Open Network Structure Research Articles

Network-based queuing model for simulating passenger throughput at an airport security checkpoint

This paper models different passenger strategies, shows potential network structures, and compares different performance cases for queuing at airport security checkpoints. Our findings show that different network structures require different passenger strategies to achieve optimal performance. The open network structure performs significantly better than the restrictive one, and the allocation of more security staff for baggage checking improves performance under the precondition that the total number of security staff remains constant. We also find that the combination of n M/M/1 systems will perform almost the same or even better than the M/M/n system when the passengers' strategies and feelings are considered. Based on these findings, some practical insights are provided on how to improve airport security checkpoints.

High Surface Area NanoCOT Catalysts on Ni Foam Framework for Efficient Water Electrolysis

We report high surface area NanoCOT catalytic materials built on porous nickel foam for enhanced oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) of complete water splitting. Ni foam was coated with NanoCOT, a highly active material containing carbon, oxygen, and titanium. NanoCOT is synthesized and deposited on Ni foam from facile carbon thermal modification of Fe3+ treated P25 TiO2 nanoparticles in an atmosphere of methane, hydrogen, and nitrogen. Both the cathode and anode are prepared on Ni foam due to its high surface area and open 3D network structure. An alloy of NiMoZn was electrodeposited on Ni foam for HER. In addition to NanoCOT, electrodeposition of amorphous FeOOH was used to promote the oxygen evolution reaction (OER) on nickel foam in this study. The enhanced catalytic activities of the as-synthesized electrodes than previously reported NanoCOT electrode on planer substrate are attributed to the nanostructured COT electrode material and high surface area of Ni foam.

Open network structures from 2D hydrogen bonded networks: diaminotriazyl tetraoxapentacenes

Crystals of1show two-dimensional hydrogen-bonded sheets that are prevented from packing closely by the large core, resulting in open network structures.

Urban Vitality in Dutch and Chinese New Towns. A comparative study between Almere and Tongzhou

Urban Vitality in Dutch and Chinese New Towns. A comparative study between Almere and Tongzhou

Porosity Governs Normal Stresses in Polymer Gels.

When sheared, most elastic solids including metals, rubbers, and polymer gels dilate perpendicularly to the shear plane. This behavior, known as the Poynting effect, is characterized by a positive normal stress. Surprisingly, fibrous biopolymer gels exhibit a negative normal stress under shear. Here we show that this anomalous behavior originates from the open-network structure of biopolymer gels. Using fibrin networks with a controllable pore size as a model system, we show that the normal-stress response to an applied shear is positive at short times, but decreases to negative values with a characteristic time scale set by pore size. Using a two-fluid model, we develop a quantitative theory that unifies the opposite behaviors encountered in synthetic and biopolymer gels.

PClass+: A Novel Evolving Semi-Supervised Classifier

A novel evolving semi-supervised classifier, namely Parsimonious Classifier+ (pClass+), is proposed in this paper. pClass+ enhances a recently developed classifier, namely pClass, for a semi-supervised learning scenario. As with its predecessor, pClass+ is capable of initiating its learning process from scratch with an empty rule base and adopts an open network structure, where fuzzy rules are evolved, pruned, and recalled automatically on demands. The novelty of pClass+ lies in an online active learning technique, which decreases operator’s annotation efforts and expedites its training process. pClass+ is also equipped with a new parameter identification strategy to cope with the class overlapping situation. The efficacy of pClass+ has been experimentally validated with numerous synthetic and real-world study cases, confirmed by thorough statistical tests and comparisons against state-of-the art classifiers, where pClass+ outperforms its counterparts in achieving the best trade-off between accuracy and complexity.

Interorganizational Alignment of Strategic Orientations in Supply Chains

This study argues that Market Orientation, Learning Orientation, Innovation Orientation and Relationship Orientation provide synergic effects to organizations in organizational and interorganizational levels. Two theoretical frameworks are presented in this theoretical essay. The first one considers the organizational level. The second one is regarded to interorganizational relations. This study argues that actors might improve their results and increase joint performance through a strategic alignment along a supply chain. Besides, network features like positioning, structural holes and density might impact on joint performance achieved through this strategic alignment. Thus, this study suggests that Learning Orientation in a competitive environment might harm joint performance, considering that some actors might act opportunistically defending their knowledge acquisition. Future studies should be focused on issues like open innovation, opportunistic behavior and network structures.

Interconnected α-Fe2O3 nanosheet arrays as high-performance anode materials for lithium-ion batteries

The electrode materials with structure stability and binder-free are urgently required for improving the electrochemical performance of lithium-ion batteries. In this work, interconnected α-Fe2O3 nanosheet arrays directly grown on Ti foil were fabricated via a facile galvanostatic electrodeposition method followed by thermal treatment. The as-prepared α-Fe2O3 has an open network structure constituted of interconnected nanosheets and can be directly used as integrated electrodes for lithium-ion batteries. The α-Fe2O3 nanosheet arrays exhibit a high reversible capacity of 986.3mAhg−1 at a current density of 100mAg−1. Moreover, a reversible capacity of ca. 425.9mAhg−1 is achieved even at a superhigh current density of 10Ag−1, which is higher than the theoretical capacity of commercially used graphite. The excellent performance could be attributed to the efficient electron transport, the large electrode/electrolyte interfaces and the good accommodations for volume expansion from the interconnected nanosheet arrays structure.

MnO2-Vertical graphene nanosheets composite electrodes for energy storage devices

The vertical graphene nanosheets (VGNs) have attracted considerable attention for energy storage application due to their inherent properties such as morphology, large surface area, high electrical conductivity and three dimensional (3D) open network structures. Here, we report on the growth of VGNs using electron cyclotron resonance - chemical vapor deposition and its electrochemical storage behavior. Further, a near homogeneous dispersion of MnO2 is coated over VGNs by dip casting to enhance the effective capacitance. Electrochemical charge storage behavior of VGNs and MnO2/VGNs composites are investigated using cyclic voltametry and electrochemical impedance spectroscopy (EIS) and also the results are compared. The MnO2/VGNs composites exhibit the highest areal capacitance of 5.6 mF/cm2, which is 110 times higher than that of VGNs (51.95 μF/cm2) at a scan rate of 50 mV/s. The enhanced capacitance is due to highly conductive 3D network of VGNs which provide fast electron and ion transport and also a large pseudo-capacitance from MnO2 coating. The EIS results are analyzed with equivalent circuit model which reveals the charge storage mechanism in the materials. Scanning electron microscopy and Raman spectroscopy are also used to understand the morphology and structure – property correlations of the films. These results demonstrate clearly that the MnO2/VGNs composite is a potential candidate for energy storage applications.

Structural diversity in metal–organic nanoparticles based on iron isopropoxide treated lignin

The magnetic nature of iron-containing nanoparticles enables multiple high-end applications.

Facile Synthesis and Characterization of Two Dimensional Layered Tin Disulfide Nanowalls

Two dimensional layered metal chalcogenides, especially tin sulfides, have recently received great interest due to their enticing physical and chemical properties and hold promise for various applications. We report on synthesis of phase-pure two dimensional tin disulfide nanowalls by a facile vapor-phase synthesis method on insulator substrates such as silicon dioxide and magnesium oxide using tin dioxide and sulfur powders as precursors. The synthesized tin disulfide nanowalls have been characterized to study their fundamental properties by using various techniques such as scanning electron microscopy, x-ray diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. The synthesized films have an open network structure constituted of very uniform interconnected nanowalls with high crystallinity.

(Invited) Impact of Nafion Dispersion Morphology on Fuel Cell Performance and Durability

Los Alamos National Laboratory fuel cell team has discovered that Nafion dispersion morphology in dilute liquid media ca. solid content: 2.5 wt.% has distinctive characteristics, depending on dispersing fluid:[ref. 1] Small angle neutron scattering (SANS) and 19F NMR analysis indicated (i) a well-defined cylindrical dispersion in polyhydric alcohols, (ii) a gel particles that have as open network structure with sufficiently sparse physical network connections in some aprotic dispersing fluids, and (iii) a less-defined highly solvated large particle in water-monohydric alcohol mixtures. In this talk, we present the impact of dilute Nafion dispersion morphology on film/electrode formation, fuel cell performance and durability. Following subjects will be discussed with some details: 1. Change of particle morphology and gelation behavior of Nafion dispersion during evaporation process (Fig.1).[ref. 2] 2. Characterization of fuel cell electrode by microscopy and electrochemical methods. 3. Impact on fuel cell initial and long-term performance during potential cycles.[ref. 3] Other critical effects including mechanical toughness of dispersion-cast membranes and electrode reaction uniformity [ref. 4] will be also discussed at the meeting. This presentation will give some insights on recent progress of engineering production and processing of perfluorinated sulfonic acid ionomers and their application for fuel cell membrane and electrode processing. Acknowledgment U.S. Department of Energy Fuel Cell Technologies Program (Dr. Dimitrios Papageorgopoulos)

Synthesis of Supported Gold Nanocatalysts for the Oxidation of Alkyl Benzenes

Selective oxidation of alkyl benzene, to its corresponding oxygen containing products, is a crucial reaction in organic researches and industrial manufacturing. In particular, the direct oxidation of lavish and cheapest aromatics, having carbon-hydrogen bonds, into corresponding ketones are the key transformations as the oxidation products are very important platform compounds for the production of useful prime, special chemicals and high economic valued fine chemicals, agrochemicals, pharmaceutical and perfumes in large scale. However, the oxidations of aromatic hydrocarbons have been remaining a challenging task due to the limitations of a suitable catalyst and requirement of chemical treatments (potassium permanganate/dichromate and ammonium cerium nitrate) which have been proven to be corrosive, not reusable, hazardous, and environmentally unfriendly and, also, have no selectivity at all. Instead of, scientists are paying more attention to use heterogeneous green catalysts along with support as well as novel oxidants e.g. hydrogen peroxide, tert-butyl peroxide and so on, due to its ecofriendly nature and availability. Silica/carbon/metal oxide supported nanoporous gold is a favorable catalyst due to its three dimensional open pore network structures, high surface to volume ratio, high reusability, distinct optolectronic and physio-chemical properties. Mesoporous carbon/silica/metal oxide supports provide well scattering of metal nanocatalysts and facilitate the transportation of molecules through the nanopores/nanochannels, thus increase the product with lowest cost and time. This paper has reviewed various gold-skeleton green catalysts and their synthetic method and mechanistic schemes for the selective oxidation of alkyl substituted aromatics.

Photocatalytic activity of reticulated ZnO porous ceramics in degradation of azo dye molecules

Reticulated ZnO ceramics with an open cell three-dimensional network structure were processed in the present study by polymer sponge replication method. The fabricated highly porous ceramics were used as catalysts in ultraviolet (UV) light-assisted degradation of an azo dye (Reactive Red 180 (RR180)). Decolorization of a model 50mg/L aqueous solution of RR180 and removal of its by-products (total organic carbon (TOC) efficiencies) were significantly improved by this reticulated ZnO structure as compared with those of “solid” plate-shaped catalysts produced by tape casting method for our previous investigations. After 180min total processing time for the 500mL solution under UVC irradiation and for the same amount of catalyst (11g), the performances of 82.6% and 48.0% for color removal and 18.3% and 5.5% for TOC removal were reached in the presence of the reticulated and the plate-shaped ZnO catalysts, respectively.

Highly porous nickel@carbon sponge as a novel type of three-dimensional anode with low cost for high catalytic performance of urea electro-oxidation in alkaline medium

Highly porous nickel@carbon sponge electrode with low cost is synthesized via a facile sponge carbonization method coupled with a direct electrodeposition of Ni. The obtained electrodes are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The catalytic performances of urea electro-oxidation in alkaline medium are investigated by cyclic voltammetry (CV) and chronoamperometry (CA). The Ni@carbon sponge electrode exhibits three-dimensional open network structures with a large surface area. Remarkably, the Ni@carbon sponge electrode shows much higher electrocatalytic activity and lower onset oxidation potential towards urea electro-oxidation compared to a Ni/Ti flat electrode synthesized by the same procedure. The Ni@carbon sponge electrode achieves an onset oxidation potential of 0.24 V (vs. Ag/AgCl) and a peak current density of 290 mA cm−2 in 5 mol L−1 NaOH and 0.10 mol L−1 urea solutions accompanied with a desirable stability. The impressive electrocatalytic activity is largely attributed to the high intrinsic electronic conductivity, superior porous network structures and rich surface Ni active species, which can largely boost the interfacial electroactive sites and charge transfer rates for urea electro-oxidation in alkaline medium, indicating promising applications in fuel cells.

Nanoclustered Gold: A Promising Green Catalysts for the Oxidation of Alkyl Substituted Benzenes

Catalytic oxidation of alkyl substituted benzenes is an essential route for the synthesis of a number of important chemicals, perfumes, drugs and pharmaceuticals. The oxidation products of ethyl benzene are important precursors for a wide range of pharmaceuticals and synthetic materials. Acetophenone and 1-phenylethanol are two oxidation products of ethyl benzene which are the precursors of optically active alcohol, benzalacetophanones, hydrazones and so on. However, the oxidations of alkyl substituted benzenes have been remaining a challenging task. This is because of the limitations of an appropriate catalyst and requirement of corrosive chemical treatments (potassium permanganate/dichromate and ammonium cerium nitrate) which are hazardous and environmentally unfriendly. The current industrial practice in the oxidation of ethyl benzene unfortunately involves high temperature thermal autoxidation in the absence of catalysts. Although few catalysts have been tested for the oxidation of ethyl benzene, many of them found to be inefficient. For example, cobalt (II) oxide-immobilized on mesoporous silica (Co/SBA-15) was used to catalyze oxidation of alkyl benzene at high temperature (125-150°C) but only 70% conversion was obtained after prolong treatment at 150°C. Additionally, the catalyst formed mixed uncontrolled oxidation products like 1-phenylethyl hydro peroxide, benzoic acid, acetophenone and phenyl ethanol. Carbon/silica/metal oxide supported nanoporous gold is a promising green catalyst for heterogenous molecular transformation. This is because of their three dimensional open pore network structures, high surface to volume ratio, high reusability, distinct optolectronic and physio-chemical properties. Mesoporous carbon/silica/metal oxide thin film supports provide increase dispersion of metal nanocatalysts and facilitate transport of molecules, ions or electrons through the nanopores/nanochannels, enhancing product yields with minimum cost and time. This paper has reviewed various gold-skeleton green catalysts and their preparation and mechanistic schemes for the selective oxidation of alkyl substituted benzenes.

High-Performance Multifunctional Graphene Yarns: Toward Wearable All-Carbon Energy Storage Textiles

The successful commercialization of smart wearable garments is hindered by the lack of fully integrated carbon-based energy storage devices into smart wearables. Since electrodes are the active components that determine the performance of energy storage systems, it is important to rationally design and engineer hierarchical architectures atboth the nano- and macroscale that can enjoy all of the necessary requirements for a perfect electrode. Here we demonstrate a large-scale flexible fabrication of highly porous high-performance multifunctional graphene oxide (GO) and rGO fibers and yarns by taking advantage of the intrinsic soft self-assembly behavior of ultralarge graphene oxide liquid crystalline dispersions. The produced yarns, which are the only practical form of these architectures for real-life device applications, were found to be mechanically robust (Young's modulus in excess of 29 GPa) and exhibited high native electrical conductivity (2508 ± 632 S m(-1)) and exceptionally high specific surface area (2605 m(2) g(-1) before reduction and 2210 m(2) g(-1) after reduction). Furthermore, the highly porous nature of these architectures enabled us to translate the superior electrochemical properties of individual graphene sheets into practical everyday use devices with complex geometrical architectures. The as-prepared final architectures exhibited an open network structure with a continuous ion transport network, resulting in unrivaled charge storage capacity (409 F g(-1) at 1 A g(-1)) and rate capability (56 F g(-1) at 100 A g(-1)) while maintaining their strong flexible nature.

1,3,5,7-Tetrakis(tetrazol-5-yl)-adamantane: the smallest tetrahedral tetrazole-functionalized ligand and its complexes formed by reaction with anhydrous M(II)Cl2 (M = Mn, Cu, Zn, Cd).

1,3,5,7-Tetrakis(tetrazol-5-yl)-adamantane (H4L) was probed as a building block for the synthesis of tetrazolato/halido coordination polymers with open-network structures. MCl2 (M = Cu, Cd, Zn, Mn) was reacted with H4L in DMF at 70 °C to yield [Cu4Cl4L(DMF)5]·DMF, ; [Cd4Cl4L(DMF)7]·DMF, ; [Zn3Cl2L(DMF)4]·2DMF, and [Mn2L(DMF)2(MeOH)4]·DMF·2MeOH·2H2O, . and (Fddd) are nearly isostructural and have zeolitic structures with a {4(3)·6(2)·8}, gis or gismondine underlying net, where the role of the tetrahedral nodes is served by the coordination bonded clusters and the adamantane moiety. (P21/n) has a porous structure composed of coordination bonded layers with a (4·8(2)) fes topology joined via trans-{Zn(tetrazolate)2(DMF)4} pillars with an overall topology of {4·6(2)}{4·6(6)·8(3)}, fsc-3,5-Cmce-2. (Pca21) is composed of stacked {Mn2L} hexagonal networks. In and the ligand fulfills a symmetric role of a tetrahedral building block, while in and it fulfills rather a role of an effective trigonal unit. Methanol-exchanged and activated displayed an unusual type IV isotherm with H2 type hysteresis for N2 sorption with an expected uptake at high P/P0, but with a smaller SBET = 505.5 m(2) g(-1) compared to the calculated 1789 m(2) g(-1), which is a possible result of the framework's flexibility. For H2 sorption 0.79 wt% (1 bar, 77 K) and 0.06 wt% (1 bar, RT) uptake and Qst = -7.2 kJ mol(-1) heat of adsorption (77 K) were recorded. Weak antiferromagnetic interactions were found in and with J1 = -9.60(1), J2 = -17.2(2), J3 = -2.28(10) cm(-1) and J = -0.76 cm(-1) respectively. The formation of zeolitic structures in and , the concept of structural 'imprinting' of rigid building blocks, and design opportunities suggested as a potential hexafunctionalized biadamantane building block.

Facile synthesis of ZnWO4nanowall arrays on Ni foam for high performance supercapacitors

In this report, ZnWO4 nanowall arrays (NWAs) were grown on Ni foam by a hydrothermal route and investigated for application in supercapacitors for the first time. The resulting NWAs were analyzed by using X-ray diffraction spectroscopy, scanning electron microscopy, and transmission electron microscopy. ZnWO4 NWAs exhibited high electrochemical property with a specific capacitance of 2.5 F cm−2 at a charge and discharge current density of 20 mA cm−2 (1250 F g−1 at current density of 10 A g−1). Furthermore, they showed an excellent cycling ability at different current densities up to 100 mA cm−2, and 92% (2.3 F cm−2) of the initial capacitance remained after 4000 cycles. The open network structure consisting of interconnected ZnWO4 NWAs directly grown on current collectors is advantageous for electron transport and electrolyte diffusion which can facilitate the electrochemical reaction. Our work not only demonstrated a facile hydrothermal method for ZnWO4 NWAs directly grown on Ni foam, but also revealed ZnWO4 to be a promising electrode for high-property supercapacitors.

Carbon aerogels from bacterial nanocellulose as anodes for lithium ion batteries

Carbon aerogels with large open pores and high surface area are fabricated via pyrolysis of a readily available natural resource, e.g., bacterial nanocellulose (BNC) aerogels. Freeze-drying of the BNC hydrogels is used to preserve the 3D open network structure upon calcination whereas using Fe(III) improves the yield and H/C ratio. These carbon aerogels are explored as anodes in lithium ion batteries where it is shown that they deliver superior capacity retention and rate performance compared to other carbon-based materials.