• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.2
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• pp.92-103
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• 1989

This study was performed in order to produce the basic data for devising irrigation project and desalinization countermeasure through analyzing salt movement and desalinzation effects. The Desalinization experiments with water management practices were carried out, using the soil samples collected in New Manguem tideland. The changes of electrical conductivity, exchangeable sodium percentage, pH and hydraulic conductivity during the desalinization experiments, and the correlations between various factors influencing desalinization, were analyzed by the statistical method. The results obtained from this study were summarized as follows: 1. The sample soils used in this study were salin-sotlic soils with the high electrical conductivity and the high exchangeable sodium percentage, and the soil texture was silt loam. 2. A large amount of the soluble salts was removed in the begining of desalinization experiments. The initial electrical conductivity and the initial exchangeable sodium percentage decreased considerably in the beginning, and were gradually slow in the rate of decrease 3. The value of pH showed a tendency to increase during the desalinization and were little by little slow in the rate of increase, and could be estimated by the regression equation. 4. The initial hydraulic conductivity were raised greatly with gypsum treatment and the penmeability was maintained adequately, The hydraulic conductivity and the leaching time elapsed during the desalinization could be estimated by the regression equation. 5. The water requirement for desalinization with various water management practices could be estimated for a given electrical conductivity, exchangeable sodium percentage, and pH reading respectively.

• Journal of The Korean Association For Science Education
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• v.12 no.2
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• pp.55-65
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• 1992

The purpose of the study is to compare the learning contents of theme acids and bases that are commonly dealed with in elementary, middle and high schools m Korea and to investigate the acid-base-concepts of secondary students. The results of the study were as follows: 1) Many students did not have an interest in the chemistry and they pointed out the necessity of many experiments and practices and its application to the practical life. 2) It is found that most of textbooks used in the elementary school are written to make the students have an interest in the science through the experiments and pratices. However the textbooks used in the secondary school are too theoretically written so that many students are likely to lose the interests in the chemistry. 3) Although students had already learned Arrhenius's acid-base-concept, many students tried to solve the question with Liebig's theory as a acid-base-concept. This misconception might be caused by learning by cramming and teaching too theoretically. Accordingly, it is necessary that the education of science is carried out to make the students have an interest in the science by providing the students with the much more experiments and practices and also applying it to the practical life.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.5
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• pp.136-146
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• 2002

Land application of manure compost is considered one of the widely-used animal waste management practices. Many livestock farms adopt composting for their animal waste disposal and apply the compost to crop fields. While standard rates have been established based on researches with respect to land application of manure compost recently, there have been few discussions on water quality impact of the application. Water quality impact should be taken into account in land applications of manure compost. In this study, management practices were proposed based on the investigation of water quality of leachate from manure compost under rainfall simulation, field studies, and monitoring runoff water quality from farm fields after land application of animal waste. The concentrations of major water quality parameters of the leachate were significantly high, whereas those of runoff from soils after tillage for soil incorporation, were not affected by the application based on a series of experiments. Runoff water from farm fields after land application also showed high concentrations of pollutants. Appropriate management practices should be employed to minimize pollutant loading from manure applied fields. Proposed major management practices include 1) application of recommended amounts, 2) proper tillage for complete soil and manure incorporation, 3) field management to prevent excessive soil erosion, 4) complete diversion of inflow into the field from outside, 5) implementation of vegetative buffer strips near boundaries, and 6) prevention of direct discharge of runoff water front fields Into streams.

• Journal of The Korean Association For Science Education
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• v.25 no.2
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• pp.146-161
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• 2005

This case study searched two secondary school science teachers' faiths on experiments in science classes. For this study, scaled questionnaires, open-ended questionnaires, structured and semi-structured interviews were conducted. Classroom activities were observed, and instructional plans and materials were collected. In addition, students of the two teachers' classes were interviewed with respect to their thoughts on the lessons. Data sources were analyzed inductively. The triangulation and the member checking guaranteed the validity of this study. As the results, the teachers' faiths on experiments were related to the constructivism, but the faiths were not in accord with their classroom practices. From these results, it was concluded that the teachers' misjudgments about the students' inquiry levels and unfit reorganizations of the experimental activities were the causes of the gap between the teachers' faiths on experiments and classroom practices.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.5
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• pp.468-476
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• 2005

The purpose of this study is to investigate actual air quality in newly-constructed multi-family houses and to improve Indoor Air Quality (IAQ). The field measurement was conducted in four different newly-constructed multi-family house complexes in Seoul and one existing multi-family house complex in Kyong-gi province. The result of the measurement shows that indoor concentrations of Formaldehyde and TVOC in newly-constructed multi-family houses are much higher than the foreign standards. To establish a proper process for reducing indoor air pollutants, various experiments have been conducted; application of natural materials, bake-out practice, closure of all openings without ventilation, and use of mechanical ventilation system. The result indicates that three practices (natural materials, bakeout, mechanical ventilation) can reduce the level of indoor air pollutants almost in half during the experiments. However, each practice has its limitation and is insufficient to satisfy IAQ standards. Therefore, the study proposes a proper reduction process of indoor air pollutants which combines four different practices in time sequence.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.4
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• pp.80-96
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• 1992

This study was carried out in order to determin optimum irrigation requirements and water management practices for normal growth of dry field crops in reclaimed tidelands, and apply m planning of the irrigation projects. Desalinization experiments were performed by water management practices in the experimental field with high salt concentration, and growth experiments were conducted by irrigation point treatments using tomato and beet with relatively high salt tolerance. The results obtained from this study were summarized as follows : 1. Leaching or rinsing-leaching method was found to be effective in desalinizing the reclaimed tideland with rather high permeability. In this case, the water requirement for desalinizing the root zone layer of 40cm in depth, was estimated to be 1,200mm in depth. 2.The gypsum treatment in the desalinization of reclaimed tidelands, was ineffective in water requirements ; however, it could produce the desired effect in the facility of desalinization and the shortening of desalinization period with the sustaining permeability, in case of the desalinization by leaching method. 3.The optimum irrigation point which maintains the salt concentration within salt tolerance and maximizes the crop yield in reclaimed tidelands of silt loam soil, was found to be pF 1.6 in tomato and pF 1.8 in beet. The interval of irrigation date within 2 days was proved to he effective in both cases. 4.The optimum irrigation requirement and the water reguirement for the prevention of salt rise during the growing period after transplanting, were estimated to be 602mm(6.7mm/day) and 232mm for tomato, respectively. 5.The optimum irrigation requirement and the water requirement for the prevention of salt rise during the growing period after transplanting, were estimated to be 261mm(3.7mm/day) and 66mm for beet, respectively.

• Journal of Digital Contents Society
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• v.14 no.2
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• pp.161-169
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• 2013

Experiments and practices are critical instructional activities for teaching and learning natural sciences. However, by learning the experimental procedures in advance with the help of Virtual Experiments, natural science majors may address danger of handling chemicals before carrying out experiments in the laboratories. Virtual Experiments, a mobile learning app, provides learners with interactions between the learners and the contents by using the sensor built-in Android-platform smart phones. With the app, learners may handle the chemicals and experiment apparatuses, verify the reactions and assembly of the chemicals and instruments in advance. This paper describes the design and development of the Virtual Experiments in hope to promote the integration of mobile learning apps in order to better engage learners in the laboratories.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.1
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• pp.16-19
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• 2012

Increasing rice grain yield is critical for feeding rapid increasing of Asian population. However, global warming effect may be negative for sustainable rice production. Therefore it is essential to develop technologies not only for increasing grain yield but also for reducing global warming effect. Biochar, which is carbonized biomass, has a great potential of carbon sequestration and soil quality improvement, which can contribute grain yield increasing. In this study, rice yield responses to biochar application on the rice cropping system were evaluated with field experiments under different water management practices at the research farm of the University of Missouri-Columbia Delta Research Center, Portageville, MO. Biochar (i.e., $4Mg\;ha^{-1}$) was produced using field scale pyrolyzer and incorporated into the field 4 months prior to planting. Rice was grown under three different water management practices. Result showed that no significant yield difference was found in the biochar application plots compared to rice hull and control plots from the 2 years field study at the very fertile soil. However, rainfed management results in severe reduction of yield. Research concludes that the biochar application does not significantly influence on rice yield increasing especially for very fertile soils.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.1
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• pp.66-74
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• 2001

Pollutant loading potential was evaluated for manure application practices on farm fields, through survey and pot experiments. The survey indicated that most farmers applied the manure during the early spring. About 74% farmers apply the manure during the period from December to May. Considering the monthly rainfall amount in this period, the pollutant loading potential is not high. Leachate obtained from pot piled up with manure compost, using a rainfall simulator, showed that average concentrations of COD, SS, TKN, N $O_{3-}$N, TP were up to 2,000mg/L, 240mg/L, 107mg/L, 10mg/L, 50mg/L, respectively. These concentrations could be affected by rainfall intensity and the amount of piled manure compost. Therefore, implementation of management practices are recommended to control or minimize of leachate from manure compost piled on farm field.

• Journal of The Korean Association For Science Education
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• v.43 no.4
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• pp.403-414
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• 2023

In this study, we examined the adaptive practices of science teachers in their classrooms and their perspectives on the distinguishing features of these practices within science subjects. Our analysis comprised 339 cases from 128 middle and high school science teachers nationwide, and 199 cases on the characteristics of adaptive practices in science disciplines. The primary findings were as follows: First, the most significant characteristic of adaptive practice in science disciplines pertained to experimental procedures. Within the 'suggestion of additional materials/activities' category, the most frequently cited adaptive practice, teachers incorporated demonstrations to either facilitate student comprehension or enhance motivation. Additionally, 'experimental equipment manipulation or presentation of inquiry skills' emerged as the second most common adaptive practice related to experiments. Notably, over 50% of teacher responses regarding the characteristics of adaptive practices in science pertained to experiment guidance. Second, many adaptive practices involving difficulties experienced by students in learning situations were presented, particularly in areas such as numeracy and literacy. Many cases were related to the basic ability of mathematics used as a tool in science learning and understanding scientific terms in Chinese characters. Third, beyond 'experiment guidance', the characteristic adaptive practices of science subjects were related to 'connections between scientific theory and the real world', 'misconception guidance in science', 'cultivation of scientific thinking', and 'convergence approaches'. Fourth, the cases of adaptive practice presented by the science teachers differed by school level and major; therefore, it is necessary to consider school level or major in future research related to adaptive practice. Fifth, most of the adaptive action items with a small number of cases were adaptive actions executed from a macroscopic perspective, so it is necessary to pay attention to related professionalism. Finally, based on the results of this study, the implications for science education were discussed.