BACKGROUND: Previous research has shown that the ventilatory threshold (VT) correlates highly with onset of lactate accumulation and maximal steady-state exercise (MSS) level. Also, studies have shown the VT is useful in prescribing exercise for cardiac patients in that it gives an exercise intensity at which the patient is metabolically stable. METHODS: The purpose of this study was to determine if a MSS response could be achieved at an exercise intensity corresponding to the VT for patients with CAD. A group of 31 patients with CAD performed a maximal effort treadmill exercise test in which respiratory gas exchange was measured. The VT was determined using the V-slope method of computer regression analysis of the plot of carbon dioxide production versus oxygen consumption. Subjects then performed a constant load treadmill test a speed and grade that corresponded to the VT. Heart rate (HR), systolic blood pressure (SBP), and rating of perceived exertion (RPE) evaluated for steady-state responses. If subjects showed a steady-state response in two of these three parameters they were scored as having achieved a maximal steady-state (MSS+) response; those not meeting this standard were scored as failing to achieve maximal steady-state (MSS-) response. Subjects were analyzed as an entire group (N=31), as well as analyzed in subsets according to history of myocardial infarction (MI+, N=20; MI-, N=11) and administration of beta-blocker medications (BB+, N=16; BB-, N=15). RESULTS: Overall, subjects demonstrated significantly more MSS+ responses than MSS- responses (80% Vs 20%, P<0.05). Analysis of the subgroup data showed that it was the patient s with a history of MI (MI+ =85%, P<0.05) and those not receiving beta-blocker medications (BB- = 93%, P<0.05) who had significantly greater proportions of subject achieving MSS+ responses in the fixed load exercise condition. Conversely patient in the MI- (73 %, P < 0.05) and BB (69% P < 0.05) groups showed no significant differences in the number of MSS+ and MSS- responses. CONCLUSIONS: The VT, as measured during ramp exercise testing on the treadmill, provided a basis for establishing a maximal steady-state load in terms of cardiovascular and perceptual variables for 80% of the patients in the CAD study group. The measurements of HR, SBP, and RPE are easily obtained in a clinical setting and thus enable the VT to be used in bringing about a more efficacious exercise prescription. The validity of this method may be questioned, however, for patient with out a history of MI and for those receiving beta-blocker medications. / Master of Science

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Yes / Desalination has become one of the obvious solutions for the global water crisis due to affording high-quality water from seawater and brackish water resources. As a result, there are continuing efforts being made to improve desalination technologies, especially the one producing high-quantity freshwater, i.e., thermal desalination. This improvement must be accomplished via enhancement of process design through optimization which is implicitly dependent on providing a generic process model. Due to the scarcity of a comprehensive review paper for modeling multi-effect distillation (MED) process, this topic is becoming more important. Therefore, this paper intends to capture the evolution of modeling the forward feed MED (most common type) and shed a light on its branches of steady-state and dynamic modeling. The maturity of the models developed for MED will be thoroughly reviewed to clarify the general efforts made highlighting the advantages and disadvantages. Depending on the outputs of this review, the requirements of process development and emerging challengeable matters of modeling will be specified. This, in turn, would afford a possible improvement strategy to gain a reliable and sustainable thermal desalination process.

<p> Steady state response of a single degree of freedom system with impact damper, with the main emphasis of two impacts (symmetric or unsymmetric)/cycle motion, and its asymptotic stability criterion are derived analytically. Stability regions are determined for wide range of parameters of the impact damper by using digital computer. </p> <p> Experimental study is also made to verify the assumptions taken in the analytical solution and to obtain general response of the system for wide range of parameters of the impact damper. </p> <p> As a result, it is found that unsymmetric two impacts per cycle motion exists and is stable for a wide range of parameters of the impact damper. </p> <p> Also, it is found that three and four impacts/cycle motions exist and are stable. </p> <p> Stability boundaries are found to be a complicated function of the impact damper parameters. </p> / Thesis / Master of Engineering (MEngr)

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There are increasing economic incentives within the chemical process industry towards demand driven operation with product diversification, requiring flexible operation in responsive plants. In continuous processes, this is realized through steady-state transitions but requires consideration of process dynamics arising from operation that is inherently transient in nature. The steady-state economic optimum is typically defined at the intersection of constraints, and requires multivariable control with optimal constraint handling capabilities. Thus, constrained model predictive control is well-suited to realize the profit potential at the economic optimum. In this thesis, feasible and optimal steady-state transitions are achieved using reference management with consideration of the closed-loop dynamics of constrained model predictive control. The supervisory control scheme is used to determine the optimal setpoint trajectory which is subsequently tracked by regulatory control, incorporating feedback for the rejection of high frequency disturbances and eliminating steady-state offset in the presence of model mismatch. The separation of economic and control objectives enables the lower level to be tuned for stability and the upper level to be tuned for performance. The mathematical formulation results in a multi-level optimization problem with an economic objective function at the upper level, and a series of control performance objective functions arising from constrained model predictive control at the lower levels. The solution strategy proposed converts the multi-level optimization problem into a single-level optimization problem using the Karush-Kuhn-Tucker conditions, and solves the resulting complementarity conditions using an interior point approach. Alternative objective formulations are investigated based on maximizing profit during transient operation. The first formulation is typically based on a quadratic objective function minimizing the transition time, indirectly improving economic operation by reducing the amount of off-specification product produced. The second formulation is based on the explicit consideration of economics. The profit calculated during transient operation is based on the difference between the revenue generated by the production of acceptable product within specified univariate product quality bands, and the operational costs of raw materials and utilities. The resulting linear objective function is further extended to incorporate control performance considerations to improve conditioning for gradient based optimization. The proposed methodology is applied to a single-input single-output linear system, demonstrating the potential benefits of simultaneous rather than sequential optimization in terms of computational efficiency and solution reliability. Alternative objective function and constraint formulations are investigated, and the effect on the optimal solution assessed. In particular, the possibility of indeterminacy is shown and handled using hierarchical optimization. The methodology is also demonstrated on additional examples including non-minimum phase systems and multi-input multi-output linear systems. Application to a multi-input multi-output nonlinear system corresponding to styrene polymerization using the proposed methodology is detailed. The set of differential and algebraic equations defining the process is discretized using orthogonal collocation on finite elements. The optimal operation during grade transitions based on explicit consideration of economics is determined, and additional improvements realized by manipulating the production rate. Finally, reference management with online re-optimization is investigated for a single-input single-output linear system based on a bias update, and the improvement in closed-loop performance assessed for output disturbances and model mismatch. The methodology is also demonstrated on a multi-input multi-output system based on a linear model when applied to the nonlinear process. The proposed methodology developed for steady-state transitions may also be applied to batch operation, startups and shutdowns. Future extensions include analysis of closed-loop stability due to the incorporation of feedback within the cascade control scheme, and the explicit consideration of uncertainty. / Thesis / Master of Applied Science (MASc)

The cosmologist Dennis W. Sciama (1926-1999) was a long-standing advocate of the steady state model of the universe. This theory, originally proposed in 1948 by Hermann Bondi, Thomas Gold, and Fred Hoyle, suggested that the universe was eternal, and unchanging on the largest scales. Contrary to the popular image of a scientist as a dispassionate, unbiased investigator of nature, Sciama fervently hoped the steady state model to be correct. In addition, and also pace the stereotypical image of a scientist, Sciama was motivated significantly by "extrascientific" or aesthetic factors in his adoption of the model. Finally, Sciama, in a stark contrast to the naive falsificationism usually presented as a virtue of the "scientific method," went through a several-year period of attempting to "save" the model from hostile data. However, Sciama abandoned the model in 1966 due to increasingly reliable data relating to the distribution of quasars. Thus the Sciama case also stands as a counterexample to irrationalist criticisms of science, according to which scientists can and will always find ways to hold on to their "pet" theories until they die, regardless of contradictory data. Sciama's conversion also sheds light on the iterative process that goes on as scientists localize and attempt to repair faults in their theories. / Ph. D.

abstract: Pseudo-steady state (PSS) flow is an important time-dependent flow regime that quickly follows the initial transient flow regime in the constant-rate production of a closed boundary hydrocarbon reservoir. The characterization of the PSS flow regime is of importance in describing the reservoir pressure distribution as well as the productivity index (PI) of the flow regime. The PI describes the production potential of the well and is often used in fracture optimization and production-rate decline analysis. In 2016, Chen determined the exact analytical solution for PSS flow of a fully penetrated vertically fractured well with finite fracture conductivity for reservoirs of elliptical shape. The present work aimed to expand Chen’s exact analytical solution to commonly encountered reservoirs geometries including rectangular, rhomboid, and triangular by introducing respective shape factors generated from extensive computational modeling studies based on an identical drainage area assumption. The aforementioned shape factors were generated and characterized as functions for use in spreadsheet calculations as well as graphical format for simplistic in-field look-up use. Demonstrative use of the shape factors for over 20 additional simulations showed high fidelity of the shape factor to accurately predict (mean average percentage error remained under 1.5 %) the true PSS constant by modulating Chen’s solution for elliptical reservoirs. The methodology of the shape factor generation lays the ground work for more extensive and specific shape factors to be generated for cases such as non-concentric wells and other geometries not studied. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2017