• ETRI Journal
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• 제36권5호
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• pp.841-846
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• 2014

This study proposes a novel optical sensor structure based on a refractometer combining a bend waveguide with an air trench. The optical sensor is a $1{\times}2$ splitter structure with a reference channel and a sensing channel. The reference channel has a straight waveguide. The sensing channel consists of a U-bend waveguide connecting four C-bends, and a trench structure to partially expose the core layer. The U-bend waveguide consists of one C-bend with the maximum optical loss and three C-bends with minimum losses. A trench provides a quantitative measurement environment and is aligned with the sidewall of the C-bend having the maximum loss. The intensity of the output power depends on the change in the refractive index of the measured material. The insertion loss of the proposed optical sensor changes from 3.7 dB to 59.1 dB when the refractive index changes from 1.3852 to 1.4452.

• Transactions on Electrical and Electronic Materials
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• 제12권4호
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• pp.131-134
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• 2011

Back-end-of-line using ultra low-k (ULK; k < 2.5) has been required to reduce resistive capacitance beyond 45 nmtechnologies, because micro-processing units need higher speed and density. There are two strategies to manufacture ULK inter-layer dielectric (ILD) materials using an air-gap (k = 1). The former ULK and calcinations of ILD degrade the mechanical strength and induce a high cost due to the complication of following process, such as chemical mechanical polishing and deposition of the barrier metal. In contrast, the air-gap based low-k ILD with a relatively higher density has been researched on the trench-type with activity, but it has limited application to high density devices due to its high air-gap into the next metal layer. The height of air-gap into the next metal layer was reduced by changing to the via-typed air-gap, up to about 50% compared to that of the trench-typed air-gap. The controllable ULK was easily fabricated using the via-typed air-gap. It is thought that the via-type air-gap made the better design margin like via-patterning in the area with the dense and narrow lines.

• 한국측량학회지
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• 제33권3호
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• pp.181-192
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• 2015

Bathymetry change due to the 2011 Tohoku (M9.0) earthquake was investigated through satellite altimetry-derived free-air gravity anomalies (SAFAGA) and shipborne measurements. The earthquake occurred at the plate boundaries near the northeastern coast of Japan, where the oceanic plate subducts beneath the continental plate along deep-sea trench. Data analyzed in this study include SAFAGA from Scripps Institution of Oceanography (SIO), shipborne bathymetry (SB) from the U.S. National Geophysical Data Center (NGDC) and the Japan Agency for Marine-Earth-Science And Technology (JAMSTEC). To estimate the bathymetry change, a reference bathymetry before the earthquake was predicted by gravity-geologic method (GGM) and Smith & Sandwell’s (SAS) method. In comparison with the bathymetry models before the earthquake, GGM bathymetry model generated by a tuning density contrast of 17.04 g/cm³ by downward continuation method was selected because it shows better bathymetry in the short wavelength below about 6 km. From the results, remarkable bathymetry change of about ±50 m was found on the west side of the Japan Trench caused by the earthquake.

• 한국습지학회지
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• 제20권1호
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• pp.63-71
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• 2018

강우유출 조건에서 침투도랑의 여과기작은 수리학적 조건에 따라 변화할 수밖에 없다. 침투도랑에서 유출시간에 따른 다양한 여과조건이 입자상 물질의 제거에 미치는 영향을 이해하는 것은 매우 중요하다. 본 연구에서는 도로강우 유출수 처리를 위해 설치된 우드칩 충진 침투도랑에서 일어나는 여과기작을 조사 분석하였다. 유출수문곡선을 몇 개의 영역으로 분리하고 각 영역에서의 여과 메커니즘을 분석한 결과 여과는 수직흐름과 수평흐름, 그리고 불포화 흐름, 부분 포화흐름, 그리고 포화흐름을 거치면서 진행되는 것으로 나타났다. 불포화 흐름조건에서는 입자상 물질의 제거효율은 55-76%를 나타냈으며 주요 기작은 물리적인 억류(trapping)로 나타났으며 유출유량이 크게 증가하여 침투도랑에서 포화흐름이 조성되었을 때 제거효율은 75-95%로 크게 증가하였는데 이는 확산기작의 작용 때문인 것으로 분석되었다. 강우 중단 후 유출량 감소로 침투도랑이 부분 포화흐름으로 전환되는 시점에는 음으로 하전된 공기와 물의 경계면의 존재로 여과효율이 감소한 것으로 추정된다. 강우시 급격히 변화하는 수리학적 조건에서 발생하는 흐름조건 및 여과 메커니즘과 이와 같은 인자가 여과효율에 미치는 영향을 도출하기 위하여 변수통제가 비교적 용이한 실험실 규모의 침투도랑에 대한 연구가 필요하다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.40-41
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• 2007

$SnO_2$ nanowires are used at the nanoscale level for the electrical transduction of the gas interaction with these sensing materials. We report on a study of high sensitivity and fast NOx gas sensor. We focused on improving the response time and refresh time by growth nanowires on the trench structure of Si substrate as air path. To improve refresh time we applied the trench structure with depth of $10\;{\mu}m$ by the inductively coupled plasma reactive ion etching(ICP-RIE). The fabricated device was measured at temperature of $200{\sim}300^{\circ}C$. The sensor exhibit ultra-fast and reversible electrical response (t90% ~4 s for response and ~3 s for recovery).

• Asian Journal of Atmospheric Environment
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• 제8권1호
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• pp.15-24
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• 2014

The capital city of Himalayan Country Nepal, Kathmandu Valley is surrounded by consecutive high mountains, which limits the air distribution and mixing effects significantly. It in turn generates steady air flow pattern over a year except in monsoon season. The air shed in the Valley is easily trapped by the surrounded mountains and the inversion layer formulated as the cap. The $PM_{10}$ concentration was noticeably higher than the standard level (120 ${\mu}g/m^3$) in urban and suburban area of Kathmandu valley for all seasons except monsoon period. The Valley area experiences similar wind patterns (W, WWS, and S) for a year but the Easterly wind prevails only during the monsoon period. There was low and calm wind blows during the winter season. Because of this air flow structure, the air emission from various sources is accumulated within the valley air, high level of air pollution is frequently recorded with other air polluted cities over the world. In this Valley area, brick kilns are recognized as the major air pollution source followed by vehicles. Mostly Bull Trench Kiln (BKT), Hoffman Kiln and Vertical Shaft Brick Kiln (VSBK) are in operation for brick firing in Kathmandu valley where the fuels such as crushed coal, saw dust, and natural gas are used for processing bricks in this study. Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) was used for screening and quantifying the potential impacts of air emission from firing fuels. The total Environmental Performance Score (EPS) was estimated and the EPS of coal was approximately 2.5 times higher than those of natural gas and saw dust. It is concluded that the crushed coal has more negative impact to the environment and human health than other fuel sources. Concerning the human health and environment point of view, alternative environment friendly firing fuel need to be used for brick industry in the kiln and the air pollution control devices also need to be applied for minimizing the air emissions from the kilns.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.611-614
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• 2005

It is well known that tire tread pattern has much influence on the tire pattern noise. The paper describes the method of pattern noise reduction by using the pitch sequence, both on the smooth asphalt roads and on the trenched concrete roads. The noise of tire is classified as either airborne or structure borne noise. Pattern noise through the airborne is considered as a major noise source at high speeds. As block impacting and air pumping by tread patterns are major noise source, tire pattern noise can be greatly influenced by optimal pitch sequence. The goal of this paper is to provide tire engineers with pitch sequence to reduce pattern noise effectively.

• 한국지구과학회지
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• 제18권6호
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• pp.559-564
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• 1997

뉴헤브리디스 해분은 태평양판과 인도-오스트레일리아판의 경계부에 위치한 고령의 비활동적 비배호상 해분이다. 46 Ma에서 60 Ma 사이에 형성된 뉴헤브리디스 해분은 형성과정상 34 mm/a(42 Ma$\sim$47 Ma)와 17 mm/a(47 Ma$\sim$60 Ma)의 두가지 상이한 확장율을 보이며, 해분의 표층은 0.65 sec두께의 퇴적층으로 전반적으로 고르게 피복되어 있다. 본 연구에서 산출된 해분의 생장 발달 곡선은 $Depth(m)=2689+312\sqrt{Age}(Ma)$라는 수식으로 표현될 수 있으며, 여기서 냉각계수 312는 일반대양저의 350과 매우 유사함을 보이는 것이 특징이다. 이러한 특징은 해분의 암권의 생장 발달과정이 일반대양저와 유사할 가능성을 강력히 시사하고 있는 것으로 사료된다. 해분의 전반적인 후리-에어 중력 이상치는 -22.3 mgal에서 +59.0 mgal까지 심한 변화폭을 보이고 있다. 평균 중력이상치는 +30.2 mgal로 일반대양저에 비해 현저히 높은 값을 나타내고 있다. 이는 일반적으로 잘 나타나지 않는 매우 특이한 현상이다. 이것은 해분 자체가 섭입하는 판경계에 위치해 있어 marginal swell의 형상을 취하고 있기 때문인 것으로 해석된다. 이 swell들은 일반적으로 해구축상에서 대양저를 향해 약 200 km 범위내에서 관찰되어지며, 이들의 후리-에어 중력이상치는 평균 $+50{\sim}160mgal$을 보이는 것이 일반적이다. 해분의 높은 양의 중력이상은 이러한 지형적인 특수성에 기인하는 것으로 보여진다. 해분의 위치적 특성 및 암권 자체의 구부러짐에 따른 불안정성은 뉴 헤브리디스 해분의 대표적인 지질 지구물리학적 특징이라고 할 수 있다.

• 센서학회지
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• 제16권5호
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• pp.377-383
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• 2007

We describe the fabrication and characterization of a doubly clamped multi-walled carbon nanotube (MWNT). The device was assembled by an application of electric field in solution. The MWNT was clamped on end of metal trench electrodes in solution and deposited with additional platinum (Pt) on edge of electrode for firmly suspending the MWNT by focused ion beam (FIB). The MWNTs range of diameter and length were 100 to 150 nm and 1.5 to $2{\mu}m$, respectively. Electrical characteristics of fabricated devices were measured by I-V curve and impedance analysis. The mechanical deformation was observed by resistivity in high air pressure. Resonant frequency around 6.8 MHz was detected and resistivity was linearly varied according to the magnitude of air pressure. This device could have potential applications in nanoelectronics and various sensors.

• 설비공학논문집
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• 제23권5호
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• pp.356-364
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• 2011

Storage and transfer heat in soils is governed by the soil thermal properties and these properties are therefore needed in many engineering applications, including horizontal ground heat exchanger for ground-coupled heat pumps. This paper presents the evaluation results of the thermal diffusivity of soils (silica, quartzite, limestone, sandstone, granite, and two masonry soils used for the trench backfilling materials of the horizontal ground heat exchanger. To assess this thermal property, we (i) measure the soil thermal conductivities using single-probe method and (ii) use the de Vries method of summing the heat capacities of the soil constituents. The results show that the thermal diffusivity tends to increase as dry soil begins to wet, but it approaches a constant value or even decreases as the soil continues to wet. Combined algorithm with and improved model for the thermal conductivity of soils and the constituent equation provides accurate estimates of the soil thermal diffusivity.