Search

Kevlar pulp treated with low-temperature plasma and nano cellulose fibrils (NCFs) have been introduced as reinforcements in the preparation for composite insulating paper with low relative permittivity, dielectric loss, good mechanical properties, and thermal stability. More polar groups of Kevlar fibers could be exposed after plasma treatment. Results showed that the relative permittivity of the composite paper containing 20% Kevlar pulp, 10% NCF, and 70% softwood pulp is decreased by 29.6% and the dielectric loss is decreased by 43.2% at 50 Hz, 25°, compared with the conventional paper formed by pure softwood pulp. The change was due to the introduction of Kevlar pulp with intrinsic low dielectric constant and loss, which decreases the whole polarizability of the paper. The mechanical properties of the composite paper became worse after introducing 20% Kevlar pulp. About 10% NCF can work as a mechanical reinforcement to compensate for the tensile and Yang's modulus loss. Scanning electron microscopy results showed that NCF could fill the void defects and improve the interface bonding of the fibers to enhance the paper mechanical properties. The composite paper also had better insulating and thermal properties than the conventional paper. It has been concluded that the Kevlar pulp/NCF/softwood pulp composite paper has the potential to replace the pure softwood paper for the application of high-voltage ac transformer insulation.

Tight assembly of stator windings with no insulation paper damage is a manufacturing challenge. We evaluate different sets of parts according to the following parameters: magnet wire thickness, stator slot smoothness, length of the straight magnet wire after the slot end, and type and amount of insulation cap at the end of the slot. These parameters have discrete values with small differences between them. The damage criterion is the decrease of the insulation paper breakdown voltage after assembly/disassembly of parts, assembled in a small set of designed experiments. Parameter values, i.e., levels at individual experiments are set by an orthogonal experiment matrix. Repetition of each experiment provides statistical significance. Data analysis shows that the additive model alone is not sufficient due to the high correlation of the parameters’ influences. We extend the model to include interparameter influences, which we model by adding a virtual parameter. The extended additive model generates parameter values that do not degrade the insulation paper breakdown voltage within the manufacturing process. These values are verified by repetitions of the control experiment.

This Special Issue is assembled from a selection of highly-rated technical papers presented at the 4th IEEE Electron Devices Technology and Manufacturing Conference 2020, EDTM 2020. It took place during April 6-21, 2020 and signified the 1st of its kind as a virtual conference financially-sponsored by the Electron Devices Society (EDS). The original EDTM 2020 was planned as a full three-day event at the Hotel Equatorial , Penang, Malaysia from March 16 to 18, 2020. However, due to the COVID-19 pandemic, EDTM 2020 was held as a virtual event .

The papers in this special section were presented at the Optical Fiber Communications Conference (OFC) 2020, which took place in March 2020 in San Diego, CA.

This paper presents the design of a novel rectenna based on a tapered annular slot and a single-diode rectifier, optimized to operate in the Wi-Fi band and in presence of low input power (Pavs=-15 dBm). In order to obtain a compact layout a double-layer architecture has been considered, according to which the interior metal surface of the annular slot is employed as ground plane for the rectifying circuit placed on the other side of the substrate. As a result, a rectenna with an active area of only 40 × 33 mm2 and an efficiency included between 26.5 and 28% has been obtained. The antenna has been fabricated in paper substrate and tested in the anechoic chamber. Then, the rectifier has been designed and optimized within the Advanced Design System suite. Finally, the rectenna performance has been discussed and compared to the State of the Art (SoA).

J.A. Moral-Munoz holds a FPU scholarship (AP2012-1789) from the Spanish Ministry of Education., Citation classics offer an outlook on those papers that have attracted great and historical interest by a research community and that could be also considered the basis of the research field. A new approach, which is called H-Classics, has been developed to identify such highly cited papers. It is based on the H-index and is sensitive to both the own characteristics of the corresponding research discipline and its evolution. The present study provides a useful insight into the development of the intelligent transport systems research field, revealing those scientific actors (authors, countries, and institutions) that have made the biggest research contribution to its development., Spanish Government AP2012-1789

This Special Section follows from a selection of highly-rated, high impact technical papers presented at the 11th International Conference on Computer-Aided Design for Thin Film Transistor Technologies (CAD-TFT) 2020. The CAD-TFT 2020 was held as a virtual conference on November 10th and 11th, 2020 from the operations center at Tianjin, China. The pre-conference virtual presentations on November 9th, 2020 included six tutorials from internationally recognized experts in their technical fields as well as six posters from China, India, and Canada.

This paper presents the design and implementation in paper substrate of a harmonic RFID chipless sensing tag. The proposed sensor is based on a Wheatstone bridge, where two of the four impedances change dynamically according to a physical parameter that has to be monitored. The passive tag is interrogated by a signal at f 0 = 1.04 GHz and the signal transmitted back to the reader at 2f 0 = 2.08 GHz is proportional to the magnitude of the parameter variation. A harmonic RFID experiment proves that this kind of architecture is capable of providing a dynamic range of more than 40 dB.

This paper introduces a microrobotic platform to make, manipulate and break individual paper fiber bonds. An individual paper fiber bond is the construction unit of a paper sheet and its properties affect the strength of the entire network of a paper sheet. In one hand, conventional laboratory tests on paper fiber bonds are mainly performed in a hand-sheet level. On the other hand, reported methods for paper fiber bond strength tests in individual bond level are either direct which are manual, laborious and have a low throughput or indirect which require data interpretation. The microrobotic platform presented in this paper performs direct and individual tests on paper fiber bonds. Making, manipulating and breaking individual paper fiber bonds are accomplished successfully demonstrating the first steps towards individual bond strength measurement.

A dual band antenna is inkjet-printed and then folded as part of a paper unmanned aerial vehicle (UAV). The patterns of the antenna are reproduced on a standard photo paper substrate using an off the shelf inkjet printer. Readily available cartridges with nanoparticle silver conductive ink are employed. A single-layer planar antenna is fed by coplanar waveguide (CPW). The geometry of the radiating element consists of a semicircle with a centered square slot. In order to examine the effect of bending on performance, the antenna is tested unfolded and then folded when integrated onto the airplane. Two configurations of the folded antenna on the plane are analyzed. The aim is to investigate the feasibility of fabricating foldable antennas for paper airplanes using low-cost inkjet printing techniques. The antenna operates at the existing 2.4 GHz and 5.2 GHz WLAN bands. Finite different time domain simulations compare well with measurement.

In industry an engineer is often required to keep a logbook for recording developments within projects. In higher education, logbooks are a commonly used tool thought to be one that encourages active independent learning and reflective thinking. In School of Engineering, at University of Portsmouth, paper and more recently online logbooks have been in use for recording work for final year projects and project based learning tasks. The work presented here benefits from a unique opportunity within the School of Engineering, where online logbooks alongside traditional paper based logbooks are being used within final year projects. A recent cohort of students (N=127) on ENG600 project module was given the option, through their Supervisors, to use paper logbooks and or online logbooks for recording their work. This work aims to investigate the use of both paper and online logbooks. A mix of Qualitative Research methods and quantitative techniques will be used in this project. The use of content analysis will provide an insight into student reflections and their motivations for using their logbook. Furthermore focus groups, involving live editing of documents in an individual and collaborative fashion, will be used to gather more data for analysis. Quantitative methods (questionnaire, analytics and quantitative content analysis) will also be used in this study. When this work is completed, it will provide guidance and comparison on using the two types of logbooks, backed by knowledge of student motivations and approaches.

In this study, we explore three different strategies for such situation; 1) Extreme approach that reprovisions all connections in danger with full or degraded bandwidth, 2) relax approach that reprovisions only critical connections, and 3) careful approach that reprovisions some or all connections based on the alarm level. We compare these strategies for a case study, an earthquake on San Andreas Fault Line. We conduct numerical examples over a 24-node US-wide topology where the connections have heterogeneous bandwidth and availability requirements. The numerical examples show that careful approach provides a better solution than extreme and relax approaches, especially for heavy network loads in terms of expected penalty in case of an earthquake.

This research aims at establishing criteria for the automatic identification of defects in paper/oil insulation systems. Statistical analysis of partial discharge (PD) data collected in a reference database (built up from tests on artificial defects: internal PD, surface PD, corona and discharges due to bubbles in oil) is carried out to highlight the best identification markers. The development of an automatic identification system based on fuzzy logic is presented. Eventually, applications of identification are discussed.

This paper investigated the influence of paper-wrapped on the deposition of sulfur corrosion on the insulation winding (paper-wrapped copper conductor) in oil-immersed insulation containing dibenzyl disulfide (DBDS). The distribution of sulfur corrosion deposit on a 500-kV electric reactor was investigated and analyzed, and the properties of oil were analyzed. Aging experiments were also conducted for oil-paper insulation with 500-mg/kg DBDS under IEC 62535 corrosion test condition. The corrosion degree of insulation winding was evaluated, and the properties of oil were also discussed. Results showed that the enwinding pattern of the insulating paper on the copper conductor affected the deposition distribution of copper sulfide to be an alternate appearance of a non-corroded crevice and a strip-shaped corrosion deposit on the copper conductor according to the results of field and laboratory. Furthermore, for the insulation winding, the increased number of paper layers on the copper conductor led to the aggravation of sulfur corrosion, prevented the diffusion of copper ions in the oil, and accelerated the formation of acids, which co-affected the properties of the oil. The enwinding of insulating paper on the copper conductor led to the appearance of a tiny crevice on the insulation winding, which is an important occurrence precondition of crevice corrosion. Finally, the mechanism underlying crevice corrosion for insulation winding was theorized as electrochemical corrosion leading to copper sulfide formation.

A 2017 systematic review on engineering non-functional requirements in agile projects revealed a number of published proposals for approaching security requirements in agile settings. While these proposals acknowledge the urgent need for methods to systematically engineer security requirements in agile projects, they were designed mostly in academic settings. Very little empirical evaluation of these proposals happened in real-life contexts. In turn, little is known about how agile developers understand security requirements and how they devise their coping strategies regarding these requirements. This position paper presents a qualitative analysis that sought to discover how agile practitioners reason about security requirements, what contextual factors they consider important for shaping the pro-cess of coping with security requirements in agile projects, and what these strategies are. We conclude with some implications for practice and research.

Power transformers are one of the most critical components of power systems, and failures often result in significant economic loss from the interruption of power and damage of assets. The establishment of maintenance programs that signal abnormal conditions in transformers is essential for the reliable operation of these equipments. However, in a competitive market, it is important to maximize investments by depleting the remaining life of the equipments before replacing them. The end of life of a transformer comes about by aging of its solid insulation, which is mainly Kraft paper, pressboard, and wood, and these materials age mainly by hydrolysis reactions. Although transformer lifetimes are considered to be about 30 years, experience shows that some transformers remain in service for more than 50 years [1]. Aging of cellulosic insulation depends mainly on operating temperature, moisture, oxygen, and acids. The value of these factors depends on the operating conditions and maintenance practices, which are not always accurately quantified. Having a method to estimate the remaining life of a transformer is essential for owners to assess the risk of keeping a transformer in service or the necessity of replacing it. Unfortunately, estimating the remaining life of transformer insulation is not an easy task because it is not possible to extract paper samples from the active part of the transformer to make direct determinations, and estimations are always based on indirect estimations. On the other hand, the transformer temperature is not homogeneous, so the condition of the paper varies within the transformer, which makes the analysis even more complex. The determination of the furanic compounds content in the transformer oil is one of the more valuable methods to diagnose the aging condition of transformer solid insulation [2]. Unlike other markers, for example CO or CO2, which are produced during the degradation of cellulosic insulation but also mineral oil, furanic compounds are exclusively generated as a by-product of the aging reactions of only cellulose insulation, and that makes the diagnosis more reliable.

An innovative conception of indoor localization for human beings is proposed. A person, moving within a building can be localized and tracked by using a self-powered RFID system consisting of a nomadic reader interrogating an array of passive tags embedded in the floor tiles. The whole system is based on environmentally friendly technologies: the piezoelectric (PZT) based energy harvesting to power the hardware as well as the on-paper inkjet printing for the tag antenna.