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Numerical study on particle deposition in rough channels with large-scale irregular roughness
Wenpeng Hong,Xin Wang 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.7
We studied particle deposition in rough channels, using the W-M fractal function to characterize a largescale irregular surface with a root-mean-square roughness of 0.5mm. The flow was numerically investigated by Reynolds stress model, and the particles were tracked by a Lagrangian particle model. An analysis of the flow field in a rough channel shows that the roughness enhances the max flow velocity and the pressure drop in the channel. It induces several eddies in the concave of the rough surface. We also compared particle deposition in a rough channel with particle deposition in a smooth channel. This comparison shows that the roughness significantly enhances the particle deposition of small particles, but the enhancement decreases with the increase of particle size. Moreover, the particle deposition ratio decreases with increasing flow velocity.
Hou, Wenpeng,Zhao, Ning-Jiu,Meng, Dongli,Tang, Jing,Zeng, Yi,Wu, Yu,Weng, Yangziwan,Cheng, Chungui,Xu, Xiulai,Li, Yi,Zhang, Jian-Ping,Huang, Yong,Bielawski, Christopher W.,Geng, Jianxin American Chemical Society 2016 ACS NANO Vol.10 No.5
<P>The installation of heterojunctions on the surfaces of carbon nanotubes (CNTs) is an effective method for promoting the charge separation processes needed for CNT-based electronics and optoelectronics applications. Conjugated polymers are proven state-of-the-art candidates for modifying the surfaces of CNTs. However, all previous attempts to incorporate conjugated polymers to CNTs resulted in unordered interfaces. Herein we show that well-defined chains of regioregular poly(3-hexylthiophene) (P3HT) were successfully grown from the surfaces of multiwalled CNTs (MWNTs) using surface-initiated Kumada catalyst-transfer polycondensation. The polymerization was found to proceed in a controlled manner as chains of tunable lengths were prepared through variation of the initial monomer-to-initiator ratio. Moreover, it was determined that large-diameter MWNTs afforded highly ordered P3HT aggregates, which exhibited a markedly bathochromically shifted optical absorption due to a high grafting density induced planarization of the polymer chains. Using ultrafast spectroscopy, the heterojunctions formed between the MWNTs and P3HT were shown to effectively overcome the binding energy of excitons, leading to photoinduced electron transfer from P3HT to MWNTs. Finally, when used as prototype devices, the individual MWNT-g-P3HT core-shell structures exhibited excellent photoresponses under a low illumination density.</P>
Statistical inference for Cox model under case-cohort design with subgroup survival information
Shang Wenpeng 한국통계학회 2022 Journal of the Korean Statistical Society Vol.51 No.3
With the explosive growth of data, it is a challenge to infer the quantity of interest by combining the existing different research data about the same topic. In the case-cohort setting, our aim is to improve the efficiency of parameter estimation for Cox model by using subgroup information in the aggregate data. So we put forward the generalized moment method (GMM) to use the auxiliary survival information at some critical time points. However, the auxiliary information is likely obtained from other studies or populations, two extended GMM estimators are proposed to account for multiplicative and additive inconsistencies. We establish the consistency and asymptotic normality of the proposed estimators. In addition, the uniform consistency and asymptotic normality of Breslow estimator are also presented. From the asymptotic normality, we show that the proposed approaches are more efficient than the traditional weighted estimating equation method. In particular, if the number of subgroups is equal to one, the asymptotic variance-covariances of the GMM estimators are identical with the weighted score estimate. Some simulation studies and a real data study demonstrate the proposed methods and theories. In the numerical studies, our approaches are even better than the full cohort estimator and the extended GMM methods are robust.
Li Deng,Wenpeng Jia,Wen Zheng,Hao Liu,Degang Jiang,Zimeng Li,Yu Tian,Wenling Zhang,Jingquan Liu 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.58 No.-
Ni–Al layered double hydroxides (Ni–Al LDHs) are adopted as an electrorheological (ER) materialascribed to their special layered structure, ample polarizable groups and good dispersibility. Themagnetite nanoparticles (Fe3O4 NPs) are utilized as classical magnetorheological (MR) materials onaccount of their excellent paramagnetic property. In this work, we report the rational design of highperformanceER/MR materials by integrating the structural merits of Fe3O4 NPs onto a binary layeredstructure system. The obtained Fe3O4/Ni–Al LDH NCs dispersed in silicone oil displayed appealing dualER/MR performances. The work opens a new path toward novel stimuli-responsive materials forindustrial applications.
On the $r$-th hyper-Kloosterman sums and its hybrid mean value
Tianping Zhang,Wenpeng Zhang 대한수학회 2006 대한수학회지 Vol.43 No.6
The main purpose of this paper is using the propertiesof Gauss sums, primitive characters and the mean value theoremsof Dirichlet L-functions to study the hybrid mean value of the r-thhyper-Kloosterman sums Kl (h;k+1 ;r;q) and the hyper Cochranesums C(h;q;m;k);and give an interesting mean value formula.
Hybrid mean value of generalized Bernoulli numbers, general Kloosterman sums and Gauss sums
Huaning Liu,Wenpeng Zhang 대한수학회 2007 대한수학회지 Vol.44 No.1
The main purpose of this paper is to use the properties ofprimitive characters, Gaus ums and Ramanujan’s um to stu dy thehybrid mean value of generalized Bernouli numbers, general Klostermansums and Gaus ums, and give two asymptotic formulae.
A new mean value related to D. H. Lehmer's problem and Kloosterman sums
Di Han,Wenpeng Zhang 대한수학회 2015 대한수학회보 Vol.52 No.1
Let $q>1$ be an odd integer and $c$ be a fixed integer with $(c, q)=1$. For each integer $a$ with $1\le a \leq q-1$, it is clear that there exists one and only one $b$ with $0\leq b \leq q-1$ such that $ab \equiv c $ (mod $q$). Let $N(c, q)$ denote the number of all solutions of the congruence equation $ab \equiv c$ (mod $q$) for $1 \le a, b \leq q-1$ in which $a$ and $\overline{b}$ are of opposite parity, where $\overline{b}$ is defined by the congruence equation $b\overline{b}\equiv 1$ $(\bmod q)$. The main purpose of this paper is using the mean value theorem of Dirichlet $L$-functions to study the mean value properties of a summation involving $\left(N(c, q)-\frac{1}{2}\phi(q)\right)$ and Kloosterman sums, and give a sharper asymptotic formula for it.
A note on the twisted Lerch type Euler zeta functions
Yuan He,Wenpeng Zhang,서종진,김대산 대한수학회 2013 대한수학회보 Vol.50 No.2
In this note, the q-extension of the twisted Lerch Euler zeta functions considered by Jang [Bull. Korean Math. Soc. 47 (2010), no. 6, 1181–1188] is further investigated, and the generalized multiplication theorem for the q-extension of the twisted Lerch Euler zeta functions is given. As applications, some well-known results in the references are deduced as special cases.
Zhaoxia Wu,Wenpeng Zhang 대한수학회 2012 대한수학회보 Vol.49 No.6
Let $p$ > 2 be a prime, and let $k{\geq}1$ be an integer. Let χ be a Dirichlet character modulo $p$, and let $L(s,{\chi})$ be the Dirichlet L-function corresponding to χ. In this paper we consider the mean values of $$\sum_{{\chi}\;mod\;p\\{\chi}(-1)=-1}{\chi}(2^k)|L(1,\chi)|^2$$.
On the 2k-th power mean value of the generalized quadratic Gauss sums
Yanfeng He,Wenpeng Zhang 대한수학회 2011 대한수학회보 Vol.48 No.1
The main purpose of this paper is using the elementary and analytic methods to study the properties of the 2k-th power mean value of the generalized quadratic Gauss sums, and give two exact mean value formulae for k=3 and 4.