External Boundary Research Articles

Experimental Investigation on Juncture Flow Associated with a Surface-Mounted Circular Cylinder Trailed by a Backward-Facing Step

Juncture flows associated with surface-mounted obstacles can be characterized by a U-shaped tubular vortical flow known as a horseshoe vortex (HSV). Horseshoe vortices are usually detrimental to engineering applications. In order to identify a boundary geometry that may effectively reduce a HSV’s strength for further design of HSV-reduction devices, or otherwise enhance it for further disaster prevention by avoiding such a geometry in design, the characteristics of HSVs influenced by external boundary geometries must first be understood. Thus, we experimentally investigated a juncture flow field associated with a fundamental geometry—a circular cylinder mounted perpendicular to a plane surface—with a trailing backward-facing step (BFS) representing a novel idea of downstream effects on upstream-formed flow structures. This setup is not only one of the simplest nonplanar geometries that generates flow features such as an unsteady separated shear layer that may considerably affect an HSV, but it is also a new attempt without prior knowledge. We used the particle image velocimetry (PIV) and PIV-based flow visualization techniques combined with a vortex-fitting algorithm to measure the juncture flow and identify the HSV and its kinematic modes at the low Reynolds number of 1166. We observed from the flow-visualization results regarding HSV’s kinematic modes and their duration percentages as follows: (1) without the BFS: “oscillation with a small displacement” (98.6%) and “breakaway to roll-up” (1.4%); (2) with the BFS (step height/cylinder diameter = 1.5): “oscillation with a small displacement” (83.3%), “merging” (4.5%), and “mixed” (12.2%). It is clearly evident that the BFS increased the number and complexity of kinematic modes, i.e., the unsteadiness of the HSV. Moreover, the PIV results show that the BFS reduced HSV stretching, which resulted in increased vortex diameter by 8.24% and increased circulation by 6.37%, i.e., the strength of the HSV was enhanced by the BFS.

Взаимосвязь стрессоустойчивости и суверенности психологического пространства личности у студентов с инвалидностью и ОВЗ

The study involved 61 students aged 20 to 23 years, including 23 boys and 38 girls belonging to different nosological groups (hearing disorders, speech disorders, disorders of the musculoskeletal system). The questionnaire “Sovereignty of psychological space” (S.K. Nartova-Bochaver) and “Stress tolerance test” (Yu.V. Shcherbatykh) were used as diagnostic material. For statistical data processing, the Mann-Whitney U test and the Pearson correlation coefficient (r-Pearson) were used. Statistically significant relationships were revealed between indicators of sovereignty - personality deprivation of students with disabilities and their tendency to complicate everything, react sharply to life events and even minor facts, as well as predisposition to psychosomatic diseases and destructive ways of coping with stress. It is concluded that in the system of inclusive higher education, specially organized programs of psychological support for the process of socialization of students with disabilities and disabilities in the university, aimed at helping them to establish the external and internal boundaries of the psychological space of their personality, are important and significant.

Quantifying Temperature Effects in Large-Scale PEM Water Electrolysis Stacks

Introduction Large-scale water electrolysis is needed for scaling up the production of hydrogen as a renewable energy carrier. The required size and number of cells of the PEMWE stack exceed laboratory-scale settings, which leads to additional effects that could impact the operation and performance [1]. The interaction of large, neighbouring cells with each other are expected to lead to significant temperature differences within the stack of cells, which cause deviations in the contribution to the loss mechanisms and uneven stresses or loading of the members. Methods This contribution presents a dynamic PEMWE-stack model, which is formulated in two dimensions: through the stack and along the channel. Due to the high electric conductivity of the bipolar plates the cell voltage of each cell is independent of the cell/channel flow coordinate. The model is based on mass and enthalpy balances of the fluids on the anodic and cathodic side. Conductive heat transport along the cell and through the stack is considered as well as convective transport by the fluids. Time-dependency of mass and enthalpy balances is considered to capture unsteady operation of the stack. In addition, a temperature-dependent polarisation model for determining the cell voltage is included in the model. The polarisation model includes the contributions of activation overpotentials, mass transport losses and ionic membrane and contact resistances. The cells on both edges of the stack are modelled with dedicated boundary conditions to capture the physical arrangement and convective heat exchange with the environment. Water flow and electrical settings are prescribed as external boundary condition. The model is validated with experimental data from industrial stacks. Results The temperature profile inside the stack is found unevenly distributed in both spatial directions between the cells with colder boundary and warmer inner cells. The colder outer cells operate at a higher cell voltage in an electrical series connection. For the inner cells, a significant temperature gradient is found in flow direction. As the polarisation loss mechanisms depend on temperature, the share of the losses is unevenly distributed in both coordinates. This leads to higher current densities at the parts of a cell that experience elevated temperatures (Fig. 1). These mechanisms depend on the macroscopic design of the cell, boundary and operating conditions. Load variations induce a dynamic stack response in temperature, cell voltage and the fluids until a steady state is reached. At the same time local temperature and current density variation, can be analyzed as performance drivers, including degradation. Both aspects can be used for design and optimization of industrial scale PEMWE stacks.

Fashion, Thresholds, and Borders

Fashion, Thresholds, and Borders

Expansion characteristics of concrete with free lime based expansive additives under uniaxial restraint conditions

Expansive additives in higher dosages induce chemical prestress in concrete by imparting higher early-age expansion. However, induced stress and concrete expansion can vary significantly, depending on different restraint conditions. In addition, concrete expansion can be highly anisotropic depending on the nature of external restraints and boundary conditions. Experimentations have been performed to study the effect of uniaxial (anisotropic) restraint on the concrete expansion (in both restraint and stress-free directions) and induced prestress. A higher degree of restraint resulted in a substantial decrement in the longitudinal expansion. In contrast, expansion in the stress-free (lateral) direction was not much affected by the restraint in other direction. As a result, an overall decrement in the volumetric expansion was observed with an increase in the reinforcement ratios. Stress induced in concrete due to the restraint expansion in the longitudinal direction was found to be higher for a higher reinforcement ratio. Data provided from the current work can be used for the comprehensive modelling of expansive concrete under external restraints.

Influences of Boundary-Spanning Leadership on Job Performance: A Moderated Mediating Role of Job Crafting and Positive Psychological Capital.

Due to the pursuit of a flexible organization, the interest in internal as well as external boundary management has increased as a key to achieve high performance. This study identified boundary-spanning leadership (BSL) as a critical factor enhancing job crafting and job performance of subordinates. By examining the mediating effect of job crafting and the moderating effect of positive psychological capital (PsyCap), the authors aimed to present the effects of BSL assimilating job resources, such as external information and knowledge into organization. Data were collected from 238 workers of 11 companies using questionnaires in South Korea to test the moderated mediation model. The results of regression analysis using LISREL and SPSS, revealed that the manager’s BSL provoked job crafting, which in turn achieved job performance of subordinates. Moreover, PsyCap positively moderated the effect of BSL on job crafting of subordinates. The findings suggested, therefore, in order to maximize the positive effects of BSL in an organization, it should also be necessary to understand and boost PsyCap along with enhancing job crafting.

Remote trajectory tracking of a rigid body in an incompressible fluid at low Reynolds number

In this paper we study the motion of a rigid body driven by Newton’s law immersed in a stationary incompressible Stokes flow occupying a bounded simply connected domain. The aim is that of trajectory tracking of the solid by the means of a control in the form of Dirichlet boundary data on the outside boundary of the fluid domain. We show that it is possible to exactly achieve any smooth trajectory for the solid that stays away from the external boundary, by the means of such a remote control. The proof relies on some density methods for the Stokes system, as well as a reformulation of the solid equations into an ODE.

Multiband homogenization of metamaterials in real-space: Higher-order nonlocal models and scattering at external surfaces

This work develops a dynamic homogenization approach for metamaterials. It finds an approximate macroscopic homogenized equation with constant coefficients posed in space and time; however, the resulting homogenized equation is higher order in space and time. The homogenized equation can be used to solve initial-boundary-value problems posed on arbitrary non-periodic macroscale geometries with macroscopic heterogeneity, such as bodies composed of several different metamaterials or with external boundaries. First, considering a single band, the higher-order space derivatives lead to additional continuity conditions at the boundary between a homogeneous material and a metamaterial. These provide predictions of wave scattering in 1-d and 2-d that match well with the exact fine-scale solution; compared to alternative approaches, they provide a single equation that is valid over a broad range of frequencies, are easy to apply, and are much faster to compute. Next, the setting of two bands with a bandgap is considered. The homogenized equation has also higher-order time derivatives. Notably, the homogenized model provides a single equation that is valid over both bands and the bandgap. The continuity conditions are applied to wave scattering at a boundary, and show good agreement with the exact fine-scale solution. Using that the order of the highest time derivative is proportional to the number of bands considered, a nonlocal-in-time structure is conjectured for the homogenized equation in the limit of infinite bands. This suggests that homogenizing over finer length and time scales -- with the temporal homogenization being carried out through the consideration of higher bands in the dispersion relation -- is a mechanism for the emergence of macroscopic spatial and temporal nonlocality, with the extent of temporal nonlocality being related to the number of bands considered.

A structure‐preserving finite element approximation of surface diffusion for curve networks and surface clusters

AbstractWe consider the evolution of curve networks in two dimensions (2d) and surface clusters in three dimensions (3d). The motion of the interfaces is described by surface diffusion, with boundary conditions at the triple junction points lines, where three interfaces meet, and at the boundary points lines, where an interface meets a fixed planar boundary. We propose a parametric finite element method based on a suitable variational formulation. The constructed method is semi‐implicit and can be shown to satisfy the volume conservation of each enclosed bubble and the unconditional energy‐stability, thus preserving the two fundamental geometric structures of the flow. Besides, the method has very good properties with respect to the distribution of mesh points, thus no mesh smoothing or regularization technique is required. A generalization of the introduced scheme to the case of anisotropic surface energies and non‐neutral external boundaries is also considered. Numerical results are presented for the evolution of two‐dimensional curve networks and three‐dimensional surface clusters in the cases of both isotropic and anisotropic surface energies.

Digital transformation: A review and research agenda

The ongoing and ubiquitous digital transformation challenges the raison d'être of firms and forces managers to rethink business strategies and operations and academics to reconsider related theories. To aid these efforts, we conduct a systematic review of research on firms' digital transformation, generating a database of 537 peer-reviewed academic articles and analyzing it using a novel multi-layered framework. The framework separates three layers: an organization's core activities, its peripheral activities, and its external environment. We find that firms that have come far in their transformations are more embedded in platform ecosystems with unclear business boundaries. Relatedly, we identify a tension between decentralizing versus centralizing power across organizational layers during a firm's digital transformation and how this dynamic affects corporate strategies and firms' internal and external boundaries.

Consistency of the boundary value problem of an elastic body involving surface tension in small deformations

Surface tension has a significant influence on the mechanical response of solids at small scales to external loadings. Conventional small deformation theories remain effective in capturing such an influence provided the corresponding boundary condition incorporates some measure of the deformed configuration of the solid’s surface in evaluating the surface tension–induced traction acting on the solid. Since the governing equations arising from conventional small deformation theories for the bulk of the solid are defined strictly in the undeformed configuration, they may be sometimes incompatible with the surface tension–related boundary condition incorporating certain measure of the deformed configuration, leading to an inconsistent boundary value problem. To clarify how to pose a self-consistent boundary value problem involving surface tension, we consider the plane deformation of a perforated medium with its internal boundary endowed with surface tension and surface elasticity and its external boundary subjected to a mechanical loading. We first review three kinds of related boundary conditions on the internal boundary of the medium: the Gurtin–Murdoch-type boundary condition and two modified boundary conditions based on the change-in-curvature formula. We then derive the resultant force and moment of the traction caused by surface tension and surface elasticity for each of the boundary conditions. We show that for the Gurtin–Murdoch-type boundary condition, the resultant force vanishes unconditionally but the resultant moment depends on the rigid-body rotation of the medium, while for the two modified boundary conditions, both the resultant force and resultant moment (about a certain point) rely on local deformation gradients and the curvature of the internal boundary of the medium. Consequently, for the Gurtin–Murdoch-type boundary condition, one may easily establish a self-consistent boundary value problem by specifying an appropriate mechanical loading, while for the two modified boundary conditions, the boundary value problem is only occasionally self-consistent for some special and compatible combinations of the geometry of the internal boundary and the mechanical loading. Nevertheless, if the medium becomes infinitely large with its external boundary extremely distant from the internal boundary, then the boundary value problem corresponding to either of the three boundary conditions is always self-consistent for an arbitrary configuration of the internal boundary and an arbitrary far-field loading.

Effect of Phase-Selective Nanoscale Precipitates on the Bauschinger Effect in Austenitic–Ferritic Duplex Stainless Steels

The Bauschinger effect in austenitic–ferritic duplex stainless steel 1.4462 was investigated using tension–compression tests combined with electron backscatter diffraction (EBSD). A major focus was on the impact of phase-selective nanoscale α′ precipitates formed in the ferritic phase due to 475 °C embrittlement. Contrary to the general knowledge that coherent precipitates have only a short-range effect and thus no significant influence, a strong increase in the Bauschinger effect was detected. Based on EBSD data and cyclic micro-indentations in individual grains, it was demonstrated that α′ precipitates enhance the phase difference between austenite and ferrite and increase deformation incompatibility and local dislocation density gradients at phase boundaries. Thus, despite their small size and coherence, α′ precipitates lead to long-range back stresses that significantly enhance the Bauschinger effect. In addition, the influence of precipitation was shown to depend on the extent of pre-strain during initial loading. The insights demonstrate that the influence of precipitates on the Bauschinger effect is highly complex and always needs to be analyzed with respect to precipitation characteristics, microstructure, and external boundary conditions.

Topological Chiral Edge States in Deep‐Subwavelength Valley Photonic Metamaterials

AbstractTopological valley photonics has emerged as a new frontier in photonics with many promising applications. Previous valley boundary transport relies on kink states at internal boundaries between two topologically distinct domains. However, recent studies have revealed a novel class of topological chiral edge states (CESs) at external boundaries of valley materials, which have remained elusive in photonics. Here, topological CESs are proposed and experimentally demonstrated in valley photonic metamaterials (VPMMs) by accurately tuning on‐site edge potentials. Moreover, the VPMMs work at deep‐subwavelength scales. Thus, the supported CESs are highly confined and self‐guiding without relying on a cladding layer to prevent leakage radiation. Via direct near‐field measurements, the bulk bandgap, the edge dispersions, and the robust edge transport passing through sharp corners, which are hallmark signatures of the CESs, are observed. This work paves a way to explore novel topological edge states in valley photonics and sheds light on robust and miniaturized photonic devices.

Dynamic property control of bridge girders

The dynamic properties of bridge girders depend on the design solutions, namely the replacement of the roadway slab by the orthotropic, deviation from standard solutions in the formation of longitudinal schemes, and the use of a new type of supports causing the dissipation of vibration energy and gyropendulum effect.The control for dynamic properties with regard to multifactorial defects, is characterized by ignoring the shock dampers of vehicles moving on the roadway. In this case, it is advisable to control the dynamic properties with regard to the energy dissipation of oscillatory processes within the internal and external strain boundaries, each of which can be functionally solved by the dependencies between the parameters of static and dynamic conditions of elasticity and plasticity. Long experience in diagnosing bridges under varying conditions of moving load allows identifying critical moments and limiting values of dynamic properties, at which the integrity of the span-vehicle system is violated. The difference in the operation of the system elements is complicated by the influence of a wide range of dynamic impacts, whose nature is opposite to the mechanical impact of vibra-tion dampers such as all-round moving supports. In this case, the criterion for the dynamic property control are anti-phase vibrations of the girder and supports and their stiffness ratio. Based on the results, the dynamic property control includes the identification of the critical speed of the moving load based on various forms of energy of the deformed state of the structure, including resonance; conditions of the energy dissipation of the vibration process of the span-vehicle system; new parameters and requirements for bridge structures with controlled dynamic properties adequate to those of numerical simulation of bridge girders of 40 to 60 or 80 m and longer; optimization and modernization of bridge vibration-based diagnostics.

Component-Based Reduced Order Modeling of Large-Scale Complex Systems

Large-scale engineering systems, such as propulsive engines, ship structures, and wind farms, feature complex, multi-scale interactions between multiple physical phenomena. Characterizing the operation and performance of such systems requires detailed computational models. Even with advances in modern computational capabilities, however, high-fidelity (e.g., large eddy) simulations of such a system remain out of reach. In this work, we develop a reduced‐order modeling framework to enable accurate predictions of large-scale systems. We target engineering systems which are difficult to simulate at a high-enough level of fidelity, but are decomposable into different components. These components can be modeled using a combination of strategies, such as reduced-order models (ROM) or reduced-fidelity full-order models (RF-FOM). Component-based training strategies are developed to construct ROMs for each individual component. These ROMs are then integrated to represent the full system. Notably, this approach only requires high-fidelity simulations of a much smaller computational domain. System-level responses are mimicked via external boundary forcing during training. Model reduction is accomplished using model-form preserving least-squares projections with variable transformation (MP-LSVT) (Huang et al., Journal of Computational Physics, 2022, 448: 110742). Predictive capabilities are greatly enhanced by developing adaptive bases which are locally linear in time. The trained ROMs are then coupled and integrated into the framework to model the full large-scale system. We apply the methodology to extremely complex flow physics involving combustion dynamics. With the use of the adaptive basis, the framework is demonstrated to accurately predict local pressure oscillations, time-averaged and RMS fields of target state variables, even with geometric changes.

Modified thoracoscopic wedge resection of limited peripheral lesions in S10 for children with congenital pulmonary airway malformation: Initial single-center experience.

ObjectiveThe present study aimed to evaluate the safety and feasibility of modified thoracoscopic wedge resection of limited peripheral lesions in the posterior basal segment (S10) in children with congenital pulmonary airway malformation (CPAM).Materials and methodsWe retrospectively analyzed the clinical data of children with CPAM who underwent thoracoscopic modified wedge resection at our institution from November 2020 to February 2022. The surgical method was as follows: we marked the external boundary of the lesion with an electric hook, dissected and retained the segmental vein between the lesion and normal lung tissue as the internal boundary, cut the arteries, veins, and bronchus entering the lesion, and cut and sealed the lung tissue between the internal and external boundaries with LigaSure™ to complete the modified wedge resection.ResultsA total of 16 patients were included, aged 3.8−70.0 months and weighing 6.5−21.0 kg. The intraoperative course was uneventful in all patients. The median operation time and intraoperative bleeding volume were 74 min (50−110 min) and 5 mL (5−15 mL), respectively. The median postoperative drainage tube indwelling time was 3 days (2−4 days), and the median postoperative hospital stay was 6 days (4−8 days). Pathological diagnosis included two cases of type 1, 10 cases of type 2, and four cases of type 3 CPAM. There were no cases of intraoperative conversion, surgical mortality, or major complications. However, subcutaneous emphysema occurred in two children, which spontaneously resolved without pneumothorax orbronchopleural fistula development. All patients were followed up for a median period of 10 months (3–18 months), and there were no cases of hemoptysis or residual lesions on chest computed tomography.ConclusionModified thoracoscopic wedge resection via the inferior pulmonary ligament approach is safe and feasible for children with CPAM with limited peripheral lesions in S10.

Natural convection in vertical enclosures with conjugate boundary conditions

A numerical investigation and reduced-order modelling of natural convection in a cavity with differentially heated sidewalls is discussed. The effect of conjugate boundary conditions on the cavity's heat transfer and natural flow circulation with varying aspect ratios and Rayleigh numbers is examined. Validation of the canonical differentially heated cavity reveals that a modification to the definition of the Rayleigh number (Ra) is required to reconcile the $Nu\sim Ra^{1/4}$ scaling (where Nu is the Nusselt number) and validity of previously proposed correlations for the heat transfer in vertical enclosures. Dynamic mode decomposition is used to uncover the underlying time-dependent flow structures and the results are compared with stability bifurcation studies in the literature. A flow mode previously associated with smaller aspect ratio cavities is identified as the unstable mode for a larger aspect ratio of 4. The effect of conjugate boundary conditions is scaled based on the ratio of the internal and external boundary layers, wherein higher external Reynolds numbers aid in the heat transfer as the Nusselt number approaches the isothermal limit. A reduced-order theoretical model is proposed to predict the Nusselt number for the conjugate boundary conditions. The performance of conjugate boundary conditions is connected to the flow stability, with the parallel-flow configuration acting in a destabilizing manner while the counterflow configuration has a stabilizing effect and results in the highest heat transfer. We also found that relatively large heat transfer can be achieved with substantially lower external actuation with intermediate aspect ratios, translating to less power in practice.

History of Anvers-Hugo Trough, western Antarctic Peninsula shelf, since the Last Glacial Maximum. Part I: Deglacial history based on new sedimentological and chronological data

Reconstructing the advance and retreat of past ice sheets provides important long-term context for recent change(s) and enables us to better understand ice sheet responses to forcing mechanisms and external boundary conditions that regulate grounding line retreat. This study applies various radiocarbon dating techniques, guided by a detailed sedimentological analyses, to reconstruct the glacial history of Anvers-Hugo Trough (AHT), one of the largest bathymetric troughs on the western Antarctic Peninsula (WAP) shelf. Existing records from AHT indicate that the expanded Antarctic Peninsula Ice Sheet (APIS) advanced to, or close to, the continental shelf edge during the Last Glacial Maximum (LGM; 23-19 cal kyr BP [ = calibrated kiloyears before present]), with deglaciation of the outer shelf after ∼16.3 cal kyr BP. Our new chronological data show that the APIS had retreated to the middle shelf by ∼15.7 cal kyr BP. Over this 600-year interval, two large grounding-zone wedges (GZW) were deposited across the middle (GZW2) and inner shelf (GZW3), suggesting that their formation occurred on centennial rather than millennial timescales. Expanded sequences of sub-ice shelf sediments occur seaward of the inner GZW3, which suggests that the grounding line remained stationary for a prolonged period over the middle shelf. Grounding-line retreat rates indicate faster retreat across the outer to middle shelf compared to retreat across the middle to inner shelf. We suggest that variable retreat rates relate to the broad-scale morphology of the trough, which is characterised by a relatively smooth, retrograde seabed on the outer to middle shelf and rugged morphology with a locally landward shallowing bed and deep basin on the inner shelf. A slowdown in retreat rate could also have been promoted by convergent ice flow over the inner shelf and the availability of pinning points associated with bathymetric highs around Anvers Island and Hugo Island.

한미 현대 연작시 비교 연구

This study compared and studied “The Raven” representing the United States and Korea. Edgar Allan Poe's “The Raven” and Gu Sang’s “The Raven” were considered in symbolic appropriation of poetic material, in series form, intertextuality and semantic horizons. First, in the case of Poe, the choice of poetic material was ‘raven’ as a poetic material. This was intended to achieve the highest artistic effect. It also tried to best represent beauty. And the chorus "nevermore" was intended to maximize the poetic effect. On the other hand, Gu Sang chose the target of shock, impact, tension and emotion. The subject selected the raven as an allegory to criticize and inform the situation of the times. Edgar Allan Poe symbolizes fear and fear, based on the image of an ancient sinister bird. And the raven symbolizes the person who rules and delivers the dark world in the Age of Chaos. Also, the appearance of a raven is symbolized by ‘nevermore’ as ‘mournful, never-ending recollection’. On the other hand, Gu Sang's “Raven” criticizes the times of materialism and technologyism. In Korea, the raven is an ominous bird. However, the raven is symbolized as a bird longing for a spiritual and pure soul. And it is symbolized as a bird that foretells injustice and calamity. It is also symbolized as a savior who can save humans from golden universalism and materialism. Second, it is a series form. Poe transformed the sestina form of 6 lines and 6 stanzas into a finite series of 18 stanzas and 108 lines. On the other hand, Gu Sang has no external boundaries or external boundaries. He made it into an infinite series where only the theme changes. And Poe reinforces the negative expression with ‘nothing more’ (limited negation) < ‘nevermore’ (future negation) against the backdrop of the night. On the other hand, Gu Sang's poems are titled with numbers. The number does not impose a continuous development and process. It is united by the same rhetorical pattern(allegory), the same rhythm, and the same repetition. Finally, in Poe's poem, he dreams of becoming one with his lost lover. However, he feels death, fear and loss from the raven who repeats only 'nevermore'. And the story and intertextuality of Greco-Roman mythology appear. Poe made a series of symbols and series of perpetually recurring sadness of loss. On the other hand, in the poems of Gu Sang, it is symbolized as a bird giving warnings and prophecies through cries. And the legend of the Tower of London in England is intertextual and denounces human cruelty and savagery. Gu Sang delivers the message of harmony between humans and nature, restoration of humanity, and saving lives. As described above, the poems of Poe and Gu Sang are different in symbol and form. However, the sadness, mourning, and anxiety of the loss of an object are common.

The Impacts of Environmental Dynamism on Chinese Tour Guides' Sustainable Performance: Factors Related to Vitality, Positive Stress Mindset and Supportive Policy.

Although previous research shows great interest in improving the sustainability of organizations’ performance, little is known about individual sustainable performance, especially for special groups such as tour guides. Drawing on the Conservation of Resources (COR) theory, this study aimed to investigate the effect of environmental dynamism caused by COVID-19 on tour guides’ sustainable performance and mediating role of vitality and intervention mechanism in this relationship. Adopting a quantitative research method, we collected data from 382 professional tour guides in China via three surveys. The Structural Equation Model (SEM) and PROCESS were used to test the hypotheses. The results revealed that: (1) environmental dynamism was negatively related to tour guides’ sustainable performance and (2) vitality at work mediated this negative effect; (3) a positive stress mindset moderated the relationship between environmental dynamism and vitality; (4) supportive policy’s moderating role in the relationship of vitality and sustainable performance was not significant. The above conclusions contribute to the literature about the external environment, emotional state, performance management and application boundary of COR theory in the context of the COVID-19 pandemic.