• 전기학회논문지
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• 제59권2호
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• pp.285-290
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• 2010

We investigate the outage probability in terms of QoS (quality of service) in indoor PLC network. We consider various kinds of appliances for realistic indoor PLC network. For estimation of the outage probability, we calculate the time-varying channel responses considering the loading conditions based on regular human activities and include the additive noise. We calculate the outage probability for each terminal and investigate relationship between the outage probability and the channel length, and transmit powers. Our results suggest that the outage probability is increased when the channel length becomes longer because more appliances affect the amount of reduced channel capacity and is not improved distinctly for very high and low outage threshold by increasing the transmit power. However, we can see outage probability improvement for 30% outage threshold case by increasing the transmit power.

• 한국산업융합학회 논문집
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• 제26권6_2호
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• pp.1063-1071
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• 2023

Unmanned aerial vehicles (UAVs, drones) are becoming increasingly useful in a variety of fields. Advances in UAV and camera technology have made it possible to equip them with ultra-high resolution sensors and capture images at low altitudes, which has improved the reliability and classification accuracy of object identification on the ground. The distinctive contribution of this study is the derivation of sensor-specific performance metrics (GRD/GSD), which shows that as the GSD increases with altitude, the GRD value also increases. In this study, we identified the characteristics of various onboard sensors and analysed the image quality (discrimination resolution) of aerial photography results using UAVs, and calculated the shooting conditions to obtain the discrimination resolution required for reading ground objects.

• 대한영양사협회학술지
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• 제26권3호
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• pp.196-207
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• 2020

This study was undertaken to provide basic data for revitalizing the school meal support centers and improving school meals, by analyzing the purchase conditions and satisfaction of food according to an adoption of a school meal service support center. Comparing the purchasing efficiency, convenience to purchase, and higher overall satisfaction was achieved when a school meal service support center was adopted by the local government, as compared to non-adopted school meal service support centers. Therefore, it is considered that the adaption of a school meal service support center is urgently required by non-adoption local governments. Moreover, the stability of food material supplies was also higher in the adopted rather than the non-adopted centers. Satisfaction with the quality of food ingredients was also found to be significantly higher in the adopted centers. These results indicate that if the local government adopts and introduces the school meal support center, inconsistencies observed in the return and exchange processes experienced by the non-adopted centers can be resolved, and food quality satisfaction can be improved. We, therefore, propose the necessity to implement a system for determining reasonable pricing by establishing systematic cooperation among schools, manufacturing entities (suppliers), and the School Meal Service Support Center.

• 한국시뮬레이션학회논문지
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• 제15권2호
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• pp.41-50
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• 2006

휴대인터넷 서비스가 조만간 제공될 예정이다 하지만 아직까지 다양한 서비스 유형의 패킷에 대한 스케줄링 방법은 명확하게 결정되지 못하고 있다. 한정된 자원인 무선 채널의 효율을 높이려면 서로 다른 QoS를 요구하는 다양한 서비스 유형에 대한 패킷 스케줄링이 필요하다. 본 연구에서는 보다 많은 호를 수용하고 채널 효율을 향상시키기 위하여 개선된 상향링크 스케줄링 방법을 제안한다. 제안하는 방법은 채널의 전송률과 효용을 높이기 위하여 단말의 셀내 위치에 따른 채널 상태를 반영한다. 시뮬레이션 결과에 따르면 제안하는 방법이 상향링크의 수율과 용량 측면에서 좋은 성능을 보임을 알 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권12호
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• pp.5917-5935
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• 2018

Adaptive Multi-Rate Codec is one of the codecs which is used for making voice calls. It helps to connect people who are scattered in various geographical areas. It adjusts its bit-rate according to the user's channel conditions. It plays a vital role in providing an improved speech quality of voice connection in Long Term Evolution (LTE). There are some constraints which need to be addressed in providing this service profitably. Quality of Service (QoS) is the dominant mechanism which determines the quality of the speech in communication. On several occasions, number of users are trying to access the same channel simultaneously by standing in a particular region for a longer period of time. It refers to Multi-user channel sharing problem which leads to resource loss very often. The main aim of this paper is to develop a novel RSA - QoS scheduling algorithm for reducing the Resource Loss Ratio. Eventually, it increases the throughput.The simulation result shows that the RSA - QoS increases the number of users for accessing the resources better than the existing algorithms in terms of resource loss and throughput. Ultimately, it enhances the QoS in Mobile Networks.

• 기록학연구
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• 제50호
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• pp.351-388
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• 2016

정부 3.0의 원문정보공개서비스의 대상인 전자기록물이 기록학적인 관점에서 체계적이고 효율적으로 활용되고 있는지를 파악하고자 공공기관의 정보공개담당자들을 대상으로 관련 설문을 조사 분석하였다. 이를 위해 InterPARES의 전자기록물 구성요소에 대하여 기록물의 4대 원칙인 진본성, 신뢰성, 무결성, 이용가능성을 지표로 하는 전자기록물의 구성요소를 분석하였다. 이러한 분석을 통하여 원문정보공개서비스에서 전자기록구성요소에 따라 관리하며 향상시킬 수 있는 요인을 찾아 개선해야 할 점을 밝혔다. 그 결과를 바탕으로 원문정보공개서비스 시 전자기록물의 요소들의 개선과 기능보완, 특성에 맞는 서비스 등을 제시하였다.

• 농업과학연구
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• 제49권2호
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• pp.367-377
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• 2022

The purpose of this study was to analyze the deterioration of trail conditions and to obtain information for desirable maintenance and restoration of a trail in Deogyusan National Park. The physical characteristics of a trail were surveyed at a total of 412 sites over 79.8 km length. The average trail degree and width were found to be 14.31° and 1.60 m, respectively, while the average bare trail width was 1.40 m and the average maxim trail depth was 5.66 cm. Major deterioration types of trail were trail deepening (36.6%), rock exposure (33.9%), and root exposure (12.5%) in order of frequency. Deterioration classes of the trail were 0.626 km (0.8%), 3.110 km (3.9%) and 8.935 km (11.2%) for heavily, moderately, and lightly deteriorated, respectively, with a deterioration rate of 12.671 km (15.9%). Compared to other national parks, the ratio damaged trail to the total trail was 15.9%, which is slightly higher than other, including Jirisan National Park 9.6% (2019), Bukhansan National Park 13.6% (2019), Sokrisan National Park 11.7% (2019), Chiaksan National Park 12.3% (2015), and Woraksan National Park 10.5% (2015). The section of trail in Deokyusan National Park where the damage grade is analyzed as "Heavy" should therefore be restored in consideration of the field conditions. In particular, the damage status of the trail is expected to be greatly improved when the trail surface maintenance level is restored.

• Tribology and Lubricants
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• 제31권1호
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• pp.1-5
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• 2015

In this study, we apply an ultrasonic nanocrystal surface modification (UNSM) technique to radial journal bearings (JBs) and disks made of SUJ2 and SCM440, respectively. We investigate frictional properties of untreated and UNSM-treated specimens using a ball-on-disk tester. We construct the Stribeck curve at the boundary, under mixed and full hydrodynamic lubrication conditions for the specimens using friction data obtained from JB tests. The friction at the boundary lubrication condition and the transition period to mixed lubrication condition on the UNSM-treated specimens is reduced, which improves the service life of JBs. The major effects of this reduction in the three lubrication regimes can be explained in the terms of improved mechanical properties and the presence of micro dimples. Moreover, we estimate the friction and fatigue properties of SCM440 specimens using a ball-on-disk specimen under dry and oil-lubricated conditions. Friction test results reveal that the UNSM-treated specimens show lower friction coefficient than the untreated specimens under both dry and oil-lubricated conditions. We evaluate the fatigue properties of SCM440 specimens by calculating the Hertzian stress with respect to the failure cycles. Fatigue tests results also reveal that the UNSM-treated specimens possess a longer fatigue life than the untreated specimens. The improved properties are effective in increasing the energy efficiency of bearings.

• 대한간호학회지
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• 제38권4호
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• pp.612-619
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• 2008

Purpose: The purpose of this study was to examine health problems and to estimate economic impact based on health problems of workers. Methods: The subjects of this study consisted of 301 workers who received a group occupational health service. Data was collected from February 1 to March 30, 2006. The questionnaire contained questions based on general characteristics and the Stanford Presenteeism Scale. Data was analyzed with descriptive statistics, t-test using SPSS program. Results: The primary health conditions as reported by workers were ranked in order as stomach or bowel disorders, back or neck disorders, or liver function disorders. The reason of absenteeism per worker was ranked in order as asthma, or a breathing disorder. The reason of presenteeism was ranked in order as asthma, insomnia or a sleep disorder. The cost of the total economic impact on the workplace in this study was 8,851,838 won. The cost of absenteeism per worker was 8,390 won. The cost of presenteeism per worker was 941,732 won. Conclusion: Presenteeism had a strong correlation to health conditions of the workers. Therefore, improving the work conditions of the workers is very important. If employers improve the health condition of workers, they will benefit from improved productivity in their business.

• 한국산업보건학회지
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• 제33권4호
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• pp.447-454
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• 2023

Objective: This study aims to investigate the impact of changes in working conditions on job-related stress and musculoskeletal disorders using the results of seven surveys conducted at a single workplace from 2004 to 2022 regarding factors hazardous to the musculoskeletal system. Additionally, the study aims to propose alternative methods of investigating factors hazardous to the musculoskeletal system. Methods: A car parts manufacturing plant where the same survey was taken seven times from 2004 to 2022 was selected and the survey data was analyzed. The main contents of the survey were weekly working hours, Borg's scale, work intensity, job-related stress, and the prevalence of musculoskeletal symptoms. The statistical analysis was performed using SAS (version 9.4). Results: The results of this study are as follows. Firstly, changes in working conditions have an impact on job-related stress. Secondly, changes in working conditions have an impact on work intensity indicators. Thirdly, changes in working conditions have an impact on the prevalence of musculoskeletal symptoms. Fourthly, even with an increase in age and length of service, job-related stress and musculoskeletal symptoms were alleviated when working conditions were improved. Conclusions: In order for measures to reduce musculoskeletal disorders to be successful, working conditions must not deteriorate, and it is necessary to demand revisions to regulations, etc. to reflect these points in the investigation of hazardous factors to the musculoskeletal system.