• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.221-221
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• 2010

본 실험에서는 축전결합형 고주파 플라즈마와 $BCl_3$와 He의 혼합가스를 이용하여 화합물 반도체인 GaAs와 AlGaAs의 건식식각에 대해 연구하였다. 공정변수로는 첫째, BCl3와 He의 혼합가스 비율을 0%에서 100%까지 변화시켰다. 둘째, 고주파 파워를 50 W에서 200W 까지 변화를 주었고, 셋째, 공정압력을 120 mTorr~300 mTorr 까지 변화시켰다. 식각 실험을 마친 시료는 표면 단차 측정기와, 주사전자현미경을 이용하여 식각률과 선택비, 표면거칠기, 표면형상에 대하여 분석을 진행하였다. 또한, 광학발광분석계 (OES)를 이용하여 건식식각 실험 중 혼합가스에 의해 발생하는 플라즈마의 발광특성에 대한 실시간 분석을 하였다. 결과에 따르면, 1) 혼합가스에서 He의 비율이 20%일 때 GaAs와 AlGaAs 시료의 식각율이 $0.7\;{\mu}m/min$ 와 $0.6\;{\mu}m/min$ 로 가장 높게 나타났다. 2) 감광제에 대한 시료의 선택비 또한 동일 조건에서 GaAs의 경우 1 : 12, AlGaAs의 경우 1:8로 가장 높게 나타났다. 3)고주파 파워의 변화에 따른 식각률의 경우 100 W에서 GaAs 의 경우 $0.6\;{\mu}m/min$, AlGaAs의 경우 $0.5\;{\mu}m/min$ 이었고, 고주파 파워가 증가할수록 식각률은 감소하였다. 4) 감광제에 대한 시료의 식각 선택비의 경우 50 W에서 GaAs 시료가 1:14, AlGaAs 시료가 1:10으로 가장 높은 선택비를 보였고 고주파 전원이 증가할수록 선형적으로 감소하였다. 5) 표면거칠기는 50~100 W 구간에서는 1.0~1.5 nm 으로 큰 증가폭이 없다가 150 W 이상에서는 3.0~5.0 nm 으로 증가하였다. 반응기의 압력이 120 mTorr에서 300 mTorr로 변화할 때 식각률과 선택비는 비교적 선형적으로 감소하였으며, 표면거칠기 또한 증가하였다. 결론적으로 $BCl_3/He$ 고주파 플라즈마에서 약 20%의 He을 포함하고 있을 때 가장 우수한 건식 식각 결과를 얻었다.

• Journal of Energy Engineering
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• v.20 no.4
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• pp.303-308
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• 2011

The present study has been carried out to predict the heat transfer characteristics of reverse heat loss method for a residential refrigerator by using numerical analysis and corresponding experiment. From the measured values of temperature and heat input, one can conclude that, the temperature inside the refrigerator has a nearly linear relationship with heat input. The effect of gasket heat loss was examined with the change of thermal conductivity of gasket region. The appropriate thermal conductivity of gasket region was acquired from the comparison of heat losses with the experimental result and numerical analysis. The result of calculated heat losses had accuracy within 1.8% error with the experimental result. With the selected thermal conductivity of gasket region, the effectiveness of reverse heat loss method was examined with the change of thermal conductivity of vacuum insulation panel.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.28-39
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• 2014

This paper reviews past literatures relevant to fire-resistance properties of high strength concrete and investigates spalling mechanism of high strength concrete in fire. First, literatures were reviewed on spalling occurrence and fire-resistance methods. Second, a chemical change of concrete components in an elevated temperature was presented. Finally, the mechanism of the spalling occurrence and spalling resistance were examined in terms of hybrid fiber content. The focus of the experimental study as part of this research is to investigate the effects of fire on the variation of thermal properties of high strength concrete, which tends to be used in super tall buildings. This experimental study was devised to investigate the fire-resistance performance of high strength concrete containing hybrid fibers. A total of 48 test specimens were exposed to high temperature ranging from $100^{\circ}C$ to $700^{\circ}C$, including room temperature (${\sim}20^{\circ}C$). Test results provide valuable information regarding fire-resistance properties of strength concrete with 100 MPa or greater.

• Journal of Digital Convergence
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• v.15 no.1
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• pp.355-362
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• 2017

The purpose of this study was to analyze the management behavior in patients with hypertension and diabetes through the total inspection of a specific rural area. Data was collected through self-administered questionnaires from May 19th to September 21st in 2014. As the result, Among 355 (36.6%) patients who were diagnosed with hypertension, 337 (94.9%) were currently undergoing treatment, and among 109 (11.2%) patients who were diagnosed with diabetes mellitus, 96 (80.1%) were currently undergoing treatment. Among the total of 211 people in hypertension potential risk group, 89 (42.2%) were diagnosed with hypertension, and among the total of 356 people in hypertension potential risk group, 78 (22.0%) were diagnosed with diabetes mellitus. In conclusion, from the results of the analysis, we suggest that effective national strategies for prevention and management for patients with hypertension and diabetes should be established and implemented.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.63-71
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• 2015

The objective of the present study is to investigate how elevated temperature ranging from $100^{\circ}C$ to $800^{\circ}C$ as well as room temperature affects the variation of mechanical properties of high strength concrete ($over\;f_{ck}=60MPa\;grade$). In this experiment, specimens were exposed for a period of $2^{\circ}C/min$ to temperatures of $20^{\circ}C$, $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$ $400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$, $700^{\circ}C$ and $800^{\circ}C$, respectively. Accordingly, the study investigated the fire resistance performance of high strength concrete mixed with composite fibers which composed with hybrid fibers and steel fibers. After cooling down to ambient temperature, the following basic mechanical properties were then evaluated and compared with reference values obtained prior to thermal exposure: (i) compressive strength in room temperature; (ii) residual compressive strength; (iii) Poisson's ratio; (iv) weight change; (v) SEM analysis & XRD analysis In addition, XRD and SEM Images analyses were performed to investigate chemical and physical characteristics of high strength concrete with composite fibers according to high temperature.

• The Journal of Korean Association of Computer Education
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• v.12 no.5
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• pp.49-62
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• 2009

The Extra-Curriculum in The Air and Correspondence High School(ACHS), which play a role as an organization of lifelong learning, has not been operating properly for lack of appropriate circumstances and also educational research. So this research applied the Extra-Curriculum on-line contents to ACHS as an example to search for the effective operation solution in ACHS Extra-Curriculum, and derived the implications which are necessary to class operation. According to the implications which are obtained by the analysis of the application result, selected the five main areas in Blended-Learning which are necessary to the operation of ACHS Extra-Curriculum, and developed the direct instruction model by blending the teaching-learning method and strategy which is suitable for the ACHS Extra-Curriculum. Finally, based on these research results, this research developed the Blended-Learning Teaching Model for ACHS Extra-Curriculum by reflecting the peculiarity of ACHS student and characteristics of Extra-Curriculum contents.

• Journal of Digital Convergence
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• v.12 no.5
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• pp.1-12
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• 2014

Recently, the need for non-stop service is increasing by the business mission-critical Internet banking, e-payment, e-commerce, home shopping, securities trading, and petition business increases, clustered in a single database of existing, redundant research on high-availability technologies related to technique, etc. is increasing. It provides an API based on the Active Log in addition to the technique of redundancy, ALTIBASE$^{TM}$ Log Analyzer (below, ALA), provides scalability and communication of the same model or between heterogeneous. In this paper, we evaluated the performance of ALA by presenting the design of the database system that you can use the ALA, to satisfy all the synchronization features high scalability and high availability, real-time.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1057-1060
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• 2008

For high performance concrete, due to its low water cement ratio (water binder ratio) and addition of mineral admixtures, pretty high autogenous shrinkage and thermal deformation occur at very early age of casting (especially before hardening). This may lead to early age cracking of HPC structures, and then may influence the durability of HPC. This paper has monitored the early age properties of HPC successfully by embedded FBG strain sensor. The results showed that the deformation increased rapidly within the first day after HPC casting. And its value is up to $85{\mu}{\varepsilon}$, which is the 30% of two-month deformation ($280{\mu}{\varepsilon}$). Considering the durability and permeability of HPC, the first-day deformation is pretty high and can not be neglected. Also the superior capability of FBG sensors such as continuity, stability and multiplexed technique etc, has been demonstrated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.632-638
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• 2011

This paper presents on-chip Design-for-Testability (DFT) circuit for radio frequency System-on-Chip (SoC) applications. The proposed circuit measures functional specifications of RF integrated circuits such as input impedance, gain, noise figure, input voltage standing wave ratio (VSWRin) and output signal-to-noise ratio (SNRout) without any expensive external equipment. The RF DFT scheme is based on developed theoretical expressions that produce the actual RF device specifications by output DC voltages from the DFT chip. The proposed DFT showed deviation of less than 2% as compared to expensive external equipment measurement. It is expected that this circuit can save marginally failing chips in the production testing as well as in the RF system; hence, saving tremendous amount of revenue for unnecessary device replacements.

• The Journal of the Acoustical Society of Korea
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• v.36 no.4
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• pp.238-246
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• 2017

High frequency ultrasound imaging typically suffers from low sensitivity due to the small aperture of high frequency transducers and shallow imaging depth due to the frequency-dependent attenuation of ultrasound. These limitations should be overcome to obtain high-frequency, high- resolution ultrasound images. One practical solution to the problems is a high-performance signal receiver capable of detecting a very small signal and amplifying the signal with minimal electronic noise addition. This paper reports a recently developed low-noise, wideband ultrasound receiver for high-frequency, high-resolution ultrasound imaging. The developed receiver has an amplification gain of up to 73 dB and a variable amplification gain range of 48 dB over an operating frequency of 80 MHz. Also, it has an amplification gain flatness of ${\pm}1dB$. Due to these high performances, the developed receiver has a signal-to-noise ratio of at least 8.4 dB and a contrast-to-noise ratio of at least 3.7 dB higher than commercial receivers.