• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.109-111
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• 2001

Modern power grids are becoming more and more stressed with the load demands increasing continually. Therefore large stressed power systems exhibit complicated dynamic behavior when subjected to small disturbance. Especially, it is needed to analyze special conditions which make small signal stability structure varied according to operating conditions. This paper shows that the relation between small signal stability and operating conditions can be predicted well using node-focus point and 1:1 resonance point. Also, the weak point which limits operating range can be identified by the analysis of resonance condition. The proposed method is applied to test systems, and the results illustrate its capabilities.

• Journal of the Korean Institute of Rural Architecture
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• v.17 no.3
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• pp.37-44
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• 2015

The purpose of this study is to find important factors for establishment of masterplanner operating model in residents' participation regeneration project suitable for small provincial city compared with Seoul city's which were already operated these days. The study showed the following results: 1) Conditions required for masterplanners are professional, regionality, sustainability, balance, independence. 2) Regionality and professionality can be guaranteed by expert-recommendation and perform manual suitable for character of project and regional conditions. 3) Conditions required for masterplanners are applied flexibly depending on the size and duration of project.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.4 s.247
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• pp.381-388
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• 2006

The objective of this study is to predict the etching characteristics using spray characteristics for the optimization on the etching process of Lead-Frame. The etching characteristics such as etching factor, uniformity were investigated on the actual operating conditions. The correlation between the etching characteristics and the spray ones obtained by measurement were analyzed to simulate the etching characteristics according to actual conditions of lead-frame etching process. These conditions of lead-frame process were spray pressure, distance from nozzle tip to substrate, pipe pitch, and nozzle pitch. To improve the etching characteristics in the lead-frame process, effects of the various operating conditions should be understood in detail. The spray characteristics obtained by experiment using PDA system were simulated by the Monte-Carlo method. The etching process model was coded by Java language. It was found that simulation results generally agreed well with the measured results of etching characteristics in lead-frame etching process. The optimal operating parameters were successfully found under variable conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.11
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• pp.2076-2082
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• 2011

The goal of this paper is to find an operating conditions of the single direct ethanol fuel cell such as the cell temperature, and flow rates of ethanol and oxygen. To investigate the output characteristics, the electrical current increased from 0[A] with interval of 0.001[A] every 2[s], and the cell voltage was increased until the voltage became 0.05[V]. Related to the effect of the cell temperature, the output characteristics both voltage and power were increased upto 80[$^{\circ}C$] according to the increase of the current density, but those were decreased over that temperature. In addition, the optimal flow rate of ethanol in anode was identified as of 2[mL/min] due to the dependence of generation rate such as the hydrogen ion and electron. And the flow rate of oxygen in cathode was desirable to about 300[sccm/min], it might be affected by the chemical reaction rate of the water formation among hydrogen ion, electron, and oxygen. Consequently, the fundamental conditions were identified in this work, and it will be carried out to find the best conditions of membrane by the effect of the plasma surface treatment, and the effect of other catalysts except for a platinum.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.9
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• pp.2314-2333
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• 2023

It is significant to predict the performance degradation of complex electromechanical systems. Among the existing performance degradation prediction models, belief rule base (BRB) is a model that deal with quantitative data and qualitative information with uncertainty. However, when analyzing dynamic systems where observable indicators change frequently over time and working conditions, the traditional belief rule base (BRB) can not adapt to frequent changes in working conditions, such as the prediction of aeroengine performance degradation considering working condition. For the sake of settling this problem, this paper puts forward a new hidden belief rule base (HBRB) prediction method, in which the performance of aeroengines is regarded as hidden behavior, and operating conditions are used as observable indicators of the HBRB model to describe the hidden behavior to solve the problem of performance degradation prediction under different times and operating conditions. The performance degradation prediction case study of turbofan aeroengine simulation experiments proves the advantages of HBRB model, and the results testify the effectiveness and practicability of this method. Furthermore, it is compared with other advanced forecasting methods. The results testify this model can generate better predictions in aspects of accuracy and interpretability.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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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.

• Journal of ILASS-Korea
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• v.24 no.1
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• pp.1-7
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• 2019

This study was carried out to analyze the spray characteristics as a function of the operating parameters of urea injector used in Urea-SCR system of passenger diesel vehicle. Spray visualization and PDPA experiment were performed to analyze the macroscopic spray development and atomization performance of urea-water-solution. For the urea injector, the deformation of the spray head does not appear to be significant because it operates at a low pressure conditions, and the liquid core and primary droplet are observed throughout the operating conditions. No increase in atomization is seen when the operating pressure is increased, and the spray develops linearly due to poor atomization characteristics. The macroscopic spray behavior of the low-pressure urea injector is predictable through the modification of the Hiroyasu equation.

• Journal of Environmental Health Sciences
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• v.31 no.1
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• pp.55-60
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• 2005

The occurrence and abundance of protozoa at advanced wastewater treatment plant were compared with operating parameters and effluent quality using statistical procedures. In correlation analysis between the distribution of protozoa and operating parameters, the distribution of protozoa was showed the operating condition of plant. Regression analysis between the distribution of protozoa and effluent quality up to 7 days, showed the R-square values of most regression equation were more than 0.6 and constant was higher than slope and could indicate effluent quality from sampling day to 7 days. Once enough data concerning protozoa, operating parameters and effluent has been gathered, the operator has a valuable tool for predicting plant performance and near-future effluent quality based on microscopic examination. Plant operator manipulates operating conditions if he knows near-future data of effluent is deteriorating. Perhaps more importantly it can be used to actually control the plant to adjust the operating conditions to obtain the protozoal populations that have been shown to provide the best effluent quality.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.7
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• pp.1183-1191
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• 2000

Operating conditions for reduction of membrane fouling in treatment of dissolved organic matter by UF membrane process were investigated by pilot-scale plant using various operating conditions. As inlet pressure increased, increament of transmembrane pressure and flux decline were faster. The reason was due to the increase in adsorption of dissolved organic matter and the development of cake layer compression on the membrane surface. When efficient pressure (the difference of pressure between backwash and transmembrane pressures) was high, small amount of pollutant was retained on the membrane surface. When backwash was frequently conducted, low concentration of pollutant was maintained in recycling water. Therefore, backwash could be efficiently conducted with high efficient pressure and high frequency. Fouling rate was correlated with backwash and inlet pressures, recovery rate and cumulative permeated volume. Among the operating parameters backwash pressure was most closely related to fouling rate and inlet pressure was next to backwash pressure. It seems that the fouling was strongly related to pressure which leads to the cake layer compression and adsorption of dissolved organic matter.

• Journal of Biosystems Engineering
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• v.25 no.6
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• pp.463-470
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• 2000

For maximum seeding efficiency of a nozzle type seeder, the performance of the nozzle should be considered sufficiently. This study was carried out to investigate the optimum operating conditions of a seeder attached the vacuum nozzle which was modified syringe needle acting on the plug seedling tray and the seed plate. Such operating factors as the hole diameter of the nozzle (d), the distance from the nozzle tip to the bottom plate of seed hopper(D) the absorbing air pressure of the nozzle tip(P) the bounding height of seed from the vibrated bottom plate of seed hopper and the seeding speed were selected based on the weight of a grain of seed(W). The treated materials were pepper seed as the flat type, cucumber seed as the oval type and radish seed as the spherical type. The optimum operating conditions of the experimental seeder were revealed as follows: 1. The height of the seed bounding from the bottom plate of seed hopper and the distance from nozzle tip to bounded seed were 5 mm and 0.5 mm at all seeds. The hole diameter of the nozzle and the absorbing pressure for pepper seed, cucumber seed and radish seed was 0.45 mm, 0.65 mm. 0.65mm and 39.2 kPa, 88.3 kPa, 58.8 kPa, respectively. 2. The absorbing pressure P was represented as P=η.4W/$\pi$d$^2$ where η was 100. The seeding speed using a 128 cell tray was 2.4 cm/s which was same transfer as 2.5 trays per minute. 3. The maximum seeding rate in case of the pepper seed was 97% the cucumber seed was 95% and the radish seed was 100% under the optimum operating conditions of the seeder.