질의문 키워드의 가중치 부여 방법을 이용한 정답 문서 순위화 시스템

강유환,안영민,서영훈 충북대학교 컴퓨터정보통신 연구소 2005 컴퓨터정보통신연구 Vol.13 No.1

본 논문에서는 자연어로 된 질의문에 대한 키워드 추출 및 가중치 부여 방법을 이용하여 정답 문서를 상위로 순위화하는 방법을 제안한다. 정답 문서를 상위로 순위화하기 위해 자연어 질의문과 정답 문서에서 나타나는 키워드의 특성을 분석하고, 색인어로써 중요한 역할을 할 수 있는 키워드를 다양한 형태로 추출한 후, 추출된 키워드에 차별화된 가중치를 부여한다. 끝으로 문서에 나타난 키워드의 출현 횟수와 문서 가중치를 이용하여 문서를 순위화한다. 실험에서는 20개의 질의문에 대해 상위 5위 안에 들어 있는 정답 문서의 수를 측정하였다. 실험결과 상위 5위 안에 들어 있는 정답 문서의 평균 개수는 3.05개로 키워드의 출현횟수와 키워드의 근접상을 이용한 방법보다 높은 성능 향상을 보였다. This paper describes a method of weighting keywords in the question that is written in a natural language for ranking answer documents. We extract keywords from the question using characteristic of question and keywords that are used in answer documents. And we assign differentiated weight to each keyword. Finally, we rank documents in order that answer documents can be ranked in high position using frequency of keywords and weight of documents. In experiment, we tested the number of answer documents that are ranked in top 5 for 20 questions. Experimental results show that the average number of answer documents that are ranked in top 5 was 3.05 and the accuracy of the proposed method was improved comparing with the existing method using frequency and proximity of keywords.

迎日灣의 ECOSYSTEM 硏究 2. 기후적 要因 : 氣溫, 日射量, 증발량, 바람, 강우량

朴相來,金基台,崔銀珠,李東澈,安由煥,尹伊鏞 嶺南大 海洋科學硏究所 1988 Marine Nature Vol.1 No.1

In order to understand phytoplankton ecology in the Gulf of Yeong-il, climatic factors such as air-temperature, solar-radiation, evaporation, direction and strength of winds, and precipitation are studied from January 1982 to December 1985. Annual average of air-temperature during the four-years period is about 13.6C, ranging from 1.7C (January) to 26.5C (August). The maximum value of solarradiation is measured in spring (520MJm²in May), the minimun : in winter (62 MJm²in December, January or February), and the total annual value : about 4987MJm². Annual average of evaporation is about 1200mm (Maximum: 169 in May : Minimun: 56 in February), close to precipitation (about 1050mm). Annual average of strength of "North Winds" (350°-90°)is about 550m·sec for 156 frequences during 191 days, "West Winds" (170°-340°) : 511m·sec¹for 185 frequences during 148 days, and "South Winds" (100°-160°) about 61m·sec¹for frequences during 24 days. "N" winds is about 30% more violant than "W" winds, but both winds are influential in terms of water movements in the Gulf.

迎日灣의 ECOSYSTEM 硏究 3. 水溫

尹伊鏞,朴相來,李東澈,金基台,崔銀珠,安由煥 嶺南大 海洋科學硏究所 1988 Marine Nature Vol.1 No.1

In order to observe hydrological characteristics in the Gulf of Yoeng-il, measurements of water temperature have been carried out from February to August 1983, and from August 1985 to December 1986. Surface water temperatures are closely linked to air temperature and solar-radiation for all littoral stations. Seasonal and annual variations of all horizontal stations are very similar to one another. Vertical variations of water temperatures for the stations located along the central-line of the Gulf are characteristic (and observed) as thermoclines and thermal stratification in the hottest summer-time (August). It is interesting to note that water column temperature of July and September are rather warmer than August, on account of a cold water mass coming from NE direction. For example, surface temperature in June 1982 was above 19℃, but the water below a depth of about 30m drastically drops to 4℃. It is indicative of invasion of water mass from cold current or deep sea.

Development of Suspended Particulate Matter Algorithms for Ocean Color Remote Sensing

Ahn, Yu-Hwan,Moon, Jeong-Eun,Gallegos, Sonia The Korean Society of Remote Sensing 2001 大韓遠隔探査學會誌 Vol.17 No.4

We developed a CASE-II water model that will enable the simulation of remote sensing reflectance($R_{rs}$) at the coastal waters for the retrieval of suspended sediments (SS) concentrations from satellite imagery. The model has six components which are: water, chlorophyll, dissolved organic matter (DOM), non-chlorophyllous particles (NC), heterotrophic microorganisms and an unknown component, possibly represented by bubbles or other particulates unrelated to the five first components. We measured $R_{rs}$, concentration of SS and chlorophyll, and absorption of DOM during our field campaigns in Korea. In addition, we generated $R_{rs}$ from different concentrations of SS and chlorophyll, and various absorptions of DOM by random number functions to create a large database to test the model. We assimilated both the computer generated parameters as well as the in-situ measurements in order to reconstruct the reflectance spectra. We validated the model by comparing model-reconstructed spectra with observed spectra. The estimated $R_{rs}$ spectra were used to (1) evaluate the performance of four wavelengths and wavelengths ratios for accurate retrieval of SS. 2) identify the optimum band for SS retrieval, and 3) assess the influence of the SS on the chlorophyll algorithm. The results indicate that single bands at longer wavelengths in visible better results than commonly used channel ratios. The wavelength of 625nm is suggested as a new and optimal wavelength for SS retrieval. Because this wavelength is not available from SeaWiFS, 555nm is offered as an alternative. The presence of SS in coastal areas can lead to overestimation chlorophyll concentrations greater than 20-500%.

Spatial and Temporal Aspects of Phytoplankton Blooms in Complex Ecosystems Off the Korean Coast from Satellite Ocean Color Observations

Ahn, Yu-Hwan,Shanmugam, Palanisamy,Chang, Kyung-Il,Moon, Jeong-Eon,Ryu, Joo-Hyung The Korean Society of Oceanography 2005 Ocean science journal Vol.40 No.2

Complex physical, chemical and biological interactions off the Korean coast created several striking patterns in the phytoplankton blooms, which became conspicuous during the measurements of ocean color from space. This study concentrated on analyzing the spatial and temporal aspects of phytoplankton chlorophyll variability in these areas using an integrated dataset from a Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Advanced Very High Resolution (AVHRR) sensor, and Conductivity Temperature Depth (CTD) sensor. The results showed that chlorophyll concentrations were elevated in coastal and open ocean regions, with strong summer and fall blooms, which appeared to spread out in most of the enclosed bays and neighboring waters due to certain oceanographic processes. The chlorophyll concentration was observed to range between 3 and $54\;mg\;m^{-3}$ inside Jin-hae Bay and adjacent coastal bays and 0.5 and $8\;mg\;m^{-3}$ in the southeast sea offshore waters, this gradual decrease towards oceanic waters suggested physical transports of phytoplankton blooms from the shallow shelves to slope waters through the influence of the Tsushima Warm Current (TWC) along the Tsushima Strait. Horizontal distribution of potential temperature $(\theta)$ and salinity (S) of water off the southeastern coast exhibited cold and low saline surface water $(\theta<l9^{\circ}C;S<32.4)$ and warm and high saline subsurface water $({\theta}>12^{\circ}C; S>34.4)$ at 75dBar, corroborating TWC intrusion along the Tsushima Strait. An eastward branch of this current was called the East Korean Warm Current (EKWC), tracked with the help of CTD data and satellite-derived sea surface temperature, which often influenced the dynamics of mesoscale anticyclonic eddy fields off the Korean east coast during the summer season. The process of such mesoscale anticyclonic eddy features might have produced interior upwelling that could have shoaled and steepened the nutricline, enhancing phytoplankton population by advection or diffusion of nutrients in the vicinity of Ulleungdo in the East Sea.

The Present Status of Ocean Color Remote Sensing in Korea

Ahn, Yu-Hwan 영남대학교 해양과학연구소 2000 국제심포지움 일정 및 발표논문집 Vol.2000 No.1

해색 원격탐사에서 가장 큰 문제가 되는 것은 다양한 광학적 특성을 갖는 해양에서 어떻게 하면 일차생산량의 지표인 클로로필 농도를 정확하게 얻을 수 있는가하는 것이다. 한국 해양연구소(KORDI)에서는 이러한 기술적 문제 해결과 한반도 주변의 해양의 생물학적 생태를 모니터링을 위한 도구로 사용하여 왔다. 지금까지는 주로 NOAA, CZCS, 그리고 SeaWiFS를 사용하여 기존의 생물광학 알고리즘을 개선하고, 현재는 CASE-II 해수 알고리즘, 탁도 등 해양환경분석 알고리즘을 개발하고 있다. 국립수산진흥원(NFRDI)에서는 이들 자료를 활용하여 현장의 어민들에게 매일매일 자료를 어장 정보를 위한 서비스와 위성 분석자료의 검증을 위한 현장 관측을 수행하고 있다. 현재 SeaWiFS 수신시스템을 갖추고 있는 곳은 한국해양연구소, 국립수산진흥원, 그리고 기타 1곳에 갖추고 있다. 그러나 대학에서는 한곳도 없는 것이 특징이다. 이 사실은 한국 내 Ocean color 분양의 자료 이용자나 알고리즘 개발분야에 인력이 그렇게 많지 않음을 시사한다. 그럼에도 불구하고 1999년 12월 국내에서는 육상 관측센서인 ECO를 주 탑재체로 하고, 해색센서(OSMI)가 탑재된 아리랑 위성 1호를 개발하여 발사하였다. OSMI의 bands 특성은 SeaWiFS와 거의 유사하나 band 수가 6개 뿐이다. 현재는 이들 자료를 활용을 위한 CAL/VAL 사업이 KORDI/NFRDI에서 동시에 수행 중에 있으며 자료의 해양분야 활동은 거의 없는 실정이다. 미래의 해색 기술연구를 위하여 현재 KORDI의 해양과학 및 해색원격탐사 개발팀은 남해에서 연중 발생하는 적조의 조기예보를 위한 정밀 적조 알고리즘을 개발하고 있으며, 앞으로 몇몇 적조의 종까지 구분이 가능한 기초연구를 수행하고 있다. The initial difficulty in ocean color remote sensing lies in the concentration determination of various ocean constituents (phytoplankton, total seston, etc.) found in surface ocean wafers. The Korea Ocean Research and Development Institute (KORDI) carries out most of researches on ocean color satellite technique. KORDI has utilized and improved earlier techniques for analyzing sea surface temperature (SST), chlorophyll concentrations as well as water turbidity using CZCS, NOAA and SeaWiFS data. The National Fisheries Research and Development Institute (NFRDI) of Korea provides information on daily distribution of SST to fishermen of the area of concerns. Receiving stations for SeaWiFS are limited to only KORDI and NFRDI in Korea. The first Korean Multi-purpose Satellite (KOMSAT) is in operation with two sensors, ocean color (OSMI) and land (EOC) sensors. OSMI band characteristics of KOMSAT are very similar to those of the SeaWiFS of NASA. The ocean color-group at KORDI has been developing algorithms for the accurate detection of initialization of red-tides in order to predict in advance. At the present, the group is working on an optical calibration and validation of OSMI sensor

ChlorophyII and suspended sediment specific absorption coefficient in the sea

Ahn, Yu Hwan,Moon, Jeong Eon 대한원격탐사학회 1998 International Symposium on Remote Sensing Vol.14 No.1

Absorption coefficient per mass unit of particles, specific absorption coefficient, is one of main parameters in developing algorithms for ocean color remote sensing. Specific absorption coefficient of chlorophyll (a*_(ph)) and suspended sediment (SS) were analyzed by $quot;wet filter technique$quot; and $quot;Kishino method$quot; for data sets observed in the Yellow and Mediterranean Seas. A new data-recovering method for the filter technique was also developed using spectrum slopes. This method recovered the baseline of spectrum that was often missed in the Kishino method. High a^*_(Ph)( λ ) values in the oligotrophic Mediterranean Sea and low values in the Yellow Sea were observed, spanning over the range of 0.02 to 0.12 ㎡/mg, at the chlorophyll maximum absorption wavelength 440nm. The empirical relationship between a^*_(Ph) and chlorophyll concentration was found to fit a power function, which was slightly different from that proposed by Bricaud et al. (1995). Absorption specific coefficients for suspended sediment (a^*_(ss)) didn't show any relationship with concentrations of suspended sediment. However, the average value of a^*_(ss) at 440nm was close to the specific absorption coefficient of soil (loess) measured by Ahn (1990). The more-pronounced variability of a^*_(ss) than a^*_(Ph) perhaps can explain more wide range of size-distribution for SS, which were determined by their specific gravity and agitation of water mass in the sea surface.

Derivation and analysis of the fluorescence algorithms to estimate phytoplankton pigment concentrations in optically complex coastal waters

Ahn, Yu-Hwan,Shanmugam, Palanisamy Institute of Physics Publishing in association wit 2007 Journal of optics A, Pure and applied optics Vol.9 No.4

<P>This paper presents an analysis of several in-water algorithms developed using a large number of bio-optical data collected in Korean and neighbouring ocean waters. The upward and downward light fields measured in these waters were normalized to provide remote sensing reflectance (<I>R</I><SUB>rs</SUB>) from which the variations in sun-induced chlorophyll-a (Chl-a) fluorescence from phytoplankton biomass were analysed and the fluorescence line height (ΔFlu) was measured using a baseline method. ΔFlu measurements were related to <I>in situ</I> Chl-a concentrations (used as an index for quantifying the algal material) to obtain the ΔFlu(681), ΔFlu(688) and ΔFlu<SUB>(area)</SUB> algorithms, which were compared with those from standard spectral ratios of the remote sensing reflectance, <I>R</I><SUB>rs</SUB>(444)/<I>R</I><SUB>rs</SUB>(554) and <I>R</I><SUB>rs</SUB>(490)/<I>R</I><SUB>rs</SUB>(554). Comparison revealed the correlation coefficients (<I>r</I><SUP>2</SUP>) 0.88–0.90 for the fluorescence algorithms and 0.79–0.85 for the spectral ratios algorithms. A validation analysis using a new data set illustrated the merits of these algorithms in Case II waters. Fluorescence-based algorithms tended to reproduce <I>in situ</I> Chl-a concentrations (from 0.1 to 82?mg?m<SUP>−3</SUP>), whereas standard spectral ratios algorithms gave inconsistent estimates, probably caused by the interference of inorganic sediment and dissolved organic matter in these waters. For measurements of the sun-induced Chl-a fluorescence signal in coastal waters, this study discusses the requirements and provides the optimal channels to be adopted in the design of the new generation ocean colour sensors planned in the near future.</P>

High Resolution Visible and IR sensor on the Geostationary Satellite

Ahn, Yu Hwan 대한원격탐사학회 2001 International Symposium on Remote Sensing Vol.17 No.1

The High Resolution Visible and IR Sensor (HiRVIS; an assumed name) is a future ocean color and IR sensor to be loaded on the Korean Multifunctional GEO Satellite (in 2008) for the purpose of obtaining multispectral visible and infra-red images of the ocean (land) surface at high repeat observation. These images will be used to monitor and study processes which can vary rapidly in time in the ocean surface. HiRVIS has a spatial resolution of 250m x 250m (for visible bands) and an image size of 500km x 500km. It has the capability of providing an image of eleven spectral bands (visible NIR 8, IR 3) every 30minute, which greatly expands the capability of OSMI or SeaWiFS in spatial and temporal resolution. HiRVIS is designed to remedy the coverage and revisiting rate contractions imposed by polar orbiting platform. The high frequency observing rate can also increase of cloud-free area through cloud filtering and composition of multiple images. The images are needed in management of coastal zone resources; and mitigation of marine hazards such as inflow of turbid fresh water in the ocean, up-welled cold water, and harmful algal bloom etc.. Data will be processed in near real time by KORDI and NFRDI. Research data products will be available through KORDI.

Evolution of suspended sediment patterns in the East China and Yellow Seas

Ahn, Yu-Hwan,Shanmugam, Palanisamy,Gallegosi, Sonia The Korean Society of Oceanography 2004 Journal of the Korean Society of Oceanography Vol.39 No.1

The evolution of intricate and striking patterns of suspended sediments (SS), which are created by certain physical dynamics in the East China and Yellow Seas, has been investigated using satellite ocean color imageries and vertical profiles of particle attenuation and backscattering coefficients. The structure of these patterns can reveal a great deal about the process underlying their formation. Sea surface temperature (SST) analyzed from the Advanced Very High Resolution Radiometer (AVHRR) thermal infrared data were used to elucidate the physical factors responsible for the evolution of suspended sediment patterns in the East China Sea. The concomitant patterns of suspended sediments were tracked from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color data. The detailed examination about these patterns gave birth to the definition of the evolution of suspended sediments (SS) into four stages: (1) Youth or Infant stage, (2) Younger stage, (3) Mature stage, and (4) Old stage. We describe about the three directional forces of the tidal currents, ocean warm currents and estuarine circulations that lead to occurrence of various stages of the evolution of suspended sediments that increase turbidity at high levels through out the water column of the inner and outer shelf areas during September to April. The occurrence of these four stages could be repeatedly observed. In contrast, vertical profiles of the particle attenuation ($c_{p}$) and backscattering ($b_{bp}$) coefficients displayed obvious patterns of the propagation of suspended sediment plume from the southwestern coastal sea that leads to eventual collision with the massive sediment plume originating from the Yangtze banks of the East China Sea.