• Journal of environmental and Sanitary engineering
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• v.13 no.3
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• pp.72-78
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• 1998

For investigation into gas permeation characteristics, the porous alumina membrane with asymmetrical structure, having upper layer with 10 nanometer under of pore diameter and lower layer with 36 nanometer of pore diameter, was prepared by anodic oxidation using DC power supply of constant current mode in an aqueous solution of sulfuric acid. The aluminium plate was pre-treated with thermal oxidation, chemical polishing and electrochemical polishing before anodic oxidation. Because the pore size depended upon the electrolyte, electrolyte concentration, temperature, current density, and so on, the the membranes were prepared by controling the current density, as a very low current density for upper layer of membrane and a high current density for lower layer of membrane. By control of current quantity, the thicknesses of upper layer of membranes were about $6{\;}{\mu}m$ and the total thicknesses of membranes were about $80-90{\;}{\mu}m$. We found that the mechanism of gas permeation depended on model of the Knudsen flow for the membrane prepared at each condition.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.15-25
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• 2008

Contamination level assessment of harbor dredged materials is carried out for beneficial use, which generated annually due to port construction and maintenance of harbor channel. The basic purpose of environmental risk assessment was a scientific approach to susceptibility of hazard risk to human's health from different dredged materials. And this paper proposes a guideline of safely beneficial use of dredged materials at both industrial area and residental area, generated from major port execution throughout a sound investigation of their contamination levels. Newly proposed guidelines were in general higher levels compared to both current guidelines of treatment and use of dredged materials and soil environment protection levels. Finally, environmental assessment results of dredged material contamination generated in major ports of Korea for beneficial use based on pre-assessment environmental levels show that some port's dredged materials contain heavy metals such as Cd, As, Cr and Zn, more than base levels which requires more precise contamination investigation. Others were found to be very appropriate for beneficial use.

• Journal of the Korean GEO-environmental Society
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• v.13 no.12
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• pp.35-42
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• 2012

There are many large-scale coastal region landfill and land development by loading to use territory efficiently, this regions are mostly soft clay ground. Constructing structures and road on the soft ground bring about engineering problems like ground shear fracture and a big amount of consolidation by bearing capacity. Improvement of soft soil is required to secure soil strength and settlement control. In improvement of soft soil, predict for the amount of settlement based on field surveyed reports are important element for estimating pre-loading banking height and the final point of consolidation. In this study, there is calculating theoretical settlement by analyzing field surveyed report and ground investigation to improvement of soft soil with pre-loading and vertical drain method. And present settlement prediction method reflect soil characteristics in Gimpo Hangang site by analysing prediction settlement and observational settlement during compaction using hyperbolic, ${\sqrt{s}}$, Asaoka method.

• Journal of Environmental Health Sciences
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• v.36 no.3
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• pp.199-207
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• 2010

In this study, breast milk levels of indicator polychlorinated biphenyls (PCBs) were estimated, and statistics drawn, for 22 Koreans in the general population, aged 26-38, who had resided in metropolitan areas for more than 5 years without occupational exposure to organochlorine pollutants. Concentrations of indicator PCBs were measured using the isotope dilution method with a high resolution gas chromatograph/high resolution mass detector, which provided accurate and precise data for investigation of trends, and international comparisons. The geometric mean of total indicator PCB levels was 22.3 ng/g lipid, which is significantly lower than the level in individuals from European countries. Overall, the geometric mean and 95th percentile of the most abundant congener PCB 153 were 8.04 ng/g lipid and 16.4 ng/g lipid, respectively. PCB congeners 138, 153 and 180 together accounted for about 75% of the indicator congeners analyzed. Breast milk total indicator PCB concentrations were significantly associated with age and parity, but not with body mass index (BMI), rate of body weight increase, or smoking habits. The geometric mean level of PCB 153 in breast milk from mothers with a pre-pregnant BMI < $21\;kg/m^2$ was significantly higher than in pre-pregnant women with a BMI of ${\geqslant}\;21\;kg/m^2$ (p<0.05). Women who ate more fish, meat, and milk products did not have significantly higher total indicator PCB levels than those who ate less of these products, but a significant difference in PCB 153 levels was demonstrated between the subjects consuming higher (11.45 ng/g lipid) and lower (6.79 ng/g lipid) amounts of fish (p<0.05), after adjusting for confounders. These results suggest that age, parity and fish intake are the important factors affecting the concentrations of indicator PCBs in these subjects.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.577-589
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• 2021

Drone mapping systems can be applied to many fields such as disaster damage investigation, environmental monitoring, and construction process monitoring. To integrate individual sensors attached to a drone, it was essential to undergo complicated procedures including time synchronization. Recently, a variety of composite sensors are released which consist of visual sensors and GPS/INS. Composite sensors integrate multi-sensory data internally, and they provide geotagged image files to users. Therefore, to use composite sensors in drone mapping systems, mapping accuracies from composite sensors should be examined. In this study, we analyzed the mapping accuracies of a composite sensor, focusing on the data acquisition area and pre-calibration effect. In the first experiment, we analyzed how mapping accuracy varies with the number of ground control points. When 2 GCPs were used for mapping, the total RMSE has been reduced by 40 cm from more than 1 m to about 60 cm. In the second experiment, we assessed mapping accuracies based on whether pre-calibration is conducted or not. Using a few ground control points showed the pre-calibration does not affect mapping accuracies. The formation of weak geometry of the image sequences has resulted that pre-calibration can be essential to decrease possible mapping errors. In the absence of ground control points, pre-calibration also can improve mapping errors. Based on this study, we expect future drone mapping systems using composite sensors will contribute to streamlining a survey and calibration process depending on the data acquisition circumstances.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.120-127
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• 2014

Robustness and controllability are the key factors in internal combustion engine commercialization. This study focuses on the combustion strategy to commercialize the low temperature diesel combustion technology. Various LTC combustion methods such as PPCI, MK and highly diluted mixing controlled LTC were conducted on 6.0L heavy duty diesel engine. To find the best feasible LTC strategy, emission level, fuel consumption and combustion safety during the combustion mode change were considered. Experiments were carried out under various engine operating conditions; engine speed & load, EGR level, injection timing. Finally, this study suggests realizable LTC combustion strategy; moderate EGR level and slight early injection are possible to considerably lower PM, NOx emission and expand LTC operating range up to 50% load without CO and HC emission.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.133-141
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• 2014

This study was carried out to establish the database system by using the safety inspection and in-depth inspection results for infrastructures such as bridges, tunnels, dams, and water supplies. A classification system of each facility was proposed by standardizing items for inspection & diagnosis in order to automatize work process. Also, it justifies data structure based on database from pre-investigation to field survey, evaluation of facilities, and report making. In addition to this, it suggests improvement plans of relative regulations and guidelines such as Facility Management System(FMS), operational regulation, and inspection detailed guideline to make inspection result database of infrastructures which can be used effectively.

• Safety and Health at Work
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• v.13 no.2
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• pp.227-234
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• 2022

Background and Purpose: In 2021, lung cancer in school food workers was first recognized as an occupational cancer. The classification of the carcinogenicity of cooking fumes by International Agency for Research on Cancer (IARC) was based on Chinese epidemiological data. This study aimed to determine the hazard levels of school cooking fumes in Korea. Materials and Methods: Based on public school cafeterias in one area, 25 locations were selected for the survey according to the number per school type, ventilation states, and environmental pre-assessments of cafeterias. Two inside cooking areas using a heat source and one outside cooking area were selected as control measurement points. Measurements of CO, CO₂, polycyclic aromatic hydrocarbons (PAHs), and total volatile organic compounds (TVOCs), including benzene, formaldehyde, and particulate matter (PM10, PM2.5, PM1, respectively), were taken. The concentrations and patterns of each substance in the kitchens were compared with the outdoor air quality. Result: Known carcinogens, such as the concentrations of PAHs, formaldehyde, TVOC (benzene), and particulate matter in school cooking fumes, were all detected at similar or slightly higher levels than those found outside. Additionally, substances were detected at relatively low concentrations compared to the Chinese cooking fumes reported in the literature. However, the short-term exposure to high concentrations of CO (or composite exposure with CO₂) and PM2.5 in this study were shown. Conclusion: The school cooking fumes in South Korea was a relatively less harmful than Chinese cooking fumes, however short-term, high exposure of toxic substances can cause a critical health effect.

• Journal of Electrochemical Science and Technology
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• v.15 no.1
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• pp.178-189
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• 2024

This work aims to investigate the efficiency of electrocoagulation (EC) of pistachio processing industrial wastewater (PPIW) using the continuous EC process. The tubular reactor made of stainless steel with an internal diameter of 60 mm was used as a cathode electrode. The effect of some parameters was examined on the removal of chemical oxygen demand (COD) and total phenols (TP) removal efficiency. The influences of the initial pH of wastewater (from 4 to 8), flow rate (from 25 to 125 mL/min), current density (from 7 to 21 mA/cm²), and supporting electrolyte type (NaCl, NaNO₃, and Na₂SO₄), supporting electrolyte concentration (from 10 to 100 mg/L NaCl) on removal efficiency were investigated to determine the best experimental conditions. The examination of the physico-chemical parameters during the EC treatment showed that the best removal efficiency was obtained under conditions where the flow rate was 25 mL/min (20 min reaction time), the pH value was 5.2, and the current density was 21 mA/cm² has set. Under these experimental conditions, COD and TP removal efficiency were found to be 75% and 97%, respectively, while energy consumption was 18.5 kW h/m³. The study results show that the EC can be applied to PPIW pre-treatment.

• Journal of the Korean Society of Industry Convergence
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• v.3 no.2
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• pp.155-166
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• 2000

In order to elucidate the interrelationship between electrolytes and exercise the investigation was undertaken to determine the electrolyte levels in young males took on varied environmental temperatures ($13^{\circ}C$, $24^{\circ}C$ or $34^{\circ}C$). 10 healthy young males were used for the experiments. Our results showed the following significant changes; 1. The raising of the environmental temperature, the weight reduction were increased due to marked sweating. 2. In the electrolytes of serum, decreased the $K^+$ concentration at $13^{\circ}C$, but increased the $Na^+$ or $Cl^-$ concentration at $24^{\circ}C$, and increased the $Na^+$ or $Cl^-$, or $Mg^{+}^{+}$ concentrations at $34^{\circ}C$. 3. The raising of environmental temperature appear to be increased PRA,Ang I, Ang II and ALD levels, whereas no changed ADH level. 4. Serum levels of PRA, Ang I, Ang II and ALD were incresed after exercise, and their increments were incresed paralel ttie incresed environmental temperature. However, there no significant change in ADH, level. In conclusion, exercise induced not only changes of serum electrolytes levels such as $Na^+$, $Cl^-$, $K^+$, $Mg^{+}^{+}$, but also serum hormonal changes such as PRA, Ang I, Ang II, ALD. However, ADH level was not changed significantly, These changes were more prominent in exercise at hot temperature than in lower temperature.