5,309 research outputs found
Hortibot: Feasibility study of a plant nursing robot performing weeding operations – part IV
Based on the development of a robotic tool carrier (Hortibot) equipped with weeding tools, a feasibility study was carried out to evaluate the viability of this innovative technology. The feasibility was demonstrated through a targeted evaluation adapted to the obtainable knowledge on the system performance in horticulture.
A usage scenario was designed to set the implementation of the robotic system in a row crop of seeded bulb onions considering operational and functional constraints in organic crop, production. This usage scenario together with the technical specifications of the implemented system provided the basis for the feasibility analysis, including a comparison with a conventional weeding system. Preliminary results show that the automation of the weeding tasks within a row crop has the potential of significantly reducing the costs and still fulfill the operational requirements set forth.
The potential benefits in terms of operational capabilities and economic viability have been quantified. Profitability gains ranging from 20 to 50% are achievable through targeted applications. In general, the analyses demonstrate the operational and economic feasibility of using small automated vehicles and targeted tools in specialized production settings
Linear interpolation method in ensemble Kohn-Sham and range-separated density-functional approximations for excited states
Gross-Oliveira-Kohn density functional theory (GOK-DFT) for ensembles is in
principle very attractive, but has been hard to use in practice. A novel,
practical model based on GOK-DFT for the calculation of electronic excitation
energies is discussed. The new model relies on two modifications of GOK-DFT:
use of range separation and use of the slope of the linearly-interpolated
ensemble energy, rather than orbital energies. The range-separated approach is
appealing as it enables the rigorous formulation of a multi-determinant
state-averaged DFT method. In the exact theory, the short-range density
functional, that complements the long-range wavefunction-based ensemble energy
contribution, should vary with the ensemble weights even when the density is
held fixed. This weight dependence ensures that the range-separated ensemble
energy varies linearly with the ensemble weights. When the (weight-independent)
ground-state short-range exchange-correlation functional is used in this
context, curvature appears thus leading to an approximate weight-dependent
excitation energy. In order to obtain unambiguous approximate excitation
energies, we propose to interpolate linearly the ensemble energy between
equiensembles. It is shown that such a linear interpolation method (LIM) can be
rationalized and that it effectively introduces weight dependence effects. As
proof of principle, LIM has been applied to He, Be, H in both equilibrium
and stretched geometries as well as the stretched HeH molecule. Very
promising results have been obtained for both single (including charge
transfer) and double excitations with spin-independent short-range local and
semi-local functionals. Even at the Kohn--Sham ensemble DFT level, that is
recovered when the range-separation parameter is set to zero, LIM performs
better than standard time-dependent DFT.Comment: 26 pages, 8 figure
Alternative separation of exchange and correlation energies in range-separated density-functional perturbation theory
An alternative separation of short-range exchange and correlation energies is
used in the framework of second-order range-separated density-functional
perturbation theory. This alternative separation was initially proposed by
Toulouse et al. [Theor. Chem. Acc. 114, 305 (2005)] and relies on a long-range
interacting wavefunction instead of the non-interacting Kohn-Sham one. When
second-order corrections to the density are neglected, the energy expression
reduces to a range-separated double-hybrid (RSDH) type of functional, RSDHf,
where "f" stands for "full-range integrals" as the regular full-range
interaction appears explicitly in the energy expression when expanded in
perturbation theory. In contrast to usual RSDH functionals, RSDHf describes the
coupling between long- and short-range correlations as an orbital-dependent
contribution. Calculations on the first four noble-gas dimers show that this
coupling has a significant effect on the potential energy curves in the
equilibrium region, improving the accuracy of binding energies and equilibrium
bond distances when second-order perturbation theory is appropriate.Comment: 5 figure
Exploration of H2 binding to the [NiFe]-hydrogenase active site with multiconfigurational density functional theory
The combination of density functional theory (DFT) with a
multiconfigurational wave function is an efficient way to include dynamical
correlation in calculations with multiconfiguration self-consistent field wave
functions. These methods can potentially be employed to elucidate reaction
mechanisms in bio-inorganic chemistry, where many other methods become either
too computationally expensive or too inaccurate. In this paper, a complete
active space (CAS) short-range DFT (CAS-srDFT) hybrid was employed to
investigate a bio-inorganic system, namely H2 binding to the active site of
[NiFe] hydrogenase. This system was previously investigated with
coupled-cluster (CC) and multiconfigurational methods in form of
cumulant-approximated second-order perturbation theory, based on the density
matrix renormalization group (DMRG). We find that it is more favorable for H2
to bind to Ni than to Fe, in agreement with previous CC and DMRG calculations.
The accuracy of CAS-srDFT is comparable to both CC and DMRG, despite that much
smaller active spaces were employed. This enhanced efficiency at smaller active
spaces shows that CAS-srDFT can become a useful method for bio-inorganic
chemistry.Comment: 22 page
Decay of low-lying 12C resonances within a 3alpha cluster model
We compute energy distributions of three -particles emerging from the
decay of C resonances by means of the hyperspherical adiabatic expansion
method combined with complex scaling. The large distance continuum properties
of the wave functions are crucial and must be accurately calculated. The
substantial changes from small to large distances determine the decay
mechanisms. We illustrate by computing the energy distributions from decays of
the and -resonances in C. These states are dominated by
direct and sequential decays into the three-body continuum respectively.Comment: 5 pages, 3 figures. Proceedings of the Clusters '07 conference held
in Stratford-upon-Avon in September 200
Shareholder Theory/Shareholder Value
Shareholder theory states that the primary objective of management is to maximize shareholder value. This objective ranks in front of the interests of other corporate stakeholders, such as employees, suppliers, customers, and society.Shareholder theory argues that shareholders are the ultimate owners of a corporate’s assets, and thus, the priority for managers and boards is to protect and grow these assets for the benefit of shareholders. Shareholder theory assumes that shareholders value corporate assets with two measurable metrics, dividends and share price. There-fore, management should make decisions that maximize the combined value of dividends and share price increases. However, shareholder theory fails to consider that shareholders and corporates may have other objectives that are not based on financial performance. For example, as early as1932, Berle and Means argued that corporations have a variety of purposes and interests including encouraging entrepreneurship, innovation, and building communities. This wider view is gaining more traction in recent decades as evidenced by an increased interest in ethical investment funds.This suggests that shareholders and potential shareholders are not only interested in financial gains but are also interested in corporates being socially responsible (Kyriakou2018). Therefore shareholder value creation is important; however,it needs to be balanced with other stakeholders’ interests. This is referred to as an enlightened approach to shareholder value maximization
Performance of range-separated long-range SOPPA short-range density functional theory method for vertical excitation energies
In this paper benchmark results are presented on the calculation of vertical
electronic excitation energies using a long-range second-order polarisation
propagator approximation (SOPPA) description with a short-range density
functional theory (srDFT) description based on the Perdew-Burke-Ernzerhof (PBE)
functional. The excitation energies are investigated for 132 singlet states and
71 triplet states across 28 medium sized organic molecules. The results show
that overall SOPPA-srPBE always performs better than PBE, and that SOPPA-srPBE
performs better than SOPPA for singlet states, but slightly worse than SOPPA
for triplet states when CC3 results are the reference values
Evolutionary dynamic optimisation of airport security lane schedules
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Reducing costs whilst maintaining passenger satisfaction is an important problem for airports. One area this can be applied is the security lane checks at the airport. However, reducing costs through reducing lane openings typically increases queue length and hence passenger dissatisfaction. This paper demonstrates that evolutionary methods can be used to optimise airport security lane schedules such that passenger dissatisfaction and staffing costs can be minimised. However, it is shown that these schedules typically over-fit the forecasts of passenger arrivals at security such that in actuality significant passenger delays can occur with deviations from the forecast. Consequently, this paper further demonstrates that dynamic evolutionary re-optimisation of these schedules can significantly mitigate this over-fitting problem with much reduced passenger delays
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