• 한국레이저가공학회지
• /
• 제9권3호
• /
• pp.7-13
• /
• 2006

Auto focusing system to find optimized focal position of laser beam used for material process has been investigated by using fiber confocal method. Wavelength of laser diode (LD) and diameter of single-mode fiber are 780nm and $5.3{\mu}m$, respectively. Intensity distributions of beam reflected from the surface of mirror and silicon bare wafer have been observed in a gaussian form. Experimental results show that focal position obtained by LD is shifted from one observed from surface scribed by laser about $80{\mu}m$. It is due to the difference of wavelength and each divergence of between LD and laser used for material process. It is confirmed that auto focusing control system through position calibration has operated steadily.

• 디자인학연구
• /
• 제11권1호
• /
• pp.229-236
• /
• 1998

컴퓨터가 컬러 색 체계를 갖게됨에 따라 컴퓨터 그래픽스는 중요한 기술적 진보를 이루게 되었다. 그러나 컴퓨터에서 구현되는 색 체계는 컴퓨터 모니터 상에서 빛으로 존재하기 때문에 인쇄 잉크나 물감에 의한 기존의 색 체계와는 전혀 다른 구조로 되어 있다. 따라서 기존의 디자인 프로세스나 사진에서의 색 재현이나 호환성에 여러 문제가 제기되고 있다. 컴퓨터에 의해 디자인 프로세스가 통합되어 조절, 관리되는 현재의 디자인 시스템에서는 정확한 색의 재현과 관리는 매우 중요하다고 할 수 있다. 본 연구는 기존의 색 체계의 역할과 그 기능을 고찰하고, 컴퓨터 그래픽스에 있어 컴퓨터 색 체계의 특성을 전통적인 색 체계와 비교, 분석하여 컴퓨터의 기술적인 표현이 가져다주는 조형적 특성을 고찰함으로써 컴퓨터를 이용한 재현과 디자인 프로세스의 새로운 가능성을 탐구하는데 그 목적이 있다.

• 한국레이저가공학회:학술대회논문집
• /
• 한국레이저가공학회 2006년도 추계학술발표대회 논문집
• /
• pp.41-45
• /
• 2006

Auto focusing system to find optimized focal position of laser beam used for material process has been investigated by using fiber confocal method. Wavelength of laser diode (LD) and diameter of single-mode fiber we 780nm and $5.3{\mu}m$, respectively. Intensity distributions of beam reflected from the surface of mirror and silicon bare wafer have been observed in a gaussian form. Experimental results show that focal position obtained by LD is shifted from one observed from surface scribed by laser about $80{\mu}m$. It is due to the difference of wavelength and each divergence of between LD and laser used for material process. It is confirmed that auto focusing control system through position calibration has operated steadily.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제16권4호
• /
• pp.395-404
• /
• 2016

A 6-bit 3.4 GS/s flash ADC in a 65 nm CMOS process is reported along with the proposed 4x time-domain interpolation technique which allows the reduction of the number of comparators from the conventional $2^N-1$ to $2^{N-2}$ in a N-bit flash ADC. The proposed scheme effectively achieves a 4x interpolation factor with simple SR-latches without extra clocking and calibration hardware overhead in the interpolated stage where only offset between the $2^{N-2}$ comparators needs to be calibrated. The offset in SR-latches is within ${\pm}0.5$ LSB in the reported ADC under a wide range of process, voltage supply, and temperature (PVT). The design considerations of the proposed technique are detailed in this paper. The prototype achieves 3.4 GS/s with 5.4-bit ENOB at Nyquist and consumes 12.6 mW power at 1 V supply, yielding a Walden FoM of 89 fJ/conversion-step.

• 한국환경과학회지
• /
• 제24권4호
• /
• pp.481-494
• /
• 2015

Groundwater level hydrographs from observation wells in Jeju island clearly illustrate distinctive features of recharge showing the time-delaying and dispersive process, mainly affected by the thickness and hydrogeologic properties of the unsaturated zone. Most groundwater flow models have limitations on delineating temporal variation of recharge, although it is a major component of the groundwater flow system. Recently, a convolution model was suggested as a mathematical technique to generate time series of recharge that incorporated the time-delaying and dispersive process. A groundwater flow model was developed to simulate transient groundwater level fluctuations in Pyoseon area of Jeju island. The model used the convolution technique to simulate temporal variations of groundwater levels. By making a series of trial-and-error adjustments, transient model calibration was conducted for various input parameters of both the groundwater flow model and the convolution model. The calibrated model could simulate water level fluctuations closely coinciding with measurements from 8 observation wells in the model area. Consequently, it is expected that, in transient groundwater flow models, the convolution technique can be effectively used to generate a time series of recharge.

• Ocean Systems Engineering
• /
• 제7권2호
• /
• pp.107-120
• /
• 2017

Spud-can is used for fixing jack-up rig on seabed. It needs to be inserted up to the required depth during the installation process to secure enough soil reaction and prevent overturning accidents. On the other hand, it should be extracted from seabed soils as fast as possible during the extraction process to minimize the corresponding operational cost. To achieve such goals, spud-can may be equipped with water-jetting system including monitoring and control. To develop such a smart spud-can, a reliable numerical simulation tool is essential and it has also to be validated against physical model tests. In this regard, authors developed a numerical simulation tool by using a commercial program ANSYS with extended Drucker-Prager (EDP) formula. Authors also conducted small-scale (1/100) physical model tests for verification and calibration purpose. By using the numerical model, a systematic parametric study is conducted both for sand and K(kaolin)-clay with varying important soil parameters and the best estimated soil properties of the physical test are deduced. Then, by using the selected soil properties, the numerical and experimental results for a sand/K-clay multi-layer case are cross-checked to show reasonably good agreement. The validated numerical model will be useful in the next-stage study which includes controllable water-jetting.

• Water Engineering Research
• /
• 제2권1호
• /
• pp.49-61
• /
• 2001

A grid-based KIneMatic wave soil-water EROsion and deposition Model(KIMEROM) that predicts temporal variation and spatial distribution of sediment transport in a watershed was developed. This model uses ASCII-formatted map data supported from the regular gridded map of GRASS (U.S. Army CERL, 1993)-GIS(Geographic Information Systems), and generates the distributed results by ASCII-formatted map data. For hydrologic process, the kinematic wave equation and Darcy equation were used to simulated surface and subsurface flow, respectively (Kim, 1998; Kim et al., 1998). For soil erosion process, the physically-based soil erosion concept by Rose and Hairsine (1988) was used to simulate soil-water erosion and deposition. The model adopts single overland flowpath algorithm and simulates surface and subsurface water depth, and sediment concentration at each grid element for a given time increment. The model was tested to a 162.3 $\textrm{km}^2$ watershed located in the tideland reclaimed ares of South Korea. After the hydrologic calibration for two storm events in 1999, the results of sediment transport were presented for the same storm events. The results of temporal variation and spatial distribution of overland flow and sediment areas are shown using GRASS.

• 한국세라믹학회지
• /
• 제20권1호
• /
• pp.43-48
• /
• 1983

The formation of strontium titanate from several molar $SrCO_3$ and $TiO_2$ mixtures was studied in air and $CO_2$ gas Mixtures of $SrCO_3$ and $TiO_2$ were heated in air at 400-$600^{\circ}C$ DTA-TG was used to obtain thermal histories of simples heated in air and $CO_2$ gas. X-ray diffraction analysis was used to determine both the phase composition and the amounts of each phase present. The phase relationship of various compounds $SrTiO_3$, $Sr_2TiO_4$, $Sr_2Ti_3O_7$ and $Sr_4Ti_3O_{10}$ formed by the sintering in each composition was shown by the calibration curves. High temperature X-ray analysis was used to determine both the formation process and deformation process of each products. Small amount of SrTiO3 is formed first at the surface af contact SrTiO3 reacts with $SrCO_3$ to form Sr2TiO4 this is affected on the $CO_2$ pressure.

• Nuclear Engineering and Technology
• /
• 제25권4호
• /
• pp.548-551
• /
• 1993

원자력 산업의 변환공정에서 발생하는 폐수용액중의 우라늄 농도를 레이저 유발형광법을 사용하여 쉽게 측정할 수 있는 새로운 분석방법을 개발하였다. 실험 결과 시료의 약 10배 이상의 부피로 4M-인산용액을 첨가함으로써 효율적으로 형광 quencher의 영향을 배제시킬 수 있었으며, 폐액 시료에서의 우라늄 농도 3.0$\times$$10^{-6}$－6.0$\times$$10^{-5}$ M U $O_2$$^{2＋}$의 범위에서 농도에 대한 형광강도의 직선성이 우수하였다.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2001년도 학술발표회 논문집(I)
• /
• pp.25-34
• /
• 2001

A grid-based KIneMatic wave soil-water EROsion and deposition Model (KIMEROM) that predicts temporal variation and spatial distribution of sediment transport in a watershed was developed. This model uses ASCII-formatted map data supported from the regular gridded map of GRASS (U.S. Army CERL, 1993)-GIS (Geographic Information Systems), and generates the distributed results by ASCIIl-formatted map data. For hydrologic process, the kinematic wave equation and Darcy equation were used to simulate surface and subsurface flow, respectively (Kim, 1798; Kim et al., 1993). For soil erosion process, the physically-based soil erosion concept by Rose and Hairsine (1988) was used to simulate soil-water erosion and deposition. The model adopts sing1e overland flowpath algorithm and simulates surface and subsurface water depth, and sediment concentration at each grid element (or a given time increment. The model was tested to a 162.3 km$^2$ watershed located in the tideland reclaimed area of South Korea. After the hydrologic calibration for two storm events in 1999, the results of sediment transport were presented for the same storm events. The results of temporal variation and spatial distribution of overland flow and sediment areas are shown using GRASS.