9,388 research outputs found

    Manipulating Federated Recommender Systems: Poisoning with Synthetic Users and Its Countermeasures

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    Federated Recommender Systems (FedRecs) are considered privacy-preserving techniques to collaboratively learn a recommendation model without sharing user data. Since all participants can directly influence the systems by uploading gradients, FedRecs are vulnerable to poisoning attacks of malicious clients. However, most existing poisoning attacks on FedRecs are either based on some prior knowledge or with less effectiveness. To reveal the real vulnerability of FedRecs, in this paper, we present a new poisoning attack method to manipulate target items' ranks and exposure rates effectively in the top-KK recommendation without relying on any prior knowledge. Specifically, our attack manipulates target items' exposure rate by a group of synthetic malicious users who upload poisoned gradients considering target items' alternative products. We conduct extensive experiments with two widely used FedRecs (Fed-NCF and Fed-LightGCN) on two real-world recommendation datasets. The experimental results show that our attack can significantly improve the exposure rate of unpopular target items with extremely fewer malicious users and fewer global epochs than state-of-the-art attacks. In addition to disclosing the security hole, we design a novel countermeasure for poisoning attacks on FedRecs. Specifically, we propose a hierarchical gradient clipping with sparsified updating to defend against existing poisoning attacks. The empirical results demonstrate that the proposed defending mechanism improves the robustness of FedRecs.Comment: This paper has been accepted by SIGIR202

    Constructing a Theological Framework That Revitalizes the Missional Nature of Churches of Christ in South Australia

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    This thesis addresses the need for a theological framework that revitalizes the missional nature of Churches of Christ in South Australia. The problem identified within this ministry context was a lack of clear theological principles that informed a common understanding of identity for missional engagement. The purpose of the project was to create a study guide that informs common theological commitments and grounds congregations for missional vitality. A research and development team made up of seven Church of Christ ministers from different backgrounds was assembled to design a curriculum that addressed the problem. Through eight two-hour sessions over four months in the first half of 2022, the team discussed a theological framework that could revitalize mission. This was informed by a Trinitarian theological rationale introduced as perichoresis. The conceptual framework for discussions included (1) the historical and theological foundations of Churches of Christ, (2) a Trinitarian doctrine of God presented as perichoresis, (3) contemporary congregational practices, and (4) a theological proposal for re-imagining mission. The team developed a study guide that promotes a dynamic theological framework for practicing theology and revitalizing the missional nature of the church. The artifact, Movement & Identity: Participating in the Life of God’s Mission, was evaluated by the team and members of Church of Christ congregations in South Australia. The curriculum is designed to assist participants with practical theological interpretation through (1) discovering new ideas about God in the context of Churches of Christ traditions, (2) engaging with contextual theology in community, (3) participating in God’s mission, and (4) reflecting on how God’s agency transforms the church. The development of the study guide will stimulate a practical theological framework that promotes dynamic theological dialogue and missional vitality for Churches of Christ in South Australia

    A Decision Support System for Economic Viability and Environmental Impact Assessment of Vertical Farms

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    Vertical farming (VF) is the practice of growing crops or animals using the vertical dimension via multi-tier racks or vertically inclined surfaces. In this thesis, I focus on the emerging industry of plant-specific VF. Vertical plant farming (VPF) is a promising and relatively novel practice that can be conducted in buildings with environmental control and artificial lighting. However, the nascent sector has experienced challenges in economic viability, standardisation, and environmental sustainability. Practitioners and academics call for a comprehensive financial analysis of VPF, but efforts are stifled by a lack of valid and available data. A review of economic estimation and horticultural software identifies a need for a decision support system (DSS) that facilitates risk-empowered business planning for vertical farmers. This thesis proposes an open-source DSS framework to evaluate business sustainability through financial risk and environmental impact assessments. Data from the literature, alongside lessons learned from industry practitioners, would be centralised in the proposed DSS using imprecise data techniques. These techniques have been applied in engineering but are seldom used in financial forecasting. This could benefit complex sectors which only have scarce data to predict business viability. To begin the execution of the DSS framework, VPF practitioners were interviewed using a mixed-methods approach. Learnings from over 19 shuttered and operational VPF projects provide insights into the barriers inhibiting scalability and identifying risks to form a risk taxonomy. Labour was the most commonly reported top challenge. Therefore, research was conducted to explore lean principles to improve productivity. A probabilistic model representing a spectrum of variables and their associated uncertainty was built according to the DSS framework to evaluate the financial risk for VF projects. This enabled flexible computation without precise production or financial data to improve economic estimation accuracy. The model assessed two VPF cases (one in the UK and another in Japan), demonstrating the first risk and uncertainty quantification of VPF business models in the literature. The results highlighted measures to improve economic viability and the viability of the UK and Japan case. The environmental impact assessment model was developed, allowing VPF operators to evaluate their carbon footprint compared to traditional agriculture using life-cycle assessment. I explore strategies for net-zero carbon production through sensitivity analysis. Renewable energies, especially solar, geothermal, and tidal power, show promise for reducing the carbon emissions of indoor VPF. Results show that renewably-powered VPF can reduce carbon emissions compared to field-based agriculture when considering the land-use change. The drivers for DSS adoption have been researched, showing a pathway of compliance and design thinking to overcome the ‘problem of implementation’ and enable commercialisation. Further work is suggested to standardise VF equipment, collect benchmarking data, and characterise risks. This work will reduce risk and uncertainty and accelerate the sector’s emergence

    GENDERED EMBODIMENT, STABILITY AND CHANGE: WOMEN’S WEIGHTLIFTING AS A TOOL FOR RECOVERY FROM EATING DISORDERS

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    This thesis explores the everyday embodied experiences of women who use amateur weightlifting as a vehicle for recovery from eating disorders. Within online spaces and on social media, women frequently share their experiences of using weightlifting to overcome issues relating to disordered eating, body image, and mental health. In particular, women with a history of eating disorders credit weightlifting to be integral to their recovery journey. However, there is a dearth of research on women’s experiences with exercise during eating disorder recovery and no research that identifies weightlifting as beneficial to this process. To the contrary, discursive links are drawn between the practices of self-surveillance exercised by both eating disorder sufferers and weightlifters alike. In this regard, engagement with weightlifting during eating disorder recovery may signal the transferal of pathology from one set of behaviours to another. That is, from disordered eating to rigid and self-regulatory exercise routines. This thesis examines how women subjectively navigate and make sense of this pathologisation. The data for this research comes from longitudinal semi-structured interviews and photo elicitation with 19 women, living in the United Kingdom, who engaged in weightlifting during their eating disorder recovery. In addition, to build up a holistic picture and to explore how this phenomenon also ‘takes place’ online, I conducted a netnography of the overlapping subcultures of female weightlifting and eating disorder recovery on Instagram. Women’s standpoint theory and interpretative phenomenological analysis are combined to form the underpinning theoretical and analytical tools used to engage with these three rich data sets. Moreover, throughout I draw on an eclectic range of disciplinary perspectives, in order to bring together multiple fields of research and develop novel theoretical frameworks. In the findings, I argue that women’s experiences using weightlifting as a tool for recovery from eating disorders manifests in an embodied sense of multiplicity. In this sense, understandings of the body that are often viewed as ontologically distinct (muscularity/thinness/fatness) hang-together at once in the lived experience of a single individual. I argue that women, particularly those who have previously struggled with an eating disorder, are too readily positioned as vulnerable to media and representation. To theoretically combat these ideas regarding women’s assumed passivity, I develop the concept of ‘digital pruning’ to account for women’s agency in relation to new media. I contend that weightlifting offers women in recovery from eating disorders a new framework for approaching eating and exercise. Specifically, weightlifting’s norms and values legitimate occupying a larger body, which gives women in recovery permission to eat and gain-weight in a way that is both culturally sanctioned and health-promoting. Finally, I explore identity transformation as a specific tenet of recovery from eating disorders. I argue that, on social media, recovery identities are characterised by personal empowerment, resilience, and independence. While offline, quieter and less culturally glorified aspects of recovery (such as relationships of care) are central to women’s accounts of developing a new sense of self as they transition away from an eating disorder identity. In summary, this thesis is an examination of the ways in which women strategically navigate pathology in relation to their bodies, social media, food/exercise practices, and identity. I argue that women develop a set of ‘DIY’ recovery practices that allow them to consciously channel and draw on their negative experiences with eating disorders, to develop new ways of living that serve their overall wellbeing. Weightlifting is integral to this process, as it provides women transitioning out of this difficult phase in their lives with new ways of relating to their bodies and of being in the world. I situate this phenomenon within a neoliberal socio-political climate in which individuals are required to take personal responsibility for their mental health and wellbeing, despite living within conditions which are not conducive to recovery

    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

    Ten-tier and multi-scale supplychain network analysis of medical equipment: Random failure and intelligent attack analysis

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    Motivated by the COVID-19 pandemic, this paper explores the supply chain viability of medical equipment, an industry whose supply chain was put under a crucial test during the pandemic. This paper includes an empirical network-level analysis of supplier reachability under Random Failure Experiment (RFE) and Intelligent Attack Experiment (IAE). Specifically, this study investigates the effect of RFA and IAE across multiple tiers and scales. The global supply chain data was mined and analyzed from about 45,000 firms with about 115,000 intertwined relationships spanning across 10 tiers of the backward supply chain of medical equipment. This complex supply chain network was analyzed at four scales, namely: firm, country-industry, industry, and country. A notable contribution of this study is the application of a supply chain tier optimization tool to identify the lowest tier of the supply chain that can provide adequate resolution for the study of the supply chain pattern. We also developed data-driven-tools to identify the thresholds for breakdown and fragmentation of the medical equipment supply chain when faced with random failures or different intelligent attack scenarios. The novel network analysis tools utilized in the study can be applied to the study of supply chain reachability and viability in other industries.Comment: 47 page
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