15,577 research outputs found

    Foster-Miller's development of dry coal feed systems

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    Dry coal feeder systems developed for pressurized conversion processes were carried through a laboratory scale development program. These concepts include: (1) a centrifugal solids feeder; (2) a fluidized piston feeder; (3) a linear pocket feeder; and (4) a compacted coal plug feeder. Results of laboratory model testing of all concepts are reviewed

    Calibration of the seasonal growth model. Final report

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    Response of a one-dimensional Vlasov plasma to external electric fields

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    Numerical results of calculated response of collisionless electron plasma to externally imposed electric fiel

    The Effect of Statutory Rape Laws on Teen Birth Rates

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    Policymakers have often been explicit in expanding statutory rape laws to reduce teenage pregnancies and live births by teenage mothers, often with the goal of reducing associated welfare outlays. In this paper, we explore whether expansions in such laws are indeed associated with reductions in teen birth rates. In order to codify statutory-rape-law expansions, we use a national micro-level sample of sexual encounters to simulate the degree to which such encounters generally implicate the relevant laws. By codifying statutory-rape laws in terms of their potential reach into sexual encounters, as opposed to using crude binary treatment variables, this simulation approach facilitates the use of multi-state difference-in-difference designs in the face of highly heterogeneous legal structures. Our results suggest that live birth rates for teenage mothers fall by roughly 4.5 percent (or 0.1 percentage points) upon a 1 standard-deviation increase in the share of sexual activity among a given age group that triggers a felony for the elder party to the encounter. This response, however, is highly heterogeneous across ages and weakens notably in the case of the older teen years. Furthermore, we do not find strong results suggesting a further decline in birth rates upon increases in punishment severities

    Using a Laplace approximation to estimate the random coefficients logit model by non-linear least squares

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    Current methods of estimating the random coefficients logit model employ simulations of the distribution of the taste parameters through pseudo-random sequences. These methods suffer from difficulties in estimating correlations between parameters and computational limitations such as the curse of dimensionality. This paper provides a solution to these problems by approximating the integral expression of the expected choice probability using a multivariate extension of the Laplace approximation. Simulation results reveal that our method performs very well, both in terms of accuracy and computational time.

    Probing millisecond pulsar emission geometry using light curves from the Fermi Large Area Telescope

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    An interesting new high-energy pulsar sub-population is emerging following early discoveries of gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope (LAT). We present results from 3D emission modeling, including the Special Relativistic effects of aberration and time-of-flight delays and also rotational sweepback of B-field lines, in the geometric context of polar cap (PC), outer gap (OG), and two-pole caustic (TPC) pulsar models. In contrast to the general belief that these very old, rapidly-rotating neutron stars (NSs) should have largely pair-starved magnetospheres due to the absence of significant pair production, we find that most of the light curves are best fit by TPC and OG models, which indicates the presence of narrow accelerating gaps limited by robust pair production -- even in these pulsars with very low spin-down luminosities. The gamma-ray pulse shapes and relative phase lags with respect to the radio pulses point to high-altitude emission being dominant for all geometries. We also find exclusive differentiation of the current gamma-ray MSP population into two MSP sub-classes: light curve shapes and lags across wavebands impose either pair-starved PC (PSPC) or TPC / OG-type geometries. In the first case, the radio pulse has a small lag with respect to the single gamma-ray pulse, while the (first) gamma-ray peak usually trails the radio by a large phase offset in the latter case. Finally, we find that the flux correction factor as a function of magnetic inclination and observer angles is typically of order unity for all models. Our calculation of light curves and flux correction factor for the case of MSPs is therefore complementary to the "ATLAS paper" of Watters et al. for younger pulsars.Comment: 51 pages, 23 figures, 3 tables; low-resolution figures; accepted for publication by Ap
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