Equal Spacing Research Articles

A new type of WENO scheme in SPH for compressible flows with discontinuities

In the past few decades, the weighted essentially non-oscillatory (WENO) scheme has been widely used in mesh-based methods and has achieved great success, but its application to the smoothed particle hydrodynamics (SPH) is still limited. In this paper, a simple and accurate implementation of the WENO scheme to the SPH method is proposed for solving compressible flows with discontinuities and small-scale structures. In the proposed scheme, several equal spacing points along the line joining two interacting particles are selected to constitute candidate stencils. However, due to the Lagrangian characteristic of SPH, some points may be lost. To solve this problem, we first search the particles closest to these missing points, and then the first-order Taylor series expansion is used to obtain the corresponding primitive variables of these points. After that, through the WENO strategy, the left and right states at the interface between two interacting particles are reconstructed. Finally, the inter-particle interactions are determined by using Roe’s approximate Riemann solver. Several numerical tests show that the proposed WENO-SPH method is robust and able to accurately capture shockwaves, and benefiting from the low-dissipation property, it also has a good performance in resolving small-scale structures in flows.

Effects of row spacing and sowing rate on vertical distribution of photosynthetically active radiation, biomass, and grain yield in winter wheat canopy.

To clarify the effects of row spacing and sowing rate on the vertical distribution of canopy PAR, biomass, and grain yield in winter wheat, a field experiment was conducted without increa-sing water and fertilizer input. There were two row spacing modes, R1 (equal spacing, 20 cm+20 cm) and R2(wide and narrow row spacing, 12 cm+12 cm+12 cm+24 cm), and three sowing rates, D1 (low, 120 kg·hm-2), D2 (medium, 157.5 kg·hm-2), D3 (high, 195 kg·hm-2). The canopy photosynthetically active radiation (PAR) interception and utilization rate in different heights, population photosynthetic capacity, biomass, and grain yield were measured during the main growth stages of winter wheat. The results showed that both total PAR interception and upper layer PAR interception of winter wheat canopy under R1 treatment were significantly higher than those in R2 treatment, but those of the middle layer and lower layer were higher in R2 than in R1, and with significant difference in the middle layer. From flowering to maturity, the photosynthetic potential (LAD), population photosynthetic rate (CAP), PAR conversion rate, and utilization rate in R2 were all significantly higher than those in R1 under the same sowing rate, with the highest value under R2D2 treatment. With the increasing sowing rate, the population biomass (BA) and leaf biomass (BL) at different layers increased, but the individual biomass (BP) showed an opposite trend. Under the same sowing rate, BA, BL and BP in R2 were higher than that in R1 after the flowering stage. Among them, BA and BP had significant difference in row spacing treatments at the maturity stage, with significant difference between the two row spacing treatments being observed in BL of the middle and lower layers under D2 and D3 sowing rates. The spike number, grain number per spike, 1000-kernel weight, and grain yield of winter wheat among different treatments were the highest in R2D3, R2D1, R2D1, and R2D2, respectively. The 1000-kernel weight, grain number per spike and grain yield in R2 treatment were significantly higher than R1. In summary, the PAR interception in the middle and lower layers of winter wheat canopy was improved by changing row spacing, with positive consequence on the photosynthetic capacity of individual plant and population, PAR utilization and transformation efficiency, which finally increased biomass and grain yield. Therefore, optimizing the field structure and shaping the ideal population photosynthetic structure should pay more attention during the high-yield cultivation of winter wheat. Making full use of light resources per unit land area and excavating the photosynthetic production potential of crops were also critical to achieve high yield and efficiency. In this experiment, the population photosynthetic capacity, photosynthetic effective radiation utilization rate, and yield were the highest under the treatment of R2D2.

Is Expanding Spacing More Effective than Equal Spacing for L2 Vocabulary Learning

Is Expanding Spacing More Effective than Equal Spacing for L2 Vocabulary Learning

Acoustic finite-difference modeling beyond conventional Courant-Friedrichs-Lewy stability limit: Approach based on variable-length temporal and spatial operators

Conventional finite-difference (FD) methods cannot model acoustic wave propagation beyond Courant-Friedrichs-Lewy (CFL) numbers 0.707 and 0.577 for two-dimensional (2D) and three-dimensional (3D) equal spacing cases, respectively, thereby limiting time step selection. Based on the definition of temporal and spatial FD operators, we propose a variable-length temporal and spatial operator strategy to model wave propagation beyond those CFL numbers while preserving accuracy. First, to simulate wave propagation beyond the conventional CFL stability limit, the lengths of the temporal operators are modified to exceed the lengths of the spatial operators for high-velocity zones. Second, to preserve the modeling accuracy, the velocity-dependent lengths of the temporal and spatial operators are adaptively varied. The maximum CFL numbers for the proposed method can reach 1.25 and 1.0 in high velocity contrast 2D and 3D simulation examples, respectively. We demonstrate the effectiveness of our method by modeling wave propagation in simple and complex media.

Deployable Convex Generalized Cylindrical Surfaces Using Torsional Joints

Abstract The ability to deploy a planar surface to a desired convex profile with a simple actuation can enhance foldable or morphing airfoils, deployable antennae and reflectors, and other applications where a specific profile geometry is desired from a planar sheet. A model using a system of rigid links joined by torsional springs of tailorable stiffness is employed to create an approximate curved surface when two opposing tip loads are applied. A system of equations describing the shape of the surface during deployment is developed. The physical implementation of the model uses compliant torsion bars as the torsion springs. A multidimensional optimization algorithm is presented to place joints to minimize the error from the rigid-link approximation and account for additional manufacturing and stress considerations in the torsion bars. A proof is presented to show that equal torsion spring spacing along the horizontal axis of deployed parabolic profiles will result in minimizing the area between the model’s rigid-link approximation and smooth curve. The model is demonstrated through the physical construction of a deployable airfoil surface and a metallic deployable parabolic reflector.

Symmetries versus the spectrum of $ J\bar T$-deformed CFTs

It has been recently shown that classical J\bar TJT‾ - deformed CFTs possess an infinite-dimensional Witt-Kac-Moody symmetry, generated by certain field-dependent coordinate and gauge transformations. On a cylinder, however, the equal spacing of the descendants’ energies predicted by such a symmetry algebra is inconsistent with the known finite-size spectrum of J\bar TJT‾ - deformed CFTs. Also, the associated quantum symmetry generators do not have a proper action on the Hilbert space. In this article, we resolve this tension by finding a new set of (classical) conserved charges, whose action is consistent with semiclassical quantization, and which are related to the previous symmetry generators by a type of energy-dependent spectral flow. The previous inconsistency between the algebra and the spectrum is resolved because the energy operator does not belong to the spectrally flowed sector.

Effects of SiC Fibers and Laminated Structure on Mechanical Properties of Ti-Al Laminated Composites.

Ti/Ti–Al and SiCf-reinforced Ti/Ti–Al laminated composites were fabricated through vacuum hot-pressure using pure Ti foils, pure Al foils and SiC fibers as raw materials. The effects of SiC fiber and a laminated structure on the properties of Ti–Al laminated composites were studied. A novel method of fiber weaving was implemented to arrange the SiC fibers, which can guarantee the equal spacing of the fibers without introducing other elements. Results showed that with a higher exerted pressure, a more compact structure with fewer Kirkendall holes can be obtained in SiCf-reinforced Ti/Ti–Al laminated composites. The tensile strength along the longitudinal direction of fibers was about 400 ± 10 MPa, which was 60% higher compared with the fabricated Ti/Ti–Al laminated composites with the same volume fraction (60%) of the Ti layer. An in situ tensile test was adopted to observe the deformation behavior and fracture mechanisms of the SiCf-reinforced Ti/Ti–Al laminated composites. Results showed that microcracks first occurred in the Ti–Al intermetallic layer.

Effects of Mechanically Transplanting Methods and Planting Densities on Yield and Quality of Nanjing 2728 under Rice-Crayfish Continuous Production System

Rice–crayfish continuous production system offers high economic and ecology benefits, which developed rapidly in China. To investigate the effects of different mechanical transplanting methods and planting densities on rice yield and quality, Nanjing 2728 was used to determine rice growth performance under mechanically transplanted carpet seedling (MTCS) with equal row spacing (30 cm) at five spacings and mechanically transplanted pot seedling (MTPS) with wide and narrow rows (23 + 33 cm) at five spacings. The results showed that MTPS presented significantly higher rice yields than MTCS as more spikelets per panicle. Rice yields of both mechanical transplanting methods first increased and then reduced with decreasing planting density, and its highest value was obtained at 77.9 × 104 seedlings ha−1. Compared with MTCS at the same stage, rice tiller dynamics of MTPS first increased and then decreased. Additionally, its dry matter accumulation per stem at jointing, heading, and maturity stages, leaf area index, photosynthetic potential, crop growth rate, and net assimilation rate were all significantly higher relative to MTCS. For each mechanical transplanting method, dry matter accumulation per panicle, leaf area index, photosynthetic potential, crop growth rate, and net assimilation rate from the sowing to jointing stages declined with decreasing planting density, while dry matter accumulation per stem and net assimilation rate from the heading to maturity stages increased. Compared with MTCS, MTPS significantly improved rice milling and appearance quality, decreasing density was also beneficial to rice milling and appearance quality, while grain content of amylose and protein were not sensitive to both transplanting method and planting density. Consequently, MTPS with 13.8 cm plant spacing is a suitable mechanical transplanting method for Nanjing 2728 to obtain better yield and quality under rice–crayfish continuous production system.

Majorana and non-Majorana modes in a nanowire in partially proximity to a superconductor

We investigate the Majorana and non-Majorana modes in a nanowire in partial proximity to a superconductor, in which the gapped superconductor will play different roles in different topological regimes. In the gapped topological superconducting phase, it plays the role of a topological barrier, which confines some localized edge modes in the quantum dot (QD) region. The probability for the wave function in this region can approach unity by tuning the system parameters. These low-lying localized modes exhibit linear spectra with equal energy level spacing, with eigenvalues εn=vFnπ/(2L), where vF is the Fermi velocity, L is the size of the QD region, and n∈Z. We demonstrate these features using a spinless nanowire in proximity to a p-wave superconductor and a spin–orbit coupled semiconductor nanowire in proximity to a s-wave superconductor. A simple picture is proposed to understand the behavior of these results. However, in the trivial superconducting phase when both bands are occupied in the spin–orbit coupled mode, we observe some non-Majorana modes, with complicated low-lying excited spectra, which resembles that reported in experiments. These differences are rooted deeply in the bulk-edge correspondence. These observations may be able to facilitate the identification of Majorana zero modes in experiments.

DEVELOPEMENT OF A VEGETABLE DRYER

A Vegetable dryer of dimension 1.50 m (high) x 0.72 m (wide) x 0.59 m (breadth) was developed using mild steel iron and its performance evaluated. The device consists of a drying chamber with three drying trays; fans incorporated for heat circulation, a heating element of 2000 W, four swivel caster rollers for ease of mobility, a thermostat to regulate the heat generated in the drying chamber and a thermo-gauge inserted to monitor the temperature in the drying chamber. The vegetable dryer has a drying capacity of 34 kg and three compartments of 0.25 m equal spacing. The dryer is partitioned at 0.75 m, 0.1 m and 1.25 m from the heating element, with the first (bottom) tray, the second tray (middle) and the third (upper) respectively. The device performance was evaluated under no-load and load conditions at 50 °C, 60 °C, and 80 °C temperatures with three replications. Results obtained under no-load indicated that temperatures very close to the preset values (by the thermostat) were attained within 5 mins. Under load condition, the dryer was evaluated by drying 16.74 kg of tomatoe slices at 50 °C, 60 °C, and 80 °C. Weight reduction (degree of moisture loss) from the slices was recorded at intervals of 1hour until a nearly constant weight was obtained. The result revealed that the dryer has a mean drying efficiency of 80.6 % and drying rate of 0.02 kg/hr. At a drying time of 10 hours and temperatures of 50 °C and 60 °C, 16.74 kg of tomatoes were reduced to 1.23 kg and 1.13 kg representing 93 % (wb) of removed moisture, while a final weight of 1.08 kg dry matter was obtained from the same starting weight of wet tomatoes at 80 °C representing 94 % (wb) of moisture loss for the same drying time. ANOVA studies indicated that the effect of temperature and tray level on drying of vegetable (tomatoes) were highly significance at (P< 5 %). The dried vegetable (tomatoes) is free from dust and any form of contamination making it healthy for consumption.

Performance reliability analysis and optimization of lithium-ion battery packs based on multiphysics simulation and response surface methodology

Reliability optimization has always been an important topic in the application of lithium-ion batteries in electric vehicles. To optimize the redundancy and layout design of battery packs accurately and efficiently, a novel reliability optimization method based on a multiphysics coupling simulation and a response surface methodology is proposed. An electrochemical-thermal-fluid dynamics model, a temperature-dependent stochastic degradation model and a multistate performance reliability model are developed. A response surface method with the Box-Behnken design method is applied to reduce the number of simulation trials. Then, the redundancy scheme and two layouts of a battery pack are optimized, followed by a sensitivity analysis of the design parameters. The results show that a large spacing in the direction of air flow contributes to improving system reliability. In this case, for the layout of a cross arrangement with equal spacing, the optimal reliability design scheme of a 5 × 5 parallel series with optimal design parameters can improve the cycle life from approximately 1989 to 2933 when taking 90% system reliability as the criterion. The collaborative optimization of redundancy and layout is of great importance to extend the service life and improve the system reliability of battery packs.

Numerical Study of Supersonic Mixed Compression Air Intake With an Array of Air Jets

Abstract Computational study of flow physics inside the mixed compression air intake has been carried out with and without air jets (AJs) at design Mach number of 2.2. Reynolds-averaged Navier–Stokes (RANS) equations were solved with k–ω turbulence model by using commercially available software ansys. The scope of this research is to improve the flow field inside the air intake and efficiency of supersonic air intake by implementing AJs on the ramp surface. An array of AJs containing two, four, and five AJ holes, respectively, of 1 mm each has been made on the ramp surface perpendicular to the flow with equal spacing between them. The injection pressure through AJ has been kept constant for all the cases. Flow distortion (FD) and total pressure recovery (TPR) were selected to measure the performance of air intake. All the simulations have been performed at a back-pressure ratio of 6. The results obtained suggest that implementation of proper spacing between AJs can improve the performance of air intake due to the mixing of vortices generated by AJs with freestream flow. It is revealed that an array of AJs containing four holes on ramp surface works best and helps in controlling the shock-induced separation.

Characteristic of Fault Structures in the south coastal Zone of Taizhou Based on High-Precision Aeromagnetic Data

The south coastal zone of Taizhou lies on the magmatic rock belt of southeast coast of China, which has complex regional geological structure, intense tectonic movement and frequent magmatic activities. Based on the latest high-precision aeromagnetic data, integrated interpretation was completed, combining with regional geology, regional gravity and magnetic susceptibility information. According to the block features in different zones of the RTP aeromagnetic data, the magnetic field characteristics and the relationship with the structure division were described in detail. It showed that the different characteristics of magnetic field is the concentrated reflection such as tectonic movement, magmatic activity and stratigraphic distribution, and the fault structure was inferred and studied, especially the deep and large fault structures. The fault structures were mainly distributed in NE, NNE and NW direction, with approximately equal spacing distribution. The magnetic anomaly is mainly characterized by the boundary, gradient zones and beaded anomalies in different magnetic field. The faults act not only as the important tectonic boundaries in this region, but also the important tectonic belts, controlling the distribution of mineralization. Under the interaction of these faults, they form the basic structural pattern of East-West zone and North-South block; Among them, the NE faults have the largest scale and obviously control over different magnetic field and magmatic activity. The results presented in the paper can provide reference for further study on the distribution and activity characteristics of magmatic rocks in the coastal zone.

Application of Cubic B-Spline Curves for Hull Meshing

This paper describes the development of a regular hull meshing code using cubic B-Spline curves. The discretization procedure begins by the definition of B-Spline curves over stations, bow and stern contours of the hull plan lines. Thus, new knots are created applying an equal spaced subdivision procedure on defined B-spline curves. Then, over these equal transversal space knots, longitudinal B-spline curves are defined and subdivided into equally spaced knots, too. Subsequently, new transversal knots are created using the longitudinal equally spaced knots. Finally, the hull mesh is composed by quadrilateral panels formed by these new transversal and longitudinal knots. This procedure is applied in the submerged Wigley hulls Series 60 Cb=0.60. Their mesh volumes are calculated using the divergence theorem, for mesh quality evaluation.

Design of aperiodic spherical antenna arrays for wideband performance

This paper illustrates a highly nonlinear problem related to the design of aperiodic antenna arrays using spherical geometry for maximum performance. This synthesis of aperiodic spherical antenna arrays considers two design cases: (1) aperiodic arrays with a nonuniform spacing between rings assuming equal element spacings on the same ring (ASANRUE case) and (2) aperiodic arrays with a nonuniform spacing between rings and between antenna elements of the same ring (ASANRNE case). This process is carried out by using the differential evolution (DE) optimization technique with the goal of finding the optimum angular position of each element on the elevation and azimuthal planes to achieve the maximum performance in terms of the side lobe level, directivity, and number of antenna elements used in the array for three design objectives: natural response of the radiation pattern, beam scanning, and the restriction of a minimum distance among elements. The innovative contribution of this paper is the application of the differential evolution algorithm to a nontrivial and highly complex design problem: the aperiodic element distribution over a spherical antenna arrangement. The advantage of this approach with respect to the state of the art on the topic of spherical array design is that a lower side lobe level and maximum directivity for a spherical antenna array can be obtained for aperiodic element distributions with a reduced number of antenna elements and hence a smaller radius, which means less complexity and lower fabrication costs. Simulation results based on CST Microwave Studio are provided to take mutual coupling into account.

Geometric model of lockstitch seam and prediction of thread consumption

This article presents models for predicting thread consumption of lockstitch seam. Various fabric and sewing thread parameters like fabric thickness, number of plies and sewing thread diameter were found to be the control factors in thread consumption calculations. New equations were developed from real stitch images by creating realistic stitch models of lockstitch seam. Lockstitch was modeled using elliptical, racetrack and circular geometry. Elliptical and racetrack models were verified by stitching samples at different feed rates by comparing actual and predicted thread consumption. Scatter plots of both models were made to check the level of accuracy with actual values. The proposed model offers relatively less error% as compared to previous rectangular and elliptical models. Racetrack model came out as the most simpler, versatile and accurate model of thread consumption calculation of lockstitch. It was found that circular model is suitable for the samples stitched at equal stitch spacing and fabric assembly thickness.

Learning With Fewer Images via Image Clustering: Application to Intravascular OCT Image Segmentation.

Deep learning based methods are routinely used to segment various structures of interest in varied medical imaging modalities. Acquiring annotations for a large number of images requires a skilled analyst, and the process is both time consuming and challenging. Our approach to reduce effort is to reduce the number of images needing detailed annotation. For intravascular optical coherence tomography (IVOCT) image pullbacks, we tested 10% to 100% of training images derived from two schemes: equally-spaced image subsampling and deep-learning- based image clustering. The first strategy involves selecting images at equally spaced intervals from the volume, accounting for the high spatial correlation between neighboring images. In clustering, we used an autoencoder to create a deep feature space representation, performed k-medoids clustering, and then used the cluster medians for training. For coronary calcifications, a baseline U-net model was trained on all images from volumes of interest (VOIs) and compared with fewer images from the sub-sampling strategies. For a given sampling ratio, the clustering based method performed better or similar as compared to the equally spaced sampling approach (e.g., with 10% of images, mean F1 score for calcific class increased from 0.52 to 0.63, with equal spacing and with clustering, respectively). Additionally, for a fixed number of training images, sampling images from more VOIs performed better than otherwise. In conclusion, we recommend the clustering based approach to annotate a small fraction of images, creating a baseline model, which potentially can be improved further by annotating images selected using methods described in active learning research.

Objective Structured Assessment of One-Day Surgical Suture Training Using a New Interactive Training Model

Objective: Evaluate the acquired surgical suture skills in veterinary medicine students after one-day training using new designed interactive surgical suture training (ISST) model. Methodology: 150 students were subjected to one-day surgical suture training. An objective structured assessment of technical skills (OSATS) task-specific checklist of 20 tasks was performed by three faculty members. A questionnaire was completed by each student. Results: tasks like square knot using hand tie, appropriate tension of knotting, correct edge distance, and equal spacing between sutures were well performed by final year students significantly. For other tasks, the final year student got better scores without distinct differences (P > 0.05). More than 90% of students confirmed the easy use of the ISST model and it simulated the real training. They strongly recommended the ISST training model. Conclusions: one-day surgical suture training was very suitable for undergraduate students; also the ISST model was convenient and easy to use during training. The OSATS’s checklist and the questionnaire were a reasonable way of objective assessment of surgical suture training. We suggest training surgical sutures on the ISST model and using the OSATS checklist with a questionnaire for training evaluation to all medical students and trainees.

Equal spacing control of particle via cycloidal beam (Invited)

Equal spacing control of particle via cycloidal beam (Invited)

Application of DIC method to modal vibration study for structure health monitoring of WT tower

ABSTRACT In recent years, wind power generation has been widely promoting by government policy. If the structural health of wind turbines can be screened effectively and quickly, the cost for operation and maintenance will be reduced. Such techniques are desirable since a vast number of wind turbines are scheduled to be operational in the next decade in Taiwan. This certainly sets the stage for research on developing the vibration analysis and monitoring techniques for the supporting structure of wind turbine (WT) systems. The authors demonstrated in a previous study that the defect location can be discovered using the frequency displacement mode output of the numerical model. In the current study, a PVC pipe with a mass attached at the top has been applied to validate the results of the numerical simulation. The displacement in three axes of each target of equal spacing on the PVC pipe is determined by using a technique based on digital image correlation. The resulted first modal vibration pattern in the frequency domain can be linked to the dynamic behaviour of this sized-reduced model of the wind turbine tower. The experimental data show that the proposed method has a good potential for damage assessment.