• School Mathematics
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• v.10 no.2
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• pp.139-154
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• 2008

The primary purpose of this study was to investigate how sixth grade elementary school students react to the types of letters use, what levels of understanding letters students are in and what difficulties are in understanding letters, and to raise issues about instructional methods of algebra. A descriptive study through pencil-and- paper tests was conducted. The test instruments consisted of 18 questions with 6 types of letters use. According to the results of testing, students' types of letter use and the levels of understanding letters were classified. The conclusions from the results of this study were as follows: First, the higher the types of letters use, the more sixth grade elementary school students had low scores on the types. Therefore, teaching methodologies of letters and expressions in the classroom need to encourage for students to improve their ability of using and understanding letter. Second, approximately 40% of students were categorized in level 3. Accordingly it is necessary to have a program of teaching and learning to improve their understanding levels of letters. Third, approximately 15% of students were categorized in level 0. In order to develop understanding of letters, it is important that students use letter evaluated and letter used as an object. Fourth, students had the difficulties in understanding letters. It is informative for teachers to understand these students' difficulties and thinking processes. Finally, we must treat the different uses of letters and introduce them successively according to the student's understanding levels of letters.

• Journal of Elementary Mathematics Education in Korea
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• v.14 no.2
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• pp.465-486
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• 2010

Studying the definition and building a foundation about variables during elementary school is a crucial factor before students study the variable in depth in middle school. So, forming a basis for understanding variable in this period should be treated with importance, because it is the first step in forming a clear understanding of the concept of variables. According to analysis of the types of letters used in current textbooks, we can see that too much emphasis was placed on type 1(letter evaluated), type 3(letter used as an Object). By not utilizing the various types of letter usage we reduce the situation to one which is removed from the context and an automatous style of learning. Therefore, the purpose of this study was the development about early algebra learning materials which use diverse types of letters. We have analyzed the types of letters used from the 4-ga to 6-na mathematics textbooks and the 4-ga to the 6-na workbooks. To make learning materials for well-balanced letter use, we developed learning materials focused on early algebra with the 6-ga and the 6-na textbooks.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.12
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• pp.495-518
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• 1999

Since the end of World War II, the standby letters of credit have been used as a surety device, serving as a performance bond and guarantee in the world. In Korea, the standby letters of credit have been also being used in international transactions. But there have been a few studies on the standby letters of credit. This study is carrying out to reveal the characteristics of the standby letters of credit and the documentary letters of credit and also between the standby letters of credit and guarantees. Secondly, this study is carrying out to indicate types of practical use of standby letters of credit in international transactions, i.e. bid bonds, performance bonds, advanced payment guarantees etc.. Finally, this study is carrying out to indicate governig rules regarding standby letters of credit, i.e. URCG, URDG, UCP, UN Convention on Independent Guarantees and Standby Letters of Credit, ISP etc..

• The Korean Journal of Archival Studies
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• no.66
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• pp.317-355
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• 2020

Moon Ik-hwan's prison letters are valuable historical materials managed by the Moon Ik-hwan House of Unification, reflecting an aspect of modern and contemporary South Korea. He wrote these prison letters during a period of approximately 11 years and three months. Today about 800 of them remain and are in an urgent need for measures to ensure their long-term preservation and Use. This study set out to introduce their current state that had been made to the public only in fragments, analyze their characteristics as objects of records management, and propose directions and strategies to provide them as part of online service. For these purposes, the investigator analyzed Moon's personal life and life in prison as the backgrounds of their creation and examined their unique characteristics as prison letters according to the scope and size, recipients, reproduction and circulation process, and the medium of lettercards. Based on these efforts, the study shed new light on the significance of use in private archives and provided a case of online utilization tasks and strategies based on the characteristics of letters as one of the representative types of personal records.

• Biomedical Science Letters
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• v.28 no.4
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• pp.223-228
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• 2022

It has well reported that tumor markers have many advantages like minimally invasive, convenient use, low cost but also has many limitations like low sensitivity and specificity, relevance of prognosis, low organ specificity. Although no tumor markers are ideal, many tumor markers are used for cancer diagnosis, treatment monitoring, and surveillance monitoring after treatment. We review the classification and characteristics of tumor markers according cancer types and clinical roles in current times.

• Mass Spectrometry Letters
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• v.14 no.4
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• pp.160-165
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• 2023

Citronella oil, an essential oil extracted through steam distillation from the leaves and stems of Cymbopogon, is a natural complex substance (NCS) regulated by the Korean government for its use in insect repellents. The component ratios of NCSs like citronella oil vary due to differences in manufacturing processes and origins, presenting a challenge in identifying and quantifying these substances in consumer chemical products. This study analysed ten commercially available products of the most commonly used types of citronella oil, specifically Java and Ceylon types, using gas chromatography (GC)-mass spectrometry (MS) and GC with flame ionization detection (FID). Through chromatographic data, we aimed to determine the components that can qualitatively identify citronella oil and the indicator ingredients that can be used for content analysis.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.2 no.1
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• pp.102-131
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• 1974

The author's thesis is that the types used for the large-sized characters seen in the two metal type-printed books "Kyosik chubopop karyong"(交食推步法假令) and "Yok-hak kemong yohae"(易學啓蒙要解) both printed in 1458 belong to a new metal font hitherto unnamed. The former book was compiled by Yi Sun-ji(李純之) and Kim Sok-je(金石梯) in January of 1458 in accordance to King Sejo's order. A new font was created to be used for the large-sized characters of the book. Several. months after completion of the compilation, the book was printed with mixed use of the new font and the Kabin-ja(甲寅字) for medium- and small-sized characters. The latter book had been written by King Sejo before his accession to the throne. Ascending the throne the king had his scholar-subjects examine the writing to correct it where necessary. The examination was completed in July of 1458 and printing was immediately done with the two fonts the above-mentioned, new font for the large-sized letters and the Kabin-ja for the medium- and small-sized ones. The books were granted to the scholar-subjects and the students of the Sung Kyun Kwan Academy as a royal gift. The matrix seems to have been modeled after the calligraphy of King Sejo. Because the new font was created to print the large-sized letters of the two books in 1458, it may be proper to name it "Muin-ja" using the "kanji"(干支) of the year. The author is happy to identify and include another font in the list of Korean movable types as a result of the present study.

• Journal of Korean Library and Information Science Society
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• v.34 no.3
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• pp.111-124
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• 2003

The number of elderly people is increasing rapidly in Korea. A large part of their information seeking behaviors are changed form a few conventional types of media such as letters to computers and Internet. Their use of computers and Internet, however, was difficult due to various problems including the interface especially. This work has examined and analysed the basic elements and components of interface design for the elderly people into the previous papers. The result of the study would be applied to the public libraries for the elderly and the interface design within the institution.

• Carbon letters
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• v.17 no.1
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• pp.11-17
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• 2016

Recently, with continuous developments in the field of materials science, graphene oxide (GO) has emerged as a promising material with excellent electrical, thermal, mechanical, and optical properties, which play important roles in most fields. Researchers have achieved considerable progress with graphene. Chitosan (CS) is a natural polymer that has been studied intensively owing to its specific formation, high chemical resistance, and excellent physical properties. These outstanding properties have led to its universal use in applications such as textile fabrics, tissue engineering, medicine and health, coatings, and paints. By combining the advantages of GO and CS, different types of promising materials can be obtained. This review discusses the preparation of GO-CS fibers, hydrogel and aerogel, and the applications of GO-CS nanocomposites. In addition, directions for future research on graphene material composites are discussed.

• Biomedical Science Letters
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• v.28 no.2
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• pp.67-82
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• 2022

The prevalence of SARS-CoV-2 led to inconsistent public health policies that resulted in COVID-19 containment failure. These factors resulted in increased hospitalization and death. To prevent viral spread and achieve herd immunity, the only safe and effective measure is to provide to vaccinates. Ever since the release of the SARS-CoV-2 nucleotide sequence in January of 2020, research centers and pharmaceutical companies from many countries have developed different types of vaccines including mRNA, recombinant protein, and viral vector vaccines. Prior to initiating vaccinations, phase 3 clinical trials are necessary. However, no vaccine has yet to complete a phase 3 clinical trial. Many products obtained "emergency use authorization" from governmental agencies such as WHO, FDA etc. The Korean government authorized the use of five different vaccines. The viral vector vaccine of Oxford/AstraZeneca and the Janssen showed effectiveness of 76% and 66.9%, respectively. The mRNA vaccine of Pfizer-BioNTech and Moderna showed effectiveness of 95% and 94.1%, respectively. The protein recombinant vaccine of Novavax showed an effectiveness of 90.4%. In this review, we compared the characteristics, production platform, synthesis principles, authorization, protective effects, immune responses, clinical trials and adverse effects of five different vaccines currently used in Korea. Through this review, we conceptualize the importance of selecting the optimal vaccine to prevent the COVID-19 pandemic.