Technical University of Denmark

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    Recent advances in the potential of modeling and simulation to assess the performance of modified atmosphere packaging (MAP) systems for the fresh agricultural product:Challenges and development

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    Background: The metabolic process and physiological activities of fresh fruit and vegetables continue after harvesting and lead to quality reduction and waste enhancement. Modified atmosphere packaging (MAP) is a well-proven method to avoid anaerobiosis activities and extend the shelf life of agricultural products. As a result, researchers have proposed MAP technology as an appropriate and cost-effective method. The design of MAP systems depends on various factors, including the respiration and transpiration rates of the product, the temperature and humidity of the environment, and the permeability rate of the package. Therefore, the integration of mentioned information in the design of a successful MAP system is crucial.Scope and approach: The modeling approach is a reliable method for understanding the incorporation of the effective parameters and achieving the mass balance equation to determine the optimal conditions of the MAP. This review investigates the developed models for achieving a MAP design for various agricultural products. Also, the existing challenges in the developed models are discussed. In addition, the strengths and shortcomings of the integrated models are described, and the prospects for the optimization of MAP are highlighted.Key findings and conclusions: Considering the interaction of effectual parameters and sub-models, mathematical modeling revealed acceptable accuracy to predict the shelf life of fresh produce under the actual supply chain conditions and MAP systems. Due to the difference in the optimum MAP requirements based on specific parameters such as gas concentration, research is needed to optimize the effective factors by taking into account the perm-selectivity of the packaging materials. More efforts should focus on developing the comprehensive mathematical model and simulation, including product characteristics, package properties, environmental conditions, and mass and heat transfer phenomena for optimal MAP design

    A Sequent Calculus for First-Order Logic Formalized in Isabelle/HOL

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    We formalize in Isabelle/HOL soundness and completeness of a one-sided sequent calculus for first-order logic. The completeness is shown via a translation from a semantic tableau calculus, whose completeness proof we base on the theory entry ‘First-Order Logic According to Fitting’ by Berghofer in the Archive of Formal Proofs. The calculi and proof techniques are taken from Ben-Ari’s textbook Mathematical Logic for Computer Science (Springer, 2012). We thereby demonstrate that Berghofer’s approach works not only for natural deduction but also constitutes a framework for mechanically checked completeness proofs for a range of proof systems

    Co-existence of γ<sup>'</sup><sub>N</sub> phase and γ<sub>N</sub> phase in nitrided austenitic Fe-Cr-Ni alloys - II. a pragmatic modeling approach

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    A recent investigation of the nitriding response of austenitic Fe-Cr-Ni alloys with various compositions showed that the surface adjacent zone generally identified as expanded austenite consists of a duplex structure. In the near-surface part, with the highest N content, long-range ordering (LRO) among the nitrogen atoms occurs in addition to short-range ordering (SRO) of N and Cr atoms; and in the near-matrix part, with a lower N content, only SRO of N and Cr atoms is encountered. These zones are dubbed γ'N and γN, respectively. In the present contribution, a pragmatic model is presented to effectively describe the nitrogen arrangements in γN and γ'N and the transition of one into the other by changing the Cr and N contents. The model considers the occupancy of octahedral interstices surrounded by more than one Cr atom and, depending on the number of Cr atoms constituting the octahedron, distinguishes between strong and weak interactions between the octahedral sites and N atoms. In order to account for the competition between Cr-N SRO and Fe4N-like LRO, the occupancy of neighboring interstices with N surrounding a central metal atom is taken into consideration. The distribution of N atoms over differently coordinated interstices is obtained by pragmatically fitting the model to experimental data. The model is validated by comparison of the predicted distributions of occupied interstices to literature data for Mössbauer spectroscopy and Extended X-ray Absorption Fine Structure, respectively. Furthermore, the model provides a consistent interpretation of thermodynamics and diffusion data for nitrogen-stabilized expanded austenite

    Impact of glacier changes and permafrost distribution on debris flows in Badswat and Shishkat catchments, Northern Pakistan

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    Knowledge of glacier changes and associated hazards is of great importance for the safety consideration of the population and infrastructure in the mountainous regions of Upper Indus Basin (UIB). In this study, we assessed the variations in glacier velocity, glacier surface elevation change, meteorological conditions, and permafrost distribution in Badswat and Shishkat catchments located in UIB to access the potential impact on the occurrence of debris flow in both catchments. We find that the glacier surface velocity increased during the debris flow event in the Badswat catchment and the mean daily temperature was 3.7°C to 3.9°C higher in most of the locations. The enhanced glacier surface elevation lowering period coincide with the rise in temperature during spring and autumn months between 2015 to 2019 in Badswat catchment. The source region of debris flow falls within the lower boundary of permafrost occurrence zone and lies below the 0°C isotherm during late spring and summer months. In Shishkat catchment the 0°C isotherm reaches above the debris flow source area during August and the glacier do not show any significant variations in velocity and surface elevation change. The debris flow source area is adjacent to the slow-moving rock glacier in Shishkat catchment while in Badswat catchment the debris flow initiated from the former glacier moraine. Both catchments are largely glacierized and thus sensitive to changes in climatic conditions and changes in the cryosphere response possess significant threats to the population downstream. Continuous monitoring of cryosphere-climate change in the region can contribute toward the improvement of disaster risk reduction and mitigation policies.</p

    First Light and Reionization Epoch Simulations (flares) - XIV. The Balmer/4000 Å breaks of distant galaxies

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    With the successful launch and commissioning of JWST we are now able to routinely spectroscopically probe the rest-frame optical emission of galaxies at z &gt; 6 for the first time. Among the most useful spectral diagnostics used in the optical is the Balmer/4000 Å break; this is, in principle, a diagnostic of the mean ages of composite stellar populations. However, the Balmer break is also sensitive to the shape of the star formation history, the stellar (and gas) metallicity, the presence of nebular continuum emission, and dust attenuation. In this work, we explore the origin of the Balmer/4000 Å break using the synthesizer synthetic observations package. We then make predictions of the Balmer/4000 Å break using the First Light and Reionization Epoch Simulations at 5 &lt; z &lt; 10. We find that the average break strength weakly correlates with stellar mass and rest-frame far-ultraviolet luminosity, but that this is predominantly driven by dust attenuation. We also find that break strength provides a weak diagnostic of the age but performs better as a means to constrain star formation and stellar mass, alongside the ultraviolet and optical luminosity, respectively.</p

    A new likelihood inequality for models with latent variables

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    Likelihood-based approaches are central in statistics and its applications, yet often challenging since likelihoods can be intractable. Many methods such as the EM algorithm have been developed to alleviate this. We present a new likelihood inequality involving posterior distributions of a latent variable that holds under conditions similar to the EM algorithm. Potential scopes of the inequality includes maximum-likelihood estimation, likelihood ratios tests and model selection. We demonstrate the latter by performing selection in a non-linear mixed-model using MCMC.</p

    Considerations on how to conduct a survey about long-distance travel with reduced memory effect

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    The paper presents a survey about international trips with overnight stays. Contrary to traditional retrospective long-distance travel surveys, respondents are asked for their 3-4 most recent trips. Due to this, the traditional huge memory effect is eliminated. The main part of the paper is dedicated to considerations on how to estimate the annual number of trips with this concept. Estimations based on the cumulated hazard function, which is a normal mathematical solution, are rejected because a new journey cannot start until the former was finished. Instead, extra trips should be simulated until all trips during a year are included

    Temporal collaborative attention for wind power forecasting

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    Wind power serves as a clean and sustainable form of energy. However, its generation is fraught with variability and uncertainty, owing to the stochastic and dynamic characteristics of wind. Accurate forecasting of wind power is indispensable for the efficient planning, operation, and grid integration of wind energy systems. In this paper, we introduce a novel forecasting method termed Temporal Collaborative Attention (TCOAT). This data-driven approach is designed to capture both temporal and spatial dependencies in wind power generation data, as well as discern long-term and short-term patterns. Utilizing attention mechanisms, TCOAT dynamically adjusts the weights of each input variable and time step based on their contextual relevance for forecasting. Furthermore, the method employs collaborative attention units to assimilate directional and global information from the input data. It also explicitly models the interactions and correlations among different variables or time steps through the use of self-attention and cross-attention mechanisms. To integrate long-term and short-term information effectively, TCOAT incorporates a temporal fusion layer that employs concatenation and mapping operations, along with hierarchical feature extraction and aggregation. We validate the efficacy of TCOAT through extensive experiments on a real-world wind power generation dataset from Greece and compare its performance against twenty-two state-of-the-art methods. Experimental results demonstrate that TCOAT outperforms existing methods in terms of both accuracy and robustness in wind power forecasting. Moreover, we conduct a generality study on an additional real-world dataset from a different climate condition and wind power characteristics. The results show that TCOAT can achieve comparable or better performance than the state-of-the-art methods, confirming the generalization ability of TCOAT

    A numerical investigation of nitridation in solid oxide fuel cell stacks operated with ammonia

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    Operating solid oxide fuel cell (SOFC) stacks with ammonia induces the risk of nitriding in the fuel electrode and other metallic surfaces in the stack. This study aims to investigate the nitriding in the fuel electrode of an ammonia-fueled SOFC stack using a 3D Multiphysics model of a full stack. Based on the resulting species concentrations, a so-called nitriding potential is determined and compared to its critical level for various operating conditions and design modifications. The effects of the gas inflow temperatures, counter-flow configuration, and nickel coating over the inlet header of the stack are investigated. The results show that nitriding occurs in the first few centimeters of the fuel electrode for all investigated operating conditions considered in this study. Moreover, it is indicated that higher gas inflow temperatures and counter-flow configuration reduce the nitriding in the fuel electrode. Furthermore, the model illustrates the nitriding in the fuel active electrode for the gas inflow temperatures up to 700 °C. Finally, a significant reduction in nitriding in the fuel electrode is shown for a proposed nickel coating over the metallic inlet header due to a spreading of the ammonia decomposition

    Sørensen, Louise Amanda Bünger

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