Guided waves of porous FG nanoplates with four edges clamped

Zhao, Jing-Lei,She, Gui-Lin,Wu, Fei,Yuan, Shu-Jin,Bai, Ru-Qing,Pu, Hua-Yan,Wang, Shilong,Luo, Jun Techno-Press 2022 Advances in nano research Vol.13 No.5

Based on the nonlocal strain gradient (NSG) theory and considering the influence of moment of inertia, the governing equations of motion of porous functionally graded (FG) nanoplates with four edges clamped are established; The Galerkin method is applied to eliminate the spatial variables of the partial differential equation, and the partial differential governing equation is transformed into an ordinary differential equation with time variables. By satisfying the boundary conditions and solving the characteristic equation, the dispersion relations of the porous FG strain gradient nanoplates with four edges fixed are obtained. It is found that when the wave number is very small, the influences of nonlocal parameters and strain gradient parameters on the dispersion relation is very small. However, when the wave number is large, it has a great influence on the group velocity and phase velocity. The nonlocal parameter represents the effect of stiffness softening, and the strain gradient parameter represents the effect of stiffness strengthening. In addition, we also study the influence of power law index parameter and porosity on guided wave propagation.

The Precambrian geology of the northern part of the Korean Peninsula and its relations with North China Craton

Lei Zhao,Ming-Guo Zhai,Yan-Bin Zhang,Peng Peng 대한지질학회 2022 대한지질학회 학술대회 Vol.2022 No.10

CFD-DEM modeling of snowdrifts on stepped flat roofs

Lei Zhao,Zhixiang Yu,Fu Zhu,Xin Qi,Shichun Zhao 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.23 No.6

Snowdrift formation on roofs should be considered in snowy and windy areas to ensure the safety of buildings. Presently, the prediction of snowdrifts on roofs relies heavily on field measurements, wind tunnel tests and numerical simulations. In this paper, a new snowdrift modeling method by using CFD (Computational Fluid Dynamics) coupled with DEM (Discrete Element Method) is presented, including material parameters and particle size, collision parameters, particle numbers and input modes, boundary conditions of CFD, simulation time and inlet velocity, and coupling calculation process. Not only is the two-way coupling between wind and snow particles which includes the transient changes in snow surface topography, but also the cohesion and collision between snow particles are taken into account. The numerical method is applied to simulate the snowdrift on a typical stepped flat roof. The feasibility of using coupled CFD with DEM to study snowdrift is verified by comparing the simulation results with field measurement results on the snow depth distribution of the lower roof.

Delay Feedback Control Based on Discrete-time State Observations for Highly Nonlinear Hybrid Stochastic Functional Differential Equations With Infinite Delay

Lei Zhao,Qiuqiu Fan 제어·로봇·시스템학회 2024 International Journal of Control, Automation, and Vol.22 No.2

In this paper, it is proved that an unstable highly nonlinear hybrid stochastic functional differential equation with infinite delay (HNHISFDE) can be stabilized by designing a controller that not only depends on discretetime state observations, but only produces different time lags in each observation. Firstly, common conditions are imposed on the original system to ensure the existence and uniqueness of the solution. Secondly, the design method of delay feedback control is presented to stabilize a class of HNHISFDEs. Notably, new assumptions based on Lyapunov functional and M-matrix methods are provided to construct the controller step by step. Then, the sufficient criteria of H∞ stabilization, asymptotic stabilization and exponential stabilization are established by applying the Lyapunov stability theory. Finally, the effectiveness of the theoretical results is illustrated by a numerical example.

An approach for failure analysis of composite bridge deck systems with openings

Zhao, Lei,Karbhari, Vistasp M. Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.1

Design details pertaining to the connection between some recently developed fiber reinforced polymer (FRP) composite deck systems and the supporting girders require openings through cells of the deck. This significantly changes the stress distribution in these components. As a result, the conventional assumptions that deck designs are controlled by their stiffness, and not strength, needs a closer examination. This paper proposes an analytical method to investigate the stress states and failure mechanisms using a type of "global-local" modeling perspective, incorporating classical lamination theory and first ply failure criterion with use of appropriate stress concentration factors around the cutouts. The use of a "smeared-stress" approach is presented as a potential means of simplifying certain FRP specific complexities, while still enabling prediction of overall failure.

Research on the Wood Cell Contour Extraction Method Based on Image Texture and Gray-scale Information

Zhao Lei,Wang Jianhua,Li Xiaofeng 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.6

The traditional Snake model and GVF-Snake model set high requirements on noise and initial contour in wood cell contour extraction. To solve this problem, on the premise of considering the image texture and gray-scale information, the area information is directly introduced into the active contour extraction model through force equilibrium equation. Experiments show that the contour extracted with this method is not only more close to real cell contour, but also improved in anti-noise property. In particular, in the convergence of high noise and deep sunken areas, it has some advantages not found in other traditional methods.

A Novel Method of Phase-Shifted Full-Bridge Converter to Improve Efficiency under Light Load Condition

Lei Zhao,Haoyu Li,Yanxue Yu,Yutian Wang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

The main theme of this paper is to propose a novel peak current mode control method to reduce the loss of phase-shifted full-bridge (PSFB) converter under light load condition. The proposed control method can adjust the switching frequency of the converter to keep the on-time of switches fixed. According to the loss analysis model in discontinuous current mode operation, the switching frequency is proportional to load current and the efficiency is independent from the load. Moreover, the small signal model of the PSFB converter with the proposed control method is presented. A digital-controlled experimental system is set up. The proposed method is investigated and confirmed by experimental results. Experimental results show that the efficiency and dynamic performance can be improved. These results confirm the effectiveness of the proposed control method.

MiR-200c-3p inhibits LPS-induced M1 polarization of BV2 cells by targeting RIP2

Zhao Lei,Liu Xiaosong,Yang Jiankai,Wang Xiaoliang,Liu Xiaomeng,Wu Jianliang,Li Chen,Xu Donggang,Hu Yuhua 한국유전학회 2022 Genes & Genomics Vol.44 No.4

Background: Microglia are important immune cells, which can be induced by lipopolysaccharide (LPS) into M1 phenotype that express pro-inflammatory cytokines. Some studies have shown that microRNAs play critical roles in microglial activation. Objective: This study was designed to investigate the role of miR-200c-3p in regulating inflammatory responses of LPS-treated BV2 cells. Methods: The expression of miR-200c-3p in BV2 cells was detected by real-time PCR. Receptor-interacting protein 2 (RIP2) was predicted as a target gene of miR-200c-3p. Their relationship was verified by dual-luciferase reporter assay. The function of miR-200c-3p and RIP2 in microglial polarization and NF-κB signaling was further evaluated. Results: LPS treatment reduced miR-200c-3p expression in a dose-dependent and time-dependent manner in BV2 cells. LPS treatment increased the expression of M1 phenotype markers inducible nitric oxide synthase (iNOS) and major histocompatibility complex class (MHC)-II, promoted the release of pro-inflammatory cytokines interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α, and enhanced the nuclear translocation and phosphorylation of nuclear factor-kappaB (NF-κB) p65. Reversely, miR-200c-3p mimics down-regulated the levels of these inflammatory factors. Furthermore, RIP2 was identified to be a direct target of miR-200c-3p. RIP2 knockdown had a similar effect to miR-200c-3p mimics. Overexpression of RIP2 eliminated the inhibitory effect of miR-200c-3p on LPS-induced M1 polarization and NF-κB activation in BV2 cells. Conclusions: MiR-200c-3p mimics suppressed LPS-induced microglial M1 polarization and NF-κB activation by targeting RIP2. MiR-200c-3p/RIP2 might be a potential therapeutic target for the treatment of neuroinflammation-associated diseases.

Isolation, identification and characterization of a novel elastase from Chryseobacterium indologenes

Lei, Yunlong,Zhao, Peipei,Li, Chenglei,Zhao, Haixia,Shan, Zhi,Wu, Qi The Korean Society for Applied Biological Chemistr 2018 Applied Biological Chemistry (Appl Biol Chem) Vol.61 No.3

Elastase is a type of protease that specifically degrades elastin. It has broad application prospects in medicine, food industry, and daily-use chemical industry. In this study, we isolated a bacterial strain WZE87 with high elastin-hydrolysis activity, which was identified as Chryseobacterium indologenes based on morphology, physiological and biochemical characteristics, and 16S rDNA sequence analysis. The elastase produced by this strain was purified by three steps: ammonium sulfate precipitation, Q-Sepharose fast-flow anion-exchange chromatography, and Sephadex G-75 gel-filtration chromatography. The purified elastase was 2376.5 U/mg in activity (a 8.3-fold increase in specific activity), and the recovery was 5.8%. Its molecular mass was estimated to be 26 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This enzyme was stable in the pH range of 5.0-10.5 at $37^{\circ}C$. The optimal temperature and pH were $37^{\circ}C$ and 7.5, respectively. The activity of this elastase was found to decrease when the temperature was higher than $50^{\circ}C$. The activity was also inhibited by $Zn^{2+}$, $Fe^{2+}$, $Fe^{3+}$, and $Mn^{2+}$ ions. The specific hydrolytic ability of this enzyme was similar to that of papain on substrates like gelatin, casein, soybean-isolated protein and bovine hemoglobin. However, this elastase preferentially hydrolyzed elastin in a protein mixture because of its specific adsorption. Considering its promising properties, this protease may be considered a potential candidate for applications in related industries.

Archean basement components and their multiple metamorphic overprintings of the Rangnim Massif in the northern part of the Korean Peninsula

Lei Zhao,Mingguo Zhai,Chang-Whan Oh,Yanbin Zhang,Peng Peng 대한지질학회 2019 대한지질학회 학술대회 Vol.2019 No.10