6,927 research outputs found

    Modelling and Solving the Single-Airport Slot Allocation Problem

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    Currently, there are about 200 overly congested airports where airport capacity does not suffice to accommodate airline demand. These airports play a critical role in the global air transport system since they concern 40% of global passenger demand and act as a bottleneck for the entire air transport system. This imbalance between airport capacity and airline demand leads to excessive delays, as well as multi-billion economic, and huge environmental and societal costs. Concurrently, the implementation of airport capacity expansion projects requires time, space and is subject to significant resistance from local communities. As a short to medium-term response, Airport Slot Allocation (ASA) has been used as the main demand management mechanism. The main goal of this thesis is to improve ASA decision-making through the proposition of models and algorithms that provide enhanced ASA decision support. In doing so, this thesis is organised into three distinct chapters that shed light on the following questions (I–V), which remain untapped by the existing literature. In parentheses, we identify the chapters of this thesis that relate to each research question. I. How to improve the modelling of airline demand flexibility and the utility that each airline assigns to each available airport slot? (Chapters 2 and 4) II. How can one model the dynamic and endogenous adaptation of the airport’s landside and airside infrastructure to the characteristics of airline demand? (Chapter 2) III. How to consider operational delays in strategic ASA decision-making? (Chapter 3) IV. How to involve the pertinent stakeholders into the ASA decision-making process to select a commonly agreed schedule; and how can one reduce the inherent decision-complexity without compromising the quality and diversity of the schedules presented to the decision-makers? (Chapter 3) V. Given that the ASA process involves airlines (submitting requests for slots) and coordinators (assigning slots to requests based on a set of rules and priorities), how can one jointly consider the interactions between these two sides to improve ASA decision-making? (Chapter 4) With regards to research questions (I) and (II), the thesis proposes a Mixed Integer Programming (MIP) model that considers airlines’ timing flexibility (research question I) and constraints that enable the dynamic and endogenous allocation of the airport’s resources (research question II). The proposed modelling variant addresses several additional problem characteristics and policy rules, and considers multiple efficiency objectives, while integrating all constraints that may affect airport slot scheduling decisions, including the asynchronous use of the different airport resources (runway, aprons, passenger terminal) and the endogenous consideration of the capabilities of the airport’s infrastructure to adapt to the airline demand’s characteristics and the aircraft/flight type associated with each request. The proposed model is integrated into a two-stage solution approach that considers all primary and several secondary policy rules of ASA. New combinatorial results and valid tightening inequalities that facilitate the solution of the problem are proposed and implemented. An extension of the above MIP model that considers the trade-offs among schedule displacement, maximum displacement, and the number of displaced requests, is integrated into a multi-objective solution framework. The proposed framework holistically considers the preferences of all ASA stakeholder groups (research question IV) concerning multiple performance metrics and models the operational delays associated with each airport schedule (research question III). The delays of each schedule/solution are macroscopically estimated, and a subtractive clustering algorithm and a parameter tuning routine reduce the inherent decision complexity by pruning non-dominated solutions without compromising the representativeness of the alternatives offered to the decision-makers (research question IV). Following the determination of the representative set, the expected delay estimates of each schedule are further refined by considering the whole airfield’s operations, the landside, and the airside infrastructure. The representative schedules are ranked based on the preferences of all ASA stakeholder groups concerning each schedule’s displacement-related and operational-delay performance. Finally, in considering the interactions between airlines’ timing flexibility and utility, and the policy-based priorities assigned by the coordinator to each request (research question V), the thesis models the ASA problem as a two-sided matching game and provides guarantees on the stability of the proposed schedules. A Stable Airport Slot Allocation Model (SASAM) capitalises on the flexibility considerations introduced for addressing research question (I) through the exploitation of data submitted by the airlines during the ASA process and provides functions that proxy each request’s value considering both the airlines’ timing flexibility for each submitted request and the requests’ prioritisation by the coordinators when considering the policy rules defining the ASA process. The thesis argues on the compliance of the proposed functions with the primary regulatory requirements of the ASA process and demonstrates their applicability for different types of slot requests. SASAM guarantees stability through sets of inequalities that prune allocations blocking the formation of stable schedules. A multi-objective Deferred-Acceptance (DA) algorithm guaranteeing the stability of each generated schedule is developed. The algorithm can generate all stable non-dominated points by considering the trade-off between the spilled airline and passenger demand and maximum displacement. The work conducted in this thesis addresses several problem characteristics and sheds light on their implications for ASA decision-making, hence having the potential to improve ASA decision-making. Our findings suggest that the consideration of airlines’ timing flexibility (research question I) results in improved capacity utilisation and scheduling efficiency. The endogenous consideration of the ability of the airport’s infrastructure to adapt to the characteristics of airline demand (research question II) enables a more efficient representation of airport declared capacity that results in the scheduling of additional requests. The concurrent consideration of airlines’ timing flexibility and the endogenous adaptation of airport resources to airline demand achieves an improved alignment between the airport infrastructure and the characteristics of airline demand, ergo proposing schedules of improved efficiency. The modelling and evaluation of the peak operational delays associated with the different airport schedules (research question III) provides allows the study of the implications of strategic ASA decision-making for operations and quantifies the impact of the airport’s declared capacity on each schedule’s operational performance. In considering the preferences of the relevant ASA stakeholders (airlines, coordinators, airport, and air traffic authorities) concerning multiple operational and strategic ASA efficiency metrics (research question IV) the thesis assesses the impact of alternative preference considerations and indicates a commonly preferred schedule that balances the stakeholders’ preferences. The proposition of representative subsets of alternative schedules reduces decision-complexity without significantly compromising the quality of the alternatives offered to the decision-making process (research question IV). The modelling of the ASA as a two-sided matching game (research question V), results in stable schedules consisting of request-to-slot assignments that provide no incentive to airlines and coordinators to reject or alter the proposed timings. Furthermore, the proposition of stable schedules results in more intensive use of airport capacity, while simultaneously improving scheduling efficiency. The models and algorithms developed as part of this thesis are tested using airline requests and airport capacity data from coordinated airports. Computational results that are relevant to the context of the considered airport instances provide evidence on the potential improvements for the current ASA process and facilitate data-driven policy and decision-making. In particular, with regards to the alignment of airline demand with the capabilities of the airport’s infrastructure (questions I and II), computational results report improved slot allocation efficiency and airport capacity utilisation, which for the considered airport instance translate to improvements ranging between 5-24% for various schedule performance metrics. In reducing the difficulty associated with the assessment of multiple ASA solutions by the stakeholders (question IV), instance-specific results suggest reductions to the number of alternative schedules by 87%, while maintaining the quality of the solutions presented to the stakeholders above 70% (expressed in relation to the initially considered set of schedules). Meanwhile, computational results suggest that the concurrent consideration of ASA stakeholders’ preferences (research question IV) with regards to both operational (research question III) and strategic performance metrics leads to alternative airport slot scheduling solutions that inform on the trade-offs between the schedules’ operational and strategic performance and the stakeholders’ preferences. Concerning research question (V), the application of SASAM and the DA algorithm suggest improvements to the number of unaccommodated flights and passengers (13 and 40% improvements) at the expense of requests concerning fewer passengers and days of operations (increasing the number of rejected requests by 1.2% in relation to the total number of submitted requests). The research conducted in this thesis aids in the identification of limitations that should be addressed by future studies to further improve ASA decision-making. First, the thesis focuses on exact solution approaches that consider the landside and airside infrastructure of the airport and generate multiple schedules. The proposition of pre-processing techniques that identify the bottleneck of the airport’s capacity, i.e., landside and/or airside, can be used to reduce the size of the proposed formulations and improve the required computational times. Meanwhile, the development of multi-objective heuristic algorithms that consider several problem characteristics and generate multiple efficient schedules in reasonable computational times, could extend the capabilities of the models propositioned in this thesis and provide decision support for some of the world’s most congested airports. Furthermore, the thesis models and evaluates the operational implications of strategic airport slot scheduling decisions. The explicit consideration of operational delays as an objective in ASA optimisation models and algorithms is an issue that merits investigation since it may further improve the operational performance of the generated schedules. In accordance with current practice, the models proposed in this work have considered deterministic capacity parameters. Perhaps, future research could propose formulations that consider stochastic representations of airport declared capacity and improve strategic ASA decision-making through the anticipation of operational uncertainty and weather-induced capacity reductions. Finally, in modelling airlines’ utility for each submitted request and available time slot the thesis proposes time-dependent functions that utilise available data to approximate airlines’ scheduling preferences. Future studies wishing to improve the accuracy of the proposed functions could utilise commercial data sources that provide route-specific information; or in cases that such data is unavailable, employ data mining and machine learning methodologies to extract airlines’ time-dependent utility and preferences

    Political Islam and grassroots activism in Turkey : a study of the pro-Islamist Virtue Party's grassroots activists and their affects on the electoral outcomes

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    This thesis presents an analysis of the spectacular rise of political Islam in Turkey. It has two aims: first to understand the underlying causes of the rise of the Welfare Party which -later became the Virtue Party- throughout the 1990s, and second to analyse how grassroots activism influenced this process. The thesis reviews the previous literature on the Islamic fundamentalist movements, political parties, political party systems and concentrates on the local party organisations and their effects on the party's electoral performance. It questions the categorisation of Islamic fundamentalism as an appropriate label for this movement. An exploration of such movements is particularly important in light of the event of 11`x' September. After exploring existing theoretical and case studies into political Islam and party activism, I present my qualitative case study. I have used ethnographic methodology and done participatory observations among grassroots activists in Ankara's two sub-districts covering 105 neighbourhoods. I examined the Turkish party system and the reasons for its collapse. It was observed that as a result of party fragmentation, electoral volatility and organisational decline and decline in the party identification among the citizens the Turkish party system has declined. However, the WP/VP profited from this trend enormously and emerged as the main beneficiary of this process. Empirical data is analysed in four chapters, dealing with the different aspects of the Virtue Party's local organisations and grassroots activists. They deal with change and continuity in the party, the patterns of participation, the routes and motives for becoming a party activist, the profile of party activists and the local party organisations. I explore what they do and how they do it. The analysis reveals that the categorisation of Islamic fundamentalism is misplaced and the rise of political Islam in Turkey cannot be explained as religious revivalism or the rise of Islamic fundamentalism. It is a political force that drives its strength from the urban poor which has been harshly affected by the IMF directed neoliberal economy policies. In conclusion, it is shown that the WP/VP's electoral chances were significantly improved by its very efficient and effective party organisations and highly committed grassroots activists

    Chinese Benteng Women’s Participation in Local Development Affairs in Indonesia: Appropriate means for struggle and a pathway to claim citizen’ right?

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    It had been more than two decades passing by aftermath the devastating Asia’s Financial Crisis in 1997, subsequently followed by Suharto’s step down from his presidential throne which he occupied for more than three decades. The financial turmoil turned to a political disaster furthermore has led to massive looting that severely impacted Indonesians of Chinese descendant, including unresolved mystery of the most atrocious sexual violation against women and covert killings of students and democracy activists in this country. Since then, precisely aftermath May 1998, which publicly known as “Reformasi”1, Indonesia underwent political reform that eventually corresponded positively to its macroeconomic growth. Twenty years later, in 2018, Indonesia captured worldwide attention because it has successfully hosted two internationally renowned events, namely the Asian Games 2018 – the most prestigious sport events in Asia – conducted in Jakarta and Palembang; and the IMF/World Bank Annual Meeting 2018 in Bali. Particularly in the IMF/World Bank Annual Meeting, this event has significantly elevated Indonesia’s credibility and international prestige in the global economic powerplay as one of the nations with promising growth and openness. However, the narrative about poverty and inequality, including increasing racial tension, religious conservatism, and sexual violation against women are superseded by friendly climate for foreign investment and eventually excessive glorification of the nation’s economic growth. By portraying the image of promising new economic power, as rhetorically promised by President Joko Widodo during his presidential terms, Indonesia has swept the growing inequality in this highly stratified society that historically compounded with religious and racial tension under the carpet of digital economy.Arte y Humanidade

    Graphical scaffolding for the learning of data wrangling APIs

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    In order for students across the sciences to avail themselves of modern data streams, they must first know how to wrangle data: how to reshape ill-organised, tabular data into another format, and how to do this programmatically, in languages such as Python and R. Despite the cross-departmental demand and the ubiquity of data wrangling in analytical workflows, the research on how to optimise the instruction of it has been minimal. Although data wrangling as a programming domain presents distinctive challenges - characterised by on-the-fly syntax lookup and code example integration - it also presents opportunities. One such opportunity is how tabular data structures are easily visualised. To leverage the inherent visualisability of data wrangling, this dissertation evaluates three types of graphics that could be employed as scaffolding for novices: subgoal graphics, thumbnail graphics, and parameter graphics. Using a specially built e-learning platform, this dissertation documents a multi-institutional, randomised, and controlled experiment that investigates the pedagogical effects of these. Our results indicate that the graphics are well-received, that subgoal graphics boost the completion rate, and that thumbnail graphics improve navigability within a command menu. We also obtained several non-significant results, and indications that parameter graphics are counter-productive. We will discuss these findings in the context of general scaffolding dilemmas, and how they fit into a wider research programme on data wrangling instruction

    SUBSUMPTION AS DEVELOPMENT: A WORLD-ECOLOGICAL CRITIQUE OF THE SOUTH KOREAN "MIRACLE"

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    This work offers a critical reinterpretation of South Korean "economic development" from the perspectives of Marxian form critique and Jason Moore's world-ecology. Against the "production in general" view of economic life that dominates the extant debates, it analyzes the rise, spread, and deepening of capitalism's historically specific social forms in twentieth-century (South) Korea: commodity, wage-labor, value, and capital. Eschewing the binary language of development and underdevelopment, we adopt Marx's non-stagist distinctions regarding the relative degree of labor's (and society's) subsumption under capital: hybrid, formal, and real. Examining the (South) Korean experience across three dialectically interrelated scales – regional, global, and "national" – we outline the historical-geographical contingency surrounding South Koreas emergence by c.1980 as a regime of (industrialized) real subsumption, one of the only non-Western societies ever to do so. Crucial to this was the generalization of commodification and proletarianization that betokened deep structural changes in (South) Korea's class structure, but also a host of often-mentioned issues such as land reform, foreign aid, the developmental state, and a "heaven sent" position within the US-led Cold War order. Despite agreeing on the importance of these latter factors, however, the conclusions we draw from them differ radically from those of the extant analyses. For although regimes of real subsumption are the most materially, socially, and technologically dynamic, they are also the most socio-ecologically unsustainable and alienating due to the dualistic tensions inherent to capital's "fully developed" forms, in particular the temporal grounding of value. US protestations about the generalizability of these relations aside, moreover, these regimes have always been in the extreme minority and, crucially, have depended on less developed societies for their success. Historically, this has been achieved through widening the net of capitalist value relations; however, four decades of neoliberalization has all but eliminated any further large-scale "frontier strategies" of this sort. Due to its relatively dense population vis-a-vis its geographical size, contemporary South Korea faces stark challenges that render it anything but a model of "sustainable development," but rather signal the growing anachronism of value as the basis for regulating the future of nature-society relations in the "developed world" and beyond

    The Weight of (Im)possibility: Exploring body weight and shape with trans and gender non-conforming people

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    In recent decades, theorising around trans embodiment has sought to move away from narratives of the ‘wrong’ and pathological trans body. Emergent analytical and theoretical frameworks have instead highlighted the ways in which particular bodies become designated as trans, and what this means for the kinds of possibilities for embodiment that are opened up and closed down at the levels of both individual relationships and contexts, and structural and systemic constraints. The significance of weight and shape in relation to these embodied possibilities has not yet been fully explored within sociology. Drawing upon qualitative interviews with 21 participants who identified as trans and/or gender non-conforming, this thesis examines the intersection of body weight and shape with trans and gender non-conforming positionality in order to address gaps in existing knowledge around the meaning and significance of weight and shape for trans and gender non-conforming people and communities in the UK. Phenomenological epistemology informs this thesis and the thematic analysis (TA) undertaken, centring participants’ experiential claims. In discussion of the findings presented, I argue that weight and shape are enmeshed with the constraints and possibilities of gendered positionality in ways that indicate the need for wide-reaching and profound transformation in order for relationships with the body based on connection, acceptance, and pleasure to be more consistently and widely possible for trans and gender non-conforming people. Relationships with weight and shape, as I illustrate in this thesis, were not simply shaped by the conditions and possibilities for embodiment in which they were situated, but represented sites of agentic engagement within and through conditions of embodied possibility

    Epistemologies of possibility: social movements, knowledge production and political transformation

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    Urgent global problems - whether military conflicts, economic insecurities, immigration controls or mass incarceration-not only call for new modes of political action but also demand new forms of knowledge. For if knowledge frameworks both shape the horizons of social intelligibility and chart t he realms of political possibility, then epistemological interventions constitute a crucial part of social change. Social movements play a key role in this work by engaging in dissident knowledge practices that open up space for political transformation. But what are the processes and conditions through which social movements generate new ways of knowing?'What is politically at stake in the various knowledge strategies that activists use to generate social change? Despite a growing literature on the role of epistemological dimensions of protest, social movement studies tend to neglect specific questions of epistemological change. Often treating knowledge as a resource or object rather than a power relation and a social practice, social movement scholars tend to focus on content rather than production, frames rather than practices, taxonomies rather than processes. Missing is a more dynamic account of the conditions, means and power relations through which transformative knowledge practices come to be constituted and deployed. Seeking to better understand processes of epistemological transformation, this thesis explores the relationship between social movements, knowledge production and political change. Starting from an assumption that knowledge not only represents the world, but also works to constitute it, this thesis examines the role of social movement knowledge practices in shaping the conditions of political possibility. Drawing from the context of grassroots queer, transgender and feminist organizing around issues of prisons and border controls in North America, the project explores how activists generate new forms of knowledge and forge new spaces of political possibility. Working through a series of concepts-transformation, resistance, experience, co-optation, solidarity and analogy - this thesis explores different ways of understanding processes of epistemological change with in social movement contexts. It considers processes that facilitate or enable epistemological change and those that limit or prohibit such change. Bringing together a range of theoretical perspectives, including feminist, queer, critical race and post-structuralist analyses, and drawing on interviews with grassroots activists, the thesis explores what is politically at stake in the different ways we conceptualise, imagine and engage in processes of epistemological change

    Towards thinking classrooms: foundation stage possibilities in Northern Ireland

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    The integration of thinking skills programmes into primary and secondary school curricula has gained increasing prominence in global educational policy over the past two decades. This research investigated the factors that influence how a particular approach to the development of thinking skills adopted in the Northern Ireland (NI) context is interpreted and implemented by teachers in early years classrooms. The Thinking Skills and Personal Capabilities Framework (TSPC) was introduced as a statutory component of the revised NI curriculum in 2007 and this study explores its enactment through the perceptions of key groups that interface with the policy from a range of different contexts: teachers and Head Teachers, Curriculum Advisory and Support staff, university academics and Initial Teacher Education staff. The study adopted an interpretive approach, utilising interviews with members of these key groups to explore their perceptions of the factors that influence the effective and consistent implementation of the TSPC and to explain possible reasons why it has embedded effectively in some NI primary schools and not in others. In addition to interviews, policy analysis of key texts that shape teachers’ approaches to the TSPC was undertaken using a framework based on Fairclough’s three-dimensional approach to critical discourse analysis. The purpose of this analysis was to explore the connection between the discourses used in these texts, and the extent to which the ideological cues that underpin them exert an influence on how teachers interpret and implement thinking skills in their practice. The study also explored how human capital theory, and an ecological approach to the enactment of the TSPC based on Bronfenbrenner’s Ecological Systems Model (1979), provide different frameworks for understanding how the TSPC is interpreted and implemented in practice, with particular reference to Northern Ireland. The findings suggest that there are a number of significant factors that both enable and constrain the effective implementation of the TSPC across schools. The region’s political, social and historical context was viewed by participants as playing a key role in how policy reforms are interpreted and implemented. School leaders can play a central role in mediating the impact of these reforms to ensure that they are implemented in ways that take account of diverse and specific school contexts. From the perspective of participants, Head Teachers and school leaders also play a pivotal role in nurturing teachers’ professional learning, skill, and motivation in the teaching of thinking skills. Consistent opportunities for professional development, including collaborative working, and sharing of practice, both in and beyond the school, was viewed as the primary means of ensuring the development of a shared vision and language about thinking skills, and participants agreed that this is central to its consistent implementation across all schools. Analysis of the participants’ understandings of the purpose of teaching thinking skills, and the aims of education more broadly, highlighted a tension between approaches to education that focus on children’s holistic development, and policy discourses, especially those related to Human Capital Theory that view education as a mechanism for achieving economic goals. The influence of these discourses across a range of public policy areas, as well as the disconnect between what participants and policy-makers viewed as the purpose of thinking, was highlighted in the analysis. For participants, the integration of thinking skills into the curriculum was about developing autonomy, criticality, and independence in children’s thinking, whereas policy-makers viewed it from a human capital perspective and strongly linked it to discourses of ‘lifelong learning’, ‘employability’ and ‘skill’. From the perspective of participants, the findings indicate that for policy makers in Northern Ireland to better understand how to embed the TSPC as a core component of the curriculum in all schools a number of cross-system actions need to be undertaken. These include a baseline review of the impact of the TSPC in the ten years since its inception as part of the comprehensive review of education announced by the Minister for Education in January 2021. The data suggests that this review should ensure that teachers and school leaders are central to its design and approach and that it is fully inclusive of all schools in Northern Ireland that sit within its scope. A return to more localised support and advice services with a coordinated approach to the development of the TSPC in all schools was also viewed by participants as essential to its development and embedding in all schools. A more coordinated, multi-disciplinary approach to implementation would, it was argued, ensure that ongoing professional learning in thinking skills was accessible, including the establishment of more strategic, collaborative partnerships with higher education, ITE and Inspection Services. This changed focus, I conclude, requires a move away from human capital and sector specific approaches to the consistent development of thinking skills programmes in all Northern Ireland schools. Recommendations also centre on future policy reforms that are inclusive and that give teachers their professional place as the primary implementers for the development of thinking skills programmes in schools

    Using Social Media to build a Counter-Power Movement: Multiple Sclerosis and CCSVI, a Case Study

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    The research is focused on a patient-based social media movement which advocated for clinical research into a discovery rejected by key elements of the medical establishment. This thesis aims to examine how social media interactions empowered patients, what motivated them to become a movement, and the elements which propelled the movement to create alternative patient associations. This research comprises 62 individual, in-person, audio-recorded interviews with movement activists, and the researcher’s autoethnography as the founder and administrator of the movement’s Facebook Page. These methods are triangulated with academic publications, newspaper and television news, as well as other publicly-sourced materials relating to the case study. The research finds that while the movement’s activities, from planning through protest, occurred solely on the streets of social media, activists experienced the same passion and urgency as the academic literature has described for on-the-street activists. That is, social media paralleled the “real streets” as a forum for the movement’s core activities. The research further finds that the traditional patient associations’ initial strategy of stonewalling the contested discovery was undercut by the momentum of the social media movement’s activities. They subsequently sought to quell the movement by lambasting social media as well as deploying a co-optation strategy, as described by the activists. To conclude, social media function as streets and city halls where decisions taken can be implemented in the real world and permit geographically distributed as well as differently abled people to gather in significant numbers. The space where human interactions can foster social life and deepen personal emotional relations could be named the space of humanity. This is the space where timeless time and the realities of the counter power experience can happen, independent of whether that space is surrounded by real or digital bricks

    Understanding diversity in farmers' routinized crop protection practices

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    Present-day agricultural crop protection relies heavily on synthetic pesticides, which are known to adversely affect the environment and human health. As remediation, European agricultural policies strive for a transition to low-pesticide agriculture. However, these policy efforts have so far shown limited success. We argue that neglecting the diversity of the according routinized practices belongs to the reasons for that limited success. We specifically investigate how farmers' current local crop protection practices differ. Methodologically, the article is based on semi-structured interviews with farmers and crop protection experts as well as on qualitative data from a survey among Swiss farmers. Using practice theory to analyze our data, we identify the meanings, materials and competences in farmers' practice narratives. From our analysis, five types of routinized crop protection practice emerge, revealing a picture of diversity, also in their responses to current incentive-based agri-environmental policy instruments. This diversity cannot be accommodated by a one-size-fits-all policy approach but rather requires a balanced mix, for example of command-and-control instruments, financial incentives and extension services
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