15 research outputs found
Local convergence of the Levenberg-Marquardt method under H\"{o}lder metric subregularity
We describe and analyse Levenberg-Marquardt methods for solving systems of
nonlinear equations. More specifically, we propose an adaptive formula for the
Levenberg-Marquardt parameter and analyse the local convergence of the method
under H\"{o}lder metric subregularity of the function defining the equation and
H\"older continuity of its gradient mapping. Further, we analyse the local
convergence of the method under the additional assumption that the
\L{}ojasiewicz gradient inequality holds. We finally report encouraging
numerical results confirming the theoretical findings for the problem of
computing moiety conserved steady states in biochemical reaction networks. This
problem can be cast as finding a solution of a system of nonlinear equations,
where the associated mapping satisfies the \L{}ojasiewicz gradient inequality
assumption.Comment: 30 pages, 10 figure
Environmental impact assessment of the pangasius sector in the Mekong Delta
In the past seven years the export of white pangasius fillets grew fast. The culture method shifted to intensive production of striped catfish (Ca Tra) in deep ponds because this is more efficient than the pen and cage culture of Ca Basa. Today, striped catfish comprises more than 90 % of the culture. The increased production was achieved by producers investing in large ponds. The market chain is gearing towards vertical integration. Most farms keep fish at relatively high densities of 15 to 25 fish/m3 in ponds having a depth of up to 4m, and are advised to exchange daily 20 to 40% of the water. The sustainability of the sector is threatened due to the increased environmental pressure, and hampered by the growing cost of inputs and reduced farm-gate prices of the fish. The Environmental Impact Assessment (EIA) intends to identify measures for preventing or mitigating the environmental impacts of catfish culture in the Mekong Delta. The EIA was a seven-step process during which we interacted twice with part of the main stakeholders. To build trust among the stakeholders from the sector, we conducted the scoping and goal setting with them
Potential benefits from the adoption of new groundnut varieties in northern Vietnam: An ex ante assessment
Enabled by land reforms and fuelled by technological change, agricultural production in Vietnam grew tremendously after the mid-1980s. Focusing on groundnut, an export-oriented cash and food crop, this paper provides estimates of potential benefits from the adoption of improved varieties in northern Vietnam. At farm level, switching over to improved varieties generates additional revenue of VND1.8 to 3.9 million per hectare (US35.8 million) at a real discount rate of 5%. These benefits will be 14% larger if the groundnut area continues to expand at the rate achieved in the recent past
The DUNE far detector vertical drift technology. Technical design report
DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals
Global exponential stability of a neural network for inverse variational inequalities
We investigate the convergence properties of a projected neural network for solving inverse variational inequalities. Under standard assumptions, we establish the exponential stability of the proposed neural network. A discrete version of the proposed neural network is considered, leading to a new projection method for solving inverse variational inequalities, for which we obtain the linear convergence. We illustrate the effectiveness of the proposed neural network and its explicit discretization by considering applications in the road pricing problem arising in transportation science. The results obtained in this paper provide a positive answer to a recent open question and improve several recent results in the literature.</p
Approximating optimal finite horizon feedback by model predictive control
We consider a finite-horizon continuous-time optimal control problem with nonlinear dynamics, an integral cost, control constraints and a time-varying parameter which represents perturbations or uncertainty. After discretizing the problem we employ a Model Predictive Control (MPC) approach by first solving the problem over the entire remaining time horizon and then applying the first element of the optimal discrete-time control sequence, as a constant in time function, to the continuous-time system over the sampling interval. Then the state at the end of the sampling interval is measured (estimated) with certain error, and the process is repeated at each step over the remaining horizon. As a result, we obtain a piecewise constant function of time representing MPC-generated control signal. Hence MPC turns out to be an approximation to the optimal feedback control for the continuous-time system. In our main result we derive an estimate of the difference between the MPC-generated state and control trajectories and the optimal feedback generated state and control trajectories, both obtained for the same value of the perturbation parameter, in terms of the step-size of the discretizatihttps://pure.soton.ac.uk/admin/editor/dk/atira/pure/api/shared/model/researchoutput/editor/contributiontojournaleditor.xhtml#on and the measurement error. Numerical results illustrating our estimate are reported
Versions of the Subgradient Extragradient Method for Pseudomonotone Variational Inequalities
Phytoplasma diseases on major crops in Vietnam
The nested-PCR technique was applied to detect and identify phytoplasmas associated with major crops in Vietnam
including sugarcane, cassava and longan. Phylogenetic analysis confirmed that phytoplasmas associated with the
sugarcane grassy shoot and white leaf diseases belong to the rice yellow dwarf group (16SrXI). In cassava showing witches’ broom symptoms a mixed infection of phytoplasmas related to ‘Candidatus Phytoplasma asteris’ (group 16SrI) and ‘Ca. P. aurantifolia’ (group 16SrII) was detected. In samples showing longan witches’ broom disease three phytoplasmas including ‘Ca. P. aurantifolia’ (group 16SrII), elm yellows (group 16SrV) and “stolbur” (group 16SrXII) were identified
Passive smoking exposure and perceived health status in children seeking pediatric care services at a vietnamese tertiary hospital
10.3390/ijerph17041188International Journal of Environmental Research and Public Health174118