• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.415-422
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• 2014

Reinforced trackbeds are an important layer that has a significant effect on the deformation of the track, therefore, a deeper understanding of reinforced trackbeds is necessary. In this paper, we conduct a large triaxial test in order to evaluate the resilient modulus ($M_R$) of reinforced trackbed materials through considering several factors such as the grain size distribution (GSD) and loading conditions. It is identified that the maximum size of the particle, GSD, and compacted water content affect the $M_R$ but the loading frequency does not. Because these tests are performed with consideration of the field environment, the test results are useful for analyzing tracks including reinforced trackbeds. The data are limited to evaluating the parameters of $M_R$ model; however the parameters of the deviatoric and bulk stress models that can be used in various loading conditions are proposed.

• Ocean Systems Engineering
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• v.14 no.2
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• pp.171-210
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• 2024

This paper focuses on the rigorous and holistic fatigue analysis of mooring chains for a deep draft semi-submersible platform in the challenging environment of the central Gulf of Mexico (GoM). Known for severe hurricanes and strong loop/eddy currents, this region significantly impacts offshore structures and their mooring systems, necessitating robust designs capable of withstanding extreme wind, wave and current conditions. Wave scatter and current bin diagrams are utilized to assess the probabilistic distribution of waves and currents, crucial for calculating mooring chain fatigue. The study evaluates the effects of Vortex Induced Motion (VIM), Out-of-Plane-Bending (OPB), and In-Plane-Bending (IPB) on mooring fatigue, alongside extreme single events such as 100-year hurricanes and loop/eddy currents including ramp-up and ramp-down phases, to ensure resilient mooring design. A detailed case study of a deep draft semi-submersible platform with 16 semi-taut moorings in 2,500 meters of water depth in the central GoM provides insights into the relative contributions of wave scatter diagram, VIMs from current bin diagram, the combined stresses of OPB/IPB/TT and extreme single events. By comparing these factors, the study aims to enhance understanding and optimize mooring system design for safety, reliability, and cost-effectiveness in offshore operations within the central GoM. The paper addresses a research gap by proposing a holistic approach that integrates findings from various contributions to advance current practices in mooring design. It presents a comprehensive framework for fatigue analysis and design optimization of mooring systems in the central GoM, emphasizing the critical importance of considering environmental conditions, OPB/IPB moments, and extreme single events to ensure the safety and reliability of mooring systems for offshore platforms.

• Journal of Preventive Medicine and Public Health
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• v.22 no.4 s.28
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• pp.495-505
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• 1989

This study was conducted as a nationwide survey In Korea to determine the THM (trihalomethane) concentration levels in the drinking water of 14 selected cities. The survey was underdtaken in one city (Kwangju) during September and October of 1988 and 14 cities in January through February of 1989. The results were as follows : 1. The $KMnO_4$ consumption was 10.6mg/l-11.6mg/l in Pusan and Ulsan, exceeding the drinking water standard of 10mg/l. Pusan, Inchon, Kwangju, Ulsan, Mokpo and Junju areas also exceeded the ammonia nitrate standard of 0.5mg/l. Other tap waters surveyed were detected below the drinking water standards. 2. The THM concentrations of tap water measured in January and February of 1989 were detected in the range $1.20{\mu}g/l-150.8{\mu}g/l$. 3. In the comparative study of the THM concentration of tap water measured in the Kwangju area during September and October of 1998, the average THM concentation of $145.63{\pm}70.72{\mu}g/l$ showed a sixfold increase compared to that of $23.8{\pm}8.31{\mu}g/l$ surveyed in January and February 1989. 4. The proportion of the four THM compounds found in tap water was bromoform, 47% ; chloroform, 30% ; chlorodibromomethane, 13% ; and dichlorobromomethane, 10%. 5. Since the results indicate that the concentration of bromoform was 2-10 times higher than that of chloroform measured in the seaside district of Pusan, Ulsan and Cheju Island, it is reasonable to assume that the raw water was somehow Influenced by seawater. 6. The average lifetime cancer rate of the population exposed to chloroform measured in the surveyed areas was 17 cancer incidences per 1 million population. From the above results, the existence of THM in the distribution systems seems to be inevitable, since chlorine disinfection is performed in water treatment plants In our country. There seems to be a trend of increasing. THM cncentrations due to the contamination of raw water. In order to establish my form of regulations, health risk assessment is an imminent subject.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.61-66
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• 2006

Over the past 20 years there has been a revolution involving the use of nano or macro size particles as drainage and retention systems during the manufacture of paper. More recently a group of patented technologies called Synthetic Mineral Microparticles (SMM) has been invented and developed. This system has potential to further promote the drainage of water and retention of fine particles during papermaking. Prior research, as well as our on preliminary research showed that the SMM system has advantages in both of drainage and retention compared with montmorillonite (bentonite), which one of the most popular materials presently used in this kind of application. In spite of the demonstrated advantages of this SMM system, the properties and activity of SMM particles in the aqueous state have not been elucidated yet. Streaming current titrations with highly charged polyelectrolytes were used to measure the charge properties of SMM and to understand the interactions among SMM particles, fibers, fiber fines, and cationic polyacrylamide (cPAM) as a retention aid. It was found that pH profoundly affects the charge properties of SMM, due to the influence of Al-ions and the Si-containing particle surface. SEM pictures, characterizing the morphology, geometry and size distribution of SMM, showed an broad distribution of primary particle size. Dilution of SMM mixturee appeared to wash out particles smaller than 100 nm from the surface of larger particles, which themselves appeared to be composed of fused primary particles. DSC thermoporometry was used to measure the size distribution of nanopores within SMM particles.

• Membrane and Water Treatment
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• v.6 no.4
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• pp.263-276
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• 2015

This paper deals with the influence of chemical oxygen demand to nitrogen ratio ((COD/N) ratio) on the performance of an membrane bioreactor. We aim at establishing relations between COD/N ratio, organisms' distribution and sludge properties (specific resistance to filtration (SRF) and membrane fouling). It is also essential to define new criteria to characterize the autotrophic microorganisms, as the measurements of apparent removal rates of ammonium seem irrelevant to characterize their specific activity. Two experiments (A and B) have been carried on a 30 L lab scale membrane bioreactor with low COD/N ratio (2.3 and 1.5). The obtained results clearly indicate the role of the COD/N ratio on the biomass distribution and performance of the membrane bioreactor. New specific criteria for characterising the autotrophic microorganisms activity, is also defined as the ratio of maximum ammonium rate to the specific oxygen uptake rate in the endogenous state for autotrophic bacteria which seem to be constant whatever the operating conditions are. They are about 24.5 to 23.8 $gN-NH_4{^+}/gO_2$, for run A and B, respectively. Moreover, the filterability of the biological suspension appear significantly lower, specific resistance to filtration and membrane fouling rate are less than $10^{14}m^{-2}$ and $0.07\;10^{12}m^{-1}.d^{-1}$ respectively, than in conventional MBR confirming the adv < antage of the membrane bioreactor functioning under low COD/N ratio.

• Journal of the korean society of oceanography
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• v.39 no.1
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• pp.57-71
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• 2004

Based on the data obtained under the China-Korea joint project (1997-2001) and historic observations, the distribution, transportation and sedimentation of sediment in the southern Yellow Sea (SYS) are discussed, and the controversial formation mechanism of muddy sediments is also explored. The sediment transport trend analysis indicates that the net transport direction of sediment in the central SYS (a fine-grained sediment deposited area) points to $123.4^{\circ}E,\;35.1^{\circ}N$, which is a possible sedimentation center in the central SYS. The sediment transport pattern is verified by the distribution of total suspended matter (TSM) concentration and ${\delta}^{13}C$ values of particulate organic carbon (POC), the latter indicates that the bottom water plays a more important role than the surface water in transporting the terrigenous material to the central deep-water area of the SYS, and the Yellow Sea circulation is an important control factor for the sediment transport pattern in the SYS. The carbon isotope signals of organic matter in sediments indicate that the Shandong subaqueous delta has high sedimentation rate and the deposited sediments originate mainly from the modern Yellow River. The terrigenous sediments in deep-water area of the SYS originate mainly from the old Yellow River and the modern Yellow River, and only a small portion originates from the modern Yangtze River. The analytical results of TSM and stable carbon isotopes are further confirmed by another independent tracer of sediment source, polycyclic aromatic hydrocarbons (PAHs). Five light mineral provinces in the SYS can be identified and they indicate inhomogeneity in sources and sedimentary environment. The modern shelf sedimentary processes in the SYS are controlled by shelf dynamic factors. The muddy depositional systems are produced in the shelf low-energy environments, which are controlled by some meso-scale cyclonic eddies (cold eddies) in the central SYS and the area southwest of the Cheju Island. On the contrary, an anticyclonic muddy depositional system (warm eddy sediment) appears in the southeast of the SYS (the area northwest of the Cheju Island). In this study, we give the cyclonic and anticyclonic eddy sedimentation patterns.

• Korean Journal of Microbiology
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• v.53 no.3
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• pp.156-162
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• 2017

Legionnaires' disease (LD) is a severe and potentially fatal pneumonia caused by colonization of human-made water system and subsequent aerosolization and inhalation of Legionella bacteria. A total of 147 Legionella strains was isolated from environmental water sources from public facilities in Gyeonggi-do, South Korea. The distribution of Legionella isolates was investigated according to facility type, and sample type. L. pneumophila was distributed broadly throughout Gyeonggi-do, accounting for 85.7% of the isolates, and L. pneumophila serogroup (sg) 1 predominated in all of the public facilities. L. wadsworthii predominated among non-L. pneumophila species. We performed comparative analyses of L. pneumophila sg 1 isolated from environment water of public facilities in Gyeonggi-do by pulsed field gel electrophoresis (PFGE) and sequence-based typing (SBT). Thirty-two isolates were classified into 22 types by PFGE and 9 sequence types (STs) by SBT and categorized into 3 groups. ST1 was the most prevalent sequence type and two STs obtained in this study had unique allelic profiles. The use of SBT data from different countries for epidemiology study of LD constitutes a technically uncomplicated and relatively easy method for strain subtyping, especially compared to other contemporary techniques.

• The Journal of Engineering Geology
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• v.23 no.1
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• pp.37-46
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• 2013

Leakage of leachate from animal carcass disposal is a significant issue because disease can easily spread to humans and other livestock. In this study, we analyzed the physicochemical properties of leachate and tested for the presence of aerobic bacteria in leachate using molecular biology methods, for 16 animal carcass disposals in the first stage (after burial for 5 months). Leachate physicochemical analysis revealed higher total coliforms, TOC, $NH^{4+}$, and $NO^{3-}$ concentrations compared with previously published data. In most leachate samples, the concentrations of $NH^{4+}$ and $NO^{3-}$ exceeded the Korean guideline values for drinking water. In 16S rRNA sequence analysis of the distribution of leachate under aerobic conditions, Bacillus pumilus, Lysinibacillus sphaericus, and B. sphaericus were observed with high frequency, whereas no food-poisoning-related bacteria such as B. cereus or Salmonella were detected. The present findings improve our knowledge of the transport of leachate from animal carcass disposal sites through geologic media, and are useful in risk analysis and for subsequent studies.

• Korean Journal of Environmental Biology
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• v.40 no.3
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• pp.352-362
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• 2022

Photosynthesis and respiration of seagrasses are mainly controlled by water temperature. In this study, the photosynthetic physiology and respiratory changes of the Asian surfgrass Phyllospadix japonicus, which is mainly distributed on the eastern and southern coasts of Korea, were investigated in response to changing water temperature (5, 10, 15, 20, 25, and 30℃) by conducting mesocosm experiments. Photosynthetic parameters (maximum photosynthetic rate, P_max; compensation irradiance, I_c; and saturation irradiance, I_k) and respiration rate of surfgrass increased with rising water temperature, whereas photosynthetic efficiency (α) was fairly constant among the water temperature conditions. The P_max and I_k dramatically decreased under the highest water temperature condition (30℃), whereas the I_c and respiration rate increased continuously with the increasing water temperature. Ratios of maximum photosynthetic rates to respiration rates (P_max : R) were highest at 5℃ and declined markedly at higher temperatures with the lowest ratio at 30℃. The minimum requirement of H_sat (the daily period of irradiance-saturated photosynthesis) of P. japonicus was 2.5 hours at 5℃ and 10.6 hours at 30℃ for the positive carbon balance. Because longer H_sat was required for the positive carbon balance of P. japonicus under the increased water temperature, the rising water temperature should have negatively affected the growth, distribution, and survival of P. japonicus on the coast of Korea. Since the temperature in the temperate coastal waters is rising gradually due to global warming, the results of this study could provide insights into surfgrass responses to future severe sea warming and light attenuation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.304-315
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• 2018

Harmony Search (HS) is a recently developed metaheuristic algorithm that is widely known to many researchers. However, due to the increasing complexity of optimization problems, the optimal solution cannot be efficiently found by HS. To overcome this problem, there have been many studies that have improved the performance of HS by modifying the parameter settings and incorporating other metaheuristic algorithms. In this study, Copycat HS (CcHS) is suggested, which improves the parameter setting method and the performance of searching for the optimal solution. To verify the performance of CcHS, the results were compared to those of HS variants with a set of well-known mathematical benchmark problems. The effectiveness of CcHS was proven by finding final solutions that are closer to the global optimum than other algorithms in all problems. To analyze the applicability of CcHS to engineering optimization problems, it was applied to a design problem for Water Distribution Systems (WDS), which is widely applied in previous research. As a result, CcHS proposed the minimum design cost, which was 21.91% cheaper than the cost suggested by simple HS.