Control Data Distribution Research Articles

GeoBroker: A pub/sub broker considering geo-context information

Abstract The majority of today’s pub/sub brokers only focus on data content when deciding where to distribute data. In this paper, we introduce the GeoBroker pub/sub broker software that additionally considers the geo-context associated with data producers and consumers. As a result, data consumers only receive relevant messages which preserves bandwidth and compute power while data producers can use the geo-context of clients to control data distribution, e.g., for enhanced privacy or as an alternative to credential-based authentication.

GeoBroker: Leveraging geo-contexts for IoT data distribution

In the Internet of Things, the relevance of data often depends on the geographic context of data producers and consumers. Today’s data distribution services, however, mostly focus on data content and not on geo-context, which could help to reduce the dissemination of excess data in many IoT scenarios. In this paper, we propose to use the geo-context information associated with devices to control data distribution. We define what geo-context dimensions exist and compare our definition with concepts from related work.Furthermore, we designed GeoBroker, a data distribution service that uses the location of things, as well as geofences for messages and subscriptions, to control data distribution. This way, we enable new IoT application scenarios while also increasing overall system efficiency for scenarios where geo-contexts matter by delivering only relevant messages. We evaluate our approach based on a proof-of-concept prototype and several experiments.

Pelvic excursion during walking post-stroke: A novel classification system

BackgroundResearchers and clinicians often use gait speed to classify hemiparetic gait dysfunction because it offers clinical predictive capacity. However, gait speed fails to distinguish unique biomechanical characteristics that differentiate aspects of gait dysfunction. Research questionHere we describe a novel classification of hemiparetic gait dysfunction based on biomechanical traits of pelvic excursion. We hypothesize that individuals with greater deviation of pelvic excursion, relative to controls, demonstrate greater impairment in key gait characteristics. MethodsWe compared 41 participants (61.0 ± 11.2yrs) with chronic post-stroke hemiparesis to 21 non-disabled controls (55.8 ± 9.0yrs). Participants walked on an instrumented split-belt treadmill at self-selected walking speed. Pelvic excursion was quantified as the peak-to-peak magnitude of pelvic motion in three orthogonal planes (i.e., tilt, rotation, and obliquity). Raw values of pelvic excursion were compared against the distribution of control data to establish deviation scores which were assigned bilaterally for the three planes producing six values per individual. Deviation scores were then summed to produce a composite pelvic deviation score. Based on composite scores, participants were allocated to one of three categories of hemiparetic gait dysfunction with progressively increasing pelvic excursion deviation relative to controls: Type I (n = 15) – minimal pelvic excursion deviation; Type II (n = 20) – moderate pelvic excursion deviation; and Type III (n = 6) – marked pelvic excursion deviation. We assessed resulting groups for asymmetry in key gait parameters including: kinematics, joint powers temporally linked to the stance-to-swing transition, and timing of lower extremity muscle activity. ResultsAll groups post-stroke walked at similar self-selected speeds; however, classification based on pelvic excursion deviation revealed progressive asymmetry in gait kinematics, kinetics and temporal patterns of muscle activity. SignificanceThe progressive asymmetry revealed in multiple gait characteristics suggests exaggerated pelvic motion contributes to gait dysfunction post-stroke.

Distributed shared arrays: A distributed virtual machine with mobility support for reconfiguration

Distributed Shared Arrays (DSA) is a distributed virtual machine that supports Java-compliant multithreaded programming with mobility support for system reconfiguration in distributed environments. The DSA programming model allows programmers to explicitly control data distribution so as to take advantage of the deep memory hierarchy, while relieving them from error-prone orchestration of communication and synchronization at run-time. The DSA system is developed as an integral component of mobility support middleware for Grid computing so that DSA-based virtual machines can be reconfigured to adapt to the varying resource supplies or demand over the course of a computation. The DSA runtime system also features a directory-based cache coherence protocol in support of replication of user-defined sharing granularity and a communication proxy mechanism for reducing network contention. System reconfiguration is achieved by a DSA service migration mechanism, which moves the DSA service and residing computational agents between physical servers for load balancing and fault resilience. We demonstrate the programmability of the model in a number of parallel applications and evaluate its performance by application benchmark programs, in particular, the impact of the coherence granularity and service migration overhead.

Distributed Shared Arrays: An Integration of Message Passing and Multithreading on SMP Clusters

This paper presents a Distributed Shared Array runtime system to support Java-compliant multithreaded programming on clusters of symmetric multiprocessors (SMPs). As a hybrid of message passing and shared address space programming models, the DSA programming model allows programmers to explicitly control data distribution so as to take advantage of the deep memory hierarchy, while relieving them from error-prone orchestration of communication and synchronization at run-time. The DSA system is developed as an integral component of mobility support middleware for grid computing so that DSA-based virtual machines can be reconfigured to adapt to the varying resource supplies or demand over the course of a computation. The DSA runtime system also features a directory-based cache coherence protocol in support of replication of user-defined sharing granularity and a communication proxy mechanism for reducing network contention. We demonstrate the programmability of the model in a number of parallel applications and evaluate its performance on a cluster of SMP servers, in particular, the impact of the coherence granularity.

Inverse Techniques and Geologic Models

The development is well advanced of inverse procedures for assessing the resolution, precision, uniqueness, and sensitivity of behaviors geologic models. This paper provides a set of illustrations illuminating the general concepts, examining the array of different models that are amenable to inverse techniques, and portraying the degrees of resolution of behaviors. The sensitivity of results to variations in input assumptions, input parameters and functional dependences, and input quality, quantity, and distribution of control data are also examined.