Some aspects of flox-methane rocket engine throttling

Four injector designs and two chamber profiles were experimentally evaluated for structural integrity, combustion efficiency, and resistance to combustion instabilities. Vacuum thrust measurements were used as a primary measure of combustion efficiency. Stability rating to test the sensitivity of the injectors to high frequency combustion was conducted, but not extensively. To map the boundary between stable operation and chugging instability, chamber pressure was throttled downward from 689.5 to 206.9 kN/sq m abs (100 to 30 psia). Best operational results were obtained with an injector configuration having no hydraulic swirlers, a 0.00102-m (0.040-in.) recessed FLOX tube, and a nonflared exit in the methane annulus. This injector design exhibited stable combustion and good integrity of hardware, and it exceeded the design goal efficiency (88 percent) at the 10 to 1 throttled condition

On shape optimization for compressible isothermal Navier-Stokes equations

The steady state system of isothermal Navier-Stokes equations is considered in two dimensional domain including an obstacle. The shape optimisation problem of drag minimisation with respect to the admissible shape of the obstacle is defined. The generalized solutions for the Navier-Stokes equations are introduced. The existence of an optimal shape is proved in the class of admissible domains. In general the solution to the problem under consideration is not unique

Theory for the ultrafast ablation of graphite films

The physical mechanisms for damage formation in graphite films induced by femtosecond laser pulses are analyzed using a microscopic electronic theory. We describe the nonequilibrium dynamics of electrons and lattice by performing molecular dynamics simulations on time-dependent potential energy surfaces. We show that graphite has the unique property of exhibiting two distinct laser induced structural instabilities. For high absorbed energies (> 3.3 eV/atom) we find nonequilibrium melting followed by fast evaporation. For low intensities above the damage threshold (> 2.0 eV/atom) ablation occurs via removal of intact graphite sheets.Comment: 5 pages RevTeX, 3 PostScript figures, submitted to Phys. Re

The dynamical equivalence of modified gravity revisited

We revisit the dynamical equivalence between different representations of vacuum modified gravity models in view of Legendre transformations. The equivalence is discussed for both bulk and boundary space, by including in our analysis the relevant Gibbons-Hawking terms. In the f(R) case, the Legendre transformed action coincides with the usual Einstein frame one. We then re-express the R+f(G) action, where G is the Gauss-Bonnet term, as a second order theory with a new set of field variables, four tensor fields and one scalar and study its dynamics. For completeness, we also calculate the conformal transformation of the full Jordan frame R+f(G) action. All the appropriate Gibbons-Hawking terms are calculated explicitly.Comment: 17 pages; v3: Revised version. New comments added in Sections 3 & 5. New results added in Section 6. Version to appear in Class. Quantum Gravit

Developing a smart monitoring system for leakage currents from insulators on wooden poles

In Australia and many other countries, power distribution lines are carried on wooden poles. These lines suspended on insulators, which are fixed to wooden poles, pass cities as well as bushlands. Under different weather conditions, insulators become contaminated, and in particular, with damp weather, these insulators lose their ability to provide a perfect insulation between the high voltage conductor and the ground (through high impedance objects such as wood). A leakage current, small in magnitude, starts flowing from the high voltage conductor to the ground across the polluted insulator and through the wooden pole. If this phenomenon continues over some time, the currents start heating the wood where there is an abundance of wood-to-metal contact. At a certain stage, it will start smoking and this may lead to a pole fire. The obvious consequences of this are the loss of power to customers, public safety hazards and potential disasters such as bushfires. This thesis aims at determining which measure or combination of measures of leakage current are best suited for creating a ‘Leakage Current Health Index’ (LCHI) that can be later used to provide a power system operator with health status for a feeder or system, indicating how urgent a response is needed. To achieve this goal, the impedance characteristics of wooden poles altering the leakage current from insulators are investigated to better understand the role of wood in leakage current signatures. The effective impedance of wood used for poles in Victoria, Australia is established for the first time. Examining the impedance properties of typical Copper Chromium Arsenate (CCA) impregnated wood for 66 kV distribution poles shows dangerous conductance properties of wood at this voltage, providing an explanation for these poles catching fire at triple the rate of 22 kV distribution poles. After a systematic investigation of wood used for poles, a typical impedance characteristic is established for a weathered CCA impregnated wooden pole operating at 22 kV under both dry and wet weather conditions. Next, the leakage current from a single high voltage insulator is examined for various contamination levels and under different weather conditions. A new nonlinearity measure is established which utilises the Pearson correlation coefficient to measure the degree of leakage current nonlinearity and to build leakage current profiles of a single insulator under different conditions prior to flashover. Several fractal dimensions are also considered for the first time to measure characteristics of the leakage current profile of a single insulator. These measures are able to quantitatively differentiate between various levels of insulator contamination and different weather conditions, showing an enhanced level of nonlinear activity in the stage prior to insulator flashover. After developing an understanding of a single insulator, systematic modelling is used to build measure profiles of leakage currents for a simple power line, a lossless power line and a lossy power line. Finally, power utility zone substation data for a pole top fire are examined to verify the validity of the profiles observed utilising the measuring techniques determined suitable for establishing a LCHI

General practitioner characteristics and delay in cancer diagnosis. a population-based cohort study

<p>Abstract</p> <p>Background</p> <p>Delay in cancer diagnosis may have serious prognostic consequences, and some patients experience delays lasting several months. However, we have no knowledge whether such delays are associated with general practitioner (GP) characteristics. The aim of the present study was to analyse whether GP and practice characteristics are associated with the length of delay in cancer diagnosis.</p> <p>Methods</p> <p>The study was designed as a population-based cohort study. The setting was the County of Aarhus, Denmark (640,000 inhabitants). Participants include 334 GPs and their 1,525 consecutive, newly diagnosed cancer patients. During one year (September 2004 to August 2005), patients with incident cancer were enrolled from administrative registries. GPs completed questionnaires on the patients' diagnostic pathways and on GP and practice characteristics. Delay was categorised as patient-related (more than 60 days), doctor-related (more than 30 days) and system-related (more than 90 days). The associations between delay and characteristics were assessed in a logistic regression model using odds ratios (ORs).</p> <p>Results</p> <p>No GP characteristics (seniority, practice organization, list size, participation in continuing medical education, job satisfaction and level of burnout) were associated with doctor delay. Patients of female GPs more often had a short <it>patient delay </it>than patients of male GPs (OR 0.44, 95% confidence interval (95%CI) 0.28 to 0.71). Patients whose GPs provided many services (OR 0.66, 95%CI 0.44 to 0.95) and patients attending GPs with little former knowledge of their patients (OR 0.68, 95%CI 0.47 to 0.99) more often experienced a short <it>system delay </it>than patients attending GPs with less activity and more knowledge of their patients. Patients listed with a female GP more often experienced a long system delay than patients of male GPs (OR 1.50, 95%CI 1.02 to 2.21). Finally, patients with low GP-reported compliance more often experienced a long system delay (OR 1.73, 95%CI 1.07 to 2.80) than patients with higher compliance.</p> <p>Conclusions</p> <p>GP characteristics were not statistically significantly associated with doctor delay. However, some GP characteristics were associated with patient and system delay, which indicates that these factors may be important for understanding patient delay (e.g. perceived GP accessibility and the GP-patient relationship) and system delay (e.g. the GP's experience and opportunities for referring and coordinating diagnostic work-up).</p

Ultra high purity, dimensionally stable INVAR 36

An INVAR 36 material having long-term dimensional stability is produced by sintering a blend of powders of nickel and iron under pressure in an inert atmosphere to form an alloy containing less than 0.01 parts of carbon and less than 0.1 part aggregate and preferably 0.01 part individually of Mn, Si, P, S and Al impurities. The sintered alloy is heat treated and slowly and uniformly cooled to form a material having a coefficient of thermal expansion of less than 1 ppm/C and a temporal stability of less than 1 ppm/year

On shape optimization for compressible isothermal Navier-Stokes equations

The steady state system of isothermal Navier-Stokes equations is considered in two dimensional domain including an obstacle. The shape optimisation problem of drag minimisation with respect to the admissible shape of the obstacle is defined. The generalized solutions for the Navier-Stokes equations are introduced. The existence of an optimal shape is proved in the class of admissible domains. In general the solution to the problem under consideration is not unique

Future Practices and Technologies in Anthropometrics and Body Scanning

There have also been great strides in software development, to convert and manipulate 3D scan data, to make mannequins, lasts, patterns, tooling files, etc. The presenters invited to this special topic session are at the forefront of these research spaces, either through evaluating or utilizing these technologies for product design and developmen