Wyniki wyszukiwania - BazTech

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Ecological assessment of water quality in the Kabul River, Pakistan, using statistical methods

Khuram I., Barinova S., Ahmad N., Ullah A., Ud Din S., Jan S., Hamayun M.

Oceanological and Hydrobiological Studies

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2017

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Vol. 46, No. 2

140--153

EN

We identified 209 species of algae and cyanobacteria at 4 sites in the Kabul River. Green algae, diatoms, and charophytes dominated in the river, which reflects regional features of agricultural activity. Species richness and algal abundance increased down the river. The Water Quality Index characterizes the quality of water down the river as medium to bad. The index of saprobity S reflects Class III water quality. The Water Ecosystem Sustainability Index (WESI) shows contamination with nutrients. According to the River Pollution Index (RPI), waters in the river have low alkalinity and low salinity, and are contaminated with nutrients. Pearson coefficients showed that water temperature plays a major role in the total species richness distribution (0.93*) and in the green algae distribution (0.89*), while cyanobacteria were stimulated also by water salinity (0.91*). Stepwise regression analysis indicated water temperature as the major regional factor that determines riverine algal diversity. Surface plots and Canonical Correspondence Analysis (CCA) showed that salinity, nitrates, temperature, and Biochemical Oxygen Demand (BOD) can be defined as major factors affecting algal diversity. Dendrites mark the upper site of the Warsak Dam as the source of the community species diversity. Bioindication methods can give relevant and stable results of water quality and self-purification assessment that can be employed to monitor the regional water quality.

2

Processing and microwave dielectric properties of Sr5Ta4TiO17 ceramics

Manan A., Ahmad A. S., Ullah A., Shah A. A.

Materials Science Poland

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2017

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Vol. 35, No. 4

767--772

EN

Sr5Ta4TiO17 ceramics was processed via solid state mixed oxide sintering route. X-ray diffraction revealed single phase formation of Sr5Ta4TiO17 ceramics that crystallized into an orthorhombic crystal structure with a space group Pnnm with lattice parameters of a = 5.681 Å, b = 32.542 Å and c = 3.968 Å, refined by the least squares method. The unit cell density (ρth) was 6.71 g/cm3. The microstructure consisted of plate-like grains and the average size was increased from 2 µm to 5 µm with an increase in sintering temperature from 1450 °C to 1575 °C. Optimum microwave dielectric properties, i.e. єr ~ 66, Qufo ~ 8500 GHz and τf ~ 180 ppm/°C, were achieved for Sr5TaTiO17 ceramics sintered at 1550 °C for 4 h.

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Raman spectroscopy and microwave dielectric properties of Sn substituted SrLa4Ti5O17 ceramics

Manan A., Ullah A., Ahmad A. S.

Materials Science Poland

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2016

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Vol. 34, No. 1

1--5

EN

SrLa4Ti5-xSnxO17 (0 ≤ x ≤ 2) ceramics were fabricated through solid state ceramic route and their microwave dielectric properties were investigated in an attempt to tune their temperature coefficient of resonant frequency to zero. The compositions were sintered to single phase SrLa4Ti5 O17 and SrLaa4Ti4,5Sn0,5O17 ceramics at x = 0 and x = 0.5, and SrLa4Ti4-xSnxO17 along with a small amount of La2Ti2O7 at x = 1. The major phase observed at x = 2 was La2Ti2O7 but along with SrLa4Ti4SnO17 and SrLa4Ti4O15 as the secondary phases. Τf decreased from 117 to 23.0 ppm/°C but at the cost of dielectric constant ("r) and quality factor multiplied by resonant frequency (Qufo) which decreased from 65 to 33.6 and 11150 to 4191 GHz, respectively. The optimum microwave dielectric properties, i.e. τf = 38.6 ppm/°C, εr = 45.5 and = 7919 GHz, correspond to the SrLa4Ti5-xSnxO17 composition with x = 1.

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Phase, microstructure and microwave dielectric properties of Mg0:95Ni0:05 Ti0:98Zr0:02O3 ceramics

Manan A., Khan D. N., Ullah A., Ahmad A. S.

Materials Science Poland

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2015

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Vol. 33, No. 1

95--99

EN

Mg0.95Ni0.05 Ti0.98Zr0.02O3 ceramics was prepared via conventional solid-state mixed-oxide route. The phase, microstructure and microwave dielectric properties of the sintered samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and a vector network analyzer. The microstructure comprised of circular and elongated plate-like grains. The semi quantitative analysis (EDS) of the circular and elongated grains revealed the existence of Mg0.95Ni0.05 T2O5 as a secondary phase along with the parent Mg0.95Ni0.05 Ti0.98Zr0.02O3r~17.1, Qufo~195855 ± 2550 GHz and tf ~ -46 ppm/K was achieved for the synthesized Mg0.95Ni0.05 Ti0.98Zr0.02O3 ceramics sintered at 1325 °C for 4 h.

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Phase, microstructure and dielectric properties of 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 ceramics prepared by sol-gel technique

Uddin S., Iqbal Y., Ullah A.

Materials Science Poland

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2013

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Vol. 31, No. 3

410--414

EN

0.94Bi0.5Na0.5TiO3-0.06BaTiO3 ceramics were fabricated by sol-gel technique. The XRD results revealed the formation of a single phase perovskite structured Bi0.5Na0.5TiO3-BaTiO3 at 600 °C. The SEM images showed dense microstructure and the optimum density of the ceramics sintered at 1100 °C was 5.2 g/cm3. The saturation polarization (P s ) was found to be increased with increasing temperature while the remnant polarization (P r ) was found to be increased gradually and then decreased abruptly near 85 °C, which could be attributed to the phase transformation. The coercive electric field (E c ) was found to be decreased gradually with increasing temperature. The maximum value of dielectric constant (ɛ r ) at room temperature was 800 and dielectric loss at 1 MHz was 0.07.