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POLYMER NETWORKS BY MOLECULAR DYNAMICS SIMULATION: FORMATION, THERMAL, STRUCTURAL AND MECHANICAL PROPERTIES

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Chinese Journal of Polymer Science 2013年第1期31卷 21-38页

作者： Rong-liang Wu Ting Li erik Nies Division of Polymer Chemistry and Materials Department of ChemistryThe Leuven Mathematical Modeling and Computational Science Centre (LMCC) and The Leuven Materials Research Centre (LMRC)Katholieke Universiteit Leuven

A molecular dynamics simulation method is presented and used in the study of the formation of polymer networks. We study the formation of networks representing the methylene repeating units as united atoms. The network formation is accomplished by cross-linking polymer chains with dedicated functional end groups. The simulations reveal that during the cross-linking process, initially branched molecules are formed before the gel point; approaching the gel point, larger branched entities are formed through integration of smaller branched molecules, and at the gel point a network spanning the simulation box is obtained; beyond the gel point the network continues to grow through the addition of the remaining molecules of the sol phase onto the gel （the network）; the final completion of the reaction occurs by intra-network connection of dangling ends onto unsaturated cross-linkers. The conformational properties of the strands in the undeformed network are found to be very similar with the conformational properties of the chains before cross-linking. The uniaxial deformation of the formed networks is investigated and the modulus determined from the stress-strain curves shows reciprocal scaling with the precursor chain length for networks formed from sufficiently large precursor chains （N≥ 20）.

关键词： Crosslinking Polymer network Network topology Molecular dynamics Mechanical properties.

Botanicals and plant strengtheners for potato and tomato cultivation in Africa

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Journal of Integrative Agriculture 2020年第2期19卷 406-427页

作者： Tewodros MULUGETA Jean-Baptiste MUHINYUZA Reinette GOUWS-MEYER Lerato MATSAUNYANE erik ANDREASSON erik ALEXANDERSSON Department of Zoological Sciences Addis Ababa UniversityAddis Ababa 1000Ethiopia Department of Biology Kotebe Metropolitan UniversityAddis Ababa 1000Ethiopia College of Agriculture Animal Science and Veterinary Medicine(UR-CAVM)Busogo CampusUniversity of RwandaMusanze 210Rwanda Department of Crop Sciences Tshwane University of TechnologyPretoria 0183South Africa Department of Plant Breeding Agricultural Research Council-Vegetable and Ornamental PlantsPretoria 0001South Africa Department of Plant Protection Biology Swedish University of Agricultural Sciences(SLU)Alnarp SE-23053Sweden

This review provides a summary of botanicals and plant strengtheners that have potential uses for disease and pest management in potato and tomato cultivation in *** discuss their possible use to prevent major diseases and pests which infest potato and tomato,such as early and late blight,bacterial wilt,potato tuber moth,and tomato *** are several examples of the successful uses of botanicals for pathogen and pest control relevant for different African climatic conditions;however,most of these studies have been conducted in vitro and often lack field *** strengtheners(substances that induce and improve crop resistance,yield,and quality)are little studied and used in Africa in comparison to North America and *** possible benefits of using botanicals and plant strengtheners instead of conventional pesticides are discussed here in relation to human health and the environment as well as their modes of action and accessibility to *** of knowledge of the composition and active ingredients of extracts,environmental concerns,uncertainties regarding stability and formulation,lack of legislation and limited support from governments,hamper the development of botanicals and plant strengtheners for use in sustainable African agriculture.

关键词： African agriculture botanicals crop protection pathogen plant strengtheners pesticide pests diseases potato tomato

Simulation of the response of base-isolated buildings under earthquake excitations considering soil flexibility

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Earthquake Engineering and Engineering Vibration 2012年第3期11卷 359-374页

作者： Sayed Mahmoud Per-erik Austrell Robert Jankowski Department of Construction Sciences Division of Structural MechanicsLund University Faculty of Engineering at Mataria Helwan University Faculty of Civil and Environmental Engineering Gdansk University of Technology

The accurate analysis of the seismic response of isolated structures requires incorporation of the flexibility of supporting soil. However, it is often customary to idealize the soil as rigid during the analysis of such structures. In this paper, seismic response time history analyses of base-isolated buildings modelled as linear single degree-of-freedom （SDOF） and multi degree-of-freedom （MDOF） systems with linear and nonlinear base models considering and ignoring the flexibility of supporting soil are conducted. The flexibility of supporting soil is modelled through a lumped parameter model consisting of swaying and rocking spring-dashpots. In the analysis, a large number of parametric studies for different earthquake excitations with three different peak ground acceleration （PGA） levels, different natural periods of the building models, and different shear wave velocities in the soil are considered. For the isolation system, laminated rubber bearings （LRBs） as well as high damping rubber bearings （HDRBs） are used. Responses of the isolated buildings with and without SSI are compared under different ground motions leading to the following conclusions：（1） soil flexibility may considerably influence the stiff superstructure response and may only slightly influence the response of the flexible structures; （2） the use of HDRBs for the isolation system induces higher structural peak responses with SSI compared to the system with LRBs; （3） although the peak response is affected by the incorporation of soil flexibility, it appears insensitive to the variation of shear wave velocity in the soil; （4） the response amplifications of the SDOF system become closer to unit with the increase in the natural period of the building, indicating an inverse relationship between SSI effects and natural periods for all the considered ground motions, base isolations and shear wave velocities; （5） the incorporation of SSI increases the number of significant cycles of large amplitude acce

关键词： base-isolated buildings rubber bearings earthquakes soil-structure interaction

Controlling Membrane Phase Separation of Polymersomes for Programmed Drug Release

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Chinese Journal of Polymer Science 2022年第9期40卷 1006-1015页

作者： Shuai Chen erik Jan Cornel Jian-Zhong Du Department of Orthopedics Shanghai Tenth People’s HospitalSchool of MedicineTongji UniversityShanghai 200072China Department of Polymeric Materials School of Materials Science and EngineeringTongji UniversityShanghai 201804China

Programmed release of small molecular drugs from polymersomes is of great importance in drug delivery.A significant challenge is to adjust the membrane permeability in a well-controlled ***,we propose a strategy for controlling membrane phase separation by photo-cross-linking of the membrane-forming blocks with different molecular *** synthesized three amphiphilic block copolymers with different membrane-forming blocks,which are poly(ethylene oxide)_(43)-b-poly((ε-caprolactone)_(45)-stat-((α-(cinnamoyloxymethyl)-1,2,3-triazol)caprolactone)_(25))(PEO_(43)-b-P(CL_(45)-stat-CTCL_(25))),PEO_(43)-b-P(CL_(108)-stat-CTCL_(16)),and PEO_(43)-b-PCTCL_(4)-b-PCL_(79).These polymers were self-assembled into polymersomes using either a solvent-switch or powder rehydration method,and the obtained polymersomes were characterized by dynamic light scattering and transmission electron *** the phase separation patterns within the polymersome membranes were investigated by mesoscopic dynamics(MesoDyn)*** further confirm the change of the membrane permeability that resulted from the phase separation within the membrane,doxorubicin,as a small molecular drug,was loaded and released from the *** to the incompatibility between membrane-forming moieties(PCTCL and PCL),phase separation occurs and the release rate can be tuned by controlling the membrane phase pattern or by ***,besides the compacting effect by formation of chemical bonds in the membrane,the cross-linking process can act as a driving force to facilitate the rearrangement and re-orientation of the phase pattern,which also influences the drug release behavior by modulating the cross-membrane distribution of the amorphous PCTCL *** this way,the strategy of focusing on the membrane phase separation for the preparation of the polymersomes with finely tunable drug release rate can be envisioned and designed accordingly,which is of great signifi

关键词： Polymersome Drug delivery Phase separation Programmed drug release

Experimental Investigation of Effects of Reynolds Number and Incidence Angle on Secondary Flow within a Linear Blade Cascade

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Journal of Thermal Science 2021年第6期30卷 2122-2136页

作者： FLÍDR erik JELÍNEK Tomáš KLADRUBSKÝMilan Laboratory of High Speed Aerodynamics Czech Aerospace Research CenterBeranovych 130Prague 19905Czech Republic

The kinetic energy loss and the secondary loss downstream of a high turning nozzle cascade were *** of the incidence angle(i=-25°,0°and 25°)and Reynolds number(Re_(2,is)=0.8×10^(5),1.2×10^(5),2.5×10^(5) and 4.5×10^(5))were studied on two cascade configurations defined by different pitch to chord ratio(t/c=0.6 and 0.9),*** at the cascade inlet were performed by means of Preston tube,while at the cascade outlet by means of miniature pyramid five-hole pressure *** effect of studied parameters on the flow field at the cascade outlet was shown by the distribution of the kinetic energy loss,secondary loss,mix-out loss and streamwise vorticity.

关键词： linear blade cascade secondary loss pressure measurement

Comparison of the Kobayashi-Royden and Sibony metrics on ring domains

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Science China Mathematics 2009年第12期52卷 2610-2616页

作者： FORN■SS John erik Department of Mathematics University of MichiganAnn ArborMichigan 48109USA

In this paper we show that the Kobayashi-Royden metric and the Sibony metric are different on ring domains,i.e.,the difference of two concentric balls,in higher dimension.

关键词： Kobayashi-Royden metric Sibony metric ring domain 32F45 32U05

Note on Resonant and Non-resonant Peaks in Electron-Atom Total Scattering Cross Sections

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Communications in Theoretical Physics 2018年第1期69卷 28-30页

作者： Karl-erik Thylwe Patrick McCabe KTH-Mechanics Royal lnstitute of Technology CCDC

Certain broad low-energy peaks caused by a single partial wave in total cross sections are explained in terms of phase shifts. Such peaks have been associated with the real part of a Regge pole trajectory, having a maximum near an integer value of the angular momentum quantum number. At the peak energies, the pertinent partial-wave phase shift was shown to have a local maximum near a value π/2 modulo π. This implies no time delay in the semiclassical context. The phenomenon is a quantum effect, lacking a semiclassical interpretation.

关键词： scattering resonances quantum mechanics cross sections

Ultrasonic prediction of crack density using machine learning:A numerical investigation

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Geoscience Frontiers 2022年第1期13卷 114-126页

作者： Sadegh Karimpouli Pejman Tahmasebi erik HSaenger Mining Engineering Group Faculty of EngineeringUniversity of ZanjanZanjanIran Department of Petroleum Engineering University of WyomingLaramieWY 82071USA Bochum University of Applied Sciences 44801 BochumGermany Fraunhofer IEG Fraunhofer Research Institution for Energy Infrastructure and Geothermal Systems44801 BochumGermany Ruhr-University Bochum 44801 BochumGermany

Cracks are accounted as the most destructive discontinuity in rock, soil, and concrete. Enhancing our knowledge from their properties such as crack distribution, density, and/or aspect ratio is crucial in geo-systems. The most well-known mechanical parameter for such an evaluation is wave velocity through which one can qualitatively or quantitatively characterize the porous media. In small scales, such information is obtained using the ultrasonic pulse velocity(UPV) technique as a non-destructive test. In large-scale geo-systems, however, it is inverted from seismic data. In this paper, we take advantage of the recent advancements in machine learning(ML) for analyzing wave signals and predict rock properties such as crack density(CD) – the number of cracks per unit volume. To this end, we designed numerical models with different CDs and, using the rotated staggered finite-difference grid(RSG) technique, simulated wave propagation. Two ML networks, namely Convolutional Neural Networks(CNN) and Long Short-Term Memory(LSTM), are then used to predict CD values. Results show that, by selecting an optimum value for wavelength to crack length ratio, the accuracy of predictions of test data can reach R2> 96% with mean square error(MSE) < 25e-4(normalized values). Overall, we found that:(i) performance of both CNN and LSTM is highly promising,(ii) accuracy of the transmitted signals is slightly higher than the reflected signals,(iii) accuracy of 2D signals is marginally higher than 1D signals,(iv)accuracy of horizontal and vertical component signals are comparable,(v) accuracy of coda signals is less when the whole signals are used. Our results, thus, reveal that the ML methods can provide rapid solutions and estimations for crack density, without the necessity of further modeling.

关键词： Machine learning Crack density Ultrasonic wave Numerical computation

On Calculations of Legendre Functions and Associated Legendre Functions of the First Kind of Complex Degree

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Communications in Theoretical Physics 2015年第7期64卷 9-12页

作者： Karl-erik Thylwe Patrick McCabe KTH-Mechanics Royal Institute of Technology CCDC

Formulas for calculating Legendre functions and associated Legendre functions of the first kind of complex degree using an Ermakov–Lewis invariant are presented. These formulas are straight-forward to implement numerically and are motivated by the lack of computational routines in standard university tools like those of Mat Lab and *** waves propagating in opposite directions are also obtained. The results are particularly useful in complex angular momentum theories and nearside/farside analysis of spin-dependent angular scattering from central potentials.

关键词： ordinary differential equations scattering theory