• Journal of Biosystems Engineering
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• v.18 no.4
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• pp.328-343
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• 1993

To control depth of tractor implement, an automatic depth control system based upon microcomputer was developed. This system consists of data aquisition system to measure and to record travel speed, draft and depth of the implement, hydraulic system to control the implement depth and 3-point hitch to attach the implement. Program, written in C language, was able to select position control, draft control and mixed control. To analyze parameters affecting this system, the performance of the system was evaluated through use of computer simulation and verified in soil bin experiments. 3-point hitch was lifted by hydraulic pressure and lowered by implement weight. Dead band was one of the important factors which affect the stability and the accuracy of the system. The system became unstable when the flow rate was increased or when the dead band was decreased. The position control mode with on-off control showed the great ability to control the implement at the given plowing depth. With the draft control, the tractor load could be reduced, however the plowing depth was changed unexpectedly when the soil was hard and inconsistent. The mixed control could improve the performance of the system to maintain the plowing depth without overload of the tractor.

• Fisheries and Aquatic Sciences
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• v.7 no.1
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• pp.23-28
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• 2004

Olive flounder (Paralichthys olivaceus) was exposed to waterborne iron (0.1, 0.5, 1, 5 and 10 mg/L) for 50 days. The effects of iron on blood iron status and iron binding capacity were studied. The serum iron concentration was significantly higher than in the group exposed to iron (1, 5 and 10 mg/L) in comparison to the control after 30 days of exposure to iron. A significant decrease in unsaturated iron binding capacity was found between the control and the group exposed to iron (5 and 10 mg/L, respectively) at 40 and 50 days, respectively. The total iron binding capacity of serum in the fish exposed to iron concentrations (5 and 10 mg/L) showed a significant decrease compared to that of the control at 40 days after iron exposure. Serum iron saturation values increased in the flounder exposed to iron concentration (5 and 10 mg/L) at 50 days. Our data suggest that sub-lethal exposure of waterborne iron alters the blood iron concentration and iron binding capacity, and these parameters seems to be valuable factors for screening and diagnosis of iron overload syndromes in fish.

• The Journal of Information Systems
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• v.24 no.1
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• pp.147-168
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• 2015

Why people reduce or stop using social network services(SNS), which are regarded as a mean of relationship and communication, unlike the early trend? To explain the phenomenon, this study tries to predict psychological decision making process of users from perspectives of cognitive dissonance theory. From this perspective, this study attempted an integrative approach that reflected 'User's literacy' indicating the ability of individuals to use SNS, and 'negative mass media influence' such as media reports on side effects or the bad experiences of acquaintances, along with the 3 factors used in the SNS Prior research. This study conducted an empirical analysis by surveying 256 facebook users, and the major findings are as follows:- First, Social-overload, complexity, uncertainty and negative media influence are significantly affect dissonance on the use of SNS. Second, Dissonance on the use of SNS significantly affects the behavior that possibly reduces and limits the use of SNS. In other words, the users who have experienced psychological dissonance respond passively by avoiding the use of SNS to resolve the dissonance. Third, the moderating effect of User's literacy wasn't a significant. This study presents a clue to understand psychological decision making process of use of SNS and a guideline for establishing practical strategies. In addition, it is important to note that this study contributes to expansion of theoretical discussion about usage.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.513-522
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• 2016

We propose a mechanism for monitoring load in quality of service (QoS)-enabled wireless networks and show how it can be used for network management as well as for dynamic pricing. Mobile network traffic, especially video, has grown exponentially over the last few years and it is anticipated that this trend will continue into the future. Driving factors include the availability of new affordable, smart devices, such as smart-phones and tablets, together with the expectation of high quality user experience for video as one would obtain at home. Although new technologies such as long term evolution (LTE) are expected to help satisfy this demand, the fact is that several other mechanisms will be needed to manage overload and congestion in the network. Therefore, the efficient management of the expected huge data traffic demands is critical if operators are to maintain acceptable service quality while making a profit. In the current work, we address this issue by first investigating how the network load can be accurately monitored and then we show how this load metric can then be used to provide creative pricing plans. In addition, we describe its applications to features like traffic offloading and user satisfaction tracking.

• Korean Journal of Occupational Health Nursing
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• v.28 no.3
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• pp.125-137
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• 2019

Purpose: The purpose was to investigate the literature on depression among South Korean nurses in order to identify overall trends regarding depression. Methods: Forty-five papers published between 1998 and 2017 in three Korean databases-RISS4U, DBPIA, and KISS-were analyzed. Results: Depression showed significant positive associations with job stress, burnout, intent to leave, and somatic symptoms such as fatigue and trouble sleeping. Poor work environments such as staff shortage, work overload, and shift work were also positively associated with depression. Higher job satisfaction, resilience, self-efficacy, self-esteem, and social support were negatively correlated with and acted as significant buffers against depression. Conclusion: These results indicate that healthcare policymakers must pay more attention to the management and prevention of nurses' depression. In order to effectively do so, poor work conditions, which involve long working hours, high patient-to-nurse ratios, and extreme workloads, should be improved. Simultaneously, nursing managers should implement initiatives such as counseling and competency improvement programs, and stress management to reduce and prevent depression among nurses and strengthen their positive competency. Also, further research is required to clarify the prevalence of depression in South Korean nurses, with more meta-analyses also required to identify variations in depression rates owing to various factors.

• Journal of the Korean Society of Safety
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• v.37 no.4
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• pp.1-10
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• 2022

The purposes of this study were to suggest 1) a future direction for Korea's machine tool industry and 2) how to secure the safety and reliability of emerging intelligent or automated machine tooling. The study concludes that, overseas, the machine tool industry is growing again while promoting innovation by converging with ICT. Accordingly, Korea also promotes ICT innovation to advance the machine tool industry, which is at the core of the national economy. As a result, unlike in the past, the frequency of serious injuries like entrapment accidents has recently decreased, while the proportion of collision accidents has increased. In addition, a new type of accident has become possible. Since ICT is network-based, the distinction between work and rest can become ambiguous; there is a risk of hacking, working hours and places are flexible and there are risk factors for diseases like chronic fatigue due to overload of specific personnel. As robots and automation are introduced, there is also a high probability of problems caused by physical and psychological burdens on system operators and resulting fatigue.

• Safety and Health at Work
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• v.13 no.3
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• pp.350-356
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• 2022

Background: Although sick leave is a complex phenomenon, it is believed that there is potential for prevention at the workplace. However, little is known about this potential and what specific measures should be implemented. The purpose of the study was to identify perceived reasons to take work-related sick leave and to suggest preventive measures. The study was completed before the COVID-19 pandemic emerged, and the risk factors identified may have been amplified during the pandemic. Methods: An in-depth cross-sectional survey was conducted across a randomly selected sample of hospital nurses in Norway. The national sample comprised 1,297 nurses who participated in a survey about their sick leave during the previous 6 months. An open-ended question about perceived reasons for work-related sick leave was included to gather qualitative information. Results: Among hospital nurses, 27% of the last occurring sick leave incidents were perceived to be work-related. The most common reasons were high physical workload, high work pace, sleep problems, catching a viral or bacterial infection from patients or colleagues, and low staffing. Conclusions: Over a quarter of the last occurring sick leave incidents among Norwegian hospital nurses are potentially preventable. To retain and optimize scarce hospital nursing resources, strategies to reduce work-related sick leave may provide human and financial benefits. Preventive measures may include careful monitoring of nurses' workload and pace, optimizing work schedules to reduce the risk of sleep problems, and increasing staffing to prevent stress and work overload.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.10
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• pp.2609-2626
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• 2023

The hotel industry is an example of experiential services. As consumers cannot fully evaluate the online review content and quality of their services before booking, they must rely on several online reviews to reduce their perceived risks. However, individuals face information overload owing to the explosion of online reviews. Therefore, consumer cognitive fluency is an individual's subjective experience of the difficulty in processing information. Information complexity influences the receiver's attitude, behavior, and purchase decisions. Individuals who cannot process complex information rely on the peripheral route, whereas those who can process more information prefer the central route. This study further discusses the influence of the complexity of review information on hotel ratings using online attraction review data retrieved from TripAdvisor.com. This study conducts a two-level empirical analysis to explore the factors that affect review value. First, in the Peripheral Route model, we introduce a negative binomial regression model to examine the impact of intuitive and straightforward information on hotel ratings. In the Central Route model, we use a Tobit regression model with expert reviews as moderator variables to analyze the impact of complex information on hotel ratings. According to the analysis, five-star and budget hotels have different effects on hotel ratings. These findings have immediate implications for hotel managers in terms of better identifying potentially valuable reviews.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.3
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• pp.278-285
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• 2016

The key features of maritime accidents are the change of their attributes by new risks from time to time. To prevent maritime accidents in Korea, the impacts by new risks on domestic safety environments should be identified or predicted. The purpose of this paper is to find the hazard factors by new risks on maritime safety in Korea. The meaning of new risks is the elements of accident hazard which is compiled from new or rare or unprecedented events in the worldwide maritime transportations. The problems of new risks are the lacks of optimum countermeasures to mitigate accident risks. Using the questionnaires with 152 event scenarios classified by 20 accident causes, the hazard identification and risk analysis of new risks was performed based on the Formal Safety Assessment (FSA) by IMO. A total of 22 Influence Diagrams, which is to depict the transit flows between accident causes to consequences, is used in the construction of 152 event scenarios. A total of 20 accidents causes is the same contents as the causation factors represented in Statistical Year Book for Maritime Accidents of Korean Maritime Safety Tribunals. After defining the evaluation equations to the response results of questionnaires by 46 experts, the work for risk analysis is carried out. As results from the analysis of 152 scenarios, it is known that the root cause to affect on maritime safety in Korea is the pressure of business competition and it led to the lacks of well experienced crews, the overload of vessel operations and crew's fatigue. In addition, as results from the analysis of 20 accident causes, the three accident causes are to be candidate as main issues in Korea such as the inadequate preparedness of departure, the neglecting of watch keeping in bridge and the inadequate management of ship operations. All of the results are thought to be as basic hazard factors to safety impediments. It is thus found that the optimum Risk Control Options to remove the hazard factors and to mitigate consequences required are the following two factors: business competition and crewing problems.

• Safety and Health at Work
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• v.8 no.3
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• pp.276-281
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• 2017

Background: The present study was carried out to assess the relationship between sickness absence and occupational stress, sleep quality, and amplitude and stability of circadian rhythm as well as to determine contributing factors of sickness absence. Methods: This cross sectional study was conducted on 400 randomly selected employees of an Iranian gas company. The data were collected using Pittsburgh sleep quality index, Karolinska sleepiness scale, circadian type inventory, and Osipow occupational stress questionnaires. Results: The mean age and job tenure of the participants were $33.18{\pm}5.64years$ and $6.06{\pm}4.99years$, respectively. Also, the participants had been absent from work on average 2.16 days a year. According to the results, 209 participants had no absences, 129 participants had short-term absences, and 62 participants had long-term absences. The results showed a significant relationship between short-term absenteeism and amplitude of circadian rhythm [odds ratio (OR) = 6.13], sleep quality (OR = 14.46), sleepiness (OR = 2.08), role boundary (OR = 6.45), and responsibility (OR = 5.23). Long-term absenteeism was also significantly associated with amplitude of circadian rhythm (OR = 2.42), sleep quality (OR = 21.56), sleepiness (OR = 6.44), role overload (OR = 4.84), role boundary (OR = 4.27), and responsibility (OR = 3.72). Conclusion: The results revealed that poor sleep quality, amplitude of circadian rhythm, and occupational stress were the contributing factors for sickness absence in the study population.