Search Results (16)

The aim of the present study is to investigate the influence of Nickel–Hexagonal Boron Nitride (Ni-hBN) nanocomposite coatings, deposited using the pulse reverse current electrodeposition technique. This experimental study focuses on assessing the tribological and corrosion properties of the produced coatings on the SS304 substrate. The microhardness of the as-deposited (AD) sample and heat-treated (HT) sample were 49% and 83.8% higher compared to the control sample. The HT sample exhibited a grain size which was approximately 9.7% larger than the AD sample owing to the expansion–contraction mechanism of grains during heat treatment and sudden quenching. Surface roughness reduced after coating, where the Ni-hBN-coated sample measured a roughness of 0.43 µm compared to 0.48 µm for the bare surface. The average coefficient of friction for the AD sample was 42.4% lower than the bare surface owing to the self-lubricating properties of nano hBN. In particular, the corrosion rate of the AD sample was found to be 0.062 mm/year, which was lower than values reported in other studies. As such, findings from the present study can be particularly beneficial for applications in the automotive and aerospace industries, where enhanced wear resistance, reduced friction, and superior corrosion protection are critical for components such as engine parts, gears, bearings and shafts. Full article

We discuss different quench protocols for Ising and XY spin chains in a transverse magnetic field. With a sudden local magnetic field quench as a starting point, we generalize our approach to a large class of local non-sudden quenches. Using finite time path field theory (FTPFT) perturbative methods, we show that the difference between the sudden quench and a class of quenches with non-sudden switching on the perturbation vanishes exponentially with time, apart from non-substantial modifications that are systematically accounted for. As the consequence of causality and analytic properties of functions describing the discussed class of quenches, this is true at any order of perturbation expansion and thus for the resummed perturbation series. The only requirements on functions describing the perturbation strength switched on at a finite time $t=0$ are as follows: (1) their Fourier transform $f\left(p\right)$ is a function that is analytic everywhere in the lower complex semiplane, except at the simple pole at $p=0$ and possibly others with $\Im \left(p\right)<0$; and (2) $f\left(p\right)/p$ converges to zero at infinity in the lower complex semiplane. A prototypical function of this class is $tanh\left(\eta t\right)$, to which the perturbation strength is proportional after the switching at time $t=0$. In the limit of large $\eta$, such a perturbation approaches the case of a sudden quench. It is shown that, because of this new type of universal behavior of Loschmidt echo (LE) that emerges in an exponentially short time scale, our previous results for the sudden local magnetic field quench of Ising and XY chains, obtained by the resummation of the perturbative expansion, extend in the long-time limit to all non-sudden quench protocols in this class, with non-substantial modifications systematically taken into account. We also show that analogous universal behavior exists in disorder quenches, and ultimately global ones. LE is directly connected to the work probability distribution, and the described universal behavior is therefore appropriate in potential concepts of quantum technology related to spin chains. Full article

Quantum information scrambling refers to the spread of the initially stored information over many degrees of freedom of a quantum many-body system. Information scrambling is intimately linked to the thermalization of isolated quantum many-body systems, and has been typically studied in a sudden quench scenario. Here, we extend the notion of quantum information scrambling to critical quantum many-body systems undergoing an adiabatic evolution. In particular, we analyze how the symmetry-breaking information of an initial state is scrambled in adiabatically driven integrable systems, such as the Lipkin–Meshkov–Glick and quantum Rabi models. Following a time-dependent protocol that drives the system from symmetry-breaking to a normal phase, we show how the initial information is scrambled, even for perfect adiabatic evolutions, as indicated by the expectation value of a suitable observable. We detail the underlying mechanism for quantum information scrambling, its relation to ground- and excited-state quantum phase transitions, and quantify the degree of scrambling in terms of the number of eigenstates that participate in the encoding of the initial symmetry-breaking information. While the energy of the final state remains unaltered in an adiabatic protocol, the relative phases among eigenstates are scrambled, and so is the symmetry-breaking information. We show that a potential information retrieval, following a time-reversed protocol, is hindered by small perturbations, as indicated by a vanishingly small Loschmidt echo and out-of-time-ordered correlators. The reported phenomenon is amenable for its experimental verification, and may help in the understanding of information scrambling in critical quantum many-body systems. Full article

Energy storage devices are imperative to damp out the oscillations caused by sudden magnified disturbances occurring in a power system. The presence of a small rating of storage device in each area can alleviate the system oscillations effectively. Therefore, in this work, redox flow batteries (RFBs) have been integrated in each area of a five-area interconnected system for effective load frequency control (LFC). The RFB pumps up the active power into the system quickly to meet the short-time overload; in turn, the efficacy of the LFC in the system is boosted. Despite the presence of the RFB in the power system, a secondary controller is necessary to quench the deviation of frequency and tie-line power caused by the power mismatch between demand and generation. In this perspective, a cascade controller incorporated with a fractional operator (FO) has been endorsed and designed through a nascent selfish herd optimizer technique to evaluate the transient response of the system. Besides this, the unprecedented performance of fractional-order cascade controllers has been compared with one-stage classical controllers with and without a fractional operator. Further, the robustness of the proposed controller has been inspected through subjecting it to a random load in the presence/absence of an RFB and parametric variation. Finally, the proposed model has been simulated in the OPAL-RT-4510 platform to validate the performance of the proposed controller that has produced in the MATLAB environment. Full article

The gelation time $t_{\mathrm{g}}$ necessary for a solution of functional (associating) molecules to reach its gel point after a temperature jump, or a sudden concentration change, is theoretically calculated on the basis of the kinetic equation for the stepwise cross-linking reaction as a function of the concentration, temperature, functionality f of the molecules, and multiplicity k of the cross-link junctions. It is shown that quite generally $t_{\mathrm{g}}$ can be decomposed into the product of the relaxation time $t_{\mathrm{R}}$ and a thermodynamic factor Q. They are functions of a single scaled concentration $x\equiv \lambda \left(T\right)\varphi$, where $\lambda \left(T\right)$ is the association constant and $\varphi$ is the concentration. Therefore, the superposition principle holds with $\lambda \left(T\right)$ as a shift factor of the concentration. Additionally, they all depend on the rate constants of the cross-link reaction, and hence it is possible to estimate these microscopic parameters from macroscopic measurements of $t_{\mathrm{g}}$. The thermodynamic factor Q is shown to depend on the quench depth. It generates a singularity of logarithmic divergence as the temperature (concentration) approaches the equilibrium gel point, while the relaxation time $t_{\mathrm{R}}$ changes continuously across it. Gelation time $t_{\mathrm{g}}$ obeys a power law $t_{\mathrm{g}}^{-1}\sim x^n$ in the high concentration region, whose power index n is related to the multiplicity of the cross-links. The retardation effect on the gelation time due to the reversibility of the cross-linking is explicitly calculated for some specific models of cross-linking to find the rate-controlling steps in order for the minimization of the gelation time to be easier in the gel processing. For a micellar cross-linking covering a wide range of the multiplicity, as seen in hydrophobically-modified water-soluble polymers, $t_{\mathrm{R}}$ is shown to obey a formula similar to the Aniansson–Wall law. Full article

The diagenesis of welded tuffs is a process in which volcanic debris undergoes degassing, compaction, and quenching, and vitreous rheologic, which indicates that the welding occurred in a high-temperature, high-pressure diagenetic environment and that different temperatures and pressures result in different degrees of welding in the welded tuffs, which can also result in differences in the mechanical properties of the rock. In this study, based on petrographic identification, mineral composition analysis, and pore structure characterization, uniaxial compression combined with linear accelerator CT and Brazilian splitting tests was carried out to investigate the influence of the welding degree on the strength and failure modes. The test results showed that although they had almost similar mineral composition and porosity, the uniaxial compression strength and tensile strength of the strongly welded tuffs were greater than that of the weakly welded tuffs. Their failure modes were also different. Fractures in the weakly welded tuffs developed gradually, while the strongly welded tuffs showed a higher brittleness with sudden failure. The results of this study shed light on the influence of the diagenetic environment on the mechanical properties of rock from a geological perspective and can provide a mechanical basis for rockfall risk evaluation in scenic areas of welded tuff. Full article

Boiling conjugate heat transfer is an active field of research encountered in several industries, including metallurgy, power generation and electronics. This paper presents a computational fluid dynamics approach capable of accurately modelling the heat transfer and flow phenomena during immersion quenching: a process in which a hot solid is immersed into a liquid, leading to sudden boiling at the solid–liquid interface. The adopted methodology allows us to couple solid and fluid regions with very different physics, using partitioned coupling. The energy equation describes the solid, while the Eulerian two-fluid modelling approach governs the fluid’s behaviour. We focus on a film boiling heat transfer regime, yet also consider natural convection, nucleate and transition boiling. A detailed overview of the methodology is given, including an analytical description of the conjugate heat transfer between all three phases. The latter leads to the derivation of a fluid temperature and Biot number, considering both fluid phases. These are then employed to assess the solver’s behaviour. In comparison with previous research, additional heat transfer regimes, extra interfacial forces and separate energy equations for each fluid phase, including phase change at their interface, are employed. Finally, the validation of the computational approach is conducted against published experimental and numerical results. Full article

Pines have heteroblastic foliage (primary and secondary needles) during seedling stage, but how heteroblastic foliage affects carbon storage and biomass accumulation, contributing to seedling quality, is unclear. We investigated the influences of heteroblastic foliage on photosynthetic physiological characteristics, non-structural carbohydrate (NSC) and biomass accumulation in current-year seedlings; the key factors determining biomass accumulation were mainly determined by principal component screening, Spearman correlation, and path analysis. The results indicated that (1) primary needles have high photosynthetic pigments (chlorophyll a and total chlorophyll), net photosynthetic rates (Pn), the potential maximum photochemical efficiency (Fv/Fm), and leaf instantaneous water use efficiency (WUEi), whereas higher non-photochemical quenching (NPQ) suggested that sudden light increases induce the initiation of quenching mechanism in primary needles; additionally, secondary needles had a lower transpiration rate (Tr), limiting stomata (Ls), and light saturation point. (2) Secondary needles promoted soluble sugar (fructose and glucose) increases in leaves compared to that of primary needles and increased the leaf biomass accumulation (from 47.06% to 54.30%), enhancing the overall ability of photosynthetic organs; additionally, secondary needles can enhance the proportion of starch storage in the roots, and NSC accumulation was significantly increasing in the seedling leaves and roots. (3) Photosynthetic pigments (carotenoids, chlorophyll a, and total chlorophyll) had direct positive effects on primary needle seedling (PNS) biomass and promoted biomass by indirectly increasing soluble sugar synthesis in the stems. The Pn was the main physiological factor determining PNS biomass accumulation. In addition, the WUEi, Ls, and NPQ had direct negative effects on PNS biomass accumulation, inhibiting photosynthesis to limit seedling growth. Considering the functional traits in heteroblastic foliage is necessary when assessing different leaf types of Pinus massoniana (Lamb.) seedlings, in particular those threats implicated in light, water, and temperature relations. Our results can be beneficial to guide the establishment of seedling management and afforestation measures. Full article

Snow cover on sea ice is the most important factor controlling light availability for sea ice algae, but it is predicted by climate models to become more variable and stochastic. Here, we document effects of a sudden, complete loss of the entire snow cover on first-year sea ice at Kangerlussuaq Fjord, West Greenland, due to a natural Föhn wind event that caused a ca. 17 °C air temperature increase over 36 h. We applied Imaging-PAM fluorometry to examine effects of snow cover on algal distribution and photobiology and observed a rapid decrease in algal biomass associated with loss of the skeletal ice crystal layer on the underside of the ice that had supported most of the visible algae. Furthermore, the remaining algae were photobiologically stressed, as seen in a significant decrease in the dark-acclimated fluorescence yield (Φ_{PSII_max}) from 0.55 before snow loss to 0.41 after. However, recovery in the dark suggested that non-photosynthetic quenching was successfully dissipating excess energy in the community and that there was little photodamage. An observed decrease in the photosynthetic efficiency α from 0.22 to 0.16 µmol é m⁻² s⁻¹ is therefore likely to be due to photoacclimation and the change in community composition. Centric diatoms and flagellates were the main taxa lost in the snow loss event, whereas the sea ice specialist Nitzschia frigida increased in numbers. These observations are similar to those seen in artificial snow-clearing experiments and consistent with snow clearing being a useful approach for investigating the complex interactions between snow cover, irradiance fluctuations, and ice algal performance. Full article

In this paper, we study non-equilibrium dynamics induced by a sudden quench of strongly correlated Hamiltonians with all-to-all interactions. By relying on a Sachdev-Ye-Kitaev (SYK)-based quench protocol, we show that the time evolution of simple spin-spin correlation functions is highly sensitive to the degree of k-locality of the corresponding operators, once an appropriate set of fundamental fields is identified. By tracking the time-evolution of specific spin-spin correlation functions and their decay, we argue that it is possible to distinguish between operator-hopping and operator growth dynamics; the latter being a hallmark of quantum chaos in many-body quantum systems. Such an observation, in turn, could constitute a promising tool to probe the emergence of chaotic behavior, rather accessible in state-of-the-art quench setups. Full article

Zirconium doped calcium phosphate-based bioglasses are the most prominent bioactive materials for bone and dental repair and regeneration implants. In the present study, a 8ZnO–22Na₂O–(24 − x)CaO–46P₂O₅–xZrO₂ (0.1 ≤ x ≤ 0.7, all are in mol%) bioglass system was synthesized by the conventional melt-quenching process at 1100 °C. The glass-forming ability and thermal stability of the glasses were determined by measuring the glass transition temperature (T_g), crystallization temperature (T_c), and melting temperature (T_m), using differential thermal analysis (DTA). The biological activity of the prepared samples was identified by analyzing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive spectra (SEM-EDS), before and after immersion in simulated body fluid (SBF) for various intervals of 0, 1 and 5 days, along with the magnitude of pH and the degradation of glasses also evaluated. The obtained results revealed that the glass-forming ability and thermal stability of glasses increased with the increase in zirconia mol%. The XRD, FTIR, and SEM-EDS data confirmed a thin hydroxyapatite (HAp) layer over the sample surface after incubation in SBF for 1 and 5 days. Furthermore, the development of layer found to be increased with the increase of incubation time. The degradation of the glasses in SBF increased with incubation time and decreased gradually with the increase content of ZrO₂ mol% in the host glass matrix. A sudden rise in initial pH values of residual SBF for 1 day owing to ion leaching and increase of Ca²⁺ and PO₄³⁻ ions and then decreased. These findings confirmed the suitability of choosing material for bone-related applications. Full article

We provide a detailed study of the properties of a few interacting spin $1/2$ fermions trapped in a one-dimensional harmonic oscillator potential. The interaction is assumed to be well represented by a contact delta potential. Numerical results obtained by means of direct diagonalization techniques are combined with analytical expressions for both the non-interacting and strongly interacting regime. The $N=2$ case is used to benchmark our numerical techniques with the known exact solution of the problem. After a detailed description of the numerical methods, in a tutorial-like manner, we present the static properties of the system for $N=2,3,4$ and 5 particles, e.g., low-energy spectrum, one-body density matrix, ground-state densities. Then, we consider dynamical properties of the system exploring first the excitation of the breathing mode, using the dynamical structure function and corresponding sum-rules, and then a sudden quench of the interaction strength. Full article

We consider the nonadiabatic energy fluctuations of a many-body system in a time-dependent harmonic trap. In the presence of scale-invariance, the dynamics becomes self-similar and the nondiabatic energy fluctuations can be found in terms of the initial expectation values of the second moments of the Hamiltonian, square position, and squeezing operators. Nonadiabatic features are expressed in terms of the scaling factor governing the size of the atomic cloud, which can be extracted from time-of-flight images. We apply this exact relation to a number of examples: the single-particle harmonic oscillator, the one-dimensional Calogero-Sutherland model, describing bosons with inverse-square interactions that includes the non-interacting Bose gas and the Tonks-Girdardeau gas as limiting cases, and the unitary Fermi gas. We illustrate these results for various expansion protocols involving sudden quenches of the trap frequency, linear ramps and shortcuts to adiabaticity. Our results pave the way to the experimental study of nonadiabatic energy fluctuations in driven quantum fluids. Full article

Simultaneous differential scanning calorimetry, DSC, and acoustic emission, AE, measurements were carried out for single crystals of quenched and stress-induced martensite stabilized (SIM-aged) shape memory Ni₅₁Fe₁₈Ga₂₇Co₄ alloy. The transformation temperatures were shifted to higher values, the forward (from austenite to martensite) and reverse transitions became sharper and the width of the hysteresis increased in the SIM-aged sample. The energy distributions of acoustic hits showed similar behaviour to those of the quenched sample and the energy exponents, characterizing the power law behaviour, were also similar. For SIM-aged alloys at heating, in accordance with the sharper (burst-like) transition observed in the DSC run, few high-energy solitary hits were observed, and these hits did not fit to the energy distribution function fitted for smaller energies. Thus, these high-energy events were attributed to high sudden jumps in the phase transition during heating. The effect of long-range order (by applying a heat treatment at 573 K for 6 h to transform the B2 austenite to ordered L2₁ structure) and the SIM-aging on the transformation entropy was also investigated by DSC. It was found that the entropy was about 36% smaller after SIM-aging of the quenched sample and it was practically unchanged after austenite stabilization. Full article

The concept of spontaneous symmetry breaking and off-diagonal long-range order (ODLRO) are associated with Bose–Einstein condensation. However, as in the system of reduced dimension the effect of quantum fluctuation is dominating, the concept of ODLRO becomes more interesting, especially for the long-range interaction. In the present manuscript, we study the correlation dynamics triggered by lattice depth quench in a system of three dipolar bosons in a 1D triple-well optical lattice from the first principle using the multiconfigurational time-dependent Hartree method for bosons (MCTDHB). Our main motivation is to explore how ODLRO develops and decays with time when the system is brought out-of-equilibrium by a sudden change in the lattice depth. We compare results of dipolar bosons with contact interaction. For forward quench $(V_f>V_i)$ , the system exhibits the collapse–revival dynamics in the time evolution of normalized first- and second-order Glauber’s correlation function, time evolution of Shannon information entropy both for the contact as well as for the dipolar interaction which is reminiscent of the one observed in Greiner’s experiment [Nature, 415 (2002)]. We define the collapse and revival time ratio as the figure of merit ( $\tau$ ) which can uniquely distinguish the timescale of dynamics for dipolar interaction from that of contact interaction. In the reverse quench process $(V_i>V_f)$ , for dipolar interaction, the dynamics is complex and the system does not exhibit any definite time scale of evolution, whereas the system with contact interaction exhibits collapse–revival dynamics with a definite time-scale. The long-range repulsive tail in the dipolar interaction inhibits the spreading of correlation across the lattice sites. Full article