A new consideration for validating battery performance at low ambient temperatures

Existing validation methods for equivalent circuit models (ECMs) do not capture the effects of operating lithium-ion cells over legislative drive cycles at low ambient temperatures. Unrealistic validation of an ECM may often lead to reduced accuracy in electric vehicle range estimation. In this study, current and power are used to illustrate the different approaches for validating ECMs when operating at low ambient temperatures (−15 °C to 25 °C). It was found that employing a current-based approach leads to under-testing of the performance of lithium-ion cells for various legislative drive cycles (NEDC; FTP75; US06; WLTP-3) compared to the actual vehicle. In terms of energy demands, this can be as much as ~21% for more aggressive drive cycles but even ~15% for more conservative drive cycles. In terms of peak power demands, this can range from ~27% for more conservative drive cycles to ~35% for more aggressive drive cycles. The research findings reported in this paper suggest that it is better to use a power-based approach (with dynamic voltage) rather than a current-based approach (with fixed voltage) to characterise and model the performance of lithium-ion cells for automotive applications, especially at low ambient temperatures. This evidence should help rationalize the approaches in a model-based design process leading to potential improvements in real-world applications for lithium-ion cell

A Barren Landscape?

We consider the generation of a non-perturbative superpotential in F-theory compactifications with flux. We derive a necessary condition for the generation of such a superpotential in F-theory. For models with a single volume modulus, we show that the volume modulus is never stabilized by either abelian instantons or gaugino condensation. We then comment on how our analysis extends to a larger class of compactifications. From our results, it appears that among large volume string compactifications, metastable de Sitter vacua (should any exist) are non-generic.Comment: 14 pages, comments adde

Energy and momentum of Bianchi Type VI_h Universes

We obtain the energy and momentum of the Bianchi type VI_h universes using different prescriptions for the energy-momentum complexes in the framework of general relativity. The energy and momentum of the Bianchi VI_h universe are found to be zero for the parameter h = -1 of the metric. The vanishing of these results support the conjecture of Tryon that Universe must have a zero net value for all conserved quantities.This also supports the work of Nathan Rosen with the Robertson-Walker metric. Moreover, it raises an interesting question: "Why h=-1 case is so special?

Locating the minimum : Approach to equilibrium in a disordered, symmetric zero range process

We consider the dynamics of the disordered, one-dimensional, symmetric zero range process in which a particle from an occupied site $k$ hops to its nearest neighbour with a quenched rate $w(k)$. These rates are chosen randomly from the probability distribution $f(w) \sim (w-c)^{n}$, where $c$ is the lower cutoff. For $n > 0$, this model is known to exhibit a phase transition in the steady state from a low density phase with a finite number of particles at each site to a high density aggregate phase in which the site with the lowest hopping rate supports an infinite number of particles. In the latter case, it is interesting to ask how the system locates the site with globally minimum rate. We use an argument based on local equilibrium, supported by Monte Carlo simulations, to describe the approach to the steady state. We find that at large enough time, the mass transport in the regions with a smooth density profile is described by a diffusion equation with site-dependent rates, while the isolated points where the mass distribution is singular act as the boundaries of these regions. Our argument implies that the relaxation time scales with the system size $L$ as $L^{z}$ with $z=2+1/(n+1)$ for $n > 1$ and suggests a different behaviour for $n < 1$.Comment: Revtex, 7 pages including 3 figures. Submitted to Pramana -- special issue on mesoscopic and disordered system

The universality class of fluctuating pulled fronts

It has recently been proposed that fluctuating ``pulled'' fronts propagating into an unstable state should not be in the standard KPZ universality class for rough interface growth. We introduce an effective field equation for this class of problems, and show on the basis of it that noisy pulled fronts in {\em d+1} bulk dimensions should be in the universality class of the {\em (d+1)+1}D KPZ equation rather than of the {\em d+1}D KPZ equation. Our scenario ties together a number of heretofore unexplained observations in the literature, and is supported by previous numerical results.Comment: 4 pages, 2 figure

Gravitating dyons and the Lue-Weinberg bifurcation

Gravitating t'Hooft-Polyakov magnetic monopoles can be constructed when coupling the Georgi-Glashow model to gravitation. For a given value of the Higgs boson mass, these gravitating solitons exist up to a critical value of the ratio of the vector meson mass to the Planck mass. The critical solution is characterized by a degenerate horizon of the metric. As pointed out recently by Lue and Weinberg, two types of critical solutions can occur, depending on the value of the Higgs boson mass. Here we investigate this transition for dyons and show that the Lue and Weinberg phenomenon is favorized by the presence of the electric-charge degree of freedom.Comment: RevTeX, 6 pages, 8 figure

Rapid Breast Cancer Disease Progression Following Cyclin Dependent Kinase 4 and 6 Inhibitor Discontinuation.

Background: CDK 4 and 6 inhibitors (CDK4/6i), which arrest unregulated cancer cell proliferation, show clinical efficacy in breast cancer. Unexpectedly, a patient treated on a CDK4/6i-based trial, as first-line therapy in metastatic breast cancer, developed rapid disease progression following discontinuation of study drug while receiving standard second-line therapy off trial. We thus sought to expand this observation within a population of patients treated similarly at The University of Texas MD Anderson Cancer Center. Methods: Using an IRB-approved protocol, 4 patients previously enrolled on CDK4/6i trials were analyzed for outcomes after discontinuing study drug. These patients were treated on a randomized trial of first-line endocrine therapy +/- a CDK4/6i. Rapid disease progression was defined as progression occurring within 4 months of CDK4/6i discontinuation. Results: In total, 4 patients developed rapid disease progression and died; 2 of whom died within 6 months of CDK4/6i discontinuation. Conclusion: This case series suggests a potential for rapid disease progression following CDK4/6i discontinuation. However, the clinical course following progression must be validated in large CDK4/6i clinical trials and standard-of-care cohorts. If confirmed, such observations may alter the algorithm for subsequent therapy in patients with disease progression on CDK4/6i. Nevertheless, the need remains to define a mechanistic basis for this rapid progression and formulate alternative therapeutic strategies

Gravitating dyons and dyonic black holes in Einstein-Born-Infeld-Higgs model

We find static spherically symmetric dyons in Einstein-Born-Infeld-Higgs model in 3+1 dimensions. The solutions share many features with the gravitating monopoles in the same model. In particular, they exist only up to some critical value of a parameter \a related to the strength of the gravitational interaction. We also study dyonic non-Abelian black holes. We analyse these solutions numerically.Comment: Minor modifications, few more references added. To appear in Phys. Lett.

Magnetization distribution in the transverse Ising chain with energy flux

The zero-temperature transverse Ising chain carrying an energy flux j_E is studied with the aim of determining the nonequilibrium distribution functions, P(M_z) and P(M_x), of its transverse and longitudinal magnetizations, respectively. An exact calculation reveals that P(M_z) is a Gaussian both at j_E=0 and j_E not equal 0, and the width of the distribution decreases with increasing energy flux. The distribution of the order-parameter fluctuations, P(M_x), is evaluated numerically for spin-chains of up to 20 spins. For the equilibrium case (j_E=0), we find the expected Gaussian fluctuations away from the critical point while the critical order-parameter fluctuations are shown to be non-gaussian with a scaling function Phi(x)=Phi(M_x/)=P(M_x) strongly dependent on the boundary conditions. When j_E not equal 0, the system displays long-range, oscillating correlations but P(M_x) is a Gaussian nevertheless, and the width of the Gaussian decreases with increasing j_E. In particular, we find that, at critical transverse field, the width has a j_E^(-3/8) asymptotic in the j_E -> 0 limit.Comment: 8 pages, 5 ps figure

Low temperature performance of Lithium-ion batteries for different drive cycles

Lithium-ion batteries, suitable for Battery-electric vehicles (BEVs) due to their high energy and power densities, and lifetime demonstrate deterioration in energy and power available at lower temperatures. It is attributed to reduction in capacity and increase in internal resistance. Investigations are carried out to determine energy, and power decline for four drive-cycles: FTP, NEDC, UDDS and US06. The minimum temperatures where the battery meets the drive-cycles’ energy and power requirements are determined. The impact of regenerativebraking and self-heating on battery performance is discussed. The minimum temperature where any drive-cycle is met by the battery is directly proportional to its aggressiveness