• Journal of Biosystems Engineering
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• v.15 no.4
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• pp.339-345
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• 1990

공기통풍 건조시 공기흐름(airflow)에 대한 곡물저항(grain resistance)은 송풍시스템에서 fan의 선정시 매우 중요하다. 지금까지는 공기흐름에 대한 곡물저항은 주로 Shedd의 curve에 준하여 정해졌다. 그러나 실제의 경우 곡물수확 또는 건조시 기계적 원인에 의하여 미세립자(fine material)가 생성된다. 이에 본 연구에서 밀(red hard winter wheat)을 대상으로 송풍량, 함수율, 미세립자량이 정압강하(static pressure drop)에 미치는 영향을 규명하였고, 이러한 변수가 포함된 수학적 모델을 개발하였다. 독립변수는 0.051로부터 $0.203m^3/m^2.sec$에 이르는 7단계의 각각 다른 송풍량과 3단계의 함수율 (11, 13, 15%w.b), 4단계의 미세립자량(0, 2, 4, 8%)이고, 종속변수는 정압강하이다. 정압강하와 test bed에서의 송풍량은 micromanometer를 사용하여 측정하였다. 결과는 독립변수(송풍량, 함수율, 미세립자량)는 모두 정압강하에 significant하게 영향을 미치는 것으로 나타났다. 규정된 범위내에서 함수율이 증가함에 따라 정압강하는 최고 45% 까지 감소되었고, 반면 미세립자량이 증가함에 따라 정압강하는 최고 195%까지 증가되었다. 수집된 data로서 다음과 같은 regression equation이 개발되었다($P=AV+BV^2+C(MO)V+D(FM)V$). 본 연구의 결과는 공기송풍시스팀에서 송풍량, 함수율, 미세립자량이 정압강하에 미치는 영향을 규명하였고, 에너지 절약적 송풍시스템을 설계하는 데 도움이 될 수 있을 것이다.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.5
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• pp.453-464
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• 2012

This is a research of an adaptive longitudinal control system for situated cognition in wide range, traffic accidents reduction and safety driving environment by integrated system which graft a road infrastructure's information based on IT onto the intelligent vehicle combined automobile and IT technology. The road infrastructure installed by laser scanner in intersection, speed limited area and sharp curve area where is many risk of traffic accident. The road infra conducts objects recognition, segmentation, and tracking for determining dangerous situation and communicates real-time information by Ethernet with vehicle. Also, the data which transmitted from infrastructure supports safety driving by integrated with laser scanner's data on vehicle bumper.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.1
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• pp.1-8
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• 1996

Recently, much attention has been paid to problems which is concerned with voltage instability phenomena and much works on these phenomena have been made. In this paper, by substituting d $P_{k}$ d $e_{k}$ ( $v^{\rarw}$= e +j f) for $P_{k}$ in conventional load flow, direct method for finging the limit of voltage stability is proposed. Here, by using the fact that taylor se- ries expansion in .DELTA. $P_{k}$ and .DELTA. $Q_{k}$ is terminated at the second-order terms, constraint equation (d $P_{k}$ d $e_{k}$ =0) and power flow equations are formulated with new variables .DSLTA. e and .DELTA.f, so partial differentiations for constraint equation are precisely calculated. The fact that iteratively calculated equations are reformulated with new variables .DELTA.e and .DELTA.f means that limit of voltage stability can be traced precisely through recalculation of jacobian matrix at e+.DELTA.e and f+.DELTA.f state. Then, during iterative process divergence may be avoid. Also, as elements of Hessian mat rix are constant, its computations are required only once during iterative process. Results of application of the proposed method to sample systems are presented. (author). 13 refs., 11 figs., 4 tab.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1900-1902
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• 2005

본 연구에서는 scanning probe microscopy(SPM)을 이용하여 국소영역에서 silicon nanocrystal(Si NC)의 전기적 특성을 분석하였다. Si NCs은 압축된 silicon powder를 laser로 분해하는 laser ablation 방식으로 제조되었고, sharpening oxidation 과정을 통하여 Si NC 주변에 oxide shell을 형성시켰다. 이 과정에서 Si NCs은 $10{\sim}50 nm$의 크기와 약 $10^{11}/cm^2$의 밀도로 $SiO_2$층에 증착되었다. SPM의 conducting tip을 통하여 전하는 각각의 Si NC로 주입되게 되고, 이로 인하여 발생하는 SCM image와 dC/dV curve의 변화를 통하여 Si NC에서 전하 거동을 모니터 하였다. 또한 국소영역에서 Si NC의 전기적 특성을 MOS capacitor 구조에서의 C-V 특성과 비교 분석하였다.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.564-568
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• 1999

The 8-hydroxyquinoline Zinc(Znq2) were prepared successfully from zinc chloride and zinc acetate as two kinds of starting material. The organic electroluminescent devices(ELDs) were fabricated by the structure of ITO/TPD/Znq2/Al with N-N'-diphenyl-N-N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine(TPD) which acts hole trasporting layer and bis(8-oxyquinolino) zinc(II)(Znq2) which acts as emission and electron transporting layer. EL efficiency of Znq2 prepared by heating was investigated. The 570nm of main emission peak which is yellowich green was investigated by photo luminesence(PL) and this results shows that electro luminescence(EL) is from Znq2. The V-J curve shows that carrier injection were investigated from 4V. Maximum luminance and luminance efficiency were 1600cd/$\m^2$, 0.9lm/W. From this results, the Znq2 can be one of the useful organic EL material.

• Journal of the Korean Mathematical Society
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• v.59 no.2
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• pp.353-365
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• 2022

Let 𝓐 be the collection of analytic functions f defined in 𝔻 := {ξ ∈ ℂ : |ξ| < 1} such that f(0) = f'(0) - 1 = 0. Using the concept of subordination (≺), we define $$S^*_{\ell}\;:=\;\{f{\in}A:\;\frac{{\xi}f^{\prime}({\xi})}{f({\xi})}{\prec}{\Phi}_{\ell}(\xi)=1+{\sqrt{2}{\xi}}+{\frac{{\xi}^2}{2}},\;{\xi}{\in}{\mathbb{D}}\}$$, where the function 𝚽_ℓ(ξ) maps 𝔻 univalently onto the region Ω_ℓ bounded by the limacon curve (9u² + 9v² - 18u + 5)² - 16(9u² + 9v² - 6u + 1) = 0. For 0 < r < 1, let 𝔻_r := {ξ ∈ ℂ : |ξ| < r} and 𝒢 be some geometrically defined subfamily of 𝓐. In this paper, we find the largest number 𝜌 ∈ (0, 1) and some function f₀ ∈ 𝒢 such that for each f ∈ 𝒢 𝓛_f (𝔻_r) ⊂ Ω_ℓ for every 0 < r ≤ 𝜌, and $${\mathcal{L} _{f_0}}({\partial}{\mathbb{D}_{\rho})\;{\cap}\;{\partial}{\Omega}_{\ell}\;{\not=}\;{\emptyset}$$, where the function 𝓛_f : 𝔻 → ℂ is given by $${\mathcal{L}}_f({\xi})\;:=\;{\frac{{\xi}f^{\prime}(\xi)}{f(\xi)}},\;f{\in}{\mathcal{A}}$$. Moreover, certain graphical illustrations are provided in support of the results discussed in this paper.

• Journal of the Semiconductor & Display Technology
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• v.14 no.1
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• pp.27-30
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• 2015

SiC based Schottky barrier diodes were prepared by using the facing targets sputtering method. In this research, 4H-SiC polytypes of SiC were adopted and Molybdenum, Titanium was employed as the Schottky metal of the metal-semiconductor contacts. Both structures showed the rectifying nature in their forward and reverse J-V characteristic curve and the ideality factors calculated from these plots that were close to unity were represented the nearly ideal behavior. Difference of Schottky barrier height between prepared devices was also corresponding with the electrical characteristics of themselves. Therefore the suitability of the facing targets sputtering method for fabrication of Schottky diodes could be suggested from these results.

• Journal of the Korean Society for Nondestructive Testing
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• v.11 no.1
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• pp.13-22
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• 1991

In this paper, 3-dimensional fracture phenomena in the local area near a through notch tip located between the surface and the canter were investigated by using embedded dyeing grids with the pitch of $50.8{\mu}$. It was confirmed that displacement V and square root of distance from notch tip $y^{1/2}$ are not proportional in the local area of $\sqrt{{\mid}y{\mid}}\;<\;0.3mm^{1/2}$ and the maximum shea strain ${\varepsilon}_{xymax}$ near a notch tip occurred at the curvature beginning point of the notch curve. It was also noted that the maximum strain ${\varepsilon}_{xymax}$ in the thickness direction occurred at the interior, where the ratio of the distance measured from surface to the half of thickness of specimen is 0.3.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.672-672
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• 2013

본 연구에서는 수열합성법을 기반으로 한 3차원 ZnO 나노구조의 합성을 통해 효율적인 양자점 감응형 태양전지로의 응용을 하고 그 특성을 평가하였다. 기존의 1차원 ZnO 나노구조의 경우 높은 전자이동도와 구조적으로 얻을 수 있는 방향성 있는 전자의 효율적인 전달을 통해 효과적인 광전극으로 많은 관심을 받아왔다. 하지만 나노파티클 기반의 필름에 비해 표면적이 크게 떨어지기 때문에 효과적인 흡광이 어렵다는 단점이 존재하여 높은 효율특성을 내지는 못하였다. 본 연구에서는 이러한 단점을 극복하면서 기존 ZnO 나노선의 장점을 극대화 하기 위해 성장시킨 ZnO 나노선 위에 추가적으로 가지를 형성하여 표면적 향상과 효과적인 전자전달 특성을 얻고자 하였다. 3차원 ZnO 나노구조는citrate 계열의 capping agent의 첨가를 통한 수열 합성법을 통해 1차원의 ZnO 나노선 위에 nanosheet 형식의 가지를 형성하였고 이는 빛의 효과적인 산란특성 및 표면적 향상을 통한 CdS, CdSe의 양자점 증착량을 증가시키는 효과를 얻을 수 있었다. 이러한 태양전지의 소자 특성은 SEM, TEM을 통한 구조 특성평가 및 DRS, J-V curve 및 IPCE를 통한 광학적 특성평가를 통해 확인하였다.

• Journal of Magnetics
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• v.1 no.2
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• pp.94-100
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• 1996

A hysteresis loop tracer using a pulsed high magnetic field of 113.4 kOe, which is suitable for rare earth based permanent magnets, is constructed. The high pulsed magnetic field is generated by discharging a large capacitance charge (5 mF) with a voltage of 600 V into an air solenoid with the inner diameter of 14 mm, outer diameter of 36 mm and the lingth of 34 mm. A computer simulation method is used for the construction of an electromagnet to optimize the many parameters such as the discharge current, generated pulsed magnetic field intensity, thermal dissipation, capacitance, charged voltage, period of damping oscillation and solenoid geometry. By using the hysteresis loop tracer constructed in this work, we are able to measure hystersis loops of several rare earth based permanent magnets with large values of the remanent magnetization, coercvity and energy product.