• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.87-90
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• 2007

Many moderncommunication technologies are developing based on internet protocol (IP) and there is many work to archive seamless mobility service. IETF proposed MIPv6 protocol that uses IPv6 to provide mobility services to mobile node however it has some limits like sending and receiving too many messages during binding update (BU) procedure. So, now a day it makes HMIPv6(Hierarchical Mobile IPv6). HMIPv6 solves overhead and transmission delay problem in MAP(Mobile Anchor Pointer), but it can't accomplish effectively Macro handover between MAPs. This paper introduces use of FMIPv6 and Selective handover mechanisms based on hierarchical MAP information in HMIPv6 for improvement of handover efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12A
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• pp.1113-1121
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• 2010

The Vehicle Safety Communications (VSC) is one of VANET applications for preventing vehicle accidents, and it utilizes vehicle-to-vehicle communication to exchange emergency messages. To propagate such messages in VSC, several schemes based on selective flooding have been proposed. Their common idea is that an emergency message is relayed by one of vehicles receiving the message. However, the schemes do not consider the transmission errors and duplications of an emergency event. In the schemes, if there are transmission errors and a vehicle detects a hazard, there may be vehicles which fail to receive an emergency message. If k vehicles detect a hazard, k emergency messages are created and propagated. The duplications of an event increase reliability of the message delivery but decrease efficiency. In this paper, we propose an emergency message delivery scheme which is efficient and robust to transmission errors. Our proposed scheme utilizes clustering for massage aggregation and retransmissions in a cluster. It also uses an acknowledgment mechanism for reliable inter-cluster communication. Our simulation results show that the proposed scheme outperforms Least Common Neighbor Flooding which is one of the selective flooding schemes.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2007.02a
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• pp.87-96
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• 2007

Ubiquitous is a Latin-derived word meaning "to exist at any time and place" like water or air. In computing, the word "ubiquitous" indicates an environment in which users have access to networks without any limitation regarding computer networks or places. Important issues in building Ubiquitous Korea (U-Korea) are the social problems appearing with a rapid increase in the old age population. Nowadays, with the rise of the nuclear family, the increase in the number of elderly people living alone, and the change in the status of women, both wives and husbands are employed outside the home, and the relatives who would be responsible for supporting the elderly sometimes are on long or short business trips, and it happens that old people can't be looked after. Therefore the government developed a wireless paging system for the sick, disabled, old and weak so that when an emergency happens, by just simply dialing 119, an emergency aid center could take prompt action. However, the present wireless paging systems composing the under-layer of the emergency aid information system have some problems, such as, a lack of reliability, problems among terminals, mobile transmitters and receiving terminals, the users' refusal to admit the need for the system and poor operational skills, administrators' perfunctory management and checks, etc. On account of these problems, the system efficiency has degraded and therefore a system upgrade is necessary. In this paper, we attempt to evaluate the newly implemented SAFE119 system, a new wireless paging system seeking to correct the problems of the current system.

• Journal of Powder Materials
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• v.25 no.2
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• pp.120-125
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• 2018

Boron nitride nanotubes (BNNTs) are receiving great attention because of their unusual material properties, such as high thermal conductivity, mechanical strength, and electrical resistance. However, high-throughput and high-efficiency synthesis of BNNTs has been hindered due to the high boiling point of boron (${\sim}4000^{\circ}C$) and weak interaction between boron and nitrogen. Although, hydrogen-catalyzed plasma synthesis has shown potential for scalable synthesis of BNNTs, the direct use of $H_2$ gas as a precursor material is not strongly recommended, as it is extremely flammable. In the present study, BNNTs have been synthesized using radio-frequency inductively coupled thermal plasma (RF-ITP) catalyzed by solid-state ammonium chloride ($NH_4Cl$), a safe catalyst materials for BNNT synthesis. Similar to BNNTs synthesized from h-BN (hexagonal boron nitride) + $H_2$, successful fabrication of BNNTs synthesized from $h-BN+NH_4Cl$ is confirmed by their sheet-like properties, FE-SEM images, and XRD analysis. In addition, improved dispersion properties in aqueous solution are found in BNNTs synthesized from $h-BN+NH_4Cl$.

• Health Policy and Management
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• v.11 no.4
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• pp.54-69
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• 2001

This study was conducted to assess factors associated with the degree of performance of qualify improvement(QI) activities. A mailed questionnaire survey was conducted between September 15 and October 30, 2000, with the staffs being charge of QI at each of the hospitals with 400 beds or greater. Of the 108 hospitals eligible for inclusion in our study, 79 participated, yielding a response rate of 73.1%. After excluding 12 hospitals that did not perform any QI activities, 117 responses from 67 hospitals were used for the analysis. Using the Malcolm Baldrige National Quality Award Criteria(MBNQAC), perceived performance of QI was measured in terms of the improvement of the quality of clinical practice, clinical supporting department, administrative procedure of receiving care, customer satisfaction, efficiency and standardization of work process. Factors evaluated for the association were the extent of QI implementation, compliance to 5 QI principles, participation of hospital CEOs, budget allocation, history of QI, and bed size. Path analysis was performed to assess the relationship between QI performance and these factors. Major findings of this study are as follows. Hospitals showing higher degree of QI implementation (path coefficient=0.5967, p<0.001)) and better compliance with the basic principes of QI(0.5736, p<0.05) tended to achieve better performance. Path analysis results showed that interest and participation of hospital CEOs(0.1954, p<0.05) and compliance with the basic principes of QI(0.4028, p<0.0001) indirectly affected the outcomes of QI by influencing the intermediate variable of the level of QI implementation. This study results suggest that having employees have a good orientation of the basic concept and principes of QI through relevant training be the most important requirement to achieve better outcomes from QI activities. In addition, to educate leaders of hospitals the need of active implementation of QI is important to encourage their participation and draw strong support for QI programs.

• Korean Journal of Materials Research
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• v.23 no.3
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• pp.183-189
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• 2013

$Cu_2ZnSn(S,Se)_4$ material is receiving an increased amount of attention for solar cell applications as an absorber layer because it consists of inexpensive and abundant materials (Zn and Sn) instead of the expensive and rare materials (In and Ga) in $Cu(In,Ga)Se_2$ solar cells. We were able to achieve a cell conversion efficiency to 4.7% by the selenization of a stacked metal precursor with the Cu/(Zn + Sn)/Mo/glass structure. However, the selenization of the metal precursor results in large voids at the absorber/Mo interface because metals diffuse out through the top CZTSe layer. To avoid the voids at the absorber/Mo interface, binary selenide compounds of ZnSe and $SnSe_2$ were employed as a precursor instead of Zn and Sn metals. It was found that the precursor with Cu/$SnSe_2$/ZnSe stack provided a uniform film with larger grains compared to that with $Cu_2Se/SnSe_2$/ZnSe stack. Also, voids were not observed at the $Cu_2ZnSnSe_4$/Mo interface. A severe loss of Sn was observed after a high-temperature annealing process, suggesting that selenization in this case should be performed in a closed system with a uniform temperature in a $SnSe_2$ environment. However, in the experiments, Cu top-layer stack had more of an effect on reducing Sn loss compared to $Cu_2Se$ top-layer stack.

• Journal of Digital Convergence
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• v.10 no.4
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• pp.119-128
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• 2012

The changing paradigm due to the emergence of smart phone and the rapid spread of internet-based social media usage is considerably impacting the politics, economy, society, culture and many other fields. As the new communication tools, social media is receiving spotlight for its advantage of low cost but high efficiency. With the accelerating of the fulfillment of knowledge-based economy, country image is more and more recognized as the core competitiveness of a country. Therefore, it is very important to grasp the factors that affect country image. In this study, a literature review on the factors provided was conducted and affecting factors on country image were analyzed. In addition, on the assumption that social media, which are widely used on current days, have meaningful effects on country image and purchasing intention, features of social media are added as variables and analyzed. The results of analysis show that social media has meaningful effects on the country image and purchasing intention.

• The Korean Journal of Food And Nutrition
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• v.28 no.4
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• pp.717-727
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• 2015

Although the NutriPlus program has shown considerable evidence of enhancing users' nutritional status, the budget does not cover all eligible mothers and children. This study aimed to conduct a cost-benefit analysis of the NutriPlus program to assess its economic efficiency. 53 families with 79 users in the NutriPlus program at Daejeon Dong-gu Health Center participated in this study with informed consent. The costs and benefits were estimated from both the administrator's and users' perspectives. We converted the time cost into Korean currency based on the minimum wage in 2014. The value of nutrition education and service (B2), estimated by contingency valuation method (CVM), was counted as an economic benefit. 6 families (11.3%) were recipients of national medical care and 22 families (41.5%) paid 10% of the food package cost by themselves. The total cost was \7,450,167 and the total benefit was \12,402,239. The budget for the health center (C1+C2+C3+C4) was \5,984,381 a month. Time and transportation cost for receiving nutrition education (C6) differed significantly according to the economic status of families. Household food consumption increase (C4-B4) was 40,379 in the poverty group, which was four times more than in the other groups. The net benefit (B-C) was \4,852,172 and the B/C ratio was 1.66. Therefore, the NutriPlus program is beneficial in the economic aspect as well as in the nutritional aspect. If the enhancement of nutritional status was also considered, the total benefit would be even higher. These results confirm the legitimacy of a secure budget for the NutriPlus program. And we suggest expanding its budget to cover more eligible individuals to improve people's health and welfare.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.525-530
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• 2008

Construction industry is based on receiving an order. So, it has a special feature that market and manufacture activity is formed by a user. For this reason, it has a great influence on other industry compare construction industry with other industry. Specially when build public structure as infrastructure, importance of owner is emphasized then private construction because the primary role of owner have a great effect on national finance. Inspite of that, the importance of a faculty and role of an owner and an ordering organ, it is weak that a study about objective and meaningful evaluation of the specially, common standard and ability of public ordering organ as a major user of domestic construction industry. So, this study define the evaluation sphere and an element of an ordering ability for develop an ordering ability evaluation guide which can evaluate objective ability of an ordering organ. Apply its evaluation sphere and element, judge a standard of an owner, thought the judgement, it can judge accurately of short ability and if it can make future oriented strategy, it can elevate the efficiency of an owner organization management.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.3
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• pp.69-74
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• 2009

A novel protocol is proposed to achieve sub-carner-based rate adaptation in OFDM-based wireless systems. The protocol requires the addition of one OFDM symbol to the Clear-to-Send (CTS) packet defined in the IEEE 802.11 standard_ When receiving a Ready-To-Send (RTS) packet, the receiver determines the number of bits to be allocated in each sub-carrier through channel estimation. This decision is delivered to the sender using an additional OFDM symbol. That is, bit-allocation over sub-carriers is achieved using only one additional OFDM symbol. The protocol also provides an error recovery process to synchronize the bit-allocation information between the sender and receiver. The protocol enhances the channel efficiency in spite of the overhead of one additional OFDM symbol.