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关键词： indoor radon   ionization chamber   mechanical ventilation   trace detector  

摘要： A study of the radon activity concentration was carried out at the School of Computer Science of 'Universidade da Coruna' (UDC, Spain). For this purpose, building location, the type of soil and the construction materials were analysed. Subsequently, the radon activity concentration was determined using two different techniques: measurement in situ with an on-site ionization chamber detector (short term) and measurement with trace detectors (long term). Based on the results obtained, and according with the Spanish Law (Spanish Official Bulletin-Boletin Oficial del Estado, of 21 December 2011, IS-33 Instruction), corrective works were performed, consisting on the installation of a forced ventilation system underneath the extent of the suspended floor in order to mitigate the high radon specific activity in the building. Four months and 3 years after the works, new measurements were carried out in order to verify the effectiveness of the new ventilation system, obtaining a decrease of the radon gas values ranging between 87% and 90%, which confirmed long term effectivity.

关键词： Routing   Topology   Network topology   Monitoring   Approximation algorithms   Computer science   Weight measurement   Communication technology   communication systems   computer networks   Internet  

摘要： The recent introduction of SDN allows deploying new centralized network algorithms that dramatically improve network operations. In such algorithms, the centralized controller obtains a network-wide view by merging measurement data from Network Measurement Points (NMPs). A fundamental challenge is that several NMPs may count the same packet, reducing the accuracy of the measurement. Existing solutions circumvent this problem by assuming that each packet traverses a single NMP or that the routing is fixed and known. This work suggests novel algorithms for three fundamental network-wide measurement problems without making any assumptions on the topology and routing and without modifying the underlying traffic. Specifically, this work introduces two algorithms for estimating the number of (distinct) packets or byte volume in the measurement, estimating per-flow packet and byte counts, and finding the heavy hitter flows. Our work includes formal accuracy guarantees and an extensive evaluation consisting of the realistic fat-tree topology and three real network traces. Our evaluation shows that our algorithms outperform existing works and provide accurate measurements within reasonable space parameters.

关键词： Students  

摘要： We have been training spatial skills for Computing Science students over several years with positive results, both in terms of the students' spatial skills and their CS outcomes. Te delivery and structure of the training has been modifed over time and carried out at several institutions, resulting in variations across each intervention. Tis article describes six distinct case studies of training deliveries, highlighting the main challenges faced and some important takeaways. Our goal is to provide useful guidance based on our varied experience for any practitioner considering the adoption of spatial skills training for their students. © 2021 ACM.

关键词： Pattern matching   Hardware   Optimization   IP networks   IEEE transactions   Computer science   Throughput   Ternary rule   cache   TCAM   forwarding  

摘要： Ternary Content Addressable Memory (TCAM) is widely used by modern routers and switches to support policy-based forwarding due to its incomparable lookup speed and flexible matching patterns. However, the limited TCAM capacity does not scale with the ever-increasing rule table size due to the high hardware cost and high power consumption. At present, using TCAM just as a rule cache is an appealing solution, but one must resolve several tricky issues including the rule dependency and the associated TCAM updates. In this paper, we propose a new approach which can generate dependency-free rules to cache. By removing the rule dependency, the complex TCAM update problem also disappears. We provide the complete T-cache system design including slow path processing and cache replacement, and implement a T-cache prototype on Barefoot Tofino switches. We conduct comprehensive software simulations and hardware experiments based on real-world and synthesized rule tables and packet traces to show that T-cache is efficient and robust for network traffic in various scenarios.

关键词： computer science   student-directed   projects   project-based learning   PBL   assessment   feedback  

摘要： Student-directed projects are a promising approach to supporting powerful learning, yet uncertainty about how to assess these projects presents a barrier to widespread incorporation in K-12 classrooms. Drawing on interviews with computer science teachers and an interdisciplinary literature review, Karen Brennan, Sarah Blum-Smith, and Paulina Haduong offer four principles to guide assessment of student-directed projects: recognizing the individuality of the learner, illuminating process, engaging multiple perspectives, and cultivating capacity for personal judgment. They describe the research behind these principles and provide and example of what they look like in practice.

关键词： Kaupapa Maori   software engineering process   community engagement   participatory design   co-design  

摘要： We describe a collaboration between Maori (Indigenous people of Aotearoa/New Zealand) and Tauiwi (non-Maori) researchers on a software engineering project. Te Tiriti o Waitangi (The Treaty of Waitangi) provides the basis for Maori to lead research that involves Maori as participants or intends to impact Maori outcomes. Through collaboration, an extension of the traditional four-step software design process was created, culminating in a nine-step integrated process that included Kaupapa Maori (Maori ideology) principles. The collaboration experience for both Maori and Tauiwi highlighted areas of misunderstanding within the research context based on differing worldviews and our ability to navigate and work through this. This article provides context, guiding principles, and recommended research processes where Maori and Tauiwi aim to collaborate.

关键词： Elementary education   Gender studies   Teaching/learning strategies  

摘要： Many stakeholders have suggested that if girls are not engaged in computer science at an early age, the field of computer science (CS) (and computing-related fields) will continue to lack gender diversity. We need more explorations of how curriculum impacts girls' interest in computer science at the elementary level. The focus of this research project was to examine how an elementary problem-based learning (PBL) curriculum impacted girls' understanding of and interest in CS. By utilizing a curriculum focused on a problem that emphasized social activism, we hypothesized that PBL CS could increase interest in CS for girls. This study used a mixed-method sequential explanatory research design to examine the implementation of a CS PBL curriculum with four 6th grade teachers and their 263 students. We collected student CS knowledge pre-tests and post-tests, student attitude surveys, student focus group interviews, teacher interviews, and researcher observation reflection notes. The knowledge tests were analyzed using a mixed measures ANOVA. The survey responses were analyzed using ANOVAs and effect sizes for each comparison were calculated using partial eta squared. The qualitative data was analyzed using a thematic approach that required four researchers to come to a consensus. Results suggested that although girls had less understanding of CS at the beginning, by the end of the curriculum, girls and boys performed similarly. However, there were still elements that were not successful. Girls' attitudes towards computer science were significantly lower than the boys at the end of the curriculum. Conceptually, the curriculum needs to specifically address how CS could impact values held by girls.

关键词： Justice-centered computing   counter-hegemonic   music   video games   making  

摘要： Students' lives, both in and out of school, are full of different forms of value. Wealthy students enjoy value in the form of financial capital;their fit to hegemonic social practices;excellent health care and so on. Low-income students, especially those from African American, Native American, and Latinx communities, often lack access to those resources. But there are other forms of value that low-income students do possess. Most examples of what we will call Counter-Hegemonic Practice (CHP) in the African American community involve some mixture of Indigenous African heritage, contemporary innovation in the Black community, and other influences. Moving between these value forms and the computing classroom is a non-trivial task, especially if we are to avoid merely using the appearance of culture to attract students. Our objective in this paper is to provide a framework for deeper investigations into the computational potentials for CHP;its potential as a link between education and community development;and a more dignified role for its utilization in the CS classroom. We report on a series of collaborative engagements with CHP, largely focused on African American communities.