• 청정기술
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• 제28권1호
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• pp.32-37
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• 2022

Food waste is produced from food factories, food services, and home kitchens. The generated mass reached 5.4 million tons/year in 2020. The basic management technology for such waste has been biological degradation under an anaerobic environment. However, the whole process is intrinsically slow and considerably affected by the inner physicochemical properties of the waste and other surrounding conditions, which makes optimization of the process difficult. The most promising options to counter this massive generation of waste are eco-friendly treatments or recycling. As a preliminary step for these options, attempts were made to evaluate the feasibility and usability of three simulative models based on reaction kinetics. Model (A) predicted relative changes over reaction time for reactant, intermediate, and product. Overall, an increased reaction rate produced less intermediate and more product, thereby leading to a shorter total reaction time. Particle diminishing model (B) predicted reduction of the total waste mass. The smaller particles diminished faster along with the dominant effect of microbial reaction. In Model (C), long-chain cellulose was predicted to transform into reducing sugar. At a standard condition, 48% of cellulose molecules having 10⁵ repeating units turned into reducing sugar after 100 h. Also it was found that the optimal enzyme concentration where the highest amount of remnant sugar was harvested was 1 mg L^-1.

• Environmental Engineering Research
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• 제21권2호
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• pp.164-170
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• 2016

Since most of the existing wastewater treatment options lack the ability to treat micro-contaminants, the increased use of pharmaceuticals and personal care products (PPCPs) and release as human waste have become a serious concern in recent years. Constructed wetlands (CWs) are a low-cost technology for wastewater treatment, however, its performance in term of PPCPs removal has not yet been fully investigated. This study aimed to characterize the removal factors and efficiency of acetaminophen (ACT) removal by CWs. The results revealed the decreased concentrations of ACT with increasing hydraulic retention times (HRT) of 0, 3, 5 days. The contribution of removal factors was found to be varied with initial ACT concentration. At the low ACT concentration (i.e. 1 ppb), plant uptake was the dominant, followed by microbial and photolytic removal. In contrast, at the high ACT concentration (i.e. 100 ppb), microbial and photolytic removal were found as dominant factors. On the other hand, hydrogen peroxide ($H_2O_2$) concentration was found at higher level in the plant shoot than in the root probably due to occurrence of the Fenton reaction resulting in PPCPs removal.

• 대한인간공학회지
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• 제29권4호
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• pp.575-584
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• 2010

The aim of study is to suggest the design procedure of automobile headlamp by considering driver's experience in regard of the visibility and glare during nighttime driving. The characteristics of driver were investigated in terms of the drivers' cognitive ability and reaction time, headlamp specification and visibility, light source and glare. And, the degree of visual discomfort was categorized and recognized as a tool to represent the subjective user experience. The UX point of view was stated when the existing results were seemingly lacking of it. The visual comfort and safety of elderly drivers were also discussed by reviewing the studies of ageing regarding the visibility and driving responses. Finally, this study suggested how to reduce the negative effect of nighttime driving due to the height of headlamp, angle of lighting, color spectrum, discomfort glare, source of light by using the UX perspective and methodology.

• 대한기계학회논문집B
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• 제32권5호
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• pp.359-366
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• 2008

A two-dimensional thermal model of proton exchange membrane fuel cell with large active area is developed to investigate the performance of fuel cell with large active area over various thermal management conditions. The core sub-models of the two-dimensional thermal model are one-dimensional agglomerate structure electrochemical reaction model, one-dimensional water transport model, and a two-dimensional heat transfer model. Prior to carrying out the simulation, this study is contributed to set up the operating temperature of the fuel cell with large active area which is a maximum temperature inside the fuel cell considering durability of membrane electrolyte. The simulation results show that the operating temperature of the fuel cell and temperature distribution inside the fuel cell can affect significantly the total net power at extreme conditions. Results also show that the parasitic losses of balance of plant component should be precisely controlled to produce the maximum system power with minimum parasitic loss of thermal management system.

• 대한안전경영과학회지
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• 제20권4호
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• pp.7-13
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• 2018

This study investigates the enhancement of the oxygen diffusion rate in the cathode channel of a proton exchange membrane fuel cell (PEMFC) by pure oscillating flow, which is the same as the mechanism of human breathe. Three-dimensional numerical simulation, which has the full model of the fuel cell including electrochemical reaction, ion and electronic conduction, mass transfer and thermal variation and so on, is performed to show the phenomena in the channel at the case of a steady state. This model could analysis the oscillating flow as a moving mesh calculation coupled with electrochemical reaction on the catalyst layer, however, it needs a lot of calculation time for each case. The two dimensional numerical simulation has carried on for the study of oscillating flow effect in the cathode channel of PEMFC in order to reduce the calculation time. This study shows the diffusion rate of the oxygen increased and the emission rate of the water vapor increased in the channel by oscillating flow without any forced flow.

• 한국환경보건학회지
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• 제27권1호
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• pp.44-50
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• 2001

This study was carried out to investigate characteristics of water quality and THMs formation in lake-waters at kunsan. Of the parameters examined for water quality, pH, alkalinity, SO$_4$$^{-2}$ and Co- reflected the characteristics according to the origin, geography and water source of lakes while COD, SS, T-P, T-N and chlorophyll-a corelatively reflected well the influence of pollution factors around factors around lakes. The result of water quality analysis showed that most lakes in Kunsan area have the severe eutropnication problem, especially in summer. In lake-waters, THMFP overally continued to increase until 48 hour with the reaction time and THMs formation was largely achieved within 24 hour of the reaction time. The average formation ratio were 68.2% for CHCl$_3$, 23.6% for CHCl$_2$Br, 7.6% for CHClBr$_3$ and 0.6% for CHBr$_3$respectively and much difference depending on the reaction time was not shown. Overally, 96h-THEFP levels in lakes were high during June~September and showed higher tencency in lakes where could be regarded more contaminated on the whole. These results suggest that THMFP may be available for the management of lake-water quality as one if the useful parameters for the general evaluation of contamination. 96h-THEMFP failed to show the strong corelation individually with pH, TOC, COD and chlorphyll-a.

• The Korean Journal of Pain
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• 제18권2호
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• pp.210-213
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• 2005

Acute viral meningitis and myositis are rare complications of varicella-zoster virus (VZV) reactivation. A 71-years-old immunocompetent man, who presented with lower back pain radiating to the left lower extremities, developed vesicles on the L5 dermatomal area. The next day, he had complained of aberrant vesicles on the trunk, face and scalp, with generalized myalgia, headache and dizziness. He was confirmed with VZV meningitis and myositis, as demonstrated by the presence of VZV DNA in the blood and cerebral spinal fluid using a polymerase chain reaction (PCR) amplification. PCR has been used in patients with a VZV infection associated neurological symptoms, and provides a useful tool for the early diagnosis of VZV-associated neurological disease. The patient was treated with bed rest, with intravenous acyclovir for the VZV infection, and intravenous Patient-controlled Analgesia for pain management and the prevention of postherpetic neuralgia. When he visited the outpatient department 3 months later, the skin lesion, leg pain, headache and myalgia had all improved, without sequelae. Here, this case is reported, with a discussion of the relevant literature on its diagnosis and management.

• 수산해양기술연구
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• 제47권4호
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• pp.419-427
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• 2011

Simulation technique for the fish behavior was applied to estimate fish school movement in the cage net. Individual-based fish behavior model (Huth and Wessel, 1991) was evaluated in a free area to understand the characteristics for the model, and the movement in the cage net was simulated by defining the fish reaction against the displacement of cage net. As a result, the distance to the net was not considerably changed and the space among fishes in cage net was slightly decreased by reducing the net space. Swimming area was, however, significantly affected by changing the net space and the relationship between swimming area and net displacement was theoretically estimated as y=-0.21x+1.02 ($R^2$=0.96). these results leads the conclusion that individual-based model was appropriated to describe the fish school reaction in the cage net and be able to use for evaluating the influence on cultured fish.

• 산경연구논집
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• 제10권6호
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• pp.19-27
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• 2019

Purpose - The purpose of this study was to examine quality improvement priorities by examining not only quality classifications but also PCSI (Kano, 1984) of mobile app service qualities of general hospitals in the Metropolitan Area and offer potential improvements. Research design, data, and methodology - The study examined five of service qualities, including app design, reaction, convenience, safety and supply of information by precedent studies. 20 test items were selected. A total of 60 positive and negative questions to estimate customer satisfaction and PCSI was investigated. The author collected 300 copies from interviewees who made use of the app services of 13 general hospitals within one year, and classified quality factors by using table of quality assessment and also estimated the customer satisfaction index (Timko, 1993). The study made quality improvement priority by the PCSI index. Results - Reaction of the mobile app service quality ranked the highest PCSI, and payment safety ranked the highest, and customer support and supply of the information ranked high as well. It was observed that design ranked comparatively lower in these categories. Conclusion - Safety, reaction and supply of information should be prioritized to reorganize and improve the mobile app services.

• 한국환경농학회지
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• 제29권4호
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• pp.402-407
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• 2010

Zerovalent iron (ZVI) is one of the most commonly used metallic reducing agents for the treatment of toxic contaminants in wastewater. Traditional ZVIs are less effective than nanoscale ZVI (nZVI) due to prolonged reaction time. However, the reactivity can be significantly increased by reducing the size of ZVI particles to nanoscale. In this study, nZVI particles were synthesized under laboratory condition and their efficiency in removing hexavalent chromium (Cr(VI)) from aqueous solutions were compared with commercially available ZVI particles. The results showed that the synthesized nZVI particles (SnZVI) reduced >99% of Cr(VI) at the application rate of 0.2% (w/v), while commercial nZVI (CnZVI) particles resulted in 59.6% removal of Cr(VI) at the same application rate. Scanning electron micrographs (SEM) and energy dispersive spectra (EDS) of the nZVI particles revealed the formation of Fe-Cr hydroxide complex after reaction. Overall, the SnZVI particles can be used in treating chromium contaminated wastewater.