Prismatic Structures Research Articles

Manganese-centered ten-vertex germanium clusters: the strong field Ge10 ligand encapsulating a transition metal

The experimental realization of pentagonal prismatic structures for M@ (M = Co, Fe) containing interstitial transition metal atoms makes of interest the chemistry of corresponding manganese derivatives Mn@. The neutral Mn@Ge10 may be regarded as a complex of a polyhedral ligand with an interstitial Mn in the +2 oxidation state. However, the lowest energy Mn@Ge10 structure with the expected sextet spin state for high-spin d5 Mn(II) lies ~23 kcal mol−1 in energy above the lowest energy isomer thereby suggesting that such germanium polyhedra function as strong field ligands for encapsulated transition metals. The lowest energy structures for the Mn@ anions (z = −1 to −5) are all centered pentagonal prisms. Higher energy Mn@ structures have outer Ge10 polyhedra based on the tetracapped trigonal prism similar to the lowest energy Co@ structure and on the bicapped square antiprism similar to the B10 deltahedron. Other Mn@ structures have outer Ge10 polyhedra with four or five quadrilateral faces as well as six or eight triangular faces, respectively. Bioctahedral (Ge5)2Mn5− structures were also found for the pentaanion with a manganese vertex common to two MnGe5 octahedra. The cationic species Mn@ was found to have a more complicated potential surface than the anions. Tetracapped trigonal prismatic and bicapped square antiprismatic structures as well as a variety of more open structures were found for Mn@.

Comparison of three models describing bromide transport affected by different soil structure types

This study was conducted to investigate the effects of soil structure on bromide (Br) transport through three soils with granular, prismatic, and single-grain structures. The breakthrough curve (BTC) of the single-grain structure was sigmoidal, symmetrical and similar to a piston flow, showing the dominance of mass flow. In contrast, the BTCs of the granular and prismatic structures were initially steep, becoming more gradual at high pore volumes (PVs). The stable structure and preferential pathways caused the early breakthrough of Br in the leachate of these columns. The convection–dispersion equation (CDE), mobile–immobile water (MIM), and dual-permeability (DP) models were fitted to observed data using the program HYDRUS-1D. The equilibrium transport model (CDE) was not as successful as non-equilibrium (MIM and DP) models in describing the Br transport in prismatic and granular soil columns, although it was able to describe the Br transport in single-grain column well. Overall, the results demonstrated the importance of soil structure in pollutant transport through soils.

Carbon nanoscrolls on the surface of nanocrystalline graphite and diamond films

Nanocrystalline graphite and diamond films with needlelike nanostructures on their surface have been obtained by plasma-enhanced chemical vapor deposition. According to the experimental data, these aggregates have the same nature for films of both types: they are tubular carbon nanoscrolls with a polygonal cross section. Nanoscrolls are formed by a helically folded graphene sheet; they look like twisted prisms. The needlelike prismatic structures have an average diameter in the range of 50‒500 nm, and their length reaches several micrometers. Possible mechanisms of formation of carbon nanostructures are discussed.

A Comparative Study of [CaEDTA](2-) and [MgEDTA](2-): Structural and Dynamical Insights from Quantum Mechanical Charge Field Molecular Dynamics.

Structure and dynamics of [MgEDTA](2-) and [CaEDTA](2-) complexes in aqueous solution have been investigated via quantum mechanical/molecular mechanical (QM/MM) simulations. While for the first a 6-fold octahedral complex has been observed, the presence of an additional coordinating water ligand has been observed in the latter case. Because of rapidly exchanging water molecules, this 7-fold coordination complex was found to form pentagonal bipyramidal as well as capped trigonal prismatic configurations along the simulation interchanging on the picosecond time scale. Also in the case of [MgEDTA](2-) a trigonal prismatic configuration has been observed for a very short time period of approximately 1 ps. This work reports for the first time the presence of trigonal prismatic structures observed in the coordination sphere of [MgEDTA](2-) and [CaEDTA](2-) complexes in aqueous solution. In addition to the detailed characterization of structure and dynamics of the systems, the prediction of the associated infrared spectra indicates that the ion-water vibrational mode found at approximately 250 cm(-1) provides a distinctive measure to experimentally detect the presence of the coordinating water molecule via low-frequency IR setups.

Periodic microstructures for improved lens-to-waveguide coupling efficiency in microlens array planar solar concentrators

Thin form-factor planar sunlight concentrators fabricated using low-cost materials in conjunction with high-efficiency solar cells may prove economically competitive with silicon photovoltaics. A periodic structure with planar interfaces employing an array of microlenses and coupling structures is amenable to high-volume imprint manufacturing and hence a drastic cost reduction. A numerical study of periodic prismatic void structures aligned with microlenses to efficiently couple incoming light into a constant cross-section channel waveguide is reported. Three different prism-like cut-out structures: a bare prism, a planar connected prism, and a pointed prism are proposed. Numerical results show that the proposed pointed prism design offers a high-efficiency coupling with one-sided output (90.8% and 85.4% peak efficiency at concentration ratios of 320× and 400×, respectively).

An Interview with NASA Principal Investigator Vytas SunSpiral: Expert Opinion on the Advantages and Limitations of Soft Robotics

Soft RoboticsVol. 2, No. 2 InterviewAn Interview with NASA Principal Investigator Vytas SunSpiral: Expert Opinion on the Advantages and Limitations of Soft RoboticsBarry TrimmerBarry TrimmerSearch for more papers by this authorPublished Online:18 Jun 2015https://doi.org/10.1089/soro.2015.28999.btrAboutSectionsView articleView Full TextPDF/EPUB ToolsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View articleFiguresReferencesRelatedDetailsCited BySoft Robotic Perspective and Concept for Planetary Small Body Exploration Ruoyu Feng, Yu Zhang, Jinyu Liu, Yonglong Zhang, Junfeng Li, and Hexi Baoyin13 October 2022 | Soft Robotics, Vol. 9, No. 5A review on tensegrity structures-based robotsMechanism and Machine Theory, Vol. 168Thin Piezoelectric Mobile Robot Using Curved Tail OscillationIEEE Access, Vol. 9Fascicular module of nylon twisted actuators with large force and variable stiffnessSensors and Actuators A: Physical, Vol. 315An Adaptive Bioinspired Foot Mechanism Based on Tensegrity Structures Jianwei Sun, Guangsheng Song, Jinkui Chu, and Luquan Ren12 December 2019 | Soft Robotics, Vol. 6, No. 6Automatically assembled large-scale tensegrities by truncated regular polyhedral and prismatic elementary cellsComposite Structures, Vol. 184 Volume 2Issue 2Jun 2015 InformationCopyright 2015, Mary Ann Liebert, Inc.To cite this article:Barry Trimmer.An Interview with NASA Principal Investigator Vytas SunSpiral: Expert Opinion on the Advantages and Limitations of Soft Robotics.Soft Robotics.Jun 2015.51-58.http://doi.org/10.1089/soro.2015.28999.btrPublished in Volume: 2 Issue 2: June 18, 2015PDF download

A modified elasto-dynamic model based static stiffness evaluation for a 3-PRS PKM

This paper proposes a modified elasto-dynamic model for a three-prismatic revolute spherical parallel kinematic machine, in which the flexibility of the prismatic revolute spherical limb structures are accounted in and modeled as a hollowed spatial beam with nonuniform cross section. The governing equations are derived through substructure synthesis and finite element formulation. The stiffness matrix of the platform is then extracted from global stiffness matrix and its characteristics at typical configurations are calculated to reveal complicated coupling effects of diagonal and nondiagonal elements of the stiffness matrix. The concept of principle stiffness and coupled stiffness are proposed and their distributions over the workspace are predicted with numerical simulations in a quick manner. Then the stiffness of the platform is physically interpreted as a kinematically unconstrained rigid body suspended by six screw springs with equivalent spring constants and pitches through eigenscrew decomposition. The distributions of screw spring constants over the workspace are then plotted to demonstrate a duality property. At last, the effects of some design variables such as structural and dimensional parameters on system rigidity performance are investigated with the purpose of providing useful information for the structural design and performance enhancement of the parallel kinematic machine.

A New Paleocene Species ofBentharca(Bivalvia; Arcidae) from Eastern Hokkaido, with Remarks on Evolutionary Adaptation of Suspension Feeders to the Deep Sea

Abstract. We describe a new deep-sea arcid species, Bentharca steffeni sp. nov., from the Paleocene Katsuhira Formation in Urahoro Town, eastern Hokkaido. This is the oldest certain record of this genus. Shell microstructure of this new species is similar to the Recent species, B. asperula (Dall, 1891) in having an outer layer composed of thin simple lamellar fibrous prismatic and crossed lamellar structures and an inner layer composed of irregular complex crossed lamellar and irregular prismatic structures. Of these, the simple lamellar fibrous prismatic and the irregular prismatic structures have never previously been recognized even in B. asperula. From the occurrence of the new species, it has been elucidated that the genus Bentharca adapted to the deep sea as a refuge at least in the Paleocene.

Hybrid MPI/OpenMP cloud parallelization of harmonic coupled finite strip method applied on reinforced concrete prismatic shell structure

This paper discusses the cloud computing based approach for parallelization of large displacement stability analysis of orthotropic prismatic shell structures with simply supported boundary conditions along the diaphragm-supported edges. We review the harmonic coupled finite strip method (HCFSM), and describe a software system for nonlinear analysis of reinforced concrete (RC) structures. We combine different parallelization models – MPI and OpenMP – in order to cope with the increased computational complexity, which originates from coupling of all series terms in the HCFSM formulation. We discuss the effects of parallelization from the perspective of a cloud environment. Our results show that rational usage of cloud resources can lead to significant performance improvements and monetary savings. In certain cases, the achieved performance can be very close to the maximum one.

On Strength Reserve Assessment for Prismatic Folded Plate Roof Structures

The paper presents the results of experimental studies and numerical simulation of straining and failure of reinforced concrete folded-plate roof structures in limit and out-of-limit states performed on models and real structures, taking into account the combined mechanical loads and environmental actions. The results of the study show that in the process of reconstruction design for concrete prismatic roof structures of operated industrial and public buildings, along with the traditional limit state methods of calculation it is reasonable to carry out a residual strength reserve analysis.

Characterization of crystalline structures in Opuntia ficus-indica.

This research studies the crystalline compounds present in nopal (Opuntia ficus-indica) cladodes. The identification of the crystalline structures was performed using X-ray diffraction, scanning electron microscopy, mass spectrometry, and Fourier transform infrared spectroscopy. The crystalline structures identified were calcium carbonate (calcite) [CaCO3], calcium-magnesium bicarbonate [CaMg(CO3)2], magnesium oxide [MgO], calcium oxalate monohydrate [Ca(C2O4)•(H2O)], potassium peroxydiphosphate [K4P2O8] and potassium chloride [KCl]. The SEM images indicate that calcite crystals grow to dipyramidal, octahedral-like, prismatic, and flower-like structures; meanwhile, calcium-magnesium bicarbonate structures show rhombohedral exfoliation and calcium oxalate monohydrate is present in a drusenoid morphology. These calcium carbonate compounds have a great importance for humans because their bioavailability. This is the first report about the identification and structural analysis of calcium carbonate and calcium-magnesium bicarbonate in nopal cladodes, as well as the presence of magnesium oxide, potassium peroxydiphosphate and potassium chloride in these plants. The significance of the study of the inorganic components of these cactus plants is related with the increasing interest in the potential use of Opuntia as a raw material of products for the food, pharmaceutical, and cosmetic industries.

Crashworthiness analysis of multi-cell prismatic structures

This paper presents a numerical and experimental study of several configurations of multi-cell columns compared to single-walled and double-walled columns subjected to dynamic axial impact forces. The impact of the columns was numerically analysed using FEM and also verified by experimental testing. The effect of the column mass and thickness of the multi-cell columns compared to single- and double-walled columns was also studied. The results showed that, by analysing a group of columns with the same thickness and weight, the energy absorption efficiency can be significantly improved by introducing internal ribs to the double-walled columns. The results showed that the crushing force of the middle ribs (MR) multi-cell columns was the highest, followed by the corner ribs (CR) multi-cell columns, the double-walled (DW) columns and the single-walled (SW) columns, respectively.

Spatial structure and electronic spectrum of TiSi n − clusters (n = 6–18)

Results from optimizing the spatial structure and calculated electronic spectra of anion clusters TiSin− (n = 6–18) are presented. Calculations are performed within the density functional theory. Spatial structures of clusters detected experimentally are established by comparing the calculated and experimental data. It is shown that prismatic and fullerene-like structures are the ones most energetically favorable for clusters TiSin−. It is concluded that these structures are basic when building clusters with close numbers of silicon atoms.

Prismatic tensegrity structures with additional cables: Integral symmetric states of self-stress and cable-controlled reconfiguration procedure

A simple energy method is put forward to determine the prestress distribution for symmetric tensegrity structures with multiple states of self-stress and a class of prismatic tensegrities with additional cables are introduced to show the accuracy of presented method. For the purpose of modifying structural shape as well as mechanical properties, a cable-controlled reconfiguration procedure is subsequently proposed for these structures. By defining the length adjustments as the control parameters, the reconfiguration procedure is regarded as a quasi-static process, consisting of a sequence of equilibrium configurations with varying control parameters. Then the nonlinear iterative algorithm based on the tangent stiffness of the structure is presented to simulate and follow this reconfiguration process. By way of example, a particular class of reconfigurations coined symmetrical reconfigurations are investigated carefully and the key features as well as the potential applications are given.

Oxygen spectroscopy and polarization-dependent imaging contrast (PIC)-mapping of calcium carbonate minerals and biominerals.

X-ray absorption near-edge structure (XANES) spectroscopy and spectromicroscopy have been extensively used to characterize biominerals. Using either Ca or C spectra, unique information has been obtained regarding amorphous biominerals and nanocrystal orientations. Building on these results, we demonstrate that recording XANES spectra of calcium carbonate at the oxygen K-edge enables polarization-dependent imaging contrast (PIC) mapping with unprecedented contrast, signal-to-noise ratio, and magnification. O and Ca spectra are presented for six calcium carbonate minerals: aragonite, calcite, vaterite, monohydrocalcite, and both hydrated and anhydrous amorphous calcium carbonate. The crystalline minerals reveal excellent agreement of the extent and direction of polarization dependences in simulated and experimental XANES spectra due to X-ray linear dichroism. This effect is particularly strong for aragonite, calcite, and vaterite. In natural biominerals, oxygen PIC-mapping generated high-magnification maps of unprecedented clarity from nacre and prismatic structures and their interface in Mytilus californianus shells. These maps revealed blocky aragonite crystals at the nacre-prismatic boundary and the narrowest calcite needle-prisms. In the tunic spicules of Herdmania momus, O PIC-mapping revealed the size and arrangement of some of the largest vaterite single crystals known. O spectroscopy therefore enables the simultaneous measurement of chemical and orientational information in CaCO3 biominerals and is thus a powerful means for analyzing these and other complex materials. As described here, PIC-mapping and spectroscopy at the O K-edge are methods for gathering valuable data that can be carried out using spectromicroscopy beamlines at most synchrotrons without the expense of additional equipment.

Novel coral-like hexagonal MoO3 thin films: Synthesis and photochromic properties

MoO3 thin films were obtained by varying the precursor concentration (Cp) using a hydrothermal method. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), ultraviolet–visible diffuse reflectance spectroscopy and a color difference meter were employed for the characterization of synthesized thin films. With the increase of precursor concentration, the morphology of MoO3 thin films changed from hexagonal prismatic structures to coral-like structures and finally straw-like structures. XRD results showed that all samples can be indexed to the hexagonal structure of MoO3. Additionally, the band gap of all MoO3 thin films was around 3.16eV calculated from UV–vis diffuse reflectance spectrum. The as-prepared MoO3 film with coral-like structures possessed the maximum color difference value (ΔC=2.33). This result indicates that MoO3 film prepared with the precursor concentration of 0.18M exhibits excellent photochromic properties due to the large exposed surface provided by coral-like hierarchical structure.

Instabilidade aerodinâmica por flutter em estruturas prismáticas de secção retangular

This paper is dedicated to the study of the occurrence of flutter instability in slender prismatic structures of rectangular cross section. A two degree of freedom model is considered and its non dimensional formulation is derived so that a minimum number of non dimensional parameters governing the occurrence of flutter instability are put in evidence. A very good agreement has been obtained by comparing the results of the two degree of freedom model with the results available in the literature. The goal of this document is twofold: (i) to summarize the conditions for which slender structures with rectangular cross sections may get unstable by flutter under the action of steady wind conditions and (ii) to supply a broad collection of data in the form of ready-to-use tables or graphics covering a wide range of cases, that provide a basis for designers to predict the critical wind velocities at the onset of flutter instability.

A study on use of miniature dielectric compound parabolic concentrator (dCPC) for daylighting control application

Low-concentration solid dielectric compound parabolic concentrator (dCPC) and its variations have been widely regarded as an attractive solution to reduce the cost of a photovoltaic (PV) system, particularly for building-integrated application. Different from a mirror CPC, a dCPC allows the light beyond its acceptance angle to penetrate through its lateral surface. This escaped light could be actually used for daylighting, so the dCPC offers a potential for combined PV and daylighting application suitable for the atrium buildings or large green houses. In the modern buildings, an advanced daylighting system such as prismatic panels is used to balance between harvesting daylight and preventing excessive solar heat gain. In contrast, this study aims to evaluate the advantage of the miniature solid dCPC over common prismatic structures according to their daylight transmittance values under both standard and real sky conditions. A commercial optical analysis software PHOTOPIA is firstly used to compare the daylighting control performance between a dCPC rod and two common prismatic elements. The effect of solar altitude and azimuth angles changing with time is considered. A preliminary test under a solar simulator and a real sky condition is also introduced to provide experimental evidence regarding the advantageous feature of a dCPC rod for daylighting control.

Turning film for widening the viewing angle of a blue phase liquid crystal display

We report a new turning film structure for widening the viewing angle of a vertical-field-switching blue-phase liquid crystal display, which employs a directional backlight. The turning film consists of periodic prismatic structures: each period has three prisms with different base angles so that the output light can be spread to a larger angle. Simulation results show that a full width at half-maximum of ±80° in the horizontal direction and ±45° in the vertical direction can be achieved.

A higher order model for thin-walled structures with deformable cross-sections

A higher order model for the analysis of linear, prismatic thin-walled structures that considers the cross-section warping together with the cross-section in-plane flexural deformation is presented in this paper. The use of a one-dimentional model for the analysis of thin-walled structures, which have an inherent complex three-dimensional (3D) behaviour, can only be successful and competitive when compared with shell finite element models if it fulfills a twofold objective: (i) an enrichment of the model in order to as accurately as possible reproduce its 3D elasticity equations and (ii) the definition of a consistent criterion for uncoupling the beam equations, allowing to identify structural deformation modes.The displacement field is approximated through a linear combination of products between a set of linear independent functions defined over the cross-section and the associated weights only dependent on the beam axis; this approximation is not constrained by any ab initio kinematic assumptions. Towards an efficient application of the approximation procedure, the cross-section is discretized into thin-walled elements, being the displacement field approximated for each element independently of the displacement direction. The approximation is thus hp refined enhancing the “capture” of the 3D structural mechanics of thin-walled structures. The beam model governing equations are obtained through the integration over the cross-section of the corresponding elasticity equations weighted by the cross-section global approximation functions.A criterion for uncoupling the beam governing equations is established, allowing to (i) retrieve the classic equations of the thin-walled beam theory both for open and closed sections and (ii) derive a set of uncoupled deformation modes representing higher order effects. The criterion is based on the solution of the polynomial eigenvalue problem associated with the beam differential equations, allowing to quantify the Saint-Venant principle for thin-walled structures. In fact, the solution of the non linear eigenvalue problem yields a twelve fold null eigenvalue (representing polynomial solutions) that are verified to represent beam classic solutions and sets of pairs and quadruplets of non-null eigenvalues corresponding to higher order modes of deformation.