• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1975-1976
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• 2011

소셜네트워크의 등장은 기업 환경에도 많은 변화를 가져오고 있다. 초기의 기업 소셜네트워크서비스(SNS)는 자사 고객들과의 커뮤니케이션 채널로 활용되었지만, 최근의 기업 SNS는 자사내의 조직강화 수단으로 인식되기 시작하고 있다. 직원들의 수평적인 아이디어 뱅크와 인맥 형성(Human networks)을 위해서 많은 기업들이 SNS 활용을 시도하고 있다. 기업 SNS의 활용도가 높아지기 위해서는 Anywhere, Anytime 접근 환경이 지원되어야 한다. 기존 SNS 활용도를 폭발적으로 증가시킨 스마트폰과 같은 모바일 단말 지원도 기업 SNS에서도 이루어져야 한다. 그러나, 모바일 단말은 PC와 같은 기존 사용자 환경에 비해서 보안적으로 많은 취약점을 갖고 있다. 이 논문에서는 기업 SNS에모바일 단말 활용 시 대두될 수 있는 보안 취약성을 점검하고, 그에 대한 대응책을 제시한다.

• 한국기록관리학회지
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• 제12권1호
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• pp.33-58
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• 2012

웹과 모바일 환경의 변화와 함께, SNS는 정보유통에 있어서 중요한 도구로서 대두되고 있다. 그리고 페이스북, 트위터 등으로 대표되는 SNS는 소통의 새로운 패러다임으로 자리잡아가고 있다. 따라서 본 연구에서는 모바일 SNS를 통하여 기록정보서비스의 이용과 접근성을 확대시키고 기록 이용자의 참여와 협력을 도모할 수 있는 서비스를 제공하기 위한 방안을 모색하고자 하였다. 이를 위해 기존의 SNS에 대한 문헌조사를 통하여 모바일 SNS를 기반으로 효과적인 기록정보서비스의 제공방안을 제안하였다. 또한 제안방안의 실질적인 서비스 구현을 위하여 서비스 시스템 요소와 설계를 수행하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권12호
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• pp.5928-5947
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• 2019

Multicast Mesh based Mobile Ad-hoc NETworks (MANETs) provide efficient data transmission in energy restraint areas without a fixed infrastructure. In this paper, the authors present an improved version of protocol SLIMMER developed by them earlier, and name it SLIMMER-SN. Most mesh-based protocols suffer from redundancy; however, the proposed protocol controls redundancy through the concept of forwarding nodes. The proposed protocol uses remaining energy of a node to decide its energy efficiency. For measuring stability, a new metric called Stability of Node (SN) has been introduced which depends on transmission range, node density and node velocity. For data transfer, a weighted cost function selects the most energy efficient nodes / most stable nodes or a weighted combination of both. This makes the node selection criteria more dynamic. The protocol works in two steps: (1) calculating SN and (2) using SN value in the weighted cost function for selection of nodes. The study compared the proposed protocol, with other mesh-based protocols PUMA and SLIMMER, based on packet delivery ratio (PDR), throughput, end-to-end delay and average energy consumption under different simulation conditions. Results clearly demonstrate that SLIMMER-SN outperformed both PUMA and SLIMMER.

• 한국재료학회지
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• 제20권4호
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• pp.223-227
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• 2010

Recently, one-dimensional semiconducting nanomaterials have attracted considerable interest for their potential as building blocks for fabricating various nanodevices. Among these semiconducting nanomaterials,, $SnO_2$ nanostructures including nanowires, nanorods, nanobelts, and nanotubes were successfully synthesized and their electrochemical properties were evaluated. Although $SnO_2$ nanowires and nanobelts exhibit fascinating gas sensing characteristics, there are still significant difficulties in using them for device applications. The crucial problem is the alignment of the nanowires. Each nanowire should be attached on each die using arduous e-beam or photolithography, which is quite an undesirable process in terms of mass production in the current semiconductor industry. In this study, a simple process for making sensitive $SnO_2$ nanowire-based gas sensors by using a standard semiconducting fabrication process was studied. The nanowires were aligned in-situ during nanowire synthesis by thermal CVD process and a nanowire network structure between the electrodes was obtained. The $SnO_2$ nanowire network was floated upon the Si substrate by separating an Au catalyst between the electrodes. As the electric current is transported along the networks of the nanowires, not along the surface layer on the substrate, the gas sensitivities could be maximized in this networked and floated structure. By varying the nanowire density and the distance between the electrodes, several types of nanowire network were fabricated. The $NO_2$ gas sensitivity was 30~200 when the $NO_2$ concentration was 5~20ppm. The response time was ca. 30~110 sec.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권6호
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• pp.2686-2708
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• 2020

This paper investigates the energy efficiency of energy harvesting (EH) bidirectional cooperative sensor networks, in which the considered system model enables the uplink information transmission from the sensor (SN) to access point (AP) and the energy supply for the amplify-and-forward (AF) relay and SN using power-splitting (PS) or time-switching (TS) protocol. Considering the minimum EH activation constraint and quality of service (QoS) requirement, energy efficiency is maximized by jointly optimizing the resource division ratio and transmission power. To cope with the non-convexity of the optimizations, we propose the low complexity iterative algorithm based on fractional programming and alternative search method (FAS). The key idea of the proposed algorithm first transforms the objective function into the parameterized polynomial subtractive form. Then we decompose the optimization into two convex sub-problems, which can be solved by conventional convex programming. Simulation results validate that the proposed schemes have better output performance and the iterative algorithm has a fast convergence rate.

• Applied Microscopy
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• 제49권
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• pp.1.1-1.10
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• 2019

Joints of three-dimensional (3D) rutile-type (r) tin dioxide ($SnO_2$) nanowire networks, produced by the flame transport synthesis (FTS), are formed by coherent twin boundaries at $(101)^r$ serving for the interpenetration of the nanowires. Transmission electron microscopy (TEM) methods, i.e. high resolution and (precession) electron diffraction (PED), were utilized to collect information of the atomic interface structure along the edge-on zone axes $[010]^r$, $[111]^r$ and superposition directions $[001]^r$, $[101]^r$. A model of the twin boundary is generated by a supercell approach, serving as base for simulations of all given real and reciprocal space data as for the elaboration of three-dimensional, i.e. relrod and higher order Laue zones (HOLZ), contributions to the intensity distribution of PED patterns. Confirmed by the comparison of simulated and experimental findings, details of the structural distortion at the twin boundary can be demonstrated.

• 정보보호학회논문지
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• 제19권2호
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• pp.93-103
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• 2009

본 논문에서는 3GPP 네트워크에서 USIM 기반의 사용자 인증 기법을 제안한다. 제안 기법은 기존의 3GPP 네트워크 접속을 위한 인증 방식에서 발생 가능한 Sequence Number 동기 문제, 인증 데이터 Overhead 문제, 네트워크 간 시그널링 Overhead 문제 등을 개선한다. 제안 기법은 기존의 USIM 기반의 AKA 인증 프로토콜을 기본 모델로 사용하고 단말과 SN이 공유한 SK와 Time Stamp를 통해서 AKA 인증 절차를 수행하도록 한다. 이렇게 함으로써 인증 벡터의 Sequence Number의 동기 여부를 확인할 필요 없이 Time Stamp 값으로 인증 벡터의 맵핑을 수행하여 Sequence Number 동기 문제를 해결할 수 있다. 뿐만 아니라 하나의 인증 벡터만을 관리하여 사용하기 때문에 SN에서의 인증 데이터 Overhead문제를 해결하고, SN과 HN 사이의 시그널링 Overhead 문제를 개선할 수 있다.

• 인터넷정보학회논문지
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• 제22권5호
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• pp.9-16
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• 2021

Recently, the traffic volume of mobile communications increases rapidly and the small-cell is one of the solutions using two offload schemes, i.e., local IP access (LIPA) and selected IP traffic offload (SIPTO), to reduce the end-to-end delay and amount of mobile data traffic in the core network (CN). However, 3GPP describes the concept of LIPA and SIPTO and there is no decision algorithm to decide the path from source nodes (SNs) to destination nodes (DNs). Therefore, this paper proposes a dynamic mobile data traffic offload scheme using small-cells to decide the path based on the SN and DN, i.e., macro user equipment, small-cell user equipment (SUE), and multimedia server, and type of the mobile data traffic for the real-time and non-real-time. Through analytical models, it is shown that the proposed offload scheme outperforms the conventional small-cell network in terms of the delay of end-to-end mobile data communications and probability of the mobile data traffic in the CN for the heterogeneous networks.

• 대한임베디드공학회논문지
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• 제18권4호
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• pp.173-183
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• 2023

This paper deals with a routing algorithm which can find the best communication route to a desired point considering disconnected links in the LEO (low earth orbit) satellite networks. If the LEO satellite networks are dynamic, the number and distribution of the disconnected links are varying, which makes the routing problem challenging. To solve the problem, in this paper, we propose a routing method based on Dueling DQN which is one of the reinforcement learning algorithms. The proposed method was successfully conducted and verified by showing improved performance by reducing convergence times and converging more stably compared to other existing reinforcement learning-based routing algorithms.

• 전기전자학회논문지
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• 제26권2호
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• pp.319-328
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• 2022

베어링은 기계가 작동할때 중요한 역할을 한다. 때문에, 베어링에 결함이 발생하면 기계전체의 치명적인 결함을 발생시킨다. 그러므로 베어링 결함은 조기에 발견되어야한다. 본 논문에서는 연속 웨이블릿 변환과 Switchable 정규화를 기반으로 한 합성곱 신경망(SN-CNN)을 이용한 방법을 베어링 결함 감지 모델에 대해 설명한다. 모델의 정확도는 Case Western Reserve University(CWRU) 베어링 데이터 집합을 사용하여 측정되었다. 또한 배치 정규화(BN, Batch Normalization)[1] 방법과 스펙트로그램 이미지가 모델 성능의 비교를 위해 사용되었다.