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- 저자 : Ligang Fang (검색결과 2 건)
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Support-free hollowing for 3D printing via Voronoi diagram of ellipses
Lee, Mokwon,Fang, Qing,Cho, Youngsong,Ryu, Joonghyun,Liu, Ligang,Kim, Deok-Soo Elsevier 2018 Computer aided design Vol.101 No.-
<P><B>Abstract</B></P> <P>3D printing, also called additive manufacturing, has been increasingly popular and printing efficiency has become more critical. To print artifacts faster with less material, thus leading to lighter and cheaper printed products, various types of void structureshave been designed and engineered inside of shape models. In this paper, we present a novel method for generating support-free elliptic hollowing for 3D shapes which can entirely avoid additional supporting structures. To achieve this, we perform the ellipse hollowing in one of the cross sectional polygons and then extrude the hollowed ellipses to the other parallel cross sections. To efficiently pack the ellipses in the polygon, we construct the Voronoi diagram of ellipses to reason the free-space around the ellipses and other geometric features by taking advantage of the available algorithm for the efficient and robust construction of the Voronoi diagram of circles. We demonstrate the effectiveness and feasibility of our proposed method by designing and printing support-free hollow for various 3D shapes using Poretron, the program which computes the hollow by embedding appropriate APIs of the Voronoi Diagram Machine library that is freely available from Voronoi Diagram Research Center. It takes a 3D mesh model and produces an STL file which can be either fed into a 3D printer or postprocessed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Support-free elliptic hollowing for 3D shapes via ellipse packing. </LI> <LI> Derivation of a class of support-free ellipses. </LI> <LI> Packing the support-free ellipses within a polygon (a cross-section of a 3D shape). </LI> <LI> Packing the ellipses within a polygon is solved very efficiently and precisely via Voronoi diagram. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Zhaobin Liu,Wenzhi Liu,Qiang Ma,Gang Liu,Liang Zhang,Ligang Fang,Victor S. Sheng 한국통신학회 2019 Journal of communications and networks Vol.21 No.5
To address malicious attacks generated from wirelesssensor networks (WSNs), in this paper, we study the difficulty ofdetecting uncoordinated behavior by using a model that is unreliableand has uncontrollable accuracy, trustless control, and an inextensibleprotocol. A security collaboration model involving coupledstate vectors associated with topology control and time synchronizationis proposed. The networks achieve synchronizationusing weights and by controlling the number of goals. The simplecalculation of time synchronization values between neighboringnodes serves as the basis for judging the behavior of the nodetopology control. The coupling state vector calculation is the coreof the model. The topology coupling strength rate, signal intensityreduction, clock drift, and clock delay are combined to form a comprehensivemodel. The network energy consumption is reduced byupdating the coupling state vector regularly. The coupling cooperationthreshold is set to make security decisions and effectivelydistinguish between attack nodes and dead nodes. Thus, to ensurethe security and reliability of the network, we present a securitycooperation collection tree protocol (SC-CTP) scheme that maintainsa trusted environment and isolates misbehaving nodes. Thesimulation results show that the model can detect malicious nodeseffectively, has a high detection rate, and greatly reduces the energyconsumption of the whole network. In order to verify the effectivenessof the proposed model, a large-scale wireless sensor networkwith 200 nodes was deployed on a campus. The proposed modelwas applied to optimize the deployment of key nodes on the campus. Furthermore, a candidate set of these nodes were selected toachieve coupling cooperation of key goals. This test verified the reliabilityof the model, its customizable accuracy, and the reliabilityof the control.
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