• Journal of the Korean Society of Radiology
• /
• v.13 no.6
• /
• pp.825-830
• /
• 2019

A detector module measuring a depth of interaction was developed using silicon photomultiplier (SiPM) and two layers of scintillation crystal array treated with multiple reflectors. When reconstructing an image based on a signal obtained by using different types of reflector of each layer, the interaction positions of scintillation pixels and gamma rays could be tracked by utilizing the feature that all scintillation pixels were recorded at different positions. The bottom layer uses a specular reflector, and the top layer uses a diffuse reflector to differently process the size of the signal obtained from the SiPM. The optical grease was used to recude the sharp refractive index change between the layers of scintillator and the SiPM. The signals obtained from the 16 SiPMs were reduced to four signals using the Anger equations, and the images were reconstructed using them. All the scintillation pixels composed of the two layers appeared in the reconstructed image, which distinguished the layer where the scintillation pixels and gamma rays interacted. If the detectors, which measure the interaction depth of two layers using different reflectors, will be applied to preclinical positron emission tomography, the degradation of spatial resolution appearing outside the field of interest could be solved.

• Applied Chemistry for Engineering
• /
• v.25 no.3
• /
• pp.274-280
• /
• 2014

Polysulfone (PSf) hollow fiber membranes were prepared via the nonsolvent induced phase separation technique. The cosolvent of ${\gamma}$-butyrolactone (GBL) was added to the polymer solution containing a mixture of PSf and N,N-dimethylacetamide (DMAc). Water was utilized as a precipitation nonsolvent. The morphology of prepared membranes was investigated using a field emission scanning electron microscopy. The fabricated membrane showed a typical asymmetric structure such as the dense layer on the porous support layer by the addition of GBL to the polymer solution. As the concentration of GBL increased, the asymmetric porous structure was shown to be more intensified. It was thought that the added GBL played a role of enhancing the liquid-liquid phase separation of the polymer solution, since the cosolvent of GBL might change the thermodynamic solubility parameter of the doping solution. Permeation properties through the prepared hollow fiber membranes were characterized by measuring the pure water flux and the solute rejection using $0.05{\mu}m$ polystyrene latex (PSL) beads. Experimental results revealed that the use of PEG as the internal coagulant enhanced the pure water flux up to 130 times compared to the use of EG while the rejection of the PSL beads decreased only 5%.

• Journal of the Korean Applied Science and Technology
• /
• v.34 no.4
• /
• pp.866-873
• /
• 2017

Exhaust regulations of automobile are being reinforced increasingly as environmental problems issues came to the fore by industrial development. However, it is known that the exhaust emission is not only influenced by the system of automobile but also the fuel properties. In particular, high-performance engines have required high-performance fuels with high lubricity as CRDI engines(diesel engine) have been developed and commercialized. This paper have examined that the fuel property variations affect a major parts and an exhaust gas of automobile. It was confirmed that the high pressure pump, the injector and the DPF(diesel particulate filter) were damaged and fuel efficiency was get worse due to use the fuel of lacking lubricity property($651{\mu}m$/quality standard: less in $400{\mu}m$). In addition, through an iron component was detected in the broken DPF, it was estimated that the breakage of the DPF was caused by the excessive exhaust of the particulate matter due to the iron component of the fuel.

• Korean Journal of Dental Materials
• /
• v.43 no.4
• /
• pp.343-349
• /
• 2016

This experiment was carried out to examine whether the post-firing heat treatment is effective in increasing the hardness of metal-ceramic alloy of the Pd-Au-Ag-Sn system. Precipitation hardening by holding at $600^{\circ}C$ after simulated complete porcelain firing in a metal-ceramic alloy of the Pd-Au-Ag-Sn system was examined by observing the change in hardness, crystal structure, and microstructure using a hardness test, X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The hardness of the alloy increased apparently by holding the specimen at $600^{\circ}C$ for 30 min after simulated complete porcelain firing. The formation of fine grain interior precipitates during holding at $600^{\circ}C$ caused the formation of lattice strain in the grain interior, resulting in apparent hardening. The faster cooling rate (stage 0) during simulated complete porcelain firing resulted in more effective precipitation hardening during holding at $600^{\circ}C$. From the above results, an appropriate post-firing heat treatment, such as holding at $600^{\circ}C$ for 30 min after complete porcelain firing may increase the durability of metal-ceramic prostheses composed of Pd-Au-Ag-Sn alloy.

• Korean Journal of Soil Science and Fertilizer
• /
• v.28 no.2
• /
• pp.183-190
• /
• 1995

Various factors such as sampling height in the chamber, sampling interval, sampling time at daytime and the effects of pedoturbation on methane emission during chamber installation were evaluated using a simplified closed static chamber method to measure methane flux in paddy soils. Sampling height of the chamber for representative samples was 65cm. An additional DC fan was required to attain an even methane gradient in the chamber. Considering the change of methane concentration and air temperature in the chamber, sampling is recommended to finish within 30 minutes after starting sampling. The aim of setting DC fan in the chamber was to get the thermal equilibrium in the chamber as well as the representative samples. Suitable time to collect the gas samples representing the day's methane flux was 0900~1200 hours. Gas sampling was possible even after installation of small chambers if the elapsed time was more than 6 hours and supporting stand would be to be added to minimize pedoturbation.

• Korean Journal of Optics and Photonics
• /
• v.32 no.5
• /
• pp.220-229
• /
• 2021

The optical characteristics of high-power direct-lit white light-emitting diode (LED) lighting were investigated, where a quantum dot (QD) film was adopted to enhance the color-rendering index (CRI). The transmittance of the diffuser plate and the concentration of the QD film were varied in this study. The color coordinates and the correlated color temperature (CCT) did not show any appreciable change, while the CRI values increased slightly as the transmittance of the diffuser plate decreased. The investigated optical properties were nearly independent of the viewing angle, and the luminance distribution was close to Lambertian. The CCT decreased from approximately 6000 K to approximately 4000 K as the concentration of the QD film increased from 0 to 7.5 wt%, which was due to the enhanced red component in the emission spectrum. The CRI increased to approximately 95 for some optical configurations of the lighting. These results demonstrate that glare-free, color-changeable, high-rendering LED lighting can be realized by using a combination of a diffuser plate of appropriate transmittance and a red QD film.

• Journal of the Korean Applied Science and Technology
• /
• v.35 no.4
• /
• pp.1349-1358
• /
• 2018

In addition to responding to the environmental pollution caused by fossil fuels, the enforcement of Renewable Fuel Standard(RFS) system has increased the utilization of renewable energy such as refined fuels oil. The by-product fuel oil(No. 2) and the refined fuel oil(reduced-pressure) are strictly regulated by the domestic legislation and the chemical property changes of the refined fuel oil(reduced-pressure) mixed with the by-product fuel oil(No. 2) were analyzed. As a result of analyzing the physical properties of refined fuel oil(reduced pressure) obtained by mixing 1 : 1 of by-product fuel oil(No. 2), it satisfied the quality standards stipulated by the domestic Enforcement Decree of the Wastes Control Act. However, the results of the additional tests related to the fuel showed a high aromatic content. The high content of aromatic in a fuel is likely to cause the soot and ehaust emission gas during the combustion of the used equipment.

• Journal of Environmental Science International
• /
• v.27 no.11
• /
• pp.1129-1140
• /
• 2018

Temporal and spatial characteristics of the frequency of several weather types and the change in air pollutant concentrations according to these weather types were analyzed over a decade (2007-2016) in seven major cities and a remote area in Korea. This analysis was performed using hourly (or daily) observed data of weather types (e.g., mist, haze, fog, precipitation, dust, and thunder and lighting) and air pollutant criteria ($PM_{10}$, $PM_{2.5}$, $O_3$, $NO_2$, CO, and $SO_2$). Overall, the most frequent weather type across all areas during the study period was found to be mist (39%), followed by precipitation (35%), haze (17%), and the other types (${\leq}4%$). In terms of regional frequency distributions, the highest frequency of haze (26%) was in Seoul (especially during winter and May-June), possibly due to the high population and air pollutant emission sources, while that of precipitation (47%) was in Jeju (summer and winter), due to its geographic location with the sea on four sides and a very high mountain. $PM_{10}$ concentrations for dust and haze were significantly higher in three cities (up to $250{\mu}g/m^3$ for dust in Incheon), whereas those for the other four types were relatively lower. The concentrations of $PM_{2.5}$ and its major precursor gases ($NO_2$ and $SO_2$) were higher (up to $69{\mu}g/m^3$, 48 ppb, and 16 ppb, respectively, for haze in Incheon) for haze and/or dust than for the other weather types. On the other hand, there were no distinct differences in the concentrations of $O_3$ and CO for the weather types. The overall results of this study confirm that the frequency of weather types and the related air quality depend on the geographic and environmental characteristics of the target areas.

• Journal of Environmental Impact Assessment
• /
• v.28 no.2
• /
• pp.141-151
• /
• 2019

Korea has passed the Act on the Integrated Control of Pollutant-Discharging Facilities in 2015, and the integrated environmental management under the BAT standard is underway. To summarize the nature of integrated environmental management, it is the regulation by the integration of the management of the multi-pollutant source and the technical standard of BATs. In general, in environmental economics, regulation-based on technical standards are known to be inefficient. This paper attempts to evaluate the efficiency of BAT standards from an economic point of view. A simple multi-pollutant model demonstrates that the inefficiency of the environmental tax with imperfect information in a single pollutant situation is amplified under multi-pollutant conditions. The simultaneous introduction of BAT and IPPC can be partially explained by this logic. It is also highlighted by the strengthening of BAT standards by EU, as a countermeasure to the potential deterioration of air quality caused by the change of effective environmental taxes accompanying the fuel and emission price changes.

• Journal of Korean Society of Forest Science
• /
• v.100 no.2
• /
• pp.149-153
• /
• 2011

This study was conducted to examine the uncertainty analysis of the stem density and biomass expansion factor for Pinus rigida in Korea. A total of 57 representative sample trees were harvested. The age class in Pinus rigida forests was divided into two, which were stands with less than 20 years and more than 21 years. The influence of stand ages on biomass expansion factor showed that it was statistically significant (p=0.0001), but it was not significant on stem density (p=0.8070). The results of this study based on the uncertainty evaluation method which were suggested by IPCC guide line indicated that stem density of the stand with less than 20 years were 30.92%, while were 25.12% the stands with more than 21years. The uncertainty in biomass expansion factor of less than 20 years and more than 21 years were 60.32% and 22.42%, respectively. The uncertainty of less than 20 years was higher compared to those stands with more than 21 years. In the case of old stand, it showed the lowest uncertainty results but younger stands showed the highest uncertainty results. This study could be applied to our country's emission factor by using stem density and biomass expansion factors which were less than 20 years and more than 21 years for Pinus rigida in Korea.