Control jet placement on spacecraft

For efficient operation and configuration design of multijet spacecraft control systems methods of linear programming are used to select combinations of individual jet-burn times which produce the desired impulses. Minimum-fuel and fuel-time solutions are found

Endogenous Product Choice : A Progress Report

Empirical models of differentiated product demand are widely used by both academics and practitioners. While these methods treat carefully the potential endogeneity of price, until recently they have assumed the number and characteristics of the products o.ered by firms are exogenous. This paper presents a progress report on an ongoing research agenda to address this issue. First, it summarizes how the appropriate choice of “orthogonal” instruments can yield consistent estimates of own and cross-price elasticities in the presence of endogenous product characteristics. Second, it summarizes how to measure “quality markups” and the welfare consequences of endogenous product quality in U.S. cable television markets. Related papers and extensions to consider multiple product characteristics and dynamics are also discussed.

Optical integral field spectroscopy of the extended line emission around six radio-loud quasars

We present integral field spectroscopy of a small sample of radio-loud quasars at intermediate redshift (0.26<z<0.60), most of which are associated with large radio sources. All have oxygen line emission extended over tens of kiloparcsecs, and these nebulae display a diverse range in both morphology and kinematic behaviour. Two quasars show 'plumes' of extended line emission, two show a clumpy structure and a further one shows a smooth distribution. There is no clear pattern with regard to the distribution of the ionized gas in relation to the radio source axis; the extended emission-line regions are found both parallel and perpendicular - and also totally unrelated to - the radio axis. The velocity structure of the ionized gas ranges from essentially static to apparent smooth rotation, and in two cases, show a clear association with the radio source. Given the disparity in properties, the nebulae all show a surprisingly similar ionization state, as measured by the extended lines of [OII] and [OIII]. Assuming the gas is ionized by at least the nearby quasar nucleus, we use the emission line ratios to infer a pressure in the ionized gas; in all cases we find it to be at high pressure, suggesting confinement by an external (probably intracluster) medium.Comment: 14 pages, 18 figures, 10 of which are presented separately; accepted for publication in MNRA

Monopoly quality degradation and regulation in cable television

Using an empirical framework based on the Mussa-Rosen model of monopoly quality choice, we calculate the degree of quality degradation in cable television markets and the impact of regulation on those choices. We find lower bounds of quality degradation ranging from 11 to 45 percent of offered service qualities. Furthermore, cable operators in markets with local regulatory oversight offer significantly higher quality, less degradation, and greater quality per dollar, despite higher prices

The Supreme Court, Due Process and State Income Taxation of Trusts

What are the constitutional limits on a state\u27s power to tax a trust with no connection to the state, other than the accident that a potential beneficiary lives there? The Supreme Court of the United States will take up this question this term in the context of North Carolina Department of Revenue v. Kimberley Rice Kaestner 1992 Family Trust. The case involves North Carolina\u27s income taxation of a trust with a contingent beneficiary, meaning someone who is eligible, but not certain, to receive a distribution or benefit from the trust, who resides in that state. Part I of this Article explains the background of Kaestner Trust and frames the constitutional questions that will be before the Court at oral arguments on April 16, 2019. Part II examines how and why due process applies in the state income taxation context, with a particular emphasis on how familiar concepts of general and specific jurisdiction apply uneasily to donative trusts. Part III articulates the reasons that the Court should hold that a state has no constitutional authority to impose a tax on trust income where the trust\u27s only connection with the forum state is the residence of a contingent beneficiary. Kaestner Trust is the most important due process case involving trusts that the Court has decided in over sixty years; it bears directly on the fundamental meaning of due process

Extended X-ray emission around four 3C quasars at 0.55<z<0.75 observed with Chandra

We report on the detection of a soft spatially-extended component of X-ray emission around four intermediate-redshift 3C quasars observed with Chandra: 3C254, 3C263, 3C275.1 and 3C281. The bolometric luminosity of this emission ranges over 0.3-1.6 times 10^{44}erg/s, and extends to lengthscales of over 350 kpc at the redshift of the quasar. The X-rays are most likely thermal emission from the intracluster medium of a cluster of galaxies around each quasar, which provides the working surface for the powerful radio lobes. Some X-ray emission is also seen to be associated with the radio plasma.Comment: 8 pages, 4 panelled figures, MNRAS in pres

A deep Chandra observation of the cluster environment of the z=1.786 radio galaxy 3C294

We report the results from a 200 ks Chandra observation of the z=1.786 radio galaxy 3C294 and its cluster environment, increasing by tenfold our earlier observation. The diffuse emission, extending about 100 kpc around the nucleus, has a roughly hourglass shape in the N-S direction with surprisingly sharp edges to the N and S. The spectrum of the diffuse emission is well fitted by either a thermal model of temperature 3.5 keV and abundance <0.9 solar (2-sigma), or a power-law with photon index 2.3. If the emission is due to hot gas then the sharp edges mean that it is probably not in hydrostatic equilibrium. Much of the emission is plausibly due to inverse Compton scattering of the Cosmic Microwave Background (CMB) by nonthermal electrons produced earlier by the radio source. The required relativistic electrons would be of much lower energy and older than those responsible for the present radio lobes. This could account for the lack of detailed spatial correspondence between the X-rays and the radio emission, the axis of which is at a position angle of about 45 deg. Hot gas would still be required to confine the relativistic plasma; the situation could parallel that of the radio bubbles seen as holes in nearby clusters, except that in 3C294 the bubbles are bright in X-rays owing to the extreme power in the source and the sixty fold increase in the energy density of the CMB. The X-ray spectrum of the radio nucleus is hard, showing a reflection spectrum and iron line. The source is therefore an obscured radio-loud quasar.Comment: In press (MNRAS), 10 pages, 12 figures (2 colour

Space shuttle post-entry and landing analysis. Volume 2: Appendices

Four candidate navigation systems for the space shuttle orbiter approach and landing phase are evaluated in detail. These include three conventional navaid systems and a single-station one-way Doppler system. In each case, a Kalman filter is assumed to be mechanized in the onboard computer, blending the navaid data with IMU and altimeter data. Filter state dimensions ranging from 6 to 24 are involved in the candidate systems. Comprehensive truth models with state dimensions ranging from 63 to 82 are formulated and used to generate detailed error budgets and sensitivity curves illustrating the effect of variations in the size of individual error sources on touchdown accuracy. The projected overall performance of each system is shown in the form of time histories of position and velocity error components