• Steel and Composite Structures
• /
• 제36권4호
• /
• pp.447-462
• /
• 2020

The paper aims to investigate the mechanical mechanism and seismic effect of stiffeners in blind bolt endplate connection to CFST column. A precise 3D finite element model with considering the cyclic properties of concrete and steel materials was established, and the efficiency was validated through monotonic and cyclic test data. The deforming pattern and the seismic performance of the unstiffened and stiffened blind bolt endplate connections were investigated. Then a parametric analysis was conducted to analyze the contribution of stiffeners and the joint working behaviors with endplate under cyclic load. The joint stiffness classifications were compared and a supplement stiffness classification method was proposed, and the energy dissipation ability of different class connections were compared and discussed. Results indicated that the main deformation pattern of unstiffened blind bolt endplate connections was the local bending of end plate. The vertical stiffeners can effectively alleviate the local bending deformation of end plate. And influence of stiffeners in thin endplate and thick endplate was different. Based on the stiffness of external diaphragm welded connection, a more detailed rigidity classification was proposed which included the pin, semi-rigid, quasi-rigid and rigid connection. Beam was the main energy dissipation source for rigid connection. For the semi-rigid and quasi-rigid connection, the extended endplate, stiffeners and steel beam would all participate in the energy dissipation.

• 한국수소및신에너지학회논문집
• /
• 제24권3호
• /
• pp.264-274
• /
• 2013

Piping systems play an important role in gas and oil transferring system. In the piping system, there are many elements, such as valves and flow meters. In order to check their normal operating conditions, each signal from each element is displayed on the monitor in the pipe control room. By the way, there are several accidental cases in the piping system even if all signals from the local elements are judged to be normal on the monitor in the control room. Further, opposite cases often happen even the monitor shows abnormal while the local elements work normal. To overcome this abnormal functions, it is not so easy to construct the environment in which sensors detecting the working states of all elements installed in the piping system. In this paper, a new non-contact measurement technique which can calculate the elements' delicate displacements by using a PIV(particle image velocimetry) and diagnose their working states by using a neural network is proposed. The measurement system consists of a host computer, a micro system, a telescope and a high-resolution camera. As a preliminary test, the constructed measurement system was applied to measure delicate vibrations of mobile phones. For practical application, a pneumatic system was measured by the constructed system.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
• /
• pp.1159-1160
• /
• 2006

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, this has raised potential problems of network protection on electrical power system. One of the numerous problems is an Island phenomenon. There has been an argument that because the probability of islanding is extremely low it may be a non-issue in practice. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an island can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficient to cause a trip, plus the time required to execute the trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. And, third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an island. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. So the verification of anti-islanding performance is strongly needed. In this paper, the authors propose the improved RPV method through considering power quality and anti-islanding capacity of grid-connected three-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"). And the simulation and experimental results are verified.

• Journal of Communications and Networks
• /
• 제18권4호
• /
• pp.540-550
• /
• 2016

Since energy efficiency has become a significant concern for network infrastructure, next-generation network devices are expected to have embedded advanced power management capabilities. However, how to effectively exploit the green capabilities is still a big challenge, especially given the high heterogeneity of devices and their internal architectures. In this paper, we introduce a hierarchical power management architecture (HPMA) which represents physical components whose power can be monitored and controlled at various levels of a device as entities. We use energy aware state (EAS) as the power management setting mode of each device entity. The power policy controller is capable of getting information on how many EASes of the entity are manageable inside a device, and setting a certain EAS configuration for the entity. We propose the optimal local control policy which aims to minimize the router power consumption while meeting the performance constraints. A first-order Markov chain is used to model the statistical features of the network traffic load. The dynamic EAS configuration problem is formulated as a Markov decision process and solved using a dynamic programming algorithm. In addition, we demonstrate a reference implementation of the HPMA and EAS concept in a NetFPGA frequency scaled router which has the ability of toggling among five operating frequency options and/or turning off unused Ethernet ports.

• Nuclear Engineering and Technology
• /
• 제27권4호
• /
• pp.518-531
• /
• 1995

단일수로 해석 모형을 다수로 해석 모형으로 대체할 경우 얻을 수 있는 열적 여유도 향상에 대한 연구를 수행하였다. 이를 위하여 17$\times$17 국산핵 연료 장전 노심에 적용할 수 있는 새로운 임계열속 상관식을 개발하였으며, 여기에 사용된 부수로 국부 조건은 다수로 해석 코드인 TORC로 계산하였다. 그리고, 고온부구로 DNBR 분석을 위하여 전 노심에 대한 단일단계 해석 모형을 개발하였다. 분석 결과 다수로 해석 모형인 TORC/KRB-1 체제를 사용할 경우 단일수로 해석 모형인 PUMA/ERB-2 체제에 비하여 약 5% 이상의 열적 여유도를 회복할 수 있는 것으로 나타났다. 이러한 열적 여유도의 증가는 두 코드간의 고온부수로 국부조건 예측 성능 차이와 임계열속 상관식의 특성 차이에서 기인한 것이다.

• Composites Research
• /
• 제22권6호
• /
• pp.32-38
• /
• 2009

본 연구에서는 탄소, 케블라 및 탄소-케블라 하이브리드 등 4가지 소재로 제작된 원형튜브시편에 대한 에너지 흡수능력 및 파손모드를 평가하였다. 이를 위해, 본 연구에서 일방향 프리프레그를 이용해서 원형튜브 제작하고 10mm/min의 하중속도로 준정적 압축시험을 수행하였다. 시험을 통해 취성파괴모드로 압축되는 탄소/에폭시로 제작된 튜브가 가장 우수한 에너지 흡수 특성을 보인 반면, 좌굴에 의해 압축되는 케블라/에폭시 튜브가 가장 낮은 에너지 흡수특성을 보였다. 하이브리드 [$90_C/0_K$]튜브의 경우 국부좌굴모드에 의해 에너지를 흡수했으며 우수한 압축후 구조온전성 특성을 보였다. [$90_K/0_C$] 튜브의 경우 주 파손모드는 단층굽힘모드이고 압축후 구조온전성이 확보되지 못했다.

• 한국해양환경ㆍ에너지학회지
• /
• 제7권2호
• /
• pp.98-103
• /
• 2004

최근 목포-고하 대교가 목포내항을 가로질러 건설될 계획이고 목포시 인근에 남악신도시가 건설중이다. 목포항의 모습을 자연경관과 해양환경에 어울리도록 아름답게 조성하기 위하여 미항목포가꾸기 운동에 대한 시민의 관심과 참여가 필요하다. 지역시민여론에 관한 설문조사를 통하여 연안해양환경에 관한 시민의식 수준을 확인하였으며, 설문조사 결과에 기초하여 목포항과 그 주변해역의 해양환경럴전방안를 제시하였다. 해양폐기물 발생제어에 관한 지역 정책 및 해안의 해양폐기물 수거운동에 시민의 적극적 참여가 요구된다. 도시하수처리장의 운영은 효과적·효율적으로 이루어져야 하고 일반대중, 환경운동연합 혹은 민간단체에 의하여 주기적으로 감시 및 평가를 받아야 한다. 해양 환경교육프로그램의 개발과 시행 그리고 환경보전 계몽운동이 지역주민의 협조 하에서 끊임없이 이루어져야 한다. 지자체가 시민의견을 수집하고 반영하여 목포를 세계적 미항으로 꾸준히 가꾸는 경우에는 시민들이 환경보전을 위한 시민장기실천계획에 적극적으로 참여함으로써 목포항 주변의 연안해양환경은 잘 보전될 수 있을 것이다.

• 한국멀티미디어학회논문지
• /
• 제21권6호
• /
• pp.667-677
• /
• 2018

Since sensor networks consist of sensor nodes with limited energy resources, so efficient energy use of sensor nodes is very important in the design of sensor networks. Sensor nodes consume a lot of energy for data transmission. Clustering technique is used to efficiently use energy in data transmission. Recently, mobile sink techniques have been proposed to reduce the energy load concentrated on the cluster header near a sink node. The CMS(Cluster-based Mobile sink) technique minimizes the generation of control messages by creating a data transmission path while creating clusters, and supports the inter-cluster one-hop transmission. But, there is a case where there is no connectivity between neighbor clusters, it causes a problem of having a long hop data transmission path regardless of local distance. In this paper, we propose a SCBC(Strong connection balancing cluster) to support the path of the minimum number of hops. The proposed scheme minimizes the number of hops in the data transmission path and supports efficient use of energy in the cluster header. This also minimizes a number of hops in data transmission paths even when the sink moves and establishes a new path, and it supports the effect of extending the life cycle of the entire sensor network.

• Steel and Composite Structures
• /
• 제21권3호
• /
• pp.605-628
• /
• 2016

The energy absorption characteristics of diamond core sandwich cylindrical columns under axial crushing process depend greatly on the amount of material which participates in the plastic deformation. Both the single-objective and multi-objective optimizations are performed for columns under axial crushing load with core thickness and helix pitch of the honeycomb core as design variables. Models are optimized by multi-objective particle swarm optimization (MOPSO) algorithm to achieve maximum specific energy absorption (SEA) capacity and minimum peak crushing force (PCF). Results show that optimization improves the energy absorption characteristics with constrained and unconstrained peak crashing load. Also, it is concluded that the aluminum tube has a better energy absorption capability rather than steel tube at a certain peak crushing force. The results justify that the interaction effects between the honeycomb and column walls greatly improve the energy absorption efficiency. A ranking technique for order preference (TOPSIS) is then used to sort the non-dominated solutions by the preference of decision makers. That is, a multi-criteria decision which consists of MOPSO and TOPSIS is presented to find out a compromise solution for decision makers. Furthermore, local and global sensitivity analyses are performed to assess the effect of design variable values on the SEA and PCF functions in design domain. Based on the sensitivity analysis results, it is concluded that for both models, the helix pitch of the honeycomb core has greater effect on the sensitivity of SEA, while, the core thickness has greater effect on the sensitivity of PCF.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제5권5호
• /
• pp.909-937
• /
• 2011

Energy efficiency is one of the most critical issues in the design of wireless sensor networks. In object-tracking sensor networks, the data storage and query processing should be energy-conserving by decreasing the message complexity. In this paper, a Prediction-based Energy-conserving Approximate StoragE schema (P-EASE) is proposed, which can reduce the query error of EASE by changing its approximate area and adopting predicting model without increasing the cost. In addition, focusing on reducing the unnecessary querying messages, P-EASE enables an optimal query algorithm to taking into consideration to query the proper storage node, i.e., the nearer storage node of the centric storage node and local storage node. The theoretical analysis illuminates the correctness and efficiency of the P-EASE. Simulation experiments are conducted under semi-random walk and random waypoint mobility. Compared to EASE, P-EASE performs better at the query error, message complexity, total energy consumption and hotspot energy consumption. Results have shown that P-EASE is more energy-conserving and has higher location precision than EASE.