• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.237-244
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• 2015

Entering the 20th century since the industrial revolution, the cement has been widely used in the field of construction and civil engineering due to the remarkable development of construction industry. However, result from that development, each kind of industrial by-products and waste and the carbon dioxide generated in the process of cement production cause air pollution and environmental damage so earth is getting sick now slowly. Therefore, we have to recognize importance about this. It means that the time taking specific and long-term measures have come. In this research paper, as substitution of the cement generating environmental pollution, we investigate the hydration reaction of non-Sintered Cement mortar mixed with GBFS, active stimulant of alkaline and sulphate series by using SEM and XRD, mechanical and chemical properties according to the curing method. As a result of this experiment, NSC realized outstanding strength for water curing and steam curing. It means that it has a good possibility as substitution of cement. From now on, it can be used for structure satisfying specific standard. We expect to find a substitution of outstanding cement by progressing continuous research making the best use of pros and cons according to the curing method.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.12 no.3
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• pp.163-176
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• 2017

The fourth industrial revolution and creative economy are in the center of today's economic environments. In this context, venture companies make great efforts in achieving innovative capability for sustainable growth. Especially, in order to create the innovative capability or innovation performance, they are very much interested in obtaining such characteristics of organizational ambidexterity as exploration and exploitation. Thus, this study aims to study the organizational contextual ambidexterity as a key factor to create SMEs' performance and to conduct an empirical research with the data collected from domestic SMEs in order to find the antecedent and consequence of this ambidexterity. In so doing, we selected as an antecedent of contextual ambidexterity quality management practice, which is an innovative method of enterprise innovation and enterprise level, innovation performance (radical and incremental Innovation performance) as a consequence and ran a series of regression analyses. As a result, quality management practices such as quality circle activities have had positive effect on organizational ambidexterity, that is, exploration and exploration, and contextual ambidexterity has affected positively on innovation performance. It is also found that the contextual ambidexterity plays a full mediating role in the relationship between quality management practices and innovation performance. The results of this study suggest that contextual ambidexterity is essential to achieving organizational innovation performance and quality management activities such as quality circle should be preceded in order to stimulate or stimulate contextual ambidexterity.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.2
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• pp.111-125
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• 2020

In the rapidly changing era of the Fourth Industrial Revolution, the business environment surrounding venture companies is also changing rapidly. In recent years, the government has reorganized the venture verification system, including expanding the types and scope of venture companies. This study analyzes the current status of venture preferential system from the perspective of technology-based start-up companies and in addition, this paper proposes a plan for improving the legal system. For analysis, The relevant provisions were confirmed through a search using "venture" as a keyword in the National Legal Information Center and the Korean Court of General Law. Then, meaningful texts were extracted along with relevant data to secure basic data and analyzed by benefits, by means and by content. As a result of the study, Venture preferential treatment system is focused on 'reduction of burden' by the means of benefits, and on 'financial' and 'production' by benefits. In conclusion, four suggestions for improvement are presented. First, efforts are needed to increase the practical applicability of venture-related clauses. Second, the venture preferential treatment system is mainly focused on mitigating the burden, so efforts are needed to find a balance. Third, the venture preferential treatment system is mainly focused on the 'non-research' field, so the benefits of the 'research' field should be expanded. Finally, efforts to discover and overcome blind spots in the venture preferential system should be supported.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.6
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• pp.612-618
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• 2019

In the unmanned vehicle industry, the market is exploding due to the rapid development of public and private demands along with the technological development of the 4th Industrial Revolution. In addition, unmanned mobiles are being used for communication services. In this paper, we analyzed the communication performance of unmanned aerial vehicle according to the characteristics of Doppler frequency. The Doppler frequency was calculated using the geometric model of the unmanned aerial vehicle, and the Doppler frequency of 10km, 30km, 300km, 1000km per hour and the BER performance by AWGN were measured by considering the unmanned high speed unmanned vehicle based on the position of the controller. The Doppler frequency model uses a Dent model and adds additive white Gaussian noise (AWGN) to check the bit errors of the transmitter and receiver. Low speed unmanned vehicles generally exhibited a BER performance of 0.2, while high speed unmanned vehicles generally exhibited a BER performance of 0.06. As the frequency band increases at the same speed, the BER performance increases, and when the speed increases in the same frequency band, the BER performance decreases. This is confirmed by the simulation results to predict theoretically predictable BER performance. In the frequency bands of 2.6 GHz, 5 GHz, and 28 GHz, the BER characteristics by Doppler frequency and the BER characteristics by controller function are verified. effect was confirmed.

• Journal of the Korea Institute of Building Construction
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• v.20 no.2
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• pp.155-162
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• 2020

Since the third industrial revolution has been started in the 1980s, the form of buildings has been varied and atypical by the development of building technology. Such free-form building has a curved shape unlike the existing standard buildings, and to realize this, it is necessary to manufacture the free-from panel. The shape of the free-form panel must satisfy a limited error ratio compared with the design shape, and the technology to produce free-form panels is very difficult. However, there are many problems such as enormous cost and construction waste generation when implementing free-from construction. Therefore, the development of free-form panel manufacturing technology should be made to solve the problems caused by the free-form construction. In this study, the error rate analysis of the mixed mortar panel was conducted by selecting the proper mixing ratio of the mixed mortar for the shape of the free-form panel.

• Journal of Digital Convergence
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• v.15 no.5
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• pp.37-48
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• 2017

Recently, the importance of software education is growing because computational thinking of software education is recognized as a key means of future economic development. Also human resources who will lead the 4th industrial revolution need convergence and creativity, computational thinking based on critical thinking, communication, and collaborative learning is known to be effective in creativity education. Software education is also a time needed to reflect social issues such as collaboration with developers sharing interests and open source development methods. Github is a leading social coding site that facilitates collaborative work among developers and supports community activities in open software development. In this study, we apply operational cases of basic learning of social coding sites, learning for storage server with sources and outputs of lectures, and open collaborative learning by using Github. And we propose educational model consisted of four stages: Introduction to Github, Using Repository, Applying Social Coding, Making personal portfolio and Assessment. The proposal of this paper is very effective for software education by attracting interest and leading to pride in the student.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.2
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• pp.277-295
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• 1997

After clinical adjustment of dental casting restoration, re-polishing procedure is recommanded because the smooth gold sureface is lost. But there is the possibility to get more loose contact than that intended by loss of gold alloy according to the kinds of polishing materials and polishing time. Therefore in this study I polished type II gold alloy with 390gm force, 20,000rpm speed, and 8 kinds of gold alloy polishing materials, fabricated by 4 companies and then measured the amount of loss of gold alloy with Surfcorder SEF-30D and observed alloy surfaces polished by 3 brown rubber points with SEM. The amount of loss of gold alloys polished with 8 kinds of polishing materials and the degree of smoothness of gold alloys according to polishing time and polishing materials were compared. The following results were obtained : 1. When the amount of loss of gold alloys polished with 3 kinds of brown rubber point was compared, Alphalex brown point had the most amount of alloy loss, followed in decreasing order by Shofu brown point and Eveflex brown point. There was statistically significant difference in the amount of alloy loss according to polishing materials. 2. When the amount of loss of gold alloys polished with 5 kinds of green rubber point was compared, Shofu green point had the most amount of alloy loss, followed in decreasing order by Alphaflex green point, Dedeco green clasp polisher, and Eveflex green point. There was statistically significant difference in the amount of alloy loss according to polishing materials except Alphaflex green point and Dedeco green clasp polisher. 3. When the amount of loss of gold alloys polished with all kinds of rubber point was compared, there was no significant difference in Eveflex brown point, Alphaflex green point, and Dedeco green clasp polisher. 4. When average amount of alloy loss per 1 revolution by polishing materials was compared, Alphalex brown point had the greatest value as $0.329{\mu}m$ and Shofu supergreen point had the lowest value as $0.022{\mu}m$. 5. When the degree of sureface smoothness of gold alloy polished with 3 kinds of brown rubber point was compared, In Alphalex brown point surface roughness was completely lost after 20 seconds polishing time, in Shofu brown point 30 seconds, in Eveflex brown point 40 seconds. But in every gold alloys fine scratch formed by rubber points was observed. Based on the results of this study, as rubber polishing materials used in polishing of dental casting restoration after clinical adjustment influenced on the tightness of occlusal or proximal contact, we should make dental casting restoration with minimum error through careful laboratory procedure and form very smooth surface of restoration with tripoli and rouge after use of silicone polishing materials.

• Journal of the Korea Society of Computer and Information
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• v.16 no.8
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• pp.1-10
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• 2011

Recently, cloud computing which has provided enabling convenience that users can connect from anywhere and user friendly environment that offers on-demand network access to a shared pool of configurable computing resources such as smart-phones, net-books and PDA etc, is to be watched as a service that leads the digital revolution. Now, when business practices between departments being integrated through a cooperating system such as cloud computing, data streaming between departments is getting enormous and then it is inevitably necessary to find the solution that person in charge and find data they need. In previous studies the clustering simplifies the search process, but in this paper, it applies Hash Function to remove the de-duplicates in large amount of data in business firms. Also, it applies Bayesian Network of data mining for classifying the respect data and presents handling cloud computing based data. This system features improved search performance as well as the results Compared with conventional methods and CPU, Network Bandwidth Usage in such an efficient system performance is achieved.

• Journal of Service Research and Studies
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• v.9 no.2
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• pp.41-54
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• 2019

The increasing use of mobile applications is a phenomenon that has recently come to be beneficial to people in their private life due to increased income and changes in life style. In particular, analyzing customers' consumer sentiment can be seen as a pursuit form of convenience that enables efficient use of time and effort. In this study, based on previous studies, we examine the causal relation model that influences reuse intention, which is a dependent variable through perceived value as a parameter by measuring the service convenience for cafe mobile application. In order to accomplish purpose of this study, references related to service convenience, perceived value, and reuse intention were reviewed as literature research methods. For the empirical study, the research was carried out through Macro Mill Embrain Co., Ltd. Online research was conducted for one week from October 26 to November 8, 2018. There are 13 items of the collected data were excluded and 324 items suitable for irradiation were used. Study results show that service convenience of cafe mobile application has a positive effect on perceived value and reuse intention. In addition, in the relationship that cafe mobile app's service convenience has a significant (+) influence on reuse intention, perceived value proved to have meaningful results as intermediary roles. Implications of this study are as follows. First of all, this study will be helpful for cafe companies and consumers if utilize the service convenience of cafe mobile application in perceived value and reuse intention in marketing applications. Therefore, theoretically, we propose the development direction of cafe mobile application and present academic data for marketing strategy innovation and competitive advantage in the food service industry that conforms to the fourth industrial revolution era.

• Restorative Dentistry and Endodontics
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• v.27 no.3
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• pp.249-256
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• 2002

The use of flowable composite resins as liners in class II packable composite restoration has been suggested by some manufacturers. However, the contributions of this technique are unproven. The purpose of this study was to compare the gingival microleakage in class II packable composite restorations with or without the use of flowable composite resins as liners. Slot cavities were prepared on both proximals of 80 extracted human molars and randomly assigned to 8 groups of 20 each. The gingival margins were located at 1mm above CEJ in 80 cavities (group1-4) and 1mm below CEJ in 80 cavities (group5-8). The prepared teeth were mounted in the customized tray with adjacent teeth to simulate clinical conditions and metallic matrix band (Sectional matrix) and wooden wedges were applied. After acid etching and application of Single Bond, each group was restored with the following materials using incremental placement technique: Group 1,5 (Filtek P60), group 2, 3, 4 and group 6, 7, 8 (AeliteFlo, TetricFlow, Revolution/ Filtek P60). All specimens were thermocycled 500 times between 5$^{\circ}C$ and 55$^{\circ}C$ with 1 mimute dwell time, immersed 2% methylene blue dye for 24 hours and then rinsed with tab water. The specimens were embedded in clear resin and sectioned longitudinally through the center of restoration with a low speed diamond saw. Dye penetration at gingival margin was viewed at 20 magnification and analyzed on a scale of 0 to 4. Kruscal-Wallis One way analysis and Mann-Whitney Rank sum test were used to analyze the results. The results of this study were as follows. 1. The leakage values seen at the enamel margin were significantly lower than those seen at the dentin margin(P<0.05). 2. On the enamel margin, packable composite resins with flowable liners showed lower leakage than those without flowable liners, but there were no significant differences among the four groups(P>0.05). 3. On the dentin margin, four groups demonstrated moderate to severe leakage, and there were no significant differences in leakage values(P>0.05).