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Predicted white-light solar flare emission from the F-CHROMA grid of models
No full textContext. Much of a solar flare’s energy is thought to be released in the continuum. The optical continuum, white light (WL), is of special interest since it can be observed from the ground.
Aims. We aim to investigate the prevalence of WL emissions in simulations of purely electron beam-driven solar flares, what determines the occurrence of these enhancements, and the underlying causes.
Methods. We utilized the F-CHROMA grid of flare simulations created using the radiative hydrodynamics code RADYN. We probed the spectral index, total energy, and low-energy cutoff to draw conclusions about their relationships to the WL intensity. Furthermore, we calculated the 6684 Å continuum intensities as well as the Balmer and the Paschen ratios. Finally, we analyzed two particular cases, one with a high 6684 Å intensity and one with a large Balmer ratio, to determine the dominant mechanisms in these simulations.
Results. Of the 84 flares included in the F-CHROMA grid, 33 show WL intensity enhancements that exceed 0.1% relative to the pre-flare level. We conclude that with the parameters presented in the F-CHROMA grid, purely electron beam-driven simulations of solar flares are not able to reproduce observed WL enhancements, as the maximum enhancements in the grid are below 4%, which is significantly lower than observational values. The total energy (which is correlated with the maximum beam flux) is the main factor for deciding whether excess WL emissions will be detectable or not. There is a linear relationship between the Balmer (and Paschen) ratio and the relative continuum increase. Both case studies show that during the time of maximum WL excess, hydrogen ionization and subsequent recombination in an optically thin medium is the dominant mechanism for WL continuum emission enhancements in these electron beam-driven atmospheres. Increased H− emission in the photosphere, as a result of radiative backwarming, becomes dominant during the declining phase of WL emissions in both case studies. We confirm the inability to reproduce the characteristics of type II WL flares, namely, the appearance of photospheric continuum enhancements without prior chromospheric emission increases and the lack of a clear Balmer jump, with the F-CHROMA grid
A deep ALMA Band 3 survey of HDFS/MUSE3D
No full textContext. After more than 10 years of ALMA operations, the community interest in conducting deep extra-galactic millimetre surveys resulted in varying strategic compromises between areal size and map depth to survey the sky. The current bias leans towards a galaxy population found in the field or towards rich starbursty proto-cluster groups, which are both tendentiously surveyed at coarse spatial resolutions.
Aims. We describe a survey that addresses these biases. A deep 3 mm survey was conducted with ALMA at long baselines in a 1 × 1 arcmin2 region in the Hubble Deep Field South (HDFS) that was also covered by the Multi Unit Spectroscopic Explorer (MUSE) in order to assess resolved molecular gas properties in galaxies in group environments at z > 1.
Methods. ALMA observations comprising a four-pointing mosaic with a single band 3 (3 mm) spectral tuning were conducted to cover CO transitions from different groups identified by MUSE. This work consists of a total effective on-source time of 61 hours in configurations with baselines up to 15 km.
Results. The final dataset yields an angular resolution of 0.15″–0.2″ (depending on the imaging weights) and maximum recoverable scales of 1″–2″. The final continuum map reaches an unprecedented sensitivity of RM
A supply chain model under credit period and price dependent demand: a Stackelberg approach
No full textIn many industrial practices, market demand is likely to be affected by the trade credit policy. In this regard, present study aims to develop a retailer–supplier non-cooperative replenishment model with price and credit length-dependent demand and default risk, to determine the best credit period in a supplier-Stackelberg game. The perks of credit policy include attracting new buyers and avoiding long-term price rivalry. This study was conducted under three distinct decision-making scenarios. The first section demonstrates the optimal outcomes for decentralized and centralized decisions when trade credit is unavailable. Secondly, the Stackelberg game framework employs a leader-follower relationship, where the manufacturer plays the role of leader and the retailer plays the role of follower. Using a supplier Stackelberg method, the existence and uniqueness requirements for the retailer and the supplier optimal solutions have been constructed. In this supplier Stackelberg strategy, the retailer sets the best lot-size, while the supplier chooses the best credit length. A series of theorems and corollaries were designed to determine the best response under these conditions. Sensitivity analysis of few examples have been carried out to demonstrate the proposed method and the anticipated outcomes. Also, the decision variable’s characteristics, obtained from the sensitivity analysis, have been figured out. According to the sensitivity analysis, the characteristic of the decision variable is provided, and the efficacy of the centralized decision-making approach is shown. Additionally, this research shows a high correlation between demand, credit length, and profit in the supply chain
Stabilization of control systems associated with a strongly continuous group
No full textThis paper is devoted to the stabilization of a linear control system y' = Ay + Bu and its suitable non-linear variants where (A, (A)) is an infinitesimal generator of a strongly continuous group in a Hilbert space ℍ, and B defined in a Hilbert space U is an admissible control operator with respect to the semigroup generated by A. Let λ ϵ ℝ and assume that, for some positive symmetric, invertible Q = Q(λ) ϵ ℒ(ℍ), for some non-negative, symmetric R = R(λ) ϵ ℒ(ℍ), and for some non-negative, symmetric W = W (λ) ∈ ℒ(U), it holds
AQ + QA* − BW B* + QRQ + 2λQ= 0.
We then present a new approach to study the stabilization of such a system and its suitable nonlinear variants. Both the stabilization using dynamic feedback controls and the stabilization using static feedback controls in a weak sense are investigated. To our knowledge, the nonlinear case is out of reach previously when B is unbounded for both types of stabilization
Impact of temperature change on the population dynamics of the maize pest
No full textWe provided in this work a theoretical framework to study and to simulate the population dynamics of Busseola fusca (B. fusca): maize pest. The aim is to simulate and predict the presence levels of Busseola fusca under the influence of temperature variations and control actions. Based on the life cycle of B. fusca), we first propose a mathematical model to study the population dynamics of this maize pest. Some parameters are taken to be temperature-dependent. This led to a system of non-autonomous differential equations. Also, the classical control strategies are incorporated in the model. We present the theoretical analysis of the model. For the model with constant parameters, we compute the basic offspring number 0 that determines the evolution of the population of this insect and establish that the trivial equilibrium is globally asymptotically stable whenever 0 1, the non trivial equilibrium is globally asymptotically stable. For the model with temperature variations, we find two explicit thresholds parameters max and min that bound the basic offspring number 0 (such that max ≤ 0 ≤ min), and use them to prove the extinction and the persistence of the pest within a maize field. We prove analytically and by numerical simulations that B. fusca) persists uniformly within a maize field when min > 1 and tends to disappears within a maize field when max < 1. The theoretical results are illustrated by numerical simulations. They suggest further that spraying insecticides to kill larvae and destroying residues after harvest significantly reduce the population Busseola fusca more than other control actions
Wood raw materials obtained from intermediate-use cuttings in Azerbaijan's beech forests and possibilities of their complex uses
No full textThe article examines the volume, harvesting, transportation, and integrated utilization of wood raw materials obtained from intermediate cuttings in beech (Fagus orientalis) forests of Azerbaijan. For this purpose, experimental sites were established for each thinning regime as well as for selective sanitary cuttings. Each site was subdivided into 7-10 compartments, resulting in a total of 43 sample plots with a combined area of 26 hectares. The results of the logging operations indicated that the total volume of harvested wood raw material amounted to 508.16 m3 (19.6 m3/ha), of which 53.1% was classified as merchantable timber, 28.0% as industrial (technological) wood, and 18.9% as fuelwood (green wood). To ensure the continuous collection and delivery of harvested timber in full volume, maps were developed in the forested areas of the northeastern Greater Caucasus. Two to three intermediate collection points were established in eight directions, each extending 40-50 km. Each collection point was designed to collect wood raw materials located within a 15-20 km radius. The article also explored the potential for the integrated use of low-quality wood and wood waste in the production of wood-based panel materials and bioactive substances
The current state and future prospects of green energy generation from green hydrogen
No full textGreen hydrogen, made by electrolysis of water driven by renewable energy resources, is being considered to be a crucial factor to help achieve deep decarbonization of energy systems as well as industries that are difficult to discuss. This article offers a thorough and comprehensive review of green hydrogen technology that examine their fundamental concepts as well as production routes and their current levels of maturation. The article outlines the differences between the conventional hydrogen production processes that are still heavily driven by fossil fuels and the emergence of low-carbon alternatives that rely upon renewable energy. Special attention is paid to electrolysis techniques, such as proton exchange membranes, alkaline as well as high-temperature systems and also to other methods in the process of development, including photoelectrochemical conversion and biomass conversion. The state of the global green hydrogen sector is investigated through large-scale projects, which reveal an explosive growth in capacity due to favorable renewable sources including solar and wind energy. Despite this rapid expansion, many challenges remain including the cost of production infrastructure needs, intermittent availability of renewable energy sources, and regulatory limitations. The paper wraps up by discussing future developments prospects and highlighting the crucial role played by green hydrogen to support the carbon neutrality goals and energy security as well as the shift towards the sustainable and sustainable low-carbon economy
Study of the effect of planting density in greenhouses and open fields on the yield of quinoa (
No full textAs one of the most resilient and alternative crops in the face of climate change challenges that are having a significant impact on cereals, quinoa was introduced to Morocco in 1999. However, despite two decades of development, this sector seems to suffer from a lack of knowledge of good agricultural practices. With this in mind, this research, carried out at the experimental station of the Faculty of Sciences in Oujda, aims to evaluate the yield of Chenopodium quinoa Willd in order to identify the planting density and planting method that generate the optimum yield. Three density levels, D1, D2 and D3, corresponding respectively to spacings of 30/20 cm, 40/20 cm and 40/10 cm, and two planting methods, under tunnel and in open field, were tested on the ICBA-Q5 quinoa variety. The experimental design consisted of Randomized Complete Block Design (RCBD) with three replicates. The parameters measured were harvest date, grain yield and 1000-grain weight. The results indicate that the installation mode significantly affected the harvest date, with a 24-day difference between the two modes, although planting density significantly affected quinoa yield for both installation modes. Thus, the optimum grain yield per hectare is achieved at density D2 40/20 cm for plants grown in open fields, while for plants grown under tunnels, density D1 30/20 cm remains the best. Nevertheless, no significant effect was found on the weight of 1,000 grains. These results will be useful and could be recommended for the intensification of Chenopodium quinoa Willd. cultivation
Exergy analysis of an indirect type solar dryer integrated with heat pipe technology
No full textFood drying processes require a sizable amount of energy, which contributes significantly to the carbon emissions. Therefore, the integration of sustainable energy in the food processing industries is essential to achieve net zero carbon emissions. This study aims to develop an indirect-type natural convection solar dryer integrated with heat pipes, incorporating exergy performance analysis of its drying chamber. Exergy analysis was conducted to ascertain the type and extent of exergy losses that occur throughout the solar drying process. The estimated maximum instantaneous exergy inflow and outflow were 1.248 W and 0.619 W, respectively, for the drying chamber. The overall exergy efficiency of the drying chamber is 32.49 percent. The average loss of exergy was evaluated to be 0.274 W. The corresponding Waster Energy Ratio, Improvement Potential, and Sustainability Index are 0.68, 0.19 W, and 1.48, respectively
Vulnerable urban areas and adaptability: The case of Rabat
No full textToday's urban players are faced with the challenges of mitigating climate change and adapting to its effects in the short, medium and long term. This involves, on the one hand, efforts to limit energy consumption and greenhouse gas (GHG) emissions, and on the other, strategies to reduce the vulnerability of urban areas to the climatic effects that create potential risks. Furthermore, cities are particularly vulnerable to the risk of heatwaves due to the existence of an urban heat island, which is responsible for a rise in temperature in the urban area compared with the surrounding countryside. In this respect, the integration of energy and climate issues into local and regional public policies and, more generally, into the legislative framework represents a major challenge for the success of national climate policy. In this context,this article focuses on analyzing and assessing the vulnerability and adaptability of urban areas to the impacts of climate change on their subsistence activities. The study took place in the Rabat region of Morocco