Search

Your search keyword '"Zheng, En"' showing total 21 results
Start Over Author "Zheng, En" Publisher elsevier bv
21 results on '"Zheng, En"'

12. The exact blow-up rates of large solutions for semilinear elliptic equations

Author

Qiaoyu Tian, Jinhua Xi, Zheng-en Fan, Shengzhi Zhang, and Shuibo Huang

Subjects
Elliptic curve, Pure mathematics, Series (mathematics), Continuous function (set theory), Applied Mathematics, Bounded function, Mathematical analysis, Boundary (topology), Boundary value problem, Lipschitz continuity, Analysis, Domain (mathematical analysis), Mathematics
Abstract

In this paper, combining the method of lower and upper solutions with the localization method, we establish the boundary blow-up rate of the large positive solutions to the singular boundary value problem { Δ u = b ( x ) f ( u ) , x ∈ Ω , u ( x ) = + ∞ , x ∈ ∂ Ω , where Ω is a smooth bounded domain in R N . The weight function b ( x ) is a non-negative continuous function in the domain, which vanishes on the boundary of the underlying domain Ω at different rates according to the point of the boundary. f ( u ) is locally Lipschitz continuous satisfying the Keller–Osserman condition and f ( u ) / u is increasing on ( 0 , ∞ ) . It is worth emphasizing that we obtain the main results for a large class of nonlinear terms f , which is regularly varying at infinity with index p ∈ R (that is for all ξ > 0 , lim u → ∞ f ( ξ u ) / f ( u ) = ξ p ), instead of the restriction: f ( u ) ∼ H u p for sufficiently large u and some positive constants H > 0 , p > 1 as in the series of papers of J. L. Gomez.

Published
2010

13. PEG–SO3H as an efficient and reusable catalyst for chemoselective synthesis of 1,1-diacetates

Author

Guoren Yue, Yu-Ying Niu, Ying-Xiao Zong, Xicun Wang, Zheng-Jun Quan, Zhengliang Li, Jun-Ke Wang, Yi Pan, and Zheng-En Song

Subjects
Acetic anhydride, chemistry.chemical_compound, Solvent free, Chemistry, PEG ratio, Organic chemistry, General Chemistry, Chemoselectivity, Catalysis
Abstract

An efficient and convenient procedure of the synthesis of 1,1-diacetates from aromatic aldehydes and acetic anhydride under mild and solvent-free conditions at room temperature, in the presence of PEG–SO3H is reported. PEG–SO3H acts as a catalyst and can be recovered and reused eight times without apparent loss of its catalytic activity.

Published
2013

21. Tribological properties and lubrication mechanism of molybdenum dialkyldithiocarbamate and calcium compounds in greases

Author

Qian Xiang-Lin and Zheng En-Cai

Subjects
chemistry.chemical_classification, Auger electron spectroscopy, Materials science, Base (chemistry), Inorganic chemistry, Analytical chemistry, chemistry.chemical_element, Surfaces and Interfaces, Calcium, Condensed Matter Physics, Surfaces, Coatings and Films, chemistry, Mechanics of Materials, Molybdenum, Grease, Calcium Compounds, Materials Chemistry, Lithium, Lubricant
Abstract

Different greases mixed with molybdenum dialkyldithiocarbamate (MoDTC) alone, and with calcium compounds, were tested in four-ball and Amsler-type testers. After mixing MoDTC alone with lithium or calcium base grease, the friction and wear are reduced, and the ultimate non-scuffing load Pb is increased. MoDTC and calcium petroleum sulphonate or calcium acetate are synergic on reducing wear in lithium base grease but not in calcium base grease. The effectiveness in raising the Pb value decreases in the order CaCO3 > calcium acetate > calcium petroleum sulphonate. Auger electron spectroscopy and X-ray photoelectron spectroscopy analyses show that the surface film consists mainly of MoS2, MoO3, CaCO3 and CaSO4. A model for the surface film is put forward accordingly.

Published
1989

Catalog

Books, media, physical & digital resources
See catalog results