Search

Understanding the performance of electrochemical energy storage systems requires probing the electrochemical properties at each layer and interface during cell operation. While traditional onboard and operando methods can measure impedance, voltage, or capacity, they lack spatial resolution to pinpoint the properties to specific layers and interfaces. In this work, we describe an approach of using thermal waves to measure entropy change, transport resistance, and charge-transfer resistance with depth resolution of a few microns within an electrochemical cell. We achieve this by relating heat generation at multiple harmonics of an AC current to electrochemical processes and leveraging frequency dependence of thermal penetration depth for spatial resolution. We name this frequency domain spectroscopy of the thermal signatures of the electrochemical processes measured at multiple harmonics of the alternating current as Multi-harmonic ElectroThermal Spectroscopy (METS). This technique enables isolation and measurement of solvation entropy at individual electrode-electrolyte interfaces from the first harmonic (1{\omega}) thermal signature and resolution of the overall interfacial impedance into charge-transfer and interface transport resistance components from the second harmonic (2{\omega}) thermal signature. From this, we also demonstrate an operando measurement of the growth of the solid-electrolyte interphase (SEI) layer at the lithium-electrolyte interface and show that two chemically similar electrodes can have significantly different interfacial transport resistance based on the preparation of the electrodes. Additionally, the method is not specific to lithium-ion chemistry and can therefore be generalized for all electrochemical systems of interest.

Solid-state batteries (SSBs) are promising next-generation batteries due to their high energy density and enhanced thermal stability and safety. However, their sluggish kinetics and transport at room temperature results in high internal impedance and critically reduces the attainable discharge energy density. Taking advantage of their strong temperature-dependent ionic conductivity, here we introduce ultra-high frequency ($>10^5$ Hz) self-heating (UHFSH) of SSBs, which can rapidly warm up the batteries from room temperature to operating temperature (~65 {\deg}C) in less than a minute. As proof of concept, UHFSH experiments were conducted on symmetric solid-state cells with lithium aluminum germanium phosphate (LAGP) electrolyte with different configurations. Using an experimentally validated model, pack-level simulations predict fast heating (50 K/min) and minimized heating energy consumption (less than 4%). Without any modification of the materials or structure of the batteries, our non-intrusive self-heating strategy enables the SSBs to discharge more than two-fold energy in 25 {\deg}C ambient.

One Health issues, such as the spread of highly pathogenic avian influenza (HPAI), present significant challenges at the intersection of human, animal, and environmental health. Recent H5N1 outbreaks underscore the need for comprehensive modeling that capture the complex interactions between various entities in these interconnected ecosystems, encompassing livestock, wild birds, and human populations. To support such efforts, we present a synthetic spatiotemporal gridded dataset for the contiguous United States, referred to as a digital similar. The methodology for constructing this digital similar involves fusing diverse datasets using statistical and optimization techniques. The livestock component includes farm-level representations of multiple livestock types -- cattle, poultry, hogs, and sheep -- including further categorization into subtypes, such as milk and beef cows, chicken, turkeys, ducks, etc. It also includes location-level data for livestock-product processing centers. Weekly abundance data for key wild bird species involved in avian flu transmission are included along with temporal networks of movements. Gridded distributions of the human population, along with demographic and occupational features, capture the placement of agricultural workers and the general population. The digital similar is verified and validated in multiple ways.This dataset aims to provide a comprehensive basis for modeling complex phenomena at the wild-domestic-human interfaces.

Quantum network harbours a technology of multiparty transmission and computation of quantum information. We here design a quantum circuit comprising of Hadamard and controlled-Not gates for preparation of a cluster state of symmetric and antisymmetric Bell pairs involving seventeen qubits which is later on utilized as a quantum channel. This seventeen qubits quantum channel is employed to strategize a simultaneous multiparty (quattro directional) quantum teleportation protocol in which four senders (Alice, Bob, Charlie and David) transmit their arbitrary unknown two-qubit states to respective four receivers (Fancy1, Fancy2, Fancy3 and Fancy4) under the supervision of a controller Elle. After successful accomplishment of the protocol, we assess and compare our scheme with contemporary protocols based on quantum (classical) resource consumption, transmitted qubits, operation complexity and efficiency. We found that intrinsic efficiency of our protocol pegs at 21.65 percent., Comment: 15 Pages; 02 Figures; Appendices: A and B; Tables:1, 2 and 3

Quantum teleportation is a primitive foundational protocol for exchanging quantum information in a quantum network as well as infrastructural operational strategy in the measurement-based quantum computation. Designing an efficient scheme for quantum teleportation is a vibrant field of intensive research. We propose a scheme wherein Bell-like states are being exchanged simultaneously in cyclic sequence, i.e., symmetric-cyclic bi-directional quantum teleportation, amongst three communicating parties forming a quantum network, Alice, Bob and Charlie via entanglement-swapping with the aid of a cluster of three maximally entangled GHZ-states as the quantum channel. Moreover, based upon communication- and operation- complexity, we compare our protocol with other equivalent protocols and found that the intrinsic efficiency of our protocol is maximum pegging at 33.33%., Comment: 15 pages; Figs: 1 and 2; Tables: 1 and 2; Appendix: A

Optical coherent states are experimentally realizable continuous variable quantum states of which preparation by lasers, as well as its manipulation and monitoring by linear optical gadgets are well established. We propose a strategy to send an arbitrary superposition of four-component bimodal entangled coherent states from a sender to a receiver who, simultaneously, tries to transmit an unknown Schrodinger Cat coherent state to sender via employing a cluster consisting of three superposition of two component bimodal entangled coherent states as the quantum channel and utilizing linear optical gadgets. Heralded detection of photons in laboratories of sender and receiver followed by classical communications of even and odd number of photons and local unitary operations, impeccably, accomplishes simultaneous faithful asymmetric bidirectional quantum teleportation with one eighth of probability of success. It is seen that not all detection events implement the protocol and, therefore, one has to locally apply displacement operator, a necessary evil. We analyze near faithful partial asymmetric bidirectional quantum teleportation and associated probability of success therein. We demonstrated that, for an intense coherent optical field, fidelity approach unity., Comment: 30 pages;Figs: 1-5; Appendices: A and B; Tables(1-6); To be submitted for possible publication

We present simultaneous X-ray polarimetric and spectral observations of the bright atoll source Ser~X-1 carried out with the Imaging X-ray Polarimetry Explorer (IXPE), NICER, and NuSTAR. We obtain an upper limit of 2% (99% confidence level) on the polarization degree in the 2--8 keV energy band. We detect four type-I X-ray bursts, two of which during the IXPE observation. This is the first time that has IXPE observed type-I X-ray bursts, and it allows us to place an upper limit on their polarization degree; however, due to the limited total number of counts in each burst, we obtain a relatively high upper limit (80%). We confirm the presence of reflection features in the X-ray spectrum, notably a broad iron line. Fitting the data with a relativistic reflection model, we derive a disk inclination of 25 deg. The spectral and polarization properties are comparable with other atolls observed by IXPE, suggesting a similar accretion geometry, and the relatively low polarization is consistent with the low inclination., Comment: Accepted by A&A

We report on the second observing program of the active galactic nucleus NGC 4151 with simultaneous Imaging X-ray Polarimetry Explorer (IXPE; {\sim}750 ks), NuSTAR ({\sim}60 ks), XMM-Newton ({\sim}75 ks), and NICER ({\sim}65 ks) pointings. NGC 4151 is the first Type 1 radio-quiet Seyfert galaxy with constrained polarization properties for the X-ray corona. Despite the lower flux state in which the source is re-observed and the resulting higher contribution of the constant reflection component in the IXPE energy band, our results are in agreement with the first detection. From polarimetric analysis, a polarization degree {\Pi} = 4.7 {\pm} 1.3 percent and angle {\Psi} = 77{\deg} {\pm} 8{\deg} east of north (68 percent confidence level) are derived in the 2.0 - 8.0 keV energy range. Combining the two observations leads to polarization properties that are more constrained than those of the individual detections, showing {\Pi} = 4.5 {\pm} 0.9 percent and {\Psi} = 81{\deg} {\pm} 6{\deg} (with detection significance {\sim}4.6{\sigma}). The observed polarization angle aligns very well with the radio emission in this source, supporting, together with the significant polarization degree, a slab or wedge geometry for the X-ray corona. However, a switch in the polarization angle at low energies (37{\deg} {\pm} 7{\deg} in the 2 - 3.5 keV bin) suggests the presence of another component. When it is included in the spectro-polarimetric fit, a high polarization degree disfavors an interpretation in terms of a leakage through the absorbers, rather pointing to scattering from some kind of mirror., Comment: 9 pages, 8 figures, 3 tables. Accepted to Astronomy & Astrophysics

Networked dynamical systems are widely used as formal models of real-world cascading phenomena, such as the spread of diseases and information. Prior research has addressed the problem of learning the behavior of an unknown dynamical system when the underlying network has a single layer. In this work, we study the learnability of dynamical systems over multilayer networks, which are more realistic and challenging. First, we present an efficient PAC learning algorithm with provable guarantees to show that the learner only requires a small number of training examples to infer an unknown system. We further provide a tight analysis of the Natarajan dimension which measures the model complexity. Asymptotically, our bound on the Nararajan dimension is tight for almost all multilayer graphs. The techniques and insights from our work provide the theoretical foundations for future investigations of learning problems for multilayer dynamical systems., Comment: Accepted at ICML 2024

We used the Imaging X-ray Polarimetry Explorer (IXPE) satellite to measure, for the first time, the 2-8 keV polarization of NGC 1068. We pointed IXPE for a net exposure time of 1.15 Ms on the target, in addition to two ~ 10 ks each Chandra snapshots in order to account for the potential impact of several ultraluminous X-ray source (ULXs) within IXPE's field-of-view. We measured a 2 - 8 keV polarization degree of 12.4% +/- 3.6% and an electric vector polarization angle of 101{\deg} +/- 8{\deg} at 68% confidence level. If we exclude the spectral region containing the bright Fe K lines and other soft X-ray lines where depolarization occurs, the polarization fraction rises up to 21.3% +/- 6.7% in the 3.5 - 6.0 keV band, with a similar polarization angle. The observed polarization angle is found to be perpendicular to the parsec scale radio jet. Using a combined Chandra and IXPE analysis plus multi-wavelength constraints, we estimated that the circumnuclear "torus" may sustain a half-opening angle of 50{\deg} - 55{\deg} (from the vertical axis of the system). Thanks to IXPE, we have measured the X-ray polarization of NGC 1068 and found comparable results, both in terms of polarization angle orientation with respect to the radio-jet and torus half-opening angle, to the X-ray polarimetric measurement achieved for the other archetypal Compton-thick AGN : the Circinus galaxy. Probing the geometric arrangement of parsec-scale matter in extragalactic object is now feasible thanks to X-ray polarimetry., Comment: 9 pages, 5 figures, 2 tables, submited to A&A

Exploiting the cluster of three Bell coherent-states as quantum channel, we presented a scheme wherein quantum-informations encoded in three arbitrary superposed coherent states, i.e., Schrodinger Cat coherent-states are simultaneously transmitted in unidirectional cyclic sequence among three parties by invoking usage of linear optical gadgets such as ideal beam-splitters, phase shifters and photon-number-resolving detectors. Proposed simultaneous unidirectional Cyclic Quantum Teleportation is faithful with one-eighth probability of success. Furthermore, it is seen that not every detection-events provides faithful scheme and, hence, fidelity and probability of success of near-faithful Cyclic Quantum Teleportation is evaluated and numerically interpreted., Comment: 26 pages, 3 figures

Discrete dynamical systems are commonly used to model the spread of contagions on real-world networks. Under the PAC framework, existing research has studied the problem of learning the behavior of a system, assuming that the underlying network is known. In this work, we focus on a more challenging setting: to learn both the behavior and the underlying topology of a black-box system. We show that, in general, this learning problem is computationally intractable. On the positive side, we present efficient learning methods under the PAC model when the underlying graph of the dynamical system belongs to some classes. Further, we examine a relaxed setting where the topology of an unknown system is partially observed. For this case, we develop an efficient PAC learner to infer the system and establish the sample complexity. Lastly, we present a formal analysis of the expressive power of the hypothesis class of dynamical systems where both the topology and behavior are unknown, using the well-known formalism of the Natarajan dimension. Our results provide a theoretical foundation for learning both the behavior and topology of discrete dynamical systems., Comment: Accepted at AAAI-24

Optimal allocation of agricultural water in the event of droughts is an important global problem. In addressing this problem, many aspects, including the welfare of farmers, the economy, and the environment, must be considered. Under this backdrop, our work focuses on several resource-matching problems accounting for agents with multi-crop portfolios, geographic constraints, and fairness. First, we address a matching problem where the goal is to maximize a welfare function in two-sided markets where buyers' requirements and sellers' supplies are represented by value functions that assign prices (or costs) to specified volumes of water. For the setting where the value functions satisfy certain monotonicity properties, we present an efficient algorithm that maximizes a social welfare function. When there are minimum water requirement constraints, we present a randomized algorithm which ensures that the constraints are satisfied in expectation. For a single seller--multiple buyers setting with fairness constraints, we design an efficient algorithm that maximizes the minimum level of satisfaction of any buyer. We also present computational complexity results that highlight the limits on the generalizability of our results. We evaluate the algorithms developed in our work with experiments on both real-world and synthetic data sets with respect to drought severity, value functions, and seniority of agents.