Erosive Augmentation of Solid Propellant Burning Rate: Motor Size Scaling Effect

Two different independent variable forms, a difference form and a ratio form, were investigated for correlating the normalized magnitude of the measured erosive burning rate augmentation above the threshold in terms of the amount that the driving parameter (mass flux or Reynolds number) exceeds the threshold value for erosive augmentation at the test condition. The latter was calculated from the previously determined threshold correlation. Either variable form provided a correlation for each of the two motor size data bases individually. However, the data showed a motor size effect, supporting the general observation that the magnitude of erosive burning rate augmentation is reduced for larger rocket motors. For both independent variable forms, the required motor size scaling was attained by including the motor port radius raised to a power in the independent parameter. A boundary layer theory analysis confirmed the experimental finding, but showed that the magnitude of the scale effect is itself dependent upon scale, tending to diminish with increasing motor size

Photon Conserving Radiative Transfer around Point Sources in multi-dimensional Numerical Cosmology

Many questions in physical cosmology regarding the thermal and ionization history of the intergalactic medium are now successfully studied with the help of cosmological hydrodynamical simulations. Here we present a numerical method that solves the radiative transfer around point sources within a three dimensional cartesian grid. The method is energy conserving independently of resolution: this ensures the correct propagation speeds of ionization fronts. We describe the details of the algorithm, and compute as first numerical application the ionized region surrounding a mini-quasar in a cosmological density field at z=7.Comment: 5 pages, 4 figures, submitted to ApJ

Population III star formation in a Lambda CDM universe, II: Effects of a photodissociating background

We examine aspects of primordial star formation in the presence of a molecular hydrogen-dissociating ultraviolet background. We compare a set of AMR hydrodynamic cosmological simulations using a single cosmological realization but with a range of ultraviolet background strengths in the Lyman-Werner band. This allows us to study the effects of Lyman-Werner radiation on suppressing H2 cooling at low densities as well as the high-density evolution of the collapsing core in a self-consistent cosmological framework. We find that the addition of a photodissociating background results in a delay of the collapse of high density gas at the center of the most massive halo in the simulation and, as a result, an increase in the virial mass of this halo at the onset of baryon collapse. We find that, contrary to previous results, Population III star formation is not suppressed for J$_{21} \geq 0.1$, but occurs even with backgrounds as high as J$_{21} = 1$. We find that H2 cooling leads to collapse despite the depressed core molecular hydrogen fractions due to the elevated H2 cooling rates at $T=2-5 \times 10^3$ K. We observe a relationship between the strength of the photodissociating background and the rate of accretion onto the evolving protostellar cloud core, with higher LW background fluxes resulting in higher accretion rates. Finally, we find that the collapsing halo cores in our simulations do not fragment at densities below $n \sim 10^{10}$ cm$^{-3}$ regardless of the strength of the LW background, suggesting that Population III stars forming in halos with T$_{vir} \sim 10^4$ K may still form in isolation.Comment: 46 pages, 14 figures (9 color). Accepted by the Astrophysical Journal, some minor revision

Technique for producing wind-tunnel heat-transfer models

Inexpensive thin skinned wind tunnel models with thermocouples on certain surface areas were fabricated. Thermocouples were designed for measuring aerodynamic heat transfer in wind tunnels

The Inability of Ambipolar Diffusion to set a Characteristic Mass Scale in Molecular Clouds

We investigate the question of whether ambipolar diffusion (ion-neutral drift) determines the smallest length and mass scale on which structure forms in a turbulent molecular cloud. We simulate magnetized turbulence in a mostly neutral, uniformly driven, turbulent medium, using a three-dimensional, two-fluid, magnetohydrodynamics (MHD) code modified from Zeus-MP. We find that substantial structure persists below the ambipolar diffusion scale because of the propagation of compressive slow MHD waves at smaller scales. Contrary to simple scaling arguments, ambipolar diffusion thus does not suppress structure below its characteristic dissipation scale as would be expected for a classical diffusive process. We have found this to be true for the magnetic energy, velocity, and density. Correspondingly, ambipolar diffusion leaves the clump mass spectrum unchanged. Ambipolar diffusion appears unable to set a characteristic scale for gravitational collapse and star formation in turbulent molecular clouds.Comment: 16 pages, 5 figures. ApJ accepte

Honey bee colony losses

No description supplie

Faktor-faktor Yang Mempengaruhi Tingkat Pengangguran Di Daerah Istimewa YOGYAKARTA (DIY) Tahun 1985-2011

This study aims to identify and analyze the efect of economic growth, real minimum wages, infation and the economic crisis in Indonesia in 1998 on the unemployment rate in the Special Region of Yogyakarta (DIY) in the 1985-2011 period. The data used are secondary data obtained from the Central Bureau of Statistics published in the various editions. Te analytical tool used to answer the problem formulation is the regression analysis using partial adjustment models (PAM). The analysis and hypothesis testing show that the economic growth, infation rate and the period of economic crisis in Indonesia in 1998 have a signifcant efect on the unemployment rate in the province, while the real minimum wage has no efect on the unemployment rate in the province

History of Long Cave

The story of Long Cave, later to become Grand Avenue Cave, is thoroughly intertwined in the rich history of saltpeter production and the show cave industry of Central Kentucky. The cave’s history parallels the early history of Mammoth Cave that is five miles away, the history of nearby Short Cave, and the development of Diamond Cave and Proctor Cave as show caves by the Proctor families. Today the cave is an important bat hibernaculum protected by the National Park Service. The cave is gated and locked, and entry is by research approval only