E-Collections
http://gyan.iitg.ernet.in/handle/123456789/1
Tue, 26 Jan 2021 10:25:47 GMT2021-01-26T10:25:47ZInvestigation on Different Aspects of the High-Power Coaxial Magnetron and RF windows operating in X-band
http://gyan.iitg.ernet.in/handle/123456789/1796
Investigation on Different Aspects of the High-Power Coaxial Magnetron and RF windows operating in X-band
Joshi, Mohit Kumar
The research deals with the various aspects of megawatt-class X-band pulsed power coaxial magnetron and RF windows. X-band magnetrons have a wide range of applications such as cargo scanning, medical linear accelerator (LINAC), and non-destructive testing and evaluation (NDT&E). High-power X-band magnetron is vital in developing a low cost and portable LINAC, which can also provide medical facilities to remote areas of the country. A systematic design procedure of coaxial magnetron is presented, which includes primary sub-parts such as a coaxial cavity, anode resonator, cathode, output section, unwanted mode suppressors, and frequency tuner. The simulation studies are performed using CST Studio, and some of the results are verified with the results in HFSS simulations. The output performance of the coaxial magnetron is analyzed using particle-in-cell (PIC) simulations. Output peak power of 2.12 MW with 62.04% total efficiency is achieved at 9.2987 GHz. The frequency tuning range is obtained as 9.2987 GHz ± 20 MHz. This thesis also examines high-power overmoded RF windows in X-band. Four ingenious designs of RF windows are proposed; three windows are based on the excitation of TE011 mode, and one window is based on the excitation of TE022 mode. Multiphysics and multipactor analyses are performed for the proposed RF windows.
A new approach for high-power coaxial magnetron using stacked anode resonators is proposed. A modified design of coaxial magnetron is presented with multiple anode resonators placed in a stack and multiple cathodes for high-power microwave generation. Since the output power of the conventional coaxial magnetron (with single anode resonator) is limited, and for high-power requirements, magnetron array is used. The phase-locking mechanism is essential for combining the output powers of multiple magnetrons because of their intrinsic phase inconsistency in the output signal. The proposed design enhances the output power of a coaxial magnetron substantially without requiring complex external circuitry for power combining.
Supervisor: Ratnajit Bhattacharjee
Wed, 01 Jan 2020 00:00:00 GMThttp://gyan.iitg.ernet.in/handle/123456789/17962020-01-01T00:00:00ZAppell series over finite fields and Gaussian hypergeometric series
http://gyan.iitg.ernet.in/handle/123456789/1795
Appell series over finite fields and Gaussian hypergeometric series
Tripathi, Mohit
In this thesis we study classical hypergeometric series and Appell series over finite fields, and find finite field analogues of several product and summation formulas satisfied by the classical hypergeometric series. Hypergeometric functions over finite fields are known as Gaussian hypergeometric series. As an application of the product and summation formulas, we deduce several special vlaues of 2F1, 3F2 and 4F3-Gaussian hypergeometric series. Some of our special values of Gaussian hypergeometric series are evaluated at general arguments of the parameters. Recently, finite field alanogues of Appell series F1, F2 and F3 are introduced and their relations with certain Gaussian hypergeometric series are established. Integral representations of F1, F2 and F3 are used while defining their finite field analogues. However, integral representations of F4 are more complicated than the integral representations of F1, F2 and F3. Therefore, it is not straightforward to find an appropriate finite field analogue of F4 using its integral representations. To overcome this problem, we define finite field analogues of classical Appell series F1, F2 and F3 using purely Gauss sums, and this allows us to define a finite field analogue of the Appell series F4. We then establish finite field analogues of classical identities satisfied by the Appell series and hypergeometric series. As applications, we find several transformation formulas satisfied by the Gaussian hypergeometric series. For example, we express a 4F3-Gaussian hypergeometric series as a sum of Mo 2F1-Gaussian hypergeometric series. We also express 4F3-Gaussian hypergeometric series as a product of two 2F1-Gaussian hypergeometric series. Product formulas for Gaussian hypergeometric series have many significant applications. We find finite field analogues of certain product formulas satistied by the classical hypergeometric series. We express product of two 2F1-Gaussian hypergeometric series as 4F3- and 3F2-Gaussian hypergeometric series. We use properties of Gauss and Jacobi sums and our works on finite field Appell series to deduce these product formulas satisfied by the Gaussian hypergeometric series. We then use these transformations to evaluate explicitly some special values of 4F3- and 3F2-Gaussian hypergeometric series. By counting points on CM elliptic curves over finite fields, Ono found certain special values of 2F1- and 3F2-Gaussian hypergeometric series containing trivial and quadratic characters as parameters. Later, Evans and Greene found special values of certain 3F2-Gaussian hypergeometric series containing arbitrary characters as parameters from where some of the values obtained by Ono follow as special cases. We show that some of the results of Evans and Greene follow from our product formulas including a finite field analogue of the classical Clausen’s identity
Supervisor: Rupam Barman
Fri, 01 Jan 2021 00:00:00 GMThttp://gyan.iitg.ernet.in/handle/123456789/17952021-01-01T00:00:00ZStructural and Photo-physical Properties of Cyclic Aromatic Imides or Anthracene Tethered to Nitrogen-Containing Rings: Sensing of Nitro-phenols
http://gyan.iitg.ernet.in/handle/123456789/1794
Structural and Photo-physical Properties of Cyclic Aromatic Imides or Anthracene Tethered to Nitrogen-Containing Rings: Sensing of Nitro-phenols
Singh, Munendra Pal
Different self-assemblies of cyclic aromatic imides, anthracene and their salts and metal complexes are studied through crystal engineering approach. Properties of Cyclic Imides and anthracene derivatives as well as their different salts and metal complexes with phenolic compounds in solid state are compared with the properties observed in solution.
The content of this thesis has been divided into five chapters. Chapter 1 contains a brief discussions on pharmaceutical applications, molecular or ion recognition properties, coordination chemistry and biological activities of cyclic imide derivatives and their metal complexes. Chapter 2 demonstrates the influence of photoluminescence properties of imidazole tethered cyclic imides upon interacting with mineral acids and nitrophenols. Chapter 3 contains the recognition of organic carboxylic acids and nitrophenols by an imidazole tethered anthracene derivative in solution and solid state. Chapter 4 provides
a conceptual means to detect as well as crystalize out phenolic compounds from water in presence of iron ions. Chapter 5 demonstrates the influence of π-stacking and C–H⋯O interactions on photoluminescence of a dinuclear silver(I), a mononuclear zinc(II) and a cadmium(II) formylbenzoate complex possessing N-(4-pyridylmethyl)-1,8- naphthalimide. The thesis has improvised the scope of pre-designed non-covalent
synthesis utilizing interplay of the weak interactions of cyclic aromatic imides and anthracene derivatives to generate new supramolecular assemblies with interesting optical properties in solid or solution state for molecular and ion recognitions.
Supervisor: J. B. Baruah
Wed, 01 Jan 2020 00:00:00 GMThttp://gyan.iitg.ernet.in/handle/123456789/17942020-01-01T00:00:00ZDevelopment of an efficient photovoltaic thermal collector
http://gyan.iitg.ernet.in/handle/123456789/1793
Development of an efficient photovoltaic thermal collector
Das, Dudul
Due to the rise in greenhouse gas in earth atmosphere and global climate change, attention has been focused on harvesting energy from renewable resources such as solar, wind, hydro, biomass, geothermal tidal, wave, and ocean thermal energy. The global potential of solar energy is higher than the potential of all other renewable energy sources together. Solar energy is primarily harvested using two prominent conversion methods viz. solar thermal and solar photovoltaic (PV). In practice, solar PV conversion is quite common for power generation due to its inbuilt advantages like no moving parts, easy installation, availability of raw material and life of operation. However, PV system suffers from its lower conversion efficiency as well as a decrease in efficiency with the rise in cell temperature. PV cell converts only a small fraction (less than 20%) of irradiance into electrical energy. Infra-red radiation absorbed by the PV reduces the electrical efficiency of the cell. The influence of temperature on the electrical output is significant at higher cell temperature (>42 °C). To address this difficulty, solar photovoltaic-thermal (PV/T) collectors are proposed. PV/T is a promising technology where both electrical and thermal energy generation can be possible. Cooling uniformity and efficiency of the PV/T system are major challenges for its applicability. The present study is formulated to address the current challenges associated with the existing PV/T collectors. A novel thermal model of a PV/T system (tube and sheet type collector) by considering thermal contact resistance between the layers of a PV/T system, individual resistance of each layer and Ohmic heat generation in the PV layer has been carried out. The Root Mean Square Errors (RMSE) of 3.75 K, 1.36 K and 2.71 K were found for the water outlet temperature, glass surface temperature and cell temperature, respectively. The results illustrated that consideration of thermal contact resistance and Ohmic loss at the PV layer increases the accuracy of the model significantly. Based on the numerical investigation, initially two PV/T collectors viz. only tube absorber (M1) and sheet-tube (M2)
configurations were developed. The cells in the PV/T collectors are made of Si-multicrystalline. Both the collectors have vertical oscillating tube assembly pattern. The performance of collectors are extensively studied under outdoor conditions. Higher thermal efficiency has been reported for the collector without absorber sheet. This is due to less resistance to the thermal energy transfer from the top surface of the PV/T collector to the flowing fluid in the tubes as compared to the module with sheet-tube configuration. Two more PV/T collectors namely rectangular spiral (M3) and horizontal oscillating (M4) transparent PV/T collectors without absorber sheet were developed and a comparative
experimental investigation has been carried out. The performance of the M3 collector is found to be superior and hence considered for further investigation. Finally, a form-stable phase change biocomposite has been developed using water hyacinth biochar as matrix. The developed material is applied in the M3 collector for investigation of
cooling uniformity. The results of the experiments demonstrate that the use of PCM- biocomposite improves the cooling uniformity, which further results in the enhancement of electrical output by 18.4%. Furthermore, this arrangement improves the thermal efficiency by 15.7% as compared to the M3 without the PCM- biocomposite. Based on the study M3 collector with PCM-biocomposite is found to be the best amongst all the developed collectors in terms of cooling uniformity, performance and cost.
Supervisor: Pankaj Kalita
Wed, 01 Jan 2020 00:00:00 GMThttp://gyan.iitg.ernet.in/handle/123456789/17932020-01-01T00:00:00Z