• Journal of the Korea Institute of Building Construction
• /
• v.21 no.3
• /
• pp.213-219
• /
• 2021

Change orders that occur frequently during the construction phase, af ect the construction performance in terms of cost, time, quality, safety and environment, and place a huge burden for stakeholders of given projects. This study analyzed the causes of change orders and their impact on the basis of 721 cases and a questionnaire of 164 domestic U.S. military construction participants in a total of 24 U.S. military projects. Important factors for change orders in the US military construction projects were engineering change due to design errors (348 cases, 48.3%), user requests change(86 cases, 11.9%), and different site conditions (69 cases, 9.6%). In addition, due to the change orders, construction cost increased by 6.56% on average and construction period was extended by 21.1% compared to the original schedule. As a result, it is anticipated that domestic construction companies can obtain a better understanding of change orders and construction performance, which may be difficult due to accessibility and limitations to military facilities. Also, it is proposed a successor study that guides in the right direction for the U.S. Military Construction.

• Journal of Korean Home Economics Education Association
• /
• v.33 no.1
• /
• pp.37-62
• /
• 2021

The purpose of this study is to develop a project-based teaching-learning instruction to solve the problems in family life. The developed process can be a practical plan to activate environmental education centered on living environment problems curriculum of Home Economic Education[HEE]. In order to achieve the purpose of this study, the curriculum of HEE and environmental education categories were compared and analyzed. The study selected 10 themes and developed a project-based HEE teaching-learning instruction with 8 sessions. The characteristics of the developed teaching-learning instruction are as follows. First, HEE curriculum included environmental knowledge, values and attitudes, competence, and practice and participation in environmental education and related categories in achievement standards and learning elements. Second, since HEE curriculum has a teaching-learning instruction plan based on project-based learning that allows learners to recognize and solve problems themselves was developed based on the real life-centered learning themes related to environmental education. It was also proposed that the subject of HEE has a high correlation with environmental competence and environmental practice, and thus environmental contents that can raise students' interests in society and environment should be added to the HEE curriculum. The teaching-learning instruction developed in this study can be used for classes such as HEE classes or free semeste. A follow up study would need to test the educational effects of this teaching and learning plan by implementing it to the actual class.

• Membrane Journal
• /
• v.31 no.2
• /
• pp.87-100
• /
• 2021

With a striking increase in the level of contamination and subsequent degradations in the environment, detection and monitoring of contaminants in various sites has become a crucial mission in current society. In this review, we have summarized the current research areas in membrane-based colorimetric sensors for trace detection of various molecules. The researches covered in this summary utilize membranes composed of cellulose fibers as sensing platforms and metal nanoparticles or fluorophores as optical reagents. Displaying decent or excellent sensitivity, most of the developed sensors achieve a significant selectivity in the presence of interfering ions. The physical and chemical properties of cellulose membrane platforms can be customized by changing the synthesis method or type of optical reagent used, allowing a wide range of applications possible. Membrane-based sensors are also portable and have great mechanical properties, which enable on-site detection of contaminants. With such superior qualities, membrane-based sensors examined in the researches were used for versatile purposes including quantification of heavy metals in drinking water, trace detection of toxic antibiotics and heavy metals in environmental water samples. Some of the sensors exhibited additional features like antimicrobial ability and recyclability. Lastly, while most of the sensors aimed for a detection enabled by naked eyes through rapid colour change, many of them investigated further detection methods like fluorescence, UV-vis spectroscopy, and RGB colour intensity.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.4
• /
• pp.569-577
• /
• 2021

CFRP(Carbon Fiber Reinforced Plastic) can maintain the same strength even if the diameter is reduced by about one - third, and the weight is about one - twentieth of that of the deformed reinforcing bars that have been used in the construction industry. In particular, it is resistant to corrosion, which is the weakest part of reinf orcing bars, and there is no concern that it will deteriorate over time, It is light and durable, so transportation costs are low and it is convenient for high-rise buildings. This paper experimentally clarifies the adhesive properties of CFRP and clarifies its behavior. That is, bond strength test was conducted with the directness of CFRP and the strength of concrete as experimental variables, and the bond mechanism was clarified experimentally. Furthermore, based on the experimental results, we constructed the bond stress-slip-strain relationship of CFRP compared to the existing deformed reinforcing bars.

• Journal of Marine Life Science
• /
• v.5 no.2
• /
• pp.99-106
• /
• 2020

To investigate effect of variation in physiochemical conditions due to river discharge on phytoplankton, field surveys were conducted in the Seomjin and Yeongsan River estuaries from April to November 2016. The concentrations of DIN and DSi in Seomjin River estuary were gradually low as distance from upstream. On the other hands, the concentrations of DIN and DSi in Yeongsan River estuary were critically high at upstream, due to which is characterized as semi-enclosed eutrophic area. A total of 12 phytoplankton pigments were analyzed, and the distribution of each taxa was investigated using indicator for each phytoplankton taxa. Fucoxanthin, an indicator pigment of diatoms, showed an average of 0.61±1.00 ㎍ l^-1 and 0.76±1.22 ㎍ l^-1 in the Seomjin and Yeongsan River estuaries, respectively. Concentration of fucoxanthin was more than twice that of other pigments except chlorophyll a., indicating that diatoms were dominant taxa. Peridinin, an indicator pigment of dinoflagellate, showed some similar tendency to the microscopic observation, but mismatch results were also present, indicating a technical limitation of pigment analysis. Chlorophyll b, alloxanthin, and zeaxanthin, which are indicator pigments of green algae, cryptomonads, and cyanobacteria, were detected in both estuaries even though those taxa were not detected in microscopic observation. This indicates that the two estuaries were affected by freshwater species. Here, we can suggest that phytoplankton composition in estuary was directly influenced by the inflow from upstream. In particular, the phytoplankton population dynamics in Yeongsan River estuary was greatly associated with a large-scale artificial dyke, especially in summer rainy season. On the other hands, the seasonal and horizontal distribution of phytoplankton in Seomjin River estuary has changed along the salinity gradients and inflow-related changes.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.4
• /
• pp.587-593
• /
• 2021

Since 2017, a total of 29 fire accidents have occurred in energy storage systems (ESSs) as of June 2020. The common mode voltage (CMV) is one of the electrical hazards that is assumed to be a cause of those fire accidents. Several cases of CMV that violate the allowable insulation level of a battery section are being reported in actual ESS operation sites with △-Y winding connections. Thus, this paper evaluates the characteristics of CMV. An ESS site was modeled with an AC grid, PCS, and battery sections using PSCAD/EMTDC software. As a result of a simulation based on the proposed model, it was confirmed that characteristics of CMV vary significantly and are similar to actual measurements, depending on the grounding method of the internal transformer for PCS. The insulation level of the battery section may be severely degraded as the value of CMV exceeds the rated voltage in case of a grounding connection. It was found that the value of CMV dramatically declines when the internal transformer for PCS is operated as non-grounding connection, so it meets the standard insulation level.

• Journal of vocational education research
• /
• v.36 no.4
• /
• pp.1-20
• /
• 2017

The purpose of this study is to identify the cognitive and psychological precedence factors of career preparation behaviors of university students and to clarify the structural relationships between the variables. First, the effects of reflective learning on university students' career preparation behaviors were examined and the mediating effect of grit between reflective learning and career preparation behavior was verified. The research analyzed 307 university students in the 3rd and 4th year. The results of the study have shown that the reflective learning had a significant positive relationship with all variables of grit and career preparation behavior, but non-reflective learning have an insignificance relationship with all the main variables. In addition, reflective learning has a direct positive effect on career preparation behavior, and grit has a mediating effect on the relationship between reflective learning and career preparation behavior. The results of this study indicate that the more original variables are further identified and extended to improve career preparation behaviors of university students. It is significant that they are provided with the basic data for the development of career and job preparation education programs that can be applied in the university education field. In addition, it has been confirmed that it is important for university students to improve their ability to critically reflect on themselves, their surroundings and circumstances in order to keep them engaged and to maintain their interests. Moreover, higher education institutions should provide fundamental and extensible method of practice and educational environment.

• Korean Journal of Comparative Education
• /
• v.28 no.6
• /
• pp.131-152
• /
• 2018

In terms of the fact that Innovation School is the main agent which encourages the innovation of school culture, As it has been ten years since the Innovation School was enforced, we do need a practical, indepth study on the quality of policy management. To make this actualize, this study is for analysis and comparison of basic values and operating evaluation plans which have been managed by Metropolitan City Office of Education(MCOE) & Provincial Office of Education(POE). Each of MCOE & POE have their own vision. Those visions are such things; 'Education for All' for Gangwon, Busan, Chungbuk. 'Future School Orientation' for Gyeonggi, Gyeongnam. 'Educational Community Realization' for Gwangju, Seoul, Ulsan, Jeonbuk, Jeju. 'Normalization of Public Education' for Sejong, Incheon, Chungnam. Like such things, each office possesses different vision by their distinct characteristics and in principle, all emphasis on publicness, democracy, and creativity. Management evaluations of the Innovation School is operated by Self-assessment, Intermediate evaluation, and Extensive assessment. The process and evaluation index of Intermediate evaluation and Extensive assessment are similar. Especially, Those assessment have significance in a role of administrating its management of each school and a role of offering associated documents of educational policy with educational renovations with feedback and some good examples.

• Fire Science and Engineering
• /
• v.33 no.2
• /
• pp.124-131
• /
• 2019

When a fire occurs in a road tunnel, it is likely to develop into a major disaster because of its sealed structural characteristics. Because of this, a range of disaster prevention facilities should be installed, and they should show their appropriate functions in fire prevention and response. In addition, the installation of essential disaster prevention facilities is missing due to the lack of considering an extension of continuous tunnels and soundproof tunnels. For these reasons, it was judged that an amendment to the law would be necessary. Therefore, this paper reviewed the changes in domestic laws related to the disaster prevention facilities of road tunnels, and the results of the study on the parts that need to be revised in the fire-related laws through a comparative analysis between laws are as follows. First, consecutive tunnels should consider the sum of the extensions of the individual tunnels and ensure that the soundproof tunnels are included in the category of tunnels in the law. In this way, the necessary disaster prevention facilities should be installed. Second, it is necessary to secure a legal justification for installing disaster prevention facilities in tunnels. Therefore, it is essential that water mist fire extinguishing system facilities, emergency broadcasting facilities, and leading lights, which are excluded from installation in tunnels, are specified in the Fire-related laws. Third, to specify in the law that air respirators must be provided in the tunnel is necessary from the viewpoint of the field response. Accordingly, it will make a great contribution to the fire-fighting activities and the life-saving efforts by fire-fighters.

• Journal of the Korean Geotechnical Society
• /
• v.34 no.12
• /
• pp.29-42
• /
• 2018

Shale and mudstone in Daegu-Gyungbuk area have low strength and resistance to weathering compared to other rocks. Therefore, it is necessary to evaluate their strength depending on the degree of saturation and crack development. In this study, shales and mudstones were collected from several construction sites in Daegu-Gyungbuk area. Their basic material properties such as porosity, SEM, chemical component, and durability were tested. A porosity (absorptivity) of mudstone was 31% (25%), which was 6 (8) times higher than that of shale. Some mudstone was easily disintegrated with water and it consisted of highly-active clay mineral such as smectite type. These rocks were prepared by small cube specimens for unconfined compression test. An unconfined compressive strength of dry rock was compared with saturated one. Microwave oven was operated step by step to stimulate void water within a saturated rock, which resulted into high temperature and micro crack initiation within rocks. A strength of microwaved rocks was compared with operation time and crack initiation. As a result, the average unconfined compressive strength of dry and saturated shale was 62 and 33 MPa, respectively. The strength of mudstone for each condition was 11 and 4 MPa. When a rock became saturated, its strength decreased by 47% and 64% for shale and mudstone at average. In addition to saturation, a rock was in the microwave for 15 secs, its strength decreased into 49% for shale and 52% for mudstone. When a microwave oven operated up to 20 sec, a rock was crushed into several pieces and its temperature was approximately 200 degrees.