Hexagonal Caps Research Articles

A novel anti-loosening bolt looseness diagnosis of bolt connections using a vision-based technique

Bolt looseness detection is a common problem in engineering. Most vision-based detection techniques focus on diagnosing ordinary bolt looseness, i.e., the methods used for diagnosis are based only on the sidelines of nuts. These methods cannot be used for anti-loosening bolt looseness diagnosis because of the simultaneous rotation of screws and nuts. Therefore, a novel anti-loosening bolt looseness diagnosis method based on a vision-based technique is proposed in this paper. First, a regular hexagonal cap was installed on the screw, which can be used as a reference for the nut. Then, to automatically distinguish the hexagonal borders of the screw cap and nut, a new hexagonal border reconstruction algorithm is proposed. Furthermore, the relative rotation angles of the screw cap and nut hexagons can be determined using the sidelines of the reconstructed hexagonal borders of the screw cap and nut. Finally, a novel anti-loosening bolt looseness diagnosis method is established by using the relative rotation angle of the regular hexagonal borders of the screw cap and nut under initial status and loose status. A prototype flange node of the transmission tower was used for experimental verification. The results show that the proposed method can effectively detect the loosening angle of anti-loosening bolts.

Fabrication and photocatalytic performance of highly active exposed facets ZnO hexagonal cap/Ti3C2 MXene composites

Herein, a novel zinc oxide (ZnO) hexagonal cap with exposed polar facets/MXene composite was synthesized via a simple hydrothermal method. The analysis of the morphology and structure of these composites as well as the results of photochemical property measurements showed that a heterojunction was formed between ZnO and MXene. After testing the photocatalytic degradation of methyl orange, the ZnO hexagonal cap with 3 mL MXene showed the highest photodegradation efficiency of 87.8 % within 60 min under a xenon lamp. Active species capture experiments showed that •OH and h+ species were the main contributors to the degradation of methyl orange (MO). We proposed a possible mechanism for the excellent photocatalytic activity of ZnO hexagonal cap@Ti3C2 MXene. The Schottky barrier hindering the photogenerated electron recombination, the hexagonal cap morphology with highly active exposed facets, and the hollow structure favoring the adsorption of contaminants were all beneficial to achieve a high catalytic activity. This work provides new insight into the design of metal oxide/MXene photocatalysts.

The phenomenon of staphylococcal interbacterial aggregate and net structures (SIAN) in community-associated methicillin-resistant Staphylococcus aureus CA-MRSA/J

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) usually causes skin and soft tissue infections (SSTIs), but occasionally causes invasive infections with a broad range of manifestations. Virulence factors and pathogenesis of CA-MRSA have been investigated in details with genotype ST8/SCCmecIVa (USA300), which first emerged in the United States. However, CA-MRSA evolves rapidly, with different clones dominating in different world regions; their pathogenesis remains unclear. CA-MRSA with genotype ST8/SCCmecIVl (CA-MRSA/J) emerged in 2003 in Japan, spreading widely with a fatal case. We have studied the genetic characteristics of CA-MRSA/J, and during the course of this study, we found that CA-MRSA/J has bacteriophage-like spikes with or without a hexagonal cap (spikes X and Xc). Here, we report that CA-MRSA/J strain NN55 has non-phage-like, one-μm-long/jerky spikes with or without a hexagonal cap (LSX/LSXc), and also that LSX/LSXc forms (staphylococcal) interbacterial aggregate/net structures (SIAN). Regarding the phenomenon of SIAN, NN55 first formed single short spike X, followed by multiple molecules of long and jerky LSX/LSXc, leading to the interbacterial construction of SIAN, in colonies with high cell densities. The LSX/LSXc and SIAN structures have not been reported in S. aureus. NN55 was invasive in a HEp-2 cell assay, exhibiting SIAN. The novel SIAN structures may be foci-skeletons or toxic aggregates in NN55's invasive infections. The phenomenon of SIAN suggests novel staphylococcal cell-surface dynamism, providing a new structure-and-function relationship model and advancing the understanding of CA-MRSA pathogenesis.

Triplet grain growth in a-texture polycrystalline ZnO thin films

A growth of grain triplets is identified in vapor deposited, a-texture polycrystalline zinc oxide thin films, using a combination of transmission electron microscopy-based automated crystal orientation mapping and high-resolution imaging. Each triplet consists of three wurtzite phase grains, coordinated to near tetrahedral relative growth angles by the close-packed planes of a few nanometer diameter core of metastable zinc blende phase ZnO located at their triple junction. The triplets are aligned such that two of the grains have their fast growing [21¯1¯0] axes (near-) parallel to the substrate normal, and so coarsen under the principle of competitive grain growth. In contrast, growth of the third grain with a (101¯3) texture is impeded, such that it forms a small wedge between the ends of its two larger neighbors. Remarkably, all three boundaries between the grains adhere to a [21¯1¯0]/(011¯3) coherent twin orientation relationship, which corresponds to a grain geometry that is incommensurate with a perfect crystallographic nature. This coherency is primarily achieved via the small grain having an orientation that rotates internally by 10±2° across its volume, when going between the two interfaces formed with the neighboring large grains. The energy associated with this structural distortion is compensated by the formation of the coherent twin boundaries, such that the triplets are a stable or semi-stable growth form that are abundant in the film. The small (101¯3) texture grains may renucleate persistently, taking either of two possible orientations from the underlying tetrahedral coordination. By developing a phenomenological model for the triplet geometry and form, we associate these two orientations to small hexagonal caps and angled wedges seen in the surface morphology of the film. These findings potentially carry relevance for a wide range of vapor deposited compact films and free-standing nanostructures of wurtzite phase octet binary semiconductor compounds. We therefore believe that these insights can stimulate new research, for instance to obtain a more fundamental understanding of the growth mechanisms at the atomistic level.

Efficient vapor-liquid-solid synthesis of copper doped zinc oxide (Cu:ZnO) nanonails with highly homogeneous dopant distribution

Copper doped zinc oxide (Cu:ZnO) nanonails with uniformly distributed Cu ions through the nail structure were synthesized via a vapor-liquid-solid technique using seed Cu:ZnO nanoparticles. The seed nanoparticles were prepared with a simple precipitation method. The structure and morphology of nanonails and the distribution of Cu ions were investigated using X-ray diffraction, electron energy loss spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and elemental mapping analysis. The defect states in the Cu:ZnO nanonails were characterized by room temperature photoluminescence (PL) spectra. The obtained Cu:ZnO nanonails have single phase wurtzite structure of ZnO and incorporated copper ions are in the Cu2+ oxidation state. SEM and TEM micrographs revealed that nanostructures with well-defined nail morphology composed of a hexagonal cap (~350 nm in diameter) and a prismatic shaft (~550 nm in diameter) connected with cylindrical neck (~250 nm in diameter). Both SEM and TEM elemental mapping analysis proved that the usage of Cu:ZnO seed nanoparticles resulted in highly homogeneous distribution of Cu ions into ZnO nanonails. High crystallinity of the Cu:ZnO nanonails was revealed with PL spectra composed of predominant second order diffraction peak and near band edge of UV emission peak and also weak defect related deep level green and violent emission peaks.

Synthesis and Characterization of Multi-Angular Branched ZnO Microstructures and Peculiar Nanopushpins Obtained by Thermal Treatment from Compacted ZnS Powder

Multi-angular branched ZnO microstructures with rods-shaped tips and nanopushpins with hexagonal cap on top have been synthesized by a simple thermal treatment process of compacted ZnS powder used as starting material and substrate. The structures have been grown at different temperatures (800, 900 and 1000 °C) for 60 min, in a constant nitrogen environment at atmospheric pressure via a catalyst-free process. XRD results of the as-grown products from ZnS powder show a significant reduction in the cubic zincblende phase to the hexagonal wurtzite phase with the increase of treatment temperature, as compared to the bulk value. Post-anneal analyses indicated that the transformation of morphologies of the as-grown structures also depends strongly on the treatment temperature. The proposed method represents an easy and economical way to grow complex structures of ZnO, with a relatively short time, furthermore, without the neediness of use an external substrate to grow. These new and interesting nanostructures have potential in applications such as optoelectronics.

Designing axial growth of Co-Ni bimetallic nanowires with hexagon-like caps and their catalytic hydrogenation for nitrobenzene.

Co-Ni bimetal nanocrystals, which are constructed with long wires and hexagon-like caps, were synthesized through supersaturation, precipitation, and axial growth from the prenucleated bimetal seeds. These Co-Ni bimetallic nanowires with hexagonal caps are more effective than corresponding nanoparticles for the catalytic hydrogenation of nitrobenzene to produce aniline.

Profile-broaden ultraviolet lasing from whispering gallery mode cavity in crown-like zinc oxide

The crown-like zinc oxide (ZnO) samples, which are composed of a hexagonal cap and a tower-like shaft, are prepared by vapor transport method. The hexagonal cap, working as a whispering gallery mode (WGM) resonant cavity, demonstrates density-dependent ultraviolet (UV) lasing emission with a broadened and squared photoluminescence (PL) profile under UV excitation at 355 nm. Theoretical analyses based on Fermi golden rule show that the broadened spectrum profile results from the special optical mode density characteristics in a WGM micro-cavity, which is in agreement with the observed results.

Effects of residual stress on elastic plastic behavior of metallic glass bolts formed by cold thread rolling

Metallic glass (MG) has unique mechanical properties, combining high strength and low Young's modulus. By using MG to fabricate fasteningbolts, high resistance against bolt loosening is expected. However, MG components are considered brittle because MG exhibits poor ductility when subjected to uniaxial loading at room temperature. We have developed hexagonal cap bolts made of zirconium-based MG by cold thread rolling. The MG bolts showed a 1.6% plastic strain with a tensile strength of more than 1550MPa. In addition, the load–strain curve was similar to that of a strain hardening material, although MG itself is free of strain hardening. In this study, we attempted to clarify the reasons for these characteristics, which are advantageous for bolts in terms of toughness and reliability. Various experiments and numerical analysis indicated that residual stress plays an important role in the behavior.

The Boron Conundrum: Which Principles Underlie the Formation of Large Hollow Boron Cages?

Extensive optimisation calculations are performed for the B(80) isomers in order to find out which principles underlie the formation of large hollow boron cages. Our analysis shows that the most stable isomers contain triangular B(10) or rhombohedral B(16) building blocks. The lowest-energy isomer has C(3v) symmetry and is characterised by a belt of three interconnected B(16) units and two separate B(10) units. At the B3LYP/6-31G(d) level of theory, this newly discovered isomer is 2.29, 1.48, and 0.54 eV below the leapfrog B(80) of Szwacki et al., the T(h) -B(80) of Wang, and the D(3d) -B(80) of Pochet et al., respectively. Our C(3v) isomer is therefore identified as the most stable hollow cage isomer of B(80) presently known. Its HOMO-LUMO gap of 1.6 eV approaches that of the leapfrog B(80). The leapfrog principle still remains a reliable scheme for producing boron cages with larger HOMO-LUMO gaps, whereas the thermodynamically most stable B(80) cages are formed when all pentagonal faces are capped. We show that large hollow cages of boron retain a preference for fullerene frames. The additional capping is in accordance with the following rules: preference for capping of pentagonal faces, formation of B(10) and/or B(16) units, homogeneous distribution of the hexagonal caps, and hole density approaching 1/9. Although our most stable B(80) isomer still remains higher in energy than the B(80) core-shell structure, we show that by applying the bonding principles to larger structures it is possible to construct boron cages with higher stabilisation energy per boron atom than the core-shell structure; a prototypical example is B(160). This clearly shows the continuous competition between the two suggested construction schemes, namely, the formation of multiple-shell structures and hollow cages.

S113014 金属ガラスボルトの締結特性とゆるみの評価([S113-01]機械要素の設計・製造・応用技術(1))

Bulk metallic glass (BMG) has unique mechanical properties, combining high strength and low Young's modulus. By applying BMG to the fabrication of fastening bolts, high resistance against bolt loosening is expected. The authors have developed hexagonal cap bolts made of zirconium-based BMG by cold thread rolling. The BMG bolt showed a high tensile strength of more than 1550 MPa with 1.6% plastic strain. In this study, fastening features of the BMG bolts are investigated comparing with those of conventional high tensile strength steel bolts. In addition, bolt loosening test were conducted by using newly developed test equipment which comply with Junker's test machine. The test parameters are initial clamping force and amplitude of oscillation applied to the direction perpendicular to bolt axis. The results reveal that BMG bolt maintains the clamping force at the larger oscillation amplitude with smaller initial clamping force than high tensile strength steel bolts.

Effects of Residual Stress on Elastic Plastic Behavior of Metallic Glass Bolts Formed by Cold Thread Rolling

Metallic glass (MG) has unique mechanical properties, combining high strength and low Young’s modulus. By applying MG to the fabrication of fastening bolts, high resistance against bolt loosening is expected. However, MG components are thought to be brittle because MG exhibits poor ductility when subjected to uniaxial loading at room temperature. We have developed hexagonal cap bolts made of zirconium-based MG by cold thread rolling. The MG bolt showed a 1.6% plastic strain with a tensile strength of more than 1550 MPa. In addition, the load-strain curve was similar to that of a strain hardening material although MG itself is free of strain hardening. In this study, we attempt to clarify the reasons for the behavior, which are advantageous for bolts in terms of toughness and reliability. Various experiments and numerical analysis indicate that residual stress plays an important role in the behavior.

Catalyst-free synthesis of single crystalline ZnO nanonails with ultra-thin caps

Arrays of single-crystalline ZnO nanonails with tapering diameters and ultra-thin caps have been successfully synthesized on a silicon substrate via a simple catalyst-free thermal evaporation method. Each of the ZnO nanonails consists a nanowire (stem) on the bottom and an ultra-thin symmetrical hexagonal cap on the top. Structural characterization reveals that the synthesized ZnO nanonail has a wurtzite (WZ) structure with a preferred growth direction of [0001] in the stem and in the cap. Remarkably, the ultra-thin cap shows a diameter-to-thickness ratio of over 20 : 1, which is much higher in magnitude than those reported in previous works. Based on the systematic morphological characterization and structural analysis, a self-catalyzed vapor–liquid–solid (VLS) mechanism followed by a vapor–solid (VS) process is proposed to explain the growth of the nanonails. Optical properties are also investigated with Raman and photoluminescence (PL) techniques, which show good crystal quality of the synthesized nanonails.

Growth mechanism and multiphoton-induced photoluminescence of crownlike zinc oxide

A crownlike zinc oxide crystal composed of a hexagonal cap and a towerlike shaft was synthesized by vapor-phase transport method. Based on vapor–liquid–solid and vapor–solid mechanism, the growth model of the crystal was proposed. Under the excitation of pulse laser with 1150-nm wavelength, strong ultraviolet emission at 388 nm was observed. The peak position and the relationship between the emission intensity and excitation intensity demonstrated that the ultraviolet photoluminescence was induced by three-photon absorption. The photoluminescence characteristic of the sample was investigated.

Growth and Properties of Ultra-Violet Emitting Aligned Zinc Oxide Nanocones with Hexagonal Caps

Ultraviolet-emitting, single-crystalline aligned zinc oxide (ZnO) nanocones with hexagonal caps were grown on silicon substrate via simple non-catalytic thermal evaporation process. High-purity metallic zinc powder and oxygen were used as source materials for zinc and oxygen, respectively. The detailed structural characterizations confirmed that the formed products are single-crystalline, possess a wurtzite hexagonal phase and grown along the c-axis direction. Raman-active optical-phonon E2(high) mode at 437 cm(-1) with sharp and strong UV emission at 385 nm in room-temperature photoluminescence (PL) spectrum demonstrated that the as-grown ZnO nanocones with hexagonal caps possess good-crystal quality with the excellent optical properties. Finally, a plausible growth mechanism for the formation of as-grown ZnO nanocones with hexagonal caps was also proposed.

Mn-doped ZnO nanonails and their magnetic properties

Mn-doped ZnO nanonails composed of hexagonal caps and shafts with large dopingconcentrations from 11.7 to 35.1 at.% were synthesized via a simple and straightforwardnon-aqueous solution-based route. The chemical composition, morphology and structure of theobtained nanocrystals were characterized by energy-dispersive x-ray analysis, powder x-raydiffraction and transmission electron microscopy. The results show that the nanonails possess asingle-crystal wurtzite structure. Electron paramagnetic resonance results indicate thatMn2 + ions substitute for the zinc sites in the ZnO matrix, which is also confirmedby high-resolution electron microscopy. Thermal tolerance experiments showthat the Mn-doped nanonails can maintain their crystalline structure up to700 °C. The influence of reaction conditions on the size and shape of the ZnO-based samples hasbeen investigated in detail, and the possible growth mechanism of the nanonails has alsobeen discussed.

Simple solvothermal route to synthesize S-doped ZnO nanonails and ZnS/ZnO core/shell nanorods

A simple solvothermal route was successfully utilized to fabricate S-doped ZnO nanonails with a hexagonal cap followed by a comparatively thin long needle shaped stem portion. Diameters of the hexagonal caps varied within 10–25 nm and lengths of the stem portions varied within 50–80 nm. These nanonails were found to exhibit intense green light emission property at room temperature. Similar synthesis protocol was employed to fabricate ZnS/ZnO core/shell nanorods by suitably tailoring the concentration of the sulfur source in the synthesis environment.

Catalyst-free synthesis of macro-scale ZnO nanonail arrays on Si substrate by simple physical vapor deposition

Macro-scale ZnO nanonail arrays have been synthesized on silicon wafer by a simple physical vapor deposition approach without any catalyst. These synthesized ZnO nanonails grow vertically on the substrate with their caps upside. This probably results from the crowding effect. Each ZnO nanonail has a large hexagonal cap and a thinner shaft of several microns in length. Most of the nanonails are perfect single crystals with wurtzite structure and their preferred growth orientation is along [001] direction. The growth mechanism is VS mechanism and the detailed growth process is also proposed. The macro-scale nanonail arrays on Si substrate could offer novel opportunities for both fundamental research and technological applications.

Simple Solvothermal Route To Synthesize ZnO Nanosheets, Nanonails, and Well-Aligned Nanorod Arrays

ZnO nanosheets, nanonails, and well-aligned nanorods were fabricated on Zn foils by a solvothermal approach using ethanol as the solvent. A lower synthesis temperature and a shorter time period favor the formation of nanosheets. By optimizing the synthesis temperature and time period, ZnO nanonails with a hexagonal cap and a long stem could be produced. A higher temperature was not favorable to produce uniform and smooth nanorods. Well-aligned ZnO nanorod arrays were produced with diameters within 100-250 nm and lengths up to approximately 6 microm when NaOH was added to the solvent. By optimizing the reaction parameters, the morphology, size, and orientation of the nanoforms could be tailored. The ZnO nanorods exhibit an excitonic strong UV emission and a defect-related broad green emission at room temperature. The defect-related green emission band decreased with the improvement of the degree of alignment of the nanorods.

Functional morphology and taxonomic significance of a novel cuticular Structure in Cretaceous Raninid crabs (Decapoda: Brachyura: Raninidae)

Fossil raninid crabs,Cretacoranina punctata(Rathbun, 1935), from the Pawpaw Formation (Upper Cretaceous) of Fort Worth, Texas, exhibit an unusual cuticular morphology. Comparison of the cuticle of extantRaninoides louisianensisto that ofC. punctatareveals general similarities in endocuticular, exocuticular, and epicuticular ultrastructure; however, their gross morphology is strikingly different. The surface of the carapace ofC. punctataappears pebbled, much like the surface of a basketball, with closely packed, hexagonal caps. In cross-section, these caps are the upper portion of fungiform structures within convoluted exocuticle. Along the anterior margin, anterolateral margins, and pterygostomial region of the carapace ofC. punctataeach cap dips slightly posteriorly, creating a series of tiny terraces. In contrast to terrace lines, questa lines, spines, and nodes that provide frictional resistance in interactions with coarse-grained sediments, the fine relief and contouring of the pebbled surface of the carapace ofC. punctataprovides frictional resistance in interactions with fine-grained sediments.Cretacoranina dichrous, C. trechmanni, C. testacea,andC. schloenbachi,as well asEucorystes carteriwere all found to possess variations of the exocuticular structures seen onC. punctata.This pebbled surface has not been recognized in any other decapod taxon, nor has its structure and function been described previously.