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Further numerical investigation on concrete dynamic behaviors with considering stress non-equilibrium in SHPB test based on the waveform features

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Acta Mechanica Sinica 2020年第4期36卷 873-886页

作者： T.H.Lv X.w.chen Y.J.Deng G.chen State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province Southwest University of Science and TechnologyMianyang 621000China Institute of Systems Engineering China Academy of Engineering PhysicsMianyang 621999China

In this study,with the meso-scale model reliably validated in our previous work(Construction and Building Materials,2018),the waveform features of plain concrete under various loading conditions and especially with considering stress non-equilibrium are reliably reproduced and *** with waveform features,the violation indicator of the specimen stress equilibrium in the split Hopkinson pressure bar test is identified for concrete-like damage softening *** concrete material behaviors for stress non-equilibrium are further analyzed,*** dynamic increase factor(DIF)and damage development,*** conception of“damage failure volume”is introduced,and a new method of defining the development of concrete dynamic damage is given in the nimierical ***’s more,the“compression wave”and“double peak”phenomena observed in the experiment are further interpreted based on the means of numerical *** features how to reflect the concrete material properties is also *** results show that,the disappearance of the“double peak” phenomenon of reflection curve under high strain rate can be regarded as the indicator of the violation of stress *** the violation of the stress equilibrium,the relevant DIFs of the concrete specimen will not change ***,the concrete specimen will turn into structural response from material *** conception of“damage failure volume”can well explain the generation of the“double peak”phenomenon of the reflection *** “compression wave” phenomenon of reflection curve under lower strain rates is derived from the unloading expansion recovery of the concrete ***,under the same loading condition,the amplitude of the first peak of the reflection curve can be used as the evaluation standard of the bonding quality between mortar and aggregates.

关键词： Concrete material Split Hopkinson pressure bar test Numerical investigation waveform feature Stress non-equilibrium Damage failure volume

Spherical cavity-expansion model for penetration of reinforced-concrete targets

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Acta Mechanica Sinica 2019年第4期35卷 535-551页

作者： Y.J.Deng w.J.Song X.w.chen Institute of Systems Engineering China Academy of Engineering PhysicsP.O.Box 919-416Mianyang 621999China Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province Mianyang 621000China Department of Civil Engineering and Architecture Southwest University of Science and TechnologyMianyang 621000China Department of Mechanics and Engineering Science College of EngineeringPeking UniversityBeijing 100871China Advanced Research Institute for Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China State Key Lab of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

The feature of reinforcing bars is introduced into dynamic cavity-expansion theory. Based on the elastic-plastic response penetration model of plain (i.e., unreinforced) concrete (Forrestal and Tzou, 1997), a dynamic spherical cavity-expansion penetration model for reinforced-concrete targets is developed with consideration of the circumferential restriction effect derived from reinforcing bars in the crushed region. The theoretical solution and simplified calculation formula for the cavity radial stress in incompressible and compressible reinforced concrete are obtained by introducing a reinforcement ratio as the volume fraction of rebars in the concrete target. A damping function is presented to describe the restriction effect of a single layer of reinforcing bars on the surrounding concrete, thus establishing a model to calculate the penetration resistance of multilayer reinforced-concrete targets. Compared with test data for the penetration depth, this model considering the circumferential restriction effect produces better results compared with the existing theory.

关键词： Dynamic cavity-expansion theory Reinforced concrete Penetration resistance Reinforcement ratio

Effect of Fly Ash on Rheological Properties of Cement Paste

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武汉理工大学学报 2010年第17期32卷 186-192页

作者： chen w HUANG H School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

This paper is aimed to study the factors influencing rheological properties of cement paste with fly ash,including the quantity of cement replaced by fly ash,types of the fly ash,degree of cement hydration and the microstructure of cement paste. By changing the water-cement ratio,mixing different amounts of fly ash,adding different types fly ash,the rheological parameters of cement paste are measured with a rheometer,and the needle penetration are tested by Vical needle. A ultrasound velocity test was aslo employed to monitor hydration of paste at early ages. Combinations of different factors on the rheological properties of cement paste are studied. The objective is to reveal the effect mechanism of material nature and proportion of each component on the rheological properties of cement paste with fly ash.

关键词： rheology cement paste fly ash needle penetration ultrasound velocity

Esophagogastric junction distensibility assessed using the functional lumen imaging probe

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world Journal of Gastroenterology 2017年第7期23卷 1289-1297页

作者： Joan w chen Joel H Rubenstein Department of Gastro-enterology and Hepatology University of Michigan Health SystemsAnn ArborMI 48109United States

To assess reference values in the literature for esophageal distensibility and cross-sectional area in healthy and diseased subjects measured by the functional lumen imaging probe (FLIP).METHODSSystematic search and review of articles in Medline and Embase pertaining to the use of FLIP in the esophagus was conducted in accordance with the PRISMA guidelines. Cross-sectional area and distensibility at the esophagogastric junction (EGJ) were abstracted for normal subjects, achalasia, and gastroesophageal reflux disease (GERD) patients, stratified by balloon length and volume of *** achalasia studies (n = 154), 3 GERD (n = 52), and 5 studies including healthy controls (n = 98) were included in the systematic review. Normative data varied widely amongst studies of healthy volunteers. In contrast, studies in achalasia patients uniformly demonstrated low point estimates in distensibility ≤ 1.6 mm2/mmHg prior to treatment that increased to ≥ 3.4 mm2/mmHg following treatment at 40mL bag volume. In GERD patients, distensibility fell to the range of untreated achalasia (≤ 2.85 mm2/mmHg) following *** may be a useful tool in assessment of treatment efficacy in achalasia. The drastic drop in EGJ distensibility after fundoplication suggests that FLIP measurements need to be interpreted in the context of esophageal body motility and highlights the importance of pre-operative screening for dysmotility. Future studies using standardized FLIP protocol and balloon size are needed.

关键词： Impedance planimetry Gastroesophageal reflux disease Esophageal distensibility Achalasia

微小RNA-92a-3p介导中国成年人职业噪音暴露与血压的关联性

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中华高血压杂志（中英文） 2024年第5期32卷 440-440页

作者：袁源(译) 练桂丽(审校) 不详

既往对职业噪音暴露与血压的关联性研究结论不一致,其潜在机制尚不清楚。该研究旨在评估职业噪音暴露与血压的关联性,并探索微小RNA(micro RNA,miRNA)在其中的潜在作用。研究共纳入中国武汉2家公司的894例受试者。采用累积噪音暴露评估... 详细信息

既往对职业噪音暴露与血压的关联性研究结论不一致,其潜在机制尚不清楚。该研究旨在评估职业噪音暴露与血压的关联性,并探索微小RNA(micro RNA,miRNA)在其中的潜在作用。研究共纳入中国武汉2家公司的894例受试者。采用累积噪音暴露评估职业噪音暴露,检测6种候选血浆miRNA(miR92a-3-p、miR21-5-p、miR200a-3-p、miR200b-3-p、miR200c-3-p和miR1-3-p)。

关键词：微小RNA 潜在作用暴露评估关联性研究潜在机制

Photoluminescence of ZnS Clusters in Zeolite-Y

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Journal of Materials Science & Technology 1997年第5期13卷 397-404页

作者： chen, w wang, ZG Lin, ZJ Xu, Y Lin, LY Lab. of Semiconductor Materials Sciences Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 China

Two obvious emissions are observed from the ZnS clusters encapsulated in zeolite-Y. The emission around 355 nm is sharp and weak, locating at the onset of the absorption edge. The band around 535 nm is broad, strong and Stokes-shifted. Both the two emissions shift to blue and their intensities firstly increase then decrease as the loading of ZnS in zeolite-Y or clusters size decreases. Through investigation, the former is attributed to the excitonic fluorescence, and the latter to the trapped luminescence from surface states. The cluster size-dependence of the luminescence may be explained qualitatively by considering both the carrier recombination and the nonradiative recombination rates. Four peaks appearing in the excitation spectra are assigned to the transitions of 1S-1S, 1S-1P, 1S-1D and surface state, respectively. The excitation spectra of the clusters do not coincide with their absorption spectra. The states splitted by quantum-size confinement are detected in the excitation spectra, but could not be differentiated in the optical absorption spectra due to inhomogeneous broadening. The size-dependence of the excitation spectra is similar to that of the absorption spectra. Both the excitation spectra of excitonic and of trapped emissions are similar, but change in relative intensity and shift in position are observed.

关键词： Zeolites

BEHAVIOR OF FLOw STRESS OF ALUMINUM SHEETS USED FOR PRESSURE CAN DURING COMPRESSION AT ELEVATED TEMPERATURE

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Acta Metallurgica Sinica(English Letters) 2005年第6期18卷 756-762页

作者： G.S. Fu w.Z. chen K. w. Qian School of Mechanical Engineering Fuzhou University Fuzhou 350002 China

The behavior of flow stress of Al sheets used for pressure can prepared by different melt-treatment during plastic deformation at elevated temperature was studied by isothermal compression test using Gleeble1500 dynamic hot-simulation testing machine. The results show that the AI sheets possess the remarkable characteristic of steady state flow stress when they are deformed in the temperature range of 350-500℃ at strain rates within the range of 0.01-10.0s^-1. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate, and an Arrhenius relationship with the temperature, which implies that the process of plastic deformation at elevated temperature for this material is thermally activated. Compared with the AI pieces prepared by no or conventional melt-treatment, hot deformation activation energy of AI sheets prepared by high-efficient melt-treatment is the smallest （ Q= 168.0kJ/mol）, which reveals that the hot working formability of this material is very better, and has directly to do with the effective improvement of its metallurgical quality.

关键词： Al sheets used for can melt-treatment plastic deformation at elevatedtemperature flow stress hot deformation activation energy

Analysis of Contact Melting Driven by Surface Heat Flux Around a Cylinder

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Journal of Thermal Science 2008年第1期17卷 64-68页

作者： Y.S.Zhao w.Z.chen F.R.Sun Z.Y.chen Faculty of Thermal Engineering College of Power and ShippingNaval University of EngineeringWuhan 430033China Faculty of Thermal Engineering College of Power and ShippingNaval University of EngineeringWuhan 430033China Professor

The contact melting of phase change material around a moving horizontal cylindrical heat source, which descended under its own weight, is investigated in this article. A melting model under constant surface heat flux is established. The analytical results for thickness and pressure distributions inside melt layer and steady melting velocity are obtained by using contact melting theory. The melting law is discussed, and compared with that of contact melting driven by temperature difference. It is found that quasi-steady melting velocity is determined by heat flux of heat source, and the variation of heat source density has less effect on melting velocity.

关键词： Contact melting horizontal cylinder phase change phenomena

Two Processes Comparison by Using Capability Indices Cpm

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厦门大学学报(自然科学版) 2002年第S1期 188-189页

作者： K S chen,Jann-Pygn chen,T w chen Department of Industrial Engineering & Management National Chin -Yi Institute of Technology Department of Industrial Engineering & Management National Chin -Yi Institute of Technology Department of Mechanical Engineering National Chin-Yi Institute of Technology Taiwan China

In recent years, there has been mounting interest i n measuring process performance in manufacturing industry. Based on analyzing the process capability indices, a production department can trace and improve a poor process to enhance quality levels and satisfy customers. The process capabilit y analysis can also serve as an important reference for making decisions for imp roving the global quality of all products. Since C p and C pk are failed to account for process centering, the index C pm is developed. The index C pm takes the process centering into consideration and is su itable for the processes with nominal-the-best type. There are other indices l ike C pu and C pl, and those indices are used for unilateral s pecification processes. Chou (1994) developed a procedure using estimators of C p, C pu and C pl for practitioners to determine whether two p rocesses are equal capability or not. For bilateral specifications processes, i ndex C p is failed to measure process yield and process centering. Thus, th e index C pm is used to develop a similar procedure for practitioners t o determine whether two processes are equal capability or not. The decisions mad e using the procedure to select the better supplier are, of course, more reliabl e.

关键词： process capability indices test statistic proce ss yield process centering