• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.62-71
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• 2009

In this paper, an improved drive method of piezoelectric PZT stack actuator for micro-positioning system is proposed and the performances are evaluated. This type of amplifier is based on switching technology efficiently handling the arbitrary regenerative energy from the piezoelectric actuator. The conventional voltage-feedback control method has the THD of -32dB (${\approx}2.5%$) with 100mHz sinusoidal reference, which means that the positioning performance in linearity degrades due to the hysteretic relationship between actuator voltage and the displacement. This paper proposed an improved charge-controlling method, which utilizes differential information of charge reference instead of integrating the actuator's current. The current waveform has THD under -40dBV (=1%) and the displacement waveform nearly -52dB (${\approx}0.25%$), which means that the positioning performance is very excellent. Finally, another method of the displacement feedback control has better performance than the voltage method, however there exists a limitation in performance of the system.

• Korean System Dynamics Review
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• v.12 no.4
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• pp.5-34
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• 2011

The purpose of this paper is to evaluate the policies for reducing private tutoring expenditure in Roh Mu Hyun and Lee Myeong Bak Government using Causal Loop analysis based on the Systems Thinking perspective. The results are as follows. First, high educational achievers receive more private tutoring than lowers and children who have rich parents have better chance to take private tutoring than the others. It reflects the social characteristics which emphasize the academic ability and educational background. Second, two governments implemented educational policies to control the private tutoring expenditure as balancing loops ; strengthening public education, providing after school programs and EBS KSAT teaching and improving the entrance exam of university. Third, they overlooked the unintended feedback loops coming from 1) incongruity between causes and countermeasures of shadow education 2) wrong perception of substitutional relationship between public education and shadow education 3) side effect of the policy increasing the weight of student record 4) problems of diversifying high schools 5) dilemma of easing the burden of testing through admission officer system. The conclusion is that policies of reducing the private education expenses have failed because two governments don't consider unintended Feedback Loops in the process of making education policies. So we have to make policies based on Systems Thinking and reducing private education expenses should not be the purpose of strengthening the public education.

• Journal of Biosystems Engineering
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• v.34 no.2
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• pp.95-105
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• 2009

A method was proposed which employed control of the drop location of fertilizer particles on a spinner disc to optimize the spread pattern uniformity. The system contained an optical sensor as a feedback mechanism, which measured discharge velocity and location, as well as particle diameters to predict a spread pattern of a single disc. Simulations showed that the feed gate adaptation algorithm produced high quality patterns for any given application rate in the dual disc spreader. The performance of the feed gate control method was assessed using data collected from a Sulky spinner disc spreader. The results showed that it was always possible to find a spread pattern with an acceptable CV lower than 15%, even though the spread pattern was obtained from a rudimentary flat disc with straight radial vanes. A mathematical optimization method was used to find the initial parameter settings for a specially designed experimental spreading arrangement, which included the feed gate control system, for a given flow rate and swath width. Several experiments were carried out to investigate the relationship between the gate opening and flow rate, disc speed and particle velocity, as well as disc speed and predicted landing location of fertilizer particles. All relationships found were highly linear ($r^2$ > 0.96), which showed that the time-of-flight sensor was well suited as a feedback sensor in the rate and uniformity controlled spreading system.

• Journal of Convergence for Information Technology
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• v.11 no.7
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• pp.91-103
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• 2021

As knowledge management is recognized as an important competency of organizations, organizations are continuously investing in knowledge management policies and technologies. Knowledge management preemptively requires employees to share knowledge, but sharing activities for continuous knowledge management have not been performed. The purpose of this study is to verify the effect of the organization's mutual exchange efforts through collaborative communication on the knowledge sharing intention of its employees. The study surveyed workers of organizations that operate knowledge management policies and verified the research hypothesis by applying 326 samples to structural equation modeling. As a result of the analysis, factors of collaborative communication(rationality, reciprocal feedback, formality) had a positive effect on the intention to share knowledge, and task interdependence and territoriality had a moderating effect on the relationship between collaborative communication and intention to share knowledge. The study has implications in terms of suggesting an activity strategy that an organization should pursue to improve knowledge sharing among its employees.

• Journal of Internet Computing and Services
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• v.20 no.5
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• pp.67-77
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• 2019

Today, companies are making efforts to improve the performance of workers by utilizing various IT-based mobile and internet devices. In pharmaceutical companies, salespeople are using the e-brochure to search for diverse expertise in real time. Through the e-brochure, pharmacists and doctors can be provided with the information they need, thereby increasing confidence in pharmaceuticals and salespeople. Salespeople can also use e-brochures to improve their work performance and to be more satisfied with their jobs. This study examines which functions of e-brochures satisfy salespeople and what attitudes to the e-brochures they need to have. This paper explains the effect of satisfaction and attitude to the e-brochures on job satisfaction through self-efficacy with statistical analysis. As a statistical result, the functions of e-brochures (professional knowledge, massive amount of data, easy searching, information updates, and the reflection of feedback) and attitudes to the e-brochures (importance, intention to use, belief in improvement, efficacy to use, and negative cognition) influence on self-efficacy of salespeople. Further, self-efficacy has mediating effects on the relationship between the functions of e-brochures / attitudes to e-brochures and job satisfaction. Exceptionally, the mediating effect of self-efficacy was not significant in relation to information updates / reflection of feedback and job satisfaction. These results will explain what functions should be focused for the future development of e-brochures. It will also suggest what attitudes the salespeople should have about e-brochures. Through these efforts, salespeople will be able to utilize new technology of e-brochures to satisfy their jobs and improve their performance.

• Korean Journal of Microbiology
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• v.48 no.4
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• pp.254-261
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• 2012

The purpose of this research was to optimize electric current production of sediment microbial fuel cells by injecting glucose and to investigate its impact on microbial communities involved. It was shown that injection of proper concentration of glucose could increase electric current generated from sediment microbial fuel cells. When 1,000 mg/L of glucose, as opposed to higher concentrations, was injected, electric current increased up to 3 times. This increase is mainly attributed to the mutual relationship between fermenting bacteria and exoelectrogenic bacteria. Here the organic acids generated by fermenting bacteria could be utilized by exoelectrogenic bacteria, removing feedback inhibition caused by the organic acids. When glucose was injected, the population of Clostridium increased as to ferment injected glucose. Glucose fermentation can have either a positive or negative effect on electric current generation. When exoelectrogenic bacteria may readily utilize the end-product, electric current could increase. However, when the end-product was not readily removed, then detrimental chemical reactions (pH decrease, methane generation, organic acids accumulation) occurred: exoelctrogenic bacteria population declined and non-microbial fuel cell related microorganisms prospered. By injecting a proper concentration of glucose, a mutual relationship between fermenting bacteria, such as Clostridium, and exoelectrogenic bacteria, such as Geobacter, should be fulfilled in order to increase electricity production in mixed cultures of microorganisms collected from the aquatic sediments.

• Journal of Venture Innovation
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• v.4 no.3
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• pp.69-87
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• 2021

This study was conducted focusing on the innovative behavior necessary for the long-term survival of an organization in a business environment in which uncertainty and complexity are increasing. To this end, the relationship between issue leadership and innovative behavior of organizational members was investigated from the perspective of Signaling theory, Path-Goal theory and Job Demands-Resources theory. In addition, the mediating role of learning agility and sub-components of learning agility was empirically analyzed. For empirical analysis, a survey was conducted with a total of 252 team leaders and team members working in multinational companies (142 in Korea, 110 in the US). The results of this study are as follows. Issue leadership was analyzed to have a positive (+) effect on the innovative behavior of employees. Learning agility was found to play a mediating role between issue leadership and innovative behavior. On the other hand, the mediating effect was tested for each of the sub-components of learning agility, such as feedback seeking, information seeking, reflecting, experimenting, agility. As a result, all five sub-components were found to play a mediating role between issue leadership and innovative behavior. In particular, it was analyzed that the mediating effect of agility was the largest. Next, information seeking appeared to be large. Although there are some studies that have identified the mediating role of learning agility between issue leadership and innovative behavior, this study is considered to have academic implication as there are few cases of subdivided study. At the practical level, it is expected to provide implications for where to focus more when trying to improve an organization's learning agility and innovation behavior

• Management & Information Systems Review
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• v.36 no.3
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• pp.17-35
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• 2017

This study investigates the determinants of strategic positional change. Specifically, the study suggests performance feedback affects to a firm's strategic repositioning. Performance feedback is a concept that a firm decides whether success or not by comparing its performance relative to its aspiration level. Prior studies successively discover diverse behaviors. The study suggests three unexplored relationships between performance gaps and strategic positioning. First, when a firm's performance is below relative to its aspiration level, that firm's strategic position will be deviate from the industry norm. Second, as the degree of industrial density increases, the tendency that a firm's strategic position becomes deviate from the industry norm decreases. Third, when the degree of reference group's performance decreases, the tendency that a firm's strategic position becomes deviate from the industry norm decreases. For empirical analysis, this study examines data of 538 firms that in North America crude petroleum and natural gas industry. The result reveals that the direction of a firm's strategic change is shaped when firms' performance is below relative to aspiration level. Also, this relationship is moderated as industrial density changes or when reference groups' performance decreases. This study contributes to the current literature by explaining how a firms' strategic position is decided. Also, this study reveals that reference groups' performance could affect to organizational choice.

• Journal of the Society of Disaster Information
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• v.17 no.2
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• pp.306-318
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• 2021

The dispatch law has a negative impact on safety management at construction sites as the command and command relationship to safety assistants of the original contractor are applied to the dispatch law. Purpose: The purpose is to study the importance and impact of safety management according to the dispatch law, and to propose a direction for safety management so that safety assistants can actively and proactively prevent accidents. In this study, we used AHP analysis techniques for experts to achieve the final goal and verified the suitability through logistic regression. Method: AHP analysis technique is used for experts and workers and logistic regression analysis is conducted. Result: The result of analyzing scenario data where the dispatch method can be applied showed the importance in the order of education (SkillUp education), management (work-time management) and direct instructions (feedback instruction). In logistic regression analysis, feedback is the factor that affects direct instruction, and in education management, the ratio of education management is 3.42 times lower than that of other groups when only the team leader of the company gives work instructions. Conclusion: The management of feedback and education is more important than anything else within the range in which the dispatch method is not applied, and the expansion of non-face-to-face online education is judged to avoid the violation of dispatch method because the expansion of non-face-to-face online education due to covid 19 recently has brought more various target for safety education.

• The Journal of the Convergence on Culture Technology
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• v.10 no.3
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• pp.61-67
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• 2024

Soldiers serving in military units and institutions are subject to strict security policies and technologies because they handle sensitive and confidential information related to national security, so they are likely to experience security stress. The purpose of this study is to recognize the need to manage the security stress of military personnel and to suggest management measures. To this end, a literature study was conducted on 12 KCI(Korean Journal Citation Index) journals dealing with security stress. Since 2016, research on security stress has been conducted mainly through empirical analysis through surveys. Studies related to security stress were divided into studies dealing with factors that affect stress, the relationship between security stress and security compliance intentions, and factors that reduce security stress. In particular, it was confirmed that factors such as organizational justice, organizational technical support, and security feedback can alleviate security stress. Next, by applying the results of this literature study to the defense security environment, we presented security stress management measures for military personnel in terms of improving security-related organizational justice awareness, technical support, and security feedback. The significance of this study is that we recognized the need to manage military personnel's security stress and reviewed practical measures related to this.