Dependence Of Rate Research Articles

Study of the influence of pollution particles of 5 мkм and less on the anti-wear properties of the working fluids of hydraulic drives of construction and road machinery

Problem. An analysis of the impact of contamination of the working fluid on the state of the hydraulic equipment elements of construction and road machines, the efficiency of their operation, and also the use of the coefficient of anti-wear properties to determine the service life of working fluids is presented. The equation of the dependence of the wear rate of hydraulic equipment elements on the coefficient was obtained. Operational tests of the GR165 motor grader were also carried out, which showed that the service life of the Hydro HV 46 working fluid according to the coefficient of anti-wear properties is approximately 1184 machine hours. Methodology. In the process of studying the state of the matter, the method of analysis was used, and in theoretical studies – the analytical method, which is based on the theory of interaction of working bodies with the developed environment, as well as the provisions of the theory of reliability, probability and mathematical statistics. Results. The research results showed that coefficient Kj of anti-wear properties can be the only integral indicator of the quality of working fluids and determine their service life in hydraulic drives of Construction machines. Originality. The equation was obtained for the rate of wear, taking into account the interaction of charged particles of wear with friction surfaces. For the stationary friction mode, the equation of the balance of the contamination particles that are part of the working fluids of the hydraulic actuators and the rate of wear of friction vapor were obtained. The use of KJ coefficient as an indicator of working fluids of hydraulic drives of construction machines is presented. Practical value. The research results showed that the coefficient Kj of anti-wear properties can be the only integral indicator of the quality of working fluids and determine their service life in hydraulic drives of Construction machines.

Mode I fracture properties of thermally-modified spruce wood (Picea abies) at different moisture contents

ABSTRACT The influence of moisture content and density on fracture properties of unmodified and thermally modified spruce wood (Picea abies) has been investigated. Thermal modification was done at 180 °C, 200 °C, and 230 °C, and samples were conditioned at 20%, 44%, 76%,% and 88% relative humidity. Double cantilever beam specimens with TL and RL orientation were used for testing. The crack length was determined via digital image correlation, and the compliance of the specimen was determined via multiple loading-unloading cycles of the specimen. The strain energy release rate was calculated, which decreased with an increasing degree of modification and increased with increasing wood moisture content. The analysis showed that the strain energy release rate increased more with wood moisture content for unmodified samples, while the dependence of the release rate on moisture was less obvious for modified samples. The strain energy release rate values are higher in the TL orientation than in the RL orientation, while the crack length has no significant influence. The highest strain energy release rate was 0.256 N/mm for the unmodified TL specimens exposed to 88% relative humidity, and the lowest was 0.071 N/mm for the RL orientation of the thermally modified specimens at 230 °C and then exposed to 88% relative humidity. From all measurements, functions were fitted to calculate the strain energy release rate as a function of orientation, degree of modification, moisture content, and density of the spruce wood, which can be used to calculate the strain energy release rate for any combination of the factors studied.

Dependence of the wear rate on the microhardness of the coating of the auger hehydration in a garbage truck for municipal solid waste

The article is dedicated to the study of the influence of the microhardness of the auger coating on its wear resistance during the dehydration of municipal solid waste in a garbage truck. The use of mathematical tools and appropriate regression analysis software allowed to determine the dependence between the auger wear rate and the microhardness of the coating. A graphical representation of the change in auger wear rate based on the microhardness of the coating was made up, confirming a significant convergence with the obtained dependence. The graphs illustrating the impact of the microhardness of the screw coating on its wear rate demonstrate the feasibility of increasing it. It was found that after operating and wearing out over a distance of s = 56850 m during the dehydrating of solid municipal waste in a garbage truck, increasing the microhardness of the coating from 2.7 GPa to 33.2 GPa leads to a decrease in energy consumption by 19 kWh/tons or 12% and reduces the cost of the dehydrating process. The feasibility of conducting additional research to determine further ways to increase the wear resistance of the auger was established.

The ignition of fine iron particles in the Knudsen transition regime

A theoretical model is considered to predict the minimum ambient gas temperature at which fine iron particles can undergo thermal runaway–the ignition temperature. The model accounts for Knudsen transition transport effects, which become significant when the particle size is comparable to, or smaller than, the molecular mean free path of the surrounding gas. Two kinetic models for the high-temperature solid-phase oxidation of iron are analyzed. The first model (parabolic kinetics) considers the inhibiting effect of the iron oxide layers at the particle surface on the kinetic rate of oxidation, and a kinetic rate independent of the gaseous oxidizer concentration. The ignition temperature is solved as a function of particle size and initial oxide layer thickness with an unsteady analysis considering the growth of the oxide layers. In the free-molecular limit (small particles), the thermal insulating effect of transition heat transport can lead to a decrease of ignition temperature with decreasing particle size; however, the presence of the oxide layer slows the reaction kinetics, and its increasing proportion in the small-particle limit can lead to an increase of ignition temperature with decreasing particle size. This effect is observed for sufficiently large initial oxide layer thicknesses. The continuum transport model is shown to predict the ignition temperature of iron particles exceeding an initial diameter of 30 µm to a difference of 3% or less (30 K or less) when compared to the prediction of the transition transport model. The second kinetic model (first-order kinetics) considers a porous, non-hindering oxide layer, and a linear dependence of the kinetic rate of oxidation on the gaseous oxidizer concentration. The ignition temperature is resolved as a function of particle size with the transition and continuum transport models, and the differences between the ignition characteristics predicted by the two kinetic models are identified and discussed.

Electrochemically-stimulated nanoscale mechanochemical wear of silicon

AbstractMechanochemical reactions at the sliding interface between a single-crystalline silicon (Si) wafer and a silica (SiO2) microsphere were studied in three environmental conditions: humid air, potassium chloride (KCl) solution, and KCl solution with an applied voltage. Compared to that from humid air, mechanochemical material removal from the silicon surface increased substantially in the KCl-immersed condition, and further increased when electrochemistry was introduced into the tribological system. By measuring the load dependence of the material removal rate and analyzing the results using a mechanically assisted Arrhenius-type kinetic model, the activation energy (Ea) and the mechanical energy (Em), by which this energy is reduced by mechanical activation, were compared qualitatively under different environmental conditions. In the KCl-immersed condition, mechanochemistry may decrease the required effective energy of reactions (Eeff = Ea − Em) and promote material removal mainly through improved catalysis of the mechanochemical reactions facilitated by greater availability of water molecules compared to the humid air condition. Thus, the effectiveness of the mechanochemistry is improved. In the electrochemical condition, electrochemically-accelerated oxidation of the silicon surface was confirmed by the X-ray photoelectron spectroscopy (XPS) characterization. The results strongly suggest that electrochemistry further stimulates mechanochemical reactions primarily by increasing the initial energy state of the surface via the facilitated formation of interfacial bonding bridges, i.e., a surface oxidation/hydroxylation process.

Sediment preservation and accretion rates of fluvial meander-belt deposits: variations with temporal scale and river size

Abstract The preservation and accretion rates of fluvial meander-belt deposits appear to vary with the time over which they are evaluated, but the drivers of this effect are not fully understood. Using channel trajectories tracking the temporal evolution of meandering rivers, constrained with data on past river planforms, a numerical model is used to simulate planform evolutions of meander-belt reaches that underwent different types of meander transformation behaviours and bend cutoffs. Sediment preservation and bar accretion rates are quantified for three hierarchies of depositional products: (i) accretion stages reflecting intervals of bend migration by a certain meander-transformation style, (ii) meander-belt segments encompassing multiple stages but no bend cutoffs and (iii) meander-belt segments that experienced one or multiple cutoffs. Results show that distinct power-law relationships between the accretion rate and the time of sedimentation exist for river systems of different magnitudes in scale. Within each order of magnitude in river-system size, a single power-law relationship fails to effectively capture all depositional hierarchies. Sediment preservation varies with the time over which it is computed, but systematic variations in accretion rates with time primarily portray an apparent dependency of river migration rates on time: these variations largely reflect the temporal resolution and timespan of the modelled examples, highlighting an inherent issue affecting studies of river evolutions.

Modeling of material removal rate considering the chemical mechanical effects of lubricant, oxidant, and abrasive particles for aluminum chemical mechanical polishing at low pressure

Lubricants are widely used for aluminum (Al) chemical mechanical polishing (CMP) to eliminate surface scratch damage. Understanding of the fundamental of CMP material removal mechanisms including lubrication is crucial to offer insights into the control and optimization of the polishing process. This paper proposes a novel material removal rate (MRR) model based upon molecular-scaled removal mechanism, micro-contact force equilibrium theory, chemical reaction kinetics and diffusion effects, with further considering the lubricant effect on the removal rate at low polishing pressure. Moreover, the presented model also clarifies the nonlinear dependence of removal rate on lubricant concentration, oxidizer concentration, and abrasive concentration. The model prediction results could provide qualitative insights into the influence of lubricant concentration, oxidizer concentration, and abrasive concentration on MRR, thus providing theoretical foundation and support for delineating the Al-CMP process at low pressure. Finally, it is found that the theoretical predictions possess qualitative agreement with the experimental results.

Investigation of the pulsed neutron source method measuring the fission decay properties of a subcritical assembly with low-Z reflectors

The pulsed neutron source (PNS) method measuring the fission decay properties of a subcritical system with reflectors was analyzed numerically. Using the Monte Carlo code JMCT, a spherical subcritical assembly with a low atomic number (low-Z) reflector was modeled, and the neutron and photon transport process initiated by an instantaneous neutron source was simulated. The time dependence of the leakage photon count rate and the neutron populations in the fissile region and the reflector was obtained. It is indicated that the neutron population in the assembly is dominated by that in the reflector after a relatively short period, the length of which is mainly dependent on the reflector's thickness. That is to say, the neutron population in the assembly is more affected by the reflector than by the fissile region. The leakage photon count rate is approximately proportional to the neutron population in the fissile region during the specific time window of hundreds of nanoseconds after the source pulse. The fission decay properties of the fissile region can therefore be approximately derived from the leakage photon count rate based on the PNS method. The reason for the existence of the above time window was analyzed, and the effective time range of leakage photon count rate was discussed.

Effects of overvoltage and temperature on the lithium insertion kinetics of MgMn2O4

The power capability of lithium-ion batteries strongly depends on the reaction kinetics of the lithium insertion material used in the electrodes. Previously, chronoamperometry revealed that the lithium insertion reaction of MgMn2O4 differs between static and dynamic processes and that the dynamic process consists of a nucleation–growth process followed by diffusion. Herein, we present the overvoltage and temperature dependence of the reaction rate of MgMn2O4 through chronoamperometry results under different applied voltages and temperatures. The rate constant of each process is determined by fitting the measured current profile to a solid-state reaction model. The rate constant of the nucleation-growth process exhibits an Arrhenius relationship with temperature and a Tafel-like relationship with overvoltage, whereas that of diffusion exhibits an Arrhenius relationship with temperature and does not depend on overvoltage. These dependencies are different because nucleation–growth is a reaction process on the particle surface, whereas diffusion is a reaction process occurring inside the particle. Accordingly, the rate-determining step of lithium insertion under various operating conditions is discussed.

Analysis of parameter combinations for optimal soliton microcomb generation efficiency in a simple single-cavity scheme

Dissipative Kerr solitons generated in high-Q optical microresonators provide unique opportunities for different up-to-date applications. Increasing the generation efficiency of of such signals is a problem of paramount importance. We provided comprehensive analysis and found optimal conditions providing maximal pump-to-comb conversion efficiency (up to 100\%) for the cases of a free-running and self-injection-locked pump lasers. The dependence of the optimal coupling rate on the pump power was revealed, in addition to the trade-off relations balancing the efficiency and the comb line number. The methods to increase the total comb power were also discussed.

The Role of the Photon Counting Loss Effect in Time-Resolved Measurements of Fluorescence Anisotropy

Determining the rate of rotation of molecules from their fluorescence anisotropy decay curves is a powerful method for studying molecular systems in biological applications. The single photon count detection systems used for this have a nonlinear dependence of the photon counting rate on the fluorescence intensity flux (photon counting loss effect), which can lead to a number of artifacts. Using metal complexes of phthalocyanines as a test sample, we have shown that such a nonlinearity can cause distortions in the determination of the fluorescence anisotropy lifetime and the asymptotic fluorescence anisotropy. We also assessed the dependence of the described phenomena on temperature and estimated the manifestations of the photon counting loss effect in the case of photobleaching of the fluorophores.

Particle pump-out induced by trapped electron mode turbulence in electron cyclotron heated plasmas on XuanLong-50 spherical torus

Particle pump-out effects induced by low-frequency (<200 kHz) density fluctuations were observed in solely electron cyclotron wave (ECW)-heated plasmas on the spherical torus XuanLong-50 (EXL-50) without a central solenoid. The intensity of the relative density fluctuations increases with increasing ECW power and decays when the ECW is turned off while sustaining the plasma current. The electron densities are maintained relatively high and steady when the density fluctuations are completely absent, indicating that the outward transport of electrons is dominated by the particle pump-out effect of the ECW. The density fluctuations are modulated by a supersonic molecular beam injection pulse and the modulation amplitude decreases with increasing electron density at the same ECW injection power and decreasing ECW power at the same electron density, respectively. Analysis revealed that a critical value of electron temperature gradient (ETG) triggers the density fluctuations, and the intensity of the relative density fluctuations is positively correlated with the ETG and approximately inversely proportional to the effective collision frequency. With plasma parameters similar to those of EXL-50 experiments, the HD7 code simulations demonstrate that trapped electron mode (TEM) turbulence can be excited by ETG higher than the critical value observed in the experiment. In addition, the dependence of the mode growth rate (supposed to be proportional to the saturation level of fluctuations in quasi-linear theory) and the measured intensity of the density fluctuations is comparable. The simulated outward particle flux integrated over the poloidal wave number spectrum is significant and proportional to ETG. These observations demonstrate that the density fluctuation is TEM turbulence, which is driven by ETG and induces particle pump-out when the electron density/effective electron collision frequency is low. The potential relevance of this work with the controls of plasma profiles, impurities, helium ash, and heat transport in future reactors of similar low effective collision frequency is also discussed.

Binary black holes population and cosmology in new lights: signature of PISN mass and formation channel in GWTC-3

ABSTRACT The mass, spin, and merger rate distribution of the binary black holes (BBHs) across cosmic redshifts provide a unique way to shed light on their formation channel. Along with the redshift dependence of the BBH merger rate, the mass distribution of BBHs can also exhibit redshift dependence due to different formation channels and dependence on the metallicity of the parent stars. We explore the redshift dependence of the BBH mass distribution jointly with the merger rate evolution from the third gravitational wave (GW) catalogue GWTC-3 of the LIGO–Virgo–KAGRA collaboration. We study possible connections between peak-like features in the mass spectrum of BBHs and processes related to supernovae physics and time delay distributions. We obtain a preference for short-time delays between star formation and BBH mergers. Using a power-law form for the time delay distribution ($(t^{\rm min}_d)^{d}$), we find d &amp;lt; −0.7 credible at 90 per cent interval. The mass distribution of the BBHs could be fitted with a power-law form with a redshift-dependent peak feature that can be linked to the pair instability supernovae (PISN) mass-scale MPISN(Z*) at a stellar metallicity Z*. For a fiducial value of the stellar metallicity Z* = 10−4, we find the $\rm M_{\rm PISN}(Z_*)=44.4^{+7.9}_{-6.3}$$\rm M_\odot$. This is in accordance with the theoretical prediction of the lower edge of the PISN mass-scale and differs from previous analyses. Although we find a strong dependence of the PISN value on metallicity, the model that we explored is not strongly favoured over those that do not account for metallicity as the Bayes factors are inconclusive. In the future with more data, evidence towards metallicity dependence of the PISN will have a significant impact on our understanding of stellar physics.

Kinetics of the enzyme titration process by reversible modifiers

The effect of reversible modifiers on the initial rate of enzyme catalysed reactions has been investigated in a quasi-equilibrium approximation using the general modifier mechanism of Botts and Morales. It has been shown that, when investigating the dependence of the initial rate on the modifier concentration at a fixed substrate concentration, the kinetics of enzyme titration by reversible modifiers can generally be described using two kinetic constants. Just as the dependence of the initial rate on the substrate concentration (at a fixed modifier concentration) is described using two kinetic constants: the Michaelis constant Km and the limiting rate Vm. Only one constant M50 is needed to describe the kinetics of linear inhibition, and in the case of nonlinear inhibition and activation, along with M50 the constant QM is also needed.Knowing the values of the constants M50 and QM, it is possible to unambiguously determine the modification efficiency, that is, to calculate how many times the initial rate of the enzyme catalysed reaction will change when a certain modifier concentration is added to the incubation medium.The properties of these fundamental constants have been analysed in detail and the dependence of these constants on other parameters of the Botts-Morales model have been shown. Equations describing the dependence of relative reaction rates on the modifier concentration using these kinetic constants are presented. Various ways of linearising these equations for calculating the kinetic constants M50 and QM from experimental data are also presented.

Continuous microflow visible-light photocatalytic N-formylation of piperidine and its kinetic study

N-formylation of amines, a class of synthetically important reactions, is typically conducted using metal catalysts that are relatively expensive or not readily available and usually needs harsh conditions to increase the reaction efficiency. Here, an efficient continuous microflow strategy was developed for the gas-liquid visible-light photocatalytic N-formylation of piperidine, which achieved a reaction yield of 82.97% and a selectivity of >99% at 12 min using cheap organic dye photocatalyst under mild reaction conditions. The influence of essential parameters, including light intensity, temperature and equivalents of the gas, additive and photocatalyst, on the reaction yield was systematically studied. Furthermore, kinetic investigations were conducted, exhibiting the dependence of reaction rate and equilibrium yield of N-formylpiperidine on light intensity, temperature and photocatalyst equivalent. The microflow photocatalytic approach established in this work, which realized a markedly higher space-time yield than the conventional batch method (37.9 vs. 0.212 mmol·h−1·L−1), paves the way for the continuous, green and efficient synthesis of N-formamides.

Anisotropic time-dependent behaviors of shale under direct shearing and associated empirical creep models

Understanding the anisotropic creep behaviors of shale under direct shearing is a challenging issue. In this context, we conducted shear-creep and steady-creep tests on shale with five bedding orientations (i.e. 0°, 30°, 45°, 60°, and 90°), under multiple levels of direct shearing for the first time. The results show that the anisotropic creep of shale exhibits a significant stress-dependent behavior. Under a low shear stress, the creep compliance of shale increases linearly with the logarithm of time at all bedding orientations, and the increase depends on the bedding orientation and creep time. Under high shear stress conditions, the creep compliance of shale is minimal when the bedding orientation is 0°, and the steady-creep rate of shale increases significantly with increasing bedding orientations of 30°, 45°, 60°, and 90°. The stress-strain values corresponding to the inception of the accelerated creep stage show an increasing and then decreasing trend with the bedding orientation. A semilogarithmic model that could reflect the stress dependence of the steady-creep rate while considering the hardening and damage process is proposed. The model minimizes the deviation of the calculated steady-state creep rate from the observed value and reveals the behavior of the bedding orientation's influence on the steady-creep rate. The applicability of the five classical empirical creep models is quantitatively evaluated. It shows that the logarithmic model can well explain the experimental creep strain and creep rate, and it can accurately predict long-term shear creep deformation. Based on an improved logarithmic model, the variations in creep parameters with shear stress and bedding orientations are discussed. With abovementioned findings, a mathematical method for constructing an anisotropic shear creep model of shale is proposed, which can characterize the nonlinear dependence of the anisotropic shear creep behavior of shale on the bedding orientation.

Advection-enhanced heat and mass transport from neutrally suspended droplet in simple shear flow

Advection-enhanced heat and mass transport from a single droplet neutrally suspended in a simple shear flow has been studied using high-fidelity numerical simulation. The capillary number ranges from 0.01 to 0.5, which encompasses the entire range of small deformation, large deformation, and breakup of the droplets. The Reynolds number is from 0.01 to 1, including regions of both weak and strong advection. The temperature and mass concentration are modeled as the concentration of a passive scalar released at the droplet surface. Two Schmidt numbers, 10 and 100, are considered, for which flow advection plays a role in the transport of passive scalar. For unbroken droplets, the interaction between the carrier fluid and the suspended droplet leads to several different flows around the droplet. The fluid motions together with scalar diffusion constitute a coupled transport mechanism for passive scalar. The dependence of scalar release rate on Reynolds and Peclet numbers can be roughly described by the correlation for a rigid sphere. For broken droplets, the basic flow features around the droplet during the process of elongation and breakup are similar to those of an unbroken droplet. The variation of the scalar release rate can be decomposed into several stages, corresponding to the process of droplet elongation and breakup. The variation of the scalar release rate exhibits a high correlation with the capillary, Reynolds, and Peclet numbers. This suggests that it is feasible to develop an empirical model that incorporates the effects of the number and size distributions of child droplets after breakup.

Molecular dynamics and experimental studies of the dependence of strain rate on the indentation deformation of polycarbonate

Molecular dynamics and experimental studies of the dependence of strain rate on the indentation deformation of polycarbonate

Carbon Abundance of Globular Cluster M22 (NGC 6656) and the Surface Carbon Depletion Rates of the Milky Way Globular Clusters

It is well known that metal-poor red giant branch (RGB) stars show variations in some elemental abundances, including carbon, due to the internal mixing accompanied by their own in situ CN cycle in the hydrogen burning shell. With our new photometric carbon abundance measurements of RGB stars in M22 and other globular clusters (GCs) in our previous studies, M5, M3, and M92, we derive the carbon depletion rates against the V magnitude, d[C/Fe]/M V , for individual populations in each GC. We find the metallicity dependence of the carbon depletion rates, d[C/Fe]/M V ∝ −0.25[Fe/H]. Our results also suggest that the carbon depletion rates of the second generation (SG) of stars are larger than those of the first generation (FG) of stars in our sample GCs, most likely due to different internal temperature profiles with different initial helium abundances between the FG and SG. Our results can provide critical constraints both on understanding the mixing efficiency in the theoretical models, which is largely unknown, and on interpretation of the observational carbon abundance evolution of the bright halo RGB stars.

Study of discharges in the CMS GEM GE1/1 station with LHC beam

The Large Hadron Collider (LHC) and the experiments installed there are being upgraded for the High Luminosity LHC project that will provide a greatly enlarged data sample in the search for physics beyond the Standard Model. During Long Shutdown 2, from 2018 to the first months of 2022, some of these upgrades were completed. In particular, the muon spectrometer of the CMS experiment was upgraded with installation of the GE1/1 detector station, based on Gas Electron Multiplier (GEM) technology. This station is positioned in the endcap region of the CMS muon system and covers the pseudorapidity range 1.55 < |η| < 2.18. On the 5th of July, 2022, Run 3 of the LHC began with collision energy of 13.6 TeV. The newly installed GEM detectors experienced high-voltage discharges when the beams were colliding inside CMS. To monitor these events and to understand how to safely operate the detectors, a study of these phenomena became necessary. The intensity of discharge current and the discharge rate were recorded in different detectors as a function of luminosity and time. It was observed that some chambers have a significantly higher discharge rate than the modal value of rate over the entire chamber population. The reasons responsible for this behavior are currently under investigation. In this contribution, an analysis of discharges will be presented, illustrating the dependence of discharge rate on different LHC beam configurations and the high voltage working point of the chambers.