Introduction: December 2019 marked the beginning of the outbreak of the coronavirus, a disease that began in China and the city of Wuhan, the capital of Hubei Province, and soon spread rapidly, involving individuals and health organizations. Finally, on March 11, the head of the World Health Organization identified coronavirus as a pandemic disease, and the world entered a new phase in the fight against the disease. In this article, we are going to discuss the changes in health behaviors, demographic and economic changes.

The explicitly RESTARTed Arnoldi method (ERAM) can be used to  nd some eigenvalues of large and sparse matri-ces. However, it has been shown that even this method may fail to converge. In this paper, we present two new methods to accelerate the convergence of ERAM algo-rithm. In these methods, we apply two strategies for the updated initial vector in each RESTART cycles. The implementation of the methods have been tested by nu-merical examples. The results show that we can obtain a good acceleration of the convergence compared to orig-inal ERAM.

In this paper the problem of optimal multiple-burn injection of a satellite into geostationary orbit using an upper stage with a limited thrust and RESTART CAPABILITY, and comparison with sub-optimal case is considered. The goal is finding thrust vector angle, times of the engine firings and optimal duration of active phases of the upper stage so as to minimize fuel consumption and to meet the desired boundary conditions. The contribution of this research is developing an accurate and rapid convergence algorithm for solving multiple-burn trajectory for satellite injection into geostationary orbit. To solve the multipoint boundary value problem, an improved indirect shooting method with high performance and modified Newton’s methodis presented and used for optimal solution. Moreover, the novel method presented for multi burn problem not only has very good accuracy, but also, it converges very fast to the desired end conditions. Various flight sequences with multiple burns are considered and the optimal trajectory with minimum fuel consumption criteria, for each flight sequence is derived. The verification and validation of the proposed algorithm is made via comparison with references. Finally, the results of optimal solutions are compared with the results of sub-optimal solution whose thrust direction is aligned to the velocity vector direction.

Unstart/RESTART phenomena induced by backpressure in a general inlet with a freestream of M = 2. 7 are investigated in an in-draft supersonic quiet wind tunnel. The boundary layers are turbulent on the forebody while are laminar on the lip wall, which could mimick real flight conditions. The high-speed Schlieren imaging system and the nanoparticle-based planar laser scattering (NPLS) method are used to visualize the inlet flowfield. The inlet wall pressure is measured by high-frequency pressure transducers. The backpressure is reproduced by downstream transverse jets other than mechanical throttlers, which is more suitable to mimic backpressure caused by combustion. The high spatio-temporal resolution full-view images of inlet flow features during the complete unstart/RESTART process are captured, which are seldom seen before. The formation and disappearance process of massive boundary layer separation at the entrance of the unstarted inlet is observed. The backpressure transmits upstream through the shock wave/boundary layer interaction (SWBLI) regions. The shock structures change the angles and merge upstream to balance the pressure rise. The Mach shock reflection configuration is observed in both unstart/RESTART process, accompanied by the boundary layer separation extending to the leading edge. The experiment also revealed notable hysteresis in the unstart/RESTART process.

Organizations are increasingly in search of ways to derive more business values from IT investments and the need for IT capabilities (ITC) is surging. ITC is critical significant to build enterprise agility and promote organizational performance. However, IT CAPABILITY is always treated as the causal factor already existing and there are few studies on how IT CAPABILITY is created and evaluated. Appropriate evaluation is necessary for an organization to measure, manage and improve enterprise ITC. This research aims to identify and map the dimensions of an organization's ITC. Using a mixed research method, this paper comprises two sections. The qualitative section adopts a systematic literature review (SLR) approach to identify the dimensions of ITC. The quantitative section employs factor analysis to validate identified ITC dimensions and their indicators in an attempt to develop a more precise model for ITC evaluation. The proposed ITC model includes IT management, IT human resources, IT infrastructure, and implementation of IT solutions dimensions as well as the 25 related indicators. Drawing on the results of this paper, organizations can engage in evaluation and improve/create essential ITCs based on the evaluation results.

Due to its highly changing nature and variety, competition nowadays requires capabilities that can provide competitive advantages for firms. The purpose of this research is to investigate the effect of dynamic capabilities and innovation capabilities on competitive advantage. Sensing, learning, integration, coordination and reconfigured capabilities are taken into account as the dynamic capabilities, and exploitation and exploration capabilities were taken into account as the innovation capabilities. As for competitive advantage, three dimensions including cost leadership, differentiation and focus strategy were taken into consideration. The sample consisted of 217 companies which manufactured heating and cooling systems in Tehran. They were selected by Sampling Available. The research is an applied study and, in terms of data collection, it is a descriptive and correlational study. To analyze the data, the structural equation model was used. PLS measurement, correlation test, mean comparison of one group and comparison of the mean of two independent groups were conducted too. The findings indicate that, to achieve a cost leadership strategy, all the dimensions of dynamic capabilities are of positive and significant effects. However, to reach the differentiation strategy, only the sensing CAPABILITY has a positive and significant effect, and both dimensions of innovation CAPABILITY have a positive and significant effect on the dimensions of competitive advantage.