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The nanosecond (ns) pulsed nitrogen dielectric barrier discharge (DBD) is employed to enhance the hydrophilicity of polypropylene (PP) surface and improve its application effect. The discharge characteristics of the ns pulsed nitrogen DBD with different pulse rise times (from 50 ns to 500 ns) are investigated by electrical and optical diagnostic methods and the discharge uniformity is quantitatively analyzed by image processing method. To characterize the surface hydrophilicity, the water contact angle (WCA) is measured, and the physical morphology and chemical composition of PP before and after modification are analyzed to explore the effect of plasma on PP surface. According to the experimental results the discharge becomes more uniform and the energy efficiency, electron density and electron temperature are all escalated at 50 ns pulse rise time than at the other pulse rise times. The PP surface treated with 50 ns pulse rise time DBD has a lower WCA (~47°), while the WCA of PP treated with 100 to 500 ns pulse rise time DBD expands gradually (~50°-57°). According to the fixed-point WCA values study the DBD-treated PP surface has superior uniformity under 50 ns pulse rise time (3° variation) than under 300 ns pulse rise time (8° variation). After DBD treatment, the surface roughness and hydrophilic oxygen-containing groups on the surface, i.e., hydroxyl (−OH) and carbonyl (C=O) have played the significant role to improve the hydrophilicity of the sample’s surfaces. The short pulse voltage rise time enhances the reduced electric field strength (E/n) in the discharge space and improves the discharge uniformity, which makes relatively sufficient physical and chemical reactions have taken place on the PP surface, resulting in better treatment uniformity.

It's crucial to fabricate commercial-level electrodes with high mass loading of active materials for supercapacitors (SCs) to address the growing need for commercial-level flexible energy storage devices. In this work, we reported the direct growth of ZnCo2O4 nanonest-like structure composed of nanowires with high mass loading (5 mg cm−2) on the substrate of carbon cloth (CC, hereafter denoted as ZnCo2O4@CC) via a simple hydrothermal method. The ZnCo2O4@CC electrode was characterized by a variety of techniques including SEM/TEM, XRD/XPS, and BET/BJH. The ZnCo2O4@CC electrode possesses a holey characteristic with various electroactive sites for the utilization of electrolyte and delivered high specific capacitance of 1467 (1320 C g-1) Fg−1 at 1.2 Ag-1 with outstanding cycling retention of 95% at 12 Ag-1 and high Coulombic efficiency after 10,000 cycles. In addition, we employed power's law to explore the charge storage kinetics of ZnCo2O4@CC electrode to investigate the capacitive and diffusion-controlled charge storage quantification. The ZnCo2O4@CC electrode displayed high capacitive storage properties (42% capacitive at 15 mVs−1). Thus, the admirable electrochemical performance of the ZnCo2O4 electrode highlights the potential application in supercapacitors for future endowers.

The development of smart structured cathode materials for supercapacitors (SCs) has sparked tremendous interest. However, the appropriate design to achieve high capacitance and energy density-based cathode materials remains a major problem for energy storage systems. This article describes the effective synthesis of self-supported 3D micro-flowers composed of ultrathin nanowires array of Co3O4 on Ni foam (NF) using hydrothermal conditions (Co3O4@NF). The mesoporous Co3O4@NF with a high surface area, providing a rich active state for the Faraday redox reaction and increasing the diffusion rate of the electrolyte ions. The optimized Co3O4@NF-16h electrode exhibited supreme electrochemical performance by delivering a high specific capacitance of 1878, (1127) and 1200 (720 C g−1) F g−1 at 1.0 and 20 A g−1, respectively. The Co3O4@NF electrode retained good capacitance stability of 91% over 10000 cycles at 20 A g−1 with excellent rate-performance of 67% at 20 folded high current values. The obtained results for the Co3O4@NF electrode are presented the enhanced pseudocapacitive performance, indicating the substantial potential for high-performance supercapacitor applications.

In this paper, the dependence of XLPE electrical breakdown on carrier mobility controlled by both electric field and temperature is evaluated by simulations and experiments. The molecular chain displacement model incorporating the thermoelectric effect of carrier mobility is examined to elucidate the experimental results. Trapping and de-trapping characteristics of space charge and mobility dynamics are modeled using hopping and Poole-Frenkel mechanisms. The experimental outcomes reveal that the DC electrical breakdown reduces with corresponding increment in temperature and thickness. Trapping parameters are estimated from experiments for simulations. The DC breakdown strength from experiments represents an inverse power relation with both the insulation thickness and temperature. The simulation results of molecular chain model with hopping mobility express more permanence with experimental results in comparison with Poole-Frenkel mobility.

Object detection in images is an important task in image processing and computer vision. Many approaches are available for object detection. For example, there are numerous algorithms for object positioning and classification in images. However, the current methods perform poorly and lack experimental verification. Thus, it is a fascinating and challenging issue to position and classify image objects. Drawing on the recent advances in image object detection, this paper develops a region-baed efficient network for accurate object detection in images. To improve the overall detection performance, image object detection was treated as a twofold problem, involving object proposal generation and object classification. First, a framework was designed to generate high-quality, class-independent, accurate proposals. Then, these proposals, together with their input images, were imported to our network to learn convolutional features. To boost detection efficiency, the number of proposals was reduced by a network refinement module, leaving only a few eligible candidate proposals. After that, the refined candidate proposals were loaded into the detection module to classify the objects. The proposed model was tested on the test set of the famous PASCAL Visual Object Classes Challenge 2007 (VOC2007). The results clearly demonstrate that our model achieved robust overall detection efficiency over existing approaches using fewer or more proposals, in terms of recall, mean average best overlap (MABO), and mean average precision (mAP).

This paper presents the surface modification and charge transportation mechanism of thin polyimide films. Here, we demonstrate that the surface modification of these films, by using the fluorine gas-phase, improves the charges mitigation and, thereafter, suppress the space charges. The experimental results indicate that the thermal step current for fluorine coated films reduce significantly in comparison to pure polyimide films. The thin layer of fluorine coating helps to release the surface charge, reduce the charge injection from the electrode, provide hindrance for charges to penetrate into the bulk of the films and the higher degree of charge disappearing helps to reduce the space charge growth.

This paper presents the growth law of electrical tree in glass/epoxy resin composite (GER). Two influencing factors on electrical tree growth, the relative permittivity of the glass and the adhesion type of the interface, are investigated. An improved WZ model is built to further explore the mechanism of electrical tree growth in GER. The electric field between the needle electrode and the glass is enhanced when the relative permittivity of glass is higher than that of epoxy resin, which is responsible for the attractive effect of the glass. The breakdown strength of the interface determines the growth mode of electrical tree. When the breakdown strength of the interface is as low as the air gap, the electrical tree showed ‘linear growth’ at the interface. High breakdown strength of the interface lead to ‘step growth’ of electrical tree and prolong the growth time compared to ‘linear growth’.

Objective: The aim of this study was to find out the role of depression in complete denture dissatisfaction and to determine frequencies of depression among the satisfied and dissatisfied patients. Study design: A cross sectional survey was carried out at Department of Prosthodontics, De’Montmorency College of Dentistry. Punjab Dental Hospital. The sample size was 80 edentulous patients having adequate maxillary and mandibular ridges. Methodology: The patients selected would be wearing complete dentures for the first time. All dentures were carefully designed. A socio-demographic form and depression rating questionnaire was filled by every participant involved in the study. After six months, satisfaction or dissatisfaction with the provided complete denture set was assessed through a separate questionnaire. The patients’ opinion concerning satisfaction with their dentures and depression was recorded and statistical analysis done. The results showed that 36.25% depressed versus 63.75% non-depressed. 28.75% were dissatisfied versus 71.25% satisfied. Conclusion: It was concluded that depression played a significant role in decreasing the satisfaction rating in first time denture wearers. Keywords: Depression, dissatisfaction, complete dentures

Background: Crowns and multi-unit fixed partial dentures have a limited lifetime. They fail for a number of reasons. The removal of provisional crowns and bridges is generally simple, however for permanent crowns, it becomes more challenging. Careful removal of FPD can help a dentist simplify a resto or endo procedure. The aim of this article was to analyze the different methods available for the removal of crowns and bridges and their awareness among dental practitioners Study Design & location: This was a cross-sectional study based on a questionnaire. The questionnaire was filled by a total of 250 general and specialist dentists who were practicing in various individual and group-based dental practices as well as private and government setups of Islamabad and Rawalpindi. Methodology: The questionnaire comprised a total of 13 questions to find out dentists' views about the usage of different system’s available for dental crowns and FPD removal. Participants were selected by random sampling. The results were then analyzed using SPSS version 23. Frequencies, percentages of different variables used in the study were calculated to identify the co-relation among different attributes. P-value of less than or equal to 0.05 was considered statistically significant. Results: The study reflected that out of those who answered, 247 dental professionals (98.5 %) preferred using hemostats or Morrell sliding hammer or a combination of both as they offered better control of force. A small percentage (approx 2%) of dentists used diamond or carbide burs as their first preference to trim off old crowns. Clinicians rarely used laser due to its high cost and less availability and its effectiveness primarily related to Porcelain jacket/ Zirconium crowns. Conclusion: It was concluded from this study that the majority of dentists preferred Morrell type crown remover with sliding hammer due to its ease of availability, universal acceptance, simple to use and because as it offered better control of force as opposed to spring-lock type Keywords: Crown and bridge removal, Crown and bridge disassembly, Crown and bridge failure.

Binder-free CoMoO4 hexagonal nanosheets have been directly grown on the surface of conductive carbon fabric cloth (CoMoO4@CFC) as a hybrid electrode material for pseudocapacitors (PCs) with outstanding electrochemical properties. The as-prepared CoMoO4@CFC sample was structurally and morphologically characterized using various techniques. Microstructure analysis reveals that the hexagonal like 2D structure possesses mesoporous characteristics with abundant electroactive sites as a charge storage host. The CoMoO4@CFC was evaluated as a positive electrode material for pseudocapacitors, which revealed a maximum specific capacitance of 1210 F/g at 2.5 A/g with exceptional rate capability and outstanding cycling stability of 91% after 10,000 charge/discharge cycles. The 2D mesoporous hexagonal-like structure provides improved electrolyte movement during charging/discharging process and additional active sites for redox reactions. In addition, the charge storage quantification of diffusion and capacitive charge mechanism was determined by employing Power's law, and accordingly, the CoMoO4@CFC electrode was attributed to a high capacitive charge value of (80% at rate 2.5 mV/s). Thus, this work specifies simple and cost-effective method to fabricate pseudocapacitors electrode materials with high energy density and improved cyclic life for energy storage devices.

In this study, XLPE electrical breakdown depending on insulation thickness is analyzed by simulations and experiments. The bipolar space charge and molecular chain displacement models are investigated to explain the experimental results. The results from experiments indicate that the electrical DC breakdown field decreases with increasing insulation thickness. For simulations, carrier mobility and trapping parameters are obtained from experiments. The simulation results of both models present an inverse power relationship between the DC breakdown strength and insulation thickness. The simulation results of molecular chain mobility model show consistency with experimental results as compared to a bipolar space charge model. The movement of polymer chain containing deep traps expands the free volume and this enlargement in free volume can be a major reason for the variation in the DC electrical breakdown strength of XLPE with insulation thickness.

The partial discharge (PD) in inverter-fed motors generated from high frequency and short rise time impulsive voltage are more complex than traditional sinusoidal voltage operated motors due to the noise initiated from fast switching power electronics devices. Available PD sensors and related technology for DC and sinusoidal voltage cannot be used at repetitive impulsive voltage conditions. This work aims to report the design of antenna with optimized geometry and satisfied parameters to detect PD for impulsive voltage. The antenna is verified and the influence of both impulse voltage parameters and test configuration on PD features are discussed. The envelope detection technique after the filter in the frequency domain was proposed to reduce the complexity and cost of PD test hardware under impulsive voltages with fast rise times. The frequency domain energy of PD from motor insulation is mainly distributed in the range of 0.6-1.8 GHz. By increasing the amplitude and frequency of input impulsive voltage, the range of PD energy spectrum is enlarged to (1.5-1.8 GHz) and by decreasing input amplitude the PD signal strength decays abruptly. Moreover, the high-frequency distribution of PD energy attenuates more severely with the distance and the electromagnetic energy of PD decays nonlinearly with the increase of propagation distance. Therefore, under the premise of satisfying the safety test, selecting the test distance below 15 cm can ensure that the test results have a high signal-to-noise ratio and signal integrity. The experience reported in this study could provide suggestions for off-line PD measurements for inverter-fed motor insulation evaluations for manufacturers.

This work investigates the electrical tree growth of epoxy resins. Repetitive bipolar square wave voltage is applied to the epoxy resins and different parameters rise time, frequency, and duty cycle are studied. The frequency range of repetitive square voltage ranges from 50 Hz to 20 kHz, the rise time ranges from 70 ns to 620 ns, and the duty cycle ranges from 5 to 90%. The results reveal that the initiation of the electrical tree is more rapid under the influence of high voltage frequency having a shorter rise time. Moreover, the electrical tree growth is faster under the impact of a shorter rise time with a duty cycle greater than 10%. The rise time mainly affects the initiation process of electrical trees. In comparison, the primary influence on the electrical tree initiation and its growth is attributed to the impact of the frequency applied.

Mitigation measures and control strategies relating to the novel coronavirus disease 2019 (COVID-19) have been widely applied in many countries to reduce the transmission of this pandemic disease. China was the first country to implement a strong lockdown policy to control COVID-19 when countries worldwide were struggling to manage COVID-19 cases. However, lockdown causes numerous changes to air-quality patterns due to the low amount of traffic and the decreased human mobility it results in. To study the impact of the strict control measures of the new COVID-19 epidemic on the air quality of Hubei in early 2020, the air-quality monitoring data of Hubei’s four cities, namely Huangshi, Yichang, Jingzhou, and Wuhan, from 2019 to 2021, specifically 1 January to 30 August, was examined to analyze the characteristics of the temporal and spatial distribution. All air-quality pollutants decreased during the active-COVID-19 period, with a maximum decrease of 26% observed in PM10, followed by 23% of PM2.5, and a minimum decrease of 5% observed in O3. Changes in air pollutants from 2017 to 2021 were also compared, and a decrease in all pollutants through to 2020 was found. The air-quality index (AQI) recorded an increase of 2% post-COVID-19, which shows that air quality will worsen in future, but it decreased by 22% during the active-COVID-19 period. A path analysis model was developed to further understand the relationship between the AQI and air-quality patterns. This path analysis shows a strong correlation between the AQI and PM10 and PM2.5, however its correlation with other air pollutants is weak. Regression analysis shows a similar pattern of there being a strong relationship between AQI and PM10 (r2 = 0.97) and PM2.5 (r2 = 0.93). Although the COVID-19 pandemic had numerous negative effects on human health and the global economy, it is likely that the reduction in air pollution and the significant improvement in ambient air quality due to lockdowns provided substantial short-term health benefits. The government must implement policies to control the environmental issues which are causing poor air quality in post-COVID-19.

The insulation of high voltage power cables is aged due to the impact of water treeing. The voids created due to water treeing can be filled with the injection of nanofluids and restore the insulation of cables. In this work, cross-linked polyethylene (XLPE) cable insulation is restored with the help of tetraethyl orthosilicate (TEOS) rejuvenation nanofluid. The morphological changes in aged and rejuvenated samples are analyzed with the help of scanning electron microscopy (SEM). Moreover, the molecular changes in the aged and rejuvenated samples are detected using Fourier transform infrared (FTIR) spectroscopy. Both the samples are also tested with the help of electrical breakdown tests. The results indicate a positive recovery in the insulation of cables with the injection of TEOS nanofluid. The tanδ results showed a decrease in values after the injection of nanofluid in the aged sample. Moreover, the tanδ values of rejuvenated samples are even better than the unaged cables. SEM results also showed a recovery in the voids of the aged sample due to the injection of nanofluid. FTIR results confirmed that the nanofluid penetrated in the insulation of the cable and the peaks of silicone and alumina bonds are seen in the spectrographs.

Cost-effective, clean, highly transparent, and flexible as well as a coatable packaging material is envisioned to solve or at least mitigate quality preservation issues of organic materials, originating from moisture interaction under ambient conditions. Liquid phase processing of packaging coatings using nano-clay and polyvinyl alcohol (PVOH) has been developed and reported. Detailed analysis of the developed coating revealed moisture permeability of 2.8 × 10−2 g·cm/m2·day at 40 °C and 85% relative humidity (RH), which is in close accordance with Bharadwaj’s theoretical permeability model. Moreover, the developed coatings are not only more than 90% transparent, when exposed to white light, but also exhibit excellent flexibility and even after going through 10,000 bending cycles maintained the same blocking effect against moisture.

Room temperature vulcanized (RTV) silicone rubber filled with aluminum trihydrate (ATH) is substantially engaged in electrical outdoor insulation applications. The pristine silicone rubber is highly combustible. ATH filled silicone rubber offers excellent electrical insulation but lacks in providing adequate flame retardancy. This short communication reports the novel results on improved flame retardancy of pristine and ATH filled silicone rubber whilst retaining the electrical insulation properties to a great extent. Results suggest that the presence of only one percent of graphene nanoplatelets with ATH sharply reduces the heat release rate and rate of smoke release. A minor reduction in dielectric breakdown strength and volume resistivity is noticed. Furthermore, permittivity and dielectric loss at power frequency suggest that a marginal 1% concentration of nanoplatelet with ATH is an excellent approach to fabricate flame retardant silicone rubber with an acceptable electrical insulation level.

To investigate the application of metal-doped two-dimensional (2D) nanomaterials for SF6 decomposed gases sensors, density functional theory (DFT) calculations are used for studying adsorption perf...

Ethylene propylene diene monomer (EPDM) is a polymer widely used for insulation in high voltage outdoor insulators and cables. It is well accepted that appropriate addition of micron particles to form a composite can enhance its insulation performance. This work reports improvement on the dielectric breakdown strength, tracking failure time, mechanical properties and volume resistivity of EPDM composites co-filled with boron nitride (BN) micron and nano–particles. Test specimens were fabricated by melt-blending and hot press techniques. AC breakdown tests were performed as per IEC60243-1 Standard. The tracking test was performed following IEC 60587 Standard and volume resistivity measurement as per ASTM D257. Experimental results show improvement in electrical properties with increasing particle loading up to a certain dosage but enhancement in the mechanical properties is observed up to 30 wt% particles addition. The co-filled composite exhibits considerably higher dielectric breakdown strength (89.24 kV/mm) and volume resistivity (~ 5.0 × 1015 Ω cm) relative to Micro-20 wt%. The tracking failure time of the co-filled is much improved due to excellent resistance against dry band arcing and thermal accumulation in the discharge region. Moreover, co-filled composites show improvement in mechanical properties as compared to the micron–filled counterparts. The improved thermal conductivity, better thermal stability and overall higher surface area of the particles are possible factors which impart better performance to the co-filled composites.

Objective: To assess the knowledge, attitude and practices of dental practitioners relating to different face masks and N 95 respirators. Study design and setting: This cross-sectional study was conducted in the twin cities of Islamabad and Rawalpindi from April to September 2020. Methodology: Dental practitioners whether in Government or private institutes and those in private practices were included in the questionnaire. Data was collected through non-probability, convenient sampling technique. The data was obtained using a self-administered close-ended questionnaire. Frequencies were calculated. The data was analyzed using SPSS version 23. Results: A total of 300 practitioners were included in this study. Among the participants, 64% were male and 36% were female. Participants had insufficient knowledge about the different properties of various face masks. Based on the results, 64% of the respondents were ready to be trained for learning details about the different face masks to be used in different clinical scenarios. Data showed unsatisfactory results as regards adequate knowledge about the properties of different face masks and respirators. Conclusion: Although the overall attitude of the dental practitioners regarding face masks was favorable, yet the level of knowledge as well as practice regarding respirators was found to be inadequate and a large percentage (85%) recognized the need for the introduction of the formal training among dental professionals for this essential personal protection standard. Keywords: Knowledge, Attitude, face masks, habits, respirators, N 95 mask, Dental practitioner, Practice

The steady-state electrical conduction current for single and multilayer polyimide (PI) nanocomposite films was observed at the low and high electric field for different temperatures. Experimental data were fitted to conduction models to investigate the dominant conduction mechanism in these films. In most films, space charge limited current (SCLC) and Poole–Frenkel current displayed dominant conduction. At a high electric field, the ohmic conduction was replaced by current–voltage dependency. Higher conduction current was observed for nanocomposite films at a lower temperature, but it declined at a higher temperature. PI nanocomposite multilayer films showed a huge reduction in the conduction current at higher electric fields and temperatures. The conclusions derived in this study would provide the empirical basis and early breakdown phenomenon explanation when performing dielectric strength and partial discharge measurements of PI-based nanocomposite insulation systems of electric motors.

The application of wide band-gap power electronic devices brings more challenges to insulating packaging technology. Knowing the influence of applied voltage parameters on insulation performance is helpful to evaluate the insulation condition of electric power equipment. In this paper, the effect of repetitive square wave voltage duty cycle on the growth characteristics of electrical trees in epoxy resin was studied. The experimental results show that the square wave voltage duty cycle has a significant influence on treeing features. The electrical tree proportion initiation has shown a decreasing trend, and the shape of the electrical tree changes from pine-like to branch-like by increasing the duty cycles. The length and damaged area of electrical tree increased with the increase in the duty cycle up to 10% and then decrease by increasing the duty cycle higher than 30%. It indicates that a low duty cycle will enhance the electron injection and accumulate space charges and thus accelerate electrical tree development. Under short duty cycles, the electric field due to the shielding effect near the needle tip suppresses the electrical tree growth, which results in treeing growth stagnation. The obtained results are helpful to keep these parameters in mind during the design of epoxy-based insulation such high-voltage rotating machines and power electronic device packaging.

Polymer nanocomposite-based dielectric materials are playing a vital role in the area of electrical insulation research and developments. The nanoparticle dispersion and interface region are the crucial parts of these developments. This chapter begins with the description of physical properties and their derived nanoparticles of polyimide (PI) films. Then, the detailed synthesis process of PI/nanocomposite multilayer film and its optimization is discussed in this chapter. Several factors in the synthesis process, which can influence the quality of the film, are discussed. After synthesis, the dielectric properties such as space charge were measured, and the results are compared with single and multilayer PI/nanocomposite films. Simulations and modeling help to shed light on the experimental results and create an understanding of polymer nanocomposite properties. Therefore, the PI/nanocomposite multilayer 3D model based on boundary conditions obtained from SEM/TEM images of synthesized samples was also constructed and simulated in COMSOL multiphysics software. The nanoparticle agglomeration and the impact of nanoparticle dispersion on the electrical properties of the material are described in detail in this model. The results demonstrate that the nanoparticle dispersion is improved by using a thin layer of PI/nanocomposite on PI film. As a result, fewer space charges and low electric fields are observed in multilayer films.

Silicone rubber filled with micron-alumina trihydrate (ATH) is a substantially used composite material for high voltage outdoor insulators. This article investigates the effect of nano-boron nitride (BN) addition on the dielectric, thermal stability and thermal conductivity of solely micron-ATH-filled silicone rubber by fabricating coalesced network of particles. Micron-ATH/nano-BN-filled hybrid silicone rubber composites are fabricated with a ratio of 30/0 wt% (ATH30), 29/1 wt% (ATBN1), 27/3 wt% (ATBN3), 25/5 wt% (ATBN5) and 23/7 wt% (ATBN7) using mechanical mixing and water bath sonication techniques. Results suggest that the hybrid batch of silicone rubber composites (ATBN) possess lower permittivity, dielectric loss, enhanced thermal stability and thermal conductivity relative to ATH30. ATBN1 offers low permittivity and dielectric loss values of 3.64 and 0.0086 at 1000 Hz relative to 3.87 and 0.0224 of ATH30, respectively. As far as thermal properties are concerned, ATBN5 emerges as the most promising candidate for electrical insulation with 31 and 200°C higher temperatures for 10 and 15% mass loss, whilst it has shown 20% higher thermal conductivity than ATH30.