• Journal of Mechanical Science and Technology
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• v.16 no.6
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• pp.839-850
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• 2002

A performance simulation program for the turboprop engine (PT6A-62), which is the power plant of the first Korean indigenous basic trainer KT-1, was developed for performance prediction, development of an EHMS (Engine Health Monitoring System) and the flight simulator. Characteristics of components including compressors, turbines, power turbines and the constant speed propeller were required for the steady state and transient performance analysis with on and off design point analysis. In most cases, these were substituted for what scaled from similar engine components'characteristics with the scaling law. The developed program was evaluated with the performance data provided by the engine manufacturer and with analysis results of GASTURB program, which is well known for the performance simulation of gas turbines. Performance parameters such as mass flow rate, compressor pressure ratio, fuel flow rate, specific fuel consumption and turbine inlet temperature were discussed to evaluate validity of the developed program at various cases. The first case was the sea level static standard condition and other cases were considered with various altitudes, flight velocities and part loads with the range between idle and 105% rotational speed of the gas generator. In the transient analysis, the Continuity of Mass Flow Method was utilized under the condition that mass stored between components is ignored and the flow compatibility is satisfied, and the Modified Euler Method was used for integration of the surplus torque. The transient performance analysis for various fuel schedules was performed. When the fuel step increase was considered, the overshoot of the turbine inlet temperature occurred. However, in case of ramp increase of the fuel longer than step increase of the fuel, the overshoot of the turbine inlet temperature was effectively reduced.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.41 no.4
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• pp.43-51
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• 2009

Paper mill sludges are discharged around 870,000 M/T annually. Only 30% of the paper mill sludge have been recycled and the rest has been disposed by land fill, incineration, ocean abandonment and other ways. Because of overall prohibition of sludge disposal by London Dumping Convention in 2012, a urgent counter measure for paper mill sludge must be provided. In this paper, some basic experiments were carried out to develop a tray cell pot using paper mill sludge for increasing the recycling potential of the wasted sludge. To establish the manufacturing parameters, the tray cell pots were made with three types of materials including virgin pulp, old news paper and corrugated board mixed in a blend tank of a molding machine. The bending force and moisture content of the produced tray cell pots was measured to confirm the application capability. The tray cell pot could be manufactured under the condition of over 20% of virgin pulp, 40% of old news paper added. However, the corrugated board could not be used because of the glutinous substance included. The produced tray cell pot absorbed water very easily and the bending force decreased rapidly. The waterproof material must be used to applicate the produced tray cell pot in plant growing fields.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.4
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• pp.268-275
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• 2005

Early predictions of crop yields call provide information to producers to take advantages of opportunities into market places, to assess national food security, and to provide early food shortage warning. The objectives of this study were to identify the most useful parameters for estimating yields and to compare two model selection methods for finding the 'best' model developed by multiple linear regression. This research was conducted in two 65ha corn/soybean rotation fields located in east central South Dakota. Data used to develop models were small temporal variability information (STVI: elevation, apparent electrical conductivity $(EC_a)$, slope), large temporal variability information (LTVI : inorganic N, Olsen P, soil moisture), and remote sensing information (green, red, and NIR bands and normalized difference vegetation index (NDVI), green normalized difference vegetation index (GDVI)). Second order Akaike's Information Criterion (AICc) and Stepwise multiple regression were used to develop the best-fitting equations in each system (information groups). The models with $\Delta_i\leq2$ were selected and 22 and 37 models were selected at Moody and Brookings, respectively. Based on the results, the most useful variables to estimate corn yield were different in each field. Elevation and $EC_a$ were consistently the most useful variables in both fields and most of the systems. Model selection was different in each field. Different number of variables were selected in different fields. These results might be contributed to different landscapes and management histories of the study fields. The most common variables selected by AICc and Stepwise were different. In validation, Stepwise was slightly better than AICc at Moody and at Brookings AICc was slightly better than Stepwise. Results suggest that the Alec approach can be used to identify the most useful information and select the 'best' yield models for production fields.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.414-420
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• 2006

Effluent from an anaerobic digestion system with an elutriated phased treatment(ADEPT, Anaeorbic Digestion Elutriated Phase Treatment) for piggery waste treatment using anaerobic ammonium oxidation(ANAMMOX) process was used as a substrate of partial nitrification reactor. In mesophilic condition($35^{\circ}C$), controlling parameters of nitrite accumulation were HRT, pH, free ammonia(FA) and hydroxylamine rather than dissolved oxygen. Bicarbonate alkalinity consumption ratio including bicarbonate stripping and buffering was 8.78 g $Alk._{comsumed}/g\;NH_4-N_{converted}$. In steady state for 1 day of HRT and $2.7{\sim}4.4mg/L$ of DO, $NO_2-N/NH_4-N$ ratio of partial nitrification effluent was about $1{\sim}3$, which was applicable to ANAMMOX reactor influent for the combined partial nitrification-ANAMMOX process.

• Korean System Dynamics Review
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• v.4 no.2
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• pp.153-171
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• 2003

In this study, we tried to build a model which can deal with the efficient and effective operation of electric power industry, especially focused on the nuclear industry. Here, SD(system Dynamics) approach is used to visualize the underlying phenomenon of the nuclear power industry. SD is a methodology for studying and managing complex feedback systems, such as one finds in business and other social systems, The span of SD applications has grown extensively and now encompasses work in corporate planning and policy design, public management and policy, biological and medical modeling, energy and the environment. Recently, according to the report from KEPCO(Korea Electric Power Corporation), they are considering delaying a new power plant construction. It may be based upon business fluctuation downsized from Korean economic crisis in 1997 and freezing of construction funds due to unstable foreign exchange rate. At this point, we need desperately a kind of strategic model that would contribute to cope with the current business situation, energy generation, Production, and resulting Pollution. Specifically, this model, using SD approach, starts with the detailed drawing of influence diagram, which describes those relevant key points on nuclear power generation systems in electric power industry of Korea. These include such (actors as the operation of nuclear industry and parameters related to the decision making for business policy. Based upon the above-mentioned influence diagram drawn, we developed SD simulation model to evaluate and analyze strategic management of KBPCO. Based on our analysis, we could demonstrate how simulation model can be applied to the real electric power generation in Korea.

• Horticultural Science & Technology
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• v.32 no.2
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• pp.142-148
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• 2014

Effect of silicon (Si) nutrition on growth and temperature stress tolerance of Nephrolepis exaltata 'Corditas' grown in a soilless substrate was examined. In vitro-grown acclimatized plantlets were transplanted into the pots containing a coir-based substrate. A nutrient solution containing 0, 50, or $100mg{\cdot}L^{-1}$ Si was supplied through a drip-irrigation system. After 5 months of cultiv ation, S i-treated and -untreated p lants were grown at 10, 25, or $40{\pm}1^{\circ}C$ under a 12 h photoperiod with $530{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ PPFD and 60% RH. After 7 days, chlorophyll content and chlorophyll fluorescence parameters were measured. Silicon nutrition had a negative effect on growth characteristics of N. exaltata 'Corditas'. However, Si-treated plants had more tolerance to temperature stress than the control plants. The Fv/Fm value was not significantly different when the plants were exposed to $25^{\circ}C$. However, significant difference in Fv/Fm was recorded when plants were exposed to 10 or $40^{\circ}C$. Thus, Fv/Fm could be used as an indicator of low and high temperature tolerance in ferns. The present study also suggests that application of Si may be used to enhance temperature tolerance of ferns.

• Ocean and Polar Research
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• v.36 no.1
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• pp.25-37
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• 2014

To understand the degradation processes of organic matter related to sulfate reduction by Sulfate Reduction Bacteria (SRB) in the tidal flat sediments of Hwang-do and Sogeun-ri, Tae-an Peninsula in Chungnam-do, biogeochemical characteristics were analyzed and highlighted using specific microbial biomarkers. The organic geochemical parameters (TOC, ${\delta}^{13}C_{org}$, C/N ratio, long-chain-n-alkane) indicate that most of the organic matter has been derived from marine phytoplankton and bacteria in the fine-grained sediment of Sogeun-ri, although terrestrial plant components have occasionally been incorporated to a significant degree in the coarse-grained sediment of Hwang-do. The concentration of sulfate in pore water is a constant tendency with regard to depth profile, while methane concentration appears to be slightly different with regard to depth profile at the two sites. Especially, the sum of bacteria fatty acid (a-C15:0 + i-C15:0 + C16:1w5) confirms that the these concentrations in Sogeun-ri are related to the degradation of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) compounds from the crude oil retained in the sediments as a result of the Hebei Spirit oil-spill accident in 2007. The methane-related microbial communities as shown by lipid biomarkers (crocetane, PMI) are larger in some sedimentary sections of Hwang-do than in the Sogeunri tidal flat. These findings suggest that methane production by microbiological processes is clearly governed by SRB activity along the vertical succession in organic-enriched tidal flats.

• Journal of the Korean Operations Research and Management Science Society
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• v.26 no.2
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• pp.99-109
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• 2001

In this study, we tried to build a model which can deal with the efficient and effective operation of electric power industry, especially focused on the nuclear industry. Here, SD (System Dynamics) approach is used to visualize the underlying phenomenon of the nuclear power industry. SD is a methodology for studying and managing complex feedback systems, such as one finds in business and other social systems. The spend of SD applications has grown extensively and now encompasses work in corporate planning and policy design, public management and policy, biological and medical modeling, energy and the environment. Recently, according to the report from KEPCO (Korea Electric Power Corporation), they are considering delaying a new power plant construction. It may be based upon business fluctuation downsized from Korean economic crisis in 1997 and freezing of construction funds due to unstable foreign exchange rate. At this point, we need disparately a kind of strategic model that would contribute to cope with the current business situation, energy generation, production, and resulting pollution. Specifically, this model, using SD approach, starts with the detailed drawing of influence diagram, which describes those relevant key points on nuclear power generation systems in electric power industry of Korea. These include such factors as the operation of nuclear industry and parameters related to the decision making for business policy. Based upon the above-mentioned influence diagram drawn, we developed SD simulation model to evaluate and analyze strategic management of KEPCO. Based on our analysis, we could demonstrate how simulation model can be applied to the real electric power generation in Korea.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.82-88
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• 2007

The objective of this study is to examine the effect of the waste oyster shell powder as the addition agent in bulking sludge thickening of paper manufacturing plant using DAF(Dissolved Air Flotation) and gravitational sedimentation. The effect of parameters such as dosage and size distribution of oyster shell were examined. The results showed that the optimum dosage of mixed oyster shell(size range : $\sim250{\mu}m$) was 0.8 g/L. The oyster shell addition of 5.0 g/L in sedimentation process was increased thickening concentration of 3.25 times. When 5.0 g/L of oyster shell was added in DAF process, water content of sludge was decreased from 95.5% to 82.7% in dewatering process using Buchner funnel test device. When size of oyster shell was divided four ranges($\sim53{\mu}m$, $53\sim106{\mu}m$, $106\sim150{\mu}m$, $150\sim250{\mu}m$), optimum size range for the flotation and dewatering was $53\sim106{\mu}m$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.213-217
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• 2006

An intelligent performance diagnostic program using the Neural Network was proposed for PW206C turboshaft engine. It was selected as a power plant for the tilt rotor type Smart UAV (Unmanned Aerial Vehicle) which has been developed by KARI (Korea Aerospace Research Institute). For teaming the NN, a BPN with one hidden, one input and one output layer was used. The input layer had seven neurons of variations of measurement parameters such as SHP, MF, P2, T2, P4, T4 and T5, and the output layer used 6 neurons of degradation ratios of flow capacities and efficiencies for compressor, compressor turbine and power turbine. Database for network teaming and test was constructed using a gas turbine performance simulation program. From application results for diagnostics of the PW206C turboshaft engine using the learned networks, it was confirmed that the proposed diagnostics algorithm could detect well the single fault types such as compressor fouling and compressor turbine erosion.