Impact of the COVID-19 Pandemic on the Tourism Industry: Applying TRIZ and DEMATEL to Construct a Decision-Making Model

The impact of the COVID-19 pandemic on the tourism industry is still being sustained, and the response of the tourism industry is an indispensable element that is increasingly recognized. This response has led to the emergence of literature about the impact of COVID-19 on the stakeholders of the tourism industry, thereby contributing to the industry. Nonetheless, the criteria factors and investigated practices for the implementation of decision-making by stakeholders in the tourism industry have not been fully explored. This study adopts Teorija Rezhenija Izobre-tatelskikh Zadach (TRIZ) principles and Decision-Making Trial and Evaluation Laboratory (DEMATEL) methods to construct a gap model of tourism stakeholders (GMTS) which solves the tourism industry decision-making problem under COVID-19. With a research background in Taiwan’s tourism industry stakeholders made up of 15 expert participants, GMTS identified 11 criteria factors, of which the three most important criteria factors provide decision-making directions. The causal relationship between these criteria factors was examined, and a causal diagram was drawn to clarify the most important criteria factors. This research examined the criteria factor implementation perspective. Travel “bubble zones” that ensure both “safety and quality” were concluded upon under government policies in the countries and regions of the world. Furthermore, the tourism industry is responsible for the overall “planning and management” of the travel “bubble zones”. Therefore, the “quality management” criteria factor provides important key decision-making for tourism stakeholders. The research indicates that it is recommended to attach importance to the “quality management” of the international travel “bubble zone” as the priority decision-making criteria factor under the pandemic. Furthermore, conversion policies and tourism regulations are secondary criteria factors for improvement; when these two criteria factors are immediately improved, other criteria factors will be affected simultaneously and the degree of improvement will be weakened. In addition, GMTS was developed for the tourism industry. The article also provides research literature and practice implications for stakeholders in the tourism industry, thereby providing insight for tourism to obtain a clear understanding of how to prepare for the implementation of sustainable development.

Numerical Modeling of pipes conveying gas-liquid two-phase flow

Results of studies of the oscillations of pipelines conveying a two-phase slug flow are presented in the paper. A viscoelastic model of the theory of beams and the Winkler base model are used in the study of pipeline oscillations with a gas-containing slug flowing inside. The Boltzmann-Volterra hereditary theory of the viscoelasticity is used to describe the viscoelastic properties of the pipeline material and earth bases. The effect of gas and liquid phases flow rates, influence of tensile forces in the longitudinal direction of the pipeline, parameters of Winkler bases, parameters of singularity in the heredity kernels and geometric parameters of the pipeline on the oscillations of structures with viscoelastic properties are numerically studied. It is revealed that an increase in the length of the gas bubble zone leads to a decrease in the amplitude and oscillation frequency of the pipeline. The critical rates for a two-phase slug flow are determined. It is revealed that an increase in the soil density of the bases leads to an increase in the critical rate of gas flow. It is shown that an account of viscoelastic properties of structure material and earth bases leads to a decrease in the critical flow rate.

Investigation of Bubble Frequency for Slug Flow Regime in a Uniformly Heated Horizontal Microchannel

Slug flow is an essential flow pattern observed in microchannels where its transition boundaries in microchannels are characterized by two complex hydrodynamic phenomena, the bubble confinement and the bubble coalescence. Slug flow may be classified in terms of bubble size into two major zones: isolated bubble zone and coalescence bubble zone. In this paper, a semi-analytical model is developed for predicting the main characteristics of isolated bubble zone for flow boiling in a horizontal microchannel. The influences of surface tension, shear, and inertial forces have been taken into account. The model is developed on the basis of drift flux model, and a fully developed slug unit is chosen as a control volume for deriving the equations of motion. The effects of main operating conditions, mass and heat fluxes, on bubble length and bubble frequency have been investigated. The boundaries of slug flow regime have been identified based on the most proper diabatic flow pattern maps available in the literature for the chosen database. The model has been validated using the database available in the literature for flow boiling of R134a and R245fa in 0.509 mm and 3.0 mm inner diameter horizontal mini-tubes, respectively, and over wide range of mass fluxes (300≤G≤1000 kg/m2 s). This study has shown that the mass flux has a significant effect on the slug length and the bubble frequency. The model gave a good agreement with the experimental data of bubble length and bubble frequency with a mean absolute error (MAE) of 18.0% and 27.34%, respectively.

The Preparation and Microstructure of DLC Films Deposited through Plasma Electrodeposition in Water/Ethanol Solution

On the copper substrate the DLC films is preparated by plasma elcctrodeposition in methanol aqueous solution. The plating solution composition: alcohol water proportion is 4:1, the additive KCl content is 3g/L and the AlCl3 is trace amounts. The influence of the current density and the electrode spacing to the electrode surface bubble zone thickness, uniformity and stability are discussed in the article. The film surface morphology is observed by scanning electron microscopy (SEM). The thickness of the film D=30, 350, 410 and 380 nm. The deposition rate K=150, 175, 205 and 190 nm/h. The polycrystalline structure of the film can be observed through the X-ray diffraction (XRD) pattern., the characteristic peak of the (111),(200) and (220) crystal plane are observed at 2θ= 43.9°,50.9°and75.3°. The high carbon content is observed by EDX analysis.

Amplification and attenuation of waves of finite duration by means of a bubble zone in the one-dimensional approximation

Some peculiarities of the dynamics of pressure waves in a fluid containing bubble zone of finite dimensions in the one-dimensional approximation are studied. The problem is considered taking into account nonlinear effects. The results of the action of wave pulses on a bubble area with an uneven distribution of bubbles are presented, as well as effects on a solid wall covered with a bubble area.

Estimating Flow Characteristics of Different Weir Types and Optimum Dimensions of Downstream Receiving Pool

Estimating Flow Characteristics of Different Weir Types and Optimum Dimensions of Downstream Receiving PoolThis paper presents the results of a laboratory study on the flow characteristics of sharp-crested weirs, broad-crested weirs, and labyrinth weirs. The variation of the maximum bubble penetration depth for different weir types is investigated depending on overfall jet expansion, discharge, and drop height. Moreover, most efficient depth, length and width of the downstream receiving pool in an open channel system are studied by considering the penetration depth, overfall jet expansion, jet trajectory and the bubble zone. The results show that overfall jet expansion at the labyrinth weirs is significantly wider than the rectangular sharp-crested weirs and the trapezoidal sharp-crested weir. It is demonstrated that the labyrinth weirs have the lowest values of bubble penetration depth among the weirs tested. Furthermore, it is found that the rectangular and the trapezoidal weirs are observed to have the highest bubble penetration depth among all weirs. Consequently, empirical equations are obtained for predicting the maximum penetration depth of bubbles, trajectory of free overfall nappe, jet expansion of free overfall nappe, and the length of the bubble zone.

Pressure waves in a liquid containing bubble zone of finite dimensions

Some features of the dynamics of nonlinear two-dimensional pressure waves in a liquid containing bubble zone of finite dimensions and various shapes are studied. The results of numerical experiments on the action of wave pulses on a solid wall are presented, in the cases of the absence and presence of a bubble zone on the surface under consideration. Based on the results obtained, a number of dependences of the dynamics of two-dimensional disturbances on the parameters of the signal and the medium are revealed.