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The main parameters characterizing the process of deformation of solids are displacements, strain and stress tensors. From the point of view of the strength and reliability of the structure and its elements, researchers and engineers are mainly interested in the distribution of stresses in the objects under study. Unfortunately, all boundary value problems are formulated and solved in solid mechanics mainly with respect to displacements, or an additional stress functions. And the required stresses are calculated from known displacements or stress functions. In this case, the accuracy of stress calculation is strongly affected by the error of numerical differentiation, as well as the approximation order of the boundary conditions. The formulation of boundary value problems directly with respect to stresses or strains allows to increase the accuracy of stress calculation by bypassing the process of numerical differentiation. Therefore, the present work is devoted to the formulation and numerical solution of boundary value problems directly with respect to stresses and strains. Using the well-known Beltrami-Miechell equation, and considering the equilibrium equation as ah additional boundary condition, a boundary value problem (BVP) is formulated directly with respect to stresses. In a similar way, using the strain compatibility condition, the Beltrami-Mitchell type equations for strains are written. The finite difference equations for two-dimensional BVP are constructed and written in convenient a form for the use of iterative method. A number of problems on the equilibrium of a rectangular plate under the action of various loads applied on opposite sides are numerically solved. The reliability of the results is ensured by comparing the numerical results of the 2D elasticity problems in stresses and strains, and with the exact solution, as well as with the known solutions of the plate tension problem under parabolic and uniformly distributed loads. [ABSTRACT FROM AUTHOR]

Recently, Opportunistic Networks (OppNets) are considered to be one of the most attractive developments of Mobile Ad Hoc Networks that have arisen thanks to the development of intelligent devices. OppNets are characterized by a rough and dynamic topology as well as unpredictable contacts and contact times. Data is forwarded and stored in intermediate nodes until the next opportunity occurs. Therefore, achieving a high delivery ratio in OppNets is a challenging issue. It is imperative that any routing protocol use network resources, as far as they are available, in order to achieve higher network performance. In this article, we introduce the Resource-Aware Routing (ReAR) protocol which dynamically controls the buffer usage with the aim of balancing the load in resource-constrained, stateless and non-social OppNets. The ReAR protocol invokes our recently introduced mutual informationbased weighting approach to estimate the impact of the buffer size on the network performance and ultimately to regulate the buffer consumption in real time. The proposed routing protocol is proofed conceptually and simulated using the Opportunistic Network Environment simulator. Experiments show that the ReAR protocol outperforms a set of well-known routing protocols such as EBR, Epidemic MaxProp, energy-aware Spray and Wait and energy-aware PRoPHETin terms of message delivery ratio and overhead ratio. [ABSTRACT FROM AUTHOR]

Abstract In this paper we present a new multi-resolution parallel framework, which is designed for large-scale SPH simulations of fluid dynamics. An adaptive rebalancing criterion and monitoring system is developed to integrate the CVP partitioning method as rebalancer to achieve dynamic load balancing of the system. A localized nested hierarchical data structure is developed in cooperation with a tailored parallel fast-neighbor-search algorithm to handle problems with arbitrarily adaptive smoothing-length and to construct ghost buffer particles in remote processors. The concept of "diffused graph" is proposed in this paper to improve the performance of the graph-based communication strategy. By utilizing the hybrid parallel model, the framework is able to exploit the full parallel potential of current state-of-the-art clusters based on Distributed Shared Memory (DSM) architectures. A range of gas dynamics benchmarks are investigated to demonstrate the capability of the framework and its unique characteristics. The performance is assessed in detail through intensive numerical experiments at various scales. [ABSTRACT FROM AUTHOR]

In this paper, we propose a parallel cellular automaton tumor growth model that includes load balancing of cells distribution among computational threads with the introduction of adjusting parameters. The obtained results show a fair reduction in execution time and improved speedup compared with the sequential tumor growth simulation program currently referenced in tumoral biology. The dynamic data structures of the model can be extended to address additional tumor growth characteristics such as angiogenesis and nutrient intake dependencies. [ABSTRACT FROM AUTHOR]

With the emergence of connected and autonomous vehicles, sensors are increasingly deployed within cars to support new functionalities. Traffic generated by these sensors congest traditional intra-car networks, such as CAN buses. Furthermore, the large amount of wires needed to connect sensors makes it harder to design cars in a modular way. To alleviate these limitations, we propose, simulate, and implement a hybrid wired/wireless architecture, in which each node is connected to either a wired interface or a wireless interface or both. Specifically, we propose a new protocol, called Hybrid-Backpressure Collection Protocol (Hybrid-BCP), to efficiently collect data from sensors in intra-car networks. Hybrid-BCP is backward-compatible with the CAN bus technology, and builds on the BCP protocol, designed for wireless sensor networks. We theoretically prove that an idealized version of Hybrid-BCP achieves optimal throughput. Our testbed implementation, based on CAN and ZigBee transceivers, demonstrates the load balancing and routing functionalities of Hybrid-BCP and its resilience to DoS attacks and wireless jamming attacks. We further provide simulation results, obtained with the ns-3 simulator and based on real intra-car RSSI traces, that compare between the performance of Hybrid-BCP and a tree-based data collection protocol. Notably, the simulations show that Hybrid-BCP outperforms the tree-based protocol on throughput by 12 percent. The results also show that Hybrid-BCP maintains high packet delivery rate and low packet delay for safety-critical sensors that are directly connected to the sink through wire. [ABSTRACT FROM AUTHOR]

In recent years, imbalanced utilization of medical resources is widely concerned within the tiered Chinese hospital system. Reverse referral, as a measure of promoting patient flows from upper level hospitals (ULHs) to lower level hospitals (LLHs), has demonstrated its advantages on alleviating ULH workload and balancing resource utilization between ULHs and LLHs. Nevertheless, it remains unclear on how to control the reverse referral decision process at the operational level. In this paper, we consider an ULH-dominant setting at which the LLH must accept patient referrals from the ULH whenever it has available beds. We focus our attention on an easy-to-implement threshold policy for the ULH to make the reverse referral decision. To investigate, we first formulate an analytically tractable queueing model for a simplified reverse referral process. We then investigate a more general patient flow control model, for which we analyze the patient population dynamics with a Markov chain process, and apply the concept of state-dependent Markovian arrival process to generate an infinitesimal generator of the system. We use RG factorization to compute the system performance measures. We next formulate a threshold optimization problem with the objective of maximizing the ULH profit. Simulation experiments are performed, which conclude that the threshold control policy is insensitive to the service time distribution. Finally, we report real-world inspired numerical studies, from which we generate insights into effective adjustment of the control threshold in response to the system parameters and discuss potential hindrance from the LLH incorrectly informing its real-time resource availability to the ULH. Our work is the first that applies systems engineering to the real-time reverse referral decision problem in China. It provides the novel perspective of resource balancing to patient flow control studies in the care transition management literature. Note to Practitioners—It is recognized, in almost all countries with insufficient health care delivery infrastructure, that the care coordination is a key strategy to improve the effectiveness, safety, and efficiency of the health care system. Through communicating/sharing knowledge, multiple care organizations work together to create a proactive care plan for the patients to meet their needs and preferences, especially dealing with transitions of care. With the promotion of population care management, practitioners throughout the world have increasingly acknowledged the importance of patient flow streamlining, resource alignment within each population, and linking to community care resources from acute care facilities. However, applying care coordination in everyday routines of a medical practice can be overwhelming, even when it is obvious that the changes will improve patient care and provide efficiency. In this paper, we investigate an easy-to-implement patient flow control policy in making reverse referral decisions for patients receiving postdischarge care. We expect to improve provider’s profit with improved operational management. Through our analyses, we want to stress the importance of applying systems engineering and mathematical modeling to study care coordination and interorganization patient flow control. We also want to advocate knowledge sharing and accountability establishment, as a well-functioned partnership between hospitals at different tiers may very much rely on them. [ABSTRACT FROM AUTHOR]

Abstract Numerical and experimental investigations of two highly skewed low-noise propellers with a slight alteration in the tip geometry are conducted in both wetted and cavitating flows. The performance of the propellers is measured in open water and inclined setups at different operating conditions and high speed video recordings are used to determine tip vortex cavitation inception behaviour. The numerical simulations are conducted by employing the Implicit Large Eddy Simulation on appropriate grid resolutions for tip vortex propagation, at least 32 cells per vortex diameter according to our previous studies. In order to investigate cavitation inception characteristics of the propellers, different inception prediction methods are employed and evaluated at different advance ratios. It is shown that in addition to the well-captured difference in e.g. the amount of cavitation, the simulations are capable of correctly predicting the small but crucial differences in flow features and cavitation inception characteristics of the two propeller designs. Numerical predictions of the cavitation inception charts are also compared successfully with the measured data where three different types of cavitation patterns are investigated in details. Supported by the experimental videos, the interaction between the tip vortex and trailing vortices and their impact on the pressure field and the cavitation inception are analyzed. It is shown that the numerical simulation can provide further details about the vortical flow structures, and their contributions to cavitation, and is a powerful tool in advanced propeller design stages. [ABSTRACT FROM AUTHOR]

Many fault-tolerant routing algorithms for Network-on-Chip (NoC) are developed to overcome faulty components and provide reliable transmission. However, few works have considered the traffic load around the faulty region. To solve this problem, this paper presents a Fault-Tolerant Odd-Even (FTOE) turn model and Load-Balancing Fault-Tolerant (LBFT) routing algorithm that do not use virtual channels for 2D mesh NoC. Applying FTOE rules and routing packets around faulty regions in advance, LBFT balances the traffic load around the faulty regions, and then, the fault-tolerant paths are shortened. From theory analysis, LBFT is proved to be deadlock and livelock free. Simulation results show that LBFT’s saturation throughput can be improved than related works by 5.38 and 14.23%, and the power consumption can be reduced than related works by 2 and 5%, respectively. [ABSTRACT FROM AUTHOR]

The recycled batteries can be assumed for the cost-effective grid energy storage (ES) applications, where the state of health (SOH) of recycled batteries are hard to make equal when reassembling them in one ES system. Therefore, when implementing the traditional state-of-charge balancing control methods, the batteries integrated into the same ES system will demonstrate the SOH deviation characteristics during the long-term operation due to the different degradation they suffered, which will reduce the mean time to repair, increase the maintenance duty, and shorten the life time of the ES system. Alternatively, this paper proposes an SOH balancing control method for the modular multilevel-converter-based battery energy storage system (MMC BESS) by fully using the unique modular configuration. The relationship among SOH, depth of discharge, and life cycles is analyzed in the theory, which builds the criteria for power distribution among battery packs in the MMC BESS. In addition, instead of estimating the specific SOH value, a relative SOH evaluation method is presented for easier practical implementation. And then, multiple control loops are designed for achieving the expected operational performance. MATLAB simulation and experimental results are presented to verify the proposed control method. [ABSTRACT FROM PUBLISHER]

Dynamic on-demand resource provisioning is one of the primary goals of the cloud computing task scheduling process. Task scheduling is a nondeterministic polynomial time (NP)-hard problem and is responsible for assigning tasks to virtual machines (VMs) in a way that increases the resource utilization and performance, reduces response time, and keeps the whole system balanced. In this paper, we present a static task scheduling method based on the particle swarm optimization (PSO) algorithm where the tasks are assumed to be non-preemptive and independent. We have improved the performance of the basic PSO method using a load-balancing technique. We have compared our proposed method with round robin (RR) task scheduling, improved PSO task scheduling and a load-balancing technique. The simulation results show that our method outperforms these algorithms by an increase of resource utilization of 22% and a decrease of makespan by 33%, compared with the basic PSO algorithm. The results illustrate that our proposed method converges to the near optimal solution faster than the basic PSO algorithm and is more efficacious with more tasks. [ABSTRACT FROM AUTHOR]

We introduce a high-performance simulation framework that permits the semi-independent, task-based solution of sets of partial differential equations, typically manifesting as updates to a collection of 'patches' in space-time. A hybrid MPI/OpenMP execution model is adopted, where work tasks are controlled by a rank-local 'dispatcher' which selects, from a set of tasks generally much larger than the number of physical cores (or hardware threads), tasks that are ready for updating. The definition of a task can vary, for example, with some solving the equations of ideal magnetohydrodynamics (MHD), others non-ideal MHD, radiative transfer, or particle motion, and yet others applying particle-in-cell (PIC) methods. Tasks do not have to be grid based, while tasks that are, may use either Cartesian or orthogonal curvilinear meshes. Patches may be stationary or moving. Mesh refinement can be static or dynamic. A feature of decisive importance for the overall performance of the framework is that time-steps are determined and applied locally; this allows potentially large reductions in the total number of updates required in cases when the signal speed varies greatly across the computational domain, and therefore a corresponding reduction in computing time. Another feature is a load balancing algorithm that operates 'locally' and aims to simultaneously minimize load and communication imbalance. The framework generally relies on already existing solvers, whose performance is augmented when run under the framework, due to more efficient cache usage, vectorization, local time-stepping, plus near-linear and, in principle, unlimited OpenMP and MPI scaling. [ABSTRACT FROM AUTHOR]

Without maintenance overhead make beaconless geographic routing protocol become an attractive routing scheme for wireless sensor networks (WSNs), however, without the knowledge of topology may result in high collision rate. In this paper, we firstly analyze the reason of CTS (Clear-To-Send) collision and classify it into Same-Slot collision and Distinct-Slot collision. Then, we proposed a novel routing protocol, Circular/Spherical Sector based Forwarding Area Division and Adaptive Forwarding Area Selection (FADS), which can avoid Distinct-Slot collision, reduce the probability of Same-Slot collision, and realize dynamic load balancing. 1) Forwarding area division ensures that every node within the same forwarding subarea is capable of hearing one another, thus avoiding Distinct-Slot collision. 2) Selecting forwarder from one of subarea decreases the number of contenders(candidates), hence the probability of Same-Slot collision is reduced. 3) Adaptive forwarding area selection dynamic channelizes the traffic to each subarea, thus realizing dynamic load balancing. Compared with related protocols, no matter in the 2D or 3D scenario, simulation results show the excellent performance of FADS in terms of packet delivery ratio, End-to-End latency, and energy consumption per packet, especially in dense networks and congested networks. [ABSTRACT FROM AUTHOR]

In many applications of Wireless Sensor Networks (WSNs), the network has a few mobile sinks in addition to a large number of static sensor nodes that gather information from their surrounding environment. The static sensor nodes in such applications use a location service to find the location of a mobile sink. Most of the proposed location services are useful in mobile ad hoc networks and are not efficient for WSNs. Furthermore, new protocols specifically designed for WSNs are not load balanced. Some sensor nodes relay more packets and deplete their energy quickly, hence reducing the network lifetime dramatically. In this paper, we propose a location service called Load Balanced Location Service (LBLS) for WSNs containing a few mobile sinks. LBLS selects four nodes in the network outline and only uses the location of these nodes. LBLS do not deplete the energy of specific nodes comparing to other mechanisms that forward location information messages toward selected nodes. We formally prove that in LBLS every sensor node can always locate any mobile node in the network. By using exhaustive simulation, we show that LBLS is a load balanced location service. Simulation results demonstrate the superiority of LBLS regarding the load balancing factor compared to most available related location services. [ABSTRACT FROM AUTHOR]

With the advancement in the science and technology, cloud computing has become a recent trend in environment with immense requirement of infrastructure and resources. Load balancing of cloud computing environments is an important matter of concern. The migration of the overloaded virtual machines (VMs) to the underloaded VM with optimized resource utilization is the effective way of the load balancing. In this paper, a new VM migration algorithm for the load balancing in the cloud is proposed. The migration algorithm proposed (EGSA-VMM) is based on exponential gravitational search algorithm which is the integration of gravitational search algorithm and exponential weighted moving average theory. In our approach, the migration is done based on the migration cost and QoS. The experimentation of proposed EGSA-based VM migration algorithm is compared with ACO and GSA. The simulation of experiments shows that the proposed EGSA-VMM algorithm achieves load balancing and reasonable resource utilization, which outperforms existing migration strategies in terms of number of VM migrations and number of SLA violations. [ABSTRACT FROM AUTHOR]

Wireless Multimedia Sensor Networks (WMSNs) are a particular instance of Wireless Sensor Networks that support the transmission of multimedia data such as video, image or sound. Those multimedia data should be delivered with a variety of predefined levels of Quality of Service swhich imposes the development of specific routing protocols. In this paper, we propose a new routing protocol based on clustering, that balances the number of nodes in clusters, called Equal Size Clusters to reduce Congestion in WMSNs. We seek to balance the number of members in each cluster in order to reduce intra-cluster congestion and reduce the number of congested cluster-heads. Therefore, we propose a novel metric called Maximum Cluster-heads Utilization Ratio (MCUR) that indicates the largest number of members assigned to a cluster-head to ensure a reliable transmission of multimedia data. Simulation results indicate that our proposed scheme outperforms other protocols proposed in the literature in terms of MCUR, number of cluster-heads and energy consumed. [ABSTRACT FROM AUTHOR]

Multipath transport faces a lot of challenges caused by path diversity, network dynamics, and service diversity. An effective end-to-end multipath transport control mechanism becomes essential to efficiently utilize multiple paths. On the base of the general framework of multipath transport system based on application-level relay proposed in our previous work, this paper presents a multipath transport control mechanism supporting various applications with different transmission requirements. We propose a multipath transport protocol suite, which is extensible and suitable for various applications, and a multipath transport control model in which an application-dependent splitting granularity named flow block is introduced. Two load distribution models are explored: the earliest idle path first load distribution for reliable data transmission to maximize the data throughput and the packet reordering-controlled load distribution for real-time data transmission to minimize the packet reordering thereby reducing end-to-end delay and packet loss rate of multipath transport. Simulation results show that the proposed models can effectively improve data throughput for applications with reliable transmission requirements and reduce the total packet loss rate of the destination for applications with real-time transmission requirements. [ABSTRACT FROM AUTHOR]

In high-performance computing, the application's workload must be evenly balanced among threads to deliver cutting-edge performance and scalability. In OpenMP, the load balancing problem arises when scheduling loop iterations to threads. In this context, several scheduling strategies have been proposed, but they do not take into account the input workload of the application and thus turn out to be suboptimal. In this work, we introduce a design methodology to propose, study, and assess the performance of workload-aware loop scheduling strategies. In this methodology, a genetic algorithm is employed to explore the state space solution of the problem itself and to guide the design of new loop scheduling strategies, and a simulator is used to evaluate their performance. As a proof of concept, we show how the proposed methodology was used to propose and study a new workload-aware loop scheduling strategy named smart round-robin (SRR). We implemented this strategy into GNU Compiler Collection's OpenMP runtime. We carry out several experiments to validate the simulator and to evaluate the performance of SRR. Our experimental results show that SRR may deliver up to 37.89 % and 14.10 % better performance than OpenMP's dynamic loop scheduling strategy in the simulated environment and in a real-world application kernel, respectively. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper proposes a new selection-based model for filtering nodes in heterogeneous distributed computing systems based on quality of services criteria and load balancing polices. The proposed model is composed of two levels; base and load balancing. The base level has three components: user set, enterprise service bus header and computing nodes set, communicating through net centric enterprise service bus. The load balancing level in turn is composed of two phases. The first phase selects the candidate computing nodes that satisfy the requirements of the submitted tasks. The second phase applies any of the imported load balancing policies for nominating a computing node from the list of candidate computing nodes to process submitted tasks. Moreover, a quality of service load balancing policy is proposed. This policy combines three key performance indicators in a single weighted normalized factor. The performance of the proposed model is evaluated and compared using suggested load balancing policy and other five similar load balancing policies through simulation. The results reveal that, the performance of proposed model using suggested load balancing policy outperforms that of the other studied policies in terms of average task response time, average computing node utilization, and load balancing level. [ABSTRACT FROM AUTHOR]

Mobility and limited energy resources of nodes are the most critical attributes of Mobile Ad hoc Networks (MANETs). The mobility of the nodes changes the network's topology in an unpredictable manner, which in turn, affects the stability of connected paths. In addition, it causes an excessive overhead traffic that leads to a higher energy consumption and degrades the performance of routing protocols. Therefore, a routing scheme in MANETs should comprise techniques that cope with challenges incurred by both the energy failures and node's mobility. In this paper, we proposed Multipath Battery and Mobility-Aware routing scheme (MBMA-OLSR) based on MP-OLSRv2. Specifically, the study exploits a Multi-Criteria Node Rank (MCNR) metric that comprises the residual battery energy and the speed of nodes. It aims to rank the stability of the links using a link assessment function and to select the most efficient and stable paths to the destination. Moreover, an Energy and Mobility Aware Multi-Point Relay (EMA-MPR) selection mechanism is introduced and utilized by the MBMA-OLSR to set the willingness of nodes to contribute as MPRs, for flooding topological information. We implemented the proposed scheme as an extension to the EXata network simulator. Benefits of the innovative scheme have been demonstrated and validated under various simulation scenarios based on different mobility parameters. The simulation results provided evidence of the effectiveness of our scheme, especially during the high mobility scenarios with heavy traffic load where it outperformed the conventional MP-OLSRv2 routing protocol in terms of QoS and energy related metrics. [ABSTRACT FROM AUTHOR]

In scientific computing, load balancing is a crucial step conditioning the performance of large-scale applications. In this case, an efficient decomposition of the workload to a number of processors is highly necessary. A common approach to solve this problem is to use graph representation and perform a graph partitioning in k -parts using the multilevel framework and the recursive bisection (RB) paradigm. However, in graph instances where fixed vertices are used to model additional constraints, RB often produces partitions of poor quality.In this paper, we investigate the difficulties of RB to handle fixed vertices and we compare its results with two different alternatives. The first one, called kgggp is a direct k -way greedy graph growing partitioning that properly handles fixed vertices while the second one, introduced in kPaToH , uses RB and a post-processing technique to correct the obtained partition. Finally, experimental results on graphs that represent real-life numerical simulations show that both alternative methods provide improved partitions compared to RB. [ABSTRACT FROM AUTHOR]

The Long-Term Evolution (LTE) supports peak data rates, higher bandwidth, reduced costs, improved coverage and capacity, integration and backward compatibility with the existing systems. These features are part of LTE-A release. One key feature is carrier aggregation. It refers to aggregation of existing component carriers to provide higher spectrum bandwidth. This supports deployment bandwidth of a maximum 100 MHz and would help to maintain high user data speed of 500 Mbps uplink and 1 Gbps downlink. Bandwidth is very limited and expensive. But by using carrier aggregation, we are depending on existing bandwidth and hence efficiently using it. This paper provides an overview of types, compatibility and simulation results of carrier aggregation for different carriers (Aleksandar et al., 2011). [ABSTRACT FROM AUTHOR]

Device-to-device communication can assist cellular networks by making certain users equipment (UEs) work as relays between the base station (BS) and other users. In this paper, we present the ultra-dense network (UDN) with D2D relays instead of small cells, where UEs can form into clusters according to the traffic demand in hot-spot areas. Each UE requires to decide whether to connect to the BS, or to get associated with one of the D2D relays, a.k.a. cluster heads (CHs). To optimize the downlink system performance, we propose a game-theoretic user association scheme in the UDN with D2D relays, specifically focused on load balancing among the BS and CHs. The dynamic user association is formulated as a hedonic coalition game where we adopt a simplified but efficient measurement of the utility and select the effective game players in a smaller number. In the game, we estimate the number of users associated with each CH at the Nash-stable state which can indicate the overall expected load condition, and an admission control mechanism is finally employed on the basis of these values. Simulation results show that the UDN adopting the D2D relay technology can achieve a higher system rate than the traditional cellular network, and the proposed user association scheme outperforms the existing schemes while having a small computational complexity. [ABSTRACT FROM AUTHOR]

Simulation and analysis have shown that selective search can reduce the cost of large-scale distributed information retrieval. By partitioning the collection into small topical shards, and then using a resource ranking algorithm to choose a subset of shards to search for each query, fewer postings are evaluated. In this paper we extend the study of selective search into new areas using a fine-grained simulation, examining the difference in efficiency when term-based and sample-based resource selection algorithms are used; measuring the effect of two policies for assigning index shards to machines; and exploring the benefits of index-spreading and mirroring as the number of deployed machines is varied. Results obtained for two large datasets and four large query logs confirm that selective search is significantly more efficient than conventional distributed search architectures and can handle higher query rates. Furthermore, we demonstrate that selective search can be tuned to avoid bottlenecks, and thus maximize usage of the underlying computer hardware. [ABSTRACT FROM AUTHOR]

To meet the ever-growing traffic demand and address the cell capacity shortage problem, associating end users to various tiers of cells in a multitier cellular network appears to be a promising approach. In this paper, we consider a nonuniform heterogeneous cellular network (NuHCN) and propose a cell association scheme that selectively mutes certain small-cell base stations (BSs) and covers end users by cell range extension (via cell biasing) for achieving load balancing. The envisaged NuHCN is comprised of two tiers of BSs, i.e., macro- and small-cell BSs, deployed according to three independent homogeneous Poisson point processes for BSs and end users, respectively. Accordingly, the available space is divided into two subspaces. In the inner subspace, the end users are associated only with a macrocell BS based on the unbiased maximum received power scheme since the small-cell BSs therein are deactivated. In the outer subspace, where the macrocell BS coverage is comparatively poor, the end users are associated with either a macrocell BS or a microcell BS based on the biased/unbiased maximum received power scheme. Cell range extension-based cell association allows the macrocell users in the outer subspace to efficiently utilize the resources of the lightly loaded small-cell BSs, resulting in improved network coverage and capacity. Based on the proposed cell association scheme, we analyze the signal-to-interference plus noise ratio (SINR) distribution and deduce expressions for coverage probability and rate coverage. Numerical results show that, contrary to the uniform case, biasing has distinct effects on the coverage and rate performance of an NuHCN. [ABSTRACT FROM AUTHOR]

This paper is about partitioning in parallel and distributed simulation. That means decomposing the simulation model into a number of components and to properly allocate them on the execution units. An adaptive solution based on self-clustering, that considers both communication reduction and computational load-balancing, is proposed. The implementation of the proposed mechanism is tested using a simulation model that is challenging both in terms of structure and dynamicity. Various configurations of the simulation model and the execution environment have been considered. The obtained performance results are analyzed using a reference cost model. The results demonstrate that the proposed approach is promising and that it can reduce the simulation execution time in both parallel and distributed architectures. [ABSTRACT FROM AUTHOR]

HLA-based simulation systems are prone to load imbalances due to lack management of shared resources in distributed environments. Such imbalances lead these simulations to exhibit performance loss in terms of execution time. As a result, many dynamic load balancing systems have been introduced to manage distributed load. These systems use specific methods, depending on load or application characteristics, to perform the required balancing. Load prediction is a technique that has been used extensively to enhance load redistribution heuristics towards preventing load imbalances. In this paper, several efficient Time Series model variants are presented and used to enhance prediction precision for large-scale distributed simulation-based systems. These variants are proposed to extend and correct the issues originating from the implementation of Holt’s model for time series in the predictive module of a dynamic load balancing system for HLA-based distributed simulations. A set of migration decision-making techniques is also proposed to enable a prediction-based load balancing system to be independent of any prediction model, promoting a more modular construction. [ABSTRACT FROM PUBLISHER]

Purpose The purpose of this paper is to present a methodology for parallel simulation that employs the discrete element method (DEM) and improves the cache performance using Hilbert space filling curves (HSFC).Design/methodology/approach The methodology is well suited for large-scale engineering simulations and considers modelling restrictions due to memory limitations related to the problem size. An algorithm based on mapping indexes, which does not use excessive additional memory, is adopted to enable the contact search procedure for highly scattered domains. The parallel solution strategy uses the recursive coordinate bisection method in the dynamical load balancing procedure. The proposed memory access control aims to improve the data locality of a dynamic set of particles. The numerical simulations presented here contain up to 7.8 millions of particles, considering a visco-elastic model of contact and a rolling friction assumption.Findings A real landslide is adopted as reference to evaluate the numerical approach. Three-dimensional simulations are compared in terms of the deposition pattern of the Shum Wan Road landslide. The results show that the methodology permits the simulation of models with a good control of load balancing and memory access. The improvement in cache performance significantly reduces the processing time for large-scale models.Originality/value The proposed approach allows the application of DEM in several practical engineering problems of large scale. It also introduces the use of HSFC in the optimization of memory access for DEM simulations. [ABSTRACT FROM AUTHOR]

Although the IEEE 802.11 wireless local area network (WLAN) provides users of mobile device a convenient method to connect to the Internet, the load of access points (APs) may have a strong impact on the performance of a WLAN, such as the congestion problem. To avoid this issue and to maximize the performance and scalability of a WLAN, an effective method for balancing the load of APs, called a modified multiple-search multi-start framework based micro-genetic algorithm, is presented in this paper. Simulation results show that the proposed algorithm gives a much better solution than the original genetic algorithm does in terms of both the quality and the computation time. [ABSTRACT FROM AUTHOR]

This article gives an outline of the progress of work on the Study of UWB (University of West Bohemia) test bench for partly-suspended and fully suspended variants of individual wheelset traction drives. First, a survey of existing designs of roller test benches was conducted. Its outcomes supported the idea of designing a completely new device. The main part of the article is devoted to the design of the test bench. Furthermore, the article briefly summarizes the progress and especially the partial results of the work on the task Computer simulation for optimization of the structural arrangement of the traction drive, which focuses on the development of a mathematical model of the aforementioned test bench. [ABSTRACT FROM AUTHOR]

Futuristic wireless networks are being proposed to promote a significant improvement in performance, mainly in highly dense scenarios. However, cost constraints are also a key concern for the next generation of wireless networks. In this context, Low-cost Wireless Backhauls (LWBs) can provide relevant contributions. LWBs are based on WLAN technologies, such as Wireless Mesh Networks, in which gateways to the wired networks are potential bottlenecks, and load balancing is critical for performance. In spite of several proposals to deal with load balancing, they fail to combine three key aspects: (1) stability, (2) reduction of the average path length, and (3) throughput fairness. Our proposal addresses these aspects by adopting a joint approach for routing and channel assignment. The routing part is composed of a heuristic that employs an on-demand local solution in which load balancing is combined with the three aforementioned key aspects. We have carried out an in-depth simulation study in ns-3 to assess the impact of our proposal on traffic performance when compared with the state of the art. Our proposal is superior in most of the scenarios, in particular in terms of stability and average path length. Our proposal also increases the aggregate throughput and minimum throughput per flow in the network, especially when the number of flows is large. [ABSTRACT FROM AUTHOR]

In this work we propose a two-layer Savage–Hutter type model that is the natural extension of the 1D system proposed by E. D. Fernández-Nieto et al in 2008 to simulate tsunamis generated by landslides. We describe a single GPU and a multi-GPU implementation of this model using MPI and the CUDA framework over structured meshes. The distributed implementation is tested for several artificial and realistic problems using up to 24 GPUs. We also propose a static and a dynamic load balancing algorithm in order to deal with the unbalanced computational load due to different amount of wet and dry areas among the subdomains. The validity of the model is tested by simulating the tsunami occurred in Lituya Bay, Alaska, in 1958. Numerical experiments show the efficiency of the multi-GPU solver, the usefulness of the load balancing algorithms and the validity of the model to simulate real tsunamis generated by landslides. [ABSTRACT FROM AUTHOR]

Many algorithms can uniformly distribute data to storage nodes in a storage system. However, it cannot avoid load imbalance because data has different popularity. To resolve this issue, we propose a novel dynamic replication scheme, namely, Active Replica Management (ARM). ARM actively establishes optimal number of copies for hotspot data according to data access behaviors and then efficiently distributes copies to other storage nodes based on current amount of copies related to hotspot data. To improve storage utilization, ARM automatically and gradually dereplicates the useless copies of hotspot data when they become nonhotspot data. ARM resolves load imbalance by allocating dynamic copies to adequate storage nodes, and hence it can prevent partial storage nodes from overburdening. Simulation results demonstrate that ARM is an efficient scheme with excellent performance on load balancing, significantly closer to Optimal Load Balancing (OLB). In addition, ARM’s performance outperforms both Static Load Balancing (SLB) and No Replica schemes. [ABSTRACT FROM AUTHOR]

Simulating binary black hole (BBH) systems are a computationally intensive problem and it can lead to great scientific discovery. How to explore more parallelism to take advantage of the large number of computing resources of modern supercomputers is the key to achieve high performance for BBH simulations. In this paper, we propose a scalable MPM (Mesh based Parallel Method) which can explore both the inter- and intramesh level parallelism to improve the performance of BBH simulation. At the same time, we also leverage GPU to accelerate the performance. Different kinds of performance tests are conducted on Blue Waters. Compared with the existing method, our MPM can improve the performance from 5x speedup (compared with the normalized speed of 32 MPI processes) to 8x speedup. For the GPU accelerated version, our MPM can improve the performance from 12x speedup to 28x speedup. Experimental results also show that when only enough CPU computing resource or limited GPU computing resource is available, our MPM can employ two special scheduling mechanisms to achieve better performance. Furthermore, our scalable GPU acceleration MPM can achieve almost ideal weak scaling up to 2048 GPU computing nodes which enables our software to handle even larger BBH simulations efficiently. [ABSTRACT FROM AUTHOR]

Fusion edge plasmas can be far from thermal equilibrium and require the use of a non-linear collision operator for accurate numerical simulations. In this article, the non-linear single-species Fokker–Planck–Landau collision operator developed by Yoon and Chang (2014) [9] is generalized to include multiple particle species. The finite volume discretization used in this work naturally yields exact conservation of mass, momentum, and energy. The implementation of this new non-linear Fokker–Planck–Landau operator in the gyrokinetic particle-in-cell codes XGC1 and XGCa is described and results of a verification study are discussed. Finally, the numerical techniques that make our non-linear collision operator viable on high-performance computing systems are described, including specialized load balancing algorithms and nested OpenMP parallelization. The collision operator's good weak and strong scaling behavior are shown. [ABSTRACT FROM AUTHOR]

As the offshore wind energy production units move to deeper waters the design of their foundations demand more creative and complex approaches especially for large turbines (i.e. ∼5–7 MW). In this article, a novel piled foundation alternative with closely spaced double piles at the edges of the jacket is studied for various pile spacing and lengths. A numerical parametric study was carried out to understand the effects of pile spacing and pile length on the behavior of the novel supporting system under monotonic combined loading in very dense sand. Prior to the analysis, the numerical model is validated in field tests with single-pile and double-pile configurations. The contribution of closely spaced double piles to the overall foundation response and load distribution among the piles were investigated. The response of the foundation was evaluated considering the horizontal load-head displacement, moment-head rotation, and initial stiffness of the soil-pile system. It is found that the response of the recommended foundation system is superior to that of a rather conventional system with single piles at the edges. The results indicate that the piles on the tension loading side evidently carried lower loads than those on the compression side. Moreover, the disposition of the piles is more important on the tension side, as the trailing piles carried considerably lower loads than the leading piles. It is found that the double pile system with a pile embedment length L / 2 and a pile spacing of S = 5 D , 6 D provides better response, where L is the embedded pile length of conventional system and D is the diameter of pile. [ABSTRACT FROM AUTHOR]

The Parallel Unstructured Mesh Infrastructure (PUMI) is designed to support the representation of, and operations on, unstructured meshes as needed for the execution of mesh-based simulations on massively parallel computers. In PUMI, the mesh representation is complete in the sense of being able to provide any adjacency of mesh entities of multiple topologies in O(1) time, and fully distributed to support relationships of mesh entities across multiple memory spaces in a manner consistent with supporting massively parallel simulation workflows. PUMI's mesh maintains links to the high-level model definition in terms of a model topology as produced by CAD systems, and is specifically designed to efficiently support evolving meshes as required for mesh generation and adaptation. To support the needs of parallel unstructured mesh simulations, PUMI also supports a specific set of services such as the migration of mesh entities between parts while maintaining the mesh adjacencies, maintaining read-only mesh entity copies from neighboring parts (ghosting), repartitioning parts as the mesh evolves, and dynamic mesh load balancing. Here we present the overall design, software structures, example programs, and performance results. The effectiveness of PUMI is demonstrated by its applications to massively parallel adaptive simulation workflows. [ABSTRACT FROM AUTHOR]

An equation of Monge–Ampère type has, for the first time, been solved numerically on the surface of the sphere in order to generate optimally transported (OT) meshes, equidistributed with respect to a monitor function. Optimal transport generates meshes that keep the same connectivity as the original mesh, making them suitable for r-adaptive simulations, in which the equations of motion can be solved in a moving frame of reference in order to avoid mapping the solution between old and new meshes and to avoid load balancing problems on parallel computers. The semi-implicit solution of the Monge–Ampère type equation involves a new linearisation of the Hessian term, and exponential maps are used to map from old to new meshes on the sphere. The determinant of the Hessian is evaluated as the change in volume between old and new mesh cells, rather than using numerical approximations to the gradients. OT meshes are generated to compare with centroidal Voronoi tessellations on the sphere and are found to have advantages and disadvantages; OT equidistribution is more accurate, the number of iterations to convergence is independent of the mesh size, face skewness is reduced and the connectivity does not change. However anisotropy is higher and the OT meshes are non-orthogonal. It is shown that optimal transport on the sphere leads to meshes that do not tangle. However, tangling can be introduced by numerical errors in calculating the gradient of the mesh potential. Methods for alleviating this problem are explored. Finally, OT meshes are generated using observed precipitation as a monitor function, in order to demonstrate the potential power of the technique. [ABSTRACT FROM AUTHOR]

In the modern society, most networked critical infrastructures are coupled together and can be modeled as interconnected networks. Cascading failures caused by overload in interconnected networks are extremely complicated and still lack of corresponding researches. It is crucial to explore a systematic design and load management method for complex interconnected network. In this paper, a probabilistic heterogeneous capacity allocation model and a preventive load redistribution model are firstly proposed. Based on the novel models failure cascades in interconnected networks are studied in detail. Numerical simulations and analysis results show that robustness of interconnected network depends on the network topology, capacity allocation pattern and load management strategy. The novel models have guiding significance for the design and optimal management of robust interconnected infrastructure networks. [ABSTRACT FROM AUTHOR]

Wireless Sensor Networks (WSNs) consist of hundreds or thousands of sensor nodes connected to each other through short-distance wireless links. Because sensor nodes are energy-constrained, efficient energy use is a critical issue for WSNs. In WSNs, the energy of popular nodes may be quickly depleted when a large number of sensor nodes are interested in the same popular events, and they are frequently queried. This paper proposes a data replication scheme called adjustable data replication (ADR), which is based on a virtual grid in order to improve the lifetime of data nodes. In each grid, a head node is selected as a manager, and is responsible for receiving or transmitting packets from or to other nodes in the same virtual grid. The head nodes around data nodes or replica nodes will compute the number of requested packets in order to determine how best to build a replica node in an appropriate location. ADR repeatedly builds data replica nodes close to query nodes in order to balance the overhead and energy consumption of sensor nodes. Simulation results show that the proposed ADR scheme outperforms existing approaches. [ABSTRACT FROM AUTHOR]

Parallel download protocols that establish multiple TCP connections to distributed replica servers have the potential to reduce file download times and to achieve server-side load balancing. Unfortunately, parallel download protocols are inherently unfair towards single-flow downloads and may even starve them. This paper presents a fairness-aware parallel download protocol that allows the dynamic mitigation of throughput and fairness in distributed networks. The key novelty is a receiver-based framework that allows a dynamic adjustment of the congestion and rate control of each subconnection. The proposed Fairness-aware Control Coordinator (FCC) adjusts the priority of the subconnection between the TCP-fair rate (high priority) and the TCP-LP fair rate (low priority) according to the dynamics on the network without adding to the unfairness towards other downloads. Simulation results show the flexibility of the proposed protocol in balancing performance and fairness. [ABSTRACT FROM AUTHOR]

Flexible loads are important resources to help maintain the power balance of smart grid. However, the control center is not able to exactly sense and control them because of their large quantity and wide distribution. In order to get the flexible loads to participate in the dynamic power system look-ahead scheduling, this paper proposes a three-layer ‘centralized coordination, distributed control’ structure in which the load agents are introduced to perform the coordination based on the consensus control. Then, the optimal control strategy of the control center and the consensus control strategy of the load agents are designed. With the communication among different flexible loads, the distributed cooperative control is implemented. At last, the efficiency of the proposed mode and strategies is proven through the simulation carried out under the standard IEEE 9-bus system, and the effect of topology and communication is also analyzed. [ABSTRACT FROM AUTHOR]

Software-defined networking (SDN) is currently seen as one of the most promising future network technologies, which can realize the separation between control and data planes. Furthermore, the increasing complexity in future wireless networks (i.e., 5G, wireless sensor networks) renders the control and coordination of networks a challenging task. Future wireless networks need good separation of control and data planes and call for SDN method to handle the explosive increase of mobile data traffic. Relying on a single controller in future wireless networks imposes a potential scalability problem. To tackle this problem, the thought of using multiple controllers to manage the large wide-area wireless network has been proposed, where the load balance problem of multicontroller needs to be resolved. In this paper, we propose a multicontroller load balancing approach called HybridFlow in software-defined wireless networks, which adopts the method of distribution and centralization and designs a double threshold approach to evenly allocate the load. Simulation results reveal that the proposed approach can significantly relieve the working load on the super controller and reduces the load jitter of multicontroller load in a single cluster compared with the BalanceFlow method. [ABSTRACT FROM AUTHOR]

A routing aggregation (RA) is proposed for load balancing network-on-chip (NoC). The computing nodes with dense traffic and long distance in network are gathered into the same routing node to form a super router. A load balancing routing algorithm for super router is presented to improve the overall performance of NoC. A simulation platform using System C is presented to confirm the feasibility of the proposed design in 2D mesh. The simulation results show that the proposed RA design can reduce the average packet latency and the standard deviation of host link utilization 8% and 33%, respectively compared with the reported routing methods. The area cost and power consumption compared with the reported schemes are 22% and 12% less, respectively. [ABSTRACT FROM AUTHOR]

As a typical distributed network computing environment, cloud computing has been growing tremendously recently. Although it could provide a convenient environment for the execution of data-intensive application, the primary challenge for it is how to choose the security date replica for data-intensive application from different storage resources. Considering that the security has the characteristic of fuzziness and randomness, it is quantified using the cloud model in this paper. On this basis, taking the constraints of time, cost, and security into account, a scheduling algorithm of data-intensive application based on weighted set covering problem (WSCP) is proposed. Simulation results demonstrate that the security-aware data replica selection strategy performs better than traditional selection strategy on time, cost, security utility value and load balancing deviation (LBD). [ABSTRACT FROM AUTHOR]

When significant communication costs arise in the solution of multidimensional problems on parallel computers, optimal performance cannot always be achieved by perfectly balancing the computational load across cores. Modest sacrifices in the computational load balance may facilitate substantial overall performance improvements by achieving large savings in the costs associated with communications. This general approach is illustrated by application to GS2, an initial value gyrokinetic simulation code developed to study low-frequency turbulence in magnetized plasma. GS2 is parallelised using MPI with the simulation domain decomposed across tasks. The optimal domain decomposition is non-trivial, and is complicated by the fact that several domain decompositions are needed and that these do not all optimise at the chosen task count. Application to GS2, of the novel approach outlined in this paper, has improved performance by up to $17$ percent for a representative simulation. Similar strategies may be beneficial in a broader class of problems. [ABSTRACT FROM PUBLISHER]

Distributed Virtual Environment (DVE) is a shared application consisting many objects, which can be accessed by many users. There have been many methods used to scale the DVE such as dividing simulation workload, dynamic load balancing among servers, and creating alternative architectures. However, they may not accommodate many objects and users. In this paper, we explore all approaches used to scale the DVE and then determine the characteristics of the existing approaches. With those characteristics, we compared existing approaches based on three parameters: the number of simulation per region, implementation, and the number of objects managed by simulator. The results show that all approaches use the same viewpoint, called present viewpoint, in developing the DVE. It views DVE as a world where all objects and activities are managed by a simulator. The results also show that this viewpoint contributes in terms of limitations of the current DVEs performance. In response to these results, we further propose a new viewpoint, called object-based viewpoint, to generate object-based simulators architecture. The experiment results show that our proposed architecture can provide a large scale DVE with better performances than the previous architectures. [ABSTRACT FROM AUTHOR]

Boyer-Moore (BM) algorithm is a single pattern string matching algorithm. It is considered as the most efficient string matching algorithm and used in many applications. The algorithm first calculates two string shift rules based on the given pattern string in the preprocessing phase. Using the two shift rules, pattern matching operations are performed against the target input string in the second phase. The string shift rules calculated in the first phase let parts of the target input string be skipped where there are no matches to be found in the second phase. The second phase is a time consuming process and needs to be parallelized in order to realize the high performance string matching. In this paper, we parallelize the BM algorithm on the latest many-core accelerators such as the Intel Xeon Phi and the Nvidia Tesla K20 GPU along with the general-purpose multi-core microprocessors. For the parallel string matching, the target input data is partitioned amongst multiple threads. Data lying on the threads' boundaries is searched redundantly so that the pattern string lying on the boundary between two neighboring threads cannot be missed. The redundant data search overheads increases significantly for a large number of threads. For a fixed target input length, the number of possible matches decreases as the pattern length increases. Furthermore, the positions of the pattern string are spread all over the target data randomly. This leads to the unbalanced workload distribution among threads. We employ the dynamic scheduling and the multithreading techniques to deal with the load balancing issue. We also use the algorithmic cascading technique to maximize the benefit of the multithreading and to reduce the overheads associated with the redundant data search between neighboring threads. Our parallel implementation leads to $$\sim $$ 17-times speedup on the Xeon Phi and $$\sim $$ 47-times speedup on the Nvidia Tesla K20 GPU compared with a serial implementation on the host Intel Xeon processor. [ABSTRACT FROM AUTHOR]