Loss Factor Measurements Research Articles

Measured and predicted sound transmission through a laboratory concrete floor

The direct sound transmission through a simple, massive, homogeneous building element with and without lining is investigated experimentally and compared with analytical and empirical models from the literature. A 150 mm thick concrete floor and a 100 mm thick floating floor were measured in the floor transmission facility of the National Research Council Canada, i.e. without flanking sound transmission. In addition to the sound reduction index and the normalized impact sound pressure level, loss factors, radiation efficiencies, and mean squared velocities were recorded in the laboratory. The measured data is compared to established models of sound transmission. A focus is placed on the calculation model of ISO 12354-1 (Appendix B), which uses calculated radiation efficiencies and loss factors to predict the sound reduction index of heavy, homogeneous building elements. Some difficulties with the calculation model and the examples in the standard are discussed. In principle, the results in this study show that the calculation model of ISO 12354-1 gives good estimates when the correct input parameters are used. However, deviations between the calculated and the measured loss factors and radiation efficiencies have large effects on the accuracy of the estimates, particularly in the region around the coincidence frequency.

Mineral composition, crystallinity and dielectric evaluation of Bamboo Salt, Himalaya Salt, and Ba’kelalan salt content

The mineral composition, crystallinity, and dielectric properties of salts can provide valuable insights into the quality and suitability of different types of salt for various applications. In this study, comprehensive analysis of the X-Ray Diffraction (XRD), X-ray fluorescence (XRF) and dielectric analysis of the Ba'kelalan salt, Himalaya salt and Bamboo salt have been investigated. The mineral composition of these salts, encompassing vital elements such as iodine and other trace minerals, significantly influences the salt's nutritional profile and overall excellence. Nonetheless, gauging the dispersion and density of these minerals poses difficulties due to conventional techniques that can be arduous, damaging, and expensive. Sample preparation is carried out before conducting X-ray diffraction (XRD), X-ray fluorescence (XRF), and dielectric analysis. XRD measurements are performed using the Bruker D2 Phaser to identify crystalline material phases. XRD operates on the principle of constructive X-ray interference within crystalline samples. For elemental analysis across a broad spectrum of materials, XRF is employed. Elemental peaks are scanned, starting from the lowest to the highest angle of incidence. The X-ray intensity at characteristic peaks is compared to the standard series. Dielectric spectroscopy analysis examines the dielectric behaviour of Ba'kelalan salt, Himalaya salt, and Bamboo salt. The setup involves a vector network analyser (VNA) paired with an open-ended coaxial probe, utilizing the microwave method. This approach ensures rapid, efficient, and non-destructive measurements of dielectric constants (ε′) and loss factors (ε”). The dielectric permittivity spectra are acquired within the frequency range of 4 GHz–20 GHz. ε′ of these salts increase with frequency. Meanwhile, ε” seem varies insignificantly over frequency. Mineral contents and crystallinity are the crucial factors lead to these responses. Based on the study, the quality and suitability of the selected salts for specific applications can be determined by considering their mineral composition, crystallinity, and dielectric properties in the context of the intended use. This gives an insight for some applications that may benefit from certain minerals or crystalline structures, others may require specific dielectric properties for effective use. Therefore, understanding these properties allows for decision-making in choosing the right type of salt for a given purpose, whether it's for foods, medical, industrial, healthcare, and technological applications.

Effect of 3D Printing Process Parameters on Damping Characteristic of Cantilever Beams Fabricated Using Material Extrusion

The present paper aims to investigate the process parameters and damping behaviour of the acrylonitrile butadiene styrene (ABS) cantilever beam manufactured using material extrusion (MEX). The research outcome could guide the manufacture of MEX structures to suit specific operating scenarios such as energy absorption and artificially controlled vibration responses. Our research used an experimental approach to examine the interdependencies between process parameters (nozzle size, infill density and pattern) and the damping behaviour (first-order modal damping ratio and loss factor). The impact test was carried out to obtain the damping ratio from the accelerometer. A dynamic mechanical analysis was performed for the loss factor measurement. The paper used statistical analysis to reveal significant dependencies between the process parameters and the damping behaviour. The regression models were also utilised to evaluate the mentioned statistical findings. The multiple third-order polynomials were developed to represent the relation between process parameters and modal damping ratio using stiffness as the mediation variable. The obtained results showed that the infill density affected the damping behaviour significantly. Higher infill density yielded a lower damping ratio. Nozzle size also showed a notable effect on damping. A high damping ratio was observed at a significantly low value of nozzle size. The results were confirmed using the theoretical analysis based on the underlying causes due to porosity in the MEX structure.

Experimental Investigation of Friction Damping in Blade Root Joints

Abstract The design of disk assemblies requires the capability to predict their dynamic behavior. To achieve this objective, knowledge of friction damping on the contact between blade and disk is of paramount importance. This paper proposes an experimental technique to measure the loss factor and the dynamics, in terms of natural frequencies, of blade-disk attachment. The free decay is used to infer the dynamic parameters from dummy blades. The identification method is based on the Hilbert transform that allows extracting the dynamic parameters from nonlinear system. This paper shows the test rig utilized in the experimental analysis and details the excitation system used to displace the dummy blade. This system must be a real or a “virtual” noncontact system to avoid injecting external damping into the blade under test. Tests were performed on both a dovetail and a fir-tree type attachment. On the dovetail, tests were performed both with dry contact surfaces and with contact surfaces covered by a film of lubricant to achieve a low coefficient of friction. This low coefficient of friction better simulates dry surfaces at high temperatures, as friction coefficients decrease with temperatures. This paper presents the results obtained on the first and second bending mode. The experimental results show the loss factor and the natural frequency for different axial loads. The measured loss factor depends on the amplitude of vibrations. As predicted with theoretical analyses the loss factor shows a maximum then approaching zero for large amplitude of vibrations. As a rule, it decreases with increasing centrifugal loads.

Discussion on Measurement of Dielectric Loss Factor and Capacitance of Transformer Winding and Bushing

Discussion on Measurement of Dielectric Loss Factor and Capacitance of Transformer Winding and Bushing

Effect of Annealing and Ion Beam Irradiation on AC Electrical Properties for Gold Sputtered PM-355

Deposition of different gold thickness on PM-355 cleaned by ethanol forming thin films using magnetron sputtering. Gold layer with thickness 300, 400, 500, 700, 1000, 1300, and 1500 nm were deposited to prepare Au / PM-355 thin films. Then, ac electrical properties response of thin films for a wide frequency range 20Hz - 5MHz were measured at roomtemperature. Meanwhile, the measurements of ac conductivity, dielectric constant, and dielectric loss factor were plotted at different frequencies to determine the optimum thickness. Hence, the comparison was done between optimum Au thickness thin films cleaned by two organic solvents and ethanol before annealing at different frequencies. Also, study the effect of annealing and ion beam that extracted radially from conical anode and disc cathode ion source on optimum Au thickness thin film electrical properties. It is found that the annealing increases both dielectric constant, dielectric loss, and ac conductivity of optimum Au thin film at different frequencies. Despite, the nitrogen ion beam effected on these thin films by decreasing the dielectric constant and ac conductivity for all thin films except the chloroform one. Finally, study the comparison between the annealing and followed by ion irradiation thin films. It is noticed the decrease in ac electrical conductivity and dielectric constant at different frequencies.

Efficiency, Power Loss, and Power Factor Measurement of Quadrupole Magnet Power Supplies at the Spallation Neutron Source

Efficiency, Power Loss, and Power Factor Measurement of Quadrupole Magnet Power Supplies at the Spallation Neutron Source

Multiferroic properties of Mn-substituted BiFeO3

To study the multiferroic behavior of BiFeO3 at low concentrations of Mn as dopant, BiFe1−xMnxO3 (BFMO) at x = 0.01, 0.02, and 0.03 has been successfully synthesized via chemical combustion method. X-ray diffraction reveals distorted rhombohedral structure for BiFeO3 and respective variation in lattice parameters. The particle size is studied with FESEM images. Wide-range frequencies are used to carry out dielectric constant and tan δ (loss factor) measurements. The typical behavior of BFMO samples is attributed via charge-carrier hopping mechanisms due to structural inhomogeneity and formation of vacancies. The hysteresis loop measurements are used to study the ferroelectric and magnetic response. The canting of spin moments and cation–anion–cation exchange interactions leads to observed room-temperature ferromagnetism, while ferroelectric performance enhances with increasing Mn doping in BiFeO3. The altered ferroelectric and magnetic properties along with possible magnetoelectric coupling would make BFMO as suitable candidate for magnetoelectric devices. The maximum value obtained for $${\alpha }_{\text{ME}}$$ is 29.03 mV cm−1Oe−1 at Hdc = 1.4 kOe and could be attributed due to strong antiferromagnetic character of BFO with Mn doping.

An attempt to improve reliability of loss factor measurement and evaluation of attenuation performance for laminated metallic materials

An attempt to improve reliability of loss factor measurement and evaluation of attenuation performance for laminated metallic materials

Dielectric Measurement Based Deducted Quantities to Track Repetitive, Short-Term Thermal Aging of Polyvinyl Chloride (PVC) Cable Insulation.

The effect of short-term (3- and 6-h-long) periodic thermal aging was investigated at three different temperatures on PVC cables and PVC films. Three different temperatures (110, 125, and 140 °C) were used for aging PVC cables and one (110 °C) for PVC films. PVC films were prepared for the investigation containing 0, 30, 40, and 50 weight percent of dioctyl phthalate plasticizer (DOP). The effect of short-term thermal aging was monitored by electrical (dielectric spectrum and voltage response measurement) and mechanical (Shore D hardness) methods. From the loss factor measurements, different deducted quantities were calculated and compared with Shore D hardness, which has been shown to be a parameter reflecting the effect of short-term thermal aging on PVC insulation. The measurements revealed that Shore D hardness is not the best property for monitoring aging. Instead, increasing dissipated power and the shifting behavior of tan δ–frequency curves proved to be the best phenomena for assessing the impact of thermal aging. Simple deducted quantities may provide a basis for following short-term thermal aging.

Prediction of concrete compressive strength based on early-age effective conductivity measurement

Prediction of compressive strength of concrete at early ages has attracted a lot of attention, but several defects still remain in previous research using nondestructive techniques such as the use of electrical surface resistivity. A true prediction model for the 28-day compressive strength of concrete via effective conductivity at microwave frequency is presented for the first time in this paper. The open-ended coaxial probe was used to undertake the loss factor measurement, in the frequency range of 0.1 GHz–10 GHz, of ordinary concrete with four water-cement ratios (0.40, 0.45, 0.49, 0.60) at first seven days. Traditional destructive test was used to obtain the concrete compressive strength at 3, 7, 14, and 28 days of curing. The reduction of conductivity versus curing age was modeled by using exponential decay function whereas the development of compressive strength curing age was modeled by using a nonlinear raising function. By taking curing age as an intermediate variable, a linear prediction model as a function of effective conductivity was developed. A minimum effective conductivity was discovered where the frequency of about 3 GHz was considered as the dominated loss mechanism transits from ionic conduction loss to dipole polarization loss. Our results demonstrated that the 28-day compressive strength of concrete having close water-cement ratios could be accurately predicted using effective conductivity. Moreover, the magnitude of the slope of strength-conductivity curves could give an indication on the grade of standard concrete during early ages. The model was evaluated by using data from open literature with DC conductivity and the accuracy was obtained with about 10% error in underestimation.

Analysis of space charge and charge trap characteristics of gamma irradiated silicone rubber nanocomposites

Silicone rubber is widely used for electrical insulation and may be exposed to a harsh environment. The present study envisaged to improve insulation properties of silicone rubber by adding an optimised quantity of nanofillers. The fundamental space charge and charge trap characteristics were studied by adopting the pulsed electroacoustic analysis technique and through surface potential measurement. The dielectric properties of the materials were analysed through measurement of permittivity and loss factor of the material at different frequencies and temperatures. The influence of gamma irradiation on variations in fundamental properties of the material was characterised. The results of the study indicate that 5 wt.% alumina added nanocomposites had better space charge performance under gamma irradiation compared with virgin silicone rubber.

Comparing the Performance of γ-Alumina Nanofiller and Titanium Tetraisopropoxide Catalyst in the Rejuvenation of Water Tree Degraded XLPE Cables

This article evaluates the performance of titanium tetraisopropoxide (TTIP) and γ-alumina nanofiller (Al2O3) in rejuvenation and restoration of degraded XLPE underground medium voltage–power distribution cables. These two materials will be injected into aged cables in the form of two rejuvenation composition groups based on silane coupling agents. The injected and aged specimens were then compared in terms of dielectric loss factor (tanδ) measurement, scanning electron microscopy (SEM) analysis, Fourier transform infrared spectroscopy (FTIR) and energy dispersive x-ray (EDX) analysis. After measurement of dielectric loss factor in 7-day intervals, 1 month after the injection of rejuvenation fluids, it was found that the injected cable specimen dielectric loss tangent in the second group, which contained γ-alumina nanofiller, was lower than the specimens injected with TTIP (first group); even their tanδ was lower than the new unused cables. Microstructures of the rejuvenated and aged specimens were compared by means of SEM analysis and the results indicated that titanium and aluminum nanoparticles filled the water-filled microscopic cavities and modified the polymeric insulation surface. FTIR analysis compared the chemical bonds of the insulation layer in injected and aged cables. EDX analysis also detected the element type and value on the treated insulation specimen surface area. Comparing the four afore-mentioned analysis illustrated that both fluids were efficacious in rejuvenation and rehabilitation of degraded XLPE cable insulations. However, γ-alumina nanofiller performs better than TTIP in rejuvenation of degraded XLPE power cables.

Research on Measurement of Loss Factor based on Transient State Decay Method

As an important parameter in application of the Statistical Energy Analysis (SEA), loss factor can measure damping characteristics of a system and determine the ability of vibration energy dissipation. First, the experimental models of steel plate structures are established. And then, the loss factor test is carried out based on transient state decay method. Finally, the variation characteristics of loss factor with medium, thickness and size of structures are explored. The results show that: (1) The loss factor of steel plates has the characteristics that larger at low frequency and small at high frequency, it decreases gradually with the increase of frequency. (2) For the same structure, the loss factor tested in water is greater than the loss factor tested in air. (3) The loss factor increases with the raise of thickness of plates when its cross-sectional dimension is constant.

An electromagnetic non-destructive approach to determine dispersion and orientation of fiber reinforced concretes

Including fibers in concretes improves their mechanical properties such as flexural strength, impact load resistance and limited crack propagation. The dispersion, orientation and types of the fibers placed in the concretes affect these mechanical properties. The aim of the study is to propose a standard and a novel prediction method for determining the dispersion and orientation of the concretes in which fibers are reinforced in microwave frequency range. This study demonstrates that determination of both orientation and dispersion of the fibers regardless of the fiber types in concretes is possible by extracting electromagnetic properties of the structures in microwave regime as a nondestructive method. The measurement technique requires sample under test (SUT) and two wideband linearly polarized antennas placed in the front and backside of material under the free space condition. Although there are some studies investigated the fiber content of concrete samples through certain electromagnetic techniques, the proposed novel approach concentrates on the electromagnetic behavior of the fiber reinforced concretes in a very wideband range from 3 GHz to 17 GHz. Unlike the other studies, open space measurement with the help of a vector network analyzer which is capable of measuring up to 43 GHz along with two high gain horn antennas was carried out in the laboratory environment. Time required for exact measurement of dielectric constant and loss factor of the concrete between antennas is less than a minute. A simple and confidential model is carried out to determine both orientation and dispersion of fibers in concrete by observing the changes of dielectric constant and loss factor. The determination of electromagnetic properties of concretes with fibers has potential applications for future nondestructive sensors. In addition, observation of negative dielectric constant and some other electrical properties such as low loss factor and impedance match with free space presented in the study for particular frequency intervals gives a chance for future radome applications in harsh environmental conditions.

MODELLING THE DIELECTRIC PROPERTIES OF COW'S RAW MILK UNDER VAT PASTEURIZATION

An efficient microwave milk pasteurization system requires a rigorous temperature dependent dielectric model of the milk, since the performance of milk pasteurization strongly depends on its dielectric properties. This paper describes the dielectric modelling of cow’s raw milk during batch (Vat) pasteurization which covers the frequencies from 0.2 GHz to 6 GHz. An open-ended coaxial sensor is used for the measurements of dielectric constant, loss factor, and ionic conductivity at temperature range of 25°C to 75°C with an interval of 5°C. Combinations of Cole-Davison and Debye equations are modified to fit the dielectric measurements. It was found that the measured dielectric constant decreased as the frequency increased, while the high temperature processed produce lower in a convergence manner toward 6 GHz. The loss factor exhibited high losses at higher temperature and lower frequencies, as well as converged at 1.9 GHz then diverged up to 6 GHz. Three relaxation processes are dominated at all temperature treatments within the frequency range. The relaxation time, τ, and the activation energy, Q, are modelled based on linear fitting of measured data according to Debye and Arrhenius approaches.

Loss factor measurement and indications for nonlinearities in sound insulation

The loss factor is often determined in building acoustics by measuring the structure-borne reverberation time. To do this, elements under test are excited either by a hammer or by a shaker. In several experiments with sand-lime brick walls, measured loss factors turned out to be significantly larger when hammer excitation was used instead of shaker excitation. A thorough investigation of this effect was then performed using hammer blows of different strengths and a 250-kg shaker. This way, forces are in the same order of magnitude for both excitations. Measurement results lead to the conclusion that large forces may create a nonlinear structural response. The nonlinearity is observed for a sand-lime brick wall without plastering but not for a lightweight composite wall and also not for a monolithic concrete wall. The assumption of nonlinear behaviour is furthermore supported by an additional investigation where alarm pistol shots were used to excite a sand-lime brick wall with very large airborne sound pressure levels. The airborne sound insulation of the wall turned out to be nonlinear, that is, it increased with increasing sending room levels.

Dielectric properties of hops - an effect of bulk density

Continuous detection of basic physical properties of freshly picked and cleaned wet hop cones would be very helpful for better control and automation of harvesting processes. That is why the main aim of this article was to determine the effects of bulk density changes on dielectric properties of freshly picked hop cones. Relative permittivity and loss factor were measured using a newly developed capacitance measuring device. A strong linear correlation between fresh hops relative permittivity and bulk density was found. This finding could be used e.g. for consequent hop drying process control. Significant differences between tested hop varieties were observed for both relative permittivity and loss factor measurements. These differences cannot be explained only by a slightly different moisture content of the measured varieties and ambient temperature changes. Measured material loss factor was only slightly affected by bulk density changes. However, relative permittivity was affected by bulk density changes significantly. These facts could be used for other properties of wet hop cones estimation.

S-band five-port ring reflectometer-probe system for in vitro breast tumor detection

A five-port ring reflectometer-probe system was developed to measure relative permittivity of normal and tumorous breast tissues in frequency range from 1.6 to 2.75 GHz. The calibration procedures of the study reflectometer and the coaxial probe were described in detail. In this study, the synthetic breast tissues have been used, which are the Triton TX-100-water mixture at different ratios that mimic dielectric properties of normal and tumor breast tissue samples. The comparative studies of reflection coefficient and dielectric properties of the synthetic mixture samples were conducted using study reflectometer-probe system and commercial vector network analyzer with Keysight (formerly Agilent) 85070E dielectric probe. Maximum mean errors of the linear magnitude, phase, dielectric, and loss factor measurements were recorded to be 0.02, 6.1°, 2.21, and 1.60, respectively. These measurements were significantly distinguishable for normal and tumorous breast tissues.

Open Transverse-Slot Substrate-Integrated Waveguide Sensor for Biomass Permittivity Determination

A novel open transverse-slot substrate-integrated waveguide sensor is presented. The sensor is designed and fabricated for dielectric measurements of sawdust at 8 GHz. Different configurations of the sensor were investigated by using simulation software and relationships between the simulated magnitude and phase of the reflection coefficient and dielectric properties. A suitable configuration was fabricated with a circuit board milling machine, and the performance was investigated through measurements of the magnitude and phase of the reflection coefficient from sawdust samples. The permittivity of the material was determined by fitting the voltage stand wave ratio and phase with a normalized 2-D polynomial with known dielectric values. The permittivity determination model was tested by using independent sets of training and validation measurements on sawdust at different bulk densities and moisture contents between 6.8% and 39%. The predicted dielectric properties values showed linear relationships with moisture content. Therefore, moisture content in sawdust can be determined from measurements of either dielectric constant or loss factor at a single microwave frequency without knowledge of the bulk density.