201 research outputs found
Dynamic PID loop control
The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight
9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic
control system, how to hold liquid level constant in the cryostat by regulation
of its Joule-Thompson JT-valve is very important after cryostat cool down to
2.0 K. The 72-cell cryostat liquid level response generally takes a long time
delay after regulating its JT-valve; therefore, typical PID control loop should
result in some cryostat parameter oscillations. This paper presents a type of
PID parameter self-optimal and Time-Delay control method used to reduce
cryogenic system parameters' oscillation.Comment: 7 pp. Cryogenic Engineering Conference and International Cryogenic
Materials Conference CEC-ICMC 2011, 13-17 June 2011. Spokane, Washingto
Fermilab SRF cryomodule operational experience
Fermi National Accelerator Laboratory is constructing an Advanced Accelerator
Research and Development facility at New Muon Lab. The cryogenic infrastructure
in support of the initial phase of the facility consists of two Tevatron style
standalone refrigerators, cryogenic distribution system as well as an ambient
temperature pumping system to achieve 2 K operations with supporting
purification systems. During this phase of the project a single Type III plus
1.3 GHz cryomodule was installed, cooled and tested. Design constraints of the
cryomodule required that the cryomodule individual circuits be cooled at
predetermined rates. These constraints required special design solutions to
achieve. This paper describes the initial cooldown and operational experience
of a 1.3 GHz cryomodule using the New Muon Lab cryogenic system.Comment: 7 pp. Cryogenic Engineering Conference and International Cryogenic
Materials Conference CEC-ICMC 2011 13-17 June 2011, Spokane, Washingto
Stable propagation of an ordered array of cracks during directional drying
We study the appearance and evolution of an array of parallel cracks in a
thin slab of material that is directionally dried, and show that the cracks
penetrate the material uniformly if the drying front is sufficiently sharp. We
also show that cracks have a tendency to become evenly spaced during the
penetration. The typical distance between cracks is mainly governed by the
typical distance of the pattern at the surface, and it is not modified during
the penetration. Our results agree with recent experimental work, and can be
extended to three dimensions to describe the properties of columnar polygonal
patterns observed in some geological formations.Comment: 8 pages, 4 figures, to appear in PR
Reynolds-number Dependence of Streamwise Velocity Fluctuations in Turbulent Pipe Flow
Statistics of the streamwise velocity component in fully-developed pipe flow are examined for Reynolds numbers in the range 5.5 x 10^4 < Re_D < 5.7 x 10^6. The second moment exhibits two maxima: one in the viscous sublayer is Reynolds-number dependent while the other, near the lower edge of the log region, is also Reynolds-number dependent and follows roughly the peak in Reynolds shear stress. The behaviour of both peaks is consistent with the concept of inactive motion which increases with increasing Reynolds number and decreasing distance from the wall. No simple scaling is apparent, and in particular, so-called "mixed" scaling is no better than wall scaling in the viscous sublayer and is actually worse than wall scaling in the outer region. The second moment is compared with empirical and theoretical scaling laws
and some anomalies are apparent. The scaling of spectra using y, R and u_τ is examined. It appears that even at the highest Reynolds number, they exhibit
incomplete similarity only: while spectra do collapse with either inner or outer scales for limited ranges of wave number, these ranges do not overlap. Thus similarity may not be described as complete and any apparent k_1^(-1) range does not attract any special significance and does not involve universal constants. It is suggested that this is because of the influence of inactive motion. Spectra also show the presence of very long structures close to the wall
Diversity, competition, extinction: the ecophysics of language change
As early indicated by Charles Darwin, languages behave and change very much
like living species. They display high diversity, differentiate in space and
time, emerge and disappear. A large body of literature has explored the role of
information exchanges and communicative constraints in groups of agents under
selective scenarios. These models have been very helpful in providing a
rationale on how complex forms of communication emerge under evolutionary
pressures. However, other patterns of large-scale organization can be described
using mathematical methods ignoring communicative traits. These approaches
consider shorter time scales and have been developed by exploiting both
theoretical ecology and statistical physics methods. The models are reviewed
here and include extinction, invasion, origination, spatial organization,
coexistence and diversity as key concepts and are very simple in their defining
rules. Such simplicity is used in order to catch the most fundamental laws of
organization and those universal ingredients responsible for qualitative
traits. The similarities between observed and predicted patterns indicate that
an ecological theory of language is emerging, supporting (on a quantitative
basis) its ecological nature, although key differences are also present. Here
we critically review some recent advances lying and outline their implications
and limitations as well as open problems for future research.Comment: 17 Pages. A review on current models from statistical Physics and
Theoretical Ecology applied to study language dynamic
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Superconducting radio-frequency modules test facility operating experience
Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R&D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service Fermilab SRF R&D needs. The first stage of the project has been successfully completed, which allows for distribution of cryogens for a single cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at MDB results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project
Characterization of the Cytochrome P450 epoxyeicosanoid pathway in non-alcoholic steatohepatitis
Non-alcoholic steatohepatitis (NASH) is an emerging public health problem without effective therapies. Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid into bioactive epoxyeicosatrienoic acids (EETs), which have potent anti-inflammatory and protective effects. However, the functional relevance of the CYP epoxyeicosanoid metabolism pathway in the pathogenesis of NASH remains poorly understood. Our studies demonstrate that both mice with methionine-choline deficient (MCD) diet-induced NASH and humans with biopsy-confirmed NASH exhibited significantly higher free EET concentrations compared to healthy controls. Targeted disruption of Ephx2 (the gene encoding for soluble epoxide hydrolase) in mice further increased EET levels and significantly attenuated MCD diet-induced hepatic steatosis, inflammation and injury, as well as high fat diet-induced adipose tissue inflammation, systemic glucose intolerance and hepatic steatosis. Collectively, these findings suggest that dysregulation of the CYP epoxyeicosanoid pathway is a key pathological consequence of NASH in vivo, and promoting the anti-inflammatory and protective effects of EETs warrants further investigation as a novel therapeutic strategy for NASH
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Fermilab SRF cryomodule operational experience
Fermi National Accelerator Laboratory is constructing an Advanced Accelerator Research and Development facility at New Muon Lab. The cryogenic infrastructure in support of the initial phase of the facility consists of two Tevatron style standalone refrigerators, cryogenic distribution system as well as an ambient temperature pumping system to achieve 2K operations with supporting purification systems. During this phase of the project a single Type III plus 1.3 GHz cryomodule was installed, cooled and tested. Design constraints of the cryomodule required that the cryomodule individual circuits be cooled at predetermined rates. These constraints required special design solutions to achieve. This paper describes the initial cooldown and operational experience of a 1.3 GHz cryomodule using the New Muon Lab cryogenic system
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