• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.8
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• pp.704-710
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• 2017

The supply of the liquid oxygen into a rocket combustor is simply controlled by the 'on' and 'off' positions of a main oxidizer shut-off valve. However, the partially opened position of a three-position valve can control and optimize the engine start transients by regulating the liquid oxygen flow rate during the start-up of the engine. In this paper, the design and performances of a three-position pneumatic poppet valve, which is intended to be employed in liquid rocket engines, have been presented.

• Journal of Distribution Science
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• v.17 no.2
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• pp.35-42
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• 2019

Purpose - There is little research on the market of foreign infant education materials. So, it is needed to deeply examine the development and preference factors of foreign infant education materials. Therefore, this study presents a future method and model for analyzing the important variables of buying foreign infant education materials. Research design, data, and methodology - The conjoint analysis method and model of this paper is used as follows. Conjoint analysis method is possible to derive the attributes to be analyzed through the model of the preferred factors, and then to derive the sub-attributes of the attributes. Results - This study derived preference attributes between brand benefit, equity (brand image, loyalty, awareness), distribution network (department store, specialty stores, discount store, internet mall), and service quality (tangibles, reliability, responsiveness, assurance, empathy) in infant education materials conjoint model. Conclusions - Since the opening of the education market in Korea, parents have a high education level due to low birth rate. The advantages of the conjoint analysis method have been extended to the study of infant education materials. Based on this, this paper will identify important attributes that are considered in preference of foreign infant education materials and help to establish and implement future marketing strategies.

• Journal of Biomedical Engineering Research
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• v.16 no.1
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• pp.107-113
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• 1995

It is well known that multipoint and computerized intraoperative mapping systems improve the results of surgery for Wolff-Parkinson-White syndrome and show tremendous potential for opening an entirely new era of surgical intervention for the more common and lethal types of supraventricular tachyarrhythmias such as atrial flutter and atrial fibrillation. In addition, the ability to map and ablate the sometimes fleeting automatic atrial tachycardia is greatly enhanced by computerized mapping systems. In this study, we have developed 64 channel computerized data analysis system using microcomputer (Macintosh ${II}_{x}$) for basic research of electrophysiology and electrical propagation. The bipolar electrogram information is acquired from 64 cardiac sites simultaneously at a sampling rate of 1 ksampls/sec with continuous and total data storage of up to 30 seconds. When the reference electrogram is selected and reference point is picked up, delay time from the reference point is displayed on two dimensional diagram of the heart. System design permits easy expansion to almost 256 simultaneous sites. this system is expected to enable us to study pathophysiology of cardiac arrhythmia and to improve the result of diagnosis and surgical treatment for cardiac arrhythmia.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.2
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• pp.55-65
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• 2012

In the winter season, when the ventilation system is operating, the fresh cold air from the slot-type openings of broiler house which directly reached the animal zone can cause various problems such as thermal stress, decreasing of feed and water consumption, occurrence of respiratory disease, and etc. Therefore it is very important to control the trajectory of aero-flow from the slot openings to induce an efficient thermal heat change. Jet-drop distance model was proposed to predict and control the jet-trajectory. However their study was restricted due to the small scaled model and difficulties of measuring the Jet-drop distance. In this study, CFD was applied to analyze qualitatively and quantitatively the jet-drop distance in a real broiler house. The various variables were considered such as installed slot-angle, designed ventilation rate, and the outdoor ambient temperature. From the present study, two linear-regression models using the Jet-drop factor and corrected Archimedes number, and their R-squared values 0.744 and 0.736, respectively, were used. From this study, the applicability of CFD on the analysis of Jet-drop distance model was confirmed.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.35-40
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• 2012

Since the opening of Korean high-speed rail, KTX in 2004, the use of trains in Korea soared. Improved rail technology, as well as the speed of the train was developed. However, the development of the train speed raised new issues of Doppler effect and this effect compensation. Depending on the speed of communication target, Doppler effect generates frequency shifting and this effect leads to a distortion of the signal. For this reason, the Doppler effect adversely affect the communication performance. Therefore, the Doppler effect problem must be solved for the railway wireless communication. In this paper, we present technique of compensation for the Doppler effect that occurs in high-speed railway communication and simulation result.

• The Journal of Industrial Distribution & Business
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• v.8 no.7
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• pp.13-20
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• 2017

Purpose - Performance appraisal has a significant influence on the development of low-carbon tourism distribution. Research design, data, and methodology - Data of this study are collected from 27 provinces (cities) of China. SBM-Malmquist model is used to measure the TFP and its dynamic changes of low-carbon tourism distribution; TOBIT model is used to discuss the factors of TFP of low-carbon tourism distribution. Results - The results show that, there are obvious differences among regional TFP of low-carbon tourism distribution, the average change tends to grow positively in general, and the western region grows fastest on average due to the improvement of technical efficiency and technical progress, while there are technical efficiency improvement but technical regresses in eastern and central regions. The economic scale, economic strength, structure of energy consumption, location quotient and government regulation have a significant positive effect on the TFP of low-carbon tourism; energy intensity, industrial structure and opening degree have a negative effect; investments in fixed assets, intensity of R&D fund and urbanization rate have no significant influence on the TFP of low-carbon tourism. Conclusions - Improving the productivity of low-carbon tourism and reducing regional differences are effective ways to develop low-carbon tourism and enhance tourism competitiveness.

• The Korean Journal of Physiology and Pharmacology
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• v.6 no.2
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• pp.81-85
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• 2002

Conventional views of synaptic transmission generally overlook the possibility of 'postfusional-control' the regulation of the speed or completeness of transmitter release upon vesicular fusion. However, such regulation often occurs in non-neuronal cells where the dynamics of fusion-pore opening is critical for the speed of transmitter release. In case of synapses, the slower the transmitter release, the smaller the size and rate-of-rise of postsynaptic responses would be expected if postsynaptic neurotransmitter receptors were not saturated. This prediction was tested at hippocampal synapses where postsynaptic AMPA-type glutamate receptors (AMPAR) were not generally saturated. Here, we found that the small miniature excitatory postsynaptic currents (mEPSCs) showed significantly slower rise times than the large mEPSCs when the sucrose-induced mEPSCs recorded in cyclothiazide (CTZ), a blocker for AMPAR desensitization, were sorted by size. The slow rise time of the small mEPSCs might result from slow release through a non-expanding fusion pore, consistent with postfusional control of neurotransmitter release at central synapses.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.66-78
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• 1998

Adequate ventilation with the proper amount of air to the right place is important factor to achieve a good Indoor air climate. Thus it is of prime importance that the ventilation system is working properly. This requires reliable pressure loss calculation to balance the air flow through duct systems. So a computer program for balancing CAV duct system is developed In this study. The results of CAV duct system is compared with the "Balans" code developed by Larsen from Norway. To obtain the pressure drop characteristics of damper at duct terminal, some experiments are performed using DPM(Dual Pressure Measurement) system. To adjust the resistance of damper, present study suggests that some special diffusers should be designed and damper producers should give the data of air flow vs. pressure drop to the customs when they manufacture the damper. One of the results concludes that the working time can be reduced from several minutes to several seconds per damper in the present experimental site, if the DPM system and the air volume adjusting process are used.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.3
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• pp.184-193
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• 2001

The present study develops programs simulating the internal pressure change of cars due to the change of external pressure when trains run into or passing each other in a tunnel. A new continuous ventilating system control method has been developed in order to alleviate the aural discomfort of passengers riding a high speed train. This method is based on the change of the charged and discharged flow rate by detecting the air pressures generated outside and inside of the train. When the outside and inside pressure are detected, the speed of the charge or exhaust fans and also the valve opening ratios are changed. The elementary performance of the system is checked using dta of the TGV-K high speed train at a speed of 300km/h. Moreover, applicability of the system to the Koran high speed train at a speed of 350 km/h is ascertained by simulation and its effectiveness as a means to alleviate the ear pains is confirmed. This application of the system to the Korean high speed vehicles running in the speed range of 350km/h is considered to have good prospect.

• Journal of Ocean Engineering and Technology
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• v.14 no.3
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• pp.78-83
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• 2000

In this study, CT specimens were prepared from AST SA516 Gr. 70 which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at 25$^{\circ}C $, -60$^{\circ}C $, -80$^{\circ}C $ and -100$^{\circ}C $ and in the range of stress ratio of 0.05, 0.3 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range ${\delta} K_{th}$ in the early stage of fatigue crack growth (Region I) and stress intensity factor range $\delta $K in the stable of fatigue crack growth (Region II) were increased in proportion to descending temperature. It was assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da/dN -$\delta $K in Region II, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It was assumed that the fatigue crack growth rate da/dN is rapid in proportion to descending temperature in Region II and the cryogenic-brittleness greatly affect a material with decreasing temperature.