1,201,930 research outputs found
ABOUT THE ECONOMIC CRISIS
The economic crisis that the global economy is facing nowadays has started with the financial crisis of the U.S financial system. We are talking about an unprecedented speculative boom at global level which has overcome the previous booms created by the deconomic crisis, exchange rate, metal reserves
Non-Geometric Fluxes, Quasi-Hopf Twist Deformations and Nonassociative Quantum Mechanics
We analyse the symmetries underlying nonassociative deformations of geometry
in non-geometric R-flux compactifications which arise via T-duality from closed
strings with constant geometric fluxes. Starting from the non-abelian Lie
algebra of translations and Bopp shifts in phase space, together with a
suitable cochain twist, we construct the quasi-Hopf algebra of symmetries that
deforms the algebra of functions and the exterior differential calculus in the
phase space description of nonassociative R-space. In this setting
nonassociativity is characterised by the associator 3-cocycle which controls
non-coassociativity of the quasi-Hopf algebra. We use abelian 2-cocycle twists
to construct maps between the dynamical nonassociative star product and a
family of associative star products parametrized by constant momentum surfaces
in phase space. We define a suitable integration on these nonassociative spaces
and find that the usual cyclicity of associative noncommutative deformations is
replaced by weaker notions of 2-cyclicity and 3-cyclicity. Using this star
product quantization on phase space together with 3-cyclicity, we formulate a
consistent version of nonassociative quantum mechanics, in which we calculate
the expectation values of area and volume operators, and find coarse-graining
of the string background due to the R-flux.Comment: 38 pages; v2: typos corrected, reference added; v3: typos corrected,
comments about cyclicity added in section 4.2, references updated; Final
version to be published in Journal of Mathematical Physic
The integration of input filters in electrical drives
PhD ThesisThe integration of passive components such as inductors and capacitors has gained significant
popularity in integrated drive research, and future power electronics systems will require more
integrated and standardised packages. These give rise to better power density and improved
performance. However, packaging techniques and passive components have been considered a
technological barrier which is limiting advances in power electronics. The focus on size
reduction should be turned towards the passive components, such as converter chokes, DC-link
capacitors and electromagnetic interference (EMI) filters, and achieving greater power density
depends on innovative integration concepts, flexibility in structures and extended operating
temperature ranges while system integration and modularity are not mutually exclusive.
This research considers the possibility of integrating input power filter components into electric
machines. Particular attention is paid to the integration of electromagnetic line filter inductors
to give better utilisation of the motor volume and envelope. This can be achieved by sharing
the machine’s magnetic circuit. An LCL line filter has been chosen to be integrated with a gridconnected permanent magnet synchronous machine. Machines have been proposed in this study
for low speed (3000 RPM) and high speed (25000 RPM) operation. The two machines have
similar dimensions, but the low-speed machine is less challenging in terms of losses and filter
integration, so attention is directed more to the high-speed machine. Both are supplied with
low- and high-power drives at power ratings of 4.5 kW and 38 kW respectively.
Several novel techniques have been investigated to integrate filter inductors into the electrical
machines to produce a single mechanically packaged unit without significant increases in size
and losses. Different approaches have been simulated using finite element analysis (FEA) to
assess the effectiveness of the integration of passives within the machine structure. Each design
has been iteratively optimised to determine the best mass of copper and core for the integrated
filter inductors, targeting parity in power density when compared to traditional separate
packages. The research demonstrates that an approach utilising a double-slot stator machine
(named the integrated double slot (IDS) machine) with input filters wound into the outermost
slots is the most appropriate choice in terms of achieving higher power density.
The integrated filter inductors mimic the electromagnetic behaviour of the discrete industrially
packaged inductors but with a volume reduction of 87.6%. A prototype of the IDS machine
design of a 38 kW, 25000 RPM, including filter inductors was manufactured and testedthe General Electricity Company of Libya
(GECOL), the Engineering and Physical Sciences Research Council (EPSRC), and the
Engineering Doctorate scheme at Newcastle University
The relative frequency response, as derived from individually separated targets on cod, saithe and Norway pout
The relative frequency response is an important acoustic feature used to characterise acoustic
targets. This response has been defined as the sv, volume backscattering coefficient, for a specific
frequency relative to that of a reference frequency (38 kHz). The acoustic data commonly used in
these calculations are derived from integrated measurements in a region containing multiple
targets. In this study the relative frequency responses at 18, 38, 70, 120, and 200 kHz have
additionally been measured using filtered target strength data on all frequencies. The spatial
comparability of the sv-data is thus avoided, while the single-target detection becomes a new
challenge. Target strength was extracted from in situ measurements, using calibrated and digitised
data from a Simrad EK60 with split-beam transducers transmitting simultaneously at all five
frequencies. Selected series with nearly pure catches of Atlantic cod (Gadus Morhua L.), saithe
(Pollachius virens L.) and Norway pout (Trisopterus esmarkii L.) were analysed. The frequency
response derived by the new method is compared with standard integration method
Quasi-geometric integration of guiding-center orbits in piecewise linear toroidal fields
A numerical integration method for guiding-center orbits of charged particles
in toroidal fusion devices with three-dimensional field geometry is described.
Here, high order interpolation of electromagnetic fields in space is replaced
by a special linear interpolation, leading to locally linear Hamiltonian
equations of motion with piecewise constant coefficients. This approach reduces
computational effort and noise sensitivity while the conservation of total
energy, magnetic moment and phase space volume is retained. The underlying
formulation treats motion in piecewise linear fields exactly and thus preserves
the non-canonical symplectic form. The algorithm itself is only quasi-geometric
due to a series expansion in the orbit parameter. For practical purposes an
expansion to the fourth order retains geometric properties down to computer
accuracy in typical examples. When applied to collisionless guiding-center
orbits in an axisymmetric tokamak and a realistic three-dimensional stellarator
configuration, the method demonstrates stable long-term orbit dynamics
conserving invariants. In Monte Carlo evaluation of transport coefficients, the
computational efficiency of quasi-geometric integration is an order of
magnitude higher than with a standard fourth order Runge-Kutta integrator.Comment: 38 pages, 11 figure
New interfaces between security and development: changing concepts and approaches
"For some years the nexus of development and security has been a key conceptual and also political issue. The associated debates are wide-ranging, extending from the basic question of the relationship between development and security to the concrete interaction of military and civil actors in a given post-conflict situation. The present volume seeks to contribute to this debate by considering various dimensions of the subject." (excerpt). Contents: Mark Duffield: Human security: linking development and security in an age of terror (11-38); Necla Tschirgi: Security and development policies: untangling the relationship (39-68); Clive Robinson: Whose security? Integration and integrity in EU policies for security and development (69-92); Jakkie Cilliers: New interfaces between security and development (93-106); Ann M. Fitz-Gerald: Addressing the security-development nexus: implications for joined-up government (107-126); Stephan Klingebiel: Converging the role of development policy and security policy? New approaches in Africa (127-145)
Integrated acoustic immunoaffinity-capture (IAI) platform for detection of PSA from whole blood samples.
On-chip detection of low abundant protein biomarkers is of interest to enable point-of-care diagnostics. Using a simple form of integration, we have realized an integrated microfluidic platform for the detection of prostate specific antigen (PSA), directly in anti-coagulated whole blood. We combine acoustophoresis-based separation of plasma from undiluted whole blood with a miniaturized immunoassay system in a polymer manifold, demonstrating improved assay speed on our Integrated Acoustic Immunoaffinity-capture (IAI) platform. The IAI platform separates plasma from undiluted whole blood by means of acoustophoresis and provides cell free plasma of clinical quality at a rate of 10 uL/min for an online immunoaffinity-capture of PSA on a porous silicon antibody microarray. The whole blood input (hematocrit 38-40%) rate was 50 μl min(-1) giving a plasma volume fraction yield of ≈33%. PSA was immunoaffinity-captured directly from spiked female whole blood samples at clinically significant levels of 1.7-100 ng ml(-1) within 15 min and was subsequently detected via fluorescence readout, showing a linear response over the entire range with a coefficient of variation of 13%
[68Ga]-DOTATOC-PET/CT for meningioma IMRT treatment planning
<p>Abstract</p> <p>Purpose</p> <p>The observation that human meningioma cells strongly express somatostatin receptor (SSTR 2) was the rationale to analyze retrospectively in how far DOTATOC PET/CT is helpful to improve target volume delineation for intensity modulated radiotherapy (IMRT).</p> <p>Patients and Methods</p> <p>In 26 consecutive patients with preferentially skull base meningioma, diagnostic magnetic resonance imaging (MRI) and planning-computed tomography (CT) was complemented with data from [<sup>68</sup>Ga]-DOTA-D Phe<sup>1</sup>-Tyr<sup>3</sup>-Octreotide (DOTATOC)-PET/CT. Image fusion of PET/CT, diagnostic computed tomography, MRI and radiotherapy planning CT as well as target volume delineation was performed with OTP-Masterplan<sup>®</sup>. Initial gross tumor volume (GTV) definition was based on MRI data only and was secondarily complemented with DOTATOC-PET information. Irradiation was performed as EUD based IMRT, using the Hyperion Software package.</p> <p>Results</p> <p>The integration of the DOTATOC data led to additional information concerning tumor extension in 17 of 26 patients (65%). There were major changes of the clinical target volume (CTV) which modify the PTV in 14 patients, minor changes were realized in 3 patients. Overall the GTV-MRI/CT was larger than the GTV-PET in 10 patients (38%), smaller in 13 patients (50%) and almost the same in 3 patients (12%). Most of the adaptations were performed in close vicinity to bony skull base structures or after complex surgery. Median GTV based on MRI was 18.1 cc, based on PET 25.3 cc and subsequently the CTV was 37.4 cc. Radiation planning and treatment of the DOTATOC-adapted volumes was feasible.</p> <p>Conclusion</p> <p>DOTATOC-PET/CT information may strongly complement patho-anatomical data from MRI and CT in cases with complex meningioma and is thus helpful for improved target volume delineation especially for skull base manifestations and recurrent disease after surgery.</p
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