Zero forcing in graphs is a coloring process where a vertex colored blue can force its unique uncolored neighbor to be colored blue. A zero forcing set is a set of initially blue vertices capable of eventually coloring all vertices of the graph. In this paper, we focus on the numbers z(G;i), which is the number of zero forcing sets of size i of the graph G. These numbers were initially studied by Boyer et al. [5] where they conjectured that for any graph G on n vertices, z(G;i)≤z(Pn;i) for all i≥1 where Pn is the path graph on n vertices. The main aim of this paper is to show that several classes of graphs, including outerplanar graphs and threshold graphs, satisfy this conjecture. We do this by studying various graph operations and examining how they affect the number of zero forcing sets.

This paper presents a novel method for communicating environmental information in an engaging and memorable manner. Instead of traditional visual or written communication, our approach involves physical representation of data, using weight as the key element. Using food as a case study, we demonstrate the carbon footprint of food items through life-sized models that accurately reflect their actual weight. In an educational setting, students collectively discuss and estimate emissions for sample foods, followed by hands-on interaction. Each model's weight mirrors its carbon footprint, from 50 grams for half a kilo of potatoes to 13 kilograms for half a kilo of beef. Early tests show a significant "Wow!"factor, particularly for high-emission foods. This tangible experience leaves a lasting impression, potentially influencing future choices. Our approach can extend to other areas like energy. The paper concludes with design recommendations for future work.

Effectively communicating vital sustainability topics, such as personal CO2e emissions stemming from daily activities, is challenging since there is a general lack of”carbon literacy.” Despite efforts, like employing data visualizations, conveying this information in engaging and memorable ways remains difficult, often resulting in rapid forgetfulness. Our demonstration presents a pedagogical approach aimed at addressing this challenge. Through the integration of surprise elements, data physicalization, and embodied learning, we have developed two interactive mediated non-digital learning experiences focusing on CO2e emissions from food and from consumption. At the core of our pedagogical approach are physical artifacts representing CO2e emissions where the weight of the artifacts directly corresponds to the CO2e emissions they represent. By employing a structured interactive pedagogical setup involving peer discussion, hands-on manipulation of the artifacts, and subsequent explanations, we have created an engaging experience that encourages long-term learning.

This paper explores the potential of (re)framing the smart fridge to facilitate asynchronous food-sharing practices within activist communities. Empirical data were gathered through a co-design study with FoodSharing Stockholm community members between March 2022 and December 2023. This investigation delved into the opportunities and challenges of incorporating a smart fridge into their activist efforts towards local food waste reduction. Our findings highlight managing fairness, cleaning and maintenance, and community building as crucial considerations in designing for such activist, community settings. We introduce design concepts for four adaptable and configurable smart devices to modify existing community fridges and address the above considerations. This paper contributes to HCI by illustrating the intricate relations between ‘making an impact’, ‘building community’, and the design of ‘engagement through technology’ within food-sharing communities. It underscores the significance of designing smart fridges for activist food-sharing communities with a purpose that goes beyond mere functionality, emphasising the need to consider the broader social implications of digital interventions in facilitating local food waste reduction and community building.

Solar panels add a time component to the energy provision of households. Households equipped with solar systems will experience days and hours of abundance, during which they generate a surplus of electricity, as well as times when they need to purchase power from the grid. This creates opportunities for households to utilize more 'free' energy when it is available by shifting activities in time, but while this may be possible for some activities, other practices may be seen as non-negotiable. We report on the deployment of an in-home display installed in nine households with solar panels in the south of Sweden. We conducted two sets of interviews: one before installing the display and another four months post-installation. Our results confirm that the negotiability of a certain energy practice may vary between different households. Washing, dishwashing and charging EV were seen as negotiable by everyone, whereas cooking and hot water use were seen as non-negotiable by most, but not all, the households. The in-home display worked as expected as a trigger and provided feedback for helping shifting the negotiable practices, but not for non-negotiable and it was appreciated by the users for its simplicity.

The climate impact of our food consumption is a key issue to sustainability. Yet understanding the food system and the impact it has can be difficult given its abstract nature. In this paper, we report on a Research through Design project aimed at designing and evaluating a data physicalization for supporting collective sense-making of the climate impact of food. Throughout the design process, we have explored the materiality of CO2 emissions and ways to design with less resource use. The resulting data physicalization, Carbon Scales, was evaluated in a three-week field study with 27 participants. Our findings show that collective sense-making can be enabled through interactive data physicalizations and that this can lead to carbon literacy. We expand on a) sustainability through design by arguing for the value of artifacts that let people stay in the interaction as this can support collective sense-making and b) sustainability in design by showcasing the value of designing with an interaction-first and materials-second mindset.

Power shortages and fluctuations in electricity supply are expected to become more frequent in the future, as renewable energy increases in the electricity mix. This poses a problem in that electricity might not always be available at the time of demand for industries as well as for households. Demand flexibility in households has been brought forward as part of a solution to this problem. How to engage households in this, however, is still unclear. Actors have tried to liken demand flexibility with waste sorting and other altruistic activities with connotations of contributing to the benefit of society, rather than being an activity springing from economic motives. In this article, we use design fiction to critically explore what this analogy would mean in the context of household electricity consumption. We describe fictive user scenarios for cooking, charging the electric car, laundry & dishes and heating to draw the demand flexibility analogies to the forefront. By exemplifying and concretizing these scenarios, it becomes evident that using waste sorting as an analogy for demand flexibility is not realistic. We discuss the implications of the scenarios in relation to the current visions that inform the development of the smart grid, and the emerging services and service providers. We conclude that there is a need to challenge the current images of flexible households in the smart grid in order to design systems that support thriving within limits.

Animistic and anthropomorphic principles have long been investigated along with affective computing in both HCI and HRI research, to reduce user frustration and create more emotive yet relatable devices, robots, products and artefacts. Yet such artefacts and research have mainly been from user-centric perspectives and the animistic characteristics localised to single objects. In this exploratory paper, we take these principles in a new direction by attempting to invoke animistic characteristics of a room or a space itself. Designing primarily for space itself rather than the user or a single product, allows us to create new interactions and narratives that can induce animism and empathy for the space, in users. This leads to the creation of a prototype space, which we use to investigate how users approach, interact and behave in such a space, yielding several insights and user behaviour, all of which can be used for further studies, capable of generating new interaction perspectives and providing insights into user behaviour. We conclude by discussing the potentiality of such spaces in developing new strategies for behaviour change and HCI.

While IoT and smart products have exploded onto the market in the past few years, these are typically designed from a data-driven, resource management approaches and as automation enablers. We propose a new approach to IoT ecosystems by using animistic narratives that visualise homes and cities as living entities, with IoT products as a means for them to both interact with inhabitants and to express themselves. Using design fiction, we explore the potentialities for this approach, through fictional scenarios involving a private local space such as a home.