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Communications of the ACM

121 - 130 of 233 for bentley

Check-ins in “Blau Space”: Applying Blau’s Macrosociological Theory to Foursquare Check-ins from New York City

Peter Blau was one of the first to define a latent social space and utilize it to provide concrete hypotheses. Blau defines social structure via social “parameters” (constraints). Actors that are closer together (more homogenous) in this social parameter space are more likely to interact. One of Blau’s most important hypotheses resulting from this work was that the consolidation of parameters could lead to isolated social groups. For example, the consolidation of race and income might lead to segregation. In the present work, we use Foursquare data from New York City to explore evidence of homogeneity along certain social parameters and consolidation that breeds social isolation in communities of locations checked in to by similar users.

More specifically, we first test the extent to which communities detected via Latent Dirichlet Allocation are homogenous across a set of four social constraints—racial homophily, income homophily, personal interest homophily and physical space. Using a bootstrapping approach, we find that 14 (of 20) communities are statistically, and all but one qualitatively, homogenous along one of these social constraints, showing the relevance of Blau’s latent space model in venue communities determined via user check-in behavior. We then consider the extent to which communities with consolidated parameters, those homogenous on more than one parameter, represent socially isolated populations. We find communities homogenous on multiple parameters, including a homosexual community and a “hipster” community, that show support for Blau’s hypothesis that consolidation breeds social isolation. We consider these results in the context of mediated communication, in particular in the context of self-representation on social media.

Self organized multi-agent entangled hierarchies for network security

Cyber-security management is of central importance in financial, business, and military environments. Thus, we propose an effective and efficient self organized entangled hierarchial architecture of multiple agents that decentralizes network security control and communication. Considering the Cyberspace container model, the self organized multi-agent swarms are evolved based on partially observable Markov decision process formal models. Desired network security swarm behaviors are defined and formalized to interact with these models. The "optimal" policy (agent rules and parameters) for a given behavior is evolved using a multi-objective evolutionary algorithm. Swarm effectiveness is compared in various network security scenarios using statistical testing techniques and visualization.

An optimal online algorithm for metrical task systems

In practice, almost all dynamic systems require decisions to be made online, without full knowledge of their future impact on the system. We introduce a general model for the processing of sequences of tasks and develop a general online decision algorithm. We show that, for an important class of special cases, this algorithm is optimal among all online algorithms. Specifically, a task system (S, d) for processing sequences of tasks consists of a set S of states and a cost matrix d where d(i, j) is the cost of changing from state i to state j (we assume that d satisfies the triangle inequality and all diagonal entries are O.) The cost of processing a given task depends on the state of the system. A schedule for a sequence T1, T2Tk of tasks is a sequence s1, s2sk of states where si is the state in which Ti is processed; the cost of a schedule is the sum of all task processing costs and state transition costs incurred. An online scheduling algorithm is one that chooses si only knowing T1 T2Ti. Such an algorithm operates within waste factor w if, on any input task sequence, its costs is within an additive constant of w times the optimal offline schedule cost. The online waste factor w(S, d) is the infirm waste factor of any online scheduling algorithm for (S, d). We show that w(S, d) = 2|S| - 1 for every task system in which d symmetric, and w(S, d) = &Ogr;(|S|2) for every task system.

Procuring software development services in a public administration: the perspective of suppliers

This paper deals with a real case in public administration, where a prequalification mechanism of suppliers has been developed for the procurement of services related to information systems and information technologies. Among these, we focus on the software development services, which account for the most important part of the budget, as well as for the most varied set of sub-categories of services and of involved companies. We describe the characteristics of this prequalification mechanism but we also detail how suppliers have experienced its application. We attempt to contrast the perspective of suppliers versus the perspective of the promoters of the mechanism and we try to depict how these initial intentions of promoters are translated to the actual deployment. Conclusions show that most of those intentions have not completely materialized.

A novel page-based data structure for interactive walkthroughs

Given a data layout of a large walkthrough scene, we present a novel and simple spatial hierarchy on the disk-pages of the layout that has notable advantages over a conventional spatial hierarchy on the scene geometry. Assume that each disk-page consists of a set of triangles whose bounding boxes are computed. A spatial hierarchy of the walkthrough space is constructed, not with the given scene, but with the bounding boxes of disk-pages. The leaf nodes of the spatial-hierarchy refer directly to the page numbers of the pages of the bounding box it contains. We call this hierarchy on the pages as the disk-page hierarchy. We also propose a self-contained disk-page format that would suit this data structure well. Further, we present a new cache-oblivious graph-based data layout algorithm called the 2-factor layout that would preserve the proximity and orientation properties of the primitives in the layout. Walkthrough experiments have been conducted on a city scene consisting of over 110M triangles. Our system renders this scene on a laptop within a one pixel projection error at over 20 fps with simple texture substitution based simplification of distant objects, and with no explicit data/cache management.

Explaining factors affecting telework adoption in South African organisations pre-COVID-19

The COVID-19 pandemic of 2020 saw governments across the world mandating telework for entire populations thereby bringing the topic of telework into sharp focus. Telework is a well-researched topic which dates as far back as five decades ago. While telework provides many indisputable benefits to organisations, society and individuals, it has not achieved the anticipated widespread adoption. While telework studies have examined multiple aspects, few studies have examined organisational factors which affect telework adoption. This study is an empirical investigation of telework adoption, using a set of factors identified in the literature in organisations in a South African context. These factors in prior studies were found to enable or prevent an organisation from adopting telework. The question thus asked in this study was “Which factors enable or prevent the adoption of telework within South African organisations?” A survey with 104 valid responses was analysed using Statistica. The theoretical contribution of the study is a validated model of factors influencing the adoption of telework.

Managing emotions for the treatment of patients with chronic low back pain

Improving the quality of life of people is one of the main objectives of the HCI discipline. At this point, target audience are patients with chronic low back pain (CLBP). Fear-avoidance theory explains how patients develop chronic pain. Thus, if the patient can learn to manage their emotions through biofeedback and neurofeedback her knowledge about emotions can be changed and as a result pain is avoided. To carry out this process a gamified application, in addition to the management of bio-signals such as galvanic skin response or using electroencephalograms to know what emotional state, has been designed. A pilot project is underway in primary care centers in Lleida.

The experienced "sense" of a virtual community: characteristics and processes

E-commerce strategists advise companies to create virtual communities for their customers. But what does this involve? Research on face-to-face communities identifies the concept of "sense of community:" a characteristic of successful communities distinguished by members' helping behaviors and members' emotional attachment to the community and other members. Does a sense of virtual community exist in online settings, and what does it consist of? Answering these questions is key, if we are to provide guidance to businesses attempting to create virtual communities.The paper explores the concept of sense of virtual community in a newsgroup we call Multiple Sports Newsgroup (MSN). We first demonstrate that MSN does indeed have a sense of virtual community, but that the dimensions of the sense of community in MSN differ somewhat from those reported for physical communities. The nature of these differences is plausibly related to the differences between electronic and face-to-face communication. We next describe the behavioral processes that contribute to the sense of virtual community at MSN-exchanging support, creating identities and making identifications, and the production of trust. Again, these processes are similar to those found in non-virtual communities, but they are related to the challenges of electronic communication. Lastly, we consider the question of how sense of community may come about and discuss the implications for electronic business.

CloST: a hadoop-based storage system for big spatio-temporal data analytics

During the past decade, various GPS-equipped devices have generated a tremendous amount of data with time and location information, which we refer to as big spatio-temporal data. In this paper, we present the design and implementation of CloST, a scalable big spatio-temporal data storage system to support data analytics using Hadoop. The main objective of CloST is to avoid scan the whole dataset when a spatio-temporal range is given. To this end, we propose a novel data model which has special treatments on three core attributes including an object id, a location and a time. Based on this data model, CloST hierarchically partitions data using all core attributes which enables efficient parallel processing of spatio-temporal range scans. According to the data characteristics, we devise a compact storage structure which reduces the storage size by an order of magnitude. In addition, we proposes scalable bulk loading algorithms capable of incrementally adding new data into the system. We conduct our experiments using a very large GPS log dataset and the results show that CloST has fast data loading speed, desirable scalability in query processing, as well as high data compression ratio.