An investigation of the rock mechanics aspects of a system of short face in-seam development for subsequent longwall retreat extraction

PhD ThesisThe research work undertaken in this study was sponsored by the National Coal Board and consists of an investigation into the rock mechanics feasibility of a method of in-seam development by short faces with a centre pack, creating two roadways for subsequent retreating. An elastostatic solution by an approximate analysis has been given for this method of advancing for roof behaviour and to obtain pack load with face advance and the ribside abutment pressure distribution. The elastostatic analysis for the short face advancing situation has been done for anhydrite (setting) and conventional (non-setting) packs. A method is given for assessing the ribside abutment loading during subsequent retreating and loads in the goat. The floor loadings obtained during short face advancing and subsequent retreating have been used for a floor stress analysis and for predicting the post-failure viscoelastic floor heave during retreating. Some anhydrite properties relevant to the analysis have also been investigated in the laboratory and a formula for estimating the in-situ strength of anhydrite packs has been given.National Coal Boar

Chaos in a well : Effects of competing length scales

A discontinuous generalization of the standard map, which arises naturally as the dynamics of a periodically kicked particle in a one dimensional infinite square well potential, is examined. Existence of competing length scales, namely the width of the well and the wavelength of the external field, introduce novel dynamical behaviour. Deterministic chaos induced diffusion is observed for weak field strengths as the length scales do not match. This is related to an abrupt breakdown of rotationally invariant curves and in particular KAM tori. An approximate stability theory is derived wherein the usual standard map is a point of ``bifurcation''.Comment: 15 pages, 5 figure

Accelerator modes of square well system

We study accelerator modes of a particle, confined in an one-dimensional infinite square well potential, subjected to a time-periodic pulsed field. Dynamics of such a particle can be described by one generalization of the kicked rotor. In comparison with the kicked rotor, this generalization is shown to have a much larger parametric space for existence of the modes. Using this freedom we provide evidence that accelerator mode assisted anomalous transport is greatly enhanced when low order resonances are exposed at the border of chaos. We also present signature of the enhanced transport in the quantum domain.Comment: 7 pages, 5 figures, revtex

Quantum Chaos of a particle in a square well : Competing Length Scales and Dynamical Localization

The classical and quantum dynamics of a particle trapped in a one-dimensional infinite square well with a time periodic pulsed field is investigated. This is a two-parameter non-KAM generalization of the kicked rotor, which can be seen as the standard map of particles subjected to both smooth and hard potentials. The virtue of the generalization lies in the introduction of an extra parameter R which is the ratio of two length scales, namely the well width and the field wavelength. If R is a non-integer the dynamics is discontinuous and non-KAM. We have explored the role of R in controlling the localization properties of the eigenstates. In particular the connection between classical diffusion and localization is found to generalize reasonably well. In unbounded chaotic systems such as these, while the nearest neighbour spacing distribution of the eigenvalues is less sensitive to the nature of the classical dynamics, the distribution of participation ratios of the eigenstates proves to be a sensitive measure; in the chaotic regimes the latter being lognormal. We find that the tails of the well converged localized states are exponentially localized despite the discontinuous dynamics while the bulk part shows fluctuations that tend to be closer to Random Matrix Theory predictions. Time evolving states show considerable R dependence and tuning R to enhance classical diffusion can lead to significantly larger quantum diffusion for the same field strengths, an effect that is potentially observable in present day experiments.Comment: 29 pages (including 14 figures). Better quality of Figs. 1,3 & 9 can be obtained from author

Algebraic approach in the study of time-dependent nonlinear integrable systems: Case of the singular oscillator

The classical and the quantal problem of a particle interacting in one-dimension with an external time-dependent quadratic potential and a constant inverse square potential is studied from the Lie-algebraic point of view. The integrability of this system is established by evaluating the exact invariant closely related to the Lewis and Riesenfeld invariant for the time-dependent harmonic oscillator. We study extensively the special and interesting case of a kicked quadratic potential from which we derive a new integrable, nonlinear, area preserving, two-dimensional map which may, for instance, be used in numerical algorithms that integrate the Calogero-Sutherland-Moser Hamiltonian. The dynamics, both classical and quantal, is studied via the time-evolution operator which we evaluate using a recent method of integrating the quantum Liouville-Bloch equations \cite{rau}. The results show the exact one-to-one correspondence between the classical and the quantal dynamics. Our analysis also sheds light on the connection between properties of the SU(1,1) algebra and that of simple dynamical systems.Comment: 17 pages, 4 figures, Accepted in PR

Sinteza i farmakološka evaluacija 3-cikloheksil-2-supstituiranih hidrazino-3H-kinazolin-4-ona kao analgetika i antiinflamatorika

A series of novel 3-cyclohexyl-2-substituted hydrazino-quinazolin-4(3H)-ones were synthesized by reacting the amino group of 3-cyclohexyl-2-hydrazino quinazolin-4(3H)-one with a variety of aldehydes and ketones. The starting material, 3-cyclohexyl-2-hydrazino quinazolin-4(3H)-one, was synthesized from cyclohexyl amine. Title compounds were investigated for analgesic, anti-inflammatory and ulcerogenic behavior. The compound 3-cyclohexyl-2-(1-methylbutylidene-hydrazino)-3H-quinazolin-4-one (4c) emerged as the most active compound of the series and is moderately more potent in its analgesic and anti-inflammatory activities compared to the reference standard diclofenac sodium. Interestingly, test compounds showed only mild ulcerogenic potential when compared to acetylsalicylic acid.Reakcijom amino skupine 3-cikloheksil-2-hidrazino kinazolin-4(3H)-ona s različitim aldehidima i ketonima sintetizirani su novi 3-cikloheksil-2-supstituirani hidrazino-kinazolin-4(3H)-oni. Početni spoj 3-cikoheksil-2-hidrazino kinazolin-4(3H)-on pripravljen je iz cikloheksilamina. Sintetizirani spojevi testirani su na analgetsko i protuupalno djelovanje te ulcerogena svojstva. Spoj 3-cikloheksil-2-(1-metilbutiliden-hidrazino)-3H-kinazolin-4-on (4c) imao je najjače analgetsko i protuupalno djelovanje, nešto jače nego referentni spoj diklofenak natrij. Osim toga, testirani spojevi imaju samo blago ulcerogeno djelovanje u usporedbi s acetilsalicilnom kiselinom

The performance of stochastic designs in wellbore drilling operations

© 2018, The Author(s). Wellbore drilling operations frequently entail the combination of a wide range of variables. This is underpinned by the numerous factors that must be considered in order to ensure safety and productivity. The heterogeneity and sometimes unpredictable behaviour of underground systems increases the sensitivity of drilling activities. Quite often the operating parameters are set to certify effective and efficient working processes. However, failings in the management of drilling and operating conditions sometimes result in catastrophes such as well collapse or fluid loss. This study investigates the hypothesis that optimising drilling parameters, for instance mud pressure, is crucial if the margin of safe operating conditions is to be properly defined. This was conducted via two main stages: first a deterministic analysis—where the operating conditions are predicted by conventional modelling procedures—and then a probabilistic analysis via stochastic simulations—where a window of optimised operation conditions can be obtained. The outcome of additional stochastic analyses can be used to improve results derived from deterministic models. The incorporation of stochastic techniques in the evaluation of wellbore instability indicates that margins of the safe mud weight window are adjustable and can be extended considerably beyond the limits of deterministic predictions. The safe mud window is influenced and hence can also be amended based on the degree of uncertainty and the permissible level of confidence. The refinement of results from deterministic analyses by additional stochastic simulations is vital if a more accurate and reliable representation of safe in situ and operating conditions is to be obtained during wellbore operations.Published versio