Making concentrated solar power competitive with coal: The costs of a European feed-in tariff

The European Union has yet to determine how exactly to reach its greenhouse gas emissions targets for the future. One potential answer involves large-scale development of concentrated solar power (CSP) in the North African region, transmitting the power to Europe. CSP is a relatively young and little utilized technology and is expensive when compared to other methods of generation. Feasibility studies have shown it is possible to generate enough power from CSP plants in Africa to spearhead the EUs climate goals. However, the costs of such a project are less well known. Currently, CSP must compete with low cost coal-fired electricity plants, severely hindering development. We examine the possible investment costs required for North African CSP levelized electricity cost to equal those of coal-fired plants and the potential subsidy costs needed to encourage growth until the technologies reach price parity. We also examine the sensitivity of investment and subsidies to changes in key factors. We find that estimates of subsidy amounts are reasonable for the EU and that sensitivity to such factors as perceived risk and learning rates would enable policy-makers to positively influence the cost of subsidies and time required for CSP to be competitive with coal.     

An analysis framework for applying virtual environment technology to manufacturing tasks

An empirical approach for improving the applicability of a virtual environment (VE) technology to manufacturing tasks is presented and discussed by considering the technological and economical perspectives. The three‐step analysis framework, which consists of evaluating overall feasibility, assessing potential benefits, and conducting cost/benefits analysis, was developed to support researchers in choosing an appropriate VE method and in designing a cost‐effective VE application. The usefulness and limitation of the framework were reviewed with a case study in which VE technology was used to improve the performance of dimensional inspection tasks as a means of providing the initial validation of the analysis framework. © 2002 Wiley Periodicals, Inc.     

Empirical models based on free-modulus magnitude estimation of perceived presence in virtual environments

A series of 3 studies was conducted to test free-modulus magnitude estimation as a measure of perceived presence in virtual environments (VEs) and to model the first- and second-order effects of 11 VE system parameters on perceived presence across 5 subtasks. Sequential experimentation techniques were used to build 4 empirical models using polynomial regression. An integrated empirical model of data combined across 2 experiments demonstrated that all significant factors had a positive effect on perceived presence. Three of these parameters--field of view, sound, and head tracking--had almost 3 times as much influence on presence than the other 4 significant parameters, which were visual display resolution, texture mapping, stereopsis, and scene update rate. Sequential experimentation was an efficient tool for building empirical models of perceived presence, but the subjective nature of this phenomenon and individual differences made data bridging across sequential studies problematic. It was concluded that magnitude estimation is a useful measure of perceived presence, and the resulting polynomial regression models can be used to facilitate VE system design decisions. This research has broad application in the selection and design of VE system components and overall design of VE systems.     

An application of augmented reality to thickness inspection

An experiment was conducted to evaluate the use of augmented reality (AR) for thickness inspection of manufactured parts. The inspection task consisted of determining the thickness of flat-bottomed parts via measurements, taken at predetermined locations and in a specified sequence, using a vernier height gage. Inspectors wore a head-mounted AR display, which superimposed information over the surface of the part indicating where measurements were to be taken and in what sequence. Experiments were performed to compare the AR-aided inspection method to traditional computer-aided and manual inspection methods. Results indicated that while all three methods were similar in terms of accuracy, AR-aided inspection was 2–3 times faster than the other methods. Additionally, while inspection time increased with part shape complexity for the manual and computer-aided methods, it was virtually unaffected by part shape complexity for AR-aided inspection. These results indicate the potential use of augmented reality to improve the performance of manual inspection tasks substantially when task-specific information must be conveyed to the operator. © 1999 John Wiley & Sons, Inc.     

Data bases of accommodative aids for computer users with disabilities

Computers offer an almost limitless range of opportunities for persons with nearly any type and degree of disability. Standard computer configurations, however, can be difficult to access for users with disabilities. Six of the major data bases that describe adaptive computer hardware and software for users with disabilities are reviewed. The most appropriate data base to use depends not only on the type of aid desired but also on the means of access available to the individual, the frequency of use of the data base, and the price of the data base information. None of the data bases reviewed contains the detailed information needed when choosing devices compatible with the user's physical skills and task needs. Consequently, a less-than-systematic approach is currently taken when choosing accommodative aids. An integrated approach combining a capability assessment, a comprehensive needs analysis based on the tasks to be performed, a more detailed data base describing hardware and software, and usability testing is recommended for selecting the appropriate accommodative aid for computer users with disabilities.     

The effects of multitasking on quality inspection in advanced manufacturing systems

Although the industrial quality inspection task has been extensively studied, the effect of multitasking on the performance of the operator in a hybrid inspection system is still unknown. The experiment described in this article compared the quality inspection performance for participants performing a single task, 3 multiple tasks, and 5 multiple tasks. The results of this research indicate that the performance of the operator in the quality inspection task while multitasking in an advanced manufacturing system will be determined by the interaction between the number of different types of defects that can be presented at the same time in the inspected parts and multitasking. The best performance will be obtained when the load created by additional tasks minimizes the monotony of the quality inspection task without interfering with the processing resources needed for the memorized quality criteria. © 2001 John Wiley & Sons, Inc.