| 91. |
- Abad, Alberto, 1972, et al.
(författare)
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The use of iron oxide as oxygen carrier in a chemical-looping reactor
- 2007
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 86:7-8, s. 1021-1035
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) is a method for the combustion of fuel gas with inherent separation of carbon dioxide. This technique involves the use of two interconnected reactors, an air reactor and a fuel reactor. The oxygen demanded in the fuel combustion is supplied by a solid oxygen carrier, which circulates between both reactors. Fuel gas and air are never mixed and pure CO2 can be obtained from the flue gas exit. This paper presents the results from the use of an iron-based oxygen-carrier in a continuously operating laboratory CLC unit, consisting of two interconnected fluidized beds. Natural gas or syngas was used as fuel, and the thermal power was between 100 and 300 W. Tests were performed at four temperatures: 1073, 1123, 1173 and 1223 K. The prototype was successfully operated for all tests and stable conditions were maintained during the combustion. The same particles were used during 60 h of hot fluidization conditions, whereof 40 h with combustion. The combustion efficiency of syngas was high, about 99% for all experimental conditions. However, in the combustion tests with natural gas, there was unconverted methane in the exit flue gases. Higher temperature and lower fuel flows increase the combustion efficiency, which ranged between 70% and 94% at 1123 K. No signs of agglomeration or mass loss were detected, and the crushing strength of the oxygen carrier particles did not change significantly. Complementary experiments in a batch fluidized bed were made to compare the reactivity of the oxygen carrier particles before and after the 40 h of operation, but the reactivity of the particles was not affected significantly.
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| 92. |
- Abad, Tahereh, 1989, et al.
(författare)
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Universal Fidelity Reduction of Quantum Operations from Weak Dissipation
- 2022
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 129:15
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Tidskriftsartikel (refereegranskat)abstract
- Quantum information processing is in real systems often limited by dissipation, stemming from remaining uncontrolled interaction with microscopic degrees of freedom. Given recent experimental progress, we consider weak dissipation, resulting in a small error probability per operation. Here, we find a simple formula for the fidelity reduction of any desired quantum operation, where the ideal evolution is confined to the computational subspace. Interestingly, this reduction is independent of the specific operation; it depends only on the operation time and the dissipation. Using our formula, we investigate the situation where dissipation in different parts of the system has correlations, which is detrimental for the successful application of quantum error correction. Surprisingly, we find that a large class of correlations gives the same fidelity reduction as uncorrelated dissipation of similar strength.
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| 93. |
- Abadeer, N. S., et al.
(författare)
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Interactions of Bacterial Lipopolysaccharides with Gold Nanorod Surfaces Investigated by Refractometric Sensing
- 2015
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 7:44, s. 24915-24925
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Tidskriftsartikel (refereegranskat)abstract
- The interface between nanoparticles and bacterial surfaces is of great interest for applications in nanomedicine and food safety. Here, we demonstrate that interactions between gold nanorods and bacterial surface molecules are governed by the nanoparticle surface coating. Polymer-coated gold nanorod substrates are exposed to lipopolysaccharides extracted from Pseudomonas aeruginosa, Salmonella enterica and Escherichia coli, and attachment is monitored using localized surface plasmon resonance refractometric sensing. The number of lipopolysaccharide molecules attached per nanorod is calculated from the shift in the plasmon maximum, which results from the change in refractive index after analyte binding. Colloidal gold nanorods in water are also incubated with lip opolysaccharides to demonstrate the effect of lipopolysaccharide concentration on plasmon shift, zeta-potential, and association constant. Both gold nanorod surface charge and surface chemistry affect gold nanorod lipopolysaccharide interactions. In general, anionic lipopolysaccharides was found to attach more effectively to cationic gold nanorods than to neutral or anionic gold nanorods. Some variation in lipopolysaccharide attachment is also observed between the three strains studied, demonstrating the potential complexity of bacteria nanoparticle interactions.
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| 94. |
- Abadei, S., et al.
(författare)
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DC field dependent properties of Na0.5K0.5NbO3/SiO2/Si structures at millimeter-wave frequencies
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:13, s. 1900-1902
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Tidskriftsartikel (refereegranskat)abstract
- Dielectric properties of laser-ablated 0.5-mum-thick c-axis epitaxial Na0.5K0.5NbO3 films on high-resistivity (7.7 Omega cm) silicon SiO2/Si substrate are studied experimentally at frequencies up to 40 GHz. For measurements, planar 0.5-mum-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of Na0.5K0.5NbO3 films. The slot width between the electrodes is 2 or 4 mum. 13% capacitance change at 40 V dc bias and Q factor more than 15 are observed at 40 GHz, which makes the structure useful for applications in electrically tunable millimeter-wave devices.
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| 95. |
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| 96. |
- Abadei, Saeed, 1961
(författare)
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Ferroelectric Thin Films on Si-substrate for Tunable Microwave Applications
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis presents the development of microwave tunable devices based onferroelectric thin films. The main tasks in this work are the fabrication, optimization, andintegration of ferroelectric thin film into Si-MMIC. This work has been motivated byincreased interest on advanced tunable microwave components which meet therequirements of low microwave losses, high tunability, easy to integrate to largersystems, and low cost.Dielectric permittivity, tunability, and loss tangent are the most important parameters,characterizing ferroelectrics for application in tunable microwave devices. Most of theefforts in this work have been devoted to the optimization of film fabrication processes interms of microwave loss reduction. Experimental investigations of these parameters forNa0.5K0.5NbO3 (NKN), (SrTiO3) STO, Ba0.25Sr0.75TiO3 (BSTO) and (Pb, Zr) TiO3 (PZT)films are carried out in a wide frequency, DC bias, and temperature ranges. Thesemeasurements give important information about dispersion, temperature, and dc-fielddependencies of dielectric permittivity and losses. The latter are useful for understandingthe basic physical processes in ferroelectric films and help to optimize film depositionand device fabrication processes in terms of low losses, high tunability, and temperaturestability.Coplanar-plate structure is used to integrate the ferroelectric films into the siliconcircuits. Planar varactors are fabricated by depositing tunable ferroelectric films onSi/SiO2 substrates using laser ablation, RF magnetron sputtering, and sol-gel technique,followed by metal electrode deposition. Different varactor designs based on as straightgap, interdigital gap, and circular gap have been investigated and further used in thecomponents. Experiments show the capability and potential of tunable devices based onferroelectric thin films and confirm that they are competitive with other technologies likesemiconductors at frequency above 20 GHz. It is shown that NKN films in polar phaseare also useful for tunable microwave applications demonstrating low loss and goodtunability in a frequency above 20 GHz. BSTO films, which are in paraelectric phase atroom temperature, are used to fabricate microwave varactors. These varactors are used intwo different phase shifters designs. These tunable devices show more than 60°/dB figureof merit, which is one the best value reported so far.
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| 97. |
- Abadei, Saeed, 1961, et al.
(författare)
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Low-frequency and microwave performances of laser-ablated epitaxialNa 0.5 K 0.5 NbO 3 films on high-resistivitySiO 2 /Si substrates
- 2002
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91, s. 2267-
-
Tidskriftsartikel (refereegranskat)abstract
- The dielectric properties of laser-ablated 0.5-μm-thick c-axis epitaxialNa 0.5 K 0.5 NbO 3 (NKN) films on high-resistivity (>7.7 kΩ cm) siliconSiO 2 /Si substrates are studied experimentally in the temperature interval of 30–320 K and at frequencies of 1.0 MHz–40 GHz. The films are grown by laser ablation from a stoichiometric target. For the measurements, planar 0.5-μm-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of NKN films. The slot width between the electrodes is 2.0 or 4.0 μm. At low frequencies(f 1. At microwave frequencies(f>10 GHz), the voltage dependence of the capacitance is given by the NKN film. More than a 13% capacitance change at 40 V dc bias and a Q factor of more than 15 are observed at 40 GHz, which make the structure useful for applications in electrically tunable millimeter-wave devices
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| 98. |
- Abadei, Saeed, 1961, et al.
(författare)
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Low frequency characterisation of laser ablation deposited thin Na0.5K0.5NbO3 (NKN) films for microwave application
- 2001
-
Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 263:1, s. 173-179
-
Tidskriftsartikel (refereegranskat)abstract
- Experimental results on three types of Na0.5K0.5NbO3 (NKN) film capacitor structures are presented. The epitaxial NKN thin films have been deposited on (100) Si (high resistivity), SiO2/Si (low resistivity) and Pt/Si (low resistivity) substrates using laser ablation deposition. Both straight slot and interdigital electrode have been deposited on top of the NKN films. The leakage current and low frequency dielectric properties (I-V, C-V, tanδ-V) of the structures have been measured at 1 MHz as a function of electric field at room temperature. In all three types of capacitor structures the leakage currents in a-b plane are very small, while along c-axis there are extremely large leakage currents. On low resistivity silicon substrates the tunability of the dielectric permittivity is about 12% and loss tangent is low also. On high resistivity (ρ>10 kOhm cm) silicon substrate the tunability at 1 MHz is extremely high, about 10 times, and the losses are also high. On the other hand at microwave frequencies the losses are small (tanδ
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| 99. |
- Abadei, S., et al.
(författare)
-
Microwave properties of tunable capacitors basee on magnetron sputtered ferroelectric Na0.5K0.5NbO3 film on low and high resistivity silicon substrates
- 2001
-
Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 39:1-4, s. 359-366
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this work, small signal DC voltage dependent dielectric permittivity, loss tangent, and tuneability of magnetron sputtered epitaxial Na0.5K0.5NO3 films are studied experimentally. (100)-oriented Na0.5K0.5NbO3 films are deposited onto SiO2-buffered CMOS grade low resistivity (p = 10-20 cm) and high resistivity (p = 15-45 kcm) silicon substrates. Planar capacitors with 2 or 4 m gaps between electrodes have been fabricated on top of ferroelectric films. These devices have been characterized in the frequency range 1.0 MHz to 50 GHz at temperatures 30 - 300K. Na0.5K0.5NbO3/SiO2/Si structures on high resistivity silicon substrate exhibit C-V performances typical for Metal-Insulator- Semiconductor (MIS) capacitors. At low frequencies, f 1.0 GHz, the large tuneability and large losses are associated with the MIS structure, while at higher microwave frequencies the tuneability is mainly associated with the ferroelectric, film. At 1.0 MHz and room temperature, the tuneability of Na0.5K0.5NbO3/SiO2/Si structures more than 90%, reducing to 10-15 % at 50 GHz. The losses decrease with increasing the DC bias and frequency. A Q-factor more than 15 at 50 GHz is observed. The dielectric permittivity of the Na0.5K0.5NbO3 film is in the range 50-150 at frequencies 0.045-50 GHz. On low resistivity substrate the performance of Na0.5K0.5NbO3 films is completely screened by the high losses in silicon, and the tuneability is negligible. © 2001 Taylor and Francis.
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| 100. |
- Abadikhah, Hossein, 1987, et al.
(författare)
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A hierarchy of dynamic equations for micropolar plates
- 2015
-
Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 357, s. 427-436
-
Tidskriftsartikel (refereegranskat)abstract
- This work considers homogeneous isotropic micropolar plates adopting a power series expansion method in the thickness coordinate. Variationally consistent equations of motion and end boundary conditions are derived in a systematic fashion up to arbitrary order for extensional and flexural displacement cases. The plate equations are asymptotically correct to all studied orders. Numerical results are presented for various orders of the present method, other approximate theories as well as the exact three dimensional theory. The results illustrate that the present approach may render benchmark solutions provided higher order truncations are used, and act as engineering plate equations using low order truncation.
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