• Korean Journal of Materials Research
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• v.25 no.6
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• pp.265-268
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• 2015

ZnO micro/nanocrystals at large scale were synthesized through the thermal evaporation of Al-Zn mixtures under air atmosphere. The effect of synthetic temperature and time on the morphology of the micro/nanocrystals was examined. It was found that the temperature and time affected the morphology of the ZnO crystals. At temperatures below $900^{\circ}C$, no crystals were synthesized. At a temperature of $1000^{\circ}C$, ZnO crystals with a rod shape were synthesized. With an increase in temperature from $1000^{\circ}C$ to $1100^{\circ}C$, the morphology of the crystals changed from rod shape to wire and granular shapes. As the time increased from 2 h to 3 h at $1000^{\circ}C$, tetrapod-shaped ZnO crystals started to form. XRD patterns showed that the ZnO crystals had a hexagonal wurtzite structure. EDX analysis revealed that the ZnO crystals had high purity. It is believed that the ZnO nanowires were grown via a vapor-solid mechanism because no catalyst particles were observed at the tips of the micro/nanocrystals in the SEM images.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.4
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• pp.23-30
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• 2001

In this paper, the discharge image of NO particles wire-cylinder type electrode in the discharge reactor where AC dielectric barrier type corona discharge occurred and horizontal and vertical signal intensity at each flourescence emission during discharge and the horizontal and vertical signal strength of NO particles at flourescence emission wavelength band[236[nm], 247[nm]], were measured were measured by ICCD Camera. In addition discharge images and signal intensities in accordance with discharge time were measured to figure out the discharge mechanism. It was found that the strongest horizontal and vertical signal intensity of NO particles were observed at 247[nm] band, but no big difference in the horizontal and vertical signal intensity in accordance with discharge time was seen. In particular, the phenomenon image occuring inside the discharge reactor and wavelength ware able to be carried based on the measured data.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.258-259
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• 2017

Recently, as science and technology is very growing, wire and wireless communication is merged and interconnected. Therefore, advanced internet technology allow all kinds of communication to integrate with heterogeneous device and sensors. The representative example is smart home network based on internet of things. Communication surroundings under IoT services are more complex. Conventional encryption techniques can't provide to IoT application because of its limited resources such as small memory capacity and low computing power. In this paper, we analyzed authentication procedure between home gateway and node in sensor under smart home network.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.1
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• pp.98-103
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• 2001

In this parer, the removal rate of NO in a reactor is rreasured first using nonthermal plasma generated from a wire-cylinder type reactor, then the discharge image and horizontal signal strength and vertical signal strength of NO particles is observed using ICCD(Intensified Charged Coupled Device) carrera It was fOlmd that NO rerroval rate was iflLTeased with NO concentration c1ecreasing, and that honzontal signal strength and vertical signal strength were also increased with NO concentration decreasing. Especially, this research is a1!Tffl at clarifying the discharge mechanism of NO particles by observing the images of AC discharge wnen the nonthermal plasma generated by an discharge was used.

• The KIPS Transactions:PartA
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• v.10A no.6
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• pp.691-700
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• 2003

Due to the fast development of wire&wireless internet and computer hardware, more and more internet services are being developed, such as Internet broadcast, VoD (Video On Demand), etc. So QoS (Qualify of Service) is essentially needed to guarantee the quality of these services. Traditional Internet is Best-Effort service in which all packets are transported in FIFO (First In First Out) style. However, FIFO is not suitable to guarantee the quality of some services, so more research in QoS router and QoS protocol are needed. Researched QoS router and protocol are high cost and inefficient because the existing infra is not used. To solve this problem, a new QoS control method, named Network Adaptive QoS, is introduced and applied to client/server-based streaming systems. Based on network bandwidth monitoring mechanism, network adaptive QoS control method can be used in wire&wireless networks to support QoS in real-time streaming system. In order to reduce application cost, the existing streaming service is used in NAQoS. A new module is integrated into the existing server and client. So the router and network line are not changed. By simulation in heavy traffic network conditions, we proved that stream cannot be seamless without network adaptive QoS method.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.1 s.343
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• pp.27-36
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• 2006

Conventional delay-insensitive (DI) data encodings usually require 2N+1 wires for transferring N-bit. To reduce complexity and power dissipation of wires in designing a large scaled chip, an encoder and a decoder circuits, where N-bit data transfer can be peformed with only N+l wires, are proposed. These circuits are based on a quasi delay-insensitive (QDI) model and designed by using current-mode multiple valued logic (CMMVL). The effectiveness of the proposed data transfer mechanism is validated by comparisons with conventional data transfer mechanisms using dual-rail and 1-of-4 encodings through simulation at the 0.25 um CMOS technology. In general, simulation results with wire lengths of 4 mm or larger show that the CMMVL scheme significantly reduces delay-power product ($D{\ast}P$) values of the dual-rail encoding with data rate of 5 MHz or more and the 1-of-4 encoding with data rate of 18 MHz or more. In addition, simulation results using the buffer-inserted dual-rail and 1-of-4 encodings for high performance with the wire length of 10 mm and 32-bit data demonstrate that the proposed CMMVL scheme reduces the D*P values of the dual-rail encoding with data rate of 4 MHz or more and 1-of-4 encoding with data rate of 25 MHz or more by up to $57.7\%\;and\;17.9\%,$ respectively.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.495-512
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• 2022

Due to the concentration of population in the city center, the aboveground structures are saturated, and the development of underground structures becomes important. In addition, it is necessary to apply the reinforcement construction method for the pillar part of the adjacent tunnel that can secure stability, economy, and workability to the site. In this study, the tunnel pillar reinforcement method using prestress and grouting was reviewed. There are various reinforcement methods that can compensate for the problems of the side tunnel, but as the tunnel pillar construction method using prestress and grouting is judged to be excellent in field applicability, stability, and economic feasibility, it is necessary to review the theoretical and numerical analysis of the actual behavior mechanism. Therefore, a scaled-down model experiment was conducted. The reduced model experiment was divided into PC stranded wire + steel pipe reinforcement grouting + prestress (Case 1), PC strand + steel pipe reinforcement grouting (Case 2), and no reinforcement (Case 3), and the displacement of the pillar and the earth pressure applied to the wall were measured. Through experiments, it was confirmed that the PC stranded wire + steel pipe reinforcement grouting + prestress method is the most excellent reinforcement method among various construction methods. It was judged that it could be derived.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.1
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• pp.63-70
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• 2017

In this paper, we design and fabricate a de-orbiter using drag-sail and evaluate deployment characteristics. Without employing an actuator to deploy, the de-orbiter is activated by the SMA wire based the release mechanism and driven by the restoring force of the tape-spring. For efficient storage and deployment of drag-sail, an origami method of original ISO flasher is chosen and low priced mylar film is used as the material of the drag-sail. In addition, through the fault tree analysis method which is one of the one-shot device reliability evaluation methods, we confirm the reliability of the de-orbiter(0.997572) and the Roller failure has the highest criticality. Finally, we find feasibility of the proposed de-orbiter through the deployment demonstration of drag-sail.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.2
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• pp.156-164
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• 2016

Qualification model(QM) of main payloads including concentrating photovoltaic system using fresnel lens, heating wire cutting type shockless holding and release mechanism, and MEMS-based solid propellant thruster have been developed for the STEP Cube Lab.(Cube Laboratory for Space Technology Experimental Project), which is a pico-class satellite for verification of core space technologies. In this study, we have verified structural safety and functionality of the developed payloads under a qualification temperature range through the QM thermal vacuum test. Additionally, a reliability of thermal model of the payloads has been confirmed by performing a thermal correlation based on the thermal balance test results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1919-1932
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• 1991

Experimental studies are conducted to investigate the Flow-Induced Vibration mechanism for cantilever plate model with the angle of attack (.alpha.=10.deg., 20.deg., 30.deg.). Research is divided into two parts. First, the flow fields around two dimensional flat plate model are investigated using LDV system. Second, the vortex shedding frequency and response spectra of cantilever plate are obtained experimentally using gap sensor and hot wire anemometer. Finite element method program was used in order to predict the flow field and pressure field around thin flat plate. And some predicted results were compared with the experimental data. The aspect ration of test model is d/t=25 (d; width, t; thickness). From the measurement of the flow field it was found that in the case of small inclined (.alpha.=10.deg., 20.deg.) relatively, the separated boundary layer at sharp leading edge developed smoothly downstream. With increasing the angle of attack of the plate, stagnation region was appeared on the back side of the plate and separated boundary layer was extended downstream. These trends are a good agreement with the computational results. It was found by analysis of response spectra of cantilever plate that the influences of vortex shedding frequency were important at the large of attack (.alpha.=30.deg.), and two peak values appear in entire test model at 24Hz, 150Hz.