Hexagonal Geometry Research Articles

Comparison of Neutron-Physical Parameters of EPR and WWER-1500 using MCNP Computer Code

Three-dimensional calculations of the neutron-physical parameters were performed with the MCNP computer code for two models of a reactor core. The purpose was to determine the coefficient of reproduction of neutrons keff in each of the defined cases, as well as to qualitatively illustrate the neutron flux in axial and radial directions of the reactor core. A generalized analysis of the obtained results is performed, and it can be said that the prepared models, being relatively simple, meet the goal of this paper, namely presenting the basic principles of performing criticality calculations with the MCNP computer code. All calculations for this paper were performed with MCNP5, ver. 1.4. In the present paper, two active core models are considered – one for the EPR reactor and the other for the WWER-1500. Both projects are categorized as Generation 3 nuclear reactors. The following components of the core are included in both models: fuel elements, control rods and coolant. The fuel elements are presented as solid uranium dioxide cylinders coated with zirconium alloy. The fuel elements are grouped in fuel assemblies, in the case of the EPR reactor the fuel elements are arranged in a square grid, and in the case of the WWER-1500 reactor – in a triangular grid (hexagonal geometry). The limits of both models in the radial-azimuthal direction coincide with the inner diameter of the reactor vessel, and in the axial direction the limit is 56 cm in both directions from the end of the fuel elements. The calculations performed in this paper do not aim to quantify the distribution of neutron flux in the core, nor to find with great accuracy the coefficient of reproduction of neutrons keff at different stages of the reactor campaign. The calculations are made in order to verify the accuracy of the compiled input files. A criterion for this could be the demonstration of basic neutron-physical parameters, such as an increase in the value of keff with increasing the fuel enrichment and qualitative illustration of the change in the distribution of the neutron flux when introducing control rods in the core.

A hexagonal grid geometry system for applications in 3D graphics

A hexagonal grid geometry system for applications in 3D graphics

A hexagonal grid geometry system for applications in 3D graphics

A hexagonal grid geometry system for applications in 3D graphics

PERFORMANCE ANALYSIS OF HEXAGONAL UNIT CELL STENT DESIGN AND SINGLE-LAYERED MANUFACTURABILITY WITH FDM

İlaç salınımlı stentlerden sonra geliştirilen biyobozunur polimer esaslı stentler için yapılan ön klinik çalışmalardan elde edilen sonuçlara göre polimer stentlerin kullanılabilirliği sorgulanmaktadır. Polimer stentlerde strat kalınlığının yüksek olması ve mekanik özelliklerin zayıflığı nedeniyle tasarım ve malzeme iyileştirmesine gidilerek yeni modellerin ortaya çıkarılması üzerine araştırmalara devam edilmektedir. Balonla genişleyen stentlerde oluşan uç açılması arter içerisinde intimal ve medial katmanlara zarar vermektedir. Bu zarar, erken dönemde neointimal hiperplazi ve restenoza sebep olmaktadır. Metalik stent geometrilerinden biri olan Palmaz-Schatz birim hücre modelinde balonla genişleme esnasında uç açılması ve kısalma oranı meydana gelmektedir. Bu çalışmada, Palmaz-Schatz stent geometrisinin genişlemesiyle oluşturduğu geometri dikkate alınarak PLLA malzemeden altıgen birim stent geometrisinde yeni tasarım gerçekleştirilmiştir. Sonlu elemanlar simülasyonuyla, ince strat kalınlığında tasarlanan altıgen stendin genişlemesinde oluşan uç açılması ve kısalma oranı belirlenmiştir. Ayrıca, stent genişlemesinde üç katmanlı arter ve kalsifik plak yapısında meydana gelen doku hasarı ölçülmüştür. Altıgen geometrideki stentte oluşan uç açılması ve kısalma oranı Palmaz-Schatz modeline göre azaltılmıştır. Bununla birlikte, PLA/PHA karışımı malzemeden eriyik yığma modelleme ile altıgen stent geometrisinin 3B plaka baskısı tek katmanlı olarak üretilmesi sonrası ısıtıcı bir tubular tabla üzerinde sarılarak stent formuna getirilmiştir

Pengaruh parameter proses friction stir welding dengan material aluminium alloy AA6061-T651 terhadap distorsi dan kekerasan

Welding is a process of uniting two or more materials into a form of connection using heat energy. Friction Stir Welding (FSW) is a solid-state welding method that can produce high-quality welding joints for some materials with low weldability such as aluminum. The research objective was to determine the effect of process parameters on the distortion and resistance of aluminum AA6061-T651 material through the Brinell hardness test. The FSW tool used has a hexagonal pin geometry. The experimental design used the Taguchi method. This study uses 4 factors and each factor has 4 levels, the elements used are tool rotation speed, welding speed, tool tilt angle, and concave shoulder angle. The responses analyzed are distortion and hardness of the welded joint material. The effect of process parameters on the response was analyzed using ANOVA. The results of ANOVA on distortion obtained the value of Brinell hardness in the weld metal area, and in the TMAZ area. Specimen 13 with tool rotation speed parameters of 3022 rpm, welding speed of 43 mm/min, tool tilt angle of 3.5°, and concave shoulder angle of 2° with a distortion value of 0.117°. Then we get the results of the Brinell hardness of the weld metal which is close to the target of the base metal with the parameter tool rotation speed of 3022 rpm, welding speed of 90 mm/min, tool tilt angle of 2.5°, and concave shoulder angle of 8° with a Brinell hardness value of 75. 7 BHN, and the Brinell hardness value at TMAZ with tool rotation speed parameters of 1208 rpm, welding speed of 65 mm/min, tool tilt angle of 2.5°, and concave shoulder angle of 2° with a Brinell hardness value of 74.7 BHN.

Capability Extension of the High-Resolution Thermal-Hydraulic Code ESCOT for Hexagonal Geometry Core Multiphysics Analysis

The capability of the ESCOT pin-level nuclear reactor core thermal-hydraulic (T/H) code is extended for the multiphysics analysis of hexagonal geometry cores, and its performance is assessed by a code-to-code comparison with COBRA-TF (CTF). ESCOT is an accurate yet fast core T/H solution aimed at high-fidelity and high-resolution multiphysics core analysis in the framework of massively parallel computing platforms. The coupling of ESCOT with the nTRACER direct whole-core calculation code is enhanced for the hexagonal geometry handling needed for VVER core analysis. The lateral momentum terms, the turbulent mixing coefficient values, and the parallelization algorithms are modified to handle hexagonal geometry. The newly implemented ESCOT features are verified by comparing single-assembly and full-core steady-state standalone and coupled solutions for the VVER-1000 benchmark X-2 with CTF results. The ESCOT and CTF results show differences within an acceptable range in both standalone and coupled calculations. The computing time superiority due to the use of the drift flux model (DFM) of ESCOT over the CTF two-fluid model is corroborated with a speedup factor of 1.5. The use of the DFM together with the axial-radial parallelization capability of ESCOT makes ESCOT an ideal alternative to replace the simplified built-in T/H solver in nTRACER as the coupled simulation results demonstrate.

Experimental and numerical investigation on shell and coil storage unit with biodegradable PCM for modular thermal battery applications

Thermal energy storage (TES) in automotive applications is currently growing in importance. TES can visibly reduce primary energy consumptions, decrease CO2 emission, and improve thermal comfort in electric as well as hybrid vehicles. However, to meet the new ambitious target (15% reduction of CO2 emissions in the new cars until 2025) it is required to use plug-in electric vehicles. For this reason, this paper focuses on the optimization of key coil designing parameters. For the reference geometry, both experimental and CFD results have been presented. The optimization of coil geometrical parameters has been carried out based on numerical modelling. The prototype of TES is proposed as a honeycomb battery of individual modules. The results show that increasing the diameter and pitch of the coil decreases the melting and solidification time by 13.2% and 11.8% respectively for chosen geometry. CFD calculation has also been made for TES with a hexagonal geometry. The best results were obtained for the TES with a cylindrical shell. However, the results for the TES with hexagonal shell were, very similar (the difference was less than 1% of the share of the liquid phase). It is seen that presented coil optimization is also a good fit for TES with hexagonal shell geometry.

Spectral cube extraction for the VLT/SPHERE IFS

We present a new open-source data-reduction pipeline to reconstruct spectral data cubes from raw SPHERE integral-field spectrograph (IFS) data. The pipeline is written in Python and based on the pipeline that was developed for the CHARIS IFS. It introduces several improvements to SPHERE data analysis that ultimately produce significant improvements in postprocessing sensitivity. We first used new data to measure SPHERE lenslet point spread functions (PSFs) at the four laser calibration wavelengths. These lenslet PSFs enabled us to forward-model SPHERE data, to extract spectra using a least-squares fit, and to remove spectral crosstalk using the measured lenslet PSFs. Our approach also reduces the number of required interpolations, both spectral and spatial, and can preserve the original hexagonal lenslet geometry in the SPHERE IFS. In the case of least-squares extraction, no interpolation of the data is performed. We demonstrate this new pipeline on the directly imaged exoplanet 51 Eri b and on observations of the hot white dwarf companion to HD 2133. The extracted spectrum of HD 2133B matches theoretical models, demonstrating spectrophotometric calibration that is good to a few percent. Postprocessing on two 51 Eri b data sets demonstrates a median improvement in sensitivity of 80 and 30% for the 2015 and 2017 data, respectively, compared to the use of cubes reconstructed by the SPHERE Data Center. The largest improvements are seen for poorer observing conditions. The new SPHERE pipeline takes less than three minutes to produce a data cube on a modern laptop, making it practical to reprocess all SPHERE IFS data.

Convex subspaces of Lie incidence geometries

We classify the convex subspaces of all hexagonic Lie incidence geometries (among which all long root geometries of spherical Tits-buildings). We perform a similar classification for most other Lie incidence geometries of spherical Tits-buildings, in particular for all projective and polar Grassmannians, and for exceptional Grassmannians of diameter at most 3.Mathematics Subject Classifications: 51E24Keywords: Buildings, parapolar spaces, long root geometries, hexagonal Lie incidence geometries

The Continuum Between Hexagonal Planar and Trigonal Planar Geometries.

New heterometallic hydride complexes that involve the addition of {Mg-H} and {Zn-H} bonds to group 10 transition metals (Pd, Pt) are reported. The side-on coordination of a single {Mg-H} to Pd forms a well-defined σ-complex. In contrast, addition of three {Mg-H} or {Zn-H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X-ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.

The Continuum Between Hexagonal Planar and Trigonal Planar Geometries**

AbstractNew heterometallic hydride complexes that involve the addition of {Mg−H} and {Zn−H} bonds to group 10 transition metals (Pd, Pt) are reported. The side‐on coordination of a single {Mg−H} to Pd forms a well‐defined σ‐complex. In contrast, addition of three {Mg−H} or {Zn−H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X‐ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.

Synthesis of Ni doped barium hexaferrite by microemulsion route to enhance the visible light-driven photocatalytic degradation of crystal violet dye

The pristine and Ni doped BaNixFe12-xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) NPs have been fabricated via facile microemulsion approach and the impact of dopants was explored based dielectric, optical, structural and the photocatalytic properties of BaNixFe12-xO19 nanoparticles. X-ray diffraction and Raman study confirmed the formation of regular hexagonal geometry with space group P63/mmc with crystallite size in 32–50 nm range. Functional groups were identified using FTIR analysis. The remanence (Pr), saturation polarization (Ps) and coercivity (Hc) was explored by P-E loop analysis and the value of Pr and Ps was enhanced with the concentration of dopant. According to PL spectra, highly doped materials had a higher charge separation (e−- h+) and low recombination rate, which resulted in higher photocatalytic degradation activity of fabricated nanomaterials. The optical band gap was found to be 1.78 eV versus undoped (2.60 eV for pristine BaFe12O19). Due to polarizations, the dielectric loss, dielectric constant and tangent loss values were declined, while AC conductivity was enhanced. Photocatalytic performance of doped and undoped samples under visible right irradiation was studied for crystal violet dye. For 100 min exposure to visible light, the highly doped catalyst exhibits 97% degradation versus 60% in case of pristine this is attributed to efficient electron-hole pair separation. Furthermore, quenching effect of different scavengers indicated that hydroxyl radical had a main role, and e− or h+ played a minimal role in CV dye degradation. The enhanced properties due to doping make BaNixFe12-xO19 a potential candidate for photocatalytic applications under visible light irradiation.

An internally LED illuminated photobioreactor to increase energy conversion efficiency: Design and operation

In this work, a novel internally LED illuminated prototype photobioreactor (IIPBR) was designed, rationalizing the light supply with a hexagonal geometry and matching the light spectrum to the most photosynthetically active wavelengths. The IIPBR was designed and operated to produce the biomass in a continuous mode. In this system, Acutodesmus obliquus was cultivated under different light intensities (100–400 µmol m−2 s−1) and residence times (1–1.9 d). At steady state, a maximum productivity of 40.09 ± 1.99 g m−2 d-1 and a photosynthetic efficiency around 22 % were obtained. The data collected were used to carry out a first evaluation of the costs related to illumination, finding that the correct setting of the operative conditions has a great impact on costs, which span from a minimum of 1.82 up to to 20.63 € kg−1 (with electricity supply rated at autumn–winter 2021). The photoconversion efficiency of the lamps and the plant location play an important role and should be taken into account to increase the economic feasibility of the system proposed, thus enlarging the possible fields final applications of the biomass obtained.

Auxetic hexachiral cantilever beams for piezoelectric vibration energy harvesting

This work presents an auxetic hexachiral cantilever substrate for low-frequency vibration energy harvesting applications. Auxetics are materials with negative Poisson’s ratio that develop stresses of the same nature under mechanical loading, which can be advantageously used in designing energy harvesters with enhanced power output. The proposed harvester is fabricated by attaching a piezo patch on a 3D printed polylactic acid hexachiral substrate to convert the mechanical response to electrical output. Experiments are conducted to characterize the vibration and electrical properties of the harvester. A 3D finite element (FE) model is developed and validated with experimental voltage obtained for different electrical resistance. As the first mode generates maximum power, an equivalent single degree of freedom semi-analytical model is formulated and validated with experiments and FE results. The proposed harvester has a natural frequency of 23 Hz with a voltage output of 9.1 V at 250 kΩ. The developed models are used to study the influence of hexachiral geometry, electrical and mechanical loading on the electro-mechanical response. The harvester voltage is influenced by the ligament thickness and is found to increase linearly with an increase in mechanical loading. Further, the enhancement in performance by the addition of hexachiral sub patch to a plain beam is investigated, followed by a comparison with harvesters having plain, hexagonal and re-entrant geometries. The results show that the hexachiral harvester has the lowest first mode frequency with a power output about 20 and 3 times the plain and re-entrant harvesters, respectively. Finally, random vibration analysis of the hexachiral harvester is carried out to evaluate its performance under ambient loading, and the results show that the semi-analytical model is a computationally efficient alternative to study the first mode behavior. The findings of the study demonstrate the potential of the proposed hexachiral harvester for low-frequency applications.

Novel multi jet fusion 3D-printed patient immobilization for radiation therapy.

Thermoplastic immobilizers are used routinely in radiation therapy to achieve positioning accuracy. These devices are variable in quality as they are dependent on the skill of the human fabricator. We examine the potential multi jet fusion (MJF) 3D printing for the production immobilizers with a focus on the surface dosimetry of several MJF-printed PA12-based material candidates. Materials are compared with the goal of minimizing surface dose with comparison to standard thermoplastic. We introduce a novel metamaterial design for the shell of the immobilizer, with the aims of mechanical robustness and low-dose buildup. We demonstrate first examples of adult and pediatric cranial and head-and-neck immobilizers. Three different PA12 materials were examined and compared to fused deposition modeling-printed polylactic acid (PLA), PLA with density lowered by adding hollow glass microspheres, and to perforated or perforated/stretched and solid status quo thermoplastic samples. Build-up dose measurements were made using a parallel plate chamber. A metamaterial design was established based on a packed hexagonal geometry. Radiochromic film dosimetry was performed to determine the dependence of surface dose on the metamaterial design. Full cranial and head-and-neck prototype immobilizers were designed, printed, and assessed with regard to dimensional accuracy. Build-up dose measurements demonstrated the superiority of the PA12 material with a light fusing agent, which yielded a ∼15% dose reduction compared to other MJF materials. Metamaterial samples provided dose reductions ranging from 11% to 40% compared to stretched thermoplastic. MJF-printed immobilizers were produced reliably, demonstrated the versatility of digital design, and showed dimensional accuracy with 97% of sampled points within ±2mm. MJF is a promising technology for an automated fabrication of patient immobilizers. Material selection and metamaterial design can be leveraged to yield surface dose reduction of up to 40%. Immobilizer design is highly customizable, and the first examples of MJF-printed immobilizers demonstrate excellent dimensional accuracy.

Towards Hexagonal Planar Nickel: A Dispersion‐Stabilised Tri‐Lithium Nickelate

AbstractAdvancing the understanding of lithum nickelate complexes, here we report a family of homoleptic organonickelate complexes obtained by reacting Ni(COD)2and lithium aryl‐acetylides in the presence of the bidentate donor TMEDA. These compounds represent rare examples of low‐valent transition‐metals supported solely by organolithium ligands. Whilst the solid‐state structures indicate a hexagonal planar geometry around Ni0with Ni−Li bonds, bonding analysis via QTAIM, NCI, NBO and ELI methods reveals that the Ni−Li interactions are repulsive in nature, characterising these complexes as tri‐coordinated. London dispersion forces between TMEDA and the organic substituents on nickel are found to play a crucial role in the stabilisation and thus isolation of these complexes. Preliminary reactivity studies demonstrate that the homoleptic lithium nickelates undergo stoichiometric cross‐coupling with PhI to give dinickel clusters containing both anionic acetylide and neutral alkyne ligands.

Towards Hexagonal Planar Nickel: A Dispersion-Stabilised Tri-Lithium Nickelate.

Advancing the understanding of lithum nickelate complexes, here we report a family of homoleptic organonickelate complexes obtained by reacting Ni(COD)2 and lithium aryl-acetylides in the presence of the bidentate donor TMEDA. These compounds represent rare examples of low-valent transition-metals supported solely by organolithium ligands. Whilst the solid-state structures indicate a hexagonal planar geometry around Ni0 with Ni-Li bonds, bonding analysis via QTAIM, NCI, NBO and ELI methods reveals that the Ni-Li interactions are repulsive in nature, characterising these complexes as tri-coordinated. London dispersion forces between TMEDA and the organic substituents on nickel are found to play a crucial role in the stabilisation and thus isolation of these complexes. Preliminary reactivity studies demonstrate that the homoleptic lithium nickelates undergo stoichiometric cross-coupling with PhI to give dinickel clusters containing both anionic acetylide and neutral alkyne ligands.

Pin power reconstruction for hexagonal geometry in nodal neutronics program Ants

The pin power reconstruction methodology for hexagonal geometry in the multigroup nodal neutronics program Ants is described and verified against full core Serpent Monte Carlo solutions in four VVER benchmarks. In order to provide the best possible reference solution, Serpent uses the same nuclear data libraries and simulation options both to generate the required group constants for Ants and to solve the full core reference solution. The root mean square of the relative differences in 2D pin powers between Ants and Serpent was between 0.83% and 1.11% in the four benchmarks, while the root mean square of the relative differences in the 2D intra-assembly peaking factor (Kk) was between 0.54% and 0.71%. Increasing the number of energy groups in the nodal solution tended improve the accuracy of the nodal solution as did the use of critical spectrum condensed group constant data instead of infinite spectrum group constants.

Mechanically-grown morphogenesis of Voronoi-type materials: Computer design, 3D-printing and experiments

The present work introduces a novel and versatile computer-design and experimental strategy to obtain random Voronoi-type geometries, called M-Voronoi (from mechanically grown), with smooth void shapes and variable intervoid ligament sizes that can reach very low relative densities. This is achieved via a numerical, large strain, nonlinear elastic, void growth mechanical process. Originally small circular voids embedded in a cell of arbitrary shape (triangle, circle, rectangle, trapezoid) grow when subjected to displacement (Dirichlet) boundary conditions. The deformed voids evolve into smooth Voronoi-type geometrical shapes leading to macroscopic isotropy or anisotropy depending on the prescribed boundary conditions. The void growth process is a direct consequence of mass conservation and the incompressibility of the surrounding nonlinear elastic matrix phase and the final achieved relative density may be analytically estimated in terms of the determinant of the applied deformation gradient. In order to study the mechanical properties of the M-Voronoi materials, we focus on two-dimensional porous polymer square representative isotropic and anisotropic geometries in terms of void size and realization, which are 3D-printed and experimentally tested under uniaxial compression. For comparison, we also test random polydisperse porous materials with circular voids, standard eroded Voronoi geometries and hexagonal honeycombs. The first two are also isotropic while the latter are only isotropic in the linear elastic regime. We show that the randomness of the M-Voronoi geometry and their non-uniform intervoid ligament size leads to enhanced mechanical properties at large compressive strains with no apparent peak-stress and strong hardening well before densification. By comparing them with the hexagonal geometries, which tend to exhibit a peak-stress and a plateau-type response, we show that the hardening response of the M-Voronoi is mainly due to their geometrical characteristics and less due to the polymer hardening response. Anisotropic M-Voronoi are also produced and tested indicating that anisotropy only enhances the initial stiffness along the longitudinal direction but instead leads to lower buckling loads and hardening rates than the corresponding isotropic M-Voronoi in the nonlinear regime.

New room-temperature 2D hexagonal topological insulator OsC: First Principle Calculations

The structural, electronic and topological characteristics of the two-dimensional (2D) binary compound OsC are investigated using DFT simulations. Phonon dispersion and molecular dynamics calculations confirm a strong structural, dynamic and thermal stability of the osmium carbide monolayer in hexagonal planar geometry where C−Os hybridization is sp2. Electronic band structures attest that OsC is a zero-gap semiconductor with the valence band coming mainly from osmium d orbitals and some contributions from carbon p orbitals. By tuning on the spin orbit coupling (SOC), the gap ΔSOC of 141 meV, corrected to 220 meV using HSE approximations, opens in the vicinity of the Γ point with the occurrence of a band inversion between d32−Os and d52−Os revealing that our system is a nontrivial QSH insulator with topological invariant Z2=1 and topological edge states. Our study shows that the room-temperature 2D topological insulator OsC is a potential material for possible applications in nanoelectronic and spintronic devices.