Linear 2D Research Articles

Evolution from discrete mononuclear complexes to trinuclear linear cluster and 2D coordination polymers of Mn(II) with dihydrazone Schiff bases: Preparation, structure and thermal behavior

Four Mn(II) coordination compounds based on the 2,6-diacetylpyridine bis(isonicotinoylhydrazone) (H2L1) and 2,6-diacetylpyridine bis(nicotinoylhydrazone) (H2L2), were prepared using different synthetic conditions and starting manganese salts: discrete mononuclear [Mn(H2L1)2(H2O)2](NO3)2 (1) and trinuclear [Mn3(H2L1)2(NCS)2Cl4(H2O)2] (2) complexes and two 2D coordination polymers {[Mn3(L1)3(H2O)2]·1.5C2H5OH}n (3) and {[MnL2]·dmf}n (4), where dmf = N,N-dimethylformamide. Single-crystal X-ray diffraction study shows that H2L1 and H2L2, which differ only by para- or meta- position of radicals with respect to the nitrogen atoms in the terminal pyridyl fragments, demonstrate chelate or chelate-bridging coordination mode with N3O2, or N4O2 and N5O2 donor atoms, respectively. The planar-chelate coordination of these ligands provides the pentagonal-bipyramidal surrounding of Mn(II) and the terminal pyridyl moieties promote bridging function and structure expansion in 2–4 as well as octahedral Cl2N4 coordination geometry for one of Mn(II) atoms in the trinuclear complex 2. All compounds have been investigated in the solid state by IR spectroscopy and thermal analysis in order to understand the influence of the inorganic anion presence/absence on the stability of synthesized compounds.

Analytical and Experimental Investigations of Novel Maglev Coupling Based on Opposed Halbach Array for a 2D Valve

In this paper, a novel maglev coupling based on the opposed Halbach array is proposed as the interface between the linear electro-mechanical converter and 2D valve body. This non-contact maglev coupling possesses several advantages over existing mechanical couplings such as zero friction and wear, low vibration and noise, and no lubrication, which is expected to greatly improve the control accuracy and life cycle of the 2D valve. A detailed analytical model of maglev coupling is established based on the electro-magnetic theory. Firstly, the permanent magnets of the Halbach array is decomposed into several types of basic elements to obtain their individual analytical expressions, which are then re-superimposed into the whole coupling to obtain the analytical formula of torque–displacement characteristics. In order to obtain maximum output torque of maglev coupling, a parametric analysis was performed using an analytical model and optimal pitch angle and shifted distance was explored and found. To verify the correctness of the analytical modelling and parametric analysis results, the torque–displacement characteristics were also studied through both the FEM simulation and experimental approach. The results of analytical modelling, FEM simulation and experiment were in a good agreement, which shows that the maximum magnetic torque can reach about 0.579 N·m when the external armature displacement is 1 mm. The research work provides an important reference for the future application of maglev coupling in a 2D valve.

Higher dimensional semi-relativistic time-fractional Vlasov-Maxwell code for numerical simulation based on linear polarization and 2D Landau damping instability

The “Vlasov-Maxwell system” is a groundbreaking algorithm to model, simulate and further analyze the vigorous performance of the collisionless plasma in the presence of the electromagnetic fields. In this frame of reference, the inquiry of this system with the deep conceptions of the time-fractional derivative is a novel benchmark and also the key intentions of this study. For this purpose, higher dimensional semi-relativistic time-fractional Vlasov-Maxwell system is formulated with the physical significances of the geometry. Furthermore, to fabricate the numerical consequences, we suggest an innovative algorithm which based on spectral and finite-difference approximations. The spatial and temporal variables are handled by using shifted Gegenbauer polynomials and finite-difference approximations respectively. Numerous simulations are carried out to validate the reliability and accuracy of the anticipated method. Error bound convergence and stability of the method is inspected numerically. Furthermore, the established technique can be used conveniently to observe the numerical result of other multi-dimensional time-fraction with variable-order problems of physical nature.

Features that make macromolecules 2D polymers

The article compares two-dimensional (2D) polymers with their congeners, the abundantly available linear polymers (1D) to show that both kinds of macromolecules are in fact polymer molecules. Repeat units and end (or edge) groups fully describe both kinds of structures. Both structures are obtainable as individual entities. Growth mechanisms well known for 1D polymers have now also been either elucidated or postulated for the first few 2D polymers. 2D copolymers are accessible by reacting different monomers in different feed ratios. Molar masses and molar mass distributions are obtainable when analysing 2D polymers in monolayer sheet form.The author therefore concludes that 2D polymers are in fact polymer molecules, very much as their linear 1D counterparts and that both kinds of structures therefore belong in this very subcategory of macromolecules. Dimensionality differences come with significant property differences and may therefore justify dividing the subcategory ‘polymer molecules’ further into 1D, 2D and – in the near future - 3D polymer molecules. In terms of materials, 2D polymers establish a subclass of organic 2D materials with the unique characteristic of meeting the conditions for polymer molecules.

Convection of a Colloidal Suspension in a Horizontal Layer Heated from Below with Account for Nanoparticle Interaction

We investigate linear instability and 2D nonlinear convective flows of a colloidal suspension stratified in the gravity field in the case of a horizontal colloidal suspension layer with account for the particle interaction. The dependences of the oscillatory convection threshold, the neutral oscillation frequency, and the critical wavenumber on the average volume fraction of impurity are obtained. Nonlinear terms in the diffusion and sedimentation fluxes, which reflect the interaction of nanoparticles, reduce the average concentration gradient across the layer, as well as the convection threshold and the neutral oscillation frequency as compared to an ideal colloidal solution. We perform numerical simulation of a finite-amplitude flow in the form of a traveling wave. In contrast to molecular liquids and ideal colloidal solutions, the spatial structure of the concentration field is successfully described by the first harmonic and exhibits weak spatial anharmonism.

Dysprosium(III) compounds assembled via a versatile ligand incorporating salicylic hydrazide and 8-hydroxyquinolin units: syntheses, structures and magnetic properties.

Assembly of dysprosium(iii) salts with a multidentate ligand H3L ((2-hydroxy)-N'-((8-hydroxyquinolin-2-yl)methylene)-benzohydrazide) affords a variety of products with different topological structures, namely [Dy(H2L)(HL)]·CH3OH (1), [Dy2(HL)2(C6H5COO)2(CH3OH)2]·3CH3OH (2), [Dy2(HL)2(NO3)2(DMF)4]·4DMF (3), [Dy4L4(CH3OH)4]·2CH3OH·4H2O (4) and ([Dy4(HL)4(C6H5COO)4(CH3OH)(H2O)]·2CH3OH·CH3CN·H2O)n (5). The versatile and flexible coordination modes of phenoxo groups from salicylic hydrazide prove to be a key factor in the assembly of corresponding structures depending upon the reaction conditions. It is noteworthy that ligands HL2- act as a long-distance link and further connect the Dy2 fragments into an infinite 1D chain due to the conformational flexibility resulting from the rotatable C-C bond in 5. Furthermore, the magnetic measurements were performed on all complexes. The dc magnetic susceptibility data evidence distinct magnetic coupling interactions in the dinuclear complexes 2 (antiferromagnetic) and 3 (ferromagnetic) despite their similar structures, and only complex 3 shows slow relaxation behavior of magnetization. Ab initio calculations and electrostatic potential analysis on complexes 2, 3, and three other complexes (6, 7, 8) incorporating different kinds of ligands reveal the important interrelationship of magnetic anisotropy, magnetic coupling interactions and SMM properties.

Lax-Wendroff Approximate Taylor Methods with Fast and Optimized Weighted Essentially Non-oscillatory Reconstructions

The goal of this work is to introduce new families of shock-capturing high-order numerical methods for systems of conservation laws that combine Fast WENO (FWENO) and Optimal WENO (OWENO) reconstructions with Approximate Taylor methods for the time discretization. FWENO reconstructions are based on smoothness indicators that require a lower number of calculations than the standard ones. OWENO reconstructions are based on a definition of the nonlinear weights that allows one to unconditionally attain the optimal order of accuracy regardless of the order of critical points. Approximate Taylor methods update the numerical solutions by using a Taylor expansion in time in which, instead of using the Cauchy–Kovalevskaya procedure, the time derivatives are computed by combining spatial and temporal numerical differentiation with Taylor expansions in a recursive way. These new methods are compared between them and against methods based on standard WENO implementations and/or SSP-RK time discretization. A number of test cases are considered ranging from scalar linear 1d problems to nonlinear systems of conservation laws in 2d.

Proton sponge lead halides containing 1D polyoctahedral chains

Hybrid organic/inorganic lead halides with the proton sponge moiety show face-sharing [PbX6] octahedra forming linear 1D chains. These species exhibit complete (Br, I) miscibility and exceptional anisotropic thermal expansion.

Comparison of gamma analysis with using different dosimetric systems for pre-treatment verification of intensity-modulated radiation therapy

The evaluation of the agreement between calculated and measured dose plays an essential role in the quality assurance procedures of intensity-modulated radiation therapy (IMRT). This study aimed to compare gamma analysis using portal dosimetry (PD), Epiqa, and 2D array detector for dose verification of radiotherapy treatment plans. Five field step-and-shoot IMRT plan was performed for 20 prostate IMRT patients using the dual-energy DHX linear accelerator (Varian Medical System, Palo Alto, Calif., USA). The treatment plans were created using Varian DHX Eclipse treatment planning system (TPS) version 15.1. All measurements were performed by aS500 EPID integrated into Varian DHX linear accelerator and 2D array detector. The dose distribution was evaluated with gamma area histograms (GAHs) generated using different γ criteria (1%/1 mm, 2%/2 mm, 3%/2 mm, and 3%/3 mm) for dose agreement and distance to agreement parameters. Statistical analyses were evaluated by using Mann–Whitney U test and Kruskal–Wallis test, and p-value of p < 0.01 was considered to be significant. The average pass rate for 20 IMRT plans was above 95 for all devices with 2%/2 mm, 3%/2 mm, and 3%/3 mm. The mean and standard deviation pass rates (γ ≤ 1) were found to be 99.80 ± 0.19, 99.35 ± 0.34, and 97.53 ± 0.71 for PD, Epiqa, and 2D array, respectively. All IMRT plans passed 2%/2 mm, 3%/2 mm, and 3%/3 mm gamma by more than 95 of three dosimetric systems. They are all in good agreement with the literature. All three devices are acceptable for quality control of IMRT. Due to the simplicity and fast evaluation process, PD can be preferred for quality control.

Water Dissociation and Hydroxyl Formation on Ni(110).

Nickel is an active catalyst for hydrogenation and re-forming reactions, with the reactions showing a strong dependence on the surface exposed. Here, we describe the mixed hydroxyl–water phases formed during water dissociation on Ni(110) using scanning tunneling microscopy and low-current low-energy electron diffraction. Water dissociation starts between 150 and 180 K as the H-bond structure evolves from linear one-dimensional (1D) chains of intact water into a two-dimensional (2D) network containing short rows of face-sharing hexagonal rings. As further water desorbs, the hexagonal rows adopt a local (2 × 3) arrangement, forming small, disordered domains separated by strain relief features. Decomposition of this phase occurs near 220 K to form linear 1D structures consisting of flat, zigzag water chains, with each water stabilized by donating one H to hydroxyl to form a branched chain structure. The OH–H2O chains repel each other, with the saturation layer ordering into a (2 0, 1 4) structure that decomposes to OH near 245 K as further water desorbs. The structure of the mixed OH/H2O phases is discussed and contrasted with those found on the related Cu(110) surface, with the differences attributed to strain in the 2D H-bond network caused by the short Ni lattice spacing and strong bond to OH/H2O.

Humeral head subluxation in Walch type B shoulders varies across imaging modalities.

BackgroundThe Walch type B pattern of glenohumeral osteoarthritis is characterized by posterior humeral head subluxation (PHHS). At present, it is unknown whether the percentage of subluxation measured on axillary radiographs is consistent with measurements on 2-dimensional (2D) axial or 3-dimensional (3D) volumetric computed tomography (CT). The purpose of this study was to evaluate PHHS across imaging modalities (radiographs, 2D CT, and 3D CT).MethodsA cohort of 30 patients with Walch type B shoulders underwent radiography and standardized CT scans. The cohort comprised 10 type B1, 10 type B2, and 10 type B3 glenoids. PHHS was measured using the scapulohumeral subluxation method on axillary radiographs and 2D CT. On 3D CT, PHHS was measured volumetrically. PHHS was statistically compared between imaging modalities, with P ≤ .05 considered significant.ResultsThe mean PHHS value for the entire group was 69% ± 24% on radiographs, 65% ± 23% with 2D CT, and 74% ± 24% with 3D volumetric CT. PHHS as measured on complete axillary radiographs was not significantly different than that measured on 2D CT (P = .941). Additionally, PHHS on 3D volumetric CT was 9.5% greater than that on 2D CT (P < .001). There were no significant differences in PHHS between the type B1, B2, and B3 groups with 2D or 3D CT measurement techniques (P > .102).ConclusionSignificant differences in PHHS were found between measurement techniques (P < .035). A 9.5% difference in PHHS between 2D and 3D CT can be mostly accounted for by the linear (2D) vs. volumetric (3D) measurement techniques (a linear 80% PHHS value is mathematically equivalent to a volumetric PHHS value of 89.6%). Surgeons should be aware that subluxation values and therefore thresholds vary across different imaging modalities and measurement techniques.

Linear visco-elastic 1D site response of sand-EPS geofoam layers under cyclic loading

A two-part study was undertaken to evaluate the dynamic behavior of sand-EPS geofoam composite layers. The first part aimed at evaluating the dynamic properties of both sand and expanded polystyren...

Synthetic Aperture Sonar (SAS) without Navigation: Scan Registration as Basis for Near Field Synthetic Imaging in 2D.

Sonars are essential for underwater sensing as they can operate over extended ranges and in poor visibility conditions. The use of a synthetic aperture is a popular approach to increase the resolution of sonars, i.e., the sonar with its N transducers is positioned at k places to generate a virtual sensor with transducers. The state of the art for synthetic aperture sonar (SAS) is strongly coupled to constraints, especially with respect to the trajectory of the placements and the need for good navigation data. In this article, we introduce an approach to SAS using registration of scans from single arrays, i.e., at individual poses of arbitrary trajectories, hence avoiding the need for navigation data of conventional SAS systems. The approach is introduced here for the near field using the coherent phase information of sonar scans. A Delay and Sum (D&S) beamformer (BF) is used, which directly operates on pixel/voxel form on a Cartesian grid supporting the registration. It is shown that this pixel/voxel-based registration and the coherent processing of several scans forming a synthetic aperture yields substantial improvements of the image resolution. The experimental evaluation is done with an advanced simulation tool generating realistic 2D sonar array data, i.e., with simulations of a linear 1D antenna reconstructing 2D images. For the image registration of the raw sonar scans, a robust implementation of a spectral method is presented. Furthermore, analyses with respect to the trajectories of the sensor locations are provided to remedy possible grating lobes due to the gaping positions of the transmitter devices.

Preliminary Design of Two Dimensional Vibration Assisted Machining System for Multi-Axis Micro-Milling Application

Vibration assisted machining (VAM) is a method that is widely used in improving the performance of machined products. External vibrations with high frequency to ultrasonic range along with an meso-micrometer amplitude are given to the cutting tool or workpiece. This will result in a periodic separation phenomenon, hence reducing the cutting force which has positive impacts on increasing tool life and machined surface quality. Among the high-precision machining processes, micro-milling which has the ability to produce complex components with 2D and 3D features, can also be applied with the vibration assisted method, known as vibration assisted micro-milling (VAMM). Based on the direction of vibration given in the machining process, there are 1D VAMM with linear vibrations and 2D VAMM with circular or elliptical trajectory vibrations. However to date, neither developed 1D nor 2D VAMM systems are still limited to the research of planar surfaces cutting using linear movement axes, meanwhile vibration assisted in inclination cutting of micro-milling using the rotational movement axes is still very rare. Therefore the purpose of this paper is to present the preliminary model in designing a 2D VAMM system for a 5-axis micro-milling machine. The system is powered using piezoelectric actuators as the vibration-producing actuators.

MicroCT X-ray comparison of aligner gap and thickness of six brands of aligners: an in-vitro study

BackgroundTo investigate and compare the gap (i.e. fit) and thickness of six aligner systems (Airnivol, ALL IN, Arc Angel, F22, Invisalign and Nuvola) using industrial computed tomography (CT). The null hypothesis was that there would be no detectable differences in either measurement between the aligners investigated.Materials and methodsPassive aligners of each brand were fitted to one single resin cast prototyped from an STL file from a single patient. The samples obtained were examined under high-resolution micro-CT, and the resulting tomographic microphotographs and volumetric data were compared. 3D analysis investigated the gap volume, the mean gap width and the maximum gap width of each sample. A total of 204 linear 2D measurements were made on 18 microtomographic images to investigate the aligner gap and thickness among different systems. Investigated regions were the central incisor, canine and first molar. The resulting measurements were analysed by ANOVA and compared using Tukey’s post hoc analysis (P < 0.05).Results3D analysis revealed that the F22 displayed lower gap volume and mean gap width, followed by Airnivol and Invisalign, whereas Airnivol the lowest maximum gap width. 2D analysis showed that F22 had the lowest mean gap and aligner thickness at all teeth investigated. Comparison of the 2D point values revealed statistically significant differences between brands in terms of both measurements (P < 0.05), with the exception of six points in the gap analysis and one in the thickness analysis.ConclusionsThere are differences between the six aligner systems examined in terms of 2D and 3D measurements of aligner thickness and gap.

Airfoil–slat arrangement model design for wind turbines in fuzzy environment

In this study, a multi-element wind turbine blade that consists of NACA 6411 and NACA 4412 leading-edge slat design is investigated computationally. Optimum design parameters of the slatted wind turbine blade leading to maximum value of CL/CD related to the turbine power are obtained. In the optimization process, a new fuzzy logic linear programming methodology integrating with fuzzy linear regression and 2D CFD analysis is proposed. The aerodynamic characteristics of the slatted blade are computed by using Incompressible Navier–Stokes equations and k-omega turbulence modeling. Results are compared with the results of linear programming method and direct search optimization method. The computational results reveal that the proposed methodology for performance optimization is more effective than other methods to obtain high-performance value of the CL/CD. The maximum value of the CL/CD is obtained as 25.1 leading the maximum efficiency of 0.52.

Analytical solution of open crystalline linear 1D tight-binding models

A method for finding the exact analytical solutions for the bulk and edge energy levels and corresponding eigenstates for all commensurate Aubry–André/Harper single-particle models under open boundary conditions is presented here, both for integer and non-integer number of unit cells. The solutions are ultimately found to be dependent on the behavior of phase factors whose compact formulas, provided here, make this method simple to implement computationally. The derivation employs the properties of the Hamiltonians of these models, all of which can be written as Hermitian block-tridiagonal Toeplitz matrices. The concept of energy spectrum is generalized to incorporate both bulk and edge bands, where the latter are a function of a complex momentum. The method is then extended to solve the case where one of these chains is coupled at one end to an arbitrary cluster/impurity. Future developments based on these results are discussed.

Second-order large time step wave adding scheme for hyperbolic conservation laws

This paper constructs a second-order large time step wave adding scheme (LTS-WA2) for hyperbolic conservation laws. Based on the first-order large time step wave adding scheme (LTS-WA1), a piece-wise linear reconstruction with limiter is performed on the solutions, and the band decomposition and band adding is complemented (into the discontinuity decomposition and wave adding), then the scheme is extended to second-order. The manufacture of the new scheme is simplified and written uniformly. Theoretical analyses are made for scalar cases. Numerical experiments give 11 tests which involve 1D scalar equations, 1D, 2D and 3D Euler equations. Computations show that the new scheme maintains high resolution and low dissipation of the original scheme at large CFL number, and also improves the problem of low resolution of the original scheme for rarefaction wave and contact discontinuity at small CFL number (roughly less than 2). Accuracy order is analyzed theoretically and validated using tests of 1D linear equation and 2D Burgers equation. CPU time is also compared with traditional second-order (Harten-TVD) scheme, showing that LTS-WA2 is more cost effective.

Применение криволинейных сеток для моделирования 2D волновых полей в неоднородных областях со сложной топографией

The main practical interest of geophysics is the restoration of the structure of the medium. So one can understand whether there are hydrocarbon reservoirs at depth. Studying the structure of the medium by taking numerous samples and drilling wells is a very financially and time-consuming task. Therefore, the use of mathematical modeling seems to be a good alternative. If the calculations show a result similar to the initial data of the medium, then such algorithm for restoring the medium can be applied new regions. Verification of the algorithm should be carried out on real structures of the media, but real wave field data are not provided, since they are often the subject of trade secrets. In this case, the result of this work comes to the rescue. Numerical simulation is widely used in studying the processes of wave field propagation in various complex media. One way is to discrete the domain for which the simulation is being performed, and to construct a difference scheme for further numerical implementation. This work involves the construction of a mesh with curved quadrangles, which allows good agreement with the topography of the surface. A parallel algorithm of numerical modeling based on the numerical solution of a linear 2D system of elasticity theory written in displacements using a curvilinear mesh and an explicit difference scheme is proposed. The simulation results are presented. The calculations were carried out using the resources of the SSCC SB RAS.

Self-assembly of square planar rhodium carbonyl complexes with 4,4-disubstituted-2,2′-bipyridine ligands

The impact of non-covalent interactions and reaction conditions on formation and self-assembly of ionic pairs of Rh complexes with 4,4′-disubstituted bipyridine ligands ([Rh(L1)(CO)2][Rh(CO)2Cl2])n(1), [Rh(L1)2Cl2][Rh(CO)2Cl2] (2), ([Rh(L1)(CO)2][Rh(CO)2Cl2][Rh(L1)(CO)2]n([Rh(CO)2(Cl)2])n) (3), ([Rh(L2)CO2] [Rh(CO)2Cl2])n·EtOH (4), ([Rh(L2)(CO)2])n ([Rh(CO)2Cl2])n(5) (L1 = 4,4′-dimethyl-2,2′-bipyridine, L2 = 4,4′-diamine-2,2′-bipyridine) have been studied. Packing of square planar Rh complexes favor formation of one-dimensional chains. In structure 1, the polymeric chain is formed by the alternating cationic [Rh(L1)(CO)2]+ and the anionic [Rh(CO)2Cl2]- units leading to a neutral pseudo linear 1D chain with metallophilic contacts. In compound 2, the square planar [Rh(CO)2Cl2]- anions form only dinuclear anion pairs instead of polymeric chains. Structure 3 consists of an alternative arrangement of cations and anions compared to 1, the repeating sequence of ions being [Rh(L1)(CO)2]+[Rh(CO)2Cl2]-[Rh(L1)(CO)2]+. The overall positive charge is balanced by outlying [Rh(CO)2Cl2]- counterion. In structures 4 and 5, only the cationic [Rh(L2)(CO)2]+ units are involved in formation of the polymeric chains and the positive charge of the chain is balanced by the [Rh(CO)2Cl2]- (4 and 5). In structures 1 and 3 the metallophilic interactions have an important role in chain formation. In 4 and 5, the arrangement of the square planar building blocks is dominated by the hydrogen bonding between the NH2-substituents of the bipyridine ligand and the chlorides of the anion or solvent of crystallization.