• Journal of Advanced Marine Engineering and Technology
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• v.38 no.5
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• pp.550-556
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• 2014

In this study, for the control of a single water tank system, a fuzzy-PID controller design technique based on a fuzzy model is investigated. For this purpose, a water tank system is linearized as a number of submodels depending on the operating point, and a fuzzy model is obtained by fuzzy combining. Each submodel is approximated as a first order time delay model, and a PID controller is designed using several existing tuning techniques. Then, through the fuzzy combination of this controller using the same method as that of the fuzzy model, a fuzzy-PID controller is designed. For the proposed technique, a simulation is performed using the fuzzy model of a water tank system, and the validity is examined by comparing its performance with that of a PID controller.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.270-273
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• 2011

Water management is important in proton exchange membrane fuel cell because the water balance has a significant impact on the overall fuel cell system performance. In fuel cell vehicle, the vehicle's power demand is dynamic; therefore, the dynamic water management system is required. This present study proposes a method to control the humidity of the input air in cathode side of the fuel cell vehicle. The simulation using several driving cycles shows the proposed air humidification control obtains a relatively good result. The liquid saturation level is seen constant at the target level although still there are small deviations at driving cycles which having averagely high power demands.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.164-169
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• 2006

A systematic methodology has been proposed to establish a reliable design of water pump system. A simplified steady-state dynamic model of water pump system has been developed to study the response of water pump system to the dynamic load mainly due to the run-out and unbalance. Design modifications are needed to strengthen the structural integrity of existing designs. Increasing the natural frequency of system is pursued to prevent a resonance from occurring in the engine excitation range. A computational reliability methodology combined with finite element analysis is used to identify the most significant factor affecting the system performance. This method considered influence of design control parameters for the performance of design. By including control factors to the system model in a systematic way, more reliable design is expected.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.1
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• pp.57-62
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• 2003

It is difficult to determine the feeding rate of coagulant in the water treatment plant, due to nonlinearity, multivariables and slow response characteristics etc. To deal with this difficulty, the genetic-fuzzy system genetic-equation system and the neural network system were used in determining the feeding rate of the coagulant. Fuzzy system and neural network system are excellently robust in multivariables and nonlinear problems. but fuzzy system is difficult to construct the fuzzy parameter such as the rule table and the membership function. Therefore we made the genetic-fuzzy system by the fusion of genetic algorithms and fuzzy system, and also made the feeding rate equation by genetic algorithms. To train fuzzy system, equation parameter and neural network system, the actual operation data of the water treatment plant was used. We determined optimized feeding rates of coagulant by the fuzzy system, the equation and the neural network and also compared them with the feeding rates of the actual operation data.

• Nuclear Engineering and Technology
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• v.25 no.3
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• pp.371-380
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• 1993

A model free controller utilizing a set of linguistic fuzzy logic of the human operator's experience is developed to control the steam generator water level in a pressurized water reactor. Only 9 rules for control action are generated from the inputs of water level error and mass flow error implicitly representing the time variation of the collapsed water level. The bell type membership functions of the premise side and the result side are tuned by the sensitivity study. This compact fuzzy logic controller shows a robust control during transient and no offset error and oscillation during steady state operation. For a multi-ramp power increase from start-up to full power, the proposed controller shows good performance for the entire range.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.3
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• pp.1-12
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• 2021

In this study, the effects of various operational conditions for floor radiant heating system were researched by experiments. Hot water supply set temperature, indoor air set temperature and supply water flowrate were considered as operational conditions. The control method for this system is On-Off control of automatic thermostatic valve. The purpose of this study is to evaluate indoor thermal control characteristics and energy performance, respectively. As a result, if lower supply water temperature is applied, the supply and return temperature difference is reduced and energy consumption of heat supply is also reduced.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.4
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• pp.330-338
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• 1999

Extensive research has been conducted on effects of drought stress on growth and development of soybean but information is rather restricted on the limited-irrigation system by way of precaution against a long-term drought condition in the future. The experiment for limited-irrigation was conducted in transparent vinyl shelter at Asian Vegetable Research and Development Center (AVRDC), Taiwan in 1997. Two soybean varieties, Hwangkeum and AGS292, improved in Korea and AVRDC, respectively were used for this experiment. The relationships between normalized transpiration rate (NTR) and fraction of transpirable soil water (FTSW) in both varieties were similar that the NTR was unchanged until FTSW dropped to about 0.5 or 0.6. At FTSW less than those values, NTR declined rapidly. Days required to harvest in both varieties were significantly prolonged at IR6 treatment compared to any other treatments. Daily mean transpiration rate was significantly higher at IR5 treatment, as averaged over varieties. Similarly, water use efficiency was also high at 1R5 treatment. In both varieties, seed yield was the greatest at the IR5 treatment, as compared to any other limited-irrigation treatments, due to the increased seed number and high transpirational water use efficiency. The indices of input water and seed yield for the different limited-irrigation treatments against control indicated that Hwangkeum produced 59.6% or 60.7% of seed yield using 36.1% or 44.9% of input water, as compared to control, by irrigation at only R5 or R6 stages, respectively. The AGS292 produced 56.1% of seed yield with 35.4% of input water of control, when irrigated at R5 stage. The results of this study have elucidated that the limited irrigation at R5 stage in soybean can be minimized yield loss with such small quantity of water under the environment of long-term drought stress and the expected shortage of agricultural water in the future.

• Journal of Korean Society of Forest Science
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• v.85 no.1
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• pp.66-75
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• 1996

This study was carried out to examine the forest fire effect on water storage characteristics in the forests. Water storage capacity of the burned area was analyzed by several major factors, such as soil pore, maximum water content, effective water storage, and percolation rate. The results obtained from the analysis of major factors are as follows; The deeper soil depth, the less total pore, coarse pore, effective water storage, and percolation rate. However, fine pore increased slightly in both burned area and control plot. As compared with control plot, burned area showed lower percolation rate, coarse pore, and effective water storage, but higher values of fine pore. Directly after forest fire, the soil pore is little affected. But as the time passes, top soil structure changes and soil pore also is affected even in a deep soil. Estimated effective water storage was lower at top soil of Namcheon and at deep soil of Namha in all the burned areas, but slowly decreased in deep soil compared to control plots. Therefore it was concluded that forest water storage capacity was greatly affected by the forest fire.

• Journal of Korean Society on Water Environment
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• v.20 no.3
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• pp.301-306
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• 2004

The present water quality standards for agricultural were established without considering the effects of water quality on the safety, growth, yield and quality of crops. This study was carried out to investigate the effects of irrigation water quality on the growth, yield, and grain quality of rice, and to acquire basic knowledges to set up water quality standards for irrigation. The field and pot experiments were conducted with irrigation water that was previously adjusted four concentrations (control, 5, 10, 20 mg/L) and six concentrations (control, 5, 10, 15, 20, 30 mg/L) by $NH_4NO_3$ solution and replicated three and four times with randomized block design, respectively. The results of this study showed that the inorganic nutrient of rice plant, rice protein contents and number of panicle tended to increase as the T-N concentration in irrigation water was increased. In addition, grain yield at T-N 10 mg/L and 20mg/L were significantly higher than the control at the field experiment. From the pot experiment at T-N 30 mg/L, the percentage of head rice was slightly lower due to the increase of green kernel and white belly/core kernel.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.8 no.1
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• pp.67-75
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• 1998

The objectives of this study were both to evaluate the level and correlations of hazardous agents and to suggest measures to control industrial hygiene problems caused by using water-soluble metalworking f1uids(MWF). Geometric mean of formaldehyde(0.039 ppm) was higher than criteria of NIOSH(0.016ppm). Formaldehyde, originally existed in the biocide, is released and used to kill microbes in soluble MWF. Microbe concentrations were above $10^4No./mL$ in 14 MWF tanks among 20 tanks surveyed. Nitrosamines that is formed by reaction of nitrosating group and amines was detected to $18.4-47.1{\mu}g/m^3$. Formaldehyde concentration was low when microbes were abundant(r=-0.67, p=0.011), and high when open tank area was wide(r=0.75. p=0.012). The significant relationship between pH and microbes(r=-0.76. p=0.003) was also observed. The predominant bacteria species in MWF were Pseudomonas spp., Bacillus spp., Comamonas testosteroni, Acinetobacter haemolyticus, Bordertella bronchiseptica in order. Therefore, hazardous agents emitted by using water-soluble MWF seems to be correlated microbial growth. In order to minimize worker's exposure to several hazardous agents by an water-soluble MWF and to increase productivity, microbial growth must be controlled to the lowest level as possible. Administrative control as well as engineering control must comprehensively be applied to control microbe's growth in water-soluble MWF.