Values Of Structural Parameters Research Articles

Anisotropic SST turbulence model for shock-boundary layer interaction

Menter SST k-ω is a Reynolds-averaged Navier–Stokes based two-equation turbulence model routinely used in industry for predicting aerodynamic flows. It shows excellent performance for low-speed flows, but gives inconsistent predictions for high-speed shock-induced separated flows. The model assumption of using a constant value of 0.31 for the structure parameter contradicts experimental observations. The model is also unable to predict Reynolds stress anisotropy generated by shock waves. In this work, we augment the SST model with quadratic eddy viscosity formulation of an explicit algebraic Reynolds stress model. A new relation for the structure parameter is proposed, making it a function of the local strain-rates and is no longer a constant in the regions of shock/turbulent boundary layer interaction (SBLI). Additional shock-physics is introduced using (Sinha et al., 2003) shock-unsteadiness model and an upper limit to the value of structure parameter is set in regions of shock waves. The new model, termed as SUQ-SST, is validated using a number of SBLI test cases ranging from supersonic to hypersonic speeds and near-incipient to fully-separated flows. Results show that the modifications do not alter the boundary layer prediction capability of the SST model. On the other hand, the new model gives significant improvement in predicting Reynolds stress anisotropy, flow separation, and surface properties in a wide range of SBLI flows.

Testing of linear models for optimal control of second-order dynamical system based on model-reality differences

In this paper, the testing of linear models with different parameter values is conducted for solving the optimal control problem of a second-order dynamical system. The purpose of this testing is to provide the solution with the same structure but different parameter values in the model used. For doing so, the adjusted parameters are added to each model in order to measure the differences between the model used and the plant dynamics. On this basis, an expanded optimal control problem, which combines system optimization and parameter estimation, is introduced. Then, the Hamiltonian function is defined and a set of the necessary conditions is derived. Consequently, a modified model-based optimal control problem has resulted. Follow from this, an equivalent optimization problem without constraints is formulated. During the calculation procedure, the conjugate gradient algorithm is employed to solve the optimization problem, in turn, to update the adjusted parameters repeatedly for obtaining the optimal solution of the model used. Within a given tolerance, the iterative solution of the model used approximates the correct optimal solution of the original linear optimal control problem despite model-reality differences. The results obtained show the applicability of models with the same structures and different parameter values for solving the original linear optimal control problem. In conclusion, the efficiency of the approach proposed is highly verified.

Methodologies of heat calculation and selection of rational parameters of regenerative burners operation

Decrease of energy intensity of products is an actual task for all the industries, including steel industry. One of the best solutions to increase energy efficiency of heating facilities is application of recuperative and regenerative burners, which ensure high temperature of air heating. Such high temperatures cannot be achieved at application of heating systems based on central recuperator. It was shown that many countries accomplish studies to perfect recuperative burners and simulation of their thermal operation. However at present there are no universally recognized methodologies of calculation and designing of such equipment. Results of studies presented, which were implemented in three methodologies intended for heat calculation and selection of rational parameters of regenerative burners operation. The methodologies enable also to determine a fuel utilization coefficient for a furnace system based on regenerative burners, to estimate competitiveness of solutions at creation new and modernization existing furnaces comparing with utilization of modern central recuperators. Comparative simplicity of the mathematical apparatus used in the methodologies highlighted, as well as correspondence of the used calculated expressions to the physical nature of the processes taking place. Besides, the methodologies enable during calculation to set the values of important characteristics, which can be reached based on determination of values of basic structure parameters of lining. A scheme of joint application of the elaborated methodologies proposed.

Effect of oxidation temperature on oxidation reactivity and nanostructure of particulate matter from a China VI GDI vehicle

Modern Gasoline Direct Injection (GDI) vehicles offered higher power output, improved fuel economy and reduced CO2 emissions compared with port fuel injection (PFI) vehicles. However, the particle number emission of GDI is larger than that of PFI and also higher than diesel vehicles equipped with diesel particle filter (DPF). This research sampled particle matter (PM) emitted from a China VI vehicle over the Worldwide harmonized Light vehicles Test Cycle (WLTC). The results of particle size distribution showed that ultra-fine particles in diameter below 23 nm take up majority of particle emissions. While with the oxidation temperature rising, the peak diameter of emitted particles migrated to larger section. The effect of oxidation temperature including interlayer spacing, fractal dimension, fringe length and tortuosity have been analyzed by TEM. The value of nano structural parameters increases slightly with the temperature increasing. Besides, the impact of volatile components was considered into the micromorphology and microstructure parameters of primary particles. After eliminating volatile materials, there is no presence of hollow carbon particles and all the three parameters including interlayer spacing, fringe length and fringe tortuosity showed an overall decrease. Better understanding nano structural parameters of PM under different oxidation temperatures can provide information to explain the potential impacts of particle emissions on human health and environment and the regeneration process of gasoline particle filter (GPF).

Design and Optimization of the Resonator in a Resonant Accelerometer Based on Mode and Frequency Analysis.

This study aims to develop methods to design and optimize the resonator in a resonant accelerometer based on mode and frequency analysis. First, according to the working principle of a resonant accelerometer, the resonator is divided into three parts: beam I, beam II, and beam III. Using Hamilton’s principle, the undamped dynamic control equation and the ordinary differential dynamic equation of the resonant beam are obtained. Moreover, the structural parameters of the accelerometer are designed and optimized by using resonator mode and frequency analysis, then using finite element simulation to verify it. Finally, 1 g acceleration tumbling experiments are built to verify the feasibility of the proposed design and optimization method. The experimental results demonstrate that the proposed accelerometer has a sensitivity of 98 Hz/g, a resolution of 0.917 mg, and a bias stability of 1.323 mg/h. The research findings suggest that according to the resonator mode and frequency analysis, the values of the resonator structural parameters are determined so that the working mode of the resonator is far away from the interference mode and avoids resonance points effectively. The research results are expected to be beneficial for a practical resonant sensor design.

Millimeter-wave enabled PAM-4 data transmission over hybrid FSO-MMPOF link for access networks

In this paper, we propose a full duplex architecture based on a hybrid link composed of free space optics (FSO) and multimode plastic optical fiber (MMPOF) for short-range wireless access networks. The proposed architecture employs mode group division multiplexing (MGDM) and wavelength reuse techniques to transmit data between central unit (CU) and radio access units (RAUs). An optical frequency comb source to generate multiple optical sidebands is realized using a single laser source to provide 60 GHz millimeter-wave (mm-wave) signals at each RAU by simultaneously transmitting PAM-4 signal on linearly polarized (LP) modes of each optical sideband. Data rate of 2times12 Gbps at mm-wave frequency of 60 GHz is achieved for both downlink (DL) and uplink (UL) transmissions. The transmission of 2times12 Gbps PAM-4 signal over hybrid FSO-MMPOF link is investigated at different values of refractive index structure parameter (C_n^2) by employing log-normal (LN) FSO channel model to support three RAUs in a ring topology. The acceptable receiver sensitivities below −5 and −0.6 dBm for DL and UL transmissions are achieved, respectively. The proposed hybrid architecture can be a potential candidate for future communication networks.

Numerical analysis on modal stability characteristics of 2D panel flutter at low supersonic speeds

In order to better understand the mechanism of panel flutter at low supersonic speeds, and to study the viscous effect on flutter boundary and flutter type, a coupled computational fluid dynamics and computational structure dynamics (CFD/CSD) methodology has been adopted. Detailed modal stability analyses have been conducted through the higher-order dynamic mode decomposition (HODMD) method, which has been used to extract dynamic modes from CFD/CSD time-domain data. The results show that at low supersonic speeds, for relatively small dynamic pressure, the stability of the first mode increases due to viscous effect and decreases when the dynamic pressure exceeds a certain critical value. For other higher-order modes the flow viscosity has a stabilizing effect when the dynamic pressure is small, and has a destabilizing when the dynamic pressure exceeds a certain value. The mode stability variation causes the difference of flutter boundary and flutter type between viscous and inviscid solutions at low supersonic speeds. Moreover, it is found that for a simply supported 2D panel, the higher-order single-mode flutter can still occur in the turbulent flow around Mach 1.4 within certain structural parameter values, especially when the mass ratio is small. The high frequency of this type of flutter suggest that more severe structural fatigue problem may occur on simply supported panels with large aspect ratio at certain parameter values, thus requiring due attention.

Internal resonance characteristics of hyperelastic thin-walled cylindrical shells composed of Mooney–Rivlin materials

The internal resonance characteristics are investigated for a thin-walled cylindrical shell composed of incompressible Mooney–Rivlin material, where the shell is subjected to a radial harmonic excitation. Based on the Kirchhoff–Love hypothesis, Donnell’s nonlinear shallow-shell theory and variational principle of energy, the coupled nonlinear differential equations, describing the radial motion of the shell, are obtained. The existence condition of 2:1 internal resonance is given via examining the natural frequencies of different modes. Then the multiple scale method is applied to derive the amplitude–frequency relations in the presence of 2:1 internal resonance, and the stabilities of steady-state responses are determined. In addition, the accuracy of the model is verified by using a homogeneous cylindrical shell with simply supported boundary conditions, some comparisons are made with the previous published researches and good agreement is found. The effects of excitation amplitudes and the structure parameters on the resonance responses of the system are examined. Numerical results show that the range of resonance increases along with the excitation amplitude; the typical phenomenon of double-jumping appears, and the generation and vanishing of double peaks are related to the values of structure parameters.

The structural, electronic, and optical properties of hydrofluorinated germanene (GeH1-xFx): a first-principles study.

The structural, electronic, and optical properties of hydrofluorinated germanene have been studied with different occupancy ratios of fluorine and hydrogen. The hybridization of H-1s and Ge-4p orbitals in hydrogenated germanene and F-2p and Ge-4p orbitals in fluorinated germanene plays a significant role in creating an energy bandgap. The binding energy and phonon calculations confirm the stability of hydrofluorinated germanene decreases with the increase of the F to H ratio. The value of the energy bandgap decreased by increasing the ratio of F and H. The optical properties have been studied in the energy range of 0-25eV. Six essential parameters such as energy bandgap (Eg), binding energy (Eb), dielectric constant ε(0), refractive index n(0), plasmon energy (ћωp), and heat capacity (Cp) have been calculated for different occupancies of H and F in hydrofluorinated germanene for the first time. The calculated values of structural parameters agree well with the reported values.

Analysis of the Effect of Conditions of Preparation of Nitrogen-Doped Activated Carbons Derived from Lotus Leaves by Activation with Sodium Amide on the Formation of Their Porous Structure.

This paper presents results of the analysis of the impact of activation temperature and mass ratio of activator to carbonized precursor R on the porous structure of nitrogen-doped activated carbons derived from lotus leaves by carbonization and chemical activation with sodium amide NaNH2. The analyses were carried out via the new numerical clustering-based adsorption analysis (LBET) method applied to nitrogen adsorption isotherms at −195.8 °C. On the basis of the results obtained it was shown that the amount of activator, as compared to activation temperatures, has a significantly greater influence on the formation of the porous structure of activated carbons. As shown in the study, the optimum values of the porous structure parameters are obtained for a mass ratio of R = 2. At a mass ratio of R = 3, a significant decrease in the values of the porous structure parameters was observed, indicating uncontrolled wall firing between adjacent micropores. The conducted analyses confirmed the validity of the new numerical clustering-based adsorption analysis (LBET) method, as it turned out that nitrogen-doped activated carbons prepared from lotus leaves are characterized by a high share of micropores and a significant degree of surface heterogeneity in most of the samples studied, which may, to some extent, undermine the reliability of the results obtained using classical methods of structure analysis that assume only a homogeneous pore structure.

Chamber Optimization for Comprehensive Improvement of Cone Crusher Productivity and Product Quality

This study aims to analyze the impact of key structural parameters such as the bottom angle of the mantle, the length of the parallel zone, and the eccentric angle on the productivity and product quality of the cone crusher and optimize the crushing chamber to improve the crusher performance. The amount of ore in the blockage layer was calculated by analyzing the movement state of the ore in the crushing chamber. Considering the amount of ore uplift further, the traditional mathematical model of crusher productivity was revised. Then, a mathematical model for dual-objective optimization of productivity and product quality of cone crusher was established. Furthermore, taking the existing C900 cone crusher as the research object, the influence of key parameters on the performance of the crusher was researched. And the optimal values of key structural parameters were obtained. Finally, based on the iron ore coarsely crushed by the gyratory crusher, the dynamic characteristics of the C900 cone crusher were simulated by using the discrete element method (DEM), and the simulation results are basically consistent with the numerical analysis results. Results show that considering the amount of ore uplift in the blockage layer, the revised mathematical model of crusher productivity can better characterize the actual productivity. The bottom angle of the mantle and the length of the parallel zone are within the range of 50°–60°and 140 mm–190 mm, respectively. The productivity shows a positive correlation with the bottom angle and a negative correlation with the length of the parallel zone. But the dependence of product quality on the angle and the length is just the opposite. The eccentric angle is within the range of 1.4°–2° and its decrease has a negative effect on the productivity and product quality.

Bursting Strength of Core Spun Cotton/Spandex Single Jersey and 1×1 Rib Knitted Fabrics

This research work investigates the bursting strength of core spun cotton/spandex and 100 % cotton, single jersey and 1×1 rib knitted fabrics, made with low, medium and high fabric tightness factors obtained using three machine set stitch lengths. These knitted fabric samples were relaxed under the dry relaxation to full relaxation and further relaxation up to 5th washing cycle treatments. For wash relaxation treatments, full relaxed samples were used. Course and wale densities, stitch densities, fabric thickness and bursting strength of the samples were measured at the end of each relaxation stage. Thus, before commencing the dry relaxation treatment, machine off stitch lengths of samples were also measured. It was found that, structural parameters, and fabric thickness increased with the progression of relaxation of fabrics and they depend on the fabric tightness factor (stitch length−1). Single jersey and 1×1 rib cotton/spandex knitted fabrics showed higher structural parameter values and higher fabric thicknesses than similar types of structures produced with cotton knitted fabrics at each of the relaxation treatments, even though they had the same machine set stitch lengths. Also, cotton and cotton/spandex 1×1 rib fabrics gave higher structural parameter values than their single jersey fabrics. Cotton single jersey and 1×1 rib fabrics gave comparatively higher bursting strengths than their cotton/spandex fabrics and bursting strength has gradually increased with progressing of relaxation treatments done. However, bursting strength of cotton/spandex 1×1 rib fabrics has gradually decreased with progressing of relaxation treatments, due to their longer tumble drying duration, where as cotton/spandex single jersey fabrics showed an increasing tendency of bursting strength under progressing of treatments, due to the lower tumble drying duration applied than their 1×1 rib fabrics. It was also found that the fabric tightness factor or stitch length, relaxation states of single jersey and 1×1 rib fabrics, fiber content of the yarns in these knitted fabrics and knitted structure type are significantly effect on structural parameters such as course and wale density and stitch density, fabric thickness and bursting strength of these tested knitted fabrics, under the 95 % significant level. In addition, the fiber content and the structure type are very important to consider for the bursting strength of knitted fabrics, when these knitted fabrics are subjected to tumbler drying. Thus, yarn strength can give a significant effect on bursting strength of these knitted fabrics.

Breeding behaviour of Purple Sunbird, <i>Cinnyris asiaticus</i> (Latham, 1790) in semiurban area of Punjab

During the breeding seasons 2017-2020, breeding activities of the Purple Sun-Bird (PSB), Cinnyris asiaticus were studied in 16 nesting sites located in the northern rural and semi-urban outskirts of the Khanna city in Punjab. Observations on nest building, incubation, hatching, feeding, growth, fledging and other behavioural aspects of the parents/chicks were inferred from video-records, photographs and direct observations made on 11 clutches laid in 07 nests. In the study area the breeding season extended from March to July and the mean value of the nest structure parameters, namely, nest length, nest width and entrance diameter were 15.2 ± 0.63 cm (range: 14-16 cm), 6.61 ± 0.36 cm (range: 6.0-8.0 cm) and 3.67 ± 0.34 cm (range: 3.0-4.0 cm) respectively. The clutch size was 2 eggs (n=6) or 3 eggs (n=4) and the egg (n=17) weight, length and breadth measured 1.13 ± 0.06 gm, 16.61 ± 0.43 mm and 11.49 ± 0.28 mm, respectively. Most of the eggs were laid in morning hours between 6:30 am to 7:30 am (n=25) and the incubation period was recorded 12 days (n=3), 13 days (n=6) and 16 days (n=1). Video records of 80.62 hours diurnal observation time (OT) recorded over 07 consecutive days (between 6:30am – 6:30pm each day) of full incubation revealed that the PSB female spent 51.59 hours (64% OT) and 29.03 hours (36% OT) as attentive periods and un-attentive Periods respectively. Synchronous hatching was completed in one or two successive days (within 24 hours) except for a single three-egged clutch with its youngest chick hatching asynchronously on third successive day. During nestling phase of 13 – 16 days, eyes of the altricial chicks opened on 5th day after hatching and approaching the day-10, the chick appeared fully feathered. During the biparental food provisioning OT of 54 hours referable to 05 days of the second half on nestling life, male and female PSB contributed 173 (33.20%) and 348 (66.80%) feeding visits respectively at a rate of 9.44 visits per hour. During this OT, the male and female PSB were seen carrying faecal sacs of chicks away from nest on 03 and 79 occasions respectively. The review of video-records showed that the female Purple Sunbird made use of nest fibers from the inner lining of the nest, as a tool for removing the defective egg from the nest. One of the nests was used in two consecutive breeding seasons and 04 broods were successfully raised in the same nest. The Oriental Garden Lizard, Calotes versicolor was noticed as a nest predator.

The Need for Accurate Osmotic Pressure and Mass Transfer Resistances in Modeling Osmotically Driven Membrane Processes.

The widely used van ’t Hoff linear relation for predicting the osmotic pressure of NaCl solutions may result in errors in the evaluation of key system parameters, which depend on osmotic pressure, in pressure-retarded osmosis and forward osmosis. In this paper, the linear van ’t Hoff approach is compared to the solutions using OLI Stream Analyzer, which gives the real osmotic pressure values. Various dilutions of NaCl solutions, including the lower solute concentrations typical of river water, are considered. Our results indicate that the disparity in the predicted osmotic pressure of the two considered methods can reach 30%, depending on the solute concentration, while that in the predicted power density can exceed over 50%. New experimental results are obtained for NanoH2O and Porifera membranes, and theoretical equations are also developed. Results show that discrepancies arise when using the van ’t Hoff equation, compared to the OLI method. At higher NaCl concentrations (C > 1.5 M), the deviation between the linear approach and the real values increases gradually, likely indicative of a larger error in van ’t Hoff predictions. The difference in structural parameter values predicted by the two evaluation methods is also significant; it can exceed the typical 50–70% range, depending on the operating conditions. We find that the external mass transfer coefficients should be considered in the evaluation of the structural parameter in order to avoid overestimating its value. Consequently, measured water flux and predicted structural parameter values from our own and literature measurements are recalculated with the OLI software to account for external mass transfer coefficients.

A Criterion for the Formation of Nonequilibrium Self-Assembled Structures.

Is there a criterion able to determine the type of structures formed in a nonequilibrium self-assembly process? This important question has a clear answer when the process takes place under equilibrium conditions: structures emerge at minimum values of the free energy. Experiments, however, have shown that when self-assembly takes place outside equilibrium, they do not appear at those free energy minima but rather at optimal values of structural parameters. On the basis of these observations, we propose a selection criterion for which structures come up at the minima of a nonequilibrium free energy that takes into account the energy needed to change their configuration. The criterion is able to predict the formation and configuration of structures such as Liesegang rings and patterns in magnetic colloids and could constitute a powerful tool to understand the synthesis of advanced materials, enantiomers, and nanoparticles.

Controlling Wetting Properties on Nanostructure Surfaces by the Coupled Effect of the Structural Parameter and Roughness Factor

Background: This study used molecular dynamics simulations to investigate the wetting properties of a droplet on copper surfaces with different nanostructures to determine the influence of the structural parameter and roughness factor on the wetting properties. Methods: The simulation results show that the structural parameter h/b can determine the wetting transition of droplets on surfaces. In addition, the critical structural parameter values are 1.5, 1.5, 2.08 and 2.24 for the square pillar, cylinder, frustum and cone nanostructures, respectively. Due to the restriction of the wedge surface on water molecules, the effect of the wedge surface is not the same when the theoretical gap and height of the nanostructures are changed on different surfaces. Results and Discussion: For the square pillar and the cylinder surfaces, when changing the height or the theoretical gap of the nanostructure, the wedge angle is always the same and is 90°, so the effect of the wedge surface is unchanged for water molecules. For the frustum and the cone surfaces, the wedge angle does not change when the theoretical gap of the nanostructure is changed but when the height of the nanostructure is changed, the wedge angle gradually increases but does not exceed 90° resulting in the restriction of the wedge surface on water molecules gradually increasing. Therefore, for the same height and theoretical gap, the contact angle of the frustum and the cone surfaces is larger than that of the square pillar surfaces and cylinder surfaces due to the effect of the wedge surface. It is also observed that the increased roughness factor helps increase the contact angle of the droplet. Conclusion: We propose that the wetting properties of the nanostructure surface can be controlled by the structural parameter associated with the surface roughness.

Tunnel boring machines (TBM) performance prediction: A case study using big data and deep learning

This work explores the potential for predicting TBM performance using deep learning. It focuses on a 17.5-km-long tunnel excavated for the Yingsong Water Diversion Project in Northeastern China with its 728 days’ continuous monitoring of mechanical data. The prediction uses the deep belief network (DBN) proposed by Hinton et al. (2006),on the penetration rate, cutter rotation speed, torque, and thrust force. Field Penetration Index (FPI) is introduced to quantify TBM performance in the field. The DBN algorithm trains on nth number of preceding elements and predicts the performance of the n + 1th element. Prior to the implementation of the DBN, a pilot test was performed to find the optimal values for the network structural parameters (number of input nodes, number of hidden layers, number of nodes in the hidden layers, and learning rate). Predictions on FPIs in all the three rock types were then proceeded with good agreement with the field measured data. The mean relative errors for the predicted measured FPIs are generally less than 0.15 and the correlation coefficients (R) can be higher than 0.78. The predicted and measured FPI values along the length of the tunnel graphically follow the same trends. These results confirm the usefulness of big data and the deep learning in predicting TBM performance.

Probing thermoelectric properties of high potential Ca3PbO: An Ab Initio Study

The fascinating electron transport properties of anti-perovskites have gathered incredible research consideration. In the search for novel thermoelectric materials, a Density Functional Theory (DFT) based computational assessment of electron transport properties of Ca3PbO has been made based on the grounds of Boltzmann transport theory. The variation of transport properties specifically Seeback coefficient (S), electrical conductivity (σ), electronic thermal conductivity (κe) and power factor (PF) versus chemical potential (µ) have been plotted at 300 K, 600 K and 800 K. The present study proposes Ca3PbO to be an excellent n-type high temperature thermoelectric material. The optimized values of equilibrium structural parameters have been determined. The current analysis tends to stimulate experimental work towards designing and improving thermoelectric performance of Ca3PbO for realistic applications.

Research on the Characteristics and Regularity of Evacuation in Railway Tunnel Emergency Rescue Station at High Altitude

With the development of economy, railway construction is gradually expanding to the plateau area, and the number of super-long railway tunnels at high altitude is increasing year by year. Compared with the plain area, due to the influence of hypoxia and panic, there are obvious differences in evacuation rules in plateau environment. In this paper, considering the high altitude environment, panic psychology, people’s age and gender and train structure factors, we use the Pathfinder personnel evacuation simulation technology, simulate and analyze evacuation of personnel in emergency rescue stations with different structural parameters. Finally we obtain the characteristics and rules of the evacuation of personnel in emergency rescue stations of high-altitude railway tunnels, and give the suggested design values of structural parameters of emergency rescue stations of high-altitude railway tunnels, so as to provide reference basis for its construction.

Pressure effects on electronic, elastic, and vibration properties of metallic antiperovskite PbNCa3 by ab initio calculations.

Ab initio computations are performed to study the structural, elastic, electronic, and vibrational characteristics of the cubic antiperovskite compound PbNCa3 under pressure up to 50 GPa. By using the generalized gradient approximation (GGA), the equilibrium structural parameters, energy band structure, density of states, elastic properties, and phonon frequencies for PbNCa3 have been examined. We have obtained some concerned feature as Young modulus and Poisson ratio for this compound using the elastic parameters. The computed elastic constant values show that PbNCa3 is stable up to 30GPa as mechanically. To assess the stability of this compound dynamically, we have investigated the one-phonon DOS and phonon dispersion relations under pressure. Our results indicate that the calculated structural parameter values at 0GPa are in accord with the existing data.