• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.6
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• pp.1-9
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• 2020

Using kerosene and liquid oxygen, 1.5-tonf class liquid-liquid pintle injector with rectangular two-row orifice was designed and manufactured. The combustion test of the pintle injector was carried out to verify the combustion performance and combustion stability under a supercritical condition which is the actual operation condition of the liquid rocket engine. The combustion test result showed that the pintle tip was damaged by the high temperature combustion gas in the high-mixed ratio recirculation zone of the combustion chamber. To solve this problem, the insert nozzle was installed in the pintle injector to increase cooling performance at the pintle tip. As a result of the hot firing test, installation of the insert nozzle, AR and BF had a great effect on pintle tip cooling performance.

• Journal of the Korean Society for Library and Information Science
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• v.55 no.3
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• pp.131-154
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• 2021

This study is to in-depth analysis of the copyright issues related to the library's e-book service, which is the cause of the recent conflict between the publishing industry and the library industry. To this end, the purpose and outline of the copyright system were briefly summarized. Then, the jurisprudence of the Copyright Act applied to the borrowing of paper books and e-books was analyzed, and the position of the publisher's association and the library industry were reviewed together. In addition, problems of the current copyright act related to e-book services were diagnosed and directions for improvement were sought. Unlike in the case of paper books, first sale doctrine does not apply to e-book borrowing, so the library cannot acquire the right to service just by purchasing e-books. Based on the contract signed with the distributor in the process of purchasing the e-book, the library acquires the right to service the e-book. However, if the validity period of the exclusive publication right expires, the contract itself becomes invalid, which can cause serious problems in the stability of library services and preservation of resources. In order to solve this problem, it is suggested that the first sale doctrine needs to be extended to digital works.

• Journal of Korean society of Dental Hygiene
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• v.21 no.4
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• pp.441-453
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• 2021

Objectives: This study identified problems and improvements in projects targeted to dental workers in a child-adolescent dental care service. Methods: The subjects were 40 dentists, 43 dental hygienists, and 51 others who participated in service in Seoul. A self-administered questionnaire was used to address the problems and improvements in the project. Descriptive statistics, chi-square test, and one-way analysis of variance were performed using SPSS 23.0. Results: Oral examination was performed by 99.2% of dentists, and some service items such as professional tooth cleaning, fluoride application, and scaling were performed by dental auxiliary personnel regardless of legal duties. The problem was that the subjects took a lot of time in providing services, and students or guardians participating in the project refused to receive preventive dental services. As regards improvements, the insurance fee was the highest (48.1%), followed by the provision of regular services (38.8%), and system improvement and administrative support (35.7%). Conclusions: To activate a child-adolescent dental care service, it is thought that continuous efforts such as providing financial support by the government, education to increase participants' understanding, and social consensus for the participation of service providers and beneficiaries are required.

• Journal of the Korea Convergence Society
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• v.12 no.8
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• pp.207-214
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• 2021

Existing studies have shown consistent results that a diversification discount phenomenon occurs, which means that the value of the company decreases as the degree of diversification of a company increases. Nevertheless, it is explained by the agency theory as a factor that continues to promote diversification by companies. And in order to solve the agency problem, it is important to form an effective governance structure. In order to solve these problems, this study aims to study how the directors' concurrent information affects the monitoring effect of the board of directors through this affects diversification.To this end, research was conducted on KOSPI companies for 6 years from 2011 to 2016.As a result of the analysis, in the case of the concurrent appointment of the CEO and the inside director, there was a positive (+) effect, but the significance could not be confirmed. In the case of adjunct appointments as outside directors, positive results were confirmed that were significant for diversification.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.4
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• pp.25-29
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• 2021

The strip binary is a binary from which debug symbol information has been deleted, and therefore it is difficult to analyze the binary through techniques such as reverse engineering. Traditional binary analysis tools rely on debug symbolic information to analyze binaries, making it difficult to detect or analyze malicious code with features of these strip binaries. In order to solve this problem, the need for a technology capable of effectively extracting the information of the strip binary has emerged. In this paper, focusing on the fact that the byte code of the binary file is generated very differently depending on compiler version, optimazer level, etc. For effective compiler version extraction, the entire byte code is read and imaged as the target of the stripped binaries and this is applied to the convolution neural network. Finally, we achieve an accuracy of 93.5%, and we provide an opportunity to analyze stripped binary more effectively than before.

• Journal of The Korean Association of Information Education
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• v.25 no.3
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• pp.501-510
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• 2021

This paper was described to assess the possibility of field application of the developed textbooks by developing a textbook using action learning to conduct ICT electromagnetic waves training education for elementary and middle school teachers and applying it on a pilot basis. To this end, it was organized to be used in conjunction with classes in several subjects and provided various teaching materials to facilitate teachers' convenience to use the textbook. Also, the textbook was composed of a content structure of 10 sessions. As for the proposed textbook, the overall understanding of ICT electromagnetic waves was improved through pilot application in teacher training, and problem-solving ability, cooperative learning ability, democratic citizenship, and knowledge information processing ability were improved through action learning. It can be said that it contributed to improving the understanding of ICT electromagnetic waves and teachers' competencies.

• Design & Manufacturing
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• v.15 no.4
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• pp.43-50
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• 2021

Pump-cap is a device for discharging the contents stored inside a container to the outside of the container by a simple operation by a certain amount. In particular, in recent years, as the number of cosmetic products made of functional materials has rapidly increased, the development of convenient containers for functional materials is being actively conducted. Among these, there are a growing number of products that show their efficacy only by mixing two components, so the development of a dual pump cap container is necessary. However, the conventional dual pump cap container has a problem in that it is difficult to implement a quantitative discharge as solutions having different viscosities are used. Therefore, in this study, a discharge port of a dual pump cap that can apply an optimal ratio was designed by analyzing the discharge amount of two components with different viscosities through computational fluid dynamics. Since the discharge amount is affected by the size of the discharge port, the higher the viscosity of the solution, the larger the discharge port should be set. Conversely, the lower the viscosity, the smaller the discharge port should be. Through this, it is possible to dispense a fixed amount of a heterogeneous solution by one pumping, and it is determined that the user's convenience will increase.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.1
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• pp.94-103
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• 2022

As a large amount of data generated by sensors or devices at the manufacturing site is transmitted to the server or client, problems arise in network processing time delay and storage resource cost increase. To solve this problem, considering the manufacturing site, where real-time responsiveness and non-disruptive processes are essential, QRC (Quotient Remainder Compression) and BL_beta compression algorithms that enable real-time and lossless compression were applied to actual manufacturing site sensor data for the first time. As a result of the experiment, BL_beta had a higher compression rate than QRC. As a result of experimenting with the same data by slightly adjusting the data size of QRC, the compression rate of the QRC algorithm with the adjusted data size was 35.48% and 20.3% higher than the existing QRC and BL_beta compression algorithms.

• International Journal of Computer Science & Network Security
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• v.22 no.2
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• pp.123-130
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• 2022

During the past decades, detection of gear defects remains as a major problem, especially when the gears are subject to non-stationary phenomena. The idea of this paper is to mixture a multilevel wavelet transform with a fast EMD decomposition in order to early detect gear defects. The sensitivity of a kurtosis is used as an indicator of gears defect burn. When the gear is damaged, the appearance of a crack on the gear tooth disrupts the signal. This is due to the presence of periodic pulses. Nevertheless, the existence of background noise induced by the random excitation can have an impact on the values of these temporal indicators. The denoising of these signals by multilevel wavelet transform improves the sensitivity of these indicators and increases the reliability of the investigation. Finally, a defect diagnosis result can be obtained after the fast transformation of the EMD. The proposed approach consists in applying a multi-resolution wavelet analysis with variable decomposition levels related to the severity of gear faults, then a fast EMD is used to early detect faults. The proposed mixed methods are evaluated on vibratory signals from the test bench, CETIM. The obtained results have shown the occurrence of a teeth defect on gear on the 5th and 8th day. This result agrees with the report of the appraisal made on this gear system.

• Journal of agricultural medicine and community health
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• v.47 no.1
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• pp.1-13
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• 2022

Objectives: This study aimed to establish a linkage model involving regional responsible medical institutions after analyzing the existing conditions and deriving problems through qualitative analysis within the community care system. Methods: A total of 14 participants of this study were selected through the snowball sampling method, including 7 community care service providers and 7 service users. As for the research data, primary data were collected through interviews, and as a result of analyzing according to Aday&Anderson' model, a total of 5 catergories, 8 topics, and 22 sub theme were derived. Results: The problem derived from the interview is that division services are provided for each institution due to the absence of a key central institution of community care system, and users' commercial institutions is unclear. The second is the inconsistency between the needs and supply for community care, resulting in a possibility of delay in returning to the community after discharge. Based on these problems, it is necessary to unify it as an community care window of the Dong-community center. In addition, there is a need for public health centers to play an active role, and to establish a public-private joint system with the Health and Living Support Center to establish a model that can play a certain role. Conclusions: Therefore, based on the results of this study, it can be used as basic data when constructing community care model and applying it as an expanded model in the future.