Experimental Study on Mechanical Performance and Microstructure of Polypropylene Fiber Recycled Concrete

Fangfang Wei,Liping Li,Yu Zhu,Youzheng Zhao 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7

Recycled concrete reinforced by polypropylene fibers boosts an alternative sustainable solution to address the need of reusing waste concrete. This paper reports experimental and analytical studies of static and dynamic comprehensive behavior on recycled concrete specimens reinforced with different contents of polypropylene fiber (PPF). Electro-hydraulic pressure testing was used to obtain static compressive strength, whereas 74 mm diameter Split HopkinsonPressure Bar (SHPB) was applied for dynamic impact compression tests at four strain rates. In addition, the reinforcing mechanism of polypropylene fiber on recycled concrete was analyzed of the micro-structure through Scanning Electron Microscope (SEM). Finally, ANSYS/LS-DYNA was applied for the simulation of the SHPB test, which was validated by good agreements of the stress waveform and failure modes of the fiber-reinforced recycled concrete specimen during the impact test. It appears that polypropylene fiber can optimize the microscopic pore structure inside the concrete, thus effectively improving the mechanical properties of recycled concrete which were originally defected by recycled aggregate. Also, higher strain rates significantly increase dynamic compressive strength as well as impact toughness. This study shows that the optimal content of polypropylene fiber in recycled concrete is 0.1% − 0.2%. The numerical simulation by ANSYS/LS-DYNA further proved that the HOLMQUIST-JOHNSON-COOK (HJC) constitutive model can better reflect the dynamic performance of concrete.

Parameter calibrations and application of micromechanical fracture models of structural steels

Fangfang Liao,Wei Wang,Yiyi Chen 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.2

Micromechanical facture models can be used to predict ductile fracture in steel structures. In order to calibrate the parameters in the micromechanical models for the largely used Q345 steel in China, uniaxial tensile tests, smooth notched tensile tests, cyclic notched bar tests, scanning electron microscope tests and finite element analyses were conducted in this paper. The test specimens were made from base metal, deposit metal and heat affected zone of Q345 steel to investigate crack initiation in welded steel connections. The calibrated parameters for the three different locations of Q345 steel were compared with that of the other seven varieties of structural steels. It indicates that the toughness index parameters in the stress modified critical strain (SMCS) model and the void growth model (VGM) are connected with ductility of the material but have no correlation with the yield strength, ultimate strength or the ratio of ultimate strength to yield strength. While the damage degraded parameters in the degraded significant plastic strain (DSPS) model and the cyclic void growth model (CVGM) and the characteristic length parameter are irrelevant with any properties of the material. The results of this paper can be applied to predict ductile fracture in welded steel connections.

Distributed Suboptimal Controller Synthesis for Multi-agent Systems

Fangfang Zhang,Wei Wang,Huan-Shui Zhang 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.3

In this paper, the distributed suboptimal LQR control problem for discrete-time multi-agent systems is considered. The distributed controllers that each subsystem can sense and/or exchange information with only a subset of its neighbors are designed, which are based on the topological structure of the system. Using the “averaged” optimization approach, the suboptimal feedback gain matrices are presented and the distributed suboptimal controllers are obtained. Under mild conditions, the asymptotical convergence of the modified Riccati equation is proved. Accordingly, the infinite-time distributed suboptimal controllers are presented. Examples are given to show the efficiency of the proposed results.

A New Approach to Distributed Control for Multi-agent Systems Based on Approximate Upper and Lower Bounds

Fangfang Zhang,Jinfeng Gao,Huanshui Zhang,Cheng Tan,Wei Wang 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.6

In this paper, the distributed control of the LQR problem for continuous-time multi-agent systems isconsidered. Based on the centralized optimal control, we prove that the solution of the algebraic Riccati equationis the maximal solution of the algebraic Riccati inequality. The algebraic relations of the solutions of the algebraicRiccati equations for different weighted matrices are shown and two distributed controllers are designed: the fullydistributed one and the interconnected distributed one. They can provide an upper bounds and a lower bounds ofthe centralized optimal cost function. The optimal closed-loop feedback control systems for the two distributedcontrollers are also asymptotically stable. Some examples are given to show the correctness of the proposed results.

2019 Novel Coronavirus (COVID-19) Pneumonia: Serial Computed Tomography Findings

Jiangping Wei,Huaxiang Xu,Jingliang Xiong,Qinglin Shen,Bing Fan,Chenglong Ye,Wentao Dong,Fangfang Hu 대한영상의학회 2020 Korean Journal of Radiology Vol.21 No.4

From December 2019, Coronavirus disease 2019 (COVID-19) pneumonia (formerly known as the 2019 novel Coronavirus [2019nCoV]) broke out in Wuhan, China. In this study, we present serial CT findings in a 40-year-old female patient with COVID-19 pneumonia who presented with the symptoms of fever, chest tightness, and fatigue. She was diagnosed with COVID-19 infection confirmed by real-time reverse-transcriptase-polymerase chain reaction. CT showed rapidly progressing peripheral consolidations and ground-glass opacities in both lungs. After treatment, the lesions were shown to be almost absorbed leaving the fibrous lesions.

Parameter calibrations and application of micromechanical fracture models of structural steels

Liao, Fangfang,Wang, Wei,Chen, Yiyi Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.42 No.2

Micromechanical facture models can be used to predict ductile fracture in steel structures. In order to calibrate the parameters in the micromechanical models for the largely used Q345 steel in China, uniaxial tensile tests, smooth notched tensile tests, cyclic notched bar tests, scanning electron microscope tests and finite element analyses were conducted in this paper. The test specimens were made from base metal, deposit metal and heat affected zone of Q345 steel to investigate crack initiation in welded steel connections. The calibrated parameters for the three different locations of Q345 steel were compared with that of the other seven varieties of structural steels. It indicates that the toughness index parameters in the stress modified critical strain (SMCS) model and the void growth model (VGM) are connected with ductility of the material but have no correlation with the yield strength, ultimate strength or the ratio of ultimate strength to yield strength. While the damage degraded parameters in the degraded significant plastic strain (DSPS) model and the cyclic void growth model (CVGM) and the characteristic length parameter are irrelevant with any properties of the material. The results of this paper can be applied to predict ductile fracture in welded steel connections.

Extracellular signal-regulated kinase 5 increases radioresistance of lung cancer cells by enhancing the DNA damage response

Weiwei Jiang,Guanghui Jin,Fangfang Cai,Xiao Chen,Nini Cao,Xiangyu Zhang,Jia Liu,Fei Chen,Feng Wang,Wei Dong,Hongqin Zhuang,Zichun Hua 생화학분자생물학회 2019 Experimental and molecular medicine Vol.51 No.-

Radiotherapy is a frequent mode of cancer treatment, although the development of radioresistance limits its effectiveness. Extensive investigations indicate the diversity of the mechanisms underlying radioresistance. Here, we aimed to explore the effects of extracellular signal-regulated kinase 5 (ERK5) on lung cancer radioresistance and the associated mechanisms. Our data showed that ERK5 is activated during solid lung cancer development, and ectopic expression of ERK5 promoted cell proliferation and G2/M cell cycle transition. In addition, we found that ERK5 is a potential regulator of radiosensitivity in lung cancer cells. Mechanistic investigations revealed that ERK5 could trigger IR-induced activation of Chk1, which has been implicated in DNA repair and cell cycle arrest in response to DNA double-strand breaks (DSBs). Subsequently, ERK5 knockdown or pharmacological inhibition selectively inhibited colony formation of lung cancer cells and enhanced IR-induced G2/M arrest and apoptosis. In vivo, ERK5 knockdown strongly radiosensitized A549 and LLC tumor xenografts to inhibition, with a higher apoptotic response and reduced tumor neovascularization. Taken together, our data indicate that ERK5 is a novel potential target for the treatment of lung cancer, and its expression might be used as a biomarker to predict radiosensitivity in NSCLC patients.

Mechanical behavior of steel tube encased high-strength concrete composite walls under constant axial load and cyclically increasing lateral load: Experimental investigation and modeling

Liang Bai,Huilin Wei,Bin Wang,Fangfang Liao,Tianhua Zhou,Xing-Wen Liang 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.47 No.1

This paper presented an investigation into steel tubes encased high-strength concrete (STHC) composite walls, wherein steel tubes were embedded at the boundary elements of high-strength concrete walls. A series of cyclic loading tests was conducted to evaluate the failure pattern, hysteresis characteristics, load-bearing capacity, deformability, and strain distribution of STHC composite walls. The test results demonstrated that the bearing capacity and ductility of the STHC composite walls improved with the embedding of steel tubes at the boundary elements. An analytical method was then established to predict the flexural bearing capacity of the STHC composite walls, and the calculated results agreed well with the experimental values, with errors of less than 10%. Finally, a finite element modeling (FEM) was developed via the OpenSees program to analyze the mechanical performance of the STHC composite wall. The FEM was validated through test results; additionally, the influences of the axial load ratio, steel tube strength, and shear-span ratio on the mechanical properties of STHC composite walls were comprehensively investigated.

Circ_0068655 Promotes Cardiomyocyte Apoptosis via miR-498/PAWR Axis

Chai Qiaoying,Zheng Mingqi,Wang Le,Wei Mei,Yin Yajuan,Ma Fangfang,Li Xinping,Zhang Haijun,Liu Gang 한국조직공학과 재생의학회 2020 조직공학과 재생의학 Vol.17 No.5

Background: The cardiomyocyte apoptosis is considered as one of major contributions to cardiac remodeling after myocardial infarction (MI). Numerous studies find that circular RNAs (circRNAs) play pivotal roles in a variety of biological functions. However, the role of circ_0068655 in MI and human induced pluripotent stem-derived cardiomyocytes (HCMs) remains unknown. Methods: The expression of circ_0068655, miR-498, and PRKC apoptosis WT1 regulator (PAWR) in human MI heart tissues and hypoxia subjected HCMs was evaluated with qRT-PCR and Western blot. The effects of circ_0068655 on hypoxia-induced apoptotic death and cell migration in HCMs were evaluated with qRT-PCR, cell viability, cell death ELISA (POD), and Caspase-3 activity assay, and Trans-well assay, respectively. Furthermore, luciferase assay, qRT-PCR, biotin-labeled miRNA pulldown assay, and Western blot were employed in the functional studies. Results: We found that the expression of circ_0068655 and PAWR was enhanced in MI patients and hypoxia subjected HCMs; by contrast, the expression of miR-498 decreased. Inhibited expression of circ_0068655 in HMCs counteracted hypoxia-induced apoptotic death and impaired cell migration, in sharp contrast to circ_0068655 knockdown. We identified that circ_0068655 sponged an endogenous miR-498 to sequester and inhibit its activity, leading to the increased PAWR expression. Conclusions: Our findings reveal that the expression of circ_0068655 can promote cardiomyocyte apoptosis through the modulation of miR-498-PAWR axis in vitro, which highlights the diagnostic and therapeutic value of circ_0068655 in patients with MI.

High Power Switchable Dual-Wavelength Linear Polarized Yb-Dozped Fiber Laser around 1120 nm

Xiaojuan Liu,Bangcai Huang,Gongxiang Wei,Kezhen Han,Yan Huang,Fangfang Liu 한국광학회 2016 Current Optics and Photonics Vol.20 No.6

A single-and dual-wavelength switchable polarized Yb-doped double-clad fiber laser around 1120 nmbased on a pair of fiber Bragg gratings (FBGs) is demonstrated. The polarization-maintaining (PM) linearcavity is composed of a double clad PM Yb-doped fiber (YDF) and a pair of PM FBGs. The laser canoperate in stable dual-wavelength or wavelength-switching modes due to the polarization hole burning(PHB) and the spatial hole burning (SHB) enhanced by the PM linear cavity. In dual-wavelength operation,the two orthogonally polarized wavelengths are centered at 1118.912 nm and 1119.152 nm, with an intervalof 0.24 nm and a signal to noise ratio (SNR) of 35 dB. The maximum output power is 14.67 W whenthe launched LD pump is 24 W corresponding to an optical efficiency of 61.1%. The lasing lines switchovermay be realized by adjusting the polarization controller (PC) fitted in the cavity. The two single-wavelengthsare 1118.912 nm and 1119.152 nm. When the injected LD pump is 24 W, the highest output powersare 7.68 W and 8.64 W corresponding to optical efficiencies of 32% and 36% respectively. The spectrallinewidth of the lasing lines are 0.075 nm and 0.07 nm, and the average numerical values of PER are20.3 dB and 19.9 dB, respectively.