Gokarna Sharma

SPAMMS: A sensor-based pipeline autonomous monitoring and maintenance system

Pipeline-based applications have become the indispensable part of life. Active monitoring and frequent inspections are critical to maintaining pipeline health. However, these tasks are highly expensive using the traditional maintenance systems, knowing that the pipeline systems can be largely deployed in an inaccessible and hazardous environment. In this paper, we propose a novel cost effective, scalable, customizable, and autonomous sensor-based system, called SPAMMS. It combines robot agent based technologies with sensing technologies for efficiently locating health related events and allows active and corrective monitoring and maintenance of the pipelines. SPAMMS integrates RFID systems with mobile sensors and autonomous robots. While the mobile sensor motion is based on the fluid transported by the pipeline, the fixed sensors provide event and mobile sensor location information and contribute efficiently to the study of health history of the pipeline. In addition, it permits a good tracking of the mobile sensors. Using the output of event analysis, a robot agent gets command from the controlling system, travels inside the pipelines for detailed inspection and repairing of the reported incidents (e.g., damage, leakage, or corrosion). The key innovations of SPAMMS are 3-fold: (a) the system can apply to a large variety of pipeline systems; (b) the solution provided is cost effective since it uses low cost powerless fixed sensors that can be setup while the pipeline system is operating; (c) the robot is autonomous and the localization technique allows controllable errors. The simulation experiments described in this paper along with prototyping activities demonstrate the feasibility of SPAMMS.

FAMPER: A fully autonomous mobile robot for pipeline exploration

Pipeline-based applications have become an integral part of life. However, knowing that the pipeline systems can be largely deployed in an inaccessible and hazardous environment, active monitoring and frequent inspection of the pipeline systems are highly expensive using the traditional maintenance systems. Robot agents have been considered as an attractive alternative. Although many different types of pipeline exploration robots have been proposed, they were suffered from various limitations. In this paper, we present the design and implementation of a single-moduled fully autonomous mobile pipeline exploration robot, called FAMPER, that can be used for the inspection of 150mm pipelines. This robot consists of four wall-press caterpillars operated by two DC motors each. The speed of each caterpillar is controlled independently to provide steering capability to go through 45 degree elbows, 90 degree elbows, T-branches, and Y-branches. The uniqueness of this paper is to show the opportunity of using 4 caterpillar configuration for superior performance in all types of complex networks of pipelines. The robot system has been developed and experimented in different pipeline layouts.

Window-based greedy contention management for transactional memory

We consider greedy contention managers for transactional memory for M × N execution windows of transactions with M threads and N transactions per thread. Assuming that each transaction has duration τ and conflicts with at most C other transactions inside the window, a trivial greedy contention manager can schedule them within τCN time. In this paper, we explore the theoretical performance boundaries of this approach from the worst-case perspective. Particularly, we present and analyze two new randomized greedy contention management algorithms. The first algorithm Offline-Greedy produces a schedule of length O(τ ċ (C + N log(MN))) with high probability, and gives competitive ratio O(log(MN)) for C ≤ N log(MN). The offline algorithm depends on knowing the conflict graph which evolves while the execution of the transactions progresses. The second algorithm Online-Greedy produces a schedule of length O(τ ċ (C log(MN) + N log2(MN))), with high probability, which is only a O(log(NM)) factor worse, but does not require knowledge of the conflict graph. Both of the algorithms exhibit competitive ratio very close to O(s), where s is the number of shared resources. Our algorithms provide new tradeoffs for greedy transaction scheduling that parameterize window sizes and transaction conflicts within the window.

An Analysis Framework for Distributed Hierarchical Directories

We provide a novel analysis framework for distributed hierarchical directories for an arbitrary set of dynamic (online) requests. We prove a general \({\cal O}(\eta\cdot \varphi \cdot \sigma^3 \cdot h)\) competitive ratio for any distributed hierarchical directory, where η is a write set size related parameter, ϕ and σ are stretch and growth related parameters, and h is the number of levels in the hierarchy. Through this framework, we give bounds for several known distributed directory protocols. In general network topologies, we obtain \({\cal O}(\log^2 n\cdot\log D)\) competitive ratio, where n and D are the number of nodes and the diameter, respectively, of the network. Moreover, we obtain \({\cal O}(\log D)\) competitive ratio in constant-doubling metric topologies. To the best of our knowledge, this is the first (competitive) dynamic analysis for distributed hierarchical directories.

Distributed transactional memory for general networks

We consider the problem of implementing transactional memory in large-scale distributed networked systems. We present Spiral, a novel distributed directory-based protocol for transactional memory, and theoretically analyze and experimentally evaluate it for the performance boundaries of this approach from the worst-case perspective. Spiral is designed for the data-flow distributed implementation of software transactional memory which supports three basic operations: publish, allowing a shared object to be inserted in the directory so that other nodes can find it; lookup, providing a read-only copy of the object to the requesting node; move, allowing the requesting node to write the object locally after the node gets it. The protocol runs on a hierarchical directory construction based on sparse covers, where clusters at each level are ordered to avoid race conditions while serving concurrent requests. Given a shared object the protocol maintains a directory path pointing to the object. The basic idea is to use “spiral” paths that grow outward to search for the directory path of the object in a bottom-up fashion. For general networks, this protocol guarantees an

Complete Visibility for Robots with Lights in O (1) Time

\mathcal{O}(\log ^2 n\cdot \log D)

Towards load balanced distributed transactional memory

O(log2n·logD) approximation in sequential and one-shot concurrent executions of a finite set of move requests, where