Search results

The Covid-19 pandemic has caused disruptions in many businesses. A difficult process has been experienced for businesses caught unprepared for this situation. The purpose of the study, the difficulties experienced in the business have been mapped in terms of crisis management.

For this purpose, crisis management strategies have been discussed in terms of lean six sigma (LSS) strategies. Afterward, LSS strategies have been weighted with the spherical fuzzy analytical hierarchy process (AHP) method, which has been recently introduced to the literature (Gündogdu and Kahraman, 2020). While weighting has been done with the spherical fuzzy AHP method, three experts in the field of LSS at the master blackbelt level have been studied.

The Covid-19 process has caused the usual processes of businesses to change. Businesses do not have enough time to adapt their business processes in the Covid-19 process. To eliminate waste and time in the Covid-19 process, the lean methodology was used. At the same time, quality deficiencies have been tried to be eliminated with the six sigma methodology. Therefore, the six sigma methodology and lean techniques should be considered together. With LSS, the adaptation of this process has been wanted to be accelerated. In this context, the criteria in the Covid-19 process were prioritized and losses were reduced in accordance with the LSS methodology. In this study, the most important criterion during the covid-19 pandemic has been determined as “responding to the changing needs of customers” and the least important criterion has been determined as “communication with stakeholders in enterprises.”

This study has been applied the Covid-19 pandemics. So, it has been evaluated related to these specific criteria.

Covid-19 crisis management was examined for the first time within the scope of the LSS methodology. The criteria in the Covid-19 process were determined by six sigma expert master black belts. For the first time, spherical fuzzy AHP, one of the multi-criteria decision methods, has been applied to the Covid-19 process.

This study has been aimed to create a roadmap to apply LSS steps in businesses against a possible second wave of the Covid-19 pandemic. In this context, it is thought that the study will fill the following gaps in the literature: Covid-19 crisis management was examined for the first time within the scope of LSS methodology. The criteria in the Covid-19 process were determined by six sigma expert master black belts. For the first time, spherical fuzzy AHP, one of the multi-criteria decision methods, has been applied to the Covid-19 process.

The purpose of this paper is to create models that predict exergetic sustainability index (ESI) and environmental effect factor (EEF) values with high accuracy according to various engine parameters.

In this study, models were created to estimate ESI and EEF sustainability parameters in various flight phases for a business jet with a turboprop engine using the cuckoo search algorithm (CSA) method. The database used for modeling includes the various engine parameters (torque, engine airflow, gas generator speed, fuel mass flow, power and air-fuel ratio) obtained by running a business aircraft engine more than once at different settings and the actual ESI and EEF values obtained depending on these parameters. In addition, sensitivity analysis was performed to measure the effect of engine parameters on the models. Finally, the effect of the CSA number of nest (n) parameter on the model accuracy was investigated.

It has been observed that the models predict ESI and EEF values with high accuracy. As a result of the sensitivity analysis, it was seen that the air-fuel ratio had a greater effect on the output parameters.

These models are thought to assist in the exergetic environment analysis used to find the greatest losses for turboprop business jets and identify their causes and further improve system performance. Thus, they will be a useful tool to minimize the negative impact of business jet on environmental sustainability.

To the best of the authors’ knowledge, this study stands out in the literature because it is the first exergo-metaheuristic approach developed with CSA for business aircraft engine; moreover, the data set used consists of real values.

Usage of gas turbine engines has increased by day due to rising demand for military and civil applications. This case results in investigating diverse topics related to energy efficiency and irreversibility of these systems. The purpose of this paper is to perform a detailed entropy assessment of turbojet engines for different flight conditions.

In this study, for small turbojet engines used in unmanned aerial vehicles, parametric cycle analysis is carried out at (sea level-zero Mach (hereinafter phase-I)) and (altitude of 9,000 m- Mach of 0.7 (hereinafter phase-II)). Based on this analysis, variation of performance and thermodynamic parameters with respect to change in isentropic efficiency of the compressor (CIE) and turbine (TIE) is examined at both phases. In this context, the examined ranges for CIE is between 0.78 and 0.88 whereas TIE is between 0.85 and 0.95.

Increasing isentropic efficiency decreases entropy production of the small turbojet engine. Moreover, the highest entropy production occurs in the combustor in the comparison of other components. Namely, it decreases from 2.81 to 2.69 kW/K at phase-I and decreases from 1.44 to 1.39 kW/K at phase-II owing to rising CIE.

It is thought that this study helps in understanding the relationship between entropy production and the efficiency of components. Namely, the approach used in the current analysis could help decision-makers or designers to determine the optimum value of design variables.

Due to rising isentropic efficiencies of both components, it is observed that specific fuel consumption (SFC) decreases whereas specific thrust (ST) increases. Also, the isentropic efficiency of a compressor affects relatively SFC and ST higher than that of the turbine.

Nowadays, the most important challenge in mechanical engineering, power engineering and electronics is a development of effective cooling systems for heat-generating units. Taking into account this challenge, this study aims to deal with computational investigation of thermogravitational energy transport of pseudoplastic nanoliquid in an electronic chamber with a periodic thermally producing unit placed on the bottom heat-conducting wall of finite thickness under an influence of isothermal cooling from vertical side walls.

The control equations formulated using the Boussinesq approach, Ostwald–de Waele power law and single-phase nanofluid model with experimentally based correlations of Guo et al. for nanofluid dynamic viscosity and Jang and Choi for nanofluid thermal conductivity have been worked out by the in-house computational procedure using the finite difference technique. The impact of the Rayleigh number, nanoadditives concentration, frequency of the periodic heat generation from the local element and thickness of the bottom solid substrate on nanoliquid circulation and energy transport has been studied.

It has been found that a raise of the nanoadditives concentration intensifies the cooling of the heat-generating element, while a growth of the heat-generation frequency allows reducing the amplitude of the heater temperature.

Mathematical modeling of a pseudoplastic nanomaterial thermogravitational energy transport in an electronic cabinet with a periodic thermally generating unit, a heat-conducting substrate and isothermal cooling vertical surfaces to identify the possibility of intensifying heat removal from a heated surface.

The purpose of this paper is to examine the turbulent fluid flow and heat transfer characteristics for rectangular channel provided with solid plate baffles which are arranged on the bottom and top channel walls in a periodically staggered way.

The turbulent governing equations are solved by a finite volume method with the second‐order up winding scheme and the k‐ω turbulence model to describe the turbulent structure. The velocity and pressure terms of momentum equations are solved by SIMPLE (semi‐implicit method for pressure‐linked equation) algorithm. The parameters studied include the entrance Reynolds number Re (5.10³‐2.10⁴), the baffles height are fixed at (h=0.08 m); whereas three different baffle spacing were considered S₁ = D, S₂ = D/2 and S₃=3D/2 and the working medium is air.

In this work, it is found that vortex shedding generated by the baffle on the upper wall can additionally enhance heat transfer along the baffle surfaces. The wavy flow significantly changes the recirculating zone behind the last baffle. Finally, changing the baffles spacing seemed to reduce to changing the heat transfer surface between the solid and the fluid in the sense that higher heat transfer is obtained for lower spacing between baffles.

The results of the numerical calculations of the flow field indicate that the flow patterns around the solid baffles depending on the spacing of the baffles and it significantly influences the local heat transfer coefficient distributions. The problem is inversely proportional for the friction factor.

The previous studies examining the role of subjective norm (SN), online shopping anxiety (ANX) and perceived playfulness (PPL) in predicting the consumer's adoption of online shopping yielded fragmented and inconsistent findings. Also, a high proportion of these findings assessing the regarded behaviour of consumers in the West cannot be directly applied to a cross‐cultural context. The purpose of this paper is to investigate the relationships between these variables and the variables of technology acceptance model (TAM) associated with customer's online shopping intentions in an international environment.

The research model reflecting the effects of SN, ANX and PPL on TAM constructs has been proposed. In total, 278 cases were gathered from online shoppers through a web‐based survey. Structural equation modelling was used to evaluate the proposed research model in terms of path significance, overall model fit and explanatory power.

It was found that PPL had positive direct effects on both perceived ease of use of online shopping (PEOU) and behavioural intentions to shop online (BI). Nevertheless, SN and ANX appeared to exert significant positive and negative influences respectfully on only PEOU.

The study findings were obtained from the single snapshot research, and the small dataset covering only actual online shoppers. Therefore, the future research should carry a longitudinal nature to show the temporal change effects and remedy the possibility of self‐selection bias with a broader research sample.

The paper provides additional insights for retailers and researchers into the effects of SN, ANX and PPL on online shopping intentions of Turkish consumers, which could be used in formulating online marketing strategies and considering future research directions.

This research proposes analytical valuation models throughout football players' life cycles based on crowd valuations from social media to produce dynamic sporting human capital disclosures, and therefore, supplying further useful information to capture the intellectual capital (IC) of football clubs.

This work is carried out using an econometric model that includes 658 observations of crowd judgments versus their transfer fees, for the best footballers of the three major European Leagues between 2006 and 2018. To make the model more parsimonious, the set of independent variables that really add value has been found across the stepwise methodology.

The significant differences between both models are analyzed, integrating previous academic literature based on the existence of negotiation elements in prices, and in the capacity of crowdsourcing to explain assessments of football players, from a dynamic perspective, alongside a new variable: injuries, which has not been explained before.

The broader assessments from crowdsourcing should be integrated in intellectual capital disclosures (ICD), from a critical, novel and dynamic perspective, creating a virtuous cycle between managers and fans, to increase transparency of financial information for stakeholders and society.