3-cube Research Articles

Resistance analysis of underwater towing cable based on overset grid

The method of overset grid is used to calculate the lift and drag of towing cable at various angles of attack. Compared with the past method, it effectively solves the problem of mesh distortion at high angles of attack. Overset grid is more effective, and most of the grids are formed by regular hexahedron, so the accuracy of calculation is more guaranteed. When calculating the special angle of attack, the cubic spline interpolation method is used to solve the problem.

Fitting and error evaluation for rotating paraboloid in arbitrary position using geometric iterative optimization algorithm

To realize a more accurate fitting and error evaluation for a rotating paraboloid in an arbitrary position, a new fitting and error evaluation method based on the geometrical characteristics of the paraboloid is presented for rotating paraboloid in arbitrary positions. The proposed method is named the ‘geometric iterative optimisation algorithm’. First, the initial reference vertex, focus and initial profile error of the measured rotating paraboloid are obtained based on coordinate transformations and the least-squares method, and a reference paraboloid is established by using the reference vertex and focus. Second, two regular hexahedrons are collocated by taking the reference vertex and focus as datum points, and the initial profile error as the side length. Eight auxiliary vertexes and focuses (that is, the vertexes of two regular hexahedrons) are obtained. Using the auxiliary vertexes and focuses, a series of auxiliary paraboloids defined by the auxiliary vertexes and focuses are established. Third, reference profile error and auxiliary profile errors of the measured rotating paraboloid are calculated by considering the reference paraboloid and the auxiliary paraboloids as ideal paraboloids. Fourth, the reference points are changed or the side lengths of the hexahedron are decreased by comparing the the reference profile error and the auxiliary profile errors. The minimum zone fitting and evaluation for the paraboloid profile are realized by repeating the above process. The principle and steps involved when using the proposed method to solve the rotating paraboloid profile error are described in detail, and mathematical formulas are presented. The simulation results show that this method can obtain not only accurate results but it is also stable.

Mechanobiologically optimization of a 3D titanium-mesh implant for mandibular large defect: A simulated study.

Recently, a novel 3D titanium-mesh scaffold with bone grafting material has been proposed to reconstruct the large defect of mandible. However, how to design and optimize the 3D scaffolds of mandible is still unclear. Therefore, the aim of this study was to investigate the optimization of 3D scaffolds for mandibular defect. Both the biomechanical behavior and mechanobiological property of scaffolds were considered in this study. Four configurations (regular hexahedron, cuboctahedron, regular dodecahedron, and diamond) and three strut diameters (0.2 mm, 0.5 mm and 0.8 mm) were divided into 12 groups. By employing Finite Element Analysis and bone "Mechnostat" theory, the optimal unit cell was selected from 12 scaffolds. Then, the original implant for mandible defects was designed with the optimal unit cell, and the final implant was optimized to promote osteogenesis and avoid mechanical failure under bi-lateral chewing bite (200N) and maximum force (worse-case) bite (800 N). The results illustrated a strong correlation between the configurations and the load transmission capacity, while mechanical failure highly depended on strut size and architecture. Regular dodecahedron with a strut diameter of 0.8 mm provided a good load transfer to bone tissue while resisting the mechanical failure. Ultimately, the optimized implant was constructed with regular dodecahedron unit cell, and the strut diameters of scaffold gradually varied according to the biomechanical analysis. The computational results indicated that the optimized implant can provide an excellent mechanical environment for bone regeneration, thus achieving a long-term stability and occlusal reconstruction with dental implant. This study is expected to provide a scientific basis for the design and optimization of 3D mesh scaffolds to reconstruct a mandibular functionally and aesthetically.

Cubic lattice‐based spherical uniaxial perfectly matched layer for the FDTD method

AbstractIn order to reduce the finite‐difference time‐domain (FDTD) computational area efficiently, we established spherical uniaxial perfectly matched layer (S‐UPML) with regular Yee's lattices in the Cartesian coordinate system. The boundary performed as a curved profile but is constructed with regular hexahedron cells in three‐dimensional (3‐D) and with regular quadrilateral cells in two‐dimensional (2‐D) condition. Although the S‐UPML's curvilinear outline is approximated by standard meshes, it still maintains the same performance as the orthodox methods. After it is used for absorbing outgoing wave, the computational FDTD lattices are reduced about a half and a quarter in 3‐D and 2‐D, respectively, in contrast with the conventional Cartesian boundaries. We introduce the radial components to basic formulations of the S‐UPML and facilitate the update coefficients of iterative equations. Its suitable thickness is a key parameter to guarantee the performance and is determined through balancing the efficiency and maximum reflection error level. Several numerical trials are implemented to verify the practicability of the proposed boundary in two dimensions. Results show its suitability and the higher efficiency than conventional cubic boundary.

Glutathione responsive cubic gel particles cyclodextrin metal-organic frameworks for intracellular drug delivery

Novel cubic gel particles (ssCGP) with Glutathione (GSH) triggered drug release features were prepared by crosslinking the cyclodextrin based metal-organic frameworks (CD-MOFs) templets with a newly synthesized biodegradable disulfide bond-bearing linker and removing of the potassium ion in sequence. The morphology and size of ssCGP were investigated by field emission scanning electron microscope (FESEM) and dynamic light scattering. Energy dispersive x-ray spectroscopy (EDX), fourier transform infrared spectroscopy (FT-IR), powder x-ray diffraction (PXRD) and Brunauer-Emmett-Teller (BET) were employed to characterize the structure of ssCGP. ssCGP have regular hexahedron shape with edge length about 200–400 nm. Excellent ability of drug adsorption was achieved by using doxorubicin (DOX) as a model drug. The GSH triggered drug release of ssCGP was observed both in GSH contained solutions and intracellular environments. ssCGP have been demonstrated as a biocompatible porous nanocarrier, particular for intracellular drug delivery.

Numerical Simulation on Rigid Foreign Object Exclusion in the Turboprop Engine Intake System With a Bypass Duct

By considering the exclusion characteristics of foreign objects in a new intake system with a bypass duct for turboprop engines, two kinds of common rigid foreign objects, the grains, and metal pieces, are modeled based on airworthiness standards and reference reports. On the assumption that only a perfect elastic collision occurs without any structural damage to the objects or intake walls, a numerical method based on single high-fidelity computational fluid dynamics (CFD) and dynamic unstructured mesh techniques to simulate the 6DOF motion and impacts of the rigid foreign objects is presented. A practical used intake system with a bypass duct is employed to validate the method. According to the tolerance size of the intake, two spherical grains with the radius of 0.037 m and 0.0555 m and a regular hexahedron aluminum metal piece with the dimension of 0.20 m×0.11 m×0.01 m are built to test the exclusion ability of the intake and analyze their effects on the intake performance. The simulation results indicate that, in the cases of a symmetrical flow field, geometry, and initial states, all the rigid foreign objects will move in the intake without lateral motions. The spherical grains without an initial angular velocity only translate in the intake, and the small one finally enters into the bypass duct after four impacts, while the larger one flies into the inner part of the engine after six impacts. The larger grain can lead to a more apparent loss on the intake performance due to the greater shielding effect on the flow field, and the maximum decrements of the total pressure recovery coefficient and mass flow can reach to 2% and 4.1%, respectively; the total pressure distortion rate increases 116%. A coupled motion of translation and rotation occurs for the regular hexahedron aluminum piece, and after four impacts on the intake, it finally excludes to the outer space of the nacelles from the bypass duct. Compared to the spherical grains, the aluminum piece has more significant actions on the intake performance. The maximum losses of the total pressure recovery coefficient and mass flow can be 2.3% and 1.54%, respectively, while the distortion rate increases 518%. Although the numerical method in this study is simple and ideal, it can help researchers to obtain quick and effective evaluation results in the initial design stage of the new intake system with a bypass duct for the turboprop engine to improve the design efficiency and level.

Compositionally graded SnO2/TiO2 bi-layered compounds with dramatically enhanced charge transport efficiency for self-driven water purification applications

To maximize the advantages of thin-film-based TiO2 photoelectrodes for transparent self-driven photoelectrochemical (PEC) reactions, we artificially designed a compositionally graded bi-layer compounds consisting of SnO2 and TiO2. This structure exhibited a vigorous photocatalytic activity, sufficient photovoltage, and long-term stability. A compositionally graded SnO2/TiO2 interface (G-SnTiO) for improved charge transport efficiency and sufficient photovoltage was derived by a solution process using simultaneous sintering after sol-gel coating the SnO2/TiO2 layers; the structure was verified by various analysis methods, such as transmission electron microscopy, energy dispersive X-ray spectroscopy, and secondary ion mass spectrometry. The high performance from the G-SnTiO structure was attributed to an effective charge separation from the formation of a heterostructure interface with reduced defects, resulting in a sufficient photovoltage for self-driving. To construct self-driven and sustainable overall cells without an external potential and considerable reduction in transparency, two-electrode PEC cells with a G-SnTiO photoanode and Cu2O photocathode were fabricated with a regular hexahedron shape for a color degradation test of methylene-blue-incorporated electrolytes, and exhibited enhanced purification speed and robust durability.

AN ENCODING METHOD FOR COMPRESSING GEOGRAPHICAL COORDINATES IN 3D SPACE

Abstract. This paper proposed an encoding method for compressing geographical coordinates in 3D space. By the way of reducing the length of geographical coordinates, it helps to lessen the storage size of geometry information. In addition, the encoding algorithm subdivides the whole space according to octree rules, which enables progressive transmission and loading. Three main steps are included in this method: (1) subdividing the whole 3D geographic space based on octree structure, (2) resampling all the vertices in 3D models, (3) encoding the coordinates of vertices with a combination of Cube Index Code (CIC) and Geometry Code. A series of geographical 3D models were applied to evaluate the encoding method. The results showed that this method reduced the storage size of most test data by 90 % or even more under the condition of a speed of encoding and decoding. In conclusion, this method achieved a remarkable compression rate in vertex bit size with a steerable precision loss. It shall be of positive meaning to the web 3d map storing and transmission.

Fabrication and Mechanical Properties of Porous CP-TiUsing Selective Laser Melting (SLM)

Recently, porous structure has become focus for the study of implantable devices due to the superior ability of osseointegration. Meanwhile, Selective laser melting (SLM), a versatile rapid manufacturing method, is widely utilized in medical restoration field due to its flexibility. Given the information about mechanical properties and manufacturing process of porous structure is limited, the aim of this study is to investigate the manufacturing process and static mechanical properties. Therefore, regular hexahedron structures are designed and fabricated by SLM, also the dimensions and mechanical properties are evaluated by experiments. The results show that manufacturing process and design of structure have significant influence on porosity and mechanical properties. Porous structure would reduce the elastic modulus and yield strength, and the ductility of porous structure is poor than that of solid structure. Moreover, the suitable pore size is >0.7mm. In conclusion, porous implant has great potential to use in bone repair and further study should be done to obtain more information.

Structural, spectral and theoretical aspects in the coordination of a triazine-based ligand toward lead(II) with a holodirected environment

Four complexes, [Cl(PPTA)2Pb(μ-Cl)2Pb(PPTA)2Cl] (1), [Br(PPTA)2Pb(μ-Br)2Pb(PPTA)2Br] (2), [I(PPTA)2Pb(μ-I)2Pb(PPTA)2I] (3) and [(PPTA)2Pb(NO3)2] (4), of 5-phenyl-3-(pyridin-2-yl)-1,2,4-triazine (PPTA) were prepared and identified by elemental analysis, FT-IR, 1H NMR spectroscopy and single-crystal X-ray diffraction. All the coordination modes of the 3-(pyridin-2-yl)-1,2,4-triazine-based ligands were studied by CSD software for predicting the behavior of the PPTA ligand in the reaction with metal ions. In the crystal structure of 1, the lead atom has a PbN4Cl3 environment with a distorted capped octahedral geometry. Complexes 2 and 3 are also dinuclear and isostructural with 1. The lead atom in the crystal structure of complex 4 has a coordination number of eight and a distorted cube geometry. The metal atom coordination spheres in all four structures tend to be holodirected with a decreasing deviation in the series 1–3. The thermodynamic stability of the isolated complexes and their charge distribution patterns were studied by DFT and NBO analysis. Theoretical studies reveal that the thermodynamic stability for the optimized complex 1 is more stable than those of the isostructural complexes 2 and 3.

Structural study of the coordination behavior of a tetradentate NO3-donor amino alcohol ligand toward a CdII:HgII mixture

Abstract In this work, the reaction of 2,2′,2″-nitrilotriethanol (NTE) with a 1:1 mixture of CdI2 and HgI2 is investigated. The complex [Cd(NTE)2][Hg2(μ-I)2I4] was synthesized and identified by elemental analysis, FT-IR, 1H NMR spectroscopy and single-crystal X-ray diffraction. The structure of the [HNTE]Cl salt is also presented. In the crystal structure of the complex, the cadmium atom has a CdN2O6 environment in a slightly distorted cube geometry. This geometry is one of the rare cube geometries with a minimum distortion among the Cambridge Structural Database structures for cadmium complexes. The anionic moiety has a binuclear structure with the mercury atoms being in tetrahedral environments. In the network of the complex, in addition to O−H · · · I hydrogen bonds, there are I · · · I interactions which lead to ten-membered rings.

Fabrication of right triangular prism retroreflectors through 3½½-axis ultraprecise single point inverted cutting

ABSTRACTRetroreflectors (RR) are passive optical structures that are capable of returning incident light back to the source. The focus of the current study is represented by the right triangular prism (RTP) geometry which could be a more efficient alternative to the traditional inverted corner cube geometry. While current manufacturing practices rely solely on the use of conventional pin-bundling techniques, the work reported in this study presents further enhancements of the previously introduced ultraprecise single point inverted cutting technique which can be used in a manner approximately similar to 3½½-axis kinematics. The experimental results obtained have demonstrated both the feasibility of the proposed fabrication approach as well as the optical viability of the fabricated RTP elements.

MODELING OF SCATTERING OF ELECTROMAGNETIC WAVES BY HEXAGONAL SNOW CRYSTALS

Winter snow cover plays important role in the global hydrological balance of the Earth and significantly affects on a number of processes in the atmosphere and on underlying surface. The moisture reserves on the on land depend on the thickness of the snow cover, the yield of crops, and the level of rivers in the regions of our country. The radar data in turn make it possible to avoid significant financial and property damage associated with heavy snowfalls. However, up to now, there is a problem of calculating the reflection characteristics of polydisperse medium which is consisting of snow particles. In this paper, we propose a technique for the simulation of scattering characteristics of radar cross section of snow crystals over wide wavelength range, and also the results of calculating the scattering of electromagnetic waves by polydisperse medium of snow crystals in the form of regular hexahedrons are shown.

The Research of 3 D Point Cloud Registration Method Based On Regular Hexahedron Color Targets

The Research of 3 D Point Cloud Registration Method Based On Regular Hexahedron Color Targets

Development of a Single-Longitudinal-Mode Ho:YAG Laser Based on Corner Cube**Supported by the National Natural Science Foundation of China under Grant Nos 61308009 and 61405047, the China Postdoctoral Science Foundation Funded Project under Grant No 2013M540288, the Fundamental Research Funds for the Central Universities under Grant Nos HIT.NSRIF.2014044 and HIT.NSRIF.2015042, the Science Fund for Outstanding Youths of Heilongjiang Province under Grant

We present a Tm-doped fiber laser pumped Fabry–Perot etalons Ho:YAG laser based on a corner cube. A maximum single-longitudinal-mode and fundamental transverse mode output power of 478 mW at the wavelength of 2091.06 nm is achieved with a pump power of 16.3 W, corresponding to an optical-to-optical efficiency of 2.9% and a slope efficiency of 7.9%. The single-longitudinal-mode and fundamental transverse mode are less sensitive to the rotating of the corner cube. The results indicate the potential impact of a single-longitudinal-mode Ho:YAG laser with corner cube geometry to improve the anti-maladjustment stability.

Octanuclear Ni(ii) cubes based on halogen-substituted pyrazolates: synthesis, structure, electrochemistry and magnetism

The employment of halogen-substituted pyrazole ligands in nickel(II) clusters afforded three anionic Ni(II) cubes, (HNEt3)2[Ni8(Xpz)12(OH)6] (X = Cl, 1·2CH3CN; X = Br, 2·2CH3CN; X = I, 3·12CH3CN; pz = pyrazolate). Clusters 1–3 are isolated as dianionic compounds which have similar cube geometry with each vertex occupied by a Ni(II) atom and eight μ4-OH− capped on eight square faces. The Xpz ligands adopt a bidentate mode to bind paired Ni(II) atoms on the edge of the cube. Interestingly, the three Ni8 cubes have similar symmetry, size and shape but pack together to form different lattice symmetry, which should be dictated by the halogen-related supramolecular interactions (C–X⋯H, C–X⋯π and X⋯X halogen bonding) in different crystals. The electrochemistry of 1–3 showed a Ni(II)/Ni(I) redox couple with E1/2 at ca. 900 mV and the oxidization potential order is 1 > 3 > 2 depending on the halogen substituents. 1–3 exhibit excellent electrocatalytic performances toward the oxidation of nitrite. The different packing of Ni8 cubes in 1–3 also has an important influence on their magnetic behaviors. Complex 2 showed antiferromagnetic couplings between the Ni(II) ions within the cubes, whereas 1 and 3 exclusively exhibited mixed ferromagnetic and antiferromagnetic properties, leading to frustration and typical spin glass behavior.

Corrosion Losses in Sintered (Nd, Dy)–Fe–B Magnets for Different Geometries

Sintered neodymium–iron–boron (Nd–Fe–B) magnets with cube and flat geometries were exposed to pressurized heat-humidity corrosion tests for 96 and 240 h. Measurements of weight and flux losses were performed after the corrosion tests. The corroded specimens were further characterized using scanning electron microscopy and optical profilometry. The microcrystalline anisotropy of sintered magnets gave rise to heterogeneous corrosion, where the pole faces degraded preferentially to the side faces. The magnetic field from the magnet itself thus contributed to the amount and location of detached ferromagnetic grains. The magnets with cube geometry suffered greater losses than the flat magnets, even though the flat magnets had a higher relative pole-face area. The higher total flux (due to the larger volume) of the cube-shaped magnets led to the higher overall losses. In the flat magnets, the corrosion concentrated heavily on areas near the corners.

Soft spherical nanostructures with a dodecagonal quasicrystal-like order.

We develop a theory which predicts curvature-related structural peculiarities of soft spherical nanostructures with a dodecagonal local arrangement of subunits. Spherical templates coated with a thin film of a soft quasicrystal (QC)-forming material constitute the most promising direction to realize these nanostructures. Disordered and perfect spherical nanostructures are simulated using two approaches. The first of them models a random QC-like spherical nanostructure with extended curvature-induced topological defects similar to scars in colloidal spherical crystals. The second approach is inspired by the physics of viral capsids. It deals with the most regular spherical nanostructures with a local QC-like order derived from three well-known planar dodecagonal tilings. We explain how the additional QC-like degrees of freedom assist the nanostructure stabilization and determine the point defect number and location without extended scar formation. Unusual for nanoassemblies snub cube geometry is shown to be the most energetically favorable global organization of these spherical QC nanostructures.

Details of tetrahedral anisotropic mesh adaptation

We have implemented tetrahedral anisotropic mesh adaptation using the local operations of coarsening, swapping, refinement and smoothing in MATLAB without the use of any for-N loops, i.e. the script is fully vectorised. In the process of doing so, we have made three observations related to details of the implementation: 1. restricting refinement to a single edge split per element not only simplifies the code, it also improves mesh quality, 2. face to edge swapping is unnecessary, and 3. optimising for the Vassilevski functional tends to give a little higher value for the mean condition number functional than optimising for the condition number functional directly. These observations have been made for a uniform and a radial shock metric field, both starting from a structured mesh in a cube. Finally, we compare two coarsening techniques and demonstrate the importance of applying smoothing in the mesh adaptation loop. The results pertain to a unit cube geometry, but we also show the effect of corners and edges by applying the implementation in a spherical geometry. Program summaryProgram title: trullekrul v0.1.0Catalogue identifier: AEZC_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEZC_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: New style BSD licenseNo. of lines in distributed program, including test data, etc.: 8395No. of bytes in distributed program, including test data, etc.: 92021Distribution format: tar.gzProgramming language: MATLAB/GNU Octave.Computer: Single core desktops.Operating system: Linux/Windows/Mac.RAM: Variable, from megabytes to gigabytesClassification: 4.2, 4.3, 4.12, 4.14.Nature of problem: Adaptation of tetrahedral meshes to metric fields.Solution method: Local operations, colouring and APL vectorised code.Restrictions: Region IDs/internal boundaries are not supported and 3D adaptation with 1M elements requires ≈4GB memory.Unusual features: Vectorised script implementation, signed distance functions, selection of refinement and coarsening techniques.Running time: 2D problems solve in seconds, but 3D problems can take up to an hour without running out of memory.

Method for sphericity error evaluation using geometry optimization searching algorithm

According to geometrical characteristics of the sphericity error, a new evaluation algorithm for sphericity error based on geometry optimization searching method has been presented. First, the reference point is established and the initial error is calculated by using the measured points, Second, a regular hexahedron of side length f is collocated by taking the reference point as datum point, and the maximum difference of the radius of all measured points are calculated by regarding each vertex of the hexahedron as the centre of the measured spherical surface. Third, the reference point or side length of the hexahedron is changed by comparing the initial error and the maximum difference of the radius. Step by step, the sphericity error value of corresponding evaluation method (including Minimum Zone Sphere method (MZS), Minimum Circumscribed Sphere method (MCS) and Maximum Inscribed Sphere method (MIS)) are obtained. The principle and the steps of using the algorithm to solve the sphericity error are described in detail and the mathematical formula and program flowchart are given. The experimental results show that the sphericity error can be evaluated effectively and exactly with this algorithm.