Including Temperature Effects Research Articles

Numerical identification of Preisach distribution function including temperature effects

Numerical identification of Preisach distribution function including temperature effects

Fast method for calibrated self-discharge measurement of lithium-ion batteries including temperature effects and comparison to modelling

The self-discharge rate is an important parameter to assess the quality of lithium-ion batteries (LIBs). This paper presents an accurate, efficient, and comprehensive method for measuring and understanding the self-discharge behaviour of LiB cells, considering factors such as temperature and cell to cell variability, as well as underlying electrochemical mechanisms. A method for precise potentiostatic self-discharge measurement (SDM) is demonstrated that is validated by measuring 21 commercial cylindrical 4.7 Ah cells at a state of charge (SoC) of 30%. The self-discharge current ranges between 3 and 6 μA at 23 °C, with an experimental noise level of 0.25 μA. At higher temperatures of 40 °C the self-discharge current increases to 97 μA. The temperature coefficient of voltage (TCV) is experimentally obtained by exposing the cells to a temperature profile with positive and negative step polarities and following the open circuit voltage (OCV) response. Observed TCVs range from +180 µV/K at 40% SoC to −320 µV/K at 0% SoC. For SDM temperature experiments, the cells were set to an SoC with a minimum TCV. From the SDM currents at different temperatures the Arrhenius kinetics and the electrochemical activation energy barrier is determined as 0.94 ± 0.14 eV, indicating chemical side reactions as source of self-discharge. For SDM modelling the electrochemical processes are coupled with a 3D temperature finite element model (FEM) and an electric circuit model resulting in a good overlap with the dynamics and time-constants of the experimental self-discharge curves. The primary challenges addressed are accurately measuring microampere (µA) discharge currents of high-quality cells, reducing measurement time, understanding the temperature dependence of self-discharge, determining activation energy, and demonstrating the applicability and generalization of SDM.

A comparison of phenomenlogical and micromechanical friction formulations including temperature effects

ABSTRACT Tires are the only contact points between vehicle and road and are mainly responsible for the driving safety. In the recent past, two different classes of friction formulations are predominant. Phenomenological approaches formulate a mathematical expression to describe the experimental results. By knowledge and experience, the formulations interpolate and extrapolate the behaviour captured by experiments. However, the formulations are highly dependent on the quality of the experiments and its influence factors. Therefore, a second class of friction models have been introduced, micromechanical approaches. The friction kinematics is described based on the deformation of the rubber in the contact zone, while sliding over a generalized surface. The basic idea is to obtain the friction coefficient solely by the surface properties and the material behaviour. As both approaches have advantages and disadvantages, it is hard to distinguish, which is more suitable to use in a certain application. In this contribution, different friction formulations are discussed and compared to each other. The mechanical behaviour of rubber is strongly influenced by temperature and so are its friction characteristics. Therefore, the friction formulations are expanded with respect to temperature. The discussed temperature dependent friction formulations are compared to each other for tire cornering simulations. The decrease of the cornering stiffness at large slip angles can be explained by friction induced temperature increase in the contact zone.

Effects of temporal abiotic drivers on the dynamics of an allometric trophic network model.

Current ecological research and ecosystem management call for improved understanding of the abiotic drivers of community dynamics, including temperature effects on species interactions and biomass accumulation. Allometric trophic network (ATN) models, which simulate material (carbon) transfer in trophic networks from producers to consumers based on mass-specific metabolic rates, provide an attractive framework to study consumer-resource interactions from organisms to ecosystems. However, the developed ATN models rarely consider temporal changes in some key abiotic drivers that affect, for example, consumer metabolism and producer growth. Here, we evaluate how temporal changes in carrying capacity and light-dependent growth rate of producers and in temperature-dependent mass-specific metabolic rate of consumers affect ATN model dynamics, namely seasonal biomass accumulation, productivity, and standing stock biomass of different trophic guilds, including age-structured fish communities. Our simulations of the pelagic Lake Constance food web indicated marked effects of temporally changing abiotic parameters on seasonal biomass accumulation of different guild groups, particularly among the lowest trophic levels (primary producers and invertebrates). While the adjustment of average irradiance had minor effect, increasing metabolic rate associated with 1-2°C temperature increase led to a marked decline of larval (0-year age) fish biomass, but to a substantial biomass increase of 2- and 3-year-old fish that were not predated by ≥4-year-old top predator fish, European perch (Perca fluviatilis). However, when averaged across the 100 simulation years, the inclusion of seasonality in abiotic drivers caused only minor changes in standing stock biomasses and productivity of different trophic guilds. Our results demonstrate the potential of introducing seasonality in and adjusting the average values of abiotic ATN model parameters to simulate temporal fluctuations in food-web dynamics, which is an important step in ATN model development aiming to, for example, assess potential future community-level responses to ongoing environmental changes.

Investigation of Fracture Mechanisms of Self-Reinforced Polypropylene/Polycarbonate Composites Subjected to Fatigue Loading

Self-reinforced polymeric composites have numerous advantages over traditional polymers, including increased mechanical strength, fracture toughness, and other mechanical properties. A special type of such composites can be obtained using non-conventional molding techniques. The investigated self-reinforced composites have layered structure, where layers are created by the same material in numerous molding cycles in the manufacturing process, and have gradient mechanical properties. According to this, it is of high interest to investigate structural behavior of these materials under fatigue loading, including temperature effects and fracture mechanisms occurring during fatigue. The results of the performed studies proved complex fracture mechanisms of self-reinforced polymeric composites manufactured using the applied unconventional injection molding technique due to variability of mechanical properties over the thickness.

Microscale THMC Modeling of Pressure Solution in Salt Rock: Impacts of Geometry and Temperature

Pressure solution, a mechanism that involves tight coupling between the geometry and thermal-hydro-mechanical-chemical (THMC) processes, plays an important role in diagenesis. In this study, we make the first attempt to conduct microscale THMC modeling to understand and quantify the impacts of geometry and temperature on pressure solution, taking natural salt rock as an example. This modeling capability is achieved by expanding a novel MC code that we developed previously (Hu et al. J Geophys Res: Solid Earth 126:e2021JB023112, 2021) to include temperature effects. We first conduct a simulation of an example that involves a single brine inclusion within a single halite grain and find that the temperature impact is limited for that case. We then extract geometry from an image of a natural salt rock and conduct simulations with different cases: (A) only temperature and no stress, (B) only stress and no temperature, and (C) with both stress and temperature. These different cases result in quite different phenomena. In case A, dissolution and precipitation occur across the entire system due to isolated pore space reaching a localized mass balance between dissolution, precipitation, and diffusion. In case B, intense geometric features (e.g., major asperities, inclusions) in one area undergo stress concentration, thus dominating pressure solution in that area. In case C, pressure solution is spread out at contacting highly stressed geometric features close to the hotter side. We conclude that geometric features dominate stress distribution, thus dominating pressure solution in a natural salt rock that may be affected by the temperature if a sufficient temperature gradient is applied.

Response of thin walled transversely stiffened clamped circular plates under uniform impulsive loads

Paper presents numerical models based on detailed characterization of various uncoupled damage models in a finite element analysis (FEA) setup to assess large deformations and observed ductile fracture failure modes of fully clamped circular plates as well as transversely stiffened circular plates in cross stiffened configurations under uniform impulsive loads. The numerical schemes have been based on a detailed definition of the constitutive properties based on inverse FEA simulations of the uniaxial tension test for the calibration of material and failure parameters. Experiments have been conducted using two types of freshly prepared mild steel uniaxial tension test specimens covering the envisaged range of stress tri-axialities to establish the steel plate material and fracture characteristics necessary for the calibration of the presented phenomenological damage models. Published results based on extensive experimental works by various authors on response of thin walled clamped circular plates under transversely applied uniform air blast loads, manifesting in large plastic deformations, thinning and tearing under various ductile fracture modes, have been used in the performance assessment of presented numerical models and procedure, which incorporate different damage models including temperature effects due to plastic dissipation. Based on evaluated performance of the discussed failure models within the FEA setup, a hybrid damage model with a tri-axiality based two part ductile fracture locus has been proposed, which shows very good correlation with the published experimental results, presented in terms of non-dimensional parameters over a wide range of impulsive loading. The validated numerical setup using the proposed hybrid damage model has also been used to predict the effect of transverse cross stiffened configurations of flat bar stiffeners on large deformations and ductile fracture of clamped circular plates under transverse uniform impulsive blast loads, along with some key insights in the evolution of plastic zones and damage progression.

Quantifying the effects of dissipation and temperature on dynamics of a superconducting qubit-cavity system

The superconducting circuits involving Josephson junction offer macroscopic quantum two-level system (qubit) which are coupled to cavity resonators and are operated via microwave signals. In this work, we study the dynamics of superconducting qubits coupled to a cavity with including dissipation in a subKelvin temperature domain. In the first step, a classical finite element method is used to simulate the cavities and basic circuit elements to model Josephson junctions. Then, the quantization of the circuit is done to obtain the full Hamiltonian of the system using energy participation ratios of the junctions. Once the parameters of Hamiltonian are obtained, the dynamics is studied via the Lindblad equation for an open quantum system using a realistic set of dissipative parameters and include temperature effects. Finally, we get frequency spectra and/or dynamics of the system with time which have quantum imprints. Such devices work at tens of milliKelvins and we search for a set of parameters which could enable to observe quantum behaviour at temperatures as high as 1 K.

Effect of temperature on CO oxidation over Pt(111) in two-dimensional confinement.

Confined catalysis between a two-dimensional (2D) cover and metal surfaces has provided a unique environment with enhanced activity compared to uncovered metal surfaces. Within this 2D confinement, weakened adsorption and lowered activation energies were observed using surface science experiments and density functional theory (DFT) calculations. Computationally, the role of electronic and mechanical factors responsible for the improved activity was deduced only from static DFT calculations. This demands a detailed investigation on the dynamics of reactions under 2D confinement, including temperature effects. In this work, we study CO oxidation on a 2D graphene covered Pt(111) surface at 90 and 593K using DFT-based ab initio molecular dynamics simulations starting from the transition state configuration. We show that CO oxidation in the presence of a graphene cover is substantially enhanced (2.3 times) at 90K. Our findings suggest that 2D confined spaces can be used to enhance the activity of chemical reactions, especially at low temperatures.

Численный анализ огнезащиты стальных конструкций

Introduction. A set of calculations validating the conditions of limit states is to accompany the design of buildings and structures. Calculations of standard and non-standard combinations of loads and impacts are performed. Special loads include temperature effects from explosions and fires. Such effects greatly reduce the bearing capacity of metal structures. To protect metal structures from temperature effects, optimally selected fire proofing materials (varnishes, paints, various types of cladding) should be used. Numerical calculation methods allow analyzing the performance of building structures, exposed to temperature effects, and help select the necessary characteristics and thicknesses of fire proofing materials. Materials and methods. A metal hinged beam is used to analyze the influence of fire proofing, or lining made of fire-resistant gypsum sheets (FRGSh). Analytical and numerical methods of calculations were used to obtain the fire resistance limit of beams with cladding. The analytical method is based on the laboratory studies of fire resistance, as a result of which nomograms were obtained. The numerical method is implemented by Lira 10.12 software package. Results. Analytical and numerical methods were used to identify the fire-resistance limits for a beam that had FRGSh cladding. Temperature field mosaics in the elements along the thickness of the structure, as well as graphs of temperature changes and temperature fields in time were obtained using the numerical method. The obtained results showed good convergence. Conclusions. The use of numerical methods makes it possible to quickly and optimally select the required thickness of fire proofing for a steel structure. Calculation results are highly dependent on the characteristics of the materials in question, as well as the heat transfer environment.

Dynamic stability in phosphorene bilayer with different stacking orders: A first principle study

Phosphorene, a two-dimensional (2D) material obtained by chemical and mechanical exfoliation of its bulk structure named black phosphorus, has recently been of great importance because of its interesting properties. The intercalation of lithium and sodium in phosphorene multilayer can modify the reordering atoms in the structure lead to different properties. In this work we are interested in bilayer phosphorene as the thinnest multilayer structure of phosphorene nanosheets that can provide deep understanding of the interlayer coupling and the stacking dependent phonon vibration modes and the corresponding Raman scattering. Four different stacking orders can be predicted to exist in bilayer phosphorene and needs to be explored experimentally due to the modified properties. Here, we investigate the identification of the four-bilayer stacking sequences (AA, AB, AC, and AD) using Density Functional Theory (DFT), with the GGA and HSE approximations including the van der Waals correction (Grimmes-D3). We identify the variation of the electronic band gap based on the structural difference, interlayer interactions and charge density distribution. A comparison in the phonon vibration modes and Raman spectra between the different stacking orders, show to be useful for monitoring the changes in the bilayer phosphorene structure and identify the rearrangement type of atoms in bilayer phosphorene experimentally. Including temperature effect using AIMD, a description of the structural stability of the bilayer phosphorene structures was reviewed in detail.

Augmenting zero-Kelvin quantum mechanics with machine learning for the prediction of chemical reactions at high temperatures

The prediction of temperature effects from first principles is computationally demanding and typically too approximate for the engineering of high-temperature processes. Here, we introduce a hybrid approach combining zero-Kelvin first-principles calculations with a Gaussian process regression model trained on temperature-dependent reaction free energies. We apply this physics-based machine-learning model to the prediction of metal oxide reduction temperatures in high-temperature smelting processes that are commonly used for the extraction of metals from their ores and from electronics waste and have a significant impact on the global energy economy and greenhouse gas emissions. The hybrid model predicts accurate reduction temperatures of unseen oxides, is computationally efficient, and surpasses in accuracy computationally much more demanding first-principles simulations that explicitly include temperature effects. The approach provides a general paradigm for capturing the temperature dependence of reaction free energies and derived thermodynamic properties when limited experimental reference data is available.

Reliability-based structural response of single-bay steel frames in case of fire and in post-fire conditions

The actual codes on design procedures to assess the structural reliability in case of fire allows for a whole scope of methodologies to be used. At one end of the spectrum, the codes allow to simply combine design rules with member analysis using tabulated data or simplified calculation models. On the other extreme end of the spectrum, complex performance-based design approaches are proposed, the results of which are unique and highly dependent on the system’s boundary conditions. Between those two extreme options, there are several other methodologies including the possibility to use probabilistic approaches. In this paper, reliability assessment of structures is based on the force-based method including temperature effects as well. This method is developed for single-bay portal frame and is based on the combined failure probability of five critical sections. All data needed to generate a probability density functions of the thermal actions on the structure is collected and described. Heat transfer equations of unprotected steel are used to calculate the profile temperature and reduction of mechanical characteristics during and after the fire. Coupling of the probabilistic-based thermal actions to the force-based method enables to create numerous simulations (Monte Carlo technique), and thus enable the system during and after a fire. This analysis is done for different load levels (self-weight), portal frame geometries and for several fire scenarios. Last, the post-fire behaviour of structural carbon steel single-bay portal frames is carefully investigated.

Florida’s Harmful Algal Bloom (HAB) Problem: Escalating Risks to Human, Environmental and Economic Health With Climate Change

Harmful Algal Blooms (HABs) pose unique risks to the citizens, stakeholders, visitors, environment and economy of the state of Florida. Florida has been historically subjected to reoccurring blooms of the toxic marine dinoflagellate Karenia brevis (C. C. Davis) G. Hansen & Moestrup since at least first contact with explorers in the 1500’s. However, ongoing immigration of more than 100,000 people year–1 into the state, elevated population densities in coastal areas with attendant rapid, often unregulated development, coastal eutrophication, and climate change impacts (e.g., increasing hurricane severity, increases in water temperature, ocean acidification and sea level rise) has likely increased the occurrence of other HABs, both freshwater and marine, within the state as well as the number of people impacted by these blooms. Currently, over 75 freshwater, estuarine, coastal and marine HAB species are routinely monitored by state agencies. While only blooms of K. brevis, the dinoflagellate Pyrodinium bahamense (Böhm) Steidinger, Tester, and Taylor and the diatom Pseudo-nitzschia spp. have resulted in closure of commercial shellfish beds, other HAB species, including freshwater and marine cyanobacteria, pose either imminent or unknown risks to human, environmental and economic health. HAB related human health risks can be classified into those related to consumption of contaminated shellfish and finfish, consumption of or contact with bloom or toxin contaminated water or exposure to aerosolized HAB toxins. While acute human illnesses resulting from consumption of brevetoxin-, saxitoxin-, and domoic acid-contaminated commercial shellfish have been minimized by effective monitoring and regulation, illnesses due to unregulated toxin exposures, e.g., ciguatoxins and cyanotoxins, are not well documented or understood. Aerosolized HAB toxins potentially impact the largest number of people within Florida. While short-term (days to weeks) impacts of aerosolized brevetoxin exposure are well documented (e.g., decreased respiratory function for at-risk subgroups such as asthmatics), little is known of longer term (>1 month) impacts of exposure or the risks posed by aerosolized cyanotoxin [e.g., microcystin, β-N-methylamino-L-alanine (BMAA)] exposure. Environmental risks of K. brevis blooms are the best studied of Florida HABs and include acute exposure impacts such as significant dies-offs of fish, marine mammals, seabirds and turtles, as well as negative impacts on larval and juvenile stages of many biota. When K. brevis blooms are present, brevetoxins can be found throughout the water column and are widespread in both pelagic and benthic biota. The presence of brevetoxins in living tissue of both fish and marine mammals suggests that food web transfer of these toxins is occurring, resulting in toxin transport beyond the spatial and temporal range of the bloom such that impacts of these toxins may occur in areas not regularly subjected to blooms. Climate change impacts, including temperature effects on cell metabolism, shifting ocean circulation patterns and changes in HAB species range and bloom duration, may exacerbate these dynamics. Secondary HAB related environmental impacts are also possible due to hypoxia and anoxia resulting from elevated bloom biomass and/or the decomposition of HAB related mortalities. Economic risks related to HABs in Florida are diverse and impact multiple stakeholder groups. Direct costs related to human health impacts (e.g., increased hospital visits) as well as recreational and commercial fisheries can be significant, especially with wide-spread sustained HABs. Recreational and tourism-based industries which sustain a significant portion of Florida’s economy are especially vulnerable to both direct (e.g., declines in coastal hotel occupancy rates and restaurant and recreational users) and indirect (e.g., negative publicity impacts, associated job losses) impacts from HABs. While risks related to K. brevis blooms are established, Florida also remains susceptible to future HABs due to large scale freshwater management practices, degrading water quality, potential transport of HABs between freshwater and marine systems and the state’s vulnerability to climate change impacts.

Evaluating Degradation Coefficients from Existing System Models

A generalization of the Degradation-Entropy Generation (DEG) theorem to multi-disciplinary multi-physics system-process analysis via a combination with pre-existing system models is presented in this article. Existing models and the DEG methodology are reviewed, and a method for evaluating degradation coefficients Bi is proposed. These coefficients characterize the system’s transformation based on active dissipative mechanisms, including temperature effects. The consistency of entropy generation in characterizing degradation is then inherited by these often-empirical system models, thereby rendering them more robust and applicable to similar systems without the need for numerous tests and measurements for model corrections. The approach applies to all systems and can quickly analyze and predict a system’s performance and degradation, even in the absence of experimental data (using known properties and material constants). Demonstrated applications herein include mechanically loaded systems (frictional wear, grease shearing, fatigue loading), electrochemical energy systems, thermal processes, and others.

Modeling interaction between CO2, brine and chalk reservoir rock including temperature effect on petrophysical properties

Carbon dioxide (CO2) capture and sequestration through CO2 enhanced oil recovery (EOR) in oil reservoirs is one of the approaches considered to reduce CO2 emission into the atmosphere. The injection of CO2 into a subsurface geological formation may lead to chemical reactions that may affect the formation pore structure and characteristics. In this study, the effect of CO2–brine–rock interaction on the rock petrophysical properties and mineral volume fraction was numerically investigated during CO2 injection into a chalk reservoir rock. A 3D numerical modeling and simulation were conducted using COMSOL® Multiphysics commercial software of computational fluid dynamics (CFD) to simulate CO2–brine core flooding process in a chalk core. The model was validated against a core–scale experimental data from literature. Simulation differential pressure data matched the literature experimental data closely and consistently indicating good agreement between them. Temperature effect on the performance of CO2–brine–chalk sequestration was also evaluated in the present study. Results indicated that porosity was only slightly affected by temperature increase during CO2 injection in contrast to permeability that was substantially affected by temperature. Moreover, chemical reactions enhanced as temperature increased leading to significant increase in permeability. Thus, carbonated brine sequestration excelled at elevated temperature due to increased acidity which governs the sequestration process. The developed model maybe considered as a reliable tool to optimize various operating parameters of CO2–brine sequestration.

Exotic IMPATT Oscillator for Terahertz Thermography: Feasibility Studies in Hepatic Tumor Detection

Hepatic carcinoma is a major type of malignant tumor that needs a novel non-invasive/minimal invasive method for its early diagnosis. This paper for the first time reports a new scheme of diagnosis of hepatic tumor by studying the corresponding terahertz (THz) thermographs. A solid-state source of THz radiation (IMPact-ionisation avalanche transit time oscillator), capable of working at room temperature, is proposed in this paper and the THz non-linear characteristic of the device and system are studied through an in-house developed quantum modified classical drift diffusion simulator. The validity of the model is also established by comparing the results with experimental observations. The model includes temperature effects, quantum size effect, lattice phonon scatterings, and noise study. A COMSOL-based THz-thermograph model is further developed and a comparative analysis with those of microwave thermographs is reported. To the best of authors’ knowledge, this is the first report on studying the prospects of an exotic type non-invasive terahertz <p+-n-n+> radiation source for use in T-ray thermography studies of hepatic tumors detection with two sets of different radiation exposure.

Systems Biology Model of Cerebral Oxygen Delivery and Metabolism During Therapeutic Hypothermia: Application to the Piglet Model.

Hypoxic ischaemic encephalopathy (HIE) is a significant cause of death and disability. Therapeutic hypothermia (TH) is the only available standard of treatment, but 45-55% of cases still result in death or neurodevelopmental disability following TH. This work has focussed on developing a new brain tissue physiology and biochemistry systems biology model that includes temperature effects, as well as a Bayesian framework for analysis of model parameter estimation. Through this, we can simulate the effects of temperature on brain tissue oxygen delivery and metabolism, as well as analyse clinical and experimental data to identify mechanisms to explain differing behaviour and outcome. Presented here is an application of the model to data from two piglets treated with TH following hypoxic-ischaemic injury showing different responses and outcome following treatment. We identify the main mechanism for this difference as the Q10 temperature coefficient for metabolic reactions, with the severely injured piglet having a median posterior value of 0.133 as opposed to the mild injury value of 5.48. This work demonstrates the use of systems biology models to investigate underlying mechanisms behind the varying response to hypothermic treatment.

Theoretical simulation of vibrationally resolved electronic spectra of combustion intermediates including temperature effect

It is difficult to diagnose qualitatively the radicals and ions produced by high temperature combustion of hydrocarbon fuel. An effective way is to simulate their fine electronic spectra. In this work, a method of spectral calculation considering temperature effect is proposed to simulate the vibrationally resolved electronic spectra of the typical intermediates NH* and NO+ produced by hydrocarbon fuel combustion. The results show that only the theoretical spectra simulated at high temperature are consistent with the experimental ones, indicating that temperature has an important influence on the fine electronic spectra of combustion intermediates. The vibrationally resolved electronic spectra of CH2*, CH3*, C2H* and C2H3* radicals, which are important intermediates of combustion core mechanism, are predicted by this method, and their main vibrational peaks are assigned in detail. We hope that the predicted electronic spectra can be confirmed in future experiments, which will provide a reliable theoretical basis for establishing correct combustion reaction mechanism.

Analysis of structural phase stability and thermo-elastic properties of alloy of rare earth sulfides (LaxPr1-xS) under high pressure at room temperature

The high pressure structural behavior and associated properties of mixed rare earth sulfides (LaxPr1-xS) have been investigated by applying a Realistic Interaction Potential (RIP) model, including temperature effects. This model explains the inter-atomic interactions as it incorporates long range coulomb interaction; three body interaction (TBI), vdW (van der Waals) interaction, short range overlap repulsive interaction up to second neighbors and zero point energy effects including the temperature effects. We have predicted the high pressure structural phase transition from NaCl (B1 -type) to CsCl-type (B2-type) phase and associated volume drops for these compounds. The pressure induced phase transition is found to be a first order. Estimation of the elastic, thermal properties and Every’s parameters of these compounds has been performed during study. The results obtained are found to be in reasonable agreement with experimental and other theoretical data.