Weak intermolecular interactions have very strong impact on the structures and properties of life giving molecules like H2O, DNA, RNA etc. These interactions are responsible for many biological phenomena. The directional preference of some of these interactions is used for designing different synthetic approaches in the supramolecular chemistry. The work reported in this Thesis comprises of investigations of weak intermolecular interactions in gas phase using home-built Pulsed Nozzle Fourier Transform Microwave (PN-FTMW) spectrometer as an experimental tool and ab-initio and Atoms in Molecules (AIM) theory as theoretical tools. The spectrometer which is coupled with a pulsed nozzle is used to record pure rotational spectra of the molecular clusters in a jet cooled molecular beam. In the molecular beam molecules/complexes are free from interactions with other molecules/complexes and thus, spectroscopy in the molecular beams provides information about the 'isolated' molecule/complex under investigation. The rotational spectra of the molecules/complexes in the molecular beam provide their geometry in the ground vibrational states. These experimental geometries can be used to test the performance and accuracy of theoretical models like ab-initio theory, when applied to the weakly bound complexes. Further the AIM theory can be used to gain insights into the nature and strength of the intermolecular interactions present in the system under investigation. Chapter I of this Thesis gives a brief introduction of intermolecular interactions. Other than hydrogen bonding, which is considered as the most important intermolecular interaction, many other intermolecular interactions involving different atoms have been observed in past few decades. The chapter summarizes all these interactions. The chapter also gives a brief introduction to the experimental and theoretical methods used to probe these interactions. In Chapter II, the experimental and theoretical methods used in this work are summarized. Details of our home-built PN-FTMW spectrometer are given in this chapter. The chapter also discusses briefly the theoretical methods like ab-initio, AIM and Natural bond orbital (NBO) analysis. We have made few changes in the mode of control of one of our delay generators which have also been described. Chapter III and Chapter V of this Thesis are dedicated to the propargyl alcohol complexes. Propargyl alcohol (PA) is a molecule of astrophysical interest. It is also important in combustion chemistry since propargyl radical is considered as the precursor in soot formation. Moreover, PA is a multifunctional molecule, having a hydroxyl (-OH) and an acetylenic (-C≡C-H) group. Both of the groups can individually act as hydrogen bond acceptor as well as donor and thus PA provides an exciting possibility of studying many different types of weak interactions. Due to internal motion of -OH group, PA monomer can exist in gauche as well as trans form. However, rotational spectra of PA-monomer show the presence of only gauche conformer. In Chapter III, rotational spectra of Ar•••PA complex are discussed. The pure rotational spectra of the parent Ar•••PA complex and its two deuterated isotopologues, Ar•••PA-D (OD species) and Ar•••PA-D (CD species), could be observed and fitted within experimental uncertainty. The structural fitting confirmed a structure in which PA is present as gauche conformer and argon interacts with both the O-H group and the acetylenic group leading to Ar•••H-O and Ar•••π interactions respectively. Presence of these interactions was further confirmed by AIM theoretical analysis. In all the three isotopologues c-type rotational transitions showed significant splitting. Splitting patterns in the three isotopologues suggest that it originates mainly due to the large amplitude motion of the hydroxyl group and the motion is weakly coupled with the carbon chain bending motion. No evidence for the complex with trans conformer of PA was found. Although, we could not observe Ar•••trans-PA complex experimentally, we decided to perform ab-initio and AIM theoretical calculations on this complex as well. AIM calculations suggested the presence of Ar•••H-O and a unique Ar•••C interaction in this complex which was later found to be present in the Ar•••methanol complex as well. This prompted us to explore different possible interactions in methanol, other than the well known O-H•••O hydrogen bonding interactions, and eventually led us to an interesting interaction which we termed as carbon bond. Chapter IV discusses carbon bonding interaction in different complexes. Electrostatic potential (ESP) calculations show that tetrahedral face of methane is electron-rich and thus can act as hydrogen/halogen bond acceptor. This has already been observed in many complexes, e.g. CH4•••H2O/HF/HCl/ClF etc., both experimentally and theoretically. However, substitution of one of the hydrogens of methane with -OH leads to complete reversal of the properties of the CH3 tetrahedral face and this face in methanol is electron-deficient. We found that CH3 face in methanol interacts with electron rich sites of HnY molecules and leads to the formation of complexes stabilized by Y•••C-X interactions. This interaction was also found to be present in the complexes of many different CH3X (X=OH/F/Cl/Br/NO2/NF2 etc.) molecules. AIM, NBO and C-X frequency shift analyses suggest that this interaction could be termed as "carbon bond". The carbon bonding interactions could be important in understanding hydrophobic interactions and thus could play an important role in biological phenomena like protein folding. The carbon bonding interaction could also play a significant role in the stabilization of the transition state in SN2 reactions. In Chapter V of this Thesis rotational spectra of propargyl alcohol dimer are discussed. Rotational spectra of the parent dimer and its three deuterated (O-D) isotopologues (two mono-substituted and one bi-substituted) could be recorded and fitted within experimental uncertainty. The fitted rotational constants are close to one of the ab-initio predicted structure. In the dimer also propargyl alcohol exists in the gauche form. Atoms in molecules analysis suggests that the experimentally observed dimer is bound by O-H•••O, O-H•••π and C-H•••π interactions. Chapter VI of the thesis explores the 'electrophore concept'. To observe the rotational spectra of any species and determine its rotational constant by microwave spectroscopy, the species should have a permanent dipole moment. Can we obtain rotational constants of a species having no dipole moment via microwave spectroscopy? Electrophore concept can be used for this purpose. An electrophore is an atom or molecule which could combine with another molecule having no dipole moment thereby forming a complex with a dipole moment, e.g. Argon atom is an electrophore in Ar•••C6H6 complex. The microwave spectra of Ar•••13CC5H6 and Ar•••C6H5D complexes were recorded and fitted. The A rotational constant of these complexes was found to be equal to the C rotational constant of 13CC5H6 and C6H5D molecules respectively and thus we could determine the C rotational constant of microwave 'inactive' 13CC5H6. This concept could be used to obtain the rotational spectra of parallel displaced benzene-dimer if it exists. We recently showed that the square pyramidal Fe(CO)5 can act as hydrogen bond acceptor. Appendix I summarizes the extension of this work and discusses interactions of trigonal bipyramidal Fe(CO)5 with HF, HCl, HBr and ClF. Our initial attempts on generating a chirped pulse to be used in a new broadband spectrometer are summarized in Appendix II. Preliminary investigations on the propargyl•••water complex are summarized in Appendix III.

The importance of weak interactions between molecules to life and all parts of science and engineering is unquestionable and there have been an enormous interest in such interactions. Among all the weak interactions, hydrogen bonding is the most popular and it has enjoyed the most attention of the scientific community. Halogen bonding is gaining more popularity in the recent time, as its importance to biological molecules and crystal engineering has been recognized. In this work, a Pulsed Nozzle Fourier Transform Microwave spectrometer has been used to study the rotational spectra of molecules and hydrogen bonded complexes. Structural information is obtained from the rotational spectra. Ab initio electronic structure, Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) theoretical methods have been used to characterize the weak intermolecular interactions, including hydrogen bonding, halogen bonding and lithium bonding. In Chapter I, introduction to weak interaction is discussed. A brief introduction of different experimental and theoretical methods is presented. Chapter II discusses in detail about the different methods used to investigate weak interaction, both experimentally and theoretically, in this work. In our lab, we use Pulsed Nozzle Fourier Transform Microwave spectrometer to determine the complexes spectra and structures. We generate MW radiation with the help of electronic devices and use Balle-Flygare cavity where molecular interaction takes place. We inject the sample inside the cavity in form of supersonic molecular beam through a pulsed nozzle, parallel to MW radiation. The detailed instrumental discussion about MW spectrometer has been done in this Chapter. We extensively use theoretical methods to probe weak bonding and characterize them. Ab initio and DFT calculations are used to optimize the structure of the complexes and predict their rotational spectra. Atoms in Molecules theory and Natural Bond Orbital theory are then used with the ab initio wave functions to understand the weak interactions in depth. Discussion about these methods and software used for the analysis will also be discussed. In Chapter III, rotational spectrum of Hexafluoroisopropanol (HFIP) monomer is presented. HFIP is an interesting molecule as it offers many possibilities as hydrogen bond donor and acceptor. It has the OH group which can both accept/donate a hydrogen bond and in addition it has a very acidic CH group. It is the only solvent that can dissolve polyethylene terephthalate, a normally difficult-to-dissolve polymer, and clearly it has unique interactions with this difficult to solve polymer. We have recorded and fitted rotational spectra of five different isotopologues of HFIP which helped us in determining its accurate structure. Though, it can exist in synclinical and antiperiplanar conformers, only the later has been detected in our molecular beam spectrometer. This happens to be the global minimum structure of HFIP. Combination of experimental observations and ab initio calculations provided many evidences which confirmed the presence of antiperiplanar conformer, experimentally. Since, the rotational constants for both conformers were very close, it was always challenging to pick up one conformer as experimentally observed structure. A prototype molecule, hexafluoroisobutene (HFIB) shows doubling of rotational transitions due to tunnelling/counter rotation of the two CF3 groups through a small barrier. Interestingly, such motion has no barrier in HFIP and hence no splitting in transitions was observed. Potential energy surface calculated for counter-rotation of the two CF3 groups is consistent with this observation. This barrier is different from eclipsed-staggered exchange barrier, observed by 60 counter rotation of both terminal CF3 groups, for which the barrier height is very large and tunnelling cannot occur. The origin/lack of the small barrier in HFIB/HFIP has been explored using Natural Bond Orbital (NBO) method which helped in understanding intramolecular bonding in these molecules. Along with HFIB, other prototype molecules were also considered for the analysis e.g. hexafluoroacetone, hexafluoroacetone imine, hexafluoroisobutane, hexafluoroisopropylamine. In the last section of this Chapter, we have discussed the generalized behaviour of molecules which have CF3-C-CF3 groups. In Chapter IV, rotational spectrum of HFIP•••H2O complex is presented. Aqueous solution of HFIP stabilizes α-helical structure of protein, a unique property of this solvent. The main objective of this Chapter is understanding the interaction between HFIP and H2O. Microwave spectrum of HFIP•••H2O was predicted and recorded. Three isotopologues were investigated. Though, this complex could in principle have several structural conformers, detailed ab initio calculations predicted two conformers and only one was observed. Though, the rotational constants for both structures were somewhat similar, lack of a dipole transitions, larger intensity of b-dipole transitions over c-dipole transitions and isotopic substitution analysis positively confirm the structure in which HFIP acts as the hydrogen bond donor. The linear O-H•••O hydrogen bond in HFIP-H2O complex is significantly stronger than that in water dimer with the H•••O distance of 1.8 Å. The other structure for this complex, not found in experiment is cyclic with both C-H•••O and O-H•••O hydrogen bonds, both of which are bent with H•••O distances in the range 2.2-2.3 Å. Both AIM and NBO calculations have been used to characterize the hydrogen bond in this complex. In Chapter V, a comprehensive study on hydrogen bonding, chlorine bonding and lithium bonding have been done. A typical hydrogen bonded complex can be represented as A•••H-D, where A is the acceptor unit and H-D is the hydrogen bond donor unit. Many examples are known in literature, both experimentally and theoretically, in which the A-H-D bond angles are not linear. Deviation from linearity also results in the increase in A•••H bond lengths, as noted above for the two structures of HFIP•••H2O complex. Though this has been known for long, the distance between A and D being less than the sum of their van der Waals ‘radii’ is still used as a criterion for hydrogen bonding by many. Our group has recently shown the inappropriateness of van der Waals ‘radii’ and defined hydrogen bond ‘radii’ for various donors, DH and A. A strong correlation of DH hydrogen bond ‘radii’ with the dipole moment was noted. In this Chapter, we explored in detail the angular dependence of hydrogen bond ‘radii’. Electron density topology around DH (D = F, Cl and OH) has been analyzed in detail and shown to be elliptical. For these molecules, the two constants for H atom treated as an ellipse have been determined. It is hoped that these two constants will be used widely in analyzing and interpreting H•••A distances, as a function of D-H•••A angles, rather than one ‘radius’ for H and acceptor atoms. In Chapter VI, Detailed analysis and comparisons among hydrogen bond, chlorine bond and lithium bond, have been done. Hydrogen can be placed in group 1 as well as group 17 of the periodic table. Naturally, lithium bonding and halogen bonding have been proposed and investigated. There have been numerous investigations on the nature of hydrogen bonding and the physical forces contributing to it. In this Chapter, a total of one hundred complexes having H/Cl/Li bonding have been investigated using ab initio, AIM and NBO theoretical methods. Various criteria proposed in the literature have been examined. A new criterion has been proposed for the characterization of closed shell (ionic/electrostatic) and open shell (covalent) interactions. It has been well known that the D-H bond weakens on the D-H•••A hydrogen bond formation and H•••A bond acquires a fractional covalency. This Chapter shows that for D-Li•••A complexes, the ionicity in D-Li is reduced as the Li•••A bond is formed This comprehensive investigation of H/Cl/Li bonding has led us to propose a conservation of bond order, considering both ionic and covalent contributions to both D-X and X•••A bonds, where DX is the X-bond donor and A is the acceptor with X = H/Cl/Li. Hydrogen bond is well understood and its definition has been recently revised [Arunan et al. Pure Appl. Chem., Vol. 83, pp. 1619–1636, 2011]. It states “The X–H•••Y hydrogen bond angle tends toward 180° and should preferably be above 110°”. Using AIM theory and other methods, this fact is examined and presented in Appendix A. In second part of appendix A, a discussion about calling H3¯ complex as trihydrogen bond and its comparison with FHF¯ complex, is presented. In Appendix B, there is tentative prediction and discussion about the HFIP dimer. Condense phase studies show that HFIP have strong aggregation power to form dimer, trimer etc. During, HFIP monomer study, we have unassigned lines which are suspected to be from HFIP dimer. These are tabulated in the Appendix B as well.

Rapid mixing and spreading of supersonic jets are two important characteristics in supersonic ejectors, noise reduction in jets and fuel mixing in supersonic combustion. It helps in changing the acoustic and thermal signature in supersonic exhaust. The supersonic nozzles in most cases result in compressible mixing layers. The subsonic nozzles form incompressible mixing layers but at high Mach numbers even they form compressible mixing layers. Compressible mixing layers have been found to have much lower mixing and spreading rates than incompressible mixing layer Birch & Eggers (1972). In order to enhance the spreading and mixing of mixing layers from supersonic nozzles various active and passive methods have been deviced. Active methods include fluid injection, fluid lobes and plasma actuation. Passive methods are mostly based on modifying the nozzle geometry such that the fluid expansion is ideal or the shock cell is broken. Many nozzles with exotic shapes have been developed to obtain mixing enhancements in supersonic jets Gutmark et al. (1995). To achieve enhanced mixing an innovative nozzle named as the Elliptic Sharp Tipped Shallow (ESTS) lobed nozzle has been developed in L.H.S.R., I.I.Sc., India Rao & Jagadeesh (2014). This nozzle has a unique geometry involving elliptical lobes and sharp tips. These lobes are generated using a simple manufacturing process from the throat to the exit. This lobed and sharp tipped structure introduces stream wise vortices and azimuthal velocity components which must help in enhanced mixing and spreading. The ESTS lobed nozzle has shown mixing enhancement with 4 lobes. The spreading rate was found to be double of the reference conical nozzle. This thesis is motivated by the need to investigate the flow physics involved in the ESTS lobed nozzle. The effect of varying the number of lobes and the design Mach number of the nozzle on the mixing and spreading characteristics will be further discussed. Visualisation studies have been performed. The schlieren and planar LASER Mie scattering techniques have been used to probe the flow. Instantaneous images were taken at axial planes with the reference conical and ESTS nozzles with three, four, five and six lobes. The nozzles are for design Mach number 2.0 and 2.5. The stagnation chamber pressure was maintained to obtain over expanded, ideally expanded and under expanded flows. LASER scattering was obtained by seeding the flow with water to observe the behaviour of the primary flow. The condensation of moisture due to the cold primary flow mixing with the ambient air was exploited to scatter laser and observe the flow structures in the mixing layer. A comparison of the images of the reference conical nozzle and the ESTS lobed nozzles shows changes in the mixing layers due to the ESTS lobed nozzles. The image of the reference conical nozzle shows a distinct potential core and mixing layers all along the length of the image. For the ESTS lobed nozzles this distinction becomes unclear shortly after the nozzle exit. Thus mixing of the primary flow and ambient air is seen to be enhanced in the case of all the ESTS lobed nozzles. The flow in the case of the ESTS lobed nozzles if found to be highly non axis symmetric. The starting process of the nozzles has been visualised using time resolved schlieren. Image processing was performed on the nozzles to quantify the spread rate. The shock structure of the nozzles has been studied and found to be modified due to the lobed geometry. The level of convolution of the mixing layer due to the lobed structure has been studied using fractal analysis. The four lobed nozzle was found to have the highest spread rate and th most convoluted shear layer. Hence this nozzle was further studied using background oriented schlieren and particle image velocimetry to quantify the flow field. These experimental results have been compared with CFD simulations using the commercial software CFX5. The computations and experiments don’t match accurately but the trends match. This allows for simulations to be used as a good first approximation. The acoustic properties of a jet are dependent on the flow structure behaviour. The ESTS lobes have been found to change the flow structure. Hence the ESTS lobed nozzle was predicted to change the acoustic signature of the flow. The acoustic measurements of the flow were carried out at National Aerospace Laboratories, Bengaluru. The screech of the overexpanded flow was seen to be eliminated and the overall sound levels were found to have been reduced in all cases. Thus the lobed nozzle was found to have acoustic benefits over the reference conical nozzle. Thus the ESTS lobed nozzle has been studied and compared with the conical nozzle using several methods. The changes due to the lobed structure have been studied quantitatively. Future studies would focus on the change in thrust due to the lobed structure. Also new geometries have been proposed inspired by the current design but with possible thrust benefits or manufacturing benefits.

The purpose of this research work was to develop a nozzle capable of depositing dense CoNiCrAlY coatings via cold gas dynamic spray (CGDS) as well as compare the oxidation performance of bond coats manufactured by CGDS, high-velocity oxy-fuel (HVOF) and air plasma spray (APS) at temperatures of 1000°C and 1100°C. The work was divided in two sections, the design and manufacturing of a CGDS nozzle with an optimal profile for the deposition of CoNiCrAlY powders and the comparison of the oxidation performance of CoNiCrAlY bond coats. Throughout this work, it was shown that the quality of coatings deposited via CGDS can be increased by the use of a nozzle of optimal profile and that early formation of protective α-Al2O3 due to an oxidation temperature of 1100°C as opposed to 1000°C is beneficial to the overall oxidation performance of CoNiCrAlY coatings.

This diploma thesis deals the formation of water hammer in pipes and the suppress the nega-tive effects especially for the use of protective devices (surge tank, air chamber, air valve and other). The special attention is paid to the use of the air valve, for which it was developed mathematical model. The solution is based on the use of numerical methods Lax-Wendroff with boundary conditions for the air valve.The numerical results are confronted with the ex-periment in conclusion.

Diplomová práce se zabývá hodnocením únavové životnosti v okolí konstručního uzlu tlakové nádoby, kde vzniká výrazná koncentrace napětí a je zde předpoklad primárního vlivu na únavu materiálu. Konkrétně se jedná o místo přechodu kontrolního otvoru do pláště analyzovaného zařízení. Práce obsahuje teoretickou a praktickou část. V teoretické části jsou představeny pojmy a metody hodnocení, související s danou problematikou. Na základě těchto metod je provedena analýza konstrukčního uzlu tlakové nádoby. Analýza je provedena metodou konečných prvků na skořepinovém a objemovém modelu nádoby v softwaru ANSYS Workbench, její výsledky dále zpracovány a vyhodnoceny dle aktuálního návrhu úpravy evropské harmonizované normy EN 13445--3, kapitoly 18. Výsledky analýz jsou hodnoceny v závěru práce.

This diploma thesis was focused on the possibility of using a plasma nozzle to accelerate the wound healing process. The benefits of using low-temperature plasma in medicine or biomedical applications are known from many studies, and low-temperature plasma is already used to sterilize medical devices, materials or surgical instruments. Some studies also report a high potential of usinh plasma nozzle in the treatment of skin wounds. In the experimental part of this work, an in vitro wound healing test was performed using two different low-temperature plasma sources. Source No. 1 was a surface wave microwave discharge and source No. 2 was a torch microwave discharge. An in vitro scratch healing test was performed on a monolayer of HaCaT keratinocytes and testing was performed using various parameters. The influence of the plasma treatment time was monitored, as well as the influence of the plasma discharge power and also the influence of the argon working gas flow. Especially when using a torch microwave discharge, faster wound healing was recorded at most of the parameters used compared to the control. Thus, it can be said that this source appears to be potentially suitable for faster wound healing. Furthermore, in the work using the MTT cytotoxicity test, the viability of skin cells after their plasmination was also monitored using the same conditions as in the in vitro wound healing test. When performed in the standard MTT assay, none of the settings or sources used showed any cytotoxic effects on keratinocytes. LDH cytotoxicity tests were also performed concurrently to verify the accuracy of the MTT assays. The results of both tests agreed and the use of low-temperature plasma in skin treatment can be considered as safe. Overall, the results show that the plasma nozzle can find use in medicine in the healing of skin wounds and chronic defects as a potentially fast, inexpensive and effective method.

Master work deals with the measurement of fluid flow (particularly air) pipe, with orifice and multiport averaging probe. The theoretical part is followed by practical, which verifies the properties of the measured system. In a next part of semestral work are verifies the properties of multiport averaging probes Vavra s.r.o. MQS-011 and Rosemount Annubar 485. Measured values from probes are compared.

This work describes briefly electron microscopy issue and physical model of fluid flow. Then presented diploma thesis will be describing analysis and evaluation of the impact of supersonic flow on the pressure and density in the path of the primary electron beam in the differential pumping chamber. For analysis, evaluation and examination of the issue will be used CAD and CAE (Computer Aided Engineering) programs. At the same time it will be developed a methodology of calculation applicable to supersonic flow in the low pressure system at ANSYS CFX.

The object of this thesis was Proposal and Examination of Supercharging Alternatives of CI-engine with Exhaust Gas Recirculation according required engine power parameters. This goal was meet by use of Turbocharger with Variable Nozzles and Air-Air intercooler.