• Title/Summary/Keyword: Small-scale simulation

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Prediction of Seabed Topography Change Due to Construction of Offshore Wind Power Structures in the West-Southern Sea of Korea (서남해에서 해상풍력구조물의 건설에 의한 해저지형의 변화예측)

  • Jeong, Seung Myung;Kwon, Kyung Hwan;Lee, Jong Sup;Park, Il Heum
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.31 no.6
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    • pp.423-433
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    • 2019
  • In order to predict the seabed topography change due to the construction of offshore wind power structures in the west-southern sea of Korea, field observations for tides, tidal currents, suspended sediment concentrations and seabed sediments were carried out at the same time. These data could be used for numerical simulation. In numerical experiments, the empirical constants for the suspended sediment flux were determined by the trial and error method. When a concentration distribution factor was 0.1 and a proportional constant was 0.05 in the suspended sediment equilibrium concentration formulae, the calculated suspended sediment concentrations were reasonably similar with the observed ones. Also, it was appropriate for the open boundary conditions of the suspended sediment when the south-east boundary corner was 11.0 times, the south-west was 0.5 times, the westnorth 1.0 times, the north-west was 1.0 times and the north-east was 1.0 times, respectively, using the time series of the observed suspended sediment concentrations. In this case, the depth change was smooth and not intermittent around the open boundaries. From these calibrations, the annual water depth change before and after construction of the offshore wind power structures was shown under 1 cm. The reason was that the used numerical model for the large scale grid could not reproduce a local scour phenomenon and they showed almost no significant velocity change over ± 2 cm/s because the jacket structures with small size diameter, about 1 m, were a water-permeable. Therefore, it was natural that there was a slight change on seabed topography in the study area.

A Study on Teaching-Learning and Evaluation Methods of Environmental Studies in the Middle School (중학교 "환경" 교과의 교수.학습 및 평가 방법 연구)

  • 남상준
    • Hwankyungkyoyuk
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    • v.7 no.1
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    • pp.1-17
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    • 1994
  • This study was performed to determine appropriate teaching-learning and evaluation methods for Environmental Studies. To promote the relevance of our study to the needs of the schools and concerned educational communities of environmental education, we reviewed related literature, conducted questionnaire surveys, interviewed related teachers and administrator, held meetings with experts, and field-tested our findings. For selecting and developing teaching-learning methods of Environmental Studies, findings of educational research in general are considered. moreover, principles of environmental education, general aim of environmental education, orientations of environmental education, and developmental stages of middle school students in educational psychology were attended. In addition, relevance to the purpose of the Environmental Studies curriculum, appropriateness for value inquiry as well as knowledge inquiry, small group centered class organization, social interaction centered teaching-learning process, regional environmental situation, significance of personal environment, evaluation methods of Environmental Studies, multi- and inter-disciplinary contents of the Environmental Studies textbook, suitability to the evaluation methods of Environmental Studies, and emphasis on the social interaction in teaching-learning process were regarded. It was learned the Environmental Studies can be taught most effectively in via of holding discussion sessions, conducting actual investigation, doing experiment-practice, doing games and plate, role-playing and carrying out simulation activities, and doing inquiry. These teaching-learning methods were field-tested and proved appropriate methods for the subject. For selecting and developing evaluation method of Environmental Studies, such principles and characteristics of Environmental Studies as objective domains stated in the Environmental Studies curriculum, diversity of teaching-learning organization, were appreciated. We categorized nine evaluation methods: the teacher may conduct questionnaire surveys, testings, interviews, non-participatory observations; they may evaluate student's experiment-practice performances, reports preparation ability, ability to establish a research project, the teacher may ask the students to conduct a self-evaluation, or reciprocal evaluation. To maximize the effect of these methods, we further developed an application system. It considered three variables, that is, evaluates, evaluation objectives domains, and evaluation agent, and showed how to choose the most appropriate methods and, when necessary, how to combine uses of different methods depending on these variables. A sample evaluation instrument made on the basis of this application system was developed and tested in the classes. The system proved effective. Pilot applications of the teaching-learning methods and evaluation method were made simultaneously; and the results and their implications are as follows. Discussion program was applied in a lesson dealing with the problems of waste disposal, in which students showed active participation and creative thinking. The evaluation method used in this lesson was a multiple-choice written test for knowledge and skills. It was shown that this evaluation method and device are effective in helping students' revision of the lesson and in stimulating their creative interpretations and responces. Pupils showed great interests in the actual investigation program, and this programme was proved to be effective in enhancing students' participation. However, it was also turned out that there must be pre-arranged plans for the objects, contents and procedures of survey if this program is to effective. In this lesson, non-participatory observation methods were used with a focus on the attitudes of students. A scaled reported in general description rather than in grade. Experiment-practice programme was adopted in a lesson for purifying contaminated water and in this lesson, instruction objectives were properly established, the teaching-learning process was clearly specified and students were highly motivated. On the other hand, however, it was difficult to control the class when some groups of students require more times to complete their experiment, and sometimes different results. As regards to evaluation, performance observation test were used for assessing skills and attitudes. If teachers use well-prepared Likert scale, evaluation of all groups within a reasonablely short period of time will be possible. The most effective and successful programme in therms of students' participation and enjoyment, was the 'ah-nah-bah-dah-market' program, which is kind of game of the flea market. For better organized program of this kind, however, are essential, In this program, students appraise their own attitudes and behavior by responding to a written questionnaire. In addition, students were asked to record any anecdotes relating to self-appraisal of changes on one's own attitudes and behaviours. Even after the lesson, students keep recording those changes on letters to herself. Role-playing and simulation game programme was applied to a case of 'NIMBY', in which students should decide where to located a refuse dumping ground. For this kind of programme to e successful, concepts and words used in the script should be appropriate for students' intellectual levels, and students should by adequately introduced into the objective and the procedures of the lessons. Written questionnaire was used to assess individual students' attitudes after the lesson, but in order to acquire information on the changes of students' attitudes and skills, pre-test may have to be made. Doing inquiry programme, in which advantages in which students actually investigated the environmental influence of the areas where school os located, had advantages in developing students' ability to study the environmental problems and to present the results of their studies. For this programme to be more efficient, areas of investigation should be clearly divided and alloted to each group so that repetition or overlap in areas of study and presentation be avoided, and complementary wok between groups bee enhanced. In this programme, teacher assessed students' knowledge and attitudes on the basis of reports prepared by each group. However, there were found some difficults in assessing students' attitudes and behaviours solely on the grounds of written report. Perhaps, using a scaled checklist assessing students' attitudes while their presentation could help to relieve the difficulties.

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Recent Progress in Air Conditioning and Refrigeration Research - A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2002 and 2003 - (공기조화, 냉동 분야의 최근 연구 동향 -2002년 및 2003년 학회지 논문에 대한 종합적 고찰 -)

  • Chung Kwang-Seop;Kim Min Soo;Kim Yongchan;Park Kyoung Kuhn;Park Byung-Yoon;Cho Keumnam
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.12
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    • pp.1234-1268
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    • 2004
  • A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2002 and 2003 has been carried out. Focus has been put on current status of research in the aspect of heating, cooling, air-conditioning, ventilation, sanitation and building environment/design. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation in diverse facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat transfer, humidity was also interesting to promote comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing research topics. Well developed CFD technologies were widely applied for analysis and design of various facilities and their systems. (2) Heat transfer characteristics of enhanced finned tube heat exchangers and heat sinks were extensively investigated. Experimental studies on the boiling heat transfer, vortex generators, fluidized bed heat exchangers, and frosting and defrosting characteristics were also conducted. In addition, the numerical simulations on various heat exchangers were performed and reported to show heat transfer characteristics and performance of the heat exchanger. (3) A review of the recent studies shows that the performance analysis of heat pump have been made by various simulations and experiments. Progresses have been made specifically on the multi-type heat pump systems and other heat pump systems in which exhaust energy is utilized. The performance characteristics of heat pipe have been studied numerically and experimentally, which proves the validity of the developed simulation programs. The effect of various factors on the heat pipe performance has also been examined. Studies of the ice storage system have been focused on the operational characteristics of the system and on the basics of thermal storage materials. Researches into the phase change have been carried out steadily. Several papers deal with the cycle analysis of a few thermodynamic systems which are very useful in the field of air-conditioning and refrigeration. (4) Recent studies on refrigeration and air-conditioning systems have focused on the system performance and efficiency enhancement when new alternative refrigerants are applied. Heat transfer characteristics during evaporation and condensation are investigated for several tube shapes and new alternative refrigerants including natural refrigerants. Efficiency of various compressors and performance of new expansion devices are also dealt with for better design of refrigeration/air conditioning system. In addition to the studies related with thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out. It should be noted that the researches on two-phase flow are constantly carried out. (5) A review of the recent studies on absorption refrigeration system indicates that heat and mass transfer enhancement is the key factor in improving the system performance. Various experiments have been carried out and diverse simulation models have been presented. Study on the small scale absorption refrigeration system draws a new attention. Cooling tower was also the research object in the respect of enhancement its efficiency, and performance analysis and optimization was carried out. (6) Based on a review of recent studies on indoor thermal environment and building service systems, it is noticed that research issues have mainly focused on several innovative systems such as personal environmental modules, air-barrier type perimeterless system with UFAC, radiant floor cooling system, etc. New approaches are highlighted for improving indoor environmental conditions and minimizing energy consumption, various activities of building energy management and cost-benefit analysis for economic evaluation.

Development of an Adaptive Capacity Indicator to Climate Change in the Agricultural Water Sector (농업용수의 기후변화 적응능력 지표 개발 - 가뭄에 대한 적응을 중심으로 -)

  • Yoo, Ga-Young;Kim, Jin-Teak;Kim, Jung-Eun
    • Journal of Environmental Policy
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    • v.7 no.4
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    • pp.35-55
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    • 2008
  • Assessing vulnerability to climate change is the first step to take when setting up appropriate adaptation strategies. Adaptive capacity to climate change is the important factor comprising vulnerability. An adaptive capacity index in agricultural water management system was developed considering agricultural water supply and demand for rice production in Jeolla-do, Korea. The agricultural water supply was assumed to be equal to the amount of water stored in the major agricultural reservoirs, while data on the agricultural water demand was obtained from the dynamic simulation results by Korea Agriculture Corporation(KAC). The spatial unit for analysis was conducted at the county(Si, Gun, Gu) level and temporal scale was based on every month from 1991-2003. Adaptive capacity for drought stress index(ACDS index) was calculated as the percentage of data points where the irrigated water supply was greater than the crop water demand. The ACDS index was compared with SWSCI(Standard Water Storage Capacity Index) and the relationship showed high degree of fit($R^2$=0.84) using the exponential function, indicating that the developed ACDS index is useful for evaluating the status of the balance between agricultural water supply and demand, especially for the small sized agricultural reservoirs. This study provided the methodological basis for developing climate change vulnerability index in agricultural water system which is projected to be more frequently exposed to drought condition in the future due to climate change. Further research should be extended to the study on the water demand of the crops other than rice and to the projection of the change in ACDS index in the future.

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Analysis of the effect of long-term water supply improvement by the installation of sand dams in water scarce areas (물부족 지역에서 샌드댐 설치에 의한 장기 물공급 개선 효과 분석)

  • Chung, Il-Moon;Lee, Jeongwoo;Lee, Jeong Eun;Kim, Il-Hwan
    • Journal of Korea Water Resources Association
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    • v.55 no.12
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    • pp.999-1009
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    • 2022
  • The Chuncheon Mullori area is an underprivileged area for water welfare that does not have a local water supply system. Here, water is supplied to the village by using a small-scale water supply facility that uses underground water and underground water as the source. To solve the problem of water shortage during drought and to prepare for the increasing water demand, a sand dam was installed near the valley river, and this facility has been operating since May 2022. In this study, in order to evaluate the reliability of water supply when a sand dam is assumed during a drought in the past, groundwater runoff simulation results using MODFLOW were used to generate inflow data from 2011 to 2020, an unmeasured period. After performing SWAT-K basin hydrologic modeling for the watershed upstream of the existing water intake source and the sand dam, the groundwater runoff was calculated, and the relative ratio of the monthly groundwater runoff for the previous 10 years to the monthly groundwater runoff in 2021 was obtained. By applying this ratio to the 2021 inflow time series data, historical inflow data from 2011 to 2020 were generated. As a result of analyzing the availability of water supply during extreme drought in the past for three cases of demand 20 m3/day, 50 m3/day, and 100 m3/day, it can be confirmed that the reliability of water supply increases with the installation of sand dams. In the case of 100 m3/day, it was analyzed that the reliability exceeded 90% only when the existing water intake source and the sand dam were operated in conjunction. All three operating conditions were evaluated to satisfy 50 m3/day or more of demand based on 95% reliability of water supply and 30 m3/day or more of demand based on 99% of reliability.