• Membrane Journal
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• v.30 no.2
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• pp.138-148
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• 2020

The purpose of this study was to identify the cleaning efficiency of fouled multi-bore hollow fiber membranes after purification of contaminated water. The PSf (polysulfone) based hollow fiber membrane manufactured by Pure & B Tech Co., Ltd. Was used in this study. The antifouling characteristics during the water treatment were studied using bovine serum albumin (BSA) as a model compound and the chemical resistance was evaluated after long-term impregnation in sodium hypochlorite (NaOCl) solution and Citric acid to understand the long term stability of the membranes. Water permeability and mechanical strength of the membranes after prolonged chemical exposure was measured to observe the change in mechanical stability and long term performance of the membrane. moreover, the recovery efficiency was also evaluated after chemical enhanced backwashing of a membrane contaminated with bovine serum albumin. The PSf hollow fiber membrane exhibited excellent chemical resistance, and it was confirmed that the efficiency of sodium hypochlorite was high as a result of chemical enhanced backwashing.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.1
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• pp.19-25
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• 2017

In this study, a electrostatic filter which could be applicable to road environment was developed and evaluated in adsorption capacity. The evaluation were performance for removal by particle size and adsorption amount by pressure using ASERAE 52.1 and 52.2. The range of size for removal test was $0.3{\mu}m{\sim}10.0{\mu}m$ which had 12 steps. The filter showed 91.3% removal efficiency from $2.5{\mu}m$ and under the size, average 53.5% proportional to decreasing size value. The weight removal was 96.7% from 22.6 mmaq, initial pressure to 35 mmaq, end pressure with $715.9g/m^2$, the adsorption amount. The shape of isotherm was expressed as Langmuir's one. After washing saturated filter with dust to end pressure, the initial pressure and adsorption amount of the filter showed a light drop with no removal efficiency decline.

• Journal of Dairy Science and Biotechnology
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• v.38 no.2
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• pp.99-111
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• 2020

Probiotics are actively being studied for their efficacious anticancer, anticholesterol, and antidiabetic properties. As novel probiotic strains are being developed continuously, new strain-specific safety issues may be reported. Therefore, a procedure for the safety evaluation of probiotic strains is needed. In this study, we investigated the current status of domestic and foreign guidelines for the evaluation of safety of probiotics and suggested a general probiotic safety evaluation process. In other countries, the guidelines for probiotic evaluation are provided and managed separately. However, in Korea, general guidelines are provided regarding the use of functional ingredients, and specific guidelines for the use of probiotics are lacking. A review step based on the characteristics of the probiotics has been introduced in the procedure for safety evaluation of probiotics. Additionally, it has been suggested that the safety evaluation process should consider the results of the functional and genomic analysis for strain identification. Moreover, the factors to be evaluated are presented separately for the notified and non-notified strains. The suggested evaluation procedure may ensure the safety of probiotics, thereby promoting enhanced utilization of probiotics as functional products.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.45-50
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• 2021

As the difficulty of flip chip products increases, there is a growing interest in the material of flux, which is safe from the solder wetting and reliability. In the case of no clean flux, there is merit in terms of process efficiency because there is no cleaning process. But Cu migration and delamination can be occurred if the residue remains after the reflow process. In this study, major element materials, solvent and activator, are changed and confirmed effect of non-wet and reliability in the package environment. Stability of materials were secured through storage stability evaluation, and we found out non-wet zero materials through the application of two types of solvent and activator with different boiling point and the increase of activator content. After reliability test, no delamination was found in the plane analysis, which secured the final composition of low residue flux.

• Journal of Wetlands Research
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• v.16 no.3
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• pp.347-353
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• 2014

This work was performed to find the effect of operation parameters on the permeate flux through the activated sludge dynamic layer, and to indicate the relationship between the water quality of supernatant and flux based on the results. Since the effluent can be obtained through steady and stable formation of cake layer in the bio-filter media system, it is an important subject to keep and control microbes with activated state in the bio-reactor. Filtration resistance was drastically increased at more than 18000mg/L of MLSS. With filtration time continued, the flux was gradually decreased and the water qualities of supernatant monitored by turbidity and TOC were also deteriorated. This phenomenon indicated that the organic materials generated by microbes and accumulated in the reactor might affect the flux in the system. In addition, the decrease of flux was simultaneously observed in the sludge volume index. When SVI was controlled from 150 to 250, the flux was also decreased. The proper aeration time was recommended to 30 to 60 seconds in this system. In order to operate this system steadily, therefore, the control of water quality of supernatant and SVI should be proceeded.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.545-550
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• 2012

Steam generator is one of the major components of nuclear power plant and steam generator tubes are the pressure boundary between primary and secondary side, which makes them critical for nuclear safety. As the operating time of nuclear power plant increases, not only damage mechanisms but also scaled deposits on steam generator tubes are known to be problematic causing tube support flow hole blockage and heat fouling. The ability to assess the extent and location of scaled deposits on tubes became essential for management and maintenance of steam generator and eddy current bobbin data can be utilized to measure thickness of scale on tubes. In this paper, tube reference standards with various thickness of scaled deposit has been set up to provide information about the overall deposit condition of steam generator tubes, providing essential tool for steam generator management and maintenance to predict and prevent future damages. Also, methodology to automatically measure scale thickness on tubes has been developed and applied to field data to estimate overall scale amount.

• Journal of Periodontal and Implant Science
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• v.37 no.1
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• pp.1-10
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• 2007

연구 목적 : 구취의 주된 화학적 요소는 휘발성 황 화합물 (VSCs)들이다. 이들은 치태, 설태, 타액과 혈액, 상피세포의 혐기성 그람 음성 세균에 의한 단백분해 변성으로 만들어 진다. 또한 구취는 치주질환과 타액내의 세균의 증가를 야기하는 불량한 구강 위생상태에서 기인한다고 보고되고 있다. 이 연구의 목적은 VSCs를 측정함으로 구취에 대한 비외과적 치주 치료의 영향을 평가하고, 타액내의 세균 수를 측정함으로써 VSCs와의 상관관계를 살펴보고자 하는 것이다. 연구 대상 및 방법 : 중등도의 만성치주염을 가지는 23명의 참가자들이 대조군과 실험군으로 분류되었다. 대조군은 구강위생교육 (치간청결기구와 혀세정 포함)만을 시행하였고 실험군은 구강위생교육과 함께 24시간 내에 전악 치석제거술과 치근활택술을 시행하였다. 치료 전과 치료 4주 후에 VSCs 농도를 $Halimeter^{(R)}$(Interscan Corp., CA, USA)를 사용하여 측정하였고 타액 시료는 혐기성과 호기성 조건에서 배양되었다. 결과 : 4주 후에 두 군 모두에서 휘발성 황화합물의 농도가 유의하게 감소하였고, 실험군에서의 감소량이 통계적으로 유의하게 더 크게 나타났다. 타액 내 세균의 배양에서 총세균수에 대한 혐기성 세균의 비율이 실험군에서만 통계적으로 유의하게 감소하였다. 그러나 세균의 비율과 휘발성 황화합물의 농도와의 상관관계는 낮게 나타났다. 즉 구취의 감소는 타액 요인 보다는 치주치료에 의한 다른 복합적인 인자의 작용에 의한 것으로 추론할 수 있었다. 결론 : 본 연구는 중등도의 치주염환자에서 구강위생교육만으로도 구취의 주요 화학적 요인인 휘발성 황화합물의 농도를 감소시킬 수 있으나 비외과적 치주치료를 동반하였을 때 더욱 큰 효과를 얻을 수 있는 것으로 해석된다. 그러나 실험 참가자의 수가 적었고 장기간의 분석이 이루어지지 않았으므로 앞으로 더 많은 연구가 구취에 대한 치주치료의 영향을 이해하기 위해서 필요할 것으로 사료된다.

• Journal of the Korean Society of Visualization
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• v.14 no.1
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• pp.40-45
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• 2016

Elimination of the smear layer and bacteria in the root canal is the most important in the endodontic treatment, and various irrigation devices have been developed. Nevertheless, it is hard to eliminate the smear layer and bacteria completely. In this paper, a micro bubble irrigation system has been developed for the root canal cleaning of tooth. Micro bubbles are generated when pressurized fluids passing through a porous material inside a hand-piece nozzle, and the bubbly flows excited by ultrasonic vibration are observed using a high-speed camera and a microscope. The results show that the diameter and number of bubbles increases with the applied pressure, and there found an optimum excitation frequency in order to minimize the bubble size. From in-vitro tests, it is also verified that the developed bubble irrigation system has the ability of antibacterial and infection removal. Thus, this biocompatible system would be well suited for root canal cleaning.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.2
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• pp.169-175
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• 2017

This study applied microbubbles to reduce membrane fouling in wastewater reuse membrane processes, evaluated and compared the transmembrane pressure with or without the application of microbubbles and the cleaning efficiency with the application of aeration and microbubbles. In addition, this study analyzed foulants removed from the membrane surface. Changes in the transmembrane pressure of membranes with the presence or absence of microbubbles were observed. As a result, transmembrane pressure (TMP) increasing rate decreased twofold when applying microbubbles to realize stable operations. This study compared and evaluated cleaning efficiency applying aeration and microbubbles. As a result, the cleaning efficiency was 5% higher on average when applying microbubbles. In turbidity and total organic carbon (TOC), foulants were discharged when applying microbubbles twice as much as applying aeration. It is thought that particulate foulants precipitated on the membrane surface were more likely to desorb because the adhesion between the membrane surface and particle was weakened by microbubbles. Therefore, it is considered possible to effectively control membrane fouling because of the increase in cleaning efficiency when applying microbubbles to wastewater reuse membrane processes.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.32-38
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• 2018

The purpose of this study is to assess quantitatively the amount of leaks and the extent of dispersion in case of a leak at a hydrogen fluoride tank container unloading station, and to suggest a safety improvement plan to prevent recurrence of similar accidents. In 2012, Company H leaks 8 tonnes of tank containers with a maximum storage capacity of 18 Ton, causing it to become a social issue. As a result of calculation using Gaussian plume model, the concentration was estimated to be more than 20ppm from the leak point to 1,321 m radius. The leakage of hydrogen fluoride from the company R in 2014 was estimated to be 11.02 kg, of which 2.9 kg was treated by the scrubber. As a result of calculation using Gaussian plum model, the damage range with a concentration of 20ppm or more from the leak source was estimated to be 69 m in radius. As a result of comparing the above two accidents, it was found that the leakage amount was about 987 times different and the damaged site was more than 19 times different. Therefore, it was concluded that it was necessary to control the wearing of the protective equipment, the enclosure of the unloading site, the installation of the scrubber, and the emergency training to avoid the accidental leakage of a hydrogen fluoride from the unloading site.