Showing papers on "Energy (signal processing) published in 2020"

Muon g − 2 and Δ α connection

Abstract: The discrepancy between the Standard Model theory and experimental measurement of the muon magnetic moment anomaly, ${a}_{\ensuremath{\mu}}=({g}_{\ensuremath{\mu}}\ensuremath{-}2)/2$, is connected to precision electroweak (EW) predictions via their common dependence on hadronic vacuum polarization effects. The same data for the total ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\text{hadrons}$ cross section, ${\ensuremath{\sigma}}_{\text{had}}(s)$, are used as input into dispersion relations to estimate the hadronic vacuum polarization contributions, ${a}_{\ensuremath{\mu}}^{\text{had},\mathrm{VP}}$, as well as the five-flavor hadronic contribution to the running QED coupling at the $Z$-pole, $\mathrm{\ensuremath{\Delta}}{\ensuremath{\alpha}}_{\text{had}}^{(5)}({M}_{Z}^{2})$, which enters natural relations and global EW fits. The EW fit prediction of $\mathrm{\ensuremath{\Delta}}{\ensuremath{\alpha}}_{\text{had}}^{(5)}({M}_{Z}^{2})=0.02722(41)$ agrees well with $\mathrm{\ensuremath{\Delta}}{\ensuremath{\alpha}}_{\text{had}}^{(5)}({M}_{Z}^{2})=0.02761(11)$ obtained from the dispersion relation approach, but exhibits a smaller central value suggestive of a larger discrepancy $\mathrm{\ensuremath{\Delta}}{a}_{\ensuremath{\mu}}={a}_{\ensuremath{\mu}}^{\mathrm{exp}}\ensuremath{-}{a}_{\ensuremath{\mu}}^{\mathrm{SM}}$ than currently expected. Postulating that the $\mathrm{\ensuremath{\Delta}}{a}_{\ensuremath{\mu}}$ difference may be due to unforeseen missing ${\ensuremath{\sigma}}_{\text{had}}(s)$ contributions, implications for ${M}_{W}$, ${\mathrm{sin}}^{2}{\ensuremath{\theta}}_{\mathrm{eff}}^{\mathrm{lep}}$ and ${M}_{H}$ obtained from global EW fits are investigated. Shifts in ${\ensuremath{\sigma}}_{\text{had}}(s)$ needed to bridge $\mathrm{\ensuremath{\Delta}}{a}_{\ensuremath{\mu}}$ are found to be excluded above $\sqrt{s}\ensuremath{\gtrsim}0.7\text{ }\text{ }\mathrm{GeV}$ at the 95% C.L. Moreover, prospects for $\mathrm{\ensuremath{\Delta}}{a}_{\ensuremath{\mu}}$ originating below that energy are deemed improbable given the required increases in the hadronic cross section. Such hypothetical changes to the hadronic data are also found to affect other related observables, such as the electron anomaly, ${a}_{e}^{\text{SM}}$, the rescaled ratio ${R}_{e/\ensuremath{\mu}}=\phantom{\rule{0ex}{0ex}}({m}_{\ensuremath{\mu}}/{m}_{e}{)}^{2}({a}_{e}^{\text{had},\mathrm{LO}\text{ }\mathrm{VP}}/{a}_{\ensuremath{\mu}}^{\text{had},\mathrm{LO}\text{ }\mathrm{VP}})$, and the running of the weak mixing angle at low energies, although the consequences of these are currently less constraining.

Photonic Multiply-Accumulate Operations for Neural Networks

Abstract: It has long been known that photonic communication can alleviate the data movement bottlenecks that plague conventional microelectronic processors. More recently, there has also been interest in its capabilities to implement low precision linear operations, such as matrix multiplications, fast and efficiently. We characterize the performance of photonic and electronic hardware underlying neural network models using multiply-accumulate operations. First, we investigate the limits of analog electronic crossbar arrays and on-chip photonic linear computing systems. Photonic processors are shown to have advantages in the limit of large processor sizes ( ${>}\text{100}\; \mu$ m), large vector sizes ( $N > 500)$ , and low noise precision ( ${\leq} 4$ bits). We discuss several proposed tunable photonic MAC systems, and provide a concrete comparison between deep learning and photonic hardware using several empirically-validated device and system models. We show significant potential improvements over digital electronics in energy ( ${>}10^2$ ), speed ( ${>}10^3$ ), and compute density ( ${>}10^2$ ).

Axion and neutrino bounds improved with new calibrations of the tip of the red-giant branch using geometric distance determinations

Abstract: The brightness of the tip of the red-giant branch (TRGB) allows one to constrain novel energy losses that would lead to a larger core mass at helium ignition and, thus, to a brighter TRGB than expected by standard stellar models. The required absolute TRGB calibrations strongly improve with reliable geometric distances that have become available for the galaxy NGC 4258 that hosts a water megamaser and to the Large Magellanic Cloud based on 20 detached eclipsing binaries. Moreover, we revise a previous TRGB calibration in the globular cluster $\ensuremath{\omega}$ Centauri with a recent kinematical distance determination based on Gaia data release 2. All of these calibrations have similar uncertainties, and they agree with each other and with recent dedicated stellar models. Using NGC 4258 as the cleanest extragalactic case, we thus find an updated constraint on the axion-electron coupling of ${g}_{ae}l1.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ and ${\ensuremath{\mu}}_{\ensuremath{ u}}l1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}{\ensuremath{\mu}}_{\mathrm{B}}$ (95% C.L.) on a possible neutrino dipole moment, whereas $\ensuremath{\omega}$ Centauri as the best galactic target provides instead ${g}_{ae}l1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}$ and ${\ensuremath{\mu}}_{\ensuremath{ u}}l1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}{\ensuremath{\mu}}_{\mathrm{B}}$. The reduced observational errors imply that stellar evolution theory and bolometric corrections begin to dominate the overall uncertainties.

A review of key issues for control and management in battery and ultra-capacitor hybrid energy storage systems

Abstract: The hybrid energy storage system is a kind of complex system including state coupling, input coupling, environmental sensitivity, life degradation, and other characteristics. How to accurately estimate the internal state of the system, delay the battery life degradation, realize the coordinated and optimized control of power and energy have become the focus and difficulty of the hybrid energy storage system. With the application and popularization of hybrid energy storage systems in electric vehicles and smart grids, relevant theoretical and technological breakthroughs become more and more urgent. Many new achievements, new theories, new methods and new technologies from the fields of materials, information, energy, control and artificial intelligence have been put into this field. This paper comprehensively reviewed the key issues for control and management in hybrid energy storage systems from the aspects of multi-scale state estimation, aging mechanism investigation, life prediction, and energy optimization control of the hybrid energy storage system. Through the in-depth review of key scientific issues, the latest theoretical techniques and application results are presented. Finally some future research challenges and outlooks are presented, in hopes to provide some new ideas and inspirations for the future investigation of the hybrid energy storage systems.

Non-Abelian Dirac node braiding and near-degeneracy of correlated phases at odd integer filling in magic-angle twisted bilayer graphene

Abstract: We use the density matrix renormalization group (DMRG) to study the correlated electron states favored by the Coulomb interaction projected onto the narrow bands of twisted bilayer graphene within a spinless one-valley model. The Hilbert space of the narrow bands is constructed from a pair of hybrid Wannier states with opposite Chern numbers, maximally localized in one direction and Bloch extended in another direction. Depending on the parameters in the Bistritzer-Macdonald model, the DMRG in this basis determines the ground state at one particle per unit cell to be either the quantum anomalous Hall (QAH) state or a state with zero Hall conductivity which is nearly a product state. Based on this form, we then apply the variational method to study their competition, thus identifying three states: the QAH, a gapless ${C}_{2}\mathcal{T}$-symmetric nematic, and a gapped ${C}_{2}\mathcal{T}$-symmetric stripe. In the chiral limit, the energies of the two ${C}_{2}\mathcal{T}$-symmetric states are found to be significantly above the energy of the QAH. However, all three states are nearly degenerate at the realistic parameters of the Bistritzer-Macdonald model. The single-particle spectrum of the nematic contains either a quadratic node or two close Dirac nodes near $\mathrm{\ensuremath{\Gamma}}$. Motivated by the Landau level degeneracy found in this state, we propose it to be the state observed at the charge neutrality point once spin and valley degeneracies are restored. The optimal period for the ${C}_{2}\mathcal{T}$ stripe state is found to be two unit cells. In addition, using the fact that the topological charge of the nodes in the ${C}_{2}\mathcal{T}$-nematic phase is no longer described simply by their winding numbers once the translation symmetry is broken, but rather by certain elements of a non-Abelian group that was recently pointed out, we identify the mechanism of the gap opening within the ${C}_{2}\mathcal{T}$ stripe state. Although the nodes at the Fermi energy are locally stable, they can be annihilated after braiding with other nodes connecting them to adjacent (folded) bands. Therefore, if the translation symmetry is broken, the gap at one particle per unit cell can open even if the system preserves the ${C}_{2}\mathcal{T}$ and valley $\text{U}(1)$ symmetries, and the gap to remote bands remains open.

Intelligent Security Planning for Regional Distributed Energy Internet

Abstract: The distributed energy system is used as the prototype of the energy Internet, including a variety of forms of energy networks, plenty of distributed equipment and energy storage equipment composed of energy flow, and real-time communication and data volume of information systems. As an important energy system that is closely related to people's lives, its security and stability is one of the cores of its development. With the access of a large number of distributed devices, the structure of the power system has changed greatly. The addition of various forms of energy network, distributed equipment, and energy storage equipment has made it more difficult for the energy Internet to achieve the coordination among and control over these devices. Regardless of the fluctuation of the power load and the sudden change of the thermal load, problems such as energy network failure and demand will affect the security and stability of the energy Internet. Traditional energy systems are independent of one another, while integrated energy systems include subsystems, such as the power system, thermal system, and natural gas system, which can complement one another in planning and operation. To improve the utilization rate of all kinds of energy, reduce the waste of energy, and cut the emission of pollutants, it is crucial to realize the economic utilization of energy as well as the safe and stable operation of the energy Internet.

A Combined Polynomial Chirplet Transform and Synchroextracting Technique for Analyzing Nonstationary Signals of Rotating Machinery

Abstract: Time–frequency analysis (TFA) technique is an effective approach to capture the changing dynamic in a nonstationary signal. However, the commonly adopted TFA techniques are inadequate in dealing with signals having a strong nonstationary characteristic or multicomponent signals having close frequency components. To overcome this shortcoming, a new TFA technique applying a polynomial chirplet transform (PCT) in association with a synchroextracting transform (SET) is proposed in this paper. It is shown that the energy concentration of the time–frequency representation (TFR) of a strong frequency-modulated signal from a PCT transform can be further enhanced by an SET transform. The technique can also be employed to accurately extract the signal components of a multicomponent nonstationary signal with close frequency components by adopting an iterative process. It is found that the TFR calculated from the proposed technique matches well with the ideal TFR, which demonstrates the superiority of the current technique in dealing with nonstationary signals having rapidly changing dynamics. Results from the analysis of the experimental data under varying speed conditions confirm the validity of the proposed technique in dealing with nonstationary signals from practical sources.

Error mitigation with Clifford quantum-circuit data

Abstract: Achieving near-term quantum advantage will require accurate estimation of quantum observables despite significant hardware noise. For this purpose, we propose a novel, scalable error-mitigation method that applies to gate-based quantum computers. The method generates training data $\{X_i^{\text{noisy}},X_i^{\text{exact}}\}$ via quantum circuits composed largely of Clifford gates, which can be efficiently simulated classically, where $X_i^{\text{noisy}}$ and $X_i^{\text{exact}}$ are noisy and noiseless observables respectively. Fitting a linear ansatz to this data then allows for the prediction of noise-free observables for arbitrary circuits. We analyze the performance of our method versus the number of qubits, circuit depth, and number of non-Clifford gates. We obtain an order-of-magnitude error reduction for a ground-state energy problem on 16 qubits in an IBMQ quantum computer and on a 64-qubit noisy simulator.

Energy Efficiency and Delay Tradeoff for Wireless Powered Mobile-Edge Computing Systems With Multi-Access Schemes

Abstract: The integration of Mobile-edge Computing (MEC) and Wireless Energy Transfer (WET) has been recognized as a promising technique to enhance computation capability and to prolong battery lifetime of resource-constrained wireless devices in the Internet of Things (IoT) era. However, it is challenging to jointly schedule energy, radio, and computational resources for coordinating heterogeneous performance requirements in wireless powered MEC systems. To fill this gap, this paper investigates the fundamental tradeoff between Energy Efficiency (EE) and delay in a multi-user wireless powered MEC system. Considering the random channel conditions and task arrivals, we formulate a stochastic optimization problem to study the EE-delay tradeoff, which optimizes network EE subject to network stability, maximum central processing unit frequency, peak transmission power, available communication resource, and energy causality constraints. Further, we propose the online computation offloading and resource allocation algorithm by transforming the original problem into a series of deterministic optimization problems in each time block based on Lyapunov optimization theory. In addition, theoretical analysis shows that the algorithm achieves the EE-delay tradeoff as [ ${O}(1/{V}), {O}({V})$ ] and introduces a control parameter ${V}$ to balance the EE-delay performance. Numerical results verify the theoretical analysis and reveal the impact of various parameters to the system performance.

Search for production of four top quarks in final states with same-sign or multiple leptons in proton-proton collisions at √{s }=13 TeV

Abstract: The standard model (SM) production of four top quarks ($\text {t} {}{\overline{\text {t}}} \text {t} {}{\overline{\text {t}}} $) in proton–proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016–2018 data taking of the LHC, corresponds to an integrated luminosity of 137$\,\text {fb}^{-1}$ at a center-of-mass energy of 13$\,\text {TeV}$. The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the $\text {t} {}{\overline{\text {t}}} \text {t} {}{\overline{\text {t}}} $ signal are respectively 2.6 and 2.7 standard deviations, and the $\text {t} {}{\overline{\text {t}}} \text {t} {}{\overline{\text {t}}} $ cross section is measured to be $12.6^{+5.8}_{-5.2}\,\text {fb} $. The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, $y_{\text {t}}$, yielding a limit of $|y_{\text {t}}/y_{\text {t}}^{\mathrm {SM}} | < 1.7$ at $95\%$ confidence level, where $y_{\text {t}}^{\mathrm {SM}}$ is the SM value of $y_{\text {t}}$. They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework, $\hat{H}<0.12$. Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350–470$\,\text {GeV}$ and 350–550$\,\text {GeV}$ for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.

Location of Single Phase to Ground Faults in Distribution Networks Based on Synchronous Transients Energy Analysis

Abstract: As a result of small fault current, high level of noise and a large penetration of distributed generators (DG), in the neutral non-effectively grounded medium-voltage (MV) distribution networks, it is quite difficult to locate the faulted line section for single phase to ground faults. In this paper, using a technique based on synchronized measurements in distribution networks, a fault location method based on the analysis of the energy of the transient zero-sequence current in the selected frequency band (SFB) is proposed. The equivalent impedance of the distribution network with lateral branches is studied with an equivalent network, and the phase-frequency characteristics of the equivalent impedance are analyzed. The SFB, within which the transient energy of the faulty line section is larger than that of the healthy line sections is determined. A combined fault-section location criterion is proposed and the implementation scheme is illustrated with the distribution level phasor measurement units. Numerical simulations of the IEEE 34 node system and the field experiments of a 10kV distribution network validate the feasibility and effectiveness of the proposed method.

Fast collective neutrino oscillations inside the neutrino sphere in core-collapse supernovae

Abstract: Neutrinos are believed to have a key role in the explosion mechanism of core-collapse supernovae as they carry most of the energy released by the gravitational collapse of a massive star. If their flavor is converted fast inside the neutrino sphere, the supernova explosion may be influenced. This paper is reporting the results of the extended work of our previous paper. We perform a thorough survey of the electron lepton number (ELN) crossing in one of our self-consistent, realistic Boltzmann simulations in two spatial dimensions under axisymmetry for the existence of the crossings between ${\ensuremath{ u}}_{e}$ and ${\overline{\ensuremath{ u}}}_{e}$ angular distributions, or the ELN crossing. We report for the first time the positive detections deep inside the core of the massive star in the vicinity of neutrino sphere at $r\ensuremath{\approx}16--21\text{ }\text{ }\mathrm{km}$. We find that low values of the electron fraction ${Y}_{e}$ produced by convective motions together with the appearance of light elements are critically important to give rise to the ELN crossing by enhancing the chemical potential difference between proton and neutron, and hence by mitigating the Fermi-degeneracy of ${\ensuremath{ u}}_{e}$. Since the region of positive detection are sustained and, in fact, expanding with time, it may have an impact on the explosion of core-collapse supernovae, observational neutrino astronomy, and nucleosynthesis of heavy nuclei.

Observation of Magnetic Proximity Effect Using Resonant Optical Spectroscopy of an Electrically Tunable MoSe2/CrBr3 Heterostructure

Abstract: van der Waals heterostructures combining two-dimensional magnetic and semiconducting layers constitute a promising platform for interfacing magnetism, electronics, and optics. Here, we use resonant optical reflection spectroscopy to observe the magnetic proximity effect in a gate-tunable ${\mathrm{MoSe}}_{2}/{\mathrm{CrBr}}_{3}$ heterostructure. The high quality of the interface leads to a giant zero-field splitting of the $K$ and ${K}^{\ensuremath{'}}$ valley excitons in ${\mathrm{MoSe}}_{2}$, equivalent to an external magnetic field of 12 T, with a weak but distinct electric field dependence that hints at potential for electrical control of magnetization. The magnetic proximity effect allows us to use resonant optical spectroscopy to fully characterize the ${\mathrm{CrBr}}_{3}$ magnet, determining the easy-axis coercive field, the magnetic anisotropy energy, and critical exponents associated with spin susceptibility and magnetization.

CHIRRUP: a practical algorithm for unsourced multiple access

Abstract: Unsourced multiple access abstracts grantless simultaneous communication of a large number of devices (messages) each of which transmits (is transmitted) infrequently. It provides a model for machine-to-machine communication in the Internet of Things (IoT), including the special case of radio-frequency identification (RFID), as well as neighbor discovery in ad hoc wireless networks. This paper presents a fast algorithm for unsourced multiple access that scales to $2^{100}$ devices (arbitrary $100$ bit messages). The primary building block is multiuser detection of binary chirps which are simply codewords in the second order Reed Muller code. The chirp detection algorithm originally presented by Howard et al. is enhanced and integrated into a peeling decoder designed for a patching and slotting framework. In terms of both energy per bit and number of transmitted messages, the proposed algorithm is within a factor of $2$ of state of the art approaches. A significant advantage of our algorithm is its computational efficiency. We prove that the worst-case complexity of the basic chirp reconstruction algorithm is $\mathcal{O}[nK(\log_2 n + K)]$, where $n$ is the codeword length and $K$ is the number of active users, and we report computing times for our algorithm. Our performance and computing time results represent a benchmark against which other practical algorithms can be measured.

Unified framework for early dark energy from α -attractors

Abstract: One of the most appealing approaches to ease the Hubble tension is the inclusion of an early dark energy (EDE) component that adds energy to the Universe in a narrow redshift window around the time of recombination and dilutes faster than radiation afterwards. In this paper, we analyze EDE in the framework of $\ensuremath{\alpha}$-attractor models. As is well known, the success in alleviating the Hubble tension crucially depends on the shape of the energy injection. We show how different types of energy injections can be obtained, thanks to the freedom in choosing the functional form of the potential inspired by $\ensuremath{\alpha}$-attractor models. To confirm our intuition, we perform a Markov-chain Monte Carlo analysis for three representative cases and find indeed that ${H}_{0}$ is significantly larger than in $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$, like in other EDE models. Unlike axion-driven EDE models with a super-Planckian decay constant, the curvature of the potential in the EDE models required by the data is natural in the context of recent theoretical developments in $\ensuremath{\alpha}$-attractors.

Photo-rechargeable Zinc-Ion Capacitors using V 2 O 5 -Activated Carbon Electrodes

Abstract: Electrochemical energy storage devices that can harvest energy from the environment and store it are increasingly important to address energy poverty in developing parts of the world as well as pow...

Multi-objective dynamic and static reconfiguration with optimized allocation of PV-DG and battery energy storage system

Abstract: In the paradigm of the increasing trend towards decarbonisation, the use of sustainable renewable energy is widely recommended. Network reconfiguration, together with the incorporation of battery energy storage systems (BESS), facilitates the integration of renewable power and enhances the loadability of the system, leading to prolonged utilization of the existing equipment. Optimized allocation of PV-DG and BESS is implemented using particle swarm optimization (PSO) in the present work. Dynamic hourly and static seasonal reconfiguration with optimally allocated PV-DG and BESS is presented. Moreover, static annual reconfiguration, followed by the optimal apportionment of distributed resources, is achieved. The reconfiguration objectives considered are loss minimization as well as voltage, and loadability improvement. Hourly and seasonal variations in load and PV-DG generated power are taken into account. Additionally, ‘P’ and ‘PQV’ buses are incorporated in the load flow algorithm used in reconfiguration to facilitate remote voltage regulation. A comparison of the net annual energy savings is made among the three types of reconfiguration for three scenarios, namely, a system with PV-DG only, a system with PV-DG and BESS, and a system with PV-DG, BESS and P and PQV buses.

Self-Powered Solar-Blind Photodetectors Based on α/β Phase Junction of Ga 2 O 3

Abstract: Self-powered ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$-based solar-blind photodetectors have received attention recently due to the increased demand for energy saving, miniaturization, and high efficiency in devices. An ideal device structure consisting of a ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$-based p-n junction is still difficult to obtain, since p-type doping is a major challenge. Although self-powered devices based on heterojunction are promising, there are two fatal disadvantages: (1) photosensitivity of the non-solar-blind region, on account of the narrower band gap of the heterojunction materials; and (2) poor quality of the epitaxial film due to lattice mismatch. In view of the various polymorphs of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$, we propose constructing a structure consisting of a ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ phase junction with \ensuremath{\alpha} and \ensuremath{\beta} phases (\ensuremath{\alpha}/\ensuremath{\beta} phase junction) for self-powered solar-blind photodetectors. The small lattice mismatch and similar band gap between \ensuremath{\alpha}- and \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ will solve the two problems outlined above. The formation of \ensuremath{\alpha}- and \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ is expected to result in a type-II band alignment, promoting separation of photogenerated carriers, which transfer through the junction to the corresponding electrodes. Herein, the \ensuremath{\alpha}/\ensuremath{\beta} phase junction of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ vertically aligned nanorod arrays with a thickness-controllable \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ shell layer are fabricated by a low-cost and simple process of hydrothermal and postannealing treatment. Two different types of self-powered \ensuremath{\alpha}/\ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ phase junction-based photodetectors, in the form of solid-state type and photoelectrochemical type, are constructed and realized. Our analysis shows that the constructed photodetectors are capable of highly efficient detection of solar-blind signal without any bias voltage. This work demonstrates the usefulness of using the \ensuremath{\alpha}/\ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ phase junction in a self-powered solar-blind photodetector, which is not only energy efficient, but also potentially workable in outer space, at the south and north pole, and other harsh environments without external power for a long time.

A Triple-Band High-Gain Multibeam Ambient RF Energy Harvesting System Utilizing Hybrid Combining

Abstract: Overcoming the challenge of battery recharging and replacement in industry Internet-of-Things (IoT) applications is considered by proposing the design of a triple-band high-gain multibeam ambient radio frequency (RF) energy harvesting system utilizing hybrid combining. The novelty of the design is that it simultaneously exploits frequency, space, and polarization to maximize the harvested RF energy. Wideband hybrid combining is proposed, which enables the harvesting of energy at low RF power densities while maintaining the wide frequency and space coverage necessary for ambient RF energy harvesting. The antenna design consisting of 16-ports has an average area per port of $0.3\lambda \times 0.3\lambda$ (where $\lambda$ is the freespace wavelength at 1.8 GHz) and is demonstrated to achieve a wide relative bandwidth of 38.5% covering the GSM-1800, UMTS-2100, and WiFi frequency bands. Hybrid combining of the 16-port antenna provides multiple antenna beams each with up to 11 dBi antenna gain and these provide broad beam coverage. The design for the rectifiers, using multistub impedance matching, is also provided and these are shown to be efficient over the frequency bands of interest. Measurements in an anechoic chamber demonstrate that the proposed energy harvesting system can provide an output dc voltage of more than 755 mV, an output dc power of more than $-$ 6.4 dBm and RF-to-dc efficiencies greater than 40% when the power density is more than 1400 $\mu \mathrm{W}/\mathrm{m}^{2}$ . It is also shown that the proposed system can provide output dc power of 80 $\mu \mathrm{W}$ and 7.3 $\mu \mathrm{W}$ in real outdoor and indoor ambient environments, respectively.

Energy Efficient Routing in Wireless Sensor Networks: A Comprehensive Survey

Abstract: Wireless Sensor Networks (WSNs) are among the most emerging technologies, thanks to their great capabilities and their ever growing range of applications. However, the lifetime of WSNs is extremely restricted due to the delimited energy capacity of their sensor nodes. This is why energy conservation is considered as the most important research concern for WSNs. Radio communication is the utmost energy consuming function in a WSN. Thus, energy efficient routing is necessitated to save energy and thus prolong the lifetime of WSNs. For this reason, numerous protocols for energy efficient routing in WSNs have been proposed. This article offers an analytical and up to date survey on the protocols of this kind. The classic and modern protocols presented are categorized, depending on i) how the network is structured, ii) how data are exchanged, iii) whether location information is or not used, and iv) whether Quality of Service (QoS) or multiple paths are or not supported. In each distinct category, protocols are both described and compared in terms of specific performance metrics, while their advantages and disadvantages are discussed. Finally, the study findings are discussed, concluding remarks are drawn, and open research issues are indicated.

Energy Efficiency Modeling of Integrated Energy System in Coastal Areas

Abstract: Yang, C; Gao, F, and Dong, M, 2020 Energy efficiency modeling of integrated energy system in coastal areas In: Yang, Y; Mi, C; Zhao, L, and Lam, S (eds), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering Journal of Coastal Research, Special Issue No 103, pp 995–1001 Coconut Creek (Florida), ISSN 0749-0208In order to overcome the problem of large energy consumption cost in the traditional energy efficiency modeling method of integrated energy system, the energy efficiency modeling method of integrated energy system in coastal area is proposed to reduce the energy consumption cost of integrated energy system in coastal area Based on the energy network of the integrated energy system, the energy conversion relationship of the integrated energy system is analyzed, and a group of independent variables in the energy network is selected to calculate the complexity of the energy network The time-varying energy network equation of the comprehensive energy system is established by establishing the difference matrix of the strength at both ends of the branch Combined with the process of energy efficiency modeling of integrated energy system in coastal areas, the cost of energy efficiency modeling of integrated energy system is improved, and the energy efficiency modeling of integrated energy system is realized The simulation results show that the proposed energy efficiency modeling method has lower energy consumption cost in the process of energy efficiency modeling

Constraining axion inflation with gravitational waves from preheating

Abstract: We study gravitational wave production from gauge preheating in a variety of inflationary models, detailing its dependence on both the energy scale and the shape of the potential. We show that preheating into Abelian gauge fields generically leads to a large gravitational wave background that contributes significantly to the effective number of relativistic degrees of freedom in the early universe, ${N}_{\mathrm{eff}}$. We demonstrate that the efficiency of gravitational wave production is correlated with the tensor-to-scalar ratio, $r$. In particular, we show that efficient gauge preheating in models whose tensor-to-scalar ratio would be detected by next-generation cosmic microwave background experiments ($r\ensuremath{\gtrsim}1{0}^{\ensuremath{-}3}$) will be either detected through its contribution to ${N}_{\mathrm{eff}}$ or ruled out. Furthermore, we show that bounds on ${N}_{\mathrm{eff}}$ provide the most sensitive probe of the possible axial coupling of the inflaton to gauge fields regardless of the potential.

Quarkyonic matter equation of state in beta-equilibrium

Abstract: Quark matter may appear due to a hadronic-quark transition in the core of a hybrid star. Quarkyonic matter is an approach in which both quarks and nucleons appear as quasiparticles in a crossover transition, and provides an explicit realization of early ideas concerning quark matter (e.g., the MIT bag model). This description has recently been employed by McLerran and Reddy to model chargeless (pure neutron) matter with an approach that has the virtue that the speed of sound rises quickly at a neutron-quark transition so as to satisfy observational constraints on the neutron star maximum mass ($\ensuremath{\gtrsim}2\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$) and the radius of a $1.4\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$ star (${R}_{1.4}\ensuremath{\lesssim}13.5\text{ }\text{ }\mathrm{km}$). Traditional models involving first-order transitions result in softer pressure-energy density relations that have difficulty satisfying these constraints except with very narrow choices of parameters. We propose a variation of quarkyonic matter involving protons and leptons whose energy can be explicitly minimized to achieve both chemical and beta equilibrium, which cannot be done in the chargeless formulation. Quarkyonic stellar models are able to satisfy observed mass and radius constraints with a wide range of model parameters, avoiding the obligatory fine-tuning of conventional hybrid star models, including requiring the transition density to be very close to the nuclear saturation density. Our formulation fits experimental and theoretical properties of the nuclear symmetry energy and pure neutron matter, and contains as few as three free parameters. This makes it an ideal tool for the study of high-density matter that is an efficient alternative to piecewise polytrope or spectral decomposition methods.

Signal and System Design for Wireless Power Transfer: Prototype, Experiment and Validation

Abstract: A new line of research on communications and signals design for Wireless Power Transfer (WPT) has recently emerged in the communication literature. Promising signal strategies to maximize the power transfer efficiency of WPT rely on (energy) beamforming, waveform, modulation and transmit diversity, and a combination thereof. To a great extent, the study of those strategies has so far been limited to theoretical performance analysis. In this paper, we study the real over-the-air performance of all the aforementioned signal strategies for WPT. To that end, we have designed, prototyped and experimented an innovative radiative WPT architecture based on Software-Defined Radio (SDR) that can operate in open-loop and closed-loop (with channel acquisition at the transmitter) modes. The prototype consists of three important blocks, namely the channel estimator, the signal generator, and the energy harvester. The experiments have been conducted in a variety of deployments, including frequency flat and frequency selective channels, under static and mobility conditions. Experiments highlight that a channel-adaptive WPT architecture based on joint beamforming and waveform design offers significant performance improvements in harvested DC power over conventional single-antenna/multi-antenna continuous wave systems. The experimental results fully validate the observations predicted from the theoretical signal designs and confirm the crucial and beneficial role played by the energy harvester nonlinearity.

Model-based reinforcement learning for biological sequence design

Abstract: The ability to design biological structures such as DNA or proteins would have considerable medical and industrial impact. Doing so presents a challenging black-box optimization problem characterized by the large-batch, low round setting due to the need for labor-intensive wet lab evaluations. In response, we propose using reinforcement learning (RL) based on proximal-policy optimization (PPO) for biological sequence design. RL provides a flexible framework for optimization generative sequence models to achieve specific criteria, such as diversity among the high-quality sequences discovered. We propose a model-based variant of PPO, DyNA-PPO, to improve sample efficiency, where the policy for a new round is trained offline using a simulator fit on functional measurements from prior rounds. To accommodate the growing number of observations across rounds, the simulator model is automatically selected at each round from a pool of diverse models of varying capacity. On the tasks of designing DNA transcription factor binding sites, designing antimicrobial proteins, and optimizing the energy of Ising models based on protein structure, we find that DyNA-PPO performs significantly better than existing methods in settings in which modeling is feasible, while still not performing worse in situations in which a reliable model cannot be learned.