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Investigation of bubbles escape behavior from low basicity mold flux for high-Mn high-Al steels using 3D X-ray microscope

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International Journal of Minerals,Metallurgy and Materials 2025年第1期32卷 102-110页

作者： qiang liu Xiang Li Shen Du Ming Gao Yanbin Yin Jiongming Zhang State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China

During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the *** which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid *** contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive ***,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding *** results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles *** addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually *** one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the *** findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.

关键词： mold flux low basicity bubbles three-dimensional X-ray microscope viscosity

Human-induced pluripotent stem cell-derived neural stem cell exosomes improve blood-brain barrier function after intracerebral hemorrhage by activating astrocytes via PI3K/AKT/MCP-1 axis

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Neural Regeneration Research 2025年第2期20卷 518-532页

作者： Conglin Wang Fangyuan Cheng Zhaoli Han Bo Yan Pan Liao Zhenyu Yin Xintong Ge Dai Li Rongrong Zhong qiang liu Fanglian Chen Ping Lei Department of Geriatrics Tianjin Medical University General HospitalTianjinChina School of Medicine Nankai UniversityTianjinChina Tianjin Neurological Institute TianjinChina

Cerebral edema caused by blood-brain barrier injury after intracerebral hemorrhage is an important factor leading to poor ***-induced pluripotent stem cell-derived neural stem cell exosomes(hiPSC-NSC-Exos)have shown potential for brain injury repair in central nervous system *** this study,we explored the impact of hiPSC-NSC-Exos on blood-brain barrier preservation and the underlying *** results indicated that intranasal delivery of hiPSC-NSC-Exos mitigated neurological deficits,enhanced blood-brain barrier integrity,and reduced leukocyte infiltration in a mouse model of intracerebral ***,hiPSC-NSC-Exos decreased immune cell infiltration,activated astrocytes,and decreased the secretion of inflammatory cytokines like monocyte chemoattractant protein-1,macrophage inflammatory protein-1α,and tumor necrosis factor-αpost-intracerebral hemorrhage,thereby improving the inflammatory *** sequencing indicated that hiPSC-NSC-Exo activated the PI3K/AKT signaling pathway in astrocytes and decreased monocyte chemoattractant protein-1 secretion,thereby improving blood-brain barrier *** with the PI3K/AKT inhibitor LY294002 or the monocyte chemoattractant protein-1 neutralizing agent C1142 abolished these *** summary,our findings suggest that hiPSC-NSC-Exos maintains blood-brain barrier integrity,in part by downregulating monocyte chemoattractant protein-1 secretion through activation of the PI3K/AKT signaling pathway in astrocytes.

关键词： AKT astrocyte blood-brain barrier cerebral edema exosomes human-induced pluripotent stem cells intracerebral hemorrhage neural stem cells neuroinflammation PI3K

Empirical Likelihood for Varying Coefficient EV Models under Longitudinal Data

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Acta Mathematicae Applicatae Sinica 2018年第3期34卷 585-596页

作者： qiang liu School of Statistics Capital University of Economics and Business

In this paper, a varying coefficient errors-in-variables model under longitudinal data is *** empirical likelihood based bias-correction approach is proposed. It is proved that the proposed statistics are asymptotically chi-squared under some mild conditions, and hence can be used to construct the confidence regions of the parameters of interest. Finite sample performance of the proposed method is illustrated in a simulation study. The proposed methods are applied to an AIDS clinical trial dataset.

关键词： varying coefficient EV model longitudinal Data empirical likelihood bias-correction asymptotic normality

Efflux pump gene hefA of Helicobacter pylori plays an important role in multidrug resistance

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World Journal of Gastroenterology 2008年第33期14卷 5217-5222页

作者： Zhi-qiang liu Peng-Yuan Zheng Ping-Chang Yang Department of Gastroenterology the Second Affiliated Hospital of Zhengzhou University Zhengzhou 450014 Henan Province China Department of Pathology and Molecular Medicine McMaster University Hamilton Ontario L8N 4A6 Canada

AIM: To determine whether efflux systems contribute to multidrug resistance of H pylori. METHODS: A chloramphenicol-induced multidrug resistance model of six susceptible H pylori strains (5 isolates and H pylori NCTC11637) was developed. Multidrug-resistant (MDR) strains were selected and the minimal inhibitory concentration (MIC) of eryth-romycin, metronidazole, penicillin G, tetracycline, and ciprofloxacin in multidrug resistant strains and their parent strains was determined by agar dilution tests. The level of mRNA expression of hefA was assessed by fluorescence real-time quantitative PCR. A H pylori LZ1026 knockout mutant (ΔH pylori LZ1026) for (puta-tive) efflux protein was constructed by inserting the kanamycin resistance cassette from pEGFP-N2 into hefA, and its susceptibility profiles to 10 antibiotics were evaluated. RESULTS: The MIC of six multidrug-resistant strains (including 5 clinical isolates and H pylori NCTC11637) increased signifi cantly (≥ 4-fold) compared with their parent strains. The expression level of hefA gene was significantly higher in the MDR strains than in their parent strains (P = 0.033). A H pylori LZ1026 mutant was successfully constructed and the ΔH pylori LZ1026 was more susceptible to four of the 10 antibiotics. All the 20 strains displayed transcripts for hefA that con-fi rmed the in vitro expression of these ***: The efflux pump gene hefA plays an important role in multidrug resistance of H pylori.

关键词： Efflux pump Helicobacter pylori Multidrug resistance Fluorescence real-time quantitative PCR Knockout mutant

Dynamics Analysis of a Parallel Mill-turn Tool Spindle Head Driven by Dual-linear Motors Using Extended Transfer Matrix Method

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Chinese Journal of Mechanical Engineering 2011年第5期24卷 859-869页

作者： WU Wenjing liu qiang School of Mechanical Engineering and Automation Beihang University Beijing 100191

The hybrid dynamics of multi-rigid-body and multi-flexible-body system becomes the mainstream of multi-body *** there lacks a compact approach to model the hybrid dynamics,especially in modern machine tool application,due to the difficulty of solving the hybrid equations or the limitation of current software when dealing with the hybrid *** extended transfer matrix method（E-TMM）,which extends elements in three-dimensional space with higher matrixes,is proposed to simplify the modeling process of the hybrid *** E-TMM modeling approaches of 3 basic elements including 3D vibrant rigid body,joint and flexible body are studied in details.A parallel mill-turn tool spindle head unit driven by dual-linear motors is chosen as a plant to demonstrate the E-TMM modeling *** using E-TMM,the spindle head unit is simplified as a topological network consisting of the three types of element,i.e.,3D vibrant rigid body,joint and flexible body,including 11 rigid bodies,14 joints and 1 3D-Timoshenko *** the dynamic model of the system can be easily obtained by deducing the element-network by means of state vector *** dynamic characteristics of the spindle head,such as natural frequencies,dynamic flexibility,*** be predicted by solving the obtained *** verification indicates that the E-TMM is valid with enough accuracy in the dynamic analysis of the parallel mill-turn tool spindle *** E-TMM is capable of modeling the dynamics of machine tool structure with no requirements of deducing and solving the sophisticated differential ***,the E-TMM provides a simple and elegant tool for hybrid dynamic analysis in future dynamic design of machine tools.

关键词： NC machine tools dynamics modeling transfer matrix method(TMM)

Effect of Groundwater Level Fluctuation on Phragmites australis Evapotranspiration in the Baiyangdian Lake

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湿地科学 2014年第5期12卷 552-558页

作者： liu qiang Key Laboratory for Water and Sediment Sciences Ministry of Education School of EnvironmentBeijing Normal University State Key Laboratory of Water Environment Simulation School of Environment Beijing Normal University

Abstract:Hydrological regimes influence ecological patterns and processes as well as alter rates of wetland *** study aimed to investigate the impact of groundwater fluctuation on evapotranspiration of Phragmites *** by field data obtained from the Baiyangdian Lake in northern China,the variations in groundwater levels were explored,and the changes in soil water and evapotranspiration of reed were analyzed to investigate different groundwater level scenarios using HYDRUS-1D *** results showed that soil water content,recharged by groundwater,remained stable in the lower soil layer but varied strongly in the upper layer of the soil profile;in comparison to evaporation,Phragmites australis transpiration contributed significantly more to the overall evapotranspiration rate;the high levels of evapotranspiration could be maintained when groundwater levels vary between 1.0 m and 1.8 m,while it was reduced with an increase in groundwater levels as a result of water stress *** results also indicated that the evapotranspiration of Phragmites australis could maintain higher evapotranspiration rates under natural water *** evapotranspiration,in other words,might be the main water consumer,but it nevertheless has little effect on water levels during water *** evapotranspiration of Phragmites australis responded to the changes in groundwater levels could help researchers understand water requirements of the wetlands and establish suitable water levels for the wetlands.

关键词： groundwater evapotranspiration Phragmites australis ecological water requirement Baiyangdian Lake

Modeling and Analytical Solution of Chatter Stability for T-slot Milling

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Chinese Journal of Mechanical Engineering 2010年第1期23卷 88-93页

作者： LI Zhongqun liu qiang School of Mechanical Engineering Hunan University of Technology Zhuzhou 412008 China School of Mechanical Engineering and Automation Beihang University Beijing 100191 China

T-slot milling is one of the most common milling processes in industry. Despite recent advances in machining technology, productivity of T-slot milling is usually limited due to the process limitations such as high cutting forces and stability. If cutting conditions are not selected properly the process may result in the poor surface finish of the workpiece and the potential damage to the machine tool. Currently, the predication of chatter stability and determination of optimal cutting conditions based on the modeling of T-slot milling process is an effective way to improve the material removal rate（MRR） of a T-slot milling operation. Based on the geometrical model of the T-slot cutter, the dynamic cutting force model was presented in which the average directional cutting force coefficients were obtained by means of numerical approach, and leads to an analytical determination of stability lobes diagram（SLD） on the axial depth of cut. A new kind of SLD on the radial depth of cut was also created to satisfy the special requirement of T-slot milling. Thereafter, a dynamic simulation model of T-slot milling was implemented using Matlab software. In order to verify the effectiveness of the approach, the transfer functions of a typical cutting system in a vertical CNC machining center were measured in both feed and normal directions by an instrumented hammer and accelerators. Dynamic simulations were conducted to obtain the predicated SLD under specified cutting conditions with both the proposed model and CutPro~. Meanwhile, a set of cutting trials were conducted to reveal whether the cutting process under specified cutting conditions is stable or not. Both the simulation comparison and experimental verification demonstrated that the satisfactory coincidence between the simulated, the predicted and the experimental results. The chatter-free T-slot milling with higher MRR can be achieved under the cutting conditions determined according to the SLD simulation.

关键词： machining dynamics T-slot milling chatter vibration stability lobes diagram

A Pincer Cobalt Complex as Catalyst with Dual Hydrogenation Activities for Hydrodeoxygenation of Ketones with H2

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Chinese Journal of Chemistry 2023年第24期41卷 3528-3532页

作者： Bingxue liu qiang liu Center of Basic Molecular Science (CBMS) Department of ChemistryTsinghua UniversityBeijing100084 China

Reductive deoxygenation of ketones using H_(2) is a highly desirable but also challenging transformation in both chemical synthesis,industrial-scale petroleum and biomass feedstock reforming ***,we report a cooperative cobalt/Lewis acid (LA)-catalyzed hydrodeoxygenation of ketones using H_(2) as the *** particular,the newly developed pincer cobalt catalyst possesses dual hydrogenation activities for both ketones and alkenes under the same reaction *** reaction features a broad substrate scope,excellent functional-group compatibility,and potential applicability.

关键词： Cobalt catalyst Lewis acids Homogeneous catalysis Dual hydrogenation activities Hydrodeoxygenation Ketones

High Accurate Interpolation of NURBS Tool Path for CNC Machine Tools

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Chinese Journal of Mechanical Engineering 2016年第5期29卷 911-920页

作者： liu qiang liu Huan YUAN Songmei School of Mechanical Engineering and Automation Beihang University

Feedrate fluctuation caused by approximation errors of interpolation methods has great effects on machining quality in NURBS interpolation, but few methods can efficiently eliminate or reduce it to a satisfying level without sacrificing the computing efficiency at present. In order to solve this problem, a high accurate interpolation method for NURBS tool path is proposed. The proposed method can efficiently reduce the feedrate fluctuation by forming a quartic equation with respect to the curve parameter increment, which can be efficiently solved by analytic methods in real-time. Theoretically, the proposed method can totally eliminate the feedrate fluctuation for any 2nd degree NURBS curves and can interpolate 3rd degree NURBS curves with minimal feedrate fluctuation. Moreover, a smooth feedrate planning algorithm is also proposed to generate smooth tool motion with considering multiple constraints and scheduling errors by an efficient planning strategy. Experiments are conducted to verify the feasibility and applicability of the proposed method. This research presents a novel NURBS interpolation method with not only high accuracy but also satisfying computing efficiency.

关键词： NURBS interpolation feedrate machine tool CNC