• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.38-39
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• 2006

We present experimental results that regard the effects of catalyst preparation on the structural and field-emissive properties of CNTs. The CNTs used in this research have been synthesized using the inductively coupled plasma-chemical vapor deposition (ICP-CVD) method. Catalyst materials (such as Ni, Co, and Invar 426) are varied and deposited on buffer films by RF magnetron sputtering. Prior to growth of CNTs, $NH_3$ plasma etching has also been performed with varying plasma etching time and power. For all the CNTs grown, nanostructures and morphologies are analyzed using Raman spectroscopy and FESEM, in terms of buffer films, catalyst materials, and pre-treatment conditions. Furthermore, the field electron-emission of CNTs are measured and characterized in terms of the catalyst preparation environments. The CNTs grown on Nicatalyst layer would be more effectual for enhancing the growth rate and achieving the vertical-alignment of CNTs rather than other buffer materials from results of SEM study. The crystalline graphitic structure of CNTs is improved as the catalyst dot reaches a critical size. Also, the field-emission result shows that the CNTs using Ni catalyst would be more favorable for improving electron-emission capabilities of CNTs compared with other samples.

• Journal of Communications and Networks
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• v.15 no.4
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• pp.422-429
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• 2013

Advances in wireless sensor network (WSN) technology have enabled small and low-cost sensors with the capability of sensing various types of physical and environmental conditions, data processing, and wireless communication. In the WSN, the sensor nodes have a limited transmission range and their processing and storage capabilities as well as their energy resources are limited. A triple umpiring system has already been proved for its better performance in WSNs. The clustering technique is effective in prolonging the lifetime of the WSN. In this study, we have modified the ad-hoc on demand distance vector routing by incorporating signal-to-noise ratio (SNR) based dynamic clustering. The proposed scheme, which is an efficient and secure routing protocol for wireless sensor networks through SNR-based dynamic clustering (ESRPSDC) mechanisms, can partition the nodes into clusters and select the cluster head (CH) among the nodes based on the energy, and non CH nodes join with a specific CH based on the SNR values. Error recovery has been implemented during the inter-cluster routing in order to avoid end-to-end error recovery. Security has been achieved by isolating the malicious nodes using sink-based routing pattern analysis. Extensive investigation studies using a global mobile simulator have shown that this hybrid ESRP significantly improves the energy efficiency and packet reception rate as compared with the SNR unaware routing algorithms such as the low energy aware adaptive clustering hierarchy and power efficient gathering in sensor information systems.

• Journal of the Korean Chemical Society
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• v.57 no.1
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• pp.104-108
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• 2013

The adsorption characteristics of Cd(II) and Pb(II) in aqueous solution using granular activated carbon (GAC), activated carbon fiber (ACF), modified ACF (NaACF), and a mixture of GAC and NaACF (GAC/NaACF) have been studied. The surface properties, such as morphology, surface functional groups, and composition of various adsorbents were determined using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) measurements. The specific surface area, total pore volume, and pore size distribution were investigated using nitrogen adsorption, Brunauer-Emmett-Teller (BET), and Barrett-Joyner-Halenda (BJH) methods. In this study, NaACF showed a high adsorption capacity and rate for heavy metal ions due to the improvement of its ion-exchange capabilities by additional oxygen functional groups. Moreover, the GAC and NaACF mixture was used as an adsorbent to determine the adsorbent-adsorbate interaction in the presence of two competitive adsorbents.

• Journal of Fashion Business
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• v.19 no.3
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• pp.73-87
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• 2015

The purpose of this study is 1) to compare the employment status and wage level of "Clothing and Fashion" major (CF major) graduates with those from other majors and 2) to examine factors affecting the employment status and wage level of CF major university graduates. The data were pooled from the 2009-2012 Graduates Occupational Mobility Survey Data, conducted by Korea Employment Information Service. First, when graduates of CF major were compared with other majors in the same academic area-natural science and arts-, the rate of employment was higher for CF majors than that of other majors; on the other hand, there is no difference in the wage levels between those with graduates in CF majors and those with other majors. Second, we examined factors affecting CF major graduates' employment and wage level based on graduates' individual factors, university factor, and job preparation factors. Employment status of graduates in CF major was predicted by respondent's gender and university type, and work experience. The wage level of CF major graduates was significantly predicted by individual factors (e.g., gender and age, university factors (e.g., university type, university program, location), and job preparation factors (e.g., certificates, overseas experience of foreign language training, English test scores). The results of this study would provide a guide to direct university educational program in order to assess the current capabilities in the field of clothing and fashion.

• Journal of Korea Society of Digital Industry and Information Management
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• v.17 no.4
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• pp.161-175
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• 2021

This study analyzed the efficiency and influence factors according to the main research institute type of R&D Program for the local community problem-solving. This study applied data envelopment analysis (DEA) method and Tobit regression analysis by using 20 institutions that participated in R&D Program. The results are summarized as follows. First, Analysis results according to the research institute type of R&D project, Efficient DMUs showed more regional innovation institutions than social economy enterprises. But regional innovation institutions were the lowest in the CCR and BCC model. However, efficiency dose not differ between regional innovation institutions and social economy enterprises. Second, as a result of the analysis relation between efficiency and allocation characteristics of R&D input, the participation of regional innovation organizations as participating organizations has a negative effect on efficiency. It was found that the higher the proportion of government subsidies and the higher the employment rate of the vulnerable, which is a social achievement, the positive effect on efficiency. The implication of this study is that the participation of social economy enterprises as the main R&D institution and government R&D support can provide social economy enterprises with opportunities to accumulate R&D capabilities and experience successful commercialization.

• Journal of Integrative Natural Science
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• v.11 no.4
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• pp.197-203
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• 2018

Long Term Evolution-Advanced (LTE-A) is the next drive in the broadband mobile communication, which allows operators to improve networks performance and service capabilities. LTE-A targets the peak data rates of 1Gbps in the downlink and 500Mbps in the uplink. This requirement is only fulfilled by a transmission bandwidth of up to 100MHz. However the accessibility of such large part of the contiguous spectrum is uncommon in practice. Therefore LTE-A uses some new features on top of the existing LTE standards to provide very high data rate transmission. Some of the most significant features introduced in LTE-A are carrier aggregation, heterogeneous network enhancement, coordinated multipoint transmission and reception, enhanced multiple input and multiple output, and development relay nodes with universal frequency reuse. This review paper presents an overview of the above mentioned LTE-A key features and functionalities. Based on this review, in the conclusion we discuss the current technical challenges for future broadband mobile communication systems.

• Journal of the Korean Institute of Plant Engineering
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• v.23 no.4
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• pp.85-92
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• 2018

With the increasing use of chemicals in domestic businesses, the possibility of fire explosion and poisonous material leakage accidents is also increasing. Accordingly, the Korea Occupational Safety and Health Agency(KOSHA) has implemented the process safety management (PSM) system for a long time. However, process safety report submission has been providing and operating e-PSM since 2016 to address these problems as it is difficult to increase budget spending due to the need for professional capabilities and commissioning the report to consulting institutions. Therefore, this study conducts questionnaires on whether e-PSM system that is well utilized in the field, focusing on existing PSM business sites. In order to find out the activation method that can solve the deficiency factors by analyzing various inconveniences and problems accurately, we propose three improvement methods as educational aspect, promotional direction of e-PSM system, and institutional aspect.

• New & Renewable Energy
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• v.17 no.1
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• pp.40-49
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• 2021

In this study, the optical properties, heat transfer capabilities and chemical reaction performance of a methane thermal decomposition reactor using solar heat as a heat source were numerically analyzed on the basis of the cavity shape. The optical properties were analyzed using TracePro, a Monte Carlo ray tracing-based program, and the heat transfer analysis was performed using Fluent, a CFD program. An indirect heating tubular reactor was rotated at a constant speed to prevent damage by the heat source in the solar furnace. The inside of the reactor was filled with a porous catalyst for methane decomposition, and the outside was insulated to reduce heat loss. The performance of the reactor, based on cavity shape, was calculated when solar heat was concentrated on the reactor surface and methane was supplied into the reactor in an environment with a solar irradiance of 700 W/㎡, a wind speed of 1 m/s, and an outdoor temperature of 25℃. Thus, it was confirmed that the heat loss of the full-cavity model decreased to 13% and the methane conversion rate increased by 33.5% when compared to the semi-cavity model.

• Smart Structures and Systems
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• v.30 no.2
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• pp.183-193
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• 2022

Structural health monitoring and structural vibration control are multidisciplinary and frontier research directions of civil engineering. As intelligent materials that integrate sensing and actuation capabilities, shape memory alloys (SMAs) exhibit multiple excellent characteristics, such as shape memory effect, superelasticity, corrosion resistance, fatigue resistance, and high energy density. Moreover, SMAs possess excellent resistance sensing properties and large deformation ability. Superfine NiTi SMA wires have potential applications in structural health monitoring and micro-drive system. In this study, the mechanical properties and electrical resistance sensing characteristics of superfine NiTi SMA wires were experimentally investigated. The mechanical parameters such as residual strain, hysteretic energy, secant stiffness, and equivalent damping ratio were analyzed at different training strain amplitudes and numbers of loading-unloading cycles. The results demonstrate that the detwinning process shortened with increasing training amplitude, while austenitic mechanical properties were not affected. In addition, superfine SMA wires showed good strain-resistance linear correlation, and the loading rate had little effect on their mechanical properties and electrical resistance sensing characteristics. This study aims to provide an experimental basis for the application of superfine SMA wires in engineering.

• ETRI Journal
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• v.44 no.2
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• pp.300-312
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• 2022

Recently, public safety services have attracted significant attention for their ability to protect people from crimes. Rapid detection of dangerous situations (that is, abnormal situations where someone may be harmed or killed) is required in public safety services to reduce the time required to respond to such situations. This study proposes a novel danger detection technology based on multimodal data, which includes data from multiple sensors (for example, accelerometer, gyroscope, heart rate, air pressure, and global positioning system sensors), and multilog data, which includes contextual logs of humans and places (for example, contextual logs of human activities and crime-ridden districts) over time. To recognize human activity (for example, walk, sit, and punch), the proposed technology uses multimodal data analysis with an attitude heading reference system and long short-term memory. The proposed technology also includes multilog data analysis for detecting whether recognized activities of humans are dangerous. The proposed danger detection technology will benefit public safety services by improving danger detection capabilities.