Effects of comonomer with carboxylic group on stabilization of high molecular weight polyacrylonitrile nanofibrous copolymers

Lei, Danyun,Devarayan, Kesavan,Li, Xiang-Dan,Choi, Woong-Ki,Seo, Min-Kang,Kim, Byoung-Suhk 한국탄소학회 2014 Carbon Letters Vol.15 No.4

New precursors, poly(acrylonitrile-co-crotonic acid) (poly(AN-CA)) and poly(acrylonitrile-co-itaconic acid-co-crotonic acid) (poly(AN-IA-CA)) copolymers, for the preparation of carbon fibers, were explored in this study. The effects of comonomers with acidic groups, such as crotonic acid (CA) and/or itaconic acid (IA), on the stabilization of nanofibrous polyacrylonitrile (PAN) copolymers were studied. The extent of stabilization, evaluated by Fourier transform infrared spectroscopy, revealed that the CA comonomer could retard/control the stabilization rate of PAN, in contrast to the IA comonomer, which accelerated the stabilization process. Moreover, the synthesized PAN copolymers containing CA possessed higher Mv than those of the IA copolymers and also showed outstanding dimension stability of nanofibers during the stabilization, which may be a useful property for improving the dimensional stability of polymer composites during manufacturing.

On-line integration of structural identification/damage detection and structural reliability evaluation of stochastic building structures

Ying Lei,Longfei Wang,Lanxin Lu,Dan-dan Xia 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.6

Recently, some integrated structural identification/damage detection and reliability evaluation of structures with uncertainties have been proposed. However, these techniques are applicable for off-line synthesis of structural identification and reliability evaluation. In this paper, based on the recursive formulation of the extended Kalman filter, an on-line integration of structural identification/damage detection and reliability evaluation of stochastic building structures is investigated. Structural limit state is expanded by the Taylor series in terms of uncertain variables to obtain the probability density function (PDF). Both structural component reliability with only one limit state function and system reliability with multi-limit state functions are studied. Then, it is extended to adopt the recent extended Kalman filter with unknown input (EKF-UI) proposed by the authors for on-line integration of structural identification/damage detection and structural reliability evaluation of stochastic building structures subject to unknown excitations. Numerical examples are used to demonstrate the proposed method. The evaluated results of structural component reliability and structural system reliability are compared with those by the Monte Carlo simulation to validate the performances of the proposed method

Experimental and numerical studies on mechanical behavior of buried pipelines crossing faults

Dan F. Zhang,Xue M. Bie,Xi. Zeng,Zhen. Lei,Guo F. Du 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.1

This paper presents a study on the mechanical behavior of buried pipelines crossing faults using experimental and numerical methods. A self-made soil-box was used to simulate normal fault, strike-slip fault and oblique slip fault. The effects of some important parameters, including the displacement and type of fault, the buried depth and the diameter of pipe, on the deformation modes and axial strain distribution of the buried pipelines crossing faults was studied in the experiment. Furthermore, a finite element analysis (FEA) model of spring boundary was developed to investigate the performance of the buried pipelines crossing faults, and FEA results were compared with experimental results. It is found that the axial strain distribution of those buried pipelines crossing the normal fault and the oblique fault is asymmetrical along the fault plane and that of buried pipelines crossing the strike-slip fault is approximately symmetrical. Additionally, the axial peak strain appears near both sides of the fault and increases with increasing fault displacement. Moreover, the axial strain of the pipeline decreases with decreasing buried depth or increasing ratios of pipe diameter to pipe wall thickness. Compared with the normal fault and the strike-slip fault, the oblique fault is the most harmful to pipelines. Based on the accuracy of the model, the regression equations of the axial distance from the peak axial strain position of the pipeline to the fault under the effects of buried depth, pipe diameter, wall thickness and fault displacement were given.

Few-Layered MoS2 Nanostructures for Highly Efficient Visible Light Photocatalysis

Dan Li,Jianwei Li,Caiqin Han,Xinsheng Zhao,Haipeng Chu,Wenyan Lei,Xinjuan Liu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.10

Few-layered MoS2 nanostructures were successfully synthesized by a simple hydrothermal method without the addition of any catalysts or surfactants. Their morphology, structure and photocatalytic activity were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, electrochemical impedance spectra and UV-Vis absorption spectroscopy, respectively. These results show that the MoS2 nanostructures synthesized at 180℃ exhibit an optimal visible light photocatalytic activity (99%) in the degradation of Rhodamine B owing to the relatively easier adsorption of pollutants, higher visible light absorption and lower electron–hole pair recombination.

EBV-miR-BHRF1-1 Targets p53 Gene: Potential Role in Epstein-Barr Virus Associated Chronic Lymphocytic Leukemia

Dan-Min Xu,Yi-Lin Kong,Li Wang,Hua-Yuan Zhu,Jia-Zhu Wu,Yi Xia,Yue Li,Shu-Chao Qin,Lei Fan,Jian-Yong Li,Jin-Hua Liang,Wei Xu 대한암학회 2020 Cancer Research and Treatment Vol.52 No.2

Purpose The purpose of this study was to investigate the prognostic impact of Epstein-Barr virus (EBV)–microRNA (miRNA, miR)-BHRF1-1 with chronic lymphocytic leukemia (CLL) as well as role of EBV-miR-BHRF1-1 in p53 gene. Materials and Methods Quantitative reverse transcription–polymerase chain reaction and western blotting were used to quantify EBV-miR-BHRF1-1 and p53 expression in cultured CLL. Results p53 aberration was associated with the higher expression level of EBV-miR-BHRF1-1 (p < 0.001) which was also an independent prognostic marker for overall survival (p=0.028; hazard ratio, 5.335; 95% confidence interval, 1.193 to 23.846) in 97 newly-diagnosed CLL patients after adjusted with International Prognostic Index for patients with CLL. We identified EBV-miR-BHRF1-1 as a viral miRNA regulator of p53. EBV-miR-BHRF1-1 repressed luciferase reporter activity by specific interaction with the seed region within the p53 3- untranslated region. Discordance of p53 messenger RNA and protein expression was associated with high EBV-miR-BHRF1-1 levels in CLL patients and cell lines. EBV-miR-BHRF1- 1 inhibition upregulated p53 protein expression, induced cell cycle arrest and apoptosis and decreased cell proliferation in cell lines. EBV-miR-BHRF1-1 mimics downregulated p53 protein expression, decreased cell cycle arrest and apoptosis, and induced cell proliferation in cell lines. Conclusion This study supported the role of EBV-miR-BHRF1-1 in p53 regulation in vitro. Our results support the potential of EBV-miR-BHRF1-1 as a therapeutic target in EBV-associated CLL with p53 gene aberration.

Mean Square Consensus of Multi-agent systems with multiplicative noises and time delays under directed fixed topologies

Dan Huang,Lei Song,Sing Kiong Nguang,Shan Fu 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.1

This paper investigates the mean square consensus problem of multi-agent systems impacted by thecombined uncertainty of multiplicative noises and time delays. Considering general network under directed fixedtopologies, we propose consensus protocol that take into account both the multiplicative noises and time delays. Using tools from stochastic differential delay equation (SDDE), martingale theory and stochastic inequality, weestablish sufficient conditions and obtain the explicit consensus gain and delay upper bounds under which theproposed protocol leads to mean square consensus. In addition, we compare the impact of multiplicative andadditive noise and reach the conclusion that multiplicative noises have the property of stabilizing effect. Simulationsdemonstrate the theoretical results.

A New Unsymmetrical Zinc Phthalocyanine as Photosensitizers for Dye-sensitized Solar Cells

Dan Zhang,Xue-Jun Zhang,Lei Zhang,Li-Jun Mao 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.4

A new unsymmetrical zinc phthalocyanine has been designed and synthesized based on the ‘push-pull’ and extended π-conjugation concept for the dye-sensitized solar cells. Three tert-butoxy groups, which act as electron releasing (‘push’), enhance the solubility of phthalocyanine in common organic solvents and reduce the aggregation. Hydroxy substituted 9,10-anthraquinones act as electron acceptors (‘pull’) for the study of photoinduced electron transfer processes as well as grafting onto nanocrystalline TiO2. The new unsymmetrical zinc phthalocyanine was fully characterized by FTIR, UV-vis, 1H NMR, cyclic voltammetry and differential pulse voltammetry. The new sensitizer was tested in dye-sensitized solar cells, and gave a better performance.

Salt-activated phenolic resin/PAN-derived core-sheath nanostructured carbon nanofiber composites for capacitive energy storage

Lei Danyun,Li Xiang-Dan,Ma Min-Jung,Kim Da-Young,Noh Jae-Hyun,Kim Byoung-Suhk 한국탄소학회 2023 Carbon Letters Vol.33 No.3

In this study, we have fabricated the phenolic resin (PR)/polyacrylonitrile (PAN) blend-derived core-sheath nanostructured carbon nanofibers (CNFs) via one-pot solution electrospinning. The obtained core-sheath nanostructured carbon nanofibers were further treated by mixed salt activation process to develop the activated porous CNFs (CNF-A). Compared to pure PAN-based CNFs, the activated PR/PAN blend with PR 20% (CNF28-A)-derived core-sheath nanostructured CNFs showed enhanced specific capacitance of ~ 223 F g−1 under a three-electrode configuration. Besides, the assembled symmetric CNF28-A//CNF28-A device possessed a specific capacitance of 76.7 F g−1 at a current density of 1 A g−1 and exhibited good stability of 111% after 5,000 galvanostatic charge/discharge (GCD) cycles, which verifies the outstanding long-term cycle stability of the device. Moreover, the fabricated supercapacitor device delivered an energy density of 8.63 Wh kg−1 at a power density of 450 W kg−1.

NiCo₂O₄ nanostructure-decorated PAN/lignin based carbon nanofiber electrodes with excellent cyclability for flexible hybrid supercapacitors

Lei, Danyun,Li, Xiang-Dan,Seo, Min-Kang,Khil, Myung-Seob,Kim, Hak-Yong,Kim, Byoung-Suhk Elsevier 2017 Polymer Vol.132 No.-

<P><B>Abstract</B></P> <P>Nanostructured binary metal oxide-decorated carbon nanofibers (CNFs) were utilized as flexible electrodes for hybrid supercapacitor applications. Polyacrylonitrile (PAN)/lignin based carbon nanofibers (PAN/lignin CNFs) with different contents of lignin were prepared by electrospinning, stabilization and carbonization. Afterwards, the NiCo<SUB>2</SUB>O<SUB>4</SUB> oxides were deposited on the surface of CNFs by a facile hydrothermal method without any toxic reagents. SEM images confirmed that the NiCo<SUB>2</SUB>O<SUB>4</SUB> (nanosheet and nanoneedle) nanostructures were uniformly grown on the surface of every carbon fiber. The obtained flexible NiCo<SUB>2</SUB>O<SUB>4</SUB>-decorated PAN/lignin CNFs with 50% lignin (NiCo<SUB>2</SUB>O<SUB>4</SUB>@CNF55) electrode exhibited high specific capacitance of the ∼1757 F g<SUP>−1</SUP> at 2 mA cm<SUP>−2</SUP> and excellent cyclability with ∼138% capacitance retention after 5000 cycles at 7 mA cm<SUP>−2</SUP>, suggesting lower internal resistance and higher electrochemical reversibility. In addition, the NiCo<SUB>2</SUB>O<SUB>4</SUB>@CNFs//N-rGO solid state asymmetric supercapacitor devices were assembled in order to evaluate their practical applications. The NiCo<SUB>2</SUB>O<SUB>4</SUB>@CNF55//N-rGO asymmetric supercapacitor device exhibited a specific capacitance of 134.3 F g<SUP>−1</SUP> at a current densities of 1 A g<SUP>−1</SUP>, and possessed a maximum energy density of 47.75 Wh kg<SUP>−1</SUP> with a power density of 799.53 W kg<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PAN/lignin-based carbon fibers were prepared by electrospinning, stabilization and carbonization. </LI> <LI> The NiCo<SUB>2</SUB>O<SUB>4</SUB> nanostructures were fabricated on PAN/lignin-based carbon nanofibers. </LI> <LI> The NiCo<SUB>2</SUB>O<SUB>4</SUB>-decorated fiber electrode exhibits highest specific capacitance of the ∼1757 Fg<SUP>-1</SUP>. </LI> <LI> The NiCo<SUB>2</SUB>O<SUB>4</SUB>-decorated fiber electrode shows excellent capacitance retention of ∼138% after 5000 cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nanostructured polyaniline/kenaf-derived 3D porous carbon materials with high cycle stability for supercapacitor electrodes

Lei, Danyun,Song, Kyung-Hun,Li, Xiang-Dan,Kim, Hak-Yong,Kim, Byoung-Suhk Springer-Verlag 2017 JOURNAL OF MATERIALS SCIENCE - Vol.52 No.4

<P>Kenaf-derived porous carbon (KPC) is considered to be one of the most promising materials for applications of energy storage devices due to being eco-friendly, and low cost. In this work, a facile method was introduced to prepare the nano-textured polyaniline (PANi)-decorated KPCs (PANi/KPC). Such light weighted and porous structures of KPCs were utilized as a physical framework for supporting the nanostructured PANi, which could significantly reduce the weight (and consequently cost) and furthermore improve the electrochemical performances of the supercapacitors. Firstly, we carbonized two different kinds of kenafs (kenaf stem and NaOH retting kenaf) to obtain the kenaf-derived porous carbons (KPC1 and KPC2), and then PANi was synthesized by in situ polymerization in the presence of KPCs. The three-dimensional porous structures of the obtained KPCs were confirmed by SEM images. The SEM image of PANi-decorated KPCs (PANi/KPCs) demonstrates that the PANi was uniformly formed as fibrous and nano-textured structures on the surface of the KPCs. The specific capacitance of PANi/KPC1 and PANi/KPC2 were found to be around 76 and 136 F/g, which were obviously enhanced capacitance than pure KPC1 (26 F/g) and KPC2 (37 F/g), respectively. Further, it showed good cycle stability retaining more than 97 % of their capacitance after 2000 charge-discharge cycles at a scan rate of 5 mV/s.</P>