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Yuming Qi,Tengwu He,Miaolin Feng 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7
Adding nanotwins to a metal could be a way to effectively improve its strength without suppressing its tensile ductility, whichsuggests that their unique nanostructure may alter microstructure evolution and deformation mechanisms. In this work, weperform a molecular dynamics-based tension simulation of two-dimension (2D) polycrystalline copper (Cu) with embeddednanotwins under uniaxial stress conditions. The results of MD-simulation reveal that the spacing of the twin boundarieshad a significant effect on the mechanical properties of nanotwinned materials. Specifically, an irregular relationship isfound between the twin boundary spacing ( DT ) and the strength of the material. It exhibits that the peak stress reached amaximum at DT = 12.5 nm and decreased thereafter with increasing average DT . However, flow stress reaches a maximumat a critical value of DT = 7 nm. According to the analysis of microstructure evolution, the presence of nanotwins hinder themotion of partial dislocations and stacking faults, and the stress-concentrated region leads to the transition from coherenttwin boundaries to incoherency. The stress-concentrated region locates in the step of incoherent would release the intrinsicstacking faults responsible for the formation of hierarchical contraction nanotwins stacking faults which efficiently improvesthe strength of Cu. In addition, as the tension proceeds, some samples begin to display the secondary twinning. This workwill be helpful for further investigation the nucleation and evolution of 2D nanotwinned metals and for formulating effectivestrength criteria for 2D nanotwinned metals.
Molecular Characterization of A Novel Bacillus thuringiensis Strain from China
Qi Xu Feng,Li Ming Shun,Choi Jae Young,Kim Yang-Su,Wang Yong,Kang Joong Nam,Choi Heekyu,Je Yeon Ho,Song Ji Zhen,Li Jian Hong Korean Society of Sericultural Science 2005 International Journal of Industrial Entomology Vol.11 No.1
A strain of Bacillus thuringiensis that showed significantly high toxicity to Plutella xylostella was isolated from a dust sample collected from Chinese tobacco warehouse and characterized. The isolate named B. thuringiensis LY-99 was determined to belong to subsp. alesti (H3a3c) by an H antisera agglutination test and produced bipyramidal inclusions. Plasmid and crystal protein patterns of the LY-99 were different from those of the reference strain, subsp. alesti. PCR analysis with specific primers revealed that this isolate contained abundant cry genes including crylAa, crylAc, crylB, crylD, crylE, crylF and cry2 genes, which was absolutely different from cry gene profile of the subsp. alesti. In addition, insecticidal activity of the LY-99 against P. xylostella larvae was about 44 times higher than that of the subsp. alesti.
Some properties of the Bernoulli numbers of the second kind and their generating function
Feng Qi,Jiao-Lian Zhao 대한수학회 2018 대한수학회보 Vol.55 No.6
In the paper, the authors find a common solution to three series of differential equations related to the generating function of the Bernoulli numbers of the second kind and present a recurrence relation, an explicit formula in terms of the Stirling numbers of the first kind, and a determinantal expression for the Bernoulli numbers of the second kind.
Characterization of a Novel cry1-Type Gene from Bacillus thuringiensis subsp. alesti Strain LY-99
Qi, Xu Feng,Li, Ming Shun,Choi, Jae-Young,Roh, Jong-Yul,Song, Ji Zhen,Wang, Yong,Jin, Byung-Rae,Je, Yeon-Ho,Li, Jian Hong Korean Society of Sericultural Science 2009 International Journal of Industrial Entomology Vol.18 No.1
B. thuringiensis strain LY-99 belonging to subsp. alesti (H3a3c), was isolated from Chinese tobacco warehouse and showed significantly high toxicity to Plutella xylostella. For the identification of the cry1-type genes from B. thuringiensis LY-99, an extended multiplex PCRrestriction fragment length polymorphism (PCRRFLP) method was established by using two pairs of universal primers based on the conserved regions of the cry1-type genes to amplify around 2.4 kb cry1-type gene fragments. Then the DNA fragment was cloned into pGEM-T Easy vector and digested with EcoRI and EcoRV enzymes. Through this method, a known cry1-type gene was successfully identified from the reference strain, B. thuringiensis subsp. alesti. In addition, the RFLP patterns revealed that B. thuringiensis LY-99 included a novel cry1A-type gene in addition to cry1Aa, cry1Ac, cry1Be and cry1Ea genes. The novel cry1A-type gene was designated cry1Ah2 (Genbank accession No DQ269474). An inverse PCR method was used to amplify the flank regions of cry1Ah2 gene. Finally, 3143 bp HindIII fragment from B. thuringiensis LY-99 plasmid DNA including 5' region and partial ORF was amplified, and sequence analysis revealed that cry1Ah2 gene from LY-99 showed 89.31% of maximum sequence similarity with cry1Ac1 crystal protein gene. In addition, the deduced amino acid sequence of Cry1Ah2 protein shared 87.80% of maximum identity with that of Cry1Ac2. This protein therefore belongs to a new class of B. thuringiensis crystal proteins.
Feng Qi,Qiu-Ming Luo,Bai-Ni Guo 한국수학교육학회 2004 純粹 및 應用數學 Vol.11 No.3
In this article, using the L'Hospital rule, mathematical induction, the trigonometric power formulae and integration by parts, some integral formulae for the improper integrals R1 0 [sin2m(��x)]=(x2n)dx and R1 0 [sin2m+1(��x)]=(x2n+1)dx are established, where m ¸ n are all positive integers and �� 6= 0.
COMPLETE MONOTONICITY OF A DIFFERENCE BETWEEN THE EXPONENTIAL AND TRIGAMMA FUNCTIONS
Feng Qi,Xiao-Jing Zhang 한국수학교육학회 2014 純粹 및 應用數學 Vol.21 No.2
In the paper, by directly verifying an inequality which gives a lowerbound for the first order modified Bessel function of the first kind, the authors supplya new proof for the complete monotonicity of a difference between the exponentialfunction e^(1/t) and the trigamma function ψ'(t) on (0, ∞).
Effects of Polymerization and Spinning Conditions on Mechanical Properties of PAN Precursor Fibers
Qi-Feng Qin,Yong-Qiang Dai,Kai Yi,Li Zhang,Seung-Kon Ryu,Ri-Guang Jin 한국탄소학회 2010 Carbon Letters Vol.11 No.3
PAN precursor fibers were produced via wet-spinning process, and effects of polymerization and spinning processes, especially the stretching process, were investigated on mechanical properties and micro-morphologies of precursor fibers. An increase in molecular weight, dope solid and densification and a decrease in surface defects were possible by controlling polymerization temperature, the number of heating rollers for densification and the jet stretch ratio, which improved the mechanical properties of precursor fibers. The curves for strength, modulus, tensile power and diameter as a function of stretch ratio can be divided into three stages: steady change area, little change area and sudden change area. With the increase of stretch ratio, the fiber diameter became smaller, the degree of crystallization increased and the structure of precursor fibers became compact and homogeneous, which resulted in the increase of strength, modulus and tensile power of precursor fibers. Empirical relationship between fiber strength and stretch ratio was studied by using the sub-cluster statistical theory. It was successfully predicted when the strengths were 0.8 GPa and 1.0 GPa under a certain technical condition, the corresponding stretch ratio of the fiber were 11.16 and 12.83 respectively.
Qi, Feng The Kangwon-Kyungki Mathematical Society 2019 한국수학논문집 Vol.27 No.2
In the paper, by virtue of the $Fa{\grave{a}}$ di Bruno formula, properties of the Bell polynomials of the second kind, and the Lah inversion formula, the author simplifies coefficients in a family of ordinary differential equations related to the generating function of the Mittag-Leffler polynomials.
SOME LOGARITHMICALLY COMPLETELY MONOTONIC FUNCTIONS RELATED TO THE GAMMA FUNCTION
Feng Qi,Bai-Ni Guo 대한수학회 2010 대한수학회지 Vol.47 No.6
In this article, the logarithmically complete monotonicity of some functions such as [수식],[수식],[수식] and [수식]for α ∈ R on (−1,∞) or (0,∞) are obtained, some known results are recovered, extended and generalized. Moreover, some basic properties of the logarithmically completely monotonic functions are established.
FOUR LOGARITHMICALLY COMPLETELY MONOTONIC FUNCTIONS INVOLVING GAMMA FUNCTION
Qi, Feng,Niu, Da-Wei,Cao, Jian,Chen, Shou-Xin Korean Mathematical Society 2008 대한수학회지 Vol.45 No.2
In this paper, two classes of functions, involving a parameter and the classical Euler gamma function, and two functions, involving the classical Euler gamma function, are verified to be logarithmically completely monotonic in $(-\frac{1}{2},\infty)$ or $(0,\infty)$; some inequalities involving the classical Euler gamma function are deduced and compared with those originating from certain problems of traffic flow, due to J. Wendel and A. Laforgia, and relating to the well known Stirling's formula.