• The Journal of Engineering Geology
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• v.27 no.4
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• pp.513-518
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• 2017

Groundroll is a coherent noise showing dispersive behavior in land seismic-reflection records and its rejection has been a stubborn problem in data processing because they severely degrade the continuities and resolution of reflection signals. Conventional processing schemes of attenuating noises are the kind of frequency filtering (i.e., bandpass and f-k) that uses the Fourier transform (FT) along the entire trace in the time domain. To suppress them in this study, 1D wavelet filtering (WT) that can control time-varying frequency properties is tested and performed in the land-based synthetic and field seismic data. The results are compared to the ones from conventional filtering techniques in terms of continuities and resolution of reflection events. This filtering technique enhanced the reflection events by effectively eliminating the dispersive groundroll and random noises with control of time-scale function on wavelet domain.

• Structural Engineering and Mechanics
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• v.56 no.3
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• pp.423-442
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• 2015

This study examines the wavelet transform for output-only system identification of ambient excited engineering structures with emphasis on its utilization for modal parameter estimation of high-order and closely-spaced modes. Sophisticated time-frequency resolution analysis has been carried out by employing the modified complex Morlet wavelet function for better adaption and flexibility of the time-frequency resolution to extract two closely-spaced frequencies. Furthermore, bandwidth refinement techniques such as a bandwidth resolution adaptation, a broadband filtering technique and a narrowband filtering one have been proposed in the study for the special treatments of high-order and closely-spaced modal parameter estimation. Ambient responses of a 5-story steel frame building have been used in the numerical example, using the proposed bandwidth refinement techniques, for estimating the modal parameters of the high-order and closely-spaced modes. The first five natural frequencies and damping ratios of the structure have been estimated; furthermore, the comparison among the various proposed bandwidth refinement techniques has also been examined.

• Journal of Environmental Health Sciences
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• v.30 no.5 s.81
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• pp.432-439
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• 2004

Korean certification regulation for particulate filtering respirators requires inward leakage (IL) test as European Standards (EN) and the standard levels of regulation are the same as those of EN. This study was conducted to evaluate particulate filtering respirators being commercially used in the market by using IL and assess the characteristics of IL. The study began with discussing the concept of IL, comparison of IL with fit test, and IL measurement method. Three brands of half masks and 10 brands of filtering facepieces (two top class, four 1st class and four 2nd class), total 13 brands respirators, and 10 test panels (subjects) who were classified in 9 facial grids in accordance with face length and lip length, were selected for IL test. IL tests were conducted in the laboratory of 3M Innovation Center which was established by EN standard. As expected ILs of half masks were lower than those of filtering facepiece mask. ILs of half masks and some filtering facepieces were significantly different in manufacturers. ILs of 1st class filtering facepieces were found to be much more than those of 2nd class and thus the result would cause wearers to get confused to select a mask. Four of six brands being no compliance with standards were thought that they should be tested again for certification because of a lot of differences from standards. There were no significant differences among ILs of five exercises. In 6 out of 13 brands lognormal distribution of ILs may be a better fit distribution and in 7 brands both lognormal and normal distributions were rejected. The result indicates that geometric mean may be better than arithmetic mean to establish standard.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.87-98
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• 2024

This study was conducted to investigate the efficiency of the filtering sets composed of fiberboards, which were fabricated with lignocellulosic fiber and cork oak bark-based activated carbon (COA), as well as traditional Korean paper handmade from mulberry trees (KP) for the filtration of PM, TVOC and HCHO. Three-layers fiberboards (WRF) were fabricated with wood fiber in its surface layers and recycled fiber/COA in its core layer using a protein-based adhesive with the resin content of 8%. Filtering sets were composed of three WRF and one sheet of KP. Concentrations of PM, TVOC and HCHO generated with the combustion of a incense in a sealed laboratory hood were reduced efficiently with the operation of air-purifier installed the filtering sets. Except for the WRF fabricated with 4%/4% resin contents, other WRF were prepared with 5%/3% and 6%/2% resin contents in surface/core layers, and then the WRF were used with KP for the fabrication of filtering sets. Filtration efficiency of the filtering sets was improved as the core-layer resin content applied in the fabrication of WRF decreased. In addition, filtration efficiency of the WRF-based filtering set fabricated with KP of 25 g/m² basis weight was higher than that with KP of 45 g/m² basis weight. Filtering sets composed of three-layers fiberboards (RWF) that recycled fiber and wood fiber/COA were used in its surface and core layers, respectively, and KP-25g showed higher filtration efficiency than those of WRF-based filtering sets. Air-inhalation equipment installed the RWF-based, WRF-based filtering sets and without filtering set were operated in small indoor and large outdoor spaces. Efficiency for filtering PM and TVOC of the RWF-based filtering sets was higher than that of other filtering sets. It is concluded that fiberboard-based filtering sets composed of RWF and KP-25g can be used as a filter for reducing the concentrations of PM and TVOC existed in indoor and outdoor spaces.

• Journal of Animal Environmental Science
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• v.20 no.1
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• pp.15-20
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• 2014

The present study was conducted to develop a milk filtering system for decreasing somatic cell count (SCC) in bulk tank milk. The pore sizes of the filter were 0.1, 0.3, 0.4, 0.5 and $0.8{\mu}m$. The rate of SCC reduction of $1^{st}$ grade milk on $0.1{\mu}m$ filter was 76% and significantly higher than other treatments. The rates of SCC reduction for 0.3, 0.4, 0.5 and $0.8{\mu}m$ were 35, 32, 18 and 6.4%, respectively. The effects of the milk filtering system on bacterial count and milk fat content were minimal. The milk flow rates per minute between the filter sizes were similar. But discharge pressures were increased as the pore size of the filter decreased. In conclusion, Considering the rate of SCC reduction, discharge pressure and cost, $0.4{\mu}m$ filter could be recommended.

• Journal of Environmental Science International
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• v.17 no.10
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• pp.1147-1154
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• 2008

Road runoff, one of non-point source pollutants, contains various heavy metals, most of which flow into discharge waters without being treated. The mechanism of removing the heavy metals in water is similar to that of removing micro-particles. Therefore, it is considered that it is possible to remove a lot of the heavy metals contained in the road runoff by filtering or absorbing them. In this paper, performed has been a basic study on the characteristics of UNFS (Up Flow Non-Point Source Filtering System) using carbide pellet and zeolite pellet as double-layer filtering mediums to treat the road runoff. The removal rate with filtering and absorption time has been shown as follows: 29.0% for Cr; 27.8% for Cd; 25.7% for Fe; 25.4% for Co; 21.2% for Pb; ]9.6% for Zn; 18.2% for Al; 17.0% for Mn; 11.3% for Ni; 7.5% for Cu. The overall removal rate according to influx change has been shown to be approximately 30%, and the load of heavy metals flowing out in initial precipitation could be reduced by using carbide as a recycling filtering medium. When the removal as coarse particles settle is added up, it is expected that UNFS will result in a higher removal rate.

• Journal of environmental and Sanitary engineering
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• v.23 no.2
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• pp.55-63
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• 2008

All over the world, the existing process of water purification needs more flocculants and chlorine due to a gradual decline in the quality of source water. Therefore, the problem of the remaining aluminium and DBPs in purified water is on the rise. To solve this problem, the process of membrane filter has recently come into the spotight. This study reaches the following conclusions concerning TMP variation in order to solve the dropping of flux throgh a membrane filter when operating a membrane filter system in the process of water purification. 1. In case that a cohesion-precipitation process was introduced to pre-treatment of a membrane filter, initial TMP was very satisfactory(0.27kg/cm) in producing the constantly safe quality of water, $0.04{\sim}0.1$(mean 0.05) NTU by pouring 2mg/l of PACI(10% $Al_2O_3$) used for the existing process of water purification in high-density turbidity at a dry or flood season and at occurrence of high algae. 2. As flux increased at 0.5m/day.m, TMP increased 0.05 kgf/cm. 3. As filtering, operation mode of PVDF MF membrane filtering was 48 minutes and 1 cycle of back washing was 42 minutes, flux was increased 1.5m/day.m and TMP increased $0.25{\sim}0.27kgf/cm$. Without back washing, TMP increased 0.03 kgf/cm per a cycle.

• Proceedings of the Korean Environmental Health Society Conference
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• 2004.12a
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• pp.70-70
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• 2004

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.3
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• pp.245-253
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• 2015

Objectives: One aim of the study is to compare filtering facepiece masks for healthcare workers between Korea and other countries. The other is to emphasize the importance of fit testing for these masks using an analysis of previous research. Materials: An extensive literature review was performed by searching a number of websites and existing studies. Results: KF94 and KF99 masks certified by the Korean CDC are suitable for healthcare workers as filtering facepiece masks. The standards for these respirators are similar to FFP2 and FFP3 of EN 143 and 149. The performance, such as filtering efficiency, is almost the same between KP94 and N95. It was found that fit testing of respirators for healthcare workers was important to reduce infection risk. Conclusions: KF94 should be emphasized as filtering facepiece masks for healthcare workers rather than N95. Even though Korea has no fit testing regulations, implementing fit testing in healthcare settings is strongly recommended to decrease infection risk.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.691-702
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• 2013

In this study the quantitative outlier-filtering algorithm has been developed using the smoothing method based on the day-of-the-week traffic volume variation pattern and then, in order to test the effectiveness of the algorithm, it has been used to identify outliers from the traffic volume data collected at 14 continuous traffic counts sites on the national highways in the year 2010. The test results are satisfactory since the filtering rate is 98.2% for normal days and the mis-filtering rate is 8.0% for abnormal days. Therefore, the algorithm will be able to be used for roughly-but-quickly filtering outliers from the collected traffic volume data.