Controllable Synthesis of Silver Nanoparticles Using Piezoelectric-Actuated High-Frequency Vibration Self-Circulating Microfluidic Reactor

Guojun Liu,Fang He,Yan Li,Xinbo Li,Hong Zhao,Conghui Wang,Conghong Zhan,Chunxiu Tang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.8

Based on the liquid-phase reduction mechanism, a controllable synthesis method, which uses piezoelectric-actuated high-frequency vibration self-circulating microfluidic reactor, to prepare silver nanoparticles is proposed. Firstly, the synthesis mechanism of silver nanoparticles and the working principle of the microfluidic reactor were analyzed. Then, in order to study and explore the influence of self-circulating and high frequency vibration on the synthesis of silver nanoparticles, a series of related synthesis experiments were carried out. The synthesized silver nanoparticles were characterized by UV-Visible spectroscopy and transmission electron microscopy. The effects of micropump driving voltage and high-frequency vibration on the synthesis of silver nanoparticles were analyzed. The experiment results show that when the silver nanoparticles were synthesized using piezoelectric-actuated high-frequency vibration self-circulating microfluidic reactor, the higher the driving voltage of the circulating reflux micropump, the faster the vortex rotation speed in the mixing pool and the more uniform the reagent reaction. Besides, high-frequency vibration can suppress the aggregation of silver nanoparticles, and balance the growth environment of particles, which is beneficial to the formation of silver nanoparticles with good monodispersity, high sphericity and small size deviation.

Experimental study on seismic behavior of high strength reinforced concrete frame columns with high axial compression ratios

Guojun Zhang,Jianxin Liu,Guoliang Bai,Boquan Liu 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.5

Fault Detection Observer Design for Fuzzy Systems with Local Nonlinear Models via Fuzzy Lyapunov Function

Guojun Liu,Xiao-Heng Chang,Yong-Yan Cao 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.5

This paper concerns with the problem of designing fault detection (FD) observer for Takagi-Sugeno (TS)fuzzy systems subject to local nonlinear models. Different from the quadratic Lyapunov function approaches,fuzzy Lyapunov function approach is applied to design the fault detection observer, and corresponding sufficientconditions are given in terms of linear matrix inequalities. In addition, combined with nonlinear local modelsscheme and slack variable technique, the T-S fuzzy systems have fewer fuzzy rules to reduce the computationalburden. Compared with the existing results, less conservative results on existence of fuzzy fault detection observersare derived. Moreover, the designed fuzzy fault detection observer not only guarantees the residual system stabilitybut also improves the H_ index estimation. It is noted that the H_ index is employed to measure the worst-cast faultsensitivity performance. Finally, a numerical simulation is given to illustrate the effectiveness of the designed faultdetection observer.

Analysis of differential gene expression in cold‑tolerant vs. cold‑sensitive varieties of snap bean (Phaseolus vulgaris L.) in response to low temperature stress

Chang Liu,Xiaoxu Yang,Zhishan Yan,Youjun Fan,Guojun Feng,Dajun Liu 한국유전학회 2019 Genes & Genomics Vol.41 No.12

and quality. At present, little is known about the genes and molecular regulation mechanism in cold response in snap bean exposed to low temperature. Objectives Our objectives were to identify the low temperature response genes in snap bean and to examine differences in the gene response between cold-tolerant and cold-sensitive genotypes. Methods We used two highly inbred snap bean lines in this study, the cold-tolerant line ‘120’, and the cold-sensitive line ‘093’. The plants were grown to the three leaf and one heart stage and exposed to 4 °C low temperature. We used RNA sequencing (RNA-seq) to analyze the differences of gene expression. Results 988 and 874 cold-responsive genes were identified in ‘T120 vs CK120’ and ‘T093 vs CK093’ (‘T’ stands for low temperature treatment, and ‘CK’ stands for control at room temperature), respectively. Of these, 555 and 442 genes were unique to cold-stressed lines ‘120’ and ‘093’, respectively compared to the control. Our analysis of these differentially expressed genes indicates that Ca2+, ROS, and hormones act as signaling molecules that play important roles in low temperature response in P. vulgaris. Altering the expression of genes in these signaling pathways activates expression of downstream response genes which can interact with other signaling regulatory networks. This may maintained the balance of ROS and hormones, making line ‘120’ more cold-tolerant than line ‘093’. Conclusion Our results provide a preliminarily understanding of the molecular basis of low temperature response in snap bean, and also establish a foundation for the future genetic improvement of cold sensitivity in snap bean by incorporating genes for cold tolerance.

Experimental study on seismic behavior of high strength reinforced concrete frame columns with high axial compression ratios

Zhang, Guojun,Liu, Boquan,Bai, Guoliang,Liu, Jianxin Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.5

Evaluation of Geotechnical Parameters of a Lagoonal Clay Deposit in Jiangsu Lixia River Area of China by Seismic Piezocone Tests

Guojun Cai,Songyu Liu,Anand J. Puppala 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.5

The use of the Seismic Piezocone Test (SCPTU) in geotechnical site investigation offers field assessment on stratigraphy and soil behavior. Compared with some traditional investigation methods such as drilling, sampling and field inspecting method or laboratory test procedures, SCPTU can greatly accelerate the field work and hereby reduce corresponding operation cost. The results of a site investigation on the soft, normally to slightly overconsolidated, Lixia River lagoonal clay deposit underlying several expressway lines, including a seismic piezocone penetration test, undisturbed sampling from an adjacent borehole, and laboratory testing, are reported. The determination of soil profile and the main geotechnical properties is facilitated by the use of seismic piezocone penetration test that can provide up to four independent reading with depth from a single sounding. The coupled use of normalized cone resistance and pore pressure parameter provides a simple and quick soil classification for highly interbedding of Lixia River lagoon ground. Comparison of the results reveals the validity of SCPTU tests to interpret the engineering properties of Lixia River lagoonal clay. These data will also be particularly useful for future local construction work.

Characterization of Spatial Variability of CPTU Data in a Liquefaction Site Improved by Vibro-compaction Method

Guojun Cai,Jun Lin,Songyu Liu,Anand J. Puppala 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.1

Vibro-compaction is a ground improvement technique in which the weak or loose soil deposits are compacted by the vibrating probe or vibroflot penetration. The Piezocone Penetration Test (CPTU) has been found to be one of the best methods to assess the effect of ground improvement due to its continuous, reliable and repeatable data collected. The spatial variability of a liquefactionsusceptible site improved by vibro-compaction was assessed using random field theory. The CPTU soundings were conducted to characterize the variation of random field model parameters. Given the relatively high data frequency of the cone tip resistance in vertical direction, the vertical random field parameters are determined with the modified Bartlett random field estimation procedure. Due to the lack of data in horizontal direction, the horizontal random field parameters are evaluated using a less rigorous way of the autocorrelation. It is shown that the normalized cone resistance is a well estimator of spatial variability. The statistical results suggest that both Scale of Fluctuation (SOF) and the Coefficient of Variation (COV) varied in different way after vibro-compaction.

In vitro regeneration of Phaseolus vulgaris L. via direct and indirect organogenesis

Yu Yan,Liu Dajun,Liu Chang,Yan Zhishan,Yang Xiaoxu,Feng Guojun 한국식물생명공학회 2021 Plant biotechnology reports Vol.15 No.3

A stable and efcient regeneration system is a necessary condition for the genetic transformation of Phaseolus vulgaris L. In this study, cotyledonary nodes with one cotyledon, cotyledonary nodes with two cotyledons, embryonic axes and root segments of 5-day-old germinated seeds were used as explants to evaluate explants to induce shoots and calli. Besides, using cotyledonary nodes with one cotyledon as explants, the efects of diferent concentrations of auxins and cytokinins on the direct and indirect organogenesis of common bean were investigated. As a result, embryonic axes and cotyledonary nodes with two cotyledons were the most efective explant types for the formation of shoots and calli. The cotyledonary nodes with one cotyledon were cultured in the shoot induction medium containing 7 mg L−1 6-benzyladenine (BAP) and 0.2 mg L−1 α-naphthaleneacetic acid (NAA). 74.21% of explants directly formed shoots and average number of shoots was up to 2.91. On the rooting medium supplemented with 0.5 mg L−1 indole-3-butyric acid (IBA), the rooting rate of shoots reached 100% and the number of main roots formed was the most. The addition of 0.5 mg L−1 thidiazuron (TDZ) was optimum for callus induction, and the induction rate could reach 91.51%. The shoot regeneration frequency was 93.33% when calli subcultured on the shoot induction medium supplemented with 1.0 mg L−1 BAP. Average 4.27 shoots were produced by per callus and rooted on the shoot induction medium. This report descripts an efcient common bean regeneration system through direct and indirect organogenesis, which can provide reference for its subsequent genetic transformation research.

Influence of pump start-up mode on the stability of mixed-flow pumps

Zhenbo Tang,Guojun Zhu,Jianjun Feng,Yajun Wu,Kai Liu,Qiang Lu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

To analyse the influence of the start-up mode on the stability of the mixed-flow pump, start-up experiments are performed. And the external characteristic parameters, pressure fluctuation and shaft vibration data are collected by a multi-channel synchronous signal acquisition system during start-up. These data are analyzed by the time-frequency analysis method and wavelet partial coherence analysis method. Results reveal a positive correlation between the impeller angular acceleration and the time change rate of external characteristic parameters. During the start-up process, the variation law of the external characteristic parameters similar with the law of impeller rotating speed rise. The amplitude of the shaft vibration has a positive correlation with the start-up acceleration of the impeller. The influence of guide vane pressure fluctuations on the shaft vibrations is greater within 0~2 s after the start of the mixedflow pump. With the strart-up time extension, the partial coherence between the shaft vibration and the pressure fluctuations in guide vane is enhanced in low frequency band, which increases the risk of flow-induced vibration of the pump shaft.

Optimization of an indirect regeneration system for common bean (Phaseolus vulgaris L.)

Xiong Luxi,Liu Chang,Liu Dajun,Yan Zhishan,Yang Xiaoxu,Feng Guojun 한국식물생명공학회 2023 Plant biotechnology reports Vol.17 No.6

The main problems associated with growing common bean (Phaseolus vulgaris L.) callus are low proliferation and differentiation, and high browning. In this study, common bean callus induced by cotyledon nodes was used as explant material to investigate the effects of different exogenous substances on callus regeneration, as well as the correlation between callus browning and the changes in superoxide dismutase (SOD), peroxidase (POD), and polyphenol oxidase (PPO) enzyme activities during callus culture. Adding AgNO3, CoCl2, Putrescine (Put), and 1-aminocyclopropane-1-carboxylic acid (ACC) to the callus growth medium at appropriate concentrations could significantly improve callus proliferation and differentiation efficiency, while also reducing the degree of browning, compared to controls. Callus explants were cultured in callus proliferation and differentiation medium (CPADM) containing 5 mg·L−1 AgNO3, 15 mg·L−1 Put, 5 mg·L−1 CoCl2, or 0.02 mM ACC, with optimal callus growth at these dosages. After treatment with the four exogenous substances, callus browning was inversely correlated with SOD activity but positively correlated with POD and PPO activities. The maximum rooting frequency of shoots was observed when rooting media was treated with 1 mg·L−1 Indole butyric acid (IBA) or 0.1 mg·L−1 2,4-dichlorophenoxyacetic acid (2,4-D). The average number of primary roots, root length, and root fresh weight were higher after these treatments. The indirect regeneration issue was largely resolved for common bean by the callus culture technique applied in this study, which provides a framework for genetic modification, germplasm preservation, and bean application.