			Home About us Contact

Cost Index (cost + index)

Distribution by Scientific Domains

Engineering	60%

Selected Abstracts

LMI approach to reliable guaranteed cost control with multiple criteria constraints: The actuator faults case

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 8 2009
Dengfeng Zhang
Abstract Based on the multi-objective optimization strategy and linear matrix inequality approach, the problem of reliable guaranteed cost control with multiple criteria constraints is investigated for a class of uncertain discrete-time systems subject to actuator faults. A fault model in actuators, which considers outage or partial degradation in independent actuators, is adopted. The quadratic stability is proved to be independent of the disturbance and the upper bound of a quadratic cost index is improved. The reliable feedback controller is designed to minimize the upper bound of the quadratic cost index, place all the closed-loop poles in a specified disk, constrain the H, norm level of the disturbance attenuation into a given range and guarantee the magnitudes of control inputs less than the given bound, as well. Thus, the resulting closed-loop system can provide satisfactory stability, transient behavior, disturbance rejection level and optimized upper bound of the quadratic cost performance despite possible actuator faults. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Walking on an Uneven Surface: The Effect of Common Peroneal Stimulation on Gait Parameters and Relationship Between Perceived and Measured Benefits in a Sample of Participants With a Drop-Foot

NEUROMODULATION, Issue 1 2007
Jane H. Burridge PhD
ABSTRACT Objectives., To examine the effect of using a common peroneal stimulator on an even and an uneven surface, and to compare measures with perceived response to stimulation. Method., Participants had a drop-foot caused by a stroke (N = 13) or multiple sclerosis (N = 7) and had used a common peroneal stimulator for > 3 months prior to the study. Walking speed and physiological cost index (PCI) were recorded under four conditions: with and without stimulation over an even and an uneven surface. Participants also completed a questionnaire. Results., A statistically significant increase in walking speed and decrease in PCI was identified when the stimulator was used. There was a trend to greater improvement on the uneven compared to the even surface. A correlation between perceived benefit of stimulation and a measured decrease in PCI was detected. Conclusion., Stimulation may be particularly beneficial for the more difficult task of walking on an uneven surface. Perceived benefit was related to a reduction in effort of walking, not in increased speed. [source]

STEERING A MOBILE ROBOT: SELECTION OF A VELOCITY PROFILE SATISFYING DYNAMICAL CONSTRAINTS

ASIAN JOURNAL OF CONTROL, Issue 4 2000
M.A. Benayad
ABSTRACT We present an open loop control design allowing to steer a wheeled mobile robot along a prespecified smooth geometric path, minimizing a given cost index and satisfying a set of dynamical constraints. Using the concept of "differential flatness," the problem is equivalent to the selection of the optimal time parametrization of the geometric path. This parametrization is characterized by a differential equation involving a function of the curvilinear coordinate along the path. For the minimum time problem, as well as for another index (such as the maximum value of the centripetal acceleration) to be minimized over a given time interval, the problem then reduces to the optimal choice of this function of the curvilinear coordinate. Using spline functions interpolation, the problem can be recast as a finite parameter optimization problem. Numerical simulation results illustrate the procedure. [source]

A Decision Support System Specification for Cost Escalation in Heavy Engineering Industry

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2002
Nashwan N. Dawood
The heavy civil engineering industry (railways, sewage-treatment, chemical and pharmaceutical facilities, oil and gas facilities, etc.) is one of the major contributors to the British economy and generally involves a high level of investment. Clients in this industry are demanding accurate cost estimates, proper analysis of out-turn cost and cost escalation, and a high quality risk analysis throughout the construction processes. Current practices in the industry have suggested that there is a lack of structured methodologies and systematic cost escalation approaches to achieve an appropriate cost analysis at the outset of projects and throughout the construction processes. In this context the prime objective of this research work is to develop a structured cost escalation methodology for improving estimating management and control in the heavy engineering industry construction processes. The methodology is composed of a forecasting model to predict cost indices of major items in industry and a risk knowledge-base model for identifying and quantifying causes of cost escalations. This paper reviews and discusses a knowledge-based model for applying a cost escalation factor. The cost escalation factor is made up of market variation, a risk element, and a component for bias. A knowledge elicitation strategy was employed to obtain the required knowledge for the model. The strategy included questionnaires, interviews, and workshops, and deliverables came in the form of influences and their effect on project cost escalation. From these deliverables, a decision support system and specifications for applying cost escalation to base estimates are presented. [source]

Patterns and Determinants of International Trade Costs in the Food Industry

JOURNAL OF AGRICULTURAL ECONOMICS, Issue 2 2009
Alessandro Olper
F1; F13; F14 Abstract This paper documents patterns in international trade costs in processed foods for a large cross-section of developing and developed countries, during the 1976,2000 period. A trade costs index is inferred from a micro-founded gravity equation that incorporates bilateral ,iceberg' trade costs. For 2000, the trade costs, expressed as weighted average tariff equivalent, range from 73% for the north to 134% for the south countries. The time patterns show an average reduction of about 13% in the observed period that rises to 26% for the emerging countries. However, the same does not occur for south countries. On ranking the trade costs determinants, we find that, on average, geographical and historical factors seem to dominate those of infrastructure and institutions. However, trade policy emerges as an important determinant of the trade costs between north and emerging countries. [source]