Rectangular Cube Research Articles

Finding the best shape of floating wave energy converters for different primary geometries: Experimental and numerical investigations

This research aimed to identify the optimal geometry for maximizing wave energy extraction from wave energy converters (WECs) by employing different primary geometries of floating bodies (specifically, cube, cylinder, and sphere). Laboratory experiments were conducted using a wave tank to generate waves with varying characteristics. The floats were subjected to waves of different wave conditions, including height (4 cm, 6 cm, and 9 cm) and frequency (0.9 Hz and 0.83 Hz). Multiple probes and sensors were used to collect experimental data. The results revealed that when hit by a wave with a height of 9 cm and a frequency of 0.9 Hz, the rectangular cube experienced an average displacement of 12 cm and 14 cm along its length, with the same weight and draft, respectively. Furthermore, comparisons of the experimental data across different scenarios indicated that the rectangular cube, elongated perpendicular to the incident waves, performed well in most of the test cases. The efficiency of primary wave energy conversion was evaluated for all floated bodies and wave conditions, encompassing a range of values from 0.02 to 0.34. Additionally, numerical simulations of wave and float displacement demonstrated good agreement with the experimental observations.

Problem-Based Learning to Enhance Mathematical Communication Skills and Learning Outcomes in Graade V

<p class="SekolahDiterima"><em>The implementation of the Problem-Based Learning model can improve the learning outcomes in mathematics regarding the volume of rectangular prisms and cubes among fifth-grade students at Elementary School. This study employs the Classroom Action Research method in an elementary school in the Yogyakarta region.. This is evidenced by the increased learning outcomes of the students in mathematics during Cycle I, which was 83.3%, and Cycle II, which was 86.3%. In Cycle I, the average score of the students in the first meeting was 73, and in the second meeting, it was 72. In Cycle II, the score in the first meeting was 80, and in the second meeting, it increased to 91. Problem-based learning significantly enhances the learning outcomes in mathematics and mathematical communication skills of the fifth-grade students a Elementary School. The implementation of the Problem-Based Learning model is carried out through five steps. The application of the Problem-Based Learning model can improve the learning outcomes and mathematical communication skills. This is evidenced by the observed improvement in the students' mathematical communication skills in each cycle. The average observation results in Cycle I were 75.84%, and in Cycle II, it increased to 86%.</em></p>

A comparison study between the realistic random modeling and simplified porous medium for gamma-gamma well-logging

The accurate determination of formation density and the physical properties of rocks is the most critical logging tasks which can be obtained using gamma-ray transport and detection tools. Though the simulation works published so far have considerably improved the knowledge of the parameters that govern the responses of the detectors in these tools, recent studies have found considerable differences between the results of using a conventional model of a homogeneous mixture of formation and fluid and an inhomogeneous fractured medium. It has increased concerns about the importance of the complexity of the model used for the medium in simulation works. In the present study, we have suggested two various models for the flow of the fluid in porous media and fractured rock to be used for logging purposes. For a typical gamma-gamma logging tool containing a 137Cs source and two NaI detectors, simulated by using the MCNPX code, a simplified porous (SP) model in which the formation is filled with elongated rectangular cubes loaded with either mineral material or oil was investigated. In this model, the oil directly reaches the top of the medium and the connection between the pores is not guaranteed. In the other model, the medium is a large 3-D matrix of 1 cm3 randomly filled cubes. The designed algorithm to fill the matrix sites is so that this realistic random (RR) model provides the continuum growth of oil flow in various disordered directions and, therefore, fulfills the concerns about modeling the rock textures consist of extremely complex pore structures. For an arbitrary set of oil concentrations and various formation materials, the response of the detectors in the logging tool has been considered as a criterion to assess the effect of modeling for the distribution of pores in the formation on simulation studies. The results show that defining a RR model for describing heterogeneities of a porous medium does not effectively improve the prediction of the responses of logging tools. Taking into account the computational cost of the particle transport in the complex geometries in the Monte Carlo method, the SP model can be satisfactory for gamma-gamma logging purposes.

A novel algorithm of the perfectly matched layer based on the Runge–Kutta method of order 2 accuracy

AbstractThe perfectly matched layer (PML) has the ability to terminate the finite‐difference time‐domain (FDTD) lattice successfully. It is crucial to investigate the interaction between electromagnetic waves and the PML. Utilizing the Runge–Kutta method of order 2 accuracy, we derive a novel and efficient complex frequency‐shifted (CFS) PML implementation algorithm, which is named the RK‐PML. To validate the RK‐PML, we provide two numerical examples, which include rectangular waveguide and plasma cube truncated by the PML. By analyzing the time‐domain relative reflection errors, the frequency‐domain reflection coefficients, the computational time, and the memory footprint, the proposed RK‐PML outperforms slightly the convolutional PML (CPML).

On the importance of specimen’s geometric shape effects on the slake-durability index of limestones and grain size distribution of the sediment particles obtained during the test

The slake-durability test is one of vital test method used in engineering geological studies for evaluating resistant of rocks against wetting–drying cycles in humid environments. The result of the test is related to many parameters specially specimen’s geometric shape. In the present research, eight limestone samples used as common building stones in Iran have been selected and their mineralogical and physical properties have been measured in the laboratory. In order to determine the effect of specimen’s shape on the slake-durability index of the stones, laboratory specimens were prepared in seven various shapes including lump, rounded lump, cube, sphere, square prism, square-base plate, and rectangular cube which have different shape parameters. After performing the slake-durability tests, the samples were classified as very durable rocks according to Gamble and Franklin-Chandra classifications. The results indicated that specimen’s shape has essential effects on both rock durability and grain size distribution of the obtained sediment particles, so that the spherical and lump specimens shown the highest and lowest values of the slake-durability index, respectively. This means that more unregular dimensions, nonsphericity, and angularity of the specimens lead to decrease the slake-durability index which is highly correlated to the roundness (Rc) values of the specimens. The granulation parameters (D10, D30, D60, Cu, and Cc) of the obtained sediment particles were different for the tested samples. These parameters were recognized related to the specimen’s shape so that, the D60 and Cu are also highly correlated to the roundness (Rc) values of the specimens used in the slake-durability test.

Hydrothermal Synthesis of Silver Sulfide

Silver sulfide powders with submicro- and micrometer particle sizes have been synthesized by the hydrothermal method at temperatures from 373 to 453 K in aqueous and alcoholic solutions of silver nitrate, sodium sulfide and citrate, sulfur, and thiocarbamide. The crystal structures of the synthesized powders, morphology, composition, and particle size of silver sulfide have been analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, and gas adsorption. The powder particles have a similar morphology in the form of rectangular parallelepipeds and cubes with smoothed edges; the size of the powder particles depends on the synthesis conditions and ranges from ~500 to 2000 nm.

Experimental Study of Geometric Shape and Size of Sill Effects on the Hydraulic Performance of Sluice Gates

The present research was conducted to investigate the effect of sill geometry and sill width on the discharge coefficient and hydraulic jump characteristics. For this purpose, sills with semi-cylindrical, cylindrical, pyramidal, and rectangular cube geometries with widths of 0.075, 0.10, 0.15, and 0.2 m were installed under a sluice gate. Results showed that increasing the sill width increased the sluice gate discharge coefficient compared to the no-sill mode. The results of placing a sill with different geometric shapes under a sluice gate indicate that using a semi-cylindrical sill increases the discharge coefficient. The ranked order of other sills, from the largest to smallest discharge coefficient, is: cylindrical, pyramidal, and rectangular cubic sills, respectively. The results show that the use of a sill increases the energy dissipation. Examining sills of different widths indicates that with increasing width, the increase in velocity and consequent decrease in the depth of the hydraulic jump causes an increase in energy loss. When employing sills of maximum width (b = 0.20 m) for pyramidal, semi-cylindrical, cylindrical, and rectangular shapes, the energy loss increased by 125, 119, 116, and 125% in section A, respectively. The semi-cylindrical sill is most effective in increasing the discharge coefficient, while the pyramidal sill is most effective for increasing energy dissipation.

Cartesian Meshing Spherical Earth (CMSE): A Code Package to Incorporate the Spherical Earth in SPECFEM3D Cartesian Simulations

AbstractThe SPECFEM3D_Cartesian code package is widely used in simulating seismic wave propagation on local and regional scales due to its computational efficiency compared with the one-chunk version of the SPECFEM3D_Globe code. In SPECFEM3D_Cartesian, the built-in meshing tool maps a spherically curved cube to a rectangular cube using the Universal Transverse Mercator projection (UTM). Meanwhile, the geodetic east, north, and up directions are assigned as the local x–y–z directions. This causes coordinate orientation issues in simulating waveform propagation in regions larger than 6° × 6° or near the Earth’s polar regions. In this study, we introduce a new code package, named Cartesian Meshing Spherical Earth (CMSE), that can accurately mesh the 3D geometry of the Earth’s surface under the Cartesian coordinate frame, while retaining the geodetic directions. To benchmark our new package, we calculate the residual amplitude of the CMSE synthetics with respect to the reference synthetics calculated by SPECFEM3D_Globe. In the regional scale simulations with an area of 1300 km × 1300 km, we find a maximum of 5% amplitude residual for the SPECFEM3D_Cartesian synthetics using the mesh generated by the CMSE, much smaller than the maximum amplitude residual of 100% for the synthetics based on its built-in meshing tool. Therefore, our new meshing tool CMSE overcomes the limitations of the internal mesher used by SPECFEM3D_Cartesian and can be used for more accurate waveform simulations in larger regions beyond one UTM zone. Furthermore, CMSE can deal with regions at the south and north poles that cannot be handled by the UTM projection. Although other external code packages can be used to mesh the curvature of the Earth, the advantage of the CMSE code is that it is open-source, easy to use, and fully integrated with SPECFEM3D_Cartesian.

Monte Carlo analytical-geometrical simulation of piezoresistivity and electrical conductivity of polymeric nanocomposites filled with hybrid carbon nanotubes/graphene nanoplatelets

Piezoresistivity and electrical conductivity of carbon nanotube (CNT)/graphene nanoplatelet (GNP)-filled polymer nanocomposites are investigated using a 3D Monte Carlo analytical-geometrical model. GNPs and CNTs are considered as randomly distributed solid thin rectangular cube and cylinder, respectively. After establishment of a random CNT/GNP network, electrical conductivity and relative resistance change with strain is calculated. Model considers effect of CNT and GNP deformation on filler separation distance as the dominant factor for percolation tunneling. Comparing model results with experimental data of hybrid nanocomposites showed a good agreement for electrical conductivity and piezoresitivity. Analytical model is developed on the basis of geometrical tunneling percolation theory to consider the effect of several parameters like height of barrier potential, GNP side length, CNT orientation and dimensions on electric behavior of nanocomposites. Results revealed that CNT dispersion state and GNP dimensions have significant effects on the percolation threshold and resistivity change ratio of nanocomposites with strain.

Numerical Simulation of HTPB Resin Curing Process Using OpenFOAM and Study the Effect of Different Conditions on its Curing Time

AbstractThe main purpose of this study is to optimize the curing time of HTPB, by analyzing the curing process in different conditions. Solving equations have been performed using OpenFOAM software and according to the finite volume method. To solve the curing equation, a new solver called CureFOAM was developed and added to the OpenFOAM. Using the experimental results available in the sources, the developed solver was validated. The maximum relative error is +5 %. After validating the CureFOAM solver, the effect of various factors affecting the curing process was simulated. Based on the results, an increase of 10 °C temperature reduces curing time to 2 days, and the use of a fan oven in the Reynolds 1500 range, reduces curing time by up to 50 percent. Also, the curing process in the mold of a rectangular cube is done faster than the cylindrical and spherical molds, in different aspect ratios.

THREE-DIMENSIONAL SIMULATION OF A TURBULENT FLOW AROUND A TAPERED CUBE DUG IN THE MIDDLE

To analyze the influence of the tapered form of the two upper vertices of a rectangular cube placed in a channel and the impact of the insertion of hollow in the center of the obstacle, a three-dimensional study was executed using K-ω SST turbulence model. Different models of the form of the cube were presented to examine the features of the flow with a Reynolds number Re=4×104. The turbulence kinetic energy, 2D and 3D time-averaged streamlines, trace-lines, streamwise velocity profiles, pressure profiles were obtained using the ANSYS CFX calculation code and the finite volume method were employed for resolving the governing equations. The streamlines showed in the model of the tapered cube with hollow a formation of another vortex downstream of the cube at the outlet of the hollow. For the streamwise velocity, there are two recirculation zones: one logarithmic zone due to the main flow, the other is a lower parabolic return zone due to the recirculation vortex.

Three-Dimensional Printing of Natural Materials Involving Loess-Based Composite Materials Designed for Ecofriendly Applications.

In this work, loess-based materials were designed based on a multicomponent composite materials system for ecofriendly natural three-dimensional (3D) printing involving quick lime, gypsum, and water. The 3D printing process was monitored as a function of gypsum content; in terms of mechanical strength and electrical resistance, in the cube-shaped bulk form. After initial optimization, the 3D printing composition was refined to provide improved printability in a 3D printing system. The optimal 3D fabrication allowed for reproducible printing of rectangular columns and cubes. The development of 3D printing materials was scrutinized using a multitude of physicochemical probing tools, including X-ray diffraction for phase identification, impedance spectroscopy to monitor setting behaviors, and mercury intrusion porosimetry to extract the pore structure of loess-based composite materials. Additionally, the setting behavior in the loess-based composite materials was analyzed by investigating the formation of gypsum hydrates induced by chemical reaction between quick lime and water. This setting reaction provides reasonable mechanical strength that is sufficient to print loess-based pastes via 3D printing. Such mechanical strength allows utilization of robotic 3D printing applications that can be used to fabricate ecofriendly structures.

Optimization of the Exhibition Building Form Based on the Solar Energy Absorption

In this paper, the effect of the form and the shape of the exhibition on the performance of the absorption of solar energy in both cold & mountainous and hot & dry climates has been investigated. The form as the most prominent design feature in buildings has a significant impact on energy efficiency and can be expressed in different ways in a building. In order to evaluate the energy performance of various geometries as an exhibition, the absorption of solar energy in several geometries with different shapes, such as: hexagonal / pyramid / prism / incomplete prism / rectangular cube / cube / hemisphere / cylinder / cylinder combination and the rectangle cube combination, have been numerically simulated. For all geometries, the total area and other simulation conditions are assumed to be the same. The results show that in both types of climate, the most absorbed solar energy is obtained for pyramidal geometry and the least absorption is obtained by hemispherical geometry. The hemisphere form in the hot and dry climate has the best form-to-type ratio in order to provide thermal comfort and reduce energy consumption during the exhibition. In the cold and mountainous climate, pyramidal geometry has the highest energy absorption and is the best option among all investigated geometries. The absorption of solar energy in hemispherical geometry for hot & dry and cold & mountain climate is 66% and 54% compared to pyramidal, respectively.

Diagnosing Soft Tissue Sub-Surface Masses Using the XCS Classification System

Introduction: One of the most common types of cancer is breast cancer, which is considered as the second leading cause of death in women in Iran. Due to the fatality of this type of cancer, it is very important to diagnose the disease in the early stages and starting the treatment process. One of the methods to diagnose breast cancer is using mechanical arms (robot manipulator) to touch and measure the force in terms of displacement at the site of the breast touch by the robot. The hardness of the cancer tissue can affect the force diagram in terms of displacement, which can be used as a diagnostic method. The present study was performed to prepare a simulation model of breast soft tissue behavior considering subsurface masses. Then, a proposed classification system was designed to fit it.Material and Methods: In this section, first, the soft tissue behavior of the breast is simulated by considering sub-surface masses. The simulations are performed for a piece of tissue that is in the shape of a rectangular cube, as well as different dimensions of a spherical mass that is located at different depths and coordinates. Using simulation, various force-displacement diagrams have been obtained, based on which a data network.Results: The displacement force diagram for different modes is obtained using simulation. By giving the resulting diagrams to the trained system, the size and depth of the mass is determined. By comparing the obtained results with the initial model and the actual size and depth of the mass, a very good conformity is observed, which indicates the correct operation of the designed system and the performed simulation process.Conclusion: The proposed design system was used to diagnose the presence of tumors in tissue with sub-surface mass. The results show a high percentage of this method in diagnosis. However, the accuracy of this method can be greatly increased by increasing the amount of data given to the XCS system for training. On the other hand, instead of simulation data, test data on healthy and unhealthy people can be used for training.

Numerical analysis of an ultra-wideband metamaterial absorber with high absorptivity from visible light to near-infrared.

In this study, we designed a novel ultra-wideband (UWB) absorber and numerically analyzed it to demonstrate that its light absorptivity was greater than 90% in the wavelength range of visible light and near-infrared (405-1505 nm). The structure of proposed novel UWB absorber consisted of four layers of films, including silica, titanium, magnesium fluoride, and aluminium, and the upper silica and titanium layers had rectangular cubes in them. For that, the excitations of propagating surface plasmon resonance (PSPR), local surface plasmon resonance (LSPR), and the resonance of Fabry-Perot (FP) cavity were generated at the same time and combined to reach the effect of perfect absorption and ultra-wideband. The proposed absorber had an average absorptivity of 95.14% in the wavelength range of 405 ∼ 1505 nm when the light was under normal incidence. In addition, the UWB absorber was large incident angle insensitive and polarization-independent. The absorber proposed in the paper had great prospects in the fields of thermal electronic equipment, solar power generation, and perfect cloaking.

Development of a Novel Task-oriented Rehabilitation Program using a Bimanual Exoskeleton Robotic Hand.

A robot-assisted hand is used for the rehabilitation of patients with impaired upper limb function, particularly for stroke patients with a loss of motor control. However, it is unclear how conventional occupational training strategies can be applied to the use of rehabilitation robots. Novel robotic technologies and occupational therapy concepts are used to develop a protocol that allows patients with impaired upper limb function to grasp objects using their affected hand through a variety of pinching and grasping functions. To conduct this appropriately, we used five types of objects: a peg, a rectangular cube, a cube, a ball, and a cylindrical bar. We also equipped the patients with a robotic hand, the Mirror Hand, an exoskeletonhand that is fitted to the subject's affected hand and follows the movement of the sensor glove fitted to their unaffected hand (bimanual movement training (BMT)). This study had two stages. Three healthy subjects were first recruited to test the feasibility and acceptability of the training program. Three patients with hand dysfunction caused by stroke were then recruited to confirm the feasibility and acceptability of the training program, which was conducted on 3 consecutive days. On each day, the patient was monitored during 5 min of movement in a passive range of motion, 5 min of robot-assisted bimanual movement, and task-oriented training using the five objects. The results showed that both healthy subjects and subjects who had suffered a stroke in conjunction with the robotic hand could successfully grasp the objects. Both healthy subjects and those who had suffered a stroke performed well with the robot-assisted task-oriented training program in terms of feasibility and acceptability.

Effect of modeling porous media on the response of gamma-gamma well-logging tool

The well logging is known as a technique of making petrophysical measurements in the sub-surface earth formations through a drilled borehole to reach the characterization of the physical properties of rocks and fluids. Considering the fact that reservoirs are complex fractured media which the fluid can flow through the porosities, the distribution model of oil in the medium needs to be investigated in detail and to be well quantified. To study this effect, a typical gamma-gamma logging tool containing 137Cs source and two NaI detectors was modeled by using the MCNPX code. The medium was filled with numerous matrix-shaped blocks, each including rectangular cubes for modeling the oil flow in the formation. For an arbitrary set of oil concentrations and various formation materials, the response of the detectors for this model was studied. Taking into account the results corresponding to the traditional homogeneous mixture model for the formation, it was found that the deviations between the count rates for two models reach to about 10% and 22% for short spacing and far spacing detectors, respectively. The results also show that the slopes of the straight-line fits to the count rates, which is important for the evaluation of the density, deviate between about 73.3% and 53.8% for two simulated models. Investigating the effect of the presence of the drilling fluid on the count rate of the proposed model showed that for a given thickness of mudcake and the formation density, both detectors show approximately the same percentage of change in counting rate. However, these counts for the proposed model deviate from those of the mixture model between 5.1% and 28%. It can be concluded that defining a model for describing heterogeneities of a natural porous medium can effectively account for the prediction of density measurement in logging tools.

Cube-like Cu/Cu2O/BiVO4/Bi7VO13 composite nanoparticles: Facile sol-gel synthesis for photocatalytic desulfurization of thiophene under visible light

In this paper, for the photocatalytic oxidative desulfurization of the oil derivatives under visible light, composite nanostructures of copper oxides and bismuth vanadate were prepared using Pechini sol gel method. Parameters affecting the size and morphology of nanostructures such as type of chelating and gelling agents, and molar ratio of copper salts to other metals were also investigated. The results of the analyzes showed that using ethylenediamine as a gelling agent, tannic acid as a chelating agent, and a 1:1:1 ratio for Cu:Bi:V, Cu/Cu2O/BiVO4/Bi7VO13 resulted in production of composite nanoparticles with rectangular cube morphology, which exhibit the highest efficiency (92% after 150 min) in the photocatalytic oxidation of thiophene. Experiments on the trapping of active radical species as well as the recyclability of the catalyst were also conducted and the O2− and h+ were found to be active species and the catalyst showed remarkable stability.

A Quadrupole Tensor Analysis Approach to Design a Broadband Absorber

The purpose of this paper is to design a broadband and very thin absorber with periodic structure using magneto-dielectric particles. A theoretical method has been developed for the analysis of periodic structures. This method has the ability to compute the field, reflection, transmission, and absorption for different number of layers and particles with different shapes and dimensions. In this paper, in addition to electric and magnetic dipole moments, quadrupole equivalences of particles are considered as well. This will help the analytical approach to calculate the fields more accurately. It is shown how these changes, will help to design a broadband absorber in microwave regime. Then a step-by-step method for design an absorber is presented based on this theoretical method that is called planar analysis method . In addition, due to the properties of magneto-dielectric materials that can have electrical and magnetic effects together and often have high losses; we can have broadband absorbers using these materials. In this paper, an absorber based on rectangular cube particles composing magneto-dielectric material is designed. The simulation results show that the absorber has 104% bandwidth for absorption above 90%. The thickness of this absorber with respect to center of absorption bandwidth is $\lambda /12$ .

Simulation and Analysis of a Turbulent Flow Around a Three-Dimensional Obstacle

Abstract The study of flow around obstacles is devised into three different positions: above the obstacle, upstream of the obstacle, and downstream of the latter. The behaviour of the fluid downstream of the obstacle is less known, and the physical and numerical modelling is being given the existence of recirculation zones with their complex behaviour. The purpose of the work presented below is to study the influence of the inclined form of the two upper peaks of a rectangular cube. A three-dimensional study was carried out using the ANSYS CFX calculation code. Turbulence models have been used to study the flow characteristics around the inclined obstacle. The time-averaged results of contours of velocity vectors <V>, cross-stream <v> and stream wise velocity <u> and streamlines were obtained by using K-ω shear -stress transport (SST), RANG K-ε and K-ε to model the turbulence, and the governing equations were solved using the finite volume method. The turbulence model K-ω SST has presented the best prediction of the flow characteristics for the obstacle among the investigated turbulence models in this work.