Intrinsic Quantity Research Articles

Enhancing the catalytic performance of H-ZSM-5 in bio n-butanol dehydration by zeolite crystal engineering

NH4F etching is used as an unbiased chemical etching technique to hierarchize commercially available nano-sized ZSM-5 crystals. A structure-function relationship is reported, describing how the introduction of mesoporosity in a microporous ZSM-5 zeolite significantly increases its catalytic performance in (aqueous) n-butanol dehydration. Three parent samples are etched under two severity modes: mild (5 minutes of etching) and harsh (40 minutes of etching). Intrinsic features of the parent ZSM-5’s, such as their silanol populations, influence the outcome of the etching procedure. For all materials, crystallinity is unaffected, total pore volume increases while micropore volume is almost constant, and active site accessibility increases. For all materials, etching increases the catalytic activity for n-butanol dehydration. Cofeeding water to n-butanol further increases the stability of all catalysts. Microkinetic modeling reveals that the increased activity is related to a decreased stability of dibutyl ether (DBE), the most abundant surface intermediate. A decreased DBE adsorption energy, due to the increased accessibility of the acid sites, facilitates its desorption. NH4F etching, a flexible and easy technique to engineer zeolites' textural properties, does not affect the intrinsic nature and quantity of their active sites, leading to superior catalytic performances. Our results highlight the possibility to further increase the efficiency of zeolite catalysis in biomass conversion processes.

Giant Third-Order Nonlinear Hall Effect in Misfit Layer Compound (SnS)1.17(NbS2)3.

The nonlinear Hall effect (NLHE) holds immense significance in recognizing the band geometry and its potential applications in current rectification. Recent discoveries have expanded the study from second-order to third-order nonlinear Hall effect (THE), which is governed by an intrinsic band geometric quantity called the Berry Connection Polarizability tensor. Here we demonstrate a giant THE in a misfit layer compound, (SnS)1.17(NbS2)3. While the THE is prohibited in individual NbS2 and SnS due to the constraints imposed by the crystal symmetry and their band structures, a remarkable THE emerges when a superlattice is formed by introducing a monolayer of SnS. The angular-dependent THE and its scaling relationship indicate that the phenomenon could be correlated to the band geometry modulation, concurrently with the symmetry breaking. The resulting strength of THE is orders of magnitude higher compared to recent studies. Our work illuminates the modulation of structural and electronic geometries for novel quantum phenomena through interface engineering.

New characteristic parameter of energy loss in permalloy

Characteristic parameters of energy storage and loss in soft magnetic materials (SMMs), product S of initial susceptibility and resonance frequency and product L of maximum and half width of imaginary part, were introduced in permalloy films. Expressions of characteristic parameters were derived from Landau–Lifshits–Gilbert equation with a general anisotropic free energy model. It was found S = L equals to intrinsic quantity of SMMs , where γ is the gyromagnetic ratio, is the saturation magnetization, and and are mutually orthogonal effective magnetic fields. In the presence of eddy current, it was found S remains equal to Q while L < Q results from inhomogeneity of microwave magnetic field caused by eddy current. Moreover, a linear scale of versus Gilbert damping factor α was found in permalloy films with different thicknesses. Hence, our findings provide a new perspective on energy storage and loss of SMMs.

Twisted curve geometry underlying topological invariants

Topological invariants such as winding numbers and linking numbers appear as charges of topological solitons in diverse nonlinear physical systems described by a unit vector field defined on two and three dimensional manifolds. While the Gauss-Bonnet theorem shows that the Euler characteristic (a topological invariant) can be written as the integral of the Gaussian curvature (an intrinsic geometric quantity), the intriguing question of whether winding and linking numbers can also be expressed as integrals of some other kinds of intrinsic geometric quantities has not been addressed in the literature. In this paper we provide the answer by showing that for the winding number in two dimensions, these geometric quantities involve torsions of the two evolving space curves describing the manifold. On the other hand, in three dimensions we find that in addition to torsions, intrinsic twists of the space curves are necessary to obtain a nontrivial winding number and linking number. They arise from the hitherto unknown connections that we establish between these topological invariants and the corresponding appropriately normalized global space curve anholonomies (i.e., geometric phases) that can be associated with the unit vector fields on the respective manifolds. An application of our results to a 3D Heisenberg ferromagnetic model supporting a topological soliton is also presented.

The Discrete Theorema Egregium

In 1827, Gauss proved that Gaussian curvature is actually an intrinsic quantity, meaning that it can be calculated just from measurements within the surface. Before, curvature of surfaces could only be computed extrinsically, meaning that an ambient space is needed. Gauss named this remarkable finding Theorema Egregium. In this paper, we discuss a discrete version of this theorem for polyhedral surfaces. We give an elementary proof that the common extrinsic and intrinsic definitions of discrete Gaussian curvature are equivalent.

Constraint dependence of pressure on a passive probe in an active bath

Mechanical pressure in active matter is generally not a state variable and possesses abnormal properties, in stark contrast to equilibrium systems. We here show that the pressure on a passive probe exerted by an active fluid even depends on external constraints on the probe by means of simulation and theory, implying that the mechanical pressure is not an intrinsic physical quantity of active systems. The active mechanical pressure on the passive probe significantly increases and saturates as its elastic constraint (realized by a trap potential) or kinematic constraint (realized by environmental friction) strengthens. The microscopic origin for the constraint-dependent pressure is that the constraints influence the probe dynamics, and hence change the frequency and intensity of the collisions between the probe and active particles. Our findings not only greatly advance the understanding of active mechanical pressure but also provide a new way to in situ tune it.

Unraveling electronic fluctuation in passivation hypothesis for ultralow friction in diamond

Passivation hypothesis has been widely applied to interpret the outstanding tribological properties of diamond, where the ultralow friction is often attributed to the static charge repulsion between the passivated sliding surfaces. However, the action of the dynamic charge of the contact in the sliding process is still open. Here, the mechanism of passivation hypothesis is disassembled by the electronic fluctuation in the ultralow friction sliding. Typical frictional systems of diamond contact surfaces, ranging from different crystallographic structures and interfacial passivated groups, are studied by using density-functional theory (DFT) calculations. The charge density evolution along the sliding pathway is investigated to track the frictional energy dissipation in the mutual sliding between the passivated surfaces. It finds that the shallow energy corrugation synchronously varies with the charge redistribution during the slip, giving a linear dependence of ultralow friction on the electronic fluctuation acting within the sliding interfaces. The proportionality coefficient, which indicates the response of charge density in the ultralow dissipation, gives intrinsic quantity of the friction systems and is mainly determined by both the passivation groups and the lattice parameters of the sliding surfaces. Therefore, we demonstrate the dynamic fluctuation of charge density along the sliding direction underlies the mechanism of passivation hypothesis. An electronic fluctuation model is proposed to interpret the passivation hypothesis for guiding the design of superlubric diamond-like carbon (DLC). This is in contrast with the paradigm that the super-low friction is determined by the static charge repulsion.

Interrelation between the Solid-State Synthesis Conditions and Magnetic Properties of the NiCr2O4 Spinel

The synthesis of the NiCr2O4 compound with the spinel structure via the high-temperature solid-state reaction leads to different deviations of the cationic composition from the nominal depending on the atmosphere in the furnace chamber. The samples prepared from the same starting NiO and Cr2O3 compounds but in different atmospheres differ in phase composition and orbital and spin ordering temperatures. We find that a common route of synthesis in the air and a possible presence of the Ni2O3 in initial NiO lead to the incorporation of the Ni3+ ions into the octahedral sites regularly occupied by the Cr3+ ions. This results in a decrease in the orbital ordering and an increase in the Nèel temperatures. We propose that the Nèel temperature value serves as a measure of a departure of a composition from the nominal NiCr2O4. The lowest Nèel temperature among our series was TN = 63 K which we consider the closest to the intrinsic quantity of the NiCr2O4 compound.

A robust ultrasonic characterization methodology for lithium-ion batteries on frequency-domain damping analysis

Recently, non-invasive ultrasonic-based detection has emerged as a powerful tool to estimate the state-of-charge (SOC) and state-of-health (SOH) of lithium-ion batteries with a promising accuracy and efficiency. However, the currently available non-invasive methodology is highly sensitive to experimental setups and conditions, leading to unpredictable and unstable results. To this end, from a more fundamental stress wave propagation perspective, we discover that the quantified change of ultrasonic damping can be an intrinsic physical quantity to correlate with the state-of-charge (SOC) of batteries. We employ time-harmonic waves with different frequencies to obtain the steady-state dynamic response of lithium-ion batteries at various SOCs and a quasi-periodic energy gap can be observed. A mesoscale physics-based model of lithium-ion batteries is established to explain the observed energy gap carrying the multiple reflections of ultrasonic waves within the multi-layered structure of the cell. Finally, the change of ultrasonic damping with SOC is quantified for fast and accurate SOC prediction based on the frequency-domain damping analysis. Results underpin a robust and accurate frequency-domain ultrasonic characterization methodology for batteries and highlight the promise of the fundamental understanding of wave propagation for advanced characterization of batteries.

Chinese Adolescents' Reading Motivation Profiles and Their Relations to Reading Amount.

This study used a person-centered approach to identify reading motivation profiles of 514 Chinese adolescents in seventh- to ninth-grade, based on dimensions of intrinsic reading motivation (curiosity and involvement) and extrinsic reading motivation (grades and competition). Furthermore, the effects of each profile on outcome variables (reading amount for enjoyment and for school) were investigated. Latent profile analyses revealed three reading motivation profiles: high quantity (high on all four dimensions), high intrinsic (high on curiosity and involvement, low on grades, and competition), and moderate quantity (moderate on all four dimensions). The high-intrinsic and high-quantity profiles proved to be equally successful in terms of amount of reading for enjoyment and for school, and both significantly exceeded the moderate-quantity profile. The current findings emphasize the importance of intrinsic reading motivation and the importance of quality of motivation, compared with its quantity.

Optical angular momentum in atomic transitions: a paradox

Stated simply the paradox is as follows: it is clear that the orbital angular momentum of a light beam in its direction of propagation is an intrinsic quantity, and therefore has the same value everywhere in the beam. How then can a Gaussian beam, with precisely zero orbital angular momentum, drive a (single-photon) quadrupole transition which requires the transfer of angular momentum 2ℏ to an absorbing atom?

Berry connection polarizability tensor and third-order Hall effect

One big achievement in modern condensed matter physics is the recognition of the importance of various band geometric quantities in physical effects. As prominent examples, Berry curvature and the Berry curvature dipole are connected to the linear and the second-order Hall effects, respectively. Here, we show that the Berry connection polarizability (BCP) tensor, as another intrinsic band geometric quantity, plays a key role in the third-order Hall effect. Based on the extended semiclassical formalism, we develop a theory for the third-order charge transport and derive explicit formulas for the third-order conductivity. Our theory is applied to the two-dimensional (2D) Dirac model to investigate the essential features of the BCP and the third-order Hall response. We further demonstrate the combination of our theory with the first-principles calculations to study a concrete material system, the monolayer FeSe. Our work establishes a foundation for the study of third-order transport effects, and reveals the third-order Hall effect as a tool for characterizing a large class of materials and for probing the BCP in band structure.

Label-free multiplexed microtomography of endogenous subcellular dynamics using generalizable deep learning.

Simultaneous imaging of various facets of intact biological systems across multiple spatiotemporal scales is a long-standing goal in biology and medicine, for which progress is hindered by limits of conventional imaging modalities. Here we propose using the refractive index (RI), an intrinsic quantity governing light-matter interaction, as a means for such measurement. We show that major endogenous subcellular structures, which are conventionally accessed via exogenous fluorescence labelling, are encoded in three-dimensional (3D) RI tomograms. We decode this information in a data-driven manner, with a deep learning-based model that infers multiple 3D fluorescence tomograms from RI measurements of the corresponding subcellular targets, thereby achieving multiplexed microtomography. This approach, called RI2FL for refractive index to fluorescence, inherits the advantages of both high-specificity fluorescence imaging and label-free RI imaging. Importantly, full 3D modelling of absolute and unbiased RI improves generalization, such that the approach is applicable to a broad range of new samples without retraining to facilitate immediate applicability. The performance, reliability and scalability of this technology are extensively characterized, and its various applications within single-cell profiling at unprecedented scales (which can generate new experimentally testable hypotheses) are demonstrated.

Porous Noble Metal Electrocatalysts: Synthesis, Performance, and Development.

Active sites (intrinsic activity, quantity, and distribution), electron transfer, and mass diffusion are three important factors affecting the performance of electrocatalysts. Composed of highly active components which are built into various network structures, porous noble metal is an inherently promising electrocatalysts. In recent years, great efforts have been made to explore new efficient synthesis methods and establish structural-performance relationships in the field of porous noble metal electrocatalysis. In this review, the very recent progress in strategies for preparing porous noble metal, including innovation and deeper understanding of traditional methods is summarized. A discussion of relationship between porous noble metal structure and electrocatalytic performance, such as accessibility of active sites, connectivity of skeleton structures, channels dimensions, and hierarchical structures, is provided.

Scientific understanding of the fundamentals of China's economic development

PurposeThe purpose of this paper is based on China’s economic fundamentals. Factor input, structural optimization and institutional reform, which determine the fundamentals of China's economic development, will actively prop up long-term, sustained and stable growth of the Chinese economy and keep China's potential economic growth rate stabilized within a reasonable growth range in the long term.Design/methodology/approachThe fundamentals of economic development of a country are the basic situation of economic operation determined by the country's main factors and the long-term trend thereof, and they have such characteristics as stability, internality and persistence.FindingsStability refers to economic operation that remains relatively stable within a reasonable growth range at a certain stage of development, and this does not rule out exceptional economic fluctuations in certain years due to the impact of unexpected short-term factors. For instance, the fundamentals of the Chinese economy during the period after the reform and opening-up are characterized by a sustained high growth rate.Originality/valueInternality refers to the intrinsic quantity and quality of all factors supporting the economic development of a country, especially the quantity and quality of the factors that play a decisive role in the economic development of a country at a specific stage. For instance, demographic dividend and capital formation have bolstered the high-speed growth of the Chinese economy since the reform and opening-up.

The Structure of Fluctuations in Stochastic Homogenization

Four quantities are fundamental in homogenization of elliptic systems in divergence form and in its applications: the field and the flux of the solution operator (applied to a general deterministic right-hand side), and the field and the flux of the corrector. Homogenization is the study of the large-scale properties of these objects. In case of random coefficients, these quantities fluctuate and their fluctuations are a priori unrelated. Depending on the law of the coefficient field, and in particular on the decay of its correlations on large scales, these fluctuations may display different scalings and different limiting laws (if any). In this contribution, we identify another crucial intrinsic quantity, motivated by H-convergence, which we refer to as the homogenization commutator and is related to variational quantities first considered by Armstrong and Smart. In the simplified setting of the random conductance model, we show what we believe to be a general principle, namely that the homogenization commutator drives at leading order the fluctuations of each of the four other quantities in a strong norm in probability, which is expressed in form of a suitable two-scale expansion and reveals the pathwise structure of fluctuations in stochastic homogenization. In addition, we show that the (rescaled) homogenization commutator converges in law to a Gaussian white noise, and we analyze to which precision the covariance tensor that characterizes the latter can be extracted from the representative volume element method. This collection of results constitutes a new theory of fluctuations in stochastic homogenization that holds in any dimension and yields optimal rates. Extensions to the (non-symmetric) continuum setting are also discussed, the details of which are postponed to forthcoming works.

Efficient process planning of laser peen forming for complex shaping with distributed eigen-moment

Abstract Laser peen forming (LPF) is a flexible forming process that brings many challenges for complex shaping. This study aims to develop an effective optimization method to complete efficient process planning of LPF to generate the desired geometry shape. The eigen-moment is proposed as a new intermediate variable to describe the bending deformation to relate the LPF process parameters and the geometry shape. The governing equation of eigen-moment is derived to characterize the bending deflection with a PDE equation. The numerical computation method is developed by the PDE weak form and finite element method to predict the bending shape. To achieve process planning of complex shaping, the distributed eigen-moment on both plate surfaces is prescribed, and a PDE-constrained optimization is utilized to define the process planning problem of LPF. Then, the eigen-moment field is optimized by adopting the interior-point algorithm to obtain the desired shape. The proposed eigen-moment is verified to be an intrinsic physical quantity to describe the bending behavior of LPF. A complex shape with saddle geometry is used as a typical case to demonstrate the process planning method. The experiments conducted with the planned LPF process parameters are validated to produce a shape consistent with the designed geometry.

Inversion phenomenon and effective charging quantity in capacitive deionization device

The inversion desalination in capacitive deionization (CDI) due to overcharging leads to low salt adsorption and high energy consumption. Carefully controlling the charging process can effectively avoid the energy consumption from the inversion desalination and improve the desalination performance. In this study, by using the activated carbon (AC) electrode as a representative, the CDI charging process was analyzed in detail by adjusting the charging current, voltage, and the concentration of salt solution. The effective charging quantity of the electrode, defined by the inflection point of the inversion phenomenon, was found to be the inherent property of porous carbon material, which is independent of the test conditions and only depends on the surface characteristics and pore structure of AC material. The effective charging quantity of AC was increased only through varying the surface charge state by surface modification or applying an ion exchange membrane. The improvement of the pore structure of AC by KOH treatment led to the increase of effective charging quantity by retarding the appearance of inversion phenomenon. The present study provides a vital guidance for better understanding the inversion deionization phenomenon. The discovery of the intrinsic charging quantity is very helpful to avoid overcharging in practical CDI engineering application.

Mathematical models of Markovian dephasing

We develop a notion of dephasing under the action of a quantum Markov semigroup in terms of convergence of operators to a block-diagonal form determined by irreducible invariant subspaces. If the latter are all one-dimensional, we say the dephasing is maximal. With this definition, we show that a key necessary requirement on the Lindblad generator is bistochasticity, and focus on characterizing whether a maximally dephasing evolution may be described in terms of a unitary dilation with only classical noise, as opposed to a genuine non-commutative Hudson–Parthasarathy dilation. To this end, we make use of a seminal result of Kümmerer and Maassen on the class of commutative dilations of quantum Markov semigroups. In particular, we introduce an intrinsic quantity constructed from the generator, the Hamiltonian obstruction, which vanishes if and only if the latter admits a self-adjoint representation and quantifies the hindrance to having a classical diffusive noise model.

Quantum confinement on non-complete Riemannian manifolds

We consider the quantum completeness problem, i.e. the problem of confining quantum particles, on a non-complete Riemannian manifold M equipped with a smooth measure \omega , possibly degenerate or singular near the metric boundary of M , and in presence of a real-valued potential V\in L^2_\mathrm {loc}(M) . The main merit of this paper is the identification of an intrinsic quantity, the effective potential V_\mathrm {eff} , which allows to formulate simple criteria for quantum confinement. Let \delta be the distance from the possibly non-compact metric boundary of M . A simplified version of the main result guarantees quantum completeness if V\ge -c\delta^2 far from the metric boundary and V_\mathrm {eff}+V\ge \frac3{4\delta^2}-\frac{\kappa}{\delta}, \quad \mathrm {close \:to \:the \:metric \:boundary}. These criteria allow us to: (i) obtain quantum confinement results for measures with degeneracies or singularities near the metric boundary of M ; (ii) generalize the Kalf–Walter–Schmincke–Simon Theorem for strongly singular potentials to the Riemannian setting for any dimension of the singularity; (iii) give the first, to our knowledge, curvature-based criteria for self-adjointness of the Laplace–Beltrami operator; (iv) prove, under mild regularity assumptions, that the Laplace–Beltrami operator in almost-Riemannian geometry is essentially self-adjoint, partially settling a conjecture formulated in [9].