25,700 research outputs found
Maximally Localized States in Quantum Mechanics with a Modified Commutation Relation to All Orders
We construct the states of maximal localization taking into account a
modification of the commutation relation between position and momentum
operators to all orders of the minimum length parameter. To first order, the
algebra we use reproduces the one proposed by Kempft, Mangano and Mann. It is
emphasized that a minimal length acts as a natural regulator for the theory,
thus eliminating the otherwise ever appearing infinities. So, we use our
results to calculate the first correction to the Casimir Effect due to the
minimal length. We also discuss some of the physical consequences of the
existence of a minimal length, culminating in a proposal to reformulate the
very concept of "position measurement"
Real space mapping of topological invariants using artificial neural networks
Topological invariants allow to characterize Hamiltonians, predicting the
existence of topologically protected in-gap modes. Those invariants can be
computed by tracing the evolution of the occupied wavefunctions under twisted
boundary conditions. However, those procedures do not allow to calculate a
topological invariant by evaluating the system locally, and thus require
information about the wavefunctions in the whole system. Here we show that
artificial neural networks can be trained to identify the topological order by
evaluating a local projection of the density matrix. We demonstrate this for
two different models, a 1-D topological superconductor and a 2-D quantum
anomalous Hall state, both with spatially modulated parameters. Our neural
network correctly identifies the different topological domains in real space,
predicting the location of in-gap states. By combining a neural network with a
calculation of the electronic states that uses the Kernel Polynomial Method, we
show that the local evaluation of the invariant can be carried out by
evaluating a local quantity, in particular for systems without translational
symmetry consisting of tens of thousands of atoms. Our results show that
supervised learning is an efficient methodology to characterize the local
topology of a system.Comment: 9 pages, 6 figure
Transthyretin familial amyloid polyneuropathy impact on health-related quality of life
info:eu-repo/semantics/publishedVersio
Thermoeconomic Simulation of Cascaded and Integrated Vapor Compression-Absorption Refrigeration Systems
The present work is composed by a comparative thermoeconomic analysisbetween two refrigeration systems: Vapor Compression CascadeRefrigeration System (VCCRS) and Integrated Refrigeration System byAbsorption and Vapor Compression (VCACRS). The thermoeconomicanalysis compares the systems under energy, exergy, economic andenvironmental aspects. The development of mathematical models for each ofthe systems is performed through the EES (Engineering Equation Solver)program. The optimized functions are exergy destruction and total cost rate(sum of cost rates of investment, operation, maintenance and enviromental)by minimizing these functions. The optimization method used is theweighted sum of the objectives, this can be achieved by assigning differentweights for each goal, then a new function that represents the linearrelationship between all the objectives is found. In present case the twoobjective functions are exergy destruction and total cost rate. Inmultiobjective optimization, the process of choosing among optimizedsolutions involves the definition of an equilibrium point, also called theideal point. In order to achieve a real solution of the minimum values ofthe described functions simultaneously one must determine which is thesmallest distance from the ideal point to the curve that defines theoptimized solutions. In the study the economical advantage of VCCRS inrelation to VCACRS was demonstrated. VCACRS has a cost 10.26% lowerthan VCCRS while VCCRS has a better exergetic efficiency, with itsdestruction of exergy 38.46% lower than VCACRS
Supergiant Barocaloric Effects in Acetoxy Silicone Rubber over a Wide Temperature Range: Great Potential for Solid-state Cooling
Solid-state cooling based on caloric effects is considered a viable
alternative to replace the conventional vapor-compression refrigeration
systems. Regarding barocaloric materials, recent results show that elastomers
are promising candidates for cooling applications around room-temperature. In
the present paper, we report supergiant barocaloric effects observed in acetoxy
silicone rubber - a very popular, low-cost and environmentally friendly
elastomer. Huge values of adiabatic temperature change and reversible
isothermal entropy change were obtained upon moderate applied pressures and
relatively low strains. These huge barocaloric changes are associated both to
the polymer chains rearrangements induced by confined compression and to the
first-order structural transition. The results are comparable to the best
barocaloric materials reported so far, opening encouraging prospects for the
application of elastomers in near future solid-state cooling devices.Comment: 19 pages, 7 figures, 2 table
Recommended from our members
Aplicação de Análise e Modelagem Multidimensional para o Monitoramento de Resíduos Sólidos Industriais
Giant meningioma in paranasal sinuses: an atypical nasal occupation
info:eu-repo/semantics/publishedVersio
- …