• Title/Summary/Keyword: Shelf front

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Late Quaternary Sedimentary Processes in the Northern Continental Margin of the South Shetland Islands, Antarctica (남극 남쉐틀랜드 군도 북부 대륙주변부의 후기 제 4기 퇴적작용)

  • 윤석훈;윤호일;강천윤
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.9 no.1
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    • pp.1-12
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    • 2004
  • Sedimentary facies and high-resolution echo facies were analyzed to elucidate sedimentation pattern of the late Quaternary glacial-marine deposits in the northern continental margin of the South Shetland Islands. Six sedimentary facies are classified, based on grain texture and sedimentary structures in gravity cores. The high-resolution (3.5 ㎑) echo characters are classified into 6 echo facies on the basis of clarity, continuity, and shape of bottom and subbottom echoes together with seafloor topography. Distribution of the echo and sedimentary facies suggest that there was a significant change in sedimentation pattern between the Last Glacial Maximum (LGM) and subsequent glacier-retreating period. When the grounded glaciers extended to the present shelfbreak during LGM, coarse-grained subglacial tills were widespread in the shelf area, and deep troughs in the shelf were carved beneath the fast-flowing ice steam. As the glacial margin retreated landward after LGM, dense meltwater plumes released from the retreating ice-front were funneled along the glacier-carved troughs, and accumulated channel- or cannyon-fill deposits in the shelf and the upper to mid slope. At that time, slope sediments seem to have been reworked by slope failures and unsteady contour currents, and further transported by fine-grained turbidity currents along the South Shetland Trench. After the glacial retreat, sediments in the shelf and slope areas have been mainly introduced by persistent (hemi) pelagic settling, and fine-grained turbidity currents frequently occur along the axis of the South Shetland Trench.

Design of a Software-Based GPS RF Simulator

  • Noh, Jae Hee;Jo, Gwang Hee;Bu, Sung Chun;Ko, Yo Han;Park, Chansik;Lee, Sang Jeong
    • Journal of Positioning, Navigation, and Timing
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    • v.11 no.2
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    • pp.127-134
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    • 2022
  • In this paper, a low-cost, flexible GPS simulator based on USRP is designed as a general-purpose software wireless front-end. The simulator consists of a software GPS signal generator and a USRP-based RF transmitter. The simulator supports various scenarios including specified reception time, quantization bit level, I/Q data types, IF frequency, sampling frequency, SNR, ionospheric delay and user dynamics. The generated GPS RF signal is verified using the spectrum analyzer and off-the-shelf GNSS receivers such as U-blox M8T. The experimental results shows that the difference between generated and real live signal is ignorable. It is expected that designed GPS simulator can be used to GNSS signal design, receiver design and signal processing algorithms such as anti-jamming.

Distribution of Eggs and Larvae of Maurolicus muelleri in the Thermal Front of the Korea Strait (앨퉁이 (Maurolicus muelleri) 난.자치어 분포와 수온전선)

  • Kim, Sung;Yoo, Jae-Myung
    • Korean Journal of Ichthyology
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    • v.11 no.1
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    • pp.62-71
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    • 1999
  • The seasonal distribution of Maurolicus muelleri eggs and larvae were determined using samples collected from the Korea Strait and the southern part of the East Sea in May and November, 1992, August, 1993, and January, 1994. The eggs were most abundant in summer and the larvae in spring, while, their abundance was low in winter. The eggs were mainly found from in all season around sea of the front area of latitude $35{\sim}36^{\circ}N$ and the West Channel of the Korea Strait found the middle or bottom water lower than $15^{\circ}C$. The seasonal distribution of the eggs in the western Korea Strait varied according to the structure of the bottom cold water of the Korea Strait. The M. muelleri larvae in different stage were most abundant in the front area of latitude $35{\sim}36^{\circ}N$. The spawning and hatching area of the M. muelleri was considered to be the front area located in the shelf break, and some eggs can be transported into the Korea Strait by westward cold bottom current in summer. The Korea Strait would be the southern margin of the distribution of Maurolicus muelleri eggs and larvae of the East Sea.

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Water Masses and Frontal Structures in Winter in the Northern East China Sea (동중국해 북부해역의 겨울철 수계와 전선구조)

  • 손영태;이상호;이재철;김정창
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.8 no.3
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    • pp.327-339
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    • 2003
  • During the winter in February 1998, January and April 1999, interdisciplinary research was conducted in a large area including the South Sea of Korea and northern East China Sea to examine distribution and structure. Water masses identified from the observed data are Warm Water originated from Tsushima Warm Current, Yellow Sea Cold Water (Northern or Central Cold Water) and Korean Southern Sea Cold Water. In the southern Yellow Sea, Warm Water originated from Tsushima Warm Current, flowing into the Cheju Strait after turning around the western Cheju Island, makes a front of '┍' shape, which is bounded by the Yellow Sea Central Cold Water in the southern part of Daeheuksan Island and by the Yellow Sea Northern Cold Water in the eastern part of the Yangtze Bank. This front changes its corner shape and position with strength of the warm water extension toward northwestern Yellow Sea. The position and structure of the fronts off the southwestern tip of the Korean peninsular and near the Yangtze Bank varies with observation period. In the front in the South Sea of Korea, cold coastal water which if formed independently due to local cooling, ,sinks along the sloping bottom. We explained the processes of variations in the distribution and structure of these winter fronts in terms of up-wind and down-wind flow by the seasonal monsoon, heat budget through the sea surface and density difference across the fronts.

Temporal and spatial Analysis of Sea Surface Temperature and Thermal Fronts in the Korean Seas by Satellite data

  • Yoon Hong-Joo;Byun Hye-Kyung
    • Proceedings of the KSRS Conference
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    • 2004.10a
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    • pp.696-700
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    • 2004
  • In the Korean seas, Sea Surface Temperature (SST) and Thermal Fronts (TF) were analyzed temporally and spatially during 8 years from 1993 to 2000 using NOAA/AVHRR MCSST. As the result of harmonic analysis, distributions of the mean SST were $10~25^{\circ}C,$ and generally SST decreased as latitude increased. SST increased in the order as following; the South Sea $(20\~23^{\circ}C),$ the East Sea $(17\~19^{\circ}C)$, and the West $Sea(13\~16^{\circ}C).$ Annual amplitudes and phases were $4\~11^{\circ}C,\;210\~240^{\circ}$ and high values were shown as following; the West Sea $(A1,\;9\~11^{\circ}C),$ the Northern East Sea $(A5,\;8\~9^{\circ}C),$ the Southern East Sea $(A4,\;6\~8^{\circ}C),$ the South Sea $(A3,\;6\~7^{\circ}C),$ the East China Sea $(A2,\;4\~7^{\circ}C)$ and phases; $A3\;(238\~242^{\circ}),\;A4\;(235\~240^{\circ}),\;A5\;(225\~235^{\circ}),\;Al\;(220\~230^{\circ}),\;A2\;(210\~235^{\circ}),$ respectively, Both of them were related inversely except the area A2, therefore the rest areas were affected by seasonal variations. TF were detected by Soble Edge Detection Method using gradient of SST. Consequently, TF were divided into 4 fronts; the Subpolar Front (SPF) based on the Cold Water Mass (low SST and salinity Subartic Water), resulting from the North Korea Cold Current (NKCC) and the East Sea Proper Cold Water in the middle and low layer, and the Warm Water Mass (high SST and salinity Subtropical Water), resulting from the Tsushima Warm Current (TWC) in area A4 and 5, the Kuroshio Front (KF) based on the Kuroshio Current (KC) and shelf waters in the East China Sea (ESC) in A2, and the South Sea Coastal Front (SSCF) based on the South Sea Coastal Water (SSCW) and TWC in A3. Also, the Tidal Front was weakly appeared in AI. TF located in steep slope of submarine topography. Annual amplitudes and phases were bounded in the same place, and these results should be considered to influence of seasonal variations.

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Implementation of a Bluetooth-LE Based Wireless ECG/EMG/PPG Monitoring Circuit and System (블루투스-LE 기반 심전도/근전도/맥박 무선 모니터링 회로 및 시스템 구현)

  • Lee, Ukjun;Park, Hyeongyeol;Shin, Hyunchol
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.6
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    • pp.261-268
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    • 2014
  • This paper presents a electrocardiogram(ECG), electromyogram(EMG), and Photoplethysmography(PPG) signal wireless monitoring system based on Bluetooth Low Energy (BLE). ECG and EMG sensor interface analog front-end circuits are designed by using off-the-shelf parts. Texas Instruments(TI)'s CC2540DK is used for BLE-based communication. Two CC2540DK modules are used as Peripheral and Central nodes. In peripheral device, vital signals are acquired by the analog front-ends and fed to ADC for analog-to-digital conversion. The peripheral transmitts the data through the air to the central device. The central device receive the data and sends them to PC using UART. GUI is designed using Labview for displaying the acquired vital signals. The developed system can be used for future ubiquitous wireless healthcare system based on bluetooth 4.0.

Basic Marine Environmental Characteristics of Suspended Sediments in the Inner Shelf Zone off Tae-An Peninsula, West Coast of Korea (한반도 서해 태안반도 연근해 부유퇴적물의 기초 해양환경적 특성)

  • 최진용;박용안
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.1 no.1
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    • pp.46-54
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    • 1996
  • A study on the concentrations of total suspended matters (TSM) and their distribution pattern was conducted off the west coast of Tae-An Peninsula during the spring season. Especially non-destructive and fine-tuned analysis for the size-distribution of suspended matters was made using SPECTREX instrument. Water masses were characterized by the typical tidal front, with vertically homogenous coastal waters and the strong thermoclines on the offshore area. Concentrations of suspended matters were generally less than 10 mg/l, but the concentrations increased up to 25 mg/l at the bottom waters and mid-depth waters. Mean particle size of the suspended matters were generally 5-6$\mu\textrm{m}$ and 8-10$\mu\textrm{m}$ for the fine-grained suspended matters and the coarse-grained suspended matters, respectively. They are considered to be composed dominantly of detrital materials. On the coastal area, landward side of tidal front, bottom sediments can be easily resuspended by the strong tidal currents, and therefore, deposition of suspended materials are thought to be rather limited. On the offshore area, however, suspended sediments mostly supplied from the northern part of the present study area near Kyunggi Bay are thought to be transported southward and/or southwestward along the mid- depth layer of strong thermocline.

SIEVING NONLINEAR INTERNAL WAVES IN SATELLITE IMAGES

  • Liu, Cho-Teng;Chao, Yen-Hsiang;Hsu, Ming-Kuang;Chen, Hsien-Wen
    • Proceedings of the KSRS Conference
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    • v.2
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    • pp.820-823
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    • 2006
  • Nonlinear internal waves (NLIW) were studied as a unusual phenomena in the ocean decades ago. As the quality, quantity and variety of satellite images improve over decades, it is founded that NLIW is a ubiquitous phenomenon. Over the continental shelf of northern South China Sea (SCS), both optical and microwave images show that there are trains of NLIW packets near Dongsha Atoll (20.7N, 116.8E). Each packet contains several NLIW fronts. These NLIW packets are nearly parallel to each other and they are refracted, reflected or diffracted by the change of ocean bottom topography. Based on Korteweg de Vries (KdV) theory and the assumption that the bright/dark lines in the satellite images are centers of convergence/divergence of NLIW fronts, one may (1) sort NLIW packets in the same satellite image into groups of the same source, but generated at different tidal cycles, (2) relate NLIW packets in consecutive satellite images of one day apart, (3) locating faint signals of NLIW fronts in a satellite image. The NLIWs travel more than 100 km/day near Dongsha Atoll, with higher speed in deeper water. The bias and standard deviation of predicted location of NLIW front from its true location is about 1% and 5.1%, respectively.

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A Seasonal Circulation in the East China Sea and the Yellow Sea and its Possible Cause

  • Oh, Kyung-Hee;Pang, Ig-Chan
    • Journal of the korean society of oceanography
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    • v.35 no.4
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    • pp.161-169
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    • 2000
  • A seasonal circulation in the East China Sea and the Yellow Sea and its possible cause have been studied with CSK data during 1965-1989. Water mass distributions are clear in winter, but not in summer because the upper layer waters are quite influenced by atmosphere. To solve the problem, a water mass analysis by mixing ratio is used for the lower layer waters. The results show that the distribution of Tsushima Warm Current Water expands to the Yellow Sea in winter and retreats to the East China Sea in summer. It means that there is a very slow seasonal circulation between the East China Sea and the Yellow Sea: Tsushima Warm Current Water flows into the Yellow Sea in winter and coastal water flows out of the Yellow Sea in summer. By the circulation, the front between Tsushima Warm Current Water and coastal water moves toward the shelf break in summer so that the flow is faster in the deeper region. The process eventually makes the transport in the Korea Strait increase. The Kuroshio does not seem to influence the process. A possible mechanism of the process is the seasonal change of sea surface slope due to different local effects of surface heating and diluting between the East China Sea and the Yellow Sea.

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Seasonal Cycle of Sea Surface Temperature in the East Sea and its Dependence on Wind and Sea Ice

  • Park, Kyung-Ae;Chung, Jong-Yul;Kim, Kuh
    • Proceedings of the KSRS Conference
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    • 2003.11a
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    • pp.618-620
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    • 2003
  • Harmonics of sea surface temperature (SST) in the East Sea and their possible causes are examined by analyzing NOAA/AVHRR data, SSM/I wind speeds, NSCAT wind vectors, and NCEP heat flux data. Detailed spatial structures of amplitudes and phases of the seasonal cycles and their contributions to the total variance of SST have quantitatively. The Subpolar front serves as a boundary between regions of high annual amplitudes (${\geq}$10$^{\circ}$C) in the cold continental region and low amplitudes (${\leq}$10$^{\circ}$C) in the Tsushima Warm Current region. The low phase center of annual cycle is located over a seamount at 132.2$^{\circ}$E, 41.7$^{\circ}$N south of Vladivostok. Semi-annual amplitudes are significantly large leaching over 20% of the annual amplitudes in the Tatarskiy Strait and along the continental shelf off Russian coast in fall and spring, but its forcings are substantially annual. We have shown that fall cooling is attributed by direct and local wind forcing, while spring cooling is remotely forced by cold waters from sea ices in the Tatarskiy Strait.

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