• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.2
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• pp.258-264
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• 2022

The smart farm for livestock, in which information and communication technology (ICT) is combined with livestock farm, is mostly based on the cloud computing paradigm. A cloud-based smart livestock farm has disadvantages such as increased response time, burden on cloud resource caused by the increased number of IoT sensors, traffic burden on the network, and lack of failure resilience mechanisms through collaboration with adjacent IoT devices. In this paper, with these problems in mind, we propose an IoT collaboration system based on edge computing. By using the relatively limited computing resources of the edge device to share the cloud's web server function, we aim to reduce the cloud's resources needed and improve response time to user requests. In addition, through the heartbeat-based failure recovery mechanism, IoT device failures were detected and appropriate measures were taken.

• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.470-475
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• 2016

In this paper, the effects of filter parameters on a supercontinuum-based all-optical thresholder are experimentally investigated. By tuning the filter parameters, the power transfer function and power transmission function are tailored. The experimental results show that a thresholder with short center wavelength has a better power function, and the slope in the middle level of the thresholder increases with increasing bandwidth. Through tuning the filter parameters, the thresholder can achieve a steplike power transfer function for optical thresholding, and a steplike power transmission function for optical self-switching. This makes the supercontinuum-based thresholder more flexible, and allows customization of performance to meet different demands in various applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.8
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• pp.623-631
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• 2013

Wireless LAN (WLAN) interface is one of the major sources drastically depleting the battery power of mobile devices such as smartphones and tablets. Most commercial mobile devices employ a power saving technique putting their WLAN interface into a sleep state when there is no network traffic, and thereby, save the battery power. However, since an access point (AP) just transmits the packet(s) received from a server to the corresponding mobile device immediately, it may cause a problem that the mobile device constantly remains in an awake state so that its battery power is rapidly drained. In this paper, we point out this problem and propose a new scheme that can save the mobile device's battery power with an adaptive packet scheduling at the AP side. From the experimental results based on a testbed, we found that the proposed scheme outperforms existing schemes over 50% in terms of power saving.

• Journal of the Korean Vacuum Society
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• v.19 no.6
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• pp.397-407
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• 2010

For sustainable and responsible development of nanomaterials technology, the establishment of ethical system for sound social acceptance of the technology as well as the development of the technology itself is necessary. In this paper, global efforts to identify and resolve the ethical issues regarding nanotechnology is reviewed, in particular the environmental, health and safety issues in nanomaterials, and the tools such as communication and engagement of stakeholders, regulations, certifications and workplace guidelines are scrutinized. Finally the policy recommendations for the establishment of ethical systems for safe usage of nanomaterials.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.220-220
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• 2013

Surface-normal transmission electro-absorption modulator (EAM) are attractive for high-definition (HD) three-dimensional (3D) imaging application due to its features such as small system volume and simple epitaxial structure [1,2]. However, EAM in order to be used for HD 3D imaging system requires uniform modulation performance over large area. To achieve highly uniform modulation performance of EAM at the operating wavelength of 850 nm, it is extremely important to remove the GaAs substrate over large area since GaAs material has high absorption coefficient below 870 nm which corresponds to band-edge energy of GaAs (1.424 eV). In this study, we propose and experimentally demonstrate a transmission EAM in which highly selective backside etching methods which include lapping, dry etching and wet etching is carried out to remove the GaAs substrate for achieving highly uniform modulation performance. First, lapping process on GaAs substrate was carried out for different lapping speeds (5 rpm, 7 rpm, 10 rpm) and the thickness was measured over different areas of surface. For a lapping speed of 5 rpm, a highly uniform surface over a large area ($2{\times}1\;mm^2$) was obtained. Second, optimization of inductive coupled plasma-reactive ion etching (ICP-RIE) was carried out to achieve anisotropy and high etch rate. The dry etching carried out using a gas mixture of SiCl4 and Ar, each having a flow rate of 10 sccm and 40 sccm, respectively with an RF power of 50 W, ICP power of 400 W and chamber pressure of 2 mTorr was the optimum etching condition. Last, the rest of GaAs substrate was successfully removed by highly selective backside wet etching with pH adjusted solution of citric acid and hydrogen peroxide. Citric acid/hydrogen peroxide etching solution having a volume ratio of 5:1 was the best etching condition which provides not only high selectivity of 235:1 between GaAs and AlAs but also good etching profile [3]. The fabricated transmission EAM array have an amplitude modulation of more than 50% at the bias voltage of -9 V and maintains high uniformity of >90% over large area ($2{\times}1\;mm^2$). These results show that the fabricated transmission EAM with substrate removed is an excellent candidate to be used as an optical shutter for HD 3D imaging application.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.141-148
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• 2012

Android that was made by Google and Open Handset Alliance is the open source software toolkit for mobile phone. Nowadays, Smart phone users have been rapidly increasing, by that reason a lot of application contents have been released and especially contents which focus on user convenience have been developed. In this paper, we develop a new application content smart alarm based on Google Android flatform. The features of the developed content are as follows. First, users set their day's schedules. So they can notify easily what they have to do at the moment. Second, when users set their alarms not to forget several sequential tasks, they can set their schedules by not only alarm method but also timer method. In the performance evaluation, we show the results of simulation using AVD(Android Virture Device).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.271-279
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• 2008

In this paper, we investigate interference between short-range radiocommunication devices(SRDs) with frequency hopping spread spectrum(FHSS) and direct sequence spread spectrum(DSSS) methods when they are in the same frequency bands. In order to analyze interference from unwanted emission of SRD with DSSS to that of FHSS, Monte-carlo(MC) simulation method is employed and interference probabilities are calculated. We simulate interference scenarios in accordance with several duty cycles and bandwidths. It is also assumed that the propagation model is free space. The effect of distance between interfering transmitter and victim receiver is analyzed and bit error rate(BER) is simulated. From the interference analysis results, it is shown that duty cycle affects compatibility more than band-width does. Also, we can make sure of the separation distance which satisfies BER criterion when there are only one interfering transmitter and multiple interfering transmitters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.5
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• pp.251-259
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• 2014

In this paper, we propose Low Energy Service Discovery (LESD) protocol for common discovery mode of IEEE 802.15.8 Peer Aware Communications (PAC). In order to minimize power consumption, Basic Repetition Block (BRB) is defined. Device is able to select operating mode and synchronize other devices through it. Proposed MAC procedure is Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) based on overhearing technique. Even if device has not been received response signal since transmitted request signal, it is able to discover other devices of same group through the overhearing technique. IEEE 802.15.8 PAC has required that performances of common discovery mode are presented about discovered devices during the simulation time, discovery latency and average power consumption. By considering the number of devices per group and channel environment, two scenarios are evaluated through system level simulation and the simulation results of proposed scheme are compared with CSMA/CA in same simulation conditions. As a result, proposed scheme is able to get high energy efficiency of devices as well as increase the number of discovered devices during simulation time when the longer the number of devices is distributed over a limited area.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3A
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• pp.141-150
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• 2012

The WiMedia Alliance has specified a Distributed Medium Access Control (D-MAC) protocol based on UWB for high speed wireless home networks and WPANs. In this paper, firstly, a time slot reservation protocol for relay transmission is proposed. Furthermore, we propose a novel relay node selection algorithm adaptive to current UWB link transmission rate. The proposed relay node selection algorithm has compatibility with current WiMedia D-MAC standard and is executed at each device according to the SoQ as a QoS criterion.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.725-729
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• 2012

In this paper, the standardization of the Web technology of HTML5/CSS3 and JQuery Mobile, using a variety of mobile platforms, run independently within an environment as possible to implement the Mobile Office System. In addition, user friendly Web interface and dynamic web design through a mobile device in a Mobile Office system provides convenience to the user when a hybrid Web application based mobile office system implement.