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Surface-enhanced Raman scattering (SERS), a simple, highly sensitive, and fast analytical method can be used to detect corrosion components on the surface of bronze ware, a difficult problem. The silver mirror reaction is suggested for depositing precious metal nanoparticles on cellulose filter paper in order to create a quick, easy, and low-cost approach for creating SERS substrates. After an 8-minute deposition time, optical microscopy and scanning electron microscopy (SEM) revealed a uniform dispersion of precious metals on cellulose filter paper. To examine the SERS characteristics of the substrate, copper chloride oxide, the main ingredient in the damaging rust of trace bronze ware, was used as the probe molecule. The findings show that cellulose filter paper with a uniform distribution of precious metals achieves the best SERS performance. The flexible substrate enables effective trace analysis of damaging rust on bronze surfaces.

In order to reasonably evaluate the effectiveness of UHF sensor arrangement in online monitoring of partial discharge of bushing, it is necessary to study the electromagnetic wave propagation characteristics of partial discharge UHF in the bushing. In this paper, a three-dimensional model of a real transformer bushing is established, the XFDTD software is used to simulate the raised seat defects and internal capacitive core defects of the bushing, field strength sensors are arranged at different locations inside and outside the bushing, and the propagation process of partial discharge UHF signals leaking from the oil-paper insulated bushing to the external free space is simulated and analyzed. The results show that the time difference between the signals received by the field strength sensors at different locations is not significant and can be neglected in practice. The partial discharge electromagnetic wave signal generated by the bushing elevated seat defect leaks from the upper porcelain sleeve to the external space, and the leaked electromagnetic wave energy is mainly gathered at the upper and lower ends of the upper porcelain sleeve. The partially discharged electromagnetic signal at the capacitor core inside the bushing will propagate along the coaxial waveguide structure formed between the capacitor screens towards the two ends of the capacitor core, the downward propagating electromagnetic wave energy is confined within the elevated seat, the upward propagating electromagnetic wave energy propagates from the top of the upper porcelain bushing to the external space, the leaked electromagnetic wave energy is mainly concentrated at the top of the upper porcelain bushing. The simulation results provide ideas for optimizing the arrangement of external antenna sensors for UHF detection of partial discharges in transformer oil-paper insulated bushings.

This paper reports the use of non destructive, microstrip patch antenna as paper moisture sensor. Microstrip patch antenna is designed to resonate at 2.4GHz. This design is simulated and fabricated on copper clad type FR4 (εr= 4.4) having thickness of 1.6mm. Patch dimension are 27mm × 30mm and substrate dimension is 63mm × 60mm. The microstrip transmission line is used to provide excitation for the antenna. This design for microstrip patch antenna after fabrication showed a resonance at 2.38 GHz on vector network analyzer at S11=-19.38dB with impedance =49Ω. The variations in frequency in relation with water content in the paper is measured using Vector Network Analyzer by placing wet paper on the patch antenna. Moisture content in the paper was found out by taking wet weight and dry weight of the paper. The model of the wet paper is recommended primarily on the basis of water-dry paper reactions, along with the thickness and surface roughness explaining tendencies of the sensitivity graphs. Paper samples of 13 different types, with different GSM values and thicknesses, havingdimensions same as that of the substrate were tested. From the results it is observed that as the moisture content in the paper increases the frequency decreases. The change in frequency with respect to the moisture content is seen to have quadratic relation with moisture. The variations in the frequency are fitted in the form of equations. The calculated %Mwet indicates an error around ±0-4% in the calculated value as compared to the actual value. The response of sensor is almost linear with respect to the references but the coefficients depend non-linearly with the paper dimension.

Determining the optimal clusters can be regarded as a grouping problem that has produced many cluster approach methods in various studies. Each method has provisions that can solve one or more grouping problems in generating information from data set with a number of k being tested. The advantages and disadvantages of each method actually complement to each other in solving the grouping problems. This paper aims to describe the performance of cluster approach methods in determining the optimal clusters through a review by paying attention to the criteria of the problem which is an obstacle to the grouping problem. The results of this review are expected to be a reference for developing the new optimal cluster approach method through possible combinatorial optimization.

When partial discharge occurs in the power transformer, the arc can further develop on the oil-paper interface between high and low potentials, and then form a path, resulting in large-area flashover. This will lead to a wide range of insulation damage, insulation failure, equipment shutdown and even large-scale economic losses. For the insulation damage caused by surface discharge of oil paper insulation, relevant scientific research institutions have carried out a large number of experimental studies. However, limited by the test conditions, the research focuses on the small-size model below 50mm, and mostly adopts the test device of uneven electric field. The research on the “large-size“ of the same scale inside the transformer is still blank. In this study, an oil-paper insulation surface discharge test platform with a large size of 50-150mm is built, the electric field conditions at the oil paper interface during the operation of transformers in engineering are simulated, and the surface discharge test of insulating paperboard is carried out by taking the same sample processing means as the engineering. Combined with the test results, a typical design optimization case of setting along surface corner ring to improve the allowable value of along surface discharge field and enhance along surface insulation margin is proposed. It lays a foundation for enriching the transformer oil-paper insulation design parameter system and improving the transformer oil paper insulation performance and operation reliability.

A tapered glass capillary MeV-ion microbeam setup, previously home-developed, was recently upgraded. To check the upgraded microbeam system quality and accuracy, microbeam particle induced X-ray emission (PIXE) mapping of potassium permanganate (KMnO4) solution diffusion in filter paper was carried out to study how the measured solvent diffusion followed the diffusion laws. Two initial boundary conditions and diffusion situations were applied: (1) the paper vertically placed in air with one end soaked in the solution for ten minutes, and (2) the paper horizontally placed on water with the solution dropped at a side of the paper for three minutes. 2-MeV-proton microbeam PIXE analyzed the paper pixel by pixel and the GUPIXWIN software was used to calculate the elemental concentrations in the pixels to map the concentration changes in the pixels as a function of the distance between the pixel position and the origin of the solution. The resulting maps demonstrated the solution diffusions in two cases indeed well following the diffusion laws, a steady-state diffusion dominated process where the elemental concentration was a linear function with the distance but joined by other non-diffusion factors for case 1, and a pure diffusion process where the elemental concentration was an error function with the distance for case 2.

A method for detecting paper’s surface defects is proposed, which is based on mathematical morphology algorithm and computer vision technique. Firstly, the mean filtering and wavelet denoising in image pre-processing are used to eliminate the image noise, and wavelet analysis can achieve image enhancement and increase the contrast between the target area and the background. And then, an improved threshold Canny operator is used to segment the image to extract the complete scratch line and other defect edges. Finally, the target region features are coloured by mathematical morphology processing. The method’s stimulating result is verified in the Matlab software, from which we can conclude that the method’s detecting effect is very effective.

Sensors with accurate detection of various liquids have attracted increasing research interests in environmental protection and organic solvents transporation. In this paper, liquid sensor based on laser induced graphene paper (LIGP) was proposed, and successfully used for the rapid detection of micro volume liquid. The processing-structure-property relationship was systemically studied. LIGPs with different morphologies exhibited various sensitivities and showed good reproducibility and fast response. The response mechanism related to contact resistance between some adjacent graphene flakes/fibers was proposed. With the key findings, LIGP liquid sensors can be used as the detector for accurate identification of different solvents and have great potential in monitoring organic solvent leakages of pipelines and fabrication of smart anti-corrosion composite structures.

Kojic acid is an antioxidant used by the cosmetics industry but the excessive usage of kojic acid may cause harm to human health. Therefore, it is important to detect the content of kojic acid in cosmetic products. In this work, the low-cost and simple paper-based analytical devices (μPADs) based on double-sided adhesive tape were developed for the colorimetric detection of kojic acid. The μPADs were fabricated by dissolving double-sided adhesive tape in toluene and then making the patterned adhesive tape penetrate into the filer paper. Ferric nitrate was used as the reagent to react with kojic acid, and the product of their chelating reaction caused the color change from colorless to orange-red. The ImageJ software was used to analyze the color intensity and the corresponding correction curve was determined. The μPADs for the detection of kojic acid exhibited a wide linear range (0.05 - 4 mM) and the detectable limit was 0.05 mM. The good selectivity and reproducibility were also demonstrated.

Light-reflecting characteristics play a crucial role in optically rewritable liquid crystal display (electronic paper). By using a special optimizer software, light-reflecting characteristics of the twisted nematic cell were calculated. The achieved values of the normalized reflection coefficients range within ∼ 0.03 - 0.43, which is comparable or better than other commercial technologies. The calculated contrast ratio of the device is 10 : 1. A 2D image, which can be displayed on the electronic paper was obtained. Comparison of the simulated background color and contrast ratio is very similar with the results, which were obtained in experimental cells of other studies. Our calculations indicate that angular dependence of the reflectance coefficient is almost uniform within a wide range of viewing angles.

Physics teachers’ training and professional development play a crucial role in preparing schools for the countless challenges they face. One of the central issues in the preparation of teachers is to provide them with tools, strategies, and methods to be able to build bridges between school and society, particularly to find fruitful links between formal, non-formal, and informal teaching, starting from primary school. In this paper, we report on some discussions developed during the Malta 2020 webinar by the Work Group 4 (WG4) participants, together with some questions and answers that emerged.

Pre-service physics teacher education is key in preparing prospective physics teachers to effectively support student learning and interest development alike. In order to do this, pre-service teachers must acquire, among other things, a profound teaching-oriented content knowledge and positive stance regarding teaching and motivation towards teaching. However, there are many more issues related to pre-service physics teacher education. In this paper, we report about some questions raised and answers proposed about this subject during the GIREP Malta 2020 Webinar Work Group 5 discussions.

The paper summarizes the results of discussion of the work group that focused on different aspects of experiments and laboratory work in teacher education. The discussion evolved around the following four guiding questions: What is the role of experiments in learning physics in general?; What are the labs supposed to help students learn?; How to achieve these goals in practice?; and How do we help future teachers develop skills/knowledge/competences so they will be successful in achieving these goals? About 30 participants shared their experience, views and ideas. The resulting views are summarized into general findings and recommendations.

In this article the discussion of Working Group 3 during the GIREP online seminar 2020 on teaching and learning quantum physics in teacher education is summarized. Conclusions are drawn and research desiderata formulated.

The waste Tetra pack impose a great pressure on environment. In this paper, we use hydrothermal liquefaction technique to convert it into valuable crude oil. The paper fibre and LDPE were studied in supercritical water at 420 °C, 25 MPa and residence time of 30 min. Effect of paper fibre: LDPE on the crude oil yield, components distribution and high heat value were investigated in depth. Results showed that maximum crude oil yield of 27.33 wt% was obtained at paper fibre to LDPE of 8:2, minimum O/C of 0.094 was obtained at paper fibre to LDPE of 5:5, which reflect that HTL of paper fibre and LDPE had a synergetic effect. And the highest high heat value of the crude oil reach 37.7 MJ/kg at the ratio of 5:5• The CH radicals produced from LDPE chain can promote the hydrogenation reaction that then decrease the production of oxygen-containing groups, and also the broken of C-C bond in lignin will be accelerate, which increased the diesel (C16-C47) compound.

Since cellulose is an important element for the production of tissue paper, many researchers used natural-based materials as an alternative in the manufacture of tissue paper so that it will be more environmentally friendly and safe to use for the community. Previous studies have found that cassava peel waste (57% cellulose) or durian peel (60-65%) each can be an alternative raw material for making tissues with quality does not differ much from tissue products in general. This study aims to determine the influence of durian peel and cassava peel mixture composition with a variation of mass ratio as 1:1; 1:1,5 ; 1:2 ; 1:2,5 ; 1:3 ; 1,5:1 ; 2:1 ; 2,5:1 ; 3:1. This research uses sodium hydroxide 10% for chemical pulping and bleached by 2% of hydrogen peroxide. Once the lignin has been rinsed out from the pulp, sheeting should be carried out by adding tapioca, chitosan and virgin coconut oil. Based on the test analysis and referring to SNI 0103:2008, the optimal composition of durian peel and cassava peel mixture is on the mass ratio of 3:1 which has a gramatur value of 41 g/m2, water absorption of 6.3cm, crushed resistance of 46 seconds and color does not fade, with a clean appearance, a little soft and not perforated so that it almost resembles tissues on the market, although it still has some stiffness to the surface.

Abstract.The measured spectral line based on frequency domain dielectric spectrum contains multiple superpositions of conductance and polarization processes. In view of the lack of methods to separate the polarization and the conductance processes and the lack of unique methods to characterize the model conductance parameters, the micro conductance processes are studied in depth according to the real and imaginary Kramers-Kronig relation. Firstly, different water content insulation samples were prepared during the laboratory conditions, and dielectric lines in frequency domain were obtained by measurement. Secondly, according to the k-K relation, the relaxation loss spectrum line is obtained by numerical integration of the measured real part of the complex polarization spectrum line, and then the conductivity loss spectrum line is obtained. Finally, the least square method is used to fit the conductivity spectrum line and calculate the conductivity value. The experimental results show that the conductance of the virtual part of the repolarization measurement can be separated from the relaxation loss line by k-K transformation, and the dc conductance can be calculated. At the same time,with the oil-paper insulating sample’s water content increasing, its electrical conductivity is gradually enhanced.

This experiment initially explored the clean production process of nanocellulose fibrils (NFC) using commercial softwood pulp as raw materials, and selected appropriate biological enzyme pretreatment to prepare NFC1 with a higher concentration. Compared with NFC2 obtained by TEMPO oxidation method, it is found that the diameter of NFC1 obtained by enzymatic pretreatment method (10-30nm) is similar to that of NFC2 (20-30nm). But the length of NFC1 (1-4μm) is much longer than the length of NFC2 (400-600nm). In addition, the influence of two kinds of NFC on the physical strength of paper is also explored. Experimental results show that: NFC1 is better than NFC2 in enhancing the physical strength of paper. And when cationic starch and NFC act synergistically, the enhancement effect is obviously better than using NFC alone or cationic starch alone. When the addition amount of NFC1 is (1.5±0.5)%, the tensile index, burst index, and tear index of the resulting paper increase by (43±3)%, (55±1)%, (37±2), respectively %. When the amount of NFC2 added is (1.5±0.5)%, the paper tensile index is (29±2)%. When the amount of NFC2 added is about (3±1)%, the paper’s bursting index and tearing index growth rate are (29±1)% and (33±1)% respectively.

To provide a reference for practical engineering application of fiber composite materials, this work researches on the impact resistance of type-B quartz fiber/modified cyanate ester composite material laminates and NOMEX paper honeycomb sandwich panels. Firstly, low-speed impact tests are carried out on the quartz fiber laminates and the NOMEX paper honeycomb sandwich panels by setting different parameters to analyze the impact energy and punch mass on impact damage; secondly, based on the experimental results, impact responses are analyzed; and the damage morphology of the two composite materials is observed through visual inspection and with the aid of the CT scanning technology. The results show that according to time-load curves, the NOMEX paper honeycomb sandwich panels have two peak load moments, respectively corresponding to the moments when the upper and lower panels are penetrated; the quartz fiber laminates show three different types of failures, namely substrate cracking, fiber fracture and delamination. As for the NOMEX paper honeycomb sandwich panels, two types of damage are found: fiber fracture and honeycomb core extrusion fracture. When the punch mass is constant, the greater the impact energy is, the more serious the damage is; and when the impact energy is constant, the greater the punch mass is, the more serious the damage is.

Before COVID-19, although the online assessment platform has developed, it is relatively slow, and people prefer to organize on-site examinations. After the outbreak of the epidemic, people realize the urgency and necessity of information construction in all walks of life. More and more researchers begin to pay attention to and explore the use of advanced machine learning methods to improve the practicability of online examinations platform. The test paper generation function is the core link, and a good test paper generation function can ensure the quality of a test paper. In this paper, an advanced unsupervised algorithm DPC(Clustering by Fast Search and Find of Density Peaks) is used to conduct deep mining and test paper generation adaptive based on the question bank and historical assessment such as assessment frequency, accuracy or score rate, and a more reasonable test paper generation function is realized. By comparing and testing the experimental results, it can be proved that the idea is correct and feasible.