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Life Cycle Assessment of Icelandic Volcanic Pozzolans as Low-Carbon Supplementary Cementitious Materials
(Springer Science and Business Media Deutschland GmbH, 2026) Hamdallah, Mohammed; Costa, Diego; Heinonen, Jukka; Finger, David Christian; Bragança, Luís; Mateus, Ricardo; Tsikaloudaki, Katerina; Giarma, Christina; Kontoleon, Karolos; Askar, Rand; Salles, Adriana; Cervantes, Camila; Department of Engineering
The cement industry is a major contributor to global greenhouse gas emissions, predominantly due to clinker production. Supplementary Cementitious Materials (SCMs) represent an effective mitigation strategy, yet conventional SCMs such as Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBFS) are becoming increasingly scarce. Volcanic pozzolans offer a promising natural alternative, and Iceland possesses extensive deposits that have not yet been evaluated from an environmental perspective. This study presents the first cradle-to-gate Life Cycle Assessment (LCA) of Icelandic Volcanic Pozzolan (VPI) production, drawing on primary data from three extraction sites and a planned processing facility in Þorlákshöfn—Lambafell, Litla Sandfell, and Landeyjahöfn—and secondary data from GaBi and Ecoinvent. A declared unit of one tonne of VPI is assessed across all ReCiPe 2016 midpoint impact categories. Results show that VPI’s climate change impact of 25.5 kg CO2-eq/t falls between FA (3–10 kg CO2-eq/t) and GGBFS (50–80 kg CO2-eq/t), confirming its competitiveness with established SCMs while offering the strategic advantage of abundant local supply. Marine dredging operations emerge as the dominant environmental hotspot, accounting for approximately 48.1% of total CO2-equivalent emissions. The findings confirm VPI as a robustly low-carbon SCM and support its large-scale adoption in sustainable cement production.
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Clock Distribution with Gradient TRIX
(Association for Computing Machinery, 2025-06-13) Srinivas, Shreyas; Lenzen, Christoph; Department of Computer Science
Gradient clock synchronization (GCS) algorithms minimize the worst-case clock offset between the nodes in a distributed network of diameter D and size n. They achieve optimal offsets of ⊙(log D) locally, i.e., between adjacent nodes [14] and ⊙(D) globally [2]. A key open problem in this area is to achieve fault tolerance at minimal edge replication overhead.In this work, we achieve this goal under the assumption of an average-case distribution of faults, i.e., nodes fail with independent probability p ϵ o(n-1/2). In more detail, we present a self-stabilizing GCS algorithm for a grid-like directed graph with in- and out-degrees of 3. Note that even for tolerating a single fault, this degree is necessary, and if p was larger, it would not hold with probability 1 - o (1) that each node has at most one faulty in-neighbor. Our algorithm achieves asymptotically optimal local skew of ⊙(log D) with probability 1 - o(1); this holds under general worst-case assumptions on link delay and clock speed variations, provided they change slowly relative to the speed of the system.On the one hand, our results are of practical interest. As we discuss, the fault model is suitable for synchronously clocked hardware. Since our algorithm can simultaneously sustain a constant number of arbitrary changes due to faults in each clock cycle, it achieves sufficient robustness to dramatically increase the size of synchronously clocked systems.On the other hand, our results are of a theoretical interest. We show that for a worst-case distribution of f faulty nodes within our fault model's locality constraints, our algorithm achieves local skew O(5f log D). With probabilistically distributed faults, this becomes O(log D). Moreover, our work opens up avenues for further investigation of fault-tolerant synchronization, in particular trade-offs between fault distribution and edge density.
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The Case of the Curious Robot : On the Social Viability of Curious Behavior in Non-Human Agents
(Association for Computing Machinery, Inc, 2024-12-26) Weatherwax, Kevin; Dooley, Doug; Carstensdottir, Elin; Takayama, Leila; Department of Computer Science
Curiosity is increasingly being looked at to develop interactive nonhuman agents capable of lifelong learning, particularly in the space of Ai driven agents. However, the way a non-human agent’s mental state is described could prime expectations in human counterparts as well as alter perceptions of an agent’s behavior. We conducted an online experiment examining people’s perceptions of four levels of curious behavior portrayed by a robot agent and whether this behavior matched people’s expectations when primed to anticipate a “curious” vs. “learning” vs. “autonomous” robot agent. As curiosity increased, the ratings of the robot agent’s thinking ability also increased. This was juxtaposed by a decrease in the robot’s ratings as an effective worker and social agent. Further, we captured a unique trajectory of expectation matching showing that agents’ internal mental states should be matched with analogous external behaviors. Our findings have implications for the design and development of non-human agents that engage in learning modeled on forms of human cognition.
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GRandLine : Adaptively Secure DKG and Randomness Beacon with (Log-)Quadratic Communication Complexity
(Association for Computing Machinery, Inc, 2024-12-09) Bacho, Renas; Lenzen, Christoph; Loss, Julian; Ochsenreither, Simon; Papachristoudis, Dimitrios; Department of Computer Science
A randomness beacon is a source of continuous and publicly verifiable randomness which is of crucial importance for many applications. Existing works on randomness beacons suffer from at least one of the following drawbacks: (i) security only against static (i.e., non-adaptive) adversaries, (ii) each epoch takes many rounds of communication, or (iii) computationally expensive tools such as proof-of-work (PoW) or verifiable delay functions (VDF). In this work, we introduce GRandLine, the first adaptively secure randomness beacon protocol that overcomes all these limitations while preserving simplicity and optimal resilience in the synchronous network setting. We achieve our result in two steps. First, we design a novel distributed key generation (DKG) protocol GRand that runs in O(?n2 logn) bits of communication but, unlike most conventional DKG protocols, outputs both secret and public keys as group elements. Here, ? denotes the security parameter. Second, following termination of GRand, parties can use their keys to derive a sequence of randomness beacon values, where each random value costs only a single asynchronous round and O(?n2) bits of communication. We implement GRandLine and evaluate it using a network of up to 64 parties running in geographically distributed AWS instances. Our evaluation shows that GRandLine can produce about 2 beacon outputs per second in a network of 64 parties. We compare our protocol to the state-of-the-art randomness beacon protocols OptRand (NDSS ‘23), BRandPiper (CCS ‘21), and Drand, in the same setting and observe that it vastly outperforms them.
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Together in the Mikrokosmos : Exploring Disabled Embodied Experiences in Designed Sociotechnical Worlds
(2024-11-08) Ringland, Kathryn E.; Carstensdottir, Elin; Tung, Matthew; Seetharaman, Bhavani; Eagle, Tessa; Baltaxe-Admony, Leya Breanna; Weatherwax, Kevin; Department of Computer Science
For geographically dispersed communities, including professional, academic, hobbyist, and fandom communities, in-person events and meetups play a crucial role in the function and health of the whole community. Building off prior literature, we take a nuanced look at large scale community events that blend online and offline interactions across digital and physical embodied experiences in order to build understanding of how this knowledge can be leveraged to build more accessible hybrid modalities for community events. Building on this foundation, this paper presents a comprehensive study using ethnographic methods to examine large scale community events, specifically stadium music concerts of varying modalities (e.g., in-person, live-streamed). Using a disability lens, we explore how such community events are experienced and technologically mediated, as well as how the community and individuals design and construct their own sociotechnical worlds across multiple modalities and embodied experiences. By centering the disabled embodied experience, we examine how community members navigate the concert environment, time, and the social experience of concert attendance. Based on our findings, we highlight the nuanced complexities of inclusive community-centered large scale, multi-modal events.

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