• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.10
• /
• pp.916-927
• /
• 2010

In general water treatment process, the disinfection process by chlorine is used to prevent water borne disease and microbial regrowth in water distribution system. Because chlorines were reacted with organic matter, carcinogens such as disinfection by-products (DBPs) were produced in drinking water. Therefore, a suitable injection of chlorine is need to decrease DBPs. Rechlorination in water pipelines or reservoirs are recently increased to secure the residual chlorine in the end of water pipelines. EPANET 2.0 developed by the U.S. Environmental Protection Agency (EPA) is used to compute the optimal chlorine injection in water treatment plant and to predict the dosage of rechlorination into water distribution system. The bulk decay constant ($k_{bulk}$) was drawn by bottle test and the wall decay constant ($k_{wall}$) was derived from using systermatic analysis method for water quality modeling in target region. In order to predict water quality based on hydraulic analysis model, residual chlorine concentration was forecasted in water distribution system. The formation of DBPs such as trihalomethanes (THMs) was verified with chlorine dosage in lab-scale test. The bulk decay constant ($k_{bulk}$) was rapidly decreased with increasing temperature in the early time. In the case of 25 degrees celsius, the bulk decay constant ($k_{bulk}$) decreased over half after 25 hours later. In this study, there were able to calculate about optimal rechlorine dosage and select on profitable sites in the network map.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.41 no.2
• /
• pp.11-18
• /
• 2023

This study aims to distinguish what can be used in consideration of the national situation with Korea for Chinese Scenic and Historic Interest Areas, and the results are as follows; First, the Chinese Scenic and Historic Interest Areas expanded to the existing scenic cruise culture, travel, and tourism culture in the process of the influx of Western culture in the modern and contemporary era, and became popular as a travel destination. Accordingly, the Chinese government developed the tourism industry around the scenic sites, and thanks to the development of transportation and communication, the Scenic and Historic Interest Areas has become an important national heritage. This influenced the establishment of the system related to Scenic and Historic Interest Areas, and today, it is operated around the Scenic and Historic Interest Areas ordinance. Second, the designation of the Scenic and Historic Interest Areas is divided into the size of the site according to the area, and the process of selecting the Scenic and Historic Interest Areas classification, rating evaluation, and comprehensive value evaluation according to evaluation indicators and rating standards is carried out. Accordingly, according to the results of the classification, it is subdivided from the national level to the Scenic and Historic Interest Areas at the local level. Third, the central government is in charge of managing and supervising Scenic and Historic Interest Areas across the country, and the local government's construction department is in charge of supervising Scenic and Historic Interest Areas in the region. The management organization of Scenic and Historic Interest Areas established by local governments above the county level has a system that actually protects, utilizes, and manages Scenic and Historic Interest Areas. In addition, 14 detailed indicators are used to monitor Scenic and Historic Interest Areas. Based on these results, considering the application of the domestic scenic site policy, the method of developing the policy that has established the system from the perspective of the utilization of the people is worth considering. On the other hand, the evaluation of the designation and management system through the setting of various indicators has limitations in that it is difficult to secure objectivity in impressing or evaluating the landscape. Therefore, rather than blindly introducing quantified evaluation, it seems that guidance and promotion on how to expand consensus on scenic values and enjoy heritage should be prioritized.

• The Korean Journal of Malacology
• /
• v.28 no.1
• /
• pp.45-54
• /
• 2012

We investigated environmental characteristics of the tidal flat oyster aquafarms to clarifyeffects of the tidal flat environmental factors on growth and mortality of the tidal flat oyster Crassostrea gigas by the Net Bag Rack Culture System in two districts in Western Korea. In this study, we have carried out the basic environmental investigation on growth of the single tidal flat, water quality and sediments, etc. in Taean and Seosan districts, Choongcheongnam-do, where the single tidal flat oyster aquaculture have been performed by the net bag rack culture system. In June 2011 when the final survey carried out at the two districts in western Korea, the mortality in Seosan district was higher than that in Tae-an district. Judging from the results of growth and mortality of the single tidal flat oysters investigated at two sites of Jinsan-ri in Taean and Chang-ri in Seosan districts, two results of Taean district showed higher growth and lower mortality than those of Seosan district. It is assumed that the proper acceptable density possible for growth of the tidal flat seeds and the secure of economics, in case of plastic cultivate net with the size of $50{\times}80cm$, are about 200 individuals. In this study, It was clarified that selection of the suitable sites, the input into the net bag of high quality oyster seeds and selective dispersion in the optimal density of the single tidal flat oyster have an effect on growth and mortality of the tidal flat oyster.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.2
• /
• pp.139-147
• /
• 2021

Livestock manure is used as an organic fertilizer to replace chemical fertilizers after sufficient fermentation in an aerobic bioreactor. On the other hand, liquid manure disposal problems occur repeatedly because soil spraying is restricted during the summer when the crops are growing. To use liquid fertilizer (LF) as an additional nutrient source for crops, it is necessary to reduce the amount of suspended solids (SS) in the liquid fertilizer and secure stability problems against pathogenic microorganisms. This study examined the effects of the simultaneous SS removal and E.coli sterilization in the LF using the microbubble (MB) generator (FeMgO catalyst insertion). The remaining SS were further removed using the integrated microbubble and microfilter system. During the floating process in the MB device, the SS were removed by 57.9%, and the coliform group was not detected (16,200→0 MPN/100 mL). By optimizing the HRT of the integrated system, the removal efficiency of the SS was improved by 92.9% under the 0.1h of HRT condition. After checking the properties of the treated LF, 64.5%, 70.1%, 54.9%, and 51.5% of the TCOD, SCOD, PO4-P, and TN, respectively, were removed. The treated effluent from such an integrated system has a lower SS content than that of the existing LF and does not contain coliforms; therefore, it can be used directly as an additional fertilizer.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.40 no.2
• /
• pp.14-23
• /
• 2022

The purpose of this study is to preserve the sustainable traditional landscape of the "Terraced Paddy Fields of Gacheon Village, Namhae". To this end, the changes in the traditional landscape and its factors were analyzed, and a conservation plan was sought to coexist with local communities. The results are as follows; First, the traditional scenery of "Terraced Paddy Fields of Gacheon Village, Namhae" is characterized by stonework built on a steep topography to secure cultivated land and narrow rice fields. To this end, local communities have maintained the traditional landscape through their long-established traditional knowledge, but after the designation of cultural heritage, the unique landscape of the "Terraced Paddy Fields of Gacheon Village, Namhae" changed as standardized stone construction methods were applied. Recently, the Cultural Heritage Administration recognized these problems and returned to the direct repair system of local communities, so cultivated land is regaining the scenery of the past. Second, the factors that changed the traditional landscape of the "Terraced Paddy Fields of Gacheon Village, Namhae" were largely found to be a decrease in voluntary conservation consciousness, a limited management range of preservation society, a decrease in agricultural population, and a lack of skilled traditional skills. After the designation of cultural heritage, expectations for policy support by the state or local governments accelerated the damage as existing farmland was neglected, and the lack of agricultural population also resulted in the same result. The preservation society is making efforts to preserve it, but the phenomenon of excessive and insufficient management personnel is intensifying. Conflicts between residents due to profit polarization have spread to the problem of escalating. In addition, there are concerns about the loss of traditional knowledge such as step farming technology and stone construction functions. Third, to suggest a win-win plan with local communities for preserving the traditional landscape, it is necessary to seek the ways to expand farming participants and generate profits through the placement of professional careers and public-private linkage system. In addition, it is desirable to improve the profit distribution system through the preservation society to strengthen the management authority and induce participation. And a support system is required for education on the transmission of terraced farming technology and stone construction functions.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.3
• /
• pp.21-29
• /
• 2023

In this study, the stress characteristics of temporary fixed steel rods were analyzed in the "temporary fixing system using internal prestressing tension", which is mainly applied to the construction of superstructures by FCM. It was difficult to confirm the changes in initial tensile force in this system because the steel rod was internally connected to the pier and the PSC BOX. Therefore, measurement was performed before and after the completion of each segment using an FBG sensor to measure the change in the micro length of the steel rod. The results of the analysis showed that 75% to 90% of the maximum vertical contraction of the steel rod that occurred until the completion of the cantilever segment occurred in the fixing ~ 1segment, and the maximum loss of initial prestressing force was 39%. Such excessive loss of tension force to 1 segment means that tension is needed to improve the precision of construction during the fixation, and re-tension is needed to secure stability for conduction of cantilever segments after the completion of 1segment. In the 2 ~ last segment, the stress of the steel rod decreased gradually, and in the summer, the decrease in stress tended to partially recover due to the increase in the length of the steel rod corresponding to the increase in the vertical volume of PSC BOX. The dominant factor in the stress change in 2~ last segment in this phenomenon is judged to be the change in the length of the steel rod according to the temperature. Unlike the change in length, the relaxation was 1.2-2.7%, which was mostly offset by the opposite stress corresponding to the temperature stress. Therefore, a plan was proposed to improve the internal stress, such as adjusting the fixation time.

• Journal of Digital Convergence
• /
• v.12 no.9
• /
• pp.313-323
• /
• 2014

Recently, there has been an effort to convert standardized educational system to customized one considering students' individual differences and aptitude. Flipped learning has been regarded as a teaching method fitting to this movement and has gained much interest by educators. Despite its increasing interest, its studies fall short in the quantity above all. This study investigated the concept of flipped learning and explored its educational value in terms of student' and teacher' perspectives. The study also examined the requirements to apply flipped learning to its practice. Flipped learning was found to accomplish mastery learning and to promote interaction between teacher and students and also peer-to-peer interaction. It was expected to reduce the burden of teacher's duties and secure his or her interest in students and the tutorial time for individual students. Essential elements in its application in practice included students' voluntary participation, the consent of their parents and support from their school and government. In addition, teachers' professional development was found to be important to improve their understanding and application of flipped learning in practice.

• Journal of Intelligence and Information Systems
• /
• v.14 no.2
• /
• pp.137-156
• /
• 2008

The purpose of this study is to implement evaluation on domestic cyber University web site to analyze web usability and web accessibility in order to present how much cyber University provides various personalized services and qualitative contents to users on web site. And also with this result, I hope to contribute in qualitative development of web site and reliability of remote education. For this purpose, I developed checklist suitable to remote University by applying SM-ABCDE assessment method of Moonhyeongnam, the professor in Sookmyung Women's University, and implemented evaluation on web sites of 17 cyber University over the five aspects of attraction, business, contents, design, and engineering. As the result of this study, it was found that Busan Digital University was best in the respect of attraction, both Kyunghee Cyber University and Cyber University of foreign studies were best in the respect of business, Kyunghee University was best in the respect of contents, and Hanyang Cyber University was best in the respect of design. It was also evaluated in the comprehensive view and the order was found that Kyunghee Cyber University, Busan Cyber University, and Hanyang Cyber University. However in the respect of engineering, it came out that all the sites did not observe the regulation on web accessibility. If domestic Cyber Universities are to observe the regulation on web accessibility with the long term view, on the base of this study, web usability would be increasing. Then they can secure various classes of customers as well as ordinary people so that they will be able to take the real place of educational institution orienting the most advanced educational method in the society of knowledge and information in addition to advance in themselves.

• Journal of KIISE:Information Networking
• /
• v.35 no.5
• /
• pp.437-452
• /
• 2008

IEEE 802.16j MR networks introduce RSs (Relay Stations) within the IEEE 802.16 system in order to enhance the data throughput and extend the coverage. However, the current standardization defines that the BS (Base Station) controls MS's (Mobile Station's) handover, not only it induces the large signaling overhead but also handover latency could increase. In this paper, we propose a handover protocol in the MR networks where the high capability RSs that can process the MS's control functions are deployed. First, we classify the handover scenarios for the MR networks with the high capability RSs. Then, we define the MAC handover procedure, corresponding MAC management messages and the transmission routes for the proposed messages so that an 802.16e MS can perform seamless handover without noticing it is attached to an MR network. The simulation results show that the proposed handover protocol not only reduces the MAC management message overhead transferred through the wireless links compared to IEEE 802.16j/D1, which is the current standard for MR networks, but also performs the rapider and more secure MS handover than IEEE 802.16e and IEEE 802.16j/D1.

• Journal of the Korea Concrete Institute
• /
• v.20 no.1
• /
• pp.59-66
• /
• 2008

This study is about manufacturing and producing girder, which is an essential component of bridge structure, in a composite of FRP + concrete. This has a higher competitive power in price than steel girder. The girder used in this study is made of glass fiber which has a lower elastic modulus than steel and thus has some technical limitations such as excessive deflection compared to steel girder and lack of production facilities in FRP production companies to make a large-section component material. Thus, this study suggested a section of a new module that will allow for applying a large section in order to solve the technical difficulties mentioned above and to secure low stiffness of FRP, developed a new FRP+concrete composite girder that is filled with the appropriate amount of concrete. To identify the structural behavior of this FRP+concrete composite girder, experiments were conducted to measure its flexural strength according to the difference in the strength of confined concrete and the existence of stud. The results of the flexural strength test confirmed the composite effect from confining concrete and the effect of increase in strength proportional to the strength of concrete. In developing FRP+concrete composite girder, NDT study was also conducted to analyze the interface characteristics of concrete and FRP.