5111320
Work rhythms: analyzing visualizations of awareness histories of distributed groups
We examined records of minute-by-minute computer activity coupled with information about the location of the activity, online calendar appointments, and e-mail activity. We present a number of visualizations of the data that exhibit meaningful patterns in users' activities. We demonstrate how the patterns vary between individuals and within individuals according to time of day, location, and day of the week. Some patterns augment the schedule information found in people's online calendars. We discuss applications for group coordination (especially across time zones) plus opportunities for future research. In light of the popularity of instant messaging, this research identifies some of the benefits and privacy risks associated with the uses of online presence and awareness information.
1186186
Piazza: a desktop environment supporting impromptu and planned interactions
Much of the support for communication across distributed communities has focused on meetings and intentional contact. However, most interactions within co-located groups occur when people happen to run into each other. Such unintended interactions should also be supported among distributed communities. We conducted a study of the communication patterns of a large, distributed organization and found that people tend to disseminate information using formal techniques, even though people usually receive information informally. We then designed a system called Piazza that is intended to support the range of communication styles evident in large communities, paying particular attention to adchessing the problems revealed in our study. Piazza allows people to be aware of others who are doing similar tasks when they are using their computers, the~by enabling unintended interactions. It also supports intentiomd contacts and planned meetings. We discuss issues for analysis in an upcoming use study.
18533540
Beyond Instant Messaging
The recent rise in popularity of IM (instant messaging) has driven the developmentof platforms and the emergence of standards to support IM. Especially as theuse of IM has migrated from online socializing at home to business settings,there is a need to provide robust platforms with the interfaces that businesscustomers use to integrate with other work applications. Yet, in the rush todevelop a mature IM infrastructure, it is also important to recognize that IMfeatures and uses are still evolving. For example, popular press stories1 haveraised the concern that IM interactions may be too distracting in the workplace.This concern suggests that we still need to fine-tune the interface design forIM so the benefits of quick, lightweight communication can be gained withoutcreating a distracting burden for users. How can the industry meet the demandfor robust platforms and standards for IM without locking out innovation anddevelopment?
43821577
When Can I Expect an Email Response? A Study of Rhythms in Email Usage
A study of email responsiveness was conducted to understand how the timing of email responses conveys important information. Interviews and observations explored users' perceptions of how they responded to email and formed expectations of others' responses to them. We identified ways in which users maintain and cultivate a responsiveness image for projecting expectations about their email response. We also discuss other contextual cues people use to discover email responsiveness, which include using other tools such as the calendar and phone, accounting for the amount of work time overlap available, and establishing a pacing between email correspondents. These cues help users develop a sense of when to expect a response and when breakdown has occurred, requiring further action.
12875596
Exploring patterns of social commonality among file directories at work
We studied files stored by members of a work organization for patterns of social commonality. Discovering identical or similar documents, applications, developer libraries, or other files may suggest shared interests or experience among users. Examining actual file data revealed a number of individual and aggregate practices around file storage. For example, pairs of users typically have many (over 13,000) files in common. A prototype called LiveWire exploits this commonality to make file backup and restore more efficient for a work organization. We removed commonly shared files and focused on specific filetypes that represent user activity to find more meaningful files in common. The Consolidarity project explores how patterns of file commonality could encourage social networking in an organizational context. Mechanisms for addressing the privacy concerns raised by this approach are discussed.
6543572
Findings from Observational Studies of Collaborative Work
Abstract The work activity of small groups of three to four people was videotaped and analysed in order to understand collaborative work and to guide the development of tools to support it. The analysis focused on the group's shared drawing activity—their listing, drawing, gesturing and talking around a shared drawing surface. This analysis identified specific features of collaborative work activity that raise design implications for collaborative technology: (1) collaborators use hand gestures to uniquely communicate significant information; (2) the process of creating and using drawings conveys much information not contained in the resulting drawings; (3) the drawing space is an important resource for the group in mediating their collaboration; (4) there is a fluent mix of activity in the drawing space; and (5) the spatial orientation among the collaborators and the drawing space has a role in structuring their activity. These observations are illustrated with examples from the video data, and the design implications they raise are discussed.
13492639
Relay node placement in large scale wireless sensor networks
Scalability and extended lifetime are two critical design goals of any large scale wireless sensor network. A two-tiered network model has been proposed recently for this purpose. This is a cluster-based network model composed of relay and sensor nodes. Relay nodes are placed in the playing field to serve as cluster heads and to form a connected network topology for information dissemination at the higher tier. The relay nodes are capable of aggregating data packets from the sensor nodes in their clusters and transmitting them to the sink node via wireless multi-hop paths. In this paper, we study the relay node placement problem in large scale wireless sensor networks. Our objective is to place the fewest number of relay nodes in the playing field of a sensor network such that (1) each sensor node can communicate with at least one relay node and (2) the network of relay nodes is connected. However, placement strategies realizing goals (1) and (2) do not provide any fault-tolerance as the network may lose functionality after failure of some of the relay nodes. In order to incorporate fault-tolerance in such a network, we ensure that every sensor node is able to communicate with at least two relay nodes and the induced network topology is 2-connected. This strategy will ensure survivability of the network in the event of single fault, in lieu of higher relay node placement cost. We formulate the relay node placement in wireless sensor networks as two optimization problems: (i) Connected Relay Node Single Cover (CRNSC) problem and (ii) 2-Connected Relay Node Double Cover (2CRNDC) problem. We present two polynomial time approximation algorithms to solve the CRNSC problem. We prove that the ratio of the number of relay nodes needed by the approximation algorithm to the number of relay nodes needed by the optimal algorithm is bounded by 8 for the first algorithm and 4.5 for the second. In addition, for the 2CRNDC problem we provide two approximation algorithms with performance bounds 6 and 4.5, respectively.
8476755
Succinct Text Indexes on Large Alphabet
In this paper, we first consider some properties of strings who have the same suffix array. Next, we design a data structure to support rank and select operations on an alphabet Σ using nlog|Σ| + (nlog|Σ|) bits in O(log|Σ|) time for a text of length n. It also supports an extended rank, namely rank≤, such that rank$^{\rm \leq}_{\alpha}$(T,i) returns the number of letters which are smaller than α in string T, plus the number of αs up to position i. Also, it runs in O(log|Σ|) time. By this structure, we implement the DAWG succinctly. The main structure only takes nlog|Σ| + o(nlog|Σ|) bits and supports basic operations of DAWG efficiently.
41425816
Acceleration of Preconditioned Krylov Solvers for Bubbly Flow Problems
We consider the linear system which arises from discretization of the pressure Poisson equation with Neumann boundary conditions, coming from bubbly flow problems. In literature, preconditioned Krylov iterative solvers are proposed, but these show slow convergence for relatively large and complex problems. We extend these traditional solvers with the so-called deflation technique, which accelerates the convergence substantially. Several numerical aspects are considered, like the singularity of the coefficient matrix and the varying density field at each time step. We demonstrate theoretically that the resulting deflation method accelerates the convergence of the iterative process. Thereafter, this is also demonstrated numerically for 3-D bubbly flow applications, both with respect to the number of iterations and the computational time.
1134742
Improving Tree Search in Phylogenetic Reconstruction from Genome Rearrangement Data
A major task in evolutionary biology is to determine the ancestral relationships among the known species, a process generally referred as phylogenetic reconstruction. In the past decade, a new type of data based on genome rearrangements has attracted increasing attention from both biologists and computer scientists. Methods for reconstructing phylogeny based on genome rearrangement data include distance-based methods, direct optimization methods (GRAPPA and MGR), and Markov Chain Monte Carlo (MCMC) methods (Badger). Extensive testing on simulated and biological datasets showed that the latter three methods are currently the best methods for genome rearrangement phylogeny. However, all these tools are dealing with extremely large searching spaces; the total number of possible trees grows exponentially when the number of genomes increases and makes it computationally very expensive. Various heuristics are used to explore the tree space but with no guarantee of optimum being found. In this paper, we present a new method to efficiently search the large tree space. This method is motivated by the concept of particle filtration (also known as Sequential Monte Carlo), which was originally proposed to boost the efficiency of MCMC methods on massive data. We tested and compared this new method on simulated datasets in different scenarios. The results show that the new method achieves a significant improvement in efficiency, while still retains very high topological accuracy.
14586033
Dynamic Data-Driven Fault Diagnosis of Wind Turbine Systems
In this multi-university collaborative research, we will develop a framework for the dynamic data-driven fault diagnosis of wind turbines which aims at making the wind energy a competitive alternative in the energy market. This new methodology is fundamentally different from the current practice whose performance is limited due to the non-dynamic and non-robust nature in the modeling approaches and in the data collection and processing strategies. The new methodology consists of robust data pre-processing modules, interrelated, multi-level models that describe different details of the system behaviors, and a dynamic strategy that allows for measurements to be adaptively taken according to specific physical conditions and the associated risk level. This paper summarizes the latest progresses in the research.