• Journal of Korean Society on Water Environment
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• v.21 no.2
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• pp.153-157
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• 2005

The purpose of this study was to find out the effect of oxidation by-products for the formation of haloacetic acid (HAA) during ozonation. The phenol was used as a model precursor of HAA, and its oxidation by-products, such as hydroquinone, catechol, glyoxal, glyoxylic acid and oxalic acid were investigated to find out how much HAA formation potential (HAAFP) they have. As the result, among the phenol and its oxidation by-products, the highest reactivity with chlorine was found from the phenol, showing the highest HAAFP. Even though the tested by-products had a lower HAAFP than phenol, it was confirmed that all of them can act as the precursor of HAA. From the ozonation of phenol-containing water, it was found that the efficiency of ozone in controlling of HAAs can be reduced due to the oxidation by-products. In addition, the ozonation of HAAFP was performed under the both pH conditions (acid and base), and the result indicates that OH radical play a important role to decrease HAAFP.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.203-214
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• 2018

Ballast water treated by sodium dichloroisocyanurate (NaDCC) injection method in ballast water management system (BWMS) contains reactive bromine, chlorine species and disinfection by-products (DBPs). In this study, we conducted whole effluent toxicity (WET) testing and ecological risk assessment (ERA) to investigate its ecotoxicological effects on the marine environment. WET testing was carried out for eight marine and fresh water organisms, i.e. diatom, Skeletonema costatum, Navicula pelliculosa, green algae, Dunaliella tertiolecta, Pseudokirchneriella subcapitata, rotifer, Brachionus plicatilis, Brachionus calyciflorus and fish, Cyprinodon variegatus, Pimephales promelas. The WET test revealed that diatom and green algae were the only organisms that showed apparent toxicity to the effluent; it showed no observed effect concentration (NOEC), lowest observable effect concentration (LOEC) and effect concentration of 50 % (EC50) values of 25.0 %, 50.0 % and over 100.0 %, respectively, in seawater conditions. In contrast, rotifer and fish showed no toxicities to the effluent in the all salinity conditions. Meanwhile, chemical analysis revealed that the BWMS effluent contained total of 25 DBPs such as bromate, isocyanuric acid, formaldehyde, chloropicrin, trihalomethanes (THMs), halogenated acetonitriles (HANs) and halogenated acetic acids (HAAs). Based on ERA, the 25 DBPs were not considered to have persistency, bioaccumulation and toxicity (PBT) properties. The ratio of predicted environmental concentration (PEC) to predicted no effect concentration (PNEC) of the all DBPs did not exceed 1.0 for general harbour environments, but isocyanuric acid, tribromomethane, chloropicrin and monochloroacetic acid exceed 1.0 for near ship environments. However, when NOEC (25.0%) of the WET test results where actual effluent was applied, it was concluded that the NaDCC injection method did not have unacceptable ecological risks to the general harbor including near ship environments.

• Fire Science and Engineering
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• v.25 no.5
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• pp.100-107
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• 2011

In this study, a simulated situation in which the visions of the evacuees were blocked by the smoke, which is one of the most dangerous factors that cause casualties in case of an emergency, was conducted for the evaluation of the performance of an evacuation guidance system. For this purpose, the behavior and time taken by the experiment subjects in simulated evacuation test were measured and analyzed. When the evacuation guidance sound signals were given by 4 speakers at the same time, most of the subject were disoriented and took generally longer in getting to the pre-designated evac point. And, using only one speaker instead of two showed a better result in terms of the evacuation behavior or and orientation. Also, when there were two or more speakers used for the broadcasting of the guidance message, it turned out that using Hass effect, and placing the speakers closer, could result in higher awareness of the guidance message and maintenance of the orientation, while it also made the subjects took short to get to the evac point.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.2
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• pp.41-47
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• 1999

In this paper, we report 3D-simulations of a plasma etching process by employing cell-removal algorithm takes into account the mask shadow effect os well as spillover errors. The developed simulator haas an input interface to take not only an analytic form but a Monte Carlo distribution of the ions. The graphic user interface(GUI) was also built into the simulator for UNIX environment. To demonstrate the capability of 3D-SURFILER(SURface proFILER), we have simulated for a typical contact hole structure with 36,000($30{\times}40{\times}30$) cells, which takes about 20 minutes with 10 Mbytes memory on sun ultra sparc 1. as an exemplary case, we calculated the etch profile during the reactive ion etching(RIE) of a contact hole wherein the aspect ratio is 1.57. Furthermore, we also simulated the dependence of a damage parameter and the evolution of topography as a function of the chamber pressure and the incident ion flux.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.382-383
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• 2013

Gate-controlled spin-orbit interaction parameter is a key factor for developing spin-Field Effect Transistor (Spin-FET) in a quantum well structure because the strength of the spin-orbit interaction parameter decides the spin precession angle [1]. Many researches show the control of spin-orbit interaction parameter in n-type quantum channels, however, for the complementary logic device p-type quantum channel should be also necessary. We have calculated the spin-orbit interaction parameter and the effective mass using the Shubnikov-de Haas (SdH) oscillation measurement in a GaSb two-dimensional hole gas (2DHG) structure as shown in Fig 1. The inset illustrates the device geometry. The spin-orbit interaction parameter of $1.71{\times}10^{11}$ eVm and effective mass of 0.98 $m^0$ are obtained at T=1.8 K, respectively. Fig. 2 shows the gate dependence of the spin-orbit interaction parameter and the hole concentration at 1.8 K, which indicates the spin-orbit interaction parameter increases with the carrier concentration in p-type channel. On the order hand, opposite gate dependence was found in n-type channel [1,2]. Therefore, the combined device of p- and n-type channel spin transistor would be a good candidate for the complimentary logic device.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.513-520
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• 2006

The effect of chlorination on disinfection byproducts (DBPs) production from bloom-forming freshwater algae including 7 strains of cyanobacteria and 6 strains of diatoms was investigated. The release and degradation of hepatotoxin (microcystins) by the chlorination on Microcystis under differential condition of the chlorination time and dose were also investigated. The disinfection byproducts formation potentials (DBPFP) of cyanobacterial species and diatoms were ranged from 0.017 to $0.070{\mu}mol\;DBPs/mg$ C and from 0.129 to $0.708{\mu}mol\;DBPs/mg$ C respectively. Among three major groups of DBPs, haloacetonitrils (HANs) was major product in most test strains except Aphanizomenon sp. and Oscillatoria sp. Haloacetic acids (HAAs) was less than 5 % of total DBPs. Chloroform and dichloroacetonitril (DCAN) were dominant compounds in trihalomethanes (THMs) and HANs respectively. After 4 hours chlorination of toxic Microcystis aeruginosa under the dose range of 0.5 to $10mg\;Cl_2/L$, the concentration of intracellular microcystins decreased, but dissolved dissolved microcystins concentration increased with the treatment of more than $3mg\;Cl_2/L$. However the total amount of microcystins was almost constant even at $10mg\;Cl_2/L$ of chlorination. To conclude, our results indicate that the chlorination causes algal cell lysis and release of intracellular microcystins in the intact form to surrounding waters.

• Korean Journal of Materials Research
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• v.22 no.11
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• pp.587-590
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• 2012

Recently, the demand for the miniaturization of package substrates has been increasing. Technical innovation has occurred to move package substrate manufacturing steps into CMP applications. Electroplated copper filled trenches on the substrate need to be planarized for multi-level wires of less than $10{\mu}m$. This paper introduces a chemical mechanical planarization (CMP) process as a new package substrate manufacturing step. The purpose of this study is to investigate the effect of surfactant on the dishing and erosion of Cu patterns with the lines and spaces of around $10/10{\mu}m$ used for advanced package substrates. The use of a conventional Cu slurry without surfactant led to problems, including severe erosion of $0.58{\mu}m$ in Cu patterns smaller than $4/6{\mu}m$ and deep dishing of $4.2{\mu}m$ in Cu patterns larger than $14/16{\mu}m$. However, experimental results showed that the friction force during Cu CMP changed to lower value, and that dishing and erosion became smaller simultaneously as the surfactant concentration became higher. Finally, it was possible to realize more globally planarized Cu patterns with erosion ranges of $0.22{\mu}m$ to $0.35{\mu}m$ and dishing ranges of $0.37{\mu}m$ to $0.69{\mu}m$ by using 3 wt% concentration of surfactant.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.110-114
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• 2011

In this paper, in order to eliminate Limnoperna fortunei inhabiting the water conduction pipeline, prechlorination at the intake station was employed to improve the degradation of water quality due to the high pH of raw water taken at the downstream of Paldang Dam, algal growth, etc.. With the prechlorination concentration of 1.0mg/L at the intake station, the pH in the water well at the treatment plant decreased by 0.4, and with 1.5mg/L, by 0.6. Also, it eliminated Chlorophyll-a by about 95%, and the population of algae by about 49%. Such disinfection by-products (DBPs) as Trihalomathanes (THMs), Haloacetic Acids (HAAs), and Chloral Hydrate (CH) were under the quality standard for potable water, showing no change by the prechlorination, while raising the prechlorination rate from 1.0 up to 1.5mg/L, the DBPs in the water well increased by 1.5 to 3.1 times. As a consequence of testing Kyungan Stream, a branch stream flowing into Lake Paldang, the prechlorination (0.57mg/L, 1.14mg/L, 1.71mg/L) had no effect of eliminating the taste and odor compounds and total organic carbon (TOC) which is the DBPs precursor. As for the efficiency of Geosmin elimination by the rates of prechlorination and powder activated carbonation (PAC), it was found that the higher the concentration of PAC was (30ppm>20ppm>10ppm), the higher the efficiency was; the higher the rate of prechlorination was, the lower the efficiency by PAC was. Therefore, when taste and odor occur from raw water, suspending prechlorination at the intake or lowering the rate was proved to be more effective in eliminating the taste and odor compounds by PAC.

• Korean Journal of Weed Science
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• v.6 no.1
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• pp.85-96
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• 1986

From the two differently located orchards (even-site with adult tree and slope-site with young tree), weed emergence and the effect of various orchard herbicides on them were comparatively experimented. Weed emergence was assessed in emergence frequency, biomass, relative frequency, and herbicide responses were checked with the variarions in the above weed emergence characters and the weeding values. Herbicides applied were paraquat, glyphosate, oxyfluorfen, napropamide and ustinex using the recommended rates, respectively. Weeds emerged were 7 life-forms, 23 families and 45 species. Among other families, weeds Umbelliferae, Commelinaceae, Gramineae and Polygonaceae couldn't classified in any similarly correlated cluster. However, according to "1-Q mode cluster analysis" of each herbicide performances, "paraquat or glyphosate" with "napropamide or oxyfluorfen" were selected as the most unrelated herbicide pairs expecting the best combination value in mixture model, respectively.

• Environmental Analysis Health and Toxicology
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• v.12 no.3_4
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• pp.31-41
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• 1997

Public concerns about hazardous health effect from the exposure to organic by-products of the chlorination have been increased. There are numerous studies reporting that chlorination of drinking water produces numerous chlorinated organic by-products including THMs, HAAs, HANs. Some of these products are known to be animal carcinogens. The purpose of this study was to estimate health risk of DBPs by chlorinated drinking water ingestion in Seoul based on methodologies that have been developed for conducting risk assessment of complex-chemical-mixture. The drinking water sample was collected seperately at six water treatment plant in Seoul at March, April, 1996. In tap water of households in Seoul, DBPs were measured wilfh the mean value of 36.6 $\mu$g/L. Risk assessment processes,. which include processes for the estimation of human cancer potency using animal bioassay data and calculation of human exposure, entail uncertainties. In the exposure assessment process, exposure scenarios with various assumptions could affect the exposure amount and excess cancer risk. The reference dose of haloacetonitriles was estimated to be 0.0023 mg/kg/day by applying dibromoacetonitrile NOAEL and uncertainty factor to the mean concentration. In the first case, human excess cancer risk was estimated by the US EPA method used to set the MCL (maximum contaminant level). In the second and third case, the risk was estimated for multi-route exposure with and without adopting Monte-Carlo simulation, respectively. In the second case, exposure input parameters and cancer potencies used probability distributions, and in the third case, those values used point estimates (mean, and maximum or 95% upper-bound value). As a result, while the excess cancer risk estimated by US EPA method considering only direct ingestion tended to be underestimated, the risk which was estimated by considering multi-route exposure without Monte-Carlo simulation and then using the maximum or 95% upper-bound value as input parameters tended to be overestimated. In risk assessment for Trihalomethanes, considering multi-route exposure with adopting Monte-Carlo analysis seems to provide the most reasonable estimations.