In 1867, James Clerk Maxwell introduced a thought experiment involving a micro-scopic being (observer) capable of making precise measurements of microscopic quantitiesthrough observation of the micro-dynamics in a thermodynamic system. This observerlater became known as Maxwell’s demon due to its devious impact on thermodynamics,particularly the perceived violation of the second law. Subsequently, Leo Szilard pro-posed a machine, the so-called Szilard Machine, which, by utilising a Maxwell’s demon,successfully extracts work from thermal fluctuations in a closed system, seemingly vio-lating the second law. This thesis re-evaluates the second law of thermodynamics in the context of the Szi-lard Machine and Maxwell demons. The study explores the intersection of informationtheory and thermal physics, both theoretically and practically, with the aid of MonteCarlo simulations. The results indicate that machines with information feedback control,such as those utilising a Maxwell demon, challenge classical statements of the second lawof thermodynamics. This is because classical formulations, such as Clausius’ and Kelvin’sstatements, do not account for the entropic content of information. Simulations of thesefeedback processes, in conjunction with the detailed fluctuation theorem, provide a basisfor understanding feedback processes in so-called information machines. Ultimately, thesecond law of thermodynamics is upheld by an alternative statement endorsed by thedetailed fluctuation theorem.

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Call number: LD2668 .T4 1963 C45 / Master of Science

Under light wind conditions, the alternation of daytime heating and nighttime cooling creates a characteristic response in the oceanic boundary layer known as the diurnal cycle. The Mellor/Yamada Level II turbulence closure model is used to analyze this response pattern. The diurnal cycle has three phases. During morning and early afternoon, radiative solar heating produces stable stratification in the upper ocean, which inhibits the vertical transport of heat and momentum. Mean current speed at the surface increases as the effects of wind stress become confined to a shallow layer. This diurnal jet produces a mixed layer in the second phase, where turbulence generated by the vertical velocity shear balances the stabilizing buoyancy flux. At night, wind mixing and convective overturning due to surface cooling rapidly deepen the surface mixed layer during the third phase. / Graduation date: 1986

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Approved for public release; distribution is unlimited / Presently ice extent forecast models such as the U.S. Navy Polar Ice Prediction System (PIPS) neglect or treat small-scale thermodynamic processes and entrainment unrealistically. Incorporating better algorithms that include more complete physics of the mixed layer dynamics will allow for improved prediction of ice thickness and distribution, open water boundaries, polynyas, and deep-water formation in the polar seas. A one-dimensional mixed layer turbulent kinetic energy (TKE) budget model based on Garwood's NPS mixed layer model for deep convection (Garwood, 1991) was written in MATLAB. The model consisted of a system of ten equations derived by vertically integrating the budgets for heat, momentum, salinity, and turbulent kinetic energy between the sea-ice-air interface and the base of the turbulent mixed layer. The NPS mixed layer model was tested using atmospheric forcing and ocean profiles collected at the Surface Heat Budget of the Arctic Ocean Experiment (SHEBA) site. Sensitivity studies using ocean profiles of the Greenland Sea were also conducted to address thermodynamics and ocean profiles that enhance thermohaline circulation. Findings and results as well as recommendations for further study are addressed to extend the relationships determined from small 1-D scales to the larger 3-D scales suitable for improvements to current ice models. / Lieutenant, United States Navy

The use of detonations to achieve thrust in pulse detonation engines (PDEs) offers significant advantages in efficiency, simplicity, and versatility. An enabling mechanism for practical PDE implementation will likely utilize an efficient deflagration-todetonation transition (DDT) process. This method simplifies detonation generation, but the required length is prohibitive in many applications and limits the frequency of repeatability. Obstacles have historically been employed to minimize the DDT distance, but often result in significant total pressure losses that degrade the delivered efficiency advantages of PDEs. This thesis explored the use of straight and swept ramp obstacles to accelerate DDT while minimizing the overall pressure losses. Computer modeling examined three-dimensional disturbances caused by such obstacles. Experimental tests measured combustion shockwave speed, flame velocity, and flame front interactions with obstacles. Evaluations were completed for several straight ramp obstacle configurations in a modeled two-dimensional flow. The placement of consecutive ramps resulted in flame acceleration accompanied by significant pressure spikes approaching 500 psi. Although detonation was not verified across the instrumented section, experimental data prove that straight ramp obstacles successfully accelerate the DDT process. Computer modeling predicts that swept ramps may be even more effective by introducing streamwise vorticity with a relatively low pressure drop.

Ni-based superalloys are used for high-temperature components of gas turbines in both industrial and aerospace applications due to their ability to maintain dimensional stability under conditions of high stress and strain. The oxidation resistance of these alloys often dictates their service lifetime. This study focuses on the isothermal oxidation behaviour of three nickel-based superalloys; namely, polycrystalline cast IN738LC, single-crystal N5 and a ternary Ni-Fe-Cr (TAS) powder metallurgy alloy. The isothermal oxidation tests were conducted at 900°C in the static air up to 1000h and the specific aspects studied were the oxidation behaviour of these chromia-forming and alumina-forming alloys that are used extensively in industry. In particular, the behaviour of oxide scale growth and subsurface changes were analysed in detail using various techniques such as SEM, EDS and AFM. From the isothermal oxidation kinetics, the oxidation rate constant, kp was calculated for each alloy and found to be; kp = 2.79 x 10-6 mg2.cm-4.s-1 for IN738LC, kp = 1.42 x 10-7 mg2.cm-4.s-1 for N5 and kp = 1.64 x 10-7 mg2.cm-4.s-1 for TAS. Based on a microstructural analysis, IN738LC exhibited a continuous dense outer scale of Cr2O3 and discontinuous inner scale of Al2O3, whereas N5 and TAS showed a dense outer scale of Al2O3 alone. The results suggested that the N5 and PM-TAS alloys are more oxidation resistant than the IN738LC under these conditions. / October 2016