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Made available in DSpace on 2022-04-29T08:31:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-10-01 Organization and planning of reverse logistics networks make sustainable processes more efficient. Thus, an important sector for connecting the collection and waste paper recycling echelons is the intermediate center. In this study, a Mixed Integer Linear Programming model, which is multi-objective, multi-product, multi-level and multi-period, was developed to optimize the waste paper logistics processes of intermediate centers. The formulation includes the following echelons: collection, considering vehicle routing with different capacities; inventory of non-baling materials; baling sorted waste and inventory of bales; selling bales; disposal of non-recyclable waste. The aims of the model include: maximizing the collected waste; minimizing distances; maximizing both the production and sale of bales, and minimizing costs. According to research carried out in the literature, the developed model is a new proposal and to implement it, the Weighted Goal Programming and Revised Multi-Choice Goal Programming approaches were used to deal with multiple objectives and incorporate uncertainty into the quantity of waste available for collection. To analyze the proposed model, computational tests were executed with instances based on real data from a Brazilian company in the sector. For all performed tests, General Algebraic Modeling System 23.6.5 modeling language and CPLEX 12.2.0.2 solver were used for modeling and optimization. The results show that this study presents formulation and technological approaches that represent real situations and provide competitive solutions to the problem. Sáo Paulo State University “Júlio de Mesquita Filho” [Universidade Estadual Paulista Júlio de Mesquita Filho] School of Engineering of Guaratinguetá [Faculdade de Engenharia de Guaratinguetá] Production Department, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas Agulhas Negras Military Academy [Academia Militar das Agulhas Negras] Rodovia Presidente Dutra, km 306, s/n Escola Preparatória de Cadetes do Exército Avenida Papa Pio XII 350 Jardim Chapadão Campinas - SP Brazil, Avenida Papa Pio XII, 350, Jardim Chapadão, Campinas - SP Sáo Paulo State University “Júlio de Mesquita Filho” [Universidade Estadual Paulista Júlio de Mesquita Filho] School of Engineering of Guaratinguetá [Faculdade de Engenharia de Guaratinguetá] Production Department, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas

Natural yellow plant dyes and traditional medicines were used widely on historical papers in ancient China for religious reasons and conservation considerations. This study aims to evaluate some traditional yellow botanical sources of dyes that contain different chemical colorant compositions in order to understand their effects on the properties of traditional handmade paper. The physical and chemical changes in paper specimens treated with plant dyes were studied by examining properties such as the color, pH, thermogravimetric (TG) characteristics, tensile strength, folding endurance and microstructure by scanning electron microscopy (SEM). The results indicated that different colorants had different toning effects and that the main components, including carboxyl and ketone groups, could affect the paper stability at high temperatures. The results also revealed that the mechanical properties of paper specimens were improved after treatment with plant dyes. The significant improvements in the tensile strength and folding endurance and the slightly higher decomposition temperature of Amur cork tree-dyed paper could be ascribed to the strong interaction between the colorants’ main components and the fibers. The scientific evaluation of the property changes is therefore valuable information for weighing the advantages and disadvantages of the various yellow toning materials for paper conservation treatment.

An innovative survey was conducted of the collections of the historical Biblioteca Classense, located in the urban area of Ravenna (Northern Italy). The survey aimed to evaluate the current conservation state of the book collections, where 297 paper-based items, including incunabulae, manuscripts and books, dating from the 14th to the 20th century, were selected for analysis. This innovative survey was carried out non-destructively by assessing degradation visually and by measuring NIR spectral data followed by multivariate data analysis. Chemical and physical paper properties, important for paper characterisation and implementation of conservation strategies were determined, including paper type, pH, degree of polymerisation, tensile strength, lignin, protein, and rosin content. This survey provided a significant quantitative dataset for rag paper covering a 600-year period. The analysis of DP changes over time allowed the first experimental estimation of the rate constant for historical rag paper, i.e., (4.2 ± 0.6)·10−7 year−1, which was validated with predictions based on the Collections Demography dose response function for historic paper taking into account the past climate in Ravenna. Statistical methods were employed to describe the correlations between the measured variables and different features of the books, suggesting that the degree of polymerisation can be used as a general proxy for rag paper mechanical strength.

There is a relative lack of research on the development of creepage discharge in aged oil-paper insulation subjected to AC-DC combined voltage in converter transformers. In this study, based on the physical and chemical properties of oil-paper, we propose a sphere-plate electrode model to study the creepage discharge parameters and characteristic spectra of aged oil-paper subjected to AC-DC combined voltage. The results show that the creepage discharge inception voltage of aged oil-paper is related to the AC voltage component of the AC-DC combined voltage. However, when the DC voltage component is 60 kV, the flashover phenomenon was found to occur in one of the severely aged samples before the AC voltage was applied. Despite being subjected to the same DC voltage, the flashover phenomenon did not occur in three other samples aged to different degrees. Large-amplitude discharges were found to appear earlier in the severely aged samples. At the same creepage discharge stage, as the aging time of the oil-paper increased, the number of large-amplitude discharges was found to rapidly increase, and the time interval between adjacent discharges was found to gradually decrease. At each stage of the creepage discharge, the small-amplitude discharge has a “hump” shaped distribution. The larger the DC voltage component, the shorter the endurance time of aged oil-paper, and the more severe the damage to the oil-paper. The DC voltage component was found to have an accelerating effect on the development of creepage discharge in aged oil-paper insulation.

This paper presents an improved method for detecting methanol and the concentration of methanol in transformer oil-paper. Acetonitrile is used as an extractant, and methanol is detected by gas chromatography-mass spectrometry. Experiments show a linear correlation coefficient of this method that reaches 0.99 and the minimum detected concentration of methanol in transformer oil can be as low as 5.57 μg/L. In order to investigate the relationship between the methanol concentration and the degree of aging of insulating paper, an oil-paper insulation simulation system is designed. The experiment shows that there is a linear relationship between the logarithm of methanol concentration and the degree of polymerization, the linear correlation coefficient is greater than 0.94. An actual oil sample from a transformer is used to show that the method can be used to further study the methanol concentration.

This paper presents an experimental study on the physicochemical properties of rice oil, peanut oil, corn oil and Kraft paper immersed in these oils in the presence of antioxidants (butylated hydroxytoluene, tertiary butyl hydroquinone and Naugalube¯ 750). The experiments are performed on new and aged conditions. Ageing of oils is carried at 115 °C for 96 hours while Kraft paper is aged in oils at 130 °C for 164 hours. Both closed and open cup methods are used for ageing. The results show that ageing insignificantly affects the breakdown voltage, but markedly increases the acid number and the viscosity of the vegetable oils. The combination of tertiary butyl hydroquinone and either butylated hydroxytoluene or Naugalube¯ 750 slightly increases the breakdown voltage, but significantly raises the oxidation stability of the vegetable oils. This results in a reduction in the viscosity and the acid number of the vegetable oils. Moisture significantly affects the breakdown voltage of both vegetable and mineral oil. High moisture content results in low breakdown voltage. The results also show that ageing insignificantly affects the breakdown voltage, but markedly decreases the tensile strength of oil-impregnated paper. Although the presence of antioxidants does not increase the breakdown voltage of aged paper, these additives slow down the ageing process. This results in an increase in tensile strength of the paper.

Abstract Tissue paper softness relies on two major factors, the bulk softness, which can be indicated by the elasticity of the sheet, and surface softness. Measurement of surface softness is complicated and often requires a multi-step process. A key parameter defining surface softness is the topography of the surface, particularly the crepe structure and its periodicity. Herein, we present a novel approach to measure and quantify the tissue paper surface crepe structure and periodicity based on the detection of waviness along the sample using laser scanning confocal microscopy (LSM) and X-ray tomography (XRT). In addition, field emission scanning electron microscope (FESEM) was used to characterize the tissue paper surface. We demonstrate that surface topography is directly correlated to the erosion of the doctor blade, which is used to remove the dry tissue paper from the Yankee cylinder. Because of its accuracy and simplicity, the laser confocal microscopy method has the potential to be used directly on the production line to monitor the production process of the tissue paper. XRT revealed more structural details of the tissue paper structure in 3D, and it allowed for the reconstruction of the surface and the internal structure of the tissue paper. Graphic abstract

As sugar is an important intermediate in the early stage in the degradation of cellulose, this paper proposes to use the concentration of total sugar as an indicator of the degree of aging of insulating paper in an oil-paper insulation system. The oil-paper insulation system was simulated at 90, 100 and 110°C, and total sugar concentration in insulating paper and in transformer oil was measured by spectroscopy. The spectrum of sugar reaction was obtained by spectrometer, and TQ Analyst software was used to process the data. Our experiments have shown that the total sugar concentration increases significantly in the early stage of aging, and there is a linear relationship between the logarithm of total sugar concentration and the degree of polymerization. We obtained the relationship between absorbance and total sugar concentration using the partial least square method and the regression goodness of fit is better than 0.91.

The recently adopted Ariel ESA mission will measure the atmospheric composition of a large number of exoplanets. This information will then be used to better constrain planetary bulk compositions. While the connection between the composition of a planetary atmosphere and the bulk interior is still being investigated, the combination of the atmospheric composition with the measured mass and radius of exoplanets will push the field of exoplanet characterisation to the next level, and provide new insights of the nature of planets in our galaxy. In this white paper, we outline the ongoing activities of the interior working group of the Ariel mission, and list the desirable theoretical developments as well as the challenges in linking planetary atmospheres, bulk composition and interior structure., Experimental Astronomy, 53, ISSN:0922-6435, ISSN:1572-9508

Carbonization of biomasses is an effective and important approach to recycle biomass waste. The tissue papers are one of the most common household trash and waste lots of natural resources and energies. Herein, the one-step carbonization and activation treatment was applied on two kinds of tissue papers to transform them into porous carbons. It was found the precursor structure and composition as well as the calcination temperatures play key roles to control the pore structures. As the active materials of supercapacitor electrodes, the resultant porous carbons obtained from different paper precursors and calcination temperatures (700–900 °C) presented different electrochemical performances. The microporous carbons derived from the 700 °C calcination of the tissue paper using the wood pulp as the raw material showed high capacitance up to ~ 200 F/g, providing a simple but effective way to recycle biomasses.

Trap plays an important role in the charge transportation of three-layer oil-paper and the investigation of trap parameters at different degradation degree is of great significance for further research of the partial discharge (PD) mechanism. This article considers the turn-to-turn structure of on-board traction transformer. A defect model of three-layer oil-paper insulation was designed for PD test. The PD degradation samples are selected from the inception of PD to the breakdown of PD to study the characteristics of surface potential decay on degradation samples by using isothermal surface potential decay method. Given that, the trap distribution at different degradation stages was calculated and its influence on PD characteristics was investigated. The result shows that AC fluctuation voltages caused by inter-harmonic has a great influence on PD distribution, surface charge distribution and trap distribution. With the increase of degradation, the decay rate of surface potential increases and the decay rate of AC fluctuation voltages is larger than that pure AC. And also, the number of shallow trap with AC fluctuation voltages is larger than that with pure AC. The rate of free charge increases with the number of shallow trap increasing. More free electrons involves in the process of PD, accelerating the aging rate of three-layer oil paper samples. Therefore, it can be concluded that surface charge and trap distribution are helpful to clarify PD mechanism.

Insulated tubular busbar is a new type of current-carrying equipment with excellent performance. However, the research on this equipment is insufficient because of the short application and the lack of technical digestion, which has resulted in many accidents. In this paper, the full-scale model of epoxy-impregnated-paper insulated tubular busbar with bubble defects was designed and produced, its electrical breakdown process was investigated by withstand voltage test. In the experiment, the failure mode of breakdown caused by gas expansion was found for the first time. The research showed that the electrical-mechanical breakdown process could be divided into two stages: gas increase stage and breakdown threshold stage. The research also obtained the characteristics and the change criterions of the two stages. The gas in the bubble defects generated from epoxy decomposition which caused by partial discharge. When the gas pressure exceeds the critical fracture toughness of the bubble defects wall, the unstable crack extension occurs, therefore, improving the ability about resistance to partial discharge of epoxy resin or improving the fracture toughness of epoxy resin by modifying would enhance the breakdown performance of insulated tubular busbar. The result also has reference significance for other epoxy-impregnated-paper insulated electrical equipment.

The low frequency section of frequency domain spectroscopy (FDS) of oil-paper insu- lation system can effectively reflect the ageing state and moisture of the oil-immersed paper. Meanwhile, steady-state insulation resistance is the one of indexes for the condition of transformer. In actual measurement, these two both are time-consuming and poor accessibility, thereby restraining their field applications. Aim at this problem, this paper analyses the polarization process of the oil-paper insulation in transformer, and adopts a low frequency equivalent circuit model for the oil-paper insulation to characterize the polarization process at low frequency. The simulated annealing particle swarm optimization (SAPSO) algorithm is proposed to identify the parameters in equivalent circuit, which are affected by change of insulation state. Compared with the experimental results, the errors of the steady-state insulation resistance and the tan δ below 10-3 Hz, which are calculated by the identified parameters, are less than 2.5%. This method can avoid the influence from external environment and reduce the measurement time. The time and frequency domain parameters calculated can provide reference for the ageing assessment of oil-immersed paper.

The present study sets out to devise a universal function model to explain the characteristic curve obtained in the frequency domain spectroscopy (FDS) test on oil-paper insulation, based on its microscopic conduction and relaxation processes, and thus to enhance the accuracy and applicability of the test. First, from the analysis of the relationship between the real and imaginary parts of the dielectric's complex permittivity, it is demonstrated that a relaxation peak co-exists with the conduction process in the low-frequency band of an FDS curve obtained for oil-impregnated paper sample. Second, values for polarization barrier heights, essential to the determination of the microscopic polarization mechanisms, are presented as results of FDS and thermally stimulated depolarization current experiments carried out on oil-impregnated paper samples. The polarization peaks obtained in the imaginary permittivity frequency spectrum are determined as, respectively, space charge polarization and interface polarization. Finally, a function model in good agreement with experiment data is proposed, which quantitatively describes the FDS curve in oil-impregnated sample, including two relaxation processes and one conduction process.

The AC breakdown properties of Kraft paper, pressboard and the enamel insulation layer in rice oil, peanut oil and corn oil were investigated under both new and aged conditions. The ageing of paper insulators and the enamel insulation layer in oils with the open cup method was carried out at 130 oC for 500 h in an air circulation oven. The puncture breakdown strength was determined by varying the number of layers and thickness of Kraft paper, while various electrode gap distances were used to measure the surface breakdown strength. Experimental results show that the breakdown strength and the tensile strength of paper insulators impregnated with these vegetable oils are comparable to that in mineral oil, and the surface breakdown strength of paper insulators is slightly affected by types of impregnating oils. The ageing significantly reduces both the breakdown strength and the tensile strength of paper insulators in investigated oils. In addition, it was also found that the enamel layer in vegetable oils withstood higher puncture breakdown strength than in mineral oil, and the ageing process significantly reduced the puncture breakdown strength of the enamel layer. This enamel layer was observed to markedly enhance the surface breakdown strength of pressboard.

As the main material of the converter transformer dry-type bushing, the dielectric properties of epoxy/crepe paper at different temperatures and frequencies are related to the electric field and thermal field distribution of the bushing, which directly affects the safe and stable operation of the bushing. Here we report the dielectric response of samples of dry-type bushing insulation measured at a range of temperatures appropriate to operation and down to frequencies below those usually used. A significant loss peak observed below power frequency is interpreted as originating from the charging of internal epoxy resin interfaces by the transport of charge carriers on structured paths in the epoxy-impregnated crepe paper layers. A simulation model is proposed that allows estimation of the space charge and field distribution at any given frequency.

High voltage transformer is an essential power apparatus that determine the reliability and continuity of power transmission and distribution system. It comprises solid and liquid insulating materials. Kraft paper as solid insulation should have an ability to insulate the winding connection, while oil transformer, aside of its main function as insulation, it is also used as a coolant. This paper analyzes the accelerated thermal aging performance of kraft paper immersed in the natural ester from RBD palm oil by using X-Ray Diffraction (XRD) characterization. XRD characterization was used to determine the existence of crystalline structure in kraft paper. Crystalline structure in kraft paper is composed by cellulose. The toughness of kraft paper was determined by its amorphous region, lignin, that bind the cellulose and make them hard. The influence of thermal expansion was observed to discover the effect of thermal stress to the crystallinity of kraft paper. Besides, thermal degradation characteristics of kraft paper were examined by using thermogravimetric analysis. The sample was aged in 120°C and 150°C for two weeks. The results also show that crystalline region of the sample that heated in higher aging temperature tends to drop faster than the sample with lower aging temperature.

Furfural content in oil is widely accepted as an effective parameter to mirror aging of insulation paper. However, pressboards are also abundant in transformers, which are always neglected in furfural analysis. Different masses of insulation paper and pressboard produce different amounts of furfural during the aging process. Thus, the furfural content in oil may differ in systems with different oil-paper-pressboard mass ratios. To address this problem, accelerated thermal aging experiments and furfural equilibrium experiments with different oil-paper-pressboard mass ratio systems were conducted under laboratory conditions. Furfural contents in oil, paper, and pressboard were measured. In a simplified oil-paper system, the furfural content in oil differs in systems with different oil-paper mass ratios. Further analysis shows the furfural amount produced by 1 g insulation paper is the same with good repeatability in groups with different mass ratios. Different oil-paper mass ratios change the distribution coefficient of furfural between oil and paper, and an increase in the mass of insulation paper leads to more furfural remaining in the insulation paper. The pressboards in field transformers produce little furfural during the aging process, but absorb part of the furfural from oil, which decreases the furfural content in oil. Therefore, more pressboard in an oil-paper-pressboard system indicates lower furfural content in oil. An increase in insulation paper in the oil-paper-pressboard system causes a decrease in the effect of pressboard on furfural content in oil.

In this study, the space charge in oil-impregnated thick pressboard and Kraft paper were measured by the pulsed electroacoustic (PEA) method from -20 to +60 °C. A bipolar charge transport model was used to simulate the transport processes of homocharge and heterocharge, and the acoustic attenuation process in the samples. The test results show that space charge accumulates in the thick pressboard and Kraft paper increases first and then decreases with temperature, and its maximum appears at 40°C, while little space charge accumulates at -20°C. The space charge near the lower electrode shrinks in the oil-impregnated thick pressboard at high temperature and the shrinkage is larger at 60°C. In the oil-impregnated Kraft paper, the accumulation and charge density of positive charge is different from negative charge. The ion transport process model simulates the charge shrinkage near the electrode, and disappears at the upper electrode after the acoustic attenuation simulation. The model established in this paper can well simulate the space charge distribution of oil-impregnated thick pressboard and Kraft paper under different temperatures.

This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Applied Materials and Interfaces, copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acsami.9b01287., Progress toward the concept of "a trillion sensor universe" requires sensor devices to become more abundant, ubiquitous, and be potentially disposable. Here, we report a paper-based disposable molecular sensor device constructed from a nanowire sensor based on common zinc oxide (ZnO), a wood-derived biodegradable cellulose nanofiber paper substrate, and a low-cost graphite electrode. The ZnO nanowire/cellulose nanofiber composite structure is embedded in the surface of the cellulose nanofiber paper substrate via a two-step papermaking process. This structure provides a mechanically robust and efficiently bridged network for the nanowire sensor, while ensuring efficient access to target molecules and allowing reliable electrical contact with electrodes. The as-fabricated paper sensor device with pencil-drawn graphite electrodes exhibits efficient resistance change-based molecular sensing of NO2 as a model gas. The performance of our device is comparable to that of noble metal electrodes. Furthermore, we demonstrate cut-and-paste usability and easy disposal of the sensor device with its uniform in-plane sensing properties. Our strategy offers a disposable molecular sensing platform for use in future sensor network technologies.

This study investigated the influence of the main metal materials of transformers on the oil-paper insulation performance. Ten types of insulating specimens were subjected to accelerated thermal aging at 120°C. Some aging parameters, including oil acid number, furfural content and degree of polymerization (DP) of insulating paper, were measured and compared. At the same time, we conducted frequency domain spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry on the insulating paper. The following conclusions were drawn: silicon lamination slightly deteriorates the insulating oil, copper increases the acidity and accelerates the production of furfural, metal materials can decrease DP of insulating paper and the effect of copper is greater than that of silicon lamination. During thermal aging, the dielectric dissipation factor of insulating paper increases and the carbon content of insulating paper increases. Metal materials can significantly increase the dielectric dissipation factor and carbon content of insulating paper and the effect of copper is greater than that of silicon lamination.

International audience; Ultrasonic welding is a serious candidate in the development of methods to assemble papers and paperboards without using additional substances. However, the ultrasonic welding of papers remains a technological challenge considering the low weldability of lignocellulosic materials. This study aims to investigate on the ultrasonic welding process applied to papers in order to identify the processing conditions which favor the formation of strong welded joints. To reach such purpose, an experimental strategy was developed by combining the characterization of welded materials and the monitoring of process parameters. Experimentations were performed using a reference paper displaying a good weldability to specifically highlight the contribution of process parameters. Results indicate that the process is highly sensitive to vibration amplitude, power supplied by the high frequency generator, and sample thickness. Power seems to be a reliable indicator of the severity of the process. A strong decrease in the strength of the welded joints is observed when working with low thicknesses. It seems that the layers coated on top of papers are the main part of the material contributing in the development of adhesion at the welding joint. Overall, instrumenting the device has led to a better understanding of the ultrasonic welding of papers.

A composite formed of NiO nanoflakes assembled on carbonized filter paper (CFP) has been successfully synthesized by a hydrothermal route with subsequent annealing. The CFP substrate presented a three-dimensional (3D) network structure. The composite electrode demonstrated high capacity and good cyclic and rate capabilities. It delivered a capacity of 724 mA h g−1 at current density of 100 mA g−1 after 100 cycles without apparent capacity fading during cycling. It delivered a capacity of 446 mA h g−1 even at high current density of 1000 mA g−1. The composite achieves better battery performance through ZnCl2 activation compared with conventional HNO3 activation.

An innovative method to quantitatively assess the state of degradation of paper in a non-destructive way has been developed by using THz time-domain spectroscopy (THz-TDS). The method relies on the observation that the hydrolytic and oxidative degradation of cellulose in paper is accompanied with rearrangement of the hydrogen bonds (H-bond) network of cellulose polymers. This gives clear fingerprints in the THz spectral profiles. THz-TDS is a suitable approach to study low-energy vibrational properties of biological materials in a non-destructive way. The THz photon energy range (about 1-40 meV) is particularly suitable to probe the H-bonds between molecules. However, the quantitative assessment of the state of preservation of artworks poses significant challenges, in particular when measurements on low refractive index and thin samples, such as ancient documents and drawings, must be carried out [1]. In the present study, we have successfully solved this problem obtaining a precise determination of the absorption by cellulose fibers in the 0.2-3.5 THz (7-117cm-1) range in single freely standing paper sheets. This has been achieved by developing a new procedure to remove from the experimental signals the spurious interference effects generated by the Fabry-Pérot resonances in the sheet. By using this approach, the THz absorption coefficient of cellulose fibers in ancient and modern samples artificially aged has been obtained. The THz absorption spectra are explained in terms of absorption peaks of the cellulose crystalline phase superimposed to a background contribution due to a disordered H-bonds network [2]. The complex evolution of the spectra as a function of natural and artificial aging is explained with a reduction up to 30% of the H-bond density in the cellulose polymer networks and a parallel increasing of the sample crystallinity evident in the peaks at about 2.1 and 3.1 THz. The comparison with density functional theory ab-initio calculations suggests that the observed THz spectral changes could be related not only to the recrystallization of amorphous regions, but also to the progressive degradation of the external surfaces of crystalline domains. These results demonstrate a significant potential in the non-destructive analysis of the structural modifications of cellulose and paper artifacts by aging, resulting, at a macroscopic scale, in a progressive weakening of the mechanical properties of paper [3]. [1] T. Trafela, M. Mizuno, K. Fukunaga, and M. Strlic, Appl. Phys. A, 111, 2013, 83-90. [2] E. Scarpellini, M. Ortolani, A. Nucara, L. Baldassarre, M. Missori, R. Fastampa, and R. Caminiti, J. Phys. Chem. C 120, 2016, 24088-24097. [3] L. Teodonio, M. Missori, D. Pawcenisc, J. ?ojewskac, F. Valle, Micron 91, 2016, 75-81.

The continuity of transformer operation is very necessary for utilities to maintain a continuity of power flow in networks and achieve a desired revenue. Most failures in a transformer are due to the degradation of the insulating system, which consists of insulating oil and paper. The degree of polymerization (DP) is a key detector of insulating paper state. Most research in the literature has computed the DP as a function of furan compounds, especially 2-furfuraldehyde (2-FAL). In this research, a prediction model was constructed based on some of most periodical tests that were conducted on transformer insulating oil, which were used as predictors of the insulating paper state. The tests evaluated carbon monoxide (CO), carbon dioxide (CO2), breakdown voltage (VBD), interfacial tension (IF), acidity (ACY), moisture (M), oil color (OC), and 2-furfuraldehyde (2-FAL). The DP, which was used as the key indicator for the paper state, was categorized into five classes labeled 1, 2, 3, 4, and 5 to express the insulating paper normal aging rate, accelerating aging rate, excessive aging danger zone, high risk of failure, and the end of expected life, respectively. The classification techniques were applied to the collected data samples to construct a prediction model for the insulating paper state, and the results revealed that the fine tree was the best classifier of the data samples, with a 96.2% prediction accuracy.

The aging of power transformers causes several defects and damages in the insulating system, especially in the insulating paper. The degradation of the insulating paper generates dissolved gases in the insulating oil, which are measured by gas chromatography and used as an indicator of the insulation status. The state of the insulating paper can be identified based on the degree of polymerization (DP) measurement. In some cases, when the measurement of DP is difficult, estimating DP can be accomplished through gathering information about some of the testing parameters, such as the dissolved gases (DGA), breakdown voltage (BDV), oil interfacial tension (IF), oil acidity (ACI), moisture content (MC), oil color (OC), dielectric loss (Tan δ), and furans concentration specifically (2-furfuraldhyde (FA)). The statistical tools (correlation and multiple linear regression), based on 131 transformer samples, can be used to build a relation linking DP and one or more of the previous parameters to identify the insulating paper status and the percentage of remaining life of the transformer. The results indicated that it is difficult to build a mathematical model to relate between the DP and the testing variables, except with FA, where the trend of DP with FA is more obvious than with other variables. The empirical formula to compute DP based on the FA concentration was developed and gave promising results to compute DP and the remaining life of the power transformers.

A fair assignment of credit for multi-authored publications is a long-standing issue in scientometrics. In the calculation of the $h$-index, for instance, all co-authors receive equal credit for a given publication, independent of a given author's contribution to the work or of the total number of co-authors. Several attempts have been made to distribute the credit in a more appropriate manner. In a recent paper, Hirsch has suggested a new way of credit assignment that is fundamentally different from the previous ones: All credit for a multi-author paper goes to a single author, the called ``$\alpha$-author'', defined as the person with the highest current $h$-index not the highest $h$-index at the time of the paper's publication) (J. E. Hirsch, Scientometrics 118, 673 (2019)). The collection of papers this author has received credit for as $\alpha$-author is then used to calculate a new index, $h_{\alpha}$, following the same recipe as for the usual $h$ index. The objective of this new assignment is not a fairer distribution of credit, but rather the determination of an altogether different property, the degree of a person's scientific leadership. We show that given the complex time dependence of $h$ for individual scientists, the approach of using the current $h$ value instead of the historic one is problematic, and we argue that it would be feasible to determine the $\alpha$-author at the time of the paper's publication instead. On the other hand, there are other practical considerations that make the calculation of the proposed $h_{\alpha}$ very difficult. As an alternative, we explore other ways of crediting papers to a single author in order to test early career achievement or scientific leadership., Comment: 6 pages, 4 figures

Paper sludge is the water treatment waste, which produced during paper production. Paper sludge (PS) waste utilization is the common problem in the EU and internationally. According to authors Frias et al. paper sludge is the main waste in the paper processing factories, the percentage reach 35% of product volume. According to the waste management directive No. 2008/98/EC, paper sludge waste should not be utilised in landfills. Such legislation generates the motivation of this study. This study deals with paper sludge as sound absorbing material. In this paper panels made of paper sludge is studied. Sound absorption coefficient of the panels predicted with Horoshenkov and Swift acoustic model for granular media. The aim of this paper is to predict sound absorption coefficient using non-acoustic parameters of the material. DOI: https://doi.org/10.3846/enviro.2020.820

Molecular simulation technology is a new technology emerging with the rapid development of computer technology. It has the advantages of clear microscopic models, in-depth and precise calculation etc., it has been widely used in the oil–paper insulation system of transformer in recent years. Based on the application of molecular simulation technology in the oil–paper insulation system of transformers in this study, the current research status and progress of molecular simulation in these area are elaborated in detail from the aspects of transformer insulating oil and insulating paper according to the domestic and foreign literature, and the application of molecular simulation technology in plant insulating oil and nano-modified insulating oil is emphatically analysed. The complementing research method of molecular simulation and experiment is pointed out, which provides certain reference for solving many problems existing in the field of oil–paper insulation system of transformers.

In recent years, concrete in the construction industry has rapidly increased worldwide, including developing countries like India. The raw materials required to produce such a quantity require huge depletion of natural resources. On the other hand, disposal of paper waste, fly ash, and plastic waste is one of the biggest problems faced by many countries, including India, the amount of waste collected and recycled is less compared to disposal quantity. The use of these wastes in concrete reduces the disposal of waste in nature. In this experiment work, the use of these wastes in the concrete has been studied. Preliminary tests like specific gravity, fineness modulus, and water absorption have been carried out on the materials. Various mix designs are prepared by partial replacement of cement with fly ash and paper pulp, and sand is completely replaced with the quarry dust, and coarse aggregate is replaced with shredded plastic waste to create sustainable concrete. A comparative study on the properties like slump cone, the weight of the cubes, compressive strength and split tensile strength, and feasibility of such concrete has been carried out. Results indicated that the weight of cubes started to decrease with the addition of waste. Compressive strength and split tensile strength show that the strength started to fall with the addition of plastic. The cost of concrete decreased with the addition of waste. 5 % of plastic waste in concrete and 3 % of paper pulp, and 5 % of fly ash is considered the optimal replacement percentage.

Studies on recycled materials emerged during recent years. This paper investigates samples&rsquo, sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (&alpha, avg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (&alpha, avg. = 0.51).

Significance: Cardiac troponin I (cTnI) is a primary biomarker for diagnosis of myocardial infarction (MI). In contrast to central laboratory tests for cTnI, point-of-care (POC) testing has the advantage of providing results when the patient is first encountered, which helps high-risk patients to be treated more rapidly and low-risk patients to be released in a timely fashion. A paper fluidic platform is good for POC testing because the paper is abundant, low cost, and disposable. However, current cTnI assays on paper platforms use antibodies as the recognition element, which has limitations due to the high cost of production and antibody stability issues at the POC. Aim: To develop an aptamer-based assay on a paper strip using surface-enhanced resonance Raman spectroscopy (SERRS) for detection of cTnI in the clinically relevant range at the POC. Approach: Gold nanoparticles (AuNPs) were functionalized with a Raman reporter molecule, malachite green isothiocyanate. The functionalized AuNPs were encapsulated in a silica shell and provided a SERRS signal using a handheld Raman system with a 638-nm excitation wavelength. A primary aptamer and a secondary aptamer of cTnI were used in a sandwich assay format to bind the cTnI on a test line of a paper fluidic platform. By measuring the SERRS signal from the test line, the concentration of cTnI was quantitatively determined. Results: The aptamer-based SERRS assay on a paper strip had a detection range of 0.016 to 0.1 ng/ml for cTnI, had good selectivity for cTnI compared to three other markers, had good stability over 10 days, and had good performance in the more complex serum sample matrix. Conclusions: The aptamer-based SERRS assay on a paper strip has the potential to provide a sensitive, selective, stable, repeatable, and cost-effective platform for the detection of cTnI toward eventual use in diagnosis of MI at the POC.

This paper presents the effect of the impact of moisture in paper insulation used as insulation of transformer windings on its thermal conductivity. Various types of paper (cellulose and aramid) and impregnated (mineral oil, synthetic ester, and natural ester) were tested. The impact of paper and impregnated types on the changes in thermal conductivity of paper insulation caused by an increase in moisture were analyzed. A linear equation, describing the changes in thermal conductivity due to moisture, for various types of paper and impregnated, was developed. The results of measuring the thermal conductivity of paper insulation depending on the temperature are presented. The aim of the study is to develop an experimental database to better understand the heat transport inside transformers to assess aging and optimize their performance.

This paper systematically studies the effect of Fe3O4 nanoparticle size on the insulation performance of nanofluid impregnated paper. Three kinds of Fe3O4 nanoparticles with different sizes and their nanofluid impregnated papers were prepared. Environmental scanning electron microscopy (ESEM) and infrared spectroscopy were used to analyze the combination of Fe3O4 nanoparticles and nanofluid impregnated paper. The effect of nanoparticle size on breakdown voltage and several dielectric characteristics, e.g., permittivity, dielectric loss, of the nanofluid impregnated paper were comparatively investigated. Studies show that the Fe3O4 nanoparticles were bound to impregnated paper fibers by O&ndash, H bonds, while the relative permittivity and dielectric loss of the nanofluid impregnated papers were increased. Meanwhile, the increase of trap depth, caused by the nanoparticles, can trap the electric charge and improve the breakdown strength. The test results show that the direct current (DC) and alternating current (AC) breakdown voltages of nanofluid impregnated paper increased by 9.1% and 10.0% compared to FR3 nanofluid impregnated paper, respectively.

The use of vegetable oil (natural ester) in electrical devices like power transformers is increasing due to their high biodegradability and better safety. The lifespan of power trans- formers is mainly defined by cellulose insulation condition, which usually works together with dielectric oil as electrical insulation and also as mechanical winding protector and compactor. That is why the aim and results of this research shows us not only the dielectric parameters evolution, but also the relationship between the mechanical factors and the moisture content of thermal accelerated ageing processes, with commercial vegetable oil, of Kraft paper and Diamond Dotted Paper (DDP). These are two of the most common insulating materials in electric power transformers. In addition, the new tests have been done by a different method of paper ageing analysis. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement Nº 823969 - BIOTRAFO.

The interest in and use of microfluidic paper-based analytical devices (μPADs) has grown exponentially over the last decade. Cellulose, and modified cellulose, has been used for centuries for making chemical measurements but devices made with this material traditionally suffered from either poor detection limits and/or limited ability to provide quantitative measurements. μPADs address these problems by patterning paper to create microfluidic channel networks that can direct flow to different regions of the device without the need for external pumps used in most traditional microfluidic devices. Furthermore, because the devices are made from cellulose or modified cellulose using inexpensive manufacturing methods, the devices can be inexpensive and disposable. The ability to carry out multiplexed analysis without external pumps using inexpensive, disposable devices makes μPADs ideal for point-of-care (POC) analysis. The interest in μPADs has led to a number of excellent comprehensive reviews in the field; in this review, we do not attempt to reference the entire field but instead seek to highlight major developments as well as areas that will be important for future development of this field.

In order to develop a novel detection method for the degree of polymerization (DP) of insulating papers, methanol was used as an indicator to explore the relationship between methanol concentration and DP in this paper. After extraction from oil, the methanol was oxidized and reacted with chromotropic acid to generate a purple-red compound. The spectral detection method was used to detect the concentration of methanol by absorbance, and then, the corresponding relationship between the concentration of methanol and the DP of insulating paper was established. Moreover, the detection methods based on furfural and methanol were compared. The results showed that methanol appeared during the initial aging period of the insulation paper, and the linear relationship between the methanol concentration and the DP of insulating paper was good. Compared with furfural, methanol was more sensitive to the change of DP in the early aging period, which proved that methanol could be used as a new type of indicator of insulating paper.

Oil-immersed insulation paper (OIP) bushing is one of the most important equipment in power transmission and distribution systems. Moisture is one of the most serious factors that affect the insulation status of OIP bushing. In this paper, the OIP bushing was assumed to be in a stable and simplicity condition, and then the transient moisture distribution of capacitor core and its effects on the electric field were studied. First, by dissecting a 110 kV OIP bushing, the specific sizes for modelling were obtained. Afterwards, a moisture diffusion model for OIP bushing was established based on COMSOL Multiphysics software, and it was also verified by moisture diffusion experiment. Then, the moisture distribution for different conditions were obtained and analyzed. Finally, a model for the electric field of OIP bushing was established, and then the effects of moisture on the electric field were studied.

When the inner insulation of oil-impregnated paper bushing breaks down in service, gases decomposed by oil and paper may cause an explosion. The explosion of bushing occurs from time to time because of the lack of an effective monitoring method. In order to provide an effective online monitoring method for the bushing to avoid explosion, this paper presents a method to monitor the PD defect in bushing by measuring the inner pressure of bushing. In this paper, the relationship of variation between characteristic gases content and inner pressure is studied, the effect of inner temperature on inner pressure is analyzed and the method for reducing this effect is also presented, and the monitoring method is proved to be useful by PD tests on a real bushing. The results show that the inner pressure increases obviously due to the generation of characteristic gases by internal discharge in oil-impregnated paper bushing, and the pressure increases with the deterioration of the discharge; although the inner pressure has a great influence on the inner pressure, the influence can be reduced or eliminated greatly by the method of common-mode rejection. According to the results, the internal discharge defect of the oil-impregnated paper bushing can be detected by monitoring the pressure, and the bushing explosion can be avoided.

Failures of bushing caused by corrosive sulfur has gradually appeared in recent years. Apart from copper and sulfur, certain amount of aluminum was also found both in oil and paper after disassembling. The corrosion mechanism of the aluminum foil and its effect on oil-paper insulation were unknown. In this study, series of sulfur corrosion experiments were taken to investigate the sulfur corrosion of aluminum foil. The results showed the aluminum foil could certainly be corroded in oil containing corrosive sulfur (DBDS). Thermal products of insulting paper triggered the corrosion by removing the alumina film on the surface. Then, the contact corrosion occurred between aluminum and DBDS. In addition, the mechanisms of corrosion products generation both in oil and on paper were studied. The corrosion products in oil was DBDS-Al(3,4) and that on paper was RCOOAln. It caused the decrease of electrical properties of oil-paper. Particularly, the dielectric loss of oil and paper were dramatically enhanced.

Transformer insulation paper is a key indicator for transformer remaining operational life. Paper decomposition is evaluated using the degree of polymerization (DP) which calls for samples of insulation paper from operating transformers. Since collecting such paper samples is extremely difficult, other indicators have been used to indirectly reveal the DP value of insulation paper. This includes dissolved gases in transformer oil such as carbon oxides and hydrocarbon gases, furan compounds, methanol, ethanol, and moisture along with some oil characteristics such as interfacial tension. However, for the same oil sample, these individual parameters lead to different DP values. This is attributed to the lack of accuracy of the established mathematical and artificial intelligence models correlating DP with each of the above mentioned individual parameters. This paper presents a self-learning method to estimate the DP value of transformer insulation paper based on multiple transformer oil aging parameters. The proposed method comprises data processing, fuzzy c-means and linear regression. Results reveal that estimating the DP value based on multiple aging parameters is more accurate than estimating it using one single parameter as per the current practice. The proposed method not only helps to understand the correlation between multiple oil aging parameters and the DP value of paper insulation, but also promotes the establishment of more accurate life assessment models for power transformers based on these oil aging parameters.

Epoxide-bearing filter paper was first prepared by surface-initiated reversible addition-fragmentation chain transfer (RAFT) copolymerization of glycidyl methacrylate (GMA) and poly(ethylene glycol)methacrylate (PEGMA). Without the need for activation step, the capture peptide nucleic acid (PNA) probes carrying a C-terminal lysine modification can be directly immobilized on the surface-grafted poly[glycidyl methacrylate-ran-poly(ethylene glycol)methacrylate] (P(GMA-ran-PEGMA)) through ring-opening of epoxide groups in the GMA repeating units by amino groups in the PNA’s structure. The success of P(GMA-ran-PEGMA) grafting on the filter paper and subsequent PNA immobilization was confirmed by fluorescence microscopy, Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy. Colorimetric detection with signal amplification upon DNA hybridization relies on sandwich-hybridization assay employing another biotinylated PNA strand as a reporter probe together with streptavidin-horseradish peroxidase conjugate (SA-HRP) and o-phenylenediamine (OPD) substrate. It was found that increasing ionic strength during the DNA hybridization step by addition of NaCl can increase the signal intensity, which can be visualized by naked eye. The sensing platform showed the best performance in preventing non-specific adsorption from the non-complementary DNA and discriminating between complementary and single-mismatched targets of at least 50 fmol without the requirement for stringent hybridization or washing condition. This superior ability to suppress non-specific adsorption of non-target DNA as well as other non-DNA components may be explained as a result of hydrophilic PEGMA repeating units in the surface-grafted copolymer.

Furfural content in oil has been shown to be a powerful indicator of the deterioration of cellulose paper. The furfural content in oil may increase greatly when the moisture content increases in transformers. The increase of furfural content in oil can be attributed to various factors, such as aging of cellulose paper with the increase of moisture content and the difference in furfural production mechanism. In this research, thermal aging tests of oil-paper system with different moisture contents are conducted under laboratory conditions to determine the cause of such increase. Furfural content, both in insulation oil and in insulation paper, and the degree of polymerization values of insulation paper were regularly measured. Results show that the moisture content plays a significant role on the production of furfural, and the high initial moisture content in insulation paper leads to large amount of furfural produced when DP decreases to the same values. The difference in the moisture content apparently affects the distribution of furfural between oil and paper, and the increase in the moisture content in oil-paper system increases the diffusion of furfural from the insulation paper to the oil.

Here, we follow the stable propagation of a roughening crack using simultaneously Digital Image Correlation and Infra-Red imaging. In a quasi-two-dimensional paper sample, the crack tip and ahead of that the fracture process zone follow the slowly, diffusively moving “hot spot” ahead of the tip. This also holds when the crack starts to roughen during propagation. The well-established intermittency of the crack advancement and the roughening of the crack in paper are thus subject to the dissipation and decohesion in the hot spot zone. They are therefore not only a result of the depinning of the crack in a heterogeneous material.

Breakdown (BD) and partial discharge (PD) characteristics of insulating paper and transformer board materials are investigated as cost-effective alternatives to high-price materials like polyimide (PI) or polytetrafluoroethylene and fiber reinforced plastic materials typically used in superconducting devices based on high temperature superconductors cooled with liquid nitrogen (LN 2 ). Three different cotton and cellulose based insulating papers are tested in LN 2 at atmospheric pressure and compared to synthetic sheet materials and polypropylene laminated paper (PPLP). Additionally, the BD performance and PD characteristics of three different transformer board materials are investigated in LN 2 . The results reveal that the paper and board materials have nearly the same or even slightly higher BD voltages in LN 2 in comparison to the values in insulating oil. The pure paper materials with thicknesses of 130 μm have a dielectric strength of 70-90 kV/mm, whereas values of 130-140 kV/mm are measured for PPLP and PI with nearly the same thickness. The dielectric strength of the board materials has a maximum value of 76 kV/mm. In the frame of the investigations, the BD performance of the pure paper materials in LN 2 is not influenced by the water content of the materials, dried and undried specimens have nearly the same BD voltage. Only the PPLP material has a 15% higher BD voltage in the dried state in comparison to the undried state.

The existing research on furfural analysis mainly focuses on the relationship between the furfural content in oil and the degree of polymerization (DP) of the paper, which are always obtained by accelerated thermal aging at high temperatures. However, the operating temperature of a winding is relatively low, approximately 60°C to 90°C. Thus, the relationship established at high temperature may be not suitable for the operating temperatures. In this research, aging tests of oil-paper systems at different temperatures ( from 100°C to 130°C) were carried out, with the DP, furfural content in oil and furfural content in paper being measured regularly to analyze the effect of temperature variation on the production and diffusion behavior of furfural in oil–paper insulation. The results show that temperature influences the production of furfural, i.e., there is no obvious difference in the amount of furfural produced by paper in the initial aging periods; however, a higher temperature results in more furfural being produced when the DP decreases to values below 600. An obvious diffusion process occurs after furfural is produced in paper in accelerated aging experiments, resulting in most of the furfural content remaining in the cellulose paper in the initial aging period.

In the last decade, much effort has been invested in using methanol as an oil-soluble chemical marker for assessing the condition of insulating paper. The use of this marker as paper life index presents many advantages particularly with new transformers insulated with thermally upgraded papers. However, until now, no interpretation model has been available for its extensive use by the transformer community. In this paper, a methanol-based interpretation model is presented for the first time using postmortem paper analysis on core-type transformers. This model allows the evaluation of the average degree of polymerization of a transformer's cellulose winding. Furthermore, threshold values based on the methanol concentration are given using this approach. Finally, model validation was performed on a limited number of papers taken from transformers being assessed in the repair shop.

A 4D imaging study (3D + time) combining synchrotron tomography with in situ tensile testing has been carried out to observe the fibre and network level micromechanics of paper made from northern bleached softwood kraft (NBSK). Quantitative image analysis and digital volume correlation is used to characterize local deformation, the evolution of fibre-fibre contacts, and fibre straightening in a ”freeze-dried” handsheet as well as standard handsheets low consistency refined at different refining energies. In the freeze-dried handsheet having low fibre conformability, the results show that deformation at the network level occurs because of fibre straightening and possible inter-fibre bond breakage. Further, significant out-of-plane deformation near the failure regions was observed, which led to auxetic behaviour. In the refined handsheets, a strong inverse correlation is seen between refining energy, thickness expansion, and the number of broken fibres. The use of out-of-plane strain norms is proposed as a method to determine network efficiency (i.e. the ratio of the network’s elastic modulus to that of the constituent fibres) as well as the relative contribution of fibre pull-out to the overall failure of the handsheet.

The article presents the results of comparative investigations of partial discharges in two insulation systems, aramid-enhanced cellulose paper-mineral oil, and pure cellulose paper-mineral oil. Partial discharges were investigated in a diagonal electric field with vertical and horizontal components. This field is treated as the most dangerous for insulation. The research was carried out on Nomex&reg, 910 paper and cellulose paper samples, each paper being 0.25 mm thick. Samples of the two materials were tested at four levels of moisture. The inception voltage of partial discharges of all samples tested decreased as their moisture content increases. It was also proved that Nomex&reg, 910 has a significantly higher partial discharge inception voltage than the cellulose paper, although this difference decreased with increasing moisture content.

Managing a large fleet of ageing assets has become a technical challenge faced by many electricity utilities in developed countries. Asset managers are increasingly interested in techniques that can help extend the useful lifetime of a transformer. Oil regeneration is one of such techniques. In this paper, oil regeneration experiments were performed on a 6.4/0.4 kV retired distribution transformer to investigate the effect of oil regeneration on improving paper conditions. Oil regeneration was conducted in two stages, with the first stage aimed at ‘cleaning the oil’ and the second stage targeted at ‘cleaning the paper’. Oil samples were collected at regular intervals throughout the process and paper samples were obtained from the transformer before and after each oil regeneration stage. It was found that oil regeneration restores oil parameters, including moisture and acidity, similar to those of new oils at the end of stage 1. Analysis of paper samples indicated a reduction in paper moisture at the end of stage 2 by nearly 40%, while low molecular weight acids (LMA) in paper exhibited a reduction by around 30% on average. It is found that the extended oil regeneration period, i.e., stage 2, is necessary to improve the paper condition and hence to reduce the paper ageing rate.