1,721,846 research outputs found
Pk_household_access_final
No full textHousehold survey deidentified data for access to surgical care in Pakista
FUEL PROCESSING: MODELLING AND STRUCTURED CATALYTIC REACTORS
No full textEnergy consumption is the important component in the debates of global climate change and sustainable energy future. According to International Energy Agency, world energy consumption will rise by 56% from 2010 to 2050 with 80% share of fossil fuels resulting in increased emissions of greenhouse gases. Research & development is required to supply clean fuel, increase efficiency of energy utilization and eliminate pollutant emissions. Renewable energy (solar, wind etc.,) systems are important but their penetration in the vast existing energy system is slow, painful and highly uncertain. Hydrogen is the proposed solution to future energy availability, environmental challenges and developing new energy industry. Hydrogen is an energy carrier like electricity; can be produced from renewable and non-renewable energy resources (natural gas, petroleum, coal etc.,) through water electrolysis, reforming, gasification etc. Transition from fossil fuel based energy systems to hydrogen based energy systems involves significant scientific, technological and socioeconomic barriers. Hydrogen produced from fossil fuels through fuel processing can be used for stationary and mobile fuel cell based applications and additionally will help to develop hydrogen infrastructure due to its availability at acceptable cost from the existing wide network. Small scale natural gas and petroleum reformers and hydrogen purification technologies represent an important technology for hydrogen production to create hydrogen filling stations that will help for transition to larger hydrogen supply. The doctoral thesis is focused on: (1) modelling in Aspen plus to compare different standalone fuel processor and integrated with auxiliary power unit for syngas and electricity production; (2) preparation, characterization and testing of structured catalytic reactors (monoliths, foams and plate reactor) for methane steam reforming. Chapter 1 describes the introductory materials of fuel processing and structured catalytic reactors. In chapter 2, the performance of the CO preferential oxidation (PROX) process was compared with the CO selective methanation (SMET) one, both applied as the last clean-up process step of a fuel processor unit (FPU) to remove CO from syngas. The FPU was completed with the reformer (autothermal reformer ATR or steam reformer SR) and a non-isothermal water gas shift (NI-WGS) reactor. Furthermore, the reforming of different hydrocarbon fuels, among those most commonly found in service stations (gasoline, light diesel oil and compressed natural gas) was examined. The comparison, in terms of different FPU configurations and fuels, was carried out by a series of steady-state system simulations in Aspen Plus®. In chapter 3, the performances of four different auxiliary power unit (APU) schemes, based on a 5 kWe net proton exchange membrane fuel cell (PEM-FC) stack, are evaluated and compared. The fuel processor section of each APU is characterized by a reformer (autothermal ATR or steam SR), a non-isothermal water gas shift (NI-WGS) reactor and a final syngas catalytic clean-up step: the CO preferential oxidation (PROX) reactor or the CO selective methanation (SMET) one. Furthermore, three hydrocarbon fuels, the most commonly found in service stations (gasoline, light diesel oil and natural gas) are considered as primary fuels. The comparison is carried out examining the results obtained by a series of steady-state system simulations in Aspen Plus® of the four different APU schemes by varying the fed fuel. In chapter 4, performance of Ru/La-Al2O3 catalysts was evaluated over different structures monoliths and foams for methane steam reforming. Structures of different materials, cpsi/ppi were prepared and characterized with different loadings of 1.5%Ru/3%La-Al2O3 catalyst and tested to find optimum loading at S/C of 3.0 with different temperatures and weight hourly space velocity (WHSV). Preparation and characterization of catalyst coated structures were carried out in University of Basque Country, San Sebastian Spain and experimentations were performed in Politecnico di Torino, Italy. In chapter 5, catalyst (5%Pt/Al2O3) preparation, characterization and experimentations were performed to couple methane steam reforming and combustion on alternate side of catalyst (5%Pt/Al2O3) coated plate reactor. Preliminary experimentations were performed to find out the most active side to use for methane steam reforming. Then, performance of catalytic plate reactor was evaluated by coupling both reactions in co-current and counter-current flow arrangement
Fish Swimming Performance: Insights from Theory and Experiments
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Circular intensity differential scattering of light for biophotonics applications
No full textThis thesis demonstrate the application of a label-free, non-invasive biophysical method based on angle-resolved light scattering calculations to characterize different biological samples; virus particles, chromatin fiber, and hierarchical chiral polymers.
Chapter 1 provides an introduction on the foundation of electromagnetic theory, light scattering phenomenon, Mueller scattering matrix and its applications to characterize various samples based on numerical simulations and experimental measurements. A numerical method to calculate light scattering quantities, discrete dipole approximation (DDA) method is discussed. In this thesis we have performed the electromagnetic scattering calculations using the DDA method implemented as ADDA code.
Chapter 2 demonstrates the angle-resolved circularly polarized light scattering calculations to characterize virus model particles. A coronavirus particle is modeled as having a spherical shaped envelope with cylindrical spikes projected from the envelope surface, and the single-stranded RNA genome polymer has been mimicked with a toroidal helix. The influence of genome polymer packaged as a standard helix in the virion core is also demonstrated. We investigated four different electromagnetic models: (i) a nucleated sphere with spikes that is a coronavirus particle, (ii) a nucleated sphere with no spikes, (iii) a homogeneous sphere, and (iv) a respiratory fluid containing a virus particle. The angular pattern of scattered circularly polarized light, the circular intensity differential scattering of light (CIDS), served as a particle's signature. This scattering signature is found sensitive to the chiral parameters that reveal information about the particles. The effect of changes in the RNA polymer, changes in its packaging, number of turns, handedness, and size are demonstrated on the scattering calculations. Additionally, the extinction efficiency, the depolarization ratio, the total scattered intensity, and the effect of changes in the wavelength of incident light on these scattering quantities are investigated. This biophysical method can offer a label-free identification of virus particles and can help understand their interaction with light.
Chapter 3 focus on the the characterization of chromatin organization. Understanding the structural organization of chromatin is essential to comprehend the gene functions. The chromatin
organization changes in the cell cycle, and it conforms to various compaction levels. We investigated a chromatin solenoid model with nucleosomes shaped as cylindrical units arranged in a helical array. The solenoid with spherical-shaped nucleosomes was also modeled. The changes in chiral structural parameters of solenoid induced different compaction levels of chromatin fiber. We calculated the angle-resolved scattering of circularly polarized light to probe the changes in the organization of chromatin fiber in response to the changes in its chiral parameters. The electromagnetic scattering calculations were performed using discrete dipole approximation (DDA). In the chromatin structure,
nucleosomes have internal interactions that affect chromatin compaction. The merit of performing computations with DDA is that it takes into account the internal interactions. We demonstrated sensitivity of the scattering signal's angular behavior to the changes in these chiral parameters: pitch, radius, the handedness of solenoid, number of solenoid turns, the orientation of solenoid, the orientation of nucleosomes, number of nucleosomes, and shape of nucleosomes. These scattering calculations can potentially benefit applying a label-free polarized-light-based approach to characterize chromatin DNA and chiral polymers at the nanoscale level.
Chapter 4 demonstrates the differential scattering of circularly polarized light to characterize the macromolecular structures consisting of hierarchical chirality. We modeled the B-DNA structure composed of a double-helix and a base-pairs helical structure. The angle-resolved scattering of circularly polarized light calculated for the B-DNA shows the additive behavior of the scattering signal contributed from the two individual chirality levels of B-DNA structure, a double-helix and a base-pairs helix. This additive behavior of angle-resolved scattering signal has also been demonstrated for other macromolecular structures comprising different chirality levels; a biological cell is also mimicked as a nucleated sphere, a sphere with a helical nucleus in its core. The individual chiral features of a structure add up to the angle-resolved scattering signal of circularly polarized light produced by the parent structure. These electromagnetic wave scattering calculations can offer a label-free approach to characterize chiral macromolecular structures with hierarchical chirality
Sensitivity and economical analysis of fuel processors based on SR integrated with WGS and PSA for pure hydrogen production from natural gas
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Performance evaluation and comparison of fuel processors integrated with PEM fuel cell based on steam or autothermal reforming and on CO preferential oxidation or selective methanation
No full textThe performances of four different auxiliary power unit (APU) schemes, based on a 5 kWe net proton exchange membrane fuel cell (PEM-FC) stack, are evaluated and compared. The fuel processor section of each APU is characterized by a reformer (autothermal ATR or steam SR), a non-isothermal water gas shift (NI-WGS) reactor and a final syngas catalytic clean-up step: the CO preferential oxidation (PROX) reactor or the CO selective methanation (SMET) one. Furthermore, three hydrocarbon fuels, the most commonly found in service stations (gasoline, light diesel oil and natural gas) are considered as primary fuels. The comparison is carried out examining the results obtained by a series of steady-state system simulations in Aspen Plus® of the four different APU schemes by varying the fed fuel. From the calculated data, the performance of CO-PROX is not very different compared to that of the CO-SMET, but the performance of the SR based APUs is higher than the scheme of the ATR based APUs. The most promising APU scheme with respect to an overall performance target is the scheme fed with natural gas and characterized by a fuel processor chain consisting of SR, NI-WGS and CO-SMET reactors. This processing reactors scheme together with the fuel cell section, notwithstanding having practically the same energy efficiency of the scheme with SR, NI-WGS and CO-PROX reactors, ensures a less complex scheme, higher hydrogen concentration in the syngas, lower air mass rate consumption, the absence of nitrogen in the syngas and higher potential power of the stack anode exhaust. The stack anode exhaust, in fact, is recycled to the fuel processor section, thanks to the presence of methane produced in the final clean-up methanation reacto
Polarization-Resolved Light Scattering Spectroscopy (pLSS) to Study Chromatin-DNA Organization
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