Excitation Mechanisms of the Nitrogen First‐Positive and First‐Negative Radiation at High Temperature

The kinetic mechanisms responsible for the excitation of the first-positive and first-negative emission of nitrogen have been investigated in a re-examination of previously reported shock-tube measurements of the nonequilibrium radiation for these systems. The rate coefficients of the collisional quenching reactions, N_2(A^(3)Σ^(+)_u)(^(k^(N)_(-2))⇒) N_2(X^(1)Σ^(+)_g) + N(^(4)S) and N^(+)_2(B^(2)Σ^(+)_u) + N_2(X^(1)Σ^(+)_g)(^(k^(N)_(q))⇒) N^(+)_2(X^(2)Σ^(+)_g) or N^(+)_2(A(^(2)II_u)+N_2(X^(1)Σ^(+)_g) were found to be given by the empirical expressions, k_(2^(N))=5.1x10^(-3)T^(-2.23) cm^3 sec^(-1) and k_(q^(N_2))=1.9x10^(-2)T^(-2.33)cm^3 sec^(-1), respectively, over the approximate temperature range 6000-14 000°K

A stochastic model of turbulent mixing with chemical reaction: Nitric oxide formulation in a plug-flow burner

A stochastic model of turbulent mixing was developed for a reactor in which mixing is represented by n-body fluid particle interactions. The model was used to justify the assumption (made in previous investigations of the role of turbulent mixing on burner generated thermal nitric oxide and carbon monoxide emissions) that for a simple plug flow reactor, composition nonuniformities can be described by a Gaussian distribution function in the local fuel:air equivalence ratio. Recent extensions of this stochastic model to include the combined effects of turbulent mixing and secondary air entrainment on thermal generation of nitric oxide in gas turbine combustors are discussed. Finally, rate limited upper and lower bounds of the nitric oxide produced by thermal fixation of molecular nitrogen and oxidation of organically bound fuel nitrogen are estimated on the basis of the stochastic model for a plug flow burner; these are compared with experimental measurements obtained using a laboratory burner operated over a wide range of test conditions; good agreement is obtained

Elliptical Distance Transforms And Object Splitting

The classical morphological method to separate fused objects in binary images is to use the watershed transform on the complement of the distance transform of the binary image. This method assumes roughly disk-like objects and cannot separate objects when they are fused together beyond a certain point. In this paper we revisit the issue by assuming that fused objects are unions of ellipses rather than mere disks. The problem is recast in terms of finding the constituent primary grains given a boolean model of ellipses. To this end, we modify the well-known pseudo-Euclidean distance transform algorithm to generate arbitrary elliptical distance transforms to reduce the dimension of the problem and we present a goodness-of-fit measure that allows us to select ellipses. The results of the methods are given on both synthetic sample boolean models and real data

Enhanced dust heating in the bulges of early-type spiral galaxies

Stellar density and bar strength should affect the temperatures of the cool (T ~ 20–30 K) dust component in the inner regions of galaxies, which implies that the ratio of temperatures in the circumnuclear regions to the disk should depend on Hubble type. We investigate the differences between cool dust temperatures in the central 3 kpc and disk of 13 nearby galaxies by fitting models to measurements between 70 and 500 μm. We attempt to quantify temperature trends in nearby disk galaxies, with archival data from Spitzer/MIPS and new observations with Herschel/SPIRE, which were acquired during the first phases of the Herschel observations for the KINGFISH (Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel) sample. We fit single-temperature modified blackbodies to far-infrared and submillimeter measurements of the central and disk regions of galaxies to determine the temperature of the component(s) emitting at those wavelengths. We present the ratio of central-region-to-disk-temperatures of the cool dust component of 13 nearby galaxies as a function of morphological type. We find a significant temperature gradient in the cool dust component in all galaxies, with a mean center-to-disk temperature ratio of 1.15 ± 0.03. The cool dust temperatures in the central ~3 kpc of nearby galaxies are 23 (±3)% hotter for morphological types earlier than Sc, and only 9 (±3)% hotter for later types. The temperature ratio is also correlated with bar strength, with only strongly barred galaxies having a ratio over 1.2. The strong radiation field in the high stellar density of a galactic bulge tends to heat the cool dust component to higher temperatures, at least in early-type spirals with relatively large bulges, especially when paired with a strong bar

Delineating Differences in How US High Schools Are Racialized

Schools’ overt or explicit practices are a dominant lens through which education researchers and policymakers attempt to understand how schools are racially inequitable. Yet, Lewis and Diamond argue that contemporary racial inequalities are largely sustained through implicit factors, like institutional practices and structural inequalities. Ray’s framework on racialized organizations similarly outlines how our racialized sociopolitical structure becomes embedded in organizations, legitimating and perpetuating the racialized hierarchy. We apply illustrative cluster analysis techniques to rich data on schools, teachers, and students from the nationally representative High School Longitudinal Study of 2009 to find that structural inequities (e.g., student body, sector, average achievement) appear to be most salient in delineating the racialization of US high schools, whereas the characteristics of schools and teachers that are typically emphasized for closing racial inequities in educational outcomes (e.g., teacher qualifications, courses offered, stratification practices) are not salient differentiators across schools