• Weed & Turfgrass Science
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• 제7권3호
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• pp.239-245
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• 2018

Comparative drought resistances of 11 perennial warm-season turfgrasses were evaluated in the field after withholding irrigation for 48 days in summer I and 57 days in summer II. There were significant variations among the grasses in their drought resistances. From two years study of field shoot recovery from drought stress, the relative rankings among the 11 warm-season turfgrasses was as follows. 'Arizona Common' and 'Texturf 10' bermudagrasses [Cynodon dactylon (L.) Pers.], 'Tifgreen' hybrid bermudagrass [C. dactylon (L.) Pers. ${\times}$ C. transvaalensis Davy], and 'Georgia Common' centipedegrass [Eremochloa ophiuroides (Munro.) Mack.] possessed good drought resistances, whereas 'Texas Common' St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] and 'Tifway' hybrid bermudagrass [Cyndon dactylon (L.) Pers ${\times}$ C. transvaalensis Davy] possessed poor drought resistances. 'Texas Common' buffalograss [Buchloe dactyloides (Nutt.) Engelm.], 'Pensacola' bahiagrass (Paspalum notatum Flugge.), and 'Adalayd' seashore paspalum (Paspalum vaginatum Swartz), 'Meyer' zoysiagrass (Zoysia japonica Steud.), 'Emerald' zoysiagrass (Z. japonica Steud. ${\times}$ Z. tenuifolia Willd. ex Trin.) were found to rank intermediate. Visual leaf firing showed the highest correlation (r=-0.84) to shoot recovery from drought stress. Visual leaf rolling (r=-0.59) and canopy-air temperature differential (r=-0.64) also showed very significant correlations, whereas leaf water potential (r=0.54) showed relatively lower correlation.

• 한국환경과학회지
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• 제4권2호
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• pp.151-158
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• 1995

A numerical model has been developed to predict the deposition of air pollutants considering canopy effect. In this model, the deposition velocity is calculated using the deposition resistances(aerodynamic resistance, viscosity resistance, surface resistance). Using the results, a comparative study was made between the model calculation and observation results. The calculated daily variation of deposition resistances and in daytime most of the model cases are well agreed with observation results, and a slight difference was found in nighttime. From the results, it is suggested that the present model is capable of estimating the deposition velocity of air Pollutants considering characteristics of canopy layer.

• 전기학회논문지P
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• 제63권3호
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• pp.212-217
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• 2014

The electric power output characteristics of magnesium fuel cell were investigated with regard to internal resistance. A equivalent circuit with the series-connected three internal resistance was introduced to analyze of the response to change of power. The power output analysis was employed in order to investigate the effect of internal resistances for the electrolyte concentration, air electrode area, Mg electrode area and distance between the electrodes. It was confirmed that internal resistance is generated by the electrolyte, air electrode and metal electrode, then those Internal resistances had a significant effect on the power output decrease. The power output was a maximum when the load resistance maches the internal resistance of the magnesium fuel cell. The fuel efficiency was only 50% at maximum power output. Higher fuel efficiency was achieved when the load resistance is greater than the internal resistance.

• 설비공학논문집
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• 제18권10호
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• pp.783-790
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• 2006

A one-dimensional numerical model coupled with parameter estimation is used to predict the effective thermal conductivities of soil formations and borehole resistances from in situ field test data. In this application a new method of using initial ignoring time (IIT) obtained from error estimation is tried and turned out to be successful in determining soil thermal conductivities. This method is used for single-U and double-U borehole system. The results of this method are compared and agreed well with those of existing software (GPM) in the analysis of single-U borehole data. In the analysis of double-U borehole data this method seems to be better in predicting soil and borehole properties.

• 한국환경보건학회지
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• 제38권5호
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• pp.415-423
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• 2012

Objectives: This study was performed in order to evaluate antibiotic resistance and analyze the multiple antibiotic resistance of food-borne pathogens isolated from indoor air and an air cleaner at a lunch room in a child care center. Methods: An antibiotic test of food-borne pathogens, including four Staphylococcus aureus and 23 Bacillus cereus was conducted through the disk diffusion method from Clinical and Laboratory Standard Institute. Results: All Staph. aureus was resistant to Ampicillin and Penicillin, while B. cereus was also resistant to Ampicillin, Cefepime and Penicillin. All isolates showed Vancomycin susceptibility but three out of four Staph. aureus and all B. cereus were resistant to Oxacillin. Staph. aureus and B. cereus presented two or more multiple antibiotic resistances. Conclusions: The results indicated that food-borne pathogens isolated from indoor air and an air cleaner at a lunch room in a child care center showed multiple antibiotic resistances. The repeated control of indoor environment quality is required and continuous surveillance of antibiotic resistant strains is demanded.

• Advances in aircraft and spacecraft science
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• 제4권6호
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• pp.651-677
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• 2017

For the past ten years' efforts have been made to introduce environmentally-friendly "green" electric-taxi and maneuvering airplane systems. The stated purpose of e-taxi systems is to reduce the taxiing fuel expenses, expedite pushback procedures, reduce gate congestion, reduce ground crew involvement, and reduce noise and air pollution levels at large airports. Airplane-based autonomous traction electric motors receive power from airplane's APU(s) possibly supplemented by onboard batteries. Using additional battery energy storages ads significant inert weight. Systems utilizing nose-gear traction alone are often traction-limited posing serious dispatch problems that could disrupt airport operations. Existing APU capacities are insufficient to deliver power for tractive taxiing while also providing for power off-takes. In order to perform comparative and objective analysis of taxi tractive requirements a "standard" taxiing cycle has been proposed. An analysis of reasonably expected tractive resistances has to account for steepest taxiway and runway slopes, taxiing into strong headwind, minimum required coasting speeds, and minimum acceptable acceleration requirements due to runway incursions issues. A mathematical model of tractive resistances was developed and was tested using six different production airplanes all at the maximum taxi/ramp weights. The model estimates the tractive force, energy, average and peak power requirements. It has been estimated that required maximum net tractive force should be 10% to 15% of the taxi weight for safe and expeditious airport movements. Hence, airplanes can be dispatched to move independently if the operational tractive taxi coefficient is 0.1 or higher.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권4호
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• pp.194-202
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• 1999

Various ways of designing heat sink are available for commercial high power converters and among them, the method of air cooling is the most popular and practical method than any other ones. In this paper, a practical method of cooling high power converter, which includes a method of reducing noise and vibration caused by the fan and a method of estimating the gap and contact resistances existing between the thyristor and heat sink, is presented. Finally, the heat transfer analysis and implementation methods of heat sink for high power converter is presented.

• 한국자동차공학회논문집
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• 제24권6호
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• pp.677-683
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• 2016

In this study, the pressures due to air resistances on the models of 1, 2, 3 and 4 as the automotive bodies grafted on various spoilers are investigated through the flow analysis. Model 1 has the flat type and model 2 has the shape that a flat plane is projected. Model 3 is attached with the slanted plate and model 4 has the shape that two slanted plates are installed on both sides. At the flow streams on the models of 1, 2, 3 and 4, the flow velocities are shown to become highest above the roofs of automotive bodies. The maximum flow velocities are also shown at the beginning points at the roofs of car bodies on the side planes of automotive bodies. The maximum pressures of 102,500 to 102,553 Pa as air resistances are shown at the bumpers of the front car bodies. The flow velocities on the inlet and middle planes become nearly same at the models of 1, 2, 3 and 4. But these velocities on the inlet plane at model 2 projected with the spoiler of flat plate become lower than the models of 1, 3 and 4. The air streams throughout the models become uniform at all models. The flow stream is shown most uniformly at model 2 projected with the spoiler of flat plate. But the flow stream is shown most irregularly at model 3 projected with the spoiler of slanting plate. By using the result of this flow analysis, it is thought to reduce the power of car effectively in driving by changing the configuration of automotive spoiler.

• 한국의류학회지
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• 제22권5호
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• pp.565-574
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• 1998

The purpose of the study was to determine the effect of air velocity on the thermal resistance of wool ensembles. Three suits for men with different weaving structure and density were made with the same design and size for the study. In addition, Y-shirt, underwear, and socks were prepared for constructing the ensembles. Thermal insulation of air layer and 3 ensembles were measured by using thermal manikin in environmental chamber controlled at 2$0^{\circ}C$ and 65% RH with various air velocity. The results were as follows: 1. Thermal resistance of air layer was 0.079 m2.$^{\circ}C$/W with no air velocity(less than 0.2m/sec). 2. Thermal resistance of air layer decreased with increasing the air velocity rapidly. When the air velocity was 0.25 and 2.89 m/sec, the decreasing rate was 15% and 61%, respectively compared with no air velocity. 3. While there was little difference among the effective thermal insulation of 3 ensembles having different weaving structure and density with no air velocity, there was sharp difference among them when the air velocity increased. That is, the decreasing rate of effective thermal insulation of the ensemble which has higher air permeability was higher. 4. The decreasing rates of the effective thermal resistances of plain, twill and satin ensemble were 61, 54, and 49%, respectively when the air velocity was 2.89 m/sec which was a maximum air velocity in this study.

• 전기학회논문지P
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• 제65권3호
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• pp.210-215
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• 2016

The transient characteristics of the Mg/Air fuel cell were ascribed to the load current, electrolyte concentrations, air electrode area and electrode distance. It was found that transient phenomena occurred in the load current, which is due to activate of the oxidation and reduction reaction process. The transient time increase with the load current increase. The transient characteristics were investigated with regard to internal resistance. The maximum power output analysis was employed in order to explain the delayed action under various experimental conditions. The internal resistances had a significant effect on the transient characteristics. The transient curves thus obtained were in almost agreement with internal resistance characteristics.