Hexagonal Network Research Articles

Quinoxaline-annelated hexadehydro[12]annulene: use of a new building block to construct a hydrogen-bonded hexagonal molecular network

A new hexatopic carboxylic acid with a quinoxaline-annelated hexadehydro[12]annulene core (TQ12) was synthesized and subjected to spectroscopy for comparison with tribenzohexadehydro[12]annulene derivative (T12).

Unique orientation of 1D and 2D nanoparticle assemblies confined in smectic topological defects.

New collective optical properties have emerged recently from organized and oriented arrays of closely packed semiconducting and metallic nanoparticles (NPs). However, it is still challenging to obtain NP assemblies which are similar everywhere on a given sample and, most importantly, share a unique common orientation that would guarantee a unique behavior everywhere on the sample. In this context, by combining optical microscopy, fluorescence microscopy and synchrotron-based grazing incidence X-ray scattering (GISAXS) of assemblies of gold nanospheres and of fluorescent nanorods, we study the interactions between NPs and liquid crystal smectic topological defects that can ultimately lead to unique NP orientations. We demonstrate that arrays of one-dimensional - 1D (dislocations) and two-dimensional - 2D (grain boundaries) topological defects oriented along one single direction confine and organize NPs in closely packed networks but also orient both single nanorods and NP networks along the same direction. Through the comparison between smectic films associated with different kinds of topological defects, we highlight that the coupling between the NP ligands and the smectic layers below the grain boundaries may be necessary to allow for fixed NP orientation. This is in contrast with 1D defects, where the induced orientation of the NPs is intrinsically induced by the confinement independently of the ligand nature. We thus succeeded in achieving the fixed polarization of assemblies of single photon emitters in defects. For gold nanospheres confined in grain boundaries, a strict orientation of hexagonal networks has been obtained with the 〈10〉 direction strictly parallel to the defects. With such closely packed and oriented NPs, new collective properties are now foreseen.

Chiral copper(i)–organic frameworks for dye degradation and the enantioselective recognition of amino acids

Four novel chiral CMOFs with a 2D layered hexagonal network have been prepared and used for dye adsorption and degradation. Furthermore, one exhibits different adsorption rates and efficiencies for chiral amino acids.

Ab initio Study of the Electronic and Optical Properties of Stable Boron Sheet

Utilizing first principles calculations within PW91 exchange-correlation method, we investigated a boron sheet that exhibits related electronic properties. The 2-dimensional boron sheet is flattened and has an atomic structure where the pair cores of every three ordered hexagons within the hexagonal network are loaded up by extra atoms, which saves the triangular lattice symmetry. The boron sheet takes possession of intrinsic metal properties and the electronic bands are comparable to the bands of the graphene that are close to the Fermi level. The real and imaginary parts of the dielectric function show a metallic or semiconductor behaviour, depending on the electric field direction.

Coordinated Multi Point Transmission and Reception for Mixed-Delay Traffic

This paper analyzes the multiplexing gains (MG) for simultaneous transmission of delay-sensitive and delay-tolerant data over interference networks. In the considered model, only delay-tolerant data can profit from coordinated multipoint (CoMP) transmission or reception techniques, because delay-sensitive data has to be transmitted without further delay. Transmission of delay-tolerant data is also subject to a delay constraint, which is however less stringent than the one on delay-sensitive data. Different coding schemes are proposed, and the corresponding MG pairs for delay-sensitive and delay-tolerant data are characterized for Wyner's linear symmetric network and for Wyner's two-dimensional hexagonal network with and without sectorization. For Wyner's linear symmetric also an information-theoretic converse is established and shown to be exact whenever the cooperation rates are sufficiently large or the delay-sensitive MG is small or moderate. These results show that on Wyner's symmetric linear network and for sufficiently large cooperation rates, the largest MG for delay-sensitive data can be achieved without penalizing the maximum sum-MG of both delay-sensitive and delay-tolerant data. A similar conclusion holds for Wyner's hexagonal network only for the model with sectorization. In the model without sectorization, a penalty in sum-MG is incurred whenever one insists on a positive delay-sensitive MG.

An All‐Fabric Droplet‐Based Energy Harvester with Topology Optimization

AbstractThe output power density of a triboelectric nanogenerator can be enhanced by several orders of magnitude by a field‐effect transistor like structure. However, the previously reported strip top electrode is not ideal for optimum generation and stable transfer of charges under practical dynamic conditions. Switched on by an impinged droplet, the bridged closed‐loop electric circuit transfers the accumulated charges by converting the conventional interfacial effect into a bulk effect. Randomly falling droplets cannot always exactly impinge the electrode with the desired spreading contact to achieve a high peak voltage, and a large fraction of low‐voltage direct‐contact and sliding‐contact modes will lead to low output and instability. To address this critical challenge, a topology‐optimized droplet energy harvesting fabric (TO‐DEHF) for stable and efficient output from randomly falling droplets is reported. The optimized fabric electrodes in a hexagonal network feature a stable open‐circuit voltage under moving and rotating patterns, threefold over that with the strip electrodes. The peak power density of the TO‐DEHF (71.8 mW m–2) is 4.8‐fold versus the latter (14.8 mW m–2). Moreover, the all‐fabric TO‐DEHF has high flexibility and breathability, based on which a self‐powered wireless wearable prototype is successfully demonstrated for detection of crucial droplet properties, including temperature, pH, and salinity.

Coordinated Multi Point Transmission and Reception for Mixed-Delay Traffic

This paper analyzes the multiplexing gains (MG) for simultaneous transmission of delay-sensitive and delay-tolerant data over interference networks. In the considered model, only delay-tolerant data can profit from coordinated multipoint (CoMP) transmission or reception techniques, because delay-sensitive data has to be transmitted without further delay. Transmission of delay-tolerant data is also subject to a delay constraint, which is however less stringent than the one on delay-sensitive data. Different coding schemes are proposed, and the corresponding MG pairs for delay-sensitive and delay-tolerant data characterized for Wyner’s linear symmetric network and for Wyner’s two-dimensional hexagonal network with and without sectorization. Information-theoretic converses are established for these models. For Wyners linear symmetric network the bounds match whenever the cooperation rates are sufficiently large or the delay-sensitive MG is small or moderate. These results show that on Wyner’s symmetric linear network and for sufficiently large cooperation rates, the largest MG for delay-sensitive data can be achieved without penalizing the maximum sum-MG of both delay-sensitive and delay-tolerant data. Our achievable schemes show that a similar conclusion holds for Wyner’s hexagonal network only for the model with sectorization. In the model without sectorization, a penalty in sum-MG is incurred whenever one insists on a positive delay-sensitive MG.

On Degree Based Topological Indices of Polycyclic Certain Interconnection Networks

Topological indices are the significant numerical quantities in the fields of chemical graph theory. Quantitative structure-property and structure-activity relationships of the Honeycomb Network, Hexagonal Network and Silicate Network SiO4 necessitate expressions for the molecular topological features of these networks. ev-degree and ve-degree established topological indices demarcated as analogous to their relating spouses. In this paper, we have computed topological indices based on ev-degree and ve-degree for the Honeycomb Network, Hexagonal Network and Silicate Network.

On the Study of Reverse Degree-Based Topological Properties for the Third Type of p th Chain Hex-Derived Network

Vertices and edges are made from a network, with the degree of a vertex referring to the number of connected edges. The chance of every vertex possessing a given degree is represented by a network’s degree appropriation, which reveals important global network characteristics. Many fields, including sociology, public health, business, medicine, engineering, computer science, and basic sciences, use network theory. Logistical networks, gene regulatory networks, metabolic networks, social networks, and driven networks are some of the most significant networks. In physical, theoretical, and environmental chemistry, a topological index is a numerical value assigned to a molecular structure/network that is used for correlation analysis. Hexagonal networks of dimension t are used to build hex-derived networks, which have a wide range of applications in computer science, medicine, and engineering. For the third type of hex-derived networks, topological indices of reverse degree based are discussed in this study.

Networked configurations as an emergent property of transverse aeolian ridges on Mars

Transverse aeolian ridges – enigmatic Martian features without a proven terrestrial analog – are increasingly important to our understanding of Martian surface processes. However, it is not well understood how the relationships between different ridges evolve. Here we present a hypothesis for the development of complex hexagonal networks from simple linear forms by analyzing HiRISE images from the Mars Reconnaissance Orbiter. We identify variable morphologies which show the presence of secondary ridges, feathered transverse aeolian ridges and both rectangular and hexagonal networks. We propose that the formation of secondary ridges and the reactivation of primary ridge crests produces sinuous networks which then progress from rectangular cells towards eventual hexagonal cells. This morphological progression may be explained by the ridges acting as roughness elements due to their increased spatial density which would drive a transition from two-dimensional bedforms under three-dimensional flow conditions, to three-dimensional bedforms under two-dimensional flow conditions.

Reducing Power Consumption in Hexagonal Wireless Sensor Networks Using Efficient Routing Protocols

Power consumption and network lifetime are vital issues in wireless sensor network (WSN) design. This motivated us to find innovative mechanisms that help in reducing energy consumption and prolonging the lifetime of such networks. In this paper, we propose a hexagonal model for WSNs to reduce power consumption when sending data from sensor nodes to cluster heads or the sink. Four models are proposed for cluster head positioning and the results were compared with well-known models such as Power Efficient Gathering In Sensor Information Systems (PEGASIS) and Low-Energy Adaptive Clustering Hierarchy (LEACH). The results showed that the proposed models reduced WSN power consumption and network lifetime.

A Heteromeric Carboxylic Acid Based Single-Crystalline Crosslinked Organic Framework.

The development of large pore single-crystalline covalently linked organic frameworks is critical in revealing the detailed structure-property relationship with substrates. One emergent approach is to photo-crosslink hydrogen-bonded molecular crystals. Introducing complementary hydrogen-bonded carboxylic acid building blocks is promising to construct large pore networks, but these molecules often form interpenetrated networks or non-porous solids. Herein, we introduced heteromeric carboxylic acid dimers to construct a non-interpenetrated molecular crystal. Crosslinking this crystal precursor with dithiols afforded a large pore single-crystalline hydrogen-bonded crosslinked organic framework HC OF-101. X-ray diffraction analysis revealed HC OF-101 as an interlayer connected hexagonal network, which possesses flexible linkages and large porous channels to host a hydrazone photoswitch. Multicycle Z/E-isomerization of the hydrazone took place reversibly within HC OF-101, showcasing the potential use of HC OF-101 for optical information storage.

A Heteromeric Carboxylic Acid Based Single‐Crystalline Crosslinked Organic Framework

AbstractThe development of large pore single‐crystalline covalently linked organic frameworks is critical in revealing the detailed structure‐property relationship with substrates. One emergent approach is to photo‐crosslink hydrogen‐bonded molecular crystals. Introducing complementary hydrogen‐bonded carboxylic acid building blocks is promising to construct large pore networks, but these molecules often form interpenetrated networks or non‐porous solids. Herein, we introduced heteromeric carboxylic acid dimers to construct a non‐interpenetrated molecular crystal. Crosslinking this crystal precursor with dithiols afforded a large pore single‐crystalline hydrogen‐bonded crosslinked organic framework HCOF‐101. X‐ray diffraction analysis revealed HCOF‐101 as an interlayer connected hexagonal network, which possesses flexible linkages and large porous channels to host a hydrazone photoswitch. Multicycle Z/E‐isomerization of the hydrazone took place reversibly within HCOF‐101, showcasing the potential use of HCOF‐101 for optical information storage.

Micrograin structure evolution associated with grain boundary characteristics in grade 91 steel during long-term creep exposure

Micrograin structure evolution in ASME Grade 91 steel after 233,823 h of creep exposure at 600 °C was characterized after grain boundary classification in terms of misorientation angle (MOA), boundary energy, and lath martensite substructure. Under long-term creep with an applied stress of 5.9 MPa, micrograin coarsening occurs by annihilation of lath boundaries, consisting of hexagonal dislocation networks (HDN), thanks to the “knitting-out” of dislocations from the boundary, and the absorption of interior mobile dislocations into the boundary. This annihilation is expectedly faster when the original lath boundary shows a small MOA, and is decorated by little precipitation (MX carbonitrides and boundary M23C6 carbides). Under long-term creep with an applied stress of 86.7 MPa, micrograin coarsening occurs not only by lath boundary annihilation, but also by the migration of all other boundary types found in the lath martensite microstructure. This migration is described as a strain-induced boundary migration (SIBM), and mainly occurs when boundaries are relatively precipitation-free, and a gradient of stored internal energy is present between adjacent grains. Even within the same class of boundary, the progress of SIBM differs due to the local evolution of precipitates and the actual boundary energy.

Design and manufacture of three-dimensional auxetic warp-knitted spacer fabrics based on re-entrant and rotating geometries

Warp knitting technology is a fabric-forming technologies that is very suitable to fabricate three-dimensional (3D) auxetic fabrics due to its high efficiency and powerful pattern designing possibilities. In this study, two typical auxetic geometries, namely the re-entrant hexagonal network and rotating square solids, were selected as the design prototypes for the design and manufacture of 3D warp-knitted spacer fabrics. While two 3D warp-knitted spacer fabric structures with representative units of different sizes designed based on the re-entrant hexagonal geometry were manufactured by using a RD7 double needle bar Raschel machine with seven yarn guide bars, two 3D jacquard warp-knitted spacer fabrics with different base fabric structures designed based on the rotating squares geometry were fabricated by using a RDPJ4/2 double needle bar jacquard machine with two ground yarn guide bars and four jacquard guide bars. The Poisson’s ratios of these 3D warp-knitted fabrics in the course direction and wale direction were evaluated respectively through constant-rate tensile tests. The results revealed that the re-entrant hexagonal fabric structure with double chain stitches has auxetic behavior across a wide range of tensile strains along the course direction, while the rotating square fabric structure with elastic chain stitches as the base is auxetic within a narrow range of tensile strains along the wale direction. The study provides an alternative method to directly produce auxetic warp-knitted spacer fabrics through a single knitting process instead of using an additional post-compression and heat-setting process.

Structural Transformation of Surface-Confined Porphyrin Networks by Addition of Co Atoms.

The self‐assembly of a nickel‐porphyrin derivative (Ni‐DPPyP) containing two pyridyl coordinating sites and two pentyl chains at trans meso positions was studied with scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) on Au(111). Deposition of Ni‐DPPyP onto Au(111) gave rise to a close‐packed network for coverages smaller or equal to one monolayer as revealed by STM and LEED. The molecular arrangement of this two‐dimensional network is stabilized via hydrogen bonds formed between the pyridyl's nitrogen and hydrogen atoms from the pyrrole groups of neighboring molecules. Subsequent deposition of cobalt atoms onto the close‐packed network and post‐deposition annealing at 423 K led to the formation of a Co‐coordinated hexagonal porous network. As confirmed by XPS measurements, the porous network is stabilized by metal‐ligand interactions between one cobalt atom and three pyridyl ligands, each pyridyl ligand coming from a different Ni‐DPPyP molecule.

Void-Defect Induced Magnetism and Structure Change of Carbon Material-Ⅲ: Hydrocarbon Molecules

Void-defect induced magnetism of graphene molecule was recently reported in our previous paper of this series study. This paper investigated the case of hydrogenated graphene molecule, in chemical term, polycyclic aromatic hydrocarbon (PAH). Molecular infrared spectrum obtained by density functional theory was compared with astronomical observation. Void-defect on PAH caused serious structure change. Typical example of C23H12 had two carbon pentagon rings among hexagon networks. Stable spin state was non-magnetic singlet state. This is contrary to pure carbon case of C23, which show magnetic triplet state. It was discussed that Hydrogen played an important role to diminish magnetism by creating an SP3-bond among SP2-networks. Such a structure change affected molecular vibration and finally to photoemission spectrum in infrared region. The dication-C23H12 showed featured bands at 3.2, 6.3, 7.7, 8.6, 11.2, and 12.7 micrometer. It was surprising that those calculated bands coincided well with astronomically observed bands in many planetary nebulae. To confirm our study, large size molecule of C53H18 was studied. Calculation reproduced again similar astronomical bands. Also, small size molecule of C12H8 showed good coincidence with the spectrum observed for young stars. This paper would be the first report to indicate the specific PAH in space.

Ultra-hard rhombohedral carbon by crystal chemistry and ab initio investigations

A new ultra-hard rhombohedral carbon rh-C4 (or hexagonal h-C12) is reported as derived from 3R graphite through crystal chemistry construction and ground state energy within the density functional theory. A resulting cohesive extended hexagonal three-dimensional network of h-C12 is identified as formed of C4 tetrahedra like in cubic and hexagonal diamond. The electronic band structure of rh-C4 is characteristic of insulator with Egap ​= ​4 ​eV similarly to diamond. From the energy-volume equations of state and the set of elastic constants a larger value of bulk modulus versus lonsdaleite, and the largest Vickers hardness (HV) versus both forms of diamond were revealed. The phonon band structure showing only real wave numbers further confirms the stability of the new carbon phase.

Targeting cooling for quantum dots by 57.3°C with air-bubbles-assembled three-dimensional hexagonal boron nitride heat dissipation networks

The non-radiative electron transitions of Quantum dots (QDs) in White light-emitting diodes (WLEDs) not only generates thermal phonons with temperature rise but also degrades their photonic properties. These nanoscale heat sources are usually embedded in low-thermal-conductivity polymer matrix, which is difficult for building efficient heat dissipation pathways without sacrificing the optical performance simultaneously. Herein, we reported an air-bubbles-assembly strategy to construct three-dimensional (3D) thermal dissipation network inside the QDs-WLEDs. Owing to the lateral expulsion of massive microscale air-bubbles, an interconnected hexagonal boron nitride (hBN) network was established under an extremely low hBN loading of 2.74 wt%. With this efficient 3D/hBN network, the highest working temperature of QDs was dramatically decreased by 57.3°C at 700 mA. More than that, the 3D/hBN-WLEDs also show high luminous efficacy of 84.6 lm/W as well as superior color rendering index of Ra = 94.1 and R9 = 93.8, which are comparable to those of traditional WLEDs. The proposed strategy is expected to pave a new door for targeting cooling QDs and other photoluminescent nanoparticles at high-power applications.

Computation of Nirmala Indices of Some Chemical Networks

Chemical graph theory is a branch of graph theory whose focus of interest is to finding topological indices of chemical graphs which correlate well with chemical properties of the chemical molecules. In this paper, we compute the Nirmala index, first and second inverse Nirmala indices for some chemical networks like silicate networks, chain silicate networks, hexagonal networks, oxide networks and honeycomb networks along with their comparative analysis.