Tracking Continuous Topological Changes of Complex Moving Regions

A moving region whose location and extend change over time can imply topological changes such as region split and hole formation. To study this phenomenon is useful in many applications, e.g. the topology control of wireless sensor networks and emergency handling. It is challenging to detect the topological changes of a moving region since we lack the ability to capture its continuous change of shapes all the time. Moreover, for a complex moving region containing multiple components, it is hard to determine which component before the change corresponds to which component after the change. In this paper, we propose a model to determine topological changes of a complex moving region through snapshots called observations. We introduce a twophase strategy that the first phase partitions the observations into several evaluation units and uniquely maps a unit before the change to exactly one unit after the change; the second phase interprets the topological change by integrating all basic topological changes from evaluation units

Evaluation of cardinal direction developments between moving points

Recently, a wide range of applications like hurricane research, fire management, navigation systems, and transportation has shown increasing interest in managing and analyzing space and time-referenced objects, so-called moving objects, that continuously change their positions over time. In the same way as moving objects can change their location over time, the spatial relationships between them can change over time. An important class of spatial relationships are cardinal directions like north and southeast. In spatial databases and GIS, they characterize the relative directional position between static objects in space and are frequently used as selection and join criteria in spatial queries. Transferred to a spatiotemporal context, the simultaneous location change of different moving objects can imply a temporal evolution of their directional relationships, called development. The goal of this paper is to illustrate, explain, and formally define cardinal direction developments between two moving points. Categories and Subject Descriptors

Research of grounded DC electrical tree growth properties in XLPE

Grounded DC tree is a serious threat for the safe operation of XLPE cable. In this paper, growth properties of grounded DC electrical trees in XLPE under ±40kV DC voltage were investigated and analyzed. The results showed that DC voltage polarity had a remarkable impact on the growth characteristics of grounded electrical tree. Sparse-branch and dense-branch electrical trees were more likely to form under positive and negative voltage, respectively. Meanwhile, the time of typical grounded DC tree samples growing to 1mm was also calculated. The results indicated that the average growing time under positive voltage could be a bit shorter than that under negative voltage. The results in this paper can help in the understanding of DC tree mechanism and provide a support for the later experiments

The Reactive Sites of Methane Activation: A Comparison of IrC3+ with PtC3+

The activation reactions of methane mediated by metal carbide ions MC3+ (M = Ir and Pt) were comparatively studied at room temperature using the techniques of mass spectrometry in conjunction with theoretical calculations. MC3+ (M = Ir and Pt) ions reacted with CH4 at room temperature forming MC2H2+/C2H2 and MC4H2+/H2 as the major products for both systems. Besides that, PtC3+ could abstract a hydrogen atom from CH4 to generate PtC3H+/CH3, while IrC3+ could not. Quantum chemical calculations showed that the MC3+ (M = Ir and Pt) ions have a linear M-C-C-C structure. The first C–H activation took place on the Ir atom for IrC3+. The terminal carbon atom was the reactive site for the first C–H bond activation of PtC3+, which was beneficial to generate PtC3H+/CH3. The orbitals of the different metal influence the selection of the reactive sites for methane activation, which results in the different reaction channels. This study investigates the molecular-level mechanisms of the reactive sites of methane activation

Blending Modification of Alicyclic Resin and Bisphenol A Epoxy Resin to Enhance Salt Aging Resistance for Composite Core Rods

In order to promote the application of composite insulators in coastal areas with high temperature, high humidity and high salt, it is of great importance to develop matrix resin with salt corrosion resistance for composite core rods. In this study, bisphenol A epoxy resin was modified by blending with alicyclic epoxy resin (2021P). Three different proportions of 2021P/DGEBA blend resins (0% 2021P/DGEBA, 10% 2021P/DGEBA and 20% 2021P/DGEBA) were prepared, and the high salt medium corrosion test was carried out. The physicochemical (FTIR, DMA, TGA) and electrical properties (dielectric loss, leakage current and breakdown field strength) of the blend resin before and after aging were tested and analyzed, and the optimal blend proportion was determined. The results showed that after salt aging, the Tg of 0% 2021P/DGEBA decreased to 122.99 °C, while the Tg of 10% 2021P/DGEBA reached 134.89 °C; The leakage current of 0% 2021P/DGEBA increased to 48.994 μA, while that of 10% 2021P/DGEBA only increased to 44.549 μA; The breakdown field strength of 0% 2021P/DGEBA dropped to 40.36 kv/mm, while that of 10% 2021P/DGEBA only dropped to 43.63 kv/mm. The introduction of 2021P enhanced the salt corrosion resistance of the blend resin, which could hinder the penetration, diffusion and erosion of external media (such as Na+, Cl−, H2O, etc.) to the matrix resin. The comprehensive properties of 10% 2021P/DGEBA blend system reached the best, which was better than other blending resins, showing great application potential

The curing characteristics and properties of bisphenol A epoxy resin/maleopimaric acid curing system

Epoxy resins are widely used as insulation materials for power systems and are mainly prepared from petrochemical materials, which have the disadvantage of being non-recyclable and environmentally harmful. In this paper, the maleopimaric acid (MPAc) curing agent was prepared from a renewable resource, rosin, and blended with a petroleum-based curing agent (methylhexahydrophthalic anhydride) to cure bisphenol A epoxy resin. The effects of the blending ratio on the curing characteristics as well as on the thermal, mechanical, and electrical properties of the epoxy resins were examined. From the results obtained, as for thermal properties, the introduction of MPAc enhanced the rigidity, glass transition temperature, and thermal decomposition temperature. As for mechanical properties, the brittleness was increased while the tensile strength and bending strength were weakened. When the mass fraction of MPAc was 20–30 wt%, the electrical properties reached the optimum, meeting the application requirements of electrical equipment. This study shows that using rosin-based curing agent maleicpine acid (MPAc) as a partial replacement for petroleum-based curing agents can make electrical equipment environmentally friendly, demonstrating the potential application prospects of rosin-based epoxy resins

Current Status of Research on the Modification of Thermal Properties of Epoxy Resin-Based Syntactic Foam Insulation Materials

As a lightweight and highly insulating composite material, epoxy resin syntactic foam is increasingly widely used for insulation filling in electrical equipment. To avoid core burning and cracking, which are prone to occur during the casting process, the epoxy resin-based syntactic foam insulation materials with high thermal conductivity and low coefficient of thermal expansion are required for composite insulation equipment. The review is divided into three sections concentrating on the two main aspects of modifying the thermal properties of syntactic foam. The mechanism and models, from the aspects of thermal conductivity and coefficient of thermal expansion, are presented in the first part. The second part aims to better understand the methods for modifying the thermal properties of syntactic foam by adding functional fillers, including the addition of thermally conductive particles, hollow glass microspheres, negative thermal expansion filler and fibers, etc. The third part concludes by describing the existing challenges in this research field and expanding the applicable areas of epoxy resin-based syntactic foam insulation materials, especially cross-arm composite insulation