Hybrid aluminum composites obtained with stir casting were investigated in this study. Aluminum alloy EN AW 6061 was reinforced with particles of Al2O3 and walnut-shell ash (WSA). The weight fraction ...of Al2O3 was constant (5 w/%) and for the walnut-shell ash, it was (1, 2 and 3) w/%. The morphology of the composites and particle distribution were examined with an optical microscope and scanning electron microscope. Microstructural studies showed a uniform distribution of the reinforced particles in all the investigated samples. A chemical analysis of the reinforcing particles on the samples’ surfaces was done using an energy-dispersive spectrometer. The changes in the mechanical properties including the hardness, tensile strength and elongation in relation to the increase in the weight fraction of ash were investigated. The results showed that the hardness and tensile strength increase, while the elongation decreases with an increase in the weight fraction of ash in the composites. The mechanical properties of the obtained composites showed improvement compared to the EN AW 6061 alloy.
V preglednem članku se osredotočamo na alternativni pristop varstva krompirja (Solanum tuberosum) pred koloradskim hroščem (Leptinotarsa decemlineata), ki pri nas in v svetu velja za najpomembnejšega ...škodljivca te pomembne poljščine. V prispevku predstavljamo uporabo različnih inertnih prahov za zatiranje tega škodljivca. Osredotočili smo se na kategorizacijo prahov, predstavitev posameznih skupin inertnih prahov in opis ene ali več snovi, ki pripadajo specifični skupini. Poleg splošne predstavitve načinov delovanja posameznih prašiv navajamo tudi praktične zglede uporabe prašiv proti koloradskemu hrošču, s čimer želimo predstaviti potencial različnih prašiv za uporabo v praksi. Ugotavljamo, da veljata lesni pepel in diatomejska zemlja za bolj perspektivna inertna prahova pri zatiranju škodljivih žuželk. Lesni pepel učinkovito deluje proti ličinkam ter v manjši meri tudi na odrasle osebke, diatomejska zemlja pa prav tako vpliva na zmanjšanje številčnosti koloradskega hrošča na krompirju. Ostala inertna prašiva so v strokovni literaturi izpostavljena kot manj učinkovita oz. sploh še niso bila preizkušena ali uporabljena proti temu škodljivcu. Za dokončno določitev učinkovitosti prašiv bodo potrebne nadaljnje raziskave, tako v laboratorijskih razmerah kot na prostem.
In this paper, we report on synthesizing xonotlite, calcium silicate hydrate (CSH), via a hydrothermal reaction using rice husk from the Mekong Delta, Vietnam. The rice husks were burnt at 1000 °C ...for 3 h. Grey rice husk ash was collected, then mixed with Ca(OH)2 at a Ca/Si molar ratio of 1 : 1. This was followed by a hydrothermal reaction at 180 °C for 24 h and 48 h to obtain the xonotlite mineral. Before and after adsorption, 3-mm xonotlite pellets were thoroughly characterized using X-ray diffractometry (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and ultraviolet-visible (UV-VIS) spectroscopy. This material has potential application in chromium(III) removal during a chrome-plating process. The adsorption efficiency of the 3-mm pellet samples reached more than 76 % after 12 h.
Treatment of the sludge from water-purification plants is becoming more and more urgent due to the inability to increase its storage area. To avoid CO2 emissions, the use of non-Portland cement ...binders is recommended. The application of geopolymerization of waste sludge (WS) from water-purification plants is a novel solution. Curing conditions including high temperature, pressure or microwaves enhance the formation of geopolymer bonds. This paper presents the results of a research on the treatment of the WS of the Thu Duc water-purification plant (Vietnam) with the geopolymerization method. Solid phases were prepared by mixing the WS and fly ash (FA). The FA proportions of the solid phases were (10, 40, 70) w/%. The alkali-activated solution (AAS) was a mixture of a 40 w/% NaOH 6M solution and 60 w/% water glass (WG: Na2O.nSiO2 with n = 1.75 and volumetric density r = 1.40 kg/L). The geopolymer materials were mixtures containing an 80 w/% solid phase and a 20 w/% liquid phase of the AAS. Geopolymer samples were formed in a cylindrical steel mold with a diameter of 10 mm at a high pressure. The samples were cured in a 112 W microwave oven for 30 s or in a dryer at 110 °C for 24 h. The compressive strength and volumetric density of both sample groups were determined and compared to each other. The formation of geopolymer bonds was investigated using XRD, FTIR and SEM.
Tired of Weeping Einarsdottir, Jonina
2004, c2004., 20040101
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In this comprehensive and provocative study of maternal reactions to child death in Guinea-Bissau, West Africa, anthropologist Jónína Einarsdóttir challenges the assumption that ...mothers in high-poverty societies will neglect their children and fail to mourn their deaths as a survival strategy. Based on ethnographic fieldwork conducted from 1993 to 1998 among the matrilineal Papel, who reside in the Biombo region, this work includes theoretical discussion of reproductive practices, conceptions of children, childcare customs, interpretations of diseases and death, and infanticide. Einarsdóttir also brings compelling narratives of life experiences and reflections of Papel women.
Messing penning. Voorzijde: naar links varend schip, waaraan sloep is bevestigd; bij mast:man; op achterplecht:man en vlag met wapenschild. Keerzijde: opschrift
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