Are Slit Pores in Carbonaceus Materials Real?

2009 ◽  
Vol 1216 ◽  
Author(s):  
Cristina Romero ◽  
Ariel A. Valladares ◽  
R. M. Valladares ◽  
Alexander Valladares
Keyword(s):  
Ad Hoc ◽  
Computational Cost ◽  
Experimental Results ◽  
Pore Model ◽  
Graphene Layers ◽  
Porous Semiconductors ◽  
Carbon Chains ◽  
Slit Pore ◽  
Potential Applications ◽  
Slit Pores

AbstractNanoporous carbon is a widely studied material due to its potential applications in hydrogen storage or for filtering undesirable products. Most of the developments have been experimental although some simulation work has been carried out based on the use of graphene sheets and/or carbon chains and classical molecular dynamics. The slit pore model is one of the oldest models proposed to describe porous carbon. Developed by Emmet in 1948 [1] it has been recurrently used and in its most basic form consists of two parallel graphene layers separated by a distance that is taken as the width of the pore. Its simplicity limits its applicability since experimental evidence suggests that the walls of the carbon pores have widths of a few graphene layers [2], but it still is appealing for computational simulations due to its low computational cost. Using a previously developed ab initio approach to generate porous semiconductors [3] we have obtained porous carbonaceous materials with walls made up of a few graphene layers (four layers), in agreement with experimental results; these walls are separated by distances comparable to those used in the slit pore model [4]. This validates the idea of a modified slit pore model obtained without the use of ad hoc suppositions. Structures will be presented, analyzed and compared to available experimental results.

scholarly journals Composite Poly(vinyl alcohol)-Based Nanofibers Embedding Differently-Shaped Gold Nanoparticles: Preparation and Characterization

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1604
Author(s):  
Andrea Dodero ◽  
Maila Castellano ◽  
Paola Lova ◽  
Massimo Ottonelli ◽  
Elisabetta Brunengo ◽  
...  
Keyword(s):  
Vinyl Alcohol ◽  
Ad Hoc ◽  
Chemical Reduction ◽  
Chemical Properties ◽  
Single Step ◽  
Gold Nanostructures ◽  
Poly Vinyl Alcohol ◽  
Spherical Nanoparticles ◽  
Potential Applications ◽  
New Perspective

Poly(vinyl alcohol) nanofibrous mats containing ad hoc synthesized gold nanostructures were prepared via a single-step electrospinning procedure and investigated as a novel composite platform with several potential applications. Specifically, the effect of differently shaped and sized gold nanostructures on the resulting mat physical-chemical properties was investigated. In detail, nearly spherical nanoparticles and nanorods were first synthesized through a chemical reduction of gold precursors in water by using (hexadecyl)trimethylammonium bromide as the stabilizing agent. These nanostructures were then dispersed in poly(vinyl alcohol) aqueous solutions to prepare nanofibrous mats, which were then stabilized via a humble thermal treatment able to enhance their thermal stability and water resistance. Remarkably, the nanostructure type was proven to influence the mesh morphology, with the small spherical nanoparticles and the large nanorods leading to thinner well defined or bigger defect-rich nanofibers, respectively. Finally, the good mechanical properties shown by the prepared composite mats suggest their ease of handleability thereby opening new perspective applications.

Vehicular Cloud Computing

2014 ◽  
pp. 262-274 ◽  
Author(s):  
Kayhan Zrar Ghafoor ◽  
Marwan Aziz Mohammed ◽  
Kamalrulnizam Abu Bakar ◽  
Ali Safa Sadiq ◽  
Jaime Lloret
Keyword(s):  
Cloud Computing ◽  
Vehicular Networks ◽  
Vehicular Ad Hoc Networks ◽  
Ad Hoc ◽  
Vehicular Cloud Computing ◽  
Vehicular Cloud ◽  
Performance Improvements ◽  
Potential Applications ◽  
Research Outcome ◽  
Hoc Networks

Recently, Vehicular Ad Hoc Networks (VANET) have attracted the attention of research communities, leading car manufacturers, and governments due to their potential applications and specific characteristics. Their research outcome was started with awareness between vehicles for collision avoidance and Internet access and then expanded to vehicular multimedia communications. Moreover, vehicles’ high computation, communication, and storage resources set a ground for vehicular networks to deploy these applications in the near future. Nevertheless, on-board resources in vehicles are mostly underutilized. Vehicular Cloud Computing (VCC) is developed to utilize the VANET resources efficiently and provide subscribers safe infotainment services. In this chapter, the authors perform a survey of state-of-the-art vehicular cloud computing as well as the existing techniques that utilize cloud computing for performance improvements in VANET. The authors then classify the VCC based on the applications, service types, and vehicular cloud organization. They present the detail for each VCC application and formation. Lastly, the authors discuss the open issues and research directions related to VANET cloud computing.

Constructing and Utilizing Video Ontology for Accurate and Fast Retrieval

2011 ◽  
Vol 2 (4) ◽  
pp. 59-75 ◽  
Author(s):  
Kimiaki Shirahama ◽  
Kuniaki Uehara
Keyword(s):  
Knowledge Base ◽  
Large Scale ◽  
Video Retrieval ◽  
Computational Cost ◽  
Semantic Content ◽  
Video Data ◽  
Experimental Results ◽  
Huge Number ◽  
Dempster Shafer Theory ◽  
Shafer Theory

This paper examines video retrieval based on Query-By-Example (QBE) approach, where shots relevant to a query are retrieved from large-scale video data based on their similarity to example shots. This involves two crucial problems: The first is that similarity in features does not necessarily imply similarity in semantic content. The second problem is an expensive computational cost to compute the similarity of a huge number of shots to example shots. The authors have developed a method that can filter a large number of shots irrelevant to a query, based on a video ontology that is knowledge base about concepts displayed in a shot. The method utilizes various concept relationships (e.g., generalization/specialization, sibling, part-of, and co-occurrence) defined in the video ontology. In addition, although the video ontology assumes that shots are accurately annotated with concepts, accurate annotation is difficult due to the diversity of forms and appearances of the concepts. Dempster-Shafer theory is used to account the uncertainty in determining the relevance of a shot based on inaccurate annotation of this shot. Experimental results on TRECVID 2009 video data validate the effectiveness of the method.

scholarly journals Wavelength dependent nonlinear optical response of tetraphenylethene aggregation-induced emission luminogens

2018 ◽  
Vol 2 (12) ◽  
pp. 2263-2271 ◽  
Author(s):  
Jianbo Xiong ◽  
Xinyue Li ◽  
Chunqing Yuan ◽  
Sergey Semin ◽  
Zhaoquan Yao ◽  
...  
Keyword(s):  
Optical Properties ◽  
Nonlinear Optical ◽  
Theoretical Calculations ◽  
Experimental Results ◽  
Nlo Properties ◽  
Aggregation Induced Emission ◽  
Non Linear ◽  
Potential Applications ◽  
Linear Optical Properties ◽  
Linear Optical

Studies of the non-linear optical properties of classical AIEgens are rare, despite their important potential applications in organic composite photonic circuits. Here, we present experimental results, supported by theoretical calculations, of the non-linear optical (NLO) properties of TPE and its halogenated derivates.

scholarly journals An efficient cooperative message authentication based on reputation mechanism in vehicular ad hoc networks

2019 ◽  
Vol 15 (6) ◽  
pp. 155014771985491
Author(s):  
Yong Xie ◽  
Songsong Zhang ◽  
Xiang Li ◽  
Yanggui Li
Keyword(s):  
Ad Hoc Networks ◽  
Vehicular Ad Hoc Networks ◽  
Ad Hoc ◽  
Computational Cost ◽  
Message Authentication ◽  
Selfish Behavior ◽  
Reputation Mechanism ◽  
Single Vehicle ◽  
Detection Ratio ◽  
Hoc Networks

Vehicular ad hoc networks have emerged as a promising approach to increasing road safety and efficiency. Vehicles periodically broadcast traffic-related status messages. Message authentication is a common way for ensuring information reliability, but it is an unaffordable computational cost for single vehicle. In this article, we propose an efficient cooperative message authentication based on reputation mechanism. In the proposed scheme, reputation model is used to assess authentication efforts of vehicles, which enhances initiative for cooperative message authentication and inhabits selfish behavior; sequence optimization algorithm solves messages overflowing on condition limited computation of onboard unit and improves the speed of message authentication at the premise of ensuring the reliability of message authentication. Simulation results show that our scheme presents a nice performance of authentication efficiency, packet loss ratio, and missing detection ratio.

scholarly journals Single-Step Formation of Ni Nanoparticle-Modified Graphene–Diamond Hybrid Electrodes for Electrochemical Glucose Detection

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2979 ◽  
Author(s):  
Naiyuan Cui ◽  
Pei Guo ◽  
Qilong Yuan ◽  
Chen Ye ◽  
Mingyang Yang ◽  
...  
Keyword(s):  
Glucose Sensing ◽  
Single Step ◽  
Diamond Surface ◽  
Glucose Detection ◽  
Ni Nanoparticles ◽  
Step Method ◽  
Detection Range ◽  
Graphene Layers ◽  
Potential Applications ◽  
Modified Graphene

The development of accurate, reliable devices for glucose detection has drawn much attention from the scientific community over the past few years. Here, we report a single-step method to fabricate Ni nanoparticle-modified graphene–diamond hybrid electrodes via a catalytic thermal treatment, by which the graphene layers are directly grown on the diamond surface using Ni thin film as a catalyst, meanwhile, Ni nanoparticles are formed in situ on the graphene surface due to dewetting behavior. The good interface between the Ni nanoparticles and the graphene guarantees efficient charge transfer during electrochemical detection. The fabricated electrodes exhibit good glucose sensing performance with a low detection limit of 2 μM and a linear detection range between 2 μM–1 mM. In addition, this sensor shows great selectivity, suggesting potential applications for sensitive and accurate monitoring of glucose in human blood.

scholarly journals A Tomograph Prototype for Quantitative Microwave Imaging: Preliminary Experimental Results

2018 ◽  
Vol 4 (12) ◽  
pp. 139 ◽  
Author(s):  
Alessandro Fedeli ◽  
Manuela Maffongelli ◽  
Ricardo Monleone ◽  
Claudio Pagnamenta ◽  
Matteo Pastorino ◽  
...  
Keyword(s):  
Ad Hoc ◽  
Microwave Imaging ◽  
Experimental Results ◽  
Network Analyzer ◽  
Reconstruction Algorithms ◽  
Quantitative Reconstruction ◽  
Qualitative And Quantitative ◽  
Switching Matrix ◽  
3D Printed ◽  
Transmission Measurements

A new prototype of a tomographic system for microwave imaging is presented in this paper. The target being tested is surrounded by an ad-hoc 3D-printed structure, which supports sixteen custom antenna elements. The transmission measurements between each pair of antennas are acquired through a vector network analyzer connected to a modular switching matrix. The collected data are inverted by a hybrid nonlinear procedure combining qualitative and quantitative reconstruction algorithms. Preliminary experimental results, showing the capabilities of the developed system, are reported.

Ab initio Computationally Generated Nanoporous Carbon and its Comparison to Experiment

2008 ◽  
Vol 1145 ◽  
Author(s):  
Cristina Romero ◽  
Ariel A. Valladares ◽  
R. M. Valladares ◽  
Alexander Valladares ◽  
Alipio G. Calles
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Nanoporous Carbon ◽  
Group Iv ◽  
Distribution Functions ◽  
Graphene Sheets ◽  
Radial Distribution Functions ◽  
Carbon Chains ◽  
Potential Applications ◽  
Dynamics Process

AbstractNanoporous carbon is a widely studied material due to its potential applications in hydrogen storage or for filtering undesirable products. Most of the developments have been experimental although some simulation work has been carried out based on the use of graphene sheets and/or carbon chains and classical molecular dynamics. Here we present an application of our recently developed ab initio method [1] for the generation of group IV porous materials. The method consists in constructing a crystalline diamond supercell with 216 atoms of carbon and a density of 3.546 g/cm3, then lengthening the supercell edge to obtain a density of 1.38 g/cm3, yielding a porosity of 61.1 % in order to be able to compare with experimental results reported in the literature [2]. We then subject the resulting supercell to an ab initio molecular dynamics process at 1000 K during 295 steps. The radial distribution functions obtained are compared to experiment to discern coincidences and discrepancies.

Development of a Computational Fluid Dynamics Model to Simulate Three-Dimensional Gap Resonance Driven by Surface Waves

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Hongchao Wang ◽  
Scott Draper ◽  
Wenhua Zhao ◽  
Hugh Wolgamot ◽  
Liang Cheng
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Computational Cost ◽  
Three Dimensional ◽  
Domain Size ◽  
Experimental Results ◽  
Mode Shapes ◽  
Transient Wave ◽  
Mesh Topology ◽  
Gap Resonance

This paper expounds the process of successfully establishing a computational fluid dynamics (CFD) model to accurately reproduce experimental results of three-dimensional (3D) gap resonance between two fixed ship-shaped boxes. The ship-shaped boxes with round bilges were arranged in a side-by-side configuration to represent a floating liquefied natural gas offloading scenario and were subjected to NewWave-type transient wave groups. We employ the open-source CFD package openfoam to develop the numerical model. Three-dimensional gap resonance differs from its two-dimensional (2D) counterpart in allowing spatial structure along the gap and hence multiple modes can easily be excited in the gap by waves of moderate spectral bandwidth. In terms of numerical setup and computational cost, a 3D simulation is much more challenging than a 2D simulation and requires careful selection of relevant parameters. In this respect, the mesh topology and size, domain size and boundary conditions are systematically optimized. It is shown that to accurately reproduce the experimental results in this case, the cell size must be adequate to resolve both the undisturbed incident waves and near-wall boundary layer. By using a linear iterative method, the NewWave-type transient wave group used in the experiment is accurately recreated in the numerical wave tank (NWT). Numerical results including time series of gap responses, resonant amplitudes and frequencies, and mode shapes show excellent agreement with experimental data.

Explicit Aerodynamic Model Characterization of a Multirotor Unmanned Aerial Vehicle in Quasi-Steady Flight

2020 ◽  
Vol 15 (8) ◽  
Author(s):  
Carlos Rodríguez de Cos ◽  
José Ángel Acosta
Keyword(s):  
Controller Design ◽  
Control Strategies ◽  
Computational Cost ◽  
Unmanned Aerial Systems ◽  
Nonlinear Phenomena ◽  
Aerodynamic Forces ◽  
Aerodynamic Model ◽  
Potential Applications ◽  
Aerial Vehicle ◽  
Aerial Systems

Abstract In the last years, the research on unmanned aerial systems (UASs) has shown a marked growth and the models to simulate UASs have been deeply studied. Although onboard controller algorithms have increased their complexity, most of them still rely on simplistic models. In essence, aerodynamic forces/torques are generally considered either insignificant compared to propulsion and inertial forces or acceptably modeled with constant aerodynamic coefficients estimated in a particular flight regime. However, the increase of power in the onboard computers allows to make controller algorithms more complex, and therefore, to increase the total performance of the UAS. In this regard, this work provides an explicit aerodynamic model for multirotor UAS that, unlike most of the current models, does not need iterations to be adjusted to the flight conditions at a higher computational cost. This explicit nature makes it an excellent choice for being implemented in onboard computers, thus covering a broad range of applications, from controller design to numerical analysis (e.g., the capture nonlinear phenomena like bifurcations). To obtain this accurate explicit mathematical aerodynamic model, a thorough analysis of a batch of simulations is carried out. In these simulations, the aerodynamic forces and torques are estimated using computer fluid dynamics (CFD), and the propulsive effects are taken into account via blade element momentum theory (BEMT). A study of its implementation for different regimes and platforms is also provided, as well as some potential applications of the solution, like robust control strategies or machine learning.

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