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LABORATORY STUDIES ON MIC OF AISI TYPE 304 STAINLESS STEEL USING BACTERIA ISOLATED FROM A W ASTEWATER TREATMENT SYSTEM

  • Sreekumari, Kurissery R.;Kyozo, Hirotani;Katsuya, Akamatsu;Takashi, Imamichi;Yasushi, Kikuchi
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.260-265
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    • 2002
  • Microbiologically influenced Corrosion (MIC) is one of the most deleterious effects of metal microbe interactions. When a fresh metal surface comes in contact with a non-sterile fluid, biofilm formation is ensued. This might result in the initiation of corrosion. The sites and materials where MIC is implicated are versatile. Industries such as shipping, power generation, chemical etc are reported to be affected. The rapid and unexpected failure of AISI type 304 stainless steel was investigated in the laboratory by simulation studies for a period of 4 months. Slime and water samples from the failure site were screened for corrosion causing bacteria. Both aerobic and anaerobic nora were enumerated and identified using PCR techniques. Pseudomonas sp. and Bacillus sp. were the most common aerobic bacteria isolated from the water and slime samples, whilst sulfate reducing bacteria (SRB) were the major anaerobic bacteria. The aerobic bacteria were used for the corrosion experiments in the laboratory. Coupon exposure studies were conducted using a very dilute (0.1%V/V) nutrient broth medium. The coupons after retrieval were observed under a Scanning Electron Microscope (SEM) for the presence of MIC pits. Compared to sterile controls, metal coupons exposed to Pseudomonas sp and Bacillus sp. showed the initiation of severe pitting corrosion. However, amongst these two strains, Psudomonas sp. caused pits in a very short span of 14 days. Towards the end of the experiment, severe pitting was observed in both the cases. The detailed observation of pits showed they vary both in number and shapes. Whilst the coupons exposed to Bacillus sp. showed widely spread scales like pits, those exposed to Pseudomonas sp. showed smaller and circular pits, which had grown in number and size by the end of the experiment. From these results it is inferred that the rapid and unexpected failure of 304 SS might be due to MIC. Pseudonwnas sp. could be considered as the major responsible bacteria that could initiate pits in the metallic structures. As the appearance of pits was different in both the tested strains, it was thought that the mechanisms of pit formation are different. Experiments on these lines are being continued.

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Development and Validation of Reservoir Operation Rules for Integrated Water Resources Management in the Geum River Basin (금강유역의 유역통합수자원관리를 위한 저수지 운영률 개발 및 적용성 검토)

  • Cheong, Tae-Sung;Kang, Sin-Uk;Hwang, Man-Ha;Ko, Ick-Hwan
    • Journal of Korea Water Resources Association
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    • v.41 no.4
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    • pp.433-444
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    • 2008
  • In recent, the integrated water resources management should consider not only existing management objects such as water supply, power generation, and instream flows but also new management objects such as water quantity, water quality, and water habitats which management system is large and complex. Moreover, integrated basin plan or operation are needed for solving conflicts problems between basins and between water usages and to maximize water resources usages. To increase use of optimization method for actual operation and apply various objects, a reservoir operation rule was developed and the KModSim's hydrologic states for integrated water resources management were tested in this study. The simulation results show that the developed operation rules applied in hydrologic states good represent the actual storages of both the Yongdam and the Daecheong Reservoirs so, it is possible to improve the water allocation method usually used in the basin management and manage the integrated basin water resources if new operating rules are applied in optimized programming.

Application of the SCE-UA to Derive Zone Boundaries of a Zone Based Operation Rule for a Dam (저수지 수위 구간별 운영률의 구간 경계 도출을 위한 집합체 혼합진화 알고리즘의 적용)

  • Kang, Shinuk;Kang, Taeuk;Lee, Sangho
    • Journal of Korea Water Resources Association
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    • v.47 no.10
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    • pp.921-934
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    • 2014
  • The purpose of the study is to derive a long term reservoir operation method that is easy to understand and apply to practical use for dam operators. The zone based operation rule is a simple method to make operation decisions by criteria corresponding to storage zones. The reservoir storage levels dividing a reservoir, however, must be determined by some methods. We developed a reservoir operation model based on the zone based operation rule and the shuffled complex evolution algorithm (SCE-UA) was used to determine storage levels for zone division. The model was applied to Angat Dam in the Philippines that has trouble in water supply due to imbalance between supply and demand. We derived a zone based operation rule for Angat Dam and applied it to the reservoir simulation of Angat Dam using the historical inflow. The simulation results showed water supply deficit and power generation were improved by 34.5% and 21.2%, respectively, when compared with the historical records. The current study results may be used to derive a long term reservoir operation rule.

Image Processing Algorithms for DI-method Multi Touch Screen Controllers (DI 방식의 대형 멀티터치스크린을 위한 영상처리 알고리즘 설계)

  • Kang, Min-Gu;Jeong, Yong-Jin
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.48 no.3
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    • pp.1-12
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    • 2011
  • Large-sized multi-touch screen is usually made using infrared rays. That is because it has technical constraints or cost problems to make the screen with the other ways using such as existing resistive overlays, capacitive overlay, or acoustic wave. Using infrared rays to make multi-touch screen is easy, but is likely to have technical limits to be implemented. To make up for these technical problems, two other methods were suggested through Surface project, which is a next generation user-interface concept of Microsoft. One is Frustrated Total Internal Reflection (FTIR) which uses infrared cameras, the other is Diffuse Illumination (DI). FTIR and DI are easy to be implemented in large screens and are not influenced by the number of touch points. Although FTIR method has an advantage in detecting touch-points, it also has lots of disadvantages such as screen size limit, quality of the materials, the module for infrared LED arrays, and high consuming power. On the other hand, DI method has difficulty in detecting touch-points because of it's structural problems but makes it possible to solve the problem of FTIR. In this thesis, we study the algorithms for effectively correcting the distort phenomenon of optical lens, and image processing algorithms in order to solve the touch detecting problem of the original DI method. Moreover, we suggest calibration algorithms for improving the accuracy of multi-touch, and a new tracking technique for accurate movement and gesture of the touch device. To verify our approaches, we implemented a table-based multi touch screen.

University Students' Awareness of Radiation (대학생들의 방사선에 대한 인식도)

  • Kim, Chang-Gyu
    • Journal of the Korea Convergence Society
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    • v.3 no.1
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    • pp.27-34
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    • 2012
  • After Fukushima Nuclear Accident on Mar11, 2011, to grasp the thought of university students in Korea on radiation and medical radiation and seek for the right mass communication on the radiation safety of the people and the proper teaching method on radiation, 790 questionnaires from the universities which had a four-year department of radiological science in 5 provinces(Gyeonggi, Gangwon, Chungcheong, Jeolla, and Gyeongsang-do) all over the country were collected and analyzed. The questionnaire was composed of 36 items, and it was analyzed that one of the important causes that made them feel that radiation was dangerous was 'even if they were exposed to the small quantity of radiation, they could have trouble later.' ($3.28{\pm}1.05$). In the item of the control of radiation, there were the respondents who answered that the government should take action rather than an individual($3.87{\pm}0.89$). In the item of 'Fukushima Nuclear Accident made me think that 'We should not keep nuclear power generation', the result was $2.79{\pm}0.95$. In the item of 'My thought on the medical radiation has negatively changed since Fukushima Nuclear Accident', the students who hadn't taken the course related with radiation showed a negative thought on the medical radiation, such as, there was $2.64{\pm}1.02$ as a whole, $2.31{\pm}1.00$ in department of radiological science, $2.94{\pm}0.95$ in department of dental hygiene, and $3.13{\pm}0.82$ in other departments. And also, those who thought that the education of radiation was necessary were 82.28%, and T.V or Internet was thought as the most effective teaching method.

Engineering Characteristics of CLSM with Regard to the Particle Size of Bottom Ash (저회의 입도변화에 따른 CLSM의 공학적특성)

  • Lee, Yongsoo;Kim, Taeyeon;Lee, Bongjik
    • Journal of the Korean GEO-environmental Society
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    • v.21 no.10
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    • pp.5-10
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    • 2020
  • As the demand for the recycling of industrial by-products increases due to various environmental restrictions including the prohibition of ocean disposal, various studies regarding the recycling of industrial by-products are currently being carried out. One of the industrial by-product, coal ash is produced from thermal power generation; studies on the recycling of fly ash have been actively carried out and it is currently recycled in various fields. In the case of bottom ash, however, only a portion of the total amount generated is primarily processed into a particle size of 2~4mm or less than 2mm to be used for gardening purpose and light weight aggregate and so on. The remaining amount is buried at ash disposal sites. Therefore, various studies are needed to develop measures to use bottom ash. This study aimed at identifying the optimal particle size and mixing ratio of bottom ash to be used as CLSM aggregate. To this end, it evaluated the usability of bottom ash as CLSM aggregate, by investigating the flowability and strength change characteristics of CLSM produced with regard to the mixing ratio of weathered granite soil and bottom ash, particle size of bottom ash to be mixed and soil binder addition rate and conducting a heavy metal leaching test.

Electrochemical Reduction Process for Pyroprocessing (파이로프로세싱을 위한 전해환원 공정기술 개발)

  • Choi, Eun-Young;Hong, Sun-Seok;Park, Wooshin;Im, Hun Suk;Oh, Seung-Chul;Won, Chan Yeon;Cha, Ju-Sun;Hur, Jin-Mok
    • Korean Chemical Engineering Research
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    • v.52 no.3
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    • pp.279-288
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    • 2014
  • Nuclear energy is expected to meet the growing energy demand while avoiding CO2 emission. However, the problem of accumulating spent fuel from current nuclear power plants which is mainly composed of uranium oxides should be addressed. One of the most practical solutions is to reduce the spent oxide fuel and recycle it. Next-generation fuel cycles demand innovative features such as a reduction of the environmental load, improved safety, efficient recycling of resources, and feasible economics. Pyroprocessing based on molten salt electrolysis is one of the key technologies for reducing the amount of spent nuclear fuel and destroying toxic waste products, such as the long-life fission products. The oxide reduction process based on the electrochemical reduction in a LiCl-$Li_2O$ electrolyte has been developed for the volume reduction of PWR (Pressurized Water Reactor) spent fuels and for providing metal feeds for the electrorefining process. To speed up the electrochemical reduction process, the influences of the feed form for the cathode and the type of anode shroud on the reduction rate were investigated.

Model development for site selection considering the characteristics of LNG receiving terminal (LNG 특성을 고려한 저장기지 입지선정 모델 개발)

  • Jeong, Nam Hoon;Liu, An Qi;Hwang, Geon Wook;Jang, Woosik;Han, Seung Heon
    • Korean Journal of Construction Engineering and Management
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    • v.16 no.1
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    • pp.82-91
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    • 2015
  • Recently, due to the increasing concern of environmental factors and low carbon usage, the use of natural gas has been inclining steadily. In order to meet the growing demand of natural gas, government have established strategies to secure the sufficient amount of gas that is mainly used by industries, power generation and residential use by constructing additional receiving terminals for Liquid Natural Gas (LNG). In the process of selecting the optimal site for the terminals, the characteristics of the terminals are not considered where the decision making is done through internal meetings or outsourcing. In respect to site selection, researches are done to derive the factors that are considered for optimal site selection. However, there have not yet been researches in creating a systematic model for analyzing the optimal site selection. To this aim, the paper aims to propose a model for site selection of LNG receiving terminals that considers the characteristics of the terminal construction. Total of 47 factors considered in site selection is derived through interviews with experts and analyzing the previous cases of site selection by various firms. Furthermore, the derived 47 factors are used for the survey for the previous LNG terminals in PT, IC, TY, SC and BR areas where the survey data is analyzed by factor analysis and multiple regression models to depict the optimal site. By applying the model for site selection, practitioners are able to make decisions for site selection in a systematic approach for new candidates of sites.

An Early Spectrum Sensing for Efficient Radio Access in Cloud-Conceptual Base Station Systems (클라우드 기지국 시스템에서 효율적 무선 접속을 위한 이른 스펙트럼 감지 기법)

  • Jo, Gahee;Lee, Jae Won;Na, Jee-Hyeon;Cho, Ho-Shin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.1
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    • pp.68-78
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    • 2013
  • In this paper, we propose an early spectrum sensing(ESS) as an advance preparation for radio-access trial, which enables multi-mode terminals to access the most appropriate radio-access system in a cloud-conceptual base station system where multiple radio access technologies(RATs) coexist. Prior to a random access to one of RATs, a multi-mode terminal conducts a spectrum sensing over entire frequency bands of whole RATs, then select the RAT with the lowest sensing power, that is likely to have the most available spectrum. Thus, an access failure caused by that the selected RAT has no available radio spectrum could be avoidable in advance. In computer simulation, we consider as various RATs as possible. First, circuit and packet systems are taken into consideration. In addition, the packet systems are classified according to the feasibility of carrier aggregation(CA). In case of terminal, three modes are considered with circuit-only, packet-only, and multi-mode. Subsequently, packet traffic is classified into real-time and non-real-time traffic with three different tolerable delay levels. The simulation includes a call process starting with a call generation and ending up with a resource allocation reflecting individual user's QoS requirements and evaluates the proposed scheme in terms of the successful access probability, system access time, system balancing factor and packet loss probability.

Applicable Building Range for the Introduction of the Building Separation and Dismantling System (건축물 분별해체 제도 도입을 위한 적용 대상 건축물 범위 설정)

  • Park, Ji-Sun;Song, Tae-Hyeob;Choi, Dong-Ho
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.1 no.3
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    • pp.189-196
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    • 2013
  • In order for efficient recycling and eco-friendly treatment of construction waste, there is a need to apply a building separation and dismantling technique early on in the stage of waste generation. This study was conducted to analyze the relevant domestic circumstances and propose the applicable range of buildings in order to introduce a building separation and dismantling system to Korea. For this purpose, related policies and systems implemented overseas and the current situation of buildings were examined, and the workability of separation and dismantling of buildings according to their uses was compared. Also, the economic impact of the separation and dismantling system was examined and a survey was conducted, seeking the opinions of the relevant companies regarding the need for the system and the selection criteria for eligible buildings. Based on the results, it was determined that it would be impossible to apply the separation and dismantling system to all buildings in Korea, considering the current technical power and economic situation, and that the system should be introduced in phases, according to the building classification determined based on floor area and use, as the cost may vary depending on a number of variables including the level of difficulty and field conditions.