• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.117-124
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• 2005

Appropriate removal of pollutants from combined sewer overflows(CSOs) and stormwater runoff is of primary concern to watershed managers trying to meet water quality standards even under a wet weather condition. Harmful substances associated with particles besides TSS and BOD are subjected to removal prior to discharge into the natural waters. Effectiveness of five major hydrodynamic separation technologies, Vortechs, Downstream Defender including Storm King for CSOs control, CDS, Stormceptor, and IHS, were evaluated in this study. There is not sufficient information for accurate evaluation of the removal efficiency for the pollutants from the stormwater runoff and CSOs. Based upon limited engineering data, however, all technologies were found to be effective in separation of heavy particles and floating solids. Technologies utilizing screens seem to have advantage in the treatment capacity than the other technologies relied fully on hydrodynamic behavior. The IHS system seems to have a strong potential in application for control of CSOs because of unique hydrodynamic behavior as well as a flexibility in opening size of the screens. Size of the particulate matter in the CSOs and stormwater runoff is found to be the most important parameter in selection of the type of the hydrodynamic separators. There exists an upper limit in the solids removal efficiency of a hydrodynamic separator, which is strongly dependent upon the particle size distribution of the CSOs and stormwater runoff.

• Membrane Journal
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• v.29 no.2
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• pp.105-110
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• 2019

Porous membranes are widely used in industry for removing particulate matter. Unlike conventional porous membrane fabrication methods, the solution spreading phase separation method can form pores very simply. The first step is to wet the mesh with the support layer, then to let the polysulfone solution flow into a solvent without water. The solvent is readily vaporized and the polysulfone is made into a thin film. When the polysulfone solution is mixed with water to form pores, the pore size can be adjusted according to the concentration ratio of the polysulfone solution. The thickness of the membrane is easily controlled by the concentration of the solution. The porous separator has the formation of meshes intact and is very useful for forming a three-dimensional structure. The solution spreading phase separation method proposed in this study is characterized by its high cost competitiveness compared with conventional membranes due to its low production cost and easy process control.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.119-128
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• 2020

An ultrasonic multiple scattering simulation using cross-section of fine dust particles were proposed. These days, along with awareness of air pollution, social interest in fine dust is increasing. In the construction field, awareness of fine dust is increasing, and research on preparing various countermeasures is underway. The light scattering method fine dust meter currently in use is affected by environmental factors such as relative humidity, and reliability problems in terms of accuracy are continuously reported. However, the transmission of ultrasonic waves can directly reflect the physical change of the medium based on the mechanical wave. Using these advantages of ultrasonic waves, fine dust measurement simulation was performed using the scattering cross section and ultrasonic multiple scattering theory. The shape data of the fine dust particles were collected using a SEM (Scanning Electron Microscope), and a cross-section according to the fine dust particles was derived through numerical analysis. As a result of signal processing, the error for the number density corresponding to each cross-section is minimum 19, maximum 3455.

• Korean Journal of Remote Sensing
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• v.36 no.6_3
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• pp.1681-1690
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• 2020

A scanning lidar system has been developed. The system has two wavelength observation channels of 532 and 1064 nm and is capable of 360-degree horizontal scanning observation. In addition, an analysis method that can classify the measured particle as an indicator of coarse-mode particle (PM2.5-10) and an indicator of fine-mode particles (PM2.5) and calculate the mass concentration of each has been developed by using the backscatter coefficient at two wavelengths. It was applied to the data calculated by observation. The mass concentrations of PM10 and PM2.5, which showed a distribution of 22-110 ㎍/㎥ and 7-78 ㎍/㎥, respectively, were successfully calculated in the Ulsan Onsan Industrial Complex using the developed scanning lidar system. The analyzed results showed similar values to the mass concentrations measured on the ground around the lidar observation area, and it was confirmed that high concentrations of 80-110 ㎍/㎥ and 60-78 ㎍/㎥ were measured at points discharged from factories, respectively.

• Ocean and Polar Research
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• v.44 no.3
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• pp.221-233
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• 2022

A sediment trap had been deployed at 1250 m depth in the Eastern Tropical Pacific (ETP) from September 2009 to July 2010, with the aim of understanding the temporal and vertical variability of particle flux. During the monitoring period, total particle flux varied from 12.4 to 101.0 mg m^-2day^-1, with the higher fluxes in January-March 2010. Biogenic particle flux varied in phase with the total particle flux. The increase in total particle flux during January-March 2010 was attributed to the enhanced biological production in the surface layer caused by wind-driven mixing in response to the seasonal shifts in the location of the Intertropical convergence zone. The export ratio (e-ratio) was estimated using the particulate organic carbon flux and satellite-derived net primary production data. The estimated e-ratios changed between 0.8% and 2.8% (1.4±0.6% on average). The ratio recorded in the negative phase of Pacific decadal oscillation (PDO) was similar to the previous results obtained from the ETP during the 1992/93 periods in the positive phase of PDO. This suggests that the regime shift of the PDO is not related to the carbon export ratio.

• Composites Research
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• v.35 no.5
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• pp.309-316
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• 2022

The demand for cold-resistant cable material is increasing due to the rapid increase in the development of devices that operate in a low temperature environment. Cold tolerance of a thermoplastic polymer largely depends on the type and content of about 20 or more additives used to make the polymer. The phenomenon of polymer hardening at low temperature can be classified into hardening by simple temperature effect, embrittlement at the glass transition temperature, and hardening by crystallization of polymers that tend to crystallize. In this study, a thermoplastic polymer having a low glass transition temperature, a flame retardant, and an additive were mixed to evaluate the mechanical properties of a thermoplastic polymer composite material for electric wires. It has been confirmed that mechanical properties and processability are determined depending on the additives and compatibilizers added, and this study is considered to be useful as basic data for optimization to meet the performance requirements of wires developed for low-temperature use.

• Journal of The Korean Association For Science Education
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• v.28 no.5
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• pp.471-481
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• 2008

This study investigated connecting errors by students' field independence-dependence in learning chemistry concepts with multiple external representations in current science textbooks. Seventh graders (N=196) at a middle school were assigned to the BL and CL groups, which were respectively taught "Boyle's Law" and "Charles's Law." A field independence-dependence test was administered. After learning the target concept with text and picture emphasizing the particulate nature of matter, a connecting test was also administered. Five types of connecting errors were identified: Insufficient connection, misconnection, rash connection, impossible connection, and failing to connect. 'Failing to connect,' 'Misconnection,' and 'Rash connection' were found to be the frequent types of connecting errors regardless of the target concepts. The frequencies and percentages of the types of connecting errors were not significantly different between the field independent and field dependent students. Educational implications of these findings are discussed.

• Journal of ILASS-Korea
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• v.29 no.2
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• pp.68-74
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• 2024

As awareness of environmental pollution problems increases worldwide, interest in air pollutants is increasing. In particular, NOx and PM, which are major pollutants in diesel vehicles, are contributing significantly to emissions. As a result, its importance is increasing. In this study, based on research results applied to large diesel vehicles, the problem of natural regeneration caused by low exhaust gas temperature during low speed and low load operation is solved by applying a complex regeneration DPF that is not affected by temperature conditions to small diesel vehicles. The feasibility of application to small diesel vehicles was reviewed by measuring the emission reduction efficiency. As a result of the engine test, the power reduction rate and fuel consumption rate before and after device installation under full load conditions were 2.9% decrease and 3.5% increase, respectively, satisfying the standard for a 5% reduction, and as a result of the regeneration equilibrium temperature (BPT) test, the regeneration temperature was 310℃. appeared at the level. The reduction efficiency test results for the actual vehicle durability test equipment showed 97.3% PM, 51.0% CO, and 31.1% HC, while the city commuter vehicle had PM 97.5%, CO 61.7%, HC 40.0%, and the school bus vehicle had PM 96.8%, CO 44.4%, HC 34.3%, and low-speed logistics vehicles showed a reduction efficiency of 98.2% for PM, 36.0% for CO, and 45.7% for HC. Based on the results of this study, in the future, it is necessary to secure DPF technology suitable for all vehicle types through actual vehicle application research on temperature condition-insensitive composite regenerative DPF for medium-sized vehicles.

• Journal of The Korean Institute of Defense Technology
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• v.6 no.1
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• pp.13-18
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• 2024

While fine dust is currently spreading around the world, fine dust is so small that it easily enters indoors and deteriorates indoor air quality, so it is an essential issue that must be solved to maintain cleanliness and improve air quality in households. Research on nanoradiation technology is continuously being conducted to effectively block fine dust and secure air permeability and dust collection rate. In this study, a PVDF fine dust dust-proof net was manufactured through electrospinning, and an experiment was conducted to confirm the external environmental resistance and indoor air quality improvement efficiency of the manufactured dust-proof net. It was verified that this dustproof net can be a practical alternative to effectively block fine dust and prevent diseases caused by fine dust.

• Journal of the Korean earth science society
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• v.37 no.7
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• pp.434-447
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• 2016

This study analyzed mass concentrations of PM10 and PM2.5, as measured at Tae-ahn and Gang-nae, Cheongju in central Korea over the period from 2011 to 2015. Higher mass concentrations of PM10, with the exception of dustfall cases during the period of winter and spring, reflected the influence of a prevailing westerly airflow, while the level of PM10 stayed at a low level in summer, reflecting the influence of North Pacific air mass and frequent rainfall. Accordingly, cases where a daily PM10 average of $81{\mu}gm^{-3}$ or over (exceeding the status of fine dust particles being 'a little bit bad') were often observed during the period of winter and spring, with more cases occurring in parts of Tae-ahn that are located close to the sources of pollutant emission in eastern China. Dustfall usually originated from dust storms made up of particles $2.5{\mu}m$ or over in diameter. However, anthropogenic haze displayed a high composition ratio of particulate less than $2.5{\mu}m$ in diameter. Accordingly, brightness temperature difference (BTD) values from the Communication, Ocean and Meteorological Satellite (COMS) were $-0.5^{\circ}K$ or over in haze with fine particulate. PM10 mass concentrations and NOAA 19 satellite BTD for haze cases were analyzed. Though PM10 mass concentrations were found to be lower than $200{\mu}g\;m^{-3}$, the mass concentration ratio of PM2.5/PM10 was measured as higher than 0.4 and BTD was found to be distributed in the range from -0.3 to $0.5^{\circ}K$. However, the BTD of dustfall cases exceeding $190{\mu}g\;m^{-3}$, were found to be less than 0.4 and BTD was found to be distributed in the range less than $-0.7^{\circ}K$. The result of applying BTD threshold values of the large-scale transport of haze proved to fall into line with the range over which aerosols of MODIS AOD and OMI AI were distributed.