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Researchers face difficulties in finding relevant papers to their research interest as the number of scientific publication is rapidly increasing on the web. Scientific paper recommenders have emerged as a leading solution to help researchers by automatically suggesting relevant and useful publications. Several approaches have been proposed on improving recommender systems. However, most existing approaches depend on priori user profiles, and thus they cannot recommend papers to new user. Furthermore, the existing approaches utilize non-public contextual information, and thus it cannot adequately find similarities between papers due to copyright restrictions. Also, the existing approaches consider only single level paper-citation relation to identify similarities between papers. Considering the above challenges, this paper presents a collaborative filtering based recommendation approach for scientific papers that does not depend on priori user profiles and which utilizes only public contextual information. Using citation context, we utilized 2-level paper-citation relations to find hidden associations between papers. The rational underlying this approach is that, two papers are co-occurred with same cited paper(s) and two papers are co-occurring with same citing paper(s) are significantly similar to some extent. To evaluate the performance of the proposed approach, publicly available datasets are used to conduct extensive experiments. The experimental results demonstrate that the proposed approach has significantly outperforms the baseline approaches in terms of precision, recall, F1, mean average precision, and mean reciprocal rank, which are commonly used information retrieval metrics. The novelty of this study is that, with the proposed approach, researchers are able to find relevant and useful publications over the internet regardless of their previous research experiences and research area.

Paper-based strain sensors have attracted attention as a cost-effective and environmentally friendly approach to wearable electronic devices. This paper proposes a paper-based strain sensor created solely using hand-painting, which is a simple, equipment-free process utilized in green electronics. Commercial printing paper is coated with polydimethylsiloxane diluted with heptane, which provides moisture resistance and mechanical robustness while increasing the hydrophobicity of the surface. The electrodes and conduction channels are fabricated using a pencil for graphite deposition and a brush for the deposition of tin-doped indium oxide nanoparticles, respectively. With a gauge factor of 41.98 in tensile strain tests and 21.36 in compressive strain tests, our strain sensor exhibits a good sensitivity that is similar to that of previously reported paper-based sensors. We also demonstrate that our proposed strain sensor can be used as a weak motion detection device for humans and robots.

Objective: We propose a MATLAB-based tool to convert electrocardiography (ECG) waveforms from paper-based ECG records into digitized ECG signals that is vendor-agnostic. The tool is packaged as an open source standalone graphical user interface (GUI) based application. Methods and procedures: To reach this objective we: (1) preprocess the ECG records, which includes skew correction, background grid removal and linear filtering; (2) segment ECG signals using Connected Components Analysis (CCA); (3) implement Optical Character Recognition (OCR) for removal of overlapping ECG lead characters and for interfacing of patients’ demographic information with their research records or their electronic medical record (EMR). The ECG digitization results are validated through a reader study where clinically salient features, such as intervals of QRST complex, between the paper ECG records and the digitized ECG records are compared. Results: Comparison of clinically important features between the paper-based ECG records and the digitized ECG signals, reveals intra- and inter-observer correlations of 0.86–0.99 and 0.79–0.94, respectively. The kappa statistic was found to average at 0.86 and 0.72 for intra- and inter-observer correlations, respectively. Conclusion: The clinically salient features of the ECG waveforms such as the intervals of QRST complex, are preserved during the digitization procedure. Clinical and Healthcare Impact: This open-source digitization tool can be used as a research resource to digitize paper ECG records thereby enabling development of new prediction algorithms to risk stratify individuals with cardiovascular disease, and/or allow for development of ECG-based cardiovascular diagnoses relying upon automated digital algorithms.

To improve the accuracy of user implicit rating prediction, we combine the traditional latent factor model (LFM) and bidirectional gated recurrent unit neural network (BiGRU) model to propose a hybrid model that deeply mines the latent semantics in the unstructured content of the text and generates a more accurate rating matrix. First, we utilize the user’s historical behavior (favorites records) to build a user rating matrix and decompose the matrix to obtain the latent factor vectors of users and literature. We also apply the BERT model for word embedding of the research papers to obtain the sequence of word vectors. Then, we apply the BiGRU with the user attention mechanism to mine the research paper textual content and to generate the new literature latent feature vectors that are used to replace the original literature latent factor vectors decomposed from the rating matrix. Finally, a new rating matrix is generated to obtain users’ ratings of noninteractive research papers and to generate the recommendation list according to the user latent factor vector. We design experiments on the real datasets and verify that the research paper recommendation model is superior to traditional recommendation models in terms of precision, recall, F1-value, coverage, popularity and diversity.

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.

Usability and the use of automated static analysis tools in the software development process have been an evolving subject of research in the last decades. Several studies shed light on issues like high false positive rates and low comprehensibility, which hinder tool adoption for even software engineers. Yet, the tools' perceived usefulness and ease of use play a much larger role when it comes to untrained software developers, as is usually the case in scientific software development. In this paper, we outline a multi-stage interview study to learn more about how scientists come to accept and use static analysis tools.

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 .

Most existing studies and public datasets for handwritten Chinese text recognition are based on the regular documents with clean and blank background, lacking research reports for handwritten text recognition on challenging areas such as educational documents and financial bills. In this paper, we focus on examination paper text recognition and construct a challenging dataset named examination paper text (SCUT-EPT) dataset, which contains 50 000 text line images (40 000 for training and 10 000 for testing) selected from the examination papers of 2 986 volunteers. The proposed SCUT-EPT dataset presents numerous novel challenges, including character erasure, text line supplement, character/phrase switching, noised background, nonuniform word size, and unbalanced text length. In our experiments, the current advanced text recognition methods, such as convolutional recurrent neural network (CRNN) exhibits poor performance on the proposed SCUT-EPT dataset, proving the challenge and significance of the dataset. Nevertheless, through visualizing and error analysis, we observe that humans can avoid vast majority of the error predictions, which reveal the limitations and drawbacks of the current methods for handwritten Chinese text recognition (HCTR). Finally, three popular sequence transcription methods, connectionist temporal classification (CTC), attention mechanism, and cascaded attention-CTC are investigated for HCTR problem. It is interesting to observe that although the attention mechanism has been proved to be very effective in English scene text recognition, its performance is far inferior to the CTC method in the case of HCTR with large-scale character set.

Since its first discovery in 2014, laser-induced graphene (LIG) has gained increasingly attention as a simple and low-cost alternative to printing techniques, which instead require additional materials such as functional ink or adhesive layers. While there are several works on LIG supercapacitors, gas sensors, and triboelectric generators, this method is still very unexplored for antennas, especially if realized on eco-friendly paper substrates. In this paper, we realized a microstrip patch antenna using LIG on a food-derived cellulose-based paper. The antenna was first designed and simulated using a High-Frequency Structure Simulator (HFSS) software, using different values of relative permittivity ϵ r (from 2 to 3.6), to understand the impact of laser-induced graphitization of the substrate on the resonance frequency. The subsequently fabricated antenna showed a strong resonance peak of −25dB at 2.4 GHz, corresponding to an ϵ r of 2.2, in agreement with experimental results.

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.

The publication of the 2020 Special Section of Invited Papers on Emerging Topics in the Power and Energy Society (PES) received broad interest from diverse readers of the PES community. We continued to publish the special section for another year. After a rigorous peer-review process, a total of 13 papers [A1]–[A13] were accepted for publication in this invited section of the IEEE Open Access Journal of Power and Energy (OAJPE) in 2021.

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 manuscript considers a secondary system sharing the spectrum with the primary system at the same time and on teh same frequency. We propose a cognitive overlay system in which the secondary system relays the primary signal and piggybacks its own data on it. Furthermore, the secondary system uses the channel coding based on the dirty paper coding (DPC). The result of the analysis shows that the proposed scheme allows the secondary system to communicate at the same speed as the primary system without any harm to it.

International audience; Texture characterization of photographic papers is likely to provide scholars with valuable information regarding artistic practices. Currently, texture assessment remains mostly based on visual and manual inspections, implying long repetitive tasks prone to inter- and even intra-observer variability. Automated texture characterization and classification procedures are thus important tasks in historical studies of large databases of photographic papers, likely to provide quantitative and reproducible assessments of texture matches. Such procedures may, for instance, produce vital information on photographic prints of uncertain origins. The hyperbolic wavelet transform, because it relies on the use of different dilation factor along the horizontal and vertical axes, permits to construct robust and meaningful multiscale and anisotropic representation of textures. In the present contribution, we explore how unsupervised clustering strategies can be complemented both to assess the significance of extracted clusters and the strength of the contribution of each texture to its associated cluster. Graph based filterbank strategies are notably investigated with the aim to produce small size significant clusters. These tools are illustrated at work on a large database of about 2500 exposed and non exposed photographic papers carefully assembled and documented by the MoMA and P. Messier's foundation. Results are commented and interpreted.

The F composite fading model was recently proposed as an accurate and tractable statistical model for the characterization of the simultaneous occurrence of multipath fading and shadowing conditions encountered in realistic wireless communication scenarios. In the present contribution we capitalize on the distinct properties of this composite model to derive the achievable capacity over F composite fading channels assuming fixed rate quality of service requirements. To this end, novel exact and tractable analytic expressions are derived for both the exact and the truncated channel inversion strategies. This also enables the derivation of additional simplified approximate and asymptotic expressions for these cases, which provide meaningful insights on the effect of fading conditions on the overall system performance. This is particularly useful in the context of numerous emerging wireless applications of interest that exhibit stringent fixed rate requirements such as vehicular communications, body area networks and telemedicine, among others. acceptedVersion

Software packages that support data analysis in a scientific research can be understood as a mean to assisting the researcher in the treatment, organization and analysis phases, with the main objective of collaborate to the development of research or projects. These tools stand out and are sought by allowing data analysis to be done in a variety of formats (audio, video, image, text) providing collaborative work (two or more research working on the same research project) and the searched data. Considering this reality this article aims to carry out a bibliographic survey in journals evaluated with the Qualis A1, about which software packages the scientific publications – especially in the Brazilian scenario - have chosen to explore in their scientific analyzes in the field of Education. This research presents itself as a qualitative study with its bibliographical and documentary analysis. The dimensions of this work are delimited in the understanding of the reality from the use of software that the researcher chooses to work in i) qualitative, quantitative or mixed, and ii) which software packages could be identified in a researched universe of 121 journals were consulted of which 13 were selected for this study. published

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 novel approach is here presented to embed a low-priority data stream into a high-priority data stream for OFDM wireless communications. The main improvement with respect to conventional hierarchical modulations is that the low-priority data stream can be decoded from the received subcarrier symbols without any previous equalization in case of multipath fading channel. As a consequence, the expected performance is independent of the channel estimation method used to equalize the channel. The low-priority signal is superimposed on the high-priority symbols using a dirty paper coding technique. As a result of the analysis of the proposed method, several improvements to reduce the interference on the high-priority symbols are introduced. The performance of our scheme has been compared with that of a conventional hierarchical modulation using DVB-T system parameters, showing a considerable improvement for multipath fading channels.

© 2018 IEEE. During the secure boot process for a trusted execution environment, the processor must provide a chain of certificates to the remote client demonstrating that their secure container was established as specified. This certificate chain is rooted at the hardware manufacturer who is responsible for constructing chips according to the correct specification and provisioning them with key material. We consider a semi-honest manufacturer who is assumed to construct chips correctly, but may attempt to obtain knowledge of client private keys during the process. Using the RISC-V Rocket chip architecture as a base, we design, document, and implement an attested execution processor that does not require secure non-volatile memory, nor a private key explicitly assigned by the manufacturer. Instead, the processor derives its cryptographic identity from manufacturing variation measured by a Physical Unclonable Function (PUF). Software executed by a bootloader built into the processor transforms the PUF output into an elliptic curve key pair. The (re)generated private key is used to sign trusted portions of the boot image, and is immediately destroyed. The platform can therefore provide attestations about its state to remote clients. Reliability and security of PUF keys are ensured through the use of a trapdoor computational fuzzy extractor. We present detailed evaluation results for secure boot and attestation by a client of a Rocket chip implementation on a Xilinx Zynq 7000 FPGA.

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.

International audience; Worst-case delay analysis of real-time networks is mandatory, since distributed real-time applications require bounded end-to-end delays. Switched Ethernet technologies have become popular solutions in the context of real-time systems. Several approaches, based on Network Calculus, trajectories, ..., have been proposed for the worst-case analysis of such technologies. They compute pessimistic upper bounds of end-toend delays. Since this pessimism leads to an over-dimensioning of the network, it is important to quantify the pessimism of the computed upper bounds. In this paper, we propose such a pessimism analysis, based on Network Calculus. In a first step we focus on avionics switched Ethernet network (AFDX) with Fixed Priority/First In First Out (FP/FIFO) scheduling.

An institutional repository is a system for archiving research outputs such as scholarly papers. In order to increase the number of archived papers in institutional repositories, the registration process controlled by repository managers should be improved. The authors of this paper conducted an investigation on the efforts involved in paper registration with institutional repositories in several universities. The paper shows the result as a formalized workflow of the process. The investigation showed that one of the hardest tasks for repository managers is confirmation of the copyright policy of publishers. The authors developed a system that automatically searches the copyright policy on external databases.

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.

We demonstrate a compact wavelength-tunable and -switchable mode-locked Yb-doped fiber (YDF) laser based on single-walled carbon nanotube (SWCNT) wall paper absorber. Two mechanisms coexist in the fiber cavity. The switchable mode-locked state can be obtained between two wavelengths depending on the fiber-loop-induced cavity birefringence. Because of the intensity-dependent transmission distribution, the proposed fiber laser can be operated in the tunable wavelength mode-locked state from 1025 to 1037 nm. The spectral bandwidth varied from 1.1 to 2.4 nm depending on the operating wavelength and the pump power with pulse duration of hundreds of picoseconds. The average wavelength spacing is 3.6 nm, which can be changed, corresponding to the birefringence of the fiber cavity. Moreover, stable wavelength-tunable mode locking is obtained at room temperature.

We consider the problem of matching the topics of a scientific paper with those of possible publication venues for that paper. While every researcher knows the few top-level venues for his specific fields of interest, a venue recommendation system may be a significant aid when starting to explore a new research field. We propose a venue recommendation system which requires only title and abstract, differently from previous works which require full-text and reference list: hence, our system can be used even in the early stages of the authoring process and greatly simplifies the building and maintenance of the knowledge base necessary for generating meaningful recommendations. We assessed our proposal using a standard metric on a dataset of more than 58000 papers: the results show that our method provides recommendations whose quality is aligned with previous works, while requiring much less information from both the paper and the knowledge base.

The typical pricing policy, offered by service providers, is on a pay-as-you-go basis, which is proportional to the resources consumed by services. However, providers do not expose the specification of the resource consumption of services. Thus, providers offer cost pre-calculators that are service-agnostic. Such cost pre-calculators take into account upper bounds of provided facilities, instead of an estimation of the resource consumption of a service. To help service providers in specifying the resource consumption of services, we propose an initial version of an automated approach that captures the resource consumption of services. To make it in an independent way of the used measurement units and of the infrastructure over which a service is hosted, our approach builds for a service a mathematical model of computation, estimating its computational performance that is directly related to its resource consumption. Our approach moves beyond the state-of-the-art, since it automatically builds a model of computation based on the interface of a service, instead of its source code, and based on the monitoring of the execution of a service by using its executable files, instead of the monitoring or the theoretical analysis of its source code. The evaluation of our approach in a set of basic case studies shows promising results.

Resin impregnated paper (RIP) is a relatively new insulation system recommended for the use in transformer bushings. In the recent past, RIP has acquired prominence as insulation in bushings, over conventional oil impregnated paper (OIP), in view of its overwhelming advantages the more important among them being low dielectric loss and possibility for positioning the bushing at any desired angle over the transformer. In addition, the fact that such systems do not pose problems of fire hazard is counted as a very important consideration. The disadvantage of RIP compared to OIP, however, is its much higher cost and involved manufacturing process. The temperature rise in RIP bushings under normal operating conditions is seen to be a difficult parameter to control in view of the limited options for effective cooling. It is therefore essential to take serious note of this aspect, to arrest rapid deterioration of bushing. The degradation of dry- type insulation such as RIP is often due to thermal stress. The long time performance thereof, depends strongly, on the maximum operating temperature. With this in view, the Authors have developed a theoretical model and computational method to study the temperature distribution in the body of insulation. The Authors consider that the basis for the model as being the temperature and electric stress aided AC conductivity. The ensuing heat balance (continuity) equations in 2-D cylindrical geometry are treated as a Dirichelet-Neumann boundary value problem.

The paper introduces a Web system which supports registration of scholarly papers to institutional repositories. Institutional repository is an important service for academic societies, however the number of archived papers is not enough in most of institutions. The authors of the paper developed a system that supports authors of papers (that is, researchers) and managers of repositories in registration of papers. By connecting with external databases of published research papers, the system urges researchers register their papers to repository. Additionally, the system automatically searches the copyright policy for each paper also using external databases. This paper makes clear the problem of current institutional repositories, and then describes the detailed idea of the developed system as a solution. The system is expected to decrease the efforts of researchers and managers for paper registration, and increase the number of archived papers in institutional repositories thereby.

Digital pen and paper technologies provide the basis for linking digital content and services to printed materials in the form of interactive paper publications. To realise the potential of these technologies, it is important to develop platforms and tools that can support the large-scale publishing of interactive paper documents. We show how an extensible content management system that was developed to support context-aware publishing was used for the production of interactive paper documents. The publishing process consists of two phases and requires one channel to support the production of the document together with cross-media link definitions and a second channel to support interaction with the document.

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.

The single-mode properties and design issues of three vertical-cavity surface-emitting laser (VCSEL) structures incorporating nano structures are rigorously investigated. Nano structuring enables to deliver selective pumping or loss to the fundamental mode as well as stabilizing the output polarization state. Comparison of three vectorial simulation methods reveals that the modal expansion method is suitable for treating the nano structured VCSEL designs.

In this paper the selection of suitable content-based features for the reconstruction of shredded notebook paper is examined. An algorithm for the detection of squared paper is proposed, based on the Hough transform. Experimental results show a good performance of the algorithm.

Partial discharge (pd)-based risk assessment in electrical insulation systems becomes effective only if the nature of the defect generating pd can be ascertained. In oil/paper insulation systems this is a fundamental item since e.g. harmfulness of pd generated by gas bubbles is much smaller than that of pd occurring between paper layers. For such reasons, partial discharge analysis of oil/paper insulated systems often lacks a clear correlation between cause (i.e., defect type) and effect (partial discharge recording). Results relevant to partial discharge measurements performed on lab-scale objects having different electrode configuration are presented in the paper with the purpose to spotlight characteristic features aimed at identifying the basic nature of partial discharge-generating defects in oil/paper insulated systems.

Published version

HVDC cables play an important role in a growing number of HVDC links. For almost all of these cables, mass impregnated paper is used as electrical insulation. The electrical conductivity of this insulation is given by a commonly used empirical formula. This formula takes into account the temperature and stress dependency of the conductivity. This paper derives a physics-based equation describing ionic conduction. In good approximation this theoretical formula gives the same results as the empirical one. This makes it most likely that the conduction in paper mass impregnated cables is of the ionic kind. The derived formula uses some physical parameters like the inter-potential well distance, the potential well depth and the carrier concentration. Numerical values of these quantities for mass impregnated paper are given. According to the proposed model, the stress dependency results from the inter-potential well distance only. The temperature dependency results merely from the depth of the potential energy wells. In addition some possible underlying physical processes are described. >

The main purpose of this paper is to present the methodology for calculating the electromagnetic behaviour of real integrated circuit (IC) parts using a no-mesh local Finite Differential Method (FDM). Furthermore, the comparison of computational results and measurements is presented. All considerations are based on typical long transmission lines (TLs) in modern ICs. The obtained results have been analysed in detail and compared with measured values. The measurement data are de-embedded using the test board model. This problem is illustrated in this paper based on a practical example of the Multi-Conductor Transmission Lines test structure whose electrical responses to various excitations are presented and analysed in detail.

With the wide application of vegetable insulating oil in power transformers, it is essential to investigate the influence of moisture on the frequency domain dielectric spectrum (FDS) analysis in order to propose an accurate moisture assessment method for vegetable oil-paper insulation system. In this regard, various vegetable oil-paper samples are prepared in a laboratory environment. FDS curves for all samples are obtained at different moisture contents and operating temperatures. A new method to estimate the moisture content in insulation paper is proposed based on the low-frequency characteristic quantity. Also, the effect of operating temperature and water migration between the oil and paper insulation on the FDS analysis is investigated. Based on this analysis, a compensation factor is introduced to eliminate the influence of temperature on paper moisture assessment. Furthermore, an improved normalization method for the temperature effect on the FDS of vegetable oil-paper insulation with different moisture contents is proposed. The proposed moisture assessment and temperature normalization methods are validated thorough their application on an operating power transformer.

Delivering confidential messages in wireless network is gaining continuous attraction as a fundamental building block for the Internet of things (IoT). This paper overviews the confidential message transmission techniques in broadcast channel (BC) where a transmitter serves multiple users by delivering confidential messages to their intended users. Each confidential message must be prevented from extracting its information by any unintended users. First, we consider a basic network consisting of two users. In the two-user BC, the secret dirty paper coding (S-DPC) achieves the secrecy capacity region. However, since the DPC requires a high computational complexity for characterizing the capacity region, two sub-optimal transmission techniques with low complexities are explained. Second, we extend our discussion to the network including more than two users. For $K$ -user BC with confidential messages, the optimal transmission scheme and the secrecy capacity region have not yet been derived. Instead of presenting the optimal scheme, we explain two sub-optimal transmission techniques and compare their features and performances. In conclusion, we discuss the open problems in the confidential message transmission for networks with more than two users.

Voice-over IP (VoIP) technology is a kind of digital transmission technology based on IP network. It is one of the important methods to use voice service in VoIP as steganographic carrier to ensure secure transmission. However, the traditional steganographic code has some problems, such as low embedding efficiency and weak concealment, which cannot meet the requirements of VoIP streaming media information hiding for the security of secret information. Therefore, a steganographic algorithm combining F5 and simplified wet paper code (SWPC) algorithm is proposed. The main idea is to embed secret messages in each row of the carrier matrix using the F5 algorithm, and then the SWPC algorithm is used to embed the columns according to the wet and dry characteristics of the wet paper code without affecting the results before row embedding. We use the VoIP streams encoded by the ITU-T G.729a codec as a carrier to verify the proposed scheme. The experimental results demonstrate that the proposed scheme can achieve relatively better IP speech data steganographic transparency and that it can outperform F5-WPC and SWPC approaches.

Trust is a fundamental factor in how users engage in interactions with Visual Analytics (VA) systems. While the importance of building trust to this end has been pointed out in research, the aspect that trust can also be misplaced is largely ignored in VA so far. This position paper addresses this aspect by putting trust calibration in focus – i.e., the process of aligning the user’s trust with the actual trustworthiness of the VA system. To this end, we present the trust continuum in the context of VA, dissect important trust issues in both VA systems and users, as well as discuss possible approaches that can build and calibrate trust.

Machine learning tools, like deep neural networks, are perceived to be black boxes. That is, the only way of changing their internal data models is to retrain these models using different inputs. This is ineffective in dynamic systems that are prone to changes, like concept drift. A new promising solution is transparent artificial intelligence, based on the notions of interpretation and explanation, whose objective is to correlate the internal data models with predictions. The research question being addressed is whether we can have a self-adaptive machine learning system that is able to interpret and explain its data model in order for it to be controlled. In this position paper, we present our initial thoughts whether this can be achieved.

Recent studies have proposed the use of experiments to guide software development in order to build features that the user really wants. Some authors argue that this approach represents a new way to develop software that is different from the traditional requirement-driven one. In this position paper, we propose the discipline of Hypotheses Engineering in comparison to Requirements Engineering, highlighting the importance of proper handling hypotheses that guide experiments. We derive a set of practices within this discipline and present how the literature has tackled them up to now. Finally, we propose a set of research questions that could guide future work towards helping practitioners. peerReviewed

Software companies are increasingly adopting DevOps and continuous software engineering practices to support short feedback loops, gain better control and visibility over deployments, and decrease the need for manual work with the help of automated processes. While adopting DevOps practices can lead to various benefits, companies also face many kinds of challenges in the transition. This short paper presents the results of a case study conducted in a large Danish software service house about their experiences of transitioning towards DevOps. We got 30 completed survey responses and interviewed four persons in software engineering related roles. We present the current state of the company with challenges and suggestions to improvement. To reach DevOps, the company will need a major cultural change. However, the respondents were positive that the adoption of continuous software engineering practices would mitigate some of their prevailing challenges.

This paper presents, for the first time, a 24-GHz Continuous Wave (CW) radar front-end, entirely realized on a cellulose-based (i.e. paper) substrate. The front-end uses a microstrip circuitry that is fabricated using a copper adhesive laminate to have low conductor losses. A single dielectric layer is adopted to reduce complexity and, in perspective, costs. The radar exploits an external oscillator and transmits a power of about 2 mW. The antenna has a gain of 7 dBi and features an half-power beam width of 42 degrees. Its efficiency is 25%, including the feeding line. A singly-balanced diode mixer is adopted in the receiver chain. The mixer conversion loss is 11 dB with a local oscillator driving level of 0 dBm. In Doppler mode, the radar is able to detect a small fan (i.e. the movement of its rotor) at 1 m distance from the antenna. This contribution demonstrates that circuits on cellulose are capable to operate up to the boundary between microwave and millimeter-waves.

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.

Graphene is a monolayer of carbon atoms with remarkable electronic and mechanical properties amenable to sensor applications. While the plasmonic nature of graphene at terahertz frequency has been widely reported, investigations on the practical utility of graphene at the microwave frequencies used in wireless sensor nodes are sparse. In this paper, graphene films with different amounts of graphene (12.5 wt%, 25 wt%) are characterized at the microwave frequencies. Dielectric spectroscopy is used to study variation in surface impedance of the film. A simple circuit model of the film based on lumped elements is obtained by fitting the measured scattering parameters with the ADS simulations on graphene loaded microstrip lines.

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.