• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.343-344
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• 2007

Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350 nm was illuminated on the surface of a-Se with thickness of $400\;{\mu}m$. The measured transit times of hole and electron were about $8.73\;{\mu}s\;and\;229.17\;{\mu}s$, respectively. The experimental results showed that the hole and electron drifting mobility were $0.04584\;cm^2V^{-1}S^{-1}\;and\;0.00174\;cm^2V^{-1}s^{-1}\;at\;10\;V/{\mu}m$.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.5
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• pp.139-146
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• 2008

Wireless sensor network-related application system can perform functions such as environmental pollution monitoring, building control, home automation in future. In this paper, we present wireless sensor network based system for subway station in order to reduce the damage of the people and the subway station due to fire. Sensor nodes in this system can sense temperature, illumination, smoke, and human body in real time and detect the accident in the subway station. These real-time sensing and wireless networking minimize casualties and damage to property.

• Bulletin of the Korean Chemical Society
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• v.18 no.5
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• pp.519-522
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• 1997

A series of new ligands having convergent dicarboxylic acid functions, based-upon Rebek's cleft-type ionophore, have been prepared and their ion binding properties were investigated by the competitive extraction and transport experiments. The main purpose of the modification was to increase the lipophilicity of the Rebek's ionophore, which was attempted by utilizing propyl analog of Kemp's triacid or by changing the bridging unit. Ionophores 5 and 6 were found to have a pronounced ion-binding property toward Ca2+ ion. The selectivity in competitive extraction of ionophore 5 at pH 9 for Ca2+ over Mg2+ and Sr2+ is 2.0 and 59.3, respectively. The selectivity in competitive transport of ionophore 5 for Ca2+ over Mg2+ and Sr2+ is 29.8 and 99.3, and that of ionophore 6 is 10.0 and 23.2, respectively.

• Journal of the Korean Institute of Navigation
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• v.8 no.1
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• pp.1-16
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• 1984

The economical property of a shipping enterprise, as well as other transportation industries, is determined by the difference between the freight earned and expense paid. This study can be regarded as a division of optimizing ship allocation to routes under the integrated port transport system. Fleet planning and scheduling require complicated allocations of cargoes to ships and ships to routes in order to optimize the given criterion function for a given forecast period. This paper deals with the optimum ship allocation problem minimizing the operating cost of ships in a shipping company. Optimum fleet operating for a shipping enterprise is very important, since the marine transportation is a form of large quantity transport requiring long-term period, and there is a strong possibility to bring about large amount of loss in operation resulting from a faulty ship allocation. Where there are more than one loading and discharging ports, and a variety of ship's ability in speed, capacity, operating cost etc., and when the amount of commodities to be transported between the ports has been determined, then the ship's schedule minimizing the operating cost while satisfying the transport demand within the predetermined period will be made up. First of all a formula of ship allocation problems will be established and then will be constructed to solve an example by the Integer Programming application after consideration of the ship's ability, supply and demand of commodity, amount of commodity to be transported, operating costs of each ship etc. This study will give good information on deciding intention for a ship oprator or owner to meet the computerization current with shiping management.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.93-97
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• 2022

We report highly efficient quantum dot light-emitting diodes (QLEDs) with TiO₂ nanoparticles (NPs) as an alternative electron transport layer (ETL) and poly (methyl methacrylate) (PMMA) as an insulating layer. TiO₂ NPs were applied as ETLs of inverted structured QLEDs and the effect of the addition of PMMA between ETL and emission layer (EML) on device characteristics was studied in detail. A thin PMMA layer supported to make the charge balance in the EML of QLEDs due to its insulating property, which limits electron injection effectively. Green QLEDs with a PMMA layer produced the maximum luminance of 112,488 cd/m² and a current efficiency of 25.92 cd/A. We expect the extended application of TiO₂ NPs as the electron transport layer in inverted structured QLEDs device in the near future.

• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.567-572
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• 2011

A sensitivity analysis of the methods used to evaluate the transport properties of a CdZnTe detector was performed using two different radiations (${\alpha}$ particle and gamma-ray) emitted from an $^{241}Am$ source. The mobility-lifetime products of the electron-hole pair in a planar CZT detector ($5{\times}5{\times}2\;mm^3$) were determined by fitting the peak position as a function of biased voltage data to the Hecht equation. To verify the accuracy of these products derived from ${\alpha}$ particles and low-energy gamma-rays, an energy spectrum considering the transport property of the CZT detector was simulated through a combination of the deposited energy and the charge collection efficiency at a specific position. It was found that the shaping time of the amplifier module significantly affects the determination of the (${\mu}{\tau}$) products; the ${\alpha}$ particle method was stabilized with an increase in the shaping time and was less sensitive to this change compared to when the gamma-ray method was used. In the case of the simulated energy spectrum with transport properties evaluated by the ${\alpha}$ particle method, the peak position and tail were slightly different from the measured result, whereas the energy spectrum derived from the low-energy gamma-ray was in good agreement with the experimental results. From these results, it was confirmed that low-energy gamma-rays are more useful when seeking to obtain the transport properties of carriers than ${\alpha}$ particles because the methods that use gamma-rays are less influenced by the surface condition of the CZT detector. Furthermore, the analysis system employed in this study, which was configured by a combination of Monte Carlo simulation and the Hecht model, is expected to be highly applicable to the study of the characteristics of CZT detectors.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.398-399
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• 2003

의복 쾌적감은 착용자가 환경변화에 대하여 쾌적한 감정을 갖는 것을 의미한다. 직물의 쾌적성은 접촉감 뿐만 아니라 공기, 열, 수분을 전달하는 직물의 물리적 특성과 관계가 있는데 특별히 직물의 표면특성과 관련하여 변화하는 쾌적인자는 온냉감과 열, 수분 및 공기전달성이다. 따라서 직물의 표면 형태 및 두께에 따라 열, 수분 및 공기전달 특성은 달라질 뿐만 아니라 인체에 접촉하였을 때 접촉면적이 달라지므로 촉감에 큰 영향을 미친다. 본 연구에서는 의복의 쾌적성 향상의 중요한 인자로 대표적인 직물의 역학 특성과 열 및 수분전달특성을 직물 구성사의 단면형상을 달리하였을 때의 그 상관 관계에 대하여 알아보았다. (중략)

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.3-4
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• 2002

The stainless steel sheathed MgB$_2$ tapes with Cu addition were fabricated by PIT method without heat treatment. The $J_{c}$ value of 5,600 A/ $cm^{2}$and 16,000 A/$cm^{2}$ at 4.2 K and 5 T were obtained for the $MgB_{2}$ tape and 10 vol % of Cu added $MgB_{2}$ tape respectively. The $J_{c}$-B curve shows enhancement in J$_{c}$ under magnetic field, which suggests enhancement in flux pinning property with Cu addition.n.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.274-286
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• 2003

Numerical simulations are performed to investigate the turbulent convective heat transfer of the supercritical carbon dioxide flows in vertical and horizontal square ducts. The gas cooling process at the supercritical state experiences a sudden change in thermodynamic and transport properties. This results in the extraordinary variations of the heat transfer coefficients in the supercritical state, which are much different from those of single or two phase flows. Algebraic second moment closure which can include the effects of large thermophysical property variations of carbon dioxide and of buoyancy is employed to model the Reynolds stresses and turbulent heat fluxes in the governing equations. The previous correlations for the turbulent heat transfer coefficient for the supercritical carbon dioxide flows couldn't reflect the buoyancy effect. The present results are used to establish a new heat transfer coefficient correlation including the effects of large thermophysical property variation and buoyancy on in-duct cooling process of supercritical carbon dioxide.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.184-189
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• 1995

The electrical property of ultra thin PVA films(several hundreds .angs.-several .mu.m in thickness) formed by sphere bulb blowing technique, has been studied. The electrical conductivity of relatively thick films(>several thousands .angs.) has been very high and enhanced by the exposure either to high humidity of air or $NH_3$, which can be explained in terms of the role of ionic transport. The use of PVA films as NH$_{3}$ sensor is also proposed. In ultra thin PVA films less than 1500.angs., two conducting states ; high conducting and low conducting states, are observed. The nonlinear current-voltage characteristics in the low conducting state and the switching between these two states are also confirmed. These properties are discussed in terms of electronic conduction processes. The breakdown strength of the ultra thin PVA film is found to be very high(-30MV/cm), supporting the electron avalanche process in a thick polymer films.