22,476 research outputs found
An Attempt to Reshape Capitalism’s Image
John Stuart Mill claimed to be a disciple of both Jeremy Bentham and David Ricardo. This was a strange proclamation because each man advocated a competing theory of value; Bentham’s utilitarianism laid the foundation for the utility theory of value and Ricardo developed the labor theory of value. Mill’s goal in attempting to unify these theories of value was to provide a solution for the growing class conflict that plagued capitalism. Class conflict arose as feudalism was phased out and industrial capitalism replaced merchant capitalism as the dominant economic system. The Corn Laws symbolized this competition between classes. Capitalists were against the Corn Laws because the subsequent tariffs would lower their rate of profit. Landowners supported the Corn Laws because they increased the rent on land. Even Karl Marx held spoke out against the Corn Laws on behalf of the working class. Capitalism fostered persistent antagonism between classes as each struggled to gain or maintain power; no class was immune from this contest. Class conflict was therefore ubiquitous in capitalist society and generated widespread scrutiny and debate over capitalism. Jeremy Bentham and David Ricardo took opposing sides in this debate. Bentham was initially supported it but died a reformist. Class conflict was resolvable but not under the current form of capitalism. Ricardo’s labor theory of value promoted the view that class division occurred naturally in a capitalist society. And since capitalism was the best possible economic system, class division was a necessary evil and could not be remedied. Both Ricardo and Bentham acknowledged that class conflict was inherent in capitalism but each treated it differently. In claiming to be a disciple of both men, Mill hoped to show that capitalism could exist alongside social harmony. His goal was to change the nature of capitalism. [excerpt
Center-of-mass angular momentum and memory effect in asymptotically flat spacetimes
Gravitational-wave (GW) memory effects are constant changes in the GW strain
and its time integrals, which are closely connected to changes in the charges
that characterize asymptotically flat spacetimes. The first GW memory effect
discovered was a lasting change in the GW strain. It can occur when GWs or
massless fields carry away 4-momentum from an isolated source. Subsequently, it
was shown that fluxes of intrinsic angular momentum can generate a new type of
memory effect called the spin memory, which is an enduring change in a portion
of the time integral of the GW strain. In this paper, we note that there is
another new type of memory effect. We call it the center-of-mass (CM) memory
effect, because it is related to changes in the CM part of the angular momentum
of a spacetime. We first examine a few properties of the CM angular momentum.
Specifically, we describe how it transforms under the supertranslation symmetry
transformations of the Bondi-Metzner-Sachs group, and we compute a new
expression for the flux of CM angular momentum carried by GWs in terms of a set
of radiative multipole moments of the GW strain. We then turn to the CM memory
effect. The CM memory effect appears in a quantity which has units of the time
integral of the GW strain. We define the effect in asymptotically flat
spacetimes that start in a stationary state, radiate, and settle to a different
stationary state. We show that it is invariant under infinitesimal
supertranslation symmetries in this context. To determine the magnitude of the
flux of CM angular momentum and the CM memory effect, we compute these
quantities for nonspinning, quasicircular compact binaries in the
post-Newtonian approximation. The CM memory effect arises from terms in the
gravitational waveform for such binaries beginning at third and fourth
post-Newtonian order for unequal- and equal-mass binaries, respectively.
[Abstract abridged]Comment: v2: 26 pages; updated to match version published in Phys. Rev.
Thermal vacuum testing techniques for spacecraft
Cesium frequency standards are to be flown on the NTS-2 satellite which is a program conducted to develop technology and time standards for NAVSTAR Global Positioning System. Mission requirements for the thermal design of this frequency standard called for a low nominal temperature (15 C) and the removal of most of the heat generated by the standard from the spacecraft. The test program run to determine the thermal properties of the frequency standard is described. A simulator was constructed for these tests. Special mathematical analysis techniques were developed and were used to predict the thermal environment for different orbital conditions. Thermal vacuum tests of the flight frequency standard and the integrated spacecraft demonstrated the validity of this technique
Oceanographic satellite remote sensing: Registration, rectification, and data integration requirements
The problem of data integration in oceanography is discussed. Recommendations are made for technique development and evaluation, understanding requirements, and packaging techniques for speed, efficiency and ease of use. The primary satellite sensors of interest to oceanography are summarized. It is concluded that imaging type sensors make image processing an important tool for oceanographic studies
Digital frequency control of satellite frequency standards
In the Frequency and Time Standard Development Program of the TIMATION System, a new miniaturized rubidium vapor frequency standard has been tested and analyzed for possible use on the TIMATION 3A launch, as part of the Defense Navigation Satellite Development Program. The design and construction of a digital frequency control was required to remotely control this rubidium vapor frequency standard as well as the quartz oscillator in current use. This control must be capable of accepting commands from a satellite telemetry system, verify that the correct commands have been sent and control the frequency to the requirements of the system. Several modifications must be performed to the rubidium vapor frequency standard to allow it to be compatible with the digital frequency control. These include the addition of a varactor to voltage tune the coarse range of the flywheel oscillator, and a modification to supply the C field current externally. The digital frequency control for the rubidium vapor frequency standard has been successfully tested in prototype form
Hybrid method for understanding black-hole mergers: Inspiralling case
We adapt a method of matching post-Newtonian and black-hole-perturbation theories on a timelike surface (which proved useful for understanding head-on black-hole-binary collisions) to treat equal-mass, inspiralling black-hole binaries. We first introduce a radiation-reaction potential into this method, and we show that it leads to a self-consistent set of equations that describe the simultaneous evolution of the waveform and of the timelike matching surface. This allows us to produce a full inspiral-merger-ringdown waveform of the l=2, m=±2 modes of the gravitational waveform of an equal-mass black-hole-binary inspiral. These modes match those of numerical-relativity simulations well in phase, though less well in amplitude for the inspiral. As a second application of this method, we study a merger of black holes with spins antialigned in the orbital plane (the superkick configuration). During the ringdown of the superkick, the phases of the mass- and current-quadrupole radiation become locked together, because they evolve at the same quasinormal-mode frequencies. We argue that this locking begins during the merger, and we show that if the spins of the black holes evolve via geodetic precession in the perturbed black-hole spacetime of our model, then the spins precess at the orbital frequency during the merger. In turn, this gives rise to the correct behavior of the radiation, and produces a kick similar to that observed in numerical simulations
Properties of an affine transport equation and its holonomy
An affine transport equation was used recently to study properties of angular
momentum and gravitational-wave memory effects in general relativity. In this
paper, we investigate local properties of this transport equation in greater
detail. Associated with this transport equation is a map between the tangent
spaces at two points on a curve. This map consists of a homogeneous (linear)
part given by the parallel transport map along the curve plus an inhomogeneous
part, which is related to the development of a curve in a manifold into an
affine tangent space. For closed curves, the affine transport equation defines
a "generalized holonomy" that takes the form of an affine map on the tangent
space. We explore the local properties of this generalized holonomy by using
covariant bitensor methods to compute the generalized holonomy around geodesic
polygon loops. We focus on triangles and "parallelogramoids" with sides formed
from geodesic segments. For small loops, we recover the well-known result for
the leading-order linear holonomy ( Riemann area), and we derive
the leading-order inhomogeneous part of the generalized holonomy (
Riemann area). Our bitensor methods let us naturally compute
higher-order corrections to these leading results. These corrections reveal the
form of the finite-size effects that enter into the holonomy for larger loops;
they could also provide quantitative errors on the leading-order results for
finite loops.Comment: 18 pages, 4 figures, new short section (Sec. 5) in v3; updated to
match article published in GR
Modeling and inference of multisubject fMRI data
Functional magnetic resonance imaging (fMRI) is a
rapidly growing technique for studying the brain in
action. Since its creation [1], [2], cognitive scientists
have been using fMRI to understand how we remember,
manipulate, and act on information in our environment.
Working with magnetic resonance physicists, statisticians, and
engineers, these scientists are pushing the frontiers of knowledge
of how the human brain works.
The design and analysis of single-subject fMRI studies
has been well described. For example, [3], chapters 10
and 11 of [4], and chapters 11 and 14 of [5] all give accessible
overviews of fMRI methods for one subject. In contrast,
while the appropriate manner to analyze a group of
subjects has been the topic of several recent papers, we do
not feel it has been covered well in introductory texts and
review papers. Therefore, in this article, we bring together
old and new work on so-called group modeling of fMRI
data using a consistent notation to make the methods more
accessible and comparable
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