Wide Plateau Research Articles

Assessment of Hysteresis Models for LiFePO4

The selection of the cathode material is an important task in the design phase of batteries for mobile applications. One material of increasing interest is LiFePO4 (LFP) due to its improved energy density, good thermal stability and durability. In contrast to other commonly used cathode materials, LFP features a clear phase separation between the lithium rich and the lithium poor phase, leading to a pronounced voltage plateau over wide ranges of state of charge (SOC). The level of this plateau also changes for charge and discharge operation, even at very low C-rates. This voltage hysteresis in combination with the wide plateau gives some ambiguity to the correlation between voltage and SOC, which is a challenge for battery management systems. Thus its correct description is crucial if a cell model is meant to serve as virtual twin supporting control function development and calibration. Beyond that, a highly dynamic battery development process requires models that run significantly faster than real-time and parametrization processes which allow for accurate validation and easy adaptation to modified electrodes. A simulation approach complying with these requirements is the electrochemical pseudo-two dimensional (P2D) model, though adaptions to the core model are needed to appropriately capture hysteresis-affected voltage plateau characteristics for phase-separating materials such as LFP.The goal of this study is to extend an existing P2D framework with two approaches capable of describing hysteresis effects and analyzing these extensions regarding result plausibility, computational cost and effort of parametrization. The first model of interest is based on the one-state hysteresis model proposed by Plett. This approach allows for fast simulation and accurate reproduction of the charge and discharge voltages at low C-rates but lacks deeper physical consideration of the phase-separating origin of the hysteresis and thus might lose accuracy to predict system responses on dynamic pulses. In this approach, the voltage hysteresis is not a simulation result, it is due to the input of two separate open circuit voltages for charge and discharge. The second model of interest applies variable solid diffusion (VSSD) featuring a reduced Fickian diffusion coefficient in the plateau region. Lower diffusion at a given C-rate leads to steeper concentration gradients between lithium rich and lithium poor phase. With this approach, effective phase boundaries within the representative particles can be obtained. In the limiting case, when the Fickian diffusion coefficient becomes zero or even negative at some lithium concentration, phase separation persists also when no current is applied. In this setting, the voltage hysteresis at low C-rates is an emergent phenomenon, it is not an input. The physical basis of the approach also allows to consider mechanical stresses and their impact on the voltage gap between charge and discharge. Concentration gradients cause a mismatch of volume demands and thus lead to local stresses, which in turn alter the chemical potential.Results emphasizing advantages and disadvantages of the two hysteresis models are presented. Charge and discharge simulations are performed for several C-rates and the voltage hysteresis is extrapolated to infinitely small currents. Furthermore, the effect of resting phases with zero current as in Galvanostatic Intermittent Titration Technique measurements is discussed. As hysteresis models are often tested only on charge/discharge cycles with constant currents over large SOC regions, the responses of the simulation models are also assessed in pulse tests and dynamic profiles giving a realistic picture of automotive applications. Here special focus is put on energetical aspects of the one-state model and on intra-particle concentration profiles for the VSSD model.

Long-Lifespan Fibrous Aqueous Ni//Bi Battery Enabled by Bi2O3-Bi2S3 Hierarchical Heterostructures.

Bismuth oxide (Bi2O3) materials are considered as great promising anodes for aqueous batteries on account of the high capacity as well as wide potential plateau. Nevertheless, the low conductivity and severe volumetric change of Bi2O3 in the course of cycling are the main limiting factors for their application in energy-storage systems. Herein, we propose and design unique hierarchical heterostructures constructed by Bi2O3 and Bi2S3 nanosheets (NSs) manufactured immediately on the surface of carbon nanotube fibers (CNTFs). The Bi2O3-Bi2S3 (BO-BS) exhibits enhanced conductivity and increased stability in comparison with pure Bi2O3 and Bi2S3. The BO-BS NSs/CNTF electrode indicates exceptional rate capability and cycling stability, while creating a high reversible capacity of 0.68 mAh cm-2 at 4 mA cm-2, as anticipated. Additionally, the quasi-solid-state fibrous aqueous Ni//Bi battery that was built with the BO-BS NSs/CNTF anode delivers an exceptional cycling stability of 52.7% capacity retention after 4000 cycles at 80 mA cm-2, an ultrahigh capacity of 0.35 mAh cm-2 at 4 mA cm-2, and a high energy density of 340.1 mWh cm-3 at 880 mW cm-3. This work demonstrates the potential of constructing hierarchical heterostructures of bismuth-based materials for high-performance aqueous Ni//Bi batteries and other energy-storage devices.

Imprints of a supercooled phase transition in the gravitational wave spectrum from a cosmic string network

A network of cosmic strings (CS), if present, would continue emitting gravitational waves (GW) as it evolves throughout the history of the Universe. This results in a characteristic broad spectrum making it a perfect source to infer the expansion history. In particular, a short inflationary period caused by a supercooled phase transition would cause a drop in the spectrum at frequencies corresponding to that event. However, the impact on the spectrum is similar to the ones caused by an early matter-dominated era or from particle production, making it difficult to disentangle these different physical origins. We point out that, in the case of a short inflationary period, the GW spectrum receives an additional contribution from the phase transition itself. This leads to a characteristic imprint of a peak on top of a wide plateau both visible at future GW observatories.

Late Miocene large-sized Bovidae (Mammalia) from Dimeh, SW Iran: Contribution to depositional diachrony and palaeobiogeography

We describe here cranial and dental material of large bovids (Bovidae, Mammalia) from the Upper Miocene fossil site of Dimeh, SW Iran. Six taxa have been recognized: Palaeoryx cf. pallasi, Skoufotragus laticeps, Plesiaddax? sp., Samokeros minotaurus, Tragoportax cf. amalthea and the new species Tragoportax perses. The (i) shortened, rectangularly shaped basioccipital with strong anterior tuberosities, (ii) weakly textured and subtriangularly shaped rugose area delimited by strong temporal ridges, (iii) deep and wide intercornual plateau, (iv) narrow interparietal, (v) wide nasals, and (vi) strongly tilted backwards, clearly heteronymously twisted horncores with sharp, flaring anterior keel, and highly positioned distal demarcation, are features that in combination differentiate T. perses nov. sp. from any other known Eurasian species of this genus. Ιn addition, its particular morphological features bring it closer to certain specimens of the Afro-Arabian region assigned to T. cyrenaicus. The new data, along with previous and revised ones on the small antelopines, complete the systematics of the Dimeh bovid assemblage and allow further discussing its significance at local and regional scales.

Crystallization-controlled fusion mechanism of the amorphous fly ash from the Shell coal gasifier by particle sieving

The mineral in coal is transformed to the fly ash of different particle sizes during the entrained flow coal gasification, causing the ash deposition problem on the radiant syngas cooler. In this study, the fusion behavior of fly ash collected from a Shell coal gasifier was analyzed by particle sieving. Results indicated that the fusibility of amorphous fly ash was influenced by the anorthite crystallization at high temperature. The fusion process of fly ash particle was divided into the sintering stage, plateau stage, and melting stage, which were caused by the flow of the amorphous fly ash, anorthite crystallization, and anorthite melting, respectively. The high theoretical anorthite content and the low fly ash viscosity improved the anorthite crystallization reaction in the fly ash particles <45 μm, resulting in a wide plateau stage, narrow melting stage, and high ash fusion temperatures (AFTs). Therefore, the fusion behavior of fly ash particles <45 μm followed “melting-dissolution” mechanism. In contrast, the fusion of fly ash particles >45 μm belonged to the “softening-melting” mechanism for the weak anorthite crystallization behavior. The fly ash particles <45 μm may cause the serious ash deposition problems for its low viscosity.

20 ps time resolution with a fully-efficient monolithic silicon pixel detector without internal gain layer

A second monolithic silicon pixel prototype was produced for the MONOLITH project. The ASIC contains a matrix of hexagonal pixels with 100 μm pitch, readout by a low-noise and very fast SiGe HBT frontend electronics. Wafers with 50 μm thick epilayer of 350 Ωcm resistivity were used to produce a fully depleted sensor. Laboratory and testbeam measurements of the analog channels present in the pixel matrix show that the sensor has a 130 V wide bias-voltage operation plateau at which the efficiency is 99.8%. Although this prototype does not include an internal gain layer, the design optimised for timing of the sensor and the front-end electronics provides a time resolutions of 20 ps.

Quasi-static compressive behaviour of epoxy composites reinforced with crumb rubber

Quasi static compressive response of crumb rubber-epoxy composites was examined by varying the crumb rubber composition (0, 10, 20 and 30 vol.%). All the composites, irrespective of the strain rates, depict elastic regions tailed by a wide plateau area that is credited with the densification of rubber particulates. Higher strains to failure of composites were revealed as compared with neat epoxy signifying higher energy absorption ability of constituents. The modulus of elasticity of composites was noted to be lower than neat epoxy specimens, irrespective of the strain rates. Irrespective of strain rates, the strength of all the composites were inferior to neat epoxy specimens. Energy absorption of EC-30 was higher compared to EC-20 and EC-10 and noted to be increased in the range of 6–14% for 0.1 mm/min strain rate while it increases in the range of 5–9% for 0.01 mm/min strain rate, respectively. Rubber-toughening mechanism was credited with the increase in energy absorption of composites. Higher energy absorption of composites was mainly due to higher strain realisation indicating more deformation ability. Fracture features of specimens were analysed by scanning electron microscope.

Selecting optimal R6TX2 intermetallics (R = Gd, Tb, Dy; T = Mn, Fe, Co, Ni; X = Sb, Te) for magnetic refrigeration.

A complete experimental study of the physical properties playing a relevant role in the magnetic refrigeration application (structural, magnetic, magnetocaloric and thermal) has been performed over nine selected Fe2P-type R6TX2 (R = Gd, Tb, Dy; T = Mn, Fe, Co, Ni; X = Sb, Te) intermetallic compounds, to work close to room temperature. Two magnetic phase transitions are observed for these materials: a paramagnetic to ferromagnetic transition in the range of 182-282 K and a spin reorientation transition in the range of 26-76 K. As a consequence, two peaks related to a direct magnetocaloric effect (DMCE) appear with the magnetic entropy change, generating a wide table-like plateau region in between both peaks, which is required to improve the efficiency of refrigerators following an Ericsson cycle. The highest magnetic entropy peak value for μ0ΔH = 5 T is found for Tb2Dy4FeSb2, with 7.72 J kg-1 K-1 around 182 K. For the same applied field the other compounds show moderate values around room temperature (2.88-4.53 J kg-1 K-1). However, the superposition of the two peaks results in huge refrigerant capacity values, up to RCFWHM(5 T) = 1103.04 J kg-1 in the case of Tb2Dy4FeSb2. The thermal diffusivity, thermal effusivity, thermal conductivity and specific heat capacity have been measured at room temperature, and the temperature dependence of the former has been obtained around the relevant magnetic phase transition region, with values in the range of 1.3-2.3 mm2 s-1, which are good for magnetic refrigerators at high working frequencies. The study is completed with a rigorous critical behavior analysis of the second order PM-FM transition. The critical exponent γ points to long range order interactions, in general, while β values are in the range of 0.59-0.90, indicating a deviation from theoretical models as a reflection of the magnetic complexity in these compounds. The critical exponents have been used to confirm the scaling relations of magnetocaloric properties, and the scaling of refrigerant capacity (RC) values in materials exhibiting two magnetic phase transitions is addressed, concluding that for a correct scaling of RC the magnetic entropy change peak must be considered symmetric. The role of each atom in the properties of the compounds is discussed.

Influence of Climate and Tectonics on the Crystallization of Carnallite and Related Salts in the Congolese Atlantic Basin during the Lower Cretaceous, Republic of Congo

Lithological, petrographic, and morphoscopic studies were conducted on cuttings and cores from three boreholes drilled in the Loemé salt, Kanga site, Republic of the Congo, to determine 1) the preferential conditions for crystallization of carnallite and associated salts and 2) to reconstruct paleoenvironmental and paleoclimatic conditions at the time of sedimentation. Sequential analysis of logs, sedimentary structures, carnallitite facies and associated salts concluded to the existence of a potassic carnallitite lagoon basin with low water cover, on a very wide and extensive plateau, affected by coastal waves and swells resulting from successive collapses. This basin evolved in two phases: confined and then open. The regular stratifications of halite, the rhythmicity of the halite-carnallitite elementary sequences are characteristic of salts that precipitated in relatively stable brines. These salts are therefore tectonosedimentary. The brecciated facies of the carnallitites sometimes associated with tachyhydrite result from the evolution of these deposits into salt crusts reworked by the surges into subaquatic allochemical gravelly cords under water. These crusts mark stages of partial and complete drying of the basin in a very hot and arid climate. Prolonged exposure of halite brines as well as their homogenization by surges accelerated evaporation and their abrupt evolution into carnallite brines obstructing the fossilization of sylvite. The precipitation of tachyhydrite marks the final stage of the successive complete drying of the basin.

Grain boundary re-crystallization and sub-nano regions leading to high plateau figure of merit for Bi2Te3 nanoflakes

Solvothermally synthesized Bi2Te3 nanoflakes can re-crystallize preferentially at the grain boundaries to form sub-nano boundary regions with a width &lt;2 nm leading to a wide plateau figure of merit (zT) of &gt;1.2 (from ∼323 to ∼423 K).

Insight into ground-state spin arrangement and bipartite entanglement of the polymeric coordination compound [Dy[formula omitted]Cu[formula omitted]][formula omitted] through the symmetric spin-1/2 Ising–Heisenberg orthogonal-dimer chain

The ground-state spin arrangement and the bipartite entanglement within Cu2+-Cu2+ dimers across the magnetization process of the 4f-3d heterometallic coordination polymer [Dy(hfac)2(CH3OH)2Cu(dmg)(Hdmg)2]n (H2dmg = dimethylglyoxime, Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) are theoretically examined using the symmetric isotropic spin-1/2 Ising–Heisenberg orthogonal-dimer chain. The numerical results point to five possible ground states of the compound with three different degrees of the quantum entanglement within Cu2+-Cu2+. Besides the standard ferrimagnetic and saturated phases without quantum entanglement of Cu2+ ions, which are manifested in low-temperature magnetization curve as wide plateaus at the non-saturated magnetization 16.26μB and at the saturation value 20.82μB, respectively, one also finds an intriguing singlet-like phase with just partial entanglement within Cu2+-Cu2+ and two singlet phases with fully entangled Cu2+-Cu2+ dimers. The former quantum phase can be identified in the low-temperature magnetization process as very narrow intermediate plateau at the magnetization 9.27μB per unit cell, while the latter ones as zero magnetization plateau and intermediate plateau at the magnetization 18.54μB. Non-monotonous temperature variations of the concurrence, through which the entanglement within cooper dimers is quantified, point to the possible temporary thermal activation of the entangled states of Cu2+-Cu2+ also above non-entangled ferrimagnetic and saturated phases.

Decoupled Lithospheric Folding, Lower Crustal Flow Channels, and the Growth of Tibetan Plateau

AbstractThe growth mechanism of the Tibetan Plateau, postulated by a number of hypotheses, remains under intense debate. Our analysis of recent satellite‐based gravity model reveals that Tibetan lithosphere has been decoupled and folded. It is further evidenced by the existence of crustal melts and channel flow that have been observed by seismic and magnetotelluric explorations. Based on 3D geodynamic simulations, we elucidate the exact buckling structures in the upper crust and lithospheric mantle: at mixed wavelengths between ∼240 and ∼400 km, the lower crustal viscosity is smaller than ∼1019 Pa·s, implicating weak lower crustal flow beneath the Plateau. This mixed wavelength is consistent with the result of our inverse gravity modeling. Our results facilitate a new plausible hypothesis that the decoupled lithospheric folding mechanism can explain the growth mechanism of the anomalously thick and wide Tibetan Plateau by conflating our idea and contemporary hypothesized scientific findings.

Usability of alloys with different composition as electrode for electrochemical reduction of ferricyanide ion

An experimental work was performed to investigate the usability of 8 metallic alloys with different composition in electrochemical limiting diffusion current technique employing the cathodic reduction of ferricyanide. All the alloys exhibited a limiting current plateau region in their voltage–current behaviour, but not all gave a wide and smooth plateau, except one with almost pure Ni. With the alloys of including more than 50% Ni, as Ni ratio of the metal increased, smoother and wider plateau was attained, and the electrode containing 99% Ni gave the smoothest plateau. The other alloys tested can only be used as electrode in the limiting diffusion current technique in low flow velocities in which the transfer of the active ion to the electrode surface is as slow as that the mass transfer controls the rate of system.

Impact damping and vibration attenuation in nematic liquid crystal elastomers

Nematic liquid crystal elastomers (LCE) exhibit unique mechanical properties, placing them in a category distinct from other viscoelastic systems. One of their most celebrated properties is the ‘soft elasticity’, leading to a wide plateau of low, nearly-constant stress upon stretching, a characteristically slow stress relaxation, enhanced surface adhesion, and other remarkable effects. The dynamic soft response of LCE to shear deformations leads to the extremely large loss behaviour with the loss factor tanδ approaching unity over a wide temperature and frequency ranges, with clear implications for damping applications. Here we investigate this effect of anomalous damping, optimising the impact and vibration geometries to reach the greatest benefits in vibration isolation and impact damping by accessing internal shear deformation modes. We compare impact energy dissipation in shaped samples and projectiles, with elastic wave transmission and resonance, finding a good correlation between the results of such diverse tests. By comparing with ordinary elastomers used for industrial damping, we demonstrate that the nematic LCE is an exceptional damping material and propose directions that should be explored for further improvements in practical damping applications.

Influence of Friction Stir Welding Parameters on Joint Defects, Temperature and Hardness of AA6061-T6 and S27JR Mild Steel FSW Joint

The influence of welding parameters such as tool plunge depth, tool travel speed and tool tilt angle on welding temperature during friction stir welding of AA6061-T6 and S275JR mild steel was the focus of this research. Thermocouple placed in the aluminum alloy plate prior to welding was used to measure the temperature during the welding of joints under different set of parameter values. Joint appearance as well as defects occurring on the surface or within the joint was observed. Microhardness profiles were also taken by measuring microhardness values across the cross section of joints. Excessive flash, tunnel defects and insufficient welding were the type of weld defects observed on different joints with different parameters. Defects were attributed to the varied parameter values affecting the heat generation as well as the flow of the plasticized material. Highest temperature was recorded by the joint fabricated using the largest tool plunge depth, owing to the increased downwards pressure. Microhardness profiles were seen to be similar for all the welded joints. A “plateau” of low microhardness value was observed for all joints associated with the thermomechanically affected zone (TMAZ) and heat affected zone (HAZ). A wider plateau was observed for joints welded with higher tool plunge depth due to higher temperature.

May thermal imaging be useful in the assessment of dental anaesthesia? Preliminary study

The main goal of this study was to find out if thermal imaging may be useful in the evaluation of two types of anaesthetic injections—with and without a vasoconstrictor. There were 20 patients (13 women and 7 men) involved in the study. The group was divided into two subgroups. Patients from the first subgroup received infiltration anaesthesia (so-called: IA) of lidocaine (2 mL) and the second group included patients, who received infiltration anaesthesia (so-called: IAN) of lidocaine with 2% noradrenaline (2 mL). The obtained results showed a significant increase in the average temperature 10 min after the injection. In the IA group, the temperature increase was nearly 1.0 °C what was 0.3 °C higher than in the IAN group. Moreover, temperature changes showed a wide plateau between 10 and 25 min after anesthesia administration. The effect of temperature rise was also observed on the contralateral cheek where there was no intervention renders by a contralateral reflex.

Losing the dogmatic view of cerebral autoregulation.

In 1959, Niels Lassen illustrated the cerebral autoregulation curve in the classic review article entitled Cerebral Blood Flow and Oxygen Consumption in Man. This concept suggested a relatively broad mean arterial pressure range (~60–150 mmHg) wherein cerebral blood flow remains constant. However, the assumption that this wide cerebral autoregulation plateau could be applied on a within‐individual basis is incorrect and greatly variable between individuals. Indeed, each data point on the autoregulatory curve originated from independent samples of participants and patients and represented interindividual relationships between cerebral blood flow and mean arterial pressure. Nonetheless, this influential concept remains commonly cited and illustrated in various high‐impact publications and medical textbooks, and is frequently taught in medical and science education without appropriate nuances and caveats. Herein, we provide the rationale and additional experimental data supporting the notion we need to lose this dogmatic view of cerebral autoregulation.

From Acid Rain to Low Precipitation: The Role Reversal of Norway Spruce, Silver Fir, and European Beech in a Selection Mountain Forest and Its Implications for Forest Management

Research Highlights: We make use of long term observation data from a selection forest in Bavaria. Despite the changing environmental conditions, stand level productivity remains constant over time. Maintaining species and structural diversity by forest management can contribute to resilient forest ecosystems. Background and Objectives: Forests in mountains are similarly affected by environmental changes like those in northern latitudes as species are closer to the edge of their ecological niche. There are recent studies that report species-specific responses to climate change in unmanaged, mono-layered mountain mixed forests. We analyze how environmental changes modify the growth of multi-layered, managed selection forest, which are often targeted for stabilization and risk prevention. We pose the central hypothesis that different species-specific susceptibility to disturbances and structural diversity contribute to ecosystem stability. Materials and Methods: Based on the long-term experiment Freyung 129 in the montane zone of the Bavarian Forest, Germany we analyze long term chronologies of periodic single tree and stand growth of Norway Spruce, silver fir, and European beech in dependence of environmental factors and forest management. Results: First, we show that despite environmental changes in terms of air pollution and drought stress, productivity at stand level persists constantly because of structural diversity and species traits. Second, we show that the species-specific contribution to total stand growth and growth distribution among stem diameter classes may change over time; the species interactions balance total growth. Third, we reveal a role reversal of tree species growth pattern. N. spruce was superior in growth in the first half and was replaced by s. fir in the second half of the survey period. Fourth, we identify the interplay of different stress factors on species-specific growth as the main cause for species-specific asynchronous but growth stabilizing reaction pattern. Finally, we show that density regulation was limited in its impacts to mitigate prevailing stress factors. Conclusions: We discuss the reasons for the observed stability of productivity. We interpret results, where especially the diversity of species and structure typical for selection forests result in stable productivity and wider plateau of the density-productivity relationship, and the suitability of the selection forest concept for risk prevention and stress resilience. We conclude that species composition and stand structure of selection forestry in mixed mountain contribute to climate smart forestry.

An Overview of the Geomorphological Characteristics of the Pergamon Micro-Region (Bakırçay and Madra River Catchments, Aegean Region, West Turkey)

Current landforms are the basis for understanding past geomorphodynamics and human activities. Based on multiple materials and methods, including geomorphometric analyses of a digital elevation model and visual interpretations of satellite images, different landscape units of the Bakırçay and Madra River catchments in the environs of ancient Pergamon are described. The area was mainly shaped by tectonics that formed a horst-and-graben structure; small Miocene horsts and NE-trending subgrabens in the Kozak and Yunt Dağı Mountains were separated by the NEE-trending Plio-Pleistocene Bergama Graben. The asymmetry in relief, drainage network, and sediment accumulation between the Kozak Mountains to the north and the Yunt Dağı Mountains to the south of the lower Bakırçay plain characterize the Pergamon Micro-Region. The regional relief characteristics, with wide flat basin and plateau areas, are suitable for agriculture. Complemented by its richness in natural resources, the Pergamon Micro-Region became a preferred settlement area, with evidence of human impact since the Hellenistic–Roman period at the latest. As a consequence of settlement activities, several landscape engineering measures were implemented simultaneously with a parallel change in morphodynamics.

Tunable thermal conductivity of ternary alloy semiconductors from first-principles

We compute the thermal conductivity, κ, of five representative III–V ternary alloys—namely In x Ga1 − x As, GaAs1 − x P x , InAs1 − x Sb x , GaAs1 − x N x , and GaP1 − x N x —in the whole range of compositions, and in zincblende and wurtzite crystal phases, using a first-principles approach and solving the phonon Boltzmann transport equation beyond the relaxation time approximation. We discuss the tunability of the thermal conductivity with the composition of the alloy, reporting a steep decrease in the thermal conductivity, followed by a wide plateau and a steep increase common in systems with lattice disorder. We also test the approximation consisting in considering impurities at small values of x as bare mass defects, neglecting their chemical identity, and discuss its validity.