Drivers of change, adaptation and resilience of agricultural systems facing increased salinity intrusion in deltaic coastal areas of Vietnam

This PhD research aimed to examine historical and present drivers of agricultural changes in the Mekong (MKD) and Red River (RRD) deltas in Vietnam since 1975 as well as explore adaptation pathways and resilience of agricultural systems facing increased salinity intrusion in these deltas. The research ultimately used the lens of complex adaptive systems theory to examine interactions and feedbacks in agricultural systems and their drivers of change at multiple levels in deltaic social-ecological systems. In addition, this study applied an adaptation pathway approach to identify various adaptation options and potential lock-ins in agricultural systems and the subjective resilience assessment method to quantify the resilience of agricultural systems in these deltas. Currently, the RRD is protected from salinity intrusion by a concrete sea dyke and sluicegate system. In the MKD, salinity is naturally happening as it is a tide-dominated delta and there are fewer protective structures in place. Case study research was carried out in villages located along salinity gradients in the MKD, and at different distances to sea dykes in the RRD in Vietnam. Empirical data consisted of 27 in-depth interviews with officials of local and national authorities as well as 11 focus group discussions, 198 semi-structured interviews, 226 structured-interviews and 3 role-playing games conducted with farmers in both deltas in 2015-2016. This study reveals that agricultural systems in the RRD and MKD since the end year of the war in 1975 have experienced considerable changes. The analysis of drivers of change and adaptation pathways shows that a dynamic interplay and feedback of various drivers of change such as policy intervention, farmers' desire for profit maximization, changing salinity conditions, and technological development at different levels of the deltaic social-ecological system have shaped the changes and adaptations in agricultural systems over the last decades. In response to increased salinity intrusion, as exemplified by the highest salinity levels in 90 years which were recorded in the MKD in 2015-2016, various adaptation options have been considered. These include adaptations that would lock-in agricultural production in particular agricultural systems or constrain changes in others, potentially problematic in light of the high uncertainty related to future changes. The study recognizes the need to apply both incremental and transformative changes and select adaptation pathways which allow for continuous change or that are reversible in order to avoid lock-ins and address future challenges. In addition, this study implemented a subjective resilience assessment method based on farmers' perception of the three resilience components i) the sensitivity of their agricultural systems to increased salinity intrusion, ii) the capacity to recover from salinity damage, and iii) the capacity to change to other systems if salinity increases in the future. Results from the subjective resilience assessment reveal that none of the agricultural systems received a higher score than the others when considering all three resilience components, implying that an increase in one resilience component by switching agricultural systems would negatively impact others. Improving resilience components (e.g. through policies and interventions, resource allocation and farming system changes) to sustain agricultural production or facilitate transformation to alternative systems when necessary is critically important for agricultural systems facing stress. For a methodological implication, this research emphasizes the need to complement subjective resilience assessment with qualitative data to enhance understandings of drivers of resilience in order to improve components of resilience for agricultural systems in the respective deltas. In summary, attention should be drawn to interactions and feedbacks in future changes within and across adaptation pathways as well as trade-offs involved in farming system shifts regarding resilience components. Consideration of this could contribute to preventing further increases in salinity intrusion and lock-in effects in agricultural systems in the deltas.Das Ziel der Arbeit ist historische und gegenwärtige Treiber für den Wandel der Landwirtschaft im Mekong Delta (MKD) und Red River Delta (RRD) in Vietnam zu identifizieren. Weiterhin sollen Anpassungspfade und die Widerstandsfähigkeit der landwirtschaftlichen Systeme im Hinblick auf die zunehmende Salzanreicherung in den beiden Deltas untersucht werden. Die Forschung baut auf der komplexen, adaptiven Systemtheorie auf, um Wechselwirkungen und Rückkopplungen in landwirtschaftlichen Systemen zu untersuchen. Der Ansatz zielt darauf ab, ein besseres Verständnis der Treiber des Systemwandels auf mehreren Ebenen im sozial-ökologischen System der Deltaregionen zu erreichen. Darüber hinaus hat diese Studie einen Anpassungspfad-Ansatz angewandt, um verschiedene Anpassungsoptionen und mögliche "Lock-ins" in landwirtschaftlichen Systemen zu identifizieren sowie die Methode der subjektiven Resilienzbewertung verwendet, um die Widerstandsfähigkeit von landwirtschaftlichen Systemen in diesen Deltas zu quantifizieren. Derzeit ist das RRD durch einen Deich und ein Schleusensystem vor dem Eindringen von Salzgehalt geschützt. Im MKD tritt der Salzgehalt natürlich auf, da es sich um ein von den Gezeiten dominiertes Delta handelt und es weniger Schutzstrukturen gibt. Im MKD wurden empirische Erhebungen entlang von Salzgehaltsgradienten durchgeführt. Im RRD lag der Fokus darin, den Einfluss von Deichen auf die landwirtschaftliche Entwicklung zu untersuchen. Die empirischen Daten wurden in den Jahren 2015-2016 erhoben und setzen sich zusammen aus 27 Interviews mit Vertretern von regionalen und überregionalen Behörden, elf Fokusgruppen-Diskussionen, 198 semi-strukturierten Interviews, 226 strukturierten Interviews sowie den Auswertungen von Rollenspielen mit Landwirten. Die Ergebnisse der Studie zeigen, dass sich die landwirtschaftlichen Systeme im RRD und im MKD seit dem Kriegsende 1975 erheblich verändert haben. Die Analyse der Treiber von Veränderungs- und Anpassungspfaden zeigt, dass ein dynamisches Zusammenspiel von verschiedenen Faktoren wie Politikintervention, Gewinnmaximierung der Landwirte, veränderte Salzgehalte und technologische Entwicklung in den letzten Jahrzehnten den Wandel und die Anpassung der landwirtschaftlichen System geprägt haben. Als Reaktion auf die zunehmende Versalzung, wie die seit 90 Jahren in 2015-2016 höchsten gemessenen Salzgehalte im MKD zeigen, wurden verschiedene Anpassungsoptionen in Betracht gezogen. Dazu gehören Anpassungen, die die landwirtschaftliche Produktion in bestimmten Agrarsystemen einschränken oder Veränderungen in anderen Systemen unterbinden. Angesichts der hohen Unsicherheit im Zusammenhang mit künftigen Veränderungen könnte dies problematisch sein. Die Studie erkennt die Notwendigkeit an, sowohl inkrementelle als auch transformative Veränderungen vorzunehmen und Anpassungspfade zu wählen, die kontinuierliche Veränderungen ermöglichen oder reversibel sind, um "Lock-ins" zu vermeiden und zukünftige Herausforderungen anzugehen. Darüber hinaus führte diese Studie eine subjektive Methode zur Bewertung der Widerstandsfähigkeit ein, welche basierend auf der Wahrnehmung der Landwirte die drei Komponenten von Widerstandsfähigkeit einschätzt: i) die Sensitivität ihrer landwirtschaftlichen Systeme gegenüber einem erhöhten Salzgehalt, ii) die Fähigkeit sich von den Schäden durch Versalzung zu erholen und iii) die Fähigkeit auf andere Systeme umzusteigen, wenn der Salzgehalt in der Zukunft weiter ansteigen wird. Die Ergebnisse der subjektiven Bewertung von Widerstandsfähigkeit zeigen, dass keines der landwirtschaftlichen Systeme bei der Betrachtung aller drei Komponenten eine höhere Bewertung erhielt als die anderen. Dies zeigt, dass die Erhöhung der Widerstandsfähigkeit gemessen an einer Komponente, beispielsweise durch einen Wechsel der landwirtschaftlichen Systeme, andere Komponenten negativ beeinflussen würde. Die Erhöhung der Widerstandsfähigkeit im Hinblick auf die drei Komponenten (z.B. durch politische Maßnahmen und Interventionen, der gezielte Einsatz von Ressourcen oder Änderungen der Anbausysteme), ist für landwirtschaftliche Systeme, die unter Stress durch Versalzung leiden, von entscheidender Bedeutung, um die Produktion aufrechtzuerhalten oder bei Bedarf die Umstellung auf alternative Systeme zu erleichtern. Die Ergänzung der subjektiven Bewertung der Widerstandsfähigkeit mit qualitativen Daten ist daher entscheidend für das Verständnis der Treiber von Widerstandsfähigkeit, um die Komponenten der Widerstandsfähigkeit für landwirtschaftliche Systeme in den jeweiligen Deltas zu verbessern. Zusammenfassend ist darauf hinzuweisen, dass Wechselwirkungen und Rückkopplungen bei künftigen Veränderungen innerhalb und zwischen den Anpassungspfaden sowie Kompromisse hinsichtlich der Komponenten der Widerstandsfähigkeit zu berücksichtigen sind. Dies könnte dazu beitragen, eine weitere Erhöhung des Salzgehalts und "Lock-in" Effekte in landwirtschaftlichen Systemen in den Deltas zu verhindern

Electronic materials based on conducting metallopolymers and self-assembly

Conducting metallopolymers (CMPs) have been extensively studied due to their potential for various applications in sensing, catalysis, light-emitting diodes, and energy harvesting and storage. The incorporation of metal centers into conjugated organic polymer backbones not only makes these materials multi-functional, but also changes the properties, such as electroactivity and conductivity. In this work, we aim to take advantage of the direct electronic interaction between metal centers and polymer backbones in these metallopolymers to make novel materials that could be used for photovoltaic and spintronic applications. Furthermore, a fundamental study on the interactive role of transition metals in conducting metallopolymers has been conducted, which could help to provide insights for the rational design of metallopolymers for certain applications. Charge transfer in hybrid photovoltaics is often inhibited by the capping ligands on inorganic semiconductors. To bypass the ligand effect, my study was focused on preparing a conducting metallopolymer, in which metal ions are directly bound to the conjugated organic backbone. These metal ions will serve as nucleation or seed points upon which the inorganic semiconductor can grow directly within the polymer matrix. This fabrication method provides materials with direct bonds between the inorganic semiconductor and the conducting polymer backbone and therefore results in direct electronic communication between the donor and acceptor. With this material, the charge transfer limited by capping ligands could be overcome and can result in highly efficient devices when utilized in solar cells. Besides the efforts to harvest energy form renewable resources, changing the way that we use energy (e.g., in lighting and information storage) could also help to reduce our energy demand. The bistability offered by spin-crossover (SCO) complexes has resulted in sustained research interest due to potential applications in molecular electronics such as memory storage. Interested in making memory devices with a bottom up approach, we have designed and prepared CMPs that are not only conductive but also possess spin-crossover behavior. The novelty of this study lies in the fact that spin-switching could be possibly obtained by changing the oxidation states of metal centers, which could be done at room temperature, offering a new method for spin switching compared to conventional methods for SCO such as in thermal-induced spin transition. To study the charge delocalization and charge transport in CMPs, a series of conducting polymers of Schiff-base ligands and metal complexes have been prepared and characterized. Our successful syntheses of ligand polymers allows for full characterization and direct comparison of these polymers to the corresponding metal-containing polymers, from which the role of the metal centers is elucidated. The effects of conjugation length on electrochemical and spectroscopic properties are also investigated and discussed.Chemistr

Modeling of parallel power MOSFETs in steady-state

In high-power applications, multiple power MOSFETs are connected in parallel and treated as a single switch in order to handle much larger total currents. In this paper, a parallel power MOSFETs model from the turnoff state until they reach their steady state is introduced. The model represents the relationship between each power MOSFET's gate voltage and the current distribution among them. The study's key purpose is to use the model for dealing with the asymmetry in sharing current and power loss between these semiconductor devices during the steady state region.Comment: 10 pages, 7 figures, The 2023 INTERNATIONAL SYMPOSIUM ON ADVANCED ENGINEERING (ISAE2023

UIT-ADrone: A Novel Drone Dataset for Traffic Anomaly Detection

Anomaly detection plays an increasingly important role in video surveillance and is one of the issues that have attracted various communities, such as computer vision, machine learning, and data mining in recent years. Moreover, drones equipped with cameras have quickly been deployed to a wide range of applications, starting from border security applications to street monitoring systems. However, there is a notable lack of adequate drone-based datasets available to detect unusual events in the urban traffic environment, especially in roundabouts, due to the density of interaction between road users and vehicles. To promote the development of anomalous event detection with drones in the complex traffic environment, we construct a novel large-scale drone dataset to detect anomalies involving realistic roundabouts in Vietnam, covering a large variety of anomalous events. Traffic at a total of three different roundabouts in Ho Chi Minh City was recorded with a camera-equipped drone. The resulting dataset contains 51 videos with total data traffic of nearly 6.5 h, captured across 206K frames with ten abnormal event types. Based on this dataset, we comprehensively evaluate the current state-of-the-art algorithms and what anomaly detection can do in drone-based video surveillance. This study presents a detailed description of the proposed UIT-ADrone dataset, along with information regarding data distribution, protocols for evaluation, baseline experimental results on our dataset, and other benchmark datasets, discussions, and paves the way for future work

Drivers of change and adaptation pathways of agricultural systems facing increased salinity intrusion in coastal areas of the Mekong and Red River deltas in Vietnam

Agricultural systems are increasingly considered complex adaptive systems. They are dependent on the integrated nature of biophysical and social sub-systems, continuously adapt to changing conditions and often display non-linear responses to various drivers of change at multiple scales. This research applied the lens of complex adaptive systems theory to analyze current and historical drivers of change and adaptation pathways of agricultural systems to increased salinity intrusion in coastal areas of the Red River and Mekong deltas in Vietnam since 1975. The analysis is based on 27 in-depth interviews with officials of local and national authorities as well as 198 semi-structured interviews and 11 focus group discussions conducted with farmers along three salinity transects in both deltas in 2015-2016. The results show that a dynamic interplay and feedback of various drivers of change such as policy intervention, farmers’ desire for profit maximization, changing salinity conditions, and technological development at different levels of the deltaic social-ecological system have shaped the changes and adaptations in agricultural systems over the last decades. In response to increased salinity intrusion, as exemplified by the historic salinity levels recorded in the Mekong Delta in 2015–2016, various adaptation options have been considered. These include adaptations that would lock-in agricultural production in particular systems or constrain changes in others, which is potentially problematic in light of the high uncertainty related to future changes. The study recognizes the need to apply both incremental and transformative changes and select adaptation pathways which allow for continuous change or that are reversible in order to avoid lock-ins and address future challenges. Additionally, attention should be drawn to interactions and feedbacks in future changes within and across adaptation pathways in order to prevent further increases in salinity intrusion and lock-in effects in agricultural systems within the deltas

Resilience of agricultural systems facing increased salinity intrusion in deltaic coastal areas of Vietnam

The resilience concept has provided a new insight and approach to the conventional perspective of agricultural management by emphasizing the need to maintain a diversity of future options to adapt to inevitable and often unpredictable changes. The concept has been taken up by various academic disciplines and development sectors, yet ways to define and operationalize resilience as a measurable concept are still being developed. We contributed to this ongoing effort by implementing a subjective resilience assessment method based on farmers’ perceptions of three resilience components: (1) the sensitivity of their agricultural systems to increased salinity intrusion, (2) the capacity to recover from salinity damage, and (3) the capacity to change to other systems if salinity increases in the future. We conducted 27 in-depth interviews with local and national authorities, 11 focus group discussions, and 118 semistructured and 219 structured interviews with farmers in case study villages located along salinity transects in the Mekong Delta and at different distances to sea dikes in the Red River Delta in Vietnam in 2015-2016. Results from the subjective resilience assessment reveal that none of the agricultural systems studied systematically scored higher than the other systems on all three resilience components, implying that an increase in one resilience component by switching agricultural systems would negatively affect others. Agricultural responses to this salinity problem will influence current and long-term adaptability of the systems to future changes in salinity intrusion and other social-ecological developments in the deltas. Improving resilience components, e.g., through policies and interventions, resource allocation, and farming system changes, to sustain agricultural production or facilitate transformation to alternative systems when necessary is critically important for agricultural systems facing stress. Complementing subjective resilience assessments with qualitative data is thus crucial for understanding the drivers of resilience to improve components of resilience for agricultural systems in the respective deltas

Approximate Cloaking for The Heat Equation via Transformation Optics

In this paper, we establish approximate cloaking for the heat equation via transformation optics. We show that the degree of visibility is of the order $\epsilon$ in three dimensions and $|\ln\epsilon|^{-1}$ in two dimensions, where $\epsilon$ is the regularization parameter