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Your search keyword '"Li, Weigu"' showing total 24 results
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24 results on '"Li, Weigu"'

1. MoS2/C @ Polyurethane Composite Sponges for Synergistic High-Rate Solar Steaming and Mercury Removal

Author

Li, Weigu, Tekell, Marshall C, Huang, Yun, Bertelsmann, Karina, Lau, Max, and Fan, Donglei

Subjects
Physics - Applied Physics
Abstract

Solar steam generation, a sustainable water-purification technology, holds substantial promises in resolving the global issue of shortage of drinkable water. Here, we report the design, fabrication, and performance of an innovative three-dimensional (3-D) solar steamer, offering synergistic high-rate steaming and heavy metal removal functions. The device is made of synthesized carbon-molybdenum-disulfide microbeads electrostatically assembled on a 3-D polyurethane sponge. The mesoporous composite sponge also serves as a freestanding water reservoir that avoids one-side contact to bulk water, effectively suppressing the commonly observed parasitic heat loss, and offering a high energy efficiency of 88%. When being sculptured into a 3-D spoke-like structure, the composite sponge achieves one of the highest evaporation rates of 1.95 kg m-2 h-1 at 1 sun. The solar steamer is demonstrated for water treatment, i.e. decontamination of metal ions, disinfection, and reducing alkalinity and hardness of river water. Particularly, the strong mercury adsorption of MoS2 reduces Mercury from 200 to 1ppb, meeting the stringent standard set by the Environmental Protection Agency, which is the first demonstration of mercury-removal powered by solar energy. The unique design, fabrication, water-handling strategy, and mercury-removal function of this high-performance solar steamer could inspire new paradigms of water treatment technologies.

Published
2018

5. Polynomial systems : a lower bound for the weakened 16th Hilbert problem

Author

Li, Chengzhi, Li, Weigu, Llibre, Jaume, and Zhang, Zhifen

Subjects
ComputingMethodologies_SYMBOLICANDALGEBRAICMANIPULATION, MathematicsofComputing_NUMERICALANALYSIS, Polinomis, MathematicsofComputing_DISCRETEMATHEMATICS, Polynomial systems
Abstract

In this paper we provide the greatest lower bound about the number of (non-infinitesimal) limit cycles surrounding a unique singular point for a planar polynomial differential system of arbitrary degree.

Published
2021

7. The uniqueness of limit cycles for classical Liénard equations of degree four under singular perturbations

Author

LI WeiGu and LI ChengZhi

Subjects
Singular perturbation, Conjecture, Dynamical systems theory, Singular solution, Simple (abstract algebra), General Mathematics, Mathematical analysis, Applied mathematics, Uniqueness, Limit (mathematics), Singular integral, Mathematics
Abstract

The Lins-de Melo-Pugh conjecture for $n=4$ was proved in 2012, but the proof is complicated. In this article we give a simple proof for this problem under singular perturbations. We want to show the role of singular perturbation method in the study of qualitative theory of dynamical systems, and to show the application of a new formula of the slow divergence integral.

Published
2016

23. Structural design and manufacturing of three-dimensional monolithic porous superstructures for flexible self-powered electronics, energy conversion and storage devices, and water purification systems

Author

Li, Weigu, Ph. D.

Subjects
3D superstructures, Graphene, MoS₂, Supercapacitors, Solar steaming, Polypyrrole
Abstract

Three dimensional (3D) porous superstructures with designed hierarchy have received intensive research interest due to the grand potencies in applications of energy devices, environment remediation, and flexible electronics. Three dimensional metallic foams or polymer sponges have been utilized as catalytic substrates or templates for the growth of a variety of functional 3D materials with replicated morphologies, including 3D foams made of the unique class of 2D materials (graphene, molybdenum disulfide), metal and metal oxides/hydroxides, as well as polymers. Here, we developed a rational approach to create innovative nickel foams with hierarchical porosity to substantially enhance the specific surface area by up to 3 folds compared to that of commercial nickel foam. The resulted 3D graphite foams (GF) provide enhanced electrochemical performances when applied as supercapacitor electrode supports. The as-fabricated flexible supercapacitor can be readily integrated with our wearable GF/polymer strain sensors or nanomotor manipulation systems as self-powered devices, which can detect both large and small motion induced strains, or compel nanomotors to trace letters, such as “U” and “T”, respectively. After sulfurizing and electrochemically activate the surface of the unique nickel foams with dendritic microstructures, we obtained ternary metal oxyhydroxides that are utilized as high-performance and stable oxygen evolution reaction catalysts for water splitting. We also exploited electrostatic assembly to achieve 3D composite foams with hydrothermally synthesized MoS₂/C microbeads attached on polyurethane sponges for high-rate solar-steaming water treatment with synergistic mercury removal. Finally, we achieved one of the best solar-steaming performances in both energy-conversion efficiency and evaporation rate via strategical origami folding of photothermal thin films into 3D-structured roses that exhibit optimized performances in light absorption and water evaporation. Moreover, a portable low-pressure water purification-collection uni-system was developed that can remarkably enhance the efficiency of water collection, which is the first to the best of our knowledge. This dissertation work, exploring innovative structural design and manufacturing paradigms of 3D monolithic porous superstructures has made an important forward step in the interdisciplinary field of nanomanufacturing, 3D porous materials, flexible energy storage systems, self-powered devices, and solar water treatment.

Published
2019

24. Synergistic High‐Rate Solar Steaming and Mercury Removal with MoS2/C @ Polyurethane Composite Sponges.

Author

Li, Weigu, Tekell, Marshall C., Huang, Yun, Bertelsmann, Karina, Lau, Max, and Fan, Donglei

Subjects
*POLYURETHANES, *MERCURY removal in flue gases, *FABRICATION (Manufacturing), *ENERGY consumption, *DISULFIDES
Abstract

Solar steam generation, a sustainable water‐purification technology, holds substantial promise in resolving the global issue of shortage of drinkable water. Here, the design, fabrication, and high‐performance of an innovative 3D solar steamer, offering synergistic high‐efficiency steaming and heavy metal removal functions are reported. The device is made of synthesized carbon‐molybdenum‐disulfide microbeads electrostatically assembled on a 3D polyurethane sponge. The mesoporous composite sponge also serves as a freestanding water reservoir that avoids one‐side contact to bulk water, effectively suppressing the commonly observed parasitic heat loss, and offering a high energy efficiency of 88%. When being sculpted into a 3D spoke‐like structure, the composite sponge achieves one of the highest evaporation rates of 1.95 kg m−2 h−1 at 1 sun. The solar steamer is demonstrated for water treatment, i.e., decontamination of metal ions, disinfection, and reducing alkalinity and hardness of river water. Particularly, the strong mercury adsorption of MoS2 reduces mercury levels from 200 to 1 ppb, meeting the stringent standard set by the Environmental Protection Agency, which is the first demonstration of mercury‐removal powered by solar energy. The unique design, fabrication, water‐handling strategy, and mercury‐removal function of this high‐performance solar steamer can inspire new paradigms of water treatment technologies. Dually functional solar steamers made of molybdenum‐disulfide/amorphous carbon microbeads assembled on 3‐D polymer sponges are strategically designed and fabricated for high‐efficiency solar steaming and synergistic mercury removal. The device offers an evaporation rate up to 1.95 kg m‐2 h‐2 and an energy conversion efficiency as high as 88% under 1 sun. In one steaming operation, mercury can be removed from water, meeting stringent drinking standards. [ABSTRACT FROM AUTHOR]

Published
2018
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