• 한국대기환경학회지
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• 제13권5호
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• pp.383-396
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• 1997

Numerical prediction of the pollutant dispersion over a two-dimensional hilly terrain is presented. The dispersion model used in the present work is based on the gradient diffusion theory and the finite-volume method on a non-orthogonal boundary-fitted grid system. The numerical model is validated by comparing the results with the available experimental data for the flat-floor dispersion within a turbulent boundary-layer. The numerical error analysis is performed based on the guideline of Kasibhatla et al.(1988) for the elevated-source dispersion in the flat-floor boundary layer having a power-law velocity and linear eddy-diffusivity profile. The influences of the two-dimensional hilly terrain on the dispersion from a continuously released source are numerically investigated by changing the emission locations and heights. It is found that the distributions of ground-level concentration are strongly influenced by the source location and the emission height. Hence, the terrain amplification factor is greatly enhanced when the pollutant source is located within a flow separation region. Dispersion from a source of short duration is also simulated and the duration time of the pollutant is compared at several downstream locations on a hilly terrain. The results of the numerical prediction are applied to the evaluation of environmental impacts due to the automobile exhausts at the seashore highway with a parallel mountain range.

• 해양환경안전학회지
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• 제19권6호
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• pp.658-665
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• 2013

본 연구에서는 국제해사기구(IMO)의 뜨거운 관심분야로 부상되고 있는 선박기인 입자상물질(PM)과 오염물질 배출에 관하여 한국해양대학교 실습선 한바다호를 이용하여 계측하였다. 특히, PM은 TEM 그리드를 이용해 채취하고 전자현미경으로 구조를 파악하였으며, NOx, $CO_2$, CO 등의 배기가스는 연소가스분석기(PG-250A, HORIBA)를 이용해 측정하였다. 본 연구의 결과는 다음과 같다. 1) 선박이 항구에서 출항할 때, Bunker Change로 인한 PM 배출량은 최대 30 % 정도 차이가 있었다. 2) 정속 운항을 하면서 Bunker-A에서 L.R.F.O(3 %)로 변경할 때 측정한 PM 배출량은 $1.34mg/m^3$, L.R.F.O(3 %)로 고정해 측정한 PM 배출량은 $1.19mg/m^3$, L.R.F.O(3 %)만 사용하며 주기관 회전수를 20 % 증가시키면서 계측한 PM 배출량은 $1.40mg/m^3$ 이었다. 또한, 저질유(L.R.F.O(3 %))로 변경시 CO 농도는 약 16 % 증가하는데 비해 RPM을 20 % 상승시킨 경우에는 152 % 이상 급격한 증가를 보였다. 이러한 결과로부터 배기가스 배출의 증가는 연료유종의 영향도 있으나, RPM의 변화에 민감하다는 것을 알 수 있었다. 3) TEM 그리드로 채취한 PM은 약 $4{\sim}10{\mu}m$ 정도의 다양한 입경을 가지는 다공질 응집체 형상의 구조인 것으로 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1367-1369
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• 2002

The pitch and stall schemes have some problems such as, mechanical stress, tear and wear on the transmission line, noise emission and disturbance to the grid, due to a delaying factor of mechanical process. In this paper, a novel control is developed. It serves to compensate delaying of pitch or stall schemes and allows the generate power to control in fast response. The validity of the proposed control scheme is verified by experiment results with the actual 660KW wind power system model.

• 천문학회보
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• 제38권2호
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• pp.67.2-67.2
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• 2013

Part of mid-J CO emission detected by the Herschel/PACS observations of embedded young stellar objects (YSOs) has been attributed to the UV-heated outflow walls. We have applied our newly developed self-consistent models of Photon Dominated Region (PDR) and Non-LTE line Radiative transfer In general Grid (RIG) to the Herschel FIR CO observations. If the black body radiation of T = 15,000 K is used, the observed mid-J CO line fluxes can be produced in inner dense regions (n ${\geq}$ 106 cm-3) with -4.5 ${\leq}$ log Gdust/n ${\leq}$ -2.5, where gas temperatures are larger than 300 K and CO abundances are ${\geq}$ 10-5, along the UV-heated outflow walls. The contribution of the UV heated outflow cavity wall in Class I seems to be larger than that in Class 0.

• 한국태양광발전학회지
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• 제6권1호
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• pp.45-55
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• 2020

Although Sri Lanka's current carbon footprint is much less compared to other developing countries, the country's existing and planned economic developments have raised the demand for power, resulting an increased GHG (Greenhouse gas) emission. GHG in Sri Lanka is emitted mostly by the burning of fossil fuels for energy generation including transport. However, the most effective way of reducing GHG emissions from the energy sector is to use renewable energy sources. Solar is in the top list of renewable resources that has much potential to use to meet the demand for electricity generation in the country. The purpose of this study is to evaluate the current status of solar power generation and opportunities, barriers for implementing the programs of solar energy in Sri Lanka. Literature reviews mainly used as the primary tool for this study. Sri Lankan government had set the targets for adding 200 MW to the national grid by 2020, and to increase up to 1000 MW by 2025 of solar electricity. To achieve these targets the prevailing barriers have to be considered.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1008-1011
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• 2005

In this study, the field emission display with carbon nanotube emitter is developed for the large size HDTV application. Two structures for electron beam focusing are developed on the typical top-gate cathode. The metal grid and focusing gate structure are proved to be effective for the focusing. The data switching voltage for the double gate structure is lower than 30V which is competitive value in respect of the cost for driver electronics. The brightness and color gamut are comparable to those of the commercial product such as CRT.

• 전자공학회논문지A
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• 제30A권1호
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• pp.44-50
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• 1993

In an attempt to improve the electrical characteristics of tantalum pentoxide dielectric film, silicon substrate was reacted with a nitrogen plasma to form a silicon nitride of 50.angs. and then tantalum pentoxide thin films were formed by reactive sputtering in the same chamber. Breakdown field and leakage current density were measured to be 2.9 MV/cm and 9${\times}10^{8}\;A/cm^{2}$ respectively in these films whose thickness was about 180.angs.. With annealing at rectangular waveguides with a slant grid are investigated here. In particular, 900.deg. C in oxygen ambient for 100 minutes, breakdown field and leakage current density were improved to be 4.8 MV/cm and 1.61.6${\times}10^{8}\;A/cm^{2}$ respectively. It turned out that the electrical characteristics could also be improved by oxygen plasma post-treatment and the conduction mechanism at high electric field proved to be Schottky emission in these double-layered films.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.215-222
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• 2002

It has been well acknowledged that intake system plays great role in the performance of reciprocating engine. Well-designed intake system is expected to not only increase engine efficiency but also decrease engine emission, which is one of the most urgent issues in the automotive society. Thorough understanding of the flow in intake system helps great to design adequate intake system. Even though both experimental and numerical methods are used to study intake flow, numerical analysis is more widely used due to its merits in time and economy. Intake system of In-line 6-Cylinder CNG engine was chosen for the analysis ICEM CFD HEXA was used to create 3-D structured grid and FIRE code was used for the flow analysis in the intake system. Due to the complexity of the geometry standard ${\kappa}-{\varepsilon}$ turbulence model was applied. Numerical analysis was performed for various inlet and outlet boundary conditions under both steady and transient flow. Inlet mass flow rate and outlet pressure variation were changing parameters with respect to engine speed. Flow parameters, such as velocity, pressure and flow distribution, were evaluated to provide adequate data of this intake system.

• 천문학회보
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• 제38권1호
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• pp.49.2-49.2
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• 2013

We present a result of $^{13}CO$(1-0) survey toward the Outer Galactic Plane using the multi-beam receiver system recently installed on the 14 m telescope at Taeduk Radio Astronomy Observatory(TRAO). Our target region is from l=$120^{\circ}$ to $133^{\circ}$ and b=$-1^{\circ}$ to $+1^{\circ}$, and some extended regions are included where emission is still arising. All data are on 50" grid. Velocity resolution is 0.63 km/sec, and the total velocity range is from -150 km/sec to 100 km/sec. A total of 140,000 spectra were obtained. The rms noise is about 0.18 K per channel for unsmoothed raw data. We will present a few initial results of the survey database.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.490.2-490.2
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• 2014

Since the general solar cells accept sun light at the front side, excluding the electrode area, electrons move from the emitter to the front electrode and start to collect at the grid edge. Thus the edge of gridline can be important for electrical properties of screen-printed silicon solar cells. In this study, the improvement of electrical properties in screen-printed crystalline silicon solar cells by contact treatment of grid edge was investigated. The samples with $60{\Omega}/{\square}$ and $70{\Omega}/{\square}$ emitter were prepared. After front side of samples was deposited by SiNx commercial Ag paste and Al paste were printed at front side and rear side respectively. Each sample was co-fired between $670^{\circ}C$ and $780^{\circ}C$ in the rapid thermal processing (RTP). After the firing process, the cells were dipped in 2.5% hydrofluoric acid (HF) at room temperature for various times under 60 seconds and then rinsed in deionized water. (This is called "contact treatment") After dipping in HF for a certain period, the samples from each firing condition were compared by measurement. Cell performances were measured by Suns-Voc, solar simulator, the transfer length method and a field emission scanning electron microscope. According to HF treatment, once the thin glass layer at the grid edge was etched, the current transport was changed from tunneling via Ag colloids in the glass layer to direct transport via Ag colloids between the Ag bulk and the emitter. Thus, the transfer length as well as the specific contact resistance decreased. For more details a model of the current path was proposed to explain the effect of HF treatment at the edge of the Ag grid. It is expected that HF treatment may help to improve the contact of high sheet-resistance emitter as well as the contact of a high specific contact resistance.