818 research outputs found
DETOXIFICATION OF SELECTED CHLORO-ORGANICS BY OXIDATION TECHNIQUE USING CHELATE MODIFIED FENTON REACTION
The use of hydroxyl radical based reaction (Fenton reaction) for the destruction of organic pollutants has been widely reported in the literature. However, the low pH requirement and rapid hydrogen peroxide consumption rate make the application of conventional Fenton reaction difficult for in-situ treatment. In this study, we conducted a modified Fenton reaction by introducing a chelating agent into the reaction system that could prevent Fe(OH)3 (s) precipitation even at a neutral pH condition and reduce the H2O2 consumption rate by controlling the Fe2+ concentration. A chelating agent (mono-chelate or poly-chelate) combines with Fe2+ or Fe3+ to form stable metal-chelate complexes in solution. This decreases the concentration of Fe2+ in the solution so that reactions can be carried for longer contact times. Experimental results (citrate was the chelating agent) for 2,4,6-trichlorophenol (TCP) showed that TCP degradations were greater than 95% after 2.5 h and 24 h reaction times at fixed pH 5 and 6, respectively. For the same reaction time, the normalized chloride formations were 85% at pH 5 and 88% at pH 6. Several other chlorinated organic compounds were also chosen as the model compounds for detoxification studies because of their chemical structures: trichloroethylene (unsaturated hydrocarbon), carbon tetrachloride (highly oxidized compound), 2,2-dichlorobiphenyl, and biphenyl (a dual-aromatic ring structure). Poly-chelating agents (such as polyacrylic acid-PAA) provide multiple Fe2+/Fe3+ binding sites in the modified Fenton reaction for the oxidation of contaminants (2,2-dichlorobiphenyl, and biphenyl) at a neutral pH environment. Numerical simulation based on the kinetic model developed from the well known Fenton reaction and iron-chelate chemistry fits experiment data well for both standard and chelate modified Fenton reactions. In this dissertation, it was proven that both monomeric (citrate) and polymeric (PAA) chelate modified Fenton reactions were effective for dechlorination of carbon tetrachloride from aqueous phase by the superoxide radical anion. On the other hand, PAA (a poly-chelating agent) can also be used for solid surface modification by polymerization of acrylic acid (monomer). The successful degradations of biphenyl and trichloroethylene by the PAA functionalized silica particles/membrane demonstrate the versatile applications of the chelate modified Fenton reaction
Scale-aware Test-time Click Adaptation for Pulmonary Nodule and Mass Segmentation
Pulmonary nodules and masses are crucial imaging features in lung cancer
screening that require careful management in clinical diagnosis. Despite the
success of deep learning-based medical image segmentation, the robust
performance on various sizes of lesions of nodule and mass is still
challenging. In this paper, we propose a multi-scale neural network with
scale-aware test-time adaptation to address this challenge. Specifically, we
introduce an adaptive Scale-aware Test-time Click Adaptation method based on
effortlessly obtainable lesion clicks as test-time cues to enhance segmentation
performance, particularly for large lesions. The proposed method can be
seamlessly integrated into existing networks. Extensive experiments on both
open-source and in-house datasets consistently demonstrate the effectiveness of
the proposed method over some CNN and Transformer-based segmentation methods.
Our code is available at https://github.com/SplinterLi/SaTTCAComment: 11 pages, 3 figures, MICCAI 202
Prospects of gravitational waves in the minimal left-right symmetric model
The left-right symmetric model (LRSM) is a well-motivated framework to
restore parity and implement seesaw mechanisms for the tiny neutrino masses at
or above the TeV-scale, and has a very rich phenomenology at both the
high-energy and high-precision frontiers. In this paper we examine the phase
transition and resultant gravitational waves (GWs) in the minimal version of
LRSM. Taking into account all the theoretical and experimental constraints on
LRSM, we identify the parameter regions with strong first-order phase
transition and detectable GWs in the future experiments. It turns out in a
sizeable region of the parameter space, GWs can be generated in the phase
transition with the strength of to at the frequency of
0.1 to 10 Hz, which can be detected by BBO and DECIGO. Furthermore, GWs in the
LRSM favor a relatively light -breaking scalar , which is
largely complementary to the direct searches of a long-lived neutral scalar at
the high-energy colliders. It is found that the other heavy scalars and the
right-handed neutrinos in the LRSM also play an important part for GW signal
production in the phase transition.Comment: 41 pages, 10 figures, 5 tables, added references, improved tex
Time-Delayed Data Informed Reinforcement Learning for Approximate Optimal Tracking Control
This paper proposes a time-delayed data informed reinforcement learning
method, referred as incremental adaptive dynamic programming, to learn
approximate solutions to optimal tracking control problems (OTCPs) of
high-dimensional nonlinear systems. Departing from available solutions to
OTCPs, our developed tracking control scheme settles the curse of complexity
problem in value function approximation from a decoupled way, circumvents the
learning inefficiency regarding varying desired trajectories by avoiding
introducing a reference trajectory dynamics into the learning process, and
requires neither an accurate nor identified dynamics using time-delayed
signals. Specifically, the intractable OTCP of a high-dimensional uncertain
system is first converted into multiple manageable sub-OTCPs of low-dimensional
incremental subsystems constructed using time-delayed data. Then, the resulting
sub-OTCPs are approximately solved by a parallel critic learning structure. The
proposed tracking control scheme is developed with rigorous theoretical
analysis of system stability and weight convergence, and validated
experimentally on a 3-DoF robot manipulator
Design of the Tsinghua Tabletop Kibble Balance
The Kibble balance is a precision instrument for realizing the mass unit, the
kilogram, in the new international system of units (SI). In recent years, an
important trend for Kibble balance experiments is to go tabletop, in which the
instrument's size is notably reduced while retaining a measurement accuracy of
. In this paper, we report a new design of a tabletop Kibble balance
to be built at Tsinghua University. The Tsinghua Kibble balance aims to deliver
a compact instrument for robust mass calibrations from 10 g to 1 kg with a
targeted measurement accuracy of 50 g or less. Some major features of the
Tsinghua Kibble balance system, including the design of a new magnet, one-mode
measurement scheme, the spring-compensated magnet moving mechanism, and
magnetic shielding considerations, are discussed.Comment: 8 pages, 9 figure
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