• Environmental Analysis Health and Toxicology
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• v.28
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• pp.6.1-6.7
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• 2013

Objectives In this study, we investigated the influence of ionic strength and natural organic matter (NOM) on aggregation and soil adsorption of citrate-coated silver nanoparticles (AgNPs). Methods Time-resolved dynamic light scattering measurements and batch adsorption experiments were used to study their aggregation and soil adsorption behaviors, respectively. Results The aggregation rate of AgNPs increased with increasing ionic strength and decreasing NOM concentration. At higher ionic strength, the AgNPs were unstable, and thus tended to be adsorbed to the soil, while increased NOM concentration hindered soil adsorption. To understand the varying behaviors of AgNPs depending on the environmental factors, particle zeta potentials were also measured as a function of ionic strength and NOM concentration. The magnitude of particle zeta potential became more negative with decreasing ionic strength and increasing NOM concentration. These results imply that the aggregation and soil adsorption behavior of AgNPs were mainly controlled by electrical double-layer repulsion consistent with the Derjaguin-Landau-Verwey-Overbeek theory. Conclusions This study found that the aggregation and soil adsorption behavior of AgNPs are closely associated with environmental factors such as ionic strength and NOM and suggested that assessing the environmental fate and transport of nanoparticles requires a thorough understanding of particle-particle interaction mechanisms.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.33 no.1
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• pp.38-44
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• 2001

The effects of refining load on the paper properties were investigated. HwBKP, SwBKP and SwUKP were refined with PFI mill at the load of 3.33 N/mm and 6.00 N/mm. Higher Scott bond was obtained at the higher refining load for three pulp used in this study. However any changes in the light scattering coefficient with the change of refining load were not observed. Although the effect of refining load on the formation index for SwUKP was not observed, higher refining load gave the better formation for HwBKP and SwBKP. The fiber mass and fiber crowding factor were not affected by the refining load. Higher apparent density and tensile index were obtained with the higher refining load. However, the higher refining load did not improve the tensile index at the same apparent density. The tear index was decreased with the increase of refining load.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1699-1710
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• 2001

The characteristics of methanol and methanol blended (M85) sprays were investigated under atmospheric conditions at various temperature, ranging from on-vaporizing to vaporizing ambient conditions (298∼353 K). From laser scattering images, the macroscopic characteristics of the spray, such as the spray tip penetration and the spray angle, were determined. Entropy concept was introduced to represent homogeneity and PIV analysis was adopted to determine the fluid dynamic information at each location of the spray. The correlation between entropy and vorticity strength enabled us to find their relations. The effect of ambient composition, mainly of viscous effect as affected by CO$_2$levels, was investigated using PIV and entropy analysis. Spray width and entropy value were found to tend to decrease at increased CO$_2$levels.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.114.2-114.2
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• 2011

We have developed a PDR code to reproduce the high rotational transitions of CO observed with Herschel-PACS. Part of these high-J CO line emission is produced by UV heated outflow walls around protostars. The local FUV radiation flux is calculated by using Monte Carlo method in (${\gamma}$, ${\alpha}$) grid taking anisotropic scattering into account. Kinetic temperature and Abundance of molecules were computed self-consistently. CO Line fluxes are calculated using RIG. We compare our PDR model with the results by Visser et al (2011) to show that the derived FUV radiation field strength can be affected by the grid resolution near the outflow wall and dust scattering.

• Journal of the Korea Society for Simulation
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• v.9 no.3
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• pp.1-11
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• 2000

This paper proposes the practical echo-signal synthesis models - UTAHID (Underwater TArget by Highlight Distribution) & M-UTAHID(Modified UTAHID) - of underwater target for active sonar engineering At high frequencies all the echo components that are the specular reflected waves and various elastic scattering wave scan be regarded the summation of individual echo from some equivalent scattering centers, so the underwater target is characterized by highlights distributed in spatial target structure. Proposed models are compared with characteristics of random distributed model & equivalent interval highlight model, and analyzed target strength, echo-elongation effect, target time spread loss and so on. Thus these can be efficiently used in various real systems related to underwater target echo-signal synthesis on active sonar and acoustic countermeasure.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.3
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• pp.205-213
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• 2005

A hydroacoustic and a close-open-close zooplankton net survey were conducted to understand the distribution characteristics of the deep scattering layer (DSL) and to estimate the density of zooplankton in the DSL, in the Uljin coastal area. The survey was carried out during March 13-14 and June 4-5, 2003 at each station for zooplankton. The vertical migration mechanisms of zooplankton are very variable to the taxa. In this study, after we grasp the vertical migration of zooplankton through the results of an echo-sounder survey, we verified the mechanisms of their vertical migration in the Uljin coastal area. Also, to estimate effectively the biomass of zooplankton, we researched the acoustic scattering strength according to the species. On the basis of these results, we devised a method for estimating zooplankton biomass through comparing net and echo-soundings. We obtained the results as a follows; 1) According to the examination of collections from the net sampling, in March, 2003, Euphausia pacifica comprised $38\%$ of zooplanktons inhabiting the sound scattering layer, while copepods, chaetognaths, and amphipods accounted for $29\%,\;23\%\;and\;10\%$, respectively. And in June, 2003, the ratio of E. pacifica was $51\%$, copepods $43\%$, and the others comprised $6\%$. In both March and June E. pacifica showed dominance among the species of zooplankton. 2) The analysis of vertical distribution through acoustic data in the scattering layer was more apparent in June (spring/summer) of 2003, than in March (winter/spring) of that year. The vertical migration of zooplankton peaked around sunrise and sunset in both March and June. 3) As for the sound scattering layer, it distributed in the open sea in March, and in the inland sea in June. Therefore it is suggested that some zooplankton species such as E. pacifica performed ontogenic horizontal migration througth the spring and early summer.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.2
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• pp.152-159
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• 2017

Rockfish was a commercially important fish specie in marine ranching areas in Korea. To estimate density and biomass of rockfish using acoustic method, target strength (TS) information is required on the species. This study measured TS dependence on tilt angle and size on 14 live rockfish individuals at 38, 70, and, 120 kHz by ex-situ measurement (tethered method) and acoustic scattering model (Krichhoff ray mode, KRM). The swimbladdered angle ranged from 18 to $30^{\circ}$ ($mean{\pm}s.d.=26{\pm}4^{\circ}$). The mean TS for all individuals was highest -35.9 dB of tilt angle $-17^{\circ}$ at 38 kHz, -35.4 dB of tilt angle $-25^{\circ}$ at 70 kHz, and -34.9 dB of tilt angle $-22^{\circ}$ at 120 kHz. The ex-situ TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-67.1$, $TS_{70kHz}=20log_{10}(TL)-68.6$, and $TS_{120kHz}=20log_{10}(TL)-69.9$, respectively. The model TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-66.4$, $TS_{70kHz}=20log_{10}(TL)-67.0$, $TS_{120kHz}=20log_{10}(TL)-67.0$. The two measurements between the ex-situ TS and KRM model for TS-tilt angle and fish size were found to be significantly correlated.

• The Journal of the Acoustical Society of Korea
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• v.23 no.8
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• pp.562-569
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• 2004

An experiment for observation of the distribution of the seagrass (zostera marina) beds and characteristics of high-frequency backscattering by the photosynthesis was conducted off the coast. Acoustic data were taken as a function of the grazing angles and the relative azimuth angles on the seagrass beds of which bottom type was sandy-mud. The transmitted source signal was a 120 kHz CW waveform. Mapping of the seagrass beds distribution was drawn up using the seagrass backscattering strength with azimuth and grazing angles. The result of the comparison backscattering strength distribution of the seagrass beds was shown to be the similar to the photograph of real seagrass beds. The seagrass backscattering strength was also compared between day and night to verify the effects of the acoustical scattering by the bubbles of Photosynthetic oxygen formed on the seagrass. In these results. it is clear that observation of the seagrass beds between day and night showed the different characteristics because the bubbles of Photosynthetic oxygen affect the acoustical scattering.

• Journal of The Korean Astronomical Society
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• v.36 no.2
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• pp.55-60
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• 2003

In Lee, Kang & Byun (2001) the discovery of Raman scattered 6545 A feature was reported in symbiotic stars and the planetary nebula M2-9. The broad emission feature around 6545 A is formed as a result of Raman scattering of He II n = 6 $\to$ n = 2 photons by atomic hydrogen. In this paper, we introduce a method to compute the equivalent width of He II $\lambda$ 1025 line and present an optical spectrum of the symbiotic star RR Telescopii as an example for a detailed illustration. In this spectrum, we pay attention to the broad H$\alpha$ wings and the Raman scattered He II 6545 feature. The broad Ha wings are also proposed to be formed through Raman scattering of continuum around Ly$\beta$ by Lee (2000), and therefore we propose that the equivalent width of the He II $\lambda$ 1025 emission line is obtained by a simple comparison of the strengths of the 6545 feature and the broad H$\alpha$ wings. We prepare a template H$\alpha$ wing profile from continuum radiation around Ly$\beta$ with the neutral scattering region that is supposed to be responsible for the formation of Raman scattered He II 6545 feature. Isolation of the 6545 feature that is blended with [N II] $\lambda$ 6548 is made by using the fact that [N II] $\lambda$ 6584 is always 3 times stronger than [N II] $\lambda$ 6548. We also fit the 6545 feature by a Gaussian which has a width 6.4 times that of the He II $\lambda$ 6527 line. A direct comparison of these two features for RR Tel yields the equivalent width $EW_{Hel025} = 2.3{\AA}$ of He II $\lambda$ 1025 line. Even though this far UV emission line is not directly observable due to heavy interstellar extinction, nearby He II lines such as He II $\lambda$ 1085 line may be observed using far UV space instruments, which will verify this calculation and hence the origins of various features occurring in spectra around H$\alpha$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.2
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• pp.209-217
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• 2020

The purpose of this study was to compare the model-predicted and experimentally measured target strength (TS) of golden cuttlefish Sepia esculenta cuttlebones. Ultrasonic signals used to estimate frequency-dependent TS and the speed of sound in cuttlebones were measured by pulse-echo and through-transmission techniques, using a chirp sonar system and an ultrasonic pulser/receiver system under controlled laboratory conditions. The model appeared to slightly underestimate the predicted TS values in the frequency range of 100-160 kHz. However, there was good agreement between the predicted and measured TS values in the frequency range of 160-200 kHz. The significant similarity between the model-predicted and experimentally measured TS values supports the use of the Kirchhoff-ray mode (KRM) model for acoustic scattering analysis of cuttlebones. Accordingly, we concluded that the KRM model can be used as a tool to evaluate the frequency-dependent variability of TS due to changes in golden cuttlefish swimming depth.