16,110 research outputs found
The Use of Multi-beam Sonars to Image Bubbly Ship Wakes
During the past five years, researchers at Penn State University (PSU) have used upward-looking multi-beam (MB) sonar to image the bubbly wakes of surface ships. In 2000, a 19-beam, 5° beam width, 120° sector, 250 kHz MB sonar integrated into an autonomous vehicle was used to obtain a first-of-a-kind look at the three-dimensional variability of bubbles in a large ship wake. In 2001 we acquired a Reson 8101 MB sonar, which operates at 240 kHz and features 101-1.5º beams spanning a 150º sector. In July 2002, the Reson sonar was deployed looking upward from a 1.4 m diameter buoy moored at 29.5 m depth in 550 m of water using three anchor lines. A fiber optic cable connected the sonar to a support ship 500 m away. Images of the wake of a small research vessel provided new information about the persistence of bubble clouds in the ocean. An important goal is to use the MB sonar to estimate wake bubble distributions, as has been done with single beam sonar. Here we show that multipath interference and strong, specular reflections from the sea surface adversely affect the use of MB sonars to unambiguously estimate wake bubble distributio
Art and Medicine: A Collaborative Project Between Virginia Commonwealth University in Qatar and Weill Cornell Medicine in Qatar
Four faculty researchers, two from Virginia Commonwealth University in Qatar, and two from Weill Cornell Medicine in Qatar developed a one semester workshop-based course in Qatar exploring the connections between art and medicine in a contemporary context. Students (6 art / 6 medicine) were enrolled in the course. The course included presentations by clinicians, medical engineers, artists, computing engineers, an art historian, a graphic designer, a painter, and other experts from the fields of art, design, and medicine. To measure the student experience of interdisciplinarity, the faculty researchers employed a mixed methods approach involving psychometric tests and observational ethnography. Data instruments included pre- and post-course semi-structured audio interviews, pre-test / post-test psychometric instruments (Budner Scale and Torrance Tests of Creativity), observational field notes, self-reflective blogging, and videography. This book describes the course and the experience of the students. It also contains images of the interdisciplinary work they created for a culminating class exhibition. Finally, the book provides insight on how different fields in a Middle Eastern context can share critical /analytical thinking tools to refine their own professional practices
Effect of high glucose concentration on the synthesis of monocyte chemoattractant protein-1 in human peritoneal mesothelial cells: Involvement of protein kinase C
Human peritoneal mesothelial cells (HMC) contribute to the activation and control of inflammatory processes in the peritoneum by their potential to produce various inflammatory mediators. The present study was designed to assess the effect of glucose, the osmotic active compound in most commercially available peritoneal dialysis fluids, on the synthesis of the C-C chemokine monocyte chemoattractant protein-1 (MCP-1) in cultured HMC. The MCP-1 concentration in the cell supernatants was determined by enzyme-linked immunosorbent assay and the MCP-1 mRNA expression was examined using Northern blot analysis. Incubation of HMC with glucose (30-120 mM) resulted in a time- and concentration-dependent increase in MCP-1 protein secretion and mRNA expression. After 24 h the MCP-1 synthesis was increased from 2.8 +/- 0.46 to 4.2 +/- 0.32 ng/10(5) cells (n = 5, p 2001 S. Karger AG. Basel
Seafloor Characterization for Trawlability Using the Simrad ME70 Multibeam Echosounder in the Gulf of Alaska
Techno-economic WEC system optimisation – Methodology applied to Wavebob system definition
The overall system optimisation of wave energy
converters remains a challenging task. Firstly, this
is associated with the large number of system
parameters and their related constraints, secondly,
the complexity of numerical system representations
capturing overall system behaviour and, thirdly, the
uncertainties in the prediction and formulation of
appropriate overall economic system performance
objectives.
The parameterisation and the modelling
challenges require a staged approach for an overall
system optimisation. This ranges from simplified
system representations exposed to variations within
a large parameter space to more sophisticated
system models subject to evaluation for a reduced
and focused parameter zone. The description of the
system dynamics, operation and performance needs
to capture the key characteristics of the WEC
concept functionality, the technical implementation
and the economic application from the beginning
and throughout the optimisation and development
process.
The paper describes the problems that are
associated with the widely employed sequential
development of wave energy converter (WEC)
systems from concept through technology to
economic application and presents the methodology
applied to the overall techno-economic system
optimisation and development process of Wavebob
WECs
Integrable and Nonintegrable Classical Spin Clusters: Trajectories and Geometric Structure of Invariants
This study investigates the nonlinear dynamics of a pair of exchange-coupled spins with biaxial exchange and single-site anisotropy. It represents a Hamiltonian system with 2 degrees of freedom for which we have already established the (nontrivial) integrability criteria and constructed the integrals of the motion provided they exist. Here we present a comparative study of the phase-space trajectories for two specific models with the same symmetry properties, one of which (the XY model with exchange anisotropy) is integrable, and the other (the XY model with single-site anisotropy) nonintegrable. In the integrable model, the integrals of the motion (analytic invariants) can be reconstructed numerically by means of time averages of dynamical variables over all trajectories. In the nonintegrable model, such time averages over trajectories define nonanalytic invariants, where the nonanalyticities are associated with the presence of chaotic trajectories. A prominent feature in the nonintegrable model is the occurrence of very long time scales caused by the presence of low- ux cantori, which form sticky coats on the boundary between chaotic regions and regular islands or leaky walls between dierent chaotic regions. These cantori dominate the convergence properties of time averages and presumably determine the long-time asymptotic properties of dynamic correlation functions. Finally, we present a special class of integrable systems containing arbitrarily many spins coupled by general biaxial exchange anisotropy
Integrable and Nonintegrable Classical Spin Clusters: Integrability Criteria and Analytic Structure of Invariants
The nonlinear dynamics is investigated for a system of N classical spins. This represents a Hamiltonian system with N degrees of freedom. According to the Liouville theorem, the complete integrability of such a system requires the existence of N independent integrals of the motion which are mutually in involution. As a basis for the investigation of regular and chaotic spin motions, we have examined in detail the problem of integrability of a two-spin system. It represents the simplest autonomous spin system for which the integrability problem is nontrivial. We have shown that a pair of spins coupled by an anisotropic exchange interaction represents a completely integrable system for any values of the coupling constants. The second integral of the motion (in addition to the Hamiltonian), which ensures the complete integrability, turns out to be quadratic in the spin variables. If, in addition to the exchange anisotropy also single-site anisotropy terms are included in the two-spin Hamiltonian, a second integral of the motion quadratic in the spin variables exists and thus guarantees integrability, only if the model constants satisfy a certain condition. Our numerical calculations strongly suggest that the violation of this condition implies not only the nonexistence of a quadratic integral, but the nonexistence of a second independent integral of motion in general. Finally, as an example of a completely integrable N-spin system we present the Kittel-Shore model of uniformly interacting spins, for which we have constructed the N independent integrals in involution as well as the action-angle variables explicitly
Techno-economic WEC system optimisation – Methodology applied to Wavebob system definition
The overall system optimisation of wave energy
converters remains a challenging task. Firstly, this
is associated with the large number of system
parameters and their related constraints, secondly,
the complexity of numerical system representations
capturing overall system behaviour and, thirdly, the
uncertainties in the prediction and formulation of
appropriate overall economic system performance
objectives.
The parameterisation and the modelling
challenges require a staged approach for an overall
system optimisation. This ranges from simplified
system representations exposed to variations within
a large parameter space to more sophisticated
system models subject to evaluation for a reduced
and focused parameter zone. The description of the
system dynamics, operation and performance needs
to capture the key characteristics of the WEC
concept functionality, the technical implementation
and the economic application from the beginning
and throughout the optimisation and development
process.
The paper describes the problems that are
associated with the widely employed sequential
development of wave energy converter (WEC)
systems from concept through technology to
economic application and presents the methodology
applied to the overall techno-economic system
optimisation and development process of Wavebob
WECs
Regular and Chaotic Dynamics of Classical Spin Systems
An international workshop on Elementary Excitations and Fluctuations in Magnetic Systems was held in Turin for five days beginning 25 May, 1987. The workshop followed much the same format as the one with the same title held in San Miniato in 1984 (proceedings: Springer Series in-Solid-State Sciences, Vol. 54), that most participants contributed talks and provided papers for the proceedings. While many of the participants had attended the first workshop, 15 of the 40 invited review papers were presented by scientists who had not. The majority of the talks reported theoretical work concerned with the introduction of new techniques. However, experimental work was also well represented, not least because many of the reported theoretical studies were motivated by experimental findings, and a highlight of the workshop was an extremely stimulating session devoted to recent neutron scattering measurements, on various systems, that exploited polarization analysis. The fine venue of the workshop, Villa Gualino, with its excellent facilities and spacious accommodation, helped to produce a delightful relaxed and friendly atmosphere. For the use of Villa Gualino and significant financial support we are indebted to our host organization, the Institute for Scientific Interchange (lSI). Additional financial support came from the Consiglio Nazionale delle Ricerche (CNR), Centro Interuniversitario di Struttura della Material del Ministero della Pubblica Istruzione (CISM-MPI) and Gruppo Nazionale di Struttura della Materia (GNSM-CNR)
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