• 한국물환경학회지
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• 제20권1호
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• pp.86-92
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• 2004

Lab-scale experiments have been carried out to investigate ammonia stripping with a modified spray tower for removing ammonia nitrogen from swine wastewater. The operating conditions such as initial pH, temperature, air flow, hole size of distributor determining the diameter of water drops, and influent solids concentration were closely examined focusing on removal efficiency of ammonia. As a result of the experiment, in order to achieve high rate of ammonia removal by the air stripping system, the air flow rate must be supplied at high rate with sufficiently high initial pH, temperature. The optimum operating condition to meet the residual ammonia concentration of 300 mg/L was the initial pH of 11.0 at $35^{\circ}C$ with the air flow rate of 20 L/min. It also showed that the smaller hole size is, the higher removal rate of ammonia is expected. However, when used a small sized distributor (2 mm), the flooding problem at the upper column occurred due to clogging of the hole. With regard to the influent solids concentration, it was showed that the lower concentration of solids, the higher removal rate of ammonia. The removal of particulate materials in influent led to improve the removal efficiency of ammonia, rather than to control the operating condition including initial pH, temperature, and air flow. The empirical correlation between KLa and operating parameters would be driven as, $K_{La}=(0.0003T-0.0047){\cdot}G^{0.3926}{\cdot}L^{-0.5169}{\cdot}C^{-0. 1849}$. The calculated $K_{La}$ from proposed formula can be used effectively to estimate the optimum reaction time and to calculate the volume of modified spray tower system.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.28-35
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• 1999

In this study, investigation of transient knock characteristics in a spark-ignition engine has been carried out. The universal knock threshold values were found by a DFDD method and a NSDBP method which is a non-dimensional version of the SDBP method. Also modified NSDBP method could be used for transient knock detection. In a commercial ECU , spark timing was retarded from the steady -state spark timing during rapid throttle opening to avoid uncomfortable feeling and knock. Knock usually occurred just after the start of rapid throttle opening when spark timing was set, as values for the steady state condition. We found that air/fuel ratio deeply involved with the knock during transient condition. Due to the difference of initial heat release rate, knock occurred more easily at rich air/fuel ratio than at lean air/fuel ratio.

• KSBB Journal
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• 제13권5호
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• pp.547-553
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• 1998

For the efficient production of a new exo-polysaccharide from Ganoderma lucidum ASI 7004, the optimum conditions and methods in submerged cultivation were investigated with an airlift fermenter system. The optimum aeration rate was 2.5 Wm at the initial pH 5.0 and 28$^{\circ}C$. The increase of dissolved oxygen concentration by pure oxygen supply during cultivation did not improved the exo-polysaccaride production and the mycelial growth. The maximum exo-polysaccharide production and the mycelial growth under the optimum culture condition were obtained in media of glucose 60g/L, yeast extract 6g/L, (NH4)2HPO4 1g/L and KH2PO4 0.5g/L. Under these optimum medium and culture conditions, about 7.15g/L of exo-polysaccharide and 13.9g/L of mycelial growth were producted, respectively.

• 한국국방경영분석학회지
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• 제30권1호
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• pp.153-167
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• 2004

This study focuses on building the wartime air operation model to evaluate the airfield capability. There are some uncertainties in the process of air operation such as mission flying time, turn around time, mission damage or kill rate, weather condition, and so on. Airplanes, on the way to the airbase after completing mission flight, may have been in queue on the holding point due to the unusable condition of airfield. And then, they may sometimes need to go other airbases due to the shortage of fuel. Under those uncertainties, this model is to evaluate the airfield capability in the wartime air operation using simulation.

• Journal of information and communication convergence engineering
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• 제8권1호
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• pp.99-102
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• 2010

Large-scaled area and aligned copper oxide nanowires have been synthesized by a vapor-phase approach to the facial synthesis of copper oxide nanowires supported on the surface of a copper gasket. The effects of annealing temperature and time were investigated. Long and aligned nanowires can only formed within a narrow temperature range from 400 to $500^{\circ}C$ for 4 hrs. Annealing copper gasket in static air produces large-area, uniform, but not well vertically aligned nanowires along the copper gasket surface. The surface of copper gasket is converted into bicrystal CuO nanowires was observed after the copper gasket is annealed under static air condition.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제23회 KOSCO SYMPOSIUM 논문집
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• pp.153-160
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• 2001

The combustion test used DTF was performed to obtain the characteristics of NOx emission and reduction. In this test, major factor of NOx emission was a stoichiometric air ratio. At the onset of combustion to be rich oxygen, NOx was produced rapidly. Optimum condition for NOx reduction was formed under about AR:0.7 in the combustion test of Alaska coal. Investigations were undertaken with 200KW(th) test combustor. In combustion test, the major variables were coal feed ratio of center/outer, stoichiometric air ratio at the onset of combustion. The lowest NOx emission, 182ppm(6% O2 base), was achieved at about AR:0.6 of the first combustion stage with low NOx burner. Also, unburned carbon content of char collected in this combustion condition was about 1wt%.

• 대한기계학회논문집
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• 제19권3호
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• pp.796-805
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• 1995

For the purpose of improving performances of a turbocharged diesel engine at low speed, this study investigates the effects of the injected air for the performances and flow characteristics in the intake and exhaust pipes by using the computer simulation with test bed. In the theoretical analysis, the whole flow system, including engine cylinders and intake and exhaust pipes, is calculated numerically by the method of filling and emptying. From the results of this study, the following conclusions may be summarized. Increasing injected air pressure into the pipe of compressor exit brings about the improvement in a performance and flow characteristics of intake and exhaust pipes under full load operating conditions at 1000 rpm of the engine speed, but shows trends of the inferior performances under no load operating conditions at 2000 rpm of the engine speed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.167-171
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• 2001

Air-staging combustion is a relatively well-known technique to reduce NOx emission and used in combination with other techniques nowadays. However, the design variables are still selected depending upon operating circumstances. Though the fuel-rich condition of the primary combustion zone is very helpful to NOx reduction, its range is known to be restricted by the increase of carbon monoxide. However, in many cases carbon monoxide level is so low not to be the restriction at all. So we tried to expand the equivalence ratio range to the richer condition in the primary combustion zone and make the function of each burner component and its contribution to the overall NOx production clear.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.447-452
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• 2009

The objectives of this paper are to study the effects of thermal and geometric conditions on the performance of indoor heat exchanger with R410A. This study carried out experimental and numerical analysis for indoor heat exchangers. In the experimental study, capacity of the indoor unit was estimated 8.3 kWh with the valve opening rate of 95% for the 50% partial operation condition. The air temperatures were measured using 80 thermocouples. This study also compared experimental data with the calculated data for the outlet temperature and the tube length. It is found that the relative errors between the experiment data and the calculated result are 4.2% and 0.5% for the outlet temperature and the tube length, respectively.

• 한국초전도ㆍ저온공학회논문지
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• 제4권1호
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• pp.145-150
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• 2002

The distillation column is one of large energy consumable units in the cryogenic air separation process and the accurate energy analysis of this unit is necessary for choice of energy saving process. In this work, the energy method was adopted for energy analysis of a cryogenic nitrogen distillation column. In order to designing the energy saving distillation column, the exergy distribution of feed air, exergy efficiency and exergy loss for process condition was investigated and the optimal process condition to minimize the exergy loss was found. The result from this work can be used as a guideline for the choice of the process design conditions and efficiency improvement of cryogenic distillation column.