Synthesis and characterization of silicon dioxide thin films by low pressure chemical vapor deposition using ditertiarybutylsilane and oxygen

This study is focused on the synthesis and characterization of silicon dioxide thin films deposited on silicon wafers by Low Pressure Chemical Vapor Deposition (LPCVD), using ditertiarybutylsilane (DTBS) as a precursor and oxygen as the oxidant. The dependence of film growth rate on various process parameters were studied. The growth rate was found to follow an Arrhenius curve with the variation in the temperature with an activation energy of 12.6 kcal/mol. The growth rate was found to be inversely proportional to the temperature in the range 550-750 °C. The refractive index and density were observed to be close to 1.47 and 2.71 g/cm3 respectively with flow rate ratio O2/DTBS = 2/1. Producing crack-free thick oxide films were performed at two different conditions. One was at 850 °C with flow rate ratio O2/DTBS = 5/1 which produced compressive stress with lower growth rate, and the other was at 700 °C with flow rate ratio O2/DTBS = 10/1 which produced tensile stress with higher growth rate. Both conditions were able to produce about 10 μm oxide films with no sign of cracking

The Octonions

The octonions are the largest of the four normed division algebras. While somewhat neglected due to their nonassociativity, they stand at the crossroads of many interesting fields of mathematics. Here we describe them and their relation to Clifford algebras and spinors, Bott periodicity, projective and Lorentzian geometry, Jordan algebras, and the exceptional Lie groups. We also touch upon their applications in quantum logic, special relativity and supersymmetry.Comment: 56 pages LaTeX, 11 Postscript Figures, some small correction

An Observed Transition of Galaxy Spins on the Void Surfaces

In the linear theory, the galaxy angular momentum vectors which originate from the initial tidal interactions with surrounding matter distribution intrinsically develop perpendicular alignments with the directions of maximum matter compression, regardless of galaxy mass. In simulations, however, the galaxy spins exhibit parallel alignments in the mass-range lower than a certain threshold, which depends on redshift, web type, and background cosmology. We show that the observed three dimensional spins of the spiral galaxies located on the void surfaces from the Sloan Digital Sky Survey indeed transit from the perpendicular to the parallel alignments with the directions toward the nearest void centers at the threshold zone, $9.51\le\log [M_{th,\star}/(h^{-1}\,M_{\odot})]\le10.03$. This study presents a first direct observational evidence for the occurrence of the mass-dependent spin transition of the real galaxies with respect to the non-filamentary structures of the cosmic web, opening a way to constrain the initial conditions of the early universe by measuring the spin transition threshold.Comment: Accepted by ApJ Letters, 5 figures and 1 table, improved statistics and data analysis after referee's revie

The Density Parity Model for the Evolution of the Subhalo Inner Spin Alignments with the Cosmic Web

We develop a new model within which the radius-dependent transition of the subhalo inner spins with respect to the cosmic web and the variation of the transition threshold radius ($r_{\rm th}$) with subhalo mass ($M_{\rm vir}$), smoothing scale ($r_{f}$), and redshift ($z$) can be coherently explained. The key tenet of this model is that the competition between the pressure effect of the inner mass and the compression effect of the local tidal field determines which principal direction of the tidal field the inner spins are aligned with. If the former predominates, then only the tidal torques turn on, resulting in the alignments of the inner spins with the intermediate principal axes of the tidal field. Otherwise, the subhalo spins acquire a tendency to be aligned with the shortest axes of the subhalo shapes, which is in the major principal directions of the tidal field. Quantifying the two effects in terms of the densities, we make a purely analytical prediction for $r_{\rm th}(M_{\rm vir}, z, r_{f})$. Testing this model against the numerical results from a high-resolution dark matter only N-body simulation in the redshift range of $0\le z\le 3$ on the galactic mass scale of $11.8\le \log[M_{\rm vir}/(h^{-1}M_{\odot})]\le 12.6$ for two different cases of $r_{f}/(h^{-1}{\rm Mpc})=0.5$ and $1$, we find excellent agreements of the model predictions with the numerical results. It is also shown that this model naturally predicts the alignments between the inner spins of the present subhalos with the principal axes of the high-$z$ tidal field at the progenitors' locations.Comment: Accepted for publication in ApJ, revised version after a referee's report, improved analysi

Identifying the Effect of Persuasion

We set up an econometric model of persuasion and study identification of key parameters under various scenarios of data availability. We find that a commonly used measure of persuasion does not estimate the persuasion rate of any population in general. We provide formal identification results, recommend several new parameters to estimate, and discuss their interpretation. Further, we propose methods for carrying out inference. We revisit the empirical literature on persuasion to show that the persuasive effect is highly heterogeneous. We also show that the existence of a continuous instrument opens up the possibility of point identification for the policy-relevant population

Reoriented Memory of Galaxy Spins for the Early Universe

Galaxy spins are believed to retain the initially acquired tendency of being aligned with the intermediate principal axes of the linear tidal field, which disseminates a prospect of using them as a probe of early universe physics. This roseate prospect, however, is contingent upon the key assumption that the observable stellar spins of the present galaxies measured at inner radii have the same alignment tendency toward the initial tidal field as their dark matter counterparts measured at virial limits. We test this assumption directly against a high-resolution hydrodynamical simulation by tracing back the galaxy component particles back to the protogalactic stage. It is discovered that the galaxy stellar spins at $z=0$ have strong but {\it reoriented} memory for the early universe, exhibiting a significant signal of cross-correlation with the {\it major} principal axes of the initial tidal field at $z=127$. An analytic single-parameter model for this reorientation of the present galaxy stellar spins relative to the initial tidal field is devised and shown to be in good accord with the numerical results.Comment: Accepted for publication in ApJ, revised version, improved analysis and more details about analytic modelin

Evaluation of primary water stress corrosion cracking growth rates by using the extended finite element method

AbstractBackgroundMitigation of primary water stress corrosion cracking (PWSCC) is a significant issue in the nuclear industry. Advanced nickel-based alloys with lower susceptibility have been adopted, although they do not seem to be entirely immune from PWSCC during normal operation. With regard to structural integrity assessments of the relevant components, an accurate evaluation of crack growth rate (CGR) is important.MethodsFor the present study, the extended finite element method was adopted from among diverse meshless methods because of its advantages in arbitrary crack analysis. A user-subroutine based on the strain rate damage model was developed and incorporated into the crack growth evaluation.ResultsThe proposed method was verified by using the well-known Alloy 600 material with a reference CGR curve. The analyzed CGR curve of the alternative Alloy 690 material was then newly estimated by applying the proven method over a practical range of stress intensity factors.ConclusionReliable CGR curves were obtained without complex environmental facilities or a high degree of experimental effort. The proposed method may be used to assess the PWSCC resistance of nuclear components subjected to high residual stresses such as those resulting from dissimilar metal welding parts