Adopting Tolerance Regions in Environmental Economics

Uncertainty often lies when there is limited knowledge about the process one has to follow regarding the investigation of a real-world problem. In practice, uncertainty is related with the assumed estimation model of the physical problem, and mainly concerns the involved parameters. A typical examplecan be an Environmental Economics system. There are many model specifications that estimate the so-called Benefit Area of such system. For the evaluation of the optimal level of pollution, we can adopt the corresponding tolerance region, and hence we can refer to this optimal level via future observations rather than some parameters estimation. Tolerance regions can be either classical or expected tolerance regions. The associated (four) Benefit Areas can be evaluated through a proposed tolerance region procedure, and not through the usual confidence interval/region approach. Therefore, four possible optimal levels of pollution can be obtained, as well as the corresponding tolerance region for the reduction pollution point.

Power Allocation Optimization Design for the Quadrichromatic LED Based VLC Systems with Illumination Control

For requiring high communication rate and high-quality illumination, multi-color light-emitting diodes (LEDs) have been utilized in visible light communication (VLC) systems and attracted substantial research interests. It should be noted that multiple colors are not independent from each other since they are jointly limited by the chromaticity constraint. Thus, taking full consideration of the multi-color crosstalk problem and actual communication and illumination constraints, this paper formulates a power-efficient illumination control optimization design to reduce power consumption for the quadrichromatic LED (QLED) based VLC systems where signal to interference plus noise ratio (SINR) and quadrangle chromaticity tolerance region constraints should be satisfied. Simulation results illustrate that our proposed optimal power allocation strategy can significantly increase power efficiency for the VLC system compared with the uniform power allocation method. Moreover, the proposed scheme can provide optimal performance under different given correlated color temperature (CCT) values.

Estimating Non-Conformance Using the Modified Tolerance Region Method and the Target Distance Method

In many cases, the quality of a manufactured product is determined by more than one characteristic and often, these quality characteristics are correlated. A number of methods for dealing with quality evaluation of multivariate processes have been proposed in the literature. However, some of these studies do not consider correlation among quality characteristics. In this paper, two new approaches for estimating the proportion of non-conformance for correlated multivariate quality characteristics with nominal specifications are proposed: (i) the modified tolerance region approach and (ii) the target distance approach. In the first approach, the p number of correlated variables are analysed based on the projected shadow of the p-dimensional hyper ellipsoid so that the ability to visualise the tolerance region and the process region for is preserved. In the second approach, the correlated variables are combined and a new variable called the target distance is introduced. The proportion of non-conformance results estimated using both methods were used to compute the multivariate capability index and the total expected quality cost. This study also suggest modification to the NMCp index as proposed in Pan and Lee (2010) such that the process capability for can be measured correctly. The application of both approaches is demonstrated using two examples and it is shown that both methods i.e. the modified tolerance region and the target distance methods are capable of estimating the capability of multivariate processes.