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Quantifying Degradation Parameters of Single-Crystalline Ni-Rich Cathodes in Lithium-Ion Batteries
No full textSingle-crystal LiNixCoyMnzO2 (SC-NCM, x+y+z=1) cathodes are renowned for their high structural stability and reduced accumulation of adverse side products during long-term cycling. While advances have been made using SC-NCM cathode materials, careful studies of cathode degradation mechanisms are scarce. Herein, we employed quasi single-crystalline LiNi0.65Co0.15Mn0.20O2 (SC-NCM65) to test the relationship between cycling performance and material degradation for different charge cutoff potentials. The Li/SC-NCM65 cells showed >77 % capacity retention below 4.6 V vs. Li+/Li after 400 cycles and revealed a significant decay to 56 % for 4.7 V cutoff. We demonstrate that the SC-NCM65 degradation is due to accumulation of rock-salt (NiO) species at the particle surface rather than intragranular cracking or side reactions with the electrolyte. The NiO-type layer formation is also responsible for the strongly increased impedance and transition-metal dissolution. Notably, the capacity loss is found to have a linear relationship with the thickness of the rock-salt surface layer. Density functional theory and COMSOL Multiphysics modeling analysis further indicate that the charge-transfer kinetics is decisive, as the lower lithium diffusivity of the NiO phase hinders charge transport from the surface to the bulk
Pure edge-contact devices on single-layer-CVD-graphene integrated into a single chip
Full text linkWe present a simple and cost-effective fabrication technique for on-chip integration of pure edge contact two-terminal (2T) and Graphene field effect transistor (GFET) devices with low contact resistance and nonlinear characteristics based on single-layer chemical-vapor-deposited (CVD) graphene. We use a smart print-based mask projection technique with a 10X magnification objective lens for maskless lithography followed by thermal evaporation of the contact material Cr-Pd-Au through three different angles (90\ub0 and \ub1 45\ub0) using a customized inclined-angle sample-holder to control the angle during normal incidence evaporation for edge-contact to graphene. Our fabrication technique, graphene quality, and contact geometry enable pure metal contact to 2D single-layer graphene allowing electron transport through the 1D atomic edge of graphene. Our devices show some signatures of edge contact to graphene in terms of very low contact resistance of 23.5\ua0Ω, the sheet resistance of 11.5\ua0Ω, and sharp nonlinear voltage-current characteristics (VCC) which are highly sensitive to the bias voltage. This study may find application in future graphene-integrated chip-scale passive or active low-power electronic devices
Okounkov Bodies and\ua0the\ua0K\ue4hler Geometry of\ua0Projective Manifolds
No full textGiven a projective manifold X equipped with an ample line bundle L, we show how to embed certain torus-invariant domains D⊆ Cn into X so that the Euclidean K\ue4hler form on D extends to a K\ue4hler form on X lying in the first Chern class of L. This is done using Okounkov bodies Δ (L), and the image of D under the standard moment map will approximate Δ (L). This means that the volume of D can be made to approximate the K\ue4hler volume of X arbitrarily well. As a special case we can let D be an ellipsoid. We also have similar results when L is just big
The Origin of Dust Polarization in the Orion Bar
Full text linkThe linear polarization of thermal dust emission provides a powerful tool to probe interstellar and circumstellar magnetic fields, because aspherical grains tend to align themselves with magnetic field lines. While the Radiative Alignment Torque (RAT) mechanism provides a theoretical framework for this phenomenon, some aspects of this alignment mechanism still need to be quantitatively tested. One such aspect is the possibility that the reference alignment direction changes from the magnetic field ("B-RAT") to the radiation field k-vector ("k-RAT") in areas of strong radiation fields. We investigate this transition toward the Orion Bar PDR, using multiwavelength SOFIA HAWC+ dust polarization observations. The polarization angle maps show that the radiation field direction is on average not the preferred grain alignment axis. We constrain the grain sizes for which the transition from B-RAT to k-RAT occurs in the Orion Bar (grains & GE; 0.1 & mu;m toward the most irradiated locations), and explore the radiatively driven rotational disruption that may take place in the high-radiation environment of the Bar for large grains. While the grains susceptible to rotational disruption should be in suprathermal rotation and aligned with the magnetic field, k-RAT aligned grains would rotate at thermal velocities. We find that the grain size at which the alignment shifts from B-RAT to k-RAT corresponds to grains too large to survive the rotational disruption. Therefore, we expect a large fraction of grains to be aligned at suprathermal rotation with the magnetic field, and to potentially be subject to rotational disruption, depending on their tensile strength
Operating conditions combination analysis method of optimal water management state for PEM fuel cell
Full text linkThe water content of proton exchange membrane fuel cells (PEMFCs) affects the transport of reactants and the conductivity of the membrane. Effective water management measures can improve the performance and extend the lifespan of the fuel cell. The water management state of the stack is influenced by various external operating conditions, and optimizing the combination of these conditions can improve the water management state within the stack. Considering that the stack\u27s internal resistance can reflect its water management state, this study first establishes an internal resistance-operating condition model that considers the coupling effect of temperature and humidity to determine the variation trend of total resistance and stack humidity with single-factor operating conditions. Subsequently, the water management state optimization method based on the ANN-HGPSO algorithm is proposed, which not only quantitatively evaluates the influence weights of different operating conditions on the stack\u27s internal resistance but also efficiently and accurately obtains the optimal combination of five operating conditions: working temperature, anode gas pressure, cathode gas pressure, anode gas humidity, and cathode gas humidity to achieve the optimal water management state in the stack, within the entire range of current densities. Finally, the response surface experimental results of the stack also validate the effectiveness and accuracy of the ANN-HGPSO algorithm. The method mentioned in this article can provide effective strategies for efficient water management and output performance optimization control of PEMFC stacks
Interaction-Aware Trajectory Prediction for Autonomous Vehicle Based on LSTM-MLP Model
No full textTrajectory prediction is one of the core functions of the autonomous vehicle, it greatly affects the rationality and safety of the decision-making module and the planning module. This is challenging because the motion of the target vehicle is affected by the interactive behavior of its surrounding vehicles. In this paper, we propose the interaction-aware trajectory prediction model for autonomous vehicles based on LSTM-MLP model. The encoder module encoded the history trajectories to extract the dynamic feature of each vehicle in the scenarios by the LSTM model, and then the interaction module captures the interactive feature using the MLP-Max Pooling model. In the end, the decoder module decodes the fusion feature which consists of the dynamic feature of the target vehicle and the interactive feature to output the future trajectory based on the LSTM model. The experiments are carried out on the publicly available NGSIM dataset, and the results show that the proposed model outperforms prior works in terms of RMSE value
Variationally consistent modeling of a sensor-actuator based on shape-morphing from electro-chemical–mechanical interactions
Full text linkThis paper concerns the computational modeling of a class of carbon fiber composites, known as shape-morphing and strain-sensing composites. The actuating and sensing performance of such (smart) materials is achieved by the interplay between electrochemistry and mechanics, in particular the ability of carbon fibers to (de)intercalate Li-ions repeatedly. We focus on the actuation and sensing properties of a beam in conjunction with the appropriate “through-the-thickness” properties. Thus, the electro-chemo-mechanical analysis is essentially two-dimensional, and it is possible to rely heavily on the results in Carlstedt et al. (2020). More specifically, the cross-sectional design is composed of two electrodes, consisting of (partly) lithiated carbon fibers embedded in structural battery electrolyte (SBE), on either side of a separator. As a result, the modeling is hierarchical in the sense that (macroscale) beam action is combined with electro-chemo-mechanical interaction along the beam. The setup is able to work as sensor or actuator depending on the choice of control (and response) variables. Although quite idealized, this design allows for a qualitative investigation. In this paper we demonstrate the capability of the developed framework to simulate both the actuator and sensor modes. As proof of concept, we show that both modes of functionality can be captured using the developed framework. For the actuator mode, the predicted deformation is found to be in close agreement with experimental data. Further, the sensor-mode is found to agree with experimental data available in the literature
Associations of gestational and early-life exposure to toxic metals and fluoride with a diagnosis of food allergy or atopic eczema at 1 year of age
Full text linkStudies have indicated that early-life exposure to toxic metals and fluoride affects the immune system, but evidence regarding their role in allergic disease development is scarce. We aimed to evaluate the relations of exposure to such compounds in 482 pregnant women and their infants (4 months of age) with food allergy and atopic eczema diagnosed by a paediatric allergologist at 1 year of age within the Swedish birth-cohort NICE (Nutritional impact on Immunological maturation during Childhood in relation to the Environment). Urinary cadmium and erythrocyte cadmium, lead, and mercury concentrations were measured by inductively coupled plasma mass spectrometry (ICP-MS), urinary inorganic arsenic metabolites by ICP-MS after separation by ion exchange chromatography, and urinary fluoride by an ion-selective electrode. The prevalence of food allergy and atopic eczema was 8 and 7%, respectively. Gestational urinary cadmium, reflecting chronic exposure, was associated with increased odds of infant food allergy (OR [95% CI]: 1.34 [1.09, 1.66] per IQR [0.08 μg/L]). Both gestational and infant urinary fluoride were associated, albeit at a statistically non-significant level, with increased atopic eczema odds (1.48 [0.98, 2.25], 1.36 [0.95, 1.95], per doubling, respectively). By contrast, gestational and infant erythrocyte lead was associated with decreased odds of atopic eczema (0.48 [0.26, 0.87] per IQR [6.6 μg/kg] and 0.38 [0.16, 0.91] per IQR [5.94 μg/kg], respectively), and infant lead with decreased odds of food allergy (0.39 [0.16, 0.93] per IQR [5.94 μg/kg]). Multivariable adjustment had marginal impact on the estimates above. After additional adjustment for fish intake biomarkers, the methylmercury associated atopic-eczema odds were considerably increased (1.29 [0.80, 2.06] per IQR [1.36 μg/kg]). In conclusion, our results indicate that gestational cadmium exposure might be associated with food allergy at 1 year of age and, possibly, early-life exposure to fluoride with atopic eczema. Further prospective and mechanistic studies are needed to establish causality
Investigation of LD-slag as oxygen carrier for CLC in a 10 kW unit using high-volatile biomasses
Full text linkA steel slag from the Linz-Donawitz process, called LD-slag, having significant calcium and iron-fractions, was investigated as an oxygen carrier in a recently developed 10 kWth chemical-looping combustor with three high-volatile biomass fuels. In order to improve operability, the LD-slag was found to require heat-treatment at high temperatures before being used in the unit. In total, operation with the biomasses was conducted for more than 26 h at temperatures of 870–980 \ub0C. The fuel thermal power was in the range of 3.4–10 kWth. The operation involved chemical looping combustion (CLC), chemical looping gasification (CLG) and oxygen carrier aided combustion (OCAC). Around 12 h was in CLC operation, 13.3 h was conducted in CLG-conditions, while the remaining 0.7 h was OCAC. Here, the results obtained during the CLC part of the campaign is reported. Increased temperature in the fuel reactor and higher airflows to the air reactor both lead to better combustion performance. Steam concentration in the fuel reactor has little effect on the performance. The LD-slag showed higher oxygen demand (31.0%) than that with ilmenite (21.5%) and a manganese ore (19.5%) with the same fuel and normal solids circulation. However, with the LD-slag, there is possibility to achieve a lower oxygen demand (15.2%) with high solids circulation
The Lorentz Gas with a Nearly Periodic Distribution of Scatterers
Full text linkWe consider the Lorentz gas in a distribution of scatterers which microscopically converges to a periodic distribution, and prove that the Lorentz gas in the low density limit satisfies a linear Boltzmann equation. This is in contrast with the periodic Lorentz gas, which does not satisfy the Boltzmann equation in the limit