Time Domain Reflectometry Technique Research Articles

Self and hetero-association in Benzaldehyde/Quinoline − Formamide solutions: Time Domain Reflectometry studies

The complex permittivity spectra of binary solutions of Benzaldehyde (PhCHO)/Quinoline (QUI) with Formamide (FMD) have been obtained at different mole fractions of FMD in the frequency range from 10 MHz to 30 GHz using the Time Domain Reflectometry (TDR) technique. The complex permittivity spectra have been fitted with Debye function. Dielectric relaxation time values have been interpreted in terms of the nature and size of the self and hetero associates of the binary solutions. The effective Kirkwood correlation factor (geff) has been correlated with closed and open associates of the solutions. The geff∼0.51 is the characteristic value of closed dimers. It appears that geff∼0.75 signifies the presence of both closed and open dimers. The Excess static dielectric constant (εE) shows negative deviation. The corrective Kirkwood correlation factor (gf) and Bruggeman factor (fB) have been used to investigate the strength of the H-bond interactions. The Geometry optimization has been carried out using Density Functional Theory (DFT) with B3LYP/6–311++G (d, p) basis set. Population analysis on the optimized geometries shows that PhCHO has 53.61 and 46.39 % closed and open geometries, respectively, while FMD has 17.11 % open dimers and remaining are closed dimers.

Recent Advances in Dielectric Properties-Based Soil Water Content Measurements

Dielectric properties are crucial in understanding the behavior of water within soil, particularly the soil water content (SWC), as they measure a material’s ability to store an electric charge and are influenced by water and other minerals in the soil. However, a comprehensive review paper is needed that synthesizes the latest developments in this field, identifies the key challenges and limitations, and outlines future research directions. In addition, various factors, such as soil salinity, temperature, texture, probing space, installation gap, density, clay content, sampling volume, and environmental factors, influence the measurement of the dielectric permittivity of the soil. Therefore, this review aims to address the research gap by critically analyzing the current state-of-the-art dielectric properties-based methods for SWC measurements. The motivation for this review is the increasing importance of precise SWC data for various applications such as agriculture, environmental monitoring, and hydrological studies. We examine time domain reflectometry (TDR), frequency domain reflectometry (FDR), ground-penetrating radar (GPR), remote sensing (RS), and capacitance, which are accurate and cost-effective, enabling real-time water resource management and soil health understanding through measuring the travel time of electromagnetic waves in soil and the reflection coefficient of these waves. SWC can be estimated using various approaches, such as TDR, FDR, GPR, and microwave-based techniques. These methods are made possible by increasing the dielectric permittivity and loss factor with SWC. The available dielectric properties are further synthesized on the basis of mathematical models relating apparent permittivity to water content, providing an updated understanding of their development, applications, and monitoring. It also analyzes recent mathematical calibration models, applications, algorithms, challenges, and trends in dielectric permittivity methods for estimating SWC. By consolidating recent advances and highlighting the remaining challenges, this review article aims to guide researchers and practitioners toward more effective strategies for SWC measurements.

Study of molecular interaction in aqueous sucrose in the GHz region using Time Domain Reflectometry (TDR)

Dielectric relaxation of aqueous sucrose [C12H22O11] has been carried out over the temperature range of 278.15 K to 298.15 K in the frequency region of 0.01 GHz to 30 GHz using time domain reflectometry technique (TDR). Two modes of relaxation processes were observed, namely low-frequency (primary) and high-frequency (secondary) relaxation. The rotating motion of sucrose molecules is primarily responsible for the low-frequency dispersion of relaxation, whereas the reorientation of bulk water is responsible for the high-frequency dispersion of relaxation. Dielectric parameters, i.e., static dielectric constant (εj), relaxation time (τj), dipole moment (û), Kirkwood factor of low frequency relaxation (g1), and thermodynamic parameters, i.e., free energy of activation (ΔFj), enthalpy of activation (ΔHj) and entropy of activation (ΔSj) were calculated. The static dielectric constant (εj), which was detected for both relaxation processes, i.e., ε1 and ε2, was shown to be decreasing with increasing temperature and solute molecule concentration. Over the course of all the concentrations used, it was observed that the τ1 and τ2 both increased with the sucrose concentration and also towards the low temperature. The decreasing trend of correlation factor (g1) suggests a strong possibility of antiparallel alignment of dipoles between sucrose molecules towards higher concentrations. Solute-solute antiparallel correlation seems to be reduced at lower temperature. Higher values of dipole moments at lower sucrose concentrations imply reduced antiparallel alignment between sucrose molecules, while lower values of effective dipole moments (μeff) obtained using Cavell and Kirkwood-Frohlich (KF) equations increase the likelihood of antiparallel alignment of sucrose dipoles. In terms of hydration dynamics, the total water molecules that are effectively locked by the sucrose molecules (Zib) were also calculated. Finally, dielectric parameters have been corroborated by thermodynamic parameters.

Non-Intrusive Online Time Domain Reflectometry Technique for Power Cables

Non-Intrusive Online Time Domain Reflectometry Technique for Power Cables

Dielectric relaxation studies of 1-nitropropane-dimethyl sulfoxide mixtures using a Time Domain Reflectometry

ABSTRACT Complex dielectric measurements were performed in 1-nitropropane (NTP) and DMSO mixtures at various concentrations in the frequency range of 10 MHz to 50 GHz using time domain reflectometry technique. The excess inverse relaxation time values were found to be negative, indicating that the dipoles rotated more slowly. Alenka Luzar’s hydrogen-bonded theory is used to calculate theoretical estimates of the static dielectric constant. The variations in dielectric parameters such as dielectric constant, relaxation time, Kirkwood correlation factor and excess properties observed in the study confirm the existence of intermolecular interactions within the NTP-DMSO mixtures.

Dielectric and Hydration Study of Aqueous Cellulose Derivative Solutions

Dielectric and hydration studies have been done on hydroxypropyl methyl cellulose (HPMC) (Molecular weight 1261 g/mole) in 15 centipoise (cPs) and 50 cPs and methyl cellulose (MC) (Molecular weight 454 g/mole) in 450 cPs and 4000 cPs aqueous solutions using a time domain reflectometry technique. The static dielectric constant, density, and hydration numbers were determined at various concentrations. The results revealed that the formation of bound water molecules around the cellulose derivative (CD) decreased with increasing concentrations of the CD. The higher value of the hydration number of the CD suggested that water-CD interactions were stronger in aqueous solutions of CD at the lower concentration of the solute; i.e., the CD-water interactions were progressively weaker as the CD concentration was increased.

Dielectric relaxation and thermodynamic study of aqueous Glycine using time domain reflectometry technique

Using the Time Domain Reflectometry technique in the frequency range of 10 MHz to 50 GHz, the complex permittivity spectra of Glycine (Gly) with water combination have been determined over the complete concentration range of mole fractions and in temperature range of 10–25 °C. The Cole-Davidson model was used to fit the intricate permittivity spectra for Gly and water.The non-linear least square fit method has been used to compute the static dielectric constant (ε0), relaxation time (τ), effective Kirkwood correlation factor (geff), excess permittivity (ε0E), (1/τ)E excess inverse relaxation time (1/τ)E and Bruggeman factor (fB). An automated density and sound velocity meter, the Anton Paar DSA 5000 M and viscosity with Lovis 2000 M/ME, was used to measure the density, sound velocity, and viscosity of aqueous solutions. FT-IR spectra are used to identify the conformation assessments of hydrogen bonding development between complicated mixtures.

Dielectric relaxation and hydrogen bonding studies of 1-iodobutane 1,4-dioxane mixture using TDR technique

Complex dielectric measurements by using the Time Domain Reflectometry technique between the frequency range 10 MHz to 30 GHz have been accomplished for different concentrations of 1-iodobutane (IDB) and 1, 4-Dioxane (DX) binary mixtures at 5 °C to 25 °C temperatures. Debye model was used to fit the complex permittivity spectra of IDB-DX binary mixture. The Luzar model is applied to calculate the average number of hydrogen bonds in IDB-IDB and IDB-DX molecules. The measured value of hydrogen bond density is found to be maximum for this binary mixture at dioxane concentration VDX ≈ 0.7. To study the dielectric behavior and to observe the modification in the strength of hydrogen bond in the presence of other nonpolar molecule is the main aim of the proposed work. Measurement of Kirkwood correlation factor and Bruggeman factor provide the valuable information regarding the formation of hydrogen bonded molecular multimers and intermolecular interaction in the binary mixture. Information on the molecular interactions in binary mixtures is also provided by the study.

Structural and dielectric relaxation studies of 1, 4, and 1, 3 -butanediol–1, 4-dioxane mixtures using TDR technique

Time domain reflectometry (TDR) was used to examine the complex dielectric permitivity spectra (CPS) of binary mixtures of 1,4, and 1,3 butanediol (BD) with 1,4 Dioxane (Dx) at high frequencies (10 MHz–50 GHz). Both systems show the Cole–Davidson type of relaxation process. The least squares fit (LSF) method is applied to compute dielectric relaxation parameters from the CPS. The interest of the ongoing research is to understand the molecular associations, orientation of electric dipoles, and change in electric dipole density in the liquid mixture with the help of excess dielectric parameters, Bruggeman factor (fB) and the Kirkwood correlation factor for both systems.

Thermodynamic hydration behaviour of glycine below room conditions using time domain reflectometry

The present work reports the concentration-dependent hydrophobicity of glycine below room temperature. The dynamics of aqueous glycine have been studied by means of dielectric relaxation spectroscopy using Time Domain Reflectometry (TDR) technique in the frequency region of 10 MHz–30 GHz. Complex permittivity spectra are obtained using TDR that allowed evaluation of the static dielectric constant (ε0) and average relaxation time (τ). As dielectric relaxation spectroscopy provides information on the average relaxation time (τ) related to the mechanism of hydrogen bond (HB) formation and breaking, therefore the concentration-temperature dependence of τ was used to evaluate and study hydration behaviour through dielectric parameters such as dipole moment (μ), correlation factor (g), and the dynamics of irrationally bound water molecules (Zib). Aqueous glycine relaxes in two different relaxation modes in the broad microwave frequency region from MHz to GHz. The low-frequency relaxation process (l-process) observed is associated with glycine relaxation, while the detected peak in the high-frequency relaxation process (h-process) is attributed to water associated with glycine. We have attempted a concentration-temperature-dependent hydrogen bonding mechanism in both relaxation processes, and the results were corroborated with thermodynamical parameters such as molar entropy of activation (∆Sj), molar enthalpy of activation (∆Hj), and molar free energy of activation (∆Fj).

Water dynamics on the structural properties of some NSAID’s with leucine in the picosecond region using time domain spectroscopy

Concentration-dependent dielectric response for non-steroidal anti-inflammatory drugs (NSAIDs): Aceclofenac (ACF) and Diclofenac (DCF) in the aqueous leucine solution have been reported at different concentrations and temperatures (298.15 K to 283.15 K). The time domain reflectometry technique in the frequency region of 1 GHz to 30 GHz was used for the present study. Complex permittivity (ε*), static dielectric constant (ε), dielectric relaxation time (τ), dipole moment (μ) and Kirkwood correlation factor (g) have been calculated and discussed in terms of the molecular interaction of water and the used drugs. To give more insights into the structural dynamics of drug-induced amino acids, the study includes molar enthalpy of activation (ΔH), entropy of activation (ΔS), and free energy of activation (ΔF). The overall study concludes that the drug (DCF) having a potent inhibitor of cyclooxygenase found a higher static dielectric constant (ε0) than that of the drug (ACF) having more carbon (C), hydrogen (H), and oxygen (O) in the chain, which is more efficient in controlling pain. Communicated by Ramaswamy H. Sarma

Temperature dependent dielectric relaxation spectroscopy of amyl acetate-xylene solutions – An approach to molecular and co-operative dynamics

Dielectric relaxation parameters of AMA-Xylene solutions have been investigated thoroughly to discern the associativeness as well as heterogeneous behavior among the hetero molecules in the solutions such that dielectric constant (εo) and relaxation time (τ) of solutions has been determined. Complex permittivity spectra (CPS) for Amyl Acetate (AMA)-Xylene solutions were measured in 10 MHz–50 GHz frequency range using Time domain reflectometry (TDR) technique. It is exciting to explore the cooperative nature and association between AMA-Xylene. With co-operative domains (CDs), dynamics in AMA-AMA and AMA-Xylene molecules have been explicated while Kirkwood validates CDs with diverse exchanges through bonding. The experimental values of εo are compared with theoretical values obtained from the molecular parameters suggested by the Luzar. Thermodynamic parameters for AMA-Xylene show positive values of Enthalpy and Entropy for all concentrations, indicating that the system is endothermic and less ordered. Gibbs free energy decreases with increase in volume fraction of amyl acetate (VAMA).

Time Domain Reflectometry Technique using for Dielectric Relaxation Study of Biomolecules

We have established the Time Domain Reflectometry (TDR) technique that provides information regarding dielectric permittivity in the frequency range 10 MHz to 30 GHz. A time domain spectroscopy technique has been effectively used to acquire information on the essential and active parameters of molecular dynamics. The dimension of complex permittivity of Biomolecules (i.e. amino acids, enzymes and proteins) in the frequency range from 10 MHz to 30 GHz has been carried out using time domain reflectometry technique.

Radio Frequency-Based Diagnostics for Superconducting Magnets

Operation of high-field superconducting magnets relies on diagnostic instrumentation for measuring strain, temperature, and magnetic field variations, detecting quenching, and identifying performance problems. Discrete sensor implementation is costly, requires multi-channel data acquisition systems, and sensor density is often insufficient to resolve problematic locations spatially. Distributed sensing is a viable alternative approach providing location-specific diagnostic information over single terminal output. In particular, it can be the key to quench protection of high-temperature superconductor (HTS)-based magnets where hot spots are known to form and persist before a quench. Fiber-optic technology offers distributed sensing solution for magnets but suffers from drawbacks such as fiber fragility, high costs of optical interrogators, and difficulty in differentiating between physical quantities such as temperature and strain. We propose an alternative, robust, and easily integrable way of implementing distributed sensing in magnets using radio-frequency (RF) technologies. RF Time Domain Reflectometry (TDR) technique has been around for nearly 60 years, and it is an essential diagnostic tool used in multiple areas of technology and applied research. We discuss operational principles and practical implementation of RF TDR sensors capable of detecting local variations of strain, temperature, and magnetic field through changes in RF impedance and wave propagation time. Results of cryogenic testing of our TDR sensors with HTS tape conductors are presented. The perspective of enabling a new diagnostics paradigm for high-energy physics and fusion energy applications based on distributed RF sensing is discussed.

In-situ evaluation of chitosan-based materials containing fertilizer by time-domain reflectometry (TDR) technique

Population growth and resource reduction have created tremendous pressure on the current world scenario to meet the increasing food demands. To face this challenge, strategies are needed to promote the rational use of natural resources since overusing agricultural inputs such as chemical fertilizers may lead to severe environmental problems. In the present work, we evaluated (i) the nutrient release profile of macrospheres, microspheres, and microcapsules based on chitosan, montmorillonite clay, and KNO3 by TDR technique and (ii) the influence of controlled water replacement on the nutrient release in soil. TDR probes inserted in containers with sandy soil evaluated the nutrient release from materials, with and without tracking of field capacity, obtaining results for soil moisture and electrical conductivity. The nutrient release was dependent on soil water management, improving fertilization oversight. Microcapsules released the nutrient slower and for longer periods (higher than 46 days). Also, the water content corroborated the swell ability of materials, which affected and controlled the release of nutrients. These findings validate that chitosan-based materials matched the requirements for a more efficient and sustainable fertilizer, and the TDR technique effectively determined the release of nutrients.

Early monitoring of pore wetting in membrane distillation using ultrasonic time-domain reflectometry (UTDR)

Pore wetting induced by surfactants and salt scaling is a major obstacle to the industrial application of membrane distillation (MD). Identifying the transition of wetting stages and achieving early monitoring of pore wetting are crucial for wetting control. Herein, we made a pioneering attempt to use ultrasonic time-domain reflectometry (UTDR) technique to non-invasively detect the pore wetting in a direct contact MD, and explain the UTDR waveform with the help of optical coherence tomography (OCT) imaging. The results showed that the water–vapor interface had a strong reflection to ultrasound (reflection coefficient = 0.9995), while the water-membrane and water-scaling layer interfaces showed relatively weak reflection. Therefore, UTDR could effectively detect the movement of water–vapor interface with the low interference from the signals generated by the membrane and scaling layer. For the surfactant-induced wetting, the occurrence of wetting could be successfully detected by the right-shift in phase and the reduction in amplitude of the UTDR waveform. Moreover, the wetting depth could be accurately calculated by the time of flight (ToF) and ultrasonic velocity. For scaling-induced wetting, the waveform slightly shifted to the left at the beginning due to the growth of scaling layer, then to the right because the left-shift was surpassed by the right-shift of the waveform caused by pore wetting. Both for the surfactant- and scaling-induced wetting, the variation of the UTDR waveform was sensitive to wetting dynamics, and the right-shift of phase and the reduction in amplitude of the waveform could act as early monitoring signals to the occurrence of wetting.

A Noncontact Planar Microstrip Sensor for Power Line Fault Detection

In this letter, a novel TM0 mode launcher is presented as a sensor for the fault detection on a single conductor line (SCL). The launcher is designed at 2.4 GHz frequency on an FR4 substrate with the microstrip technology. Simulated S-parameter results of the launcher are verified with the measured results of the fabricated prototype. Experiments are performed to demonstrate the signal propagation on a bent SCL, to measure the isolation between the launchers and to measure backward propagating signal. Open circuit fault location experiment is performed on a 6 m long cable using the Time domain reflectometry (TDR) technique. An average error of 0.15 m (5.04%) is observed in fault location. The proposed sensor is non-conductor-contact, non-intrusive, planar (16 cm*16 cm) and easy to install on the existing power lines for fault detection and power line communication.

Rod Insertion TDR for Detecting Corrosion Damage in Vertical Grounding Electrodes

Faults in a grounding network pose a serious threat to power system equipment protection and worker safety. A large number of vertical electrodes are used in a grounding network and break-points in these due to soil induced corrosion is one of the prime reasons for faults. We present a rod insertion time domain reflectometry (TDR) technique for vertical grounding electrode break-point detection. A secondary bare rod is inserted adjacent to the grounding electrode while a fast risetime pulse is continuously applied to excite a transverse electromagnetic (TEM) wave that propagates along the rods and reflects back from the break-point. The reflected signals for different depths of the secondary rod are analyzed to identify the location and severity of the break-point. We show that fault detection is possible without prior knowledge of soil electrical parameters. To show the feasibility of the proposed technique, a full wave simulation approach is used to evaluate the wideband input impedance of the grounding and inserted rod system and then FFT is applied to obtain TDR responses. The results show the method is capable of detecting faults for a wide range of soil conductivity for a system bandwidth of 300MHz.

Molecular interactions studies of methyl cellulose-water solutions using dielectric spectroscopy

ABSTRACT Time Domain Reflectometry (TDR) and frequency domain techniques have been used for the dielectric measurement of methyl cellulose (MC) with water for different concentrations and frequency ranges from 20 Hz to 2 MHz and 10 MHz to 30 GHz at 25°C. The dielectric relaxation in these mixtures can be represented by the Debye relaxation behaviour. The dielectric parameters such as complex permittivity ε*(ω), complex electrical modulus M*(ω), complex electrical conductivity σ*(ω), loss tangent (tan δ), static dielectric constant (ε0) and relaxation time (τ) have been determined. The variation of dielectric parameters of methyl cellulose (MC) in water suggested that methyl cellulose (MC) bonds with water alter its structure and electric dipole moment.

Dielectric Behaviour of Metal Complexes Cu (II), Ni (II) and UO2 ((VI) Of the Ligand Oxaloanilic Acid Hydrazone

Abstract: The dielectric behaviour and molecular structure of metal complexes Cu(II),Ni(II) and UO2((VI) of the ligand oxaloanilic acid hydrazine have been investigated using Time Domain Reflectometry (TDR) technique in the frequency range 10 MHz to 10GHz. Cole-Davidson model has been applied for fitting the complex permittivity spectra [ ε* (ω)]. The parameters εs –the static permittivity, τ- the dielectric relaxation time are evaluated at different temperatures from 2880K to 3330K and are discussed in respect of their molecular structural behaviours. The thermodynamic parameters, such as ΔH* - molar enthalpy, ΔS* - the molar entropy are obtained using Eyring.s rate equation. In the light of such data the possible structures of the present complexes are discussed.