Study on the strengthening mechanisms of Cu/CNT nano-composites

Long, Xiang,Bai, Yuanli,Algarni, Mohammed,Choi, Youngsik,Chen, Quanfang Elsevier 2015 Materials science & engineering. properties, micro Vol.645 No.-

<P><B>Abstract</B></P> <P>Recent experimental studies by Chen et al. showed that copper (Cu) matrix reinforced by a small amount of carbon nanotubes (CNT, about 4% volume fraction) will increase material strength by about 300% while sacrificing some material ductility. The strengthening mechanisms of Cu/CNT nano-composites were firstly studied numerically using 2D axial symmetric unit cell finite element (FE) models in Ls-Dyna, which consist of both copper matrix and CNTs. The simulation results were verified by existing experimental data. A round of parametric studies was performed to investigate the effects of several modeling parameters in the FE simulations. These parameters include the volume fraction of CNTs, aspect ratio of CNTs, size of hardening zone, and the “equivalent” hardened plastic strain in the hardened zone. Two main strengthening mechanisms are found that affect CNTs reinforcement prediction. The first one is the load-bearing effect resulting from boundary condition imposed in the models. The CNTs significantly affect the plastic flow of copper around CNTs during plastic deformation, which is one important reinforcement mechanism because of high aspect ratio ( H / D ) of CNTs. The second strengthening mechanism is found to be the hardened zone of Cu matrix around CNTs, which is introduced by manufacturing processes and/or the Orowan effect. The Orowan effect plays a key role in reinforcement especially in the nano-scale, which results in a very small inter-particle spacing. The Orowan effect was also studied using analytical methods. Both analytical solution and unit cell FE modeling well correlated with the experimental results for various Cu/CNT composites with different CNT outside diameters.</P>

Dialogue is Therapy: Philosophical Practice Returning to Authentic State of Philosophy

LongXiang Luo 강원대학교 인문과학연구소 2018 Journal of Humanities Therapy Vol.9 No.2

The mantra of the philosophical practice movement is that philosophy is philosophizing. From the perspective of application, philosophy is an effective therapy for mental illness, leading to the doctrine “analysis is therapy.” Furthermore, the analytical method applied in therapy must be based on dialogue. Therefore, “dialogue is therapy” is a more profound thought. Tracing back to ancient Socratic philosophy and linking the object of philosophy with its efficacy, we find that philosophical practice not only embodies the philosophical nature of returning to “soul dialogue” but also restores the ancient tenet of “mental therapy” in philosophy. Thus, philosophical practice undoubtedly assists in “returning to the original and opening up the new.”

New results on stochastic comparison of order statistics from heterogeneous Weibull populations

Longxiang Fang,Xinsheng Zhang 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.1

Let X1, . . . , Xn be independent random variables with Xi ∼ W(α, λi), i = 1, . . . , n. Let Y1, . . . , Yn be a random sample of size n from a Weibull distribution with common parameters α, λ. Let λmin denote the minimum of λi, i = 1, . . . , n. If λ ≥ (ni =1 λαi )1n λα−1min ,where α > 1, it is shown that the largest order statistics Xn:n is greater than the largest order statistics Yn:n according to the dispersive ordering

Preparation of Spherical Bi3.25La0.75Ti3O12 Nanocrystals by a Sol-Gel Inverse Mini-Emulsion Approach

Han Longxiang,Zheng Lingjing,Hu Zhenxing,Yin Shilong,Zeng Yanwei 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1

Monodisperse and spherical lanthanum bismuth titanate (Bi3.25La0.75Ti3O12, BLT) nanocrystals with an average size of ~60 nm were synthesized by in situ crystallization of spherical gel particles (~120 nm in diameter) at elevated temperatures in a carbonate environment. The gel particles were obtained by a sol-gel inverse mini-emulsion manipulation and a gelation process at 60°C. X-ray diffraction technique and Raman spectrum measurement were used to trace the formation of crystalline phases in the gel particles during heat treatment, and single-phase BLT nanocrystals were obtained after firing at 500°C for 4 h. The morphology and size of the gel particles and BLT nanocrystals were characterized by field-emission scanning electron microscopy and transmission electron microscopy. The possible mechanism underlying the formation of spherical BLT nanocrystals through a sol-gel inverse mini-emulsion approach was discussed.

Sum rate and Energy Efficiency of Massive MIMO Downlink with Channel Aging in Time Varying Ricean Fading Channel

( Lihua Yang ),( Longxiang Yang ),( Hongbo Zhu ),( Yan Liang ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.3

Achievable sum rate and energy efficiency (EE) are investigated for the massive multiple-input multiple-output (Massive MIMO) downlink with channel aging in the time varying Ricean fading channel. Specifically, the expression of the achievable sum rate of the system for the maximum ratio transmission (MRT) precoder with aged channel state information (CSI) in the time varying Ricean fading channel is first presented. Based on the expression, the effect of both channel aging and the Ricean factor on the power scaling law are studied. It is found that the transmit power of base station (BS) is scaled down by 1/√M (where M is the number of the BS antennas) when the Ricean factor K is equal to zero (i.e., time varying Rayleigh fading channel), indicating that aged CSI does not affect the power scaling law. However, the transmit power of the BS is scaled down by for the time varying Ricean fading channel (where K≠0) indicating that the Ricean factor affects the power scaling law and sum rate, and channel aging only leads to a reduction of the sum rate. Second, the EE of the system is analyzed based on the general power consumption model. Both the theoretical analysis and the simulations show that the channel aging could degrade the sum rate and the EE of the system, and it does not affect the power scaling law.

Opportunistic Multiple Relay Selection for Two-Way Relay Networks with Outdated Channel State Information

( Sijia Lou ),( Longxiang Yang ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.2

Outdated Channel State Information (CSI) was proved to have negative effect on performance in two-way relay networks. The diversity order of widely used opportunistic relay selection (ORS) was degraded to unity in networks with outdated CSI. This paper proposed a multiple relay selection scheme for amplify-and-forward (AF) based two-way relay networks (TWRN) with outdated CSI. In this scheme, two sources exchange information through more than one relays. We firstly select N best relays out of all candidate relays with respect to signal-noise ratio (SNR). Then, the ratios of the SNRs on the rest of the candidate relays to that of the Nth highest SNR are tested against a normalized threshold μ∈[0, 1], and only those relays passing this test are selected in addition to the N best relays. Expressions of outage probability, average bit error rate (BER) and ergodic channel capacity were obtained in closed-form for the proposed scheme. Numerical results and Simulations verified our theoretical analyses, and showed that the proposed scheme had significant gains comparing with conventional ORS.

Virtual Resource Allocation in Virtualized Small Cell Networks with Physical-Layer Network Coding Aided Self-Backhauls

( Yulun Cheng ),( Longxiang Yang ),( Hongbo Zhu ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.8

Virtualized small cell network is a promising architecture which can realize efficient utilization of the network resource. However, conventional full duplex self-backhauls lead to residual self-interference, which limits the network performance. To handle this issue, this paper proposes a virtual resource allocation, in which the residual self-interference is fully exploited by employing a physical-layer network coding (PNC) aided self-backhaul scheme. We formulate the features of PNC as time slot and information rate constraints, and based on that, the virtual resource allocation is formulated as a mixed combinatorial optimization problem. To solve the problem efficiently, it is decomposed into two sub problems, and a two-phase iteration algorithm is developed accordingly. In the algorithm, the first sub problem is approximated and transferred into a convex problem by utilizing the upper bound of the PNC rate constraint. On the basis of that, the convexity of the second sub problem is also proved. Simulation results show the advantages of the proposed scheme over conventional solution in both the profits of self-backhauls and utility of the network resource.

Joint Relay Selection and Power Alloca-tion for Two-way Relay Channels with Asymmetric Traffic Requirements

( Sijia Lou ),( Longxiang Yang ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.8

This paper studiesrelay selection and power allocationfor amplify-and-forward (AF)based two-way relay networks (TWRN)with asymmetric traffic requirements (ATR).A joint relay selection and power allocation algorithm is proposed to decrease the outage probability of TWRN with ATR.In this algorithm,two sources exchange information with the help of the relay during two time slots. We first calculatethe optimal power al-location parameters based on instantaneous channel state information (CSI), and then de-rivea tight lower bound of outage probability. Furthermore,weproposea simplified relay selection criterion,which can be easilycalculated as harmonic mean of instantaneous channel gains, according tothe outage probability expressions. Simulationresults verifiedthe theoretical analyses we presented. It is shown that theoutage probability of ouralgo-rithm improves3-4dBcomparing with that of otherexisting algorithms,and the lower bound is tight comparing with actual valuefor the entiresignal-to-noise ratio (SNR) re-gion.

Iterative Channel Estimation for MIMO-OFDM System in Fast Time-Varying Channels

( Lihua Yang ),( Longxiang Yang ),( Yan Liang ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.9

A practical iterative channel estimation technique is proposed for the multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system in the high-speed mobile environment, such as high speed railway scenario. In the iterative algorithm, the Kalman filter and data detection are jointed to estimate the time-varying channel, where the detection error is considered as part of the noise in the Kalman recursion in each iteration to reduce the effect of the detection error propagation. Moreover, the employed Kalman filter is from the canonical state space model, which does not include the parameters of the autoregressive (AR) model, so the proposed method does not need to estimate the parameters of AR model, whose accuracy affects the convergence speed. Simulation results show that the proposed method is robust to the fast time-varying channel, and it can obtain more gains compared with the available methods.

Resveratrol suppresses the epithelial-to-mesenchymal transition in PC-3 cells by down-regulating the PI3K/AKT signaling pathway

Zhi Wang,Longxiang Wu,Shiyu Tong,Xiheng Hu,Xiongbing Zu,Yuan Li,Wei He,Longfei Liu,Minfeng Chen,Lin Qi 한국통합생물학회 2016 Animal cells and systems Vol.20 No.2

Resveratrol possesses a wide spectrum of pharmacological properties and has been an ideal alternative drug for the treatment of different cancers, including prostate cancer. However, the mechanisms by which resveratrol inhibits the growth of prostate cancer are still not fully elucidated. To understand the effect of resveratrol on the apoptosis and the epithelial-tomesenchymal transition (EMT) of prostate cancer as well as its related mechanism, we investigated the potential use of resveratrol in PC-3 prostate cancer cells in vitro using real-time PCR, fluorescence-activated cell sorting, Western blotting, etc. Resveratrol suppresses the PC-3 prostate cancer cell growth and induces apoptosis. Resveratrol also influences the expression of EMT-related proteins (increased E-cadherin and decreased Vimentin expression). Finally, resveratrol also suppressed Akt phosphorylation in PC-3 cells. This study indicates that resveratrol may be a potential anti-cancer treatment for prostate cancer; moreover, it provides new evidence that resveratrol suppresses prostate cancer growth and metastasis.