Large Decay Research Articles

Improved Capacity Retention of SiO2-Coated LiNi0.6Mn0.2Co0.2O2 Cathode Material for Lithium-Ion Batteries

Surface degradation of Ni-enriched layered cathode material Li[Ni0.6Mn0.2Co0.2]O2 (NMC622) is the main reason that leads to large capacity decay during long-term cycling. In the frame of this research, an amorphous SiO2 coating was applied onto the surface of the commercially available NMC622 powder by a wet coating process, through the condensation reaction of tetraethyl orthosilicate. The chemical composition of the coating layer was analyzed by inductively-coupled plasma. The morphology was studied by scanning electron microscopy and transmission electron microscopy. Electrochemical properties, including cyclic voltammetry, galvanostatic cycling, and rate capability measurements in a half-cell configuration, were tested to compare the electrochemical behavior of the non-coated and coated NMC622 materials. It is shown that the rate performance of the NMC622 materials is not affected by the coating layer. After 700 cycles in the range of 3.0–4.3 V at 2 C discharge, the cells with SiO2-coated NMC622 materials retained 80% of their initial capacity, which is higher than the uncoated ones (74%). Physicochemical characterizations, e.g., XRD and SEM, were performed post-mortem to reveal the stabilizing mechanism of the SiO2-coated NMC622 electrodes after long-term cycling. Based on these results, this is due to the shielding effect of the coating between the NMC622 particle surface and the liquid electrolyte, along with its scavenging effect on HF. SiO2 coating is therefore a facile surface modification method that results in potentially significant enhancement of the cyclic stability of Ni-rich NMC materials.

Squeezing‐Enhanced Atom–Cavity Interaction in Coupled Cavities with High Dissipation Rates

AbstractThe realization of the strong coupling regime is requisite for implementing quantum information tasks. Here, a method for enhancing the atom–field coupling in highly dissipative coupled cavities is proposed. By introducing parametric squeezing into the primary cavity, which is only virtually excited under specific parametric conditions, coupling enhancement between the atom and the auxiliary cavity is realized for appropriate squeezing parameters. This enables the system to be robust against large cavity decay and atomic spontaneous emission. The observation of vacuum Rabi oscillations show that the originally weakly coupled system can be enhanced into an effective strong coupling regime.

CUPID-0: A double-readout cryogenic detector for Double Beta Decay search

CUPID-0 is the first large mass neutrino-less double beta decay (0νββ) experiment based on cryogenic calorimeters with dual read-out of light and heat for background rejection. The detector assembly, consisting of 26 ZnSe crystals, 2 natural and 24 enriched at 95% in 82Se, all coupled with bolometric light detectors, has been constructed respecting very strict protocols and procedures, from the material selection during crystal growth to the new and innovative detector framework, in the attempt to achieve the best performance of the array. The successful construction of the detector lead to promising preliminary results, here presented. The array is in fact taking data underground at LNGS (Italy) since March 2017 and the particle identification, enabled by the light read-out, provides an unprecedented background level, for cryogenic calorimeters, of only 3.2 countskeV−1t−1yr−1 in the region of interest of the 0νββ search for 82Se, namely around 3 MeV.

Upper and lower bounds of decay rates for [formula omitted] weak solutions of the surface quasi-geostrophic equation

This study is concerned with the large time decay estimates for weak solutions of the surface quasi-geostrophic equation with H˙−12 initial data. Due to some special observation together with applying the decay characters to the class of H˙−12-functions, we may show the upper and lower bounds of decay rates for the H˙−12 weak solution of the surface quasi-strophic equation. Moreover, as a 12-order derivative of H˙−12 weak solution, we further derive an improved upper and lower bounds of decay rates for L2 weak solution. The findings may be of independent interest and the technique can be also applied to the other related fluid dynamical model with solutions in the negative Sobolev spaces.

Studies on the decays in the perturbative QCD approach**Research exercises for excellent undergraduate students.

The decays are investigated for the first time in the perturbative QCD formalism based on the kT factorization theorem, where the light scalar κ is assumed as a two-quark state. Our numerical results and phenomenological analyses on the CP-averaged branching ratios and CP-violating asymmetries show that: (a) the and decays have large decay rates around , which could be examined by the upgraded large hadron collider beauty and/or Belle-II experiments in the near future; (b) a large decay rate of about appears in the pure annihilation channel, which could provide more evidence to help distinguish different QCD-inspired factorization approaches, even understand the annihilation decay mechanism; (c) the pure penguin modes and would provide a promising ground to search for the possible new physics because of their zero direct and mixing-induced CP violations in the standard model. The examinations with good precision from the future experiments will help to further study the perturbative and/or nonperturbative QCD dynamics involved in these considered decay modes.

Dissipative property for higher order nonlinear Schrödinger equation

We consider the Cauchy problem for the higher-order nonlinear Schrödinger equation (0.1)i∂tu+12∂x2u−14∂x4u=i3λ1u3+λ2u2u,t>1,x∈R,u1,x=u0x,x∈R,where the coefficients 0<λ1<λ2. The aim of the present paper is to prove the global existence of solutions to (??). Also we find the large time decay estimates for the solutions.

The social lives of married women: Peer effects in female autonomy and investments in children

In patriarchal societies, sticky norms affect married women's social circles, their autonomy, and the outcomes of intra-household bargaining. This paper uses primary data on women's social networks in Uttarakhand, India; the modal woman has only three friends, and over 80 percent do not have any friends of another caste. This paper examines the effect of a shock to friends' empowerment on a woman's autonomy, specifically physical mobility, access to social safety nets, and employment outside the household; perceived social norms; and an outcome of household bargaining: investments in her children. The analysis instruments for endogenous network formation using a woman's age and her caste network in the village. The key peer effect is the impact of having a friend who received an empowerment shock on a woman who did not receive that shock. The results show significant peer effects on only a few of the examined measures of women's autonomy. In contrast, peer effects exist on all considered outcomes of a daughters' diet and time spent on chores. The findings suggest a large decay rate between effects on own empowerment and peer effects. Interventions targeting child welfare through women's empowerment may generate second-order effects on intra-household decision-making, albeit with substantial decay rates, and thus benefit from targeted rather than randomized rollout. In contrast, interventions on gender roles and women's autonomy may be limited by the stickiness of social norms.

Air-Coupled and Resonant Pulse-Echo Ultrasonic Technique.

An ultrasonic, resonant, pulse-echo, and air-coupled nondestructive testing (NDT) technique is presented. It is intended for components, with regular geometries where it is possible to excite resonant modes, made of materials that have a high acoustic impedance (Z) and low attenuation coefficient (α). Under these conditions, these resonances will present a very large quality factor (Q) and decay time (τ). This feature is used to avoid the dead zone, produced by the echo coming from the first wall, by receiving the resonant echo from the whole specimen over a longer period of time. This echo is analyzed in the frequency domain to determine specimen resonant frequency, which can be further used to determine either velocity or thickness. Using wideband air-coupled transducers, we tested the technique on plates (steel, aluminum, and silicone rubber) by exciting the mode of the first thickness. As expected, the higher the Z and the lower the α, the better the technique performed. Sensitivity to deviations of the angle of incidence away from normal (±2°) and the possibility to generate shear waves were also studied. Then, it was tested on steel cylindrical pipes that had different wall thicknesses and diameters. Finally, the use of this technique to generate C-Scan images of steel plates with different thicknesses was demonstrated.

Global stability for solutions to the exponential PDE describing epitaxial growth

In this paper we prove the global existence, uniqueness, optimal large time decay rates, and uniform gain of analyticity for the exponential PDE h_t=\Delta e^{-\Delta h} in the whole space \mathbb{R}^d_x . We assume the initial data is of medium size in the Wiener algebra A(\mathbb{R}^d) ; we use the initial condition \Delta h_0 \in A(\mathbb{R}^d) which is scale-invariant with respect to the invariant scaling of the exponential PDE. This exponential PDE was derived in [18] and more recently in [22].

Search for neutral Higgs bosons within type-I 2HDM at future linear colliders

In this study, we investigate observability of the neutral scalar (H) and pseudoscalar (A) Higgs bosons in the framework of the type-I 2HDM at SM-like scenario at a linear collider operating at sqrt{s}= 500 and 1000 GeV. The signal process is e^- e^+ rightarrow A H rightarrow ZHHrightarrow jj b{bar{b}}b{bar{b}} where jj is a di-jet resulting from the Z boson decay and b{bar{b}} is a b-jet pair from scalar Higgs boson decay. Several benchmark scenarios with different mass hypotheses are studied. The assumed signal process is mainly motivated by the large decay rate of Arightarrow ZH (at high tan beta and enough Higgs boson mass splitting) and Hrightarrow b{bar{b}} in the type-I. After event generation the detector response is simulated based on the SiD detector at the ILC. The ISR and beamstrahlung effects are also included for each center of mass energy assuming unpolarized beams. The simulated events are analyzed to obtain candidate mass distributions of the Higgs bosons. Among standard model backgrounds, the top quark pair production process is the main background but is under control. Results indicate that, in all considered scenarios, both Higgs bosons H and A are observable with signals exceeding 5sigma with possibility of mass measurement. Final results are shown as 5sigma contours in (m_H,m_A) or (m_A,tan beta ) space.

Axion misalignment driven to the bottom

Several theoretical motivations point to ultralight QCD axions with large decay constants {f}_asimeq mathcal{O}left({10}^{16}-{10}^{17}right) mathrm{GeV} , to which experimental proposals are dedicated. This regime is known to face the problem of overproduction of axion dark matter from the misalignment mechanism unless the misalignment angle θmis is as small as mathcal{O}left({10}^{-3}-{10}^{-4}right) , which is generally considered a fine-tuning problem. We investigate a dynamical explanation for a small θmis. The axion mass arises from strong dynamics and may be sufficiently enhanced by early dynamics so as to overcome Hubble friction and drive the field value to the bottom of the potential long before the QCD phase transition. Together with an approximate CP symmetry in the theory, this minimum is very closely related to today’s value and thus θmis can automatically be well under unity. Owing to such efficient relaxation, the isocurvature perturbations are essentially damped. As an existence proof, using supersymmetric theories we illustrate that the Higgs coupling with the inflaton energy can successfully achieve this axion damping in a consistent inflationary cosmology.

A multiscale reconstructing method for shale based on SEM image and experiment data

Owing to the presence of multiscale pore structures, characterization of laminated shales is both extremely difficult and substantially different from that of conventional reservoirs, and defies conventional methodologies. In this paper, a multiscale reconstructing method for shale is proposed to generate 3D layer representative elementary volume (lREV)-scale digital-experimental models to characterize the multiscale pore structure of the shale by means of the combination of a large area SEM image, nitrogen adsorption and pressure pulse decay experiment result. In this method an improved multiscale superposition algorithm is introduced to integrate the reconstructed complex models from nanoscale to mesoscale together, and it can preserve the details and main features enormously of each typical component (nanoscale organic pores in organic matter and pyrites, micro-nano inorganic pores and micro slits) in the shale. Especially, to accurately reproduce the realistic morphology for shale, the proposed method uses the experimental pore size distribution and permeability as constrain conditions to adjust and optimize the lREV-scale digital-experimental model. Our proposed method was tested on Longmaxi and Wufeng shale samples, and the reconstructed lREV-scale digital-experimental model are proved to accurately describe the representative structure of the complex multiscale pore space of the typical layer of the shale. The success of this method provides a promising way for reconstructing more realistic model to continuously and systematically characterize the pore (slits) structure from the nanopore-scale to the lREV-scale. It can advance the understanding of the various gas transport mechanisms at different scales and will be helpful for understanding the quality of the shale reservoir.

Global existence of strong solutions with vacuum to the multi-dimensional inhomogeneous incompressible MHD equations

In this paper, we are concerned with the Cauchy problem of the multi-dimensional inhomogeneous incompressible magnetohydrodynamic equations with fractional dissipation. We prove the unique global strong solution with vacuum to the magnetohydrodynamic equations over the whole space. In addition, the large time decay rates of the corresponding strong solution are also obtained. Note that our result is proved without any smallness on the initial data. Moreover, the initial density is allowed to be nonnegative, and in particular, the initial vacuum is allowed. To our best knowledge, this is the first result on the inhomogeneous fractional magnetohydrodynamic equations.

Non-Hermitian degeneracies of internal–external mode pairs in dielectric microdisks

Open quantum and wave systems can exhibit non-Hermitian degeneracies called exceptional points, where both the eigenvalues and the corresponding eigenstates coalesce. Previously, such exceptional points have been investigated in dielectric microcavities in terms of optical modes which are well confined inside the cavity. However, beside these so-called “internal modes” with a relatively high quality factor, there exists another kind of mode called “external modes,” which have a large decay rate and almost zero intensity inside the cavity. In the present paper, we demonstrate the physical significance of the external modes via the occurrence of exceptional points of internal–external mode pairs for transverse electric polarization. Our numerical studies show that these exceptional points can be achieved by either a boundary deformation of the microdisk or by introducing absorption into a circular cavity.

Three-state Landau-Zener model in the presence of dissipation

A population transfer based on adiabatic evolutions in a three-state system undergoing an avoided crossing is considered. The efficiency of the process is analyzed in connection with the relevant parameters, bringing to light an important role of the phases of the coupling constants. The role of dissipation is also taken into account, focusing on external decays that can be described by effective non-Hermitian Hamiltonians. Though the population transfer turns out to be quite sensitive to the decay processes, for very large decay rates the occurrence of a Zeno-phenomenon allows for restoring a very high efficiency.

Three-dimensional modeling of magneto-optical trapping of MgF molecules with multilevel rate equations

We present a theoretical study of magneto-optical trapping (MOT) force exerted on magnesium monofluoride (MgF) with 3D rate equations, in which we have considered the complex vibrational and rotational levels and the effects of small internal splittings and degeneracies,including fine and hyperfine structures and the magnetic quantum numbers. We investigate the feasibility of MOT for MgF with a very small excited state g-factor ($g_{e} = -0.0002$) and a large radiative decay reate (${\Gamma} = 2{\pi}\times22$MHz) for the electronic transition of X$^2{\Sigma}^{+}$ to A$^2\Pi_{1/2}$ states. We also optimize the MOT with reference to the three-, four- and more-frequency component models with various polarization configurations and detunings. By applying the dual frequency arrangement to more than one hyperfine level, we suggest a configuration of the 3+1 frequency components for achieving the MOT of MgF.

Large field ranges from aligned and misaligned winding

We search for effective axions with super-Planckian decay constants in type IIB string models. We argue that such axions can be realised as long winding trajectories in complex-structure moduli space by an appropriate flux choice. Our main findings are: the simplest models with aligned winding in a 2-axion field space fail due to a general no-go theorem. However, equally simple models with misaligned winding, where the effective axion is not close to any of the fundamental axions, appear to work to the best of our present understanding. These models have large decay constants but no large monotonic regions in the potential, making them unsuitable for large-field inflation. We also show that our no-go theorem can be avoided by aligning three or more axions. We argue that, contrary to misaligned models, such models can have both large decay constants and large monotonic regions in the potential. Our results may be used to argue against the refined Swampland Distance Conjecture and strong forms of the axionic Weak Gravity Conjecture. It becomes apparent, however, that realising inflation is by far harder than just producing a light field with large periodicity.

Unexpectedly Large Decay Lengths of Double-Layer Forces in Solutions of Symmetric, Multivalent Electrolytes.

Double-layer forces acting between micron-sized silica particles are measured with the atomic force microscope in solutions of symmetric, multivalent electrolytes. In particular, the 2:2 electrolytes, CuSO4 and MgSO4, and the 3:3 electrolyte LaFe(CN)6 were investigated. For the multivalent electrolytes, the measured decay lengths are substantially larger than the ones expected on the basis of simple Debye-Hückel (DH) theory. These deviations can be explained quantitatively by the formation of neutral ion pairs. The measured surface charge density decreases in magnitude with increasing valence. Both effects are caused by ion-ion correlations, which are not included in the classical DH theory. However, this theory remains applicable, provided one considers the formation of ion pairs in solution and an effective surface charge density. This effective charge is substantially smaller in magnitude than the one of the bare surface. This reduction results from adsorption of counterions, which becomes stronger with increasing valence. These observations reveal that DH theory is applicable even in the presence of multivalent ions, provided the effective parameters are chosen appropriately.

Cavity-assisted atomic Raman memories beyond the bad cavity limit: Effect of four-wave mixing

Quantum memories can be used not only for the storage of quantum information, but also for substantial manipulation of ensembles of quantum states. Therefore, the speed of such manipulation and the ability to write and retrieve the signals of relatively short duration becomes important. Previously there have been considered the limits on efficiency of the cavity-enhanced atomic Raman memories for the signals whose duration is not much larger than the cavity field lifetime, that is, beyond the bad cavity limit. We investigate in this work the four-wave mixing noise that arises by the retrieval of the relatively short signals from the cavity-assisted memories, thus complementing recent considerations by other authors, who mainly concentrated on the limit of large cavity decay rate. The four-wave mixing noise is commonly recognized as an important factor, able to prevent achieving a high memories quality in a variety of the atomic, solid state etc. implementations. The side-band noise sources (with respect to the quantized signal, supported by the cavity) play important role in the four-wave mixing. We propose an approach that allows one to account for the side-band quantum noise sources of different physical origin in the cavity-assisted atomic memories using a unified theoretical framework, based on a two-band spectral filtering of the noise sources. We demonstrate that in such spectrally-selective memories the side-band atomic noise sources essentially contribute to the four-wave mixing noise of the retrieved signal on a par with the side-band quantized field entering the cavity.

Global Existence and Large Time Asymptotic Behavior of Strong Solution to the Cauchy Problem of 2D Density-Dependent Boussinesq Equations with Vacuum

We dedicate to the 2D density-dependent nonhomogeneous incompressible Boussinesq equations with vacuum on . At infinity, if the attenuation of initial density and temperature is not very slow. And it is gained that there is a global strong solution and is unique for the 2D Cauchy problem with the initial density which can allow vacuum conditions and even have compact support. Besides, the large time decay rates of the gradients of velocity, temperature and pressure can also be obtained which are also the same as those of the homogeneous case.