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Fuel and lubricating oil leaks produce an oily wastewater that creates an environmental problem for industries. Dissolved air flotation (DAF) has been successfully employed for the separation of oily contaminants. Collectors constitute an auxiliary tool in the DAF process that enhances the separation efficiency by facilitating the adhesion of the contaminant particles. The use of biosurfactants as...
Opportunistic grids are distributed computing infrastructures that harvest the idle computing cycles of computing resources geographically distributed. In these grids, the demand for resources is typically bursty. During bursts of resource demand, many grid resources are required, but on other times they remain idle for long periods. If the resources are kept powered on even when they are neither...
Awerbuch and Scheideler have shown that peer-to-peer overlays networks can survive Byzantine attacks only if malicious nodes are not able to predict what will be the topology of the network for a given sequence of join and leave operations. In this paper we investigate adversarial strategies by following specific protocols. Our analysis demonstrates first that an adversary can very quickly subvert...
Computational grids are an infrastructure to aggregate computing power to support and improve performance of parallel applications. Some of them evolved in the sense of forming free-to-join communities over the Internet and became peer-to-peer (P2P) grids. One of the main problems associated with users freely joining and leaving grid communities is that cheating users may corrupt the final computation...
BitTorrent, one of the most popular content distribution protocols nowadays, has an identification generation scheme that is completely autonomous. Furthermore, BitTorrent uses a random mechanism to discover new peers. This leaves the system vulnerable to a sybil attack, by which an entity associates multiple identifications to itself in an attempt to fool the other peers that execute the agreed protocol...
In this paper we consider a peer-to-peer grid system which provides multiple services to its users. An incentive mechanism promotes collaboration among peers. It has been shown that the use of a reciprocation-based incentive mechanism in such a system prevents free-riding and, at the same time, promotes the clustering of peers that have mutually profitable interactions. On the other hand, an issue...
It has been shown that the use of a reciprocation mechanism in peer-to-peer grid systems which provide multiple services to their users is an efficient way to prevent free-riding and, at the same time, to promote the clustering of peers that have mutually profitable interactions. However, when peers are subject to resource limitations, they may be unable to offer all possible services and shall select...
This paper presents PeerCube, a DHT-based system aiming at minimizing performance penalties caused by high churn while preventing malicious peers from subverting the system through collusion. This is achieved by i) applying a clustering strategy to support quorum-based operations; ii) using a randomized insertion algorithm to reduce the probability with which colluding Byzantine peers corrupt clusters,...
Peer-to-peer grids are large-scale, dynamic environments where autonomous sites share computing resources. Producing and maintaining relevant and up-to-date resource information in such environments is a challenging problem, due to the grid scale, the resource heterogeneity, and the variety of user demand. This work proposes a peer-to-peer annotation approach where users can freely annotate available...
Scheduling parallel applications on computational grids is a difficult task. In order to map the parallel application's tasks onto resources in a efficient way, grid schedulers apply scheduling heuristics. The existing scheduling heuristics can be broadly classified in two approaches: i) bin-packingschedulers,andii)replicationschedulers. The first approach requires complete and accurate information...
With the emergence of utility computing and the continuous search for reducing the cost of running information technology (IT) infrastructures, we will soon experience an important change on the way these infrastructures are assembled, configured and managed. In this paper we consider the problem of managing a hybrid high-performance computing infrastructure whose processing elements comprise in-house...
In this paper we consider a peer-to-peer grid system which provides multiple services to its users. In this system, an incentive mechanism promotes collaboration among peers. It has been shown that the use of a reciprocation mechanism in such a system is able to prevent free riding and, at the same time, promotes the clustering of peers that have mutually profitable interactions. However, when peers...
This paper discusses an approach to avoid incorrect results in the execution of automatic tests of multi-threaded systems. We argue that such incorrect results have two main sources. First, it is typically difficult to determine when all threads have finished processing and thus when it is safe to perform the test assertions. Second, background threads can change the system state while assertions...
Consensus services have been recognized as fundamental building blocks for fault-tolerant distributed systems. Many different protocols to implement such a service have been proposed, however, not a lot of effort has been placed in evaluating their performance. In particular, in the context of round-based consensus protocols for asynchronous systems augmented with failure detectors, there has been...
BitTorrent is currently a de facto standard for scalable content-distribution. However, its peer-to-peer model for resource allocation does not provide high availability and its performance depends on best-effort contributions given by peers. This has motivated several content-providers to use a hybrid model in which they operate a superpeer in order to attain a higher quality of service. In this...
High performance computing is currently not affordable for those users that cannot rely on having a highly qualified computing support team. To cater for these users' needs we have proposed, implemented and deployed OurGrid. OurGrid is a peer-to-peer grid middleware that supports the automatic creation of large computational grids for the execution of embarrassingly parallel applications. It has been...
Grid computing enables different institutions to access each other's resources, and hence requires very strong security guarantees. We here explore how visualization was used to provide security for OurGrid, an easy-to-use free-to-join grid that supports bag-of-tasks applications. OurGrid poses interesting security challenges. It is free-to-join (which means one runs unknown applications) and strives...
As Web services and service oriented architectures are adopted, it is increasingly important to have standard and interoperable means to deploy and configure Web services. Within the Global Grid Forum, HP, NEC, and Softricity have been developing a standard for configuration description, deployment, and lifecycle management (CDDLM). In order to prove its feasibility, reference implementations are...
In this paper we study reciprocation-based mechanisms to encourage donation in peer-to-peer grids in which multiple services, such as processing power and data transfers, are shared explicitly. We have modeled such a system and established how peers should assess whether it is profitable to exchange services with another peer, an issue that is not present in the single service case. Unfortunately,...
We here discuss how to run Bag-of-Tasks applications on computational grids. Bag-of-Tasks applications (those parallel applications whose tasks are independent) are both relevant and amendable for execution on grids. However, few users currently execute their Bag-of-Tasks applications on grids. We investigate the reason for this state of affairs and introduce MyGrid, a system designed to overcome...
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