• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1663-1668
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• 2017

A BLDC motor with higher number of phases has several advantages, compared to the conventional three-phase BLDC motors. It can reduce the commutation torque ripple and the iron loss without increasing the voltage per phase and increase the reliability and power density. Higher number of phases increase the torque-per-ampere ratio for the same machine volume and output power by widening the electrical conduction period. In this paper, the proposed seven-phase BLDC motor drive system is made into several functional modular blocks, so that it can be easily extended to other ac motor applications: back-EMF block, hysteresis current control block, pwm inverter block, phase current block, and speed/torque control block. Also in a system of BLDC motor drive, the PI controller has been widely used in the speed controller because of the simple implementation. To obtain a good speed response in a general drive system using the PI controller, the high bandwidth of a controller is established. therefore, in this paper, a Fuzzy controller is applied to the 7-phase BLDC motor drive system in order to improve the speed control performance. The Fuzzy controller is compared with a conventional PI controller through the experiment with respect to speed dynamic responses. These experimental results show that the Fuzzy controller of the 7-phase BLDC motor drive system is superior over the conventional PI controller. The algorithm using the Fuzzy controller can improve a comfortable ride in the field of high performance 7-phase BLDC motor drive applications.

• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.803-816
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• 2014

Defense-in-depth is a fundamental safety principle for the design and operation of nuclear power plants. Despite its general appeal, defense-in-depth is not without its drawbacks, which include its potential for concealing the occurrence of hazardous states in a system, and more generally rendering the latter more opaque for its operators and managers, thus resulting in safety blind spots. This in turn translates into a shrinking of the time window available for operators to identify an unfolding hazardous condition or situation and intervene to abate it. To prevent this drawback from materializing, we propose in this work a novel safety principle termed "observability-in-depth". We characterize it as the set of provisions technical, operational, and organizational designed to enable the monitoring and identification of emerging hazardous conditions and accident pathogens in real-time and over different time-scales. Observability-in-depth also requires the monitoring of conditions of all safety barriers that implement defense-in-depth; and in so doing it supports sensemaking of identified hazardous conditions, and the understanding of potential accident sequences that might follow (how they can propagate). Observability-in-depth is thus an information-centric principle, and its importance in accident prevention is in the value of the information it provides and actions or safety interventions it spurs. We examine several "event reports" from the U.S. Nuclear Regulatory Commission database, which illustrate specific instances of violation of the observability-in-depth safety principle and the consequences that followed (e.g., unmonitored releases and loss of containments). We also revisit the Three Mile Island accident in light of the proposed principle, and identify causes and consequences of the lack of observability-in-depth related to this accident sequence. We illustrate both the benefits of adopting the observability-in-depth safety principle and the adverse consequences when this principle is violated or not implemented. This work constitutes a first step in the development of the observability-in-depth safety principle, and we hope this effort invites other researchers and safety professionals to further explore and develop this principle and its implementation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.5
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• pp.315-323
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• 2005

The recent development of embodiment technology of the medical images makes most medical institutions introduce PACS in haste. However, while many older HIS and PACS systems are not yet capable of some of the integration, several new systems are moving rapidly in that direction. Typical PACS system architecture begins with the HIS since this is where the correct patient demographic information and in many cases the orders originate. So, PACS developed convenience of users and to satisfy user's demand because of financial limitations and administrator-oriented considerations in the process of development. Therefore, we have developed a CDA (Clinical Document Architecture) based PACS with HIS, by which we can search and refer to the patient's medical images and information with few restrictions of time and space for diagnosis and treatment. Target model of this research limited to 135 of hospital have 200 beds. We'll make more effort to develop the application which insures the better quality and information of medical images. Medical Image History manages the patient's image files and various medical informations like film chart in connection with time. This trial will contribute to the reduction of the financial loss caused by unnecessary devices and improve the quality in the medical services. The demand on the development of the program which refers to the medical data quickly and keeps them stable will be continued by the medical institute. This will satisfy the client's demand and improve the service to the patients in that the program will be modified from the standpoint of the users.

• Journal of KIISE:Computing Practices and Letters
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• v.12 no.4
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• pp.254-263
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• 2006

Ontology-based context models are widely used in ubiquitous computing environment because they have advantages in the acquisition of conceptual context through inferencing, context sharing, and context reusing. Among the benefits, inferencing enables context-aware applications to use conceptual contexts which cannot be acquired by sensors. However, inferencing causes processing delay and thus becomes the major obstacle to the implementation of context-aware applications. The delay becomes longer as the amount of contexts increases. In this paper, we propose a context pre-fetching method to reduce the size of contexts to be processed in a working memory in attempt to speed up inferencing. For this, we extend the query-tree method to identify contexts relevant to the queries of a context-aware application. Maintaining the pre-fetched contexts optimal in a working memory, the processing delay of inference reduces without the loss of the benefits of ontology-based context model. We apply the proposed scheme to our ubiquitous computing middleware, Active Surroundings, and demonstrate the performance enhancement by experiments.

• The Journal of Korean Association of Computer Education
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• v.7 no.4
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• pp.93-102
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• 2004

For children with hearing impairment, unlike the children without hearing impairment who can reconstruct their languages through the process of hearing and uttering, the inherent mechanism for language acquisition do not operate due to the loss of hearing ability. Therefore, to help hearing-impaired children develop their language ability, web-based language learning system should be constructed depending on the special qualities which the children possess in language learning process. When the system is being designed, it is necessary that words or expressions describing actions or situations be animated and that active situation-based language learning system be constructed to help them develop their power of observation. Moreover, the system needs to be developed through the use of alternative thinking strategy, antonyms, and contrastive words, and emphasis on facial expressions. This paper presents web-based language learning system which is suitable for hearing-impaired children in the way to reduce the grammatical errors they make and to improve their language learning.

• Journal of Digital Convergence
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• v.14 no.9
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• pp.317-323
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• 2016

Big Data is now seen as a major asset in the company's competitiveness, its influence in the future is expected to grow. Companies that recognize the importance are already actively engaged with Big Data in product development and marketing, which are increasingly applied across sectors of society, including politics, sports. However, lack of knowledge of the system implementation and high costs are still a big obstacles to the introduction of Big Data and systems. It is an objective in this study to build a Big Data system, which is based on open source Hadoop and Hive among Big Data systems, utilizing POS sales data of small and medium-sized offline markets. This approach of convergence is expected to improve existing sales systems that have been simply focusing on profit and loss analysis. It will also be able to use it as the basis for the decisions of the executive to enable prediction of the consumption patterns of customer preference and demand in advance.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.4 s.316
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• pp.1-9
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• 2007

An embedded system is implemented in this work by removing PCMCIA dedicate controller chip from ARM processor based embedded Linux system. In this paper, we propose PCMCIA interface architecture by using Ad hoc methods for wireless network. The proposed system is developed based on S3C2410A processor and it is interfaced with PCMCIA socket by using combinational digital logic circuits. It is interesting to observe that Ad hoc interface provides $97.9%{\sim}102.49%$ performance when compared with dedicate controller systems. The results indicate that the proposed method simplifies the system without loss of performance.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.6
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• pp.695-701
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• 2014

Blackhole attacks having a unauthorized change of routing data will cause critical effects for transmission performance. The transmission performance will be improved to the a certain level by using or having IDS(Intrusion Detection System)/IPS(Intrusion Prevention System) as countermeasures to blackhole attacks. In this papar, the effects of IDS to ene-to-end performance of packet aggregation transmission are analyzed on MANET(Mobile Ad-hoc Network) with IDS under blackhole attacks. MANET simulator based on NS-2 is used to analyze performance parameters as MOS, connection ratio, delay and packet loss rate as standard performance parameters, an another performance factor which is suggested in this paper. VoIP(Voice over Internet Protocol) traffics, one of voice services, is used for performance analysis. A suggestion for IDS implementation on MANET with packet aggregations under blackhole is shown as one of results.

• Korean Journal of Social Welfare
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• v.69 no.3
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• pp.9-33
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• 2017

This study estimated the socioeconomic costs of child poverty. Based on previous studies, the present study organized component categories for direct and indirect costs of child poverty, and estimated the cost of each category in 2015 through the collection of existing data and Delphi survey techniques among experts. The total socioeconomic costs of child poverty were compared to Korea's GDP. The results of this study were as follows. First, the socioeconomic costs of child poverty in Korea in 2015 ranged from 55 trillion KW(3.5% of GDP) to 99 trillion KW(6.5% of GDP). Second, the indirect socioeconomic costs of child poverty are much higher than the direct costs. Third, among the total cost categories, costs related to productivity loss and unemployment accounted for the largest portion of both the socioeconomic costs based upon absolute poverty and relative poverty. Crime costs are the second largest. Based on these results, we discussed the importance of early intervention for children in poverty; implementation of two-generation program that intervenes simultaneously with parents and children; and long-term, continuous and integrated intervention for high-risk groups such as poor children.

• Korean Institute of Interior Design Journal
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• v.17 no.2
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• pp.111-121
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• 2008

In recent years, Korean population aged 65 and over has grown faster(7.2% in 2000, 14.4% projected in 2018 and 20.0% in 2026) than the other age groups and average life expectancy has increased from 65.8 years in 1980 to 75.9 years in 2000. The Aging Simulation Center(ASC) was built for people to give educational chance for further understanding of the elderly and the environment for the aged. People are able to recognize the changes including hearing loss, vision changes, and changes in the ability to touch and move after experiencing the simulated daily life of older persons. In general, ASC is composed of residential setting area and exhibition area of daily commodities for the elderly and care person. Currently, there are four ASCs in Korea. The purpose of this study is to evaluate the characteristics of space design and design elements of ASCs and to suggest design implementation for better residential environment for the elderly. For the research purpose, design characteristics such as floor plans and spatial design elements of three ASCs were analyzed and compared. As a whole, space design of three ASCs was almost same without distinguished characteristics. The major finding of this study indicates that the ASC is considerably helpful environment to understand aging. However, some of design elements such as lighting should be supplemented for safety issue. It is recommended for future design of ASC to include exterior space including outdoor stairs, paths and roads and so on. In addition, reception and preparation area should be arranged with universally designed furniture.