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8. Increasing hypoxia on global coral reefs under ocean warming

Author

Pezner, Ariel K., Courtney, Travis A., Barkley, Hannah C., Chou, Wen-Chen, Chu, Hui-Chuan, Clements, Samantha M., Cyronak, Tyler, DeGrandpre, Michael D., Kekuewa, Samuel A. H., Kline, David I., Liang, Yi-Bei, Martz, Todd R., Mitarai, Satoshi, Page, Heather N., Rintoul, Max S., Smith, Jennifer E., Soong, Keryea, Takeshita, Yuichiro, Tresguerres, Martin, Wei, Yi, Yates, Kimberly K., and Andersson, Andreas J.

Published
2023
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17. Coral growth along a natural gradient of seawater temperature, pH, and oxygen in a nearshore seagrass bed on Dongsha Atoll, Taiwan.

Author

Pezner, Ariel K., Courtney, Travis A., Chou, Wen-Chen, Chu, Hui-Chuan, Frable, Benjamin W., Kekuewa, Samuel A. H., Soong, Keryea, Wei, Yi, and Andersson, Andreas J.

Subjects
CORAL reefs & islands, OCEAN temperature, CORALS, PORITES, LOW temperatures, SYMBIODINIUM, SEAGRASSES
Abstract

Coral reefs are facing threats from a variety of global change stressors, including ocean warming, acidification, and deoxygenation. It has been hypothesized that growing corals near primary producers such as macroalgae or seagrass may help to ameliorate acidification and deoxygenation stress, however few studies have explored this effect in situ. Here, we investigated differences in coral growth rates across a natural gradient in seawater temperature, pH, and dissolved oxygen (DO) variability in a nearshore seagrass bed on Dongsha Atoll, Taiwan, South China Sea. We observed strong spatial gradients in temperature (5°C), pH (0.29 pH units), and DO (129 μmol O2 kg-1) across the 1-kilometer wide seagrass bed. Similarly, diel variability recorded by an autonomous sensor in the shallow seagrass measured diel ranges in temperature, pH, and DO of up to 2.6°C, 0.55, and 204 μmol O2 kg-1, respectively. Skeletal cores collected from 15 massive Porites corals growing in the seagrass bed at 4 sites revealed no significant differences in coral calcification rates between sites along the gradients. However, significant differences in skeletal extension rate and density suggest that the dynamic temperature, pH, and/or DO variability may have influenced these properties. The lack of differences in coral growth between sites may be because favorable calcification conditions during the day (high temperature, pH, and DO) were proportionally balanced by unfavorable conditions during the night (low temperature, pH, and DO). Alternatively, other factors were simply more important in controlling coral calcification and/or corals were acclimated to the prevailing conditions at each site. [ABSTRACT FROM AUTHOR]

Published
2024
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23. Probabilistic Dynamic Design Curves Optimized for High-Speed Reinforced Concrete Railway Bridges Using First-Order Reliability Method.

Author

Allahvirdizadeh, Reza, Andersson, Andreas, and Karoumi, Raid

Subjects
*BRIDGE vibration, *STRUCTURAL reliability, *RAILROAD bridges, *REINFORCED concrete, *JOINT use of railroad facilities
Abstract

Increasing the operating speed of trains in modern railway networks can induce greater actions on the infrastructure than was previously the case. This is due, in particular, to the occurrence of the resonance phenomenon in railway bridges, which is the focus of this paper and was not traditionally considered as a concern. In this context, the vibrations experienced by bridges, both vertical accelerations and displacements, are limited by design regulations to ensure that the safety of train passages over bridges and the comfort of passengers are guaranteed. However, previous studies have shown that the conventional dynamic design methods do not always result in conservative designs, nor is the achieved safety always consistent. Therefore, a probabilistic approach is adopted in this study to optimize the cross-section properties of various railway bridges in a wide design range including section types, span lengths, and number of spans. For this purpose, an iterative line search-based optimization problem is formulated to minimize the thickness of the cross-sections under consideration and consequently the linear mass of the bridges. Meanwhile, the associated failure probabilities of the above dynamic limit states are constrained to be less than the desired level of safety by incorporating them into the optimization constraint. In this regard, First-Order Reliability Method (FORM) is adopted to perform reliability analyses. Thus, the obtained results are presented in the form of design curves that may assist designers to select minimum cross-section dimensions satisfying the desired level of safety in terms of dynamic limit states. This objective can be achieved using the proposed design curves without the need to construct associated complex computational models and perform computationally expensive dynamic analyses. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Dynamic behaviour of bridges under critical conventional and regular trains: Review of some regulations included in EN 1991-2.

Author

Museros, Pedro, Andersson, Andreas, and Pinazo, Benjamín

Abstract

In the field of structural analysis dedicated to the study of vibrations of high-speed railway bridges, one reference load model is the well-known HSLM-A, which limits of validity are stated in Eurocode EN 1991-2, Annex E. In a recent paper published in the Journal of Rail and Rapid Transit, the authors investigated the degree of coverage provided by HSLM-A to critical articulated trains. Now in the present article, the authors have extended those analyses to critical conventional and regular trains as well. This is an important aspect because HSLM-A as such is an articulated-type model, so it is of interest to understand how it deals with covering the various resonance phenomena generated by other train types. Therefore, the main goal of this work is to establish whether the conventional and regular trains that stem from the validity rules given in Annex E/EN 1991-2, produce vibratory effects that are duly covered by HSLM-A. Following the aforementioned validity rules, one first aspect analysed is the importance of near-to-integer wheelbase ratios in the coupled vibrations produced by conventional trains. Subsequently, seven realistic, conventional and regular high-speed train models have been synthesised; these models have been made publicly available in Mendeley Data, and comprise almost 3800 different sequences of axle loads. Finally, the response of simply-supported bridges has been analysed with a view to compare the seven synthesised models versus HSLM-A. The exceedance and required speed increase have been computed for both displacements and accelerations, in a comprehensive ensemble of spans and speeds. The results provide a diagnosis of the degree of coverage of HSLM-A with respect to those conventional and regular trains compliant with Annex E/EN 1991-2. [ABSTRACT FROM AUTHOR]

Published
2024
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38. Physical and Biological Controls on the Annual CO2 Cycle in Agua Hedionda Lagoon, Carlsbad, CA.

Author

Shipley, Kenisha, Martz, Todd, Hales, Burke, Giddings, Sarah N., and Andersson, Andreas

Subjects
LAGOONS, MARINE fishes, FISH hatcheries, SUMMER, RECREATION, MASS budget (Geophysics), HATCHERY fishes, RESPIRATION in plants
Abstract

Agua Hedionda Lagoon (AHL), a tidal estuary located on the southern California coast, supports a diverse ecosystem while serving numerous recreation activities, a marine fish hatchery, a shellfish hatchery, and the largest desalination plant in the western hemisphere. In this work, a 1-year time series of carbon dioxide data is used to establish baseline average dissolved inorganic carbon conditions in AHL. Based on a mass balance model of the outer basin of the lagoon, we propose that AHL is a source of inorganic carbon to the adjacent ocean, through advective export, at a rate of 5.9 × 106 mol C year−1, and a source of CO2 to the atmosphere of 0.21 × 106 mol C year−1 (1 mol C m−2 year−1), implying a net heterotrophic system on the order of 6.0 × 106 mol C year−1 (30 mol C m−2 year−1). Although variable with a range throughout the year of 80% about the mean, the ecosystem remained persistently heterotrophic, reaching peak rates during the summer season. Using results from the mass balance, the annual cycle of selected properties of the aqueous CO2 system (pH, pCO2, and CaCO3 saturation state) were mathematically decomposed in order to examine the relative contribution of drivers including advection, ecosystem metabolism, and temperature that act to balance their observed annual cycle. Important findings of this study include the identification of advection as a prime driver of biogeochemical variability and the establishment of a data-based estimate of mean flushing time for AHL. [ABSTRACT FROM AUTHOR]

Published
2024
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42. Biochar and district heating : The path to negative emissions

Author

Widlund, Amanda, Norström, Thomas, Isaksson, William, and Andersson, Andreas

Subjects
carbon sink, Teknik och teknologier, Engineering and Technology, biochar, climate impact, pyrolysis, district heating
Abstract

Uppsala Kommun is developing a new city district called Sydöstra staden (SÖS) as an innovative and transformative city district. A technical supply system that aligns with the district’s goals is pyrolysis. Pyrolysis is a process where biomass is heated without the supply of oxygen. This leads to carbonization where the energy is converted to biochar and heated gas that can be used for district heating. The biochar, which is considered as a carbon sink, could be the path for the municipality to achieve their climate goals for 2050. The aim of this project is to investigate the viability of providing district heating to SÖS through pyrolysis. Three scenarios based on biomass assets of garden waste, manure, and wooden chips will be evaluated from four perspectives: climate impact, economic feasibility, district heating coverage, and placement considerations. The method is a model constructed in python that simulates how much heat and biochar that can be produced including an income statement and how the price of biochar relates to the return of investment. The biochar price and biomass flow are two parameters that are examined in the sensitivity analysis. The model enables comparisons between the outcomes of the pyrolysis process and the heat energy demands in SÖS, the biochar usage in Uppsala and the municipality’s CO2 emissions. The results show profitable reactor alternatives in all three scenarios even without selling CORCs. However, the profitability is heavily reliant on maximizing the utilization of burned biomass. Furthermore, the first two scenarios had a negligible climate impact while the most profitable reactor in scenario 3 had a large impact on the municipality’s climate goals. Also, the coverage of district heating has been evaluated due to the asset of biomass as well as placement requirements have been stated.

Published
2023

43. Facing Challenges and Overcoming Resistance for Industry 4.0 Implementation : A Descriptive Study of Swedish Manufacturing SMEs

Author

Andersson, Andreas, Härnstam, Erik, and Martinez Linder, David

Subjects
Manufacturing Industry, Barriers of Implementation, Drivers of Implementation, Industry 4.0, Business Administration, Företagsekonomi
Abstract

The fourth industrial revolution also known as Industry 4.0 ushers in new advanced manufacturing technologies that enables companies to improve efficiency and reduce waste. The promising outlook of this era suggests that the implementation degree for Swedish manufacturing SMEs operating in a high-tech context should be high, this is however not empirically observed. The purpose of the paper is to investigate the implementation level of Industry 4.0 technologies in the chosen context, identify barriers that hinder implementation, as well as investigate how the use of the new technologies can be increased. The paper uses a quantitative data approach, using empirical data derived from a survey that was sent out to relevant practitioners acting in the manufacturing industry. Findings indicate that the barriers derived from previous literature match what is experienced by the practitioners surveyed, but that the perceived impact between each barrier is varied depending on if they have implemented Industry 4.0 or not. By combining key themes and findings of the paper, a model is constructed and applied to reduce the perceived impact of the barriers leading to higher implementation levels of new advanced technologies.

Published
2023

44. The Relevance of Social Class : A Content Analysis of EFL Coursebooks for Swedish Upper Secondary School

Author

Andersson, Andreas

Subjects
Upper Secondary School, EFL Coursebooks, Social Class, Specific Literatures, Litteraturstudier, Social Sciences, Samhällsvetenskap, Neo-Marxist Theory
Abstract

This study focuses on social class in Swedish EFL coursebooks. The aim is to investigate what different social classes are represented and how much space they are given, as well as how they are portrayed in three Swedish EFL coursebooks aimed at English 5 for upper secondary school. The selected coursebooks Viewpoints 1, Blueprint A 3.0, and Pioneer 1 have been analyzed using qualitative content analysis, focusing on texts and images presented in the materials. The analysis emanates from Neo-Marxist theory in order to point to different social class conditions. The results show lower-, middle-, and upper-class representation to various degrees. Mostly the lower class and upper class are visible, while the middle class is underrepresented. The lower class, in most cases, is shown together with the upper class in exploitative circumstances. This is made apparent through the lower class, in most cases, lacking the ability to decide for themselves in relation to their upper-class counterparts. Further, this indicates that the upper class rules the world on behalf of the lower class. Meanwhile, when the middle class is shown, they are mainly depicted through overconsumption, and as victims of upper-class dominance. Despite previous research showing the importance of social class on a global, European and Swedish scale, the coursebooks somewhat disregard its importance in different texts and images.

Published
2023

45. Utilizing Neural Networks To Adaptively Demodulate And Decode Signals In An Impulsive Environment

Author

Andersson, Andreas

Subjects
Impulsive Noise, Demodulation, Decoding, Communication Systems, Neural Network, Alpha-stable Noise, Kommunikationssystem
Abstract

Electromagnetic disturbance can be detrimental to the performance of a radio communication system, and in today’s society where more and more electronic devices are present in our everyday life it is increasingly vital to consider man-made interference. A communication system can take into consideration the noise characteristics and by doing so will excel in such areas, however, this follows that the algorithms utilized in such systems are more computationally complex and are therefore slow. This master thesis aims to explore the possibility of a neural network-based solution that reaches the same accuracy, as existing methods, but more quickly. Numerous different existing model alternatives have been explored and a plethora of different improvement techniques have been outlined. Two models, Hannet and Lannet, have been designed and improved to enable adaptive demodulation both including or excluding decoding at the receiver in an end-to-end communication system. The evaluation results demonstrate that the proposed models are comparable and in some cases even more accurate than current standardized methods. However, the models are unable to fully learn the decoding algorithms present in the experiments. Thus even though demodulation by itself thrives, performing decoding in conjunction with demodulation is out of reach for these models.

Published
2023

48. Understanding Ocean Acidification Impacts on Organismal to Ecological Scales

Author

Andersson, Andreas J., Kline, David I., Edmunds, Peter J., Archer, Stephen D., Bednaršek, Nina, Carpenter, Robert C., Chadsey, Meg, Goldstein, Philip, Grottoli, Andrea G., Hurst, Thomas P., King, Andrew L., Kübler, Janet E., Kuffner, Ilsa B., Mackey, Katherine R.M., Menge, Bruce A., Paytan, Adina, Riebesell, Ulf, Schnetzer, Astrid, Warner, Mark E., and Zimmerman, Richard C.

Published
2015

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