• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.4
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• pp.191-201
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• 2016

A stochastic process has been used to develop a condition-based model for preventive maintenance of armor units of rubble-mound breakwaters that can make a decision the optimal interval at which some repair actions should be performed under the perfect maintenance. The proposed cost model in this paper based on renewal reward process can take account of the interest rate, also consider the unplanned maintenance cost which has been treated like a constant in the previous studies to be a time-dependent random variable. A function for the unplanned maintenance cost has been mathematically proposed so that the cumulative damage, serviceability limit and importance of structure can be taken into account, by which a age-based maintenance can be extended to a condition-based maintenance straightforwardly. The coefficients involved in the function can also be properly estimated using a method expressed in this paper. Two stochastic processes, Wiener process and gamma process have been applied to armor stones of rubble-mound breakwaters. By evaluating the expected total cost rate as a function of time for various serviceability limits, interest rates and importances of structure, the optimal period of preventive maintenance can easily determined through the minimization of the expected total cost rate. For a fixed serviceability limit, it shows that the optimal period has been delayed while the interest rate increases, so that the expected total cost rate has become lower. In addition, the gamma process tends to estimate the optimal period more conservatively than the Wiener process. Finally, it is found that the more crucial the level of importance of structure becomes, the more often preventive maintenances should be carried out.

• Korea Journal of Hospital Management
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• v.24 no.4
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• pp.13-32
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• 2019

Purposes: This research is an empirical research to analyze the effect of self-leadership on the job satisfaction and organizational citizenship behavior and the mediating effect of psychological capital. Methods: This research investigates the effect of self-leadership and psychological capital on job satisfaction and organizational citizenship behavior of public health workers. The analysis was carried out to 4 local medical staffs in Chungcheongnam-do province, which distributed 330 copies and recovered 313 copies (94.8% recovery) and analyzed 304 copies (effective response rate 92.1%). Findings: First, causality was found in self-leadership and psychological capital. Second, it was found to have a significant effect on psychological capital and job satisfaction. Third, psychological capital was found to have a significant effect on organizational citizenship behavior. Fourth, psychological capital has a positive effect on both Self-leadership's behavior-oriented strategy, natural reward strategy, and strategic thinking pattern strategy. In the job satisfaction relationship, there was a partial mediating effect. Fifth, psychological capital has a positive effect on both self-leadership and organizational citizenship behavioral behavior-oriented strategy, natural reward strategy, and strategic thinking pattern strategy. The organizational citizenship behavioral relationship was found to have a partial mediating effect. Practical Implications: Taken together, the results indicate that the members of the four public health care organizations run by Chungcheongnam-do have a high weight on the natural reward strategy of achieving job satisfaction through the pleasures of doing their favorite activities or jobs.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.6
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• pp.75-81
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• 2022

Autonomous vehicles, which can dramatically solve the lack of parking spaces, are making great progress through deep reinforcement learning. Activation functions are used for deep reinforcement learning, and various activation functions have been proposed, but their performance deviations were large depending on the application environment. Therefore, finding the optimal activation function depending on the environment is important for effective learning. This paper analyzes 12 functions mainly used in reinforcement learning to compare and evaluate which activation function is most effective when autonomous vehicles use deep reinforcement learning to learn parking. To this end, a performance evaluation environment was established, and the average reward of each activation function was compared with the success rate, episode length, and vehicle speed. As a result, the highest reward was the case of using GELU, and the ELU was the lowest. The reward difference between the two activation functions was 35.2%.

• Journal of the Korea Society of Computer and Information
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• v.23 no.8
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• pp.115-121
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• 2018

This study inquires into employee's intent to leave in South Korean dental clinics. A systematic research was undertaken on theories of leadership types, job satisfaction, organizational commitment and empowerment, and then interaction between these variables was verified based on quantitative data by using Structural Equation Model (SEM). The findings suggest that making improvements of empowerment, job satisfaction, and organizational commitment demand individualized consideration and charisma, the components of transformational leadership. As a way to reduce turnover intention, the role of job satisfaction and organizational commitment was more influential than that of empowerment. Also, a combination of charisma of transformational leadership and contingent reward of transactional leadership turned out to be the ideal leadership type to reduce turnover intention. Lastly, the harmony of individual goal with that of organization, apparent documentation of reward system, and stress control were recommended as practical solutions to improve organizational profitability and effectiveness and to reduce turnover rate in dental clinics.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.217-226
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• 2014

In this research, we study the problem of opportunistic spectrum access (OSA) in a time-varying environment with fading channels, where the channel state is characterized by both channel quality and the occupancy of primary users (PUs). First, a finite-state Markov channel model is introduced to represent a fading channel. Second, by probing channel quality and exploring the activities of PUs jointly, a two-dimensional partially observable Markov decision process framework is proposed for OSA. In addition, a greedy strategy is designed, where a secondary user selects a channel that has the best-expected data transmission rate to maximize the instantaneous reward in the current slot. Compared with the optimal strategy that considers future reward, the greedy strategy brings low complexity and relatively ideal performance. Meanwhile, the spectrum sensing error that causes the collision between a PU and a secondary user (SU) is also discussed. Furthermore, we analyze the multiuser situation in which the proposed single-user strategy is adopted by every SU compared with the previous one. By observing the simulation results, the proposed strategy attains a larger throughput than the previous works under various parameter configurations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.12
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• pp.3133-3151
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• 2012

The optimal price strategy selection of two bounded rational cognitive mobile virtual network operators (MVNOs) in a duopoly spectrum sharing market is investigated. The bounded rational operators dynamically compete to sell the leased spectrum to secondary users in order to maximize their profits. Meanwhile, the secondary users' heterogeneous preferences to rate and price are taken into consideration. The evolutionary game theory (EGT) is employed to model the dynamic price strategy selection of the MVNOs taking into account the response of the secondary users. The behavior dynamics and the evolutionary stable strategy (ESS) of the operators are derived via replicated dynamics. Furthermore, a reward and punishment mechanism is developed to optimize the performance of the operators. Numerical results show that the proposed evolutionary algorithm is convergent to the ESS, and the incentive mechanism increases the profits of the operators. It may provide some insight about the optimal price strategy selection for MVNOs in the next generation cognitive wireless networks.

• Korean journal of food and cookery science
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• v.28 no.2
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• pp.97-110
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• 2012

The purposes of this study were to examine the levels of job stress and job burnout perceived by nutrition teachers and dietitians in school foodservice in Gyeongsangnam province and to analyze job stress factors affecting job burnout. A total of 270 questionnaires were distributed from December 10 to 29, 2010 and 252 were returned (response rate : 93.3%). A total of 245 were used in the final analysis (usage rate : 90.7%), excluding seven improper questionnaires. The results of this study were as follows : 100% of the respondents were women, and their mean age was 38. 60% were nutrition teachers and 40% were dietitians. The level of job stress and job burnout of the respondents were 2.89 points (on a 5-point Likert scale) and 3.70 (on a 7-point Likert scale), respectively. In regard to job stress factors, job demand (3.97) recorded the highest scores, followed by organizational system (2.99), lack of reward (2.85), interpersonal conflict (2.69), job insecurity (2.63), organizational climate (2.63), and insufficient job control (2.45) in that order. Exhaustion burnout (4.60) recorded the highest points among job burnout factors, followed by cynicism (3.46), and professional efficacy (3.04) in that order. Job stress factors affecting job burnout were organizational system (p<.001), job insecurity (p<.001), lack of reward (p<.001), and organizational climate (p<.01). In conclusion, it is necessary to provide human resources management strategies to lower job demand and workload in order to reduce job stress and job burnout for dietitians and nutrition teachers in school foodservice.

• Asia Marketing Journal
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• v.13 no.3
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• pp.25-53
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• 2011

This study probes the effect of loyalty program on the customer retention based on the real transaction data(n=2,892) acquired from education service industry. We try to figure out the outcomes of reward program through more than 1 year-long data gathered and analyzed according to quasi-experimental design(i.e., before and after design). We adopt this kinds of research scheme in regard that previous studies measured the effect of loyalty program by dividing the customers into two group(i.e., members vs. non-members) after the firms or stores had started the program. We believe that it might not avoid the self-selection bias. The research questions of this study could be explained such as: First, most research said that the loyalty programs could increase the customer loyalty and contribute to the sustainable growth of company. But there are little confirmation that this promotional tool could be justified in terms of financial perspective. Thus, we are interested in both the retention rate and financial outcomes caused by the introduction of loyalty programs. Second, reward programs target mainly current customer. Especially CRM(customer relationship management) said that it is more profitable for company to build positive relationship with current customer instead of pursuing new customer. And it claims that reward program is excellent means to achieve this goal. For this purpose, we check in this study whether there is a interaction effect between loyalty program and customer type in retaining customer. Third, it is said that dis-satisfied customers are more likely to leave the company than satisfied customers. While, Bolton, Kannan and Bramlett(2000) claimed that reward program could contribute to minimize the effect of negative service by building emotional link with customer, it is not empirically confirmed. This point of view explained that the loyalty programs might work as exit barrier to current customer. Thus, this study tries to identify whether there is a interaction effect between loyalty program and service experience in keeping customer. To achieve this purpose, this study adopt both Kaplan-Meier survival analysis and Cox proportional hazard model. The research outcomes show that the average retention period is 179 days before introducing loyalty program but it is increased to 227 days after reward is given to the customers. Since this difference is statistically significant, it could be said that H1 is supported. In addition, the contribution margin coming from increased transaction period is bigger than the cost for administering loyalty programs. To address other research questions, we probe the interaction effect between loyalty program and other factors(i.e., customer type and service experience) affecting it. The analysis of Cox proportional hazard model said that the current customer is more likely to engage in building relationship with company compared to new customer. In addition, retention rate of satisfied customer is significantly increased in relation to dis-satisfied customer. Interestingly, the transaction period of dis-satisfied customer is notably increased after introducing loyalty programs. Thus, it could be said that H2, H3, and H4 are also supported. In summary, we found that the loyalty programs have values as a promotional tool in forming positive relationship with customer and building exit barrier.

• Korean Journal of Occupational Health Nursing
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• v.11 no.2
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• pp.150-157
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• 2002

The purpose of this study is to analyze papers of smoking cessation program into method and effect 13 papers that purblished from January, 1980 to Oct., 2001 in the country and 30 papers that purblished from Jan., 1980 to Jun., 1999 in other countries were analized. The result of this study can be summarized as follows 1) The most of subjects were students(46.5%) and residents(30.2%). 2) There were a few of papers based on the Theory(9.3%). 3) Programs included education(58.3%), reward (13.9%) and support(12.5%). 4) There were experimental design(46.5%), non-experimental design(29.5%) and experimental design(25.0%). The most of papers of non-experimental desigs were significant. 5) Behavior(48.7%), knowledge(15.4%) and attitude(12.8%) were evaluated as a effect of program. Knowledge had higher significant rate than other evaluation items. 6) Programs that was from a year to two years had the highest significant rate.

• Korean Journal of Biological Psychiatry
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• v.23 no.4
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• pp.123-129
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• 2016

Depression has a relatively high lifetime prevalence rate in spite of a genetic influence on its etiology and a high mortality rate in untreated cases. This suggests the possibility that depression gives us evolutionary benefits which we do not exactly know yet. There have been several hypotheses which tell us what evolutionary advantages depression could give us. The psychic pain hypothesis considers sad or depressed mood as a negative reward just like physical pain which we have to avoid for our protection and survival. The social rank hypothesis holds that depressed mood is very similar to the emotional state of the defeated in social competition which prevents him from further protesting or fighting that might cause additional damage to him. The inclusive fitness hypothesis views suicide as a sacrifice phenomenon to contribute to inclusive fitness. These hypotheses gives us new insights into mood disorders and also some suggestions about the conditions in which depressed mood or suicidal behaviors increase and the ways to reduce them.