181 research outputs found
Evaluation of a New Method to Estimate the Micropore Volume and External Surface Area of Single-walled Carbon Nanotubes
Since the discovery of carbon nanotubes in 1991, significant progress has been made to understand their electrical, mechanical, magnetic and optical properties. However, as the ideal adsorbent for adsorption of gases and vapors, nanotubes, especially the single-walled carbon nanotubes (SWNTs), and their adsorption properties remain not been investigated enough. The unique microporous structure of SWNTs gives them remarkable adsorption properties, i.e. surface area and porosity. Several methods exist to determine the surface area and pore volume of adsorbents: t-plot method, Dubinin-Radushkevich (DR) method, and Dubinin-Astakhov (DA) method. The results are usually specific to a certain method and to the segment of the adsorption isotherm which is fitted to the method used. Therefore, the main objective of this study is to find the most appropriate and suitable method to characterize micropore volume and external surface area of SWNTs.
The surface area and porosity results are often used to evaluate the effectiveness of an adsorbent for removal of odors and trace concentrations of organic vapors from air and process streams. The objective is accomplished by evaluating the results of t-plot method, DR method, DA method and a method that was recently developed. Some of the commonly used methods were developed as far back as 1940s. Additionally, the methods were developed for various adsorbents such as carbon black, zeolites and activated carbon. However, nanotubes are fairly recent adsorbent materials. All of these can render the characterization results open to the interpretation by a specific user.
In this study standard N2 adsorption was carried out at 77 K for four commerciallyavailable SWNT sample. The impurities of SWNTs were able to be incorporated into the adsorption isotherm, the results of which could be confirmed by thermogravimetric analysis (TGA) and X-ray photo spectroscopy (XPS) experiments. To make the new developed method applicable to impure SWNT samples, new definition of statistical thickness has been proposed in this study. The consistent results showed the advantages of the modified new method, which is applicable and specific to SWNT samples. Multiple adsorbates should be used in the future analysis, such as water vapor, hexane, and other organic vapors
Dimensional Analysis and the Time Required to Urinate
According to the recently discovered 'Law of Urination', mammals, ranging in
size from mice to elephants, take, on the average, 21s to urinate. We attempt
to gain insights into the physical processes responsible for this uniformity
using simple dimensional analysis. We assume that the biological apparatus for
urination in mammals simply scales with linear size, and consider the scenarios
where the driving force is gravity or elasticity, and where the response is
dominated by inertia or viscosity. We ask how the time required for urination
depends on the length scale, and find that for the time to be independent of
body size, the dominant driving force must be elasticity, and the dominant
response viscosity. Our note demonstrates that dimensional analysis can indeed
readily give insights into complex physical and biological processes
Exploring Metaverse Addiction: Lenses of Technology Affordance and Compensatory Actualization
As technology further evolves, the metaverse is becoming an increasingly plausible reality. In this process, it is crucial to consider potential risks that come with its development. This study focuses on the potential risk of metaverse addiction and considers the influencing factors from the perspective of technology affordance and virtual reality compensatory effect. Mainly, we identify metaverse affordances based on key characteristics (i.e., accessibility, immersion, spatiotemporality, sustainability, interoperability, and scalability). It also highlights two kinds of affordance actualization factors (i.e., escapism and digital perfectionism) that arise from virtual reality compensatory theory. The research model suggests that metaverse affordance is actualized through compensation, ultimately forming reliance behavior like an addiction. This conceptual research potentially contributes to further investigation of the dark side of the metaverse and provides insights into research considering the compensatory effects to mitigate potential risks and ensure the healthy development of the metaverse
Theoretical investigation of the dynamic electronic response of a quantum dot driven by time-dependent voltage
We present a comprehensive theoretical investigation on the dynamic
electronic response of a noninteracting quantum dot system to various forms of
time-dependent voltage applied to the single contact lead. Numerical
simulations are carried out by implementing a recently developed hierarchical
equations of motion formalism [J. Chem. Phys. 128, 234703 (2008)], which is
formally exact for a fermionic system interacting with grand canonical
fermionic reservoirs, in the presence of arbitrary time-dependent applied
chemical potentials. The dynamical characteristics of the transient transport
current evaluated in both linear and nonlinear response regimes are analyzed,
and the equivalent classic circuit corresponding to the coupled dot-lead system
is also discussed
Exact dynamics of dissipative electronic systems and quantum transport: Hierarchical equations of motion approach
A quantum dissipation theory is formulated in terms of hierarchically coupled
equations of motion for an arbitrary electronic system coupled with grand
canonical Fermion bath ensembles. The theoretical construction starts with the
second--quantization influence functional in path integral formalism, in which
the Fermion creation and annihilation operators are represented by Grassmann
variables. Time--derivatives on influence functionals are then performed in a
hierarchical manner, on the basis of calculus--on--path--integral algorithm.
Both the multiple--frequency--dispersion and the non-Markovian reservoir
parametrization schemes are considered for the desired hierarchy construction.
The resulting formalism is in principle exact, applicable to interacting
systems, with arbitrary time-dependent external fields. It renders an exact
tool to evaluate various transient and stationary quantum transport properties
of many-electron systems. At the second--tier truncation level the present
theory recovers the real--time diagrammatic formalism developed by Sch\"{o}n
and coworkers. For a single-particle system, the hierarchical formalism
terminates at the second tier exactly, and the Landuer--B\"{u}ttiker's
transport current expression is readily recovered.Comment: The new versio
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