• 제어로봇시스템학회논문지
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• 제13권9호
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• pp.920-926
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• 2007

Establishing a fixed path for the message delivery through a wireless network is impossible due to the mobility. Among the number of routing protocols that have been proposed for wireless ad-hoc networks, the AODV(Ad-hoc On-demand Distance Vector) algorithm is suitable in the case of highly dynamic topology changes, along with ZigBee Routing(ZBR), with the exception of route maintenance. Accordingly, this paper introduces a routing scheme focusing on the energy efficiency and route discovery time for wireless alarm systems using IEEE 802.15.4-based ZigBee. Essentially, the proposed routing algorithm utilizes a cluster structure and applies ZBR within a cluster and DSR (Dynamic Source Routing) between clusters. The proposed algorithm does not require a routing table for the cluster heads, as the inter-cluster routing is performed using DSR. The performance of the proposed algorithm is evaluated and compared with ZBR using an NS2 simulator. The results confirm that the proposed Cluster-based AODV (CAODV) algorithm is more efficient than ZBR in terms of the route discovery time and energy consumption.

• 대한기계학회논문집A
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• 제28권8호
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• pp.1221-1228
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• 2004

The vertical roller mill is the important machine grinding and mixing various crude materials in the manufacturing process of portland cement. Table liner is one of grinding elements of vertical roller mill and is subjected to the cyclic bending stress by rollers load and the centrifugal force by rotation of table. It demands $4{\times}10^7$ cycle but has $4{\times}10^6{\sim}8{\times}10^6$ cycle. It fractures at the edge of grinding path of outside roller. The repair expense for it amounts to $30\%$ of total maintenance of vertical roller mill. Therefore, this study shows the fracture mechanism of table liner for vertical roller mill using HDM and fatigue analysis and makes the estimation for safety of vertical roller mill.

• 한국건설관리학회논문집
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• 제3권1호
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• pp.115-123
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• 2002

공간의 효율적 이용 및 법정 주차대수 확보 등으로 아파트 단지의 지하층은 대부분 지하주차장으로 활용되고 있으며, 주차장상부도 시공 중에 성토 및 포장공사가 완성되지 않은 상태에서 작업차량의 통로 및 자재 야적장으로 사용되고 있어 과하중이 작용되고 있는 실정이다. 그러므로 시공중이거나 완공된 지하구조물에서 지속적으로 균열 및 누수현상이 발생하여 구조물의 성능저하는 물론 많은 금액의 하자보수비 투입, 민원유발 및 대외적인 신뢰도 저하 등 많은 문제점이 발생하고 있다. 따라서 본 연구의 목적은 시공중인 아파트와 준공된 아파트 지하주차장을 대상으로 현장조사를 실시하고, 그동안 실시한 안전진단 사례를 참고하여 아파트 지하주차장의 균열 및 누수현상 원인을 파악하고 그에 따른 설계 및 시공상의 방지대책을 마련하는데 있다.

• 한국압력기기공학회 논문집
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• 제11권1호
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• pp.61-68
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• 2015

The function of Feed Water Ring is to provide the flow path from Feedwater Nozzle to inside of SG(steam generator). Significant amounts of general FAC on the outside of the Feed Water Ring are not likely due to the low flow velocities in this area. However, on the interior of the Feed Water Ring, there may be areas of local higher flow velocity which could lead to higher FAC rates. These may include the inlet tee from the Feedwater Nozzle into the Feed Water Ring, the areas where the Feed Water Ring changes diameter, and especially the entrance area to the J-Nozzles. In this paper, the results of root cause analysis of through-wall hole observed at domestic WH 51F SG Feed Water Ring and its effect on the integrity and performance of SG are described. And, the maintenance strategy for WH 51F SG Feed Water Ring and the monitoring strategy for Downcomer Feed Water Ring of CE System 80 SG are presented.

• 한국정밀공학회지
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• 제27권12호
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• pp.99-106
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• 2010

Gas turbines operation for power generation increased rapidly since 1990 due to the high efficiency in combined cycle, relatively low construction cost and low emission. But the operation and maintenance cost for gas turbine is high because the expensive superalloy hot gas path parts should be repaired and replaced periodically This study analyzed the initiation and propagation of the crack at the gas turbine blades which are coated with MCrAIY as a bond coat and TBC as a top coat. The sample blades had been serviced at the actual gas turbines for power generation. Total 7 sets of blades were analyzed and they have different EOH(equivalent operation hour). Blades were sectioned and the cracking distribution were measured and analyzed utilizing SEM(scanning electron microscope) and optical microscope. The blades which had 52,000 EOH of operation had cracks at the substrate and the maximum depth was 0.2 mm. Most of the cracks initiated at the boundary layer between TBC and bond coat and propagated down to the bond coat. Once bond coat is cracked, the base metal is exposed to the oxidation condition and undergoes notch effect. Under this environment, the crack branched at the inter-diffusion layer and propagated to the substrate. Critical cracks affecting the blade life were analyzed as those on suction side and platform.

• 센서학회지
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• 제14권3호
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• pp.198-205
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• 2005

Recently, the systems using multiple sensors such as magnetic, acoustic and pressure sensor are used for detection of underwater objects or vehicles. Those systems have difficulty of maintenance and repair because they operate underwater. Thus, this paper describes a hybrid detection system with long term operating reliability. This has a multi-signal transmission structure to have a high reliability. First, a signal transmission & receiving part, which transfers data from underwater sensors to land and receive control message from land through optical cable, has 4 multi-path. Second, the nodes for signal transmission are connected dually each other with single-hop construction and sensors are connected to a couple of neighboring nodes. This enables the output signal to transmit from a node to the next node and the next but one node together. Also, the signal from a sensor can be transmitted to two nodes at the same time. Therefore, the system with this construction has high reliability in long term operation because it makes possible to transmit sensor data to another node which works normally although a transmission node or cable in system have some faults.

• 한국시뮬레이션학회논문지
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• 제15권4호
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• pp.107-117
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• 2006

무선 센서 네트워크는 센서노드와 싱크로 구성되며, 센서 노드로부터 생성된 신호들은 싱크로 전송되어 처리된다. 센서네트워크는 모든 노드들이 한정된 에너지를 가지고 운용되기 때문에 센서 네트워크를 오랫동안 유지하기 위한 연구가 많이 진행되어 왔다. 대부분의 연구들은 싱크를 고정으로 가정하였다. 그러나 실제 환경에서는 사람이나 자동차등에 의해 싱크가 이동성을 가지는 경우가 많다. 본 논문에서는 이동 싱크에 기반한 그리드 방식을 적용하여 노드의 에너지 소비를 줄이기 위한 방안을 제안한다. 이 방안은 대부분의 라우팅 작업량을 이동 싱크가 처리하고, 무선 센서지역을 세분화하여 운용함으로써 전력 소비를 줄인다. 또한 시뮬레이션에 의한 성능 평가를 통해 제안방안에 대해 분석하였다.

• 수산해양교육연구
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• 제28권2호
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• pp.456-464
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• 2016

NCS development for construction of marine terminal structure was carried out through following procedures such as analysis on characteristics, analysis on duty, development of the first draft for standards, validation of industry sites, duty competency standards through expert committee, and utilizing package. The results were as follows. Firstly, duty competency was classified as levels from 3 to 7. Educational training institutions were followed by 22 universities, 21 colleges, 16 graduate schools, and 10 high schools. Secondly, developed standards were consisted of duty and competency unit. The name of duty was construction of marine terminal structure and competency units were consisted of 9 items as survey on economic effect, evaluation of conditions on construction environment, plan for construction of structure, construction of transfer, mooring, and power equipment, and construction, startup test, and maintenance of terminal structure. 33 competency unit elements below 9 competency units were developed. Thirdly, utilizing package was developed into 3 areas of life-long career path, training criteria, and guidelines for exam according to national competency standards for in order to develop development of labor's career and perform personal management such as hiring and promotion in industry sites.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2007년도 정기학술발표대회 논문집
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• pp.840-843
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• 2007

첨단기술의 발달로 인해 건물은 대형화, 복합화되고 있으며, 이로 인해 실내공간을 효율적으로 관리할 수 있는 시스템의 필요성이 증가 하고 있다. 또한 객체지향 3D CAD의 출현으로 인해 건물의 설계와 시공프로세스에서 계속적인 이용이 가능한 정보들이 제작되고 있다. 이런 정보들을 활용하여 건물의 유지관리 단게에서 실내공간을 효율적으로 관리할 수 있는 시스템을 구축하는 것이 필요한 시점이라 할 수 있다. 본 연구에서는 첨단기술을 융합한 공간정보 관리 시스템을 구축하기 위한 기초 연구로서 공간네트워크 모델을 자동으로 생성하는 프로세스를 정의하는 방법론을 제시하고 이의 효용성을 검토해본다.

• 전기학회논문지
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• 제57권8호
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• pp.1392-1397
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• 2008

The mechanical integrity of generator stator windings is one of the critical point because the electric power is generated and conducted to power system through these windings. De-mineralized water is used to cool stator bars during the normal operation of generator in large power plants because the water cooled method has highest cooling efficient. Water absorption of bar insulation is progressed by several causes such as generation of water leak path by corrosion, delamination of insulation by vibration, and inadequate water treatment, etc.. Reliable water absorption diagnostics of generator stator bar is important to ensure the availability of power plant and to reduce maintenance cost by generator accident. It is described that the water absorption characteristics for generator stator bar insulation used in 500MW capacity standard fossil power plant by cooling water temperature. It is verified that the management of stator cooling water temperature is one of the important factors to decrease water absorption rate of generator stator bars.