The present work proposes a computer-aided methodology
sustainable supply chains in terms of sustainability metrics by utilizing
the P-graph framework. The methodology is an outcome of the collaboration
between the Office of Research and Development (ORD) of the U.S. EPA
and the research group led by the creators of the P-graph framework
at the University of Pannonia. The integration of supply chain design
and sustainability is the main focus of this collaboration. The P-graph
framework provides a mathematically rigorous procedure for synthesizing
optimal and alternative suboptimal networks subject to multiple objectives
and constraints, which include profitability and sustainability in
the proposed methodology. Specifically, to evaluate the sustainability
of a given process under construction including its supply chain,
sustainability metrics are incorporated into the design procedure.
The proposed methodology is demonstrated with the optimal design of
a supply chain for providing heat and electric power to an agricultural
region with relatively limited land area where agricultural wastes
can potentially be recovered as renewable resources. The objective
functions for optimization comprise the profit and the ecological
footprint. The results of the study indicate that, compared to using
electricity from the grid and/or natural gas, using renewable energy
resources can yield substantial cost reductions of up to 5%, as well
as significant ecological footprint reductions of up to 77%. It may,
therefore, be possible to design more sustainable supply chains that
are both cost-effective and less environmentally damaging.
Public sector bodies are increasingly relying on the Internet. On this channel, indispensable information is transmitted to the public and a wide range of services is already available. Therefore, the usability, accessibility, and the security of these websites are very important. Accessibility is particularly crucial for persons with disabilities. The accessibility of public service websites is regulated by a number of laws; among others, the directive "on the accessibility of the websites and mobile applications of public sector bodies" adopted by the European Parliament in 2016. This obliges all European Union member states to make all public sector websites and mobile applications accessible by 23 September 2021. In practice, this means that websites must fulfil the level AA recommendations in WCAG 2.1. In our study, a website assessment method is developed by comparing different analytical tools. With this method, we analysed how Hungarian websites of public sector bodies fulfil the requirements of the directive. We have also investigated how well they comply with usability and security guidelines. The results showed that none of the 25 websites of the examined Hungarian public sector bodies could completely fulfil the recommendations of the Web Content Accessibility Guidelines (WCAG) and that half of the websites had only the lowest level of compliance in usability tests. From the security point of view, almost half of the websites use outdated server versions and programming language, which is very critical. We have proposed several suggestions to address the major problems, so website developers and administrators can improve the accessibility, usability, and security aspects of these websites.
The P-graph framework introduced by Friedler et al. (Chem Eng Sci. 1992;47:1973-1988) is a general mathematical methodology based on Graph Theory which is applicable to many process design problems. We propose an extension of the P-graph framework and the associated MILP model to account for operating units and systems where the inputs and outputs are variable. This is important because the P-graph framework in its current form would otherwise apply only to systems where the ratios of inputs to outputs are fixed. Consequently, it is difficult to apply the method to many emerging systems without the new mathematical model presented here. We discuss and develop the model in detail, and we then illustrate its application with the case study of an energy system. We establish a structure with optimal cost for a baseline heat demand, and we further explore how the energy system structure and the feedstocks change as the heat demand increases.
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