77,967 research outputs found
Conditions implying the uniqueness of the weak*-topology on certain group algebras
We investigate possible preduals of the measure algebra M(G) of a locally compact group and the Fourier algebra A(G) of a separable compact group. Both of these algebras are canonically dual spaces and the canonical preduals make the multiplication separately weak*-continuous so that these algebras are dual Banach algebras. In this paper we find additional conditions under which the preduals
C0(G) of M(G) and C*(G) of A(G) are uniquely determined. In both cases we consider a natural comultiplication and show that the canonical predual gives rise to the unique weak*-topology making both the multiplication separately weak*-continuous and the comultiplication weak*-continuous. In particular, dual cohomological properties of these algebras are well defined with this additional structure
Control System Design Philosophy for Effective Operations and Maintenance
A well-designed control system facilitates the functions of machine
operation, maintenance and development. In addition, the overall effectiveness
of the control system can be greatly enhanced by providing reliable mechanisms
for coordination and communication, ensuring that these functions work in
concert. For good operability, the information presented to operators should be
consistent, easy to understand and customizable. A maintainable system is
segmented appropriately, allowing a broken element to be quickly identified and
repaired while leaving the balance of the system available. In a research and
development environment, the control system must meet the frequently changing
requirements of a variety of customers. This means the system must be flexible
enough to allow for ongoing modifications with minimal disruptions to
operations. Beyond the hardware and software elements of the control system,
appropriate workflow processes must be in place to maximize system uptime and
allow people to work efficiently. Processes that provide automatic electronic
communication ensure that information is not lost and reaches its destination
in a timely fashion. This paper discusses how these control system design and
quality issues have been applied at the Thomas Jefferson National Accelerator
Facility.Comment: ICALEPCS 200
Variable dimension automatic synthesis programs (VASP)
Variable dimension FORTRAN 4 version of the Automatic Synthesis Program (ASP) compensates for limitations within the program itself. Improvements are versatile programming language, convenient input/output format, new subprograms, variable dimensioning, and efficient storage
Preduals of semigroup algebras
For a locally compact group G, the measure convolution algebra M(G) carries a natural coproduct. In previous work, we showed that the canonical predual C 0(G) of M(G) is the unique predual which makes both the product and the coproduct on M(G) weak*-continuous. Given a discrete semigroup S, the convolution algebra ℓ 1(S) also carries a coproduct. In this paper we examine preduals for ℓ 1(S) making both the product and the coproduct weak*-continuous. Under certain conditions on S, we show that ℓ 1(S) has a unique such predual. Such S include the free semigroup on finitely many generators. In general, however, this need not be the case even for quite simple semigroups and we construct uncountably many such preduals on ℓ 1(S) when S is either ℤ+×ℤ or (ℕ,⋅)
Using A Nameserver to Enhance Control System Efficiency
The Thomas Jefferson National Accelerator Facility (Jefferson Lab) control
system uses a nameserver to reduce system response time and to minimize the
impact of client name resolution on front-end computers. The control system is
based on the Experimental Physics and Industrial Control System (EPICS), which
uses name-based broadcasts to initiate data communication. By default, when
EPICS process variables (PV) are requested by client applications, all
front-end computers receive the broadcasts and perform name resolution
processing against local channel name lists. The nameserver is used to offload
the name resolution task to a single node. This processing, formerly done on
all front-end computers, is now done only by the nameserver. In a control
system with heavily loaded front-end computers and high peak client connection
loads, a significant performance improvement is seen. This paper describes the
name server in more detail, and discusses the strengths and weaknesses of
making name resolution a centralized service.Comment: ICALEPCS 200
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Flood- and Weather-Damaged Homes and Mental Health: An Analysis Using England's Mental Health Survey
There is increasing evidence that exposure to weather-related hazards like storms and floods adversely affects mental health. However, evidence of treated and untreated mental disorders based on diagnostic criteria for the general population is limited. We analysed the Adult Psychiatric Morbidity Survey, a large probability sample survey of adults in England (n = 7525), that provides the only national data on the prevalence of mental disorders assessed to diagnostic criteria. The most recent survey (2014–2015) asked participants if they had experienced damage to their home (due to wind, rain, snow or flood) in the six months prior to interview, a period that included months of unprecedented population exposure to flooding, particularly in Southern England. One in twenty (4.5%) reported living in a storm- or flood-damaged home in the previous six months. Social advantage (home ownership, higher household income) increased the odds of exposure to storm or flood damage. Exposure predicted having a common mental disorder over and above the effects of other known predictors of poor mental health. With climate change increasing the frequency and severity of storms and flooding, improving community resilience and disaster preparedness is a priority. Evidence on the mental health of exposed populations is key to building this capacity
The Structure and Clustering of Lyman Break Galaxies
The number density and clustering properties of Lyman-break galaxies (LBGs)
are consistent with them being the central galaxies of the most massive dark
halos present at z~3. This conclusion holds in all currently popular
hierarchical models for structure formation, and is almost independent of the
global cosmological parameters. We examine whether the sizes, luminosities,
kinematics and star-formation rates of LBGs are also consistent with this
identification. Simple formation models tuned to give good fits to low redshift
galaxies can predict the distribution of these quantities in the LBG
population. The LBGs should be small (with typical half-light radii of 0.6-2
kpc/h), should inhabit haloes of moderately high circular velocity (180-290
km/s) but have low stellar velocity dispersions (70-120 km/s) and should have
substantial star formation rates (15-100 Msun/yr). The numbers here refer to
the predicted median values in the LBG sample of Adelberger et al. (1998); the
first assumes an Omega=1 universe and the second a flat universe with
Omega=0.3. For either cosmology these predictions are consistent with the
current (rather limited) observational data. Following the work of Kennicutt
(1998) we assume stars to form more rapidly in gas of higher surface density.
This predicts that LBG samples should preferentially contain objects with low
angular momentum, and so small size, for their mass. In contrast, samples of
damped Lyman alpha systems (DLSs), should be biased towards objects with large
angular momentum. Bright LBGs and DLSs may therefore form distinct populations,
with very different sizes and star formation rates, LBGs being smaller and more
metal-rich than DLSs of similar mass and redshift.Comment: 27 pages, 9 figures, MNRAS submitte
Wilson line approach to gravity in the high energy limit
We examine the high energy (Regge) limit of gravitational scattering using a
Wilson line approach previously used in the context of non-Abelian gauge
theories. Our aim is to clarify the nature of the Reggeization of the graviton
and the interplay between this Reggeization and the so-called eikonal phase
which determines the spectrum of gravitational bound states. Furthermore, we
discuss finite corrections to this picture. Our results are of relevance to
various supergravity theories, and also help to clarify the relationship
between gauge and gravity theories.Comment: 33 pages, 5 figure
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