• 설비공학논문집
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• 제15권3호
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• pp.177-186
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• 2003

In the present study, the flow characteristics of developing turbulent flows are investigated at the exit region of a square cross-sectional 180" curved duct with dimensions of 40mm$\times$40mm$\times$4000mm (height $\times$ width $\times$length). Smoke particles produced from mosquito coils were used as seed particles for the LDV measurement. Experiments were carried out to measure axial velocity profiles, shear stress distributions and entrance lengths by using an LDV system and Rotating Machinery Resolver RMR with PHASE software. Experimental results clearly show that the time-averaged Reynolds number does not affect oscillatory flow characteristics because the turbulent components tend to balance the oscillatory components in the fully developed flow region. Also, the velocity profiles are in good agreement with 1/7power law such as the results of steady turbulent flows. The turbulent intensity linearly increases along the walls and is slightly higher, especially in the period of deceleration. On the other hand, the LDV measurements show that shear stress values in slightly higher in the period of deceleration due to the flow characteristics in the exit region. The entrance length where flows become stable appears at the point that is 40 times the length of hydraulic diameter.eter.

• 한국정보전자통신기술학회논문지
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• 제5권3호
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• pp.117-126
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• 2012

논문에서는 극저속 영역 및 저속 영역에서 안정적이고 동특성이 우수한 벡터제어 시스템을 구성하여, 축소차원 상태관측기를 이용한 순시속도 관측기와 극저속 제어에 관한 방법을 제안하였다. 본 시스템에서 제안된 관측기는 축소차원 상태관측기를 부하토크 추정에 적용하여 속도추정에 이용함으로서 시스템구성을 간단히 구현하면서도 극저속 영역에서 정확한 순시속도 추정이 가능하였다. 또한, 시스템 잡음에 의한 영향을 줄이고, 관측기의 극을 변화시키는 일 없이 부하외란이나 모델화 오차, 측정 잡음 등에 강인한 유도전동기 속도제어 시스템을 제시하였다.

• 한국정밀공학회지
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• 제8권2호
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• pp.27-35
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• 1991

We propose the crack growth rate equation which applied over three regions (threshold region, stable region, unstable region) of fatigue crack propagation. Constant stress amplitude fatigue tests are conducted for four materials under three stress ratios of R=0.05, R=0.2 and R=0.4. Materials which have different mechanical properties i.e. stainless steel, low carbon steel, medium carbon steel and aluminum alloy are used. The fatigue crack growth rate equation is given by $da/dN={\beta} (1-R)^{\delta}\({\DELTA}K-{\DELTA}K_t)^{\alpha} / (K_{cf}-K_{max})$${\alpha}, {\beta}$ , and ${\delta}$ are constants, and ${\Delta}K_t$ is stress intensity factor range at low ${\Delta}K$ region. The constants are obtained from nonlinear least square method. $K_{ef}$is critical fatigue stress intensity factor. The relation between half crack length and number of cycles obtained by integrating the crack growth rate equation is in agreement with the experimental data. It is also experimented with constant maximum stress and decreasing stress ratios, and the fatigue growth rate of each material is in accord with the proposed equation.

• East Asian Economic Review
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• 제28권1호
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• pp.3-35
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• 2024

This paper utilizes social network analysis to examine the structural characteristics and trade dynamics of the renewable energy (hydropower, wind energy, and solar energy) trade network within the RCEP region from 2011 to 2020. The findings reveal: (1) The renewable energy trade network within the RCEP exhibits dynamism, heterogeneity, and an uneven development. The solar energy network is the most balanced and stable, while the wind energy network lags and shows marked fluctuations, with the hydropower network falling between these two. This demonstrates the diversity of energy trade within the region. (2) China, Singapore, and Japan are identified as the key exporting and importing countries, with Vietnam showing substantial growth potential. Individual analyses shed light on the stark disparities in trade status among nations, reflecting the diverse roles and future potential of member countries. (3) The QAP regression analysis reveals a significant influence of environmental pressure, particularly carbon dioxide emissions, on the renewable energy trade network. This study contributes to promoting environmental sustainability and energy security in the RCEP region and provides empirical evidence for global renewable energy trade strategies.

• 한국산림과학회지
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• 제94권6호
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• pp.377-386
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• 2005

김해시 상동면 매리 산사태지의 발생특성을 밝히기 위한 일련의 연구를 진행중에 있으며, 본보에서는 지반조사, 시추공내영상촬영, 탄성파탐사 및 실내시험 후 안정해석을 실시하였다. 안정해석결과, 영역 I 지역은 집중호우 시 땅밀림 산사태가 발생될 위험이 있으므로 계측기를 설치하여 지표의 변위발생을 모니터링하고, 변위가 발생될 경우 긴급복구가 필요한 지역으로 판단된다. 영역 II는 토사유실이 장기간 지속될 경우 붕괴(slope failure)가 예상되므로, 향후 지속적인 관찰과 보수가 필요할 것으로 사료된다. 영역 Ill은 상부로부터 집수되는 지표수 배제 및 상부 너덜(talus)지역으로부터 침투된 지하수의 배제를 위한 시공이 필요할 것으로 사료된다. 영역 IV는 현재 안정한 지역으로 가능하면 절취 등 훼손이 발생하지 않도록 하는 것이 바람직할 것이다.

• Earthquakes and Structures
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• 제3권1호
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• pp.1-15
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• 2012

An empirical predictive relationship correlating bracketed duration to earthquake magnitude, site-to-source distance, and local site conditions (i.e. rock vs. stiff soil) for stable continental regions of North America is presented herein. The correlation was developed from data from 620 horizontal motions for central and eastern North America (CENA), consisting of 28 recorded motions and 592 scaled motions. The bracketed duration data was comprised of nonzero and zero durations. The non-linear mixed-effects regression technique was used to fit a predictive model to the nonzero duration data. To account for the zero duration data, logistic regression was conducted to model the probability of zero duration occurrences. Then, the probability models were applied as weighting functions to the NLME regression results. Comparing the bracketed durations for CENA motions with those from active shallow crustal regions (e.g. western North America: WNA), the motions in CENA have longer bracketed durations than those in the WNA. Especially for larger magnitudes at far distances, the bracketed durations in CENA tend to be significantly longer than those in WNA.

• 센서학회지
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• 제27권1호
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• pp.40-46
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• 2018

In this paper, we focus on optimization of a boron ($^{11}B$)-implanted n type Si epi substrate for obtaining near-zero temperature coefficient of resistance (TCR) at temperature range from 25 to $125^{\circ}C$. The $^{11}B$-implantation on the N type-Si epi substrate formed isolation from the rest of the N-type Si by the depletion region of a PN junction. The TCR increased as the temperature of rapid thermal anneal (RTA) was increased at the temperature range from $900^{\circ}C$ to $1000^{\circ}C$ for the $p^+$ contact with implantation at dose of $1E16/cm^2$, but sheet resistance of this film was decreased. After the optimization of anneal process condition, the TCR of $1126.7{\pm}30.3$ (ppm/K) was obtained for the $p^-$ resistor-COB package chips contained $p^+$ contact with the implantation of $5E14/cm^2$. This shows the potential of the $^{11}B$-implanted n type Si epi substrate as a resistor for pressure sensor in thermal stable environment applications..

• 산업과 과학
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• 제2권1호
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• pp.15-20
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• 2023

본 연구의 목적은 4차산업혁명 시대의 빅데이터 분석 기술을 활용한 충청도 복지정책 변화와 중요성을 분석하고 사회적 약자를 포함한 모든 세대의 안정적 복지정책을 제안하였다. 충청도 정책 관련 빅데이터를 파이선으로 코딩하여 시각화분석 결과를 토대로 안정적인 정부 정책을 제안한다. 연구 결과 충청도 정부 정책의 키워드는 지역, 사회, 정부 및 지원, 교육, 여성 등의 순으로 확인되었으며, 지역 건강정책과 사회 복지 향상을 중심으로 복지 정책을 강화해야 한다. 향후 연구 방향은 해외사례를 비교하고, 전국적인 복지정책의 안정적인 영향에 관한 정책 제안이 필요할 것이다.

• 한국정밀공학회지
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• 제29권8호
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• pp.873-878
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• 2012

Putting a conductive rod between rotating axial electrodynamic wheels composed of repetitive permanent magnets, three-axial magnetic forces generate on the conductive rod. It is possible to levitate and transfer the rod on space with the forces. However, the forces vary in direction and magnitude for a position of the rod between the electrodynamic wheels. Thus, the position influences the stability of the rod also. To guarantee the stability of a levitated object, the force acting on the object should have negative stiffness like a spring. So, we analyze the stable operating range of the conductive rod levitated by the axial wheels with the commercial finite element tool in this paper. Specially, as the pole number and the radial width of permanent magnets has much influence on the generated force and thereby the stable region, their sensitivities are analyzed also. The analytic result is compared with experimental result.

• Journal of information and communication convergence engineering
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• 제9권6호
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• pp.666-670
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• 2011

In this paper, we propose a stable active contour based tracking method which utilizes the bimodal segmentation technique to obtain a background color diminished image frame. The proposed method overcomes the drawback of the Mansouri model which is liable to fall into a local minimum state when colors appear in the background that are similar to the target colors. The Mansouri model has been a foundation for active contour based tracking methods, since it is derived from a probability based interpretation. By stabilizing the model with the proposed speed function, the proposed model opens the way to extend probability based active contour tracking for practical applications.