Force Method Research Articles

Direct calculation of the eddy viscosity operator in turbulent channel flow at Re τ = 180

This study aims to quantify how turbulence in a channel flow mixes momentum in the mean sense. We applied the macroscopic forcing method (Mani & Park, Phys. Rev. Fluids, 2021, 054607) to direct numerical simulation (DNS) of a turbulent channel flow at $Re_\tau =180$ using two different forcing strategies that are designed to separately assess the anisotropy and non-locality of momentum mixing. In the first strategy, the leading term of the Kramers–Moyal expansion of the eddy viscosity is quantified, revealing all 81 tensorial coefficients that essentially characterise the local-limit eddy viscosity. The results indicate the following: (1) the eddy viscosity has significant anisotropy, (2) Reynolds stresses are generated by both the mean strain rate and mean rotation rate tensors associated with the momentum field and (3) the local-limit eddy viscosity generates asymmetric Reynolds stress tensors. In the second strategy, the eddy viscosity is quantified as an integration kernel revealing the non-local influence of the mean momentum gradient at each wall-normal coordinate on all nine components of the Reynolds stresses over the channel width. Our results indicate that while the shear component of the Reynolds stress is reasonably reproduced by the local mean gradients, other components of the Reynolds stress are highly non-local. These results provide an understanding of anisotropy and non-locality requirements for closure modelling of momentum transport in attached wall-bounded turbulent flows.

Research on Impact Prediction Model for Corn Ears by Integrating Motion Features Using Machine Learning Algorithms

The mechanical damage of corn kernels during harvest leads to mildew in the kernel storage process, seriously affecting food safety and quality. Impact force is the primary source of mechanical damage in the corn threshing process, and its accurate detection is of great significance for corn threshing with low damage. A method for the impact force detection of corn ears was proposed in this manuscript. The momentum theorem determined the main factors influencing impact force (weight, falling height, and space attitude). Corn ear weight, falling height, and space attitude were used as experimental factors. The bench test was carried out with the impact force of corn ear as the output variable. During the experiment, piezoelectric sensors were used to collect the impact force of corn ears under different motion states. Then, the impact force detection model was constructed using four machine learning algorithms: multiple linear regression, ridge regression, random forest, and support vector regression. The results showed that the RF algorithm was more suitable for constructing the prediction model of average and maximum impact force when corn ears fall, SD, RMSE, and r were, respectively: 0.9526, 1.2685, 0.9855; 3.8389, 3.6071, and 0.8510. Secondly, the weight characteristics had the most significant influence on the impact force detection of the ear. Therefore, this method can be used as an accurate, objective, and efficient online detection method for impact force.

Residual stress and deformation of welded T-joint between low carbon steel and stainless steel

The welded structures between carbon steel and stainless steel are widely used in many sectors such as pedestrian bridges, food industry, chemical industry, petroleum, and thermal power plants, … These composite structures take advantages of each material for different parts of structure. In the welded structures between carbon steel and stainless steel, the structure is made by T-joint that is the most common. The calculation of residual stress and welding strain of the T-joint between low-carbon and stainless steel materials is the basis to evaluate the working ability of this structure. In this study, the residual stress and welding deformation of the T-joint are determined by the imaginary force method. The double-sided weld of T-joint between low carbon steel and stainless steel is welded simultaneously by MIG welding process. The obtained results of residual stress and welding deformation in this case are compared with the case of single-sided weld so that we can find the difference between residual stress and welding deformation in two cases.

The Effect of the Use of a Novel Urease Inhibitor Coated Urea on the Greenhouse Gas Emissions and Ammonia Volatilization Losses from a Maize Field

Nitrogen fertilizers are essential for enhancing agricultural productivity but are also major contributors to greenhouse gas (GHG) emissions and ammonia volatilization, which affect environmental sustainability. This study evaluated the effect of cashew nut shell liquid (CNSL)-coated urea on GHG emissions and ammonia losses from maize fields in the Indo-Gangetic Plains, known for excessive nitrogen fertilizer usage. A randomized block design was employed with four treatments: control (no nitrogen), prilled urea, neem-coated urea (NCU), and CNSL-coated urea (CCU). Gas samples were collected using the closed chamber method, and emissions of CO₂ and N₂O were analyzed via gas chromatography. Ammonia volatilization was measured using the forced air draft method. Results showed that the CCU treatment significantly reduced ammonia volatilization compared to prilled urea (15.84% reduction), with reductions of 9% to those observed with NCU. Moreover, CCU-treated plots exhibited reduced cumulative GHG and lower global warming potential (GWP) without compromising maize yields. Cumulative GHG emissions varied among the treatments in the order urea> CCU> NCU> Control. CCU treated plots exhibited a net GWP decrease of 8.59% compared to urea and an increase of 4.13% compared to NCU. These findings suggest that CNSL-coated urea can serve as an eco-friendly alternative to conventional urea, potentially mitigating environmental impacts associated with nitrogen fertilization. Further studies are recommended to assess the long-term efficacy of CNSL in various soil types and climatic conditions.

Study of Deformations in Statically Indeterminate Beam in Industrial and Shipbuilding Structures

The paper considers the analysis of deformations in a statically indeterminate beam using the example of a ship's keel – an I-beam that plays an important role in ensuring the stability and structure of the vessel. The research is carried out through a combination of theoretical and experimental approaches. The force method was chosen for theoretical analysis as a universal tool for statically indeterminate beams, allowing to estimate deformations and stresses at various points of the beam. It includes the selection of the optimal cross section, which is an advantage of this approach. The finite element method (FEM), implemented using Ansys 2021 R2 PC, is used for experimental analysis and visualization of bending deformation. This method provides a more flexible and powerful tool for analyzing complex structures, taking into account a variety of boundary conditions. The results of the study were compared, and the calculation errors turned out to be minimal and acceptable. The paper emphasizes the importance of conducting such analyses to understand the behavior of structures under loads and ensure their reliability not only in transport, but also in industrial and civil construction.

Pruning convolutional neural networks for inductive conformal prediction

Neural network pruning is a popular approach to reducing model storage size and inference time by removing redundant parameters in the neural network. However, the uncertainty of predictions from pruned models is unexplored. In this paper we study neural network pruning in the context of conformal predictors (CP). The conformal prediction framework built on top of machine learning algorithms supplements their predictions with reliable uncertainty measure in the form of prediction sets, under the independent and identically distributed assumption on the data. Convolutional neural networks (CNNs) have complicated architectures and are widely used in various applications nowadays. Therefore, we focus on pruning CNNs and, in particular, filter-level pruning. We first propose a brute force method that estimates the contribution of a filter to the CP’s predictive efficiency and removes those with the least contribution. Given the computation inefficiency of the brute force method, we also propose the Taylor expansion to approximate the filter’s contribution. Furthermore, we improve the global pruning method by protecting the most important filters within each layer from being pruned. In addition, we explore the ConfTr loss function which is optimized to yield maximal CP efficiency in the context of neural network pruning. We have conducted extensive experimental studies and compared the results regarding the trade-offs between predictive efficiency, computational efficiency, and network sparsity. These results are instructive for deploying pruned neural networks with applications using conformal prediction where reliable predictions and reduced computational cost are relevant, such as in safety-critical applications.

Modeling and analysis of non-circumferential symmetric permanent magnet spherical motor using genetic algorithm-based torque map method.

A permanent magnet spherical motor (PMSpM) is a typical multiple-degree-of-freedom apparatus. This paper proposes a torque map-based torque model and its counterpart using a genetic algorithm for the PMSpM with non-circumferential symmetric permanent magnets. The basic structure and operating principle of the PMSpM under study are presented. The analytic model of the 3D magnetic field is researched using the spherical harmonic method. The magnetic field model is verified via finite element method (FEM) analysis and an experiment of radial magnetic flux density. The analytic torque model is formulated using the Lorentz force method. The torque maps are established according to the principle, and the torque map-based torque model originates from the maps. FEM and the experimental results prove the correctness of the torque map-based torque model, and real-time performance of the torque model is also estimated. To solve the coil current calculation difficulty, the genetic algorithm is introduced for establishing the reversal torque model; MATLAB simulation is conducted for the convergence speed of the reversal torque model; and the real-time performance is studied on Qt 5.14/C++ upper software.

Enhancements in the Virtual Support Force Method for Tunnel Excavation Problems

Enhancements in the Virtual Support Force Method for Tunnel Excavation Problems

Molecular dynamics simulation for phase transition of CsPbI3 perovskite with the Buckingham potential.

The CsPbI3 perovskite is a promising candidate for photovoltaic applications, for which several critical phase transitions govern both its efficiency and stability. Large-scale molecular dynamics simulations are valuable in understanding the microscopic mechanisms of these transitions, in which the accuracy of the simulation heavily depends on the empirical potential. This study parameterizes two efficient and stable empirical potentials for the CsPbI3 perovskite. In these two empirical potentials, the short-ranged repulsive interaction is described by the Lennard-Jones model or the Buckingham model, while the long-ranged Coulomb interaction is summed by the damped shifted force method. Our molecular dynamics simulations show that these two empirical potentials accurately capture the γ ↔ β ↔ α and δ → α phase transitions for the CsPbI3 perovskite. Furthermore, they are up to two orders of magnitude more efficient than previous empirical models, owing to the high efficiency of the damped shifted force truncation treatment for the Coulomb interaction.

Calculation method of temporary cable force in incremental launching construction of large span steel box girder without auxiliary pier

The Fenshui River Bridge is a steel–concrete composite girder bridge with a main span of 90 m. Due to the topographical constraints, the steel box girder was constructed without the use of auxiliary piers, employing incremental launching techniques. This article focuses on the construction technology used for the steel box girder of the Fenshui River Bridge. Firstly, using the influence matrix method, the cable force is determined based on the maximum cantilever state of the structure, with the vertical deformation of the front end of the guide beam and the horizontal deformation of the top of the tower as the control objectives. The unstressed cable length is then calculated based on the mechanical relationship between cable deformation and cable force. A calculation method for adaptive cable force is proposed, which is based on the variation of the stress-free cable length within the adaptive structural system. Next, the finite element analysis method was employed to determine the optimal layout position for the tower. The results indicate that during the incremental launching construction of the steel box girder, the calculated cable forces using the method proposed in this paper are in close agreement with the measured cable forces. At the maximum cantilever state of the structure, the calculated and measured values of the cable force resulted in a percentage difference of 3.96%. The calculated values of deformation and stress in key sections showed a percentage difference of 6.4% for deformation and 6.6% for stress. To maximize the effectiveness of the tower and cable, the tower should be positioned above the bridge pier when the guide beam crosses the maximum span. The findings of this paper can serve as a reference for the construction of similar types of bridges.

Role of the magnetic layer interface, roughness, and thickness in the temperature-dependent magnetic properties of Al2O3/Co/CoO thin films deposited by magnetron sputtering

Using the methods of atomic force and electron microscopy and the magneto-optical Kerr effect, the role of the interface, roughness, and thickness of the magnetic layer in the temperature-dependent magnetic properties of thin Al2O3–Co films with a naturally oxidized cobalt surface was studied. The layers were deposited by magnetron sputtering. The thickness of the cobalt layer varied from 2 to 100 nm. For the first time, the dependences of coercive forces and exchange displacements on the thickness of the cobalt film in the temperature range from 80 to 300 K were obtained and analyzed. The contribution to the coercive force and exchange displacement from the oxidized cobalt surface increases as the temperature decreases below 160 K. The magnitude of the contribution depends on the base material on which the cobalt film is deposited and is maximum for a cobalt film with a thickness of ∼20 nm in the Al2O3/Co structure. A weakly magnetic layer was found at the Al2O3/Co interface. The behavior of the exchange bias in this layer is similar to the behavior of a ferromagnetic Co core with a naturally oxidized CoO shell. The thickness of this layer depends on the speed and order of deposition of the layers. When the order of deposition of layers (Co/Al2O3) changes, the behavior of the exchange displacement of the interface becomes similar to that observed in the ferromagnet/antiferromagnet system. That is, when the deposition order changes, the value of the exchange shift changes sign when the cobalt layer thickness is below 10 nm.

Research on aerodynamic characteristics of the pantograph on double-stack high container transportation lines

PurposeThe purpose of this paper is to study the aerodynamic characteristics and uplift force tendencies of pantographs within the operational height span of 1,600–2,980 mm, aiming to offer valuable insights for research concerning the adaptability of pantograph-catenary systems on double-stack high container transportation lines.Design/methodology/approachEight pantograph models were formulated based on lines with the contact wire of 6,680 mm in height. The aerodynamic calculations were carried out using the SST k-ω separated vortex model. A more improved aerodynamic uplift force method was also presented. The change rule of the aerodynamic uplift force under different working heights of the pantograph was analyzed according to the transfer coefficients of the aerodynamic forces and moments.FindingsThe results show that the absolute values of the aerodynamic forces and moments of the upper and lower frame increase with the working height, whereas those of the collector head do not change. The absolute values of the transfer coefficients of the lower frame and link arm were significantly larger than those of the upper frame. Therefore, the absolute value of the aerodynamic uplift force increased and then decreased with the working height. The maximum value occurred at a working height of 2,400 mm.Originality/valueA new method for calculating the aerodynamic uplift force of pantographs is proposed. The specifical change rule of the aerodynamic uplift force of the pantograph on double-stack high container transportation lines was determined from the perspective of the transfer coefficients of the aerodynamic forces and moments.

Optimization techniques of Assignment Problem using Trapezoidal Intuitionistic Fuzzy Numbers and Interval Arithmetic

This paper discusses the Assignment problem to optimize the assigning of jobs to workers based on their talents and efficiency. In general, scheduling jobs plays a significant role in manufacturing and is advantageous in real world applications as we face more uncertainty and ambiguity in assigning jobs. The Intuitionistic Fuzzy Assignment problem (IFAP) is employed in circumstances when decision-makers have to deal with uncertainty. The domains are Trapezoidal Intuitionistic Fuzzy Numbers (TrIFNs) and the techniques used are Hungarian Method (HM), Brute Force Method (BFM), and Greedy Method (GM). The suggested model's performance is compared with the existing approach with the help of interval arithmetic operations. Allocating work to the individual is illustrated numerically, the optimal solution of minimizing cost is obtained using R programming and the results of comparative analysis are shown diagrammatically that help viewers to easily understand and generate results from comparisons.

Diagnostics of metal structures made of ferro- and paramagnetic materials by the coercive force method

Diagnostics of metal structures made of ferro- and paramagnetic materials by the coercive force method

Assessment of a Force Method for the Resilient Seismic Design of Special Moment-Resisting Steel Frames with Hysteretic Energy Dissipation Devices

In this paper, the authors present the results of nonlinear dynamic analyses of twelve building models designed according to a methodology based upon the force method, capacity design principles and the concept of structural fuses to achieve resilient seismic designs for special moment-resisting steel frames with hysteretic energy dissipation devices mounted on chevron steel bracing. It is demonstrated that the resilient design mechanism previously checked with pushover analyses is also attained for most studied models with nonlinear dynamic analyses using an acceleration record which is compatible with the elastic design spectrum. Also, it is corroborated that the planned second line of inelastic defense is activated if the seismic action surpasses the considered design spectrum. Based upon the obtained results, it is confirmed that it is possible to perform a resilient seismic design for the studied system under the proposed methodology, even for tall and slender buildings. Therefore, the proposed initial stiffness ratio parameters and the global design parameters previously proposed by the authors to use in a code-oriented force method can be used with confidence for the resilient seismic design of this structural system.

Steel-concrete-steel sandwich composite cable-pylon anchorage of cable-stayed bridges: horizontal bearing capacity

Steel-concrete-steel sandwich composite cable-pylon is preliminarily applied to bridge engineering due to its excellent mechanical properties and high degree of assembly. However, the stress behavior of the steel-concrete-steel sandwich composite cable-pylon anchorage zone under the strong horizontal component force of the cable force is relatively unknown. In this paper, a 1:4 scaled-down steel-concrete-steel sandwich composite cable-pylon model test under horizontal force is designed and carried out to investigate the strain distribution in inner and outer steel plates, and the horizontal displacements in the pylon wall, and the crack development in the concrete pylon wall. Subsequently, a simplified analysis method is proposed for facilitating the calculation of the load distribution ratios of both steel plates and concrete, and the pylon wall stresses are obtained based on the force method. Furthermore, aiming to improve the problem of excessive stress in the anchorage region of the outer steel plate, the effects of various parameters on the mechanical properties of the anchorage region are investigated through parametric analysis, and the investigated parameters include the diameter of the reinforcement bar, area of the bearing plate, concrete strength, the thicknesses of the steel plate and perfobond ribs. The results indicate that increasing the diameter of the reinforcement bar is insignificant in improving the stress distribution and value of the outer steel plate, and appropriately increasing the bearing area, concrete strength, thicknesses of the steel plate and perfobond ribs can reduce the stress peak value of the outer steel plate, among which changing the thickness of the steel plate and bearing area is the most significant effect. The research results can provide experimental data and theoretical support for the design and optimization of steel-concrete-steel sandwich composite cable-pylon anchorage zones.

Optimal fare and headway for a demand adaptive paired-line hybrid transit system in a rectangular area with elastic demand

Demand adaptive paired-line hybrid transit systems that integrate fixed- and flex-route transit have emerged in the last decade and attracted increasing attention because of their potential to improve accessibility for passengers. To facilitate the operation of such a hybrid transit system, this study develops a model to determine the optimal fare and headways associated with fixed- and flex-route transit along a rectangular corridor. Compared with existing literature, the novelty of this study lies in designing the fare structure while simultaneously considering demand elasticity and passenger behaviour. A continuous approximation modelling approach is employed to derive the agency’s and travellers’ cost components. Using these, a nonlinear programming optimisation model is formulated to minimise the total user cost subject to the agency’s nonnegative revenue constraints and passengers’ route choice behaviour, which is characterised as a path-size logit model. Numerical experiments are performed using a stylised network to examine the properties of the model, in which the solution is obtained by combining a brute force method that enumerates headway and fare combinations and an iterative method that determines equilibrated passenger choices. The results show that as potential demand density increases, fare and headway fluctuate and drop, while the percentage of passengers choosing to ride on flex-route transit increases. In addition, there may be an optimal maximum offset distance, which is defined as the width of the corridor to be covered by the transit system, when the potential demand density is low, leading to minimum user cost and maximum travel demand within the service area.

Химический состав и качественные показатели говядины бычков мясных пород

Purpose. To study the effect of the genotype of bulls on the chemical composition and commodity-technological parameters of beef. Materials and Methods. The object of research is 18–month-old crossbred bulls, obtained as a result of industrial crossing of Kazakh white-headed cattle bulls with heifers of Kalmyk breed (group I), Kazakh white-headed bulls with heifers of Hereford breed (group II) and Kazakh white-headed bulls with heifers of Aberdeen-Angus breed (group III). Purebred bulls of the Kazakh white-headed breed were used as a control group. The slaughter qualities of the experimental animals were determined by control slaughter of three bulls from each group. Chemical analysis of beef samples was carried out according to the following methods and GOST standards: moisture content was determined by drying the sample to a constant mass at a temperature of 100-105°C according to GOST 9793-2016; protein content – by the amount of protein nitrogen by the Kjeldahl method according to GOST 25011-2017; fat content – according to GOST 23042-2015; ash content – according to GOST 31727-2012; amino acid composition was determined according to the method of measuring the mass fraction of amino acids by the CE method on the Kapel-105M system, the concentration of hydrogen ions (pH) was determined according to GOST R 51478-99. Results. It was found that the highest slaughter qualities were possessed by crossbred bulls of the III experimental group. The highest dry matter content was in the average sample of meat of bulls of the III experimental group – 35.13%, which is 0.63% more than in the control; the difference in fat content was 0.23% in favor of the control group. In terms of protein content, the largest amount was recorded in the meat of bulls of the III experimental group – 20.07%, which is higher than in the samples of the control, I and II experimental groups, respectively, by 0.60, 0.84 and 0.77%. The protein-quality index in the samples ranged from 6.30 to 6.48. The pH value of the meat varied slightly – from 5.60 to 5.77. Conclusion. The conducted research has allowed us to establish that the industrial crossing of the Kazakh white-headed cattle with different meat breeds contributes to an increase in productivity, quality indicators, and the beef produced. This is explained by good compatibility of crossed breeds and high breed qualities of studied breeds.

A numerical study of Elasto-inertial particle-focusing in straight and serpentine microchannels

Microfluidic devices have gained popularity in recent years due to their low cost and simplicity. Cell focusing linked with cell counting and cell separation used in clinical tests and point-of-care devices stands towards the top of every list of microfluidic applications. To focus and manipulate particles in a Newtonian medium, inertial microfluidics has been widely used. There is a requirement to replace a significantly more efficient approach given various particle-focusing positions near the channel walls recorded by inertial microfluidics. Here, the synergetic effect of elastic and inertial forces in relatively low-concentration viscoelastic fluids was investigated numerically. Utilizing particle-focusing behavior in straight and serpentine channels with different corner angles, by applying the numerical results obtained using the developed direct numerical simulation method (DNS) for elastic and inertial forces, we created a microchannel with a remarkable performance. As the flow regime transitions to elasto-inertial, where inertial forces are comparable to elastic forces in a straight microchannel, particles tend to concentrate at the channel centerline. As the flow rate increases, however, particle defocusing develops, and shear gradient lift forces ultimately overcome elastic forces in the channel's central region. Given that fluid flows at a higher velocity in the serpentine channel with a corner angle of 75° than in other channels, the Dean drag force induced by secondary flow serves to reduce particle defocusing rate at a given flow rate, making this channel a desirable platform for Elasto-inertial microfluidics. Particle focusing in a vertical direction was noticed as a benefit of elasto-inertial microfluidics, regardless of the geometry or flow rate of the particles passing through the channel. Finally, the impact of particle diameter on focusing behavior was studied. As particle diameter decreases, focusing width decreases and the focusing band shifts to the left side of the cross-section. We expect that the numerical evaluation of using viscoelastic medium in complex geometries can contribute to accelerate the three dimensional particle-focusing mechanism and enhance the efficiency of microdevices for cell and particle manipulation.

A Rock Breaking Force Prediction Model and Method of Wear Evaluation of Shield Disc Cutter in Hard Rock Stratum

A Rock Breaking Force Prediction Model and Method of Wear Evaluation of Shield Disc Cutter in Hard Rock Stratum