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Author

Yan Wang

Other affiliations: University of Southampton
Bio: Yan Wang is an academic researcher from University of Electronic Science and Technology of China. The author has contributed to research in topics: Space charge & Computer science. The author has an hindex of 4, co-authored 22 publications receiving 56 citations. Previous affiliations of Yan Wang include University of Southampton.

Papers
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Journal ArticleDOI
01 Apr 2018
TL;DR: In this paper, the authors used Monte-Carlo simulation to estimate the average thickness of water shell or related relaxation peak of epoxy nanocomposites with spherical particles, and concluded that surface treatment is able to reduce the water uptake, however, no obvious impact on modifying its effects on dielectric properties due to the limitation of thickness of tightly bonded layer.
Abstract: The epoxy resin was filled with nano-BN, surface treated, and untreated nano-SiO 2 . Measurements of dielectric spectroscopy cover the range of frequency from 10 -2 to 10 5 Hz and will relate to the hydration of samples. It was observed from the results that permittivity of pure epoxy was strongly affected by the water absorptions and a bit of temperature. Then it will allow us to extract the influence of water absorption on dielectric properties and proposed a relatively reliable method by using Monte-Carlo simulation to estimate the average thickness of water shell or related relaxation peak of epoxy nanocomposites with spherical particles. At the end, the authors experimentally demonstrated the existence of two layer structure of water shell and concluded that surface treatment is able to reduce the water uptake, however, no obvious impact on modifying its effects on dielectric properties due to the limitation of thickness of tightly bonded layer. The `hydrophobic' performance of BN nanocomposites is much better than silica ones, especially the no formation of water shell around the particles, and may be more suitable for application under environment with humidity.

23 citations

Journal ArticleDOI
TL;DR: Analytical and simulation results show that, in the monopoly market, offering two charging options can potentially improve the SP’s profit compared with offering one option only in theopoly market; while in the duopoly market, it is optimal for SPs to offer the quantity contract rather than the price contract to maximize profits.
Abstract: In this article, we present the optimal strategy for public plug-in electric vehicle (PEV) charging services with multiple charging options: fast charging service and slow charging service. The PEV user make decisions by firstly considering the remaining energy, travel distance to charging station, then about the charging prices, charging rates and estimated charging time. To obtain insights of such a highly coupled system, we consider both monopoly and duopoly markets, where the two services are operated by a single service provider (SP) and two different SPs, respectively. For the monopoly market, we propose a three-stage Stackelberg game model. For the duopoly market, we propose a two-stage Bertrand competition and Cournot competition. We provided the SP’s optimal pricing strategies and decisions in the monopoly market, and the optimal pricing contract and quantity contract for SPs in the duopoly market with Bertrand competition and Cournot competition. Both the analytical and simulation results show that, in the monopoly market, offering two charging options can potentially improve the SP’s profit compared with offering one option only in the monopoly market; while in the duopoly market, it is optimal for SPs to offer the quantity contract rather than the price contract to maximize profits.

14 citations

Journal ArticleDOI
TL;DR: In this paper, a simple and more direct approach based on isothermal surface potential decay combined with pulsed electro-acoustic measurements was proposed to verify the presence of deep traps in silica-based blend polyethylene nanocomposites.
Abstract: The ability to suppress space charge accumulation at high electric fields makes nanocomposites attract significant research interest as potential insulation materials in high-voltage direct current cable development. At present, the deep trap introduced by nanoparticles is frequently applied to be responsible for the observed space charge suppression in nanocomposites. However, the experimental results that support deep-trap formation have not been rigorously examined. We therefore propose herein a simple and more direct approach based on isothermal surface potential decay combined with pulsed electro-acoustic measurements to verify the presence of deep traps in silica-based blend polyethylene nanocomposites. The results indicate that the deep traps are indeed introduced by filling nanosilica and the space charge suppression observed in the nanocomposite with a low loading ratio is caused by deeply trapped charges in the sub-surface region of specimens.

11 citations

Journal ArticleDOI
TL;DR: In this article, the influence of adding nanoparticles into epoxy resins and the characteristics of the movement of charges in the materials based on combining analysis on morphology, DC conductivity and space charge measurements is discussed.
Abstract: Nanocomposites those exhibit good insulation properties have already attracted numbers of research and their electrical properties are believed to be related to charge dynamics in bulk of materials. However, it is still unclear on how nanofiller loading ratios, surface treatment and resultant changes in morphology influence the charge dynamics of nanocomposites. In this paper, we have clearly mentioned the influence of adding nanoparticles into epoxy resins and the characteristics of the movement of charges in the materials based on combining analysis on morphology, DC conductivity and space charge measurements. The presence of spherical nanoparticles (SiO2) introduced additional traps in bulk, which impaired the charge injection and reduced the mobility of charge carriers in samples of low filler loading ratios (e.g., 0.5 wt%). However, in silica-based samples of higher filler loadings, more nanoparticles further caused a higher density of traps, which resulted in lower average distance between arbitrary traps/ inter-particle surface distances and thus charge carriers required less energy when moving from one to another by hopping or the quantum tunnelling mechanism. The surface treatment of SiO2 particles introduced deep traps which helped the separation of particles or related traps, and to some extent restricted the transport of charge carriers. In addition, hBN particles seem to act as barriers to charge injection and movement due to the layered structures and large numbers of resultant shallow traps in bulk. In term of moisture effect, the presence of water led to an obvious increase in charge injection and mobility, and resulted in the higher mobility of charge carriers in both base materials and within traps/particles of nanocomposites. The existence of water shells around spherical particles could contribute to a higher probability of the quantum tunnelling process and the formation of conductive percolation channels.

11 citations

Journal ArticleDOI
TL;DR: In this paper, a combined quantification method was proposed to estimate the dispersion and distribution of spherical/ellipsoidal particles/aggregates in polymer nanocomposites based on SEM images of epoxy SiO 2 nanocomites.
Abstract: Polymer nanocomposites are more and more researched and employed as dielectrics in electrical power equipment. However, the bad dispersion and distribution of particles are often reported to deteriorate the dielectric properties of polymer nanocomposites. In most cases, researchers tend to use SEM/TEM images with imprecise descriptions to describe these two factors, and there was still no clear relationship between their quantified particle dispersion characteristics and dielectric properties of polymer nanocomposites. This work is to, first, propose a combined quantification method to estimate the dispersion and distribution of spherical/ellipsoidal particles/aggregates in polymer nanocomposites based on SEM images of epoxy SiO 2 nanocomposites. Based on the proposed quantification method, epoxy nanocomposite with surface treated SiO 2 shows overall better dispersion and distribution of particles/aggregates than those with untreated ones. The presence of agglomerations would lead to the enhancement of mobility of charge carriers and thus reduction of breakdown strength, which become more obvious with the growth of filler loadings. It is found that, in AC breakdown tests, dispersion and distribution of particles/aggregates show little influence on the reduction of AC breakdown strength. However, those should be the main factor which influences the DC breakdown strength in epoxy nanocomposites with a variation of filler loading concentrations.

6 citations


Cited by
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Proceedings ArticleDOI
17 Jul 2020
TL;DR: The SemEval-2020 Task 12 on Multilingual Offensive Language Identification in Social Media (OffensEval 2020) as mentioned in this paper included three subtasks corresponding to the hierarchical taxonomy of the OLID schema, and was offered in five languages: Arabic, Danish, English, Greek, and Turkish.
Abstract: We present the results and the main findings of SemEval-2020 Task 12 on Multilingual Offensive Language Identification in Social Media (OffensEval-2020). The task included three subtasks corresponding to the hierarchical taxonomy of the OLID schema from OffensEval-2019, and it was offered in five languages: Arabic, Danish, English, Greek, and Turkish. OffensEval-2020 was one of the most popular tasks at SemEval-2020, attracting a large number of participants across all subtasks and languages: a total of 528 teams signed up to participate in the task, 145 teams submitted official runs on the test data, and 70 teams submitted system description papers.

249 citations

Posted Content
TL;DR: The task included three subtasks corresponding to the hierarchical taxonomy of the OLID schema from OffensEval-2019, and it was offered in five languages: Arabic, Danish, English, Greek, and Turkish.
Abstract: We present the results and main findings of SemEval-2020 Task 12 on Multilingual Offensive Language Identification in Social Media (OffensEval 2020). The task involves three subtasks corresponding to the hierarchical taxonomy of the OLID schema (Zampieri et al., 2019a) from OffensEval 2019. The task featured five languages: English, Arabic, Danish, Greek, and Turkish for Subtask A. In addition, English also featured Subtasks B and C. OffensEval 2020 was one of the most popular tasks at SemEval-2020 attracting a large number of participants across all subtasks and also across all languages. A total of 528 teams signed up to participate in the task, 145 teams submitted systems during the evaluation period, and 70 submitted system description papers.

195 citations

Journal Article
TL;DR: An overview of the shared tasks and participants’ systems is provided to promote the community-driven development and evaluation of advanced natural language processing systems to detect, extract, and normalize health-related information in public, user-generated content.
Abstract: For the past seven years, the Social Media Mining for Health Applications (#SMM4H) shared tasks have promoted the community-driven development and evaluation of advanced natural language processing systems to detect, extract, and normalize health-related information in public, user-generated content. This seventh iteration consists of ten tasks that include English and Spanish posts on Twitter, Reddit, and WebMD. Interest in the #SMM4H shared tasks continues to grow, with 117 teams that registered and 54 teams that participated in at least one task—a 17.5% and 35% increase in registration and participation, respectively, over the last iteration. This paper provides an overview of the tasks and participants’ systems. The data sets remain available upon request, and new systems can be evaluated through the post-evaluation phase on CodaLab.

35 citations

Journal ArticleDOI
TL;DR: A novel classification of EVs energy trading is presented using the Stackelberg game approach to the date, and technical approaches to find corresponding optimal strategies to solve optimization problems in the current energy trading systems are presented.

21 citations