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Reduced-order controller design for uncertain plants is, in general, iterative in nature. This article identifies a class of multivariable plant transfer functions having uncertain parameters, for which a reduced-order controller with integrating action can be designed following a direct synthesis method recently reported in the literature for fixed multivariable plants. The features of observability canonical state-space representation of single-input–single-output plants are exploited to obtain such a class of multivariable plants. The plants are found to have: 1) no finite zeros in the element transfer function; 2) same pole polynomial in each element transfer function of a row; and 3) order equal to the sum of the orders of all row pole polynomials. The proposed control design methodology is applied to a laboratory-based two-degree-of-freedom helicopter system having uncertain parameters. The robust performance behavior of the proposed control is validated through real-time experiments

After over seven decades of production, most reservoirs in the Upper Assam Sedimentary Basin, India, have reached intermediate or late development stages, rendering them suitable for the adoption of enhanced oil recovery (EOR) techniques. Lighter nature of crude oil and favorable mobility ratio in most of these reservoirs opens up avenues for assessment of CO2-EOR, which also offers the added benefit of carbon storage, aligning with global climate change mitigation efforts in addition to incremental oil production. This research aims to evaluate the viability of CO2-EOR and potential for permanent storage within the reservoir, as well as to conduct an in-depth analysis of various mechanisms. The subject reservoir ABC001 is located in the Upper Assam Basin, India, which meets the screening criteria for CO2-EOR evaluation. Various CO2injection strategies have been evaluated in this research, along with the effect of impurities and quantification of trapping mechanisms. The CO2-EOR has the potential to enhance recovery from the reservoir to 43.3%, compared to 39.3% from water flood. Even though the recovery is lesser (42.3%) than CO2injection, CO2water-alternating-gas (WAG) is projected to result in the greatest retention of CO2within the reservoir. A total of 306.7 MM m3and 153.4 MM m3of CO2is injected into the reservoir corresponding to CO2injection and CO2WAG scenarios, out of which around 194.9 MM m3and 68.4 MM m3are produced, leaving behind around 36.5% and 55.4% of CO2in the reservoir, respectively. The CO2-EOR and storage studies conducted in this project will enhance the learning curve, facilitating the development of a knowledge base that can be utilized to broaden CCUS initiatives in India.

ABSTRACTLaser welding of NiTinol is a promising fabrication method. An understanding of the effects of laser heat input on different surface properties and corrosion resistance behaviour is needed for laser-welded sea water-flooded components of NiTinol. Here the effect of laser heat input on various physical, chemical and mechanical surface properties along with the corrosion resistance behaviour of the laser welded samples was investigated. The corrosion resistance performance of the phase-separated samples was found to be inferior to the other laser-welded samples. The top surface showed a superior corrosion resistance performance because of the recirculation of the melt pool and Ti enrichment on top surface.

Laser welding of NiTinol is a promising fabrication method. An understanding of the effects of laser heat input on different surface properties and corrosion resistance behaviour is needed for laser-welded sea water-flooded components of NiTinol. Here the effect of laser heat input on various physical, chemical and mechanical surface properties along with the corrosion resistance behaviour of the laser welded samples was investigated. The corrosion resistance performance of the phase-separated samples was found to be inferior to the other laser-welded samples. The top surface showed a superior corrosion resistance performance because of the recirculation of the melt pool and Ti enrichment on top surface.

Photonic crystals have garnered significant attention in the field of photonics for their exceptional ability to control the flow of light. In this study, we conduct a comprehensive evaluation of 10 materials, namely Lead Sulfide (PbS), Gallium Arsenide (GaAs), Magnesium Fluoride (MgF2), Silicon Dioxide (SiO2), Germanium Dioxide (GeO2), Magnesium Oxide (MgO), Aluminum Oxide (Al2O3), Zinc Oxide (ZnO), Mercury Sulfide (HgS), and Zinc Sulfide (ZnS), in combination with titanium dioxide (TiO2), to determine the material configuration that yields the highest reflection coefficient. Our results reveal that the combination of SiO2–TiO2 emerges as the optimal choice, as it has the maximum reflection coefficient of 0.99508 in comparison with the other evaluated materials. These findings serve as a solid foundation for further exploration, including the investigation of additional materials and the impact of geometric variations on the reflection coefficient.

Enhancement of optical to electrical conversion is vital for improving the efficiency of any solar cell. In recent years, use of thin films instead of bulk wafers has resulted in a huge reduction of production cost, and as such, efficiency enhancement of thin-film solar cells is considered in this study. Though this enhancement depends on several factors, most significant among them is the increase in light absorption within the active material of the solar cell. In this work, various types of grating structures on both sides of active solar cell material for light trapping are studied in detail, and a new type of arrangement of optimized grating structure that significantly improves the light absorption is selected. Enhancement of light absorption for change in dielectric material of the grating structure without changing the active material is also observed. Along with structural optimization, simulated electrical characterization of the samples was also performed, which yields a short-circuit current density of 29.27mA/cm^2 with conversion efficiency of 14.51%, having a fill factor of 0.83 for a typical ultrathin layer of active material of thickness 2 µm. This is quite significant because typical cells of this category have much lesser conversion efficiency.

A metal waveguide of finite width and thickness surrounded by a dielectric provides increased propagation length of the surface plasmon polariton and is therefore called long-range surface plasmon polaritons (LR-SPP). In this work, a new structure is proposed by modifying the refractive index of the dielectric surrounding the metal waveguide, leading to further improvement of the propagation length. It is shown that, when the single dielectric surrounding is replaced by a multilayered surrounding where each layer has different thicknesses and refractive index, the propagation loss gets reduced, leading to increased propagation length of the LR-SPP. The propagation loss is calculated semianalytically from the FWHM of the Lorentzian peak obtained in the plot of excitation efficiency of such waveguide for different values of the propagation constant. Before doing this calculation, the 2D variation of refractive index is first converted into a 1D effective refractive index. All the steps of analysis are discussed in detail, and, wherever necessary, the calculated results are matched with similar results of other researchers.

Metal assisted Porous Silicon formation has been reported using highly uniform nanometer scale silver films, solution-deposited using a chemical reaction. The surface morphology and the angular scattering of the porous silicon formed using this new technique has been studied. The surface morphology is comparable with that obtained using other methods of metal deposition. Moreover it is also revealed that etch depth is better than other stain etching methods and possibly vertical which is the reason for using metal assisted porous silicon etching process in making silicon nanowires. Thus the proposed method is simple, cheap and maintenance free alternative to the conventional methods of metal assisted porous silicon formation. Being a solution deposition method, it can be used to form porous silicon in interior or inaccessible areas.