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Mechanical Characterisation of Densified Hardwood with Regard to Structural Applications

Journal of Renewable Materials 2020年第9期8卷 1091-1109页

作者： Katharina Müller Walter Sonderegger Oliver Kläusler Michael Klippel edwin zea escamilla Institute of Structural Engineering(IBK) Chair of Structural Engineering–Timber StructuresSwiss Federal Institute of Technology ZurichZurich8093Switzerland Swiss Wood Solutions AG 8600 DübendorfSwitzerlandPreviously at Institute for Building Materials(IfB)Chair of Wood Materials ScienceSwiss Federal Institute of Technology ZurichZurich8093Switzerland College of Civil Engineering Nanjing Forestry UniversityNanjing210037China Sustainable Building Center for Corporate Responsibility and SustainabilityUniversity of ZurichZurich8001Switzerland

The demand for high-performance,yet eco-friendly materials is increasing on all scales from small applications in the car industry,instrument or furniture manufacturing to greater dimensions like floorings,balcony furnishings and even *** offers a good choice on all of these scales and can be modified and improved in many different *** this study,two common European hardwood species,Beech(Fagus sylvatica L.)and Ash(Fraxinus excelsior L.)were densified in radial direction by thermo-mechanical treatment and the densified product was investigated in an extensive characterisation series to determine all relevant mechanical *** in the three main directions(longitudinal,tangential,radial)and tension perpendicular to the grain(tangential,radial)were tested and compared to reference specimens with native *** and modulus of elasticity were determined in all *** addition,a Life Cycle Assessment was carried out to evaluate the environmental impact associated to the densification *** experimental investigations showed that strength and stiffness of hardwood in the longitudinal and tangential directions improve significantly by radial densification,whereas some properties in the radial direction *** Life Cycle Assessment showed that artificial wood drying has higher impact than wood ***,the transport distance of the raw material highly influences the environmental impact of the final densified *** paper then also offers an overview of possible applications in structural timber *** hardwood is a viable option as local reinforcement,where high compressive or tensile strength is *** wood densification process offers an alternative to the use of carbon-intense steel components or hardwoods from tropical forests.

关键词： Hardwood densification high-performance construction materials thermo-mechanical treatment mechanical characterisation life cycle assessment timber structures

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Maize （zea mays L.） Growth and Grain Yield under Conventional and Site-Specific Nitrogen Management in a Dryland Farming System

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Journal of Agricultural Science and Technology(B) 2014年第8期4卷 602-611页

作者： Suzan Mashego Brilliant Mareme Petja Matshwene edwin Moshia Shadrack Batsile Dikgwatlhe Limpopo Department of Agriculture Directorate of Research Services Polokwane 0700 South Africa Department of Plant Production Soil Science andAgricultural Engineering University ofLimpopo Sovenga 0727 South Africa Department of Crop Science Tshwane University of Technology Pretoria 0001 South Africa College of Agronomy and Biotechnology China Agricultural University Beij'ing 100094 China

Large amount of pre-plant nitrogen （N） fertilizer results in low N use efficiency due to poor synchrony between soil N supply and maize N demand, especially during N sensitive growth stages. The objectives of the study were to compare growth and yield of maize （zea rnays L.） under conventional and site-specific N management in a dryland farming system. The study, which was designed as randomized complete block design was conducted over three site-years under continuous maize cropping system in the semi-arid regions of the Limpopo Province in South Africa. Treatments of the study consisted of three N management strategies on a maize field planted to drought resistant SNK 2147 hybrid maize cultivar. Treatments were：（i） no N application （NO）, （ii） site-specific N at variable rates ranging between 18 kg N/ha and 33 kg N/ha based on soil analysis results （N l） and （iii） conventional and uniform N application broadcasted during planting at 58 kg N/ha （N2）. Sufficiency index as indication of N deficiency was determined using CCM-200 on maize leaves based on leaf numbers during maize vegetative growth stages V6, V10 and Vl4, and thereafter N was applied only when needed. The highest maize grain yield of 5.2 Mg/ha for N 1 was significantly higher （P 〈 0.05） than 3.2 Mg/ha and 4.0 Mg/ha of N0 and N2 in site-year I, respectively. Maize grain yield of 2.2 Mg/ha （Nl） at site-year ll was significantly higher （P _〈 0.05） than 1.7 Mg/ha of the NO. The maize growth and yield under N2 and N1 was compared, N1 required between 43% and 69% lesser N fertilizer as compared to N2 over site-years, and resulted in higher maize height, number of leaves per plant, leaf length, and leaf area than that of conventional N management strategy. Therefore, site-specific N management strategy sustains and improves growth and yield of maize using minimal N fertilizer as compared to conventional approach in low fertility soils of semi-arid regions in dryland farming systems. In examining the results of

关键词： Africa maize grain yield nitrogen management precision agriculture

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