24,112 research outputs found
Molecular Valves for Controlling Gas Phase Transport Made from Discrete Angstrom-Sized Pores in Graphene
An ability to precisely regulate the quantity and location of molecular flux
is of value in applications such as nanoscale 3D printing, catalysis, and
sensor design. Barrier materials containing pores with molecular dimensions
have previously been used to manipulate molecular compositions in the gas
phase, but have so far been unable to offer controlled gas transport through
individual pores. Here, we show that gas flux through discrete angstrom-sized
pores in monolayer graphene can be detected and then controlled using
nanometer-sized gold clusters, which are formed on the surface of the graphene
and can migrate and partially block a pore. In samples without gold clusters,
we observe stochastic switching of the magnitude of the gas permeance, which we
attribute to molecular rearrangements of the pore. Our molecular valves could
be used, for example, to develop unique approaches to molecular synthesis that
are based on the controllable switching of a molecular gas flux, reminiscent of
ion channels in biological cell membranes and solid state nanopores.Comment: to appear in Nature Nanotechnolog
Spatial and Temporal Extrapolation of Disdrometer Size Distributions Based on a Lagrangian Trajectory Model of Falling Rain
Methodologies to improve disdrometer processing, loosely based on
mathematical techniques common to the field of particle flow and fluid
mechanics, are examined and tested. The inclusion of advection and vertical
wind field estimates appears to produce significantly improved results in a
Lagrangian hydrometeor trajectory model, in spite of very strict assumptions of
noninteracting hydrometeors, constant vertical air velocity, and time
independent advection during a radar scan time interval. Wind field data can be
extracted from each radar elevation scan by plotting and analyzing reflectivity
contours over the disdrometer site and by collecting the radar radial velocity
data to obtain estimates of advection. Specific regions of disdrometer spectra
(drop size versus time) often exhibit strong gravitational sorting signatures,
from which estimates of vertical velocity can be extracted. These independent
wind field estimates can be used as initial conditions to the Lagrangian
trajectory simulation of falling hydrometeors.Comment: 25 pages, 15 figures, 4 tables. Submitted to The Open Atmospheric
Science Journal, http://www.bentham.org/open/toascj
Computational characterization and prediction of metal-organic framework properties
In this introductory review, we give an overview of the computational
chemistry methods commonly used in the field of metal-organic frameworks
(MOFs), to describe or predict the structures themselves and characterize their
various properties, either at the quantum chemical level or through classical
molecular simulation. We discuss the methods for the prediction of crystal
structures, geometrical properties and large-scale screening of hypothetical
MOFs, as well as their thermal and mechanical properties. A separate section
deals with the simulation of adsorption of fluids and fluid mixtures in MOFs
The atomic simulation environment — a python library for working with atoms
The Atomic Simulation Environment (ASE) is a software package written in the Python programming language with the aim of setting up, steering, and analyzing atomistic simula- tions. In ASE, tasks are fully scripted in Python. The powerful syntax of Python combined with the NumPy array library make it possible to perform very complex simulation tasks. For example, a sequence of calculations may be performed with the use of a simple "for-loop" construction. Calculations of energy, forces, stresses and other quantities are performed through interfaces to many external electronic structure codes or force fields using a uniform interface. On top of this calculator interface, ASE provides modules for performing many standard simulation tasks such as structure optimization, molecular dynamics, handling of constraints and performing nudged elastic band calculations
Kinetic Gas Molecule Optimization based Cluster Head Selection Algorithm for minimizing the Energy Consumption in WSN
As the amount of low-cost and low-power sensor nodes increases, so does the size of a wireless sensor network (WSN). Using self-organization, the sensor nodes all connect to one another to form a wireless network. Sensor gadgets are thought to be extremely difficult to recharge in unfavourable conditions. Moreover, network longevity, coverage area, scheduling, and data aggregation are the major issues of WSNs. Furthermore, the ability to extend the life of the network, as well as the dependability and scalability of sensor nodes' data transmissions, demonstrate the success of data aggregation. As a result, clustering methods are thought to be ideal for making the most efficient use of resources while also requiring less energy. All sensor nodes in a cluster communicate with each other via a cluster head (CH) node. Any clustering algorithm's primary responsibility in these situations is to select the ideal CH for solving the variety of limitations, such as minimising energy consumption and delay. Kinetic Gas Molecule Optimization (KGMO) is used in this paper to create a new model for selecting CH to improve network lifetime and energy. Gas molecule agents move through a search space in pursuit of an optimal solution while considering characteristics like energy, distance, and delay as objective functions. On average, the KGMO algorithm results in a 20% increase in network life expectancy and a 19.84% increase in energy stability compared to the traditional technique Bacterial Foraging Optimization Algorithm (BFO)
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