7,296 research outputs found
Planar maps, circle patterns and 2d gravity
Via circle pattern techniques, random planar triangulations (with angle
variables) are mapped onto Delaunay triangulations in the complex plane. The
uniform measure on triangulations is mapped onto a conformally invariant
spatial point process. We show that this measure can be expressed as: (1) a sum
over 3-spanning-trees partitions of the edges of the Delaunay triangulations;
(2) the volume form of a K\"ahler metric over the space of Delaunay
triangulations, whose prepotential has a simple formulation in term of ideal
tessellations of the 3d hyperbolic space; (3) a discretized version (involving
finite difference complex derivative operators) of Polyakov's conformal
Fadeev-Popov determinant in 2d gravity; (4) a combination of Chern classes,
thus also establishing a link with topological 2d gravity.Comment: Misprints corrected and a couple of footnotes added. 42 pages, 17
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Credit and Product Market Effects of Banking Deregulation: Evidence from the French Experience
Bankenreform, Deregulierung,, Industriestruktur, Frankreich, Banking reform, Deregulation, Industrial structure, France
Participatory Technology Assessment for Mars Mission Planning: Public Values and Rationales
Public support and interest are needed to design an ambitious human spaceflight program. However, it is difficult to understand what the public values and would support. And it is even more challenging and rare to consider public views prior to actually developing a mission. Participatory technology assessment (pTA) is a method that aims to understand public preferences and values in order to inform upstream government decision-making. We assess a recently completed experiment in pTA, the "Informing NASA's Asteroid Initiative" project. Through a cooperative agreement with NASA, the Expert and Citizen Assessment of Science and Technology (ECAST) network conducted a pTA-based forum on NASA's Asteroid Initiative and the Journey to Mars. ECAST organized two citizen forums in Phoenix, Arizona and Boston, Massachusetts in November 2014, with a total of 183 citizens selected so as to minimize self-selection biases. This paper focuses on the "Journey to Mars" session, which had the primary goal of soliciting citizen perceptions about different Mars exploration scenarios and mission planning approaches. Citizens were given background information about three potential Mars exploration scenarios that NASA could carry out: 1) Crewed orbital mission to direct robots on the surface of Mars; 2) Short exploratory crewed mission to the surface of Mars; and 3) establishing a permanent settlement. Citizens then engaged in structured facilitated discussions about their preferences among the scenarios and NASA's mission planning approach. Using a grounded theory coding approach, we analyzed participants' written rationales and dialogue about Mars exploration. In general, participants did not show a strong preference for any particular mission profile, but there was a slight preference for the crewed orbital robotics scenario. Participants who supported this approach saw it as the quickest, safest, and least costly road to a successful mission. However, many participants were interested in seeing "boots on the ground," as they believed this would propel scientific advancement, increase excitement about space exploration, and make humans a "two-planet species.
Alternate operating methods for improving the performance of a continuous stirred tank reactor
The effect of the pumping direction of an axial flow impeller, the feeding rate and the number of feed inlets on
the operation of a continuously-fed stirred tank has been studied using CFD. The flow patterns generated by the
up-pumping and down-pumping impeller, under both âtypicalâ and âintensifiedâ operating conditions, are
compared. The effect of various tank configurations on the performance of the vessel is assessed by analysing
the flow and power numbers, as well as the concentration field of a non-reactive tracer. Furthermore, the inlet
feed jets are reduced using traditional jet similarity analysis and are compared with that of a typical round jet.
The results show that up-pumping impellers improve circulation in the upper part of the tank and reduce shortcircuiting
of the feed stream with only a small increase in power consumption. Furthermore, by using multiple
feed inlets to increase the total throughput capacity, the amplitude of torque fluctuations is decreased and
impeller bypassing is also decreased. The ensemble of conclusions suggest that the throughput capacity and
mixing quality of a CSTR can be improved, without problems of short-circuiting, by employing up-pumping
impellers coupled with multiple surface feed points
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