• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.51-60
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• 2008

Micro-mobility protocols have been developed to reduce the control message overhead due to movements of mobile nodes. With the spread of mobile devices, services using mobile nodes are increasing and multicast services are becoming more important in providing multimedia services. In this paper we propose a new multicast protocol suitable for micro-mobility environments. The proposed protocol is designed to maintain optimal multicast routing paths and continue to provide multicast services without disruption in spite of frequent handoffs due to movements of mobile nodes. We used simulation to evaluate the proposed protocol, compared its performance with existing multicast protocols for mobile environments including bi-directional tunneling, remote subscription, and MMA, and observed that the proposed protocol exhibited better performance in terms of transmission success ratio and overhead on the network.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.6
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• pp.17-24
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• 2011

In this paper, we propose an Entropy-based Routing Protocol using Mobility (ERPM) for supporting ubiquitous convergence services efficiently in mobile ad-hoc wireless networks. The main features that the ERPM introduces to obtain the goals can be summarized as follows. First, ERPM can construct stable routing routes based on the entropy concepts using mobility of nodes. Second, ERPM can quantitatively evaluate the stability of route by entropy concepts using mobility of nodes. Third, ERPM can select the most stable route in the view points of mobility of routes between a source node and a destination node, where multiple paths are available. The performance evaluation of the proposed ERPM performed via simulation using OPNET and analysis shows that the ERPM can support the construction of stable routing routes and increase the transmission ratio of data efficiently.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2505-2511
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• 2014

Indium oxide nanocrystals ($In_2O_3$ NCs) with sizes of 5.5 nm-10 nm were synthesized by hot injection of the mixture precursors, indium acetate and oleic acid, into alcohol solution (1-octadecanol and 1-octadecence mixture). Field emission transmission electron microscopy (FE-TEM), High resolution X-Ray diffraction (X-ray), Nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FT-IR) were employed to investigate the size, surface molecular structure, and crystallinity of the synthesized $In_2O_3$ NCs. When covered by oleic acid as a capping group, the $In_2O_3$ NCs had a high crystallinity with a cubic structure, demonstrating a narrow size distribution. A high mobility of $2.51cm^2/V{\cdot}s$ and an on/off current ratio of about $1.0{\times}10^3$ were observed with an $In_2O_3$ NCs thin film transistor (TFT) device, where the channel layer of $In_2O_3$ NCs thin films were formed by a solution process of spin coating, cured at a relatively low temperature, $350^{\circ}C$. A size-dependent, non-monotonic trend on electron mobility was distinctly observed: the electron mobility increased from $0.43cm^2/V{\cdot}s$ for NCs with a 5.5 nm diameter to $2.51cm^2/V{\cdot}s$ for NCs with a diameter of 7.1 nm, and then decreased for NCs larger than 7.1 nm. This phenomenon is clearly explained by the combination of a smaller number of hops, a decrease in charging energy, and a decrease in electronic coupling with the increasing NC size, where the crossover diameter is estimated to be 7.1 nm. The decrease in electronic coupling proved to be the decisive factor giving rise to the decrease in the mobility associated with increasing size in the larger NCs above the crossover diameter.

• The Korean Journal of Emergency Medical Services
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• v.27 no.2
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• pp.7-17
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• 2023

Purpose: This study aimed to identify the factors that contribute to head injuries among drivers of personal mobility devices and provide insights into safety perceptions. Methods: This retrospective study analyzed data of 221 trauma patients obtained from electronic medical records and the National Emergency Department Information System (NEDIS) over one year, from August 1, 2021, to July 31, 2022. The patients, all in their 20s and 30s, presented to a single emergency medical center following personal mobility device accidents (motorcycles, electric scooters, and bicycles). Results: Among motorcycle riders, 18.2% were not wearing helmets, while the percentage of e-scooter riders not wearing helmets was 87.5%. Wearing a helmet was associated with a 71.2% lower likelihood of head injuries (OR=0.288, CI=0.163 to 0.509, p=0.000). Of the personal mobility devices, motorcycles had a 0.431 times lower odds ratio for head injury compared to e-scooters (p=0.009), and there was no significant difference between e-scooters and bicycles (p=0.776). Conclusion: It is imperative to strengthen safety regulations by mandating helmet use for riders of personal mobility devices. A system to enhance driving enforcement for electric scooters, which are increasingly popular among young adults, should also be established.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.75-84
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• 2014

In order to solve the problems such as overload, single point of failure, non-optimized data path, and network scalability in conventional central mobility management protocols, distributed mobility management schemes have been continually studied in and around the IETF. In this paper, a network-based partially-distributed mobility management mechanism, pDMMv6, is suggested and the performance comparison with traditional protocols such as PMIPv6 and MIPv6 is made through simulation under the various user traffic environment. The simulation results include UDP packet delivery ratio, end-to-end packet delay, binding delay for registration signaling, CPU utilization in each node, and response delays in several server-client TCP applications such as web browsing, e-mail, telnet remote login, FTP file up/down-load, and database access.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3D
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• pp.313-321
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• 2010

This study analysed the characteristics of residential mobility according to the household's life-cycle to observe the housing filtering process in Busan. The questionary subjects were adult 40 and over who inhabited in Busan and surveyed residential career about residential mobility. The analysis result of statistical data and result of questionary reveals similar result every articles, the summaries are as follows : Examining housing where the respondent live presently, apartment dominate absolutely high ratio as housing type and owner-occupation as housing tenure type, and housing size is about 30 pyeong, dwelling period is 6 years to 10 years. Saving and loan hold a large majority to make housing capital, that means, they apply housing finance to getting own housing despite it is impossible with present household's income to have owner-occupation of desired housing. This is different custom ours from foreign's that rent a house. However, as aspect of residential satisfaction, most household recognised that quality is improved, because residential mobility expanded housing size and changed tenure type and showed fairly high satisfaction with their present resident.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.15-19
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• 2007

This paper reports the effects of Ar ion beam surface treatment on a $SiO_2$ dielectric layer in organic thin film transistors. We compared the electrical properties of pentacene-based OTFTs, treated by $O_2$ plasma or Ar ion beam treatments and characterized the states of the surface of the dielectric by using atomic force microscopy and X-ray photoelectron spectroscopy. For the sample which received $O_2$ plasma treatment, the mobility increased significantly but the on/off current ratio was found very low. The Ar ion beam-treated sample showed a very high on/off current ratio as well as a moderately improved mobility. XPS data taken from the dielectric surfaces after each of treatments exhibit that the ratio of between Si-O bonds and O-Si-O bonds was much higher in the $O_2$ plasma treated surface than in the Ar ion beam treated surface. We believe that our surface treatment using an inert gas, Ar, carried out an effective surface cleaning while keeping surface damage very low, and also the improved device performances was achieved as a consequence of improved surface condition.

• Journal of the Korean GEO-environmental Society
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• v.22 no.2
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• pp.25-33
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• 2021

This study was conducted to understand the deposition characteristics of debris flow and to analyze the reduction effect of debris flow damage by installing a berm. Flume experiments were performed in consideration of various channel slope and volumetric sediment concontration. In order to analyze the reduction effect of debris flow damage by installing a berm, the cases of not installing a berm and the cases of installing a berm were compared. In this study, the runout distance, total travel distance, and mobility ratio were analyzed among the deposition characteristics of debris flow. First, the deposition characteristics of debris flow according to the change of the channel slope were analyzed, and the deposition characteristics of debris flow due to the change of volumetric sediment concentration were analyzed. In addition, the change rate of debris flow deposition characteristics when a berm was installed was calculated based on the case when a berm was not installed. As a result of the experiments, it was confirmed that the channel slope and volumetric sediment concentration had a significant effect on the deposition characteristics of debris flow. In addition, when a berm is installed on the slope, the runout distance and mobility ratio of debris flow are greatly decreased, and the total travel distance is increased. This means that installing a berm delays the movement of debris flow and reduces the potential mobility of debris flow. The results of this study will provide useful information for understanding the deposition characteristics of debris flow. Furthermore, it is expected to help in the design of a berm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5B
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• pp.721-733
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• 2010

In this paper, we propose a scalable content-based routing scheme for the tactical mobile ad-hoc networks where the nodes usually move together forming a group. Our scheme is classified as a content-based routing scheme based on publish and subscribe model. The nodes compose a cluster according to their position and interest. Our scheme allows multi-level cluster nesting. As a publish/subscribe model does, each node announces its interest to the cluster head who aggregates and announces the interests from cluster members to its neighbor cluster head. Actual data messages are delivered to the end node via cluster header in the reverse direction of the interest announcement. Using Qualnet simulator, we evaluated the performance of our scheme in comparison with two well-known content-based routing schemes. Simulation results show that our scheme maintains higher message delivery ratio as number of nodes increases whereas the two schemes show much lower delivery ratio. In addition, as the group mobility gets faster our scheme incurs less or similar control message overhead compared with the two schemes.

• Journal of Labour Economics
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• v.28 no.3
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• pp.1-37
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• 2005

This article examines the reasons for the observed discrepancy between worker's actual and required levels of schooling and the resulting economic effects in wage and labor mobility using KRIVET's Graduates Economic Activities Survey in 2005. Overeducated workers in Korea are estimated to be 10.1%-20.7% among junior college graduates and 18.8% among university graduates for their first job according to job analysis method and worker's self-assessment method each. The effects of school quality-measured by the student/teacher ratio, school building area/student ratio-on the overeducation of their graduates are found to be mostly insignificant not only junior colleges but also universities. This founding implies that the increase of education investment from schools does not acquire any recognition from the labor market. Also, the effects of overeducation and school quality on wages are found to be insignificant and job mobility has little effects on improving overeducated workers' job match.