• 한국멀티미디어학회논문지
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• 제22권6호
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• pp.676-683
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• 2019

Wireless Sensor Networks (WSNs) consist of multiple tiny and power constrained sensors which use radio frequencies to carry out sensing in a designated sensor area. To effectively design and implement reliable WSN, it is critical to consider models, protocols, and algorithms that can optimize energy consumption of all the sensor nodes with optimal amount of packet delivery. It has been observed that deploying a single sink node comes with numerous challenges especially in a situation with high node density and congestion. Sensor nodes close to a single sink node receive more transmission traffic load compared to other sensors, thus causing quick depletion of energy which finally leads to an energy hole and sink hole problems. In this paper, we proposed the use of multiple energy efficient sink nodes with brute force technique under optimized parameters to improve on the number of packets delivered within a given time. Simulation results not only depict that, deploying N sink nodes in a sensor area has a maximum limit to offer a justifiable improvement in terms of packet delivery ratio but also offers a reduction in End to End delay and reliability in case of failure of a single sink node, and an improvement in the network lifetime rather than deploying a single static sink node.

• ETRI Journal
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• 제42권6호
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• pp.872-885
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• 2020

Distributed consensus requires the consent of more than half of the congress to produce irreversible results, and the performance of the consensus algorithm deteriorates with the increase in the number of nodes. This problem can be addressed by delegating the agreement to a few selected nodes. Since the selected nodes must comply with the Byzantine node ratio criteria required by the algorithm, the result selected by any decentralized node cannot be trusted. However, some trusted nodes monopolize the consensus node selection process, thereby breaking decentralization and causing a trilemma. Therefore, a consensus node selection algorithm is required that can construct a congress that can withstand Byzantine faults with the decentralized method. In this paper, an algorithm based on the Byzantine agreement among decentralized agents to facilitate agreement between decentralization nodes is proposed. It selects a group of random consensus nodes per block by applying the proposed proof of nonce algorithm. By controlling the percentage of Byzantine included in the selected nodes, it solves the trilemma when an arbitrary node selects the consensus nodes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권6호
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• pp.1706-1727
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• 2023

Under Water Sensor Networks (UWSN) has gained attraction among various communities for its potential applications like acoustic monitoring, 3D mapping, tsunami detection, oil spill monitoring, and target tracking. Unlike terrestrial sensor networks, it performs an acoustic mode of communication to carry out collaborative tasks. Typically, surface sink nodes are deployed for aggregating acoustic phenomena collected from the underwater sensors through the multi-hop path. In this context, UWSN is constrained by factors such as lower bandwidth, high propagation delay, and limited battery power. Also, the vulnerabilities to compromise the aquatic environment are in growing numbers. The paper proposes an Energy-Efficient standalone Intrusion Detection System (EEIDS) to entail the acoustic environment against malicious attacks and improve the network lifetime. In EEIDS, attributes such as node ID, residual energy, and depth value are verified for forwarding the data packets in a secured path and stabilizing the nodes' energy levels. Initially, for each node, three agents are modeled to perform the assigned responsibilities. For instance, ID agent verifies the node's authentication of the node, EN agent checks for the residual energy of the node, and D agent substantiates the depth value of each node. Next, the classification of normal and malevolent nodes is performed by determining the score for each node. Furthermore, the proposed system utilizes the sheep-flock heredity algorithm to validate the input attributes using the optimized probability values stored in the training dataset. This assists in finding out the best-fit motes in the UWSN. Significantly, the proposed system detects and isolates the malicious nodes with tampered credentials and nodes with lower residual energy in minimal time. The parameters such as the time taken for malicious node detection, network lifetime, energy consumption, and delivery ratio are investigated using simulation tools. Comparison results show that the proposed EEIDS outperforms the existing acoustic security systems.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1061-1064
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• 2006

Optimal design of functionally graded plates is investigated considering stress and critical temperature. Material properties are assumed to be temperature dependent and varied continuously in the thickness direction. The effective material properties are obtained by applying linear rule of mixtures. The 3-D finite element model is adopted using an 18-node solid element to analyze more accurately the variation of material properties and temperature field in the thickness direction. For stress analysis, the tensile stress ratio and compressive stress ratio of the structure under mechanical load are investigated. In the thermo-mechanical buckling analysis, temperature at each node is obtained by solving the steady-state heat transfer problem and Newton-Raphson method is used for material nonlinear analysis. Finally, the optimal design of FGM plates is studied for stress reduction and improving thermo-mechanical buckling behavior, simultaneously.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.463-470
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• 1998

The boundary/finite element analysis for the seismic wave amplifications due to nonhomogeneous alluvial deposits was performed in this study. For numerical analysis, the homogeneous linear elastic soil half-space was modeled by using the 3-node isoparametric boundary elements and the inhomogeneous alluvial deposit was modeled by using the 8-node isoparametric finite elements. The two elements at interface were coupled together by the equilibrium condition of the tractions and the compatibility condition of the displacements. As a prarmetric variable, the incident angle and the dimensionsless frequency of the SH, P and SV-waves and the shear wave velocity ratio and the mass density ratio between the half-space and the alluvial deposit were selected.

• ETRI Journal
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• 제36권4호
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• pp.591-598
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• 2014

This paper proposes a new min-sum algorithm for low-density parity-check decoding. In this paper, we first define the negative and positive effects of the received signal-to-noise ratio (SNR) in the min-sum decoding algorithm. To improve the performance of error correction by considering the negative and positive effects of the received SNR, the proposed algorithm applies adaptive scaling factors not only to extrinsic information but also to a received log-likelihood ratio. We also propose a combined variable and check node architecture to realize the proposed algorithm with low complexity. The simulation results show that the proposed algorithm achieves up to 0.4 dB coding gain with low complexity compared to existing min-sum-based algorithms.

• 한국정보과학회논문지:데이타베이스
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• 제30권6호
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• pp.629-640
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• 2003

공유 디스크(Shared Disks: SD) 클러스터는 온라인 트랜잭션 처리를 위해 다수 개의 컴퓨터를 연동하는 방식으로, 각 노드들은 디스크 계층에서 데이타베이스를 공유한다. SD 클러스터에서 트랜잭션 라우팅은 사용자가 요청한 트랜잭션을 실행할 노드를 결정하는 것을 의미한다. 이때, 동일한 클래스에 속하는 트랜잭션들을 가급적 동일한 노드에서 실행시킴으로써 지역 참조성을 극대화할 수 있으며, 이를 친화도 기반 라우팅이라 한다. 그러나 친화도 기반 라우팅은 트랜잭션 클래스의 부하 변화에 적절히 대처할 수 없으며, 특정 트랜잭션 클래스가 폭주할 경우 해당 노드는 과부하 상태에 빠질 수 있다는 단점을 갖는다. 본 논문에서는 친화도 기반 라우팅을 지원하면서 SD 클러스터를 구성하는 노드들의 부하를 동적으로 분산할 수 있는 동적 트랜잭션 라우팅 기법을 제안한다. 제안한 기법은 지역 버퍼에 대한 참조 지역성을 높이고 버퍼 무효화 오버헤드를 줄임으로써 시스템의 성능을 향상시킬 수 있다.

• Asian Pacific Journal of Cancer Prevention
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• 제13권11호
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• pp.5517-5523
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• 2012

Purpose: To evaluate the diagnostic accuracy of ultrasonograph and fine-needle aspiration cytologic examination (USG-FNAC) in the staging of axillary lymph node metastasis in breast cancer patients.Methods: We conducted an electronic search of the literature addressing the performance of USG-FNAC in diagnosis of axillary lymph node metastasis in databases such as Pubmed, Medline, Embase, Ovid and Cochrane library. We introduced a series of diagnostic test indices to evaluate the performance of USG-FNAC by the random effect model (REM), including sensitivity, specificity, likelihood ratios, and diagnostic odds ratios and area under the curve (AUC). Results: A total of 20 studies including 1371 cases and 1289 controls were identified. The pooled sensitivity was determined to be 0.66 (95% CI 0.64-0.69), specificity 0.98 (95% CI 0.98-0.99), positive likelihood ratio 22.7 (95% CI 15.0-34.49), negative likelihood ratio 0.32 (95% CI 0.25-0.41), diagnostic OR 84.2 (95% CI 53.3-133.0). Due to the marginal threshold effect found in some indices of diagnostic validity, we used a summary SROC curve to aggregate data, and obtained a symmetrical curve with an AUC of 0.942. Conclusion: The results of this meta-analysis indicated that the USG-FNAC techniques have acceptable diagnostic validity indices and can be used for early staging of axillary lymph node in breast cancer patients.

• 한국정보통신학회논문지
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• 제14권9호
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• pp.2143-2149
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• 2010

본 논문에서는 지리정보 라우팅 프로토콜 중 가장 잘 알려진 GPSR의 성능을 향상시키기 위한 에이전트 기반의 로드 분산 알고리즘을 제안한다. 제안된 방법은 싱크 노드 주변 노드 중에 하나를 에이전트 노드로 설정하고 데이터 패킷을 싱크로 직접 전송하는 대신에 에이전트 노드에게 전송하고 이 패킷들은 에이전트 노드에 의하여 싱크로 전달되게 하게 함으로써 트래픽의 분산을 자동적으로 유도한다. 또한, 데이터 포워딩시에는 위치 정보뿐만 아니라 주변 노드의 현재 버퍼 사용량을 기준으로 다음 홉을 선택하게 함으로써 혼잡을 효율적으로 예방함으로써 로드 분산을 수행한다. 이러한 기능들은 패킷의 손실의 줄이게 되고 결국 패킷 전송 성공률이 높아지게 된다. 제안된 메커니즘의 성능 평가를 위하여 싱크노드로의 연결 수와 홉 수에 따른 패킷 전송 성공율을 측정한 결과 기존 GPSR 프로토콜에 비하여 향상된 성능을 확인하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제14권5호
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• pp.249-256
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• 2010

Gender differences in the trace elements of monkey sino-atrial (SA) node were investigated in a process of age-dependent alterations. Sixty hearts from Japanese and rhesus monkeys (30 male and 30 female) used were aged ranging from 1-day- to 30-year-old. The elements were analyzed using an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Advancing age decreased all the trace elements. Ca, P, S and Mg significantly decreased. The correlation coefficients of Ca and P were $-0.178{\pm}0.081$ (p<0.05) and $-0.088{\pm}0.022$ (p<0.05) in male (n=30), and $-0.095{\pm}0.026$ (p<0.05) and $-0.069{\pm}0.017$ (p<0.05) in female (n=30), respectively. The age-dependent coefficients for Fe/Ca, Zn/Ca, Fe/P, Fe/S, Zn/S, Fe/Mg and Zn/Mg were exhibited markedly in male, but all was less in female. In gender-related differences, only a ratio of P/Ca (p<0.05) was significantly observed with ageing. The trace elements such as Cu, Se and Sn were less detected in the SA nodes. These results indicate that the age-dependent changes in the ratios of elements are appeared more rapidly in male monkey SA node, and the gender difference is observed in ratio of P/Ca. The different attenuations may be involved with the age- and gender-related SA nodal functions.