A taxonomy of market‐based resource management systems for utility‐driven cluster computing

In utility‐driven cluster computing, cluster Resource Management Systems (RMSs) need to know the specific needs of different users in order to allocate resources according to their needs. This in turn is vital to achieve service‐oriented Grid computing that harnesses resources distributed worldwide based on users' objectives. Recently, numerous market‐based RMSs have been proposed to make use of real‐world market concepts and behavior to assign resources to users for various computing platforms. The aim of this paper is to develop a taxonomy that characterizes and classifies how market‐based RMSs can support utility‐driven cluster computing in practice. The taxonomy is then mapped to existing market‐based RMSs designed for both cluster and other computing platforms to survey current research developments and identify outstanding issues. Copyright © 2006 John Wiley & Sons, Ltd.     

Integrated Optimization of Control System for Smart Cylindrical Shells Using Modified GA

In this paper, modeling of the vibration of cylindrical shell components of space structures incorporating piezoelectric sensor/actuators (S/As) for optimal vibration control is proposed and formulated. The parameters of the control system, which include the placement and sizing of the piezoelectric S/As and the feedback control gains, were considered as design variables and optimized simultaneously. The effect of the amount of piezoelectric patches was investigated as well. The criterion based on the maximization of energy dissipation was employed for the optimization of the control system. A modified real-encoded genetic algorithm (GA) dealing with various constraints has been developed and applied to search for the optimal placement and size of the piezoelectric patches as well as the optimal feedback control gains. The results of three numerical examples, which include a simply supported plate, a simply supported cylindrical shell, and a clamped-simply supported plate, demonstrated significant vibration suppression based on the optimal design of the control system. It was also found that for specific controlled vibration modes, the optimal distribution of the piezoelectric S/As should be located at the areas separated by the nodal lines to achieve the optimal control effect. This finding would be useful for the practical design of smart structures.     

Tensile Strength Characteristics of Unsaturated Sands

Tensile strength characteristics of unsaturated sands are examined through a combined theoretical and experimental study. The characteristics of tensile strength in all three water retention regimes of pendular, funicular, and capillary are examined. A simple direct tensile strength apparatus is employed to determine tensile strength for sands with a broad range of particle sizes from silty sand to fine sand and medium sand over a full range of degree of saturation. Tensile strength characteristic curves (TSCC) are established experimentally for these sands and are used to validate the existing theories for tensile strength in the pendular regime. The TSCC for sand characteristically exhibits two zeros at 0 and near 100% saturation, and two peak values occurring in the pendular and capillary regimes, respectively. A minimum tensile strength is observed in the dense fine sand, indicating that either water bridges or pore pressure contributes exclusively to the tensile strength in the funicular regime of this sand. The maximum tensile strength for the silty sand is 1,448?Pa, the fine sand is 1,416?Pa, and the medium sand is 890?Pa. Comparison between the soil–water characteristic curves obtained for these sands indicates that the peak tensile strength in the capillary regime is highly correlated to the air-entry pressure. Photographs of the failure surfaces clearly delineate distinct geometric characteristics for different water retention regimes. Analysis of the patterns of failure surfaces in different water retention regimes indicates that the effective stress principle is valid for tensile stress failure in unsaturated sands.     

Hybrid Genetic Programming with Local Search Operators for Dynamic Force Identification

In this paper, based on the Darwinian and Lamarckian evolution theories, three hybrid genetic programming (GP) algorithms integrated with different local search operators (LSOs) are implemented to improve the search efficiency of the standard GP. These three LSOs are the genetic algorithm, the linear bisection search, and the Hooke and Jeeves method. A simple encoding method is presented to encode the GP individuals into the expressions that can be recognized by the different LSOs. The implemented hybrid GP algorithms are applied to identify the excitation force acting on the structures from the measured structural response, which is an important type of inverse problem in structural dynamics. Illustrative examples of a frame structure and a multistory building structure demonstrate that, compared with the standard GP, the hybrid GP algorithms have higher search efficiency which can be used as alternate global search and optimization tools for other engineering problem solving.     

New results in robust actuator fault reconstruction for linear uncertain systems using sliding mode observers

This paper presents a robust actuator fault reconstruction scheme for linear uncertain systems using sliding mode observers. In existing work, fault reconstruction via sliding mode observers is limited to either linear certain systems subject to unknown inputs, relative degree one systems or a specific class of relative degree two systems. This paper presents a new method that is applicable to a wider class of systems with relative degree higher than one, and can also be used for systems with more unknown inputs than outputs. The method uses two sliding mode observers in cascade. Signals from the first observer are processed and used to drive the second observer. Overall, this results in actuator fault reconstruction being feasible for a wider class of systems than using existing methods. A simulation example verifies the claims made in this paper. Copyright © 2007 John Wiley & Sons, Ltd.     

High Sensitivity,Wearable, Piezoresistive Pressure Sensors Based on Irregular Microhump Structures and Its Applications in Body Motion Sensing

A pressure sensor based on irregular microhump patterns has been proposed and developed. The devices show high sensitivity and broad operating pressure regime while comparing with regular micropattern devices. Finite element analysis (FEA) is utilized to confirm the sensing mechanism and predict the performance of the pressure sensor based on the microhump structures. Silicon carbide sandpaper is employed as the mold to develop polydimethylsiloxane (PDMS) microhump patterns with various sizes. The active layer of the piezoresistive pressure sensor is developed by spin coating PEDOT:PSS on top of the patterned PDMS. The devices show an averaged sensitivity as high as 851 kPa^?1, broad operating pressure range (20 kPa), low operating power (100 nW), and fast response speed (6.7 kHz). Owing to their flexible properties, the devices are applied to human body motion sensing and radial artery pulse. These flexible high sensitivity devices show great potential in the next generation of smart sensors for robotics, real‐time health monitoring, and biomedical applications.