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51.
M. Zamani M. Taghizadeh M. Naser Moghadasi B. S. Virdee 《Analog Integrated Circuits and Signal Processing》2012,71(1):143-150
In this letter, a 5th-Order single-loop low distortion Sigma–Delta Modulator (SDM) is implemented with the combination of
the comparator-based switched-capacitor (CBSC)-based and op-amp-based techniques for asymmetric digital subscriber line (ADSL)
applications. This structure, which uses integrator (CBSC-based) and IIR filter (op-amp-based) concurrently, has relatively
fewer feed-forward paths and modulator coefficients for sensitivity reduction to mismatch. To lower the power consumption
of the modulator, the integrators are implemented with CBSC, the IIR filter block is implemented by single OTA, and a passive
adder is used to realize the adder at the input of the 5-bit quantizer. The design purpose is minimizing the power consumption
while the dynamic performance maintains high. As shown in the simulation result, for a 2-MHz signal bandwidth, the modulator
achieves a dynamic range (DR) of 86.5 dB and a peak signal-to-noise and distortion ratio (SNDR) of 85 dB with an oversampling
ratio of 8. In addition it consumes 18.75 mW from a 1.8-V power supply at 32 MS/s, which obtains a figure of merit of 1.6e−3. 相似文献
52.
Naser Faisal Al Tannak 《化学与化工:英文版》2014,(5):524-529
Naloxone is a well-known opioid antagonist indicated for the treatment of CNS (central nervous system) and respiratory depression induced by natural or synthetic opioid in adults and neonates whose mothers have received opioids. While it has been reported that an injection of 0.2 mg/mL of naloxone hydrochloride is physically and chemically stable, data on photostability on continuous i.v. infusion of 0.2 mg/mL of naloxone hydrochloride has not been reported. Therefore, a method was required for assessment of naloxone hydrochloride photostability. A high performance LC-MS (liquid chromatography/mass spectrometry) method was established to evaluate the photostability of naloxone hydrochloride. Injections of naloxone hydrochloride in 0.9% sodium chloride were exposed to artificial light and stored at room temperature (22 ~C) and 37 ~C. Naloxone losses up to 9.79% of its initial concentration when exposed to light at room temperature for 192 h, but the degradation increased up to 14.91% as the storage temperature increase. The disappearance of naloxone hydrochloride was correlated with the appearance of nor-oxymorphonedegradant. Naloxone hydrochloride is photosensitive and degradation increased at highly temperature and light intensity. Therefore, naloxone i.v. infusion solutions should either be protected from light and/or be frequently replaced when being administered to patients. 相似文献
53.
Shahram?ArbabEmail author Parviz?Noorpanah Naser?Mohammadi Ahmad?Zeinolebadi 《Polymer Bulletin》2011,66(9):1267-1280
Investigation of structural development of acrylic fibers during the early stages of the wet-spinning process has great importance
both in carbon fiber and textile industries. The simultaneous effects of increasing polymer concentration, jet-stretching
and hot-drawing on porosity, morphology, and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied. The
detailed microstructure of the voids was characterized by electron microscopy, porosimetry, and thermoporometry. The effects
of jet-stretching/hot-drawing on the overall porosity of the fibers were negligible below a threshold polymer concentration.
Increasing polymer concentration from 10 to 20 vol.% reduced the total porosity. Hot-drawing was more effective in reducing
the overall porosity of the fibers in comparison with jet-stretching. Stretching and drawing replaced the macrovoids by dense
ligaments but did not change the volume fraction of nanovoids, however, shifted nanovoids size distribution toward smaller
values. In general, Young’s modulus and elongation at break increased by decreasing overall porosity, however, they depended
also on the distribution of voids size and chain orientation along the fiber axis. Strength–diameter correlation showed a
good agreement with the Griffith’s theory. 相似文献
54.
55.
Ahmad Bahmani Nader Hatami Naser Varahram Parviz Davami Mohsen Ostad Shabani 《The International Journal of Advanced Manufacturing Technology》2013,64(9-12):1313-1321
In the present work, a mathematical model was developed based on finite difference method to predict the microporosity distribution in A356 aluminum alloy casting. Heat, mass, and gas conservation equations were solved in this model. Moreover, Darcy’s equation was considered in the mushy zone. Results show that the distribution and concentration of microporosities in cast parts vary with both cooling rate and initial gas content. Simulation results were compared with experimental data where proportionally good agreement with experimental results was found. Finally, a complex cast part was simulated presenting the ability of the model to predict the porosities in industrial cast parts. 相似文献
56.
Elhagag Ahmed Hassan Mohamed Hemida Abd‐Alla Abdel‐Naser Ahmed Zohri Marwa M. Ragaey Shimaa Mohamed Ali 《国际能源研究杂志》2019,43(8):3640-3652
This study demonstrated a biotechnological approach for simultaneous production of low‐cost H2, liquid biofuels, and polyhydroxyalkanoates (PHAs) by solventogenic bacterium (Clostridium beijerinckii) from renewable industrial wastes such as molasses and crude glycerol. C beijerinckii ASU10 (KF372577) exhibited considerable performance for hydrogen production of 5.1 ± 0.84 and 11 ± 0.44 mL H2 h?1 on glycerol and sugarcane molasses, respectively. The total acetone‐butanol‐ethanol (ABE) generation from glycerol and molasses was 9.334 ± 2.98 and 10.831 ± 4.1 g L?1, respectively. ABE productivity (g L?1 h?1) was 0.0486 and 0.0564 with a yield rate (g g?1) up to 0.508 and 0.493 from glycerol and molasses fermentation, respectively. The PHA yields from glycerol and sugarcane molasses were 84.37% and 37.97% of the dried bacterial biomass, respectively. Additionally, the ultrathin section of C beijerinckii ASU10 showed that PHA granules were accumulated more densely on glycerol than molasses. Gas chromatography–mass spectrometry (GC‐MS) analysis confirmed that the PHAs obtained from molasses fermentation included 3‐hydroxybutyrate (47.3%) and 3‐hydroxyoctanoate (52.7%) as the main constituents. Meanwhile, 3‐hydroxybutyrate represented the sole monomer of PHA produced from glycerol fermentation. This study demonstrated that C beijerinckii ASU10 (KF372577) is a potent strain for low‐cost PHA production depending on its high potential to produce high‐energy biofuel and other valuable compounds from utilization of organic waste materials. 相似文献
57.
In addition to the advantage of the lightweight of magnesium alloys, magnesium composites have moderate strength and elastic modulus. The proposed application of magnesium composites as diesel truck pistons makes it necessary to assess their wear performance. Little research data have been discussed on wear behavior of Mg alloy AE42 matrix and its composites. Thus, this paper reports wear behavior of magnesium alloy AE42(Mg–Al–Mn—RE; rare earth) and its composite AE42-C, which contains 23 vol% of randomly oriented carbon short fibers. Materials characterization, including density measurements, hardness testing, microstructures investigation, and compression testing at temperatures of 25, 150,and 300 °C, were conducted. Wear tests were performed under various loads and sliding distances. Wear mechanisms were also proposed based on the examination of worn surfaces using optical microscopy and scanning electron microscopy equipped with EDX(energy-dispersive X-ray spectrometry) analysis system. The hardness of AE42-23 vol% C composite is twice the hardness of the Mg matrix alloy AE42. Significant improvements to yield stress and compressive strength at temperatures of 25, 150, and 300 °C of the composite versus the AE42 alloy are achieved. Wear resistance of the composite is improved considerably versus that of the Mg alloy AE42 at the various sliding distances. Smearing of graphite on the worn surface produces a lubricating film that delays change from mild to severe wear of the composite, especially at high loads. EDX analysis of the worn surface shows oxidation of the matrix alloy at higher wear loads, and this mechanism decreases in the presence of carbon fibers under the same loads. Abrasive wear, oxidation, and plastic deformation are the dominant wear mechanisms for the alloy matrix AE42, whereas mainly abrasive wear is the wear mechanism of AE42-23 vol% C composite under the proposed testing conditions. 相似文献
58.
Alrosan Ayat Alomoush Waleed Norwawi Norita Alswaitti Mohammed Makhadmeh Sharif Naser 《Neural computing & applications》2021,33(5):1671-1697
Neural Computing and Applications - The artificial bee colony (ABC) algorithm is a relatively new algorithm inspired by nature and has been shown to be efficient in contrast to other optimization... 相似文献
59.
Athinarayanan Jegan Jaafari Saleh Ahmed Atiah Hamad Periasamy Vaiyapuri Subbarayan Almanaa Taghreed Naser Abdulaziz Alshatwi Ali A. 《SILICON》2020,12(12):2829-2836
Silicon - Due to the large production of sorghum, the generation of associated agricultural residues, which contain high contents of silica, is inevitable. Also, these agricultural residues are not... 相似文献
60.
Ahlaam T. Nomaan Anas A. Ahmed Naser M. Ahmed M.I. Idris M.R. Hashim Marzaini Rashid 《Ceramics International》2021,47(9):12397-12409
ZnO quantum dots (QDs) with average particle size of 4.4 nm were prepared using a low temperature processing solvothermal route. ZnO QD based thin films were then prepared from the ZnO QD based solution using spin coating technique and annealed at 250, 350 and 450 °C. The average grain size and energy band gap of ZnO were respectively increased and decreased from 5.5 to 22.9 nm and 3.37 to 3.27 eV upon increasing the annealing temperature up to 450 °C. The photoluminescence analysis showed that the as-coated ZnO film and ZnO film annealed at 250 °C have high density of oxygen vacancies; these defects were reduced upon increasing the temperature to 350 and 450 °C. The photoelectric properties of the films were strongly affected by the grain size and the defects present in the films. The photo-to-dark current ratio (PDCR) was decreased from 3723 to 371%, whereas the responsivity was increased from 1.25 to 218 mA/W with the increase of temperature to 450 °C. As-coated and 250 °C-annealed films exhibited better photoresponse than others in terms of PDCR, rise time and fall time due to their larger surface-to-volume ratio, making them promising candidate as electron transport layer in perovskite solar cells. 相似文献