7,381 research outputs found
Non-Invasive Ventilation Sensor Mask (NIVSM): Preliminary Design and Testing
Previous research has emphasized the significance of mask and interface design in non-invasive ventilation (NIV) and the prevention of pressure ulcers (PUs). Multiple variables are involved in the necrosis process, but the skin-mask interface has the significant impact. A preliminary design of a custom-fit Mask (CFM) embedded with microclimate sensor has been introduced previously. This study aims to improve the comfort and safety of patients that use NIV masks for long periods. The personalized cushion fit (PCF) is designed using 3D scanning and printing technology and integrated into a pre existing mask. Integration with a preexisting mask has been achieved by fabricating a modular design that acts as a disposable PCF. Embedded sensors are added to the mask to measure the skin-mask microclimate. Real-time data is plotted and monitored for critical conditions and to identify other key features. A preliminary temperaturehumidity (T-H) monitoring of the skin-mask interface for both PCF and pre-existing mask shows fluctuation trends that could potentially induce PUs. However, there is a more sensitive reaction in the PCF test
PCF extended with real numbers: a domain-theoretic approach to higher-order exact real number computation
We develop a theory of higher-order exact real number computation based on Scott domain theory. Our main object of investigation is a higher-order functional programming language, Real PCF, which is an extension of PCF with a data type for real numbers and constants for primitive real functions. Real PCF has both operational and denotational semantics, related by a computational adequacy property.
In the standard interpretation of Real PCF, types are interpreted as continuous Scott domains. We refer to the domains in the universe of discourse of Real PCF induced by the standard interpretation of types as the real numbers type hierarchy. Sequences are functions defined on natural numbers, and predicates are truth-valued functions. Thus, in the real numbers types hierarchy we have real numbers, functions between real numbers, predicates defined on real numbers, sequences of real numbers, sequences of sequences of real numbers, sequences of functions, functionals mapping sequences to numbers (such as limiting operators), functionals mapping functions to numbers (such as integration and supremum operators), functionals mapping predicates to truth-values (such as existential and universal quantification operators), and so on.
As it is well-known, the notion of computability on a domain depends on the choice of an effective presentation. We say that an effective presentation of the real numbers type hierarchy is sound if all Real PCF definable elements and functions are computable with respect to it. The idea is that Real PCF has an effective operational semantics, and therefore the definable elements and functions should be regarded as concretely computable. We then show that there is a unique sound effective presentation of the real numbers type hierarchy, up to equivalence with respect to the induced notion of computability. We can thus say that there is an absolute notion of computability for the real numbers type hierarchy.
All computable elements and all computable first-order functions in the real numbers type hierarchy are Real PCF definable. However, as it is the case for PCF, some higher-order computable functions, including an existential quantifier, fail to be definable. If a constant for the existential quantifier (or, equivalently, a computable supremum operator) is added, the computational adequacy property remains true, and Real PCF becomes a computationally complete programming language, in the sense that all computable functions of all orders become definable.
We introduce induction principles and recursion schemes for the real numbers domain, which are formally similar to the so-called Peano axioms for natural numbers. These principles and schemes abstractly characterize the real numbers domain up to isomorphism, in the same way as the so-called Peano axioms for natural numbers characterize the natural numbers. On the practical side, they allow us to derive recursive definitions of real functions, which immediately give rise to correct Real PCF programs (by an application of computational adequacy). Also, these principles form the core of the proof of absoluteness of the standard effective presentation of the real numbers type hierarchy, and of the proof of computational completeness of Real PCF.
Finally, results on integration in Real PCF consisting of joint work with Abbas Edalat are included
Fully Unintegrated Parton Correlation Functions and Factorization in Lowest Order Hard Scattering
Motivated by the need to correct the potentially large kinematic errors in
approximations used in the standard formulation of perturbative QCD, we
reformulate deeply inelastic lepton-proton scattering in terms of gauge
invariant, universal parton correlation functions which depend on all
components of parton four-momentum. Currently, different hard QCD processes are
described by very different perturbative formalisms, each relying on its own
set of kinematical approximations. In this paper we show how to set up
formalism that avoids approximations on final-state momenta, and thus has a
very general domain of applicability. The use of exact kinematics introduces a
number of significant conceptual shifts already at leading order, and tightly
constrains the formalism. We show how to define parton correlation functions
that generalize the concepts of parton density, fragmentation function, and
soft factor. After setting up a general subtraction formalism, we obtain a
factorization theorem. To avoid complications with Ward identities the full
derivation is restricted to abelian gauge theories; even so the resulting
structure is highly suggestive of a similar treatment for non-abelian gauge
theories.Comment: 44 pages, 69 figures typos fixed, clarifications and second appendix
adde
Hybrid squeezing of solitonic resonant radiation in photonic crystal fibers
We report on the existence of a novel kind of squeezing in photonic crystal
fibers which is conceptually intermediate between the four-wave mixing induced
squeezing, in which all the participant waves are monochromatic waves, and the
self-phase modulation induced squeezing for a single pulse in a coherent state.
This hybrid squeezing occurs when an arbitrary short soliton emits
quasi-monochromatic resonant radiation near a zero group velocity dispersion
point of the fiber. Photons around the resonant frequency become strongly
correlated due to the presence of the classical soliton, and a reduction of the
quantum noise below the shot noise level is predicted.Comment: 5 pages, 2 figure
Dependence of kinetic friction on velocity: Master equation approach
We investigate the velocity dependence of kinetic friction with a model which
makes minimal assumptions on the actual mechanism of friction so that it can be
applied at many scales provided the system involves multi-contact friction.
Using a recently developed master equation approach we investigate the
influence of two concurrent processes. First, at a nonzero temperature thermal
fluctuations allow an activated breaking of contacts which are still below the
threshold. As a result, the friction force monotonically increases with
velocity. Second, the aging of contacts leads to a decrease of the friction
force with velocity. Aging effects include two aspects: the delay in contact
formation and aging of a contact itself, i.e., the change of its
characteristics with the duration of stationary contact. All these processes
are considered simultaneously with the master equation approach, giving a
complete dependence of the kinetic friction force on the driving velocity and
system temperature, provided the interface parameters are known
Bose-Fermi mixtures in the molecular limit
We consider a Bose-Fermi mixture in the molecular limit of the attractive
interaction between fermions and bosons. For a boson density smaller or equal
to the fermion density, we show analytically how a T-matrix approach for the
constituent bosons and fermions recovers the expected physical limit of a
Fermi-Fermi mixture of molecules and atoms. In this limit, we derive simple
expressions for the self-energies, the momentum distribution function, and the
chemical potentials. By extending these equations to a trapped system, we
determine how to tailor the experimental parameters of a Bose-Fermi mixture in
order to enhance the 'indirect Pauli exclusion effect' on the boson momentum
distribution function. For the homogeneous system, we present finally a
Diffusion Monte Carlo simulation which confirms the occurrence of such a
peculiar effect.Comment: 13 pages, 7 figures; final versio
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