• Ocean Science Journal
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• 제42권1호
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• pp.1-8
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• 2007

Acoustic volume backscattering strength data were collected and Conductivity Temperature Depth (CTD) measurements were conducted in the southern Yellow Sea in summer 2005 and 2006. The high temporal and vertical resolution acoustic data measured with a 307 kHz Acoustic Doppler Current Profiler (ADCP) and a 250 kHz acoustic Doppler profile (ADP) had dominant diel variation, which resulted from vertical migration of sound scatterers. Some scatterers congregating in the bottom layer in the daytime migrated upward at dusk, and migrated downward into the bottom layer at dawn. The migration speeds were estimated. More than 33 days data show that the diel migration varies with time. The feature of migration measured with ADCP and ADP is consistent to some extent with what is described in the study on vertical migration of zooplankton in the southern Yellow Sea with conventional net samples.

• 수산해양기술연구
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• 제46권4호
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• pp.449-457
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• 2010

This study shows that the vertical migration speed of sound scattering layers (SSLs), which is distributed in near Funka Bay, were measured by 3D velocity components acquired from a bottom moorng ADCP. While the bottom mooring type has a problem to measure the velocity vectors of sound scattering layer distributed near to surface, both the continuous vertical migration patterns and variability of backscatterers were routinely investigated as well. In addition, the velocity vectors were compared with the vertical migration velocity estimated from echograms of Mean Volume Backscattering Strength, and estimated to produce observational bias due to SSLs which is composed of backscatterers such as euphausiids, nekton, and fishes have swimming ability.

• ALGAE
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• 제17권1호
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• pp.1-9
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• 2002

Diel vertical distribution of phytoflagellates and interactions between the phytoplankton components and environmental and biological factors were studied in a small artificial pond for three days on the December 18, 1998 and April 9 to 10, 1999. The phytoplankton population was dominated by Mallomonas akrokomos of chrysophytes and Cryptomonas marssonii and Chroomonas sp. of cryptophytes. The vertical distribution of these phytoflagellates taxa exhibited clear diel migration pattern. Moreover their migration patterns are showed differential fluctuation between M. akrokomos, C. marssonii and Chroomonas sp. The later two species upward migrated in the evening as well as night, whereas the former species migrated downward. Their distinctive migration pattern was found during the night but was not observed in the morning. During daytime C. marssonii and Chroomonas sp. showed maximum density above 2 m depth but M. akrokomos below 2 m depth. The diel vertical distribution of the dominant phytoflagellates did not show significant correlation between physical, chemical and biotic factors.

• 수산해양기술연구
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• 제30권4호
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• pp.251-262
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• 1994

The speed of vertical migration and the volume backscattering strength of the scattering layers during the evening and morning transitions between day and night were measured in November 1990-1992 in thermally stratified waters of the East China Sea. Acoustical measurements were carried out using a scientific echo-sounder operating at t재 frequencies of 25 and 100kHz, and using an echo-integration system connected with a micro-computer. Biological sampling was accomplished by bottom trawling to identify fish species recorded on the echo sounder, and the species and length compositions were determined. The values of scattering strength were allocated to group of fishes according to the fish traces on the echo recording paper and the species composition of trawl catches. The vertical velocities of migration derived from the changes in the depths and the values of peak scattering strength of the dense layer vertically migrating toward the bottom or toward the surface. The trawl data suggest that snailfish and fishing frog were the most abundant fishes in all research stations. As sunrise approached, the fish formed a strong concentration just above the thermocline. The the highest values of scattering strength in the entire water column appeared in the depth strata above the thermocline just before the begining of downward migration. As soon as the fish began to migrate downwards across the thermocline, the values of the scattering strength in the depth strata above the thermocline rapidly decreased, while the values for the scattering layer moving slowly toward the bottom gradually increased. During the 1992 surveys, the speed of the vertical migration was estimated to be 0.38m/min in the upward migration and 0.32m/min in the downward migration, respectively. That is the rate of vertical migration was slightly higher at dusk than at dawn. Similar migration patterns were observed on different stations and under different weather conditions during the surveys in 1990.

• 지구물리와물리탐사
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• 제16권2호
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• pp.71-78
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• 2013

일방향 파동방정식(one-way wave equation)을 이용한 참반사 보정은 거꿀 참반사 보정(reverse time migration)에 비해서는 계산시간의 효율성을 향상시킬 수 있고 파선이론에 기초한 참반사 보정에 비해서는 상대적으로 정확한 영상화를 수행할 수 있다는 장점이 있다. 이 연구에서는 이러한 일방향 파동방정식을 이용하는 참반사 보정 알고리즘 중 Generalized-Screen (GS) 전파자를 이용하여 이방성 매질 중 횡적등방성(Vertical Transversely Isotropy, VTI) 매질에 적용가능한 겹쌓기 전 심도 참반사 보정(PreStack Depth Migration, PSDM) 모듈을 개발하였다. GS 전파자는 위상막(phase screen) 참반사 보정의 얇은 막(thin slab) 전파자에서 수직느리기항(vertical slowness)의 Taylor 급수 전개 시 고차항을 고려했기 때문에 수평적 속도변화가 크거나 급격한 경사를 지니는 구조에 대해서도 정확한 영상을 얻을 수 있다. 개발된 GS 참반사 보정 모듈을 검증하기 위해서 VTI 매질에 적용되는 전파자(GSVTI propagator)를 고차항의 차수에 따라 분석한 결과 차수가 증가할수록 넓은 각으로 전파하는 파동장의 정확도가 향상되었다. 그리고 수치모형실험을 통해서 이방성 매질에서 얻은 합성탄성파탐사 자료에 본 연구에서 개발된 이방성 GS 참반사 보정과 등방성 GS 참반사 보정을 각각 적용한 결과 이방성 GS 참반사 보정이 급경사나 이방성이 강한 지역에서의 구조에 대해 더욱 정확한 영상을 제공하는 것을 확인할 수 있었다.

• 펄프종이기술
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• 제48권3호
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• pp.5-13
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• 2016

This study investigated the effects of different factors on the migration of a fluorescent whitening agent (FWA) from paper treated with FWAs to non-fluorescent papers. FWA migration experiments were carried out in vertical and friction contacts between the papers dyed with FWAs and non-fluorescent papers. During the experiments, we identified the effects of the addition and types of FWAs, contact time, temperature, and relative humidity (RH) on FWA migration. The fluorescence indices of the non-fluorescent papers were measured before and after the migration experiments, and the Student's t test, a statistical tool, was utilized to compare results from different migration experiments. In vertical contact experiments, FWA migration to non-fluorescent paper was observed at $30^{\circ}C$ and 70% RH; this was attributed to the high moisture content of the paper. FWA migration did not occur significantly at $23^{\circ}C$ and 50% RH. In the friction contact experiments, FWA migrations were identified at both temperature conditions and RH percentages. The addition and types of FWAs did not increase the fluorescence index of non-fluorescent papers. Therefore, it was concluded that the moisture content of paper and the friction contact affected FWA migration from the papers containing internal and surface FWAs.

• 한국음향학회지
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• 제22권1호
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• pp.69-77
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• 2003

연안역의 천해 해저면에 설치된 ADCP (Acoustic Doppler Current Profiler, 300㎑, 1200 ㎑)를 이용, 천해에서 체적 산란강도 (volume scattering strength, Sv)의 수직분포에 대한 시변동성을 알아보았다. 수심 85m와 113m에서 ADCP로 측정한 후방 산란강도의 일주기 변동성은 동물플랑크톤 (zooplankton)으로 추측되는 산란체의 일주기 수직이동 (daily vertical migration)에 기인된 것으로 추정되었다. 그러나 수심 20m의 천해에서 관측된 산란강도의 시변동성은 경험적 직교함수 (Empirical Orthogonal Function, EOF) 분석 결과, 해저면 부근의 변화가 천해 체적 산란강도의 변동성에 큰 영향을 주는 것으로 나타났다.

• Journal of the korean society of oceanography
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• 제32권1호
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• pp.38-45
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• 1997

To find out the changes in vertical distribution patterns over the 24-h period, a key and the first step to tackle the problem of adaptive significance of diel vertical migration (DVM), vertically stratified time series samplings with multiple opening/closing plankton samplers were done in the East Sea of Korea (Sea of Japan). Sampling was done almost every 4 h for one day period following the same water parcel in Nov. 1995 and May 1996, respectively. Resultant patterns of vertical distribution showed that some species such as most abundant taxa Metridia pacifica and Scolecithyicella minor, both Copepoda, performed DVM even in the study area of strong thermal stratification. Their patterns of DVM such as distance scales and timing of movements were not the same each other, and they were separated from other taxa in the dendrogram obtained by the cluster analyses, Most minor taxa grouped in one, however, seemed not to do DVM in the study area of strong thermal stratification. They usually preferred the warmer surface layer where the foods were probably more abundant.

• 한국수산과학회지
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• 제24권6호
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• pp.472-482
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• 1991

아산만 동물 플랑크톤의 계절별 분포를 조사하였다. 년중 Labidocera euchaeta, Safitta crassa, Calanus sinicus, Acartia omorii 등이 계절에 따라 다른 점유율을 보이며 주요 우점종으로 나타났고, 기타 계절에 따라 이매패 유생(가을), 십각류 유생(봄, 여름) Paracalanus Parvus, Evadne tergestina(여름) 등이 주요 우점종에 포함되었다. 주요 우점종인 A. omorii는 계절에 따라 주야 수직분포가 다른 양상을 보였는데, 겨울철에는 정상적인 주야 수직이동, 봄철에는 역전된 주야 수직이동을 하는 것으로 여겨졌다. 대부분 표층에서는 야간과 비교하여 주간에 통상 같거나 적은 양의 개체수 분포를 보였다.

• ALGAE
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• 제21권1호
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• pp.75-82
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• 2006

Cyanobacteria regulate their buoyancy in response to changing environmental conditions. This process is essential for cyanobacterial development and can account for their dominance in eutrophic waters in summer. The present investigation was conducted to understand the 24-hour vertical distribution of cyanobacteria and water quality characteristics in Lake Daecheong. Water samples were collected and analyzed at depth intervals of 2 or 3 m and at an interval of three hours for a day on August 28, 2001 and September 24, 2002. In 2001 the accumulated standing crop of Microcystis spp. from surface to a depth of 6 m was 94.9%. Microcystis spp. showed no vertical migration below the thermocline. Microcystis spp. had maximum density near the surface, but shifted to 2 m depth at 2 p.m. A dense population of Anabaena spp. accumulated near the surface from 2 to 5 p.m. in 2002.