• ETRI Journal
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• v.42 no.6
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• pp.976-986
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• 2020

Internet of Things (IoT) is considered the future network to support wireless communications. To realize an IoT network, sufficient spectrum should be allocated for the rapidly increasing IoT devices. Through cognitive radio, unlicensed IoT devices exploit cooperative spectrum sensing (CSS) to opportunistically access a licensed spectrum without causing harmful interference to licensed primary users (PUs), thereby effectively improving the spectrum utilization. However, an open access cognitive IoT allows abnormal IoT devices to undermine the CSS process. Herein, we first establish a hard-combining attack model according to the malicious behavior of falsifying sensing data. Subsequently, we propose a weighted sequential hypothesis test (WSHT) to increase the PU detection accuracy and decrease the sampling number, which comprises the data transmission status-trust evaluation mechanism, sensing data availability, and sequential hypothesis test. Finally, simulation results show that when various attacks are encountered, the requirements of the WSHT are less than those of the conventional WSHT for a better detection performance.

• Asia-Pacific Journal of Business
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• v.11 no.1
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• pp.27-44
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• 2020

Purpose - This study examines the factors that influence the performance of contract farming by agricultural cooperatives from the agency theory and resource-based view of the firm. Design/methodology/approach - This study collected 1,090 data related to a sample of contract information between agricultural cooperatives and producers from national agricultural cooperatives federation. In order to examine the performance of contract farming, we use the multiple regression analysis. Findings - Incentives may reduce agency problems by increasing producers' motivation and discouraging their opportunistic behavior. Total asset size and education expenses function like resources that lessen the risks coming from environment uncertainty, and also facilitate the contract farming between producers and agricultural cooperatives. Research implications or Originality - By analyzing the factors that influence on the performance of contract farming between producers and agricultural cooperatives, we propose that incentives, and resources may improve the performance of contract farming between agricultural cooperatives and producers. Overall, the contract farming can co-create the economic efficiency and effectiveness while minimizing risks and uncertainty.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.902-907
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• 2023

To understand the eutectic reaction mechanism and the relocation behavior of the core debris is indispensable for the safety assessment of core disruptive accidents (CDAs) in sodium-cooled fast reactors (SFRs). This paper addresses reaction products and their distribution of the eutectic melting/solidifying reaction of boron carbide (B₄C) and stainless-steel (SS). The influence of the existence of carbon on the B₄C-SS eutectic reaction was investigated by comparing the iron boride (FeB)-SS reaction by Raman spectroscopy with Multivariate Curve Resolution (MCR) analysis. The scanning electron microscopy with dispersive X-ray spectrometer was also used to investigate the elemental information of the pure metals such as Cr, Ni, and Fe. In the B₄C-SS samples, a new layer was formed between B₄C/SS interface, and the layer was confirmed that the formed layer corresponded to amorphous carbon (graphite) or FeB or Fe₂B. In contrast, a new layer was not clearly formed between FeB and SS interface in the FeB-SS samples. All samples observed the Cr-rich domain and Fe and Ni-rich domain after the reaction. These domains might be formed during the solidifying process.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.321-327
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• 2013

Inter-organizational Relationships (IORs) governance is one of the emerging research areas that have been studied in different contexts (e.g. economics, strategy, organization, and management). This view, particularly, attracted rising attention from academics and practitioners in the context of construction projects, due to the complex forms of IORs in terms of inter-firm exchanges (e.g. engineering, procurement, finance, construction, and operation) in these projects. The focus of IORs governance is to control Inter-organizational relationships among two or more cooperative parties to alleviate conflict and achieve mutual gains. One of the mechanisms that have been identified in the related literature is formal governance mechanism. Although many empirical studies have been conducted using formal governance terms and indicators, there isn't yet a consensual definition of this mechanism and its components that may cause misinterpretation of research results and also impede future research. This paper makes contribution to the concept of IORs governance by clarifying the meaning of formal governance mechanism and identifying different indicators of this mechanism that have been used and identified in previous studies. This provides an innovative and useful framework to understand formal governance mechanism and its application in construction projects.

• Journal of Environmental Science International
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• v.32 no.10
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• pp.741-744
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• 2023

This study focused on high school laboratory research and the main purpose was to develop alternative additives for livestock waste and ammonia volatilization methods with high school students as participants and to provide information to business owners based on the results. Compared to the control groups, The bentonite and illite treatment groups had similar ammonia volatilization, pH, EC, and total nitrogen content. In particular, the alum and aluminum chloride mixed treatment group showed low pH and ammonia volatilization, and high EC and total nitrogen content for poultry litter. As a result, when focusing on high school laboratory research, the alum and aluminum chloride mixed agent treatment fulfilled its role as an alternative additive for ammonia reduction. In addition, this approach can be suggested as a method to solve difficulties in adapting to the field through a practical cooperative relationship with livestock farms.

• Korean Journal of Environment and Ecology
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• v.31 no.6
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• pp.595-605
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• 2017

This study was intended to investigate the effects of after-school forest healing programs on the pro-social behavior and self-efficacy of young children using the attributes of forest and the forest healing factors. The children attending a kindergarten located in ${\bigcirc}{\bigcirc}$ - dong, Cheongju city were divided into a test group which participated in the forest healing program activities and a control group which participated in the regular programs of the kindergarten but not in the forest healing program. Each group consisted of 20 boys and girls aged 3 to 5 years. The forest healing program was conducted once a week from 10 April to 10 July in 2017 for a total of 12 sessions, and each session lasted one hour (60 minutes). The pro-sociality behavior and self-efficacy test of the children was conducted before and after the forest healing program, and the data were analyzed using SPSS 18.0 program. The result showed that the pro-social behaviors that indicated the ability to execute the positive action and the self-efficacy that indicated the self-confidence were statistically significant (p<0.05). The young children who participated in the forest healing program improved their self-esteem through positive thoughts from being with their peer in nature. Moreover, they increased not only ecological knowledge but also consideration for others and cooperative spirit. They also greatly improved the ability to control personal emotion and the ability to form the personal relationship which are the sub-factors of pro-sociality, the ability to adapt to the early childhood education institution, and the physical efficacy which is the sub-factor of self-efficacy. It was concluded that the after-school forest healing program had a positive impact on pro-social behavior and self-efficacy.

• Korean Journal of Construction Engineering and Management
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• v.14 no.6
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• pp.49-60
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• 2013

Evacuation process has been considered as one of the most important elements to be managed in public facilities. Although the importance is highlighted through numerous literatures, disaster evacuation planning, particularly fire accidents, faces a number of human behavior related limitations for a similar application to different types of facilities/occupants. To overcome the obstacles including complexity in human behaviors, a number of simulation techniques with limited consideration on human behaviors are utilized to predict foreseeable problems in evacuation process. Therefore, this research aims to propose system dynamics models incorporating human behaviors considering different types of occupants under disaster evacuation events. Analysis on emergent human behaviors such as group forming and interactions under urgent situation are conducted based on the main stream theories in social science field. The results suggest the influences of human behavior factors including cooperative intention, information sharing, and mobility change to evacuation behavior. The implications are expected to provide safety consideration at planning/designing phase of buildings and help facility safety managers for evacuation planning with more realistic management approaches.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.610-622
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• 2021

The DECOVALEX project is one of the representative international cooperative projects to enhance the understanding of the complex Thermo-Hydro-Mechanical-Chemical(THMC) coupled behavior in the high-level radioactive waste disposal system based on the numerical simulation. DECOVALEX-2023 is the current phase consisting of 7 tasks, and Task C aims to model the THM coupled behavior in the disposal system based on the Full-scale Emplacement (FE) experiment at the Mont-Terri underground rock laboratory. This study performs the numerical simulation based on the OGS-FLAC developed for the current study. In the numerical model, we emplaced the heater with constant power horizontally based on the FE experiment and monitored the pressure development, temperature increase, and mechanical deformation at the specific monitoring points. We monitored the capillary pressure as the primary effect inducing the flow in the buffer system, and thermal stress and pressurization were dominant in the surrounding rocks' area. The results will also be compared and validated with the other participating groups and the experimental data further.

• Journal of Korean Elementary Science Education
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• v.36 no.4
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• pp.379-393
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• 2017

This study analyzed the relationship between self-directedness of science-gifted elementary students and their expression of scientific creativity in science-gifted class. A science-gifted program on the topic of Hydraulic Machine was implemented to 34 fifth-graders in the Science-Gifted Education Center of an education office in Seoul, Korea for four weeks. The self-directedness of the gifted students was divided into three types of 'General, Scientific, and Topic-Related Self-Directedness'. The products of the students' activities were assessed by using a scientific creativity assessment formula. Qualitative research, such as analysis of observations and interviews, was also conducted in order to identify characteristics that were not apparently revealed by quantitative data. The main results of this study are as follows: First, science-gifted elementary students' general self-directedness and their scientific creativity were significantly correlated (r=.373). Second, the students' scientific self-directedness and scientific creativity did not have a significant correlation (r=.294). Third, there was a positive correlation between the students' topic-related self-directedness and their expression of scientific creativity. Their self-rated scores (r=.420) for the topic-related self-directedness and the number of activity types associated with the topic had a positive correlation (r=.350). Fourth, the students were categorized into four groups according to the levels of their self-directedness and scientific creativity, and the result showed that Type HH (high self-directedness and high scientific creativity) was the most common type (15 students, 38.5%), followed by Type LL (low self-directedness and low scientific creativity) (11 students, 28.2%). Eight (20.5%) and five students (12.8 %) belonged to Type LH (low self-directedness and high scientific creativity) and Type HL (high self-directedness and low scientific creativity) respectively. Fifth, the classroom observation of the students in groups revealed that groups with more number of Type HH demonstrated better cooperation and performance. Sixth, the analysis results of the observation were almost matched to the results of the self-directedness and scientific creativity tests. The students with higher self-directedness demonstrated active class participation and good cooperative skills. The students with higher scientific creativity had a tendency to generate creative ideas more frequently in given situations. Seventh, dynamic activities were perceived as enjoyable and exciting by 76.9% of the students, but static activities that require creativity were regarded as interesting only by 23.1% of the students. Among the students who were satisfied with both the creative and static activities, Type HH accounted for the largest proportion (55.6%). In conclusion, factors such as students' interests, initiatives, and attitudes displayed through voluntary participations originated from their own daily life can predict the degree of scientific creativity associated with the topic. Also, when students were categorized into four types according to the level of self-directedness and scientific creativity, there was a tendency of active behavior in class, cooperative skill, and activity satisfaction. This suggested that we should consider self-directedness and scientific creativity in selecting the gifted, grouping them in class, and designing and executing programs for science-gifted elementary students.

• Journal of Korean Society of Forest Science
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• v.97 no.6
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• pp.669-679
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• 2008

Jirisan National Park was designated on December 29, 1967 as the first national park in Korea and that caused continuous conflicts between the violation of the right to hold property in this area due to several regulations following the designation and the nature preservation for the value of heritage for descendants. Thus, the objective of this study is to find a proposal for making decision based on the rationality that is able to solve these conflicts. To achieve the objective of this study, this study applies a game theory that supports a reasonable decision making process for solving these conflicts between interest groups around Jirisan National Park in which the component of this game consists of Jirisan National Park, residents, and interest groups. The Nash equilibrium obtained by the analysis of the strategy of interest groups for the use and preservation of forests and its rewards from the strategy as an nonecooperative game showed a behavior that chases their own benefits and causes lots of troubles. However, in the case of the results obtained from a cooperative game based on the strategy that includes some public interests accepted by interest groups and its rewards, it represented an aspect that solves conflicts through achieving a strategical set, which shows a win-win outcome even though the results of this cooperative game may present less rewards than that of the Nash equilibrium. Whereas, if there exists the public interests accepted by interest groups and truth for protecting such public interests, it is considered that it becomes a way that solves present structural troubles in the National Parks in Korea due to the fact that there exist uncertainties caused by the human rationality.