Parallel Resistance Research Articles

A comprehensive study of parallel gap resistance welding joint between Ag foil and front electrode of GaAs solar cell

When space solar cell array is subjected to harsh temperature cycle, such as planet orbit, thermal fatigue cracks in bonding area are easily induced. With the aim of improving bonding quality and elucidating failure mechanism of parallel gap resistance welding (PGRW) joints in temperature cycling environment, the present research investigates the effect of current density on bonding quality and thermal fatigue behavior of PGRW joint between Ag interconnector and front electrode of GaAs solar cell. When current density is set at 417 A/mm2, a solid diffusion bonding is achieved at the Ag/Au interface, which also possesses adequate joint strength as ensured by both pressure and input energy of PGRW. Crack initiation by thermal fatigue is found at joint edge, which subsequently propagates along the interface as the environment temperature cycling continues. Further investigation reveals that the conducted temperature cycling generates serious tensile and compressive stress in the multi-layered joint structure. Since such reciprocating forces directly induce micro-plastic deformation and strain accumulation at joint interface, failure by crack is finally generated at the joining interface.

Estimation of the reliability figures of space GaInP/Ga(In)As/Ge triple junction solar cells from very high temperature accelerated life tests with forward and reverse biasing

This paper presents a temperature Accelerated Life Test (ALT) for space solar cells. The test is carried in dark conditions to circumvent the inherent problems of illumination ALTs. This ALT is an evolution of our previous ALT in dark conditions where just forward bias was used. Now, solar cell working conditions are emulated by means of forward/reverse bias. Forward bias emulates electric performance under illumination while reverse bias emulates the shadowing at eclipse periods or any other shadowing event (for example antennas might cast also shadows). The forward to reverse time ratio is 4:1. Furthermore, the high temperatures used in the current ALT (190, 210 and 230 °C) allow a considerable time reduction of the test. The results obtained in this ALT onto commercial GaInP/Ga(In)As/Ge triple junction solar cells suggest that the degradation mode is related with the decrease of parallel resistance, namely an initial degradation by shunts occurs in the GaInP top subcell which is followed by a parallel resistance reduction in the Ga(In)As middle subcell. The activation energy in current ALT is higher (1.06 eV) than in the previous one (0.88 eV). Reverse biasing promotes similar degradation than forward one but more intensely, i.e. in a shorter time. Therefore, reverse biasing produces a significant lower reliability than in previous ALT without reverse bias. Despite this reliability reduction, the time for a reliability of 90% is 32 years of continuous operation at a nominal temperature of 80 °C (typical of many GEO missions). Therefore, these solar cells seem very robust and with a high reliability for many space applications. It should be noted that these figures are related to the degradation caused exclusively by high temperatures and other stressors like radiation are not considered here.

SPICE Simulation of Quantum Transport in Al2O3/HfO2-Based Antifuse Memory Cells

This letter reports a compact SPICE model for the electron transport characteristics of Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based nanolaminates for their use in multilevel one-time programmable (M-OTP) memories. The model comprises three simulation blocks corresponding to the electrical stimulus applied to the device, the equivalent circuit of the memory cell, and the events generator associated with the dielectric breakdown of the insulating layer. For a clear assessment of the quantum effects occurring in these structures, constant voltage stress was used as the primary electrical stimulus. The antifuse (AF) cell is represented by a combination of series and parallel resistances that account for the formation of filamentary conducting paths with quantum properties across the structure. The arrival of successive breakdown events is simulated using a power-law nonhomogeneous Poisson process. Our study indicates that a M-OTP memory device operating in the quantum regime not only is feasible but also that its stochastic features are addressable by circuit simulations.

Metallic filament domain dynamics-induced abrupt resistive switching characteristics with small hysteresis in two dimensional-crystalline VO2 films

The domain configurations in vanadium dioxide (VO2) that are interfacing with a substrate play an important role, particularly in the electronic property, due to the interface-dependent strain induction and phase coexistence across the metal-insulator transition (MIT) process. Here, we demonstrate an abrupt resistive switching behavior with a small hysteresis by utilizing the strain-induced metallic filament domains in VO2 films with puzzle-like two-dimensional single crystalline domains (2D-crystalline VO2 films), which are synthesized on a SiO2 layer. We find that an anisotropic tensile strain induced at the 2D-crystalline VO2 films /SiO2 interfaces leads to the preferential formation and propagation of metallic stripe domains along the in-plane growth direction across the MIT. We also demonstrate that based on simultaneous in situ observations of electrical characteristics and phase evolution in the 2D-crystalline VO2 films, the abrupt transition with a narrow hysteresis width (<4 °C) is attributed to the thermally activated and reversible evolution of metallic stripe domains acting as a conducting filament channel within an insulating phase, which is associated with anisotropic strain distribution. Moreover, we show that these experimental results are consistent with the theoretical analysis based on a parallel resistor model. In addition, we further demonstrate thermally-triggered abrupt and reversible resistive switching performance of the 2D-crystalline VO2 film, maintaining stable for 500 switching cycles. These results provide an important strategy to modulate and utilize the unique MIT hysteresis behavior properties through controlling the configuration of metallic and insulating stripe domains in the 2D-crystalline structure of VO2 for the development of high-performance VO2 based electrical devices.

Modelling of Bidirectional Three-Phase Four-Wire Three-Level NPC MLC under Single-Loop Current Sensorless Control

Single-loop current sensorless control allows for abolishing of the instantaneous current measurement in the control system using only a single control loop with voltage feedback to stabilise the DC-bus voltage. This approach eliminates current sensors in the control circuit, benefiting from saving space on the printed circuit board and minimising power dissipation in the current measurement circuitry. This paper focuses on the single-loop current sensorless control applied to bidirectional three-phase four-wire three-level NPC MLC by simulation analysis and demonstrates the performance of the proposed current control algorithm in the rectifier and inverter modes and the step response with power direction change and grid-voltage change. In capacitor voltage balancing, an additional controller is applied, which is capable of compensating for the voltage asymmetry caused by adding a 2.5 kOhm resistor in parallel to one of the DC-bus capacitors. Our results demonstrate good performance of the proposed control method both in the inverter and rectifier modes, showing stable current shape in the low power and full power modes with acceptable harmonics content, meeting the requirements of the IEC 61000-3-2 standard for Class A devices. The analysis showed that the proposed control approach is suitable for industrial application.

A model heterostructure with engineered Berry curvature

Molecular-beam epitaxy enables ultrathin functional materials to be combined in heterostructures to create emergent phenomena at the interface. Magnetic skyrmions are an example of an exciting phase found in such heterostructures. SrRuO3 and SrRuO3-based heterostructures have been at the center of the debate on whether a hump-like feature appearing in Hall resistivities is sufficient evidence to prove the presence of skyrmions in a material. To address the ambiguity, we synthesize a model heterostructure with engineered Berry curvature that combines, in parallel, a positive anomalous Hall effect (AHE) channel (a Sr0.6Ca0.4RuO3 layer) with a negative AHE channel (a SrRuO3 layer). We demonstrate that the two opposite AHE channels can be combined to artificially reproduce a “hump-like” feature, which closely resembles the hump-like feature typically attributed to the topological Hall effect and the presence of chiral spin textures, such as skyrmions. We compare our heterostructure with a parallel resistor model, where the inputs are the AHE data from individual Sr0.6Ca0.4RuO3 and SrRuO3 films. To check for the presence of skyrmions, we measure the current dependence, angle dependence, and minor loop dependence of Rhump in the heterostructure. Despite the clear hump, no evidence of skyrmions is found.

Inductance-to-digital converters (LDC) based integrative multi-parameter eddy current testing sensors for NDT&E

Sensors’ signal conditioning and digital interface are important for sensor technologies, digital transformation, and the Internet of Things (IoT) in particular. Frequency output sensors and inductance-to-digital converters (LDC) offer distinct advantages over Analog-to-Digital Converter (ADC) interfaces. To miniaturize the eddy current testing system and achieve multi-parameter measurements, this paper reviews eddy current signal conditioning and digital interfaces in the field of displacement sensors and non-destructive tests & evaluation (NDT&E). After review and comparison of different signal conditioning and digital interfaces, the LDC chip is used in eddy current testing for multiple parameter measurements including lift-off distance and defect detection. An LDC-based integrative eddy current non-destructive testing method is proposed. The LDC chip provides AC to drive the LC resonator composed of the sensor coil and the parallel capacitor. By measuring the resonance frequency and parallel resistance (Rp) of the LC resonator, the simultaneous measurement of the lift-off distance and the defect is achieved. Based on the method, the testing experiments of two kinds of specimens made of aluminium and steel were carried out under different lift-offs. Experimental results show that both parameters of frequency and Rp of the LC resonator can intuitively reflect the defect depth and lift-off. Frequency- Rp curves can be used to quantify defect depth and lift-off distance and differentiate the material. This work also illustrates an integrated approach of signal conditioning and digital interface for multiple parameters or feature measurement for integrated eddy current NDT&E. The work opens a new way for addressing multiple parameter measurements of eddy current NDT & E including lift-off estimation and defect characterization via digital interfaces. It has the potential to bridge the gaps in metrology of geometry, displacement measurement, and NDT&E for defect detection and material characterization.

Stomatal regulation and xylem hydraulics of limber pine and Engelmann spruce in Great Basin sky-island ecosystems

Integration of whole-plant stomatal regulation and xylem hydraulics is of critical importance for predicting species response to drought stress. Yet intraspecific variability of stomatal and hydraulic traits, and how these variabilities interact, remain largely unknown. We hypothesized that drought can drive less stomatal regulation but increase xylem hydraulic safety, resulting in stomatal-hydraulic coordination within a species. We estimated sensitivity of whole-tree canopy conductance to soil drying together with xylem hydraulic traits of two dominant conifers, i.e. limber pine (Pinus flexilis) and Engelmann spruce (Picea engelmannii). Our study was conducted using sub-hourly measurements over five consecutive years (2013–2017) at three instrumented sites with different elevations within the Nevada Eco-hydrological Assessment Network (NevCAN) in Great Basin sky-island ecosystems. Both conifers showed a reduction of stomatal sensitivity to soil drying at lower elevations, indicating an active stomatal acclimation to drought. While limber pine increased xylem embolism resistance in parallel with reduced stomatal sensitivity to soil drying, an opposite hydraulic adjustment was detected in Engelmann spruce. Our results provide evidence that mature trees can respond to climatic changes using coordinated shifts in stomatal regulation and xylem hydraulics, but such changes can differ within and between species in ways that need to be examined using in situ data. Deciphering intraspecific variability in whole-plant stomatal and hydraulic traits ultimately contributes to defining drought tolerance and vulnerability, particularly for tree species that inhabit a wide range of landscapes.

Effect of heating temperature on electrical properties and gel properties of carp surimi

AbstractFor better application of ohmic heating technology in the food industry, it is necessary to study the variation of the electrical properties of food materials with temperature. In this paper, various initial heating temperatures were applied to investigate the impact of temperature on the electrical properties of rinsed and unrinsed carp surimi. An impedance analyzer was utilized to measure the electrical parameters of carp surimi within the frequency range of 20 ~ 120 MHz. The frequency and temperature characteristics of electrical parameters were explained based on biological and electromagnetic theories. These findings furnish theoretical references and experimental evidence for applying ohmic heating technology. The results showed that the parallel inductance (Lp), parallel capacitance (Cp), parallel resistance (Rp), and impedance (Z) of surimi decreased as the internal temperature of the surimi increased. The greater the heating temperature of the water bath, the larger the parameter values. The Lp, Cp, Rp, and Z values were lower for unrinsed surimi than for rinsed surimi. During the heating and cooling process, the parameter values at the same temperature point differed due to the different states of the surimi gel. As the frequency increased, the Rp and Z of surimi showed different regular changes, with similar trends at the same temperature. Rinsing has been demonstrated to improve the gel properties of surimi effectively. Prolonged periods in the temperature range of 60 ~ 70°C can cause the modori phenomenon (gel degradation), leading to reduce the gel strength of surimi. Thus, it is essential to pass through this temperature zone as soon as possible during the preparation of surimi gel. The relationship between the internal microstructure of surimi gel and the electrical parameters needs to be further investigated.Practical ApplicationsAs an emerging technology for food heat treatment, ohmic heating has the characteristics of uniform heating and fast heat production. As a homogeneous material, surimi is ideal for ohmic heating. However, the heating process is not easy to control when the electrical parameters are unknown, so the purpose of this study is to explore the changes of the electrical parameters of surimi at different heating rates and temperatures, provide data reference for the heat treatment of surimi by ohmic heating, and promote the application of ohmic heating in surimi processing.

Design of Ultracompact Content Addressable Memory Exploiting 1T-1MTJ Cell

Content addressable memories (CAMs) are a promising category of computing-in-memory (CiM) elements that can perform highly parallel and efficient search operations for routers, pattern matching, and other data-intensive applications. Various magnetic tunnel junction (MTJ) based content addressable memory (CAM) designs have been proposed to realize zero standby power and high performance search. However, due to the relatively small tunnel magneto-resistance (TMR) ratio, MTJ based CAMs require extra transistors and differential MTJ branches to distinguish between the parallel and anti-parallel resistance states, resulting in significant area and energy overhead. In this paper, we propose a device-circuit co-design approach for an ultra-compact CAM design by only exploiting an 1T-1MTJ structure in each cell. We propose a 2-step search scheme to enable the parallel in-memory search operation across the proposed CAM array, and demonstrate the sufficient sensing margin of the array in a successful search operation. Evaluation results suggest that our proposed 1T-1MTJ based CAM design improves 179X/301X area efficiency compared with the state-of-the-art 15T-4MTJ/20T-6MTJ CAM design. Application benchmarking on hyperdimensional computing (HDC) inference shows a 54.6X/12.8X speedup compared with GPU/20T-6MTJ CAM based approaches.

Discrimination of Inner Injury of Korla Fragrant Pear Based on Multi-Electrical Parameters.

Inner-injury fragrant pears are easily prone to rot during storage. Discriminating inner injury in the Korla fragrant pear from the normal pear is difficult as the flesh may be injured while the peel of the fruit remains intact. This study demonstrated the recognition of inner-injury pears based on their electric characteristics to pick out the inner-injury pears before storage. The electrical parameters parallel equivalent capacitance, quality factor, parallel equivalent inductance, parallel equivalent resistance, complex impedance, and phase angle were measured using the fruit electrical characteristic detection instrument. Principal component analysis and correlation analysis were used to determine the characteristic parameters, connected with the qualitative value of the fragrant pear to establish three discrimination models. When the measurement frequency was 100 kHz, compared with the Naïve Bayes and K-nearest neighbor models, the Support Vector Machine model with the characteristic parameters of quality factor, parallel equivalent resistance, and phase angle performed best. The recognition accuracy of the test set was 92.00%, the precision was 92.41%, the recall was 97.33%, and the F1 score was 0.95. Therefore, the electrical characteristic technique effectively detected the inner injury of fragrant pears and provided a new way to distinguish the inner injury of fruits.

An in-depth thermo-electrical evaluation of a rooftop PV technology for a residential building using advanced infrared thermography

The investigated performance criteria of photovoltaic (PV) modules in the studies have been limited to current, voltage, power, and temperature. It means that a study with the aim of a comprehensive investigation of a number of key thermo-electrical indicators of the system, namely, photocurrent (Iph), parallel resistance (Rp), thermal voltage of diode (Vt), and diode reverse saturation current (I0), has not been done yet. Considering this point, a PV system installed on the roof of a residential building in Tehran, Iran, is experimentally studied here. For this system, the data gathered during a year is employed to find the values of the four indicated thermo-electrical characteristics. In order to enhance the accuracy, advanced infrared thermography is utilized, in which the photos taken by the thermal imaging camera is processed with developed code on the MATLAB interface. The results show that thermo-electrical indicators of the PV system change significantly throughout the year. With 32.3%, Vt is the indicator with the lowest annual variation. Rp and Iph change 1004.1 and 1943.9%, respectively, as well. Moreover, the simultaneous application of cooling techniques and concentrating strategies is suggested as a very efficient way to enhance the system performance.

Abstract 99: Apoptotic DNase DFFB mediates cancer persister cell mutagenesis and acquired drug resistance

Abstract Tumors frequently acquire resistance to therapy resulting in disease relapse and patient mortality. Therapeutic approaches to overcome acquired resistance are hindered by limited treatment options and the presence of multiple parallel resistance mechanisms. Rather than treating resistance after it emerges, it may possible to prevent it by inhibiting the adaptive processes which initiate resistance. However, these processes and the genes which control them are poorly understood. Here we report that drug-tolerant cancer persister cells, which constitute residual disease and seed relapse, undergo drug stress-induced sublethal apoptotic signaling resulting in activation of apoptotic DNase DFFB without cell death. DFFB induces DNA damage and mutagenesis in persister cells, revealing DFFB as a key regulator of stress-induced mutagenesis in persister cells. Furthermore, we found in multiple tumor types that DFFB is required for acquired resistance to targeted therapies. Mechanistically, DFFB induces multiple putative resistance mutations and may also promote epigenetic changes which result in resistance. These results reveal DFFB as a promising potential therapeutic target to prevent acquired resistance. In addition, this stress-sensing mutagenic mechanism may promote mutagenesis in other contexts including normal tissues because sublethal apoptotic signaling may result from a variety of physiological stresses. Citation Format: August Finley Williams, David Gervasio, Claire Turkal, Anna Stuhlfire, Michael Wang, Brandon Mauch, Ariel West, Michelle Paw, Mehrshad Hairani, Cooper Lathrop, Sophie Harris, Jennifer Page, Matthew Hangauer. Apoptotic DNase DFFB mediates cancer persister cell mutagenesis and acquired drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 99.

Experimental Formation and Mechanism Study for Super-High Dielectric Constant AlOx/TiOy Nanolaminates.

Super-high dielectric constant (k) AlOx/TiOy nanolaminates (ATO NLs) are deposited by an atomic layer deposition technique for application in next-generation electronics. Individual multilayers with uniform thicknesses are formed for the ATO NLs. With an increase in AlOx content in each ATO sublayer, the shape of the Raman spectrum has a tendency to approach that of a single AlOx layer. The effects of ATO NL deposition conditions on the electrical properties of the metal/ATO NL/metal capacitors were investigated. A lower deposition temperature, thicker ATO NL, and lower TiOy content in each ATO sublayer can lead to a lower leakage current and smaller loss tangent at 1 kHz for the capacitors. A higher deposition temperature, larger number of ATO interfaces, and higher TiOy content in each ATO sublayer are important for obtaining higher k values for the ATO NLs. With an increase in resistance in the capacitors, the ATO NLs vary from semiconductors to insulators and their k values have a tendency to decrease. For most of the capacitors, the capacitances reduce with increments in absolute measurement voltage. There are semi-circular shapes for the impedance spectra of the capacitors. By fitting them with the equivalent circuit, it is observed that with the increase in absolute voltage, both parallel resistance and capacitance decrease. The variation in the capacitance is explained well by a novel double-Schottky electrode contact model. The formation of super-high k values for the semiconducting ATO NLs is possibly attributed to the accumulation of charges.

A Faulty Line Selection Method for Flexible Grounding System Based on Transient Fault Data

In view of the problem of high-impedance grounding faults (HIFs) in flexible grounding systems (FGS), a faulty line selection method based on transient waveform slope is proposed in this paper. The change of zero sequence (ZS) current of faulty line and non-faulty line (before and after the neutral point parallel small resistance are put in) are analyzed. After the parallel small resistance is put into operation, the waveform slope curve of the transient zero sequence current of each line is obtained, and the modified Hausdorff distance (MHD) algorithm is used to obtain the transient slope matrix. The faulty line is identified by comparing the sizes of each row of elements in the matrix. Simulation verifies the effectiveness of the proposed faulty line selection method.

Fault location of flexible grounding distribution system based on multivariate modes and kurtosis calibration

Aiming at the problems of large fault location errors when the traditional traveling wave fault location is applied to flexible ground distribution systems. This paper proposed the fault location of flexible grounding distribution system based on multivariate modes and kurtosis calibration. Firstly, a disturbance signal is generated by putting a small resistor in parallel. This signal reaches the fault point and undergoes a sudden change, generating an aerial mode traveling wave signal. Secondly, it used the multivariate variational mode decomposition algorithm to decompose the aerial mode current and extracts the fault features. Then, the discrete kurtosis value is calculated for the highest frequency intrinsic mode function component. The moment of maximum kurtosis is the arrival time of the aerial mode current. Finally, it adopted the head-end detection device to calculate the fault distance. For the complex topology of the flexible ground distribution systems, the localization equation of the overhead line, cable line, and hybrid lines are studied, and the pseudo-fault points are excluded by adding auxiliary devices at the branch end. The simulation results demonstrate that the proposed method can accurately locate faults and is not affected by the fault's initial phase angle, transition resistance, and location.

Effect of pre-welding and welding voltage on thermal fatigue property of parallel gap resistance welded joint between Ag interconnector and Au/Ag back electrode of GaAs solar cell

Thermal reliability of Au/Ag interconnection is a crucial factor for the life of solar cell array during service in space. Although it is known that increasing the heat input can effectively improve the joint thermal fatigue resistance, such welding energy increase has to be achieved by coordination of various parameters to avoid damage to the solar cell matrix. Therefore, clarification of specific strengthening mechanism by different welding parameter is significant for the further improvement of joining quality. In this study, parallel gap resistance welding (PGRW) is used to perform micro-leveled interconnection between Au/Ag back electrode of triple-junction GaAs space solar cell and Ag interconnector. Besides the original parameter set, methods of welding voltage increase and pre-welding are used to improve the joining quality. Subsequently, the samples are subjected to temperature cycling environment between−160 °C and+120 °C for various cycles. According to the tensile-shear test results, although both methods have effectively improved the joint thermal fatigue property, quite different strengthening routes are shown. On one hand, joints strengthened by increasing welding voltage have higher tensile shear force than the ones strengthened by pre-welding. On the other hand, joints optimized by pre-welding show much stabler tensile-shear property. Material characterization by transmission electron microscopy (TEM) has explained the different strengthening routes that increase of voltage actually changes the joining mechanism from original solid-phase diffusion between Au/Ag interface into total melting, while pre-welding keeps the interface with partial solid-phase diffusion interface. Besides, electron back scattered diffraction (EBSD) results indicate that the evolution of residual stress concentration is the intrinsic reason for thermal fatigue failure of the Au/Ag interface.

Analytical solutions using special trans functions theory for current–voltage expressions of perovskite solar cells and their approximate equivalent circuits

Perovskite solar cells (PSC) have been recognized as devices with a constant increase in power conversion efficiency, confirming this promising technology’s upward trend. This paper deals with the mathematical modeling of current voltage and inverse voltage-current relationships of PSCs, in which standard equivalent circuits, as well as approximate equivalent circuits where series or parallel resistance is neglected, are investigated. Analytical solutions for voltage-current and current–voltage dependencies are derived for all investigated circuits. Furthermore, analytical solutions for short-circuit current and open-circuit voltage are derived. All nonlinear formulations of these dependencies are solved by applying special trans function theory. This paper proposes an enhanced algorithm called the Chaotic African Vultures Optimization Algorithm (Ch-AVOA) for PSC’s parameter estimation. The proposed algorithm is compared with other algorithms in terms of the convergence speed to the global solution and other statistical test measures to validate the algorithm’s efficiency.

Relationship between thermal and electrical conductivity curves of soils with a unimodal pore size distribution: Part 1. A unified series-parallel resistor model

Soil thermal conductivity (λ) and electrical conductivity (σ) characterize heat and electricity conduction through soils. Both λ and σ are affected by similar factors, such as soil water content (θ), texture, bulk density (ρb), temperature, structure, and organic matter content. Little is known about the quantitative relationship between λ and σ, and how soil texture and ρb modify the relationship. In this part one of a two-part series, we examine the correlation between λ(θ) and σ(θ) curves and develop a new model for normalized σ curves of soils with a unimodal pore size distribution. We introduce an Ohm’s law analogy to describe the λ and σ curves conceptually, based on a cubic cell unit model. A unified series–parallel resistor model considering θ and ρb effects is established for both λ(θ) and σ(θ) curves by considering heat and electrical conduction pathways (solid, solid–liquid, and liquid pathways) in the hydration, menisci, and continuous liquid ranges. Simultaneous measurements of θ, λ and σ with thermo-TDR sensors on two soils are used to examine the model performance at various values of ρb and θ. The modeled and measured λ (θ) and σ (θ) curves provide consistent trends, and the normalized λ and σ values vs. degree of saturation confirm the existence of an earlier reported “mirror image” phenomenon between the functions.

Relationship between thermal and electrical conductivity curves of soils with a unimodal pore size distribution: Part 2. Estimating bulk electrical conductivity from thermal conductivity

Soil thermal conductivity (λ) and electrical conductivity (σ) influence heat conduction and electrical conduction through soils. In Part 1 of this two-part series, we demonstrated that for soils with a unimodal pore size distribution, the λ and σ curves were interrelated and could be described with a unified series–parallel resistor model. Based on the conceptual model presented in Part 1, the “mirror image” phenomenon in the λ-σ relationship was further evaluated. Starting with the Lu et al. (2007) λ model, the “mirror image” phenomenon was used to derive a new normalized σ model. The new σ model was dependent on degree of water saturation (S), and shared the same shape parameters as those in the λ model. Here, the new σ model is examined using new datasets consisting of simultaneous thermo-TDR sensor measurements of soil water content (θ), λ and σ. New model σ values interpolated between known dry and saturated σ values agreed well with measured σ values, with RMSE values within 0.102 dS m−1 and bias values between −0.083 and 0.014 dS m−1 for a variety of soil samples. Using repeated in situ λ measurements made in soils during an evaporative drying period, the new σ model estimated normalized σ values with RMSEs within 0.015 dS m−1. The new σ model offers an effective way to estimate σ of unsaturated soils.