Tangent Of Angle Research Articles

Study of autotransformer bridges for measurements of the impedance parameters

The analysis of the existing impedance measurement methods showed that for the establishment of precision comparators that operate in a wide range of values in the audio frequency range, it is best to use transformer and autotransformer bridges. Autotransformer bridges are used for measurements in a wide range of the impedance values. The use of autotransformer bridges allows reducing the measurement error to 10–7–10–9. High metrological characteristics of transformer bridge circuits make it possible to use them in commercial devices and precision measuring equipment. Simple autotransformer bridges do not provide the opportunity to measure the impedance parameters in a wide range of values of the tangent of the loss angle (phase shift). For the synthesis of measuring circuits of bridges and their balancing, it is necessary to have a precision quadrature channel that will ensure high accuracy of the transmission coefficient both by phase and by module. The structures of universal autotransformer comparators and their properties are determined by two main factors: by the method of forming the source of the complex balancing signal and by the types of schemes for replacing the impedances of the compared objects. To determine ways to improve universal precision impedance comparators based on autotransformer bridges, it is necessary to develop and analyze mathematical models of universal comparators. The conducted theoretical analysis showed that in the process of comparison, it is possible to compare impedances with different substitution schemes with a direct reading of reactive and active parameters. By choosing the appropriate transmission direction, with a simple reconstruction of the measuring circuit, it is possible to compare two impedances with a parallel substitution scheme, two impedances with a series substitution scheme, or two impedances with a different substitution scheme. The obtained results made it possible to implement them in a universal autotransformer-comparator bridge.

The Changes of Acoustic Vibration Properties of Spruce Wood During the Multi-Layered Alcohol Varnish Coating Process

The multi-layered and multi-material structures of a violin’s surface varnish film make it more challenging to comprehensively understand the patterns of sound quality changes during the coating process. Using an alcohol varnish coating technique on one or both sides of the wood, along with a combination of micro-morphology, material characterization, and vibration signal processing, this study traced and analyzed the changes in the acoustic vibration properties of Norway spruce wood during the coating process. The results showed that the acoustic characteristics of the coated wood tended to change in an unfavorable direction throughout the coating process, and the specific dynamic elastic modulus (Esp) of the final single- and double-sided coating varied by −1.77% and −6.07%, respectively. The loss angle tangent (tanδ) had the opposite trend, with rates of change of 20.76% and 30.42%. The sizing and priming treatments in the pretreatment stage had some positive effects on the acoustic properties of the wood specimens. Additionally, significant changes in acoustic vibration performance parameters began to be highlighted at the color paint stage (p < 0.05). These insights provide reference data for the improvement of violin acoustic performance and the simplification of the coating process.

ДИНАМИЧЕСКИЙ МЕХАНИЧЕСКИЙ АНАЛИЗ МОДИФИЦИРОВАННЫХ ПОЛИВИНИЛБУТИРАЛЕМ СОПОЛИМЕРОВ НА ОСНОВЕ ДИ(1-МЕТАКРИЛОКСИ-3-ХЛОРПРОПОКСИ-2-)МЕТИЛФОСФОНАТА И 2-ГИДРОКСИПРОПИЛМЕТАКРИЛАТА

The change of elastic modulus and tangent of angle of mechanical loss of materials based on polyvinyl butyral solutions in a mixture of monomers of di(1-methacryloyloxy-3-chloropropoxy-2-)methylphosphonate and 2-hydroxypropyl methacrylate has been investigated by the method of dynamic mechanical analysis. The presence of several peaks on the temperature dependences of tgd was observed, which is probably due to the presence of regions differing in crosslinking density. At 10 wt. % of polyvinylbutyral content in the process of (co)polymerization its partial migration to the surface of the formed polymeric material occurs.

Effect of ultrasound combined with plasma protein treatment on the structure, physicochemical and rheological properties of myofibrillar protein

This study aimed to investigate the effect of ultrasound combined with plasma protein (UPP) treatment on the structure, physicochemical and rheological properties of myofibrillar protein (MP). The results indicated that the UPP group caused changes in the secondary structure, increased fluorescence intensity and enhanced surface hydrophobicity of MP. Then, UPP significantly decreased the content of free and total sulfhydryl group, and high molecular weight protein contents were observed in MP. These findings implied moderate cross-linking and aggregation between plasma protein and MP in this ultrasound treatment. Furthermore, the physical characteristics, stability and rheological properties of MP were improved in UPP, as evidenced by increased storage modulus and decreased loss angle tangent. Therefore, this study suggested that the combined treatment not only had the potential to enhance the product quality in the process of ground meat, but also improved the utilization rate and added value of plasma proteins.

Dual‐Phase Enabled Sinusoidal Current Anodizing for Efficient Preparation of High Specific Capacitance Anode Aluminum Foils

The anodized aluminum oxide prepared by anodizing is the core of aluminum electrolytic capacitors, and its quality determines the performance of aluminum electrolytic capacitors. The traditional direct current (t‐DC) anodizing method commonly used in industrial production today with low current density has the problems of low anodizing efficiency, poor crystallinity, and high formation constants of the oxide film. However, high current density direct current anodizing has the problems of severe defects of the oxide film and much thermal dissolution of aluminum foil. Herein, the dual‐phase enabled sinusoidal current (DESC) anodizing method is proposed for the preparation of 200 V anodized aluminum foil with much higher efficiency and performance. After testing, it is found that the alumina prepared by the DESC method has higher crystallinity and fewer defects. Consequently, the specific capacitance of the DESC sample is 23% greater than that of the t‐DC anodized sample, while the former displays a lower loss angle tangent and leakage current. Meanwhile, DESC anodizing takes 60% time less than t‐DC anodizing due to its high current density. The DESC anodizing method has been identified as a promising avenue for further investigation, exhibiting high efficiency and performance.

Non-destructive detection of water adulteration level in fresh milk based on combination of dielectric spectrum technology and machine learning method

To rapidly realize the identification of fresh milk for water adulteration and to predict the amount of water adulteration, this study adopts a coaxial probe and a vector network analyzer to analyze the variation laws of dielectric constant ε', dielectric loss factor ε'' and dielectric loss angle tangent tanδ in the range of 2–20 GHz under 100 frequency points. Soft independent modeling of class analogy (SIMCA), Naive Bayes (NB), K-nearest neighbors (KNN), and support vector machine (SVM) models were built based on full dielectric spectra for qualitative testing of adulteration levels in milk. Feature variables of FDS were extracted by using the successive projections algorithm (SPA) and uninformative variables elimination (UVE). Partial least squares regression (PLSR), support vector regression (SVR), and particle swarm optimization least square support vector regression (PSO-LSSVR) models were built for quantitative testing of adulteration levels in milk. The results demonstrate an increasing trend of ε'' and tanδ with increasing frequency and a decreasing trend of ε'. The ε'-SIMCA model achieves the best effect in distinguishing water adulteration in milk, showing accuracy (ACC) of 1, Sensitivity (SNS) of 1, Specificity (SPC) precision (PRE) of 1, and an F1-score (F1) of 1. The tanδ-SPA-PSO-LSSVR model optimally predicts the optimal prediction effect of moisture content of milk, showing an RP2 of 0.994 and an RMSEP of 0.016 %. This study is conducive to building a more comprehensive knowledge system of water adulteration in fresh milk. Its results can provide a theoretical reference in the development of non-destructive detection instruments for natural milk.

Study on the properties of oil-water interface after the interaction between ionized water and naphthenic acid

The properties of the oil-water interface have a great influence on improving oil recovery. However, there are few studies on the impact of the interaction between ionized water and polar components of crude oil on the properties of the oil-water interface. In this paper, the influence of ionized water and naphthenic acid on the properties of the oil-water interface was investigated by measuring the oil-water interfacial tension, dilational rheological parameters, and interfacial film thickness, and the displacement mechanism of the ionized water flooding system was discussed. The results show that after the action, the interfacial tension of oil and water continues to decrease, and 1/3 ionized water (salinity diluted to 1/3 of the prepared ionized water, 1253 ppm) decreases to a maximum of 50.89%, while 1/5 ionized water (752 ppm) only decreases 14.40%; the thickness of the oil-water interface film decreases with the salinity of ionized water, but the decrease increases after 1/3 ionized water. In addition, the interfacial shear viscosity, interfacial expansion modulus, and interfacial phase angle tangent values all reach the maximum value within 10–15 days and then decrease. The research results of this article will provide a theoretical basis for the application of ionized water in oilfields.

STUDY OF STRESS WAVE PROPAGATION PATH AND DEPTH IDENTIFICATION IN CRACKED WOOD BASED ON ACOUSTIC EMISSION

The propagation velocity models were built using AE sensors to capture stress wave on pine specimen surface.On the different specimens, cracks were made in different numbers and the depth was gradually increased from 0 mm to 90 mm at 10 mm intervals. AE experiment was combined with COMSOL to investigate propagation path.The results show that R-squared is 0.996 when fitting tangent of angle to propagation velocity.At smaller crack depths, stress wave is diffracted around crack tip and then continues to propagate in to sensor along a straight line.However, as the crack depth increases, the reflected wave at the end face will arrive at the detection location faster with significantly weaker diffraction.The area with dimensions of20×10 mm was identified about the crack tip by crack identification method.

Reconstruction of Coal Mining Subsidence Field by Fusion of SAR and UAV LiDAR Deformation Data

The geological environment damage caused by coal mining subsidence has become an important factor affecting the sustainable development of mining areas. Reconstruction of the Coal Mining Subsidence Field (CMSF) is the key to preventing geological disasters, and the needs of CMSF reconstruction cannot be met by solely relying on a single remote sensing technology. The combination of Unmanned Aerial Vehicle (UAV) and Synthetic Aperture Radar (SAR) has complementary advantages; however, the data fusion strategy by refining the SAR deformation field through UAV still needs to be updated constantly. This paper proposed a Prior Weighting (PW) method based on Satellite Aerial (SA) heterogeneous remote sensing. The method can be used to fuse SAR and UAV Light Detection and Ranging (LiDAR) data for ground subsidence parameter inversion. Firstly, the subsidence boundary of Differential Interferometric SAR (DInSAR) combined with the large gradient subsidence of Pixel Offset Tracking (POT) was developed to initialize the SAR preliminary CMSF. Secondly, the SAR preliminary CMSF was refined by UAV LiDAR data; the weights of SAR and UAV LiDAR data are 0.4 and 0.6 iteratively. After the data fusion, the subsidence field was reconstructed. The results showed that the overall CMSF accuracy improved from ±144 mm to ±51 mm. The relative errors of the surface subsidence factor and main influence angle tangent calculated by the physical model and in situ measured data are 1.3% and 1.7%. It shows that the proposed SAR/UAV fusion method has significant advantages in the reconstruction of CMSF, and the PW method contributes to the prevention and control of mining subsidence.

Tunable Dual Self-Healing Composite Coatings with Self-Assembled Structures Regulated by Janus Nanoparticles.

The durability of concrete structures can be enhanced in a convenient and permanent manner through the surface protection of cementitious materials with composite polymer coatings. However, polymer coatings are susceptible to various mechanical and physical deterioration in complex and variable environments. In this paper, the theory of polymer microstructure regulation was employed to improve the sustainability of the protective performance of composite coatings. The self-assembled core-shell structure regulated by amphiphilic Janus nanoparticles is employed to modify the tunable polystyrene acrylate-polysiloxane self-healing coatings. The results demonstrate that the adhesion strength of the prepared self-assembled coating reached 3.7 MPa, which is sufficient to resist the damage to the microstructure of cementitious materials caused by physical erosion, seepage, and ionic corrosion. The self-healing coating, regulated by Janus particles, exhibited a residual creep of only 57.03% and a maximum loss angle tangent of 0.381. Furthermore, the material exhibited a superior shape memory function due to the presence of strong hydrogen bonding. The regulated self-healing coating repaired the polymer structural damage under mechanical and thermal deformation by bridging and filling effects. The coating demonstrated a tensile strength recovery of up to 71.23% in a wetted state, accompanied by a rapid restoration of its electrochemical properties and corrosion resistance. Furthermore, the self-healing emulsion penetrates the substrate defects and forms numerous polymer crystalline particles that effectively fill the microcracks.

Research on species categorical authentication of accelerants based on flame characteristics analysis

Species categorical authentication of accelerants has traditionally relied on fire debris analysis. To explore a novel method for identifying the accelerants species, four commonly used accelerants for arson were loaded onto different substrates and ignited at different locations. The entire combustion process was recorded and flame characteristics were analyzed. The results showed that the probability density function (PDF) of flame apex angle counts within a certain period after ignition can be used to distinguish accelerant species, and this method is not affected by accelerant loading amount, ignition location, and substrate, demonstrating strong stability and universality, while the temporal variation of flame area and the value obtained by dividing half of the flame width by the flame height (tangent of flame cone angle) can effectively differentiate gasoline and diesel. The utilization of flame characteristics for identifying accelerants species holds significant implications for arson investigation.

Permittivity measurement of high-frequency substrate based on the double-sided parallel-strip line resonator method

With the development of 5G technology, the accurate measurement of the complex permittivity of a printed circuit board (PCB) in the wide frequency range is crucial for the design of high-frequency circuits. In this paper, a microwave measurement device and method based on the double-sided parallel-strip line (DSPSL) resonator have been developed to measure the complex permittivity of typical PCBs in the vertical direction. The device includes the DSPSL resonator, the DSPSL coupling probe, a pressure monitor, a Farran C4209 vector network analyzer (100 K to 9 GHz), and a FEV-10-PR-0006 frequency multiplier (75–110 GHz). Based on transmission line theory, the physical model of the DSPSL resonator was established, and the relative permittivity and loss angle tangent value of the dielectric substrate were calculated using conformal transformation. To excite the resonator, the DSPSL coupling probe with a good transmission effect was designed, which consists of DSPSL microstrip line (MSL) transition structure and an MSL-WR10 rectangular waveguide converter. To reduce the air gap between the sample and the metal guide band and dielectric support block, and to improve test accuracy, a mechanical pressure device is added to the top of the DSPSL resonator. Based on the DSPSL resonator, we have used the device to test four typical PCBs, namely, polytetrafluoroethylene, Rogers RT/duroid®5880, Rogers RO3006®, and Rogers RO3010®. The results show that the maximum error of the relative permittivity is less than 3.05%, and the maximum error of the loss angle tangent is less than 1.27 × 10−4.

Металлотермиялық тәсілмен орта көміртекті ферромарганецті балқыту процестерінің термиялық қасиеттерін зерттеу

The purpose of this work is to study the phase transformations occurring in the charge mixture during the smelting of medium-carbon ferromanganese. The study of phase transformations occurring in the charge mixture was carried out on a device for synchronous thermal analysis Labsys Evolution TG-DTA/DSC from Setaram in dynamic mode in the tem perature range of 30-1500°С. Derivatograms were obtained for two variants of the charge mixture (Option I – manganese ore, lime, silicomanganese FeSiMn17; Option II – manganese ore, lime, converted silicomanganese) in an inert atmosphere of nitrogen. Calculation of kinet ic parameters – activation energy of endo-exothermic effects occurring at different tempera tures was made. The values of the apparent activation energy determined by the tangent of the slope angle are given.

ДИСИПАЦІЯ ЕНЕРГІЇ НИЗЬКОМОЛЕКУЛЯРНИМИ РЕЧОВИНАМИ ПІД ЧАС ЗОНДУВАННЯ ЕЛЕКТРИЧНИМ ПОЛЕМ БАГАТОЖИЛЬНИХ КАБЕЛІВ АТОМНИХ ЕЛЕКТРИЧНИХ СТАНЦІЙ

A model of the piece-homogeneous interphase space of stranded cables is proposed, taking into account the influence of cracks oriented along the lines of force of the electric field. The cracks are filled with low molecular weight substances. The case of a probing electric field with a significant tangential component is considered.. The equivalent values of the tangent of the dielectric loss angle at various parameters of low molecular weight substances in the cracks of the polyethylene insulation of the conductor with a cross section of 2.5 mm2 were determined. The equivalent tangent of the angle of dielectric loss increases by (3-20) times when the dissipation of electrical energy by low molecular weight substances changes from 10% to 100% in a crack, which is 1% of the thickness of an intact section of polyethylene insulation. The distribution of the electric field for the general case of accumulation of low-molecular products in capillaries formed by slit-like gaps between isolated veins is obtained. A strong electric field in the smaller part of the gap between the insulated cores, which occurs at a core potential of 1 kV, contributes to the capillary absorption of decomposition products of both solid polyethylene insulation and water vapor from the atmosphere in the case of unshielded structures of multi-core cables. The asymmetric configuration of the probing electric field with a significant tangential component makes it possible to detect low-molecular decomposition products of solid polymer insulation, which are a sign of its aging. Differences experimentally observed in the value of tgδ with different schemes of examination of multi-core cables are related, to a greater extent, to the uneven distribution of substances dissipating electrical energy across the cross-section of the cable, and not to a change in the structure of the probing electric field. References 11, figure 5.

Multi-frequency composite wearable antenna for wireless communications

This paper proposes a multi-band composite wearable antenna for wireless communication, which uses a monopole structure as the radiating body and achieves multi-band characteristics through slit-loading and multi-branching methods. A polymer composite substrate with high dielectric constant and low dielectric loss was prepared using in situ polymerization, and the optimal dielectric constant and loss angle tangent were obtained by controlling the coating ratio of melamine formaldehyde resin to carbon nanotubes (MWCNTs) and the filler doping rate to achieve miniaturization of the antenna. Comparative experimental results show that the obtained composites have high flexibility and good dielectric properties. The antenna operates in the frequency bands of 2.21–2.52 GHz, 3.07–3.87 GHz, and 4.36–6.03 GHz, which cover the frequency bands of WLAN and WiMAX and 5G applications. The antenna was fabricated and tested, and its performance roughly matched the simulation results. Meanwhile, the antenna has passed the SAR safety test and maintained a stable performance under different curvatures, so it has potential applications in the wireless communication system.

Amplitude-Frequency Effect of Mixed Electric Field on Impedance Spectrum Parameters of Biological Tissue

This work analyzes the electric impedance spectra of liver samples. Nyquist diagrams of experimental samples of different sizes were constructed. Optimal model equivalent electrical circuits of the systems studied were obtained and processed, and the parameters of their components were calculated. Changes in parameters and the tangent of the loss angle were shown. A conclusion was made about the interdependence of the electric field strength and the occurrence of stress, caused by using certain frequencies, on the size of the sample.

Improving the energy efficiency of industrial radio frequency heat treatment by optimizing electrode sizes and reversal cycles

Radio Frequency (RF) heating technology exhibits potential advantages in the heat treatment of bulky products. The influence of electrode size on the RF heating performance by the electric field distribution, electromagnetic loss density, and temperature distribution was evaluated. An electrode reversal device was developed, facilitating the cyclic reversal of the positive and negative electrodes and the effect of electrode reversal was also investigated. Simulation results showed an optimal heating uniformity when the ratio of electrode to product width is 1.4. At that time, the influence of stray electric field between the positive electrode and the cavity on the electromagnetic energy was minimal. The variation in loss angle tangent caused by temperature change was the primary reason for the fluctuation of the electromagnetic-thermal energy conversion efficiency within the same radio-frequency field. The electrode reversal dramatically improved the heating uniformity in the direction of electromagnetic energy decay. The temperature uniformity index (TUI) can be reduced by 32.79 % to 75.41 % with the shorter reversal cycle, but the service life of the device was also curtailed due to more mechanical motions. Considering the stability of the equipment and the heating performance, the optimum reversal cycle was chosen to be 420 s. In this case, the maximum TUI didn’t exceed 0.017, demonstrating better heating uniformity as compared with the commonly used for improving heating uniformity. In conclusion, a suitable electrode width and reversal cycle can effectively avoid the thermal offset effect of larger agricultural products during RF heating, thus improving the heating performance.

An Inductance-Capacitance Measurement Method Based On Auto-Balancing Bridge

Modern measurement modules are extremely demanding on the hardware and must accurately capture the relevant parameters of capacitance and inductance. The inductance and its quality factor, capacitance and its loss angle tangent value are very important parameters, but also the current testing difficulties. To efficiently and accurately measure the inductance and its quality factor, capacitance and its loss angle tangent, this paper developed a capacitance-inductance testing method based on automatic balanced bridge circuit. Firstly, based on the DSP development board, test capacitance and inductance by switching dip switches; Then, the use of self-excited oscillation method to generate a fixed frequency sinusoidal signal, through the amplifier to increase the amplitude of its signal, and the use of adder to the signal to provide a certain bias to meet the amplitude requirements; Finally, based on the automatic balanced bridge method, through the full-wave rectification plus filter will be converted into the average of the signal to be tested, and then use the amplifier circuit to control the average value of the signal to be tested, and then use the amplifier circuit to control the average value. Then use the amplifier circuit to control the average value within the AD sampling range, and use the micro-controller to collect the test amplitude, phase and other related parameters. The test results show the effectiveness of the proposed method.

Pickering emulsions stabilized by β-Lactoglobulin-Rosmarinic acid-Pectin nanoparticles: Influence of interfacial behavior and rheology performance

Grafting polyphenols and glycosylation are effective means to enhance the wettability and emulsifying properties of natural protein particles. A stable pickering emulsion (PE) with antioxidant properties was prepared using β-Lactoglobulin-Rosmarinic acid-Pectin (β-LG-RA-PC) conjugates as stabilizers in this study. When PC and β-LG-RA with the same mass were covalently combined, the solid protein-based particles exhibited ideal wettability (84.2 ± 0.3°), emulsification performance, and molecular flexibility. PEs with an oil content of 66.7% were successfully prepared using a 10 mg/mL concentration of the complex. The intrinsic reasons for the stabilization of the PE were explored through interfacial tension (from 16.02 mN/m to 12.18 mN/m), adsorption kinetics, interfacial expansion viscoelastic modulus (the tangent of the phase angle was 0.22), microstructure, and rheological properties, revealing that the dense, ideally viscoelastic interface layer formed was the main factor. The electrostatic repulsion between droplets, and the formation of a robust spatial network structure, facilitated PEs’ stability. These studies confirmed the possibility of implementing protein-based particles to yield food-grade PE.

Effect of glass powder on mechanical properties and electromagnetic transmission properties of high alumina cement paste

The mechanical properties and electromagnetic transmission properties of high alumina cement (HAC) paste with different glass powder (GP) contents were investigated in this paper. The effects of hydration phase, unhydrated phase, GP phase and pore phase on the dielectric properties of HAC paste were quantitatively analyzed. The results show that the strength, fluidity and setting time of HAC paste decrease with the increase of GP replacement rate. The real part, imaginary part and loss angle tangent of dielectric constant decrease. The addition of GP leads to a reduction in reflectivity and absorptivity of electromagnetic waves in the paste, while increasing transmittivity.Furthermore, the real part of the dielectric constant of each phase in the HAC paste follows the order: hydration product phase > unhydrated phase > GP phase > pore phase. With an increase in GP content, the real part of the dielectric constant of the hydration product phase increases. Finally, based on the results of vector network analysis (VNA), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM), the reasons for the changes of mechanical properties and electromagnetic properties of HAC paste under different GP replacement rates were analyzed from the aspects of phase composition, pore distribution and microstructure.