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.

Practice of industrial strain improvement

Lei, Zhao-zu The Microbiological Society of Korea 1993 微生物과 産業 Vol.19 No.2

Industrial strain improvement is concerned with developing or modifying microorganisms used in production of commercially important fermentation products. The aim is to reduce the production cost by improving productivity of a strain and manipulating specific characteristics such as the ability to utilize cheaper raw materials or resist bacteriophages. The traditional empirical approach to strain improvement is mutation combined with selection and breeding techniques. It is still used by us to improve the productivity of organisms in amino acids, organic acids and enzymes production. The breeding of high L-lysine-producing strain Au112 is one of the outstanding examples of this approach. It is a homoserine auxotroph with AEC, TA double metabolic analogue resistant markers. The yield reaches 100 g/l. Besides, the citric acid-producing organism Aspergillus niger, Co827, its productivity reaches the advanced level in the world, is also the result of a series mutations especially with $^60Co{\gamma}$-radiation. The thermostable .alpha.-amylase producing strain A 4041 is the third example. By combining physical and chemical mutations, the strain A 4041 becomes an asporogenous, catabolite derepressed mutant with rifamycin resistant and methionine, arginine auxotroph markers. The .alpha.-amylase activity reaches 200 units/ml. The fourth successful example of mutation in strain improvement is the glucoamylase-producing strain Aspergillus niger SP56, its enzyme activity is 20,000 units/ml, 4 times of that of the parental strain UV-11. Recently, recombinant DNA approach provides a worthwhile alternative strategy to industrial strain improvement. This technique had been used by us to increase the thermostable .alpha.-amylase production and on some genetic researches.

Two Maternal Lineages Revealed by Mitochondrial DNA D-loop Sequences in Chinese Native Water Buffaloes (Bubalus bubalis)

Lei, Chu-Zhao,Zhang, Wei,Chen, Hong,Lu, Fan,Ge, Qing-Lan,Liu, Ruo-Yu,Dang, Rui-Hua,Yao, Yun-Yi,Yao, Li-Bo,Lu, Zi-Fan,Zhao, Zhong-liang Asian Australasian Association of Animal Productio 2007 Animal Bioscience Vol.20 No.4

Little is known about the origin and genetic diversity of swamp buffaloes in China. To obtain more knowledge on genetics of the water buffalo in China, the complete mitochondrial D-loop sequences of 30 samples from 6 native types were investigated. The results revealed 12 mitochondrial haplotypes with 50 polymorphic sites. Among these polymorphic sites, there were 49 transitions and 1 transversion. The average nucleotide diversity and haplotype diversity estimated from mtDNA D-loop region in 6 Chinese water buffalo types were 0.00684 and 0.798, respectively, showing rather abundant mitochondrial genetic diversity. The Neighbor-Joining (NJ) tree of mtDNA of Chinese water buffaloes was constructed according to the 12 haplotypes. The NJ tree indicated two lineages being designated lineage A and lineage B, in which lineage A was predominant, and lineage B was at low frequency. The new lineage B was first discovered and defined in 6 Chinese water buffalo types. These results showed that two different maternal lineages were involved in the origin of domestic swamp buffaloes in China and the lineage B was probably an introgression from Southeast Asian buffaloes.

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.

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.

CFD-DEM modeling of snowdrifts on stepped flat roofs

Zhao, Lei,Yu, Zhixiang,Zhu, Fu,Qi, Xin,Zhao, Shichun Techno-Press 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.

C-Type Natriuretic Peptide/Natriuretic Peptide Receptor 2 Is Involved in Cell Proliferation and Testosterone Production in Mouse Leydig Cells

Lei Yang,Lanjie Lei,Qihan Zhao,Ying Gong,Gaopeng Guan,Shaoxin Huang 대한남성과학회 2019 The World Journal of Men's Health Vol.37 No.2

Purpose: This study investigated the role of natriuretic peptide receptor 2 (NPR2) on cell proliferation and testosterone secre-tion in mouse Leydig cells.Materials and Methods: Mouse testis of different postnatal stages was isolated to detect the expression C-type natriuretic peptide (CNP) and its receptor NPR2 by quantitative reverse transcription polymerase chain reaction (RT-qPCR). Leydig cells isolated from mouse testis were cultured and treated with shNPR2 lentiviruses or CNP. And then the cyclic guanosine mono-phosphate production, testosterone secretion, cell proliferation, cell cycle and cell apoptosis in mouse Leydig cells were ana-lyzed by ELISA, RT-qPCR, Cell Counting Kit-8, and flow cytometry. Moreover, the expression of NPR2, cell cycle, apoptosis proliferation and cell cycle related gene were detected by RT-qPCR and Western blot. Results: Knockdown of NPR2 by RNAi resulted in S phase cell cycle arrest, cell apoptosis, and decreased testosterone secre-tion in mouse Leydig cells.Conclusions: Our study provides more evidences to better understand the function of CNP/NPR2 pathway in male reproduc-tion, which may help us to treat male infertility.

Antibacterial, Antiadherence, Antiprotease, and Anti-Inflammatory Activities of Various Tea Extracts: Potential Benefits for Periodontal Diseases

Lei Zhao,Vu Dang La,Daniel Grenier 한국식품영양과학회 2013 Journal of medicinal food Vol.16 No.5

Porphyromonas gingivalis is a key etiologic agent of chronic periodontitis. This Gram-negative anaerobic bacterium produces several virulence factors and can induce a host inflammatory response that contributes to periodontal disease. In the present study, we investigated green tea, white tea, oolong tea, and black tea extracts with a high polyphenol content for their effects on (i) the growth and adherence of P. gingivalis, (ii) the activity of host and bacterial proteases, and (iii) cytokine secretion by oral epithelial cells. All the tea extracts inhibited the growth of P. gingivalis (minimal inhibitory concentrations ranging from 200 to 500 μg/mL; minimal bactericidal concentrations=500 μg/mL). In addition, they dose dependently reduced the adherence of P. gingivalis to oral epithelial cells. Tea extracts also inhibited the catalytic activity of matrix metalloproteinase (MMP)-9, neutrophil elastase, and P. gingivalis collagenase. Lastly, the tea extracts dose dependently inhibited the secretion of interleukin (IL)-6, IL-8, and chemokine (C-C motif) ligand 5 (CCL-5) by P. gingivalis–stimulated oral epithelial cells. No marked differences in the various effects were observed among the four tea extracts. Extracts from green tea, white tea, oolong tea, and black tea show promise for controlling periodontal disease by their capacity to interfere with P. gingivalis growth and virulence properties, host destructive enzymes, and inflammatory mediator secretion. Such extracts may be incorporated to oral hygiene products or locally delivered into diseased periodontal sites.

Experimental and Numerical Investigation of Axial Tensile Strength of CHS X-Joints Reinforced with External Stiffening Rings

Lei Zhao,Lei Zhu,Hailin Sun,Lu Yang,Xi Chen 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.3

To study the reinforcement eff ect of the external stiff ening ring reinforced and unreinforced X-joints having a circular hollow section subjected to brace tensile load, an experimental and computer-simulated research has been done. Six full-scale X-joints are examined in this study: three reinforced specimens and three corresponding unreinforced ones. The test specimens cover diff erent brace to chord diameters ratios ( β ) of 0.25, 0.51, and 0.73. The experimental facilities and detailed parameters are presented. The experimental results including failure modes, load–displacement curves, and ultimate capacity are analyzed and compared. Two failure modes, weld failure and chord plastifi cation, are observed in the tests. The test results reveal an ultimate load enhancement in the reinforced joints by approximately 50% in comparison with the unreinforced joints and an initial stiff ness increase of 248.1% for the β of 0.25 and approximately 49–76% for the β of 0.51 and 0.73. A fi nite element model using shell elements is developed, which accurately predicts the static performance of the X-joints subjected to brace tensile load with and without external stiff ening rings.

A design of transmission-type multi-target X-ray tube based on electric field modulation

Zhao, Lei,Jia, Wenbao,Jin, Limin,Shan, Qing,Cheng, Can,Zhu, Hongkui,Hei, Daqian Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.9

Multi-target X-ray tube is a new type X-ray source, and can be applied in many fields such as sensitive X-ray fluorescence analysis and medical imaging. In this work, we report an electric field modulation multi-target X-ray tube, which contains four targets (Cr, Ni, Au, Mo) coated on a Beryllium (Be) window. A four-valve electric field deflector was developed to deflect the electron beam to bombard the corresponding targets. Particle dynamics analysis software was employed to simulate the particle tracking of electron beam. The results show that the 30 keV electron beam could get a 6.7 mm displacement on the target plane by 10⁵ V/m electric field. The focus areas are about 2 mm × 5 mm and 4 mm × 2.5 mm after deflection in two directions. Thermal behavior calculated by ANSYS shows that the designed target assembly could withstand a 10 W continuous power. The optimum target thicknesses and emission spectra were obtained by Geant4 when the thickness of Be window was 300 mm and the electron beam incident angle was 0.141 rad. The results indicate that this multi-target X-ray tube could provide different X-ray sources effectively.