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- 저자 : Chong-hai Xu (검색결과 4 건)
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Xu, Hai Bo,Kim, Jeong Hun,Kim, Sangtae,Hwang, Hee Jae,Maurya, Deepam,Choi, Dukhyun,Kang, Chong-Yun,Song, Hyun-Cheol Elsevier 2019 Nano energy Vol.62 No.-
<P><B>Abstract</B></P> <P>Triboelectric generators (TEG), based on contact electrification and electro-static induction, has received a significant attention because of their numerous applications. To improve the electrified surface charge density in TEG, increasing the surface area of dielectric materials or forming internal hollow structures are typically employed to increase capacitance. However, the fabrication processes of such structures are complex and time-consuming. Here, we provide a facile and cost-effective synthesis method for the porous PDMS based TEG via a novel vapor encapsulation casting (VEC). The double dielectric layer composed of the porous and dense PDMS layers are formed in-site through VEC. The thickness and the thickness ratio of the double dielectric layer can be precisely controlled by adjusting the uncured PDMS thickness and vapor penetration depth. The double dielectric layer TEG (DTEG) exhibits the improved harvesting performance because the porous dielectric layer increases the capacitance and compressibility, while the dense layer passivates the fully open pores which reduce the charging surface area as completely opening through the dielectric layer without contacting the bottom electrode. We obtain the maximum output voltage of 345 V and short circuit current of 3 μA/cm<SUP>2</SUP> from DTEG having 0.95 porous thickness ratio, resulting 330% enhancement in the power output as compared to the dense PDMS based TEG. We further investigate the performance of DTEG under various operating conditions. We also demonstrate the operation of Bluetooth distance/temperature sensors using capacitors charged by DTEG.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TEG based on the double dielectric layer composed of the sponge-like porous and flat dense elastomer is demonstrated. </LI> <LI> Facile and affordable synthesis method for the porous PDMS is provided via the novel vapor encapsulation casting. </LI> <LI> Highly deformable porous PDMS effectively enhances its capacitance under a pressure. </LI> <LI> Flat dense second layer of PDMS reduces the device impedance and improves the contact interface with an electrode. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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INVOLUTION-PRESERVING MAPS WITHOUT THE LINEARITY ASSUMPTION AND ITS APPLICATION
Xu, Jin-Li,Cao, Chong-Guang,Wu, Hai-Yan The Korean Society for Computational and Applied M 2009 Journal of applied mathematics & informatics Vol.27 No.1
Suppose F is a field of characteristic not 2 and $F\;{\neq}\;Z_3$. Let $M_n(F)$ be the linear space of all $n{\times}n$ matrices over F, and let ${\Gamma}_n(F)$ be the subset of $M_n(F)$ consisting of all $n{\times}n$ involutory matrices. We denote by ${\Phi}_n(F)$ the set of all maps from $M_n(F)$ to itself satisfying A - ${\lambda}B{\in}{\Gamma}_n(F)$ if and only if ${\phi}(A)$ - ${\lambda}{\phi}(B){\in}{\Gamma}_n(F)$ for every A, $B{\in}M_n(F)$ and ${\lambda}{\in}F$. It was showed that ${\phi}{\in}{\Phi}_n(F)$ if and only if there exist an invertible matrix $P{\in}M_n(F)$ and an involutory element ${\varepsilon}$ such that either ${\phi}(A)={\varepsilon}PAP^{-1}$ for every $A{\in}M_n(F)$ or ${\phi}(A)={\varepsilon}PA^{T}P^{-1}$ for every $A{\in}M_n(F)$. As an application, the maps preserving inverses of matrces also are characterized.
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Involution-preserving maps without the linearity assumption and its application
Jin-li Xu,Chong-guang Cao,Hai-yan Wu 한국전산응용수학회 2009 Journal of applied mathematics & informatics Vol.27 No.1
Suppose F is a field of characteristic not 2 and F ≠ Z3. Let Mn(F) be the linear space of all n×n matrices over F, and let Γn(F) be the subset of Mn(F) consisting of all n×n involutory matrices. We denote by Φn(F) the set of all maps from Mn(F) to itself satisfying A−λB∈ Γn(F) if and only if ∅(A)− λ∅(B)∈ Γn(F) for every A,B ∈ Mn(F) and λ ∈ F. It was showed that ∅∈Φn(F) if and only if there exist an invertible matrix P ∈ Mn(F) and an involutory element ε such that either ∅(A) = εPAP−1 for every A ∈ Mn(F) or ∅(A) = εPAT P−1 for every A ∈ Mn(F). As an application, the maps preserving inverses of matrces also are characterized. Suppose F is a field of characteristic not 2 and F ≠ Z3. Let Mn(F) be the linear space of all n×n matrices over F, and let Γn(F) be the subset of Mn(F) consisting of all n×n involutory matrices. We denote by Φn(F) the set of all maps from Mn(F) to itself satisfying A−λB∈ Γn(F) if and only if ∅(A)− λ∅(B)∈ Γn(F) for every A,B ∈ Mn(F) and λ ∈ F. It was showed that ∅∈Φn(F) if and only if there exist an invertible matrix P ∈ Mn(F) and an involutory element ε such that either ∅(A) = εPAP−1 for every A ∈ Mn(F) or ∅(A) = εPAT P−1 for every A ∈ Mn(F). As an application, the maps preserving inverses of matrces also are characterized.
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Size Effect on Surface Roughness in Micro Turning
Tao Zhang,Zhan-qiang Liu,Zhen-yu Shi,Chong-hai Xu 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.
The conventional model predicts that the surface roughness decreases with feed and fits well with the measured results, even in the micro turning process. But it is observed that surface roughness increases with feed decreases when the feed is in the range of micro scale. Based on the analysis of peak-to-valley formation process, a quadratic prediction model, which divides the height of peak-tovalley into two parts: one part is piled in front of the rake face while the other is piled on the flank face and is more accurate, is established considering the effect of tool geometry, cutting parameters and pile-up of work piece. The prediction model is calibrated and verified via two groups of micro turning experiments. Results show that size effect of specific cutting energy increases the surface roughness at small feeds. The difference between the theoretical and measured results at small feeds is mainly induced by the pileup of work piece material around the rear face. The best surface roughness can be obtained when the feed per revolution equals 0.1time of the cutting edge radius.
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