• 한국생물공학회:학술대회논문집
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• 2005.04a
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• pp.272-276
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• 2005

Food wastewater derived from three-stages methane fermentation system showed high concentrations of sCOD, T-N and $NH_{3}-N$. To treat the organic wastewater, the optimal operating conditions for high efficiency $UV/TiO_{2}$ photocotalytic system have been investigated. In the first process, wastewater was pre-treated with $FeCl_{3}. The optimum pH and concentration for coagulation were 4.0 and 2000 mg/L, respectively. Through this process, 52.6% of $COD_{cr}$ was removed. The second process was $UV/TiO_{2}$ photocatalytic reaction. The optimum conditions for the operation of $UV/TiO_{2}$ photocatalytic system developed in this lab have been studied. In this process, CODcr was removed from 2890 to 184 mg/L and T-N was removed from 2496 to 914 for 24 hours, respectively.

• Culinary science and hospitality research
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• v.11 no.4 s.27
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• pp.228-244
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• 2005

The objective of the study is to observe cooks first from the kitchen and those who care health and to grasp the impression regarding the kitchen environment. Also, it grasped the recognition degree of cooks against the elements of kitchen ventilation and kitchen ventilation equipments. We surveyed against 385 cooks who work in the kitchen of special grade hotels and family restaurants, used 5 scales for the object, and executed the analysis. The results of this study are as follows: (1) Health condition of the cooks appeared most highly pain in the shoulder and the neck. (2) for the impression regarding the kitchen environment, temperature was high and the insufficiency of ventilation is answered highly. (3) The importance of kitchen ventilation of cooks was recognized very high. (4) The combustion gas was recognized as very high percentage and the most effective element of the kitchen on the human body to remove first inside the kitchen. (5) Most cooks were recognized that the improvement of ventilation equipments is necessary. (6) The object of ventilation equipments is appeared to maintain comfortable kitchen environment. (7) The optimum operation method of ventilation equipment uses the automatic system of ventilation equipment from the kitchen and it is necessary to maintain the optimum. This research is based on preceding studies, investigating special grade hotels and family restaurants in Seoul. The ventilation plan of the kitchen should be accomplished to improve the health of cooks and productivity.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.2
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• pp.86-94
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• 1997

For the efficient operation and maintenance( 0 & M), irrigation facilities were graded on the basis of their indices related to the 0 & M condition and the characteristics of reservoirs managed by Farmland Improvement Association(FIA) were examined. The results obtained are summarized as follows : 1. Characteristics of reservoirs include effective storage capacity, irrigation area, basin area, height and length of bank. Each characteristic is scored by the principle component analysis method. Variables which compose one index are categorized on the basis of their unit and each variable is scored so that the score of each unit sums to 100 for each index. 2. The Optimum MAnagement System of Irrigation Facilities(OMASIF) for Pyoungtaek area was developed by connecting general data of the irrigation facilities to image data. The database system is divided into three tables; LookUp Table, Facility Table, and Image Table. Image Table is again divided into five sub-tables, Image Table, Construction Cost Table, Acreage Table, 0 & M Cost Table, and Specification Table. 3. The evaluating criteria for the 0 & M of irrigation facilities can be established using the OMASIF. Irrigation facilities evaluated as poor state by the criteria should be repaired.

• Journal of Power System Engineering
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• v.4 no.3
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• pp.34-39
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• 2000

Performance data in the literature on air lift pumps have been based primarily on pumps of long length and large diameter (high lift pumps). Since mariculture operations involve pumps of relatively short length and small diameter, performance data are required for efficient operation. To provide such data, an experimental apparatus was designed and fabricated to test all lift pumps from 2.1 to 3.4 cm inside diameter and from 40 to 300 cm in length. Instrumentation was provided to measure water flow rate and air flow rate as well as water temperature, air temperature, and pressure throughout the system. Results from this study correlate well with high lift pump data in that, for a given pump geometry, maximum water flow occurs for a specific air flow rate. Driving the pump with air flows larger or smaller than this optimum flow rate will decrease the pumping rate. The optimum flows are significantly different for low lift pumps compared to high lift pumps. However, the pumping rate for low lift pumps approaches that for high lift pumps with increasing length.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.1
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• pp.24-32
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• 2003

The PID controller has been widely used in industrial applications due to its simple structure and robustness. Even if it is initially well tuned, the PID controller must be retuned to maintain acceptable performance when there are system parameter changes due to the change of operation conditions. In this paper, a self-tuning control scheme which comprises a parameter estimator, a NN-based rule emulator and a PID controller is proposed, which can cope with changing environments. This method involves combining neural networks and real-coded genetic algorithms(RCGAs) with conventional approaches to provide a stable and satisfactory response. A RCGA-based parameter estimation method is first described to obtain the first-order with time delay model from over-damped high-order systems. Then, a set of optimum PID parameters are calculated based on the estimated model such that they cover the entire spectrum of system operations and an optimum tuning rule is trained with a BP-based neural network. A set of simulation works on systems with time delay are carried out to demonstrate the effectiveness of the proposed method.

• Tribology and Lubricants
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• v.24 no.4
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• pp.179-185
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• 2008

Microporous polymer lubricants(MPLs) are solid polymer materials containing micropores which are filled with liquid lubricants, and which are molded or formed to suit rolling bearings or other machine parts requiring lubrication. MPLs can be effectively applied to provide long-term, maintenance-free lubrication of a variety of machine elements without fully replacing of oils and greases. The application of rolling bearings packed fully with an MPL could reduce or eliminate the problems such as grease deterioration, leakage, under-lubrication caused by insertion of water or foreign matters under severe operation conditions. This paper discuss the application of MPLs for lubrication of rolling ball bearings. Two different MPLs were synthesized and the features of MPLs were tested. Characteristics of the bearings which are packed fully with synthesized MPLs were investigated using SEM, TG/DSC, extents of oil leakage, OIT, and life time test. After these preliminary tests twelve MPLs were synthesized and evaluated by measuring extents of oil leakage and OIT values. Then synthesis conditions for the optimum MPL were selected by SSRED(Six Sigma Robust Engineering Design) pro gram using extents of oil leakage and OIT values respectively. The optimum MPL by means of OIT value showed higher performance such as long life time and application at higher temperature of $140^{\circ}C$ than previous temperature of $100^{\circ}C$.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1102-1111
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• 2002

The study focuses on the heat transfer performance of two-phase closed thermosyphons with plain copper tube and tubes having 50, 60, 70, 80, 90 internal grooves. Three different working fluids(distilled water, methanol, ethanol) are used with various volumetric liquid fill charge ratio from 10 to 40%. Additional experimental parameters such as operating temperature and inclination angle of zero to 90 degrees are used for the comparison of heat transfer performance of the thermosyphon. Condensation and boiling heat transfer coefficients, heat flux are obtained using experimental data for each case of specific parameter. The experimental results are assessed and compared with existing correlations. The results show that working fluids, liquid fill charge ratio, number of grooves and inclination angle are very important factors for the operation of thermosyphons. The relatively high rate of heat transfer is achieved when the thermosyphon with internal grooves is used compared to that with plain tube. The optimum liquid fill charge ratio for the best heat transfer performance lies between 25% and 30%. The range of the optimum inclination angle for this study is 20$^{\circ}$～30$^{\circ}$ from the horizontal position.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1043-1052
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• 1993

Field experiments were conducted to determine the optimum combination of performance parameters of a single-shank, tractor-mounted oscillating subsoiler. Tests were conducted at frequencies of oscillation of 3.7 , 5.67, 7.58, 9.48 and 11.456Hz ; amplitudes of 18, 21, 23.5, 34 and 36.5 mm ; and forward speeds of 1.84, 2.19 and 3.42 kmph at moisture content close to the plastic limit of the soil. It was observed that there was a reduction in average draft but an a increase in average total power requirement for oscillating than non-oscillating subsoiling. The draft and power ratios were significantly affected by the forward speed, frequency and amplitude. Their combined interaction expressed in terms of the velocity ratio parameter( the ratio of peak tool velocity and forward speed) however has the strongest influence. At the same velocity ratio, the draft reduction and power increase were less at higher amplitude of oscillation . As the oscillating frequency is increased toward the soil resonance the draft requirement becomes less. For the field conditions tested. the optimum operation was obtained at an amplitude of 36.5mm, frequency of 9.48Hz and speed of 2.19 kmph with a draft ratio of 0.33 and a power ratio of only 1.24.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.1
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• pp.57-62
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• 2005

Grid-connected photovoltaic (PV) systems were installed and monitored at the field demonstration test center (FDTC) in Korea in October 2002. Before long-term field testing of installed PV systems, the performances of PV components were evaluated and compared through short-term performance tests of each of the PV system components such as power conditioning system and PV module under standard test conditions. A data acquisition system has been constructed for measuring and analyzing the performance of PV systems to observe the overall effect of environmental conditions on their operation characteristics. Performances of PV systems have been evaluated and analyzed not only for component perspective (PV array, power conditioning unit) but also for global perspective (system efficiency, capacity factor, electrical power energy) by review of the field test and loss factors of the systems. These results indicate that it is highly imperative to develop an optimum design technology of grid connected PV systems. The objective of this paper is not only to evaluate and analyze the performance of domestic PV systems application through long-term field testing at FDTC but also to develop evaluation, analysis and optimum technology for long-term stability and reliability of grid-connected PV systems in Korea.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.1
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• pp.16-24
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• 2005

The goal of the present paper is to show the optimum design and operation conditions on 6 kW solar water heating system by using computer simulation with verified modelling. As the object functions, we took not only the amount of acquired and auxiliary heat but LCC, which has a relative importance and decisive role in economy. As expected, the maximum heat is acquired at the slope of collector with the equal degree to the latitude, facing the south. The capacity increase of the circulation pump and the storage tank lead to the increase of acquired heat and the decrease of auxiliary heat, but do not necessarily give economical advantages owing to additional electrical power consumption. In the present system, the minimum LCC can be obtained at the storage tank volume of 450 L and the mass flow rate of 0.344 kg/s.