Search

The ejector is a crucial component of the hydrogen circulation system of proton exchange membrane fuel cell (PEMFC), which is widely used because of its simple structure, reliable operation, and no additional power consumption. However, the current research on pulsed ejectors is still lacking and in-depth. In this study, CFD modeling is conducted on the ejector, and the pulsed gas flow is simulated by user define function (UDF), and the influence of the pulsed gas flow on the entrainment performance of the ejector is analyzed. The results show that, compared with the steady-state condition, the entrainment performance of the ejector using pulsed gas flow under different primary flow pressures is improved, and the maximum entrainment ratio is 3.195 under steady-state conditions and 3.507 under transient conditions, which is increased by 9.8%. The effect is especially pronounced at low pressure, where the entrainment ratio increases by 16.6%. And by comparing the gas flow of different pulse frequencies, it is found that when the pulse frequency is 1Hz, the ejector has the best entrainment performance. • The ejector with pulsed gas flow has significantly better entrainment performance. • At the low primary inlet pressure, the pulsed gas flow has a good effect on the entrain ment performance. • Pulsed gas flow can form a lower low-pressure area at the nozzle exit. • When the frequency of the pulsed gas flow is 1Hz, the entrainment ratio is maximum. [ABSTRACT FROM AUTHOR]

Remote Sensing Archaeology (RSA) is an innovative sub-discipline within archaeology that utilizes general Remote Sensing (RS) techniques to analyze data from ancient human-made structures. This analysis significantly contributes to understanding various facets of human history, such as cultures, practices, diversity, and evolution. Our study anticipates the forthcoming changes in the roles of RS archaeologists and the research framework of RSA. Emphasizing the necessity for archaeologists to comprehend remote, proximal, in-situ, and instrumental sensing technologies, as well as rapidly evolving digital advancements, such as Artificial Intelligence/Machine Learning (AI/ML), Big Data (BD), Cloud or Cyber Infrastructure (CI), and Digitalization Technology (DT). Drawing upon successful techniques and practices, we argue the efficacy of RSA in addressing historical, contemporary, and future challenges. This effectiveness becomes particularly pronounced as RSA transitions from archaeological prospecting to knowledge discovery using space technologies, represented by RS. Space Archaeology (SA), which we propose as an evolved stage of RSA for archaeological prospecting, builds upon the experiences and lessons gleaned from RSA's century-long journey. It not only extends the legacy of RSA but also signifies a shift in both the implication and methodology of sensing-based archaeological prospecting. SA, while advancing RSA, also aligns with the current trend of spatial thinking in archaeology amidst substantial transformations in RSA research. The perspectives outlined in this review aspire to positively shape the ongoing shift in archaeological spatial thinking. • The recent advance in remote sensing archaeology is reviewed. • The new paradigm of space archaeology is first described. • Specific focus is given to the understanding of past human–environment interactions. • Emerging trends and future perspectives are highlighted in four key areas. [ABSTRACT FROM AUTHOR]

This paper focuses on the nonlinear behaviors of offset-halves journal bearings (OHJBs), particularly under dynamic loading and journal misalignment. A new tribo-dynamic model is given to perform transient thermoelastohydrodynamic analysis in the crucial yet understudied domain of this novel structure. Bearing characteristics are compared among bi-directional misalignment, single-direction misalignment as well as alignment. The results demonstrate that the influence of bi-directional misalignment exerts dominance. Moreover, the evolution mechanisms of bi-directional misalignment and step loading on the time-varying stiffness and damping are evaluated. In addition, parametric analyses are done to emphasize key factors in the bearing design, including the horizontal offset and radial clearance, for better transient lubrication performance. This study enriches the structural optimum for dynamically loaded journal bearings. [Display omitted] [ABSTRACT FROM AUTHOR]

Although offset-halves journal bearings (OHJBs) are extensively utilized in the marine powertrain, there is little research on nonlinear dynamic response and transient stability, particularly under conditions involving both thermo-elasto-hydrodynamic (TEHD) effects and sudden loads. To overcome such deficiency, a novel transient tribo-dynamic model and a modified stability criterion are developed. The influences of model parameters such as TEHD effects, load amplitude, offset coefficient, and varying lubricants on transient responses are studied. In addition, the evolution mechanisms of two typical lubricants on the transient stability of OHJBs are revealed. The results show that the model parameters have a significant impact on the nonlinear tribo-dynamic performance and transient stability of OHJBs. This study enriches theoretical foundations for the optimum bearing design. [ABSTRACT FROM AUTHOR]