An intervaltype-2 fuzzy set (IT2FS) contains the infinite number of embedded membership functions (MFs) defined as type-1 fuzzy sets. The center of gravity (COG) of an IT2FS is obtained by integrating the centroids o...
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An intervaltype-2 fuzzy set (IT2FS) contains the infinite number of embedded membership functions (MFs) defined as type-1 fuzzy sets. The center of gravity (COG) of an IT2FS is obtained by integrating the centroids of all these MFs. However, obtaining the COG of an IT2FS in a continuous domain is impossible because the number of embedded MFs is infinite and, in a discrete domain, comes with exponential time complexity. Therefore, different algorithms were proposed to find the center of centroids (COCs) instead of the COG. These algorithms do not necessarily obtain the exact value of COC;they compete to find a more accurate result in less time. In this study, we propose a simple noniterative method to obtain the COG of IT2FSs. This method only considers the MFs which form the boundary values, that is, the lower MF (LMF) and upper MF (UMF), and obtains their centroids separately. We show that the COG of an IT2FS is equal to the weighted sum of the centroids of its LMF and UMF if the relative areas of LMF and UMF are considered their corresponding weights. We call this method the Indirect COG (ICOG) method because it indirectly obtains the COG of an IT2FS. This method finds the accurate COG of an IT2FS by considering only two MFs instead of infinite MFs. It can also obtain the accurate COG of an uncommon polygonal IT2FS schematically. We use numerical examples to illustrate that the ICOG obtains the accurate COG of an IT2FS very fast in a nonexponential time. We also develop a new triangular intervaltype-2 fuzzyanalytical hierarchyprocess that uses the ICOG method to accurately defuzzify the IT2 fuzzy weights.
Selecting a rational distributed energy generation (DEG) project portfolio is the key to achieving the strategic objectives of energy enterprises. The complexity associated with the selection of DEG project portfolio ...
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Selecting a rational distributed energy generation (DEG) project portfolio is the key to achieving the strategic objectives of energy enterprises. The complexity associated with the selection of DEG project portfolio comes from uncertainties in decision-making environment, interactions between projects, and necessary alignment with the strategic objectives of enterprises. However, previous researches did not address the three issues simultaneously. To fill such gap, this study establishes a multi-criteria decision-making framework to select the optimal DEG project portfolio(s) under different strategic scenarios, where uncertainty and project interaction are considered. The framework consists of two stages. In the first phase, the weights of criteria are determined by the interval type-2 fuzzy analytic hierarchy process technique, and the strategic alignment indexes of each candidate distributed energy generation project are obtained using the intervaltype-2 fuzzy weighted averaging operator. In the second stage, considering the strategic interactions, a nonlinear 0-1 programming is formulated while satisfying the budget constraints, and the non-dominated sorting genetic algorithm-II is utilized to obtain the optimal portfolio of DEG projects under different strategic scenarios. The proposed framework is applied in a case study to illustrate its suitability and effectiveness. The results show that the selected portfolios vary with the strategic objectives of enterprises. This research has practical applied value for project managers in project portfolio management.
The purpose of this study is to assess the performance of wind power coupling hydrogen storage projects from the perspective of sustainability. Firstly, an evaluation criteria system for sustainability performance ass...
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The purpose of this study is to assess the performance of wind power coupling hydrogen storage projects from the perspective of sustainability. Firstly, an evaluation criteria system for sustainability performance assessment is established, which includes economic, environmental and social aspects. Then, the criteria performances of each alternative are determined by expert groups in the fields of energy economy, energy environment and society sciences. Later, considering the uncertainty in the decision-making, the interval type-2 fuzzy analytic hierarchy process and the intervaltype-2 fuzzy Technique for Order Preference by Similarity to an Ideal Solution technique are employed to weight the criteria and sort the alternatives, respectively. Finally, a case study in Tibet autonomous, China is given to illustrate the effective of the proposed evaluation criteria and technique. The result shows the alternatives A4 gets the highest score. Moreover, the results of sensitivity analysis reveal that the alternative A4 always secures its top ranking when its weight is floating within a certain range. Meanwhile, the weight results show that the criteria of levelized cost of energy and poverty alleviation promotion should gain more attention. This research can offer references for investors to make investment decisions and for the government to make corresponding policies. (C) 2019 Elsevier Ltd. All rights reserved.
This paper presents an integrated model based on intervaltype-2 fuzzy reasoning approach and interval type-2 fuzzy analytic hierarchy process for assessment of air quality in urban areas. In the proposed model, inter...
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This paper presents an integrated model based on intervaltype-2 fuzzy reasoning approach and interval type-2 fuzzy analytic hierarchy process for assessment of air quality in urban areas. In the proposed model, intervaltype-2 fuzzy reasoning approach is employed to determine impacts of different air pollutants to describe complex relationship between air pollutants and air quality index by considering individual weights of different air pollutants through the aggregation of toxicological impacts and concentration level of different air pollutants using interval type-2 fuzzy analytic hierarchy process. The proposed approach is advantageous over its counterparts to model the inter-personal and intra-personal uncertainties involved in classification of air quality index. Finally, the developed air quality assessment model is applied on the historical data set collected from ambient air quality monitoring stations operating near by the Victoria memorial, in Kolkata Metropolitan area. The study shows that the air quality index increased significantly during the festive season due to extensive fireworks in those areas.
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