• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.963-970
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• 2005

The dwell time and the passenger flow time are surveyed on the definition, affecting factors, several conclusions, and the forecasting models based on the regression. Also, the results of the field survey and analysis are presented for the congested subway stations in Seoul. It is claimed that the comprehensive research should be fulfilled on the passenger flow for the Korean case itself, since the results are quite different from the results from [1], Moreover, the result is a important factor for the economic assessment of construction or renewal of the rail line.

• 대한기계학회논문집B
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• 제24권11호
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• pp.1486-1496
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• 2000

The initial flame kernel development and flame propagation in a constant volume combustion chamber is analyzed by the heat release rate and the mass fraction burnt. The combustion pressure is measured with a piezoelectric type pressure sensor. In order to evaluate the effects of ignition system and ignition energy on the flame propagation, four different ignition systems are designed and tested, and the ignition energy is varied by the dwell time. Several different spark plugs are also tested and examined to analysis the effects of electrodes on flame kernel development. The results show that the when the dwell time is increased, and when the spark plug gap is extended, heat release rate and the mass burnt fraction are increased. The materials and shapes of electrodes affect the flame development, because they change the energy transfer efficiency from electrical energy to chemical energy. The diameter of electrodes influences not only the heat release rate but also the mass burnt fraction as well.

• 한국자동차공학회논문집
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• 제22권1호
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• pp.193-201
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• 2014

A numerical study has been carried out to analyze the combustion characteristics in heavy duty diesel engine with post injection for reducing NO emission. For verification of numerical study results, calculated cylinder pressure was matched to experimental data. In this study, post injection timing and amount of post injection were modified as parameters, but the total amount of injection fuel was maintained. As the results, maximum cylinder pressure increases above minimum 2% by post injection and end of pressure curve is decreased rapidly. The more dwell time and amount of post injection fuel are, the more pressure drop occurs. And trade-off relation of NO and soot are appeared. In the results, NO was reduced without deterioration of cylinder pressure under condition of $10^{\circ}$ CA dwell time and main 60%, post 40% fuel portion.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1885-1888
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• 2003

As high technology industries such as IT and display have developed, demand for application parts of micro lens and lens array has been extremely increasing. According to these trends, many researchers are studying on the fabrication technology for parts of the micro lens by a variety of methods such as MEMS, Lithography, LIGA and so on. In this paper, we have performed researches related to ultra precision micro lens, lens array mold and fabrication of Lenticular lens mold for three-dimensional display by using mechanical micro end-milling and fly-cutting fabrication method. Tools used in this research were a diamond tool of R 150$\mu\textrm{m}$. Cutting conditions set up feed rate, spindle revolution. depth of cut and dwell time as variables. And we analyzed surface quality variation of the processed products according to the cutting conditions, and then carried out experiments to search the optimum conditions. Through this research, we have confirmed that we can fabricate the ultra precision micro lens mold with surface roughness Ra=20nm and the holographic lens mold by using micro end-milling and fly-cutting fabrication method. Furthermore, we demonstrated problems happened in the fabrication of the micro lens and established the foundation of experimental study for formulating its improvement plan.

• 수산해양기술연구
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• 제51권4호
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• pp.576-582
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• 2015

The efficiencies of thermal power system using fossil fuel depend on heat exchangers which extract energy from the exhaust gas before it is expelled to the atmosphere. To increase heat transfer efficiency it is very important to maintain the surface of heat exchanger as clean condition. The accepted skill of cleaning of fouled surface of heat exchanger is soot blowing. A high pressure jet of air is forced through the flat surface of plate to remove the deposit of fouling. There is, however, little knowledge of the fundamental principles of how the jet behave on the surface and how the jet actually removes the deposit. Therefore, the study focuses on the measuring of cleaning area and cleaning dwell time after accumulating the simulated deposit on the flat surface. The deposit test rig was built for the study and simulated deposit material is used after measuring the physical property of the each material by shearing stress test. Much data was obtained for the analysis by the parameters change such as the different jet speed, different inner pressure and variable distance of the jet from the test rig surface. The experimental data was compared with the theoretical equation and most of the data matches well except some extreme cases.

• 한국재료학회지
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• 제25권10호
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• pp.571-576
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• 2015

The effects of coating thickness on the delamination and fracture behavior of thermal barrier coating (TBC) systems were investigated with cyclic flame thermal fatigue (FTF) and thermal shock (TS) tests. The top and bond coats of the TBCs were prepared by electron beam-physical vapor deposition and low pressure plasma spray methods, respectively, with a thickness ratio of 2:1 in the top and bond coats. The thicknesses of the top coat were 200 and $500{\mu}m$, and those of the bond coat were 100 and $250{\mu}m$. FTF tests were performed until 1140 cycles at a surface temperature of $1100^{\circ}C$ for a dwell time of 5 min. TS tests were also done until more than 50 % delamination or 1140 cycles with a dwell time of 60 min. After the FTF for 1140 cycles, the interface microstructures of each TBC exhibited a sound condition without cracking or delamination. In the TS, the TBCs of 200 and $500{\mu}m$ were fully delaminated (> 50 %) within 171 and 440 cycles, respectively. These results enabled us to control the thickness of TBC systems and to propose an efficient coating in protecting the substrate in cyclic thermal exposure environments.

• 한국세라믹학회지
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• 제52권5호
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• pp.361-365
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• 2015

Vanadium dioxide ($VO_2$) of monoclinic phase exhibits Metal Insulator Phase Transition (MIPT) phenomenon involving a sharp change in electrical and optical properties at $68^{\circ}C$. Solution-based process is applied to form uniform $VO_2$ coating layer on ceramic tiles. This can selectively block the near-infrared light to possibly reduce the energy loss and prevent dew condensation caused by the temperature difference. Heat treatment conditions including temperature and dwell time were examined to obtain a monoclinic $VO_2$ single phase. Both rutile and monoclinic $VO_2$ phases were observed from in the tiles post-annealed below $700^{\circ}C$. Desired monoclinic $VO_2$ single phase was grown in the tiles heat treated at $750^{\circ}C$. Nano facets of irregular size were observed in the monoclinic $VO_2$ phase involving the phase-transition. Grain growth of monoclinic $VO_2$ phase was observed as a function of dwell time at $750^{\circ}C$.

• 접착 및 계면
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• 제4권4호
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• pp.7-14
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• 2003

택(tack)은 아주 가벼운 힘으로 단시간에 피착체와 점착하는 능력이다. 택의 측정기기 중 프로브택(probe tack)은 실험적인 영향인자를 설정할 수 있기에 택의 이론적 고찰이 유리하다. SIS계 핫멜트형 점착제(SIS-based hotmelt PSA)와 수분산성 아크릴 점착제(Water-borne acrylic PSA)를 사용하여 probe가 점착제 표면에 다가가는 속도가 택에 미치는 영향을 살펴보았다.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1261-1270
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• 2022

This study was conducted to investigate the possibility of using gaze entropy to evaluate an operator's situation awareness in an emergency accident situation of a nuclear power plant. Gaze entropy can be an effective measure for evaluating an operator's situation awareness at a nuclear power plant because it can express gaze movement as a single comprehensive number. In order to determine the relationship between situation awareness and gaze entropy for an emergency accident situation of a nuclear power plant, an experiment was conducted to measure situation awareness and gaze entropy using simulators created for emergency accident situations LOCA, SGTR, SLB, and LOV. The experiment was to judge the accident situation of nuclear power plants presented in the simulator. The results showed that situation awareness and Shannon, dwell time, and Markov entropy had a significant negative correlation, while visual attention entropy (VAE) did not show any significant correlation with situation awareness. The results determined that Shannon entropy, dwell time entropy, and Markov entropy could be used as measures to evaluate situation awareness.

• 한국의학물리학회지:의학물리
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• 제28권2호
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• pp.39-44
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• 2017

This study aims to analyze dose distribution and treatment time of endobronchial brachytherapy (EBBT) by changing the position step size of the dwell position. A solid water phantom and an intraluminal catheter were used in the treatment plan. The treatment plans were generated for 3, 5, 7, and 10 cm treatment lengths, respectively. For each treatment length, the source position step sizes were set as 2.5, 5, and 10 mm. Three reference points were set 1 cm away from the central axis of the catheter, along the axis, for uniform dose distribution. Volumetric dose distribution was calculated to evaluate the dosimetric effect. The total radiation delivery time and total dwell time were estimated for treatment efficiency, which were increased with position step sizes. At half-life time, the differences between the position step sizes in the total radiation delivery time were 18.1, 15.4, 18.0, and 24.0 s for 3, 5, 7, and 10 cm treatment lengths, respectively. The dose distributions were more homogenous by increasing the position step sizes. The dose difference of the reference point was less than 10%. In brachytherapy, this difference can be negligible. For EBBT, the treatment time is the key factor while considering the patient status. To reduce the total treatment time, EBBT can be performed with 2.5 mm position step size.