• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.225-232
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• 2004

Shocks are ubiquitous in astrophysical environments and cosmic-rays (CRs) are known to be accelerated at collisionless shocks via diffusive shock acceleration. It is believed that the CR pressure is important in the evolution of the interstellar medium of our galaxy and most of galactic CRs with energies up to ${\~}\;10^{15}$ eV are accelerated by supernova remnant shocks. In this contribution we have studied the CR acceleration at shocks through numerical simulation of 1D, quasi-parallel shocks for a wide range of shock Mach numbers and shock speeds. We show that CR modified shocks evolve to time-asymptotic states by the time injected particles are accelerated to moderately relativistic energies, and that two shocks with the same Mach number, but with different shock speeds, evolve qualitatively similarly when the results are presented in terms of a characteristic diffusion length and diffusion time. We find that $10^{-4} - 10^{-3}$ of the particles passed through the shock are accelerated to form the CR population, and the injection rate is higher for shocks with higher Mach number. The time asymptotic value for the CR acceleration efficiency is controlled mainly by shock Mach number, and high Mach number shocks all evolve towards efficiencies ${\~}50\%$, regardless of the injection rate and upstream CR pressure. We conclude that the injection rates in strong quasi-parallel shocks are sufficient to lead to significant nonlinear modifications to the shock structures, implying the importance of the CR acceleration at astrophysical shocks.

• Journal of Environmental Science International
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• v.14 no.8
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• pp.749-760
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• 2005

This study examines the local ozone photochemistry in the urban air. The photochemical formation and destruction of ozone was modeled using a photochemical box model. For the model prediction of ozone budget, measurements were carried out from an urban monitoring station in Seoul ($37.6^{\circ}N,\;127^{\circ}E$), Korea for intensive sampling time period (Jun. $1\~15$, 2003). Photochemical process is likely to play significant role in higher ozone concentrations during the sampling period. The results of model simulation indicated that photochemical ozone production pathway was the reaction of NO with $HO_2$ while ozone destruction was mainly controlled by a photochemical destruction pathway, a reaction of $H_2O$ with $O(^1D).$ The contribution of NMHCs to formation and destruction of ozone in the urban was significant. This was entirely different from remote marine environment. The rates of net photochemical ozone production ranged from 0.1 to 1.3 ppbv $h^{-1}$ during the study period.

• Journal of The Korean Astronomical Society
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• v.48 no.6
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• pp.399-412
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• 2015

We study the radio properties at 1.4 GHz of Seyfert galaxies with strong forbidden highionization lines (FHILs), selected from the Sloan Digital Sky Survey - a large-sized sample containing nearly equal proportion of diverse range of Seyfert galaxies showing similar redshift distributions compiled by using the Very Large Array survey images. The radio detection rate is low, 49%, which is lower than the detection rate of several other known Seyfert galaxy samples. These galaxies show low star formation rates and the radio emission is dominated by the active nucleus with ≤10% contribution from thermal emission, and possibly, none show evidence for relativistic beaming. The radio detection rate, distributions of radio power, and correlations between radio power and line luminosities or X-ray luminosity for narrow-line Seyfert 1 (NLS1), Seyfert 1 and Seyfert 2 galaxies are consistent with the predictions of the unified scheme hypothesis. Using correlation between radio and [O III] λ 5007 Å luminosities, we show that ∼8% sample sources are radio-intermediate and the remaining are radio-quiet. There is possibly an ionization stratification associated with clouds on scales of 0.1-1.0 kpc, which have large optical depths at 1.4GHz, and it seems these clouds are responsible for free-free absorption of radio emission from the core; hence, leading to low radio detection rate for these FHIL-emitting Seyfert galaxies

• Korean Journal of Health Education and Promotion
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• v.17 no.2
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• pp.151-163
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• 2000

Adopting the theory of enter-educate, this study was conducted to prevent the smoking by middle school students who had not started smoking yet. A famous pop music singer with high popularity among teenagers was cast on the public sponsored advertisement (PSA) on smoking prevention. This PSA was televised through major TV stations for two months. The effectiveness of this project was evaluated seven times. The effectiveness of the PSA, the role of the cast singer, the rate of seeing the PSA, and the impression about the PSA were evaluated. The viewer survey since the second period of the PSA revealed that most of the middle school students (79~94 percent) watched it. Among TV stations, MBC recorded the highest viewer rate as 69.6~72.0 percent of the middle school students watched the PSA at least once from this station. Also, the viewer rates of such cable TV stations as Mnet and OCN were quite high for their advertisement prices. The overall impression about the PSA was favorable. The contribution of the singer to this positive outcome was 60 percent and over. The effect of smoking prevention was also high as 93.7 percent of the middle school students replied that they would not start smoking. However, since this study dealt with the general public, it was not possible to control the effect of other factors systematically. Also, we could not measure the differences bewteen the pre-PSA and the post-PSA periods, so that the interpretation of the results has some limitation.

• Transactions on Electrical and Electronic Materials
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• v.1 no.3
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• pp.6-9
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• 2000

Selectively excited photoluminescence(PL) spectroscopy has been carried out on the ~1540 nm $^{4}$I$_{13}$ 3/ to $^{4}$I/wub 15/2/ emissions of the multiple Er$^{3+}$ centers observed in Er-implante undoped and Mg-doped GAN at temperatures ranging from 6K to 295K. The temperature dependence of the Er$^{3+}$ PL spectra selectively excited by below -gap light demonstrates different quenching rates for the distinct Er$^{3+}$ centers, and indicates that the PL spectra with the most rapid thermal quenching rats do not contribute to the room temperature, above-p-pumped Er$^{3+}$ spectrum. In addition, selective PL spectroscopy has ben carried out on the Er$^{3+}$ emission in Er-implanted undoped and Mg-doped GaN at temperatures ranging 6K to 295K. The results indicate that the previously reported enhancement of the violet-pumped centers contribution to the low temperature above excited Er$^{3+}$ PL in Mg-doped GaN is also evident at room temperature.temperature.

• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.48-57
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• 2009

Primary production of epiphytic and planktonic algae in a shallow reed zone of a lagoon Nishinoko was investigated. Concentrations of nutrients varied widely horizontally and locally in the lagoon. It seems that the reed zone has a heterogeneous environment. The photosynthetic rates of epiphytic and planktonic algae were 7 to 14 mg C surface stem $m^{-2}hr^{-1}$ and 12 to $46mg\;Cm^{-3}hr^{-1}$, respectively. The areal primary production of epiphytic algae was estimated as 4 to $13mg\;Cm^{-2}hr^{-1}$ from the stem density of Phragmites and the water depth at each station. The production of phytoplankton, on the other hand, was 5 to $56mg\;Cm^{-2}hr^{-1}$. The contribution of epiphytic algae to total primary production averaged 53%, although the assimilation number was much lower than that of phytoplankton. The present results indicate that the epiphytic algae are one of the significant primary producers in the reed zone.

• Journal of Information Processing Systems
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• v.16 no.4
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• pp.784-794
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• 2020

In order to effectively evaluate the urban water security, the study investigates a novel system to assess factors that impact urban water security and builds an urban water poverty evaluation index system. Based on the contribution rates of Resource, Access, Capacity, Use, and Environment, the study adopts the Water Poverty Index (WPI) model to evaluate the water poverty levels of 14 cities in Gansu during 2011-2018 and uses the least variance method to evaluate water poverty space drive types. The case study results show that the water poverty space drive types of 14 cites fall into four categories. The first category is the dual factor dominant type driven by environment and resources, which includes Lanzhou, Qingyang, Jiuquan, and Jiayuguan. The second category is the three-factor dominant type driven by Access, Use, and Capability, which includes Longnan, Linxia, and Gannan. The third category is the four-factor dominant type driven by Resource, Access, Capability, and Environment, which includes Jinchang, Pingliang, Wuwei, Baiyin, and Zhangye. The fourth category is the five-factor dominant type, which includes Tianshui and Dingxi. The driven types impacting the urban water security factors reflected by the WPI and its model are clear and accurate. The divisions of the urban water security level supply a reliable theoretical and numerical basis for an urban water security early warning mechanism.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.9-17
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• 2000

The crystal growth and dissolution rates were calculated by solving a model equation, which involved the dissolution of the metastable phase($\beta$-HNIW) and growth of the stable phase($\varepsilon$-HNIW), together with the mass balance equation. The model has been successfully used to simulate available kinetic data for the $\beta$$\longrightarrow$$\varepsilon$ polymorphic transformation via a solution phase. From the effectiveness factor based on the two-step model, it was found that the surface integration contribution to the process was comparatively small, and a diffusion dependency decreased with an increase of the mass fraction of chloroform in the mixed solvents of ethyl acetate and chloroform. Appling these kinetics in process simulation allowed for the prediction of the product size of $\varepsilon$-HNIW.

• Environmental Engineering Research
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• v.23 no.4
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• pp.449-455
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• 2018

In this study, the contribution of hot biomass ash to enrichment of the mineral content and to reducing the moisture content of broiler poultry manure was investigated. For this purpose, the mixtures have been prepared by adding biomass ash at varying rates (10%, 20%, 30%, 40% and 50%) and at different temperatures ($100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$ and $250^{\circ}C$) according to the dry matter content (74.77%) of the poultry manure. The results showed that incorporation of biomass ash into poultry manure at 50% at $250^{\circ}C$ reduced the moisture content from 25.23% to 9.82%. Regarding the maximum N in the final product, the ideal temperature of biomass ash has been obtained at $150^{\circ}C$. The highest nutrient contents were obtained at 50% biomass ash incorporation. The highest dose of biomass ash application had significantly increased nutrients, such as Ca (19.34%), K (4.03%), Fe (1,545 mg/kg), Mn (812 mg/kg) and Zn (479 mg/kg) in the final organomineral fertiliser formulation. Overall, it was concluded that the addition of hot biomass ash can dramatically decrease the moisture content of poultry manure and therefore provide odour and pathogen removal and increase its plant nutrient content.

• Membrane and Water Treatment
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• v.10 no.1
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• pp.67-74
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• 2019

Apparent changes in the natural hydrologic cycle causing more frequent floods in urban areas and surface water quality impairment have led stormwater management solutions towards the use of green and sustainable practices that aims to replicate pre-urbanization hydrology. Among the widely documented applications are infiltration techniques that temporarily store rainfall runoff while promoting evapotranspiration, groundwater recharge through infiltration, and diffuse pollutant reduction. In this study, a laboratory-scale infiltration device was built to be able to observe and determine the factors affecting flow variations and corresponding solids removal through a series of experiments employing semi-synthetic stormwater runoff. Results reveal that runoff and solids reduction is greatly influenced by the infiltration capability of the underlying soil which is also affected by rainfall intensity and the available depth for water storage. For gravel-filled structures, a depth of at least 1 m and subsoil infiltration rates of not more than 200 mm/h are suggested for optimum volume reduction and pollutant removal. Moreover, it was found that the length of the structure is more critical than the depth for applications in low infiltration soils. These findings provide a contribution to existing guidelines and current understanding in design and applicability of infiltration systems.