Compact Method Research Articles

Automation in Agriculture: A Robotic Approach to Weed Control for Greenhouse Cucumber Cultivation

The increasing global population has heightened the demand for efficient food production, leading to the adoption of compact cultivation methods such as greenhouses. However, weed growth within these controlled environments significantly challenges crop productivity. The application of robots can be a useful and economic choice. This study presents an innovative, purely mechanical system for weed control in greenhouses, specifically designed to operate autonomously on a monorail. The machine stops in the distance between the two main plant rows (cucumber) and its arm goes into the gap to deploy the weeds by rotating its blades. This is continued repeatedly. The cutting is by the rotational speed of the blade. Variable-speed motions of the blade were at 3500, 2500 and 1500 rpm for 3 types of moulinex, triangular, and circular blades. The movement speed of the arm was 10 and 30 rpm and the forward movement speed of the machine was 30, 40, 50, 60, 80 and 120 rpm. The results showed that different blades, blade speeds and engine speed affect significantly (p <0.05) the percentage of weeds being cut. Although the interactions of these factors have no significant effect on percentage; the average percentages by the blades have significant differences. Although the interactions between these factors were not statistically significant, the comparison of means revealed that at lower blade speeds, the blade type had a pronounced effect on weed-cutting efficiency. As blade speed increased, differences in blade performance diminished. The most effective combination was achieved using Moulinex blades at 3500 rpm with a 10-rpm arm speed, resulting in the highest percentage of weeds cut. These findings suggest that optimizing blade type and speed can significantly enhance the mechanical weed control efficiency in greenhouse environments.

Experimental study on the critical current in highly flexible REBCO cables under copper tube compaction

The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) is developing the high-current REBCO cable-in-conduit conductor (CICC) for use in the Central Solenoid (CS) coil of the next generation nuclear fusion device. The aim is to develop a CICC comprising six REBCO sub-cables to satisfy the requirements of operation with a current of around 46 kA and a peak field of up to 20 T. Sub-cables, as crucial components within CICCs, play a pivotal role in ensuring the mechanical support strength and current-carrying stability of the entire CS coil system. Therefore, a process was developed in this paper for the first time to make a sub-cable that meets the requirements by inserting the Highly Flexible REBCO Cable (HFRC) cable into a copper tube and compacting it. Meanwhile, the feasibility and reliability of this process were evaluated and optimized using experimental methods at 77 K and self-field. The result indicated that sub-cables without copper tape protection experienced a 25.42% degradation in critical current (IC). In contrast, when at least one protective layer of copper tape was used as a protective buffer between the HFRC cable and the inner wall of the copper tube, the IC remained stable within a 1% error margin after compaction. These findings demonstrate the feasibility of this sub-cable preparation process. Meanwhile, this compaction method provides a solid process foundation for the development of full-size conductors in future magnet applications.

Formulations and numerical techniques for computation of acoustic pressure and its gradient by integral method

Starting from the Ffowcs Williams-Hawkings surface integral formulation for a moving medium, the article proposes rather simple expressions for the radiated pressure and its gradient in the time domain, that are valid for solid or porous, fixed or moving integration surfaces. Moreover, these original expressions allow calculations with integration surfaces in supersonic motion (such as rotating surfaces around propellers or rotors). Versions dedicated to fixed integration surfaces are also proposed. The usual locally compact and the fully non-compact integration techniques are recalled, with, for both, a detailed description of efficient calculation algorithms. Particular attention is devoted to the order of precision of the calculations. The time derivation techniques and integration schemes used in this study lead to a theoretical second order that can easily be increased for the locally compact integration method. The results of these expressions and integration methods are compared to the analytical solution for the case of a fixed monopole and for that of a rotating monopole. They clearly show the benefit of the direct gradient calculation over a calculation by finite differences of the pressure around the observation point, particularly for broadband signals.

A numerical algorithm based on extended cubic B-spline functions for solving time-fractional convection-diffusion-reaction equation with variable coefficients

In this research, we develop an innovative and efficient numerical method for solving a nonlinear one-dimensional time-fractional convection-diffusion-reaction equation (TFCDRE) with a variable coefficient. This method integrates the Crank-Nicolson finite difference scheme with extended cubic B-spline (ExCBS) basis functions. The Caputo fractional derivative is applied for temporal discretization, while the ExCBS functions are utilized for spatial discretization. The stability of the method was discussed by the von Neumann method, which shows unconditional stability; and the convergence analysis secure an order of $O(h^2+\triangle t^{2-\alpha})$. We demonstrated the efficiency and simplicity of our method through three numerical experiments and verified its accuracy using the absolute error $(L_2)$ and maximum error $(L_\infty)$ norms in temporal and spatial dimensions. The results are also graphically represented and show substantial agreement with the approximated and exact solution. We confirmed the effectiveness and accuracy of our approach over the local discontinuous Galerkin finite element and the compact finite difference methods, respectively, from the literature.

A compact finite-difference and Haar wavelets collocation technique for Parabolic Volterra Integro-Differential Equations

Abstract In this paper, a numerical investigation of a class of parabolic Volterra integrodifferential equations (parabolic-VIDEs) is conducted. The approach focuses on
semi-discretizing parabolic-VIDEs by utilizing a second-order compact finite difference method O(δt2
) for the time variable and approximating the integral term
using the trapezoidal rule. Further, the spatial derivative is approximated by Haar
wavelet method. This hybrid methodology leverages the strengths of both techniques to solve the equations more efficiently and accurately. The error analysis,
using L2 and L∞-norms, shows low computational costs. Numerical experiments
show that second-order accuracy in both time and space, respectively. Stability and
convergence of the proposed method are given through Sobolve space. Some numerical examples are tested for the effectiveness and accuracy of the proposed method.
Furthermore, the presented numerical approach is compared with standard finite
difference numerical methods and the results are reported in a table.

Effect of Alumina as Reinforcement on the Mechanical and Physical Properties of Recycled AA6061 Aluminium

The utilisation of reinforcement materials in aluminium metal matrix composites is widely used in the manufacturing sector due to their lightweight nature, excellent strength-to-weight ratio, enhanced fracture toughness, and improved mechanical properties. The purpose of this study is to investigate the effect of reinforcing alumina in recycled AA6061 aluminium on the properties of the resulting aluminium matrix composite. Various compositions of recycled AA6061 aluminium reinforced with alumina were prepared and analysed using the cold compaction method. The results show that the addition of alumina composition increases the hardness properties of the composite by up to 5 wt.% at 32.91 Hv compared to the unreinforced sample at 30.63 Hv, but the hardness decreases as the alumina mass composition increases. According to the analysis of physical properties, in comparison to the unreinforced sample, the density decreases with increasing mass composition of alumina up to 10 wt.%, which is from 2.4636 g/cm3 to 2.3014 g/cm3, respectively. In relation to the microstructure of the samples, the addition of alumina results in irregular shapes with larger pores. An increasing in the mass composition of alumina results in increased porosity and water absorption.

An efficient fourth-order convergent scheme based on half-step spline function for two-point mixed boundary value problems

The present work aims to introduce a novel numerical method for solving second-order two-point mixed boundary value problems. Mixed boundary value problems occur in various scientific fields, including quantum mechanics, fluid dynamics, and chemical reactor theory. The proposed method provides a highly accurate, fourth-order convergent numerical solution, achieved by implementing a compact finite difference method based on non-polynomial spline in tension approximations. Notably, the discretisation involves the use of half-step grid points, eliminating the need to modify the method at singularities while dealing with singular boundary value problems. The article also includes a comprehensive convergence analysis that demonstrates the theoretical order of convergence of the method. Additionally, the results obtained from solving six diverse mixed boundary value problems, including Burger's equation and Bratu-type equation, are compared to showcase the superiority and effectiveness of the proposed method.

Generalized result on the global existence of positive solutions for a parabolic reaction-diffusion model with an m × m diffusion matrix

Abstract The aim of this work is to study the global existence in time of solutions for the tridiagonal system of reaction-diffusion by order m m . Our techniques of proof are based on compact semigroup methods and some L 1 {L}^{1} -estimates. We show that global solutions exist. Our investigation can be applied for a wide class of nonlinear terms of reaction.

Novel conformal structure-preserving schemes for the linearly damped nonlinear Schrödinger equation

In this work, by utilizing the Strang splitting technique, some advanced conformal structure-preserving schemes are developed for solving the damped nonlinear Schrödinger equation (DNLSE). The proposed innovative numerical approaches, namely the high-order compact conformal multi-symplectic method and the conformal momentum-preserving method, have two key computational advantages. Firstly, these two approaches excel in conserving local structures, and more importantly, they are capable of maintaining exact energy dissipation rates in any time-space region, particularly under periodic boundary conditions. To validate the theoretical properties and demonstrate the efficacy and stability of these approaches in long-time integrations, we conduct through extensive numerical simulations involving both bright and dark solitons.

Shear-Wave-Velocity Profiling of a Test Embankment for a High-Speed Rail Project using the Spectral-Analysis-of-Surface-Waves (SASW) Method

Nondestructive seismic testing was conducted at 24 locations on and around the embankment to evaluate the compaction effort and lateral variabilities at the site. This embankment was being constructed as a test embankment for a high-speed railroad section in the U.S.A. Different compaction techniques were used in different embankment areas, and nuclear-gauge density measurements were performed to evaluate the compaction quality in all areas. Additionally, Spectral-Analysis-of-Surface-Waves (SASW) testing was performed to determine the Vs profiles at numerous locations on and around the embankment. The Vs values determined from the SASW testing were used to compare and evaluate areas where different compaction methods were used, as well as to help understand the overall site. The embankment was divided into three zones. In each zone, five shorter and one longer SASW arrays on top of the embankment were used to determine the Vs profiles. Also, in each zone, Vs profiles in the natural soil were determined using two additional long SASW arrays on the natural ground, one array on each longitudinal side of the embankment. These 24 Vs profiles on and around the embankment were used to evaluate lateral variability in the shear stiffnesses of the geotechnical materials at the site.

Fabrication and Properties of Adsorptive Ceramic Membrane Made from Kaolin with Addition of Dolomite for Removal of Metal Ions in a Multielement Aqueous System.

The exorbitant presence of heavy metals has emerged as one of the most serious ecological issues facing the world. The treatment processes currently employed are not effective for removing all of the contaminants completely. Therefore, it is necessary for better operational technology to be developed. Here, we fabricated effective and inexpensive kaolin-based ceramic membranes with the addition of dolomite using a simple dry compaction method. Moreover, we applied the obtained adsorptive membranes to the removal of lead, copper, zinc, and cadmium from aqueous solutions. The membranes prepared with dolomite addition (sintered at different temperatures) exhibited a high water flux between 246.78 and 1738.56 L/h·m2 at an extremely low operating pressure (0.03 MPa). Furthermore, the optimal membrane showed high removal efficiencies of 99.12, 99.82, 85.62, and 65.94% for Pb(II), Cu(II), Zn(II), and Cd(II), respectively. The utilization of dolomite enhanced the removal efficiency of the adsorptive membranes by around 32-54% in a multielement system. This work reveals that enhanced adsorptive membranes with high fluxes and strong removal abilities have great potential as a synergized system with practical applications in the removal of heavy-metal contaminants from wastewater in the future.

Matrix analysis of discrete functionals in compact difference method for nonlinear problems with higher derivatives and program code (I: 1D problem)

Matrix analysis of discrete functionals in compact difference method for nonlinear problems with higher derivatives and program code (I: 1D problem)

A fast H3N3‐2σ$_\sigma$‐based compact ADI difference method for time fractional wave equations

AbstractIn the present paper, we derive a fast H3N3‐2‐based compact alternating direction implicit (ADI) scheme for the time fractional wave equation in two‐dimensional spatial domains. The time fractional derivative involved in the equation is discretized by the H3N3‐2 formula combined with sum‐of‐exponential technique. The former was first proposed by Du et al., while the latter has become a widely used technique to reduce the computational cost in the processing of convolution integrals. The spatial discretization adopts the standard compact ADI method, which can ensure that the space can reach the fourth‐order accuracy without increasing the amount of computation. The numerical stability and convergence of the difference scheme are analyzed rigorously. As an auxiliary illustration, a numerical example is given to verify the validity of the theoretical findings.

Performance evaluation of high-performance concrete mixes incorporating recycled steel scale waste as fine aggregates

In this study, steel-scale waste (SSW), a byproduct generated during the manufacturing of steel, was investigated as a potential alternative to natural fine aggregates (sand) for preparing high-performance concrete (HPC). Three grades of sand and SSW with different particle sizes were mixed in varying combinations. Three different compaction techniques (loose, tamped, vibration) were employed. The optimum packing density for both SSW and natural aggregates was achieved using the vibration compaction method. Since the combination of 50 % sand and 50 % SSW exhibited the best packing density for both materials, this bi-grade aggregate mixture was selected for the mix preparation. The mechanical tests (compressive strength, flexural strength) and durability assessment (bulk water sorptivity, rate of water absorption, chloride ion penetration) were performed to achieve the desired objectives. The specimens were exposed to two different curing regimes i.e., normal curing and heat curing at elevated temperature. A significant increase in compressive and flexural strength was observed with the increased content of SSW. A compressive strength as high as 140 MPa was obtained for the HPC mix containing SSW aggregates and steel fibers. The replacement ratio of SSW was optimized to achieve better strength and durability. Experimental results showed that heat curing was more effective than conventional curing methods in improving the performance of the concrete.

Analyzing Lab and Field Compaction Methods for designing Roller Compacted Concrete Pavements (RCCP) with Different Curing Processes

Analyzing Lab and Field Compaction Methods for designing Roller Compacted Concrete Pavements (RCCP) with Different Curing Processes

Multi-wavelength generation in UV and green bands through SRS and parametric processes in silica fibers.

We report on multi-wavelength generation through simultaneous second-order and third-order nonlinear parametric processes following cascaded stimulated Raman scattering (SRS) in silica fibers. The fiber system consists of a short standard step-index silica fiber and a microfiber tapered from it. When this system is pumped with a 130 ps laser at 1040 nm, multiple new wavelengths in the UV (340-370 nm) and green (507-547 nm) bands arise through four-wave mixing (FWM)/sum-frequency generation (SFG) from the pump and its Raman signals. The evolution of these wavelengths with pump power is demonstrated in detail. Matching of frequencies and propagation constants in the involved processes is verified. This work provides a compact and simple method of multi-wavelength generation with fibers.

Efficacy of Acacia Gum Biopolymer in Strength Improvement of Silty and Clay Soils under Varying Curing Conditions

Acacia gum (AG), a polysaccharide biopolymer, has been adopted to improve the strength of three cohesive soils by subjecting them to diverse environmental aging conditions. Being a polysaccharide and a potentially sustainable construction material, the AG yielded flexible film-like threads after 48 h upon hydration, and its pH value of 4.9 varied marginally with the aging of the stabilized soils. The soil samples for the geotechnical evaluation were subjected to wet mixing and were tested under their Optimum Moisture Content (OMC), as determined by the light compaction method. The addition of AG modified the consistency indices of the soils due to the presence of hydroxyl groups in AG, which also led to a rise in OMC and reduction in Maximum Dry Unit weight (MDU). The Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR) were determined under thermal curing at 333 K as well as on the same day of sample preparation. The least performing condition of the soil’s CBR was evaluated under submerged conditions after allowing the AG-stabilized specimens to air-cure for a period of 1 week. The UCS specimens tested after 7 days were subjected to the initial 7 days of thermal curing at 333 K. A dosage of 1.5% of AG yielded the UCS of 2530 kN/m2 and CBR of 98.3%, respectively, for the low compressible clay (LCC) after subjecting the sample to 333 K temperature for 1 week. The viscosity of the AG was found to be 214.7 cP at 2% dosage. Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and average particle size determination revealed the filling of pores by AG gel solution, adsorption, and hydrogen bonding, which led to improvements in macroproperties.

A fourth-order compact finite volume method on unstructured grids for simulation of two-dimensional incompressible flow

This paper introduces a novel and efficient compact reconstruction procedure for high-order finite volume methods applied to unstructured grids. In this procedure, we establish a set of constitutive relations that ensure the continuity of the reconstruction polynomial and its normal derivatives between adjacent elements at control points. The paper delves into the details of the fourth-order compact reconstruction method specifically designed for two-dimensional triangular grids. This method can be considered an extension of the one-dimensional compact scheme and cubic spline interpolation methods to two-dimensional triangular unstructured grids. In the cubic polynomial reconstruction, a two-dimensional cubic polynomial is reconstructed using the cell averages of elements in the standard stencil and the function values at control points. The determination of function values at control points is achieved by adhering to the constraint of normal derivative continuity. This reconstruction is solved using a relaxation iteration method and has been verified to be solvable for triangular grids. Compared to other fourth-order implicit compact polynomial reconstructions, our method requires solving a smaller number of unknowns, which means less computational cost in reconstruction. By applying this method to solve the Poisson equation, the linear convection equation, and incompressible flow benchmarks, it demonstrates that the proposed method exhibits the expected high-order accuracy and performs well in incompressible flow problems.

Analytical Overview of the Methods of Controlling the Parameters of Vibratory Compaction of the Concrete Mixes

Introduction. A historical (retrospective) overview of the evolution and application of the methods of concrete mixture compaction by vibration, as well as an overview of the breakthrough scientific+ advancements in the studied field have been presented. The use of the dry concrete mixes that reduce cement consumption, accelerate the strength gain of concrete, reduce the shrinkage strain and heat emission and increase the strength and durability of products has been proposed. The theoretical and practical issues of vibratory compaction of the concrete mixes, the research on the effect reached by the various vibration modes of the vibrating tables, the issues of choosing an efficient mode of vibration impact during compacting the concrete mixes and optimisation of their parameters have been studied. The vibrating table design, the installation layout of the vibrator’s eccentric weights to obtain a given value of the exciting force and the layout of a vibration module with the directed vibrations have been studied in detail. The criteria of duration of the concrete mixture compaction have been defined, changes of the impact parameters during compacting the concrete mixes have been characterised and technical specifications of the vibrating tables have been defined. In the article considerable attention has been paid to the main parameters of the vibrocompacting machines: frequency, amplitude and acceleration of the working member. Most often, the parameter of intensity is used to assess the efficiency of the vibration impact received by the mixture during the compaction process.Materials and Methods. A mixture that turns into concrete after compaction, setting and hardening was selected for the research. The various methods and parameters of concrete mixture compaction to obtain the high-quality concrete were studied. The impact of the various vibration modes on the process of compaction of concrete mixes was investigated, the criteria for the efficient selection and optimisation of the vibration impact parameters were revealed. The paper presents the criteria for assessing duration of the concrete mixture compaction and describes the changes in the parameters during compaction of the concrete mixes. The technical specifications of the vibrating tables of different types and sizes were also presented. The choice of the vibration compaction mode for the concrete mixture is a complicated task, which includes many parameters.Results. Upon the research, the data on the process of concrete mixture compaction under the impact of vibration forces has been obtained. The process results in the destruction of the structural bonds and weakening the bonds between the particles, which leads to the emergence of a variable stress-strain condition. It has also been found that under such settings, the mineral particles get transferred and a denser packing is formed.Discussion and Conclusion. The resulting denser packing of the concrete mixture particles ensures the undoubted economic advantage due to reduced consumption of a binder without loss of the strength properties of concrete.

Mechanism Analysis of Strengthening the Coral Reef Sand Foundation by Dynamic Compaction Method Based on Discrete Element Theory

Mechanism Analysis of Strengthening the Coral Reef Sand Foundation by Dynamic Compaction Method Based on Discrete Element Theory