On the Cost of Participating in a Peer-to-Peer Network

In this paper, we model the cost incurred by each peer participating in a peer-to-peer network. Such a cost model allows to gauge potential disincentives for peers to collaborate, and provides a measure of the ``total cost'' of a network, which is a possible benchmark to distinguish between proposals. We characterize the cost imposed on a node as a function of the experienced load and the node connectivity, and show how our model applies to a few proposed routing geometries for distributed hash tables (DHTs). We further outline a number of open questions this research has raised.Comment: 17 pages, 4 figures. Short version to be published in the Proceedings of the Third International Workshop on Peer-to-Peer Systems (IPTPS'04). San Diego, CA. February 200

Emotional Biosensing: Exploring Critical Alternatives

Emotional biosensing is rising in daily life: Data and categories claim to know how people feel and suggest what they should do about it, while CSCW explores new biosensing possibilities. Prevalent approaches to emotional biosensing are too limited, focusing on the individual, optimization, and normative categorization. Conceptual shifts can help explore alternatives: toward materiality, from representation toward performativity, inter-action to intra-action, shifting biopolitics, and shifting affect/desire. We contribute (1) synthesizing wide-ranging conceptual lenses, providing analysis connecting them to emotional biosensing design, (2) analyzing selected design exemplars to apply these lenses to design research, and (3) offering our own recommendations for designers and design researchers. In particular we suggest humility in knowledge claims with emotional biosensing, prioritizing care and affirmation over self- improvement, and exploring alternative desires. We call for critically questioning and generatively re- imagining the role of data in configuring sensing, feeling, ‘the good life,’ and everyday experience

Participation And performance In 8.02x Electricity And Magnetism: The First Physics MOOC From MITx

Massive Open Online Courses are an exciting new avenue for instruction and research, yet they are full of unknowns. In the Spring of 2013, MITx released its first introductory physics MOOC through the edX platform, generating a total enrollment of 43,000 students from around the world. We describe the population of participants in terms of their age, gender, level of education, and country of origin, highlighting both the diversity of 8.02x enrollees as well as gender gap and retention. Using three midterm exams and the final as waypoints, we highlight performance by different demographic subpopulations and their retention rates. Our work is generally aimed at making a bridge between available MOOC data and topics associated with the Physics Education Research community.Comment: 4 pages, 5 figures, Accepted for publication in the Physics Education Research Conference Proceedings, Portland OR 201

Rooted in nature: aesthetics, geometry and structure in the shells of Heinz Isler

Reinforced concrete shells frequently constitute the most visible element of a building envelope. They dominate the architectural expression, yet the three-dimensional form is generally determined by the engineer according to its structural efficiency, rather than by the architect according to aesthetical considerations. This raises the question “Who is the author of the design?” The design philosophy of recognised shell designers is introduced, specifically that of Swiss shell designer and “structural artist” Heinz Isler, who is considered to have had particular sensitivity to the aesthetics of his shells, rooted in his admiration of the natural world and derived by natural laws. The Sicli Factory shell, 1968, is taken as a case study and is used to compare Isler’s design method with contemporary digital form-finding using the particle spring method. It is concluded that there are advantages and disadvantages to both physical and digital modelling methods. Designers should be encouraged to explore with various approaches

Design and modelling of Heinz Isler’s Sicli shell

In 1969 a thin concrete shell roof designed by the master shell builder Heinz Isler was erected for the fire extinguisher manufacturer Sicli, SA, in Geneva, Switzerland. From this research carried out at the Heinz Isler Archive at ETH Zürich, it was found that more, previously unrevealed, alternative proposals and physical models were employed to accomplish this project. This paper describes an investigation of the original physical modelling process of the Sicli shell and discusses the infinite potential of form-finding methods for shaping a good shell. Four alternative free-form design schemes proposed by Isler for the Sicli shell, in addition to the final chosen hanging cloth modelling approach, are introduced and discussed. The actual construction details of the Sicli shell will be reviewed with regard to both architectural and engineering perspectives. In conclusion, more research to be carried out on the valuable legacy of Isler’s form-finding techniques is suggested

The Application of Wavelets and Fuzzy Logic to Eddy Current Flaw Detection in Steam Generator Tubes

Eddy current testing is a widely used nondestructive testing method, especially for inspecting steam generator tubes in nuclear power plants. Due to the complex nature of this technique, the analysis of inspection data is a difficult task requiring a great deal of work by experienced human analysts. This is time consuming, expensive, and can be inconsistent due to human nature. Also, the presence in eddy current signals of interference from the tube support plates and deposits can make the data very difficult to analyze. To help overcome these obstacles, an automatic eddy-current analysis system is needed to aid the analysts