• Journal of KIISE:Databases
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• v.30 no.5
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• pp.476-493
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• 2003

Data broadcast is an effective data transmission method from a data base server to numerous mobile clients due to the restrictions on mobile environment such as low wireless communication bandwidth and energy shortage of mobile devices. There are various broadcast methods based on clients' data access frequencies or semantic relationship of data. The broadcast schedule based only on the access frequencies does not consider semantic relations of data, so that when a client needs to access a series of semantically related data, the client has to listen to the wireless channel for a long time. On the other hand, the broadcast schedule based only on semantic relationship of data makes data access time longer when clients highly request specific data which are not semantically related but frequently accessed. In this paper, we present an efficient data broadcast method based on not only data access frequencies but also semantic relationship to improve mobile clients' query response time. The new hybrid broadcast method we propose creates a data broadcast schedule according to the data access frequencies and then the schedule is adjusted to reflect semantic relationship of data. We show our method is efficient by experimental performance analysis.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.3
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• pp.45-58
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• 2020

In the current trend of increasing network traffic due to the popularization of cloud service and mobile devices, WAN bandwidth is very low compared to LAN bandwidth. In a WAN environment, a WAN optimizer is needed to overcome performance problems caused by transmission protocol, packet loss, and network bandwidth limitations. In this paper, we analyze the data deduplication algorithm of WANProxy, an open source WAN optimizer, and evaluate its performance in terms of network latency and WAN bandwidth. Also, we evaluate the performance of the two-stage compression method of WANProxy and Zstandard. We propose a new method to improve the performance of WANProxy by revising its data deduplication algorithm and evaluate its performance improvement. We perform experiments using 12 data files of Silesia with a data segment size of 2048 bytes. Experimental results show that the average compression rate by WANProxy is 150.6, and the average network latency reduction rates by WANProxy are 95.2% for a 10 Mbps WAN environment and 60.7% for a 100 Mbps WAN environment, respectively. Compared with WANProxy, the two-stage compression of WANProxy and Zstandard increases the average compression rate by 33%. However, it increases the average network latency by 2.1% for a 10 Mbps WAN environment and 5.27% for a 100 Mbps WAN environment, respectively. Compared with WANProxy, our proposed method increases the average compression rate by 34.8% and reduces the average network latency by 13.8% for a 10 Mbps WAN and 12.9% for a 100 Mbps WAN, respectively. Performance analysis results of WANProxy show that its performance improvement in terms of network latency and WAN bandwidth is excellent in a 10Mbps or less WAN environment while superior in a 100 Mbps WAN environment.

• Journal of Information Management
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• v.43 no.1
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• pp.63-87
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• 2012

This study aims to analyse the actual condition of the ebook services and propose the improvements of ebook services for children in the Korean public library. For this purpose, the current condition of the ebook services in the public libraries were analyzed and categorized by three criteria. Secondly, the ebook use analysis was conducted using PCs and mobile devices in terms of access to ebook library site, searching method, contents type and viewer, lending process, and user help. As a result of the analysis, several issues such as the difficulty in access to ebook site, the complexity of setting and usage depending on the file format, the insufficient user guide, the relatively lower quality service than the commercial's, and the lack of retrieval functions specialized for the ebook were presented. The improvement plan for the ebook services, especially for children in the public library was suggested.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.304-304
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• 2006

One method of Electric Power Generation is to use piezoelectric materials, which form transducers that are able to interchange electrical energy and mechanical force or strain. This study describes the fabrication and properties of piezoelectric transducers for Power Generation application. The structure of the transducers was ceramic-metal-ceramic 3-layered parallel type The center metal layer of phosphorous bronze was bonded by two piezoelectric layers of which have sputtered Ag/Cu(or Ni/Cu) electrode layers on both sides.. The Energy generated by the vibration of piezoelectric transducers Can be achieved by adjusting a suitable piezoelectric constant and mechanical structures. The piezoelectric material used in this application showed the electrical properties of r=4400, $d_{33}\;=\;750\;(10^{-12}\;m/V)$, $d_{31}\;=\;-300\;(10^{-12}\;m/V)$, $k_{33}\;=\;71%$, $Qm\;=\;85$, $T_c\;=\;210^{\circ}C$.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.230-236
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• 2020

In this study, an adhesive tape with water and impact resistance for mobile devices was developed using a UV-curable urethane acrylate based polymer as a substrate. The substrate fabricated by UV-curable materials shows hydrophobicity and poor wettability, which significantly deteriorates the interface-adhesions between the substrate and acrylic adhesive. In order to improve the interface adhesion, 3-glycidoxy-propyl trimethoxysilane (GPTMS), a silane coupling agent having epoxy functional groups, was selected and incorporated into UV-curable urethane acrylate based polymer resins in various contents. The changes of the chemical composition according to the contents of GPTMS was studied with Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) to know the surface bonding properties. Also mechanical properties of the substrate were characterized by tensile strength, gel fraction and water contact angle measurements. The peel strengths at 180° and 90° were measured to compare the adhesion between the substrate and adhesive according to the silane coupling agent contents. The mechanical strength of the urethane acrylate adhesive tape decreased as the silane coupling agent increased, but the adhesion between the substrate and adhesives increased remarkably at an appropriate content of 0.5~1 wt%.

• The Journal of the Korea Contents Association
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• v.19 no.4
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• pp.41-53
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• 2019

As the paradigm of healthcare shifts from the center of treatment to the center of prevention, products and services related to disease prevention are emerging at domestic and abroad. The government considers the smart healthcare industry as a solution to healthcare problems such as an increase in the number of chronic illnesses and an increase in the burden of medical expenses. The purpose of this study is to explore the factors affecting the use of smart healthcare products and services focusing on Health Literacy and health related personal characteristics and to provide policy implications. The subjects of the questionnaire are 1,027 adults over 20 in the nation, and conducted an online survey. In addition, the factors were analyzed by decision tree method. As a result, most of the respondents(76.9%) did not have experience using Smart Healthcare products and services. However, in the Health Literacy question, there was a difference in use experience depending on the degree of difficulty in using the mass media information. Other factors were the degree of intention to use new technology, the understanding of counseling about family members and friends, and health checkups. In order to enable self-healthcare through smart healthcare products and services, the ability of consumers to explore and utilize health information from the mass media should be improved. In addition, government and enterprise efforts are needed to achieve this.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.1-10
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• 2019

In terms of realizing the future e-government such as intelligent government, this paper attempts to provide an earnest and insightful reflection and suggests desirable strategies with regard to the four different crucial elements including electronic voting, electronic contract, resident registration/electronic document management, and real-estate registration as an operating strategy of intelligent government and the fourth industrial revolution regarding. The 4th industrial revolution is aimed at concentrating information or data characterized with sharing, opening, communicating and releasing in cloud computing system, analyzing big data, collecting information, and flourishing people's well-being by information and communications technology with utilizing the smart devices. Therefore, reliability of the pivotal information or data is critical and it is important for the participants being transparently shared, without the data or information being forged. In this respect, introduction or application of block chain technology is essential. This paper will review preceding studies, discuss the aspect of the 4th industrial revolution and intelligent government, then suggest operating strategies in the field of electronic voting, electronic contract, management of resident registration and electronic document and real-estate registration.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.256-259
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• 2016

The growth of mobile devices in Internet of Things (IoT) leads to a number of intelligent buildings related IoT applications. For instance, home automation controlling system uses client system such web apps on smartphone or web service to access the home server by sending control commands. The home server receives the command, then controls for instance the light system. The gateway based RESTful technology responsible for handling clients' requests attests an internet latency in case a large number of clients' requests submit toward the gateway increases. In this paper, we propose the design tasks of the IoT gateway for handling concurrency events. In the procedure of designing tasks, concurrency is best understood by employing multiple levels of abstraction. The way that is eminently to accomplish concurrency is to build an object-oriented environment with support for messages passing between concurrent objects. We also investigate the performance of event-driven architecture for building IoT gateway using node.js on one side and communication protocol based message-oriented middleware known as XMPP to handle communications of intelligent building control devices connected to the gateway through a centralized hub. The Node.JS is 40% faster than the traditional web server side features thread-based approach. The use of Node.js server-side handles a large number of clients' requests, then therefore, reduces delay in performing predefined actions automatically in intelligent building IoT environment.

• Science of Emotion and Sensibility
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• v.22 no.2
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• pp.17-28
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• 2019

The touchscreen device is now commonly found in the form of mobile phones, tablet PCs, and other devices. Varied physical and visual experiences can be experienced through touchscreens. This study intended to explore how the physical and visual experiences provided by the touchscreen would affect people through their existing associations of behavior-attitude. Previous studies have found that certain behaviors affect attitudes. In particular, the approach-avoidance behavior has been noted to influence both social and personal attitudes. It was thus deemed necessary to ascertain the approach-avoidance effect exerted by touchscreens on the attitudes of users as the technology is widely used today. Experiment 1 provided an approach-avoidance experience via a touchscreen and demonstrated that touchscreen-based approach-avoidance dragging behavior on the touchscreen can affect a user's preference and purchase intent. It was found that a product that had been approached showed both higher preference and higher purchase intent than a product that had been avoided. Experiment 2 investigated whether a similar effect would occur when only the visual experience of approach-avoidance was provided. The outcome proved that products that had been visually approached had higher scores than products that had been avoided, both in terms of preference and purchase intent. The movement of the arm on the touchscreen (Experiment 1) and the visual perception of the approach-avoidance experience (Experiment 2) were both shown to influence participants' attitudes toward products. The results of this study suggest that the behavior and perception of users may be an important factor in designing touchscreen interfaces for online shopping.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.503-509
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• 2019

The demand for smaller, faster, and multi-functional mobile devices in increasing at a rapidly increasing rate. In response to these trends, Stacked Chip Scale Package (SCSP) is used widely in the assembly industry. A film type adhesive called die attach film (DAF) is used widely for bonding chips in SCSP. The DAF requires high flowability at high die attachment temperatures for bonding chips on organic substrates, where the DAF needs to feel the gap depth, or for bonding the same sized dies, where the DAF needs to penetrate bonding wires. In this study, the mixture design of experiment (DOE) was performed for three raw materials to obtain the optimized DAF recipe for low elastic modulus at high temperature. Three components are acrylic polymer (SG-P3) and two solid epoxy resins (YD011 and YDCN500-1P) with different softening points. According to the DOE results, the elastic modulus at high temperature was influenced greatly by SG-P3. The elastic modulus at $100^{\circ}C$ decreased from 1.0 MPa to 0.2 MPa as the amount of SG-P3 was decreased by 20%. In contrast, the elastic modulus at room temperature was dominated by YD011, an epoxy with a higher softening point. The optimized DAF recipe showed approximately 98.4% pickup performance when a UV dicing tape was used. A DAF crack that occurred in curing was effectively suppressed through optimization of the cure accelerator amount and two-step cure schedule. The imizadole type accelerator showed better performance than the amine type accelerator.