• Polymer(Korea)
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• v.25 no.2
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• pp.199-207
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• 2001

In the present study the cure behavior of diglycidyl ether of bisphenol-A(DGEBA) using an anhydride-based hardener in the presence of N,N-dimethyl benzyl amine (BDMA) or 1-cyanoethyl-2-ethyl-4-methyl imidazole (2E4MZ-CN) as an accelerator has been monitored and interpreted from the viewpoint of photophysical properties by means of fluorescence spectroscopy. To do this, 1,3-bis-(1-pyrene)propane (BPP) was well incorporated in the epoxy resin system by mechanical blending. The BPP probe, which is very sensitive to conformational change of the molecule influenced by the surrounding medium, successfully formed intramolecular excimer fluorescence. It is susceptible to the micro-viscosity or local viscosity and molecular mobility according to the epoxy cure. The cure behavior was explained with monomer fluorescence intensity ($I_{M}$ ), excimer fluorescence intensity ($I_{E}$ ) and $I_{M}$ /$I_{E}$ ratio as a function of cure time, cure temperature and accelerator. The present work agreed with the previous report on the cure behavior of an epoxy-anhydride system studied using DSC or torsion pendulum method. This study also suggests that the use of fluorescence technique may provide information on cure behavior of a thermosetting resin in a low temperature region, which has not been well interpreted by other analytical methods.

• Journal of Intelligence and Information Systems
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• v.28 no.1
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• pp.45-68
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• 2022

The central and local governments of the Republic of Korea provided information necessary for disaster response through wireless emergency alerts (WEAs) in order to overcome the pandemic situation in which COVID-19 rapidly spreads. Among all channels for delivering disaster information, wireless emergency alert is the most efficient, and since it adopts the CBS(Cell Broadcast Service) method that broadcasts directly to the mobile phone, it has the advantage of being able to easily access disaster information through the mobile phone without the effort of searching. In this study, the characteristics of wireless emergency alerts sent to Seoul during the past year and one month (January 2020 to January 2021) were derived through various text mining methodologies, and various types of information contained in wireless emergency alerts were analyzed. In addition, it was confirmed through the population mobility by age in the districts of Seoul that what kind of influence it had on the movement behavior of people. After going through the process of classifying key words and information included in each character, text analysis was performed so that individual sent characters can be used as an analysis unit by applying a document cluster analysis technique based on the included words. The number of WEAs sent to the Seoul has grown dramatically since the spread of Covid-19. In January 2020, only 10 WEAs were sent to the Seoul, but the number of the WEAs increased 5 times in March, and 7.7 times over the previous months. Since the basic, regional local government were authorized to send wireless emergency alerts independently, the sending behavior of related to wireless emergency alerts are different for each local government. Although most of the basic local governments increased the transmission of WEAs as the number of confirmed cases of Covid-19 increases, the trend of the increase in WEAs according to the increase in the number of confirmed cases of Covid-19 was different by region. By using structured econometric model, the effect of disaster information included in wireless emergency alerts on population mobility was measured by dividing it into baseline effect and accumulating effect. Six types of disaster information, including date, order, online URL, symptom, location, normative guidance, were identified in WEAs and analyzed through econometric modelling. It was confirmed that the types of information that significantly change population mobility by age are different. Population mobility of people in their 60s and 70s decreased when wireless emergency alerts included information related to date and order. As date and order information is appeared in WEAs when they intend to give information about Covid-19 confirmed cases, these results show that the population mobility of higher ages decreased as they reacted to the messages reporting of confirmed cases of Covid-19. Online information (URL) decreased the population mobility of in their 20s, and information related to symptoms reduced the population mobility of people in their 30s. On the other hand, it was confirmed that normative words that including the meaning of encouraging compliance with quarantine policies did not cause significant changes in the population mobility of all ages. This means that only meaningful information which is useful for disaster response should be included in the wireless emergency alerts. Repeated sending of wireless emergency alerts reduces the magnitude of the impact of disaster information on population mobility. It proves indirectly that under the prolonged pandemic, people started to feel tired of getting repetitive WEAs with similar content and started to react less. In order to effectively use WEAs for quarantine and overcoming disaster situations, it is necessary to reduce the fatigue of the people who receive WEA by sending them only in necessary situations, and to raise awareness of WEAs.

• Journal of Communications and Networks
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• v.11 no.2
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• pp.187-195
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• 2009

The application of mathematical analysis to the study of wireless ad hoc networks has met with limited success due to the complexity of mobility, traffic models and the dynamic topology. A scenario based universal mobile telecommunications system (UMTS) time division duplex (TDD) opportunistic cellular system with an ad hoc behaviour that operates over UMTS frequency division duplex (FDD) licensed cellular network is considered. In this paper, we present a new routing metric which overall improves system performance in terms of interference and routing which operate in an ad hoc network in an opportunistic manner. Therefore we develop a simulation tool that addresses the goal of analysis and assessment of UMTS TDD opportunistic radio system with ad hoc behavior in coexistence with a UMTS FDD primary cellular networks.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2353-2358
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• 2017

A femtosecond laser pre-annealing process based on indium zinc oxide (IZO) thin-film transistors (TFTs) is fabricated. We demonstrate a stable pre-annealing process to analyze surface structure change of thin films, and we maintain electrical stability and improve electrical performance. Furthermore, dynamic electrical characteristics of the IZO TFTs were investigated. Femtosecond laser pre-annealing process-based IZO TFTs exhibit a field-effect mobility of $3.75cm^2/Vs$, an $I_{on}/I_{off}$ ratio of $1.77{\times}10^5$, a threshold voltage of 1.13 V, and a subthreshold swing of 1.21 V/dec. And the IZO-based inverter shows a fast switching behavior response. From this study, IZO TFTs from using the femtosecond laser annealing technique were found to strongly affect the electrical performance and charge transport dynamics in electronic devices.

• Analytical Science and Technology
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• v.18 no.1
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• pp.35-42
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• 2005

This study reports the effect of $Mg^{2+}$ ions on the behavior of the anionic surfactant in electrophoresis. Intractions of $Mg^{2+}$ ions with carboxylates and sulfonates resulted large changes in their apparent mobilities. A comprehensive analysis of the electroosmotic and electrophoretic mobilities reveals that major cause for the variation of the apparent mobilities of anions arises from the electroosmotic mobilities.

• Journal of Information Technology Services
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• v.11 no.3
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• pp.269-285
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• 2012

The spontaneous interoperation is an important characteristic of ubiquitous applications and is closely related with mobility. The mobile components in ubiquitous environments are liable to appear in and disappear from one physical space to another. Because this characteristic certainly influences the structure and behavior of applications, they should adapt themselves to the changed environments by configuring their structure and behaviors. Consequently, developers are faced with the above challenging issue when they design and implement ubiquitous applications. The role concept is an efficient tool to model participant entities, their relationship, and collaboration, so role-based model are appropriate to describe a structure and behavior of software system. But, little attention has been given to reflect characteristics of ubiquitous applications. To tackle the problem, this study considers a ubiquitous application as a software organization which consists of software components and proposes an enhanced role-based application model for supporting spontaneous interoperation.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.371-372
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• 2006

Poly(${\varepsilon}-caprolactone$) (PCL) is a highly crystalline polymer that is miscible with several amorphous polymers including chlorinated polyether, poly(vinylchloride), poly(hydroxyether) and Bisphenol A polycarbonate. The crystallization behavior of miscible blend of amorphous/crystalline polymers has widely been studied. Generally a depression of the crystallization ability has been found with addition of amorphous component because of the reduction of chain mobility, the change of free energy of nucleation as a result of a specific interaction, and so on [1]. In this work, for the first time, the blend of PCL and copolymer of polyurethane containing polycaprolactone as a soft segment is considered. The structural similarity of TPU soft segment with PCL affects on formation of the miscible component and crystallization behavior of PCL in the blend. This has been studied using differential scanning calorimetry (DSC) and Wide-angle X-ray Scattering (WAXS).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.2
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• pp.222-226
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• 2017

It is well known that typhoons strongly influence marine ecosystems. For example, red tides nearly disappear after the passage of typhoons, although the physical or biological mechanism underlying this has not been elucidated. Here, a particle tracking model is executed in a three-dimensional primitive equation model to understand the process of red tide extinction after the passage of a typhoon. Red tide organisms may be regarded as tracers because they have limited mobility and thus their behavior is governed entirely by currents. Initially, tracers are randomly scattered within a limited area, and their spatial and temporal behavior is tracked during and after the passage of a typhoon. This model suggests that the extinction of red tides is significantly influenced by momentum disturbances caused by the typhoon.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.459-459
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• 2011

Graphene has many fascinating material properties such as high electron mobility, high optical transparency, excellent thermal conductivity, superior Young's modulus, etc. Several studies have recently found that single-layer graphene is chemically more reactive than few-layer graphene when supported on silicon dioxide substrates with sub-nm roughness. In this study, we have investigated the influence of substrates on chemical reactivity of graphene. Morphology and thermal oxidation behavior of graphene on atomically flat mica substrates were studied by atomic force microscopy (AFM) and Raman spectroscopy compared to graphene on SiO2/Si substrates. Notably, oxidation of single-layer graphene proceeds more slowly on mica than SiO2/Si. Detailed analysis led to a conclusion that deformation along the out-of-plane direction enhances reactivity of graphene.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.385-385
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• 2011

Ion beam Sputtering (IBS)를 이용한 물질 표면의 pattern 형성은 물리적 변수 조절로 손쉽게 nano structure의 크기와 형태를 조절할 수 있어 관심을 받고 있다. 본 연구발표에서는 massless Dirac Fermion behavior로 인한 highly carrier mobility와 같은 특성으로 인해 차세대 device material로 각광받고 있는 Graphene의 layered compound (층상구조) 형태인 HOPG (Highly Ordered Pyrolysis Graphite)에 IBS (Ion beam Sputtering)를 이용해 nano structure가 형성 가능함을 보이고 그 특징에 대해 소개하려 한다. HOPG(0001)를 Sputter 했을 때, 표면에 잘 정렬된 nano ripple pattern이 형성 가능함을 확인하였으며 sputter하는 시간을 변화하면 약 10 nm에서 80 nm까지 wavelength를 조절할 수 있다. 또한 이전의 IBS를 이용한 연구들에서 확인할 수 있는 다른 물질의 곧게 뻗은 nano ripple과는 다르게 ripple의 끝에 nano swab이 생기는 것을 AFM (Atomic Force Microscope)으로 확인할 수 있었다. 이러한 Graphite에서만 나타나는 Sputter에 의한 표면의 변화의 원인을 규명하고자 Sputter가 지속됨에 따라 나타나는 mopology의 roughness와 wavelength의 시간에 따른 dynamic scaling behavior를 확인하였고 그 얼개를 알기 위해 simulation을 수행 하였다.