Primary collection is the first phase of waste collection characterized by waste pickers using human-powered vehicles. According to the primary collection route, a waste picker could get tired and have time-consuming labor. Hence, this work evaluates route generation approaches to minimize waste picker’s physical effort. The approaches include the heuristics Nearest Neighbor, Nearest Insertion, and Farthest Insertion employed to order the stop points. Moreover, the approaches also include the search algorithms Shortest Path Faster Algorithm (SPFA), Bidirectional Dijkstra, and A-star applied to create paths connecting the stop points. Besides, two scenarios of 15 and 30 stop points were implemented using geographical data of Salvador city, obtained from Open Street Map. Also, the Geomorphometric Database of Brazil provided the scenarios altitude data. The approaches were evaluated according to the processing time efficiency, distance, time, and physical power applied to push the vehicle. The simulations realized in Simulation of Urban MObility (SUMO) showed that the approach Nearest Neighbor combined with Bidirectional Dijkstra presents the shortest processing time. Finally, the Nearest Insertion minimizes the physical power applied to push the vehicle.

The demographic growth in cities has increased carbon dioxide (CO2) emissions, a significant problem that challenges societies worldwide. The CO2 emission raises the pollution levels causing health risks for the people and contributes to climate change. Moreover, the transportation sector is responsible for 20.6% of CO2 emissions. Thus, it is necessary to reduce vehicle fuel consumption to minimize CO2 emissions. This paper proposes a system based on artificial intelligence techniques: a fuzzy controller and a neural network to find the instantaneous speed, which reduces vehicle fuel consumption. The proposed system employs only vehicle and highway information, which means communication between vehicles is not required. The simulation scenario comprises a loaded truck traveling through a highway with slopes based on a data set. Results derived from simulation show that both techniques produce a lower fuel consumption than the standard Simulation of Urban MObility (SUMO) algorithm.

Software Defined Networking (SDN) and Network Function Virtualization (NFV) paradigms have been widely used to redesign the traditional mobile networks. Despite several proposals on the literature, researchers have drawn limited attention to the virtualization of user-plane functions that demand high traffic volume processing, as the case of Long Term Evolution (LTE) mobile gateways. This paper introduces an adaptive mechanism for the user plane virtualization of the LTE Packet Data Network (PDN) GateWay (P-GW), running entirely on top of OpenFlow switches. Using both SDN and NFV concepts, the proposed mechanism employs elastic computing notions to dynamically activate or deactivate the infrastructure switches so the virtualized gateway can adjust to workload changes. This work addresses both software and hardware OpenFlow infrastructure platforms, and simulation results highlight the benefits that can be achieved by the presented mechanism.

The growing data traffic demand is forcing network operators to deploy more base stations, culminating in dense heterogeneous networks that require a high-connectivity backhaul. This scenario imposes significant challenges for current and future cellular networks, and Software Defined Networking (SDN) has been pointed as an enabling technology to overcome existing limitations. This paper shows how the OpenFlow protocol can be integrated into existing Long Term Evolution (LTE) networks to provide the required Quality of Service (QoS) in the network infrastructure. Three OpenFlow-based mechanisms are proposed: a traffic routing, an admission control function, and a traffic coexistence mechanism. Together, they can effectively control the bandwidth usage in the backhaul infrastructure, improving the QoS and ensuring a better user experience. Simulations were performed to validate the proposed mechanisms and highlight the benefits that can be achieved with the flexibility offered by the SDN technology.

Cluster-based distributed file systems generally have a single master to service clients and manage the namespace. Although simple and efficient, that design compromises availability, because the failure of the master takes the entire system down. Before version 2.0.0-alpha, the Hadoop Distributed File System (HDFS) -- an open-source storage, widely used by applications that operate over large datasets, such as MapReduce, and for which an uptime of 24x7 is becoming essential -- was an example of such systems. Given that scenario, this paper proposes a hot standby for the master of HDFS achieved by (i) extending the master's state replication performed by its check pointer helper, the Backup Node, and by (ii) introducing an automatic fail over mechanism. The step (i) took advantage of the message duplication technique developed by other high availability solution for HDFS named Avatar Nodes. The step (ii) employed another Hadoop software: ZooKeeper, a distributed coordination service. That approach resulted in small code changes, 1373 lines, not requiring external components to the Hadoop project. Thus, easing the maintenance and deployment of the file system. Compared to HDFS 0.21, tests showed that both in loads dominated by metadata operations or I/O operations, the reduction of data throughput is no more than 15% on average, and the time to switch the hot standby to active is less than 100 ms. Those results demonstrate the applicability of our solution to real systems. We also present related work on high availability for other file systems and HDFS, including the official solution, recently included in HDFS 2.0.0-alpha.

One way to implement fault tolerant applications is storing its current state in stable memory and, when a failure occurs, restart the application from the last global consistent state. If the number of simultaneous failures is expected to be small a diskless check pointing approach can be used, where a failed process's state can be determined only accessing non-faulty process's memory. In the literature diskless check pointing is usually based on synchronous protocols or properties of the application. In this paper we present a quasi-synchronous diskless check pointing algorithm, called RDT-Diskless, based on Rollback-Dependency Track ability. The proposed algorithm includes a garbage collection approach that limits the number of checkpoints that must be kept in memory. A framework, called Cheops, was developed and experimental results were obtained from a commercial cloud environment.

This article proposes an original approach that applies the rollback-dependency trackability (RDT) property to implement a new non-blocking synchronous checkpointing protocol, called RDT-NBS, that takes mutable checkpoints and efficiently supports concurrent initiators. Mutable checkpoints can be saved in non-stable storage and make it possible for non-blocking synchronous checkpointing protocols to save a minimal number of checkpoints in stable storage during the construction of a consistent global checkpoint. We prove that this minimality property does not hold in presence of concurrent checkpointing initiations. Even though, RDT-NBS uses mutable checkpoints to reduce the use of stable memory assuring the existence of a consistent global checkpoint in stable storage. We also present simulation results that compare RDT-NBS to quasi-synchronous RDT

Communication-induced checkpointing protocols that ensure rollback-dependency trackability (RDT) guarantee important properties to the recovery system without explicit coordination. However, there was no garbage collection algorithm for them which did not use some type of process synchronization, like time assumptions or reliable control message exchanges. This paper addresses the problem of garbage collection for RDT checkpointing protocols and presents an optimal solution for the case where coordination is done only by means of timestamps piggybacked in application messages. The algorithm uses the same timestamps as off-the-shelf RDT protocols and ensures the tight upper bound on the number of uncollected checkpoints for each process during all the system execution

A checkpointing protocol that enforces rollback-dependency trackability (RDT) during the progress of a distributed computation must induce processes to take forced checkpoints to avoid the formation of nontrackable rollback dependencies. A protocol based on the minimal characterization of RDT tests only the smallest set of nontrackable dependencies. The literature indicated that this approach would require the processes to maintain and propagate O(n/sup 2/) control information, where n is the number of processes in the computation. In this paper, we present a protocol that implements this approach using only O(n) control information.

Checkpoint and communication patterns that enforce rollback-dependency trackability (RDT) have only online trackable checkpoint dependencies and allow efficient solutions to the determination of consistent global checkpoints. Baldoni, Helary and Raynal (1998) have explored RDT at the message level, in which checkpoint dependencies are represented by zigzag paths. They have presented many characterizations of RDT and conjectured that a certain communication pattern characterizes the minimal set of zigzag paths that must be tested online by a checkpointing protocol in order to enforce RDT. The contributions of this work are: a proof that their conjecture is false; a minimal characterization of RDT; and introduction of an original approach to analyze RDT checkpointing protocols.

A checkpoint pattern is an abstraction of the computation performed by a distributed application. A progressive view of this abstraction is formed by a sequence of consistent global checkpoints that may have occurred in this order during the execution of the application. Considering pairs of checkpoints, we have determined that a checkpoint must be observed before another in a progressive view if the former Z-precedes the latter. Based on the Z-precedence and characteristics of the checkpoint pattern, we propose original algorithms for the progressive construction of consistent global checkpoints. We demonstrate that the Z-precedence between a pair of checkpoints is a much simpler way to express the existence of a zigzag path connecting them, and we discuss other advantages of our relation.