2,498 research outputs found
On the Commutative Equivalence of Context-Free Languages
The problem of the commutative equivalence of context-free and regular languages is studied. In particular conditions ensuring that a context-free language of exponential growth is commutatively equivalent with a regular language are investigated
The Renewable Energy In A Led Standalone Streetlight
This work deals with the design of a standalone streetlight provided with a solar panel and a multiple vertical axis wind turbine (VAWT) along the structure. A prototype was built and is currently being tested in the Monte Dago campus of the UniversitĂ Politecnica delle Marche. The ongoing focus of the project is to improve the overall efficiency and the manufacturing details for the industrialization. A battery bank allows delaying the energy delivering from the energy production, while a central process unit on board collects the data from every component in the equipment. This unit allows to monitor the day-by-day efficiency of the energy-lighting system, and to send the information wirelessly with the purpose of integrating into a smart grid-like management platform. The test site includes a meteorological mast, which can measure the weather conditions, such as wind speed and solar radiation. The wind turbines included in the streetlight have been studied from an aerodynamic point of view through an extensive experimental analysis in the wind tunnel. Moreover, the structural design of the wind rotors was carried out together with the security system including a mechanical brake, which prevents the damage of the components during high wind speed conditions. The control of the hybrid energy unit, designed to track the optimal performance, has been analyzed throughout the local wind conditions. Also, it is discussed the effectiveness of this streetlight concept in various climate situations
Quantum measurement of a mesoscopic spin ensemble
We describe a method for precise estimation of the polarization of a
mesoscopic spin ensemble by using its coupling to a single two-level system.
Our approach requires a minimal number of measurements on the two-level system
for a given measurement precision. We consider the application of this method
to the case of nuclear spin ensemble defined by a single electron-charged
quantum dot: we show that decreasing the electron spin dephasing due to nuclei
and increasing the fidelity of nuclear-spin-based quantum memory could be
within the reach of present day experiments.Comment: 8 pages, 2 figures; minor changes, published versio
Building on strategic elearning initiatives of hybrid graduate education a case study approach: MHEI-ME Erasmus+ Project
Online courses are gaining popularity because they provide extensive and varied course material, information, knowledge, and skills, whilst also creating an effective educational online community. This research adopts a case study approach to focus on the teaching method and the manner in which a strategic commitment to eLearning provides scope for the development and implementation of top quality educational online fully accredited programs. Entrepreneurship focuses on developing businesses that add value and create wealth and prosperity in our societies. Therefore, entrepreneurship is a key area of learning for graduate students seeking to set up and operate their own SME organizations. It can serve as a benchmark for the teaching of other graduate subjects that require a sound correlation for the correlation of concepts and theories to the challenging complexities of the real world. The program was developed on the basis of the implementation of a state-of-the-art eLearning platform that allowed for a combination of varied self-learning and collaborative learning elements and activities within a single platform. This enabled students to access the online content material efficiently and effectively. It allows for the development of a program based on the flipped classroom teaching methodology. The underlying concept of the flipped classroom methodology is that effective eLearning should comprise both synchronous and asynchronous learning activities. This combination of self-learning and collaborative learning calls for careful planning by the tutor to ensure that the learning objectives are clearly defined for each activity and that the relevant deliverables are monitored. The content material for each subject course module was designed, developed, produced, and presented by the different project partners in a holistic manner structured to motivate participants to learn. The results of our analysis have shown that students were able to learn, discuss their projects, and cooperate during an online course in an effective and participant-focused manner with their tutors. The feedback given highlights the importance of ongoing communications between students and the tutors who often need to act as mentors to retain student engagement. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
Quantum control theory for coupled 2-electron dynamics in quantum dots
We investigate optimal control strategies for state to state transitions in a
model of a quantum dot molecule containing two active strongly interacting
electrons. The Schrodinger equation is solved nonperturbatively in conjunction
with several quantum control strategies. This results in optimized electric
pulses in the THz regime which can populate combinations of states with very
short transition times. The speedup compared to intuitively constructed pulses
is an order of magnitude. We furthermore make use of optimized pulse control in
the simulation of an experimental preparation of the molecular quantum dot
system. It is shown that exclusive population of certain excited states leads
to a complete suppression of spin dephasing, as was indicated in Nepstad et al.
[Phys. Rev. B 77, 125315 (2008)].Comment: 24 pages, 9 figure
Numerical Solution of the Dynamic Programming Equation for the Optimal Control of Quantum Spin Systems
The purpose of this paper is to describe the numerical solution of the
Hamilton-Jacobi-Bellman (HJB) for an optimal control problem for quantum spin
systems. This HJB equation is a first order nonlinear partial differential
equation defined on a Lie group. We employ recent extensions of the theory of
viscosity solutions from Euclidean space to Riemannian manifolds to interpret
possibly non-differentiable solutions to this equation. Results from
differential topology on the triangulation of manifolds are then used to
develop a finite difference approximation method, which is shown to converge
using viscosity solution techniques. An example is provided to illustrate the
method.Comment: 11 pages, 5 figure
Continuous quantum feedback of coherent oscillations in a solid-state qubit
We have analyzed theoretically the operation of the Bayesian quantum feedback
of a solid-state qubit, designed to maintain perfect coherent oscillations in
the qubit for arbitrarily long time. In particular, we have studied the
feedback efficiency in presence of dephasing environment and detector
nonideality. Also, we have analyzed the effect of qubit parameter deviations
and studied the quantum feedback control of an energy-asymmetric qubit.Comment: 11 page
Nitrate, sulphate and chloride contents in public drinking water supplies in Sicily, Italy
Water samples collected from public
drinking water supplies in Sicily were analysed
for electric conductivity and for their chloride,
sulphate and nitrate contents. The samples were
collected as uniformly as possible from throughout the Sicilian territory, with an average sampling density of about one sample for every 7,600
inhabitants. Chloride contents that ranged from
5.53 to 1,302 mg/l were correlated strongly with
electric conductivity, a parameter used as a proxy
for water salinity. The highest values are attributable to seawater contamination along the coasts
of the island. High chloride and sulphate values
attributable to evaporitic rock dissolution were
found in the central part of Sicily. The nitrate
concentrations ranged from 0.05 to 296 mg/l, with
31 samples (4.7% of the total) exceeding the
maximum admissible concentration of 50 mg/l.
Anomalous samples always came from areas of
intensive agricultural usage, indicating a clear anthropogenic origin. The same parameters were
also measured in bottled water sold in Sicily, and
they all were within the ranges for public drinking
water supplies. The calculated mean nitrate intake
from consuming public water supplies (16.1 mg/l)
did not differ significantly from that of bottled
water (15.2 mg/l). Although the quality of public
water supplies needs to be improved by eliminating those that do not comply with the current
drinking water limits, at present it does not justify
the high consumption of bottled water (at least for
nitrate contents)
Quantum-to-Classical Correspondence and Hubbard-Stratonovich Dynamical Systems, a Lie-Algebraic Approach
We propose a Lie-algebraic duality approach to analyze non-equilibrium
evolution of closed dynamical systems and thermodynamics of interacting quantum
lattice models (formulated in terms of Hubbard-Stratonovich dynamical systems).
The first part of the paper utilizes a geometric Hilbert-space-invariant
formulation of unitary time-evolution, where a quantum Hamiltonian is viewed as
a trajectory in an abstract Lie algebra, while the sought-after evolution
operator is a trajectory in a dynamic group, generated by the algebra via
exponentiation. The evolution operator is uniquely determined by the
time-dependent dual generators that satisfy a system of differential equations,
dubbed here dual Schrodinger-Bloch equations, which represent a viable
alternative to the conventional Schrodinger formulation. These dual
Schrodinger-Bloch equations are derived and analyzed on a number of specific
examples. It is shown that deterministic dynamics of a closed classical
dynamical system occurs as action of a symmetry group on a classical manifold
and is driven by the same dual generators as in the corresponding quantum
problem. This represents quantum-to-classical correspondence. In the second
part of the paper, we further extend the Lie algebraic approach to a wide class
of interacting many-particle lattice models. A generalized Hubbard-Stratonovich
transform is proposed and it is used to show that the thermodynamic partition
function of a generic many-body quantum lattice model can be expressed in terms
of traces of single-particle evolution operators governed by the dynamic
Hubbard-Stratonovich fields. Finally, we derive Hubbard-Stratonovich dynamical
systems for the Bose-Hubbard model and a quantum spin model and use the
Lie-algebraic approach to obtain new non-perturbative dual descriptions of
these theories.Comment: 25 pages, 1 figure; v2: citations adde
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