• Journal of Wetlands Research
• /
• v.7 no.2
• /
• pp.121-132
• /
• 2005

To classify the surface sedimentary facies using IKONOS image collected over Hwangdo tidal flat in Cheonsu Bay, the optical reflectance was compared for characterizing various sedimentary environments such as grain size, tidal channel pattern and area ratio of surface remnant water. The intertidal DEM (Digital Elevation Model) was generated by echo-sounder for analyzing the relationship between IKONOS image and sedimentary environments including topography. The boundary of the optical reflectance between mud-mixed facies and sand facies was distinct, and discrimination of the associated sandbar feature was also possible. The mud-mixed facies coupled with intricate tidal channels is confined to the relatively hi호 topography of Hwangdo tidal flat. The boundary between mud and mixed flat was indistinct in IKONOS optical reflectance but it would have a difference in the area ratio of surface remnant water. The dark area in the image represented the well developed sand facies having a lot of surface remnant water due to the relatively low surface topography. The overall accuracy of characterizing the surface sediment facies by maximum likelihood classification method was 86.2 %. These results demonstrate that high spatial resolution satellite imagery such as IKONOS coupled with knowledge of grain size, surface remnant water and tidal channel network can be effectively used to characterize the surface sedimentary facies (mud, mixed and sand) network of the tidal flat environments.

• Proceedings of the KOSOMBE Conference
• /
• v.1996 no.11
• /
• pp.129-134
• /
• 1996

1차 년도 G-7 개발 과제로 수행된 자기 공명 진단 장치 (Magnetic Resonance Imaging System)의 개발 내용을 간략히 소개하였다. 성공적인 IT Compact 자기 공명 진단 장치의 완성을 위해 일차적으로 (1)RF (고주파), Gradient(경사 자계), Spectrometer 등의 Hard-ware 관련 MRI 핵심부분, (2) RF, Gradient, Spectrometer, Magnet 등의 각 Sub-system을 연결, 조합, 조정하여 하나의 체계적인 시스템으로 통합하고 운영하는 과정(System Integration), (3)사용자와 시스템을 연결하는 User Interface, Data Base Management, Real time 운영 SW 등과 (4)임상에 적용하여 구체적인 성능과 효용성을 확인하는 기술 등에 대하여 집중 연구하였다. 개발 방법은 (1)지난 16년간 국내에 축적 된 연구 개발 인력들을 최대한 활용하고 (2)연구 개발을 국제화 시켜 필요한 경우 부분별로 개발 인력을 해외에서 보완하고 (3)소수 정예 전문 인력 주의와 요소 기술 또는 중요 부품을 경쟁성 검토 후 필요 시 Out-sourcing 활용으로 최저의 비용으로 개발 기간을 최소화 하는 데 두었다. 개발된 1.0Tesla자기 공명 영상 장치는 미국 물리 학회에서 규격화한 Phantom및 임상 적용을 통하여 서울대 의대 연구 팀과 지속적으로 성능을 평가해 왔다. 개발된 시스템의 해상도는 $256{\times}256$ head 영상에서 1mm 이 하의 해상도를 가짐을 resolution phantom 을 통하여 확인할 수 있었고, $512{\times}512$ 영상에서 는 약 0.5 mm 의 물체를 분리 해냄으로써 외제 시스템들 보다 우수하게 평가 되었다. 차폐 경사코일의 Eddy current영향은2%이내로 촬영 시 영향은 거의 무시할 수 있었다. 또한, 개발된 영상 기법들, 즉 Multislice/Multi Echo, Oblique angle imaging, 64 Echo train을 갖는 고속 촬영 기술들이 자기 공명 장치에 장착되어 임상 적용에 문제가 없도록 하였다. 또한 20mT/m/Amp의 강력한 능동 차폐 경사 자계 코일(Active Shield Gradient Coil)을 기본 사양으로 하고, 수신단을 최대 6개로 확장토록 하여 2차년도의 초고속 촬영 기법(EPI) 및 Phased Array 코일 촬영이 가능토록 하였다. 1차 년도 개발 과제 수행 결과와 향후 개발 과제를 바탕으로 최종 목표인 국제 경쟁력이 있는 자기 공명 진단 장치 즉 기능과 영상의 질은 선진국 제품과 동일하거나 우수하되, 저가격을 구현한 상용화 제품이 완성되어, 첨단 의료기기로서 산업 구조 고도화에 기여하고 수입대체 뿐만 아니 라 수출을 통한 국익 창출과 국가의 기술을 통한 위상 제고에 기여되길 기대한다.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.58 no.1
• /
• pp.39-48
• /
• 2022

Using environmental DNA (eDNA) in the fisheries and oceanography fields, research on the diversity of biological species, the presence or absence of specific species and quantitative evaluation of species has considerably been performed. Up to date, no study on eDNA has been tried in the area of fisheries acoustics in Korea. In this study, the biomass of a dominant species in the northwestern waters of Jeju Island was examined using 1) the catch ratio of the species from trawl survey results and 2) the ranking ratio of the species from the eDNA results. The dominant species was Zoarces gillii, and its trawl catch ratio was 68.2% and its eDNA ratio was 81.3%. The Zoarces gillii biomass from the two methods was 7199.4 tons (trawl) and 8584.6 tons (eDNA), respectively. The mean and standard deviation of the acoustic backscattering strength values (120 kHz) from the entire survey area were 135.5 and 157.7 m²/nm², respectively. The strongest echo signal occurred at latitude 34° and longitude 126°15' (northwest of Jeju Island). High echo signals were observed in a specific oceanographic feature (salinity range of 32-33 psu and the water temperature range of 19-20℃). This study was a pilot study on evaluating quantitatively aquatic resources by applying the eDNA technique into acoustic-trawl survey method. Points to be considered for high-quality quantitative estimation using the eDNA to fisheries acosutics were discussed.

• Journal of the Korean earth science society
• /
• v.44 no.6
• /
• pp.557-577
• /
• 2023

This study defines non-precipitation information as areas with weak precipitation or cloud particles that radar cannot detect due to weak returned signals, and suggests methods for its utilization in data assimilation. Previous studies have demonstrated that assimilating radar data from precipitation echoes can produce precipitation in model analysis and improve subsequent precipitation forecast. However, this study also recognizes the non-precipitation information as valuable observation and seeks to assimilate it to suppress spurious precipitation in the model analysis and forecast. To incorporate non-precipitation information into data assimilation, we propose observation operators that convert radar non-precipitation information into hydrometeor mixing ratios and relative humidity for the Weather Research and Forecasting Data Assimilation system (WRFDA). We also suggest a preprocessing method for radar non-precipitation information. A single-observation experiment indicates that assimilating non-precipitation information fosters an environment conducive to inhibiting convection by lowering temperature and humidity. Subsequently, we investigate the impact of assimilating non-precipitation information to a real case on July 23, 2013, by performing a subsequent 9-hour forecast. The experiment that assimilates radar non-precipitation information improves the model's precipitation forecasts by showing an increase in the Fractional Skill Score (FSS) and a decrease in the False Alarm Ratio (FAR) compared to experiments in which do not assimilate non-precipitation information.

• Korean Journal of Radiology
• /
• v.21 no.12
• /
• pp.1334-1344
• /
• 2020

Objective: Compressed sensing (CS) has gained wide interest since it accelerates MRI acquisition. We aimed to compare the 3D post-contrast T1-weighted volumetric isotropic turbo spin echo acquisition (VISTA) with CS (VISTA-CS) and without CS (VISTA-nonCS) in intracranial vessel wall MRIs (VW-MRI). Materials and Methods: From April 2017 to July 2018, 72 patients who underwent VW-MRI, including both VISTA-CS and VISTA-nonCS, were retrospectively enrolled. Wall and lumen volumes, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured from normal and lesion sites. Two neuroradiologists independently evaluated overall image quality and degree of normal and lesion wall delineation with a four-point scale (scores ≥ 3 defined as acceptable). Results: Scan coverage was increased in VISTA-CS to cover both anterior and posterior circulations with a slightly shorter scan time compared to VISTA-nonCS (approximately 7 minutes vs. 8 minutes). Wall and lumen volumes were not significantly different with VISTA-CS or VISTA-nonCS (interclass correlation coefficient = 0.964-0.997). SNR was or trended towards significantly higher values in VISTA-CS than in VISTA-nonCS. At normal sites, CNR was not significantly different between two sequences (p = 0.907), whereas VISTA-CS provided lower CNR in lesion sites compared with VISTA-nonCS (p = 0.003). Subjective wall delineation was superior with VISTA-nonCS than with VISTA-CS (p = 0.019), although overall image quality did not differ (p = 0.297). The proportions of images with acceptable quality were not significantly different between VISTA-CS (83.3-97.8%) and VISTA-nonCS (75-100%). Conclusion: CS may be useful for intracranial VW-MRI as it allows for larger scan coverage with slightly shorter scan time without compromising image quality.

• Investigative Magnetic Resonance Imaging
• /
• v.19 no.1
• /
• pp.31-36
• /
• 2015

Purpose: To compare the depiction of brain metastases on contrast-enhanced images with 7.0 tesla (T) and at 1.5T MRI. Materials and Methods: Four consecutive patients with brain metastases were scanned on 7.0T whole-body scanner and 1.5T MRI. A 3D T1-weighted gradient echo sequence (3D T1-GRE) at 1.5T (voxel size = $0.9{\times}0.9{\times}1.5mm^3$ after double-dose, gadoterate meglumine, Gd-DOTA) was compared to a 7.0T 3D T1-GRE sequence (voxel size = $0.4{\times}0.4{\times}0.8mm^3$, single-dose Gd-DOTA) in four patients after a 5 minute delay. The number of contrast-enhancing metastases in MPRAGE images was compared in each patient by two radiologists in consensus. We measured contrast ratio of enhancing brain metastases and white matter in 1.5T and 7.0T. Results: In all four patients 7.0T 3D T1-GRE images after single-dose Gd-DOTA and 1.5T after double-dose Gd-DOTA depicted 11 brain metastases equally. In the quantitative analysis of contrast ratios of enhancing brain metastases and white matter, the 1.5T 3D T1-GRE after double-dose showed an increased contrast ratio compared to 7.0T 3D T1-GRE after single-dose ($0.961{\pm}0.571$ versus $0.885{\pm}0.494$; n = 11 metastases). But this difference was not statistically significant (P = 0.711). Conclusion: Our preliminary results indicate that 7.0T single-dose Gd-enhanced images were not different to 1.5T double-dose Gd-enhanced images for the detection of brain metastases.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.1
• /
• pp.107-114
• /
• 1996

The in situ target strength for the anchovy (Engraulis japonica) were measured by the split beam echo sounder system at 38 kHz. This study allowed us to detect the single echos from anchovy shoals which were dispersed during trawling operation in day time. The results of our study were as fellows: We found that the anchouy occupied about $95\%$ of the total catch from the detected shoals from which target strength data were collected. Length distribution of anchovy showed a mode and ranged from 13.6 to 15.4cm with a mean of 14.4cm and a standard deviation of 0.45cm, and weight distribution showed a mode and ranged from 16 to 28 g witha mean of 21.9 g and a standard deviation of 2.7 g. The target strength distribution of anchovy ranged from -40.7 dB to -69.2 dB in the water layer of ,$10\~30\;m$ -42.19 to -67.7 dB in the $30\~50\;m$ and -42.2 to -67.7 dB in $10\~50\;m$, showing 2 modes in each layer, respectively. Overall mean target strengths were -49.7 dB/fish and -33.1 dB/kg, averaged by area backscattering cross section $(\sigma)$, and the confidence interval for target strength was less than 1 dB. With the mean total length and the mean target strength, we drived the target strength-length relationship as $TS(\sigma)=20\;Log\;L-72.9$.

• Journal of Advanced Marine Engineering and Technology
• /
• v.34 no.1
• /
• pp.168-176
• /
• 2010

Stability and durability of the artificial reefs (ARs) for wildstock enhancement have been a key issue. We surveyed the side scan sonar (SSS), multi beam echo sounder (MBES) and scuba diving surveys confirmed that the ARs stability was age and type-dependent. A case of the stability of 8,438 ARs (60 group ARs) installed at 4 sites (Yangyang, Gangeung, Donghae and Samcheok) along the Gangwon coast of the East Sea (Sea of Japan). And a confirmation amount to 85.4% ARs remained safe, the rest 14.6% being influenced by a physical parameter of the waters. The representative influences by their circumstances were of breakage (6.3%). capsizing (8.3%). A group of a ARs to 61.7% ARs remained safe, the rest 38.3% being influenced by a physical parameter of the waters. The representative influences by their circumstances were of buried.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.43 no.3 s.309
• /
• pp.41-50
• /
• 2006

This paper presents a novel ultrasonic sensor system to overcome limited distance detection range that can be measured only more than 30cm by single ultrasonic transducer. This is accomplished by separation of receiving capacitive ultrasonic transducer from transmitting capacitive ultrasonic transducer. And hardwares and software of the system are described in detail. The system makes very close range as well as long range detect by wireless precisely. Frequency of trigger pulse is 10Hz, but it is very low frequency for transmitting data in wireless module. Therefore, for triggering between receiver and transmitter, an algorithm for mixing and distinguishing trigger pulse from carrier pulse by software is proposed. The system is designed by common microprocessor 8051. The performance of the proposed method has been assessed through two types. The first, transmitting and receiving transducer are put on both sides. And then, distance of two point is measured as far as 0mm. Secondly, transmitting transducer send out ultrasonic pulse and measure the time of flight(TOF) until a first echo from an object detected by the detached receiving transducer. The distance between the detached transducers and a reflecting object is measured as far as 7cm. Images of measured ultrasonic waves and TOF for two methods presented to prove effectiveness of results.

• Investigative Magnetic Resonance Imaging
• /
• v.21 no.4
• /
• pp.242-251
• /
• 2017

Purpose: To investigate the association of carotid intraplaque hemorrhage (IPH) with acute cerebral ischemic events and progression of stenosis using magnetic resonance (MR) imaging. Materials and Methods: From April 2014 to December 2016, 53 patients underwent carotid plaque MR imaging, including magnetization-prepared rapid acquisition with gradient-echo (MPRAGE) sequence. A total of 66 carotid arteries in 53 patients had carotid stenosis, and they were included in this study. Carotid arteries were classified according to the presence of IPH, the age of hemorrhage, and degree of stenosis. We assessed ipsilateral cerebrovascular event rates and progression of stenosis between the IPH and no-IPH groups. Results: Of the 61 carotid arteries assessed, 34 (56%) had IPH, and 27 (44%) had no IPH. Acute cerebral ischemic events were more frequent in the IPH group (47% vs. 22%, P = 0.045), especially in the < 30%-stenosis group (100% vs. 0%, P = 0.028). However, there was no significant difference in the incidence of ischemic events according to the age of hemorrhage (50% vs. 44%, P = 0.492). Among the 61 carotid arteries, 20 carotid arteries had previously undergone carotid artery imaging and were evaluated for plaque progression. The trend for progression of stenosis favored the IPH group versus the no-IPH group, with a marginal P-value ($20%{\pm}12.7$ vs. $9.6%{\pm}5.7$, P = 0.063). Conclusion: IPH was associated with an increased incidence of acute ischemic events, especially in the mild-stenosis group and it was also associated with progression of stenosis. Evaluation of the carotid IPH by carotid plaque MR could improve discrimination of carotid plaques that cause ischemic events and progression of stenosis.