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.

Mitigation Effect of Waste Glass Powders on Alkali–Silica Reaction (ASR) Expansion in Cementitious Composite

Guojun Ke,Wengui Li,Ruyi Li,Yuelin Li,George Wang 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.7

The effects of different contents and particle sizes of waste glass powder on alkali–silica reaction (ASR) expansion of cementitious composite bar were investigated in this study. Waste glass powder with particle size less than 300 ㎛ exhibits an excellent mitigation effect on ASR expansion. With larger content and smaller particle size, the mitigation effect of waste glass powder on ASR expansion gradually increases. The mitigation effect of waste glass powder with particle size ranging from 38 to 53 ㎛ and 20% by weight of cement seems relatively better than that of fly ash. When the waste glass powder content reaches 30%, the mitigation effect is still effective and almost the same as that of fly ash. However, the waste glass powder with particle size larger than 300 ㎛ presents negative mitigation effect on ASR expansion when the replacement rate is larger than 30%. On the other hand, the waste glass powder and calcium hydroxide (CH) further react, and produce more calcium–silicate–hydrate gels, which apparently reduce the amount of CH. Moreover, the increasing content of waste glass powder results in a lower pH value in the pore solution of cementitious composite.

Investigation into the Prestress Loss and Thermal Expansion Performance of Steel Cables at High Temperature

Guojun Sun,Zhihao Li,Jinzhi Wu,Xiushu Qu,Jingying Ren 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.3

This study investigates the prestress loss and thermal expansion performance of steel cables under high temperatures. The calculation formula of cable prestress loss is fi rst deduced theoretically. The prestress loss value of cable under force-thermal coupling is then obtained through numerical simulation and is compared with the calculation results of the theoretical formula. Theoretical deduction is then employed to determine the relationship between the thermal expansion coeffi cient of the cable and wire in the unstressed state. A numerical analysis model is established to simulate the mechanical properties of the cable in an unstressed state. The results show that the thermal expansion coeffi cient of the cable in an unstressed state is the same as that of steel wire. Finally, considering that the cable is in the stress state in an actual structure, the high-temperature prestress loss of steel cables under force-thermal coupling is obtained through simulation analysis. The equivalent thermal expansion coeffi cient is then calculated, and the infl uence of diff erent twist angles, steel wire layers, initial prestress, section type, and cable length on the equivalent thermal expansion coeffi cient of steel cables is determined.

Theoretical research and experimental study for a new measurement method of standing wave levitation force

Xinbo Li,Hai Jiang,Xiaoyang Jiao,Kai Zhang,Guojun Liu,Jian-Fang Liu 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5

Based on the lever principle, a novel measurement method for the standing wave levitation force is investigated and the measurementdevice is developed. The relative levitation force was simulated by MATLAB software, from which the relative levitation force distributionand the curves of relative levitation force in vertical and horizontal directions were obtained. To verify the rationale of the measurementmethod, a series of experiments were carried out with the designed measurement device system. The levitation force distributionand the curves of levitation force in vertical and horizontal directions were also obtained from the experiment. Comparing the experimentalresults with the simulation, the levitation force distribution situation from the experimental results and the simulation is identical.

Effect of impurity components in stainless steel dust on the coloring properties of the prepared black ceramic pigments

Zhiqiao Li,Xiang Zhang,Guojun Ma,Dingli Zheng,Ruixiang He,Tianyu Du 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.1

Stainless steel dust (SSD) can be utilized as the primary raw material for the production of Fe-Cr-Ni-Mn system black ceramicpigments because it is high in transition metal elements. However, in addition to the ingredients required for the preparationof black pigments, it also contains some impurity elements like Ca, Mg, Si and Zn, and the influence of these impurity elementson the coloring performance of the pigments is unclear. In this paper, pure chemical reagents were used as raw materials tosimulate the main components of SSD for the solid-phase synthesis of black ceramic pigments doped with various impuritycomponents (CaO, MgO, SiO2 and ZnO). The results show that the doping of MgO can improve the purity of the preparedblack ceramic pigments, whereas CaO, SiO2 and ZnO can turn the pigments become reddish yellow. In the doped samples,ZnO and MgO mainly react with Fe2O3 to form ZnFe2O4 and MgFe2O4. In addition, CaO reacts with Fe2O3 to generateCaFe4O7. The reactions described above can increase the average crystallite size and distort the crystal lattice of the crystalsin the pigment samples. Moreover, SiO2 exists in amorphous form among spinel grains.

DISJOINT SMALL CYCLES IN GRAPHS

Gao, Yunshu,Li, Guojun,Yan, Jin The Korean Society for Computational and Applied M 2009 Journal of applied mathematics & informatics Vol.27 No.3

We call a cycle C be a small cycle if the length of C equals to 3 or 4. In this paper, we obtain two sufficient conditions to ensure the existence of vertex-disjoint small cycles in graph and propose several problems.

Disjoint small cycles in graphs

Yunshu Gao,Guojun Li,Jin Yan 한국전산응용수학회 2009 Journal of applied mathematics & informatics Vol.27 No.3

We call a cycle C be a small cycle if the length of C equals to 3 or 4. In this paper, we obtain two sufficient conditions to ensure the existence of vertex-disjoint small cycles in graph and propose several problems. We call a cycle C be a small cycle if the length of C equals to 3 or 4. In this paper, we obtain two sufficient conditions to ensure the existence of vertex-disjoint small cycles in graph and propose several problems.

Cuticular hydrocarbon pattern as a chemotaxonomy marker to assess six species of thrips

Chen Ting,Li Qunchen,Qi Guojun,Gao Yan,Zhao Chenyin,Lu Lihua 한국응용곤충학회 2020 Journal of Asia-Pacific Entomology Vol.23 No.4

Thrips constitute several families of slender insects with fringed wings and unique asymmetrical mouthparts. They have become globally important pests, infesting a variety of agriculturally important crops. Species of thrips are difficult to identify due to their small size and similarities in morphology. Recently, in addition to morphology, both molecular and non-molecular taxonomic tools have been used to identify species differences. Insect cuticular hydrocarbons have been widely used in chemotaxonomy. In this study, a Thermal Separation Probe was used to identify the cuticular hydrocarbons of Frankliniella occidentalis, Frankliniella intonsa, Thrips palmi, Thrips hawaiiensis, Haplothrips chinensis and Gynaikothrips ficorum. We analyzed the hydrocarbon com position of adults in all 6 species, and in the larvae of F. occidentalis, T. hawaiiensis and T. palmi. The results showed that the composition of cuticular hydrocarbons differed between species. All 6 species of adults and 3 species of larvae were easily distinguishable by quantitative analysis of hydrocarbon profiles. These results provide a possible method for the identification of thrips.

Crime amount prediction based on 2D convolution and long short-term memory neural network

Qifen Dong,Ruihui Ye,Guojun Li 한국전자통신연구원 2022 ETRI Journal Vol.44 No.2

Crime amount prediction is crucial for optimizing the police patrols’ arrangement in each region of a city. First, we analyzed spatiotemporal correlations of the crime data and the relationships between crime and related auxiliary data, including points-of-interest (POI), public service complaints, and demographics. Then, we proposed a crime amount prediction model based on 2D convolution and long short-term memory neural network (2DCONV-LSTM). The proposed model captures the spatiotemporal correlations in the crime data, and the crime-related auxiliary data are used to enhance the regional spatial features. Extensive experiments on real-world datasets are conducted. Results demonstrated that capturing both temporal and spatial correlations in crime data and using auxiliary data to extract regional spatial features improve the prediction performance. In the best case scenario, the proposed model reduces the prediction error by at least 17.8% and 8.2% compared with support vector regression (SVR) and LSTM, respectively. Moreover, excessive auxiliary data reduce model performance because of the presence of redundant information.

Intracellular trafficking of TREM2 is regulated by presenilin 1

Yingjun Zhao,Xiaoguang Li,Timothy Huang,Lu-lin Jiang,Zhenqiu Tan,Muxian Zhang,Irene Han-Juo Cheng,Xin Wang,Guojun Bu,Yun-wu Zhang,Qi Wang,Huaxi Xu 생화학분자생물학회 2017 Experimental and molecular medicine Vol.49 No.-

Genetic mutations in triggering receptor expressed on myeloid cells 2 (TREM2) have been linked to a variety of neurodegenerative diseases including Alzheimer’s disease, amyotrophic lateral sclerosis, frontotemporal dementia and Parkinson’s disease. In the brain, TREM2 is highly expressed on the cell surface of microglia, where it can transduce signals to regulate microglial functions such as phagocytosis. To date, mechanisms underlying intracellular trafficking of TREM2 remain elusive. Mutations in the presenilin 1 (PS1) catalytic subunit of the γ-secretase complex have been associated with increased generation of the amyloidogenic Aβ (amyloid-β) 42 peptide through cleavage of the Aβ precursor amyloid precursor protein. Here we found that TREM2 interacts with PS1 in a manner independent of γ-secretase activity. Mutations in TREM2 alter its subcellular localization and affects its interaction with PS1. Upregulation of PS1 reduces, whereas downregulation of PS1 increases, steady-state levels of cell surface TREM2. Furthermore, PS1 overexpression results in attenuated phagocytic uptake of Aβ by microglia, which is reversed by TREM2 overexpression. Our data indicate a novel role for PS1 in regulating TREM2 intracellular trafficking and pathophysiological function.