• 대한교통학회지
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• 제29권1호
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• pp.113-123
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• 2011

미시적 시뮬레이션 모형은 컴퓨터 성능이 향상되고 정교한 모형이 개발되면서 광역적인 범위까지 적용분야가 점차 확대되고 있다. 현장 교통상황을 정확하게 묘사하기 위해서는 시뮬레이션 모형의 정확한 정산이 매우 중요하다. 국내에서는 거시적 모형에 대한 정산연구는 많이 진행된 반면에 미시적 모형에 대한 정산연구는 매우 부족한 실정이다. 본 연구에서는 유전자알고리즘 이용하여 미시적 시뮬레이션 모형의 파라미터를 자동으로 최적화하는 자동정산 체계를 제시하였다. 내부순환로 지점검지기에서 수집되는 관측교통량과 미시적 시뮬레이션모형(VISSIM)의 교통량 간의 제곱오차(RMSE)를 성능지표로 하고, 최적화 목적함수는 제곱오차를 최소화 하는 것으로 설정하였다. 내부순환로에 적용한 결과, 기본 파라미터에 비해 자동정산체계의 RMSE가 60.4%($19.3{\longrightarrow}7.6$)나 감소하여 매우 효과적인 것으로 나타났다.

• 한국발생생물학회지:발생과생식
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• 제19권2호
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• pp.85-96
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• 2015

Measurements of closely related sets of classical and truss dimensions were analyzed to discriminate species of scorpaenidae including the dark banded rockfish, Sebastes inermis, the black rockfish, S. schlegeli, and gobioninae including the striped shiner, Pungtungia herzi, and the slender shiner, Pseudopungtungia tenuicorpa. The measurements of the dimensions were arc sin square root transformed, and compared as a function of the standard length of each species for statistical analysis. For values of the classical dimensions of the rockfish, 6 were greater for the dark banded rockfish than for the black rockfish, 1 value was smaller for the former, and for 2 values there was no statistically significant difference (P > 0.05). For values of the classical dimensions of the shiners, 9 values were greater for the striped shiner than for the slender shiner, 2 values were smaller for the former, and for 1 value there was no statistically significant difference (P > 0.01). For values of the truss dimensions of the rockfish, 6 were greater for the dark banded rockfish than for the black rockfish, 1 was smaller for the former, and for 4 values there was no statistically significant difference (P > 0.05). For values of the truss dimensions of the shiners, 13 values were greater for the striped shiner than for the slender shiner, 3 values were smaller for the former, and for 6 values there was no statistically significant difference (P > 0.01). The dimension sets used in this study may be useful as taxonomic indicators for discriminating among fish species in Korea.

• 한국재료학회지
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• 제27권1호
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• pp.48-52
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• 2017

In this study, we used I-V spectroscopy, photoconductivity (PC) yield and internal photoemission (IPE) yield using IPE spectroscopy to characterize the Schottky barrier heights (SBH) at insulator-semiconductor interfaces of Pt/$HfO_2$/p-type Si metal-insulator-semiconductor (MIS) capacitors. The leakage current characteristics of the MIS capacitor were analyzed according to the J-V and C-V curves. The leakage current behavior of the capacitors, which depends on the applied electric field, can be described using the Poole-Frenkel (P-F) emission, trap assisted tunneling (TAT), and direct tunneling (DT) models. The leakage current transport mechanism is controlled by the trap level energy depth of $HfO_2$. In order to further study the SBH and the electronic tunneling mechanism, the internal photoemission (IPE) yield was measured and analyzed. We obtained the SBH values of the Pt/$HfO_2$/p-type Si for use in Fowler plots in the square and cubic root IPE yield spectra curves. At the Pt/$HfO_2$/p-type Si interface, the SBH difference, which depends on the electrical potential, is related to (1) the work function (WF) difference and between the Pt and p-type Si and (2) the sub-gap defect state features (density and energy) in the given dielectric.

• Journal of Mechanical Science and Technology
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• 제19권8호
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• pp.1632-1648
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• 2005

The effects of Reynolds number on the non-nulling calibration of a typical cone-type five-hole probe have been investigated for the representative Reynolds numbers in turbomachinery. The pitch and yaw angles are changed from - 35 degrees to 35 degrees with an angle interval of 5 degrees at six probe Reynolds numbers in range between $6.60{\times}10^3\;and\;3.17{\times}10^4$. The result shows that not only each calibration coefficient itself but also its Reynolds number dependency is affected significantly by the pitch and yaw angles. The Reynolds-number effects on the pitch- and yaw-angle coefficients are noticeable when the absolute values of the pitch and yaw angles are smaller than 20 degrees. The static-pressure coefficient is sensitive to the Reynolds number nearly all over the pitch- and yaw-angle range. The Reynolds-number effect on the total-pressure coefficient is found remarkable when the absolute values of the pitch and yaw angles are larger than 20 degrees. Through a typical non-nulling reduction procedure, actual reduced values of the pitch and yaw angles, static and total pressures, and velocity magnitude at each Reynolds number are obtained by employing the calibration coefficients at the highest Reynolds number ($Re=3.17{\times}10^4$) as input reference calibration data. As a result, it is found that each reduced value has its own unique trend depending on the pitch and yaw angles. Its general tendency is related closely to the variation of the corresponding calibration coefficient with the Reynolds number. Among the reduced values, the reduced total pressure suffers the most considerable deviation from the measured one and its dependency upon the pitch and yaw angles is most noticeable. In this study, the root-mean-square data as well as the upper and lower bounds of the reduced values are reported as a function of the Reynolds number. These data would be very useful in the estimation of the Reynolds-number effects on the non-nulling calibration.

• 한국콘텐츠학회논문지
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• 제18권1호
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• pp.154-163
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• 2018

우리나라뿐만 아니라 전 지구적으로 호우발생 빈도의 증가, 태풍이나 허리케인 세기의 강화 등에 따라 대규모 자연재해의 발생횟수와 피해액은 지속적으로 증가하는 추세이다. 태풍, 홍수, 호우, 강풍, 풍랑, 해일, 조수, 대설, 가뭄, 지진, 황사 등과 같은 자연재해는 발생지점과 규모를 예측하기 어려우며, 전조현상이 명확하게 나타나지 않아 대응에 많은 어려움이 존재한다. 그러나 자연재해의 피해규모를 예측할 수 있다면, 조기대응을 통해 피해를 저감할 수 있을 것이다. 따라서 본 연구에서는 국민안전처에서 발간하는 재해연보('91년~'15년)를 기반으로 서해연안지역의 풍랑피해함수를 개발하였다. 풍랑피해함수는 지역별, 시설별로 구분하여 개발하였으며, NRMSE는 1.94%~26.07%로 분석되었다. 개발된 식을 통해 피해규모를 예측하고, 그에 대한 적절한 대응이 이루어진다면, 피해를 저감할 수 있을 것으로 사료된다.

• Smart Structures and Systems
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• 제25권1호
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• pp.65-80
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• 2020

In order to protect a structure over its full life cycle, a novel tuned mass damper (TMD), the so-called semi-active eddy current pendulum tuned mass damper (SAEC-PTMD), which can retune its frequency and damping ratio in real-time, is proposed in this study. The structural instantaneous frequency is identified through a Hilbert-Huang transformation (HHT), and the SAEC-PTMD pendulum is adjusted through an HHT-based control algorithm. The eddy current damping parameters are discussed, and the relationship between effective damping coefficients and air gaps is fitted through a polynomial function. The semi-active eddy current damping can be adjusted in real-time by adjusting the air gap based on the linear-quadratic-Gaussian (LQG)-based control algorithm. To verify the vibration control effect of the SAEC-PTMD, an idealized linear primary structure equipped with an SAEC-PTMD excited by harmonic excitations and near-fault pulse-like earthquake excitations is proposed as one of the two case studies. Under strong earthquakes, structures may go into the nonlinear state, while the Bouc-Wen model has a wild application in simulating the hysteretic characteristic. Therefore, in the other case study, a nonlinear primary structure based on the Bouc-Wen model is proposed. An optimal passive TMD is used for comparison and the detuning effect, which results from the cumulative damage to primary structures, is considered. The maximum and root-mean-square (RMS) values of structural acceleration and displacement time history response, structural acceleration, and displacement response spectra are used as evaluation indices. Power analyses for one earthquake excitation are presented as an example to further study the energy dissipation effect of an SAECPTMD. The results indicate that an SAEC-PTMD performs better than an optimized passive TMD, both before and after damage occurs to the primary structure.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 춘계종합학술대회
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• pp.625-629
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• 2005

급변하는 정보 및 통신기술의 발달에 따라 멀티미디어 데이터의 효율적인 압축 기술에 관한 심층적 연구 필요성이 더욱 커지고 있다. 본 논문에서는 멀티미디어 신호 중 음성 및 음향 신호 데이터 압축과 관련하여 웨이브렛 기반의 압축 알고리즘 구조를 설계하였다. 2-band 구조와 웨이브렛 packet 구조에서의 압축의 효율성에 대하여 조사하고, 각 구조에서 웨이브렛 기저함수로 Daubechies 웨이브렛 계수와 Coiflet 계수를 사용하여 구조에서의 효율성 및 재생오차를 조사하였다. 최종 압축은 Huffman code를 사용하여 압축율(CR) 및 재생오차(PRD)를 기존의 DCT와 비교분석하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.45-45
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• 2007

Capacitors among the embedded passive components are most widely studied because they are the major components in terms of size and number and hard to embed compared with resistors and inductors due to the more complicated structure. To fabricate a capacitor-embedded PCB for in-line process, it is essential to adopt a low temperature process (<$200^{\circ}C$). However, high dielectric materials such as ferroelectrics show a low permittivity and a high dielectric loss when they are processed at low temperatures. To solve these contradicting problems, we studied BMN materials as a candidate for dielectric capacitors. processed at PCB-compatible temperatures. The morphologies of BMN thin films were investigated by AFM and SEM equipment. The electric properties (C-F, I-V) of Pt/BMN/Cu/polymer were evaluated using an impedance analysis (HP 4194A) and semiconductor parameter analyzer (HP4156A). $Bi_2Mg_{2/3}Nb_{4/3}O_7$(BMN) thin films deposited on copper clad laminate substrates by sputtering system as a function of Ar/$O_2$ flow rate at room temperature showed smooth surface morphologies having root mean square roughness of approximately 5.0 nm. 200-nm-thick films deposited at RT exhibit a dielectric constant of 40, a capacitance density of approximately $150\;nF/cm^2$, and breakdown voltage above 6 V. The crystallinity of the BMN thin films was studied by TEM and XRD. BMN thin film capacitors are expected to be promising candidates as embedded capacitors for printed circuit board (PCB).

• 대한원격탐사학회지
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• 제26권6호
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• pp.605-615
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• 2010

This study demonstrates the feasibility of small satellite, namely PROBA platform with the compact high resolution imaging spectrometer (CHRIS), for aerosol retrieval in Hong Kong. The rationale of our technique is to estimate the aerosol reflectances by decomposing the Top of Atmosphere (TOA) reflectances from surface reflectance and Rayleigh path reflectances. For the determination of surface reflectances, the modified Minimum Reflectance Technique (MRT) is used on three winter ortho-rectified CHRIS images: Dec-18-2005, Feb-07-2006, Nov-09-2006. For validation purpose, MRT image was compared with ground based multispectral radiometer measurements and atmospherically corrected Landsat image. Results show good agreements between CHRIS-derived surface reflectance and both by ground measurement data as well as by Landsat image (r>0.84). The Root-Mean-Square Errors (RMSE) at 485, 551 and 660nm are 0.99%, 1.19%, and 1.53%, respectively. For aerosol retrieval, Look Up Tables (LUT) which are aerosol reflectances as a function of various AOT values were calculated by SBDART code with AERONET inversion products. The CHRIS derived Aerosol Optical Thickness (AOT) images were then validated with AERONET sunphotometer measurements and the differences are 0.05~0.11 (error=10~18%) at 440nm wavelength. The errors are relatively small compared to those from the operational moderate resolution imaging spectroradiometer (MODIS) Deep Blue algorithm (within 30%) and MODIS ocean algorithm (within 20%).

• Bulletin of the Korean Chemical Society
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• 제13권6호
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• pp.620-624
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• 1992

The analytical performance of glow discharge mass spectrometer (GD-MS), using a flat type ion source is discussed. The efficiency of ion extraction was maximized at the distance between anode and cathode of 6 mm. At the operation condition of 4 mA, -1000 volt, and 1 mbar for the source, the optimum voltages for sampler and skimmer were40 volt and -280 volt, respectively. The intensities of Cu, Zn, and Mn were increased as a function of square root of current approximately. Korea standard reference materials (KSRM) were tested for an application study. The detection limits of most elements were obtained in the range of several ppm at the optimized operating condition. The peaks of aluminum and chromium were interfered by those of residual gases. The depth profile of nickel coated copper specimens (3, 5, 10 ${\mu}m$ thickness) were obtained by plotting time versus intensities of Ni and Cr after checking the thickness of nickel coated using a scanning electron microscope (SEM). At this moment, the sputtering rate of 0.2 ${\mu}m/min$ at the optimum operating condition was determined from the slope of the plot of time to the coating thickness. The roughness spectra of specimen's crater after 16 min, discharge were obtained using a Talysuf5m-120 roughness tester as well.