Optimalizing control in the presence of noise interference

The performance of a modified peak-holding optimalizing control system depends in part on the ability of the controller to detect the input signal frequency component in the output of the controlled system. This paper describes several techniques that may be used for detecting this component and analyzes one of them in great detail. The subject of the detailed analysis is the method of filtering through cross-correlation. A statistical analysis is also carried out in order to demonstrate the efficiency of this method

A theory of two-dimensional airfoils with strong inlet flow on the upper surface

The two-dimensional theory of airfoils with arbitrarily strong inlet flow into the upper surface was examined with the aim of developing a thin-airfoil theory which is valid for this condition. Such a theory has, in fact, been developed and reduces uniformly to the conventional thin-wing theory when the inlet flow vanishes. The integrals associated with the arbitrary shape, corresponding to the familiar Munk integrals, are somewhat more complex but not so as to make calculations difficult. To examine the limit for very high ratios of inlet to free-stream velocity, the theory of the Joukowski airfoil was extended to incorporate an arbitrary inlet on the upper surface. Because this calculation is exact, phenomena observed in the limit cannot be attributed to the linearized calculation. These results showed that airfoil theory, in the conventional sense, breaks down at very large ratios of inlet to free-stream velocity. This occurs where the strong induced field of the inlet dominates the free-stream flow so overwhelmingly that the flow no longer leaves the trailing edge but flows toward it. Then the trailing edge becomes, in fact a leading edge and the Kutta condition is physically inapplicable. For the example in this work, this breakdown occurred at a ratio of inlet to free-stream velocity of about 10. This phenomena suggests that for ratios in excess of the critical value, the flow separates from the trailing edge and the circulation is dominated by conditions at the edges of the inlet

Analysis of peak-holding optimalizing control

The peak-holding optimalizing control is analyzed under the assumption of first-order input linear group and output linear group. Design charts are constructed for determining the required input drive speed and the consequent hunting loss with specified time constants of the input and output linear groups, the hunting period, and the critical indicated difference for input drive reversal

A Procedure for Predicting Fuel Specific Impulse of Supersonic Combustion Ramjet Engines

This report presents a procedure in order to portray the effect of design choices on SCRAMJET dynamic performance in the context of real gas effects. Procedure is based on one-dimensional fluid flow analysis. The less quantifiable aspects of boundary layer transition, mixing, and non-uniform nozzle flow are included in approximate parametric fashion by allowing for parallel flow paths through the engine and nozzle, with possibility of thermal energy exchange between various flow streams. The effect of finite recombination rates in the nozzle is included by allowing for freezing of the chemical composition at any specified static pressure in the nozzle. Exploratory results from the digital implementation of this procedure in FORTRAN language are also included

Dynamics of Return and Liquidity (Co)Jumps in Emerging Foreign Exchange Markets

We investigate the dynamics of return and liquidity (co)jumps for three of the most traded emerging market currencies vis-à-vis US dollar. We find that an increase in the average bid-ask spread significantly reduces the duration between consecutive return jumps, while liquidity and volatility only play a partial role on the duration between consecutive liquidity jumps and return-liquidity cojumps. There is also evidence of vicious return-liquidity spirals in views of the positive contemporaneous impact of liquidity jumps on volatility and return jumps on the bid-ask spread. Moreover, scheduled macroeconomic news and central bank announcements increase the likelihood of both return and liquidity (co)jumps. Finally, jump adjusted high frequency FX trading strategies are shown to have superior performance over the buy-and-hold strategy

A population-based survey of Chronic REnal Disease In Turkey—the CREDIT study

Background. Chronic kidney disease (CKD) is a growing health problem worldwide that leads to end-stage kidney failure and cardiovascular complications. We aimed to determine the prevalence of CKD in Turkey, and to evaluate relationships between CKD and cardiovascular risk factors in a population-based survey

Correlation of microseismic and chemical properties of brittle deformation in Locharbriggs sandstone

The time-dependent properties of ceramic materials such as rocks depend both on preexisting cracks and chemical properties acting at their tips. We have examined the direct effect of chemical processes on the growth of a crack population by carrying out triaxial flow-through compression tests on Locharbriggs sandstone. The tests were carried out at temperatures of 25-80 degrees C and at strain rates ranging from 10-5 to 10-8 s-1 under constant stress rate loading. The exit pore fluid was analyzed after the tests for the concentration of dissolved ions and acoustic emission was monitored in real time throughout the tests. The exit pore fluid silica concentration and microcrack damage derived from the acoustic emission (AE) data both exhibited an exponential increase during the strain hardening phase of deformation. Damage parameters inferred from the AE data predict the stress-strain curves adequately, or at least up to the point of strong microcrack coalescence. The damage parameters and silica signal were strongly correlated by a power law relationship. The observed environment and strain rate dependence of mechanical properties can hence be attributed uniquely to time-dependent crack growth by the stress corrosion mechanism

Analysis of Optimalizing Control Systems witb Special Reference to Noise Interference Effects

The optimalizing control system is designed to search out automatically the optimum state of operation of the controlled system and to confine the operation to a region near this optimum state. The performance of the system is affected by the dynamics of the controlled system and by the noise interference. The dynamic effects of the controlled system on the performance of a peak-holding optimalizing control is analyzed under the assumption that the controlled system dynamics may be represented by a first order input linear group and a first order output linear group. Design charts are constructed for determining the required input drive speed and consequent hunting loss with specified time constants of the input and output linear groups, the hunting period, and the critical indicated difference for input drive reversal. The noise interference effects on the control system performance led to a new type of optimalizing control system which is a modification of the peak-holding optimalizing controller. Performance of the modified optimalizing controller is analyzed and several possible procedures are discussed for detecting and eliminating the incorrect operation modes. A statistical analysis is made to demonstrate the efficiency of a typical detection procedure, namely, the method of filtering through cross-correlation. The modified optimalizing controller can utilize any periodically varying input. An example of this, a sinusoidal input controller, is analyzed to show the dynamic effects of the controlled system and to demonstrate the effect of noise interference on the performance of the modified optimalizing controller