Search results for "engineering.material"
showing 10 items of 2352 documents
Determination of the Soret coefficient of magnetic particles in a ferrofluid from the steady and unsteady part of the separation curve
2004
Experiments on the particle separation in a vertical thermodiffusion column are used to investigate the separation (Soret effect) in ferrofluids. The use of a two-sectional column with internal walls of low thermal capacity allows analyzing the initial part of the unsteady separation curves as well as the steady state regime. The Soret coefficient calculated from the measurements of the separation dynamics agrees well with the one found from the steady separation limit reached in long-time experiments especially if the solutal buoyancy is low.
One-dimensional Mixed MHD Convection
2006
The parallel, fully developed flow of an electrically conducting fluid between plane parallel walls under the simultaneous influence of a driving pressure head, buoyancy, and magnetohydrodynamic (MHD) forces is studied. The fluid is assumed to be internally heated and the flow is modeled as one-dimensional and incompressible, while the Boussinesq approximation is adopted for the buoyancy terms. Analytical solutions are obtained for temperature, velocity and electrical potential under different electrical boundary conditions, forced to natural convection intensity ratios and values of the magnetic induction. Generalized working charts are presented which synthetically describe the system''s …
On the influence of gravitational and centrifugal buoyancy on laminar flow and heat transfer in curved pipes and coils
2015
Abstract The effects of gravitational and centrifugal buoyancy on laminar flow and heat transfer in curved and helical pipes were investigated by numerical simulation. Six dimensionless numbers characterizing the problem were identified, and an analysis was conducted on the possible combinations of signs of the gravitational and centrifugal buoyancy effects. Two distinct Richardson numbers were introduced in order to quantify the importance of the two types of buoyancy, and it was shown that, in the case of heating from the wall, a maximum realizable value of the centrifugal Richardson number exists which is a linear function of the curvature δ (ratio of pipe radius a to curvature radius c)…
Apatite and clinopyroxene as tracers for metasomatic processes in nepheline clinopyroxenites of Uralian-Alaskan-type complexes in the Ural Mountains,…
2013
Clinopyroxene and apatite are found to trace metasomatic processes in nepheline-bearing clinopyroxenites (tilaites) from the igneous, mafic-ultramafic Uralian-Alaskan-type complexes of Kytlym and Nizhny Tagil, Ural Mountains, Russian Federation. The clinopyroxenites consist predominantly of coarse-grained, partially to totally altered clinopyroxene phenocrysts in a matrix of fine-grained olivine, clinopyroxene, plagioclase, K-feldspar, and nepheline. Apatite occurs as idiomorphic inclusions (2O-, Na2O-, and Al2O3-bearing fluid. During conversion of the plagioclase, CaO and SiO2 were partitioned into the fluid. Altered areas in the clinopyroxene phenocrysts are characterized by the redistrib…
Laser-Induced Fluorescence Imaging of Paper Surfaces
1993
Laser-induced fluorescence imaging has been used to study the microstructure of paper surfaces. Pulses from a XeCl-excimer laser, 10 ns in duration at 308 nm, were used for excitation, and fluorescence was collected at 420 nm. The excitation spot diameter was approximately 20 µm, and the sampling interval 0.15 mm. Within an area of 5*5 mm2, 1023 sampling points were recorded to generate 3D fluorescence maps of paper surfaces. Papers containing fluorescence whitening agents (FWAs) gave the highest average fluorescence signals. Coated papers with no FW As show weaker signals than the base sheet. For some thirty different paper samples, an obvious correlation between the amount of coating and…
Fluorescence and spin properties of defects in single digit nanodiamonds
2009
International audience; This article reports stable photoluminescence and high-contrast optically detected electron spin resonance (ODESR) from single nitrogen-vacancy (NV) defect centers created within ultrasmall, disperse nanodiamonds of radius less than 4 nm. Unexpectedly, the efficiency for the production of NV fluorescent defects by electron irradiation is found to be independent of the size of the nanocrystals. Fluorescence lifetime imaging shows lifetimes with a mean value of around 17 ns, only slightly longer than the bulk value of the defects. After proper surface cleaning, the dephasing times of the electron spin resonance in the nanocrystals approach values of some microseconds, …
Risk assessment of gypsum amendment on agricultural fields: Effects of sulfate on riverine biota
2022
Gypsum (CaSO4 ∙ 2H2 O) amendment is a promising way of decreasing the phosphorus loading of arable lands, and of thus preventing aquatic eutrophication. However, in freshwaters with low sulfate concentrations, gypsum-released sulfate may pose a threat to the biota. To assess such risks, we performed a series of sulfate toxicity tests in the laboratory and conducted field surveys. These field surveys were associated with a large-scale pilot exercise involving spreading gypsum on agricultural fields covering 18% of the Savijoki River catchment area. The gypsum amendment in such fields resulted in about fourfold increase in the mean sulfate concentration for a 2-month period, and a transient, …
Nanoencapsulation of promising bioactive compounds to improve their absorption, stability, functionality and the appearance of the final food products
2021
The design of functional foods has grown recently as an answer to rising consumers’ concerns and demands for natural, nutritional and healthy food products. Nanoencapsulation is a technique based on enclosing a bioactive compound (BAC) in liquid, solid or gaseous states within a matrix or inert material for preserving the coated substance (food or flavor molecules/ingredients). Nanoencapsulation can improve stability of BACs, improving the regulation of their release at physiologically active sites. Regarding materials for food and nutraceutical applications, the most used are carbohydrate-, protein- or lipid-based alternatives such as chitosan, peptide–chitosan and β-lactoglobulin nanopart…
Applications of fast field cycling NMR relaxometry
2021
Abstract Fast field cycling (FFC) NMR relaxometry is emerging as a powerful tool to investigate physical chemistry properties of many systems in a number of different scientific fields. As an example, it is used to investigate environmental issues such as soil erosion, water, and nutrient dynamics in environmentally relevant porous systems, to discriminate among different kinds of foodstuff in order to understand possible source of adulteration and fraud, to evaluate the properties of new materials, and much more. In the present study, an overview about the possible applications of FFC NMR relaxometry is given. The paper is not intended to be exhaustive. Rather, it is thought to provide an …
Effect of commercial mineral-based additives on composting and compost quality.
2009
Abstract The effectiveness of two commercial additives meant to improve the composting process was studied in a laboratory-scale experiment. Improver A (sulphates and oxides of iron, magnesium, manganese, and zinc mixed with clay) and B (mixture of calcium hydroxide, peroxide, and oxide) were added to source-separated biowaste:peat mixture (1:1, v/v) in proportions recommended by the producers. The composting process ( T , emissions of CO 2 , NH 3 , and CH 4 ) and the quality of the compost (pH, conductivity, C/N ratio, water-soluble NH 4 –N and NO 3 –N, water- and NaOH-soluble low-weight carboxylic acids, nutrients, heavy metals and phytotoxicity to Lepidium sarivum ) were monitored during…