Explore the vast range of titles available.

Dynamic brittle facture in materials with many pores/perforations has been shown experimentally to feature complex evolution of crack morphologies that include crack branching, micro-branches that arrest, cracks restarting from pores and branching soon after. Computational models of these problems need to accurately account for the dynamic interactions between strain waves and stress concentration zones induced by the perforated geometry. In this paper, we aim to improve the predictive capabilities of computational simulations of dynamic brittle/quasi-brittle fracture in samples with complex geometries, like perforated plates, by introducing a discretization method using non-uniform grids near a boundary (NB-NUG) for 2D peridynamic fracture modeling. The NB-NUG avoids the steps and the corresponding artificial stress concentrations created in PD models when using uniform grids over domains with curved boundaries. The new method also reduces numerical errors compared with general non-uniform grids used for PD models. We apply the model for dynamic fracture of thin PMMA plates with different arrangements of periodic pores/perforations. The results match the experimental observations for all of the cases considered. Fine features observed in the experiments (multiple cracks branching and cracks that arrest soon after splitting, number of branching events, etc.) are captured by the new approach and not by the other PD models with different types of grids. The results show that the high strain energy density regions created around perforations attract a nearby crack tip, deflecting the crack path, altering its propagation velocity, and promoting crack branching in its wake, thus dissipating more energy. Nonlocality of damage helps here in allowing its unrestricted evolution in problems in which complex crack morphology is sensitive to small changes in the geometrical arrangement of pores in the structure.

Recent success in strain engineering has triggered tremendous interest in its study and potential applications in nanodevice design. In this paper, we establish a coupled piezoelectric/semiconducting model for a wurtzite structure ZnO nanofiber under the local mechanical loading. The energy band structure tuned by the local mechanical loading and local length is calculated via an eight-band k · p method, which includes the coupling of valance and conduction bands. Poisson’s effect on the distribution of electric potential inversely depends on the local mechanical loading. Numerical results reveal that both the applied local mechanical loading and the local length exhibit obvious tuning effects on the electric potential and energy band. The band gap at band edges varies linearly with the applied loading. Changing the local length shifts the energy band which is far away from the band edges. This study will be useful in the electronic and optical enhancement of semiconductor devices.

PurposeWorking-from-home (WFH) practice has been adopted by many companies of a variety of industries in a diverse manner; however, it is not until the recent outbreak of the coronavirus disease 2019 (COVID-19) pandemic WFH gains worldwide popularity. With so many different views out there and based on work–family balance theory, this study aims to find out the factors which affect peoples' WFH effectiveness and whether they want the extended WFH practice when the pandemic crisis is over.Design/methodology/approachThis paper adopted an online survey approach by posting questionnaires on the university website and different social media channels to collect views from full-time Hong Kong workers who have had WFH experience during the coronavirus outbreak. A total of 1,976 effective responses were collected for the data analysis.FindingsThe findings of this study indicate that WFH effectiveness is improved by personal and family well-being but reduced by environmental and resource constraints. When workers are experiencing higher WFH effectiveness, they have a higher preference for WFH even after the pandemic; the female workers preferred WFH twice per week, while the male workers more often preferred WFH once per week. Finally, workers from the management and the self-employed levels demonstrated a lower preference for WFH, compared to the front-line and middle-grade workers.Originality/valueThis paper fulfils to provide a timely reflection on workers' post-pandemic WFH preference, the factors affecting their WFH effectiveness and the demographic differences inducing to the differentiated preferences.

Based on the acousto-optic interaction, we propose a laser deflection method for rapidly, non-invasively and quantitatively measuring the peak positive pressure of HIFU fields. In the characterization of HIFU fields, the effect of nonlinear propagation is considered. The relation between the laser deflection length and the peak positive pressure is derived. Then the laser deflection method is assessed by comparing it with the hydrophone method. The experimental results show that the peak positive pressure measured by laser deflection method is little higher than that obtained by the hydrophone, confirming that they are in reasonable agreement. Considering that the peak pressure measured by hydrophones is always underestimated, the laser deflection method is assumed to be more accurate than the hydrophone method due to the absence of the errors in hydrophone spatial-averaging measurement and the influence of waveform distortion on hydrophone corrections. Moreover, noting that the Lorentz formula still remains applicable to high-pressure environments, the laser deflection method exhibits a great potential for measuring HIFU field under high-pressure amplitude. Additionally, the laser deflection method provides a rapid way for measuring the peak positive pressure, without the scan time, which is required by the hydrophones.

•Indoor environment of 19 high-level biosafety laboratories in China was investigated.•All main rooms meet biosafety requirements.•Air changes per hour should be adjusted or set carefully.•The interaction of Air change, pressure and cleanliness deserves further study. The high-level biosafety laboratory is not only the basic support for infectious disease prevention and control, but also interrelated with key areas such as environmental security and social security, which has attracted increasing attention. A good indoor environment is the premise to ensure the smooth progress of the experiment and biological risk prevention and control. In order to better understand the indoor environment of high-level biosafety laboratories, 19 high-level biosafety laboratories in China (with a total of 65 main rooms) were carefully selected as the test objects from December 2020 to December 2022. According to the test methods specified in the Chinese standard GB 50346, the air change, cleanliness, static pressure difference, temperature, relative humidity, and illumination were tested and analyzed. The results showed that all the measured parameters met the requirements of the Chinese standard GB 50346, and the bio-safety performance was completely satisfactory. However, individual parameters showed some overlarge values: the proportion of main rooms with cleanliness levels of 7 and 8 exceeding 50% of the lower limit for air changes was 54.5% and 69.8%, respectively; the proportion of main rooms in BSL-3-b1 laboratories with atmospheric pressure differentials exceeding 50% of the standard lower limit was 94.7%; and the atmospheric pressure differential in the main rooms of BSL-3-b2 laboratories reached a maximum of nearly -160 Pa. On the premise of ensuring the cleanliness and pressure gradient of the main room, it may be possible to reduce the air change. This study, for the first time, reveals the environmental parameters of various types and levels of biosafety laboratories, which can provide reference for the design and operation of such facilities. [Display omitted]

This article introduces repassivation and salt film formation models in a peridynamic formulation for corrosion damage. The model leads to autonomous generation of lacy covers in pitting corrosion and development of secondary pits. It does not require interface conditions. The electrical current density, usually provided as an input into the problem, is obtained as part of the solution procedure. Validation against available 2D experimental results on pitting corrosion shows the model to be predictive in terms of corrosion rate and pit shape evolution in time. The influence of electrolyte potential drop, applied potential, and chloride concentration on the pit shape, corrosion rate, and the lacy cover structure are studied. Results agree well with experimental observations.

Instabilities in thermally-driven crack growth in thin glass plates have been observed in experiments that slowly immerse a hot, pre-notched glass slide into a cold bath. We show that a nonlocal model of thermomechanical brittle fracture with minimal input parameters can predict the entire phase diagram of fracture measured in experiments for the low immersion speed regime. Geometrical restrictions to crack growth commonly found in other approaches are absent here. We discuss a method for determining the appropriate size of the peridynamic horizon based on a data point around a separating line between crack-type zones in the experimental phase diagram. Once the nonlocal size is smaller than the length-scale introduced by the thermal gradient, the computational results show that no fracture criterion is needed beyond Griffith’s criterion to capture the observed instabilities. The combination of thermal gradients and competing contraction forces on the two sides of the crack are behind the observed crack path instabilities. Elastic (velocity) vortices of material points show how and why the cracks develop along the observed paths. Our results demonstrate that thermally-driven fracture in brittle materials can be predicted with accuracy. We anticipate that this model will lead to design protocols for controlled fracture in brittle materials relevant in materials science and advanced manufacturing.

Imposing local boundary conditions and mitigating the surface effect at free surfaces in peridynamic (PD) models are often desired. The fictitious nodes method (FNM) “extends” the domain with a thin fictitious layer of thickness equal to the PD horizon size, and is a commonly used technique for these purposes. The FNM, however, is limited, in general, to domains with simple geometries. Here we introduce an algorithm for the mirror-based FNM that can be applied to arbitrary domain geometries. The algorithm automatically determines mirror nodes (in the given domain) of all fictitious nodes based on approximating, at each fictitious node, the “generalized” (or nonlocal) normal vector to the domain boundary. We tested the new algorithm for a peridynamic model of a classical diffusion problem with a flux singularity on the boundary. We show that other types of FNMs exhibit “pollution” of the solution far from the singularity point, while the mirror-based FNM does not and, in addition, shows a significantly faster rate of convergence to the classical solution in the limit of the horizon going to zero. The new algorithm is then used for mirror-based FNM solutions of diffusion problems in domains with curvilinear boundaries and with intersecting cracks. The proposed algorithm significantly improves the accuracy near boundaries of domains of arbitrary shapes, including those with corners, notches, and crack tips. Graphical Abstract

Faultlines are inherent to many workgroups, but the literature has not fully explained what faultlines mean for team functioning. In this study, we investigate the curvilinear relationship between faultlines and team performance from a cross-categorization perspective. Analyses of multisource data obtained from 61 workgroups located in China support an inverted U-shaped relationship between faultlines and team performance. Additionally, we find that this curvilinear relationship is moderated by a team’s climate of psychological safety such that the curvilinear relationship is more pronounced among teams with a weaker psychological safety climate. The findings contribute to elaborating the nature of and advancing a contingency view of the relationship between faultlines and team performance. Theoretical implications are discussed along with possible limitations and directions for future research.