Effective Load Distribution Research Articles

A new step toward load balancing based on competency rank and transitional phases in Grid networks

Grid computing is a network of software–hardware capabilities. It serves as a comprehensive and complete system for organizations by which the maximum utilization from resources is achieved. Resource distribution in a heterogeneous and unstable environment and also effective load distribution among these resources are the important and difficult problems in Grid networks. Using dynamic and static algorithms or searching tree and Branch and Bound algorithm are considered to be among the available methods to reach the load balancing in Grid networks. This paper presents a new method for dynamic load balancing. In this method, we use the subtraction of forward and backward ants as a competency rank to take the priority of the sites, and we use a control word to search the suitable resource as well. Our main purpose is to devote jobs to the existing resources based on their processing power. Simulation results show that the proposed method can reduce the total completion time and also total tardiness to get the load balancing. The cost of using resources as an effective factor in load balancing is also observed.

The influence of synthetic jet excitation on secondary flow in compressor cascade

The detailed numerical simulation has been carried out to investigate the effect of synthetic jet excitation on the secondary flow at 5° incidence in a compressor cascade, in which the synthetic jet actuation is equipped on the suction surface. The influence of excitation position, one fixed near the trailing edge and the other fixed a little far from the trailing edge, has also been studied. The results show that unsteady disturbance of desirable synthetic jet effectively enhances the mixing of the fluid inside the separation region, which reduces the vortex intensity and the energy loss, improves the flow status in the cascade, and also suppresses velocity fluctuation near the trailing edge. Additionally, the actuation fixed near the separation region proves to be more effective and exit load distribution is more uniform due to the employment of the synthetic jet.

A dynamic management scheme for DVEs

Advances in computer technology and networking infrastructures in combination with advanced applications and services, have expanded the adoption of distributed virtual environments and promoted their use in a wide range of areas, such as learning and training, collaborative work, military applications and multiplayer online games. The characteristics and requirements of such DVEs differ significantly given the diverse objectives, scope and context that each virtual world aims at supporting. However, one common characteristic of DVEs is their dynamic state with users entering and leaving the system randomly, resulting in changes of the requirements for the DVE system. These changes require effective load distribution and management of the communication cost so that consistency is always maintained. This paper presents a dynamic management approach for DVEs driven by the diversity of different applications’ characteristics and requirements. This approach exploits the dynamic nature of these systems for selecting and assigning, on an on-demand basis, the resources necessary for the efficient operation of the system. The experiments conducted to validate the behavior of the approach illustrate that it can significantly minimize communication cost among the system servers together with effective workload distribution.

Task cluster scheduling in a grid system

Effective load distribution and resource management is of great importance in designing complex distributed systems as grid. This pre-assumes the capability of partitioning the arriving jobs into independent tasks that can be executed simultaneously, assigning the tasks to processors and scheduling the task execution on each processor. A simulation model, consisting of two homogeneous clusters, is considered to evaluate the performance for various workloads. The Deferred policy is applied to collect global system information about processor queues. This paper proposes a special scheduling method referred to as task clustering method. We examine the efficiency of two task routing policies – one static and one adaptive – and six task scheduling policies, which rearrange processor queues regarding to a criterion. Our simulation results indicate that the adaptive task routing policy in conjunction with SGFS-ST scheduling algorithm, which uses more efficiently the task clustering method, leads to a significant performance improvement.

Communication cost effective scheduling policies of nonclairvoyant jobs with load balancing in a grid

Effective load distribution is of great importance at grids, which are complex heterogeneous distributed systems. In this paper we study site allocation scheduling of nonclairvoyant jobs in a 2-level heterogeneous grid architecture. Three scheduling policies at grid level which utilize site load information are examined. The aim is the reduction of site load information traffic, while at the same time mean response time of jobs and fairness in utilization between the heterogeneous sites are of great interest. A simulation model is used to evaluate performance under various conditions. Simulation results show that considerable decrement in site load information traffic and utilization fairness can be achieved at the expense of a slight increase in response time.

Resource discovery and request-redirection for dynamic load sharing in multi-provider peering content delivery networks

A constellation of Content Delivery Networks (CDNs), termed as peering CDNs, endeavors to guarantee adequate delivery performance when the incoming request load is overwhelming for a single provider alone. Each user is served by an optimal Web server in terms of network cost, even under heavy load conditions. Before it could be comprehended, appropriate resource discovery and request-redirection mechanisms, coupled with an optimal server selection strategy, should be in place to perform the distribution of highly skewed loads. In this paper, we devise an effective load distribution strategy by adopting distributed resource discovery and dynamic request-redirection mechanisms, taking traffic load and network proximity into account. The load distribution strategy reacts to overload conditions, at a time instance, in any primary CDN server(s) and instantly distributes loads to the target servers, minimizing network cost and observing practical constraints. In this context, we exercise an asynchronous resource discovery protocol, reminiscent of the public/subscribe notion, and formulate the resulting redirection scheme. Extensive simulation analyses demonstrate the novelty of our approach. In particular, we show that our approach is effective to handle high load skews by preserving locality, and thus achieve service “responsiveness”. We also perform a sensitivity analysis to reveal that our redirection scheme outperforms other alternatives to handle peak loads.

On fractional approach to assessment of material resistance to cavitation

Insufficient compatibility of cavitation resistance assessments based on laboratory tests conducted under different cavitation conditions is generally considered a major methodological difficulty whenever quantitative prediction of material performance under field conditions is attempted. The present paper reports a substantial progress made recently by the authors in their efforts to develop the procedure of cavitation erosion resistance assessment yielding compatible results even in case of experimental tests having been conducted at rigs of different design and principle of operation. The approach developed assumes that the material resistance to cavitation may be described satisfactorily by its response to individual fractions of cavitation pulses amplitude distribution. The backbone of the approach is a differential superposition law, which allows modelling erosion progress under polyfractional cavitation load by keeping continuous control over erosive process inputs contributed by individual fractions of cavitation pulses distribution. The model developed allows determining reference material resistance to individual load fractions basing on laboratory tests conducted under several specified cavitation conditions, determining the effective load distribution at an arbitrary rig basing on erosion tests of a set of reference materials and predicting the structural material performance in the field, provided the load distribution has been previously established. The general concept of the approach was already presented during the ICEAW conferences in 1999 and 2003. Now, numerical codes and some preliminary results are also available. Further progress requires enhancing experimental technique of cavitation pulses measurement under laboratory conditions. An action plan aimed at full validation of the method and its implementation into laboratory practice is presented in the end of the paper.

Wind loading and its effects on single-layer reticulated cylindrical shells

In this paper, the wind load distribution as well as its effects on single-layer reticulated cylindrical shells, which are widely used in practice, is investigated. At first, wind pressure distributions on three rigid cylindrical shell models considering different shape ratios are measured simultaneously in a wind tunnel. Some special characteristics of the measured wind pressure, especially its fluctuating component, are discussed. Then, considering the special structural mechanical behaviors, the effects of wind load, especially the fluctuating component, on the limit load-carrying capacity and the stability of the shells are investigated by both equivalent static analysis and dynamic analysis. Suitable methods to get a reasonable estimation of wind load effects in estimating the equivalent static wind load distribution for such shells are investigated. Finally, with comparison analyses using different methods mentioned in this paper, the efficiency of the method in estimating the effective wind load distribution presented by the authors previously for single-layer reticulated spherical shells is demonstrated, and some advices for estimating the wind load distribution on single-layer reticulated cylindrical shells is given for wind-resistant design in practice.

Effective static load distributions in wind engineering

In this paper, the derivations of expressions for effective static wind load distributions, for all possible combinations of mean, background and resonant response, are given. The paper considers structures for which the response to wind can be considered to be quasi-static, and also those for which resonant response is either significant or dominant.

Effect of Column Parameters on FRP-Confined Concrete

Confinement effectiveness of fiber reinforced plastic (FRP) jackets (shells) in concrete columns depends on several parameters, including concrete strength, types of fibers and resin, fiber volume and fiber orientation in the jacket, jacket thickness, shape of cross section, length-to-diameter (slenderness) ratio of the column, and the interface bond between the core and the jacket. In this paper effects of shape, length, and bond on FRP-confined concrete are studied. Square sections are shown to be less effective in confining concrete than their circular counterparts. Their effectiveness is measured by a modified confinement ratio that is a function of the corner radius and the jacket's hoop strength. Length effect in short columns of up to 5:1 is shown to be similar to ACI provisions for tied columns, i.e., 10% eccentricity and 20% strength reduction in pure compression. While chemical adhesive bond does not change the confinement effectiveness of the jacket, mechanical shear connectors can enhance the load-carrying capacity of the column by providing an effective load distribution mechanism.

Along wind response of lattice towers—III. Effective load distributions

The analysis of the along-wind dynamic response of free-standing lattice towers in Parts I and II, is continued in this paper. Effective static load distributions for the mean, background fluctuating, and resonant components of the load effects are derived. As in Parts I and II, the results are all given in a ‘closed form’. An approximation to the background load distribution that is independent of the influence coefficient (load effect) is given. Finally the distributions are evaluated for a representative tower.