Coefficient K2 Research Articles

Numerical simulation of chemically reacting Darcy-Forchheimer flow of Buongiorno Maxwell fluid with Arrhenius energy in the appearance of nanoparticles

This investigation is designated for studying the inspiration of Darcy-Forchheimer flow of Maxwell nano fluid with nonlinear marvels of thermal radiation and bio convection of motile germs due to porous stretched sheet. Arrhenius energy, thermophoresis and convective Nield boundary conditions are novel aspects of this research. The exploration of heat and mass transfer in electrical conducting Maxwell fluid in the manifestation of nanoparticles is scrutinized. The misappropriate similarity functions are used to convert the couple of governing PDEs in to nonlinear set of ODEs. The resulting fasten of ODEs are numerically solved by applying the appropriate numerical tool shooting procedure with MATLAB solver code bvp4c. The encouragement of renowned parameters including Peclet number, Prandtl number, Bioconvective Lewis number, Rayleigh number, thermophoresis, Lewis number, Brownian motion and Hartmann number on momentum, energy, concentration and germ density profile has been deliberated in form of graphs and tables. We declared that the velocity curve declined for the developing value of inertia coefficient K1, magnetic number M and Deborah number Γ. The improvement in the values of the activation energy E growth in the temperature distribution.

Controllable preparation and properties of gel-casting porous mullite ceramics via lignin fiber assisted pore formation method

The preparation of high-strength porous mullite via gel-casting has emerged as a hot topic, but balancing high strength and high porosity remains challenging. Herein, we successfully prepared porous mullite with uniform pore size and high strength using natural lignin fibers as the pore-forming agent via gel-casting. Moreover, we investigated the properties of mullite slurries, as well as green bodies and sintered ceramics in details. The strong water transport capacity of the lignin fibers enabled the homogeneous dispersion of gel system and improved the flowability of slurry. The flexural strength of green body was significantly increased to 16.07 MPa by optimizing the lignin fiber content. Porous mullite ceramics sintered at 1400 °C exhibited a homogeneous microstructure with average pore size of 5.62 μm. Furthermore, mullite ceramics had a porosity of 64.73% at a total solid loading of 55 wt% and a lignin fiber content of 10 wt%, whereas the compressive strength remains high at 11.32 MPa. Permeability tests confirmed the presence of interconnected pores, its coefficients k1 and k2 increases with the total porosity of ceramics. This work provides new insights into designing the preparation of porous mullite ceramics with high performance.

Experimental study of the interaction between tsunami bores and 3D jetty models

Tsunami bores have a strong destructive ability, capable of damaging coastal structures and endangering human life. This study focuses on the interactions between tsunami bores and 3D jetty models through physical experiments. The characteristics of tsunami bores travelling at different initial water depths (IWL) were examined. The distributions of slamming pressure and quasi-steady pressure on the jetty deck in different directions were assessed. The results showed that the initial water depths, deck heights (hd) and slope angles (θ) had significant influences on the slamming pressure. New equations were proposed to calculate the tsunami slamming pressures and quasi-steady pressures on the jetty decks. The energy loss coefficients k1 (ranging from 0.40 to 0.80) and k5 (ranging from 0.65 to 0.90) are related to the initial water depth, which was found to be essential for the calculation accuracy of tsunami pressures on the jetty, and the errors were within ±20%.

Production indicators and elements of the energy balance of the relict mysida <i>Mysis relicta</i> (Loven) population on Lake Yuzhny Volos

Field studies and a retrospective analysis of distribution and life cycle features of the glacial relict Mysis relicta (Loven) on Lake Yuzhny Volos on the southern border of distribution of the species on the European continent were carried out. The size-age structure, number and density of the mysida population did not change over a half-century period on Lake Yuzhny Volos. Life cycle features, which consist in the existence of parallel lines of alternating one-year and two-year generations, remain stable. The mysida production characteristics were determined. It is shown that the somatic production of two-year generation females at the level of the individual and the population is two times higher than that of one-year generation females. During the gestation of juveniles, the female consumes the body weight energy equivalent, which is equal to 2.13 cal·individual–1 for a one-year generation and 7.32 cal·individual–1 for a twoyear generation, 9.5·108 and 25.5·108 cal for all individuals of one-year and two-year generations. Egg production for life in the mysida population was 29.5·108 cal, which is comparable to the total somatic production. The exuvial production of mysids at the level of the individual and the population turned out to be ten times higher than the somatic one. The energy spent for respiration is 900 times higher than the somatic production values for one-year generation females and 1200 times for twoyear generation females. The coefficient K2 values appeared to be close for the both generations (0.032–0.034) and are represented by very low values compared to the freshwater macrozoobenthos of temperate latitudes.

Propeller thrust tower crane slewing mechanism model identification

Any study of the dynamics and control of mechanical systems is based on adequate mathematical models that contain the dynamic parameters of the system under study. Their evaluation, in particular for the tower crane boom system, is a particularly relevant scientific and practical problem, the solution of which will provide the basis for further calculations of the optimal modes of movement of the tower crane slewing mechanism. The research aims to determine the dynamic parameters of the installation (moment of inertia of the slewing mechanism J, torque of dry friction forces M0, driving torque coefficient K1) and to plan experimental studies. The experimental method, numerical optimization methods (in particular, the modified Rot-Ring-PSO method), and statistical methods were used to conduct the research. Based on the results of the experiments, the dynamic parameters of the mathematical model of the laboratory installation of the tower crane slewing mechanism with propeller thrust were identified. The criterion that evaluates the identification error of the parameters K1, M0, and J was formed and minimized using the Rot-Ring-PSO algorithm. Plots of the kinematic characteristics of the movement of the boom system in terms of the angle of rotation of the boom and the speed of rotation of the boom were constructed. When processing the experimental data, the dependence of the error values on the supply voltage of the propeller drive was revealed. The error in the boom rotation speed at the drive supply voltage of 90% (compared to the voltage variant of 40%) decreased by almost 15%, and the error in the boom rotation angle at the drive supply voltage of 90% (compared to the supply voltage variant of 40%) decreased by almost 3 times. The regularity has been confirmed that with an increase in the supply voltage, the error value of the system decreases. In the course of processing the experimental studies, the dynamic parameters of the installation were identified: K1=4.80‧10-8 V/(rpm)2, M0=34.519 Nm, J=24.21 kgm2. The obtained results will be used to optimise the plant’s motion modes, and the developed identification algorithm can be used for other similar problems

Conjugated micro-mesoporous poly(aniline)s for ultrafast Hg (II) capture

Attempts to develop adsorbents for toxic Hg (II) removal from wastewater in an all-round high-capacity, rapid-kinetic and super-selective manner remain interesting but unsolved. Here, we report a novel class of conjugated micro-mesoporous poly(aniline)s (CMMPAs) by an ingenious integrated porosity design and decoration over porous organic polymers (POPs). We pre-create unstable ZIF-7-NH2 and crosslink it into POPs but remove it subsequently through a time-saving acid wash to allow the formation of mesopores and the “in-situ” decoration of ZIF-7-NH2 ligands as adsorption sites on the pore wall. The resulting adsorbent exhibits an ultra-high capacity of 1032 mg g−1, extremely fast kinetic with h of 1425 mg g−1 min−1 that could reduce Hg (II) from 10 to 1 ppm in 2 s and further to 2 ppb in ca. 30 min, and nearly 100% exclusive adsorption towards Hg (II). The mesopore volume within 15–50 nm as created is responsive to the diffusion coefficient k2 (k2 = 0.0215 V-0.000079); the outstanding capture is also essentially trigged by the unique affinity from N sites, thus highlighting CMMPA as an appealing platform for drinking-water purification that would significantly serve for practical environmental application.

Analytical solutions for stresses and displacements of tunnels under static and seismic loading

Analytical solutions can quickly and simply evaluate stresses and displacements in tunnels and are widely adopted in the preliminary design phase of tunnels. Tunnels must be able to withstand static loading and seismic loading. This paper proposes new analytical solutions for the stresses and displacements of tunnels under static and seismic loading. The tunnel lining is treated as a thick-walled cylinder. Moreover, the contact stiffness coefficient k0 and the stress release coefficient η0 are introduced to consider the arbitrary contact conditions at the ground–lining interface and the amount of excavation unloading. The new analytical solutions are verified by comparison with finite element analysis results. The results demonstrate the accuracy and applicability of the proposed analytical solutions. In addition, parametric analyses are conducted to explore the effects of the stress release coefficient η0 and stiffness coefficient k0 at the ground–lining interface, as well as the incident angle α of shear waves. The analysis results indicate that the proposed analytical solutions offer satisfactory performance and can be applied as an effective tool for preliminary tunnel design.

Effect of multi-scale reinforcement on fracture property of ultra-high performance concrete

This paper aims to achieve multi-scale crack control of concrete by using graphene oxide (GO) and macroscopic steel fiber in combination, and to reveal the multi-scale collaborative reinforcement mechanism of GO and steel fiber. A three-point bending fracture mechanics test was employed to analyze the macroscopic fracture properties of ultra-high performance concrete (UHPC) reinforced by GO, and a single fiber pull-out test was utilized to assess the impact of GO on the fiber–matrix interface properties. The results showed that 0.04% GO reinforced UHPC had the best fracture property, and steel fiber and GO showed good synergistic crack control effect. GO directly acted on controlling the cracking of concrete matrix at the nanoscale, thus improving the fracture energy of UHPC matrix by 14% from 73.08 N/mm to 83.39 N/mm. This micro-scale matrix reinforcement provided by GO further improved the pull-out property of steel fibers, and the pull-out energy dissipation of straight steel fibers and hook-end fibers was increased by 43.7% and 31.5%. A micromechanical prediction model for fracture energy of straight steel fiber UHPC was established, which could construct the quantitative relationship between UHPC fracture energy and micromechanical parameters. The model showed that the initial fiber–matrix bond strength (τ0) and slip hardening coefficient (k0) had a powerful influence on the UHPC fracture energy.

Adsorption Kinetics of Type-III Antifreeze Protein on Ice Crystal Surfaces.

The spatio-temporal distribution of type-III antifreeze protein (AFP-III) molecules labeled with fluorescent isocyanate (FITC) was visualized at the interfaces between ice and solutions with an FITC-labeled AFP-III (F-AFP-III) concentration of 20-800 μg/mL by fluorescence microscopy. The number density of F-AFP-III on the surface of ice microcrystals was calculated from the calibrated fluorescence intensity. The adsorption of F-AFP-III molecules on the ice crystal surfaces proceeded at a finite rate and then reached the saturation level. The time course of the number density of adsorbed F-AFP-III molecules could be well represented by Langmuir's model. The characteristic adsorption time of F-AFP-III, the adsorption coefficient k1 = (0.5 ± 0.05) × 10-4 (μg/mL)-1 s-1, and the desorption coefficient k2 = 0.005 ± 0.002 s-1 were determined using the Langmuir's model and obtained experimental data. We found that the adsorption of F-AFP-III could have different kinetics depending on the solution conditions and the type of fluorescence molecules conjugated with AFP-III.

Theoretical investigation of Rayleigh surface acoustic wave propagation characteristics in c-axis-zigzag ScAlN film/silicon substrate structure

Surface acoustic wave (SAW) resonators are key components of mobile communication systems, and the development of wideband SAW resonators is especially required because next-generation mobile communication systems require high-speed data transmission using wide frequency bands. In this study, two layered structures—(i) a c-axis-tilted ScAlN bilayer film/silicon substrate and (ii) a c-axis-zigzag ScAlN film/silicon substrate—are proposed for highly coupled SAW resonators, and the electromechanical coupling coefficient K2 of the non-leaky Rayleigh-mode SAW propagating in these structures is investigated theoretically. With a proper c-axis tilt angle and thickness selection of the ScAlN film, the first-mode Rayleigh SAW in the c-axis-tilted ScAlN bilayer film/silicon substrate and c-axis-zigzag ScAlN film/silicon substrate offers high K2. The maximum K2 was 9.56%, obtained in the c-axis-zigzag ScAlN film/silicon substrate structure, which was 2.5 times the maximum K2 in the c-axis-tilted ScAlN monolayer film/silicon substrate structure; this is because the c-axis-zigzag ScAlN films increase the shear vertical component of the SAW particle displacement, most of which is concentrated in the c-axis-zigzag ScAlN film on the silicon substrate. It is also important that the second-mode SAW (Sezawa wave) in the c-axis-zigzag ScAlN film/silicon substrate structure is not excited when the K2 value of the first-mode SAW is maximized. The techniques for fabricating a c-axis-tilted ScAlN film and a c-axis-zigzag ScAlN film have been reported, and well-established micromachining technology related to silicon semiconductors offers significant advantages in the manufacturing and processing of SAW resonators. Therefore, the c-axis-zigzag ScAlN film/silicon substrate structure has significant potential for SAW device applications.

A Micro-Acoustic Enhanced Low-Impedance Antenna System for IoT Wake-Up Receivers

In this work, we propose a passive radio frequency (RF) front-end tailored for wake-up receivers (WuRx) to be deployed in cellular IoT devices and wearables networks, featuring a low radiation resistance antenna and a high-Q matching network implemented with microacoustic resonators integrated to obtain a systematic higher node’s sensitivity at no cost in terms of power consumption. We show how these components can be co-designed to obtain high passive voltage gain, hardwarelevel blocker immunity, and increased resilience to integration parasitics, relaxing link budget for low-power IoT nodes. We report experimental validation of a PCB antenna with 2 dBi gain measured on an 11Ω input resistance at resonance, and an in-house fabricated Micro-Electro-Mechanical System (MEMS) thin-film aluminum nitride bulk acoustic resonator with a quality factor Q = 550 and a piezoelectric coupling coefficient k2 t =7%, hybridly integrated with a commercial off-the-shelf low-power WuRx circuit to benchmark the proposed RF front-end design at 850MHz. We demonstrate a passive voltage gain of 12 dB due to the MEMS resonator, and an additional 11 dB due to the proposed antenna design (for a total of an unprecedented 23 dB passive gain in this frequency range) leading to an over the air.61dBm minimum detectable input power and 23 dB blocker rejection.

Experimental Study on the Coefficient of Earth Pressure at Rest for Sand

The coefficient of earth pressure at rest K0 is a state soil variable correlated with relative density Dr. As previously conducted K0 tests could not guarantee zero lateral deformation in the sand specimens, significant errors occurred in the test results. In this paper, a centrifugal model test method is used to study the K0 of sand with varying densities. The sand specimens with varying relative densities are prepared by sand pluviation, and a 50 g-ton centrifugal force is applied. Subsequently, the relationship of K0 and Dr with different densities is analyzed. The test results show that for the same type of sand, the value of K0 gradually increased with Dr. Based on the meso-evolution characteristics of sand particle recombination, various relationships between K0, the displacement deflection angle, and the friction offset angle between particles are analyzed. Furthermore, the relationship between particle volume fraction and K0 is derived, the assumption of increasing the coefficient K0 with the increase in Dr is verified, and the effect of Dr of sand on the force transfer behavior of the internal particle fabric is briefly discussed. The research results could significantly improve the current earth pressure theories.

Structural constants of selected early-type binaries and their astrophysical implications

Theoretical values of the structural coefficient k2, have been calculated in dependance on mass and age. The results are relatively more accurately tested from observations of apsidal motion in young and massive binariy systems. For this context, values of k2 were also derived for eleven well-studied and observed eccentric eclipsing–binaries: CW Cep, V 478 Cyg, AG Per, V 453 Cyg, V 578 Mon, PV Cas, V 451 Oph, V 380 Cyg, IQ Per, HD 152,218 and NO Pup. Our new k2 values are calculated by integrating the Clairaut–Radau equation numerically using the ‘EZ-Web’ version of the Eggleton stellar modeling program. Models are in the range between 2.6 and 17.5 Mʘ, constructed with the two metallicities Z = 0.015 and Z = 0.02. From the observations, we obtained a linear regression formula relating system-mean k2 values for given logarithmic mass and age. This correlation can be used to test the match between apsidal motion results and the separately derived ages of the components of a binary system. From these findings, we conclude that empirically determined k2 values have better determined from young and massive binaries than binaries in general. Apsidal motion constants, when calculated from reliable data, can be used to test the ages of the stars. These checks can be made with our correlation for the system NO Pup, which is the subject of current studies.

Effects of site operating conditions on real site TKPH (tonne-kilometer-per-hour) of ultra-large off-the-road tires

The objective of this study is to investigate the effects of site operating conditions on the real site TKPH (tonne-kilometer-per-hour) of ultra-large off-the-road (OTR) tires. To achieve this, a novel finite element OTR tire thermal (OTRTire-T) model was developed to predict the temperatures of OTR tires. As per the results from the OTRTire-T model, the cycle length coefficient K1and the site ambient temperature coefficient K2were refined and then compared with existing coefficients in the literature for cross-verification. After cross-verification, these K1and K2coefficients were used to calculate the real site TKPHs. The real site TKPHs were investigated under different site operating conditions (i.e. average vertical tire loads, average cycle speeds, ambient temperatures, and cycle lengths). The results showed that the real site TKPH increased with a rise in average cycle speeds from 10 to 45 km/h and an elevation of ambient temperatures from −30°C to 40°C. At low ambient temperatures below 15°C, as per the real site TKPH, the loading capacity of the truck may increase (compared with its rating payload of 363 t) at mine sites. In addition, the real site TKPH increased relatively rapidly when the cycle lengths were short but rose slowly, or even leveled off, with a further increase in cycle lengths.

Super-High-Frequency Low-Loss Sezawa Mode SAW Devices in a GaN/SiC Platform.

This paper presents a comprehensive study of the performance of Sezawa surface acoustic wave (SAW) devices in SweGaN QuanFINE® ultrathin GaN/SiC platform, reaching frequencies above 14 GHz for the first time. Sezawa mode frequency scaling is achieved due to the elimination of the thick buffer layer typically present in epitaxial GaN technology. Finite element analysis (FEA) is first performed to find the range of frequencies over which the Sezawa mode is supported in the grown structure. Transmission lines and resonance cavities driven with Interdigital Transducers (IDTs) are designed, fabricated, and characterized. Modified Mason circuit models are developed for each class of devices to extract critical performance metrics. We observe a strong correlation between measured and simulated dispersion of the phase velocity (vp) and piezoelectric coupling coefficient (k2). Maximum k2 of 0.61% and frequency-quality factor product (f.Qm) of 6×1012 s-1 are achieved for Sezawa resonators at 11 GHz, with a minimum propagation loss of 0.26 dB/λ for the two-port devices. Sezawa modes are observed at frequencies spanning up to 14.3 GHz, achieving a record high in GaN microelectromechanical systems (MEMS) to the best of the authors' knowledge.

Rutting prediction of asphalt pavement with semi-rigid base: Numerical modeling on laboratory to accelerated pavement testing

Rutting development and its prediction are critically important for the long-term preservation of semi-rigid pavements. A multi-scale test was developed to analyze the rutting development and its prediction model, involving triaxial, scaled loading, and full-scale loading tests. Laboratory-based triaxial tests predicted the rheological properties of asphalt mixtures at high temperatures. The flow number FN was only related to the cohesion and internal friction angle, confining pressure, and circulating pressure of the mixture. Rutting prediction models were established using a modified Burgers finite-element model and verified through scaled and full-scale loading tests. The relationship between FN of the dynamic creep test and loading times of scaled and full-scale loading test were determined through comparative analysis. Finally, the cross-scale relationship between the multi-scale tests was established by introducing correction coefficients K1 and K2. The proposed prediction model of rutting development is suggested to be computationally reasonable, which could provide a scientific reference for the treatment and maintenance of rutting on asphalt pavements.

Studies on the Kinetics of the CH + H2 Reaction and Implications for the Reverse Reaction, 3CH2 + H.

The reaction of CH radicals with H2 has been studied by the use of laser flash photolysis, probing CH decays under pseudo-first-order conditions using laser-induced fluorescence (LIF) over the temperature range 298-748 K at pressures of ∼5-100 Torr. Careful data analysis was required to separate the CH LIF signal at ∼428 nm from broad background fluorescence, and this interference increased with temperature. We believe that this interference may have been the source of anomalous pressure behavior reported previously in the literature (Brownsword, R. A.; J. Chem. Phys. 1997, 106, 7662-7677). The rate coefficient k1 shows complex behavior: at low pressures, the main route for the CH3* formed from the insertion of CH into H2 is the formation of 3CH2 + H, and as the pressure is increased, CH3* is increasingly stabilized to CH3. The kinetic data on CH + H2 have been combined with experimental shock tube data on methyl decomposition and literature thermochemistry within a master equation program to precisely determine the rate coefficient of the reverse reaction, 3CH2 + H → CH + H2. The resulting parametrization is kCH2+H(T) = (1.69 ± 0.11) × 10-10 × (T/298 K)(0.05±0.010) cm3 molecule-1 s-1, where the errors are 1σ.

Comparative Study of Three SAW Configurations for Temperature Sensing

This paper demonstrates three SAW configurations' electrical and mechanical behaviors: a one-port resonator, a two-port resonator, and a delay line that works as temperature sensors of around 440 MHz characteristic frequencies. We investigate the sensitivity of the sensors for temperatures up to 200 °C. A linear behavior of the frequency shift versus temperature is observed; the resulting sensitivity of the sensors is evaluated at 22.74 ppm/°C for the one-port resonator, 23.17 for the two-port resonator, and 3.83 ns/°C for the delay line structure. The electromechanical coupling coefficient (k2) is 0.492 % for the delay line, 0.489 % for the one-port resonator, and 0.55% for the two-port resonator. The quality factor QFactor calculated from Y11 electrical input admittance is 2858 for the one-port resonator, 2977 for the delay line, and 2903 for the two-port resonator. The optimized piezoelectric layer thickness value, for the one port resonator, is hAlN=1.5µm.

Assessment of the cytoskeletal impact of beta-actin mutations leading to non-muscle actinopathies by means of dual laser optical tweezers (DLOT).

Actin plays crucial roles in critical cellular processes, like the dynamic remodeling of the cytoskeleton. Non-muscle actinopathies (NMAs) are disorders caused by heterozygous mutations in the genes encoding for the β- and γ-isoforms of cytoskeletal actin, whose underlying mechanisms remain to be resolved. We used a Dual Laser Optical Tweezers (DLOT) to characterize the viscoelastic properties of the membrane-cytoskeleton system of neurons wild-type and expressing the β-actin mutation R196H associated with malformations of cortical development. Ramp-and-hold pulls to generate a tether were imposed on the membrane of neuron progenitor cells (NPC) and mature neurons (NC). Tether formation-elongation is characterized by a multiphase force response: an early rise to a peak associated with the formation of the tether and followed by a drop to a minimum; a continuous rise during the ramp at a rate that exponentially decreases to a steady rate; an exponential force relaxation to a constant value during the hold. The force responses were simulated by using a 2nd order Maxwell viscoelastic arrangement that provides the estimates of both undamped (k0) and damped elastic coefficients (k1 and k2) and the friction coefficients (η1 and η2) of tether formation. In both WT and R196H neurons the undamped elastic coefficient is not significantly affected by the maturation process. During maturation, friction and damped elastic coefficients show significant reductions in WT neurons, while in mutant neurons all the coefficients in NPCs are already reduced to values similar to those in NCs. The work provides the mechanical evidence that R196H mutation induces a faster differentiation of the NPC toward the greater connectivity of the mature neuron. Supported by EJP RD 2019.

Results of the calculation of the absorber temperature in a flat solar air heater

The article discusses a method for calculating the temperature of the solar air heater absorber under conditions of still air in the collector and under conditions of low forced convection. The problem of determining the temperature of the air heater absorber tst is considered for the climatic conditions of Fergana, with a horizontal collector and when solar radiation passes through double glass. It is assumed that over the considered short period of time, the temperature of the absorber is constant and the heat loss through the insulation of the bottom of the collector is negligible. Solar radiation passes through ordinary transparent colorless glass with a reflectance of 8%. Taking into account the losses of the heat flux of solar radiation when passing through glass 1 and 2 by the reflection coefficients K1 and K2, in the first version the Stefan-Boltzmann equation is solved, as a result of which the temperature value of the absorber surface is obtained. In the second variant, the absorber temperatures were obtained taking into account convection.