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144 results on '"Ma, Zhaokun"'

30. Preparation and properties of resin matrix composites reinforced by high thermal conductivity graphite films.

Author

Wang, Yujie, Wang, Kun, Ma, Zhaokun, Meng, Taisheng, Cao, Ruixiong, and Jiang, Nan

Subjects
CARBON films, VAN der Waals forces, THERMAL conductivity, SURFACE defects, HEAT treatment
Abstract

High thermal conductivity graphite films (GFs) have a thermal conductivity, which have attracted much attention in recent years. As the surface of GFs is extremely smooth, the resin matrix and GFs are only connected by van der Waals forces, and it is difficult to produce chemical bonds between them, resulting in poor mechanical properties of the composites. In this study, the composites were prepared by etching defects on the surface of GFs by high‐temperature heat treatment. It was determined that the critical temperature range for effective etching was between 600 and 650°C. The GFs were subjected to high‐temperature heat treatment to create circular, hexagonal, and disordered groove‐like defects, and then combined with prepregs and bismaleimide resins in a single molding process. The composites exhibit a distinct layered "sandwich" structure, where surface‐induced defects enhance the interfacial adhesion between GFs and the resin matrix, creating a "nail‐punched" structure. The thermal conductivity of the S‐650 sample in the X‐direction was up to 1187.93 W/(m·K), and the flexural strength of the S‐800 sample was up to 116.18 MPa. The prepared composites are expected to be widely used in thermal interface fields such as heat exchangers, battery heat dissipation and aerospace thermal control systems. Highlights: High‐temperature treatment was used to successfully introduce defects into GFs.The formation mechanisms of the three types of defects were explained.The thermal conductivity of the composites was increased to over 1000 W/(m·K).Composites reinforced with modified GFs exhibit enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

Published
2024
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44. ON THE NUMBER OF REAL ZEROS OF POLYNOMIALS OF EVEN DEGREE.

Author

MA, LANDE and MA, ZHAOKUN

Abstract

For any real polynomial $p(x)$ of even degree k , Shapiro ['Problems around polynomials: the good, the bad and the ugly $\ldots $ ', Arnold Math. J. 1 (1) (2015), 91–99] proposed the conjecture that the sum of the number of real zeros of the two polynomials $(k-1)(p{'}(x))^{2}-kp(x)p{"}(x)$ and $p(x)$ is larger than 0. We prove that the conjecture is true except in one case: when the polynomial $p(x)$ has no real zeros, the derivative polynomial $p{'}(x)$ has one real simple zero, that is, $p{'}(x)=C(x)(x-w)$ , where $C(x)$ is a polynomial with $C(w)\ne 0$ , and the polynomial $(k-1)(C(x))^2(x-w)^{2}-kp(x)C{'}(x)(x-w)-kC(x)p(x)$ has no real zeros. [ABSTRACT FROM AUTHOR]

Published
2024
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47. Zeros of Meromorphic function

Author

Ma, Lande and Ma, Zhaokun

Subjects
Mathematics - Complex Variables, FOS: Mathematics, Complex Variables (math.CV)
Abstract

We introduce and develop the root locus method in mathematics. And we study the distribution of zeros of meromorphic functions by root locus method.

Published
2022

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