Facilitating the Use of Optimisation in the Aerodynamic Design of Axial Compressors

There is commercial pressure to design axial compressors exhibiting high levels of performance more quickly. This is despite the performance of these machines approaching an asymptote in recent years, with further gains becoming increasingly difficult to achieve. One tool that can be used to help is optimisation, effectively harnessing the speed of computational analysis to accelerate the design process and unlock additional performance improvements. The greatest potential for optimisation exists at the preliminary design stage, however, current methodologies struggle when applied at this early point in the design process due to inadequate problem formulations, an inability to fulfil the role of enhancing designer understanding and a lack of high-fidelity analysis due to computational cost. The goal of this thesis is to facilitate the use of optimisation in the preliminary aerodynamic design of axial compressors by developing an improved methodology that overcomes these limitations. The multiple dominance relations (MDR) formulation enables a larger number of performance parameters to be incorporated in a way that accurately reflects the desires of the designer. This is implemented within a Tabu Search (TS) that is capable of providing interpretable design development information to enhance designer understanding. The combined MDRTS algorithm, overcoming the limitations associated with formulation and understanding, outperforms existing methods when applied to analytic, aerofoil and six-stage axial compressor test cases, generating computational savings of up to 80%. Multi-fidelity techniques are used to accelerate the search by conducting analysis on a "need-to-know'' basis. Computational savings of over 70% are observed compared to the single-fidelity version of the algorithm across the analytic, aerofoil and six-stage axial compressor test cases, enabling high-fidelity analysis to be employed in a computationally efficient manner. The resultant methodology represents a novel and inherently flexible multi-level multi-fidelity optimisation technique. Application to an N-stage axial compressor test case, in which the optimiser is given control over the number of stages in the machine, demonstrates the capabilities of the accelerated MDRTS approach. The complex design space is effectively navigated, generating computational savings of over 90% compared to existing methodologies and producing designs that are more likely to be of interest to the designer. Interpretable design development information is also provided for this problem to enhance designer understanding. These results show that the improved methodology successfully facilitates the use of optimisation in the preliminary aerodynamic design of axial compressors, overcoming the problems associated with formulation, understanding and speed that limit existing approaches

Characterizing the thermal efficiency of thermoelectric modules

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009."June 2009." Cataloged from PDF version of thesis.Includes bibliographical references (p. 22).An experimental setup was designed and utilized to measure the thermoelectric properties as functions of temperature of a commercially available, bismuth telluride thermoelectric module. Thermoelectric modules are solid state semiconducting devices that act reversibly as both a heat pump and a power generator. The experimental setup encased the modules in an insulating container and thermal power was provided by a variable power cartridge heater, using type-K thermocouples to measure the temperature difference across the module. The measured parameters were compared against published data on a similar type of module. The thermal conductivity was measured within 21% of the accepted value on average, the Seebeck coefficient within 16%, the figure of merit within a factor two, and the thermal efficiency within 20% for low [delta]T of less than 25°C.by Samuel S. Phillips.S.B

Fourth Circuit: The Judicial Council\u27s Review on the Need for a Gender Bias Study

In 1993, the Women Judges Fund for Justice, the National Association of Women Judges, and the National Center for State Courts, sponsored a four-day conference (March 18-21) in Williamsburg, Virginia, entitled Second National Conference on Gender Bias in the Courts: Focus on Follow-up. Then Chief Circuit Judge Sam J. Ervin, III, designated the Deputy Circuit Executive to attend the conference on behalf of the Fourth Circuit. The Deputy also attended, along with a Fourth Circuit U.S. Magistrate Judge (now a U.S. District Judge), the Federal Judicial Center Gender Bias Task Force Workshop in Washington, D.C. (August 5-6, 1993)

Studies of Respiratory Rhythm Generation Maintained in Organotypic Slice Cultures

Breathing is an important rhythmic motor behavior whose underlying neural mechanisms can be studied in vitro. The study of breathing rhythms in vitro has depended upon reduced preparations of the brainstem that both retain respiratory-active neuronal populations and spontaneously generate respiratory-related motor output from cranial and spinal motor nerves. Brainstem-spinal cord en bloc preparations and transverse medullary slices of the brainstem have greatly improved the ability of researchers to experimentally access and thus characterize interneurons important in respiratory rhythmogenesis. These existing in vitro preparations are, however, not without their limitations. For example, the window of time within which experiments may be conducted is limited to several hours. Moreover, these preparations are poorly suited for studying subcellular ion channel distributions and synaptic integration in dendrites of rhythmically active respiratory interneurons because of tortuous tissue properties in slices and en bloc, which limits imaging approaches. Therefore, there is a need for an alternative experimental approach. Acute transverse slices of the medulla containing the preBötzinger complex (preBötC) have been exploited for the last 25 years as a model to study the neural basis of inspiratory rhythm generation. Here we transduce such preparations into a novel organotypic slice culture that retains bilaterally synchronized rhythmic activity for up to four weeks in vitro. Properties of this culture model of inspiratory rhythm are compared to analogous acute slice preparations and the rhythm is confirmed to be generated by neurons with similar electrophysiological and pharmacological properties. The improved optical environment of the cultured brain tissue permits detailed quantitative calcium imaging experiments, which are subsequently used to examine the subcellular distribution of a transient potassium current, IA, in rhythmically active preBötC interneurons. IA is found on the dendrites of these rhythmically active neurons, where it influences the electrotonic properties of dendrites and has the ability to counteract depolarizing inputs, such as post-synaptic excitatory potentials, that are temporally sparse in their occurrence (i.e., do not summate). These results suggest that excitatory input can be transiently inhibited by IA prior to its steady-state inactivation, which would occur as temporally and spatially summating synaptic inputs cause persistent depolarization. Thus, rhythmically active interneurons are equipped to appropriately integrate the activity state of the inspiratory network, inhibiting spurious inputs and yet yielding to synaptic inputs that summate, which thus coordinates the orderly recruitment of network constituents for rhythmic inspiratory bursts. In sum, the work presented here demonstrates the viability and potential usefulness of a new experimental model of respiratory rhythm generation, and further leverages its advantages to answer questions about dendritic synaptic integration that could not previously be addressed in the acute slice models of respiration. We argue that this new organotypic slice culture will have widespread applicability in studies of respiratory rhythm generation