1,034 research outputs found
The flow approach to swept volume
In this thesis, a method for representing swept volume based on the sweep differential equation and sweep vector field flow is developed. This method can be used to determine the boundary representation of a swept volume generated by any polygonal object undergoing a general smooth 2-D sweep. For any given sweep and object, a. set of candidate boundary points is computed using a selection criterion based on vector field behavior. The set of candidate boundary points is then trimmed in order to obtain the true boundary of the swept volume. This trimming procedure is based on some simple topological principles and it utilizes the concept of extended sweep. This method is more general and efficient than existing approaches (e. g. it can readily deal with the cases in which the swept volume area. has holes ) and can easily be extended to 3-D sweeps; the 3-D extension is discussed but only briefly. Several examples are given to illustrate the implementation of the prototype software for 2-D sweeps which has been developed in conjunction with this research
Actively controlling the topological transition of dispersion based on electrically controllable metamaterials
Topological transition of the iso-frequency contour (IFC) from a closed
ellipsoid to an open hyperboloid, will provide unique capabilities for
controlling the propagation of light. However, the ability to actively tune
these effects remains elusive and the related experimental observations are
highly desirable. Here, tunable electric IFC in periodic structure which is
composed of graphene/dielectric multilayers is investigated by tuning the
chemical potential of graphene layer. Specially, we present the actively
controlled transportation in two kinds of anisotropic zero-index media
containing PEC/PMC impurities. At last, by adding variable capacitance diodes
into two-dimensional transmission-line system, we present the experimental
demonstration of the actively controlled magnetic topological transition of
dispersion based on electrically controllable metamaterials. With the increase
of voltage, we measure the different emission patterns from a point source
inside the structure and observe the phase-transition process of IFCs. The
realization of actively tuned topological transition will opens up a new avenue
in the dynamical control of metamaterials.Comment: 21 pages,8 figure
Investigation of the Spatial Variability of Steel Weight Loss and Corrosion Cracking: A Novel X-ray Technique
The performance of corrosion-affected RC members depends strongly on localized damages of reinforcement. Therefore, modeling the spatial variability of steel corrosion is very important for the assessment of the remaining service life of corroded structures or time for maintenance. To study the changes of spatial variability of steel weight loss over time, a continuous monitoring is necessary. In this paper, a novel procedure of X-ray technique application in monitoring the spatial growth of a corroded bar in a RC specimen is demonstrated along with the digital image processing of X-ray images to estimate the steel weight loss. The relationship of steel weight loss and corrosion cracking is studied at different stages of corrosion. The validity of the estimation method of steel weight loss is also presented.
In this study, a novel procedure of X-ray technique application in monitoring the spatial growth of corroded bars in RC specimens is demonstrated along with the digital image processing of X-ray images to estimate the steel weight loss. A single RC beam (80 mm × 140 mm × 1460 mm) reinforced with a longitudinal rebar and stirrups were fabricated for the investigation. The steel corrosion was accelerated via an electrochemical test. The relationship of steel weight loss and corrosion cracking was studied at different stages of corrosion. The validity of the method was also discussed.
The outcome of spatial variability of steel weight loss might be used to validate analytical models for estimating non-uniform steel corrosion or incorporated with inspected corrosion levels of in-situ structures for the input data in a predicting model to estimate the long-term structural performance of corroded RC structures
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