• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.707-715
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• 2007

The vulnerability of concrete to its environment is significantly dependent on the fact that concrete is a porous material. For well-consolidated and well-cured concrete, its service life is a very long and an entrance of aggressive substance might be only pores. However, for cracked concrete, cracks should be preferential channel for the penetration of aggressive substance such as chloride ions. The effect of crack on chloride penetration depends on its size for example, crack width and crack depth. The purpose of this study is examining the effect of crack width and crack depth on chloride penetration. In order to visualize chloride penetration via cracks, RCM (rapid chloride migration) testing is accomplished. Crack width is examined using an optical microscope and CMOD value is used to estimate average crack width. From the examination on the trend of chloride diffusion coefficients of concrete specimens with various crack widths, a critical crack width and a critical crack depth are found out.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1113-1119
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• 2013

In this letter, a new approach is proposed for the design of a multi antenna for MIMO wireless devices. The proposed antenna covers various LTE(Long Term Evolution) service bands: band 17(704~746 MHz), band 13(746~787 MHz), band 5(824~894 MHz), and band 8(880~960 MHz). The proposed main antenna consists of a conventional monopole antenna with an inverted L-shaped slit for wideband operation. The proposed the LTE sub antenna is based on a switch loaded loop antenna structure, with a resonance frequency that can be controlled by capacitance of a logic circuit. The tuning technique for the LTE Rx antenna uses a RF MEMS(Micro-Electro mechanical system) to match the impedances to realize the bands of interest. Because the two proposed antennas are polarized orthogonally to each other, the ECC(Envelope Correlation Coefficient) characteristic between two antennas was measured to be very low (below 0.06) with an isolation characteristic below -20 dB between the two antennas in the operating overall LTE bands. The proposed antenna is particularly attractive for mobile devices that integrate LTE multiple systems.

• Korean Journal of Social Welfare
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• v.66 no.3
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• pp.133-158
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• 2014

Over the past decades, changes in economic, social and demographic structures have pushed the growth of care employment across countries around the world. Women's increasing labor force participation has squeezed the time so far available for unpaid caregiving and led to increased demand for paid care services. Population aging and increasing needs for pre-school education also have contributed to the growth in demand for care services. As a result, care workers now comprise a large and growing segment of the labor force in many countries including South Korea. But, there are not a few problems. Especially, we take underpaid and undervalued care work very seriously. care work has been generally characterized as underpaid and undervalued compared with other work in developed and developing countries alike. This study tries to show current situation of care work and estimate the wage penalty for doing care work in Korea using official employment micro-data and applying propensity matching analysis. Especially, recent expansion of social service is a big step up for Korean Welfare State. But, there are not a few problems. Especially, we take underpaid and undervalued care work very seriously. This presentation tries to show current situation of care work and estimate the wage penalty for doing care work in Korea using official employment micro-data and applying propensity matching analysis.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.3
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• pp.292-297
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• 2014

As a Social Network Service (SNS) has become an integral part of our everyday lives, millions of users can express their opinion and share information regardless of time and place. Hence sentiment analysis using micro-blogs has been studied in various field to know people's opinion on particular topics. Most of previous researches on movie reviews consider only positive and negative sentiment and use it to predict movie rating. As people feel not only positive and negative but also various emotion, the sentiment that people feel while watching a movie need to be classified in more detail to extract more information than personal preference. We measure sentiment distributions of each movie from tweets according to the Thayer's model. Then, we find similar movies by calculating similarity between each sentiment distributions. Through the experiments, we verify that our method using micro-blogs performs better than using only genre information of movies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1B
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• pp.1-8
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• 2006

Currently, there are many efforts underway to provide Internet service on integrated wireless and wired networks. Supporting IP mobility is one of the major issues to construct IP based wireless network. Mobile IP has been proposed to solve the IP Mobility problem. But, in processing frequent handoffs in cellular based wireless access network, Micro mobility protocols have been proposed to solve these problems. Micro mobility protocols proposed the Cellular IP, HAWII, and Hierarchical Mobile IP. Cellular IP attracts special attention for it's seamless mobility support in limited geographical areas. New BS must be known to occur begging of handoff in Cellular IP indirect handoff. Therefore during perceiving of hanoff, packet loss or packet duplication still can occur in Cellular IP indirect handoff, which results in the degradation of UDP and TCP performance. In this paper, we propose a enhanced indirect handoff scheme for Cellular IP. Proposed handoff scheme is using a crossover node to minimize the signalling procedure and using a buffering to minimize the packet loss or packet duplication.

• Restorative Dentistry and Endodontics
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• v.41 no.1
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• pp.22-28
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• 2016

Objectives: The goal of this study was to compare the density of gutta-percha root fillings obturated with the following techniques: cold lateral (CL) compaction, ultrasonic lateral (UL) compaction, and warm vertical (WV) compaction. Materials and Methods: Thirty-three extracted mandibular first molars, with two separate mesial canals in each, were selected. After instrumentation, the canals were stratified into three groups based on canal length and curvature, and underwent obturation with one of the techniques. No sealer was used in order to avoid masking any voids. The teeth were imaged pre- and post-obturation using micro-computed tomography. The reconstructed three-dimensional images were analyzed volumetrically to determine the amount of gutta-percha present in every 2 mm segment of the canal. P values < 0.05 were considered to indicate statistical significance. Results: The overall mean volume fraction of gutta-percha was $68.51{\pm}6.75%$ for CL, $86.56{\pm}5.00%$ for UL, and $88.91{\pm}5.16%$ for WV. Significant differences were found between CL and UL and between CL and WV (p < 0.05), but not between UL and WV (p = 0.526). The gutta-percha density of the roots treated with WV and UL increased towards the coronal aspect, but this trend was not noted in the CL group. Conclusions: WV compaction and UL compaction produced a significantly denser gutta-percha root filling than CL compaction. The density of gutta-percha was observed to increase towards the coronal aspect when the former two techniques were used.

• Journal of the Korean institute of surface engineering
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• v.42 no.3
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• pp.109-115
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• 2009

Magnesium is one of the lightest metals, and magnesium alloys have excellent physical and mechanical properties such as high stiffness/weight ratios, good castability, good vibration and shock absorption. However their poor corrosion resistance, wear resistance, hardness and so on, have limited their application. To improve these defects, many techniques are developed. Micro arc oxidation(MAO) is a one of the surface treatments under anodic oxidation in which ceramic coating is directly formed on the surface of magnesium alloy. In this study, the characteristics of anodic film were examined after coating the AZ31B magnesium alloy through the MAO process. MAO was carried out in potassium hydroxide, potassium fluoride, and various concentration of sodium silicate in electrolyte. The morphology and chemical composition of the coating layer were characterized by SEM, XRD, EPMA and EDS. The hardness of anodic films was measured by micro-vickers hardness tester. As a result, the morphology and composition of anodic film were changed by concentration of sodium silicate. Thickness and Si composition of anodic film was increased with increasing concentration of sodium silicate in electrolyte. The hardness of anodic film was highly increased when the concentration of sodium silicate was above 40 g/l in electrolyte.

• Journal of the Economic Geographical Society of Korea
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• v.12 no.4
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• pp.454-476
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• 2009

The purpose of this paper is to examine relation between trust building level and linkages's spatial characteristics on the logistics & storage industry of Busan. As a result, First, long-term & repeated interaction, information sharing & reciprocity, and interdependence & asset specificity have an important effect upon the micro trust which implies the highest trust. Proximity and uncertainty impact on the meso trust, the trust of middle level. Culture, norm, and formal institution of firms affect the macro trust, the lowest level of trust. Second, the micro, the meso, and the macro trusts mainly form in the local scale where spatial proximity is great. The higher the trust building levels become, the more spatial dimensions by linkage expand to national and international dimension, respectively. Third, these results appear more clearly in the output linkage than input linkage, in the service areas-many firm, in the horizontal linkage than vertical linkage, in the advanced evolution phases of firm connection, and in the supply chain management than outsourcing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9B
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• pp.774-782
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• 2003

Generally, in the Mobile IP technologies, the use of RSVP(Resource ReSerVation Protocol) is recommended in order to provide a mobile node real-time service. However, the handoff of a mobile node increases the registration delay, RSVP reservation delay and signalling overhead in the Mobile IP and RSVP interworking. Specially, the resource reservation on the path between a mobile node and a correspondent node is the duplicated reservation and then causes unnecessary creation of the signalling overhead and waste of the resource, since the majority of the path before handoff and after handoff is same. If the radius of a cell providing a wireless interface to a mobile node is small, the number of handoff will increase and also signalling overhead and duplicated resource reservation will increase. In this paper, we proposed the integration model of Cellular IP and RSVP with RSVP proxy scheme. Here, Cellular IP protocol minimizes registration delay, transfer delay, and loss by handoff in micro cell network, the RS VP proxy that minimizes the duplication of resource reservation prevents the path for RSVP session from change using the address for reservation of a mobile node. Proposed scheme was evaluated in comparison with the existing Mobile IP and RSVP interworking scheme using the probability of resource reservation fail to the radius of a cell and the handoff rate.

• Health Policy and Management
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• v.27 no.2
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• pp.167-176
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• 2017

Background: This study aimed to analyze the impact of community health care resources on the place of death of older adults with dementia compared to those with cancer in South Korea, using public administrative big data. Methods: Based on a literature review, we selected person- and community-level variables that can affect older people's decisions about where to die. Data on place-of-death and person-level attributes were obtained from the 2013 death certification micro data from Statistics Korea. Data on the population and economic and health care resources in the community where the older deceased resided were obtained from various open public administrative big data including databases on the local tax and resident population statistics, health care resources and infrastructure statistics, and long-term care (LTC) insurance statistics. Community-level data were linked to the death certificate micro data through the town (si-gun-gu) code of the residence of the deceased. Multi-level logistic regression models were used to simultaneously estimate the impacts of community as well as individual-level factors on the place of death. Results: In both the dementia (76.1%) and cancer (87.1%) decedent groups, most older people died in the hospital. Among the older deceased with dementia, hospital death was less likely to occur when the older person resided in a community with a higher supply of LTC facility beds, but hospital death was more likely to occur in communities with a higher supply of LTC hospital beds. Similarly, among the cancer group, the likelihood of a hospital death was significantly lower in communities with a higher supply of LTC facility beds, but was higher in communities with a higher supply of acute care hospital beds. As for individual-level factors, being female and having no spouse were associated with the likelihood of hospital death among older people with dementia. Conclusion: More than three in four older people with dementia die in the hospital, while home is reported to be the place of death preferred by Koreans. To decrease this gap, an increase in the supply of end-of-life (EOL) care at home and in community-based service settings is necessary. EOL care should also be incorporated as an essential part of LTC. Changes in the perception of EOL care by older people and their families are also critical in their decisions about the place of death, and should be supported by public education and other related non-medical, social approaches.