• Journal of Information Display
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• v.9 no.2
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• pp.18-21
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• 2008

We report on white organic light-emitting diodes (WOLEDs) based on single white dopants, $Ir(pq)_2$($F_2$-ppy) and $Ir(F_2-ppy)_2$(pq), where $F_2$-ppy and pq are 2-(2,4-difluorophenyl) pyridine and 2-phenylquinoline, respectively. The similar phosphorescent lifetime of two ligands lead to luminescence emission in two ligands simultaneously. However, the emission color of the devices was reddish, because the energy was not transferred efficiently from the 4,4,N,N'-dicarbazolebiphenyl (CBP) to the $F_2$-ppy ligand, due to the small band gap of the CBP. Accordingly, we used 1,4-phenylenesis(triphenylsilane) (UGH2) with a large band gap, instead of CBP as the host material. As a result, it was possible to adjust the emission color by the host material. The luminous efficiency of the device with $Ir(F_2-ppy)_2$(pq) doped in UGH2 was about 11 cd/A at 0.06 cd/$m^2$.

• Journal of the Korean Ceramic Society
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• v.35 no.7
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• pp.757-763
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• 1998

The effect of {{{{ {Ga }^{3+ } }} addition on the photoluminescence and cathodoluminescence of {{{{ {SrTiO}_{3 } }}:{{{{ { Pr}^{3+ } }} was stu-died by performing the excitation emission and decay time measurements. Addition of {{{{ {Ga }^{3+ } }} in {{{{ {SrTiO}_{3 } }}:{{{{ { Pr}^{3+ } }} resulted in a considerable enhancement of {{{{ { Pr}^{3+ } }} emission intensity. From the analysis of the experimental results the following mechanism is proposed. Excitation in the {{{{ {SrTiO}_{3 } }} host lattice leads to the formation of electrons in the conduction band and holes in the valence band. The electrons in the conduction band re-combine radiatively with the holes trapped at {{{{ { Ga}^{3+ } }} and the energy is transferred to {{{{ { Pr}^{3+ } }} ion which give its own characteristic red emission.

• Journal of Electrochemical Science and Technology
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• v.7 no.1
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• pp.52-57
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• 2016

Nanoporous-layer-covered TiO₂ nanotube arrays (Type II TNTs) were fabricated by two-step electrochemical anodization. For comparison, conventional TiO₂ nanotube arrays (Type I TNTs) were also prepared by one-step electrochemical anodization. Types I and II TNTs were detached by selective etching and then transferred successfully to a transparent F-doped SnO₂ (FTO) substrate by a sol-gel process. Both FTO/Types I and II TNTs allowed front side illumination to exhibit incident photon-to-current efficiencies (IPCEs) in the long wavelength region of 300 to 750 nm without the absorption of light by the iodine-containing electrolyte. The Type II TNT exhibited longer electron lifetime and faster charge transfer than the Type I TNT because of its relatively fewer defect states. These beneficial effects lead to a high overall energy conversion efficiency (5.32 %) of the resulting dye-sensitized solar cell.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.476-483
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• 2003

A mathematical model is presented to predict the two-phase flow and heat transfer phenomena of the evaporating extended meniscus region in a micro-channel. The pressure difference at the liquid-vapor interface can be obtained by the augmented Laplace-Young equation. The correlative equations for film thickness, pressure, and velocity in the meniscus region are derived by applying the mass, momentum, and energy equations into the control volume. The results show that increasing the heat flux and the liquid inlet velocity cause the length and liquid film thickness of the extended meniscus region to decrease. The variation, however, of the heat flux and liquid inlet velocity has no effect on the profile of film thickness. The majority of heat is transferred through the thin film region that is a very small region in the extended meniscus region. It is also found that the vapor velocity increases gradually in the meniscus region. However, it increases sharply at the junction of the meniscus and thin film regions.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1491-1498
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• 2003

Droplet evaporation can be used to transfer large amounts of energy since heat is transferred across a thin liquid film. Spreading the drop over a larger area can enhance this heat transfer. One method of accomplishing this is to dissolve gas into the liquid. When the drop strikes the surface, a gas bubble nucleates and can grow and merge within the liquid, resulting in an increase in the droplet diameter. In this study, time and space resolved heat transfer characteristics for a single droplet striking a heated surface were experimentally investigated. The local wall heat flux and temperature measurements were provided by a novel experimental technique in which 96 individually controlled heaters were used to map the heat transfer coefficient contour on the surface. A high-speed digital video camera was used to simultaneously record images of the drop from below. The measurements to date indicate that significantly smaller droplet evaporation times can be achieved. The splat diameter was observed to increase with time just after the initial transient dies out due to the growth of the bubble, in contrast to a monotonically decreasing splat diameter for the case of no bubbles. Bursting of the bubble corresponded to a sudden decrease in droplet heat transfer.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.3
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• pp.236-241
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• 1996

This paper presents a new eddy current testing system for inspecting tubes of steam generator in nuclear power plant. The proposed system adopted embedded expert system concept to automate tasks of the inspection such as inspection planning and flaw signal interpretation, and integrated all the tasks into a client/server type computing architecture using database management system. Therefore, human factor errors occurred during inspection could be minimized and the inspection data could be transferred in real-time. As a result, we can increase the level of inspection confidence and the productivity of a personal inspector. A prototype of the proposed system has been developed for 5 years and the test operation has been performed in domestic nuclear power plants.

• Journal of the Korean Society of Industry Convergence
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• v.3 no.3
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• pp.219-228
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• 2000

In order to evaluate the applicability of thermosyphon as an equipment of heat transfer to the case where natural of low temperature and low density is necessary and to propose the possibility of using natural energy being clean and inexhaustible, a thermosypon using methanol as working fluid was constructed and its transfer characteristics were analysed. The wall temperature of the thermosyphon was maintained relatively uniform after rapid increase until after being heated about ten minutes regardless of the level of input powers to the evaporating section. Inner pressure of the thermosyphon increased rapidly until after ten minutes, and then increased slowly depending on the level of input power. But heat transfer coefficient of the condensible section decreased in inverse proportion to input powers of 250~300W, showing $1008.3{\sim}829.8W/m^2{\cdot}^{\circ}C$. For the input powers of the thermosyphon within the range of 100~250W, heat transferred and heat flux increased relatively linearly showing, in the case of input powers of 250~300W, heat transfer efficiency considerable increased, showing 63.8%.

• Journal of Sensor Science and Technology
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• v.25 no.2
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• pp.131-137
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• 2016

In this study, a multilevel visible light communication (VLC) system based on resistor ladder circuit is designed to transmit medical data. VLC technology is being considered as an alternative wireless communication due to various advantages such as ubiquity, license free operation, low energy consumption, and no radio frequency (RF) radiation characteristics. With VLC even in places where traditional RF communication (e.g., Wi-Fi) is forbidden, significant bio-medical signal including the electrocardiography (ECG) and photoplethysmography (PPG) data can be transmitted. More lives could be saved anywhere by this potential advantage of VLC with a fast emergency response time. A multilevel transmission scheme is adopted to improve the data capacity with keeping simplicity, where data transmission rate can increase by log2m times (m is the number of voltage levels) than that of conventional VLC transmission based on on/off keying. In order to generate multi-amplitudes, resistor ladder circuit, which is a basic principle of digital to analog convertor, is employed, and information is transferred through LED (Light-Emitting Diode) with different voltage level. In the receiver side, multilevel signal is detected by optical receiver including a photo diode. Then, the collected data are analyzed to serve the necessary medical care to the concerned patient.

• Plant Biotechnology Reports
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• v.5 no.1
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• pp.35-43
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• 2011

This communication describes for the first time an efficient and reproducible protocol for large-scale multiplication of Bambusa nutans. Nodal segments collected from field-grown clumps and cultured on Murashige and Skoog (MS) medium supplemented with $4.4{\mu}M$ benzylaminopurine (BA) and $2.32{\mu}M$ kinetin (Kin) gelled with 0.2% gelrite yielded 80% aseptic cultures with 100% bud-break. The in vitro-formed shoots obtained after bud-break were successfully multiplied in MS liquid medium supplemented with $13.2{\mu}M$ BA, $2.32{\mu}M$ Kin, and $0.98{\mu}M$ indole-3-butyric acid (IBA). Sub-culturing of shoots every 3 weeks on fresh multiplication medium yielded a consistent proliferation rate of 3.5-fold. Shoot clusters containing three to five shoots were successfully rooted with 100% success on half-strength MS liquid medium supplemented with $9.8{\mu}M$ IBA, $2.85{\mu}M$ indole-3-acetic acid (IAA), $2.68{\mu}M$ naphthaleneacetic acid (NAA), and 3% sucrose. Plantlets grown in vitro were acclimatized and subsequently transferred to the field. Inter-simple sequence repeat analysis has confirmed the genetic uniformity of the tissue-cultured plants up to 27 passages.

• International Journal of Automotive Technology
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• v.8 no.1
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• pp.67-73
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• 2007

This study analyzes the interior noise that is generated during acceleration of a passenger car in terms of car body structure and panel contribution. According to the transfer method, interior noise is classified into structure-borne noise and air-borne noise. Structure-borne noise is generated when the engine's vibration energy, an excitation source, is transferred to the car body through the engine mount and the driving system and the panel of the car body vibrates. When structure-borne noise resonates in the acoustic cavity of the car interior, acute booming noise is generated. This study describes plans for improving the car body structure and the panel form through a cause analysis of frequency ranges where the sound pressure level of the rear seat relative to the front seat is high. To this end, an analysis of the correlation between body attachment stiffness and acoustic sensitivity as well as a panel sensitive component analysis were conducted through a structural sound field coupled analysis. Through this study, via research on improving the car body structure in terms of reducing rear seat noise, stable performance improvement and light weight design before the proto-car stage can be realized. Reduction of the development period and test car stage is also anticipated.