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Polyolefin-nanocomposites with special properties by in-situ polymerization

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Frontiers of Chemical Science and Engineering 2018年第3期12卷 555-563页

作者： walter Kaminsky Institute for Technical and Macromolecular Chemistry Department of Chemistry University of Hamburg 20146 Hambtlrg Germany

Exceptionally strong polyolefin nanocompo- sites are synthesized by in-situ polymerization using soluble metallocene/methylaluminoxane （MAO） as cata- lysts in a two-step process. First, the soluble metallocene/ MAO or other single site catalysts are absorbed on the surface of the nanofillers. Then by addition of ethene or propene, a polyolefin film is formed, covering the nanoparticles, layered silicates, or fibers. The resulting polyethylene and polypropylene nanocomposites are characterized by better physical and chemical properties such as stiffness, gas barrier properties, degradation temperatures, and crystallization rates. They show better mechanical properties than materials produced by mechan- ical blending. The thickness of the polyolefin can be controlled by the pressure of ethene or propene and by the polymerization time. Carbon fibers and carbon nanotubes are covered with isotactic or syndiotactic polypropylene. Because of the hydrophobic character of the carbon surface, the polymer is drawn on the fiber. This leads to a reinforced combined polymer with special properties. The crystallization temperature is 10℃ higher and therefore the crystallization rate up to 20 times faster than that of pure syndiotactic polypropylene. The form stability increases by 100% if 3 wt-% of carbon nanotubes are incorporated.

关键词： polyolefin nanocomposites metallocenes methylalttminoxane

Occurrence of organochlorine pollutants in the eggs and dropping-amended soil of Antarctic large animals and its ecological significance

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Science China Earth Sciences 2007年第7期50卷 1086-1096页

作者： Vetter walter Friedrich-Schiller-Universitt Jena Lehrbereich LebensmittelchemieDornburger Str. 25D-07743 JenaGermany

Persistent organochlorine pollutants (POPs) are analyzed for the dropping-amended soils from the habitats of Antarctic seabirds and seals in Fildes Peninsula and Ardley Island. The concentration ranges are 0.21 to 3.85 ng/g for polychlorinated biphenyls (ΣPCBs),0.09 to 2.01 ng/g for organochlorine pesticides (ΣDDT),and 0.06 to 0.76 ng/g for hexachlorocyclohexanes (HCHs). Among these,hepata-chlorobiphenyls,hexachlorobiphenyls,p,p′-DDE and α-HCH compounds are dominant. The concentra-tion ranges of ΣPCB,DDT and HCH in the eggs of skuas were 91.9―515.5 ng/g,56.6―304.4 ng/g and 0.5―2.0 ng/g respectively; those in the eggs of penguins were 0.4―0.9 ng/g,2.4―10.3 ng/g and 0.1― 0.4 ng/g; and those in the eggs of giant petrel were 38.1―81.7 ng/g,12.7―53.7 ng/g and 0.5―1.5 ng/g respectively. The dominant POP compounds in the eggs are PCB180,PCB153,p,p′-DDE and hexa-chlorobenzene (HCB). The present study shows that the concentration of POPs in the sea-bird-inhabited-dropping-amended soil varies with the extent of predation and nest occupancy of dif-ferent seabird populations. Statistical analysis on the POP concentrations from the different seabird eggs implies that the difference in the bio-concentration levels of the birds depends on the bio-habits of the species,such as the range of activity,distance of immigration,feeding pattern,and nest occupation. Among these,the most important factor is the location of the seabirds in the food chain and their feeding pattern. This shows that POPs accumulated in the seabirds resulted from the bio-concentration through the food chain. In addtion,210Pb dating for the dropping-amended soils (AD1-a and AD2) was performed,which provided the POP accumulation rate and the historic record for the soil profile. It indicates that POP will continuously affect the Antarctic ecosystem for a long time.

关键词： persistent organochlorine pollutant animal habitats dropping-amended soil seabird egg Antarctica

Development of an early warning information infrastructure using spatial web services technology

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International Journal of Digital Earth 2010年第4期3卷 384-394页

作者： Kai walter Department of Geodesy and Geoinformatics Institute for Management of Rural AreasFaculty of Agricultural and Environmental SciencesRostock UniversityJustus-von-Liebig-Weg 618059RostockGermany

Current high-performance monitoring and early warning systems are compara-tively expensive and *** project described here aims for a systematic development of a prototypical alarm and early warning system for landslides utilising low-cost ad hoc wireless sensor networks and flexible spatial web service *** web-based services as tools to exchange environmental data is an important step towards addressing today’s larger scale environmental *** project’s information system functions for notification,data access and analysis are implemented utilising Open Geospatial Consortium web service *** to implementing the orchestration of operation workflows and production of near real-time information products are illustrated.

关键词： early warning wireless sensor network Sensor Web Enablement digital earth OGC SLEWS

Perspectives on geospatial information science education:an example of urban planners in Southern Africa

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Geo-Spatial Information Science 2017年第2期20卷 201-208页

作者： walter Musakwa Department of Town and Regional Planning University of JohannesburgDoornfontein CampusJohannesburgSouth Africa

Since the introduction of geographic information systems(GIS)in the 1960s,it has evolved tremendously to an extent that it permeates our daily ***,GIS usage started in the developed countries and now increasingly filtered to developing *** town planning profession was one of the early adopters of *** information is a useful source of data that is needed in urban *** these days of the New Urban Agenda 2030,smart cities are even more required from planners in using geospatial information to face urban challenges such as sustainable urban development and climate *** GIS has promised a lot for urban planning,it has not reached its full ***,many studies have focused on developed countries with limited studies on geospatial information application in municipalities and GIS education from a perspective of developing *** this study,a survey on the usage of geospatial information science(GSIS)in two cities,namely Bulawayo in Zimbabwe and Ekurhuleni in South Africa,was conducted,and an overview of the state of GIS curricula in planning schools is *** results indicate that considerable progress has been made in the application of geospatial information in municipal planning;however,there are impediments limiting the full utilization of geospatial information in local *** impediments include:inadequate GIS curricula in planning schools,lack of resources,and lack of political *** challenges manifest differently in well-resourced municipalities and those with limited *** study proposes planning-relevant GIS curricula to improve the level of GIS use in planning practice.

关键词： Geospatial information science(GSIS) geographic information systems(GIS) urban planning developing countries GIS education municipalities southern africa

Dualities in comparison theorems and bundle-valued generalized harmonic forms on noncompact manifolds

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Science China Mathematics 2021年第7期64卷 1649-1702页

作者： Shihshu walter Wei Department of Mathematics University of OklahomaNormanOK 73019USA

We observe,utilize dualities in differential equations and differential inequalities(see Theorem 2.1),dualities between comparison theorems in differential equations(see Theorems E and 2.2),and obtain dualities in"swapping"comparison theorems in differential *** dualities generate comparison theorems on differential equations of mixed typesⅠandⅡ(see Theorems 2.3 and 2.4)and lead to comparison theorems in Riemannian geometry(see Theorems 2.5 and 2.8)with analytic,geometric,PDE's and physical *** particular,we prove Hessian comparison theorems(see Theorems 3.1-3.5)and Laplacian comparison theorems(see Theorems 2.6,2.7 and 3.1-3.5)under varied radial Ricci curvature,radial curvature,Ricci curvature and sectional curvature assumptions,generalizing and extending the work of Han-Li-Ren-Wei(2014)and Wei(2016).We also extend the notion of function or differential form growth to bundle-valued differential form growth of various types and discuss their interrelationship(see Theorem 5.4).These provide tools in extending the notion,integrability and decomposition of generalized harmonic forms to those of bundle-valued generalized harmonic forms,introducing Condition W for bundle-valued differential forms,and proving the duality theorem and the unity theorem,generalizing the work of Andreotti and Vesentini(1965)and Wei(2020).We then apply Hessian and Laplacian comparison theorems to obtain comparison theorems in mean curvature,generalized sharp Caffarelli-Kohn-Nirenberg type inequalities on Riemannian manifolds,the embedding theorem for weighted Sobolev spaces of functions on manifolds,geometric differential-integral inequalities,generalized sharp Hardy type inequalities on Riemannian manifolds,monotonicity formulas and vanishing theorems for differential forms of degree k with values in vector bundles,such as F-Yang-Mills fields(when F is the identity map,they are Yang-Mills fields),generalized Yang-Mills-Born-Infeld fields on manifolds,Liouville type th

关键词： radial curvature Hessian Laplacian Caffarelli-Kohn-Nirenberg inequality F-harmonic map F-Yang-Mills field

Water transport to the core–mantle boundary

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National Science Review 2021年第4期8卷 13-16页

作者： Michael J.walter Earth and Planets Laboratory Carnegie Institution for Science

Water can have remarkable effects when exposed to rocks at high pressures and temperatures. It can form new minerals with unique properties and often profoundly affects the physical, transport and rheological properti...

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BOUNDARY CONTROL OF TWO PDE'S SEPARATED BY INTERFACE CONDITIONS

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Journal of Systems Science & Complexity 2010年第3期23卷 431-437页

作者： Orazio ARENA walter LITTMAN Dipartimento di Matematica e Applicazioni per l'Architettura Universit di Firenze School of Mathematics University of Minnesota Minneapolis

This paper discusses the null boundary controllability of two PDE's,modeling a compositesolid with different physical properties in each *** conditions are imposed.

关键词： Heat equation interface condition null boundary control Schroinger equation.

Finite boundary effects in problem of a crack perpendicular to and terminating at a bimaterial interface

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Acta Mechanica Sinica 2005年第1期21卷 56-64页

作者： ShaohuaChen TzuchiangWang SharonKao-walter LNM InstituteofMechanicsChineseAcademyofSciencesBeijing100080China DepartmentofMechanicalEngineering BlekingeInstituteofTechnologyS-37179KarlskronaSweden

In this paper, the problem of a crack perpendicular to and terminating at an interface in bimaterial structure with finite boundaries is investigated. The dislocation simulation method and boundary collocation approach are used to derive and solve the basic equations. Two kinds of loading form are considered when the crack lies in a softer or a stiffer material, one is an ideal loading and the other one fits to the practical experiment loading. Complete solutions of the stress field including the T stress are obtained as well as the stress intensity factors. Influences of T stress on the stress field ahead of the crack tip are studied. Finite boundary effects on the stress intensity factors are emphasized. Comparisons with the problem presented by Chen et al. (Int. J. Solids and Structure, 2003, 40, 2731–2755) are discussed also.

关键词： Bimaterial structure Finite boundary Crack Stress intensity factor T stress

Formal Reduction of Interfaces to Large-scale Process Control Systems

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International Journal of Automation and computing 2007年第4期4卷 413-421页

作者： walter Hussak Department of Computer Science Loughborough UniversityLoughborough LE11 3TUUK

A formal methodology is proposed to reduce the amount of information displayed to remote human operators at interfaces to large-scale process control plants of a certain type. The reduction proceeds in two stages. In the first stage, minimal reduced subsets of components, which give full information about the state of the whole system, are generated by determining functional dependencies between components. This is achieved by using a temporal logic proof obligation to check whether the state of all components can be inferred from the state of components in a subset in specified situations that the human operator needs to detect, with respect to a finite state machine model of the system and other human operator behavior. Generation of reduced subsets is automated with the help of a temporal logic model checker. The second stage determines the interconnections between components to be displayed in the reduced system so that the natural overall graphical structure of the system is maintained. A formal definition of an aesthetic for the required subgraph of a graph representation of the full system, containing the reduced subset of components, is given for this purpose. The methodology is demonstrated by a case study.

关键词： Finite state machines process control temporal logic user interfaces user modeling.