Non-regular Shape Research Articles

Rationality in pier geometry of Kintaikyo Bridge from viewpoint of river engineering

The Kintaikyo Bridge, with its elegant wooden arches, has a unique pier shape and continues to be loved by residents and visitors alike. Although this bridge is an active footbridge and an important landscape element along with the Nishikigawa River and its river beach, the rationality or irrationality of the shape of its piers remains unknown. This paper is intended to clarify the river engineering characteristics of the piers for the first time by conducting 1/129 scale hydraulic model experiments. The shapes tested were a perfect spindle shape (which has been adopted as a common theory for many years) and a reconstructed current shape based on the spindle shape, and for comparison, an oval and a non-regular hexagon shape with the same width and area. The current shape, along with the spindle shape, suppressed the water level rise around the pier more than the others. As for the riverbed fluctuation, the current shape slightly increased the scour more than the others, but it also maximized the sedimentation around the scoured part. In other words, the current shape has the potential to facilitate the procurement of sediment for post-flood restoration. In addition, the current shape overwhelmingly reduced the statistical dispersion associated with the experiment, suggesting that it stabilizes the trend of riverbed fluctuation even during actual floods. Based on the results, the future conservation of the Kintaikyo Bridge was also discussed.

Enhanced Desalination Performance of Capacitive Deionization Using Nanoporous Carbon Derived from ZIF-67 Metal Organic Frameworks and CNTs.

Capacitive deionization (CDI) based on ion electrosorption has recently emerged as a promising desalination technology due to its low energy consumption and environmental friendliness compared to conventional purification technologies. Carbon-based materials, including activated carbon (AC), carbon aerogel, carbon cloth, and carbon fiber, have been mostly used in CDI electrodes due their high surface area, electrochemical stability, and abundance. However, the low electrical conductivity and non-regular pore shape and size distribution of carbon-based electrodes limits the maximization of the salt removal performance of a CDI desalination system using such electrodes. Metal-organic frameworks (MOFs) are novel porous materials with periodic three-dimensional structures consisting of metal center and organic ligands. MOFs have received substantial attention due to their high surface area, adjustable pore size, periodical unsaturated pores of metal center, and high thermal and chemical stabilities. In this study, we have synthesized ZIF-67 using CNTs as a substrate to fully utilize the unique advantages of both MOF and nanocarbon materials. Such synthesis of ZIF-67 carbon nanostructures was confirmed by TEM, SEM, and XRD. The results showed that the 3D-connected ZIF-67 nanostructures bridging by CNTs were successfully prepared. We applied this nanostructured ZIF-67@CNT to CDI electrodes for desalination. We found that the salt removal performance was significantly enhanced by 88% for 30% ZIF-67@CNTs-included electrodes as compared with pristine AC electrodes. This increase in salt removal behavior was analyzed by electrochemical analysis such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements, and the results indicate reduced electrical impedance and enhanced electrode capacitance in the presence of ZIF-67@CNTs.

A coupled photogrammetric–finite element method approach to model irregular shape product freezing: Mozzarella cheese case

The freezing process can be industrially performed to extend shelf life and to improve exportability of Italian high-moisture Mozzarella cheese. This cheese is usually characterized by a non-regular spheroidal shape that may be responsible for local differences of temperature on the surface and that can influence the overall freezing time. In this work, Mozzarella freezing was modelled by coupling the finite element method and a photogrammetric procedure that permitted to reconstruct the three-dimensional domain of the product. Computational models were validated by performing experimental trials, and results were accurate (root mean square error<1.47°C). With the photogrammetric technique it was possible to estimate volume, surface area, shape and size of the cheeses, and to study temperature–surface distribution that was found to be non-homogeneous. Freezing models highlighted that the surface area-to-volume ratio of the product, that ranged between 1.09 and 1.15cm−1, is one of the most critical parameters that define the freezing time of the cheese. A geometrical approximation of the cheese based on the surface area-to-volume ratio, showed good accuracy in terms of freezing times. These models can be valuable for Mozzarella cheese freezing optimization and design, to recover efficiency and to improve quality.

Soybean Oil Transesterification for Biodiesel Production with Micro-Structured Calcium Oxide (CaO) from Natural Waste Materials as a Heterogeneous Catalyst

In this study, micro-structured calcium oxide obtained from the calcination (850 °C for 3 h) of Gallus gallus domesticus (chicken) eggshells was used as a catalyst in the transesterification of soybean oil. This catalyst was characterized by Scanning Electron Spectroscopy (SEM) methods. The structure of the obtained CaO showed several agglomerates of white granular solids with a non-regular and unsymmetrical shape. In terms of calcium oxide catalytic activity, three different catalyst loadings (1%wt, 3%wt, and 5%wt) were tested for the same reaction conditions, resulting in transesterification yields of 77.27%wt, 84.53%wt, and 85.83%wt respectively. The results were compared to the current literature, and whilst they were lower, they were promising, allowing us to conclude that the tendency of yield improvement for this reaction, when the size range of catalyst particles is to be reduced to a nano scale, can be verified.

Accuracy of ITK-SNAP software for 3D analysis of a non-regular topography structure.

To evaluate the accuracy of ITK-SNAP software for measuring volumes of a non-regular shape structure, using cone beam computed tomography (CBCT) scans, besides for developing a mathematical model to correct the software measurement error in case it existed. A phantom made by moulding a rubber duck's head was filled with total (38,000 mm3) and partial volumes of water (7000 mm3, 14,000 mm3, 21,000 mm3, 28,000 mm3 and 35,000 mm3), which constituted the gold standards. The sound phantom and the phantom filled with different volumes of water were scanned in a Picasso Trio CBCT unit set at 80 kVp, 3.7mA, 0.2 mm3 voxel and 12 × 8.5cm field of view. Semi-automatic segmentation was performed with ITK-SNAP 3.0 software by two trained oral radiologists. Linear regression analyzed the relation between ITK-SNAP calculated volumes and the gold standard. Intraclass correlation coefficient was applied to analyze the reproducibility of the method. Significance level was set at 5%. Linear regression analysis showed a significant relationship between ITK-SNAP volumes and the gold standard (F = 22,537.3, p < 0.0001), with an R2 of 0.9993. The average error found was 4.7 (± 4.3) %. To minimize this error, a mathematical model was developed and provided a reduction of it. ICC revealed excellent intra-examiner agreements for both examiners 1 (ICC = 0.9991, p < 0.0001) and 2 (ICC = 0.9989, p < 0.0001). Likewise, inter-examiner agreement was excellent (ICC = 0.9991, p < 0.0001). The software showed to be accurate for evaluating non-regular shape structures. The mathematical model developed reduced an already small error on the software's measurements.

Radiative Transfer, Non-transparency, Stability Against Quench in Superconductors and Their Correlations

Radiative transfer calculations are presented for multi-filamentary BSCCO 2212 and 2223 and for thin film-coated YBaCuO 123 superconductors. A strictly radiative view allows conductor morphology of these superconductors to be interpreted as particulate or quasi-particulate objects. Problems then arising from non-regular particle shape, missing refractive indices, dependent scattering and superconductor material (diamagnetic) properties are solved in a multi-step, approximation approach. Both types of conductors are shown to be non-transparent to mid-IR radiation. Non-transparency may become critical for superconductor stability. The obtained extinction cross sections converge near the phase transition. A substantial difference of extinction properties between the superconducting and normal conducting state thus cannot be observed. As a first corollary from non-transparency, application of the additive approximation for the total thermal conductivity used in previous numerical calculations of the BSCCO and YBaCuO superconductors is confirmed. Second, within transit time intervals, the length of which depends on optical thickness, no uniform equilibrium conditions of electron pair density within the conductor cross section and near critical temperature are observed. Phase transition does not proceed uniformly, neither spatial nor temporal, and the order (succession on time scales) of local events (temperature variations, quench), in extreme cases, is completely dissolved. As another corollary, non-transparency even makes the existence of uniquely defined, physical time scales doubtful in a superconductor. The obtained results are expected to improve existing stability models and will be of practical value for future materials development.

Integration of Novel Shape Templates During Human Spatial Navigation Leads to Prototype Extraction

The ability to rapidly form stable representations of novel environments is crucial for successful navigation, yet the majority of studies involve environments composed of overlearned geometrical configurations, like rectangles. To address this gap in knowledge, participants underwent extensive pre-training with a non-regular shape and then navigated environments organized around this shape and other parametrically related novel non-regular shapes. Concurrent high-resolution fMRI indicated that, consistent with past studies on regular geometries, hippocampal neural activation patterns differentiated these environments, although with a bias toward the pre-exposed shape. Surprisingly, we found that hippocampal representations were most stable for the average geometric configuration of the novel environments, with subsequent map-drawing accuracy predictive of the stability of this average. Our findings challenge existing models of memory and navigation by suggesting unique mechanisms underlie the formation of novel spatial contexts, which may only become apparent under conditions that directly manipulate the influence of prior knowledge.

Failure Assessment Diagram (FAD) analysis of fatigue test results for X65 welded joints

Offshore pipelines transfer oil and gas from seabed to production facility on the surface. The long pipelines are formed by welding of pipe segments, where these welded joints are a source of stress concentration and defects from which fatigue cracks can grow. This work aims to study the behaviour of deep fatigue cracks. In this current work, finite-element based on a parametric study of four-point bending is used to assess the stress intensity factors (SIFs) of deep surface cracks in X65 specimens, while considering local limit load the remaining load bearing ligament. These deep cracks take on a non-regular shape and have widths that exceed that of the specimen. They will be compared to empirical expressions from derived standards such as British Standards BS7910, which may be more conservative. The existing large flaw is also assessed via the failure assessment diagram (FAD). The effects of limit load solutions and reference stresses used to determine the FAD diagram will be discussed.

Morphology effects on the bandgap of silicon nanocrystals—Numerically modelled by a full multi-grid method

Silicon nanocrystals embedded in a dielectric matrix have been considered a potential candidate for many optoelectronic and photovoltaic applications and have been under vigorous study in recent years. One of the main properties of interest in this application is the absorption bandgap, which is determined by the quantum confinement of silicon nanocrystals. The ability to predict the absorption bandgap is a key step in designing an optimum solar cell using this material. Although several higher level algorithms are available to predict the electronic confinement in these nanocrystals, most of them make regular-shape assumptions for the ease of computation. In this work, we present a model for the accurate prediction of the quantum confinement in silicon nanocrystals of non-regular shape by employing an efficient, self-consistent Full-Multi-Grid method. Confined energies in spherical, elongated, and arbitrarily shaped nanocrystals are calculated. The excited level calculations quantify the wavefunction coupling and energy level splitting arising due to the proximity of dots. The splitting magnitude was found to be as high as 0.1 eV for the 2 nm size silicon quantum dots. The decrease in confinement energy due to the elongation of dots was found to be more than 0.2 eV, and the trend was similar for different dielectric materials. Theoretical predictions were compared to the results from optical and structural characterisation and found to be in agreement. The loss of degeneracy in highly asymmetric quantum dots, such as a “horse-shoe” shaped quantum dot, significantly affects the excited state energies.

A Computational Model for Surface Welding in Covalent Adaptable Networks Using Finite-Element Analysis

Covalent adaptable network (CAN) polymers can rearrange their macromolecular network by bond exchange reactions (BERs), where an active unit attaches to and then replaces a unit in an existing bond and forms a new bond. When such macromolecular events occur on the interface, they can contribute to surface welding, self-healing, and recycling of thermosetting polymers. In this paper, we study the interfacial welding and failure of CANs involving both interfacial normal and shear stresses. To do this, we incorporate our recently developed multiscale model for surface welding of CANs with a cohesive zone modeling approach in finite-element method (FEM) simulation. The developed FEM paradigm involves a multiscale model predicting the interfacial chain density and fracture energy, which are transferred to a cohesive zone model to establish the surface traction-separation law. The simulations show good agreement with experimental results on the modulus and strength of welded samples. They also provide understanding of the interactions between surface welding and material malleability in determining the final mechanical properties of polymer structures. The developed FEM model can be applied to study other complex welding problems, such as polymer reprocessing with nonregular particle size and shape.

Crystal plasticity finite element simulation of crack growth in single crystals

A new method for 3D simulation of crack growth in single crystals is proposed. From Crystal Plasticity Finite Element (CPFE) computations of a pre-cracked single crystal, a damage indicator based on the accumulated slip, the resolved shear stress and the normal stress on each slip system is calculated at each integration point and for every time increment. The crack growth direction is then determined in 3D by analysing the damage indicator in the region around the crack front. The crack is extended via remeshing at each propagation event. At this point the CPFE computation is restarted, using the new crack configuration. Two examples in BCC single crystals featuring different crystal orientations and slip systems show the crack propagation simulations under monotonic loading over distances comparable to the crystal size and with non-regular crack shape and path.

Optical near-field enhancement at a metal tip probed by a single fluorophore

The optical near-field in the vicinity of a metal tip is mapped using a single-molecule optical probe. We observe an enhancement of the fluorescence signal by a factor of 5.7±0.3, clearly larger than the fourfold enhancement that can arise from constructive interference if the tip acts as a simple mirror. Considering the tip apex as a nanoparticle of nonregular shape, we suggest that, in the case of gold tips, the enhancement is due to resonant plasmon excitation. Consistently, no enhancement has been observed using Pt/Ir tips.

Non-regularly shaped plasmon resonant nanoparticle as localized light source for near-field microscopy.

We study numerically two-dimensional nanoparticles with a non-regular shape and demonstrate that these particles can support many more plasmon resonances than a particle with a regular shape (e.g. an ellipse). The electric field distributions associated with these different resonances are investigated in detail in the context of near-field microscopy. Depending on the particle shape, extremely strong and localized near-fields, with intensity larger than 105 that of the illumination wave, can be generated. We also discuss the spectral dependence of these near-fields and show that different spatial distributions are observed, depending which plasmon resonance is excited in the particle.

Spectral response of plasmon resonant nanoparticles with a non-regular shape

We study the plasmon resonances of 10 (nm)--100 (nm) two-dimensional metal particles with a non-regular shape. Movies illustrate the spectral response of such particles in the optical range. Contrary to particles with a simple shape (cylinder, ellipse) non-regular particles exhibit many distinct resonances over a large spectral range. At resonance frequencies, extremely large enhancements of the electromagnetic fields occur near the surface of the particle, with amplitudes several hundred-fold that of the incident field. Implications of these strong and localized fields for nano-optics and surface enhanced Raman scattering (SERS) are also discussed.

Optimized secondary concentrators for a partitioned central receiver system

We present secondary concentrators with non-regular shapes for increasing the concentration of radiation from a given field of heliostats, well suited for partitioning the receiver into several units, arranged side by side. For a general heliostat field with a non-axisymmetric directional distribution of the radiation at the entrance aperture of the secondary concentrator, concentrators with non-regular shape can significantly increase the concentration as compared to their symmetric analogs. Our optimizations indicate best results for concentrators based on rectangular entrance and exit apertures. The concentration may be increased by a factor of 2.3 at an optical efficiency of 90%. If the shape of the exit aperture is required to be close to circular, concentrators based on non-regular hexagonal apertures may reach concentration higher than their symmetric analogs by a factor of 1.3. For the given radiation, concentrators with polygonal apertures perform significantly better than concentrators with smooth elliptic apertures.

An interobject distance measure based on medial axes retrieved from discrete distance maps

A method that measures the distance between extended objects of nonregular shape is presented. The distance measure is an average of a set of minimal point-to-point distances between the borders of the objects. The set of points is collected with a well-defined criterion based on processing of distance values on a connected medial axis formed between the objects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Non-regular depth profiles of light ions implanted into organic polymer films

3He and 10B implantation profiles in several polymers are examined by means of a NRA technique with thermal neutrons. 200 keV 10B ions were implanted into different kinds of polymers. In all the cases, it is found that the resulting depth profiles have a nonregular shape. A fraction which depends on the target material distributes along a tail directed towards the surface. Due to the nonregularity of the depth profiles, we present only the most probable ranges and the full width half maxima of the distributions. These results are compared with the Ziegler, Biersack and Littmark prediction. On the other hand, 3He implanted into Mylar is found to be mobile at room temperature, as after ten days no trace of the implanted material is found in the substrate.

Implanted boron depth profiles in the AZ111 photoresist

The isotope 10B has been implanted into the photoresist AZ111 in the 30–150 keV energy range. The corresponding depth profiles have been analyzed using the 10B(n,α)7Li reaction. At 60 keV, the profile changes from a regular shape to one with an additional tail directed towards the surface. Despite the nonregular shape of the ion distributions, it is possible to extract the characteristic range parameters such as projected range Rp, most probable range R̂, and full width at half-maximum. Good agreement is found between the experimental results and the calculations by Ziegler, Biersack, and Littmark (ZBL). It is also shown that the tail distribution follows closely the ZBL calculated ionization profiles. A tentative explanation of this behavior is given.