Narrow Results

The unsteady flow within a simplified 3D centrally-actuated type artificial heart was investigated numerically using moving boundary technique. The velocities on the inlet and outlet were determined according to the motion of the diaphragm. The case with heart beat rate of 75 beats per minute (bpm) was simulated. Two models were studied. It is found that, in the diastolic cycle, a vortex ring forms in the conjunction of the blood chamber and the inlet tube. This vortex ring can provide good wash-out on the wall.

In this work, a numerical study devoted to the two-dimensional and three-dimensional flow of a viscous, incompressible fluid inside a lid-driven cavity is undertaking. All transport equations are solved using the finite volume formulation on a staggered grid system and multi-grid acceleration. Quantitative aspects of two and three-dimensional flows in a lid-driven cavity for Reynolds number Re = 1000 show good agreement with benchmark results.

An analysis of the flow evolution demonstrates that, with increments in Re beyond a certain critical value Rec, the steady flow becomes unstable and bifurcates into unsteady flow. It is observed that the transition from steadiness to unsteadiness follows the classical Hopf bifurcation. The time-dependent velocity distribution is studied in detail and the critical Reynolds number is localized for both 2D and 3D cases.

Benchmark solutions for 2D and 3D lid-driven cavity flows are performed for Re = 1500 and 6000.

The size influence of silica microspheres on the photonic band gap (PBG) of three-dimensional face-centered-cubic (fcc) photonic crystals (PCs) is studied by means of colloidal photonic crystals, which are self-assembled by the vertical deposition technique. Monodispersed SiO₂ microspheres with a diameter of 220–320 nm are synthesized using tetraethylorthosilicate (TEOS) as a precursor material. We find that the PBG of the PCs shifts from 450 nm to 680 nm with silica spheres increasing from 220 to 320 nm. In addition, the PBG moves to higher photon energy when the samples are annealed in a temperature range of 200–700°C. The large shift results from the decrease in refraction index of silica due to moisture evaporation.

A lattice Boltzmann model on Hermite basis for compressible viscous flows is presented in this paper. The model is developed in the framework of double-distribution-function approach, which has adjustable specific-heat ratio and Prandtl number. It contains a density distribution function for the flow field and a total energy distribution function for the temperature field. The equilibrium distribution function is determined by Hermite expansion, and the D3Q27 and D3Q39 three-dimensional (3D) discrete velocity models are used, in which the discrete velocity model can be replaced easily. Moreover, an artificial viscosity is introduced to enhance the model for capturing shock waves. The model is tested through several cases of compressible flows, including 3D supersonic viscous flows with boundary layer. The effect of artificial viscosity is estimated. Besides, D3Q27 and D3Q39 models are further compared in the present platform.

Theoretical research has been done on the hydromagnetic three-dimensional nanofluid flow across an inclined stretching sheet in the presence of Brownian motion and thermophoresis. It is taken into account that there are two different kinds of water-based nanofluids that contain copper and alumina. Three-dimensional nonlinear-type similarity transformations are used to convert the governing boundary-layer equations into a collection of similarity equations, which are then numerically solved by MATLAB. Further, results obtained in some limiting cases are compared to some results that have already been published, and it is found that there is good agreement. The problem is controlled by a number of physical factors, and the impact of these factors on different flow distributions is thoroughly examined with the help of graphs and tables. It has been observed that the nanofluid has better heat transfer conductivity than the ordinary base fluid.

Dissolved oxygen (DO) plays an important role in industrialized freshwater aquaculture. Such deficiencies such as the high cost of water-quality monitoring system and the failure to accurately monitor or describe aquaculture water-quality existed in freshwater aquaculture water-quality monitoring system. Here, a kind of representation method applied to characterize industrialized aquaculture fish behavior in different degrees of DO deficiency is based on three-dimensional (3D) Computer Vision. 3D coordinate values of aquaculture fishes in water acquired from 3D Computer Vision Device by processing aquaculture fish image are applied to represent such parameters as the average activity and height of aquaculture fish in water. This method for representing different behaviors of industrialized freshwater aquaculture fish under the condition of anoxia is realized by using these parameters and combing with the experience of aquaculture. The results show that the representation of industrialized freshwater aquaculture fish based on 3D Computer Vision System can be applied to describe industrialized aquaculture fish behavior and effectively compensate for the shortfall spatial location of aquaculture fish unable to acquire from 2D monitoring system, which is helpful for the accurate and reasonable control of DO in aquaculture.

During the last twenty years there has been increasing interest in studying the piecewise differential systems, mainly due to their many applications in natural science and technology. Up to now the most studied differential systems are in dimension two, here we study them in dimension three. One of the main difficulties for studying these differential systems consists in controlling the existence and nonexistence of limit cycles, and the numbers when they exist.

In this paper, we study the nonsymmetric limit cycles for a family of three-dimensional piecewise linear differential systems with three zones separated by two parallel planes. For this class of differential systems we study the nonexistence, existence and uniqueness of their limit cycles.

The excitable reaction–diffusion (R–D) systems of biological and chemical origin harbour a wealth of patterns and structures, not all of which have been modelled by the full R-D equations. The analytical and numerical facility offered by the eikonal approach to the R-D equation is exploited here in the demonstration of existence and stability of a class of solutions on a torus.

In this short note alternative time domain boundary integral equations (TDBIE) for the scalar wave equation are formulated on a surface enclosing a volume. The technique used follows the traditional approach of subtracting and adding back relevant Taylor expansion terms of the field variable, but does not restrict this to the surface patches that contain the singularity only. From the divergence-free property of the added-back integrands, together with an application of Stokes' theorem, it follows that the added-back terms can be evaluated using line integrals defined on a cut between the surface and a sphere whose radius increases with time. Moreover, after a certain time, the line integrals may be evaluated directly. The results provide additional insight into the theoretical formulations, and might be used to improve numerical implementations in terms of stability and accuracy.

This paper develops a reliability-based methodology for the evaluation of stiffness degradation of spot-welded joints under high mileage. A global-local finite element analysis is used, with the loads on the detailed three-dimensional joint model coming from finite element analysis of the entire car model with proving ground loads. Probabilistic fatigue crack propagation analysis is developed for multi-axial variable amplitude loading history on the joint. Multiple spot welds contribute to the stiffness of the joint. Hence the problem is addressed through system reliability techniques. The effect of spot-weld separation on joint stiffness, and on global vehicle stiffness, is incorporated. This results in the computation of the statistics of vehicle stiffness degradation with mileage.

Deviation of a needle from its intended path can be minimized by using a robotic device to steer the needle towards its target. Such a device requires information about the interactions between the needle and soft tissue, and this information can be obtained using finite element (FE) analysis. In this study, we present an FE analysis that integrates the Johnson–Cook damage model for a linear elastic material with an element deletion-based method. The FE analysis is used to model a bevel-tipped needle interacting with gel. The constants for the damage model are obtained using a compression test. We compare simulation results with experimental data that include tip–gel interaction forces and torques, and three-dimensional (3D) in situ images of the gel rupture obtained using a laser scanning confocal microscope. We quantitatively show that the percentage errors between simulation and experimental results for force along the insertion axis and torque about the bevel edge are 3% and 5%, respectively. Furthermore, it is also shown qualitatively that tip compression is observed at the same locations in both experimental and simulation results. This study demonstrates the potential of using an FE analysis with a damage model and an element deletion-based method to accurately simulate 3D gel rupture, and tip–gel interaction forces and torques.

Idiopathic scoliosis (IS) is a complex three-dimensional (3D) deformity. The non-operative treatments for IS have been developed for a long time. According to current studies, hard braces are more effective than soft braces for the treatment of scoliosis. Though current braces are proved to be effective for the treatment of IS, there are several shortcomings needed to be overcome: (i) Braces cannot realize precise control over a specific vertebra. (ii) Braces affect cardiopulmonary efficiency (braces limit maximal exercise performance). (iii) The brace is not modulated based on user’s needs. (iv) Braces, including motions during eating, tying shoes, sitting, and standing. (v) Braces apply forces on skin, which causes pain, skin breakdown, and abnormal deformation of bone. In order to solve these boring problems of the current braces, this paper proposed a new intelligent robotic spine brace based on the principle of human biomechanics, three point pressure treatment theory and parallel mechanism theory. This novel brace can offer 3D active dynamic adjustable corrective forces for the treatment of IS and some experiments are employed for verifying the effect of the proposed brace.

3D image reconstruction using multi-view imaging is widely utilized in several application domains: construction field, disaster management, urban planning, etc. The 3D reconstruction from the multi-view image is still challenging due to the high freedom and inaccurate reconstruction. This research introduces the hybrid deep learning technique for reconstructing the 3D image, in which the C-dual attention layer is proposed for generating the feature map to support the image reconstruction. The proposed 3D image reconstruction uses the encoder–decoder–refiner which is utilized for reconstruction. Initially, the features are extracted from the AlexNet and ResNet-50 features automatically. Then, the proposed C-dual attention layer is utilized for generating the inter-channel and inter-spatial relationship among the features to obtain enhanced reconstruction accuracy. The inter-channel relationship is evaluated using the channel attention layer, and the inter-spatial relationship is evaluated using the spatial attention layer of the encoder module. Here, the features generated by the spatial attention layer are combined to form the feature map in a 2D map. The proposed C-dual attention encoder provides enhanced features that help to acquire enhanced 3D image reconstruction. The proposed method is evaluated based on loss, IoU_3D, and IoU_2D, and acquired the values of 0.0721, 1.25 and 1.37, respectively.

In this study, we present a fourth-order and a sixth-order blended compact difference (BCD) schemes for approximating the three-dimensional (3D) convection–diffusion equation with variable convective coefficients. The proposed schemes, where transport variable, its first and second derivatives are carried as the unknowns, combine virtues of compact discretization, fourth-order Padé scheme and sixth-order combined compact difference (CCD) scheme for spatial derivatives and can efficiently capture numerical solutions of linear and nonlinear convection–diffusion equations with Dirichlet boundary conditions. The fourth-order scheme requires only 7 grid points and the sixth-order scheme requires 19 grid points. The distinguishing feature of the present method is that methodologies of explicit compact difference and implicit compact difference are blended together. The truncation errors of the two difference schemes are analyzed for the interior grid points, respectively. Simultaneously, a sixth-order accuracy scheme is proposed to compute the first and second derivatives of the grid points on boundaries. Finally, the presented methods are applied to several test problems from the literature including linear and nonlinear problems. It is found that the presented schemes exhibit good performance.

Three-dimensional (3D) γ-MnOOH networks are successfully prepared by one-pot solvothermal method without using any catalyst. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). It is found that the amounts of urea and H₂O₂ added, reaction temperature and time have important influences on the samples. It is interesting that the 3D networks are formed from the oriented attachment (OA) of Mn₃O₄ octahedrons; and that the phase transformation from Mn₃O₄ to γ-MnOOH occurs via the protonation of Mn₃O₄. This study is expected to offer a facile approach to the syntheses of new, intricate nanostructures.

Carbon materials are generally employed as supercapacitor electrodes due to their low- cost, high-chemical stability and environmental friendliness. However, the design of carbon structures with large surface area and controllable porous structure remains a daunt challenge. In this work, a three-dimensional (3D) hybrid aerogel with different contents of MoS₂ nanosheets in 3D graphene aerogel (MoS₂-GA) was synthesized through a facial hydrothermal process. The influences of MoS₂ content on microstructure and subsequently on electrochemical properties of MoS₂-GA are systematically investigated and an optimized mass ratio with MoS₂: GA of 1:2 is chosen to achieve high mechanical robustness and outstanding electrochemical performance in the hybrid structure. Due to the large specific surface area, porous structure and continuous charge transfer network, such MoS₂-GA electrodes exhibit high specific capacitance, good rate capability and excellent cyclic stability, showing great potential in large-scale and low-cost fabrication of high-performance supercapacitors.

For many tiller crops, the plant architecture (PA), including the plant fresh weight, plant height, number of tillers, tiller angle and stem diameter, significantly affects the grain yield. In this study, we propose a method based on volumetric reconstruction for high-throughput three-dimensional (3D) wheat PA studies. The proposed methodology involves plant volumetric reconstruction from multiple images, plant model processing and phenotypic parameter estimation and analysis. This study was performed on 80 Triticum aestivum plants, and the results were analyzed. Comparing the automated measurements with manual measurements, the mean absolute percentage error (MAPE) in the plant height and the plant fresh weight was 2.71% (1.08cm with an average plant height of 40.07cm) and 10.06% (1.41g with an average plant fresh weight of 14.06g), respectively. The root mean square error (RMSE) was 1.37cm and 1.79g for the plant height and plant fresh weight, respectively. The correlation coefficients were 0.95 and 0.96 for the plant height and plant fresh weight, respectively. Additionally, the proposed methodology, including plant reconstruction, model processing and trait extraction, required only approximately 20s on average per plant using parallel computing on a graphics processing unit (GPU), demonstrating that the methodology would be valuable for a high-throughput phenotyping platform.

Microbatteries are currently the best choice to power microelecronic devices. To maximize both energy density and power density of microbatteries within the areal footprint, the three-dimensional (3D) microbattery architectures have been proposed, comprising a 3D matrix of components (cathode, anode and electrolyte) arranged in either a periodic array or an aperiodic ensemble. As one of the key components, the cathode is vital to the electrochemical performance of microbatteries and the fabrication of 3D cathode is still challenging. This review describes recent advances in the development of 3D self-supported metal oxides as cathodes for lithium-ion microbatteries. Current technologies for the design and morphology control of 3D cathode fabricated using template, laser structuring and 3D printing are outlined along with different efforts to improve the energy and power densities.

Enhanced tubes are widely used in shell and tube condensers of refrigeration, air-conditioning and process industries because of their high heat transfer performance. In this study, condensation heat transfer tests were conducted for four three-dimensional enhanced tubes having different fin density and fin height using R-134a. The satuartion temperature was 40${}^{\circ }$C. The heat transfer was significantly enhanced by the present enhanced geometry. At 5K wall subcooling, the enhancement ratio is 6.3 for 1654fpm, 4.6 for 1575fpm, 4.0 for 1496fpm and 3.3 for 1102fpm tubes. Within the geometric variation of the present study, the condensation heat transfer coefficient increased with the increase of fin density and of fin height. The heat transfer coefficients of the 1654fpm tube were approximately the same as those of the commercial three-dimensional enhanced tube Turbo-C.

In this paper, a three-dimensional model of the generalized thermoelasticity with one relaxation time and variable thermal conductivity is constructed. The resulting nondimensional governing equations, together with the Laplace and double Fourier transform techniques have been applied to a three-dimensional half-space subjected to thermal loading with rectangular pulse and traction free surface. The inverses of double Fourier transforms and Laplace transforms have been obtained numerically. Numerical results for the temperature increment, the invariant stress, the invariant strain, and the displacement are represented graphically. The variability of thermal conductivity has significant effects on all the studied fields.