Z-axis Direction Research Articles

Horizontal Distribution of Temperature Effect in Rubberized Concrete Pavement: A Case Study

Temperature distribution and the deformation behavior under temperature are important parameters in the design and evaluation of concrete pavements. In this paper, in order to study the horizontal distribution of the temperature effect on rubberized concrete pavement (RCP), the distribution differences of temperature, temperature gradient and strain at different horizontal locations were analyzed based on fiber Bragg grating test technology. The relationships between temperature and strain and between temperature gradient and strain were also investigated. The results show that within a cycle of temperature or temperature gradient change, the time of temperature increase or temperature gradient increase is only 1/4 of the whole cycle, significantly less than the time of the temperature or temperature gradient decrease. Comparing the center, edges and corner of the pavement, the horizontal distribution of temperature and temperature gradients in the RCP is uneven, and the greatest negative temperature gradient is experienced at the corner of the pavement, which is 25 °C·m−1 greater than the temperature gradient at the center. The negative temperature gradient at the corner of the concrete pavement exacerbates the bottom deformation at the center and edge of the pavement, especially in the X-axis direction at the center and in the Y-axis and Z-axis directions at the edge. The relationships between temperature and horizontal strain at the center and edge of the RCP have a significant hysteresis effect and are markedly stronger than those at the corner. Moreover, when the temperature gradient is less than −23.4 °C·m−1 or greater than 14.5 °C·m−1, the curling effect at the edge of the RCP is more obvious.

Properties of CF3SO2F under the influence of external electric field: A DFT study

With the deterioration of global greenhouse effect, CF3SO2F (Trifluoromethanesulphonyl Fluoride) has become an alternative gas of SF6 (Sulfur Hexafluoride). CF3SO2F has environmentally friendly characteristics and has been widely concerned. In this work, we analyze the electric field level of the discharge in the dielectric and the direction of the molecular intrinsic dipole moment. Density functional theory and time-dependent density functional theory are used to calculate the molecular structure parameters, dipole moments, frontier orbitals and excited states at corresponding electric field levels and in specific electric field directions. C2F5SO2F and C3F7SO2F, as by-products in the synthesis of CF3SO2F, are studied together to explore the influence of carbon atom number on molecular properties. As a result, the molecular structure is clearly changed under the electric field and the molecular bond length strongly depended on the electric field. The HOMO is mainly contributed by O atoms and the LUMO is mainly contributed by S atoms. When the electric field in the -z-axis direction is applied, the HOMO energies of molecules increase, especially for C3F7SO2F molecule, and the ionization potentials decrease correspondingly. The reduced ionization potentials facilitate the liberation of electrons from the molecule and the propagation of the streamer. The excitation energy of each molecule in each excited state decreases with the increasing of electric field intensity. Therefore, during the preparation process of CF3SO2F molecule, C3F7SO2F molecule should be reduced or removed as much as possible to prevent the reduction of dielectric insulation strength. The finding of this study is beneficial to the performance improvement and application research of CF3SO2F.

NaBeAs and NaBeSb: Novel Ternary Pnictides with Enhanced Thermoelectric Performance

Thermoelectrics is a clean energy technology that converts thermal energy into electrical energy and provides an environmentally friendly and viable route to produce electricity. In this work, we thoroughly explore the thermoelectric performance of two novel ternary pnictide compounds, NaBeAs and NaBeSb, using full ab initio calculations and solving linear Boltzmann transport equations. We predict that both compounds exhibit excellent dynamical and thermal stability. The combined effect of low phonon group velocity and weak bonding interaction results in intrinsic low lattice thermal conductivities of 1.41 and 0.59 W/mK for NaBeAs and NaBeSb, respectively, in the z-axis direction at 600 K. The electronic structure exhibits high conduction band degeneracy, which results in favorable electrical transport characteristics. The unique combination of very low lattice thermal conductivity and good electrical transport properties leads to excellent n-type thermoelectric properties. Furthermore, in n-type doping, the figures of merit reach 1.82 and 4.26 for NaBeAs and NaBeSb at 600 K. Our findings show that both compounds are promising n-type thermoelectric materials at medium temperatures.

Effects of Bit Shape of Electroplated Diamond Tool Used for Drilling Small Diameter Holes in Glass Plate on Machining Fluid Flow and Chip Discharge

Our laboratory has been exploring the development of tools for drilling holes in glass plates, and the drilling techniques to be adopted for it. A devised tool shape that could prevent the occurrence of cracks at the exit holes achieved high quality through hole drilling of 100 holes or more using only the drilling cycle. However, crack-free drilling beyond this number of holes cannot be performed. This is due to the adhesion of the residual chip on the tool surface when the number of holes increases. Therefore, further improvement of chip discharge is needed to achieve crack-free drilling. In this report, we consider that chip discharge results from the flow of the machining fluid. To investigate the cause of chip discharge, we analyzed the flow of the machining fluid in the hole using computational fluid dynamics and the supposed chip discharge conditions. The results obtained in this study are summarized as follows. (1) In the case of a cylindrical tool, the Z-axis directional flow of the machining fluid did not occur in the hole. This is because the tool does not have bumps to agitate the fluid on the side, and the gap between the tool and the inner surface of the hole is narrow. (2) The plate side widened the gap between the tool and inner surface of the hole. Therefore, the fluid was likely to flow in the Z-axis direction in the hole. (3) For the tool with the plane side bit, the flow entered the hole from one plane side and exited the hole from the other plane side. (4) When the tool end is spherical, the Z-axis directional flow of the fluid occurs at the tool end. (5) The fluid flow of the devised tool weakened as the drilling depth increased. To improve the chip discharge performance of the designed tool, the Z-axis directional flow of the machining fluid must occur in an area deeper than 2 mm.

Design of functionally graded Ti–Al alloy with adjustable mechanical properties: a molecular dynamics insights

Functional gradient materials (FGMs) are a category of advanced materials that contain two (or more) different components with continuously varying compositional distributions. With the advancement in nanotechnology, FGM applications have evolved from traditional applications to complex micro- and nano-electronic and energy conversion devices. Therefore, studying the mechanical behavior of the nanostructures of different FGMs plays a crucial role in determining the feasibility of their various applications. Herein, the mechanical behavior of the shear deformation of Ti–Al FGM nano-bulks with a radial (Z-axis direction) gradient was investigated using molecular dynamics (MD) simulations. The distributions of Ti and Al in the Z-direction were obtained using the sigmoid function. The results demonstrate that the distribution function parameters are important in regulating the mechanical properties—elastic modulus and ultimate tensile strength—of Ti–Al FGMs. It gives us a new perspective on the analysis of the microstructure evolution and dislocation density of FGMs, providing theoretical support for the practical application of FGMs.

Light-driven MOF-based micromotors with self-floating characteristics for water sterilization.

Three-dimensional motion (especially in the Z-axis direction) of metal-organic frameworks (MOFs)-based micromotors (MOFtors) is essential but still in its infancy. Herein, we propose a simple strategy for designing light-driven MOFtors that move in the Z-axis direction and efficiently kill Staphylococcus aureus (S. aureus). The as-prepared polypyrrole nanoparticles (PPy NPs) with excellent photothermal properties are combined with ZIF-8 through a simple in situ encapsulation method, resulting in multi-wavelength photothermally-responsive MOFtors (PPy/ZIF-8). Under the irradiation of near-infrared (NIR)/ultraviolet (UV)/blue light, the MOFtors all exhibited negative phototaxis and high-speed motion behaviour with the highest speed of 2215 ± 338 μm s-1. In addition, it is proved that these MOFtors can slowly self-float up in an aqueous environment. The light irradiation will accelerate the upward movement of the MOFtors, and the time required for the MOFtors to move to the top is negatively correlated with the light intensity. Finally, efficient antibacterial performances (up to 98.89% against S. aureus) are achieved with these light-driven MOFtors owing to the boosted Zn2+ release by vigorous stirring motion and physical entrapment by the upward motion under light irradiation.

An investigation on the structural vibrations of multi-rotor passenger drones

In order to solve the structural damage problem of the first generation of large multi-rotor manned drones, the present work has designed to study the structural vibration problems of multi-rotor drones. On a small multi-rotor drone, the laser vibration meter verified the reliability of acceleration sensor measurement of vibration and found that circular shape carbon fiber arms have strong damping abilities, with the strongest vibration in the Z-axis direction. To improve the design of the second generation of large multi-rotor manned drones, elliptical shape carbon fiber arms were employed instead of circular arms. Experiments showed that the main vibrations of the large multi-rotor manned drone’s arm are low-frequency vibrations below 200Hz, producing mainly torsional and bending modes, and the elliptical carbon fiber arms significantly reduce vibrations in the Z-axis direction. This study provides experimental data support for multi-rotor manned drones and further presents an improvement strategy for suppressing the vibrations of the multi-rotor manned drones.

Improvement of Moving RFID Microtag Detection in Different Angular Orientations Using Multiple Tubular Coils

Directionality problem caused by the rolling of microtag with flowing fluid seriously affects the reliability of oilwell downhole radio frequency identification (RFID) system. In this paper, we propose a novel RFID reader antenna structure using multiple tubular coils for reduced orientation sensitivity. The conventional solenoid coil and saddle-coil pairs are combined to overcome the respective defects of the two coils and develop their advantages to form a complementary structure at the same time. Then, a series of coil parameters are designed in detailed to provide strong magnetic field distribution both in the x-axis, y-axis and z-axis directions. To verify the design, the proposed multiple tubular coils have been fabricated and measured. Experimental results demonstrate more potential than the conventional solenoid coil for microtag detection in different angular orientations, which is very important to improve the reliability and applicability of current oilwell downhole RFID system.

A toughening mechanism of the strain rate-optimal chain length on polymer-modified calcium silicate hydrates (CSH).

Polymers are known to effectively improve the toughness of inorganic matrices; however, the mechanism at the molecular level is still unclear. In this study, we used molecular dynamics simulations to unravel the effects and mechanisms of different molecular chain lengths of polyacrylic acid (PAA) on toughening calcium silicate hydrate (CSH), which is the basic building block of cement-based materials. Our simulation results indicate that an optimal molecular chain length of polymers contributes to the largest toughening effect on the matrix, leading to up to 60.98% increase in fracture energy. During the uniaxial tensile tests along the x-axis and z-axis direction, the configuration evolution of the PAA molecule determines the toughening effect. As the polymer unfolds and its size matches the defects of CSH, the stress distribution of the system becomes more homogeneous, which favors an increase in toughness. Furthermore, based on our simulation results and a mathematical model, we propose a theory of "strain rate/optimal chain length". This theory suggests that the optimal toughening effect can be achieved when the molecular chain length of the organic component is 1.3-1.5 times the largest defect size of the inorganic matrix. This work provides molecular-scale insights into the toughening mechanisms of an organic/inorganic system and may have practical implications for improving the toughness of cement-based materials.

Characteristics of the Z-resolution Measurement in the Digital Breast Tomosynthesis

Digital breast tomosynthesis (DBT) offers a choice of image acquisition conditions. The object of observation is the entire detector in the full depth (Z-axis) direction. In this study, we investigated the effect of each acquisition condition on Z-resolution with a micro-metallic sphere (bead) as an imaged object in DBT images. DBT images were acquired in two imaging modes with different angular ranges, varying with the height of the bead, the bead placement position, and the bead diameter. The depth profile of the bead image was obtained, and the Z-resolution was defined by its full width at half maximum. The Z-resolution was compared with each acquisition condition. The Z-resolution values decreased with increasing height from the breast support and decreasing bead diameter. The Z-resolution values were larger at the edges than at the detector center. This study shows that the bead diameter and the geometry of the bead and detector affect the Z-resolution measurement.

Free Vibration Characteristics of Bidirectional Graded Porous Plates with Elastic Foundations Using 2D-DQM

This manuscript develops for the first time a mathematical formulation of the dynamical behavior of bi-directional functionally graded porous plates (BDFGPP) resting on a Winkler–Pasternak foundation using unified higher-order plate theories (UHOPT). The kinematic displacement fields are exploited to fulfill the null shear strain/stress at the bottom and top surfaces of the plate without needing a shear factor correction. The bi-directional gradation of materials is proposed in the axial (x-axis) and transverse (z-axis) directions according to the power-law distribution function. The cosine function is employed to define the distribution of porosity through the transverse z-direction. Equations of motion in terms of displacements and associated boundary conditions are derived in detail using Hamilton’s principle. The two-dimensional differential integral quadrature method (2D-DIQM) is employed to transform partial differential equations of motion into a system of algebraic equations. Parametric analysis is performed to illustrate the effect of kinematic shear relations, gradation indices, porosity type, elastic foundations, geometrical dimensions, and boundary conditions (BCs) on natural frequencies and mode shapes of BDFGPP. The effect of the porosity coefficient on the natural frequency is dependent on the porosity type. The natural frequency is dependent on the coupling of gradation indices, boundary conditions, and shear distribution functions. The proposed model can be used in designing BDFGPP used in nuclear, marine, aerospace, and civil structures based on their topology and natural frequency constraints.

Tribological and Friction-Induced Vibration Behaviors of Inorganic Fullerene-Like Tungsten Disulfide and Three-Dimensional Graphene as Lubricant Additives

Abstract Friction and friction-induced vibration have a great impact on the service life of mechanical systems. In this study, the tribological performances and vibration characteristics of three-dimensional graphene nanosheets (3D GNS), inorganic fullerene-like tungsten disulfide (IF-WS2), and their mixed additive lubricants are investigated by experiments. The results show that IF-WS2/3D GNS (1:1) mixed additive can improve the friction-reduction and anti-wear of base oil by 62.9% and 71.4%, respectively. In terms of vibration damping, the mixed additive has an extremely strong dampening effect on vibration acceleration in all directions, especially in the Z-axis direction, where the amplitude is reduced by about 90%. The vibration damping should be attributed to the filling effect of 3D GNS and IF-WS2, which greatly flattens the friction surface, thus reducing the number of collision micro-bumps in the relative movement of the friction pair and suppressing the vibration. In addition, the unique ductile deformation of IF-WS2 makes the two additives form a flexible ball-bearing damper between the two contact surfaces, thus greatly reducing the vibration.

Development of a new bio-microscope for 3D geometry characterization of fruit single cells.

Fruit cells are living irregular three-dimensional (3D) transparent objects which makes them challenging to determine their real 3D size and shape through only two-dimensional (2D) images using the existing biological microscope. This study deals with a newly self-developed biological microscope including a microscope imaging system, a light source system, a stage and a support base for the 3D size characterization of fruit single cells. The main design concept is based on two optical path systems set up at the front (x-axis) and bottom (z-axis) directions of a transparent chamber containing single cells that allow the front view and bottom view of the single cell to be observed. Performance indicators such as mass, size, observation range, objective magnification, total magnification, focal range, focal accuracy, and resolution of the developed biological microscope were estimated. Finally, the 3D geometry size of single tomato cells was measured by the new biological microscope to demonstrate the relative ease at which accurate real 3D geometry information of single fruit cells could be obtained, which echoes its scientific value.

Layer-dependent electronic and magnetic properties for Cr[formula omitted]NO[formula omitted] and Cr[formula omitted]CO[formula omitted

Using the first-principles calculations, we study the stability, electronic and magnetic properties of monolayer, bilayer and trilayer Cr2NO2 and Cr2CO2. Stability is estimated from the thermal, mechanical and dynamical perspectives. Calculations show that the monolayer, bilayer and trilayer Cr2NO2 and Cr2CO2 are ferromagnetic ground states, and Cr2CO2 are nearly half-metals, and Cr2NO2 are half-metals with an integer total magnetic moment. For the monolayer, bilayer and trilayer Cr2NO2 and Cr2CO2, the Z-axis direction is their easy magnetization axis, and their magnetic anisotropy energies are obviously increased with the increase of layered number, the improvement of magnetic anisotropy energy origins from the enhancement of spin–orbit coupling strength. In addition, we also discuss the origin of gaps for monolayer, bilayer and trilayer half-metallic Cr2NO2.

Crushing Characteristics of Sorghum Grains Subjected to Compression and Impact Loading at Different Moisture Contents

Sorghum is an important grain crop in many countries worldwide, yet it often suffers from high levels of fragmentation during harvest due to varying maturity. To this end, a study was conducted to investigate the crushing characteristics of sorghum grains subjected to compression and impact loading at different moisture contents. By configuring sorghum kernels with varying ranges of water and determining their physical parameters, such as length, width, etc., the geometric mean diameter of sorghum kernels was 3.105–3.550 mm, and the sphericity was above 75%. Compression tests were conducted on sorghum kernels in the triaxial direction. The compression energy was calculated to be 13.409–19.229 J on the X-axis, 16.313–21.409 J on the Y-axis, and 17.609–24.741 J on the Z-axis. In contrast, the apparent contact modulus of elasticity was calculated, with the maximum modulus of elasticity up to 72 MPa in the Z-axis direction, and the variations in the X-axis and Y-axis were approximate. Finally, mechanical impact tests were conducted to measure the critical angle of seed breakage, and a mathematical model was established to predict the impact of mechanical breakage force. The error between the predicted and experimental values was within 3%. This paper conducted compression and impact mechanics tests on sorghum seeds at different moisture contents to provide a design basis for sorghum harvesting and processing and other harvesting equipment.

Anisotropy of soil water diffusivity of hillslope soil under spruce forest derived by X-ray CT and lab experiments

The idea of the study is to indicate direction-dependent differences in hydraulic conductivity, K(Se), and soil water diffusivity, D(θ), as function of the volume fraction related to the fractional capillary potential for each of the characteristic pore size classes by extended anisotropy factors. The study is exemplary focused on a BwC horizon of a Dystric Cambisol under spruce forest formed on the weathered and fractured granite bedrock in the mountainous hillslopes Uhlirska catchment (Czech Republic). Thus, undisturbed soil samples were taken in vertical (0°, y = x-axis) and horizontal (90°, z-axis) direction. The D(θ) values and especially the D(θ)-weighted anisotropy ratios showed that anisotropy increases with the volume fraction of macropores, MaP (d > 0.03 mm), with r2 between 0.89 and 0.92. The X-ray computer tomography (CT) based anisotropy ratio (ACT) is larger for the horizontal sampled soil core with 0.31 than for the vertical with 0.09. This underlines the existence of a predominantly horizontally oriented pore network and the fact that weathered bedrock strata can initiate lateral preferential flow. The study results suggest that combining the hydraulic conductivity as intensity and the capacity parameter by means of diffusivity results in an extended anisotropy ratio which unveils the role of the soil hydraulic characteristics in generation of small-scale lateral preferential flow. In future, the small-scale direction-dependent differences in the soil hydraulic capacity and intensity parameter will be used for model-based upscaling for better understanding of preferential flow at the catchment scale.

Sub Surface Structure Modelling Area around Sub district Gantiwarno, District Klatenusing by Gravity Method

The earthquake that happened on 27th May 2006 in Yogyakarta and its surrounding caused terrible damageas well as thousands of dead victims. Such an earthquake was caused by horizontal Opak’s Fault activationand it triggered the emergence of Dengkeng’s Fault movement located at the eastern part of the northernOpak’s Fault. To mitigate the disaster that might occur in the future, the channel and the condition underDengkeng’s Fault need to be mapped. One of the methods that could be used to recognize the under surfacecondition is the gravity method which is based on the measurement of gravity field variation on the earth’ssurface. The existence of a fault would change the condition of rocks in such fault channel zone so that itinfluences the local gravity change. Therefore, on this opportunity, research of Dengkeng’s Fault is carriedout using the gravity method. The measurement of the gravity field has been done in 94 points using LacosteRomberg Gravitymeter type G-1118 MVR. The height of the measurement point was measured usingGPS Altus APS-3 differential, and the research coordinate was measured using GPS Garmin III Plus. Dataon the gravity field that had been obtained was corrected so that complete anomaly Bouguer (ABL) isobtained. Further, the regional component of the ABL value is separated from its local component using anupward continuation method. The target that would be identified is shallow so that the local anomaly thatwould be analyzed uses the second vertical derivative (SVD) and modeled in 3 dimensions using OasisMontaj software. Second vertical derivative type of fault. 3-dimensional modeling was used to identify theunder surface structure of the research area comprehensively. The result of the analysis using the secondvertical derivative shows that Dengkeng’s Fault is a strike-slip fault with the west-east direction. To clarifythe under the surface condition from the 3-dimensional modeling, incisions were made to the Z-axis direction(vertically) and X-axis direction. Z-axis direction modeling shows that the fault in the research area starts tobe seen at the depth of 500 meters to 3500 meters to the west-east. X-axis direction modeling shows that thefault was located at Easting 444500 meter and Northing 9141000 meters to the Easting 456250 and Northing9139000. Based on the modeling result, it could be seen that the southern part block of Dengkeng’s movedto the east, while the northern part block moved to the west.

Localization Approach for Underwater Sensors in the Magnetic Silencing Facility Based on Magnetic Field Gradients.

Localization of the underwater magnetic sensor arrays plays a pivotal role in the magnetic silencing facility. A localization approach is proposed for underwater sensors based on the optimization of magnetic field gradients in the inverse problem of localization. In the localization system, a solenoid coil carrying direct current serves as the magnetic source. By measuring the magnetic field generated by the magnetic source in different positions, an objective function is established. The position vector of the sensor is determined by a novel multi-swarm particle swarm optimization with dynamic learning strategy. Without the optimization of the magnetic source’s positions, the sensors’ positions, especially in the z-axis direction, struggle to meet the requested localization. A strategy is proposed to optimize the positions of the magnetic source based on magnetic field gradients in the three directions of x, y and z axes. Compared with the former method, the model experiments show that the proposed method could achieve a 10 cm location error for the position type 2 sensor and meet the request of localization.

Simulation study on the deflection and expansion of hydraulic fractures in coal-rock complexes

The physical difference and structural weak surface of coal-rock complexes greatly influence the morphology of hydraulic fractures (HFs). This study aims to explore the law of deflection and expansion of HFs in coal-rock complexes under different stress conditions. First, a theoretical model for HF deflection in coal-rock complexes was derived. Besides, a numerical model for HF expansion in coal-rock complexes was established based on the traction–separation criterion, the cohesion embedding method and the finite element method for fracture expansion. With the aid of the established model, the laws of morphology and induced stress field evolutions during HF expansion were studied. The following conclusions were drawn. When the HF is closer to the interface, the effect of physical difference is more notable, and the HF is more likely to expand along the coal seam. As the difference between the maximum horizontal principal stress and the vertical ground stress decreases from 8 MPa to 0 MPa, the coal-rock complexes experience HF expansion in the horizontal direction, secondary fracture generation in the Z-axis direction, and HF deflection to the interface in the -Z-axis direction in turn. During HF expansion, a stress difference of about 19 MPa exists between the fracture tip section and the interface, which is favorable for HF initiation and expansion. The effect of physical difference between coal and rock leads to the formation of an induced stress field, which causes a 3–4 times difference in the displacement values in different areas during HF expansion. The abovementioned main causes of HF deflection can provide reference for the design and application of the hydraulic fracturing technology for complex formations with different lithologies.

Study on the Modeling and Compensation Method of Pose Error Analysis for the Fracture Reduction Robot.

Background: In the process of fracture reduction, there are some errors between the actual trajectory and the ideal trajectory due to mechanism errors, which would affect the smooth operation of fracture reduction. To this end, based on self-developed parallel mechanism fracture reduction robot (FRR), a novel method to reduce the pose errors of FRR is proposed. Methods: Firstly, this paper analyzed the pose errors, and built the model of the robot pose errors. Secondly, mechanism errors of FRR were converted into drive bar parameter’s errors, and the influence of each drive bar parameter on the robot pose error were analyzed. Thirdly, combining with Cauchy opposition-based learning and differential evolution algorithm (DE), an improved whale optimization algorithm (CRLWOA-DE) is proposed to compensate the end-effector’s pose errors, which could improve the speed and accuracy of fracture reduction, respectively. Results: The iterative accuracy of CRLWOA-DE is improved by 50.74%, and the optimization speed is improved by 22.62% compared with the whale optimization algorithm (WOA). Meanwhile, compared with particle swarm optimization (PSO) and ant colony optimization (ACO), CRLWOA-DE is proved to be more accurate. Furthermore, SimMechanics in the software of MATLAB was used to reconstruct the fracture reduction robot, and it was verified that the actual motion trajectory of the CRLWOA-DE optimized kinematic stage showed a significant reduction in error in both the x-axis and z-axis directions compared to the desired motion trajectory. Conclusions: This study revealed that the error compensation in FRR reset process had been realized, and the CRLWOA-DE method could be used for reducing the pose error of the fracture reduction robot, which has some significance for the bone fracture and deformity correction.