• 한국멀티미디어학회논문지
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• 제17권4호
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• pp.433-440
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• 2014

Wireless communication offers the flexibility to the node movement at the spatial dimension more than the wire communication not only in IP architecture but also in Content-Centric Networking. Although it gives such advantage, the intra-domain movement of a node especially the data source node affects the communication to the access point node which in the end affects the acceptance ratio of the client node that requests the data packets from the data source node. In this paper, we use time-division access method to maintain the acceptance ratio of the client node as the effect of the intra-domain data source node movement in Content-Centric Networking. The simulation result shows that the acceptance ratio of the client node can be maintained using the time-division access method as long as the interval access time is less than the coherence time.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2009년도 추계학술발표대회
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• pp.917-918
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• 2009

This study evaluated the level of performance improvement in the form of a simulated experiment by adding fixed node in the middle of the network as a way to improve mobile ad.hoc network performance. The result showed that the performance level was much higher when fixed node was used together than when mobile node was used only, and the comparison of the mobile speed of mobile node also showed that use of fixed node together had higher performance. Moreover, the evaluation in accordance with the number of fixed node showed that more number of fixed node had shorter time delay. Further study following this on how many fixed node should be added on the ad.hoc network will ensure establishment of more reliable ad.hoc network.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 춘계종합학술대회 A
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• pp.890-893
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• 2008

자율성 및 이동성 갖는 네트워크 구조의 하나인 MANET(Mobile Ad-Hoc Networks)은 각 node들은 그 특성에 따라서 clustering service을 한다. node의 전송과정 중 path access에 대하여 중요성 또한 강조되고 있다. 일반적인 무선 네트워크 상에서의 node들은 clustering을 하게 되는데 그 과정에서 발생되는 여러 가지 문제점을 가지고 전송이 이루어진다. 모든 node들이 송, 수신상의 전송 범위(Beam forming area)가지고 있으며, 이러한 각 node들의 전송범위 내에 전송이 이루어지는 전통적인 전송기술 mechanism을 찾는다. 이러한 전송상황에서의 송신하는 node와 수신된 node간에 발생되고 있는 중복성의 문제점으로 즉, 상호적용에 의한 네트워크 duplicate(overlapping)이 크게 우려가 되고 있다. 이러한 전송상의 전송 범위 중첩, node간의 packet 간섭현상, packet의 중복수신 및 broadcasting의 storming현상이 나타난다. 따라서 본 논문에서는 상황정보의 속성을 이용한 계층적 상호 head node들의 접근된 위치와 연계되는 전송속도, 보존하고 있는 head node들의 에너지 source value, doppler효과를 통한 head node의 이동방향 등 분석한다. 분석된 방법으로 전송상의 계층적 path가 구성된 경험적 path 속성을 통한 네트워크 connectivity 신뢰성을 극대화 할 뿐만 아니라 네트워크의 전송 범위 duplicate을 사전에 줄일 수 있고 전송망의 최적화를 유지할 수 있는 기법의 하나인 상황정보를 이용한 ad hoc network의 ODDMRP(Ontology Doppler effect-based Dynamic Multicast Routing Protocol) clustering 기법을 제안한다.

• 한국군사과학기술학회지
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• 제12권3호
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• pp.333-343
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• 2009

Tactical Information Communication Network(TICN) is a concept-type integrated Military Communication system that enables precise command control and decision making by unifying the diversified military communication network and conveying diverse range of battle field information on real-time, at right place at right time. TICN is designed to advance into high speed, large capacity, long distance wireless relay transmission. To support mobility in battlefield environments, the application of Ad-hoc networking technology to its wireless communication has been examined. Ad-hoc network is consist of mobile nodes and nodes in the network depends on the cooperation of other nodes for forwarding of packets. In this context, some non-cooperating nodes may delay forwarding of packets or drop the packets. This may hamper the network as a whole and disrupt communication between the cooperating nodes. To solve this problem, we present a solution with a Node Weight Management Server(NWMS), which manages each node's weight according to its behavior in local area. When the NWMS detects misbehaving node, it increases the node's weight. If the node's weight exceeds a predefined threshold then the NWMS broadcasts the node's information into network to isolate the misbehaving node from the network. These mechanisms show that they are highly effective and can reliably detect a multitude of misbehaving node.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.4223-4249
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• 2015

A novel jamming detection technique to detect the presence of jamming in the downstream direction for cluster based wireless sensor networks is proposed in this paper. The proposed technique is deployed in base station and in cluster heads. The proposed technique is novel in two aspects: Firstly, whenever a cluster head receives a packet it verifies whether the source node is legitimate node or new node. Secondly if a source node is declared as new node in the first step, then this technique observes the behavior of the new node to find whether the new node is legitimate node or jammed node. In order to monitor the behavior of the existing node and new node, the second step uses two metrics namely packet delivery ratio (PDR) and received signal strength indicator (RSSI). The rationality of using PDR and RSSI is presented by performing statistical test. PDR and RSSI of every member in the cluster is measured and assessed by the cluster head. And finally the cluster head determines whether the members of the cluster are jammed or not. The CH can detect the presence of jamming in the cluster at member level. The base station can detect the presence of jamming in the wireless sensor network at CH level. The simulation result shows that the proposed technique performs extremely well and achieves jamming detection rate as high as 99.85%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권3호
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• pp.1481-1501
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• 2019

In opportunistic network, the behavior of a node is autonomous and has social attributes such as selfishness.If a node wants to forward information to another node, it is bound to be limited by the node's own resources such as cache, power, and energy.Therefore, in the process of communication, some nodes do not help to forward information of other nodes because of their selfish behavior. This will lead to the inability to complete cooperation, greatly reduce the success rate of message transmission, increase network delay, and affect the overall network performance. This article proposes a hybrid incentive mechanism (Mim) based on the Reputation mechanism and the Credit mechanism.The selfishness model, energy model (The energy in the article exists in the form of electricity) and transaction model constitute our Mim mechanism. The Mim classifies the selfishness of nodes and constantly pay attention to changes in node energy, and manage the wealth of both sides of the node by introducing the Central Money Management Center. By calculating the selfishness of the node, the currency trading model is used to differentiate pricing of the node's services. Simulation results show that by using the Mim, the information delivery rate in the network and the fairness of node transactions are improved. At the same time, it also greatly increases the average life of the network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권8호
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• pp.2587-2605
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• 2022

In order to efficiently detect community structure in complex networks, community detection algorithms can be designed from the perspective of node similarity. However, the appropriate parameters should be chosen to achieve community division, furthermore, these existing algorithms based on the similarity of common neighbors have low discrimination between node pairs. To solve the above problems, a noval community detection algorithm using closeness similarity based on common neighbor node clustering entropy is proposed, shorted as CSCDA. Firstly, to improve detection accuracy, common neighbors and clustering coefficient are combined in the form of entropy, then a new closeness similarity measure is proposed. Through the designed similarity measure, the closeness similar node set of each node can be further accurately identified. Secondly, to reduce the randomness of the community detection result, based on the closeness similar node set, the node leadership is used to determine the most closeness similar first-order neighbor node for merging to create the initial communities. Thirdly, for the difficult problem of parameter selection in existing algorithms, the merging of two levels is used to iteratively detect the final communities with the idea of modularity optimization. Finally, experiments show that the normalized mutual information values are increased by an average of 8.06% and 5.94% on two scales of synthetic networks and real-world networks with real communities, and modularity is increased by an average of 0.80% on the real-world networks without real communities.

• 대한두경부종양학회지
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• 제26권2호
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• pp.183-186
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• 2010

Purpose : Papillary thyroid carcinoma (PTC) is known for malignant tumor which has a favorable prognosis and long-term survival. Although the prognosis for patients with PTC is generally good, PTC tends to have highly metastatic property. The purpose of this study was to analyze the central compartment lymph node in papillary thyroid cancer with no lymph node metastasis clinically and to assess the significance of prophylactic node dissection. Methods : A retrospective review was carried out in 394 patients with PTC who underwent surgery for the period from January 2004 to December 2006. The positive rate of the lymph node metastasis was analyzed. The relations between the central compartment lymph nodes and the patients' age, gender, tumor size, exrathyroidal extension(ETE), multifocality, and bilaterality were comparatively analyzed in PTC patients with preoperative no lymph node metastasis. Results : The enrolled patients were 40 male and 354 female cases. The 118 cases of them were found to have cervical lymph node metastasis. The mean age was 46 years(range, 15-77years). Tumor size(p=0.000), ETE(p=0.001), multifocality(p=0.014), and bilaterality(p=0.001) were significantly related factors for cervical lymph node metastasis clinically in papillary thyroid cancer. However, age and gender were not significantly related with lymph node metastasis. Conclusion : Although no lymph node metastasis clinically, prophylactic neck node dissection can be performed to avoid risks of local recurrence and reoperation in the light of PTC nature. The pathological status and high positive rate of central compartment lymph node relate to tumor size and extrathyroidal extension. Close surveillance for nodal status is required in follow-up.

• Asian Pacific Journal of Cancer Prevention
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• 제16권11호
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• pp.4719-4722
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• 2015

Background: This study aimed to determine the utility and a cut-off level of serum squamous cell carcinoma antigen (SCC-Ag) to predict lymph node metastasis in locally advanced cervical cancer cases. We also investigated the correlation between SCC-Ag level and lymph node status. Materials and Methods: From June 2009 to June 2014, 232 patients with cervical cancer stage IB2-IVA, who were treated at Ramathibodi Hospital, were recruited. Receiver operating characteristic (ROC) curves were used to identify the best cut-off point of SCC-Ag level to predict lymph node metastasis. Quantile regression was performed to evaluate the correlation between SCC-Ag levels and pelvic lymph node metastasis, paraaortic lymph node metastasis, and parametrial involvement as well as tumor size. Results: Pelvic lymph node metastasis and paraaortic lymph node metastasis were diagnosed in 46.6% and 20.1% of the patients, respectively. The median SCC-Ag level was 6 ng/mL (range, 0.5 to 464.6 ng/mL). The areas under ROC curves between SCC-Ag level and pelvic lymph node metastasis, paraaotic lymph node metastasis, parametrial involvements were low. SCC-Ag level was significantly correlated with paraaortic lymph node status (p=0.045) but not with pelvic lymph node status and parametrial involvement. SCC-Ag level was also related to the tumor diameter (p<0.05). Conclusions: SCC-Ag level is not a good predictor for pelvic and paraaortic lymph node metastasis. However, it is still beneficial to assess the tumor burden of squamous cell carcinoma of the cervix.

• Spatial Information Research
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• 제21권3호
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• pp.45-53
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• 2013

웹GIS는 수년 동안 사용자들에게 효율적이고 정확한 공간정보를 제공하기 위해 최신 웹기술을 기반으로 발전해왔다. 또한 웹GIS 서버는 클라이언트의 요청을 빠르게 연산 처리하고 공간정보 서비스를 제공하기 위해 성능개선을 지속해왔다. 본 연구에서는 서버 개발에 자바스크립트(JavaScript)를 사용하는 이벤트 기반의 비동기식 I/O 처리가 가능한 프레임웍 기술인 Node.js를 활용하여 NodeMap이라고 이름붙인 웹GIS 서버를 설계하고 구현하였다. NodeMap은 기본적으로 OGC 표준 인터페이스를 지원하는 웹GIS 서버이다. 이를 위해 공간 인덱스 및 표준 공간쿼리 함수를 지원하는 DBMS를 활용하여 GIS 데이터를 처리하도록 하였다. 그리고 공간 정보를 타일 맵 위에 렌더링 하기 위해 HTML5 Canvas를 지원하는 Node-Canvas 모듈을 활용하였다. 마지막으로 Node.js의 가장 많이 쓰이는 커넥트 모듈 기반의 프레임웍인 Express 모듈을 활용하였다. 구현된 NodeMap은 성능테스트를 통해 향 후 웹GIS 서버개발기술로서 Node.js의 활용 가능성을 확인하였다. 본 연구를 통해 기존 서버 개발 기술과 차별화된 기술인 Node.js를 웹GIS 서버 구현에 우선적용 함으로서 향 후 인터넷 GIS 서비스에서의 활용 가능성을 제시하였다.