Grid Method Research Articles

Active fault-tolerant control with prescribed performance and reachability judgement for the altitude ground test facility

This research proposes an active fault-tolerant control (AFTC) method based on reachability judgement with asymmetric appointed-time prescribed performance to ensure the safety of altitude ground test facility (AGTF) under potential valve actuator and sensor faults. Firstly, a long short-term memory (LSTM) neural network is employed for fault diagnosis. Given the unique characteristics of AGTF, the equivalent multiplicative fault is introduced to ensure the successful fitting of the fault diagnosis network. Then, a reachability judgement network based on the distance field on grids (DFOG) method is designed to assess the impact of faults on subsequent tasks of the system, thereby ensuring the safety of the AGTF. Subsequently, this study proposes an error transformation function of prescribed performance control (PPC) that ensures error convergence even in cases of asymmetric performance function. This enables the performance boundaries to be further reduced to improve the control performance of the system. Finally, experiments validate the effectiveness of the methods proposed in this manuscript.

Preliminary comparison of soundscape preferences in community public spaces between the individuals with visual impairment and with normal vision

Hearing is an important way for the visually impaired to perceive the environment, and the visually impaired have a different preference for urban soundscape than those with normal vision. Therefore, understanding the differences in the preference of the visually impaired and the normal vision to the urban soundscape will help to create a sound environment that is suitable for both of them, so as to enhance the inclusiveness of the urban environment. This study took the community public spaces as the typical urban environment research object, and used the Evaluation Grid Method (EGM) to conduct semi-structured in-depth interviews on soundscape preferences of 20 visually impaired individuals and 25 individuals with normal vision. By sorting out the interview results, 18 soundscape attributes preferred by the visually impaired and 12 soundscape attributes preferred by the normal vision individuals were extracted. Through comparison, it was found that visually impaired individuals have richer descriptions and preferences of soundscape compared to those with normal vision, and the particularity of their preference is mainly reflected in its semantics and its promotion of spatial cognition of the visually impaired.

Comparison of community response to road traffic noise by housing category

In 2023, a socio-acoustic survey on community response to road traffic noise was conducted in residential areas along several arterial roads in Kanagawa Prefecture as part of the Kanagawa University Cross-disciplinary Research Promotion Project. The survey targeted residents living in detached houses and apartment buildings. A questionnaire used for the survey was designed based on new findings from a survey conducted in 2021 using the Image Grid Method. Factors we focused were economic burden due to increased use of air conditioner, harmful impact of noise on family members, and importance of measures reducing noise. Regarding the noise exposure, we estimated Lden using noise maps, which were created for the survey. This paper presented the frequency distribution of the importance of measures reducing noise. In addition, applying multiple logistic regression analysis to individual data, we developed the exposure-response function for economic burden and harmful impact as well as listening disturbance and annoyance. Based on the results obtained, we discussed the importance of measures reducing noise and difference in exposure-response function between housing categories.

Simulation of creep of a rectangular wooden beam under prolonged static load

Objective. Depending on the stress level, the operation of wooden beams under prolonged load is characterized by both linear and nonlinear creep. This has been shown by numerous experimental studies of wood. The theoretical description of these processes is poorly studied or presented extremely rarely. One of the priority areas in the calculations of wooden structure elements is the derivation of resolving equations of linear or nonlinear creep for various types of stress-strain state. Method. The Maxwell-Thomson equations are used as relations establishing the relationship between stresses and deformations. The technique was tested by comparing the solution with the calculation of well-known researchers. An example of calculation is given for various boundary conditions for fixing a beam of rectangular crosssection loaded with a uniformly distributed load. The deflection value is determined by the grid method. Result. A program has been developed for calculating in the MATLAB package with the possibility of varying the initial data and displaying a graph of the dependence of displacement, bending moment on time. The comparison of the maximum deflection value with the analytical solution is given. It is noted that the stresses practically do not change during creep. Conclusion. The proposed approach can be applied to the analysis of the stress-strain state and bearing capacity of wooden beams of arbitrary cross-section. There are no restrictions on boundary conditions and loading type, and the beam material can be not only wood, but also fiberglass.

Global path planning of unmanned ship island region based on improved A* algorithm

Abstract To solve the path planning problem for unmanned boats in island and reef areas, this paper introduces an adaptive heuristic function specifically for island and reef areas based on the traditional A* algorithm, in order to effectively handle the obstacle avoidance problem. A new cost function is designed to balance the relationship between path length and safety. The sea chart is converted into a path planning map by using the grid method, and the path planning is carried out. The paper compares the performance of the new path-planning algorithm with other path-planning algorithms through experiments, and the improved A* algorithm for global path planning of unmanned boats in island and reef areas shows excellent performance in various complex environments, effectively improving the island and reef area navigation efficiency.

Accuracy and Computational Cost Comparison of Numerical Flight Dynamics Reduced-Order Models

This paper compares several approaches to model the unsteady and nonlinear longitudinal aerodynamics of a generic unmanned combat air vehicle configuration based on computational fluid dynamics (CFD). Three different reduced-order models (ROMs) are implemented through unsteady simulations to predict the evolution of forces and moments during prescribed trajectories carried out at M=0.15. The first model investigates a linear quasi-steady model based on a first-order Taylor series expansion of the aerodynamic coefficients. The second one picks up the mathematical formulation of the first model but adds a dynamic coefficient in order to take into account the unsteady effect of rotation rate variations. Finally, the third model is built on indicial functions computed from positive step changes in the angle of attack or pitch rate. The unknown parameters of the first two models and the unknown indicial functions of the third one are obtained, respectively, from the study of forced oscillations and step motions. These prescribed trajectories are performed using unsteady Reynolds-averaged Navier–Stokes simulations coupled with a grid displacement tool. Two different methods are tested and compared to carry out the CFD mesh motions: an overset method and a full moving grid (FMG) method. The indicial functions obtained using the FMG method give results equivalent to those found in the literature in half the time of the overset method. To reduce the computational costs to set up the ROMs, the FMG method is preferred to the overset method. ROMs are then applied, and their predictions are compared with CFD simulations for prescribed trajectories with different angular rates and angles of attack. A study of instantaneous and overall accuracy associated with the implementation cost of the ROMs has allowed to show their strengths and their weaknesses. Similar results are observed at low angles of attack for the ROMs studied, while a major modeling advantage of the indicial method has been identified for higher angles of attack in the nonlinear domain.

Dynamics of non-Newtonian fluid–fiber interactions and void formation mechanism based on fused filament fabrication

Due to the presence of internal defects such as voids in the composites manufactured by material extrusion additive manufacturing (MEX AM), the mechanical properties of the composites are significantly below the theoretical optimum. Under this circumstance, this paper is intended to investigate the effects of nozzle feeding angles and to analyze the void formation and evolution of multiphase flow, in which systematic computational fluid dynamics numerical simulations are conducted. The volume of fluid model and overset grid method are used to simulate the extrusion deposition process of carbon fiber-reinforced polymer composites, and the Carreau model is used to represent the shear-thinning behavior of molten polymer. The numerical method is validated against previously experimental and numerical simulation data. The numerical results show that the key factor leading to void formation is the vortices caused by fiber oscillation. The intense vortex at the front end of the fibers disrupts the interface between molten polymer and air, creating a beneficial condition for air to enter. Nozzle tilting can effectively reduce the probability of void formation by decreasing the fiber oscillation velocity. The results of the present study provide insights into the development and optimization of printer nozzles to enable the printing of longer fibers with less probability of potential void formation.

Entropy optimization of MHD second-grade nanofluid thermal transmission along stretched sheet with variable density and thermal-concentration slip effects

The goal of present investigation is to explore the influence of exponential variable density and entropy optimization on second-grade nanofluid heating efficiency and mass-concentration transmission along extended surface using external magnetic-field and temperature-concentration slip effects. To enhance the motion of nanoparticles and thermal efficiency, the influence of exponential form of temperature-based density on magnetically charged second-grade nanomaterial is main novelty of this research. For higher temperature difference, the entropy optimization is used. The defined formulation of stream functions and similarities are used to convert leading second-grade nanofluid model into ordinary differential form. The efficient Keller box method and Newton Raphson technique are applied to compute numerical results. The final algebraic equations are solved through global matrix for unknown physical quantities. The consequence of all physical constraints on velocity/U profile, temperature/θ field, concentration/ϕ shapes, skin friction coefficient, Nusselt and Sherwood number are analyzed pictorially and numerically. The following range of parameters 0.1 ≤ ≤ 2.0, 0.0 ≤ ≤ 1.2, 0.1 ≤ ≤ 2.0, 0.07 ≤ ≤ 7.0, 0.01 ≤ ≤ 0.8, 0.01 ≤ ≤ 0.9 is used. It is found that velocity field increases with maximum amplitude as variable density, magnetic force and temperature-slip constraint. It is noted that the slip behavior in temperature field and concentration field are increased with convective boundary conditions. It is depicted that local Nusselt quantity and local Sherwood quantity increases as buoyancy force and Prandtl coefficient increases.

Analysis of activation energy, chemical reaction, and variable density on magnetically driven heat transportation: Applications in nanofluid lubrication and machining

The importance of this investigation is to examine the heat and mass transportation of magneto nanofluid movement along a heated sheet with exponential temperature-dependent density, entropy optimization, thermal buoyancy, activation energy, and chemical reaction aspects. The influence of these factors in cutting tools by means of machining and nanofluid lubrication is a significant process in cutting zone, chip cleaning, lubricating, and cooling productivity in milling. The corresponding energy activation and chemical process are essential to understand the thermal behavior of nanofluid. The appropriate transformations are used to solve nonlinear partial differential equations within the framework of ordinary differential equations using stream functions and similarity variables. The Keller box method is employed to efficiently solve these equations computationally under the Newton–Raphson approach. Through tables and figures, the fluid velocity, temperature distribution, and concentration consequences are sketched using various controlling parameters. It is seen that the fluid temperature function increases with noticeable amplitude as the Eckert factor, variable density, chemical-reaction, and activation energy increase. It is found that the noticeable enhancement in heat and mass transportation is deduced for maximum Brownian motion and thermophoresis. This work is important in various applications such as cutting fluids, drilling, brake oil, engine oil, minimum quantity lubrication, enhanced oil recovery, and controlled friction between the tool-chip and tool-work during machining operations.

Modification of the dimensional doma method for linear elliptic equations

Currently, one of the most common methods for the numerical solution of boundary value problems are difference methods (grid method, finite difference method). These methods are well suited for solving problems in regular domains. In areas of complex structure, their use leads to a number of difficulties both in the construction of difference schemes, and in the implementation on a computer. One of the methods to overcome these difficulties is the method of fictitious regions. There are four interrelated directions in the development of the method of fictitious regions: study of various ways to continue the original problems in a fictitious area; obtaining unimprovable estimates in stronger metrics; extension of the class of problems on the application of the method of fictitious areas; construction of effective difference schemes for solving auxiliary problems constructed by the method of fictitious areas. For the first time, the fictitious domain method for the Navier-Stokes equation was studied in the work of A.N. Bugrova, Sh. Smagulov, Smagulov Sh. This article discusses the method of additional areas, which is an analogue of the method of fictitious areas for solving linear boundary value problems, but in the auxiliary problem of this method there is no small perimeter. This method is based on the variational principle of solving linear boundary value problems of elliptic type in an arbitrary region. The existence of a solution is proved by the Galerkin uniqueness method.

Effect of anisotropy and length dispersity on electrical and optical properties ofnanowire network based transparent electrodes: a computational study.

We have studied the impact of nanowire alignment and measurement direction at the percolation
threshold on the effective resistance (R) of two-dimensional (2D) films. This helps us to analyze the
effect of anisotropy on the conductivity and transmittance of the nanowire-based network characterized by the disorder parameter (s). These optoelectronic properties are determined for systems
with monodisperse as well as bimodal distribution of length. The 2D systems that are simulated using our computational approach are assumed to be transparent and conductive in which percolative transport is the primary conduction mechanism.
We obtain our results numerically using a computational and geometrical approach, i.e., a Discrete
(grid) method, advantageous in algorithm speed. For a particular disorder parameter s,
the conductivity and transmittance increase as the length fraction increases for the bimodal
distribution of the length of nanowires in networks. We have observed the maximum conductivity
when the nanowires are highly aligned along the measurement direction of percolation, in contrast
to the isotropic arrangement of nanowires. Significantly, alignment introduced in nanowires leads
to a higher percolation threshold which leads to a decrease in the transmittance of the network. We
show that the resistivity of the monodisperse network in the direction parallel (perpendicular) to the
alignment decreases (increases) with the disorder parameter and scales as s (s2). This scaling holds
true for the bimodal distribution of nanowires as well. For a particular length fraction, the electrical
anisotropy increases with s. The anisotropy is maximum for nearly aligned nanowires in a bimodal
network with the highest proportion of the longest wire considered. For the maximally aligned wires
and highest length fraction, we obtained an approximately 50% enhancement in the figure of merit,
denoted by ϕ. Hence, incorporating longer length wires and increasing the alignment in nanowire
networks increases the conductivity, anisotropy, and figure of merit.

Development of Hill Cipher Method For Encryption And Decryption of Drug Prescriptions to Improve Data Security

A prescription is a written request from a doctor to a pharmacist, as not everyone can know the dosage or type of a particular drug, especially patients who need a prescription for the drug must be kept secret. Rapid technological advances can have an impact on all sectors, both private and government, including the medical field. One of the medical services that utilizes IT is to send prescription messages electronically to pharmacists in response to doctors' requests. The many misuse of prescription drugs by irresponsible people and misreading prescription drugs by pharmacists can be fatal for patients, so a solution is needed to overcome these problems. The purpose of this study is to create an encrypted electronic recipe application using the Hill Cipher method. This research method generally starts from data collection, data analysis and encryption model development. Applications designed with the Hill Cipher Algorithm are developed with modified algorithm keys using postal code patterns as the matrix keys, this aims to achieve the maximum level of security. The results of the system functionality test using the black box method obtained normal results for all system test scenarios. Validity testing yields valid results. The final test, through questionnaire testing, obtained a good level of system feasibility, namely an average level of Service of 83%, Features of 78% and Performance of 81%. Overall, the system has given a good performance score as the accuracy of the system is above 70%.

Fast Two-dimensional Positioning Method of Crab Pulsar Based on Multiple Optimization Algorithms

In the two-dimensional positioning method of pulsars, the grid method is used to provide non-sensitive direction and positional estimates. However, the grid method has a high computational load and low accuracy due to the interval of the grid. To improve estimation accuracy and reduce the computational load, we propose a fast two-dimensional positioning method for the crab pulsar based on multiple optimization algorithms (FTPCO). The FTPCO uses the Levenberg–Marquardt (LM) algorithm, three-point orientation (TPO) method, particle swarm optimization (PSO) and Newton–Raphson-based optimizer (NRBO) to substitute the grid method. First, to avoid the influence of the non-sensitive direction on positioning, we take an orbital error and the distortion of the pulsar profile as optimization objectives and combine the grid method with the LM algorithm or PSO to search for the non-sensitive direction. Then, on the sensitive plane perpendicular to the non-sensitive direction, the TPO method is proposed to fast search the sensitive direction and sub-sensitive direction. Finally, the NRBO is employed on the sensitive and sub-sensitive directions to achieve two-dimensional positioning of the Crab pulsar. The simulation results show that the computational load of the FTPCO is reduced by 89.4% and the positioning accuracy of the FTPCO is improved by approximately 38% compared with the grid method. The FTPCO has the advantage of high real-time accuracy and does not fall into the local optimum.

Implementation of Teacher Attendance Monitoring Application at SMK Ibnu Sina Batam

This study aims to analyze and design a web-based teacher attendance monitoring application at SMK Ibnu Sina Batam. We expect this application to enhance the efficiency and effectiveness of teacher attendance management through the use of digital technology. The research methods used include literature studies, interviews, and direct observation of the teacher attendance management process. We design the system using the Unified Modeling Language (UML), implement it using the CodeIgniter framework, and use MySQL as its database. We conduct testing using the Black Box method to verify that all functions operate as anticipated. The results show that this application can monitor teacher attendance in real-time and improve discipline. By cutting down on manual checks and enhancing transparency and accountability in school management, the implementation of this application significantly enhances the quality of education at SMK Ibnu Sina Batam.

On the viscoelastic-electromagnetic-gravitational analogy

The analogy between electromagnetism and gravitation was achieved by linearizing the tensorial gravitational equations of general relativity and converting them into a vector form corresponding to Maxwell’s electromagnetic equations. On this basis, we use the equivalence with viscoelasticity and propose a theory of gravitational waves. We add a damping term to the differential equations, which is equivalent to Ohm’s law in electromagnetism and Maxwell’s viscosity in viscoelasticity, to describe the attenuation of the waves. The differential equations in viscoelasticity are those of cross-plane shear waves, commonly referred to as SH waves. A plane-wave analysis gives the phase velocity, the energy velocity, the quality factor and the attenuation factor of the field as well as the energy balance. To obtain these properties, we use the analogy with viscoelasticity; the properties of electromagnetic and gravitational waves are similar to those of shear waves. The presence of attenuation means that the transient field is generally a composition of inhomogeneous (non-uniform) plane waves, where the propagation and attenuation vectors do not point in the same direction and the phase velocity vector and the energy flux (energy velocity) are not collinear. The polarization of cross-plane field is linear and perpendicular to the propagation-attenuation plane, while the polarization of the field within the plane is elliptical. Transient wave fields in the space–time domain are analyzed with the Green function (in homogeneous media) and with a grid method (in heterogeneous media) based on the Fourier pseudospectral method for calculating the spatial derivatives and a Runge–Kutta scheme of order 4 for the time stepping. In the examples, wave propagation at the Sun–Earth and Earth–Moon distances using quadrupole sources is considered in comparison to viscoelastic waves. The Green and grid solutions are compared to test the latter algorithm. Finally, an example of propagation in heterogeneous media is presented.

A Circle Center Location Algorithm Based on Sample Density and Adaptive Thresholding

How to acquire the exact center of a circular sample is an essential task in object recognition. Present algorithms suffer from the high time consumption and low precision. To tackle these issues, we propose a novel circle center location algorithm based on sample density and adaptive thresholding. After obtaining circular contours through image pre-processing, these contours were segmented using a grid method to obtain the required coordinates. Based on the principle of three points forming a circle, a data set containing a large number of samples with circle center coordinates was constructed. It was highly probable that these circle center samples would fall within the near neighborhood of the actual circle center coordinates. Subsequently, an adaptive bandwidth fast Gaussian kernel was introduced to address the issue of sample point weighting. The mean shift clustering algorithm was employed to compute the optimal solution for the density of candidate circle center sample data. The final optimal center location was obtained by an iteration algorithm. Experimental results demonstrate that in the presence of interference, the average positioning error of this circle center localization algorithm is 0.051 pixels. Its localization accuracy is 64.1% higher than the Hough transform and 86.4% higher than the circle fitting algorithm.

The nanoparticles aggregation aspects on the chemically reactive unsteady flow of alumina-water based nanofluid: A Keller box approach with applications of wavelet physics inspired neural networks

The present study explores the unsteady flow of a nanoliquid past a stretching cylinder with the consequence of heat source/sink and chemical reaction. Additionally, the effect of nanoparticle aggregation, convective boundary conditions, and magnetic field on the liquid flow is taken into consideration. Utilizing similarity variables, the modeled equations are transformed into dimensionless ordinary differential equations (ODEs). Further, the obtained ODEs are numerically solved by using the Keller box method. Moreover, the physics-informed neural network (PINN) is applied to analyze the flow, heat, and mass transport features. Graphical illustrations are used to display the influence of various parameters on the velocity, concentration, and temperature profiles for aggregation and without aggregation cases. As the value of the magnetic parameter increases, the temperature and concentration profile upsurge, but the reverse trend can be seen in the velocity profile. The concentration and temperature profiles rise as the unsteadiness parameter increases, but the velocity profile declines. The concentration, velocity, and temperature profiles are strengthened by an improvement in the curvature parameter value. The intensification in the values of the chemical reaction parameter declines the concentration.

Enhancing stability and position control of a constrained magnetic levitation system through optimal fractional-order PID controller

Magnetic levitation systems are complex and nonlinear, requiring sophisticated control methods to maintain the stability and position of the levitated object. This research presents an optimized fractional order PID (FOPID) control approach for position control of a freely-suspended ferromagnetic object. The dynamic system model is mathematically modeled in MATLAB using first-principle modeling and the grey box method. The FOPID controller has five degrees of freedom (DOFs) that allow for fine-tuning of the control gains and fractional orders, enabling the system to handle the nonlinearity inherent in the magnetic levitation system. The DOFs of FOPID and integer order PID controllers are optimized using the Artificial Bee Colony (ABC) algorithm and results are compared with state-of-the-art optimization methods. The results showed that the FOPID controller can effectively control the magnetic levitation system with constraints and outperforms other methods by up to 92.14% in terms of settling time with negligible steady-state error.

Content, Sources, and Ecological Risk Assessment of Heavy Metals in Soil of Typical Karst County

Soil heavy metals in karst areas have obvious high background value characteristics. Conducting county-level soil heavy metal ecological risk assessment and identifying heavy metal sources in karst areas are of great significance for soil pollution control and land resource management. Taking Pingguo City, a typical karst county in Guangxi Province, as the study object, 3 151 surface and deep soil samples were collected using the grid method and combined to form 785 analytical samples. The contents of eight heavy metal elements, including As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, were determined. The content characteristics and sources of heavy metals were analyzed using statistical analysis, interpolation analysis, factor analysis, and the absolute principal component-multiple linear regression model （APCS-MLR）. Using the content of heavy metal elements in deep soil （150-200 cm） as background values, the ecological risk assessment of heavy metals in surface soil （0-20 cm） in the study area was conducted using the geo-accumulation index （Igeo） and potential ecological risk index （RI） methods. The results showed that the average content of heavy metal elements in the deep soil of the study area was significantly higher than the background value of the C layer soil in Guangxi Province, and the average content of heavy metal elements in the surface soil was significantly higher than the background value of the A layer soil in Guangxi Province. The spatial distribution of soil heavy metal element content generally showed the characteristics of high in karst areas and low in non-karst areas. The main sources of As, Cr, Ni, Pb, and Zn were soil parent materials, with contribution rates of 74.36%, 84.59%, 93.69%, 79.67%, and 78.17%, respectively. The main sources of Cd were soil parent material sources and unknown sources, with contribution rates of 37.33% and 31.05%, respectively. The main sources of Cu were soil parent materials and unknown sources, with contribution rates of 59.07% and 40.23%, respectively. The main sources of Hg were tectonic activity and mineralization, as well as unknown sources, with contribution rates of 52.49% and 30.65%, respectively. The geo-accumulation index （Igeo） showed that the surface soil was mainly polluted by Cd, with mild or above pollution accounting for 47.78%. The potential ecological risk index （RI） showed that the proportion of surface soil heavy metal comprehensive potential ecological hazards with mild, moderate, strong, and very strong levels was 80.78%, 14.97%, 2.51%, and 1.64%, respectively.

Numerical method research and characteristics analysis on frozen start-up process of high-temperature heat pipe

Future space exploration technology requires a long-life and reliable power source that is not reliant on solar energy. Space micro-reactors are able to meet this need, with Heat Pipe Cooled Reactors (HPR) emerging as a notable type of space micro-reactor that has attracted widespread attention in recent years. The HPR utilizes high-temperature alkali metal heat pipes for heat transfer, which presents certain complexities due to the solid state of the alkali metals working medium at room temperature. This results in a three-phase transition during the high-temperature heat pipes start-up process, which significantly impacts the heat transfer characteristics and dynamic behavior of the HPR start-up process. Consequently, thorough research is necessary in this area. Numerical simulation is a crucial tool that can effectively analyze, predict, and guide experiments. This article utilizes the Finite Volume Method (FVM) to develop a simulation code for high-temperature heat pipe frozen start-up. Various physical models are integrated to describe different components of the heat pipe: the container is represented by a two-dimensional axisymmetric heat conduction equation, the wick region utilizes a Fixed Grid Method (FGM) to depict the melting process of the medium, and the vapor channel is described through a two-dimensional axisymmetric compressible laminar flow. The wick region and vapor channel are coupled through the evaporation and condensation of the medium. For the vapor channel, numerical methods such as SIMPLE and PISO are used for solving. Adaptive time step and OpenMP acceleration are employed in the code to enhance computational efficiency. Finally, by comparing the calculated results with experimental data, the feasibility and accuracy of the code are assessed, highlighting special phenomena during the start-up process. The findings confirm that the developed code accurately predicts parameter changes during start-up, and can serve as a heat pipe analysis module for multi-physics coupling analysis of HPR.