• The Journal of the Acoustical Society of Korea
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• v.22 no.1
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• pp.69-77
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• 2003

Measurements of backscattered intensity were made over a shallow water using 300 ㎑and 1200 ㎑ bottom mounted ADCP (Acoustic Doppler Current Profiler) to determine the temporal variability of vertical distribution of high-frequency volume scattering strength (Sv). The variability of Sv in relatively deep water column(85 m and 113 m was due to the daily vertical migration, probably of larger zooplankton. However it was not found with 1200㎑ data at shallow water column. From the empirical orthogonal function (EOF) analysis using 1200㎑ data, the vertical distribution of the first mode eigenvectors of Sv is characterized by the presence of the maximum values near the bottom of the water.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.1
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• pp.20-25
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• 1990

During the summer of 1989, the authors carried out the hydroacoustic surverys to investigate the vertical distribution of volume backscattering strength in the East China Sea and simultaneously the biological sampling of the scattering layers by bottom trawling. The echoes from the scattering layers was continuously measured by using a 50 kHz echo sounder during the day and night. A data acquisition system was used to record digitally the envelope of the echoes and the echo integration technique was used to determine the scattering strength proportional to biomass density in each layer. The vertical profiles of volume backscattering strength also were compared with the one of water temperature. The results obtained can be summarized as follows: 1. The vertical profiles of mean volume backscattering strength at day and night suggested that during the night the biggest fish concentrations appeared in the mixed layer above the thermocline and during the day near the bottom. In another profiles where the thermocline was not well developed, peaks in scattering appeared at midwater depths and near the bottom. 2. The maximum values of mean volume backscattering strengths varied from -49.3 dB to -48.0 dB on different regions and at different times of the day and night. 3. Trawl data indicated that the organisms consisting of the scattering layer near the bottom were squid and various species of demersal fishes.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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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.

• International Journal of Concrete Structures and Materials
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• v.8 no.4
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• pp.309-313
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• 2014

The volume fraction of the coarse aggregate in the conventional plastic concrete is controlled relatively low to ensure a required workability. In this paper, a new type of coarse aggregate interlocking concrete with strength ranging from C30 to C80 was prepared with scattering-filling aggregate process. The strength of concrete prepared with this method increases obviously whereas the shrinkage decreases significantly, the cement dosage in the concrete decreased 20 % at the same time. The microhardness of the ITZ between the cement paste and scattering-filling aggregate is higher than that of the original aggregate, the ITZ become narrower and tighter also. The interlocking and more even distribution of the coarse aggregate and the water absorption of the addition of extra amount of coarse aggregates contribute to the strength and performance improvement of the concrete prepared with scattering-filling aggregate process.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.4
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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.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.4
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• pp.551-555
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• 2014

ADCPs have been widely used to estimate the dynamic characteristics and biomass of sound scattering layers (SSLs), and swimming speed of fish schools for analyzing SSLs spatial distribution and/or various behavior patterns. This result showed that the verification of the mean volume backscattering strength (MVBS or averaged SV, dB) acquired by the ADCP would be necessary for a quantitative analysis on the spatial distribution and the biomass estimation of the SSLs or fish school when ADCP is used for estimating their biomass. In addition, the calibrated sphere method was used to verify values of each MVBS obtained from 4 beams of ADCP (153.6 kHz) on the base of 3 frequencies (38, 120, 200 kHz) of Scientific echo sounder's split beam system. Then, the measured SV values were compared and analyzed in its Target Strength (TS, dB) values estimated by a theoretical acoustic scattering model.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.433-438
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• 2002

연안역의 천해 해저면에 설치된 ADCP(Acoustic Doppler Current Profiler, 300kHz, 1200kHz)를 이용, 천해에서 체적 산란강도(volume scattering strength) 수직분포의 시간적인 변동 특성을 알아보았다. 수심 85m와 113m에서 ADCP로 측정한 산란강도의 일주기 변동성은 동물플랑크톤(zooplankton)으로 추측되는 산란체의 일주기 수직 이동(daily vertical migration)의 원인으로 추정되었다. 그러나 수심 20m의 천해에서 관측된 산란강도의 시변동성은 경험적 직교 함수(Empirical Orthogonal Function, EOF) 분석 결과 해저면 부근의 변화가 천해 체적 산란의 변동성에 큰 영향을 주는 것으로 나타났다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.749-756
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• 2003

Hydroacoustic and open-closing zooplankton net survey were conducted to understand the characteristics of the sound scattering layer (SSL) and to estimate the density of an euphausiid (Euphausia pacifica) in the SSL, in the northwestern part of the East China Sea. The survey was carried out during July 6-9 2002 at 8 sampling stations for zooplankton. The virtual echogram technique was used to identify E. pacifica from all acoustic scatters. Mean volume backscattering strength difference $(MVBS_{120kHz-38kHz})$ and target strength equation for E. pacifica were derived from the Distorted-wave Born Approximation (DWBA) model. Although vertical migration of the SSL is similar to the general pattern, dispersion at night shows some differences. Estimated mean density using acoustic data ranged from $20.4-221.4\;mg/m^3$ over the whole depth, and $87.1-553.5\;mg/m^3$ in the SSL. The density using the zooplankton net ranged from $0.2-362.4\;mg/m^3$ and was not related to net deploying method. The results from the acoustic and net survey suggest that E. pacifica might be an important zooplankton community in the northwestern part of the East China Sea.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.1
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• pp.120-127
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• 2015

Morphological properties of dark banded rockfish (Sebastes inermis) were analysed to investigate its acoustic scattering characteristics. Total of 18 live samples was prepared for X-ray photos and collected morphological coordinates of their body and swim bladder shapes. Kirchhoff-ray mode model was used to calculate acoustic scattering pattern for broad-band frequency range. Inclination of swim bladder ranged from 17 to 30 and the averaged value was about $25.2^{\circ}$ (S.D.(standard deviation)=3.15). There were no any tendency of increase or decrease in volume and area ratio of swim bladder to fish body and ranged from 2.2 % to 4.43 % and 14.85 % to 21.31 %, respectively. The averaged value of volume and area ratio was 3.13 % (S.D.=0.52) and 17.6 % (S.D.=1.5). $b_{20}$ values were -69.01 for 38 kHz, -69.83 for 70 kHz, -70.17 for 120 kHz and -70.93 for 200 kHz, recpectively. Broadband acoustic patterns of dark banded rockfish for 20 ~ 200 kHz were similar among samples and they reflected size and morphological properties of fish species.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.66-71
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• 1998

It is required the superior materials for the parts of machines or structures, which could be endurable in severe load and environment. According to advancement of casting technology, nodular graphite cast iron is used as suitable for such condition. But nodular graphite cast iron is scattering of fatigue strength and low reliability. Therefore in this study, the effect of matrix structure and number of nodular graphite on the initiation of fatigue crack and fatigue strength. It was found that the material which has relatively high ferrite volume fraction was more easily cracked than other materials and fatigue limit was low. The material which has not found pinhole on the surface, the crack was initiated in graphite went through ferrite and propagated into through graphite, but separated graphite and ferrite grain boundary and combined with other cracks to fro large one.