Donghua University

About: Donghua University is a education organization based out in Shanghai, China. It is known for research contribution in the topics: Fiber & Nanofiber. The organization has 21155 authors who have published 21841 publications receiving 393091 citations. The organization is also known as: Dōnghuá Dàxué & China Textile University.

Finite-Horizon ${\cal H}_{\infty}$ Control for Discrete Time-Varying Systems With Randomly Occurring Nonlinearities and Fading Measurements

Abstract: This technical note deals with the ${\cal H}_{\infty}$ control problem for a class of discrete time-varying nonlinear systems with both randomly occurring nonlinearities and fading measurements over a finite-horizon. The system measurements are transmitted through fading channels described by a modified stochastic Rice fading model. The purpose of the addressed problem is to design a set of time-varying controllers such that, in the presence of channel fading and randomly occurring nonlinearities, the ${\cal H}_{\infty}$ performance is guaranteed over a given finite-horizon. The model transformation technique is first employed to simplify the addressed problem, and then the stochastic analysis in combination with the completing squares method are carried out to obtain necessary and sufficient conditions of an auxiliary index which is closely related to the finite-horizon ${\cal H}_{\infty}$ performance. Moreover, the time-varying controller parameters are characterized via solving coupled backward recursive Riccati difference equations (RDEs). A simulation example is utilized to illustrate the usefulness of the proposed controller design scheme.

Sulfurized Polyacrylonitrile Cathodes with High Compatibility in Both Ether and Carbonate Electrolytes for Ultrastable Lithium–Sulfur Batteries

Abstract: Sulfurized polyacrylonitrile (SPAN) is a promising material capable of suppressing polysulfide dissolution in lithium–sulfur (Li–S) batteries with carbonate electrolyte. However, undesirable spontaneous formation of soluble polysulfides may arise in the ether electrolyte, and the conversion of sulfur in SPAN during the lithiation/delithiation processes is yet to be understood. Here, a highly reliable Li–S system using a freestanding fibrous SPAN cathode, as well as the sulfur conversion mechanism involved, is demonstrated. The SPAN shows high compatibility in both ether and carbonate electrolytes. The sulfur atoms existing in the form of short S2 and S3 chains are covalently bonded to the pyrolyzed PAN backbone. The electrochemical reduction of the SPAN by Li+ is a single-phase solid–solid reaction with Li2S as the sole discharge product. Meanwhile, the parasitic reaction between Li+ and CN bonds exists upon the first discharge, and the residual Li+ enhances the conductivity of the backbone. The recharge ability and rate capability are kinetically dominated by the activation of Li2S nanoflakes generated during discharge. At 800 mA g−1, a specific capacity of 1180 mAh g−1 is realized without capacity fading in the measured 1000 cycles, which makes SPAN promising for practical application.

Copper-Catalyzed Oxidative Trifluoromethylation of Terminal Alkynes and Aryl Boronic Acids Using (Trifluoromethyl)trimethylsilane

Abstract: Trifluoromethylated acetylenes and arenes are widely applicable in the synthesis of pharmaceuticals and agrochemicals. In 2010, our group has reported the copper-mediated oxidative trifluomethylation of terminal alkynes and aryl boronic acids. This method allows a wide range of functional group tolerant trifluoromethylated acetylenes and arenes to be easily prepared. After the preliminary mechanistic studies of the oxidative trifluoromethylation of terminal alkyne, an efficient copper-catalyzed oxidative trifluoromethylation of terminal alkynes and aryl boronic acids has been developed. The catalytic protocol is successfully achieved by adding both the substrate and a portion of CF3TMS slowly using a syringe pump to the reaction mixture.

Bio-based epoxy vitrimers: Reprocessibility, controllable shape memory, and degradability

Abstract: The research activities in the development of recyclable and reprocessable covalently crosslinked networks, and the construction of polymers from renewable resources are both stemmed from the economical and environmental problems associated with traditional thermosets. However, there is little effort in combination of these two attractive strategies in material designs. This article reported a bio-based vitrimer constructed from isosorbide-derived epoxy and aromatic diamines containing disulfide bonds. The resulted dynamic epoxy resins showed comparable thermomechanical properties as compared to similar epoxy networks cured by traditional curing agent. Rheological tests demonstrated the fast stress relaxation of the dynamic network due to the rapid metathesis of disulfide bonds at temperature higher than glass transition temperature. This feature permitted the recycling and reprocessing of the fragmented samples for several times by hot press. The dynamic epoxy resins also exhibited shape-memory effect, and it is demonstrated that the shape recovery ratio could be readily adjusted by controlling the stress relaxation in the temporary state at programming temperature. Moreover, the degradability of the dynamic epoxy resins in alkaline aqueous solution was also demonstrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1790–1799