In the case of cold accretion disk, coupling between charge neutral gas and magnetic field is too weak such that the magneto-rotational instability will be less effective or even stop working. In such a situation it is of prime interest to investigate the pure hydrodynamic turbulence and transport phenomenon. As the Reynolds number increases, the relative importance of the non-linear term in the hydrodynamic equation increases and in the case of accretion disk where molecular viscosity is too small the Reynolds number is large enough for the non-linear term to bring new effects. We investigate a scenario, the ‘weakly non-linear’ evolution of amplitude of linear mode when the flow is bounded by two parallel walls. The unperturbed flow is similar to plane Couette flow but with Coriolis force included in the hydrodynamic equation. Although there is no exponentially growing eigenmode, due to self-interaction the least stable eigenmode will grow in an intermediate phase. Later on this will lead to higher order non-linearity and plausible turbulence. Although the non-linear term in the hydrodynamic equation is energy conserving, within the weakly non-linear analysis it is possible to define a lower bound of the energy needed for flow to transform to turbulent phase. Such an unstable phase is possible only if the Reynolds number ≥ 103−4. In Chapter-2 we set up equation of amplitude for the hydrodynamic perturbation and study the effect of weak non-linear evolution of linear mode for general angular momentum distribution, where Keplerian disk is obtained as a special case. As we know that to explain observed hard X-rays the choice of Keplerian angular momentum profile is not adequate, we consider the sub-Keplerian regime of the disk. In Chapter-3 we assume that the cooling mechanism is dominated by bremsstrahlung process (without any strict knowledge of the magnetic field structure).We show that in a range of Shakura-Sunyaev viscosity 0.2 ≥ α ≥ 0.0005, flow behavior varies widely, particularly by means of the size of disk, efficiency of cooling and corresponding temperatures of ions and electrons. We also show that the disk around a rotating black hole is hotter compared to that around a Schwarzschild black hole, rendering a larger difference between ion and electron temperatures in the former case. We finally reproduce the observed luminosities(L) of two extreme cases—the under-fed AGNs and quasars and ultra-luminous X-ray sources at different combinations of mass accretion rate, ratio of specific heats, Shakura-Sunyaev viscosity parameter and Kerr parameter. In Chapter-4 we investigate the viscous two temperature accretion disk flows around rotating blackholes. We describe the global solution of accretion flows, unlike that in Chapter-3, with a sub-Keplerian angular momentum profile, by solving the underlying conservation equations including explicit cooling processes self-consistently. Bremsstrahlung, synchrotron and inverse comptonization of soft photons are considered as possible cooling mechanisms. We focus on the set of solutions for sub-Eddington, Eddington and super-Eddington mass accretion rates around Schwarzschild and Kerr black holes with a Kerr parameter 0.998. We analyse various phases of advection–general advective paradigm to radiatively inefficient paradigm. The solution may potentially explain the hard X-rays and γ-rays emitted from AGNs and X-ray binaries. We also compare the solutions for two different regimes of viscosity. We finally reproduce the observed luminosities of the under-fed AGNs and quasars, ultra-luminous X-ray sources at different combinations of input parameters such as mass accretion rate and ratio of specific heats.

In recent years, attempts to simplify the grammatical mechanisms used in syntax have led to proposals to reduce the relationships between elements in a sentence to relations between heads and complements, doing away with free adjunction. For the analysis of modifying relations one consequence has been the rise of analyses that use the properties of selecting heads to stipulate unexpected syntactic behaviour, such as the use of light verbs to derive transparency in complex verb constructions. This thesis shows that such accounts are empirically inadequate and argues that the relationship between heads and adjuncts provides a more empirically-satisfactory model of modifying relations, such as complex verb constructions, than one restricted to the selection relation between heads and complements in the syntax. In support of the adjunct relation, I show how a modular approach to adjuncts in which the position of adjunction is licensed in the semantics and long-distance dependencies are licensed in the syntax can provide a more unified account of subextraction from two separate types of island configurations, viz. asymmetric subextraction from coordination and subextraction from participial adjuncts, either than analyses involving complementation in the syntax (Borgonovo and Neeleman, 2000; Fabregas and Jiménez-Fernández, 2016; Wiklund, 2007), or hybrid analyses mixing processing filters with syntactic licensing of long-distance dependencies (Truswell, 2009, 2011). The first part of the thesis shows that Chomsky’s (2000; 2001) phase theory gives rise to blackholes in the specifier positions of phases from which movement cannot take place. I provide a theoretical account in terms of feature-licensing, where blackholes are formed by the impossibility of licensing at least one unlicensed feature on a phase head, and show how this account derives the distinction between canonical adjuncts from which subextraction is not permitted and subextraction from single event constructions in which subextraction is permitted. The section speculatively concludes with a demonstration of how blackholes might provide a unified analysis of islandhood in general. The second part of the thesis concentrates on the empirical phenomenon of subextraction from coordination and participial adjuncts. I report the results of a series of judgement experiments run in parallel across two sets of constructions, coordination and participial adjuncts, in three languages, English, German and Norwegian. The aim was to test whether acceptability of subextraction from within coordination and participial adjuncts varied depending on the aspectual or grammatical type of matrix predicate. The results show that acceptability of subextraction does depend on the type of matrix predicate. The crucial factor is intransitivity, partially confirming the bias towards unaccusatives in subextraction from participial adjuncts observed informally in Borgonovo and Neeleman (2000); Fabregas and Jiménez-Fernández (2016); Truswell (2011) whilst providing evidence against theoretical accounts that rely primarily on unaccusativity (Borgonovo and Neeleman, 2000; Fabregas and Jiménez-Fernández, 2016), primarily on aspectual distinctions (Truswell, 2007b) or primarily on agentivity (Truswell, 2009, 2011). Interestingly, the hierarchy in acceptability between the four types of matrix predicates stays constant across all three languages, despite both pseudocoordination and subextraction from within participials being ungrammatical in German.