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exploring tree diversity and stand structure of savanna woodlands in southeastern Sudan

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Journal of Arid Land 2020年第4期12卷 609-617页

作者： Ahmed m m hASOBA Ahmed A h SIDDIG Yousif e YAGOUB Faculty of Forest Sciences and Technology University of GeziraMadani 22212Sudan Faculty of Forestry University of KhartoumKhartoum North 13314Sudan Department of environmental Conservation University of Massachusetts AmherstAmherst 01003USA

Savanna woodlands in Sudan host great biodiversity, provide a plethora of ecosystem goods and services to local communities, and sustain numerous ecological functions. Although the importance of the Acacia trees in these areas is well known, up-to-date information about these woodlands' diversity is limited and changes in their woody vegetation composition, density, diversity and relative frequency are not monitored over time. This study explored tree diversity and stand stage structure in Nuara Reserved Forest, a typical savanna woodland ecosystem in southeastern Sudan. A total of 638 circular sample plots(1000 m^2 for each) were established using a systematic sampling grid method. The distance between plots was 200 m. In each plot, all living trees with diameter at breast height(DBh) ≥5.00 cm were identified and counted, and their DBh values were recorded. From these data, tree composition, diversity, density and stage structure were assessed. There were 12,259 individual trees representing four species(Acacia seyal, Balanites aegyptiaca, Acacia Senegal and Acacia mellifera) that belong to two families. The dominant species was Acacia seyal. Average tree density was 191 trees/hm^2 and the Shannon-Weiner index for trees diversity was 0.204. Overall, young trees comprised 86.30% of the forest. The state of tree richness and density in the study area was low compared to other similar environments in the region and around the world. We recommended adoption of a proper management system that includes monitoring of woody vegetation diversity in this forest, and management actions to enhance tree diversity and sustain ecosystem services to local communities. In addition to care for the dominant Acacia seyal stands, more attention and conservation should be devoted to reestablishing Acacia senegal and Acacia mellifera trees because of their high ecological and economic values for local communities.

关键词： species diversity stand structure savanna woodland ecosystem forest monitoring forest management ecosystem services Nuara Reserved Forest

mechanical properties of Al-15mg_(2)Si composites prepared under different solidification cooling rates

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International Journal of minerals,metallurgy and materials 2022年第6期29卷 1249-1260页

作者： e.Safary R.Taghiabadi m.h.Ghoncheh Department of materials Science and metallurgy Imam Khomeini International UniversityQazvinIran Department of mechanical engineering University of New BrunswickFrederictonNBCanada

The effect of different cooling rates(2.7,5.5,17.1,and 57.5℃/s)on the solidification parameters,microstructure,and mechanical properties of Al-15mg_(2)Si composites was *** results showed that a high cooling rate refined the mg_(2)Si particles and changed their morphology to more compacted forms with less microcracking *** average radius and fraction of primary mg_(2)Si particles decreased from 20μm and 13.5%to about 10μm and 7.3%,respectively,as the cooling rate increased from 2.7 to 57.5℃/*** the cooling rate also improved the distribution of microconstituents and decreased the grain size and volume fraction of *** mechanical properties results revealed that augmenting the cooling rate from 2.7 to about 57.5℃/s increased the hardness and quality index by 25%and245%,*** high cooling rate also changed the fracture mechanism from a brittle-dominated mode to a high-energy ductile mode comprising extensive dimpled zones.

关键词： Al-15mg_(2)Si composite solidification cooling rate thermal analysis mechanical properties

Crashworthiness performance of hybrid kenaf/glass fiber reinforced epoxy tube on winding orientation effect under quasi-static compression load

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Defence Technology（防务技术） 2020年第5期16卷 1051-1061页

作者： A.B.m.Supian S.m.Sapuan m.Y.m.Zuhri e.S.Zainudin h.h.Ya Advanced engineering materials and Composites Research Centre Department of Mechanical and Manufacturing EngineeringUniversiti Putra Malaysia43400UPM SerdangSelangorMalaysia Laboratory of Biocomposite Technology Institute of Tropical Forestry and Forest Products(INTROP)Universiti Putra Malaysia43400UPM SerdangSelangorMalaysia Department of mechanical engineering Universiti Teknologi Petronas32610Seri IskandarPerakMalaysia

This research was aimed to study the effect winding orientation on the crashworthiness performance of hybrid *** specimens tested under quasi-static compression load involve of three winding parameters(q?30,45and 70)of hybrid kenaf/glass fiber reinforced epoxy and glass fiber reinforced epoxy as contrast *** automated filament winding technique has been used in fabrication of hybrid and non-hybrid composite tube and crashworthiness performance was investigated *** effects of winding orientation on energy absorption capabilities and crashworthiness characteristic were investigated through quasi-static compression load and the result are compared with the glass fiber composite tube to justify the capability of hybrid natural/synthetic as energy absorption *** samples proved to enhancing the progressive crushing capability as combination of local buckling,delaminate and brittle fracturing as progressive crushing *** the view of winding orientation aspect,the results of high winding orientation of hybrid composite tube elevated the crush load efficiency,specific energy absorption and energy absorption capability compared to glass composite tube(GFRP).The hybrid kenaf/glass composite tube with high winding orientation showed the best winding orientation to enhance the energy absorber characteristics as energy absorption application.

关键词： composite laminate winding

experimental approaches and analytical technique for determining heavy metals in fallen dust at ferrosilicon production factory in edfu, Aswan,egypt

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2005年第8期6卷 708-718页

作者： SOLTAN m.e RAGeh h.m RAGeh N.m AhmeD m.e Department of Chemistry Faculty of Science at Aswan South Valley UniversityEgypt Department of Chemistry Faculty of Science at Qena South Valley UniversityEgyptDepartment of Chemistry Faculty of Science at Qena South Valley UniversityEgyptDepartment of Environment Egyptian Ferroalloy Edfu AswanEgypt

In this study aimed to evaluate the pollution extent of metals and nonmetals inside and outside the ferrosilicon production factory in edfu, Aswan, egypt, raw materials (quartz, cokes, iron oxides), ferrosilicon alloy, silica fume, dust and suspended dust (at different sites) samples were collected from the factory, and fallen dust samples were collected from outside the factory, horizontally (at different sites and different distance and directions) and vertically (at different floors in the selected buildings). Gravimetric methods, X-ray fluorescence (XRF), flame photometer, wide range carbon determinator and atomic absorption spectroscopy tools were used for elements determination. The results indicating that the fallen dust and its element contents on southern factory walls being higher than those on eastern factory walls may be due to the nature of the dusts and effects of wind force and wind direction. Fallen dust levels in different regions outside the factory were found to be affected by the distance, direction and floors. The nature of dust samples was affected by gravity and the suspended dust in different factory units depended on the work capacity and method of handling materials by personnel in different production units. Silica fume was a complicated problem, had dangerous effect against the workers' health, and was characterized by high concentrations of SiO2(90.6%～93.6%) and heavy metals (mn, 420.6×10-6～520.3×10-6; Fe, 2354×10-6～2685×10-6; Co, 80.7×10-6～101.6×10 6 and Ni,5.3× 10-6～6.05× 10-6). The TSP (Total Suspended Particulate) levels in all factory units were higher than the recommended air quality value (70 μg/m3) under egyptian law. The effect of ferrosilicon factory fallen dust on the surrounding regions decreased with increasing distance between the factory and these regions. The suspended dust samples in the factory units and their components greatly exceeded national and international standards, so health and environmental criteria must be

关键词： Air pollution Dust heavy metals Fallen dust

Li-richening strategy in Li_(2)ZrCl_(6) lattice towards enhanced ionic conductivity

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Journal of energy Chemistry 2023年第4期79卷 348-356页

作者： haochang Zhang Zhaozhe Yu hannan Chen Yongjian Zhou Xiao huang Bingbing Tian Guangxi Key Laboratory of manufacturing Systems and Advanced manufacturing Technology Guilin University of Electronic TechnologyGuilin 541004GuangxiChina International Collaborative Laboratory of 2D materials for Optoelectronics Science and Technology of ministry of education Institute of Microscale OptoelectronicsShenzhen UniversityShenzhen 518060GuangdongChina

All-solid-state Li batteries(ASSLBs) with solid-state electrolytes(SSes) are exciting candidates for nextgeneration energy storage and receive considerable attention owing to their reliability. halide SSes are promising candidates due to their excellent stability against 4 V-class layered cathodes. Compared with Li3InCl6or Li_(3)ScCl_(6), the low ionic conductivity of Li_(2)ZrCl_(6)(LZC) is a challenge despite its low raw-material cost. herein, we report a family of Li-Richened chloride, Li_(2+2x)Zr_(1–x)mxCl_(6), which can be used in highperformance ASSLBs owing to its high ionic conductivity(up to 0.62 mS cm^(-1)). The theoretical(ab initio molecular dynamics simulations) and experimental results prove that the strategy of aliovalent substitution with divalent metals to obtain Li-Richened LZC is effective in improving Li^(+)conductivity in SSes. By combining Li_(2.1)Zr_(0.95)mg_(0.05)Cl_(6)(mg5-LZC) with a Li–In anode and a LiCoO_(2)cathode, a room-temperature ASSLBs with excellent long-term cycling stability(88% capacity retention at 0.3C for 100 cycles) and highrate capability(121 m A h g^(-1)at 1C) is reported. This exploratory work sheds light on improving the Li^(+)conductivity of low-cost LZC-family SSes for constructing high performance ASSLBs.

关键词： Li-richening Li_(2)ZrCl_(6) halide solid electrolyte All-solid-state battery Solid electrochemistry Li^(+)conductivity

modeling of Fully Nonlinear Wave Radiation by Submerged moving Structures Using the higher Order Boundary element method

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Journal of marine Science and Application 2014年第1期13卷 1-10页

作者： m.A.hannan W.Bai K.K.Ang Department of Civil and environmental engineering National University of Singapore

The higher-order boundary element method is applied to the numerical simulation of nonlinear waves radiated by a forced oscillating fully submerged vertical circular cylinder. In this time-domain approach, the mixed boundary value problem based on an eulerian description at each time step is solved using the higher order boundary element method. The 4th-order Runge–Kutta scheme is adopted to update the free water surface boundary conditions expressed in a Lagrangian formulation. Following completion of the numerical model, the problems of radiation(heave) of water waves by a submerged sphere in finite depth are simulated and the computed results are verified against the published numerical results in order to ensure the effectiveness of the model. The validated numerical model is then applied to simulate the nonlinear wave radiation by a fully submerged vertical circular cylinder undergoing various forced sinusoidal motion in otherwise still conditions. The numerical results are obtained for a series of wave radiation problems; the completely submerged cylinder is placed in surging, heaving and combined heave-pitching motions with different drafts, amplitudes and frequencies. The corresponding numerical results of the cylinder motions, wave profiles, and hydrodynamic forces are then compared and explained for all the cases.

关键词： nonlinear wave wave radiation submerged cylinder boundary element method oscillating cylinder

Wear Behavior of PTFe–hydroxyapatite Composite Fabricated by hot-Press Sintering Process

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Acta metallurgica Sinica(english Letters) 2014年第2期27卷 347-351页

作者： h.R.Zafarani m.Abdi m.e.Bahrololoom Department of materials Science and engineering School of EngineeringShiraz University

In the present work, a new biocompatible composite was fabricated by hot-press sinter-bonding of polytet- rafluoroethylene （PTFe）-hydroxyapatite composite. Furthermore, the wear properties of this composite were studied by computer-controlled pin-on-disk type tribometer in reporting volume loss per distance. The investigation was performed in three different fractions of hydroxyapatite （10, 20 and 30 wt%）. In order to improve the bonding between hydroxyapatite and PTFe, and thus to increase the wear properties of the composite, the effect of adding silane-coupling agent was investigated. Furthermore, to simulate the environment of human body, some of the wear tests were carried out in the ringer＇s solution. It was found that the wear resistance is improved at high load. moreover, an optimum fraction of hydroxyapatite （20 wt%） was found in which the best wear resistance is achieved, especially at dry sliding condition. At last, the roles of the factors such as wear load, ringer＇s solution, and silane-coupling agent are described with respect to their influences on the Lancaster wear coefficient.

关键词： hydroxyapatite composite Polymers Silane-coupling agent Wear resistance

The radial evolution of earthward BBFs during substorm

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Science China earth Sciences 2010年第10期53卷 1542-1551页

作者： Reme h DANDOURAS I LUCeK e DUNLOP m Centre d'etude Spatiale des Rayonnements Blackett Laboratory Imperial College London Rutherford Appleton Laboratory

We here study the occurrence rate,probability function of velocity and duration of earthward bursty bulk flows(BBFs) in the Inner Plasma Sheet(IPS,β>0.5) using the data of Cluster in 2001 and *** occurrence rate of earthward BBFs increases with distance from the earth up to ?19 Re,which is in agreement with the previous observations of the radial evolution of *** 54% of earthward BBFs in expansion phase have a velocity larger than 600 km/s,whereas only 38% of earthward BBFs in growth and recovery phases have a velocity larger than 600 km/*** average velocity of earthward BBFs in expansion phase is 732 km/s,larger than those in growth phase(631 km/s) and recovery phase(617 km/s).The durations of earthward BBFs decrease with the decrease of downtail distance from earth due to the braking of earthward *** duration of earthward BBFs in expansion phase is larger than that in growth and recovery *** average durations in growth,expansion,and recovery phases are respectively 49.3,71.5,and 47.6 ***,the ratios of transports of energy of earthward BBFs in growth,expansion,and recovery phases can be estimated to be 0.51:1:***,the earthward BBFs in the expansion phase have the largest capability of the transport of energy and can produce the largest braking effects,such as inertial currents and auroral activities.

关键词： substorm growth expansion recovery duration energy transport

effect of Si on austenite stabilization,martensite morphology,and magnetic properties in Fe-26%Ni-x%Si alloys

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International Journal of minerals,metallurgy and materials 2011年第2期18卷 192-196页

作者： h.Gungunes e.Yasar m.Dikici Science and Arts Faculty Department of Physics Hitit University Science and Arts Faculty Department of Physics Kirikkale University

The effect of Si on the austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si （x=3.5, 5, and 6） alloys have been studied by means of transmission electron microscopy （Tem） and m？ssbauer spectroscopy techniques. Tem observations reveal that the martensite morphology is closely dependent on the Si content. The volume fraction changes of martensite and austenite phases, the hyperfine magnetic field, and isomer shift values have been determined by mssbauer spectroscopy. The m？ssbauer study reveals that the hyperfine magnetic field, the isomer shift values and the volume fraction of martensite decrease with increasing Si content.

关键词： ferrous alloys martensite morphology magnetic properties transmission electron microscopy (Tem) m6ssbauer spectroscopy