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1,612 results on '"Zhang, Xiangwen"'

204. Measure Estimates, Harnack Inequalities and Ricci Lower Bound

Author

Wang, Yu and Zhang, Xiangwen

Subjects
Mathematics - Analysis of PDEs, Mathematics - Differential Geometry
Abstract

On a Riemannian metric-measure space, we establish an Alexandrov-Bakelman-Pucci type measure estimate connecting Bakry-\'Emery Ricci curvature lower bound, modified Laplacian and the measure of certain special sets. We apply this estimate to prove Harnack inequalities for the modified Laplacian operator and fully non-linear operators. These inequalities seem not available in the literature; And our proof, solely based on the ABP estimate, does not involve any Sobolev inequalities nor gradient estimate. We also propose a question regarding the characterization of Ricci lower bound by the Harnack inequality., Comment: 37 pages. We fix an error in the proof of Lemma 9.3 in previous version which was pointed out to us by Prof. Diego Maldonado

Published
2011

215. Z-scheme charge transfer between a conjugated polymer and α-Fe2O3 for simultaneous photocatalytic H2 evolution and ofloxacin degradation.

Author

Xiao, Ziheng, Xiao, Jie, Yuan, Luxi, Ai, Minhua, Idrees, Faryal, Huang, Zhen-Feng, Shi, Chengxiang, Zhang, Xiangwen, Pan, Lun, and Zou, Ji-Jun

Abstract

The replacement of the oxygen evolution reaction with a higher valuable oxidation process can overcome the sluggish kinetics to promote renewable hydrogen production, simultaneously achieving energy storage and environmental protection. However, the effective integration of two redox half-reactions in one photocatalytic reaction system is still a challenge. Here the p-diethynylbenzene and dibenzothiophene sulfone copolymer (PEB-DBT) is well-designed to couple with α-Fe2O3via a palladium-catalyzed Sonogashira cross-linking reaction, forming a heterojunction with strong interfacial interaction. In particular, there is a different preferred charge transfer path of PEB-DBT/α-Fe2O3via modulating the work function difference in various solutions. The results suggest that the Z-scheme electron transfer pathway is predominant in triethanolamine (TEOA) and ofloxacin (OFL) solutions, instead of the type-II heterojunction that forms in H2O or methylene blue (MB). The Z-scheme PEB-DBT/α-Fe2O3 heterojunction has excellent performance in the hydrogen evolution half-reaction and OFL degradation, which is about 2.7 times and 3.3 times higher than that of pure PEB-DBT, respectively. Finally, it successfully achieved simultaneous photocatalytic H2 evolution and OFL degradation under visible light. [ABSTRACT FROM AUTHOR]

Published
2024
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216. Advances in Heterogeneous Catalysts for Lignin Hydrogenolysis.

Author

Shen, Zhensheng, Shi, Chengxiang, Liu, Fan, Wang, Wei, Ai, Minhua, Huang, Zhenfeng, Zhang, Xiangwen, Pan, Lun, and Zou, Ji‐Jun

Subjects
HETEROGENEOUS catalysts, HYDROGENOLYSIS, LIGNINS, PETROLEUM products, LIGNOCELLULOSE, DEPOLYMERIZATION, METALS
Abstract

Lignin is the main component of lignocellulose and the largest source of aromatic substances on the earth. Biofuel and bio‐chemicals derived from lignin can reduce the use of petroleum products. Current advances in lignin catalysis conversion have facilitated many of progress, but understanding the principles of catalyst design is critical to moving the field forward. In this review, the factors affecting the catalysts (including the type of active metal, metal particle size, acidity, pore size, the nature of the oxide supports, and the synergistic effect of the metals) are systematically reviewed based on the three most commonly used supports (carbon, oxides, and zeolites) in lignin hydrogenolysis. The catalytic performance (selectivity and yield of products) is evaluated, and the emerging catalytic mechanisms are introduced to better understand the catalyst design guidelines. Finally, based on the progress of existing studies, future directions for catalyst design in the field of lignin depolymerization are proposed. [ABSTRACT FROM AUTHOR]

Published
2024
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235. Breaking the activity and stability bottlenecks for acid hydrogen evolution by strong metal–support interaction between Pt nanoparticles and amorphous MoOxElectronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d4cy00114a

Author

Ning, Bo, Huang, Zhen-Feng, Shi, Chengxiang, Pan, Lun, Gao, Ruijie, Zhang, Xiangwen, and Zou, Ji-Jun

Abstract

Commercial Pt/C is the best electrocatalyst for electrocatalytic hydrogen evolution due to its high activity and fast electron transfer kinetics. However, the poor stability under high current density and high cost limits its large-scale application. Here, we managed to fabricate a stable catalyst where MoOxstabilized Pt nanoparticles is supported on Ketjen Black viaimpregnation–annealing method. This catalyst exhibited a low overpotential of 4 mV (@10 mA cm−2) and 29 mV (@100 mA cm−2) and considerable long-term stability for 100 h toward acid hydrogen evolution reaction, outperforming commercial 20 wt% Pt/C. The excellent catalytic performances can be assigned to the existence of amorphous MoOxwhich can transport electrons to Pt nanoparticles and prevent Pt nanoparticles from agglomeration. This work provided a simple synthesis strategy to synthesize an amorphous MoOxprotected Pt nanoparticles catalyst with good activity and stability, which can be an alternative to commercial Pt/C for acid hydrogen evolution reaction.

Published
2024
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236. Optimal Regenerative Braking Control Strategy for Electric Vehicles Based on Braking Intention Recognition and Load Estimation

Author

Tang, Mingbin and Zhang, Xiangwen

Abstract

Regenerative braking technology plays a crucial role in recovering braking energy and extending the range of electric vehicles. To maximize energy recovery and ensure braking stability across various road conditions, loads, and braking intentions, an optimal regenerative braking control strategy is proposed. Firstly, the driver's braking intention is recognized using optimized modal features extracted from the brake pedal signal. Vehicle load estimation is then performed using a forgetting factor recursive least squares algorithm. Subsequently, an artificial bee colony optimization algorithm is employed to allocate optimal braking forces between the front and rear axles for different braking intentions and loads. Based on the obtained braking force distribution ratio, an optimal regenerative braking control strategy is developed, considering braking stability and energy recovery safety. The proposed strategy is validated on the dSPACE hard-in-loop platform under various simulated conditions, including different road conditions, braking intentions, and loads. The results demonstrate that braking intention, vehicle load, and road conditions all impact the regenerative braking process of electric vehicles. Moreover, the proposed regenerative braking control strategy significantly enhances the energy recovery rate and effectively reduces braking distance.

Published
2024
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247. Modulating Crystallization of MoS2 Nanostructures by Dimethyl Sulfoxide for Enhanced Hydrodesulfurization.

Author

Zhang, Tianren, Bai, Zhe, Wang, Luyao, Zhang, Xiangwen, and Li, Guozhu

Abstract

Molybdenum disulfide (MoS2) is a well-qualified active component in hydrodesulfurization (HDS). However, the crystallinity of MoS2 is hardly fine-tuned at nanoscale to increase further active sites and their accessibility for pursuing higher catalytic performance. In this study, a facile one-pot hydrothermal method is developed to prepare MoS2 with well-defined crystallinity for enhanced HDS. The crystallization rate of MoS2 is precisely adjusted using different sulfur sources and dimethyl sulfoxide (DMSO) additives. Intermediates generated during hydrothermal synthesis of MoS2 are analyzed to reveal the crystallization mechanism. DMSO alters the pathway of MoS2 reaction crystallization and changes the crystallization rate to achieve morphology control. MoS2 nanoflowers composed of 5 nm-length nanosheets are prepared, which have coexistence of 1T and 2H phases and enriched (S–S)2– surface structures. The as-synthesized MoS2 catalyst shows high HDS activity and tunable product selectivity. [ABSTRACT FROM AUTHOR]

Published
2023
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