• 한국음향학회지
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• 제41권4호
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• pp.397-409
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• 2022

본 논문에서는 거리 종속환경에서 해수면에 의한 배경소음 모델링을 수행하였다. 모델링 환경에서 음원은 해수면 근처에서 수평 방향의 전 영역에서 위치하고, 수신기 배열은 거리 종속환경의 해양 도파관 내에 위치하였다. 거리 종속환경에서의 소음원과 수신기 간의 음파전달은 연성모드법을 사용하여 계산되었으며, 이를 이용하여 수신기 간 상호 스펙트럴 밀도행렬 식을 유도하였다. 계산된 상호 스펙트럴 밀도행렬은 소음 인텐시티, 빔형성 결과, 코히런스 함수를 계산하는 데 사용되었으며, 그 결과를 거리 독립환경에서의 결과와 비교하였다. 이를 통해 해저면 특성에 의한 수직 방향성과 거리 종속환경에 의한 수평면상의 비대칭성 특성이 모델링 결과에 반영됨을 확인하였다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.34-37
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• 2006

When tsunami waves propagate across open ocean they are steered by Coriolis force and refraction due to gentle gradients in the bathymetry on scales longer than the wavelength. When the wave encounters steep gradients at the edges of continental shelves and at the coast, the wave becomes non-linear and conservation of momentum produces squirts of surface current at the head of submerged canyons and in coastal bays. HF coastal ocean radar is well-conditioned to observe the current bursts at the edge of the continental shelf and give a warning of 40 minutes to 2 hours when the shelf is 50-200km wide. The period of tsunami waves is invariant over changes in bathymetry and is in the range 2-30 minutes. Wavelengths for tsunamis (in 500-3000 m depth) are in the range 8.5 to over 200 km and on a shelf where the depth is about 50 m (as in the Great Barrier Reef) the wavelengths are in the range 2.5 - 30 km. It is shown that the phased array HF ocean surface radar being deployed in the Great Barrier Reef (GBR) and operating in a routine way for mapping surface currents, can resolve surface current squirts from tsunamis in the wave period range 20-30 minutes and in the wavelength range greater than about 6 km. There is a trade-off between resolution of surface current speed and time resolution. If the radar is actively managed with automatic intervention during a tsunami alert period (triggered from the global seismic network) then it is estimated that the time resolution of the GBR radar may be reduced to about 2 minutes, which corresponds to a capability to detect tsunamis at the shelf edge in the period range 5-30 minutes. It is estimated that the lower limit of squirt velocity detection at the shelf edge would correspond to a tsunami with water elevation of less than 5 cm in the open ocean. This means that the GBR HF radar is well-conditioned for use as a monitor of small and medium scale tsunamis, and has the potential to contribute to the understanding of tsunami genesis research.

• Carbon letters
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• 제4권2호
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• pp.57-63
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• 2003

In polymer precursor based activated carbon, the structure of starting material is likely to have profound effect on the surface properties of end product. To investigate this aspect phenolic resins of different types were prepared using phenol, mcresol and formaldehyde as reactants and $Et_3N$ and $NH_4OH$ as catalyst. Out of these resins two resol resins PFR1 and CFR1 (prepared in excess of formaldehyde using $Et_3N$ as catalyst in the basic pH range) were used as raw materials for the preparation of activated carbons by both chemical and physical activation methods. In chemical activation process both the resins gave activated carbons with high surface areas i.e. 2384 and 2895 $m^2/g$, but pore size distribution in PFR1 resin calculated from Horvath-Kawazoe method, contributes mainly in micropore range i.e. 84.1~88.7 volume percent of pores was covered by micropores. Whereas CFR1 resin when activated with KOH for 2h time, a considerable amount (32.8%) of mesopores was introduced in activated carbon prepared. Physical activation with $CO_2$ leads to the formation of activated carbon with a wide range of surface area (503~1119 $m^2/g$) with both of these resins. The maximum pore volume percentage was obtained in 3-20 ${\AA}$ region by physical activation method.

• 한국환경과학회지
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• 제13권6호
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• pp.561-570
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• 2004

This study was carried out to survey the pollution of nonylphenol (NP) in surface sediments around Gwangyang bay and Yeosu sound. NP was suspected chemicals as endocrine disruption. Gwangyang bay is located on the mid south coast of Korea. It is a semi-closed bay which Yeosu petrochemical industrial complex, POSCO (Pohang Steel Company) and Gwangyang container harbor are there. The surface sediments were collected at 15 stations with gravity corer at October, 1999, February, May and August, 2000. Also, the stream and intertidal sediment were collected at 5 sites at August, 2000. Concentrations of NP in surface sediments were in the range of 6.89 to 202.70 ng/g dry wt.. Seasonal range (mean value) of NP is 13.98 to 30.48 (23.46) ng/g dry wt. at October, 10.35 to 54.91 (28.10) ng/g dry wt. at February, 29.05 to 202.70 (82.32) ng/g dry wt. at May and 6.98 to 83.40 (25.37) ng/g dry wt. at August. NP was seasonally fluctuated, and the highest mean value and range was detected at May, 2000. NP was highly distributed in the inner part of Gwangyang bay than Yeosu sound. Concentrations of NP in stream and intertidal sediments showed the highest value in downstream near Yeosu petrochemical industrial complex and Yondung stream. It suggests that the source of NP is industrial wastewater and municipal sewage.

• 터널과지하공간
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• 제9권1호
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• pp.12-19
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• 1999

장약량, 측정거리 등과 같은 발파조건들이 지반진동에 미치는 영향을 조사하기 위하여 골프장 조성공사를 위한 지표발파와 고속도로 건설공사를 위한 터널발파에서 지반진동을 측정하였다. 지표발파에서 삼승근 환산거리방법으로 구한 입지상수 K와 n은 각각 74.1, 01.37로 나타났다. 측정거리가 멀어질수록 Khk n의 절대값은 증가하였다. 지표발파에서 주주파수 대역은 5~60 Hz 이었으며, 그 중에 80% 정도는 10~30 Hz의 범위에 분포하였다. 반면에 터널발파의 주주파수 대역은 25~98Hz로서 지표발파보다 크게나타났다.

• 한국표면공학회지
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• 제53권4호
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• pp.190-199
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• 2020

Copper pyrophosphate baths were employed in order to study the dependencies of current efficiency, residual stress, surface morphology and microstructure of electrodeposited Cu thin layers on applied current density. The current efficiency was obtained to be more than about 90 %, independent of the applied current density. Residual stress of Cu electrodeposits was measured to be in the range of -30 MPa and 25 MPa with the increase of applied current density from 0.5 to 15 mA/㎠. Relatively smooth surface morphologies of the electodeposited Cu layers were obtained at an intermediate current range between 3 and 4 mA/㎠. The Cu electrodeposits showed FCC(111), FCC(200), and FCC(220) peaks and any preferred orientation was not observed in this study. The average crystalline size of Cu thin layers was measured to be in the range of 44~69 nm.

• 한국항공우주학회지
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• 제47권3호
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• pp.228-239
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• 2019

단거리 탄도 미사일의 개념 형상을 설계하기 위하여, 부피, 공력, 추진, 구조, 안정성, 비행 궤적 등의 다양한 관점을 고려하는 최적화 문제를 정립하였다. 이를 위하여 기존의 미사일 사례를 분석하여, 설계 조건과 성능지수를 도출하였다. 각 서브 시스템의 모델을 통합하여, 전체 시스템의 성능을 분석하였다. 설계 예시를 통하여, 여러 설계변수가 최종 성능에 미치는 관계성을 분석하였다.

• 공학논문집
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• 제2권1호
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• pp.63-71
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• 1997

본 논문에서는 range 데이터로부터 평면, 또는 곡면을 갖는 물체의 표면을 인식하여 matching시키는 단순하고 효율적인 방법을 제안한다. 물체의 해당 면을 인식하기 위해 단순히 물체의 면을 나타내는 고유 값만을 비교하기 때문에 인식에 따르는 불필요한 절차를 줄일 수 있다. 여기서, 사용되는 물체의 면을 나타내는 고유값(SRV)은 그 물체의 view-point에 독립적인 특징들에 대하여 가중치를 부여한 값들의 합으로 얻어진다. 따라서, 이 방법은 단순하고 효율적이며 센서에 얻어진 데이터의 잡음과 occlusion에 덜 민감하다.

• 대한원격탐사학회지
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• 제18권5호
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• pp.273-280
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• 2002

This paper describes a mathematical model and its utilization algorithm for calculating the accurate target position on the ellipsoidal earth surface which corresponds to a range-azimuth coordinates of unprocessed synthetic aperture radar (SAR) images. A geometrical model which is a set of coordinate transformations is described. The side-looking directional angle (off-nadir angle) is determined in an iterative fashion by using the model and the accurate slant range which is calculated from the range sampling timing of the instrument. The algorithm can be applied not only for the geolocation of SAR images but also for the high quality SAR image generation by calculating accurate Doppler parameters.

• 한국환경과학회지
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• 제9권2호
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• pp.137-144
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• 2000

The observations on the seasonal fluctuation and distributional characteristic of organic matters on surface sediments and its origin were carried out at the 25 stations in Keogeum-sudo, southern coast of Korean Peninsula from February to October in 1993. I made an analysis on the environmental factors for surface sediments such as temperature, ignition loss, chemical oxygen demand, pheopigment, total sulphide, water content, mud content in grain size, COD/IL ratio and COD/sulphide ratio. The results are as follows ; 1) The range of temperature on the surface sediments was between 6.2${\circ}C$ and 24.6${\circ}C$. The highest mean temperatuer of mud was 24.0${\circ}C$ in summer, the lowest 6.6${\circ}C$ in winter. 2) Ignition loss(IL) fluctuated between 1.2% in winter and 16.8% in spring, that is to say, the seasons of increasing in temperature were very high ignition loss. 3) Chemical oxygen demand(COD) showed the highest mean value of 20.52 mg/g dry in summer within the range of 15/46~32.78 mg/g dry, while showed the lowest of 5.79 mg/g dry in winter within the range of 7.4~17.39 mg/g dry. 4) Pheopigment concentrations showed the highest mean value of 4.85 $\mu\textrm{g}$/g dry in autumn within the range of 0.84~9.21 $\mu\textrm{g}$/g dry, while it did the lowest mean value of 1.97 $\mu\textrm{g}$/g dry in summer within the range of 0.23~4.83 $\mu\textrm{g}$/g dry. 5) Total sulphide (H2S) fluctuated between no detect(ND) in spring, and 2.43 mg/g dry in sutumn. The highest mean value was 0.68 mg/g dry in sutumn, the lowest was 0.16 mg/g dry in spring. 6) Water content(WC) and mud content in grain size showed the mean value of 43.2% within the range of 26.5~59.7% and 91.0% within the range of 57.8~99.2%, respectively. 7) By the analytical results on the source of organic matter, it had been dumped from the seaweed farms in Keogeum-sudo coastal waters.