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Life expectancy of power transformers is limited by the integrity of insulating cellulosic paper wound around transformer winding. The insulating paper is subjected to thermal, electrical and mechanical stresses. There are three main factors causing degradation in the paper, i.e. moisture, oxygen and temperature. In this work, the degradation rate due to temperature is only discussed. That means that transformer life could be shortened or extended by adjusting loads which results in higher or lower temperature conditions. The temperature, namely the hot-spot temperature is typically used to estimate the relative ageing rate and loss of insulation life. Being able to estimate the hot-spot temperature accurately given load and weather data helps operators to plan about transformer replacement properly. This could also reduce costs of early replacement due to a conservative estimation. In this work, thermal models have been developed using machine learning techniques to learn thermal behavior from historical data. The data are comprised of the hot-spot temperature estimated by winding temperature indicator (WTI), load profiles, ambient temperature, rainfall, wind speed and direction and solar radiation. The proposed method has been validated using data for five 400kV/275kV, four 400kV/132kV and two 275kV/66kV autotransformers and has been shown to work effectively.

Triboelectric nanogenerators (TENGs) have been introduced as a rational and effective way of powering the low consuming electronic devices and sensors. Mostly these nanogenerators are manufactured using costly materials and complex fabrication processes that restrict their usage especially in developing countries. In this paper, we have presented an inexpensive and facile TENG for powering the environmental sensor. Readily available and cost-effective materials were used for manufacturing TENG like paper, thread sealant PTFE tape, and pencil. The manufactured paper based TENG produced short circuit current and open circuit voltage of $110\ \mu \mathrm{A}$ and 234 V respectively. The maximum power density of $96.22\ \mu \mathrm{W} /$ cm2 was achieved at 5 M $\Omega$. The rectified signal from TENG was used to charge a capacitor array of $300\ \mu \mathrm{F}$ which was successively used to power the environmental sensor. Temperature and humidity can be measured by powering the environmental sensor with the help of the proposed TENG. This facile and cost-effective TENG can be easily manufactured and deployed in resource limited environment for self-powered sensing systems.

Traction transformers have been withstood the effects of shock load, which would become more than 2~3 times rated load when the train passes, and it can result in the winding insulation under short-term high temperature frequently. And the average load far less than 50% result in relatively low oil temperature, the very uneven rise of temperature lead to the very uneven distribution of insulation aging. In order to evaluate the aging life of oil-paper insulation of traction transformer under shock load effectively, in this paper, Ekenstam aging kinetic model was optimized considering the effect of shock temperature, shock duration and shock interval on cellulose degradation rate of insulating paper. Firstly, the effects of shock temperature, shock duration and shock interval on the parameters of Ekenstam model are analyzed and determined by handing and testing experimental materials. Then, according to the test data, the Ekenstam optimization model considering shock temperature, shock duration and shock interval is obtained. Finally, the optimized model is verified by experiments. The results show that the optimization model can effectively evaluate the aging life of oil-paper insulation of traction transformer under shock load in the temperature range, which provides a basis and reference for the subsequent related research.

Flexible supercapacitors are considered as a promising candidate for power supplementation in wearable electronics due to their high power density. However, effectively fabricate flexible and low-cost supercapacitor electrodes in a big scale is still a key challenge. Herein we demonstrate a scalable fabrication method for hierarchical electrodes via metalizing air-laid paper and loading with MnO2 as cathode active materials. To be specific, we coat a thin layer of Ni on air-laid paper by magnetron sputtering, then deposit Ni nanocone arrays (NNAs) on the Ni sputtered paper and finally deposit MnO2 on the NNAs to obtain the NNAs@MnO2 paper electrode. The as-prepared paper-based electrode possesses high conductivity and fine wettability, which facilitates the electrons and ions transporting through the conductive network. Additionally, this electrode provides large specific surface area with a hierarchical architecture. Thus the electrode shows high capacitance (451 F/g) and favorable cycle performance (92.9% capacity retention after cycling for 5000 times). By coupling with activated carbon (AC) coated on the NNAs conductive paper as anode, an NNAs paper-based asymmetric supercapacitor is constructed. Benefiting from the high mechanical durability and the 3D hierarchical architecture of the electrodes, the asymmetric supercapacitor exhibits excellent mechanical flexibility and high energy density (26.9 μWh/cm2 at 1.08 mW/cm2). This method can be easily scaled up to produce lightweight and low-cost conductive paper electrodes, making it promising for the application of flexible supercapacitors in wearable electronics.

Worldwide electronic waste is one of the emerging problems which can adversely affect the human and environment. The paper based flexible eco-friendly, disposable electronics battery is the excellent way to come up with the above mentioned challenge. In this work we reported the development and optimization of a cost, disposable, biodegradable, miniaturized and lightweight conductive polymer coated exfoliated graphite paper battery. Here, anode contains aluminium foil and cathode is made using electrochemically deposited anthraquinone conductive polymers on exfoliated graphite paper with a concentrated sodium chloride salt, as electrolyte. The battery shows a electrochemical response on by applying 40–50 μL of water and produces a maximum capacity of 235 mAh g−1 along with a superior cyclability of up to 500 cycles at 200.0 mA cm−2 current density. The proposed 3–4 battery connected in series powers a LED during approximately 60–90 seconds. Still continuous effort is going on for battery performance improvement. Obtained results allow to planning potential uses to low power consumptions microelectronics such as pacemakers, cosmetics, wearable biomedical devices, and electronics.

Laser-cut paper patterns which are suitable for focusing terahertz radiation are presented. Such designs provide an extremely low-cost route for the prototyping and production of terahertz optical components. Diffractive binary Fresnel lenses have been explored using a multilayer paper stack and a liquid absorption method in order to phase shift THz radiation through paper by the optimum 180° The conventional Fresnel lens design has been extended to produce multiple focal spots and explore alternative shapes (e.g. hexagonal).

Currently, racial oil blotting papers are counted by hand. However, it takes a long time and this is hard work. Hence, an automatic counting system is necessary. In order to achieve this, we developed a cheap system using a webcam. This system firstly captures one image of arranged papers by shifting. Secondly, the paper boundaries are obtained as straight lines by utilizing the proposed image processing. By counting the acquired lines, the system outputs the number of papers. However, the captured image has noises such as the change of illumination and shadows. They make the extraction of the accurate boundaries difficult. For the accurate extraction, optimal parameters of the image processing must be set. Since the prediction of the optimal parameters in advance is difficult, the proposed method adopts genetic algorithm (GA). Also, Hough transformation for the straight line detection is improved. By applying the proposed method, the accurate paper counting is possible. For the experiment, 14 images were captured in various environments using a general webcam. Then, the proposed method was compared to a latest related work. As a result, F-measure of each method was 0.995 and 0.945.

International audience; The design of a dipole antenna printed on a paper substrate is presented in this paper. The antenna which integrates a compact balun is devoted for dual-band 2.4/5 GHz WLAN applications. The antenna is based on a double-side printed multilayer paper substrate and is fed with a coaxial cable for the testing. The simulated results of the whole structure are also presented in detail and compared with the measured performances.

Carbon materials are known to be one of the most suitable platforms for the development of cold electron emitters. Here we explore field emission (FE) performance of so-called graphene paper that is a micrometer-thick foil obtained by stacking chemically exfoliated graphene layers. We find, that shaped into triangular form, graphene paper exhibits competitive FE characteristics, such as highcurrent densitys Table in time, and low threshold fields. In addition, we study the degradation of such graphene-based emitters under high emissions currents and discuss possible application for a transmissiontype X-ray source.

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.

Utilizing the in-situ reducing method, a reduced graphene oxide (rGO) paper for 13~14 um was obtained and exhibits great Terahertz (THz) absorbing capability. The absorption of rGO paper exceeds 43% in the whole frequency band from 0.3~1.2 THz and maximum absorption reaches 59.33% at 1.13 THz. This makes it possible to realize ultra-thin broadband THz absorbing materials.

In order to realize smart factory which is appeared in the concepts of Society 5.0 and Industry 4.0, wireless Internet of Things (IoT) becomes a key technology. Inside of the factory, there are heavy DATA traffics exist between moving/movable machine tools/robots/automated guided vehicle (AGV) with wireless access point (AP) and high speed moving/rotating objects/materials with wireless sensor node (SN). Currently, wireless systems used for wireless IoT are limited such as wireless-LAN/Bluetooth/RFID. Since these system’s frequency bands are limited and narrow, the interference between these systems becomes severe. In this paper, we propose a simplified beam forming wireless IoT communication using novel Wi-Fi backscatter system to notify the existence of SN who wants to send its DATA to AP. For Wi-Fi AP with beamforming function, knowing the numbers of existing SNs in each beam area will be a help for efficient beam control. This paper describes the Wi-Fi backscatter system in which the SNs backscatter the Wi-Fi signal transmitted from the AP then the AP detects the backscatter signals from SNs and know the existing SN’s number in its beam area. Since this backscatter system uses Wi-Fi modulated signal, the separation of SNs’ backscatter signals from AP’s transmitting Wi-Fi signal becomes complicated. This paper also describes the transceiver architecture of AP which reduces the complexity of signal processing and improves the dynamic range of reception.

In recent year, Graphene has witnessed an increasing demand in diversified domains including in realizing various electronic devices due to its unique electrical and mechanical properties. In place of the conventional cumbersome approaches, recently CO 2 laser induced graphene (LIG) on various substrates, like polymers, paper, cloth, have become a reliable alternative to fabricate such devices. Even though, development of LIG zones on diverse substrate and their optimization and implementation has been reported, a process to manifest single-step, cost-effective and scalabel LIG based flexible electronic devices remains a challenge. Herein, a novel process has been demonstrated for fabricating LIG based flexible electronic device on paper and cloth using a low-power blue laser. First, a porous filter paper and a cotton cloth were soaked in liquid polyimide and phenolic resin-polyvinyl alcohol (PR-PVA) respectively. Subsequently, a 3D printer, loaded with a 2.8 W blue laser diode, was appropriately ablated to form paper-based LIG (P-LIG) and cloth-based LIG (C-LIG), with desired designs and conductivity values. P-LIG and C-LIG zones provide optimum conductivity values of 198.54 S/m and 22.23 S/m respectively. Finally, P-LIG and C-LIG were integrated with the capacitive touch sensor and microcontroller modules, and display, to employ both the devices as flexible touch sensors.

As the demand for low-carbon and eco-friendly energy is increasing and the use of wearable devices is soaring, the triboelectric nanogenerator (TENG), which can economically harvest energy, is in the spotlight. Among many materials, paper is considered a promising substrate and frame material for self-powered TENG due to its high accessibility, flexibility, and biocompatibility. Here, we present a new structure of foldable paper based TENG (FP-TENG) composed of paper and PTFE/Si-rubber. The double-folded FP-TENG generates voltages and currents of 153 V and 2.2 µA, respectively, and shows excellent durability without signal degradation under 5,000 cycles of external force. A watch strap was manufactured with FP-TENG and integrated with an electronic watch pannel to supply power, and several LEDs were turned on. Therefore, FP-TENG is expected to be utilized as a promising eco-friendly energy source for small electronic devices.

We report an eco-friendly and easy-going way of fabricating a vast range of passive electronic components and low pass filters. This is achieved by directly writing graphite on paper and cutting and pasting aluminum foil and copper tape on different substrates. Resistance was achieved from 4 kΩ to MΩ(s) by penciling several sustainable layers of different graphite to clay content pencils. Capacitors of capacitance from 2 pF to 10 μF are fabricated using graphite, aluminum foil, and copper tape as conductive materials on printing A4, baking, and butter paper as substrate and dielectric materials as for parallel plate capacitors. Pencil on paper-based interdigitated capacitors is reported to achieve lower capacitance and higher cut-off frequency values of low pass filters. Resistors and capacitors of different values are fabricated in a plane to design low pass filters with 100 Hz – 2 MHz cut-off frequency range. All the components and circuits are fabricated from foldable, eco-friendly, and readily available paper materials as substrates. These paper-based components are helpful for foldable electronics, foldable printed circuit boards, and soft robotics.

This contribution describes the feasibility of a wireless sensor that uses Micro-Electro-Mechanical Systems (MEMS) on cellulose materials. In particular, the focus is on a paper-aluminum (paper-Al) bimorph cantilever formed by an Al foil glued on top of a paper layer. It is well known that paper relaxes its fibers in the presence of humidity. This means that the length of the paper layer increases (respect to the Al layer) when humidity is absorbed, thus determining the cantilever deflection. Such a mechanism is used to control a capacitor formed by the cantilever itself (Al layer) and by a metal plate printed on a PCB. The capacitor is then applied to a planar notch filter whose resonant frequency is hence determined by the humidity. The preliminary experiments show that the developed circuit features a 2.45 GHz center frequency and a sensitivity of about 3.7 MHz ner each nercent of relative humidity variation.

The oil-impregnated paper in the converter transformer, especially in the valve side bushing, is suffered by the complicated electric field. By reason of the power electronics and non-linear equipment, the oil-impregnated paper is subject to the harmonic voltages. The insulating aging is more prominent in contrast with the power transformer. Under this condition, the charges are capable to accumulate on the surface of oil-impregnated paper, which will lead to the distorting the electric field and accelerating the insulating degradation. Consequently, the performance deterioration of oil-paper insulation is inevitable. Surface fluorination is an effective approach of modifying the chemical components of polymer matrix. Hence, this paper is dedicated to research effects of thermal aging on the surface charge dynamic characteristics of fluorinated oil-paper insulation under the harmonic superimposed DC voltages. Some conclusions can be drawn that the comprehensive effect of harmonic voltage and thermal aging can significantly enhance the de-trapping of the surface charge in deep traps, the deep trap energy level density is greatly affected by the proportion of harmonic. As the thermal aging time is prolonged, the trapped charge becomes more difficult to detrap, the charge accumulation increases.

High-frequency transformers with small size and light weight have been widely concerned by researchers at home and abroad. The oil-paper insulation of high frequency transformers is affected by the high frequency pulse produced by power electronic device, which is more prone to discharge fault and insulation failure. To study the effect of high frequency pulse voltage on the discharge characteristics of oil-paper insulation, a needle plate electrode model was used to carry out the discharge experiment of different layers of oil-paper insulation samples at 1–20 kHz bipolar high frequency square wave voltage produced by high frequency power supply. The partial discharge and breakdown characteristics of oil-paper insulation under high frequency square wave pulse voltage were studied. The results show that the discharge quantity of oilpaper insulation increases greatly with high frequency pulse voltage compared with AC voltage. There is no discharge phenomenon in the process of discharge development, which is significantly different from that under AC voltage. The intensity of discharge increases under high frequency pulse voltage and its increasement accelerates the deterioration of oil-paper insulation.

We have all had those tasks come up that on the surface seems like a very simple 5-minute job. But then things do not go quite as planned. Suddenly, that simple task has now become a major job. People will then tend to start taking short cuts and get complacent in how they complete the repair job. That is when people get hurt or equipment gets damaged. This paper will explain how a very simple task at the author's house garage to replace two ceiling light bulbs and two garage door opener light bulbs turned into over a one-week nightmare. The parallels to the industrial electrical safety world are phenomenal. The other thing that made this job unique is the worker performing the tasks was an unqualified electrical worker that was working under the direct supervision of a qualified worker in a training mode. This paper will examine all the detailed steps that were taken in compliance of NFPA 70E to keep the worker safe while performing in a training mode under difficult situations. When the job was completed, all electrical safety procedures for hazard risk analysis, job briefing, individual responsibilities, lock out tag out, PPE, and fall protection were followed. No one was injured and the unqualified worker gained a lot of new experience and is now trained to meet the NFPA 70E definition of a qualified worker to perform these tasks in the future. Moral of the story is there is no such thing as a 5-minute job in life. You must plan accordingly

Much of the literature on the link between reliability and safety—especially that written by Ron Moore, whose work is referenced throughout this paper—shows that the more reliable a plant or facility is, the safer it is. This presentation will present the unique connection between reliability and safety from a professional reliability engineering perspective. When asked, “who is responsible for safety?”, most organizations have done a great job of having the consensus answer be “everyone.” This paper serves as reinforcement of the linkage between safety and reliability, that organizations of the future might encourage their members to answer to question “who is responsible for reliability” in the same way: everyone.

In this work, capacitive touchpads are presented based on fabrication processes that are inexpensive, lab and solvent-free. Pencil and paper have been used to fabricate the sensors, and these materials are economical, biodegradable, and readily available. A touchpad comprising a combination of five sensors has been developed, and analyzed its working by interface controlling for LED's toggle operation. LCD and android app interface have been used to display the result. The sensor's response has been sensed for a gloved finger touch for sensors. The sensor's performance remained consistent, and the functionality was similar to common buttons and sensors. These sensors are recyclable and can be fabricated with ease. This can contribute to potential developments in smart packaging, medical and healthcare applications, and thin human-machine interfaces.

Human recogntion technologies are gaining significant research attention, where the model can be trained to be more precise to recognize the poses performed by objects. Activity identification is a kind of problem, which needs more research consideration and improvement. There is also an increasing need to detect different poses of objects. To tackle the issue, different sensors like Gyroscope and Accelerometer are required to classify the data in the form of images using machine learning algorithms like SVM and CNN. These approaches help us in implementing real-time applicaions such as health monitoring, tracking sports activity and security. The paper also discusses about its benefits, limitations and prominent approach for human activity recognition.

The power density and total power from the package have been increased significantly. The rapid rate of power density increases from one generation to the next not only happens at the device level but also happens at the localized area on the devices. The objective of this study is to build more understanding of the localized high-power density in silicon blocks with respect to the impact in temperature gradient and reliability of the silicon. Conventionally, individual design block power usage numbers are often reported from circuit simulations without considering physical location of transistors and metal wires. However, in a silicon block design, certain transistors may consume significantly more power than others due to higher load capacitance, current draw, frequency, or toggle rate. Therefore, the power distribution is uneven within the design block even in the same use case. In order to gain a better understanding of power density peak spot inside of a single design block, in this study, the transistor activity is dynamically analyzed with circuit simulation vectors of an actual Versal product use case and the spatial power distribution of a 0.5mm x 0.5mm design block is reported in an granularity of 10um x 10um and turn x turn respectively. The analysis results show that the local heat flux can be several magnitudes higher when the design block is analyzed in more granularity. The local heat flux creates local hot spot that was overlooked. The max hotspot temperature would not be captured by the sensor because this specific hotspot sensor location would not be known at first hand due to uncertainty of the exact location created by the local hot spot. Understanding that there can be temperature sensors located some distance(700um) away from hotspot, reporting out the temperature, the device max temperature can be higher than the system monitor readout. Given this max temperature discrepancy, a correlation for max temperature based on heat flux density, source area, heat sink resistance, and senor location would be defined to estimate the max temperature. When the semiconductor chip has hot spots, it affects reliability of the chip. Most of reliability mechanisms result in shorter lifetime with higher temperature and temperature gradients. When a small portion of product has local temperature increase by whatever reason, long-term circuit performance should be altered due to enhanced or reduced aging effect. The device long term reliability is reassessed based on the new discovered localized hot spot.

For nearly four decades 2-furfural (2-FAL) in transformer oil has been used as a chemical marker to indicate the ageing state of transformer paper insulation. Nevertheless, it has always been a challenge to define an acceptable limit for 2-FAL due to issues related to non-uniform temperature distribution in transformers, stability of 2-FAL in oil and its partitioning between liquid and solid insulation. Therefore, transformer users try to combine the laboratory findings, the operational experience and post-mortem analyses together for predicting ageing state of paper insulation through 2-FAL content in oil. Due to increase in the use of ester liquids in transformers, there is a need to investigate the ability to use 2-FAL as a paper ageing indicator for ester based insulation systems. Laboratory ageing studies have shown that 2-FAL is indeed generated in ester based insulation systems. However, there is a lack of understanding related to the partitioning of 2-FAL in ester based insulation systems. This paper studies the partitioning of 2-FAL in synthetic ester based insulation systems and compares to that in mineral oil based insulation systems with the focus on the effect of paper type and water content in paper. Under the investigated conditions the synthetic ester had higher partitioning coefficients (ratio between the 2-FAL content in oil and paper) than the mineral oil. Partitioning coefficients in both oil types decreased with the increase of the water content in paper. However, change in paper type did not significantly affect the partitioning coefficients in this study.

International audience; This paper presents a parallel-plate waveguide lens for wide-angle mechanical beam steering. A previously developed ray-tracing procedure is used for designing the quasi-optical system. The feed system is based on gap waveguide technology enabling a simple and rapid mechanical actuation. Validation of the proposed concept is given by numerical results for a Ka-band lens design. A high scanning performance over an angular range of ± 50° with a worst-case scan loss of about 3 dB is achieved. The simulated return loss is greater than 15dB in the 27.5-31 GHz band. The proposed lens beamformer is an attractive ground-segment solution for future Satcom applications. © 2021 EurAAP.

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.

IEEE 1584–2018 contains a significant update to industry models for predicting the incident energy from arc flash. These models include different box sizes, voltages, and electrode geometries. Predictions from these models are compared to tests on medium-voltage equipment. Equipment includes circuit-breaker cabinets, live-front switches, and live-front transformers. Results show what input assumptions are most applicable for each type of equipment (including vertical and horizontal electrodes). For some equipment, particularly with horizontal electrodes, the 1584–2018 predictions underpredicted measurements of incident energy, so multiplier factors may be needed.

Anti-counterfeiting technique is a research hotspot in information security domain. Common techniques are usually based on artificial physical cloneable feature which is forgeable. In this paper, we proposed an anti-counterfeit method based on microscopic translucent texture of paper (MTTP). MTTP is image of internal fiber pattern of paper (IFPP) captured by microscope under translucent light source. The IFPP has property of uniqueness and randomness, and the fiber scale of IFPP is at sub-micron or micron level. Then the IFPP is unable to be forged. Furthermore, fiber texture in IFPP is stable under disturbances (including illumination intensity change and surface damage), which guarantees the stability of the MTTP. Experiment results show that the authentication accuracy achieve 100% in our dataset (totally 13,4550 pairs of MTTPs) and the false reject rate achieves the order of magnitude of 10-136 in ideal condition and 10-59 even in condition of illumination change or surface damage. Above results indicate that our method has rather high security and reliability.

Oil-paper insulation bears AC/DC composite voltage in converter transformers. However, the AC/DC space charge behavior is still not clear, which will result in electric field distortion, material aging and even insulation failure. In this work, the space charge distribution of oil-paper under the AC/DC composite voltage with the AC/DC ratio of 1:1, 1:3, 1:5, and 1:7, is studied by pulse electroacoustic (PEA) method, respectively. It was found that as DC component increases, the accumulated charge near the electrode decreases, while the interior charge increases. It suggests that DC stress mainly influences the amount and the depth of space charge accumulation. AC component has a relatively significant impact on the injection and extraction behavior of space charge near the electrode. Furthermore, AC/DC composite voltage enhances the migration of space charge compared with that under DC voltage. This research contributes to the further understanding of the space charge characteristics of oil-paper under AC/DC composite voltage, which will benefit the safe and stable operation of converter transformers.

Oil-paper insulation high-voltage bushings are one of the most important power equipment in substations, and their insulation status is critical to the safety and the stabilization of the power system operation. During the production and operation, the bushing may be dampened because of the insufficient drying and impregnation or the intrusion of external moisture, which leads to the deterioration of oil paper insulation and threatens the reliability of bushing. Due to the special insulation structure of the bushing capacitor core, the distribution of moisture inside the bushing is usually non-uniform, especially when the moisture is intruded from the external environment. In this paper, a numerical simulation model of dual-unit laminated oil-paper and 110kV capacitor bushing is established. Then the frequency domain dielectric spectrum (FDS) characteristics of oil-paper insulation with different non-uniform moisture distribution are obtained by simulation. Different types of non-uniform moisture distribution include: non-uniform moisture distribution in different directions of the bushing, and different degrees of non-uniform moisture distribution. When the non-uniform moisture distribution of bushing is along the axial direction, different degrees of non-uniformity of moisture distribution have little effect on the FDS results; when the non-uniform moisture distribution of bushing is along the radial direction, the $\text{tan}\delta-f$ curve shows a clear dielectric loss peak, the characteristics of which are closely related to the degree of non-uniformity of the moisture distribution. Partial damping at the outermost side of the bushing or the end screen are more common in practice, and the FDS results of these two different types of damped bushing show different characteristic. This paper carried out a comprehensive FDS simulation study of different types of non-uniform dampened oil-paper insulation, which is of great significance for the evaluation of the insulation status of the oil-paper bushing.

International audience; A configuration of antenna using flexible substrate for RF energy harvesting system working at GSM frequency 1800 MHz is presented. The suspended structure is used to surpass the high loss of the substrate. By taking advantage of the flexible properties, the process of miniaturization is achieved through folding the substrate into sections. The antenna prototypes were fabricated and measured. With the compact size of 0.36 λ × 0.33 λ × 0.03 λ, the measured gain is 5.3 dB, about 10 dB gain increase compared to conventional structure.

In early 2003, CPFL Energia, a Brazilian utility, was interested on evaluating the performance of natural ester filled transformers, especially regarding the highly increased overloading capability. As a field test, in association with the transformer manufacturer “Itaipu Transformadores”, they built two prototype transformers. Based on original overhead distribution line three phases transformers of 15kV/45kVA, after small adjustments in the windings and cooling system, keeping same core and tank, associated with the use of natural ester based dielectric liquid, and increasing the average winding temperature rise limit from 55°C to 85°C and a hotspot temperature rise limit of 100°C, the transformer nominal rating was shifted to 88kVA.

This system is controlled by STM32 single-chip microcomputer. FDC2214 capacitance sensor detects different capacitance values between plates, and can accurately detect the number of paper between plates A and B. With STM32F407ZGT6 microcontroller as the core processor, data processing is carried out through the least square method of fitting the slope, eliminating the influence of parasitic capacitance on the data, improving the detection accuracy, collecting stable data of different paper Numbers between the plates in advance, generating samples and self-training and learning. When the effective data is collected, the system will find the sample value with the highest similarity of characteristic values through KNN proximity algorithm between the sample data, determine the number of detected papers, and display them on the serial port screen, at the same time, the buzzer will emit sound.

Conventional electronic components are non-foldable and non-flexible with complex and expensive fabrication processes. Considering the recent interest in foldable electronics, we report a foldable, eco-friendly, low-cost, highly sensitive, and stable microfluidic paper-based capacitive droplet $(\mu$ PCD) sensor. The sensor is fabricated using readily available materials (filter paper and copper tape) through a simplistic, easy-go- designed, and low-cost bench-top fabrication process. The design of the capacitive sensor is based on a parallel plate capacitor attained by direct deposition of copper tape on filter paper. The filter paper serves as a dielectric. Very small quantities $(\mu$ Ls) of liquid can easily flow through filter paper due to micro-pores in it. The $10 \times 10$ mm sensor can detect water droplets as small as $10 \mu \mathrm{L}$ with sensitivity $3 \pm 0.5$ pF$/ 1 \mu \mathrm{L}$. The sensor response is insensitive to bending as tested by measuring the capacitance response at different bending radius from 0 to 7mm. The sensor responds accurately and repeatedly for different volumes of water droplets at different bending radius. Foldability of the sensor makes it suitable for the environment with different geometries, shapes, and dimensions like industry, body parts, and objects for liquid detection.

In this paper we exploit graphite's thermal absorption properties to drive the process of analyte sampling in paper-based biosensors. Graphite structures can be easily patterned or drawn on paper using a standard pencil and selective heating of the patterned layers can be remotely achieved using a light source. The resulting thermal gradient manifests itself as concentration gradients across the paper substrate which then triggers the flow of analyte to the selective areas. In this paper we have validated this hypothesis using a prototype made out of a low-cost filter paper substrate and a 300mW 808nm remote infrared laser source. Compared to a control paper substrate, we show an increase in temperature by more than 70°C (from 50°C to 120°C) in areas where the graphite is patterned. As a result the proposed prototype is also shown to demonstrate a higher sample-flow rate compared to the control. We anticipate that the proposed remote triggering of sample acquisition would be useful for different variants of paper-based biosensors that need to be integrated inside the food-package.

An investigation has been made on Paper-based substrate integrated waveguide (SIW) antenna operating around 21 GHz. The proposed antenna is an SIW square cavity backed radiating rectangular slot. It has the advantage of ultra low profile which makes it suitable for high integration microwave circuits. In addition, this antenna is well shielded in order to be fabricated for application in emerging wireless communication systems. Moreover, a wide bandwidth of almost 3.5 GHz is achieved and a high gain equal to 1.82dB is noted which is not commonly performed for paper-based antenna.

Biological information can easily be monitored by installing sensors in a lavatory bowl. Lavatories are usually shared by several people, so users need to be identified. Because of the need for privacy, using cameras, microphones, or scales is not appropriate. Though personal identification can be done using a touch panel, the user may forget to use it because the action is not necessary. In this paper, we focus on the differences in the way of pulling a toilet paper roll and propose a system that identifies individuals based on features of rotating of toilet paper rolls with a gyroscope. The evaluation results revealed that 83.9% accuracy was achieved for a five-person group in a laboratory environment, and 69.2% accuracy was achieved for a five-person group in a practical environment.

Identifying the phase or stage of children’s spelling development is a regular activity in literacy classes. Usually, teachers assume some developmental theory and perform paper-and-pencil based tests. Existing digital tools often do not consider any of these known theories, nor do they capture the child’s handwriting. Therefore, some teachers prefer to continue applying the tests manually. Accordingly, this study’s research question is how to promote the performance of spelling tests on mobile devices, simulating the interaction between manual tests and the theoretical models already used by teachers. Through the Design Science Research Methodology (DSRM), we propose a method to apply child spelling tests in an automated way. In this work, we present the results of the child’s interface usability evaluation in the developed computer artifact, using guidelines of Touchscreen Interaction Design Recommendations for Children (TIDRC). The results indicate adequacy to the recommendations of 88% of items in visual and audio features (cognitive dimension), 75% in the physical dimension, and 47% in socio-emotional dimension. These results are promising and relevant compared to previous studies that evaluated apps using the TIDRC framework.

Water inside a transformer tank is undesirable because this water causes the following problems. Firstly, on overload bubbles of water may form in the oil weakening its dielectric strength and increasing the risk of catastrophic flashovers across the oil. Secondly, it shortens the life expectancy of the Kraft paper insulation, which is one of the main factors limiting the functional life of transformers. It is therefore necessary to measure the water content of paper insulation so that a utility can take corrective action when required. Cellulose adsorption isotherms have been used to determine the water content of paper using online water activity probes. A disadvantage however is that the application of this method requires that the insulation media is in thermodynamic equilibrium, which due to load cycling usually is not the case. Practically, this problem is resolved by taking a long-term average of the measurements. This solution is not optimal because actual changes in water content will also be smoothed out. The migration of water between paper and oil is a very slow process. Therefore, a low-pass mathematical filter was developed which would retain this process but reject higher frequency components. This filter was also investigated using measurement from operating power transformers.

Electric conduction of oil impregnated paper under different temperatures and different DC electric fields has significant influences on the insulation structure design of converter transformer. This paper focuses on the influence of temperature and DC Electric Field on the electric Conduction of oil impregnated paper insulation, as well as conduction mechanism of oil impregnated paper through the high-field conduction experiments. It is concluded that a raise in temperature and DC electric field leads to the higher conductivity of the oil impregnated paper sample. The activation energy representing conduction barrier height was obtained. Moreover, the mechanism of electric conduction in oil impregnated paper was analyzed, which confirms the hopping conduction model instead of space charge limited current theory. Based on the upper statement, the parameters like the electronic hopping distance δ and the parameter j0 were obtained and we explored the conductivity s changing along with the electric field under different temperatures.

Transformer oil, insulating paper, high voltage direct current (HVDC) bushings and on-load tap changer (OLTC) are essential parts of converter transformers. When the power flow of the HVDC system is reversed or a sudden outrage occurs, the charge field will deform the dielectric internal electric field, thus easily leading to the occurrence of discharge or insulation damage. In this case, it is necessary to carry out the characterization of the oil-paper interface to avoid these consequences. This paper analyses the interface charge accumulation and dissipation characteristics of an oil-paper insulation system under DC and polarity reversal voltages. Induced electrification was used to charge the composite oil-paper insulation. The amplitude of DC and polarity reversal voltages applied in this paper was 4 kV, and paper with thicknesses of 0.08 and 0.13 mm was used. From the research on different layers and thicknesses of paper, with an increase in the number of the paper layers, the interface charge density decreases. Regarding the DC polarity reversal effect, increasing the thickness of the paper is equivalent to adding paper layers. The dissipation rate of the positive interface charge is quicker than that of the negative one. In the polarity reversal test, the dissipation rate becomes smaller as the reversal time gets longer.

Under the HVDC condition, the formation of the space charge in the oil paper system could affect the electric field distribution for converter transformers. Therefore, it is important to analyze the factors that determine the space charge behavior such as the temperature, moisture, electric field, oil paper thickness ratio and multilayers such as (Oil+Paper+Oil+Paper) structure. This paper focuses on the space charge distribution affected by the multilayers (O+P+O+P) oil paper structure and different oil paper thickness ratios. The pulsed electroacoustic method (PEA) was used to measure space charge distributions. It is found that increasing oil thickness could facilitate charge injection. However, the increase of pressboard thickness could prevent the charge injection. It is also found that the same oil paper thickness ratio could lead to similar space charge injection within the oil paper sample under the same 10 kV/mm electric field. Therefore, based on the same oil paper thickness ratio, space charge measured from the thinner thickness sample were further applied to the thicker thickness sample to estimate electric field distribution using COMSOL software, which cannot be measured by the PEA system directly.

In order to assess the moisture content of insulating pressboard in oil-immersed transformer, and thus providing reliable guidance for insulation condition and life estimation of oil-immersed transformer, in this paper, we made four groups of oil-paper insulation samples with different moisture content under laboratory conditions and studied the relationship between pressboard and moisture content by using polarization and depolarization current (PDC) technique. The experiment result shows that PDC curve is very sensitive to the change of moisture content, and the change of moisture content mainly affects the tail of depolarization current curve; the extended Debye model parameters can be obtained from depolarization current curve, and as the moisture content increases the number of branches in Debye model increases, the largest time constant becomes large; the peak of time domain spectroscopy turn up at 1000s., the time constant branch which is longer than 1000s presents the pressboard branches of Debye model; the feature quantity Q paper can show the internal polarization of insulating paper and has a linear fitting relationship with moisture content, so Q paper can be used to assess the moisture content of insulating pressboard.

Recent research activities in the area of low-cost sensing and diagnostics that are realized on cellulosic paper substrate are presented. First a three-dimensional origami paper-based analytical device (omPAD) with multiple electrochemical sensors, an integrated sample reservoir and tight integration with a custom CMOS potentiostat is presented. Second, an optical sensor array with built-in microfluidic channel for sample delivery is presented. The sensors are fabricated using a combination of wax printing and screen-printing using a solution based approach in ambient conditions without the need for expensive fabrication equipment or a cleanroom. Readout is based on using existing consumer grade electronic devices like flatbed scanner (for optical sensor) or custom designed CMOS potentiostat (for electrochemical sensors). Together the 3D paper-based analytical device with integrated sensor, microfluidics and portable readout instrumentation demonstrates a low-cost, self-contained system suitable for sensing and point-of-care diagnostics.

In this paper we present a novel method to print paper and cardboard without ink. The method is based on the carbonization of paper by a combination of lasers working on different wavelengths. A prove of concept system is created based on combining existing commercial systems to demonstrate the viability of the method. The results show that no debris is generated and the quality of the mark is superior in terms of contrast and resolution with previously known methods.

Demand of wearable, portable, lightweight, foldable and eco-friendly electronics is enlarged, and compatible energy storage systems is a prominent topic of research. Highly cost efficient and foldable energy storage systems should be mounted on wearable, foldable and portable electronics. Current fabrication techniques of typical electronic systems are complex and expensive. To address these requirements, paper based foldable and easy go designed supercapacitor-based energy storage devices are suggested and reported. Electrochemical supercapacitors (ESCs) could store charges without chemical reaction and have fast charging/discharging speed. We reported an electric three-layer capacitor fabricated using aluminum foil-based electrodes on baking papers. Low cost and solvent free bench top fabrication process includes direct deposition of aluminum foil using gum on baking paper is demonstrated. Four layers of aluminum foil are stacked on baking paper to achieve high energy storage capability. This aluminum foil based layered structure gives us high conductivity and reliable charging/discharging properties. This device exhibits an excellent cyclability (>5,000 cycles). Device having minor retention in performance under continuous dynamic operations of forceful bending at different angles. The design concept is based on folding-cutting-pasting procedure that provides us flexible production protocol to design and manufacture supercapacitors with adaptable electrical characteristics and configurations. Baking paper is biopolymer-based substrate and can store 0.72 mJ energy. The Electrochemical supercapacitors are based on aluminum foil electrodes on baking paper with gum, so there can realize foldable, eco-friendly, ultra-low cost and easy go designed energy sources for foldable, portable, flexible, wearable and green electronics in the future. Electrochemical supercapacitors could be able to store energy generated from small portable energy generators like triboelectric Nanogenerators for portable, flexible and wearable electronic systems.

Contemporary digital circuits are synchronous-logic and are operationally error-free because they are designed to complete their operation within a predefined time period. In some applications, such as the MOST operating in ultra-deep subthreshold or in flexible electronics where the TFT is printed, the ensuing operation of digital circuits is prone to error. This is because the variations of the delay of the transistor are very high and the ensuing predefined time period is difficult to ascertain. In the case of the printed TFT where its substrate is flexible and hence possibly bent, the delay is possibly intractable, in part because the profile of the bending may not be known. In this paper, we will discuss the commonality between ultra-deep subthreshold and printed TFTs in terms of their variations. We describe the application of the esoteric asynchronous-logic Quasi-Delay-Insensitive (QDI) signaling protocol to design digital circuits that innately accommodate intractable delay characteristics, i.e., error-free operation despite intractable variations. To mitigate the hardware, power and timing overheads of QDI, we will present our proposed modified signaling protocol named Pseudo-QDI and our proposed Pre-Charged-Static-Logic design style.

In this paper the sensor design made by Bosch, one of the world's largest supplier of micromechanical sensors in automotive and consumer applications, is briefly introduced. The design is one of the key elements to bridge the different domains between process technology, electronics, system and customers needs. The here presented flow and methodology ensures an integration of all perspectives from prototyping to series production. Examples of typical Sensor/MEMS design including various mechanical and electronical constraints are given.

At present, transformer protection usually operates after failures. With the raise of voltage level and capacity of transformer, a fault easily becomes an accident, resulting in huge economic losses. Transformer insulation failure is the main cause of transformer accidents. In this paper, a new idea of transformer protection based on insulation critical breakdown prediction is proposed. According to the requirements of transformer protection, a prediction method of oil-paper insulation critical breakdown under DC voltage based on partial discharge analysis is proposed by studying partial discharge characteristics of oil-paper insulation defects under DC voltage and the development process. The results show that when partial discharge critical breakdown occurs in oil-paper insulation under DC voltage, the distribution of partial discharge lagging recovery time is concentrated, and dense discharge clusters are easy to form, which can be used to predict the critical breakdown of oil-paper insulation.

This paper presents a method using logistic regression to predict and detect "startup readiness" of researchers in the biopharmaceutical domain, and to suggest determinants to improve their "startup readiness," using databases of start-up finances, research papers, patents, academic organizations, and national socioeconomics. This method sorts specific industry segments by which financing activities are active, and by which related growing research topics attract increased academic attention. In research domains such as the biopharmaceutical field, which include pursuit of fundamental scientific understanding and applications intended for immediate use, abundant startups with intense scientific linkage have attracted venture capital financing and entrepreneurship for further R&D opportunities and commercialization. We hypothesized that variables composed of several features of papers, patents, research institutes, and nations related to this domain can well reflect researchers' "startup readiness." Our logistic regression model based on our selected and constructed explanatory variables yielded good predictive and classifying performance, with an AUC value of 0.73. Results carried specific implications about what variables and their combinations demand attention, to encourage the "startup readiness" of researchers. More than conventional research methods, our computational approach might provide global, comprehensive, but convenient and real-time understanding of the "start-up readiness" of researchers in user-inspired fundamental research.