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Analysis on the velocity relationship and deceleration of long-rod penetration

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Acta Mechanica Sinica 2019年第4期35卷 852-865页

作者： w.J.Jiao X.w. Chen Department of Modern Mechanics University of Science and Technology of China Hefei230027 China Institute of Systems Engineering China Academy of Engineering Physics Mianyang621999 China The State Key Lab of Explosion Science and Technology Beijing Institute of Technology Beijing100081 China Advanced Research Institute of Multidisciplinary Science Beijing Institute of Technology Beijing 100081 China

The relationship between the average penetration velocity,UˉUˉ,and the initial impact velocity, V0V0,in long-rod penetration has been studied recently. Experimental and simulation results all show the linear relationship between UˉUˉ and V0V0 over a wide range of V0V0 for different combinations of rod and target materials. However, the physical essence has not been fully *** this paper, the Uˉ?V0Uˉ?V0relationship is profoundly analyzed using hydrodynamic model and Alekseevskii-Tate model. Especially, the explicitUˉ?V0Uˉ?V0 relationships are derived fromapproximate solutions of Alekseevskii-Tate model. Besides, the decelerationin long-rod penetration is discussed. The decelerationdegree is quantified by adeceleration index,α=2μˉ/(KΦJp)≈Ypρ?1/2p(ρ?1/2p+ρ?1/2t)V?20α=2μˉ/(KΦJp)≈Ypρp?1/2(ρp?1/2+ρt?1/2)V0?2, which is mostly related to the impact velocity, rod strength and rod/target densities. Thus, the state of penetration process can be identified and designed in experiments.

关键词： Long-rod penetration Average penetration velocity Initial impact velocity Alekseevskii-Tate model Deceleration

Effect of Al addition and heat treatment on the microstructures and corrosion resistance of Mg-Cu alloys

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Journal of Materials Science & Technology 2022年第3期98卷 219-232页

作者： X.w.wang w.wang w.Chen D.M.Chen Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China College of Material Science and Engineering University of Science and Technology of ChinaShenyang 110016China

The effects of Al content and annealing condition on the microstructures and corrosion performances of Mg-3 wt.%Cu-xAl(x=0,4 wt.%,8 wt.%)alloys were *** Mg-3 wt.%Cu alloy contains Mg_(2)Cu phase,but Al-bearing alloys contain MgAlCu and Mg_(17)Al_(12) *** Mg_(2)Cu and MgAlCu phases exhibit much higher Volta potential compared to Mg_(17)Al_(12) and α-Mg,and their volume fractions are related to Al content of alloys and annealing *** weight loss measurement and electrochemical tests are conducted to explore the corrosion performances of *** close relationship between weight loss rate of alloys and volume fraction of Cu-bearing phases indicates that the corrosion performances of alloys can be controlled by adjusting Al content of alloys and annealing conditions.

关键词： Magnesium Intermetallics weight loss EIS(electrochemical impedance spectroscopy)

Approximate solutions of the Alekseevskii–Tate model of long-rod penetration

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Acta Mechanica Sinica 2018年第2期34卷 334-348页

作者： w.J.Jiao X.w.Chen Department of Modern Mechanics University of Science and Technology of China Institute of Systems Engineering China Academy of Engineering Physics Advanced Research Institute for Multidisciplinary Science Beijing Institute of Technology The State Key Lab of Explosion Science and Technology Beijing Institute of Technology

The Alekseevskii–Tate model is the most successful semi-hydrodynamic model applied to long-rod penetration into semi-infinite targets. However, due to the nonlinear nature of the equations, the rod(tail) velocity, penetration velocity, rod length, and penetration depth were obtained implicitly as a function of time and solved numerically By employing a linear approximation to the logarithmic relative rod length, we obtain two sets of explicit approximate algebraic solutions based on the implicit theoretica solution deduced from primitive equations. It is very convenient in the theoretical prediction of the Alekseevskii–Tate model to apply these simple algebraic solutions. In particular, approximate solution 1 shows good agreement with the theoretical(exact) solution, and the first-order perturbation solution obtained by walters et al.(Int. J. Impac Eng. 33:837–846, 2006) can be deemed as a special form of approximate solution 1 in high-speed penetration. Meanwhile, with constant tail velocity and penetration velocity approximate solution 2 has very simple expressions, which is applicable for the qualitative analysis of long-rod penetration. Differences among these two approximate solutions and the theoretical(exact) solution and their respective scopes of application have been discussed, and the inferences with clear physical basis have been drawn. In addition, these two solutions and the first-order perturbation solution are applied to two cases with different initial impact velocity and different penetrator/target combinations to compare with the theoretical(exact) solution. Approximate solution 1 is much closer to the theoretical solution of the Alekseevskii–Tate model than the first-order perturbation solution in both cases, whilst approximate solution 2 brings us a more intuitive understanding of quasi-steady-state penetration.

关键词： Long-rod penetration Alekseevskii–Tate model Theoretical solution Approximate solution Perturbation solution

Free vibration of a sagged cable with attached discrete elements

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Applied Mathematics and Mechanics(English Edition) 2019年第5期40卷 631-648页

作者： w.PAKOS Faculty of Civil Engineering Wroc law University of Science and Technology

An algorithm is presented to analyze the free vibration in a system composed of a cable with discrete elements, e.g., a concentrated mass, a translational spring, and a harmonic oscillator. The vibrations in the cable are modeled and analyzed with the Lagrange multiplier formalism. Some fragments of the investigated structure are modeled with continuously distributed parameters, while the other fragments of the structure are modeled with discrete elements. In this case, the linear model of a cable with a small sag serves as a continuous model, while the elements, e.g., a translational spring, a concentrated mass, and a harmonic oscillator, serve as the discrete elements. The method is based on the analytical solutions in relation to the constituent elements, which, when once derived, can be used to formulate the equations describing various complex systems compatible with an actual structure. The numerical analysis shows that, the method proposed in this paper can be successfully used to select the optimal parameters of a system composed of a cable with discrete elements, e.g., to detune the frequency resonance of some structures.

关键词： free vibration sagged cable with attachments continuous discrete model

Aromatic compound degradation by iron reducing bacteria isolated from irrigated tropical paddy soils

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Journal of Environmental Sciences 2008年第12期20卷 1487-1493页

作者： w.Reichardt University of the Philippines at Diliman(UPD) Marine Science InstituteBolinao Marine Laboratory(BML)-UP Guiguiwanen RdBolinaoThe Philippines

Forty-six candidate phenol/benzoate degrading-iron reducing bacteria were isolated from long term irrigated tropical paddy soils by enrichment *** cultures and some prepared mixed cultures were examined for ferric oxide reduction and phenol/benzoate *** the isolates were iron reducers,but only 56.5%could couple iron reduction to phenol and/or benzoate degradation,as evidenced by depletion of phenol and benzoate after one week *** of degradative capability using Biolog...

关键词： aromatic compounds degradation iron reducing bacteria paddy soil

Effects of site productivity on individual tree maximum basal area growth rates of Eucalyptus pilularis in subtropical Australia

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Journal of Forestry Research 2023年第6期34卷 1659-1668页

作者： P.w.west Forest Research Centre Southern Cross UniversityLismoreNSW 2480Australia

Inventory data were available from 96 plots of even-aged,monoculture,tall-open forests of Eucalyptus pilularis Smith,aged 2-63 years,growing in sub-tropical regions along the east coast of Australia.A model was developed relating the maximum possible stem basal area growth rate of individual trees to their stem basal *** any tree size,this maximum increased as site productivity ***,the size at which this maximum occurred decreased as productivity *** research has shown that,at any stand age,trees of a particular stem basal area are taller on more productive sites than on less productive *** trees incur greater respiratory costs to ensure maintenance of the photo synthetic capacity of their canopies;this reduces their growth *** was concluded that trees with larger basal areas will have the maximum possible growth rate on a less productive site,whilst trees with smaller basal areas will have the maximum possible on a more productive *** model developed may constitute the first stage of a complete individual tree growth model system to predict wood yields from these forests.

关键词： Growth model Individual tree Maximum growth rate Eucalyptus pilularis Physiological eff ects

Applications of Chapman-Richards model to geotechnical engineering

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第6期11卷 1286-1292页

作者： w.Nie w.Guo School of Civil Engineering Nanyang Technical UniversitySingapore Key Laboratory of Coast Civil Structure and Safety of Ministry of Education Tianjin UniversityTianjinChina School of Civil Engineering Tianjin UniversityTianjinChina

In this paper,the Chapman-Richards model is adapted to best fit three types of nonlinear curves that are generally encountered in geotechnical engineering practices,*** degree of consolidation versus time factor curves in one-dimensional consolidation and plane strain consolidation under strip loading,the compressibility and permeability curves of soft clay,and the geometry parameters of geosynthetic tube versus pumping pressure *** methods of determining unknown parameters using the Chapman-Richards model are fully *** is found that the Chapman-Richards model has its range of applications in geotechnical engineering and may provide unique insights into the complexity of geotechnical problems.

关键词： Mathematical modeling Chapman-Richards model Curve-fitting

Adventures Beyond Amdahl's Law:How Power-Performance Measurement and Modeling at Scale Drive Server and Supercomputer Design

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Journal of Computer Science & Technology 2023年第1期38卷 80-86页

作者： Kirk w.Cameron Computer Science Virginia TechWashington D.C.VA 24061U.S.A.

Amdahl’s Law painted a bleak picture for large-scale *** implication was that parallelism was limited and therefore so was potential *** Amdahl’s contribution was seminal and important,it drove others vested in parallel processing to define more clearly why large-scale systems are critical to our future and how they fundamentally provide opportunities for speedup beyond Amdahl’s *** the early 2000s,much like Amdahl,we predicted dire consequences for large-scale systems due to power *** our early work was often dismissed,the implications were clear to some:power would ultimately limit *** this retrospective,we discuss how power-performance measurement and modeling at scale led to contributions that have driven server and supercomputer design for more than a *** the influence of these techniques is now indisputable,we discuss their connections,limits and additional research directions necessary to continue the performance gains our industry is accustomed to.

关键词： Amdahl’s Law speedup power-aware computing power modeling performance modeling performance prediction power measurement

Vascular endothelial growth factor:a double-edged sword in the development of white matter lesions

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Neural Regeneration Research 2025年第1期20卷 191-192页

作者： Narek Manukjan Daniel Fulton Zubair Ahmed wMatthijs Blankesteijn Sébastien Foulquier Department of Pharmacology and Toxicology Maastricht UniversityMaastrichtThe Netherlands CARIM-School for Cardiovascular Diseases Maastricht UniversityMaastrichtThe Netherlands Neuroscience and Ophthalmology Institute of Inflammation and AgeingUniversity of BirminghamEdgbastonBirminghamUK Centre for Trauma Sciences Research University of BirminghamEdgbastonBirminghamUK MHeNs-School for Mental Health and Neuroscience Maastricht UniversityMaastrichtThe Netherlands Department of Neurology Maastricht University Medical CenterMaastrichtThe Netherlands

As the population ages,the burden of age-related diseases becomes ***,over 55 million people suffer from dementia worldwide,with Alzheimer’s disease being the most common ***,it is becoming clearer that underlying vascular pathology such as cerebral small vessel disease(cSVD)may be a more detrimental cause for dementia(Cuadrado-Godia et al.,2018).It is estimated that 10%-30%of the elderly population and 35%-90%of all dementia patients exhibit signs of *** term cSVD refers to pathology affecting the small vessels of the brain,which can lead to lacunar cerebral infarcts,enlarged perivascular spaces,and cortical hemorrhages(Cuadrado-Godia et al.,2018).CSVD is often associated with cognitive decline,gait problems,and dementia(Cuadrado-Godia et al.,2018).

关键词： pathology becoming white