Search Results (34)

An in-depth analysis of the two-phase flow in a hydraulic braking pipeline can reveal its evolution process pertinent for designing and maintaining the hydraulic system. In this study, a high-speed camera examined the two-phase flow pattern and bubble characteristics in a hydraulic braking pipeline. Bubble flow pattern recognition, bubble segmentation, and bubble tracking were performed to analyze the bubble movement, including its behavior, distribution, velocity, and acceleration. The results indicate that the gas–liquid two-phase flow patterns in the hydraulic braking pipeline include bubbly, slug, plug, annular, and transient flows. Experiments reveal that bubbly flow is the most frequent, followed by slug, plug, and transient flows. However, plug and transient flows are unstable, while annular flow occurs at a wheel speed of 200 r/min. Bubbles predominantly appear in the upper section of the pipeline. Furthermore, large bubbles travel faster than small bubbles, whereas slug flow bubbles exhibit higher velocities than those in plug or transient flows. Full article

The present study analyzes the global ionospheric response to the intense geomagnetic storm of 10–11 October 2024 (SYM—H minimum of −346 nT), using observations from COSMIC—2 and Swarm satellites, GNSS TEC, and Digisondes. Significant uplift of the F-region was observed across both Hemispheres on the dayside, primarily driven by equatorward thermospheric winds and prompt penetration electric fields (PPEFs). However, this uplift did not correspond with increases in foF2 due to enhanced molecular nitrogen-promoting recombination in sunlit regions and the F2 peak rising beyond the COSMIC—2 detection range. In contrast, in the Southern Hemisphere nightside ionosphere exhibited pronounced Ne depletion and low hmF2 values, attributed to G-conditions and thermospheric composition changes caused by storm-time circulation. Strong vertical plasma drifts exceeding 100 m/s were observed during both the main and recovery phases, particularly over Ascension Island, driven initially by southward IMF—Bz-induced PPEFs and later by disturbance dynamo electric fields (DDEFs) as IMF—Bz turned northward. Swarm data revealed a poleward expansion of the Equatorial Ionization Anomaly (EIA), with more pronounced effects in the Southern Hemisphere due to seasonal and longitudinal variations in ionospheric conductivity. Additionally, the storm excited Large-Scale Travelling Ionospheric Disturbances (LSTIDs), triggered by thermospheric perturbations and electrodynamic drivers, including PPEFs and DDEFs. These disturbances, along with enhanced westward thermospheric wind and altered zonal electric fields, modulated ionospheric irregularity intensity and distribution. The emergence of anti-Sq current systems further disrupted quiet-time electrodynamics, promoting global LSTID activity. Furthermore, storm-induced equatorial plasma bubbles (EPBs) were observed over Southeast Asia, initiated by enhanced PPEFs during the main phase and suppressed during recovery, consistent with super EPB development mechanisms. Full article

The dynamic relationship between microplastics (MPs) in the air and on the Earth’s surface involves both natural and anthropogenic forces. MPs are transported from the ocean to the air by bubble scavenging and sea spray formation and are released from land sources by air movements and human activities. Up to 8.6 megatons of MPs per year have been estimated to be in air above the oceans. They are distributed by wind, water and fomites and returned to the Earth’s surface via rainfall and passive deposition, but can escape to the stratosphere, where they may exist for months. Anthropogenic sprays, such as paints, agrochemicals, personal care and cosmetic products, and domestic and industrial procedures (e.g., air conditioning, vacuuming and washing, waste disposal, manufacture of plastic-containing objects) add directly to the airborne MP load, which is higher in internal than external air. Atmospheric MPs are less researched than those on land and in water, but, in spite of the major problem of a lack of standard methods for determining MP levels, the clothing industry is commonly considered the main contributor to the external air pool, while furnishing fabrics, artificial ventilation devices and the presence and movement of human beings are the main source of indoor MPs. The majority of airborne plastic particles are fibers and fragments; air currents enable them to reach remote environments, potentially traveling thousands of kilometers through the air, before being deposited in various forms of precipitation (rain, snow or “dust”). The increasing preoccupation of the populace and greater attention being paid to industrial ecology may help to reduce the concentration and spread of MPs and nanoparticles (plastic particles of less than 100 nm) from domestic and industrial activities in the future. Full article

We investigate the interactions between medium-scale traveling ionospheric disturbances (MSTIDs) and the equatorial ionization anomaly (EIA) as well as between MSTIDs and equatorial plasma bubbles (EPBs) on the night of 13–14 May 2013, based on observations from multiple instruments (an all-sky imager, digisonde, and global positioning system (GPS)). Two dark bands (the low plasma density region) for the MSTIDs were observed moving toward each other, encountering and interacting with the EIA, and subsequently interacting again with the EIA before eventually dissipating. Then, a new dark band of MSTIDs moved in the southwest direction, drifted into the all-sky imager’s field of view (FOV), and interacted with the EIA. Following this interaction, a new dark band split off from the original dark band, slowly moved in the northeast direction, and eventually faded away in a short time. Subsequently, the original southwestward-propagating dark band of the MSTIDs encountered eastward-moving EPBs, leading to an interaction between the MSTIDs and the EPBs. Then, the dark band of the MSTIDs faded away, while the EPBs grew larger with a pronounced westward tilt. The results from various observational instruments indicate the pivotal role played by the high-density region of the EIA in the occurrence of various interaction processes. In addition, this study also revealed that MSTIDs propagating into the equatorial region can significantly impact the morphology and evolution characteristics of EPBs. Full article

The explosion-proof performance is an important index for oil-immersed transformers. The nitrogen-sealed transformer is a new type of transformer with nitrogen gas in the upper space, which can buffer against internal stress increase caused by arc faults. However, the pressure changes in the transformer under internal faults are unclear. The authors of this study propose a method based on finite element simulation to analyze the pressure changes and the stress on the tank. First, the calculation process of arc energy and the pressure of the bubbles caused by the arc are derived. Second, the dynamic pressure wave propagation model and acoustic-solid coupling model are established. Last, the finite element simulation model is built to analyze the pressure characteristics. Taking the winding turn-to-turn and phase-to-phase short circuit faults as the analysis situations, the pressure changes in the 110 kV/20 MVA nitrogen-sealed transformer are simulated. Due to the pressure wave refraction and reflection, the pressure changes show oscillatory characteristics with time after the occurrence of an internal short circuit fault. The pressure wave travels from the arc fault position to the periphery. Compared to the conventional transformer, the pressure changes with slower variations under an internal short circuit fault and the tank suffer less stress, which indicates that the nitrogen-sealed transformer is more effective in the explosion-proof performance. Full article

The current energy policy targets reducing energy dependence and minimizing pollutant emissions. Therefore, with the growing interest in using biomass as an alternative energy source, conducting scientific studies on its behavior and optimizing the respective conversion systems has become imperative. The present study focuses on investigating the combustion of biochar pellets in a laboratory-scale traveling grate furnace at three different bed temperatures: 700, 750, and 800 °C. The biochars were obtained via the carbonization process of Pinus pinaster, Acacia dealbata, and Cytisus scoparius pellets. The biochar combustion was studied using a moving-bed carbon particle burning model, supported by kinetic information which was obtained via the combustion of the same biochars in a bubbling fluidized bed. The diffusive parameter which was representative of this traveling grate combustion technology was determined, particularly the bed bypass factor. The combustion tests were carried out with the incomplete combustion of the char pellets. In general, the increase in biochar size led to a decrease in the bypass factor. However, the furnace temperature did not influence this parameter. Full article

Detection of air bubbles in fluidic channels plays a fundamental role in all that medical equipment where liquids flow inside patients’ blood vessels or bodies. In this work, we propose a multi-parameter sensing system for simultaneous recognition of the fluid, on the basis of its refractive index and of the air bubble transit. The selected optofluidic platform has been designed and studied to be integrated into automatic pumps for the administration of commercial liquid. The sensor includes a laser beam that crosses twice a plastic cuvette, provided with a back mirror, and a position-sensitive detector. The identification of fluids is carried out by measuring the displacement of the output beam on the detector active surface and the detection of single air bubbles can be performed with the same instrumental scheme, exploiting a specific signal analysis. When a bubble, traveling along the cuvette, crosses the readout light beam, radiation is strongly scattered and a characteristic fingerprint shape of the photo-detected signals versus time is clearly observed. Experimental testing proves that air bubbles can be successfully detected and counted. Their traveling speed can be estimated while simultaneously monitoring the refractive index of the fluid. Full article

The ionospheric response at middle latitudes to geomagnetic storms is not yet very well understood. Total electron content (TEC) variations associated with eight strong geomagnetic storms between 2015 and 2022 obtained from GNSS receivers in the eastern area of the North Atlantic (Portuguese continental and insular territory) are studied in an attempt to fill this gap. It was found that for most of the studied geomagnetic storms, TEC variations are synchronous for the longitudinal ranges from 27° W and 9° W. In the southern part of the studied region (around 32° N), the amplitude of TEC variations is, in general, significantly higher than in the northern part (around 39° N). Some of the studied geomagnetic storms were associated with TEC variations that we interpret as effects of post-sunset equatorial plasma bubbles that travelled well north from their habitual region. Additionally, though most of the studied storms were accompanied by reports on different kinds of malfunction of GNSS systems (GPS; GALILEO and other), there is no clear pattern in their appearance in dependence on the geomagnetic/ionospheric storms’ strength, commencement time, and its characteristics, in general. Full article

Ground penetrating radar (GPR) has proven to be a very effective method for examining ice thickness. However, two preconditions must be met for this approach to be useful; the round-trip travel time of electromagnetic (EM) waves and radar transmission speed in the ice must be known. These issues are problematic because many factors affect radar transmission speed in ice, including impurities, physical properties such as porosity and density, and temperature. Results show that if these factors are not taken into account and a signal velocity of 0.17 m/ns in pure ice is used to estimate thickness, overestimates will result. We carried out a series of GPR surveys using dual channel host 200 MHz shielded antennas at the Toudaoguai Hydrological Station on the Yellow River, China, and collected samples to analyze ice impurities and physical properties. The results show that the ice crystal types include frazil, granular, and column at the Toudaoguai Hydrologic Station section. Our analysis of ice gas bubble and sediment content showed that the gas bubble volume content is between 11.95 and 13.0% in the frazil ice and between 7.9% and 8.6% in granular and columnar ice. At the same time, the ice sediment content ranged between 0.11‰ and 0.57‰, and the average was 0.24‰ in granular and columnar ice, which was about one-tenth that of the suspended sediment concentration in water. Additionally, a combination of GPR data as well as ice impurities, porosity, density, and temperature enabled us to provide insights on the variability of radar transmission speed and the equivalent dielectric permittivity in river ice. Our extensive observations reveal that radar transmission speed falls between 0.141 m/ns and 0.164 m/ns and that the equivalent dielectric permittivity of river ice increases in concert with ice temperature. Full article

This study presents the observations of midlatitude plasma irregularities over Eastern Asia during a moderate magnetic storm on 16 July 2003. Multi-instrumental observations, including the ground-based ionosondes, the GNSS networks, and the CHAMP and ROCSAT-1 satellites, were utilized to investigate the occurrence and characteristics of midlatitude plasma irregularities. The midlatitude strong spread F (SSF) mainly occurred in the midnight–morning sector as observed by ionosondes over Japan during this storm. SSF was related to plasma depletions, which is also recorded by GNSS network in the form of the enhancement of the rate of total electron content (TEC) change index (ROTI). The possible mechanism for the generation of SSF is that the enhanced eastward electric fields, associated with the prompt penetration electric fields and disturbance dynamo electric fields, cause the uplift and latitudinal extension of equatorial plasma bubbles (EPBs) to generate the observed midlatitude SSF further. Meanwhile, plasma density increased significantly under the influence of this storm. In addition, other common type of spread F, frequency spread F (FSF), was observed over Japan on the non-storm day and/or at high latitude station WK545, which seems to be closely related to the coupling of medium-scale traveling ionospheric disturbances (MSTIDs) and sporadic E (Es) layer. The above results indicate that various types of midlatitude spread F can be produced by different physical mechanisms. It is found that SSF can significantly affect the performance of radio wave propagation compared with FSF. Our results show that space weather events have a significant influence on the day-to-day variability of the occurrence and characteristics of ionospheric F-region irregularities at midlatitudes. Full article

This study aimed to analyze the impact of hosting large events on the spread of pandemics, taking Tokyo Olympics 2020 as a case study. A risk assessment method for the whole organization process was established, which could be used to evaluate the effectiveness of various risk mitigation measures. Different scenarios for Games participants and Japanese residents during the Tokyo Olympics were designed based on the infection control protocols proposed by the Olympic Committee and local governments. A modified Wells–Riley model considering the influence of social distance, masking and vaccination, and an SIQRV model that introduced the effect of quarantine and vaccination strategies on the pandemic spread were developed in this study. Based on the two models, our predicted results of daily confirmed cases and cumulative cases were obtained and compared with reported data, where good agreement was achieved. The results show that the two core infection control strategies of the bubble scheme and frequent testing scheme curbed the spread of the COVID-19 pandemic during the Tokyo Olympics. Among Games participants, Japanese local staff accounted for more than 60% of the total in positive cases due to their large population and most relaxed travel restrictions. The surge in positive cases was mainly attributed to the high transmission rate of the Delta variant and the low level of immunization in Japan. Based on our simulation results, the risk management flaws for the Tokyo Olympics were identified and improvement measures were investigated. Moreover, a further analysis was carried out on the impact of different preventive measures with respect to minimizing the transmission of new variants with higher transmissibility. Overall, the findings in this study can help policymakers to design scientifically based and practical countermeasures to cope with pandemics during the hosting of large events. Full article

By using ionosonde data recorded at Chiang Mai (18.8° N, 98.9° E, magnetic latitude is 9.1° N), Puer (22.7° N, 101.1° E, magnetic latitude is 12.9° N), and Leshan (29.6° N, 103.7° E, magnetic latitude is 19.8° N), the statistical features of different types of spread F (SF) occurrence at low and middle latitudes were analyzed in this study. The results showed that the SF occurrence had obvious local time, latitude, and SF-type variations. The range spread F (RSF) occurrence in equinox months decreased with the increase in latitude, while the frequency spread F’s (FSF) occurrence rate in the summer months increased and the onset time of FSF became earlier when the latitude increased. The generation of SF depends on the SF type. A plasma bubble excited by the generalized Rayleigh–Taylor instability (GRT) at the equator is more likely to produce RSF, while nighttime medium-scale traveling ionospheric disturbances (MSTIDs) induced by Perkins instability at middle latitudes is the main reason for the generation of FSF. Full article

The aim of this hermeneutic-phenomenological study was to explore the perspectives of 12 patients, 17 nurses, and 4 musicians on patient-tailored live music interventions in a hemodialysis setting. Twenty-six semi-structured interviews were collected—17 with patients, 9 with nurses. Furthermore, 18 moderate participation observations, whilst 1 semi-structured group interview with 3 nurses and 3 musicians, and 13 reflective journals from musicians were collected. Within the analysis—based on Ricoeur’s theory of interpretation—two overall themes emerged: (1) the inner space and (2) the participating space, followed by five subthemes: (1a) Entering a calm and enjoyable pause bubble; (1b) Resting in a thought-free state of mind; (1c) Traveling in the past and catching the moment through heartfelt music; (2a) Bringing positive changes into life; (2b) The artistic quality mediating a magnificent and beautiful experience. We found that patient-tailored live music was a meaningful break, influencing mental and physical well-being, time perception, community, work environment, and artistic approach. The artistic quality of the music was essential—together with the musicians’ social awareness, empathy, and ability to interact with the patients—in creating meaningful moments for patients and staff. Overall, the music interventions were a welcome change in a predictable world of stressful routines and repetitive treatments. Full article

The travel bubble program presented an appealing strategy for reopening international travel safely. However, a full vaccination regime is the foremost prerequisite of the program. Therefore, vaccination and the travel bubble are inextricably linked. This study investigated the roles of perceived vaccine efficacy, attitude towards the COVID-19 vaccine, and attitude toward the travel bubble on travel bubble intention. More importantly, the study also examined the mediating role of hope and fear among unvaccinated Korean adults between 20 and 29 years old. A total of 535 samples were collected to test the proposed conceptual model using structural equation modeling. In general, the results supported the proposed hypotheses. Notably, the intention to travel to a bubble destination was explained by 57% of the variance. Furthermore, hope mediated the relationship between vaccine attitude and travel bubble intention. Whereas fear mediated the relationship between perceived vaccine efficacy and intention. Hence, the findings suggest doubts around the vaccine efficacy and that a positive attitude towards the vaccine also install hope among the research samples. Full article

(1) Background: By summer 2021, overseas France turned COVID-19 vaccine and immunity certificates into passports to open travel bubbles. Subsequently, its territories set French records for both COVID-19 and 6-month excess all-cause mortality. (2) Methods: Official time series were collected to compare time correlations between air traffic and COVID-19 transmission and mortality in overseas France, before and after the implementation of immunity passports. (3) Results: Air traffic initially had a reversed relationship with COVID-19, which transitioned into a leader–follower relationship with the introduction of immunity passports. Essentially, air traffic increased 16 days before COVID-19 cases increased (r = 0.61) and 26 days before deaths increased (r = 0.31) in Martinique, 26 days (r = 0.72) and 40 days (r = 0.82) before in Guadeloupe, and 29 days (r = 0.60) and 31 days (r = 0.41) before in Réunion upon introduction of immunity passports. Moreover, air traffic became as correlated as community transmission to COVID-19 mortality in Guadeloupe. (4) Conclusions: Since the introduction of immunity passports, air traffic has been pacesetting COVID-19 within one month for transmission, and within an additional two weeks for mortality in overseas France. Responding to WHO’s call for real-world evidence, this study suggests that COVID-19 passports are not commensurate with health system goals. Full article