4,441 research outputs found
DNAPL source control by reductive dechlorination with iron-based degradative solidification/stabilization
Iron-based degradative solidification/stabilization (Fe(II)-DS/S) is a treatment
method that could be economically applied to smaller DNAPL-contaminated sites and to
those sites with impermeable soils. Reductive dechlorination is achieved by compounds
that are formed by reaction of ferrous iron with components of Portland cement or with
defined chemicals (FeCl3 + Ca(OH)2). These dechlorinating agents can effectively
degrade chlorinated hydrocarbons (PCE, TCE, and 1,1,1-TCA) that are dissolved in
aqueous solution. This research investigated the application of Fe(II)-DS/S to remove
chlorinated hydrocarbons that are present as DNAPLs in source zones and to compared
the reactivity of ferrous iron in different mixtures, including the conventional mixture
with cement (Fe(II)+C) and an iron-solid mixture (ISM) that was synthesized without
the addition of cement.
The modified first-order model, which the rate was proportional to the
concentration of target in the aqueous phase and it was also nearly constant when
DNAPL was present, was developed to describe dechlorination kinetics. The modified
second-order model assumed that the rate was proportional to the product of the concentration of target in the aqueous phase and the concentration of reductive capacity
of the solid reductant. The modified first-order model was used to describe degradation
of target compounds with ISM, and the modified second-order model was used to
describe removals for TCE and 1,1,1-TCA with Fe(II)+C. Results of experiments on
PCE dechlorination with ISM indicated that the increase of Fe(II) in ISM increased rate
constants and decreased the solubility of targets. The half-life was increased with
increasing total PCE concentration. The product analysis implied that degradation of
PCE with ISM was via a combination of the hydrogenolysis and β-elimination pathways.
A comparison of the types of targets and reductants indicated that Fe(II)+C had better
reactivity for chlorinated ethenes (PCE and TCE) than ISM. However, ISM could
dechlorinate a chlorinated ethane (1,1,1-TCA) as rapidly as Fe(II)+10%C. The ratio of
[RC]o/[Fe(II)]o implied that Fe(II) in Fe(II)+C was more involved in reducing
chlorinated ethenes than was Fe(II) in ISM. Dechlorination of a DNAPL mixture
followed the same order of reactivity as with individual DNAPLs with both reductants
Wave Optics by Fourier Transform. Diffractions by Identical 3D Objects
The aim of this work is to outline a method for studying wave optics in 3D space based on the well-known properties of the Fourier transform and the Heaviside, Dirac delta functions. Applications for obtaining the amplitudes of diffraction of plane waves by one then by many identical 3D objects utilizing convolution products are given. It results from this study that the forbidden (permitted) diffracted directions caused by an object is the same (altered) for many identical objects. Studies of diffractions of a plane wave k0 by sets of equidistant points, planes, prisms, spheres are given
A Generalization Bound of Deep Neural Networks for Dependent Data
Existing generalization bounds for deep neural networks require data to be
independent and identically distributed (iid). This assumption may not hold in
real-life applications such as evolutionary biology, infectious disease
epidemiology, and stock price prediction. This work establishes a
generalization bound of feed-forward neural networks for non-stationary
-mixing data
Exploiting secure performance of full-duplex decode and forward in optimal relay selection networks
In the presence of an illegitimate user, we investigate the secrecy outage probability (SOP) of the optimal relay selection (ORS) networks by applying decode-and-forward (DnF) based full-duplex (FD) relaying mode. The closed-form expressions for the allocations of the end-to-end signal-to-interference-plus-noise ratio (SINR) in each wireless network are derived as well as the closed-form expression for the exact SOP of the proposed ORS system is presented under Rayleigh fading schemes. As an important achievement, SOP is also compared between orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA) schemes. Our results reveal that the SOP of the suggested scheme can be considerably influenced by several parameters involved, including the number of relays, the average signal-to-noise ratio (SNR) of eavesdropper links, transmit power and the average residual self-interference (SI) enforced on the FD relays.Web of Science244767
Changes of guidelines diagnosing hepatocellular carcinoma during the last ten-year period
Hepatocellular carcinoma (HCC) is the third most common cause of cancer deaths in the world. There have been many advances in the diagnosis of HCC during the last ten years, especially in the imaging techniques. The Korean Liver cancer study group (KLCSG), European Association for the Study of the Liver (EASL), American Association for the Study of Liver disease (AASLD), and Asian-Pacific Association for the Study of Liver (APASL) have made and changed the HCC guidelines with the advances in the imaging techniques and according to the results of the researches on HCC. We reviewed the changes of the imaging guidelines in HCC diagnosis according to the advances in the imaging techniques. Further studies will be necessary to resolve the controversies in the diagnosis of HCC smaller than 1 cm in size
Real-Space Approach for the Electronic Calculation of Twisted Bilayer Graphene Using the Orthogonal Polynomial Technique
We discuss technical issues involving the implementation of a computational method for the electronic structure of material systems of arbitrary atomic arrangement. The method is based on the analysis of time evolution of electron states in the real lattice space. The Chebyshev polynomials of the first kind are used to approximate the time evolution operator. We demonstrate that the developed method is powerful and efficient since the computational scaling law is linear. We invoked the method to study the electronic properties of special twisted bilayer graphene whose atomic structure is quasi-crystalline. We show the density of states of an electron in this graphene system as well as the variation of the associated time auto-correlation function. We find the fluctuation of electron density on the lattice nodes forming a typical pattern closely related to the typical atomic pattern of the quasi-crystalline bilayer graphene configuration
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