• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4708-4714
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• 2022

The novelty in the present search, the Soda-Lime-Silica (SLS) glass waste to prepare free lead glass shielding was used in order to limit the accumulation of glass waste, which requires extensive time to decompose. This also saves on the consumption of pure SiO₂, which is a finite resource. Furthermore, the combining of BaO with Bi₂O₃ into a glass network leads to increased optical properties and improved attenuation. The UV-Visible Spectrophotometer was used to investigate the optical properties and the radiation shielding properties were reported for current glass samples utilizing the PhysX/PDS online software. The optical property results indicate that when BaO content increases in glass structure, the Urbach energy ΔE, and refractive index n increases while the energy optical band gap E_opt decreases. The result of the metallisation criteria (M) revealed that the present glass samples are nonmetallic (insulators). Furthermore, the radiation shielding parameter findings suggest that when BaO was increased in the glass structure, the linear attenuation coefficient and effective atomic number (Z_eff) rose. But the half-value layer HVL declined as the BaO concentration grew. According to the research, the glass samples are non-toxic, transparent to visible light, and efficient radiation shielding materials. The Ba5 sample is considered the best among all the samples due to its higher attenuation value and lower HVL and MFP values, which make it a suitable candidate as transparent glass shield shielding.

• The Journal of the Acoustical Society of Korea
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• v.27 no.1
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• pp.40-46
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• 2008

Weak target detection and localization in the presence of loud surface ship noise is a critical problem for matched field processing (MFP) in shallow water. For stationary sources, each signal component of received signal can be separated and interference can be suppressed using eigen space analysis schemes. However, source motion, in realistic cases, causes spreading of signal energies in their subspace. In this case, eigenvalues of target and interfere signal components are mixed and hard to be separated with usual phone space eigenvector decomposition (EVD) approaches. Our technique is based on mode space and utilizes the difference in their physical characteristics of surface and submerged sources. Performing EVD for modal cross spectral density matrix, interference components in the mode amplitude subspace can be classified and eliminated. This technique is demonstrated with synthetic data, and results are discussed.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.301-308
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• 2024

Ceramic materials are being explored as alternatives to toxic lead sheets for radiation shielding due to their favorable properties like durability, thermal stability, and aesthetic appeal. However, crafting effective ceramics for radiation shielding entails complex processes, raising production costs. To investigate local viability, this study evaluated Malaysian ceramic tiles for shielding in diagnostic X-ray rooms. Different ceramics in terms of density and thickness were selected from local manufacturers. Energy Dispersive X-ray Fluorescence (EDXRF) and X-ray Fluorescence (XRF) characterized ceramic compositions, while Monte Carlo Particle and Heavy Ion Transport code System (MC PHITS) simulations determined Linear Attenuation Coefficient (LAC), Half-value Layer (HVL), Mass Attenuation Coefficient (MAC), and Mean Free Path (MFP) within the 40-150 kV energy range. Comparative analysis between MC PHITS simulations and real setups was conducted. The C3-S9 ceramic sample, known for homogeneous full-color structure, showcased superior shielding attributes, attributed to its high density and iron content. Notably, energy levels considerably impacted radiation penetration. Overall, C3-S9 demonstrated strong shielding performance, underlining Malaysia's potential ceramic tile resources for X-ray room radiation shielding.

• Journal of Korean society of Dental Hygiene
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• v.10 no.3
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• pp.541-553
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• 2010

Objectives : The purpose of this study was to examine the use of dentifrice for children, the state of dentifrice for children on the market and the relationship between the bore of dentifrice and the amount of dentifrice used in an effort to provide parents, main consumers of dentifrice for children, with the right information on dentifrice. Methods : Data on the use of children's dentifrice were gathered by investigating parents in Seoul and Gyeonggi Province in July and August, 2009. The selected parents had children aged one to five in Western age. Results : 1. As to the purchase of dentifrice for children, the largest group (75.9%) were aware of the name of the toothbrush used by their children, and the greatest group (97.3%) bought the toothbrush on behalf of them. Advertising was the most dominant source of information on the choice of dentifrice (51.8%), and non-professionals were the most common providers of information on that (55.9%). 2. The amount of dentifrice used at a time was a mean of $0.467{\pm}0.270g$. There was a wide disparity in that aspect from a low of 0.100 to 1.900g. As to the influence of the size of the bore of dentifrice, the greatest amount of dentifrice was used ($0.670{\pm}0.306g$) when the bore of dentifrice was 9 mm in size, and the bore size 9 mm was significantly different from the size 3 mm and 6 mm in that aspect (p<0.001). 3. There was one kind of imported dentifrice for children on the market. Concerning the fluoride ingredient of dentifrice, the biggest number of dentifrice contained MFP only. As to the size of the bore of dentifrice, there was a difference of 3 to 9 mm. Most of dentifrice for children included the pictures of particular characters. Conclusions : The above-mentioned findings illustrated that there is a serious concern for the intake of fluoride among infants and preschoolers, it's needed to pay careful attention to the use of dentifrice. Dentifrice for children should be manufactured in consideration of the relationship between the size of the bore and the amount of dentifrice used.

• Journal of The Korean Astronomical Society
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• v.36 no.3
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• pp.89-95
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• 2003

Observations of dark matter dominated dwarf and low surface brightness disk galaxies favor density profiles with a flat-density core, while cold dark matter (CDM) N-body simulations form halos with central cusps, instead. This apparent discrepancy has motivated a re-examination of the microscopic nature of the dark matter in order to explain the observed halo profiles, including the suggestion that CDM has a non-gravitational self-interaction. We study the formation and evolution of self-interacting dark matter (SIDM) halos. We find analytical, fully cosmological similarity solutions for their dynamics, which take proper account of the collisional interaction of SIDM particles, based on a fluid approximation derived from the Boltzmann equation. The SIDM particles scatter each other elastically, which results in an effective thermal conductivity that heats the halo core and flattens its density profile. These similarity solutions are relevant to galactic and cluster halo formation in the CDM model. We assume that the local density maximum which serves as the progenitor of the halo has an initial mass profile ${\delta}M / M {\propto} M^{-{\epsilon}$, as in the familiar secondary infall model. If $\epsilon$ = 1/6, SIDM halos will evolve self-similarly, with a cold, supersonic infall which is terminated by a strong accretion shock. Different solutions arise for different values of the dimensionless collisionality parameter, $Q {\equiv}{\sigma}p_br_s$, where $\sigma$ is the SIDM particle scattering cross section per unit mass, $p_b$ is the cosmic mean density, and $r_s$ is the shock radius. For all these solutions, a flat-density, isothermal core is present which grows in size as a fixed fraction of $r_s$. We find two different regimes for these solutions: 1) for $Q < Q_{th}({\simeq} 7.35{\times} 10^{-4}$), the core density decreases and core size increases as Q increases; 2) for $Q > Q_{th}$, the core density increases and core size decreases as Q increases. Our similarity solutions are in good agreement with previous results of N-body simulation of SIDM halos, which correspond to the low-Q regime, for which SIDM halo profiles match the observed galactic rotation curves if $Q {\~} [8.4 {\times}10^{-4} - 4.9 {\times} 10^{-2}]Q_{th}$, or ${\sigma}{\~} [0.56 - 5.6] cm^2g{-1}$. These similarity solutions also show that, as $Q {\to}{\infty}$, the central density acquires a singular profile, in agreement with some earlier simulation results which approximated the effects of SIDM collisionality by considering an ordinary fluid without conductivity, i.e. the limit of mean free path ${\lambda}_{mfp}{\to} 0$. The intermediate regime where $Q {\~} [18.6 - 231]Q_{th}$ or ${\sigma}{\~} [1.2{\times}10^4 - 2.7{\times}10^4] cm^2g{-1}$, for which we find flat-density cores comparable to those of the low-Q solutions preferred to make SIDM halos match halo observations, has not previously been identified. Further study of this regime is warranted.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.22 no.4
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• pp.15-34
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• 2019

Today, there is increasing recognition of the importance of urban regeneration for better public places. Urban parks as a public area play an important role in harnessing its positive impact on people's well-being: where the standards and funding of/for the parks are getting worse. There is however less a focus on policy approach to park regeneration in the country. Neverthless, a few UK's cases of such innovative park management(PM) has shown successful park regeneration based on policy support. Therefore, the aim of this research is to draw policy implications by exploring a case of successful park regeneration. To address the aim, this research conducts an in-depth case study of 'Manor Fields Park, UK', digging into its PM structure and PM body 'Green Estate Ltd' in relation to relevant policy. The data is mainly collected by interviews including a group interview. The analytical framework 'Place-keeping(PK)' and its six dimensions are employed to determine the characteristics of MFP's PM structure. Resultingly, there is a significant shift in the approach to PM which stresses the principle of long-term and self-sustaining structure led by a non-profit organisation and strong impacts of policy. In this context, PK highlights significant drivers for parks regeneration particularly in terms of policy implications: 1)providing policy support to encourage non-profit organisations in PM, 2)extending community involvement in decision-making processes, 3)promoting income generation by community groups, 4)shifting public awareness of shared responsibility for PM, 5)completing regular park maintenance assessment by community groups, and 6)delivering low-maintenance approaches to PM. To support these implications, PM structure for successful parks regeneration does meet a holistic and multi-dimensional approach of place-keeping underlined by understanding policy contexts and rethinking current status quo of PM. Addressing these implications will shed light on urban PM in an era of austerity and ultimately contribute to improving people's well-being.

• The Journal of the Acoustical Society of Korea
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• v.25 no.7
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• pp.346-355
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• 2006

Acoustic data from a shallow water experiment in the East Sea of Korea (MAPLE IV) is Processed to investigate the Performance of matched-field geo-acoustic inversion and source localization. The receiver array consists of two legs as in an L-shape. one vertical and the other horizontal lying on the seabed. Narrowband multi-tone CW source was towed along a slightly inclined bathymetry track. The matched-field geo-acoustic inversion includes comparisons between three processing techniques. all based on the Bartlett processor as; (1) the coherent processing of the data from the full array, (2) the incoherent Product of each output from both the horizontal and vertical arrays, and (3) the cross correlation between the horizontal and vertical arrays. as well as processing each array leg separately. To verify the inversion results. matched-field source localization for low level source signal components were performed using the same Processors used at the inversion stage.