78,612 research outputs found
Earthquake source parameters and fault kinematics in the Eastern California Shear Zone
Based on waveform data from a profile of aftershocks following the
north-south trace of the June 28, 1992 Landers rupture across the Mojave
desert, we construct a new velocity model for the Mojave region which features
a thin, slow crust. Using this model, we obtain source parameters, including
depth and duration, for each of the aftershocks in the profile, and in
addition, any significant (M>3.7) Joshua Tree--Landers aftershock between
April, 1992 and October, 1994 for which coherent TERRAscope data were
available. In all, we determine source parameters and stress-drops for 45
significant (M_w > 4) earthquakes associated with the Joshua Tree and Landers
sequences, using a waveform grid-search algorithm. Stress drops for these
earthquakes appear to vary systematically with location, with respect to
previous seismic activity, proximity to previous rupture (i.e., with respect to
the Landers rupture), and with tectonic province. In general, for areas north
of the Pinto Mountain fault, stress-drops of aftershocks located off the faults
involved with the Landers rupture are higher than those located on the fault,
with the exception of aftershocks on the newly recognized Kickapoo (Landers)
fault. Stress drops are moderate south of the Pinto Mountain fault, where there
is a history of seismic swarms but no single through-going fault. In contrast
to aftershocks in the eastern Transverse ranges, and related to the 1992 Big
Bear, California, sequence, Landers events show no clear relationship between
stress-drop and depth. Instead, higher stress-drop aftershocks appear to
correlate with activity on nascent faults, or those which experienced
relatively small slip during mainshock rupture.Comment: 27 pages, 15 figures, to appear in Bull. Seism. Soc. A
A Preliminary Investigation of the Performance of a Short-length Turbojet Combustor Using Vaporized Hydrocarbon Fuels
Two short turbojet combustors designed for use with vaporized hydrocarbon fuels were tested in a one-quarter annular duct. The experimental combustors consisted of many small "swirl-can" combustor elements manifolded together. This design approach allowed the secondary mixing zone to be considerably reduced over that of conventional combustors. The over-all combustion lengths, for the two configurations were 13.5 and 11.0 inches, approximately one-half the length of the shortest conventional combustors. These short combustors did not provide combustion efficiencies as high as those for conventional combustors at low pressures. However, over the range of combustor-inlet total-pressures expected in aircraft capable of flight at Mach numbers of 2.5 and above, these short combustors gave very high efficiencies. A combustion efficiency of 97 percent was obtained at a combustor-inlet total-pressure of 25.0 inches of mercury absolute, reference velocity of 120 feet per second, and inlet-air total temperature of 1160 deg R. By proportioning the fuel flow between the manifold rows of can combustor elements, control of the combustor-outlet radial total-temperature profile was demonstrated. Combustor totalpressure loss varied from 0.75 percent of the inlet total pressure at isothermal conditions and a reference velocity of 75 feet per second to 5.5 percent at a total-temperature ratio of 1.8 and a reference velocity of 180 feet per second
The economics of split-ticket voting in representative democracies
In U.S. elections, voters often vote for candidates from different parties for president and Congress. Voters also express dissatisfaction with the performance of Congress as a whole and satisfaction with their own representative. We develop a model of split-ticket voting in which government spending is financed by uniform taxes but the benefits from this spending are concentrated. While the model generates split-ticket voting, overall spending is too high only if the president’s powers are limited. Overall spending is too high in a parliamentary system, and our model can be used as the basis of an argument for term limits.Government spending policy
Automatic assembly design project 1968/9 :|breport of economic planning committee
Investigations into automatic assembly systems have
been carried out. The conclusions show the major
features to be considered by a company operating
the machine to assemble the contact block with regard
to machine output and financial aspects.
The machine system has been shown to be economically
viable for use under suitable conditions, but the
contact block is considered to be unsuitable for
automatic assembly.
Data for machine specification, reliability and
maintenance has been provided
Recommended from our members
Smart Computer Security Audit: Reinforcement Learning with a Deep Neural Network Approximator
A significant challenge in modern computer security is the growing skill gap as intruder capabilities increase, making it necessary to begin automating elements of penetration testing so analysts can contend with the growing number of cyber threats. In this paper, we attempt to assist human analysts by automating a single host penetration attack. To do so, a smart agent performs different attack sequences to find vulnerabilities in a target system. As it does so, it accumulates knowledge, learns new attack sequences and improves its own internal penetration testing logic. As a result, this agent (AgentPen for simplicity) is able to successfully penetrate hosts it has never interacted with before. A computer security administrator using this tool would receive a comprehensive, automated sequence of actions leading to a security breach, highlighting potential vulnerabilities, and reducing the amount of menial tasks a typical penetration tester would need to execute. To achieve autonomy, we apply an unsupervised machine learning algorithm, Q-learning, with an approximator that incorporates a deep neural network architecture. The security audit itself is modelled as a Markov Decision Process in order to test a number of decisionmaking strategies and compare their convergence to optimality. A series of experimental results is presented to show how this approach can be effectively used to automate penetration testing using a scalable, i.e. not exhaustive, and adaptive approach
The Structure of the Nucleon: Elastic Electromagnetic Form Factors
Precise proton and neutron form factor measurements at Jefferson Lab, using
spin observables, have recently made a significant contribution to the
unraveling of the internal structure of the nucleon. Accurate experimental
measurements of the nucleon form factors are a test-bed for understanding how
the nucleon's static properties and dynamical behavior emerge from QCD, the
theory of the strong interactions between quarks. There has been enormous
theoretical progress, since the publication of the Jefferson Lab proton form
factor ratio data, aiming at reevaluating the picture of the nucleon. We will
review the experimental and theoretical developments in this field and discuss
the outlook for the future.Comment: arXiv admin note: text overlap with arXiv:1301.0905,
arXiv:hep-ph/0609004, arXiv:1411.6908 by other author
Recommended radiative property data for Venusian entry calculations
A compilation of experimental and calculated data on the radiative properties species important in Venusian entry is presented. Molecular band systems, atomic lines, free-bound, and free-free continua are considered for the principal radiating species of shock heated carbon dioxide. A limited amount of data pertinent to the species in the ablation layer is also included. The assumption is made that the Venus atmosphere so closely approximates pure CO2 that the inviscid layer radiation is due almost entirely to thermally excited CO2. The only exception is the inclusion of data on the Violet band system of CN. Recommendations are made as to best property values for radiative heating calculations. A review of the basic equations and the relationships of the various emission-absorption gas porperties is also included
Radiative property data for Venusian entry: A compendium
A compilation of experimental and calculated data on the radiative properties of species important in Venusian entry is presented. Molecular band systems, atomic lines, free-bound continua, and free-free continua are considered for the principal radiating species of shock-heated carbon dioxide. Data pertinent to the species in the ablation layer are included. The Venus atmosphere so closely approximates pure carbon dioxide (CO2) that the inviscid layer radiation is due almost entirely to thermally excited CO2. Data are included on the violet band system of the cyanogen radical CN. Recommendations are made as to best property values for radiative heating calculations. A review of the basic equations and the relationships of the various emission-absorption gas properties is included
Zenithal bistability in a nematic liquid crystal device with a monostable surface condition
The ground-state director configurations in a grating-aligned, zenithally bistable nematic device are calculated in two dimensions using a Q tensor approach. The director profiles generated are well described by a one-dimensional variation of the director across the width of the device, with the distorted region near the grating replaced by an effective surface anchoring energy. This work shows that device bistability can in fact be achieved by using a monostable surface term in the one-dimensional model. This implies that is should be possible to construct a device showing zenithal bistability without the need for a micropatterned surface
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