• Korean Chemical Engineering Research
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• v.62 no.2
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• pp.147-152
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• 2024

Most medical sensors are disposable products. In order to reduce inspection and diagnosis costs, it is more important to develop the inexpensive electrode materials. We fabricated the CuO NPs/PANI/E-PGE as an electrode material for disposable electrochemical sensors and applied it to a non-enzymatic glucose sensor. For surface activation of PGE, pretreatment was performed using chemical and electrochemical methods, respectively. Electrochemical properties according to the pretreatment method were analyzed through chronoamperometry (CA), cyclic voltammetry (CV) and electrochemical impedance (EIS). From these analytical results, the electrochemically pretreated PGE (E-PGE) was finally adopted. The non-enzymatic glucose sensor based on CuO NPs/PANI/E-PGE shows sensitivity of 239.18 mA/mM×cm² (in a linear range of 0.282~2.112 mM) and 36.99 mA/mM×cm² (3.75423~50 mM), detection limit of 17.6 μM and good selectivity. Based on the results of this study, it was confirmed that the modified PGE is a high-performance electrode material. Therefore, these electrodes can be applied to a variety of disposable sensors.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.83-90
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• 2024

This study investigates the 3D printing characteristics of strain hardening cement composites (SHCC) reinforced by PVA fibers. Three SHCC mixtures with diverse fiber volume fractions (1.0% for F1.0 mixture, 1.5% for F1.5 mixture, and 1.8% for F1.8 mixture) were designed. Except for the F1.0 mixture, all mixtures met the necessary conditions for multiple micro-cracking, with higher fiber volume fractions more readily satisfying these conditions. The flow values of three SHCC mixtures were within the 3D printable range of 120~160 mm, exhibiting decreased flow values with increasing the fiber volume fractions. Observation of the printed SHCC surfaces indicated that the F1.0 mixture had a Level-3 (good) rating, while F1.5 and F1.8 were rated as Level-2 (average). Higher fiber volume fractions resulted in poorer surface quality, thus, further research needs to be performed for modulating SHCC mixture suitable for 3D printing. The uniaxial tension behavior showed that the F1.0 mixture failed at lower strain, whereas F1.5 and F1.8 exhibited higher strain performance with multiple micro-cracks occurring.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.91-99
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• 2024

Piping systems are crucial facilities used in various industries, particularly in areas related to daily life and safety. Piping systems are fixed to the main structures of buildings and facilities but do not support external loads and serve as non-structural elements performing specific functions. Piping systems are affected by relative displacements owing to phase differences arising from different behaviors between two support points under seismic loads; this can cause damage owing to the displacement-dominant cyclic behavior. Fittings and joints in piping systems are representative elements that are vulnerable to seismic loads. To evaluate the seismic performance and limit states of fittings and joints in piping systems, a high-stroke actuator is required to simulate relative displacements. However, this is challenging because only few facilities can conduct these experiments. Therefore, element-level experiments are required to evaluate the seismic performance and limit states of piping systems connected by fittings and joints. This study proposed a method to evaluate the seismic performance of an elbow specimen that includes fittings and joints that are vulnerable to seismic loads in vertical piping systems. The elbow specimen was created by connecting straight pipes to both ends of a 90° pipe elbow using flexible groove joints. The seismic performance of the elbow specimen was evaluated using a cyclic loading protocol based on deformation angles. To determine the margin of the evaluated seismic performance, the limit states were assessed by applying cyclic loading with a constant amplitude.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.11 no.4
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• pp.165-171
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• 2006

This is the research to prepare a purification program for relatively less polluted stream by using phytoremediation. We calculated a treatment amount of nutrients followed by growth of Helianthus annuus (a kind of sunflower), setting up the plant reactor in the hothouse. Moreover, to investigate a field applicability, we could find increased contents of nitrogen, carbon and hydrogen in plants by setting up a H. annuus planted artificial floating island in an irrigation canal. When we changed the dissolved inorganic nitrogen(DIN) concentration of the influent from 28.5 to 199.2 mg/l and the dissolved inorganic phosphorus(DIP) concentration of the influent from 13.3 to 25.4 mg/l, growth disorder has not appeared though it is much higher than the criterion of water for irrigation. In this case, the removal rate of DIN was $81.7\sim98.6%$, and that of DIP was $81.9\sim98.4%$ in 3 days stay on average. It has appeared that the efficient hydraulic retention time(HRT) was 48 hours. The following contents of nitrogen, carbon and hydrogen of H. annuus appeared in the artificial floating island: nitrogen was $3.2\sim7.8%$ in the trunk and $3.0\sim6.3%$ in the root. Carbon was $40.1\sim57.7%$ in the trunk and $43.4\sim53.8%$ in the root.

• Journal of The Korean Association For Science Education
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• v.26 no.6
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• pp.675-690
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• 2006

This study investigated students' views in relation to a career in science as a first step towards developing science career education programs and materials. The instrument was developed through preliminary surveys. The questionnaire was sent to, administered and returned by 3608 students including 1036 primary, 1137 middle, and 1435 high school students, who were selected through stratified cluster sampling from all over the country. The results were analyzed using statistical package program. The students' image view of science, preference for science and science learning, perception of science achievement, career hope for oneself, degree of hope in getting science-related job, perception about science-related career, important factors of science career choice, and their hope for science/non-science career and the reason for their choice in the past and present were investigated. The results show that "science as an experimentation activity" was the most frequent image view of science. The preference for science and science learning was more positive than the perception of science achievement. The percentage of total students who want to have science career was 21%, and this percentage of middle school students was especially low. The most frequent answers for advantages of science career were 'useful for national development', 'possible to get new knowledge', and those for disadvantages were 'dangerous', and 'too much to study'. The most frequent reason for students' choice of a science career was 'interest in science and science learning'. Judging from these results, the basic direction for science career education should be in raising the students' preference for and interest in science learning. The positive awareness for a career in science and vision for a science job in the future should be given through a science career education and science career education proper to the students' developmental stage and characteristics is more important.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.2
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• pp.90-101
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• 2009

Analysis of multi-channel seismic reflection data from the Southern Ulleung Basin reveals that Plio-Quaternary section in the area consists of nine stacked sedimentary units separated by erosional unconformities. On the southern slope, these sedimentary units are acoustically characterized by chaotic seismic facies without distinct internal reflections, interpreted as debris-flow bodies. Toward the basin floor, the sedimentary units are defined by well-stratified facies with good continuity and strong amplitude, interpreted as turbidite/hemipelagic sediments. The seismic facies distribution suggests that deposition of Plio-Quaternary section in the area was controlled mainly by tectonic movement and sea-level fluctuations. During the Pliocene, sedimentation was mainly controlled by tectonic movements related to the back-arc closure of the East Sea. The back-arc closure that began in the Miocene caused compressional deformation along the southern margin of the Ulleung Basin, resulting in regional uplift which continued until the Pliocene. Large amounts of sediments, eroded from the uplifted crustal blocks, were supplied to the basin, depositing Unit 1 which consists of debris-flow deposits. During the Quaternary, sea-level fluctuations resulted in stacked sedimentary units (2-9) consisting of debris-flow deposits, formed during sea-level fall and lowstands, and thin hemipelagic/turbidite sediments, deposited during sea-level rise and highstands.

• Journal of The Korean Association For Science Education
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• v.27 no.7
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• pp.645-662
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• 2007

The purpose of this study was to explore the manners in which models are used in secondary science classrooms. A total of thirteen video-recordings of science lessons dealing with the domains of atmospheric and oceanic earth sciences and their verbatim transcripts were analysed both quantitatively and qualitatively. Interviews with three inservice science teachers were also conducted. Six interrelated assertions were generated as the result of the study: 1) The most frequently used models in secondary earth science classrooms include two-dimensional pictorial, symbolic, iconic, and diagrammatic ones; 2) Science teachers employ models as a mode of representation to make the subject matter available to students; 3) In earth science classrooms, teachers use typical forms of models in intensive manners; 4) Students themselves deal with models on a few occasions, but they just follow similar procedures with the same models; 5) Teachers talk rarely about the nature of scientific models and provide few opportunities for students to think about it; and, 6) Teachers in practice think that the value of using models should be appraised in consideration of the pedagogical intentions of the teacher. Implications for science education and science education research were discussed.

• Journal of The Korean Association For Science Education
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• v.27 no.1
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• pp.37-49
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• 2007

The purpose of this study was to classify the logical forms of scientific explanations provided by teachers in secondary earth science classrooms, to examine the characteristics of the scientific explanations in different forms, and to identify the roles of the teacher and students in discursive practices for scientific explanations. Data came from the earth science teachers who participated in overseas teacher in-service programs in the years 2003 and 2004. A total of 18 video-taped lessons and their verbatim transcriptions were analyzed. The result showed that deductive-nomological explanations occurred most frequently in earth science classrooms and that the deductive-nomological model was well-suited to those problems for which there existed firmly established scientific laws or principles to construct scientific explanations. However, abductive explanations were presented when the classes dealt with retrodictive tasks of earth science. The statistical-probabilistic and statistical-relevance models were also employed in explaining weather proverbs and unusual changes of weather, respectively. Most of the scientific explanations were completed through the teachers' monologic utterances, and students assumed passive roles in discursive practices for developing scientific explanations. Implications for science lessons and science education research were discussed.

• Journal of The Korean Association For Science Education
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• v.28 no.6
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• pp.649-663
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• 2008

The purpose of this study was to compare the processes of making hypotheses concerning the anomalous path of Wukong, a typhoon that came close to Korea recently, between an earth scientist and undergraduate students. Data were obtained through interviews with a practicing earth scientist as well as five undergraduate students. Inquiry reports of the students were also analysed. The result showed that while the earth scientist conducted a case study with already-established models of typhoon, the students were enabled to work on the specific case of Wukong only after they learned general theories on typhoons. Background knowledge played an important role for the scientist and students to formulate scientific hypotheses. Both the earth scientist and undergraduate students generate multiple working hypotheses, and they considered a couple of conditions to select more plausible hypotheses, including theoretical coherence, causative processes, and consistency with empirical data. Despite these similarities, there were differences in the scope and depth of background knowledge between the scientist and students. In addition, it was not likely that the undergraduate students possessed explicit perceptions of the conditions which could make a hypothesis more probable, except for the empirical consistency. Implications for science education and relevant research were discussed.

• Journal of The Korean Association For Science Education
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• v.29 no.4
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• pp.359-372
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• 2009

The purpose of this study was to develop the FPHER (problem finding, prediction & discussion, hands-on & experiment, explanation & arrangement, enrichment) instructional model emphasizing the social interactions, and as applied, characteristics of verbal interactions were examined overall and with each step. For this study, this model was applied to the students in 10th grade chemistry classes in a science high school, and their group verbal interactions were recorded and analyzed. The results of this study show that most verbal interactions were classified as on-task interactions in the FPHER instructional model, where suggestions were predominant to the acceptance of opinions. There were a few interactions in the F step, and there were many suggestions relating to the solutions and lacking in confidence in the P step. There were many suggestions relating to the process and orders in the H step. Also, there were many questions, some explanation and dissatisfaction, as well as a lack of confidence in the E step. There were many high-level interactions in the R step, and mainly interactions with worksheets showing high-level problem-solving abilities. More in-depth research is needed to develop the teaching strategies that can activate student-to-student interaction and student-teacher interaction with regard to instructions, enhancing thought as counter-argument, justification or sophistication, based on the instructional model in this study.