Exploratory flight investigation of aircraft response to the wing vortex wake generated by the augmentor wing jet STOL research aircraft

A brief exploratory flight program was conducted at Ames Research Center to investigate the vortex wake hazard of a powered-lift STOL aircraft. The study was made by flying an instrumented Cessna 210 aircraft into the wake of the augmentor wing jet STOL research aircraft at separation distances from 1 to 4 n.mi. Characteristics of the wake were evaluated in terms of the magnitude of the upset of the probing aircraft. Results indicated that within 1 n.mi. separation the wake could cause rolling moments in excess of roll control power and yawing moments equivalent to rudder control power of the probe aircraft. Subjective evaluations by the pilots of the Cessna 210 aircraft, supported by response measurements, indicated that the upset caused by the wake of the STOL aircraft was comparable to that of a DC-9 in the landing configuration

Rifle Creek Dam DIY physical modelling

The application of Computational Fluid Dynamic (CFD) models can be fraught with uncertainties for the inexperienced modeller. The simulation results can vary radically depending on assumptions made regarding; boundary conditions, model domain, turbulence parameters etc. The acquisition of valuable experience and engineering judgment comes with observation of relevant experimental data, which however is often difficult to source. For Rifle creek Dam near Mount Isa, Australia, the author took the unusual step of developing a DYI (Do it Yourself) physical model of the dam was in the backyard of the CFD modeller to do experimental comparison with VOF CFD (HELYX) results. While it was well outside of the project scope it was well within the required sleep-at-night factor. The purpose of the project was to investigate methods of increasing the spillway capacity of the 1920’s built dam as per ICOLD (International Committee on Large Dams) dam safely requirements for acceptable flood capacity. Many older dams are subject to similar investigations, due to revised estimated maximum flood sizes, which often also result in retrofit construction activities to increase spillway capacity. Comparison of the simulation and the physical model characteristic spillway flow of the spillway is demonstrated by numerous videos

An equation of state for oxygen and nitrogen

Recent measurements of thermodynamic properties of oxygen and nitrogen have provided data necessary for development of a single equation of state for both fluids. Data are available in summary report and two-part detailed study on thermodynamic properties of oxygen and nitrogen. Same data are used to develop vapor-pressure equation and heat-capacity equation

Extended two-level quantum dissipative system from bosonization of the elliptic spin-1/2 Kondo model

We study the elliptic spin-1/2 Kondo model (spin-1/2 fermions in one dimension with fully anisotropic contact interactions with a magnetic impurity) in the light of mappings to bosonic systems using the fermion-boson correspondence and associated unitary transformations. We show that for fixed fermion number, the bosonic system describes a two-level quantum dissipative system with two noninteracting copies of infinitely-degenerate upper and lower levels. In addition to the standard tunnelling transitions, and the transitions driven by the dissipative coupling, there are also bath-mediated transitions between the upper and lower states which simultaneously effect shifts in the horizontal degeneracy label. We speculate that these systems could provide new examples of continuous time quantum random walks, which are exactly solvable.Comment: 7 pages, 1 figur

Comparison of multiple typing methods for Aspergillus fumigatus

As part of studies on the spread of infections, risk factors and prevention, several typing methods were developed to investigate the epidemiology of Aspergillus fumigatus. In the present study, 52 clinical isolates of A. fumigatus from 12 airway specimens from patients with invasive aspergillosis (hospitalized in three different centres) were characterized by short tandem repeat (STR) typing and multilocus sequence typing (MLST). These isolates were previously typed by random amplified polymorphic DNA (RAPD), sequence-specific DNA polymorphism (SSDP), microsatellite polymorphism (MSP) and multilocus enzyme electrophoresis (MLEE). STR typing identified 30 genotypes and, for most patients, all isolates were grouped in one cluster of the unweighted pair group method with arithmetic mean dendrogram. Using MLST, 16 genotypes were identified among 50 isolates, while two isolates appeared untypeable. RAPD, MSP, SSDP and MLEE allowed identification of eight, 14, nine and eight genotypes, respectively. Combining the results of these methods led to the delineation of 25 genotypes and a similar clustering pattern as with STR typing. In general, STR typing led to similar results to the previous combination of RAPD, SSDP, MSP and MLEE, but had a higher resolution, whereas MLST was less discriminatory and resulted in a totally different clustering pattern. Therefore, this study suggests the use of STR typing for research concerning the local epidemiology of A. fumigatus, which requires a high discriminatory power

Towards electron transport measurements in chemically modified graphene: The effect of a solvent

Chemical functionalization of graphene modifies the local electron density of the carbon atoms and hence electron transport. Measuring these changes allows for a closer understanding of the chemical interaction and the influence of functionalization on the graphene lattice. However, not only chemistry, in this case diazonium chemistry, has an effect on the electron transport. Latter is also influenced by defects and dopants resulting from different processing steps. Here, we show that solvents used in the chemical reaction process change the transport properties. In more detail, the investigated combination of isopropanol and heating treatment reduces the doping concentration and significantly increases the mobility of graphene. Furthermore, the isopropanol treatment alone increases the concentration of dopants and introduces an asymmetry between electron and hole transport which might be difficult to distinguish from the effect of functionalization. The results shown in this work demand a closer look on the influence of solvents used for chemical modification in order to understand their influence

Rate theory for correlated processes: Double-jumps in adatom diffusion

We study the rate of activated motion over multiple barriers, in particular the correlated double-jump of an adatom diffusing on a missing-row reconstructed Platinum (110) surface. We develop a Transition Path Theory, showing that the activation energy is given by the minimum-energy trajectory which succeeds in the double-jump. We explicitly calculate this trajectory within an effective-medium molecular dynamics simulation. A cusp in the acceptance region leads to a sqrt{T} prefactor for the activated rate of double-jumps. Theory and numerical results agree