• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.425-426
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• 2013

IIIN계 물질 기반의 광 반도체는 직접 천이형 넓은 밴드갭 구조를 갖고 있기 때문에 적외선부터 가시광선 및 자외선까지를 포함한 폭 넓은 발광파장 조절이 가능하여 조명 및 디스플레이 관련 차세대 광원으로 많은 관심을 받고 있다. 일반적인 청색 및 녹색 발광영역의 활성층으로는 InGaN/GaN 다중양자우물구조를 사용하고 있으나, 장파장의 녹색 발광을 얻기 위해서는 인듐의 함유량이 증가하여야 한다. 하지만, 인듐의 함유량이 증가함에 따라서 InGaN/GaN 다중양자우물 구조내에서 인듐의 편석현상의 발생이 용이하게 되어 계면 특성을 저하할 뿐 아니라, 비발광 센터를 증가하여 발광 효율을 급격히 감소시키는 원인이 되고 있다. 또한, InGaN과 GaN의 큰 성장온도의 차이에 따라 800도 부근의 저온 영역에서 성장된 InGaN층이 1,000도 이상의 고온 영역에서 GaN층이 성장시 InGaN층의 열화 현상이 급격히 발생되고 있다. 이를 억제하기 위해서 금속유기화학증착법의 성장 변수 최적화, 응력제어, 도핑 등의 편석 억제기술 및 보호층이 사용되고 있다. 본 연구에서는 인듐함유량이 증가된 녹색 InGaN/GaN 다중양자우물구조에서 InGaN 우물층 상하부에 도입된 GaN 보호층에 따라 발생되는 양자우물구조의 광학 및 결정학적 특성 분석을 통해 GaN 보호층의 역할을 분석하고자 한다. 본 연구에서는 금속유기화학증착장치를 이용하여 사파이어 기판위에 GaN 템플릿을 성장하고, n-형 GaN, InGaN/GaN 다중양자우물구조 및 p-형 층을 성장하였다. 앞선 언급하였듯이, InGaN/GaN 다중양자우물구조내에 GaN 보호층의 역할을 규명하기 위하여 샘플 A의 경우는 보호층이 전혀 없는 구조이고, 샘플 B의 경우는 InGaN 우물층의 상단부에만, 샘플 C의 경우에는 우물층 상부 및 하단부 모두에 약 2.0 nm 두께의 GaN 보호층을 형성하였다. 이 보호층의 유무에 따른 다중양자우물구조의 계면 특성을 확인하기 위한 X-선 회절을 이용하였고, 광학적 특성을 확인하고 상온 포토루미네선스법을 이용하여 녹색 발광 파장의 변화 및 발광세기를 관찰하였다. 우선적으로, 상온 포토루미네선스법을 이용하여 각 샘플의 발광특성을 확인한 바 상하부 모두에 GaN 보호층이 존재하는 샘플 C의 경우 약 510 nm 부근에서 발광이 관찰되었지만, 상단부에 GaN 보호층이 존재하는 샘플 B는 약 495 nm영역에 발광이 확인되었다. 특히, 전혀 보호층이 존재하지 않는 샘플 A의 경우 약 440 nm에서 발광하는 현상을 관찰하였다. 이는 우물층 상단부 및 하단부에 존재하는 GaN 보호층이 In의 확산을 억제하는 것으로 판단된다. 또한, 발광파장 및 세기를 확인한 바, 보호층의 존재하지 않을수록 단파장화가 발생함에도 불구하고 발광세기는 급격히 약해지는 것으로 보아 계면특성이 저하되어 비발광센터가 증가되는 것으로 판단된다. 이를 구조적으로 확인하기 위하여 X-선 회절법을 통한 ${\omega}$/$2{\Theta}$ 스캔의 결과는 In의 0차 피크가 GaN 보호층이 없을 경우 GaN의 피크 방향으로 이동하는 것으로 보아 GaN 보호층은 우물층 성장 후 GaN 장벽층을 성장하기 위해 온도를 증가시키는 과정에서 In의 확산되는 것으로 판단된다. 또한, 하부 GaN 보호층의 경우 GaN 장벽층 성장 후 온도를 감소시키는 과정에서 성장되므로, 우물층으로부터 In의 탈착현상이 아닌 장벽층과의 상호 확산으로 판단된다. 또한, 계면특성을 확인하기 위해 InGaN의 X-선 위성 피크를 확인한 바 샘플 A의 경우 매우 넓고 약한 피크가 관찰된 반면, 보호층이 존재하는 샘플 B와 C의 경우 강하고 얇은 피크가 확인되었다. 이는 GaN 보호층의 도입으로 인해 계면특성이 향상되는 것으로 판단된다. 따라서, 우리는 InGaN/GaN 다중양자우물구조에서 GaN 보호층은 상부의 열화 억제 뿐아니라, 하부의 장벽층 및 우물층 사이의 상호확산을 억제하는 GaN 보호층의 도입을 통하여 우수한 계면 특성 및 비발광센터의 억제를 얻을 수 있을 것으로 생각되며, 이는 향후 GaN계 발광다이오드의 전계 발광특성을 증가하여 우수한 발광소자를 개발할 수 있을 것으로 기대된다.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.34 no.3
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• pp.50-66
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• 2016

This study attempts to understand and explain how "Directed Attention Restorative Environment (DARE)" is managed and fostered in "Gang-Hak (講學)" and "Yu-Sik (遊息)" spaces both inside and outside of Oksan Seowon Confucian Academy, Gyeongju. Directed Attention is a pivotal element in human information processing so that its restoration is crucial for effective thinking and learning. According to Kaplan & Kaplan's Attention Restoration Theory, an environment, in order to be restorative, should have four elements: 'Being Away,' 'Extent,' 'Fascination,' and 'Compatibility.' We could confirm OkSan Seowon Confucian Academy has an inner logic that integrates two basically different spacial concepts of "Jangsu" and "Yusik" and thus fosters the Attention Restorative Environment. Particularly, the Four Mountains and Five Platforms (四山五臺) surrounding the premises provides an excellent learning environment, and is in itself educational in terms of the Neo-Confucian epistemology with "Attaining Knowledge by way of Positioning Things (格物致知)" as its principle precept, and of its aesthetics with "Connectedness with Nature" as its central tenet. This study attempts to recapture the value of Korea's cultural heritage concerning the Human/Nature relationship; and it may provide useful insights and practical guidelines/grounds in designing today's schools and campuses, where the young people's needs for the Directed Attention- and Attention Restorative- Servicescapes seem to be greater than ever.

• Journal of the Korean earth science society
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• v.42 no.3
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• pp.311-324
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• 2021

Recently, ten geosites have been considered in Hwaseong for endorsement as national geoparks, including the Jebudo, Gojeongri Dinosaur Egg Fossils, and Ueumdo geosites. The Jebudo geosite in the southern part of the Seoul metropolitan area has great potential for development as a new geoscience educational site because it has geological, geographical (landscape), and ecological significance. In this study, we described the geological characteristics through field surveys in the Jebudo geosite. We evaluated its potential as a geo-education site based on comparative analysis with other geosites in Hwaseong Geopark. In addition, we reviewed the practical effect of field education at geosites on the essential concepts and critical competence-oriented education emphasized in the current 2015 revised science curriculum. The Jebudo Geosite is geologically diverse, with various metamorphic rocks belonging to the Precambrian Seosan Group, such as quartzite, schist, and phyllite. Various geological structures, such as clastic dikes, faults, joints, foliation, and schistosity have also been recorded. Moreover, coastal geological features have been observed, including depositional landforms (gravel and sand beaches, dunes, and mudflats), sedimentary structures (ripples), erosional landforms (sea cliffs, sea caves, and sea stacks), and sea parting. The Jebudo geosite has considerable value as a new geo-education site with geological and geomorphological distinction from the Gojeongri Dinosaur Egg Fossils and Ueumdo geosites. The Jebudo geosite also has opportunities for geo-education and geo-tourism, such as mudflat experiences and infrastructures, such as coastal trails and viewing points. This geosite can help develop diverse geo-education programs that improve key competencies in the science curriculum, such as critical thinking, inquiry, and problem-solving. Furthermore, by conducting optimized geo-education focused on the characteristics of each geosite, the following can be established: (1) the expansion of learning space from school to geopark, (2) the improvement of understanding of specific content elements and linkage between essential concepts, and (3) the extension of the education scope throughout the earth system. There will be positive impacts on communication, participation, and lifelong learning skills through geopark education.

• Journal of Food Hygiene and Safety
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• v.36 no.3
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• pp.228-238
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• 2021

The aim of this research was to develop a rapid and easy multi-residue method for determining dimethipin, omethoate, dimethipin, chlorfenvinphos and azinphos-methyl in agricultural products (hulled rice, potato, soybean, mandarin and green pepper). Samples were prepared using QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) and analyzed using gas chromatography-tandem mass spectrometry (GC-MS/MS). Residual pesticides were extracted with 1% acetic acid in acetonitrile followed by addition of anhydrous magnesium sulfate (MgSO₄) and anhydrous sodium acetate. The extracts were cleaned up using MgSO₄, primary secondary amine (PSA) and octadecyl (C₁₈). The linearity of the calibration curves, which waas excellent by matrix-matched standards, ranged from 0.005 mg/kg to 0.3 mg/kg and yielded the coefficients of determination (R²) ≥ 0.9934 for all analytes. Average recoveries spiked at three levels (0.01, 0.1, 0.5 mg/kg) and were in the range of 74.2-119.3%, while standard deviation values were less than 14.6%, which is below the Codex guideline (CODEX CAC/GL 40).

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.4
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• pp.87-100
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• 2022

Early start-up companies have an inherent limitation of lack of resources. Despite these limitations, in order to survive, the entrepreneur's personal ability to efficiently use limited resources is required. In the marketing field, various studies are needed to reduce the business failure rate through establishing growth strategies and innovation. Accordingly, it is necessary to apply the concept of entrepreneurial marketing, which has been researched and developed overseas for 30 years, to fit the domestic reality. According to the flow of this study, an empirical study should be preceded to clarify the influence relationship between entrepreneurial marketing orientation, marketing competency, and management performance, along with a theoretical theorem on entrepreneurial marketing that is suitable for early start-ups and small and medium-sized enterprises(SMEs) and can respond innovatively to changes. The establishment of entrepreneurial marketing orientation and the processes from which this concept leads to business performance through the organization's marketing capabilities and its effects will be empirically verified. For an empirical survey, a survey was conducted on founders of 220 companies, and path analysis using structural equations was used for hypothesis verification. The findings are as follows. First, it was found that the entrepreneurial marketing orientation had a positive effect on both the organization's marketing capabilities and management performance. Second, it was found that the organization's marketing capabilities also had a positive effect on management performance. Third, as a result of empirical analysis of the mediating effect of the organization's marketing capabilities on the relationship between entrepreneurial marketing orientation and management performance, it was found that marketing capabilities showed a greater mediating effect on non-financial performance than financial performance. On the other hand, it was confirmed that marketing performance had a stronger mediating effect on financial performance than non-financial performance. By confirming and presenting the concept and constituent factors of entrepreneurial marketing orientation of domestic start-ups, which were academic gaps for the purpose of this paper, the academic research is differentiated in that they were verified as six components of entrepreneurial marketing. The practical implications of the research results will be that the entrepreneurial marketing-oriented mindset of small and medium-sized companies will optimize market analysis capabilities, network with various stakeholders, and increase the organization's ability to demonstrate marketing capabilities.

• The Mathematical Education
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• v.63 no.2
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• pp.123-138
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• 2024

This study described the utilization of ChatGPT in teaching and students' learning processes for the course "Introductory Mathematics for Artificial Intelligence (Math4AI)" at 'S' University. We developed a customized ChatGPT and presented a learning model in which students supplement their knowledge of the topic at hand by utilizing this model. More specifically, first, students learn the concepts and questions of the course textbook by themselves. Then, for any question they are unsure of, students may submit any questions (keywords or open problem numbers from the textbook) to our own ChatGPT at https://math4ai.solgitmath.com/ to get help. Notably, we optimized ChatGPT and minimized inaccurate information by fully utilizing various types of data related to the subject, such as textbooks, labs, discussion records, and codes at http://matrix.skku.ac.kr/Math4AI-ChatGPT/. In this model, when students have questions while studying the textbook by themselves, they can ask mathematical concepts, keywords, theorems, examples, and problems in natural language through the ChatGPT interface. Our customized ChatGPT then provides the relevant terms, concepts, and sample answers based on previous students' discussions and/or samples of Python or R code that have been used in the discussion. Furthermore, by providing students with real-time, optimized advice based on their level, we can provide personalized education not only for the Math4AI course, but also for any other courses in college math education. The present study, which incorporates our ChatGPT model into the teaching and learning process in the course, shows promising applicability of AI technology to other college math courses (for instance, calculus, linear algebra, discrete mathematics, engineering mathematics, and basic statistics) and in K-12 math education as well as the Lifespan Learning and Continuing Education.

• Journal of Intelligence and Information Systems
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• v.19 no.2
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• pp.125-140
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• 2013

We call a data set in which the number of records belonging to a certain class far outnumbers the number of records belonging to the other class, 'imbalanced data set'. Most of the classification techniques perform poorly on imbalanced data sets. When we evaluate the performance of a certain classification technique, we need to measure not only 'accuracy' but also 'sensitivity' and 'specificity'. In a customer churn prediction problem, 'retention' records account for the majority class, and 'churn' records account for the minority class. Sensitivity measures the proportion of actual retentions which are correctly identified as such. Specificity measures the proportion of churns which are correctly identified as such. The poor performance of the classification techniques on imbalanced data sets is due to the low value of specificity. Many previous researches on imbalanced data sets employed 'oversampling' technique where members of the minority class are sampled more than those of the majority class in order to make a relatively balanced data set. When a classification model is constructed using this oversampled balanced data set, specificity can be improved but sensitivity will be decreased. In this research, we developed a hybrid model of support vector machine (SVM), artificial neural network (ANN) and decision tree, that improves specificity while maintaining sensitivity. We named this hybrid model 'hybrid SVM model.' The process of construction and prediction of our hybrid SVM model is as follows. By oversampling from the original imbalanced data set, a balanced data set is prepared. SVM_I model and ANN_I model are constructed using the imbalanced data set, and SVM_B model is constructed using the balanced data set. SVM_I model is superior in sensitivity and SVM_B model is superior in specificity. For a record on which both SVM_I model and SVM_B model make the same prediction, that prediction becomes the final solution. If they make different prediction, the final solution is determined by the discrimination rules obtained by ANN and decision tree. For a record on which SVM_I model and SVM_B model make different predictions, a decision tree model is constructed using ANN_I output value as input and actual retention or churn as target. We obtained the following two discrimination rules: 'IF ANN_I output value <0.285, THEN Final Solution = Retention' and 'IF ANN_I output value ${\geq}0.285$, THEN Final Solution = Churn.' The threshold 0.285 is the value optimized for the data used in this research. The result we present in this research is the structure or framework of our hybrid SVM model, not a specific threshold value such as 0.285. Therefore, the threshold value in the above discrimination rules can be changed to any value depending on the data. In order to evaluate the performance of our hybrid SVM model, we used the 'churn data set' in UCI Machine Learning Repository, that consists of 85% retention customers and 15% churn customers. Accuracy of the hybrid SVM model is 91.08% that is better than that of SVM_I model or SVM_B model. The points worth noticing here are its sensitivity, 95.02%, and specificity, 69.24%. The sensitivity of SVM_I model is 94.65%, and the specificity of SVM_B model is 67.00%. Therefore the hybrid SVM model developed in this research improves the specificity of SVM_B model while maintaining the sensitivity of SVM_I model.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.2
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• pp.171-178
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• 2016

Purpose : In order to minimize the dose of femoral head as an appropriate treatment plan for rectal cancer radiation therapy, we compare and evaluate the usefulness of 3-field 3D conformal radiation therapy(below 3fCRT), which is a universal treatment method, and 5-field 3D conformal radiation therapy(below 5fCRT), and Volumetric Modulated Arc Therapy (VMAT). Materials and Methods : The 10 cases of rectal cancer that treated with 21EX were enrolled. Those cases were planned by Eclipse(Ver. 10.0.42, Varian, USA), PRO3(Progressive Resolution Optimizer 10.0.28) and AAA(Anisotropic Analytic Algorithm Ver. 10.0.28). 3fCRT and 5fCRT plan has $0^{\circ}$, $270^{\circ}$, $90^{\circ}$ and $0^{\circ}$, $95^{\circ}$, $45^{\circ}$, $315^{\circ}$, $265^{\circ}$ gantry angle, respectively. VMAT plan parameters consisted of 15MV coplanar $360^{\circ}$ 1 arac. Treatment prescription was employed delivering 54Gy to recum in 30 fractions. To minimize the dose difference that shows up randomly on optimizing, VMAT plans were optimized and calculated twice, and normalized to the target V100%=95%. The indexes of evaluation are D of Both femoral head and aceta fossa, total MU, H.I.(Homogeneity index) and C.I.(Conformity index) of the PTV. All VMAT plans were verified by gamma test with portal dosimetry using EPID. Results : D of Rt. femoral head was 53.08 Gy, 50.27 Gy, and 30.92 Gy, respectively, in the order of 3fCRT, 5fCRT, and VMAT treatment plan. Likewise, Lt. Femoral head showed average 53.68 Gy, 51.01 Gy and 29.23 Gy in the same order. D of Rt. aceta fossa was 54.86 Gy, 52.40 Gy, 30.37 Gy, respectively, in the order of 3fCRT, 5fCRT, and VMAT treatment plan. Likewise, Lt. Femoral head showed average 53.68 Gy, 51.01 Gy and 29.23 Gy in the same order. The maximum dose of both femoral head and aceta fossa was higher in the order of 3fCRT, 5fCRT, and VMAT treatment plan. C.I. showed the lowest VMAT treatment plan with an average of 1.64, 1.48, and 0.99 in the order of 3fCRT, 5fCRT, and VMAT treatment plan. There was no significant difference on H.I. of the PTV among three plans. Total MU showed that the VMAT treatment plan used 124.4MU and 299MU more than the 3fCRT and 5fCRT treatment plan, respectively. IMRT verification gamma test results for the VMAT plan passed over 90.0% at 2mm/2%. Conclusion : In rectal cancer treatment, the VMAT plan was shown to be advantageous in most of the evaluation indexes compared to the 3D plan, and the dose of the femoral head was greatly reduced. However, because of practical limitations there may be a case where it is difficult to select a VMAT treatment plan. 5fCRT has the advantage of reducing the dose of the femoral head as compared to the existing 3fCRT, without regard to additional problems. Therefore, not only would it extend survival time but the quality of life in general, if hospitals improved radiation therapy efficiency by selecting the treatment plan in accordance with the hospital's situation.

• Korean Journal of Food Science and Technology
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• v.48 no.2
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• pp.133-141
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• 2016

The physicochemical properties, antioxidant capacities, and sensory optimization of taro (Colocasia esculenta) under different aging conditions were investigated to develop black taro. Black taro was processed in three steps (steaming: $95{\pm}3^{\circ}C$ for 1 h; aging: 85, 90, $95^{\circ}C$ for 20, 40, and 60 h; drying: $60^{\circ}C$ for 24 h) and ground into a powder for all experiments. Black taro showed an increased crude fiber content and browning index compared to raw taro. Calcium oxalate contents, reducing sugar contents, moisture contents, and lightness values were decreased during the processing of taro. Improvements in total polyphenol content and antioxidant activity (DPPH, ABTS, FRAP) were observed in the black taro samples aged at higher temperature. Response surface methodology was used for sensory optimization, and the optimum aging conditions with the highest acceptance values were found to be $88.73^{\circ}C$ for 39.50 h for taste, and $88.82^{\circ}C$ for 42.60 h for overall acceptance.

• The Korean Journal of Nuclear Medicine
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• v.37 no.6
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• pp.418-427
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• 2003

Objects: $^{99m}-lactosylated$ human serum albumin (LSA) is a newly synthesized radiopharmaceutical that binds to asialoglycoprotein receptors, which are specifically presented on the hepatocyte membrane. Hepatic uptake and blood clearance of LSA were evaluated in rat with acute hepatic injury induced by dimethylnitrosamine (DMN) and results were compared with corresponding findings of liver enzyme profile and these of histologic changes. Materials and Methods: DMN (27 mg/kg) was injected intraperitoneally in Sprague-Dawley rat to induce acute hepatic injury. At 3(DMN-3), 8(DMN-8), and 21 (DMN-21) days after injection of DMN, LSA injected intravenously, and dynamic images of the liver and heart were recorded for 30 minutes. Time-activity curves of the heart and liver were generated from regions of interest drawn over liver and heart area. Degree of hepatic uptake and blood clearance of LSA were evaluated with visual interpretation and semiquantitative analysis using parameters (receptor index : LHL3 and index of blood clearance : HH3), analysis of time-activity curve was also performed with curve fitting using Prism program. Results: Visual assessment of LSA images revealed decreased hepatic uptake in DMN treated rat, compared to control group. In semiquantitative analysis, LHL3 was significantly lower in DMN treated rat group than control rat group (DMN-3: 0.842, DMN-8: 0.898, DMN-21: 0.91, Control: 0.96, p<0.05), whereas HH3 was significantly higher than control rat group (DMN-3: 0.731,.DMN-8: 0.654, DMN-21: 0.604, Control: 0.473, p<0.05). AST and ALT were significantly higher in DMN-3 group than those of control group. Centrilobular necrosis and infiltration of inflammatory cells were most prominent in DMN-3 group, and were decreased over time. Conclusion: The degree of hepatic uptake of LSA was inversely correlated with liver transaminase and degree of histologic liver injury in rat with acute hepatic injury.