• Korean Journal of Metals and Materials
• /
• v.48 no.4
• /
• pp.342-346
• /
• 2010

Pd nanoparticles (NPs) were successfully functionalizedon the surfaces of single-walled carbon nanotubes (SWNTs) by dendrimer-mediated synthesis. The hydrogen sensing properties of the Pd NPs functionalized SWNTs were investigated. Pd NPs-dendrimer-SWNTs sensors show much better speedsand superior recovery rates but lower sensitivity compared to Pd NPs-functionalized SWNTs directly fabricated due to the existence of dendrimers. Pyrolysis of the dendrimers by heat treatment resulted in a fast response time and high sensitivity owing to the reduced length of the dendrimers. These results demonstrate that the heat treatment of dendrimers in Pd NPs-dendrimer-SWNTs sensors can enable significant electrical conductance modulation upon exposure to extremely low concentrations (10 ppm) of hydrogen gas ($H_2$) in air.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2012.05a
• /
• pp.488-490
• /
• 2012

Nowadays QoS / QoE using technology as part of HTTP, dynamic adaptive streaming technology that became a big issue. In this paper, using HTTP, dynamic adaptive streaming technology is introduced. This dynamic adaptive streaming using HTTP-based system design and implementation. In this system, a number of MPEG2-TS file bitrate's conversion of image quality, a certain amount of time by the division of Segment, standing before the final note of the files that are used in transmission MPD (Media Presentation Description) File creation and streaming between servers and clients using HTTP to a dynamic and adaptive network environment consists of bitrate's streamers. In a network environment in which an unspecified number of seamless continuous playback of video streaming for a variety of sectors and will be utilized in the field of multimedia.

• Journal of Digital Convergence
• /
• v.13 no.11
• /
• pp.141-148
• /
• 2015

In this paper, for developing and implementing the HLS(Http Live Streaming) transmitter based embedded linux which is operated easily and cheap and lower power, portable in all networks and client environments compared to exist video live streaming transmitters. We design the developed HLS transmitter hardware using the Arm11 core and then porting the Embedded Linux OS(Operating System) and implementing the HLS protocol using the open source FFmpeg and Segmenter. For proving the performance of developed HLS transmitter, we make the testing environment for testing the performance of HLS transmitter including the notebook, iPhone, android Phone, Notebook and then analysis the received video in the client displayer. In this paper, we suggest the developed HLS transmitter performance data values higher than the Apple company's HLS recommended specification values and the picture of developed HLS transmitter operation in the testing environment. The application field of this paper result is that the man who works in the emergency situation take HLS and transmit the live emergency situation to the head quarter using this portable HLS.

• Korean Chemical Engineering Research
• /
• v.49 no.3
• /
• pp.352-356
• /
• 2011

In this paper, we prepared new type of hydrophilic block copolymers that exhibit the long-ranged lateral ordering in thin film. It was previously demonstrated that poly(ethyleneoxide-b-styrene) and poly(ethyleneoxide-b-metharylate-b-styrene) block copolymer thin films have a high degree of lateral ordering after solvent annealing process. In these cases, the relative humidity plays an important role in long-ranged lateral ordering. However, the origin of the humidity effect on the orders of these hydrophilic block copolymers is not fully understood. To investigate the effect of the humidity further, we prepared other hydrophilic poly(N,N-dimethylacrylamide-b-styrene)(PDMA-b-PS) block copolymers via RAFT polymerization. As with PEO-containing block copolymers, PDMA-b-PS block copolymers exhibit the long-ranged lateral ordering after solvent annealing process.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.51 no.6
• /
• pp.273-284
• /
• 2002

In this paper, computer simulations of the physical Phenomena occurring in the arc region before and after current zero were carried out to evaluate the dielectric recovery characteristics of two types of double-flow nozzles. A commercial CFD Program "PHOENICS" is used for the simulation and the user-coded subroutines to consider the arcing phenomena were added to this program by the authors. The computed results were verified by the comparison with the test results presented by the research group of BBC. In order to investigate the state of the arc region after current zero, the simulation was carried out with four steps. They are cold gas flow analysis, steady state arc simulation, transient arc simulation before current zero, transient hot gas flow simulation after current zero. The semi-experimental arc radiation model is adapted to consider the radiation energy transport and Prandtl′s mixing length model is employed as the turbulence model. The electric field and the magnetic field were calculated with the same grid structure used for the simulation of the flow field. The streamer criterion was introduced to evaluate the dielectric recovery characteristics after current zero. Compared with the results obtained by assuming the current zero state in the former studies, it has been found that the results obtained by considering the state before current zerowere more accurate.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.16 no.2
• /
• pp.59-64
• /
• 2002

This paper analyzed the effect of ribs on the breakdown characteristics when a metallic particle attaches on the various spot of GIS spacer, using electric field analysis. Also, it was compared with the experimental result of breakdown voltage characteristics for the spacer with a metallic particle on its various spot and with the shape, the length, and the thickness of the ribs varying. The results of electric field analysis show that the electric field concentration of the rib is more weakened than other parts and therefore it restrains the proceeding of streamer, which occurs at the breakdown. And it is verified through experiments that the breakdown voltage of the spacer with rib is higher than that of the spacer without rib. The breakdown characteristics depend on the shape, the length, and the thickness of the rib as well. Also, it is confirmed by the electric field analysis and the experimental results that the electric breakdown characteristics could be improved by rounding the rib edge.

• Korean Journal of Optics and Photonics
• /
• v.9 no.3
• /
• pp.199-204
• /
• 1998

To increase the storage density in hologram recording, a simple scheme to obtain rotational, angular and spatial multiplexing efficiently at the same time is proposed and experimented. Both rotational multiplexing and angular multiplexing are obtained by controlling the reference beam directly by use of a pair of wedge prisms, while spatial multiplexing is obtained by shifting the recording medium in the recording plane. It is possible to get both an acute-angle geometry, in which the angle between the signal and reference beams is less than 90$^{\circ}$, and a 90$^{\circ}$ geometry, in which the angle is approximately 90$^{\circ}$. In experiment, 180 holograms were multiplexed with an acute-angle geometry where a photopolymer was used for the recording medium, and 147 holograms with 90$^{\circ}$ geometry where a Fe-doped LiNbO$_3$ crystal was used. The proposed scheme makes it easy it easy to realize a practical holographic memory system by simplifying the control of three complex mechanical motions that are necessary for the three multiplexing techniques.

• Journal of the Korean Chemical Society
• /
• v.40 no.1
• /
• pp.11-19
• /
• 1996

The cationic polymerization of energetic substituted oxetanes which have pendant energetic group such as azido and nitrato are investigated theoretically, using semiempirical HF/3-21G, MINDO/3, MNDO and AM1 method. The stereo- and electronic structure of binary molecular complex composed of energetic substituted oxetane and boron trifluoride can be explain by molecular orbital theory. The reactivity of propagation in the copolymerization of oxetanes can be presented by the positive charge on carbon(C2) atom of oxetane and energy level of the lowest unoccupied molecular orbital(LUMO) of propagating species of oxetanes. The reactivity ratios for copolymerization of oxetanes are a random copolymer-zation which is agree with MO calculated and experimental results. The relative equlibrium concentration of cyclic oxonium and open carbenium ions is found to be a major determinant of mechanism, owing to the rapid equilibrium of these cation forms and the expectation based on calculation that in the prepolymer propagation step, SN1 mechanism will be at least as fast as that for SN2 mechanism.

• Journal of the Korean Chemical Society
• /
• v.35 no.6
• /
• pp.636-644
• /
• 1991

The cationic polymerization of substituted oxethanes which have pendant energetic groups such as methoxy, azido, and nitrato are investigated theoretically using the semiempirical MINDO/3, MNDO, and AM1 methods. The nucleophilicity and basicity of substituted oxethanes can be explained by the negative charge on oxygen atom of oxetanes. The reactivity of propagation in the polymerization of oxetanes can be represented by the positive charge on carbon atom and the low LUMO energy of active species of oxetanes. The reaction of the energetic cyclic oxonium ion forms to the open chain carbenium ion forms is expected by computational stability energy of the oxonium and carbenium ion (about 10~20 kcal/mole) favoring the carbenium ion. The relative equilibrium concentration of cyclic oxonium and open carbenium ions is found to be a major determinant of mechanism, owing to the rapid equilibrium of these cation forms and the expectation based on clauclation that the prepolymer propagation step SN1 mechanism will be at least as fast as that for SN2 mechanism.

• Korean Institute of Interior Design Journal
• /
• v.25 no.4
• /
• pp.51-59
• /
• 2016

Recent modern architecture shows a lot of cases that introduce natural light in indoor space, arousing diverse emotions within a minimal space by means of changes in the light. There are various causes for the background of these streams of times, and it may be said that pursuing the relationship between natural phenomena and space, using changes in light, is an important factor among them. This is closely linked to the raise of phenomenological architecture. In the case of Japan, there are many cases where the architectural language connected to the traditional architecture has been restructured to fit to modern architectural technique. The modern reinterpretation and development of the Japanese traditional effect of light and its meaning can be seen in cases of Kuma Kengo and Tadao Anndo. Of the modern architects that have used the appearance of spatial concept of light in Japanese architectural space, Kengo Kuma shows his attempt at finding identity in his designs through the acceptance and modern reinterpretation of orientalism of nature, along with the traditional and regional interpretation through materials and ways construction. It is his use oh light input used in traditional Japanese settings that have differentiated his work. On this, the present thesis intends to analyze and synthesize what impressions Kengo Kuma's unique methods of light production create in the formation of users' spatial perception, how the unique encounter of light and materials seems to perceivers, and the characteristics of his light production and expression that harmonize space, human, and nature in the visual and perceptual experience of space;