• Journal of KIISE:Information Networking
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• v.32 no.6
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• pp.659-667
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• 2005

A Mobile Ad Hoc Network(MANET) is a multi hop wireless network with no prepared base stations or centralized administrations, where flocks of peer systems gather and compose a network. Each node operates as a normal end system in public networks. In addition to it, a MANET node is required to work as a router to forward traffic from a source or intermediate node to others. Each node operates as a normal end system in public networks, and further a MANET node work as a router to forward traffic from a source or intermediate node to the next node via routing path. Applications of MANET are extensively wide, such as battle field or any unwired place; however, these are exposed to critical problems related to network management, node's capability, and security because of frequent and dynamic changes in network topology, absence of centralized controls, restricted usage on network resources, and vulnerability oi mobile nodes which results from the special MANET's character, shared wireless media. These problems induce MANET to be weak from security attacks from eavesdropping to DoS. To guarantee secure authentication is the main part of security service In MANET because networks without secure authentication are exposed to exterior attacks. In this paper, a multistage authentication strategy based on CGSR is proposed to guarantee that only genuine and veritable nodes participate in communications. The proposed authentication model is composed of key manager, cluster head and common nodes. The cluster head is elected from secure nodes, and key manager is elected from cluster heads. The cluster head will verify other common nodes within its cluster range in MANET. Especially, ID of each node is used on communication, which allows digital signature and blocks non repudiation. For performance evaluation, attacks against node authentication are analyzed. Based on security parameters, strategies to resolve these attacks are drawn up.

• KDI Journal of Economic Policy
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• v.32 no.3
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• pp.1-32
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• 2010

The global financial crisis has exerted enormous impacts on the attainment of inflation target in Korea. The annual average CPI inflation was 3.3% during the targeting period of 2007-2009 and the target was $3.0{\pm}0.5%$. Thus Korea has succeeded in keeping annual average CPI inflation just below the upper limit of the 2007-2009 target under the global crisis. This paper intends to evaluate the performance of the inflation targeting system in Korea. First, it estimates the conventional call rate reaction equation under the global crisis and finds that the policy interest rates never reacted to expected inflation, output gap, and won/dollar exchange rate, as expected by theory. Second, it identifies the shock of global financial crisis into core and non-core, applying the structural VAR model. The core shock was defined to have no (medium- to) long-run impact on real output. The core shock was identified to have the character of the demand shock, since it has the positive impact on the inflation and output in the short run. The structural core inflation due to core shock was an attractor of headline inflation, not vice versa. Therefore, the structural core inflation that reflects the demand-side shock would be the better intermediate target for the final headline inflation target than the official core inflation that excludes the volatile inflation of agricultural and oil-related products. During the inflation targeting period of 2007-2009, the structural core inflation was more volatile than the official core inflation, because the global crisis has very large negative impacts on the domestic demand as well as the prices of agricultural and oil-related products. This paper shows that the negative core shock during the fourth quarter of 2008 was larger than that in the financial crisis in 1998. But the core shock turned into positive very quickly in 2009, as the Korean economy recovered very quickly from crisis. The volatile changes in structural core inflation suggests that the Bank of Korea barely managed to attain the 2007-2009 inflation target, owing to the very large negative impacts of the global financial crisis on the domestic demand. It also suggests that the rapid rise in core inflation with the rapid recovery of the Korean economy will lead to rapid rise in headline inflation.

• Journal of Veterinary Clinics
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• v.27 no.1
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• pp.42-45
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• 2010

Inflammatory sinonasal disease was diagnosed in five dogs and two cats with clinical signs of nasal discharge and epistaxis. Survey radiography and CT were performed in all of patients. CT scan of the rostral cranium was performed with a thickness of 2 or 5 mm. Nasal cytology and culture from nasal smear were performed immediately after CT examination. Remarkable increase of opacity in the nasal cavities and frontal sinuses was observed in only 3 cases. On CT images, the cavitating lesions were isodense in nasal cavity (7 cases), frontal sinuses (3 cases), and nasopharynx (2 cases) with destruction of the nasal septum (4 cases), maxillary turbinates (5 cases), maxilla (3 cases), and hard palate (3 cases). The lesions were enhanced after intravenous contrast administration in 5 cases and were not enhanced in 2 cases. Inflammatory cells were observed in nasal cytology. Most of the cultures from nasal smear were bacteria. CT is useful to diagnose sinonasal disease and is more accurate in demonstrating the extent and character of lesions of nasal cavity than radiography.

• Journal of Digital Contents Society
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• v.17 no.5
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• pp.307-316
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• 2016

A user usually gets the same suggesting results as everyone else in most of the multimedia social services, nowadays. To address the challenging problem of personalization in the social network, we propose a method which exploits user's activities, user's moods, and user's friend relationships from the social network to build a decision-making system. Depending on a current state of the user's mood, this system infers the most appropriated video for the user. In the system, the user evaluates a set of the given recommendation methods which extract from the user's database social network and assigns a vague value to each method by a weight. Then, we find the fuzzy collection solution for the system and classify the set of methods into subsets, and order the subsets based on its local dominance to choose the best appropriate method. Finally, we conduct an experiment using the YouTube API with a lot of video types. The experiment result shows that the channel recommendation system appropriately affords the user's character, it is more satisfying than the current YouTube based on an evaluation of several users.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.5
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• pp.324-333
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• 2013

Recently, rudder erosion due to cavitation has been frequently reported on a semi-spade rudder of a high-speed large ship. This problem raises economic and safety issues when operating ships. The semi-spade rudders have a gap between the horn/pintle and the movable wing part. Due to this gap, a discontinuous surface, cavitation phenomenon arises and results in unresolved problems such as rudder erosion. In this study, we made a rudder model for 2-D experiments using the NACA0020 and also manufactured gap flow blocking devices to insert to the gap of the model. In order to study the gap flow characteristics at various rudder deflection angles($5^{\circ}$, $10^{\circ}$, $35^{\circ}$) and the effect of the gap flow blocking devices, we carried out the velocity measurements using PIV(Particle Image Velocimetry) techniques and cavitation observation using high speed camera in Seoul National University cavitation tunnel. To observe the gap cavitation on a semi-spade rudder, we slowly lowered the inside pressure of the cavitation tunnel until cavitation occurred near the gap and then captured it using high-speed camera with the frame rate of 4300 fps(frame per second). During this procedure, cavitation numbers and the generated location were recorded, and these experimental data were compared with CFD results calculated by commercial code, Fluent. When we use gap flow blocking device to block the gap, it showed a different flow character compared with previous observation without the device. With the device blocking the gap, the flow velocity increases on the suction side, while it decreases on the pressure side. Therefore, we can conclude that the gap flow blocking device results in a high lift-force effect. And we can also observe that the cavitation inception is delayed.

• Journal of Conservation Science
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• v.30 no.3
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• pp.307-315
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• 2014

The gold textile is Korean traditional weaving technique using the gold thread since 5th century. The making technique of gold thread was written in various references, but it is severed because the gold thread weaving equipment and sumptuous moods were forbidden in the early 18th century. There are some studies of traditional gold thread which are mainly about conservation treatment of cleaning and strength. To restore traditional gold thread, investigation of material and manufacturing technique is vitally required. The gold threads are composed of gold leaf, adhesive and base sheet. Gold leaf and base sheet are available for investigation because they are exposed to the surface, whereas adhesive is not easy to investigate because it is not exposed to the surface. In this study, samples are made of pure and impure gold, animal glue and lacquer, and various types of Hanji based on domestic and foreign references to compare materials for gold threads. As a result of morphological character and stability evaluation, the optimum materials for the restoration of gold threads are pure gold, animal glue and Dochimji(smoothing paper by beating). This study is expected to be basic data for manufacturing gold threads techniques and modernization of traditional gold threads hereafter research.

• Journal of The Korean Association of Information Education
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• v.17 no.4
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• pp.421-432
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• 2013

The purpose of this study is to develop contents and an instructional model that support children's dramatic play by integrating the robot and augmented reality technology. In order to support the dramatic play, the robot shows various facial expressions and actions, serves as a narrator and a sound manager, supports the simultaneous interaction by using the camera and recognizing the markers and children's motions, records children's activities as a photo and a video that can be used for further activities. The robot also uses a projector to allow children to directly interact with the video object. On the other hand, augmented reality offers a variety of character changes and props, and allows various effects of background and foreground. Also it allows natural interaction between the contents and children through the real-type interface, and provides the opportunities for the interaction between actors and audiences. Along with these, augmented reality provides an experience-based learning environment that induces a sensory immersion by allowing children to manipulate or choose the learning situation and experience the results. In addition, the instructional model supporting dramatic play consists of 4 stages(i.e., teachers' preparation, introducing and understanding a story, action plan and play, evaluation and wrapping up). At each stage, detailed activities to decide or proceed are suggested.

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.2
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• pp.129-138
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• 2012

The aim of this in vitro study was to evaluate the effectiveness of experimental 2.26% fluoride-polyvinyl alcohol (F-PVA) tape in inhibition of enamel demineralization using enamel surface microhardness (SMH) analysis and scanning electron microscopy (SEM) examination. Enamel specimens (n=60) randomly assigned to four groups: control group, F-PVA tape group, fluoride varinish (F-varnish) group, casein phosphopeptide-amorphous calcium phosphate (CPP-ACFP) group. After topical application, pH-cycling was processed. Then, SMH was measured and the percentage loss of surface microhardness (%SML) was calculated. For the SEM examination, five sample specimens in each group were treated and the morphologic character was evaluated. After pH-cycling, the SMH values of the enamel specimens of F-PVA tape and F-varnish group were significantly higher than that of CPP-ACFP group, there was no significant difference between F-PVA tape and Fvarnish group. With SEM examination, enamel surfaces in the F-PVA tape group and F-varnish group showed numerous spherical and ovoid crystals formed on the enamel surface were also observed. The density of crystals was higher than that of both control group and CPP-ACFP group. F-PVA tape is effective in inhibition of enamel demineralization. Also, F-PVA tape's inhibition of enamel demineralization is comparable to that of F-vanish and greater than that of CPP-ACFP.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.107-115
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• 2013

The Old Town of Daejeon has significantly gone down due to population decrease and vacancy of buildings. To resolve these problems, it is necessary to develop revitalization measures with unique features, but it is also important to use historical and cultural resources from a certain point for the regeneration of local community. The Old Town of Daejeon has a number of industrial structures and architectural heritages that give character to the spaces, but most of them are being impoverished without any use although they have universal value. This study examined the standards to evaluate the importance and value of modern industrial heritages as historical resources that contributed to the development of local community and discussed case studies to review the value and use of industrial heritages that laid the foundation of Daejeon's development as a modern city to address the needs for urban regeneration through preservation and use of modern industrial heritages. Also, the limitations of administrative efforts were identified and the solutions were sought to address the needs to gather efforts with local government offices and the private sector. In conclusion, this study suggests an active and open policies to use cultural heritages through the use of modern industrial heritages for the revitalization of local communities based on the study of policies for the communication of urban users and community cultural spaces, preservation of landscapes including industrial heritages, and preservation in connection to social organizations and social companies, and that it is necessary to provide policies followed by efforts, i.e., to arbitrate the owners.

• Journal of Convergence for Information Technology
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• v.10 no.1
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• pp.169-177
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• 2020

The purpose of this study is to find ways to enhance the effectiveness of childhood teachers by recognizing both internal and external variables that affect their efficacy. Based on prior research, personality characteristics were selected as internal variables that affect the sense of teacher efficacy and social support was selected as external variables to set the effect of personality characteristics and social support on the efficacy of childhood teachers as research issues. 285 teachers from kindergartens and daycare centers located in Daegu and Gyeongsang-bukdo Province were selected for the study. The analysis of data was conducted using the SPSS 22.0 program to examine the general characteristics of the study target, and the analysis was conducted stepwise to look at the influence of each of the variables on the teacher's. Personal teacher efficacy is shown to affect Conscientiousness, nervousness, openness to experience, and evaluation support among personality characteristics, and Conscientiousness, Agreeableness and nervousness affect general teacher efficacy. The results of this study suggest that the character characteristics and social support of childhood teachers are among the variables that affect teacher efficacy.