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1
Content available remote Mimicking the morphology of long bone
100%
Ficai A. , Andronescu E. , Ficai D. , Sonmez M. , Albu M. , Voicu G.
Open Chemistry
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2012
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tom 10
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nr 6
1949-1953
EN
The aim of this work was to mimic the stratified structure of the median region of long bones. Starting from this desideratum, more COLL/HA composite materials with different morphology were synthesized and characterized, each of these materials mimicking one layer of long bone (endo- and periosteum, compact and cancellous bony tissue). Stratified bone grafts were obtained by assembling these layers; the obtained grafts were similar to the median region of long bones. Even though, natural bones have a more complex microstructure, this is a pioneering work since for the first time a stratified COLL/HA composite material similar to bone was produced. [...]
2
Content available remote Preparation and characterization of alumina-zirconia composite material with different acid ratios by the sol-gel method
100%
Ergu O. , Gürü M. , Cabbar C.
Open Chemistry
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2008
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tom 6
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nr 3
482-487
EN
Alumina-zirconia composite materials were produced with different acid ratios by the sol-gel method using aluminum isopropoxide and zirconium chloride. The composites were produced by changing acid/alkoxside ratio in alumina. The composite materials were calcinated at 600°C, 900°C and 1300°C. The effects of acid concentration and calcination temperature on the surface area and pore radius were determined from the nitrogen adsorption isotherm at 77 K. The density of the composites was also measured. The minimum density of produced material was recorded as 1.35 g cm−3 at an acid/alkoxside ratio of 0.2. The highest specific surface area and pore diameter of the lightest material are 191.86 m2 g−1 and 18.4 Ǻ, respectively. Although pore diameter and specific surface area are not changed at any of the experimental temperatures which were tested by decreasing acid/alkoxside ratio, the density is slightly increased. However, it was observed that the calcination temperature significantly affects the surface area and density of the material. [...]
3
Content available remote Dichotomies for Lorentz spaces
100%
Głąb S. , Strobin F. , Yang C.
Open Mathematics
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2013
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tom 11
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nr 7
1228-1242
EN
Assume that L p,q, $L^{p_1 ,q_1 } ,...,L^{p_n ,q_n } $ are Lorentz spaces. This article studies the question: what is the size of the set $E = \{ (f_1 ,...,f_n ) \in L^{p_{1,} q_1 } \times \cdots \times L^{p_n ,q_n } :f_1 \cdots f_n \in L^{p,q} \} $. We prove the following dichotomy: either $E = L^{p_1 ,q_1 } \times \cdots \times L^{p_n ,q_n } $ or E is σ-porous in $L^{p_1 ,q_1 } \times \cdots \times L^{p_n ,q_n } $, provided 1/p ≠ 1/p 1 + … + 1/p n. In general case we obtain that either $E = L^{p_1 ,q_1 } \times \cdots \times L^{p_n ,q_n } $ or E is meager. This is a generalization of the results for classical L p spaces.
4
Content available remote Descriptive set-theoretical properties of an abstract density operator
100%
Gła̧b S.
Open Mathematics
|
2009
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tom 7
|
nr 4
732-740
EN
Let $$ \mathcal{K} $$(ℝ) stand for the hyperspace of all nonempty compact sets on the real line and let d ±(x;E) denote the (right- or left-hand) Lebesgue density of a measurable set E ⊂ ℝ at a point x∈ ℝ. In [3] it was proved that $$ \{ K \in \mathcal{K}(\mathbb{R}):\forall _x \in K(d^ + (x,K) = 1ord^ - (x,K) = 1)\} $$ is ⊓11-complete. In this paper we define an abstract density operator ⅅ± and we generalize the above result. Some applications are included.
5
Content available remote Application of positron spectroscopy for investigation of threshold space of oil-gas rocks
88%
Arefyev K. , Grafutin V. , Prokopyev E. , Lider A. , Laptev R. , Bordulev Y.
Open Chemistry
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2014
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tom 12
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nr 12
1280-1284
EN
This article considers the possibility of applying the positron annihilation spectroscopy method for investigating the pore space of rocks from oil-gas and methane-coal deposits. The diagnostics of the structure was performed using the method of spectrometry of angular correlation of annihilation rays (ACAR). Using the samples of porous silicon, the authors have shown the applicability of the ACAR method for determination of the average dimensions of spherical and cylindrical nanosized objects and their concentration
6
Content available Hydraulic and Geoelectric relationships of Aquifers Using Vertical Electrical Sounding (VES) in parts of Obudu, Southern Nigeria
88%
Harry T. A. , Ushie1 F. A. , Agbasi O. E.
World Scientific News
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2018
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tom 94
|
nr 2
261-275
EN
Aquifer geoelectric (Formation factor and Porosity) and hydraulic parameters (Transmissivity and Hydraulic Conductivity) were estimated using VES in parts of Obudu, Southern Nigeria. Hydraulic parameters study would help in to reduce additional expenditures in carrying out pumping tests. Hydraulic parameters are used to estimate the groundwater supply potential, protective capacity rating, soil corrosivity and designation. Most of the estimated aquifers have poor protective capacity rating, low designation, smaller withdrawal for local water supply and slightly corrosive. The objectives of this study is to delineate relationship between geoelectric and hydraulic parameters in the study area, There is a strong correlation between hydraulic conductivity (K) with Porosity and Formation Factor respectively as 0.81 and 1.00, while a weak correlation exist between Transmissivity with Porosity and Formation Factor, respectively as 0.11 and 0.15. The regression equation of the hydraulic parameters and geoelectric parameters from the study area are; , , , , where K; Hydraulic Conductivity, T; Transmissivity, F; Formation Factor and ; Porosity. The range of formation factor, porosity, transmissivity and hydraulic conductivity are 11.80 – 132.50, 8.69% - 29.11%, 1.32 – 19.64 and 0.52 – 0.67 respectively.
7
Content available Structure and Mechanical Properties of the CO2 Laser Welded Joint of AZ91 Cast Magnesium Alloy
75%
Dziadoń A. , Musiał E. , Dziadoń A. , Musiał E.
|
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tom 20
|
nr 3
8
Content available Diagnosis of Performance of Four Tillage Methods by Analytical Hierarchy Procedure (AHP) and Overall Tilth Index in Clay Vertisols
63%
Elfadil A. D. , Abbas O. M. , Karar A. B. , Mohammed H. I.
World News of Natural Sciences
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2022
|
tom 44
176-191
EN
This study was carried out during seasons 2018/2019, and 2019/2020, in Tayba Block-the Sudan - Gezira central clay plains, to evaluate the field performance of four land preparation methods using three tillage equipment: chisel plow "intensive tillage", disc harrow "medium tillage", ridger "minimum or reduced tillage" and no tillage machine. An overall tilth index to reflect field performance of tillage methods was determined from four measured soil tilth indicators (bulk density, porosity, aggregate uniformity, and penetration resistance). Diagnosis of land preparation methods was made using analytical hierarchy procedure (AHP) for ranking tilth indicators by weight assignment and determination of overall tilth index using a linear relation. The results show that Bulk density of the soil surface layer was reduced by tillage implements compared to no till. High significant difference at 1 % level was observed between reduced or no tillage and intensive tillage by chisel or disc harrow on average percentage Soil porosity. Bulk density and Soil porosity are inter-related with similar trend. Aggregate stability showed highest value with no till treatment followed by chisel plow, while those obtained by harrow or ridger implements do not differ significantly. Penetration resistance was significantly lowered by tillage implement compared with using no tillage machine. The highest reduction is achieved by disc harrow followed by ridger and the least reduction is made by chisel plow. Penetration resistance is interrelated to Bulk density. Using analytical hierarchy procedure ranked the tillage indicators in descending order by weight values of 1.01, 0.62, 0.29 and 0.12 for Penetration resistance, Bulk density, Porosity, and Aggregate particle stability respectively. The diagnosis of tillage alternatives by development of the overall tillage index resulted in ranking tillage methods in descending order of preference as: ridger, disc harrow, chisel plow, and no tillage machine. It is thus recommended to use reduced tillage "ridging only" as the most technically feasible tillage method achieve an optimal seedbed with minimum energy input.
9
Content available Effects of curing time on the performance of volcanic scoria-based binder concretes
54%
al-Swaidani A. M. , al-Swaidani A. M.
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