129 research outputs found
Mechanism of PEO-PPO-PEO micellization in aqueous solutions studied by two-dimensional correlation FTIR spectroscopy
No full textThe micellization mechanism of PEO-PPO-PEO block copolymer in aqueous solutions was studied by two-dimensional correlation FTIR spectroscopy. The 1400-1000 cm(-1) region was investigated, involving the stretching vibrations of ether band, C-H wagging vibrations of EO methylene groups and C-H symmetric deformation vibrations of PO methyl groups. In the 2D correlated spectra, the hydrous and anhydrous state of the ether band, PO methyl groups, and the two conformations of EO methylene groups were observed. Molecules with different PO lengths and increasing molecular weight were investigated to determine the sequence of association of the separate groups. During temperature-induced micellization, the following changes were detected: firstly, EO methylene groups changed from a gauche state to a trans state; secondly, conformational transitions led to the dehydration of hydrated methyl groups; next, the hydrogen bonding between C-O band and water diminished; and finally, dehydrated groups approached to form hydrophobic cores, resulting in micelle formation. From this variation in the sequence of group associations, it is concluded that aggregates of unimers first formed, then hydrophobic cores formed through the hydrophobic interaction from dehydrated PPO blocks, and proper micelles eventually evolved. The temperature-induced conformational changes are suggested the reason for micellization. (C) 2010 Elsevier Inc. All rights reserved
Simultaneous determination of phenol, catechol and hydroquinone by absorbance ratio derivative method
No full textThe determination of ternary mixture of phenol, catechol and hydroquinone by derivative of ratio absorbance is studied. The relative standard deviation of four determinations was less than 6% for formulated samples. The recovery is in the range of 95%∼ 104%.link_to_subscribed_fulltex
Adaptive fuzzy dynamic surface control for unknown time delay nonlinear systems preceded by unknown asymmetric hysteresis
No full textIn this paper, a fuzzy approximator based adaptive dynamic surface control scheme is proposed for a class of unknown time delay nonlinear systems preceded by asymmetric hysteresis nonlinearities. The features of the proposed method are: 1) by combining the approximated property of the fuzzy logic systems (FLSs) with the Finite Covering Lemma, the Krasovskii functionals are disposed of, achieving the L∞ norm of the tracking error by using the initializing technique; 2) the assumptions on the time-delay functions are removed due to the use of the Finite Covering Lemma and the FLSs; 3) the proposed adaptive fuzzy dynamic surface control scheme can also compensate the asymmetric shifted Prandtl Ishlinskii (ASPI) hysteresis without constructing the inverse of the ASPI model with the density function of ASPI model being unknown and estimated on-line to compensate the hysteresis. It is proved that all the signals in the closed-loop system are ultimately uniformly bounded and can be made arbitrarily small. Simulation results show the validity of the proposed method
See How You Read? Multi-Reading Habits Fusion Reasoning for Multi-Modal Fake News Detection
No full textThe existing approaches based on different neural networks automatically capture and fuse the multimodal semantics of news, which have achieved great success for fake news detection. However, they still suffer from the limitations of both shallow fusion of multimodal features and less attention to the inconsistency between different modalities. To overcome them, we propose multi-reading habits fusion reasoning networks (MRHFR) for multi-modal fake news detection. In MRHFR, inspired by people's different reading habits for multimodal news, we summarize three basic cognitive reading habits and put forward cognition-aware fusion layer to learn the dependencies between multimodal features of news, so as to deepen their semantic-level integration. To explore the inconsistency of different modalities of news, we develop coherence constraint reasoning layer from two perspectives, which first measures the semantic consistency between the comments and different modal features of the news, and then probes the semantic deviation caused by unimodal features to the multimodal news content through constraint strategy. Experiments on two public datasets not only demonstrate that MRHFR not only achieves the excellent performance but also provides a new paradigm for capturing inconsistencies between multi-modal news
Adaptive output-feedback inverse control for a class of time delay nonlinear hysteretic systems via fuzzy approximeter
No full textIn this paper, an fuzzy approximator based output feedback adaptive dynamic surface inverse control (DSIC) scheme is proposed for a class of time-delay systems preceded by unknown asymmetric hysteresis. The main advantages are as follows: 1) by combining the Finite Covering Lemma with fuzzy logic systems (FLSs), a novel time-delay function approx-imator is proposed with the benefits of the assumptions of the conservative upper bound functions on the time-delay functions are removed and the Krasovskii functionals are not required when deal with time delays. Also, the time delay functions extends to a more general one with states variables and time-delay variables being coupled; 2) by using the proposed initial technique, the Lnorm of the tracking error is obtained; 3) by constructing the inverse of the asymmetric hysteresis and approximating the unknown time-delay functions, both time delays and asymmetric hysteresis phenomena in the actuators are mitigated simultaneously when only the output of the system is available. It is proved that all the signals in the closed-loop systems are semi-globally ultimately uniformly bounded (SUUG). Simulation results show the validity of the proposed scheme
Photochemical characteristics of Chlamydomonas mutant hpm91 lacking proton gradient regulation 5 (PGR5) during sustained H-2 photoproduction under sulfur deprivation
No full textRenewable H-2 photoproduction by Chlamydomonas reinhardtii offers a desirable bio-system for solar fuels. However, its large-scale application is hindered mainly due to lack of ideal strains. We previously isolated a mutant hpm91 which lacks PGR5 and sustains H-2 photoproduction for 25 days. To understand the photosynthetic basis for this remarkable phenotype, we hereby investigated its photochemical characteristics during sulfur-deprived H-2 photoproduction using in vivo chlorophyll fluorescence spectroscopy. Compared to wild type, effective quantum yield of PSII and PSI of hpm91 increased upto 78.9% and 147.6%, respectively. Electron transport rate of each photosystem is closely correlated with the increase of quantum yield, suggesting overall enhanced photochemistry of hpm91 under such condition. Moreover, ATP synthase activity decays slower and remains higher in this mutant. These are in vivo evidence demonstrating increased photosynthetic efficiency of hpm91 promotes its H2 photoproduction. Together with its competent photoheterotrophic growth in a larger photobioreactor, we propose that hpm91 is a valuable strain for re-engineering Chlamydomonas towards improving light energy efficiency in a large-scale system. (C) 2019 Institute of Botany, Chinese Academy of Sciences. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC
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