• International Journal of Human Ecology
• /
• v.4 no.2
• /
• pp.77-87
• /
• 2003

This paper tried to construct statistical and econometric models on the basis of economic theory in order to discuss the issue of statistical efficiency and unbiasedness including the sample selection bias correcting problem. Comparative analytical tool were one stage Tobit of Maximum Likelihood estimation and Heckman's two-step Tobit of Ordinary Least Squares. The results showed that the adequacy of model for the analysis on demand and choice, we believe that there is no big difference in explanatory variables between the first selection model and the second linear probability model. Since the Lambda, the self- selectivity correction factor, in the Type II Tobit is not statistically significant, there is no self-selectivity in the Type II Tobit model, indicating that Type I Tobit model would give us better explanation in the demand for and choice which is less complicated statistical method rather than type II model.

• KSBB Journal
• /
• v.13 no.5
• /
• pp.518-523
• /
• 1998

A large quantity of ethylene glycol(EG) is remained in the effluent after pretreating polyester weight-loss wastewater physicochemically in the fist stage and must be treated biologically in the second stage. Therefore, an excellent EG-utilizing bacteria strain was isolated from the natural system and the optimal culture conditions of the strain were investigated. The optimal culture conditions of temperature, pH, and nitrogen source were found to be 35$^{\circ}C$, 7.5 and ammonium chloride, respectively, when CODCr removal efficiency was more than 90%. The growth of stains and EG removal efficiency was slightly improved by adding elements such as niacin and biotin. With increasing inoculation size in a batch culture, the removal efficiency of EG was conspicuously increased. Growth rate was inhibited when the initial concentration of EG was more then 30g/L. The strain was identified as Pseudomonas sp. based on morphological and biological characteristics and named as Pseudomonas sp. EG1.

• The KSFM Journal of Fluid Machinery
• /
• v.9 no.3 s.36
• /
• pp.7-13
• /
• 2006

Shape optimization of a rotor blade in a single-stage transonic axial compressor has been performed using a response surface method and three-dimensional Navier-Stokes analysis. Two shape variables of the rotor blade, which are used to define a blade skew, are introduced to increase an adiabatic efficiency. Throughout the shape optimization of a rotor blade, the adiabatic efficiency is increased to about 2.2 percent compared to that of the reference shape of the stator. The increase in efficiency for the optimal shape of the rotor is due to the pressure enhancement, which is mainly caused by moving the separation position on the suction surface of rotor blade to the downstream direction.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.10 no.1
• /
• pp.65-69
• /
• 1977

The characteristics of two stage compressor which is constituted of two separated reciprocating compressors was tested measuring the volumetric efficiency of each compressor at suction of both bighandlowpressdresideusillgorificetypeflolrmeters. The volumetric efficiency of low pressure side compressor was lower than that of the high side when they were operating under the same compression ratio. And it tended to reduce obviously by lowering evaporating temperature resulting in a markable reduction of refrigerating capacity at the same time. It is assumed that the falling of volumetric efficiency at low side compressor was directed by the decrease in evaporating temperature which derives the falls of gas pressure at suction, increase in compression ratio, and gas flow resistance at suction and discharge valves.

• Asia pacific journal of information systems
• /
• v.15 no.2
• /
• pp.121-148
• /
• 2005

This study focuses on MRO e-Marketplace and attempts to research how companies select the structure of e-Marketplace governance and how it influences purchasing performance. Furthermore, a longitudinal study is conducted to analyze the dynamic relationship between variables in our research model. The research gives the following results. First, as the utilization level of e-Marketplace increases, the level of relational exchange between purchasing company and e-Marketplace increases. The increased utilization level enhances purchasing efficiency rather than reducing purchasing price. Secondly, as the level of relational exchange between purchasing companies and e-Marketplace increases, system integration increases, whereas supply externality decreases. Accordingly, system integration improves purchasing efficiency, whereas the low supply externality does not help lower purchasing price. Third, compared to the initial growth stage, the stable stage of e-Marketplace has the significantly increased level of relational exchange and purchasing efficiency through system integration, rather than the reduction of purchasing price by supply externality.

• Journal of Korea Multimedia Society
• /
• v.19 no.7
• /
• pp.1208-1215
• /
• 2016

This study suggests efficient production of game with spine tool that is 2D game tool. For this, the researcher studies process and efficiency of game development by focusing on production of a game "Shooting Monster" Version 1 in service of Google Store at present. Production tools in a contents field are sharply changed. In addition, these tools are automatized into new version and efficient product. These tools help manufacturers in increasing quality of contents and time efficiency. Therefore, the researcher examines understanding of development process of existing 2D game and problems in development stage of graphic character, and analyzes production stage of character animation using spine tool, so suggests effective process of production in terms of production. The purpose of this study is to suggest the direction about graphic efficiency of tool by accessing production process to train working-level talented people in 2D mobile game field.

• Proceedings of the KIPE Conference
• /
• 2003.11a
• /
• pp.85-89
• /
• 2003

Many single-stage PFC(power-facto.-correction) ACHC converters suffer from the high link voltage at high input voltage and light load condition. In this paper, to suppress the link voltage, a novel high power factor high efficiency PFC AC/DC converter is proposed using the single controller which generates two gate signals so that one of them is used far gate signal of the flyback DC/DC converter switch and the other is applied to the Boost PFC stage. A 130w prototype for LCD monitor adapter with universal input $(90-265V_{rms})$ and 19.5V 6.7A output is implemented to verify the operational principles and performances. The experimental results show that the maximum link voltage stress is about 450V at 270Vac input voltage. Moreover, efficiency and power factor are over $84\%$ and 0.95, respectively, under the full load condition.

• Journal of Biosystems Engineering
• /
• v.22 no.4
• /
• pp.497-502
• /
• 1997

Automation facilities of greenhouses have been continuously developed. However, the conventional two-stage worm gear reducer reveals some problems, including low transmission efficiency. The worm gear reducer also have some difficulties in manufacturing and short life. Therefore, this study was performed to develop a planetary gear reducer, having a high Sear reduction ratio and high torque transmission efficiency. The planetary gear system consisted of a fixed ring gear and a 2-teeth differential ring gear turning slow, as the planetary pinion orbits fast around the fixed ring gear. The developed gear system can achieve a high speed reduction rate at one stage. The reducing system was employed to the greenhouse ventilation system. The reducer has the transmission efficiency of 70.5%, 2∼3 times longer life time, and twofold roll-up torque at an affordable price, comparing with conventional reducers. This reducer can be also applied to many industrial equipments, such as industrial crane, hoist, elevator and gondola etc.

• Journal of Electrical Engineering and information Science
• /
• v.2 no.3
• /
• pp.123-131
• /
• 1997

Design of single stage AC/DC converter with high power factor for low power level applications is proposed. The proposed converter gives the good power factor correction, low line current harmonic distortions, and tight output voltage regulations. This converter also has a high efficiency by employing an active clamp method and synchronous rectifiers. To verify the performances of the proposed converter, a 90W-converter has been designed. The modelling of this proposed converter is power formed using an averaging technique and based on this model a detailed analysis is carried out. This prototype meets the IEC555-2 requirements satisfactorily with nearly unity power factor and high efficiency.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.33B no.10
• /
• pp.139-147
• /
• 1996

In this study a two-stage fast pulse generaor using magnetic switches is proposed. The scheme consist of a switch, an inductor and two pairs of capacitor and saturable inductors, a linear transformer. The basic principle and the operation are described using a set of given parameters. The main issue of the magnetic pulse genration scheme is the system efficiency. This study focuses on the system efficiency improvement using magnetic switches. The voltage compression ratio, energy transfer with respect to core area are investigated. The output voltage and transferred energy as a function of input voltage are also included. Also, an analysis and experiments are performed to verify the porposed topology by implementing a 10[J] class experimental circuit. The efficiency of the transferred energy a tload side is 82%.