• 대한예방의학회:학술대회논문집
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• 대한예방의학회 1994년도 교수 연수회(환경)
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• pp.651-657
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• 1994

To assess quantitatively the association between benzene exposure and leukemia, we examined the mortality rate of a cohort with occupational exposure to benzene. Cumulative exposure for each cohort member was estimated from historical air-sampling data and, when no sampling data existed, from interpolation on the basis of existing data. The overall standardized mortality ratio (a measure of relative risk multiplied by 100) for leukemia was 337 (95 percent confidence interval, 154 to 641), and that for multiple myeloma was 409 (95 percent confidence interval, 110 to 1047). With stratification according to levels of cumulative exposure, the standardized mortality ratios for leukemia increased from 109 to 322, 1186, and 6637 with increases in cumulative benzene exposure from less than 40 parts per million-years (ppm-years), to 40 to 199, 200 to 399, and 400 or more. respectively. A cumulative benzene exposure of 400 ppm years is equivalent to a mean annual exposure of 10 ppm over a 40-year working lifetime; 10 ppm is the currently enforceable standard in the United States for occupational exposure to benzene. To examine the shape of the exposure-response relation, we performed a conditional logistic-regression analysis, in which 10 controls were matched to each cohort member with leukemia. From this model, it can be calculated that protection from benzene induced leukemia would increase exponentially with any reduction in the permissible exposure limit.

• International Journal of Computer Science & Network Security
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• 제22권4호
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• pp.147-158
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• 2022

Cloud Computing offers flexible, on demand, ubiquitous resources for cloud users. Cloud users are provided computing resources in a virtualized environment. In order to meet the growing demands for computing resources, data centres contain a large number of physical machines accommodating multiple virtual machines. However, cloud data centres cannot utilize their computing resources to their total capacity. Several policies have been proposed for improving energy proficiency and computing resource utilization in cloud data centres. Virtual machine placement is an effective method involving efficient mapping of virtual machines to physical machines. However, the availability of many physical machines accommodating multiple virtual machines in a data centre has made the virtual machine placement problem a non deterministic polynomial time hard (NP hard) problem. Metaheuristic algorithms have been widely used to solve the NP hard problems of multiple and conflicting objectives, such as the virtual machine placement problem. In this context, we presented essential concepts regarding virtual machine placement and objective functions for optimizing different parameters. This paper provides a taxonomy of metaheuristic algorithms for the virtual machine placement method. It is followed by a review of prominent research of virtual machine placement methods using meta heuristic algorithms and comparing them. Finally, this paper provides a conclusion and future research directions in virtual machine placement of cloud computing.

• 한국과학교육학회지
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• 제27권6호
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• pp.519-528
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• 2007

Although science continues to be a key subject in the education of the majority of young people throughout the world, it is becoming increasingly clear that school science is failing to win the hearts and minds of many of today's younger generation. Researchers have begun to look at ways in which the learning that takes place in museums, science centres and other informal settings can add value to science learning in schools. Four case studies are used to illustrate the potential afforded by informal contexts to research aspects of science learning. The case studies involve: the European Union PENCIL (Permanent European Resource Centre for Informal Learning) project (a network of 14 museums and science centres working with schools to enhance learning in maths and science); a large natural history museum in England; the Tate Modernart gallery in London, and the Outdoor Classroom Action Research Project which involved researchers working in school grounds, field centres and farms. The range of research questions that were asked are examined as are the methodological approaches taken and the methods used to collect and analyse data. Lessons learned from the studies about research in the informal contexts are discussed critically.

• International Journal of Knowledge Content Development & Technology
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• 제13권2호
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• pp.7-22
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• 2023

The development of rural areas is expected to be holistic covering all essential infrastructure. Community information centres (CICs) are agen- cies that should be part of the infrastructures for rural development. Unfortunately, these centres are hardly seen in rural communities in Nigeria, including Afikpo in Ebonyi State. Thus, this study was conceived to explore the perceptions of citizens towards the establishment of CICs in the locality. It adopted survey research method with questionnaire as instrument for data collection, which was self-developed and validated by experts with a pre-texted reliability index of 0.72. A total of 399 copies of the questionnaire were distributed, out of which 267 copies were properly completed, representing 67% and were used for analysis. Findings revealed that the citizens have overall positive perception to- wards establishing the CICs; they are also knowledgeable of the benefits of such centres. Furthermore, there are workable suggestions on ways of establishing, funding and managing CICs in Afikpo. In addition, about 65% of the respondents indicated interest to assist and support the funding and management of the CICs when established. However, the challenges of inadequate funding and support as well as the possible politics of where to site/locate the CICs in Afikpo, are likely impediments to the project. The study concluded that citizens have strong and positive disposition towards establishing CICs in Afikpo. The implications of such CICs for technological innovations were analysed. The study recom- mends, among others, that government should see the establishment of CICs as priority projects that would significantly contribute to the growth and development of rural communities in Nigeria; communities in Afikpo should explore self-help approach to development; and political representatives from Afikpo should take advantage of establishing CICs as constituency projects for the citizens.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권11호
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• pp.5179-5202
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• 2018

Transmission Control Protocol (TCP) is the most widely used protocol in the cloud data centers today. However, cloud data centers using TCP experience many issues as TCP was designed based on the assumption that it would primarily be used in Wide Area Networks (WANs). One of the major issues with TCP in the cloud data centers is the Incast issue. This issue arises because of the many-to-one communication pattern that commonly exists in the modern cloud data centers. In many-to-one communication pattern, multiple senders simultaneously send data to a single receiver. This causes packet loss at the switch buffer which results in TCP throughput collapse that leads to high Flow Completion Time (FCT). Recently, Software-Defined Networking (SDN) has been used by many researchers to mitigate the Incast issue. In this paper, a detailed survey of various SDN based solutions to the Incast issue is carried out. In this survey, various SDN based solutions are classified into four categories i.e. TCP Receive Window based solutions, Tuning TCP Parameters based solutions, Quick Recovery based solutions and Application Layer based solutions. All the solutions are critically evaluated in terms of their principles, advantages, and shortcomings. Another important feature of this survey is to compare various SDN based solutions with respect to different performance metrics e.g. maximum number of concurrent senders supported, calculation of delay at the controller etc. These performance metrics are important for deployment of any SDN based solution in modern cloud data centers. In addition, future research directions are also discussed in this survey that can be explored to design and develop better SDN based solutions to the Incast issue.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권2호
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• pp.312-334
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• 2023

In large-scale computing, cloud computing plays an important role by sharing globally-distributed resources. The evolution of cloud has taken place in the development of data centers and numerous servers across the globe. But the cloud information centers incur huge operational costs, consume high electricity and emit tons of dioxides. It is possible for the cloud suppliers to leverage their resources and decrease the consumption of energy through various methods such as dynamic consolidation of Virtual Machines (VMs), by keeping idle nodes in sleep mode and mistreatment of live migration. But the performance may get affected in case of harsh consolidation of VMs. So, it is a desired trait to have associate degree energy-performance exchange without compromising the quality of service while at the same time reducing the power consumption. This research article details a number of novel algorithms that dynamically consolidate the VMs in cloud information centers. The primary objective of the study is to leverage the computing resources to its best and reduce the energy consumption way behind the Service Level Agreement (SLA)drawbacks relevant to CPU load, RAM capacity and information measure. The proposed VM consolidation Algorithm (PVMCA) is contained of four algorithms: over loaded host detection algorithm, VM selection algorithm, VM placement algorithm, and under loading host detection algorithm. PVMCA is dynamic because it uses dynamic thresholds instead of static thresholds values, which makes it suggestion for real, unpredictable workloads common in cloud data centers. Also, the Algorithms are adaptive because it inevitably adjusts its behavior based on the studies of historical data of host resource utilization for any application with diverse workload patterns. Finally, the proposed algorithm is online because the algorithms are achieved run time and make an action in response to each request. The proposed algorithms' efficiency was validated through different simulations of extensive nature. The output analysis depicts the projected algorithms scaled back the energy consumption up to some considerable level besides ensuring proper SLA. On the basis of the project algorithms, the energy consumption got reduced by 22% while there was an improvement observed in SLA up to 80% compared to other benchmark algorithms.

• 한국인구학
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• 제12권1호
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• pp.74-85
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• 1989

Ascertaining the actual growth rate of the population is an issue that has generated a lot of arguments amongst various scholars in the process of determining the actual census count. As such, this has had a pronounced effect in the determination of the actual growth rates for different urban populations in the country. But the effect centres much when it comes to accurately determining the major components or the factors contributing to the rapid growth of urban populations. The problem of rapid population growth centres much on its effects on the available basic social services and amenities provided for the people in these areas. Factors such as levels of medical knowledge and services, nutrition, quantity and quality of housing etc. to some extent influence the quality and duration of lives of the people. As such, their importance cannot be overemphasized when dealing with the issue of population growth. The study aims to examine the rate of population growth in the Federal Capital City, Abuja with respect to the available public provision of basic social services among other objectives. The findings from the data obtained from the Population Survey conducted in the city in 1985 show that the health care facilities available in the capital city are grossly inadequate to serve the entire inhabitants of the city. Moreso, the volume of in-migration into the city also compounds the health problems facing the city. The conclusion is that there is need for more resources to be allocated to the health sector to guarantee adequate and functional health care services in the city.

• 시큐리티연구
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• 제23호
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• pp.41-63
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• 2010

이 연구는 대형 쇼핑몰 보안서비스 품질이 고객의 안전욕구의 충족 및 이용만족에 대한 관계를 규명하기 위해 2010년 2월 용인시 소재 대형쇼핑몰 2곳과 분당소재 대형쇼핑몰 2곳, 수원 소재 쇼핑몰 1곳, 총 5곳을 이용하는 일반시민을 대상으로 표집대상을 선정한 후 유의표집법(purposive sampling method)을 이용하여 500명의 표본을 추출하였으나, 연구에 사용된 사례 수는 총 485명이다. 이 연구는 SPSS WIN 16.0을 이용하여 요인분석, 신뢰도 분석, 다중회귀분석, 경로분석을 실시하였다. 그에 따른 결론은 첫째, 표집대상인 일반인들이 인식하는 대형 쇼핑센터의 시설보안서비스품질과 보안요원의 서비스 품질은 심리적 안전욕구와 범죄예방욕구에 매우 유의한 영향을 미치는 것으로 밝혀졌다. 둘째, 시설보안 서비스품질과 보안요원 서비스품질은 보안서비스만족과 경비시스템 운용만족에 매우 유의한 영향을 미치는 것으로 나타났으며, 보안요원의 전문성은 보안서비스만족과 경비시스템 운용만족에 매우 유의한 영향을 미치는 것으로 밝혀졌다. 셋째, 심리적 안전욕구와 범죄예방욕구는 보안서비스만족과 경비시스템 운용만족에 매우 유의한 영향을 미치는 것으로 나타났으며, 보안서비스만족과 경비시스템 운용만족에 매우 유의한 영향을 미치는 것으로 밝혀졌다. 넷째, 시설보안서비스품질 보안요원서비스품질은 심리적 안전욕구와 범죄예방안전욕구에 유의한 영향을 미치는 것으로 나타났다. 따라서 시설보안서비스품질, 보안요원서비스품질, 보안요원의 전문성은 고객이용만족에 직접적인 영향을 미치고, 시설보안서비스품질, 보안요원서비스품질은 심리적 안전욕구와 범죄 예방안전욕구를 통하여 고객이용만족에 간접적인 영향을 미치는 것으로 나타났다. 즉, 대형마트의 보안서비스 품질은 고객의 안전욕구충족과 시설물에 대한 이용만족도에 영향을 미친다.

• Communications for Statistical Applications and Methods
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• 제29권2호
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• pp.225-238
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• 2022

In this paper, we propose a clustering method for advanced metering infrastructure (AMI) data in Korea. As AMI data presents non-stationarity, we consider time-dependent frequency domain principal components analysis, which is a proper method for locally stationary time series data. We develop a new clustering method based on time-varying eigenvectors, and our method provides a meaningful result that is different from the clustering results obtained by employing conventional methods, such as K-means and K-centres functional clustering. Simulation study demonstrates the superiority of the proposed approach. We further apply the clustering results to the evaluation of the electricity price system in South Korea, and validate the reform of the progressive electricity tariff system.

• Journal of the Korean Data and Information Science Society
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• 제25권3호
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• pp.655-663
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• 2014

This study aimed to investigate the prevalence of depression and suicidal ideation in community-dwelling older adults in Korea, as well as identify factors associated with their occurrence, including cognitive impairment. A cross-sectional study of 484 residents was conducted at a senior centre utilising the PHQ-9K and K-MMSE. Demographic data were also collected for analysis. Of the respondents, 38.1% had symptoms of mild to severe depression. Further, 16.7% reported having suicidal ideation, with 5% of respondents having thoughts of suicide every day. The majority of participants had 'normal' scores on the K-MMSE (88.0%), though significant differences were observed in PHQ-9K scores between cognitive-acceptable and cognitive-impaired groups. Depressive symptoms and suicidal ideation were very prevalent in community-dwelling older adults in Korea. This study indicates the need for the development of community-based mental health programs tailored to older adults, and demonstrates the viability of promoting early detection of depressive symptoms through senior centres.