Mathematical Reviews

These are unprecedented times while the world weathers the highly infectious respiratory pandemic caused by coronavirus disease-19 (COVID-19). Humanity has experienced other cataclysmic events, but something as novel as this pandemic cannot be easily described. A safe COVID-19 vaccine is often hailed as the only effective public health method to prevent the further spread of this virus. New vaccines’ cost has increased even as policymakers struggle with limited resources and budget constraints. Thus, more decision-support tools are needed to facilitate the selection of vaccine manufacturers as part of a global immunization strategy against COVID-19 or other epidemics and pandemics. This study sought to address this issue by combining three well-established operational research methods (i.e., cognitive mapping, decision-making trial and evaluation laboratory, and the Choquet integral). Based on the insights provided by a panel of experts on vaccination and infectious diseases, a vaccine manufacturer selection mechanism was developed that incorporates the World Health Organization’s guidelines. This approach facilitated the identification of multiple selection criteria regarding vaccine manufacturers, their allocation into six major clusters (i.e., soundness of scientific approach and technology used; speed of delivery; cost; liability and risk sharing; ability to supply sufficient quantities through production capacity development; and global solidarity), and subsequent analysis of the respective cause-and-effect relationships. The results of a real-life application of the proposed selection system were further consolidated by a member of Saint Francisco Xavier Hospital Infectious Diseases Unit in Lisbon, Portugal. The mechanism’s advantages and limitations are also discussed.

Urban blight is often defined as abandoned or poorly maintained real estate properties, often with overgrowth, trash-filled yards and alleys, graffiti, and broken windows. It has a detrimental impact on neighborhood safety and reputation. Blight also creates low-value areas in urban centers, reduces property values and business investment, and increases unemployment. These effects make urban blight an issue of growing interest as the need to eradicate blighted properties has significantly increased worldwide. This study adopted a constructivist, socio-technical stance that combined cognitive mapping, moving averages, and the decision-making trial and evaluation laboratory method. This methodological approach facilitated the identification of prevention strategies that control urban blight occurrences and subsequent eradication subject to seasonal constraints. Based on real-world cases, data was collected directly from a panel of urban blight experts. The members analyzed different prevention initiatives in terms of five major dimensions—governance, community involvement, economic context, territorial planning, and operations—which were previously identified during the development of a collective causal map. Practical applications of the proposed decision-support system were analyzed and validated by two independent experts from the Direção Geral do Território (General Directorate of the Territory of Portugal). No prior research was found that has adopted the proposed methodology to address urban blight. Recommendations facilitating the development of prevention strategies to eradicate urban blight are also provided.

Presented methodology is on the spread of coronavirus infection dynamics using minimax criterion with the spline approximation. The study is based at authors mathematical method of approximation the dynamic series. The fundamental difference from classical problem of Chebyshev (1854) is the introduction of limiting conditions that allow joining splines in minimax optimality criterion mode. The approximation model is improved as a result of hierarchical procedure, at each stage of which new spline is attached. In the experiments used data on the spread of the coronavirus infection in Russia for period of more than a year with daily registration of cases of infection. So, quadratic approximation function is obtained with a negative coefficient at the highest degree of the variable, indicating a sharp decrease in the spread of coronavirus infection in Russia since mid-January 2021.

The concrete cracking is simulated by the finite element method combined with the constitutive model based on the nonlinear fracture mechanics. The model uncertainties for mean and maximum crack widths are found by comparing the simulated crack widths with data obtained by laboratory testing of 18 reinforced concrete beams. The reinforcement arrangement, dimensional simplification, and numerical discretisation effects on the model uncertainty are investigated. Two reinforcement types, i.e. steel and glass fibre-reinforced polymer bars, are considered. The shrinkage effect on the cracking predictions is included. The fracture energy parameter according to fib Model Code 2010 is used in the simulations. The numerical model offers an adequate prediction of crack widths for the beams with a single layer reinforcement and exhibits less accuracy for the multilayer bar arrangement. The presented numerical model represents an advanced tool for the crack width assessment in the design of reinforced concrete structures in serviceability limit states.

Herein, we deal with the propagation of surface plasmon polaritons at the interface of metal-free metamaterial with anisotropic inclusions. The anisotropy effect of conventional and well-known nanostructured metamaterial combined of alternating layers is enhanced by employing anisotropic semiconductor sheets into the structure. The former provides a fertile ground for a wide range of tunability features with no needs of changing the geometry of the structure. Moreover, the current approach stands for as a perfect tool aiming to control propagation length of surface plasmon polaritons.

We consider an initial-boundary value problem for the $n$-dimensional wave equation, $n\geq 2$, with the variable sound speed with the nonhomogeneous Dirichlet boundary conditions. We construct and study three-level in time and compact in space three-point in each spatial direction alternating direction implicit (ADI) schemes having the approximation orders $\mathcal{O}(h_t^2+|h|^4)$ and $\mathcal{O}(h_t^4+|h|^4)$ on the uniform rectangular mesh. The study includes stability bounds in the strong and weak energy norms, the discrete energy conservation law and the error bound of the order $\mathcal{O}(h_t^2+|h|^4)$ for the first scheme as well as a short justification of the approximation order $\mathcal{O}(h_t^4+|h|^4)$ for the second scheme. We also present results of numerical experiments.

PURPOSE - An increasingly urbanized global population is facing multiple, inter-related and inter-connected challenges. By applying the so-called Living Lab concept, the authors open up innovation processes through online and offline collaborations between urban policymakers, non-profit organizations, citizens and other stakeholder groups. However, much of the current research being conducted on Living Labs is lacking in empirically tested methodologies for the co-creation of sustainable urban innovations in defined contexts. This research is intended to fill this gap by presenting a systemic approach to digital co-creation processes in Living Labs. The purpose of this paper is to present the first evaluation results of European Living Labs by applying the new developed digital co-creation monitoring technique. DESIGN/METHOD/APPROACH - By emphasizing the interplay between places, technology and people, the Digital Co-Creation Index (DCCI) calculation methodology provides a systemic understanding of the basic factors shaping the co- creative processes in Living Labs. DCCI has been used to evaluate such labs in four different European cities: Aukštamiestis in Vilnius, Lithuania; Alvalade in Lisbon, Portugal; Città Studi in Milano, Italy and Zuid Park in Ghent, Belgium. The empirical data for assessment and index calculation were collected by using a mixed-method approach (i.e. qualitative and quantitative analysis). FINDINGS. While the findings are complex and varied, the case studies in this paper share several characteristics and patterns – the attractiveness of physical spaces, opportunities for experimentation, the density and diversity of stakeholders involved and the emergence of creative communities that co-design novel initiatives. The results show that digital technologies are underused in the evaluated Living Labs. RESERCH/LIMITATIONS/IMPLICATIONS. The results are limited to a comparison of the European Living Labs in the research sample. In the absence of an index that was obtained, designed and tested in other territorial contexts, the comparative value of the outcomes of this research can be established between only four case studies. The authors anticipate that the implementation of the C3Places project and other research activities will yield even more scientific results. The findings and their implications should be discussed and tested in the broadest context possible. By focusing on creative synergy between places, technology and people, this paper presents a unified and empirically validated systemic approach to assessing digital co-creation efforts in urban planning. ORIGINALITY/VALUE - Unlike previous research, this paper presents a unified and empirically based approach to assessing digital co-creation efforts in urban planning by emphasizing interplay between place, technology and people.

Considering the undeniable role of websites in the success of interactions between citizens and governments, evaluating e-government web sites is a worthwhile topic. This research has developed a multi-attribute-decision-making technique rely on Step-Wise Weight Assessment Ratio Analysis and hesitant fuzzy weighted geometric Heronian mean decision-making methods, for evaluating e-government websites. Proposed framework overcome the limitations of previous investigations such as the possibility of aggregation of expert opinions using group decision-making and modeling the hesitancy of the experts (due to the incompleteness of their knowledge or their doubts in evaluating different aspects of the model) through hesitant fuzzy sets. The designed framework was used in Iran to evaluate e-government websites. In this regard, after a careful and systematic review of previous researches, a list of dimensions and evaluation criteria was presented in the form of a comprehensive model. Then, an expert-based process was proposed to localize the model according to the conditions of the case study. The results of the research show that the final rankings of the decision-making method used in the hesitant environment rarely changed for different operators. So as the experts have confirmed, the model used in this study has acceptable stability.

A phenomenological model of CO oxidation with NO reaction proceeding over composite (supported) catalysts is proposed and solved numerically using the finite difference method. The model is based on the coupled system of PDEs subject to nonclassical conjugate conditions at the catalyst-support interface and includes: the bulk diffusion of reactants from a bounded vessel towards the catalyst surface and the bulk one of the reaction products from the surface into the same vessel, adsorption and desorption of particles of reactants, and surface diffusion of adsorbed molecules. The readsorption of the reaction product N2O is also taken into account. The influence of the rate constants of the adsorbed particle jumping via the catalyst-support interface and reaction rate constants on the surface reactivity is investigated. It is shown that the turnover rates of the CO and NO into products N2O, CO2, and N2 are nonmonotonic time functions and depending on values of the kinetic parameters may possess one or two maxima. The N2O readsorption in case of the existence of two maxima essentially increases the turnover rates and extends the duration of their high values. The mechanism and conditions for arising of the second maximum is discussed. It is also shown that the variation of the particle jumping rate constants influences differently the size of the jump discontinuity of concentrations of different adsorbates at the catalyst-support interface.

In this paper, we consider the online uniform machine scheduling problem on mprocessors when speed si=1 for i =k +1, ..., mand si=s, s >1, for i =1, ..., k. The objective is to minimize makespan. We propose a parametric scheme with the worst-case performance 2.618 when 1 1 when the ratio m/k tends to infinity.