• Fire Science and Engineering
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• v.20 no.3 s.63
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• pp.9-14
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• 2006

In this study boundary velocity which is one of the important boundary conditions for numerical simulation for subway station on fire are experimentally obtained. The tests were conducted according to its operating mode of the ventilation systems in the platform: smoke extraction ventilation mode in occurrence of fire and normal ventilation mode for air conditioning. Velocities are measured at various points on the platform. To examine smoke extraction and air supply capacity in the platform level, air velocities were checked on opening vents. Numerical analysis under normal ventilation mode without fire is conducted by using measured boundary conditions, and the numerical results are compared with the measured velocities on the platform.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.430-436
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• 2006

Polarization-independent $Ti:LiNbO_3\;2{\times}2$ optical add/drop multiplexer for the 1550nm wavelength region is fabricated. The device consists of two input waveguides, two polarization beam splitters. two polarization conversion/electrooptic tuning waveguide sections, and two output waveguides. The single mode channel waveguides for both TE and TM polarizations are fabricated on a x-cut $Ti:LiNbO_3$substrate by Ti diffusion. Spectral section is based on phase-matched polarization conversion due to shear strain induced by a thick $SiO_2$ grating overlay film. An applied voltage tunes the device by changing the waveguide birefringence, hence the optical wavelength at which most efficient polarization conversion occurs. Tuning rate of 0.094nm/V with a maximum range of 17nm has been obtained. The nearest side-lobe is about 8.2dB. The FWHM is 3.72nm.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.9 no.9
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• pp.721-736
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• 2019

In this paper, the behavior of the fire smoke due to the operation of the ventilation systems when the fire occurred in the underground station (6 basement floors) and the tunnel at the great depth was measured. Fire smoke was generated by using a smoke generator which realized heat buoyancy effect by using hot air blower. The two locations of the fire were selected on the platform and on the platform of the tunnel located outside the screen door. A ventilation mode is generally used in which smoke is exhausted through a vent hole provided in a platform when a platform fire occurs. The tests were performed by operating the exhaust through the ventilation holes of the tunnel part located at both ends of the platform. The smoke density and the wind speed/velocity were measured at various positions, and the videos were taken to analyze the movement and smoke of the smoke. In both cases for fire inside the platform and in the railway tunnel, due to the ventilation mode operation of the fan for the platform and the exhaust of the fans in the tunnel smoke were well exhausted and the smoke propagation to the area near the smoke zone was suppressed. The smoke-control mode, which is applied to both fans for the platform and fans for in the tunnel at both ends of the platform, can provide a safer evacuation environment to the passengers from the fire smoke when the platform fire or fire train stops.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.4 s.235
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• pp.469-476
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• 2005

Numerical modeling has been carried out to investigate the two-dimensional air flow in automobile interior with a forced exhaust close to main air inlet for typical ventilation modes. The characteristics such as streamlines and temperature fields in the passenger compartment room with the forced exhaust are analyzed with comparison of the cases without a forced exhaust. The simulation results show that air flow on the floor near the front seat is increased with the forced exhaust for all ventilation modes. Flow recirculation in the cabin is most active in mode 2 with a vertical suction inlet in comparison with other two modes. In particular, less time is taken for air temperature to reach the inlet temperature due to the forced exhaust for the ventilation modes. Finally, it could be predicted that ventilating air flow is much improved with the forced exhaust in the interior Modeling results in this study can be applied to the optimal design of automobile interior fur air ventilation system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.167-174
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• 2012

The circuits including with Optical transceiver and clock data recovery, in this paper, SERDES (SERializer-DESerializer) are implemented to construct a GE-PON burst-mode transceiver supporting IEEE 802.3ah and a jig for measuring the burst-mode characteristics, that is to say, PON upstream optical transmission environment are manufactured to evaluate the performance of transceiver. we verified that the limiting amplifier compensated the gap of max. 26dB optical power by experiments. The startup acquisition lock time is 670ns in case of using VSC7123 and 2300ns in case of S2060 and the data acquisition lock time were measured to be 400ns and 600ns, respectively, in the upstream channel transmission in this work. While on the other, VSC7123 is satisfied with IEEE802.3ah recommendations.

• Journal of the HCI Society of Korea
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• v.14 no.1
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• pp.35-43
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• 2019

This study examines how interactivity and usage mode of a chatbot interface affects user experience. Chatbot has rapidly been commercialized in accordance with improvements in artificial intelligence and natural language processing. However, most of the researches have focused on the technical aspect to improve the performance of chatbots, and it is necessary to study user experience on a chatbot interface. In this article, we investigated how 'interactivity' of an interface and the 'usage mode' referring to situations of a user affect the satisfaction, flow, and perceived usefulness of a chatbot for exploring user experience. As the result, first, the higher level of interactivity, the higher user experience. Second, usage mode showed interaction effect with interactivity on flow, although it didn't show the main effect. In specific, when interactivity is high in usage mode, flow was the highest rather than other conditions. Thus, for designing better chatbot interfaces, it should be considered to increase the degree of interactivity, and for users to achieve a goal easily through various functions with high interactivity.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.205-210
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• 2008

Magnetic hysteresis loops of a nickel strip and a Fe-Co alloy strip, which have been used in magnetostrictive strip type guided wave transducers for long range ultrasonic testing of pipelines, were measured and then magnetic property effects of a strip on transducer sensitivity were analyzed. The sensitivity of an optimized Fe-Co strip transducer was superior to that of the nickel strip transducer by a factor of about 30. It was shown that this was mainly attributed to the differences in remanence magnetization and coercivity of the two magnetostrictive materials.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.2 s.29
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• pp.169-172
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• 2007

This paper presents circuit models and control algorithms of distributed generation system(DGS) which consists of Z-type converter and PWM inverter. Z-type converter which employs both the L and C passive components and shoot-through zero vectors instead qf the conventional DC/DC converter in order to step up DC-link voltage. Discrete time sliding mode control with the asymptotic observer is used for current control. This system am be used for power conversion of DC renewable energy.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.335-338
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• 2009

The process of charging an oxidizer in the liquid propellant rocket can divide into the cooling of the oxidizer tank, the high flow charge, the small flow charge, and the replenishment charge for the correction of temperature. The oxidizer of the Naro(KSLV-I) first stage uses the liquid oxygen. And the flow rate and the temperature specification corresponding to each charge mode are presented for the requirement. The flow throttling valve and heat exchanger are installed in the oxidizer filling system in order to satisfy this kind of the flow rate and temperature requirement specification. In this research, by using the Flowmaster which is a commercial one-dimension thermo-fluidic analysis program, one dimensional flow system analyses was performed to predict the exact flow rate at each specific mode. Also, the flow rate correction sensitivity of the flow control valves was analytically determined to satisfy the flow condition refinement at each mode within the limited certification test.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.460-465
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• 2007

유출지하수는 지하공간이 깊고 넓게 분포하는 건물에서 자연적으로 유출되어 배출되는 낮은 심도의 지하수이다. 본 연구에서는 신축된 교회건물에서 유출되는 지하수를 열원으로 밀폐형태와 개방형태의 열교환기를 활용하여 각각 5RT급 히트펌프시스템을 난방모드로 운전한 결과를 정리하였다. 실험은 난방순환수의 온도를 $43{\sim}49$ $^{\cdot}C$ 범위에서 제어하면서 진행하였으며, 시스템 COP에 있어서 밀폐형은 $4.12{\sim}4.75$, 개방형은 $3.42{\sim}3.98$의 범위에서 측정되었다. 이는 기존의 지열히트펌프시스템의 COP와 대동 소이한 우수한 성능이라고 판단된다. 또한 펌프동력을 제외한 히트펌프 자체 난방COP에 있어서 밀폐형은 $4.69{\sim}5.81$, 개방형은 $4.38{\sim}5.43$의 범위에서 나타났다. 유출지하수의 온도가 겨울철에도 약 $12{\sim}14^{\cdot}C$를 유지하므로 히트펌프와 시스템전체의 COP가 매우 우수한 값을 나타내고 있음이 확인되었다.