Generalized LFT-Based Representation of Parametric Uncertain Models

In this paper, we introduce a general descriptor-type linear fractional transformation (LFT) representation of rational parametric matrices. This is a generalized representation of arbitrary rationally dependent multivariate functions in LFT-form. As applications, we develop explicit LFT-realizations of the transfer-function matrix of a linear descriptor system whose state-space matrices depend rationally on a set of uncertain parameters. The resulting descriptor LFT-based uncertainty models generally have smaller orders than those obtained by using the standard LFT-based modelling approach. An example of an uncertain vehicle model illustrates the capability of the method

Assessment of Watershed Health on Intermittent Watersheds in Southwestern North Dakota

Watersheds are complex systems that are influenced by many factors including geomorphology, climate, soil, vegetation, and land management. Due to this complexity, a watershed assessment that evaluates both the riparian and upland areas has yet to be developed. We proposed investigating a combination of plant community composition within the greenline, upland ecological site function assessment with the Interpreting Indicators of Rangeland Health (IIRH) protocol, and stream morphological parameters. Stream parameters investigated were Rosgen?s classification method, bank erosion hazard index (BEHI) and bank height ratio (BHR). This research was conducted on five intermittent streams in southwestern North Dakota. We found that facultative wetland species offered the most protection to intermittent streambanks as a result of hydrology. When assessing the uplands it was determined that there is a positive correlation between rangeland health and riparian health. The stream parameter that showed the strongest relationship was the BEHI

Performance and evaluation of two liquid-metal pumps for sodium-potassium service

Performance tests on liquid metal pumps for sodium potassium loop

Dynamics of a strongly interacting Fermi gas: the radial quadrupole mode

We report on measurements of an elementary surface mode in an ultracold, strongly interacting Fermi gas of 6Li atoms. The radial quadrupole mode allows us to probe hydrodynamic behavior in the BEC-BCS crossover without being influenced by changes in the equation of state. We examine frequency and damping of this mode, along with its expansion dynamics. In the unitarity limit and on the BEC side of the resonance, the observed frequencies agree with standard hydrodynamic theory. However, on the BCS side of the crossover, a striking down shift of the oscillation frequency is observed in the hydrodynamic regime as a precursor to an abrupt transition to collisionless behavior; this indicates coupling of the oscillation to fermionic pairs.Comment: 11 pages, 11 figures v2: minor change

Observation of the Pairing Gap in a Strongly Interacting Fermi Gas

We study fermionic pairing in an ultracold two-component gas of $^6$Li atoms by observing an energy gap in the radio-frequency excitation spectra. With control of the two-body interactions via a Feshbach resonance we demonstrate the dependence of the pairing gap on coupling strength, temperature, and Fermi energy. The appearance of an energy gap with moderate evaporative cooling suggests that our full evaporation brings the strongly interacting system deep into a superfluid state.Comment: 18 pages, 3 figure