18420 research outputs found
Sort by
Strength of Concrete Structural Element Reinforced by Glass Fiber Knitted Fabric
No full textTradtionall
Preparation and Characterization of Porous Titania Scaffolds for Bone Defect Regeneration
No full textThe main reasons for using bone scaffolds are to provide an environment for bone formation, maintain the space and at the same time supply mechanical support to the skeleton during healing process. Titanium dioxide (TiO2) was chosen as scaffold materials due to is biocompatibility, good osteoconductive properties and high compressive strength compared to other porous bioceramic materials, e.g. hydroxyapatite or bioglass ceramic. The aim of present research was to produce 3D porous titania scaffolds with interconnected pore structure for bone tissue engineering
Graphene Nanosheets Grown on Ni Particles
No full textUltrathin graphite sheets or/and graphene nanosheets were obtained on the surface of
particles of Ni powder. The new method based on well known dissolution and precipitation mechanism of graphene formation on catalyst surface is reported. Fig.1a presents the Ni powder particles with as prepared graphene sheets. Graphene nanosheets can be seen on the surface of Ni beads as grey coating on light beads. Freestanding graphene sheets were obtained after dissolution of Ni. Upon dissolution of the Ni powder is possible disintegration of the coating into the individual graphene sheets or the graphene sheets are formed the carbon body in the form of the original ingot sintered powder of Ni. In the first case graphene samples were obtained by vacuum filtration, in the second after drying of carbon body. SEM images (Fig. 1b) revealed that surface of the bodies consist of randomly aggregated, crumpled sheets closely associated with each other. The thickness of these sheets was determined with XRD by (002) diffraction peak broadening (Fig. 3). The quality of the sheets was estimated by Raman scattering spectra. Obtained by us layers can be defined as a graphene nanosheets. Number of graphene monolayers in these nanosheets controllably varied from 7 to 40
Zināšanu un informācijas plūsmu formalizācija dzīvotspējīgo sistēmu modelim
No full textDzīvotspējīgo sistēmu modelis apraksta pamatsastāvdaļas, no kurām sastāv jebkura sistēma, kas ir spējīga izdzīvot laikā, kā arī pamatprincipus, pēc kuriem šāda sistēma darbojas. Uz šīs teorijas balstīta zināšanu un informācijas plūsmu identifikācija ir ļāvusi konstatēt svarīgākās saites, kurām ir jāpastāv organizācijā, lai tā būtu dzīvotspējīga, tāpat kā šo saišu saturu un dinamiku. Raksta mērķis ir formalizēt identificētās informācijas un zināšanu plūsmas dzīvotspējīgo sistēmu modelī tādā veidā, lai tās varētu izmantot datorsistēmu projektēšanā un izstrādē
Capacitors Mutual Inductance Modeling and Reduction
No full textIn this paper modeling of EMI filter capacitors
and modeling of mutual couplings between them is presented.
The modeling has been done using 3D electromagnetic software
CST MWS. Three capacitor models have been proposed and
verified experimentally. All proposed models during verification
have shown that their performance is high enough to enable PCB
mounted capacitor modeling and mutual inductance modeling
between capacitors. Additionally several mutual inductance
reduction techniques have been proposed, measured and
modeled
Biomimētiska apatīta veidošanās uz titāna dioksīda virsmas simulētajā ķermeņa šķidrumā
No full textBioaktīvs materiāls implantēts organismā tieši saistās ar kaulu nenotiekot
iekapsulēšanās procesam. Tas veido uz virsmas apatīta slāni, kurš gan pēc sastāva,
gan struktūras ir līdzīgs dabīgajam apatītam kaulos un līdz ar to nodrošina labāku
materiāla sasaisti ar organismu un dzīvo audu mijiedarbību ar implantu. Materiāla
bioaktivitāte, kuru būtiski ietekmē virsmas īpašības un morfoloģija, var tikt izvērtēta
in vitro pētījumos simulētajā ķermeņa šķidrumā. Lai veidotos biomimētiskais apatīts,
ir nepieciešamas ķīmiskas funkcionālās grupas uz materiāla virsmas, kas ierosinātu
apatīta nukleāciju.
Kā bioaktīvu implantmateriālu iespējams izmantot titāna dioksīda (TiO2)
keramiku. Darba gaitā izveidoti titāna dioksīda nanopulvera paraugi, kuri termiski
apstrādāti dažādos temperatūru režīmos. Ar UV starojumu apstaroti un neapstaroti
paraugi tiek ievietoti simulētajā ķermeņa šķidrumā uz vairākām dienām. Paraugu
virsma un sastāvs pirms un pēc ievietošanas simulētajā ķermeņa šķidrumā pētīts ar
SEM, XRD, EDS, FTIR un Ramana spektroskopiju. Termiskā apstrāde augstākās
temperatūrās samazina porainību, BET īpatnējo virsmu un palielina rutila īpatsvaru
paraugā, kas samazina apatīta veidošanos uz parauga virsmas
Composite Load–Bearing Element Based on the Perforated Steel Wastes
No full textA question of industrial wastes application is of high importance at the present moment. Repeated using of industrial wastes or recycling is a possible way to increase the effectiveness of structural materials application. In this caseperforated steel tape is considered as a raw material for producing of load-bearing units. A composite materials based on polymer matrix combined with perforated steel material is proposed. Example of load-bearing element based on perforated steel band reinforced polymer (PSBRP) composite is proposed. A manufacturing approach for PSBRP production is outlined
Petroleum Ether - Most Appropriate Solvent for Isolation of Betulin from Birch Outer Bark
No full textIn the industrial processing of birch wood as a by-product accumulates birch outer bark (BOB) which often is burned as a fuel. However, birch bark can also be a promising raw material for compounds with a very broad range of applications - in the field of pharmaceutical, cosmetic, food and material science. In recent decades, attention of scientists has deserved lupane type pentacyclic triterpenes. Betulin is main representative of triterpenes in BOB. Birch bark comprises about 12.50 wt.% of the tree mass from which up to 3.40% is outer bark which contains 25% of betulin. Such a high content of individual compound in natural resources is very uncommon; therefore it makes the isolation of betulin from birch outer bark economically favourable on an industrial scale.
Non-polar hydrocarbons is referred as most selective solvents for isolation of betulin in the extraction process [1]. Therefore, it is necessary to choose the best solvent taking into account important factors such as price, toxicity, etc. Experimental studies showed that the most suitable solvent for the extraction of BOB is petroleum ether with a boiling range of 100-140°C (PE140). It consists of a mixture of hydrocarbons, mainly of heptane, octane, nonane, decane, with an average density of 0.74 kg/m3
