3$/min , respectively. 5. not significantly difference in the collector efficiency was appeared between the rotating and fixed type of solar collector. 6. For drying of wheat with 0.6 meter of the depth in the bin, approximately 9 hours were required to reduce the moisture content from 21.6% to 13% with air follow rate of 5 $m^3$/min an initial moisture per cubic meter of wheat and with air temperature of $52^\circ C$. 7. In the drying test of rough rice with a turning operation in a grain bin approximately 21 hours were required to reduced the moisture from 21% to 14.5% with airflow rate of 2 $m^3$/min per cubic meter of rice and the air temperature of $43.5^\circ C$. 8. Over-drying at the bottom and less -drying at the top of the grain mass was resulted from the high -temperature of drying air which was obtained from the flat-plate solar collector in this test. An appropriate operation should be prepared for the uniform moisture of the grain in the bin.

• Journal of Biosystems Engineering
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• v.43 no.3
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• pp.161-172
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• 2018

Purpose: During tillage operations, the selection of a working machine (tool) depends on the soil conditions as well as the type of tillage operation to be performed. The goal of this research was to ascertain the effects of varying working machine parameters of a compact disc harrow on tillage operations under various soil moisture content (SMC) conditions. Methods: The working machine parameters were the disc spacing and machine speed. The tillage parameters under investigation were the soil inversion ratio (SIR), tillage cutting depth (TCD), and soil clod breakage ratio (SCB). To determine the SIR, the areas of the white regions before and after tillage were obtained. The ratio of the difference of the areas of the white regions before and after tillage to the area of the white regions before tillage was considered as the SIR. The SCB was obtained as the ratio of the weight of soil clods after sieving with a mesh size of <0.02 m to the total weight of the soil clods before sieving. The soil TCD was measured using a tape measure at random points after the tillage operation. The resulting data were statistically analyzed in a one-way analysis of variance. Results: The highest soil inversion was achieved when the machine speed was 0.2 m/s with the disc spaced at 0.2 m in the 16.5% SMC. At a 0.4-m/s machine speed and 0.3-m disc spacing the highest soil breakage was achieved in the 26.5% SMC. The highest TCD was achieved at a 0.2-m/s machine speed and 0.2-m disc spacing in the 16.5% SMC. Conclusions: It was concluded that varying the working machine parameters, such as the disc spacing and machine speed, could significantly affect the soil inversion and soil clod breakage; however, it had no significant impact on the TCD.