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Keywords = quasi-associated process

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13 pages, 1965 KiB  
Article
The Impact of Ten Days of Periodic Fasting on the Modulation of the Longevity Gene in Overweight and Obese Individuals: A Quasi-Experimental Study
by Nurma Yuliyanasari, Eva Nabiha Zamri, Purwo Sri Rejeki and Muhammad Miftahussurur
Nutrients 2024, 16(18), 3112; https://doi.org/10.3390/nu16183112 - 15 Sep 2024
Viewed by 737
Abstract
Background: Fasting potentially alters the aging process induced by obesity by regulating telomere integrity, which is related to longevity genes. However, the impact of periodic fasting (PF) on the expression of longevity genes, particularly Forkhead Box O Transcription Factors (FOXO3a) and the Human [...] Read more.
Background: Fasting potentially alters the aging process induced by obesity by regulating telomere integrity, which is related to longevity genes. However, the impact of periodic fasting (PF) on the expression of longevity genes, particularly Forkhead Box O Transcription Factors (FOXO3a) and the Human Telomerase Reverse Transcriptase (hTERT), is not fully understood. This study aimed to analyze the effects of PF, specifically on FOXO3a, hTERT expression, and other associated factors. Methods: A quasi-experimental 10-day study was conducted in Surabaya, East Java, Indonesia. This study consisted of an intervention group (PFG), which carried out PF for ten days using a daily 12 h time-restricted eating protocol, and a control group (CG), which had daily meals as usual. FOXO3a and hTERT expression were analyzed by quantitative real-time qPCR. A paired t-test/Wilcoxon test, independent t-test/Mann–Whitney U-test, and Spearman’s correlation test were used for statistical analysis. Result: Thirty-six young men participated in this study. During the post-test period, FOXO3a expression in the PFG increased 28.56 (±114.05) times compared to the pre-test, but the difference was not significant. hTERT expression was significantly higher in both the CG and PFG. The hTERT expression in the PFG was 10.26 (±8.46) times higher than in the CG, which was only 4.73 (±4.81) times higher. There was also a positive relationship between FOXO and hTERT in the CG. Conclusions: PF significantly increased hTERT expression in the PFG; however, no significant increase was found in FOXO3a expression. PF regimens using the 12 h time-restricted eating approach may become a potential strategy for preventing obesity-induced premature aging by regulating longevity gene expression. Full article
(This article belongs to the Section Nutrition and Obesity)
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17 pages, 767 KiB  
Review
Nursing Interventions in Primary Care for the Management of Maladaptive Grief: A Scoping Review
by Martín Rodríguez-Álvaro, Pedro Ruymán Brito-Brito, Alfonso Miguel García-Hernández, Irayma Galdona-Luis and Claudio Alberto Rodríguez-Suárez
Nurs. Rep. 2024, 14(3), 2398-2414; https://doi.org/10.3390/nursrep14030178 - 14 Sep 2024
Viewed by 383
Abstract
Grief is a natural and self-limited adaptation process to a new reality that emerges after a significant loss (whether real or perceived), with a broad variety of manifestations that exert an impact on a grieving person’s health. The study aim was to synthesize [...] Read more.
Grief is a natural and self-limited adaptation process to a new reality that emerges after a significant loss (whether real or perceived), with a broad variety of manifestations that exert an impact on a grieving person’s health. The study aim was to synthesize the evidence available about the interventions carried out by Primary Health Care nurses, by means of an individual approach to reduce maladaptive grief or maladaptive grief risk. A scoping review was conducted (November and December 2023) through searches in Medline, Cinahl, Web of Science, ProQuest and Scopus using MeSH terms combined with Booleans. Primary research of any design in adult people undergoing grief situations and receiving professional assistance by nurses in the primary, home and community care contexts published after 2009 in English, Spanish or Portuguese languages were included. Excluded publications were those conducted in in-hospital clinical settings and which did not correspond to research designs or the gray literature. The screening process was carried out by two reviewers using the appropriate JBI critical appraisal tools for each design and discrepancies were resolved by a third reviewer. A total of n = 10 studies were included (n = 4 qualitative, n = 2 RCTs, n = 1 quasi-experimental, n = 2 cross-sectional observational, and n = 2 mixed methods). The qualitative studies identified topics and subtopics of professionals’ and families’ experiences of grief. The observational studies analyzed symptoms and factors associated with the grieving process. Interventions consisted of cognitive–behavioral therapies delivered by psychological specialists who assessed the severity of grief in a range of cultural contexts using different instruments. The evidence retrieved from the studies that address the reduction in maladaptive grief or maladaptive grief risk is not conclusive. There is a need to increase both the number and the methodological quality of studies assessing the effectiveness of Nursing care in Primary Health Care for individuals experiencing maladaptive grief or maladaptive grief risk. Further research should focus on experimental studies, developing specific interventions conducted by nurses to address individual’s grief and prevent maladaptive grief. Full article
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24 pages, 2008 KiB  
Review
A Review on the Arctic–Midlatitudes Connection: Interactive Impacts, Physical Mechanisms, and Nonstationary
by Shuoyi Ding, Xiaodan Chen, Xuanwen Zhang, Xiang Zhang and Peiqiang Xu
Atmosphere 2024, 15(9), 1115; https://doi.org/10.3390/atmos15091115 - 13 Sep 2024
Viewed by 299
Abstract
In light of the rapid Arctic warming and continuous reduction in Arctic Sea ice, the complex two-way Arctic–midlatitudes connection has become a focal point in recent climate research. In this paper, we review the current understanding of the interactive influence between midlatitude atmospheric [...] Read more.
In light of the rapid Arctic warming and continuous reduction in Arctic Sea ice, the complex two-way Arctic–midlatitudes connection has become a focal point in recent climate research. In this paper, we review the current understanding of the interactive influence between midlatitude atmospheric variability and Arctic Sea ice or thermal conditions on interannual timescales. As sea ice diminishes, in contrast to the Arctic warming (cooling) in boreal winter (summer), Eurasia and North America have experienced anomalously cold (warm) conditions and record snowfall (rainfall), forming an opposite oscillation between the Arctic and midlatitudes. Both statistical analyses and modeling studies have demonstrated the significant impacts of autumn–winter Arctic variations on winter midlatitude cooling, cold surges, and snowfall, as well as the potential contributions of spring–summer Arctic variations to midlatitude warming, heatwaves and rainfall, particularly focusing on the role of distinct regional sea ice. The possible physical processes can be categorized into tropospheric and stratospheric pathways, with the former encompassing the swirling jet stream, horizontally propagated Rossby waves, and transient eddy–mean flow interaction, and the latter manifested as anomalous vertical propagation of quasi-stationary planetary waves and associated downward control of stratospheric anomalies. In turn, atmospheric prevailing patterns in the midlatitudes also contribute to Arctic Sea ice or thermal condition anomalies by meridional energy transport. The Arctic–midlatitudes connection fluctuates over time and is influenced by multiple factors (e.g., continuous melting of climatological sea ice, different locations and magnitudes of sea ice anomalies, internal variability, and other external forcings), undoubtedly increasing the difficulty of mechanism studies and the uncertainty surrounding predictions of midlatitude weather and climate. In conclusion, we provide a succinct summary and offer suggestions for future research. Full article
(This article belongs to the Special Issue Arctic Atmosphere–Sea Ice Interaction and Impacts)
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25 pages, 901 KiB  
Article
Transforming Education Leadership through Multiple Approaches to Develop and Support School Leadership
by Stephan Gerhard Huber and Jane Pruitt
Educ. Sci. 2024, 14(9), 953; https://doi.org/10.3390/educsci14090953 - 29 Aug 2024
Viewed by 351
Abstract
This article elaborates on the multiple approaches to develop and support school leadership. In a 5-year quasi-experimental longitudinal mixed-methods study based on a sample of 122 schools in three regions in a German state, 75 school leaders and their teams participated in a [...] Read more.
This article elaborates on the multiple approaches to develop and support school leadership. In a 5-year quasi-experimental longitudinal mixed-methods study based on a sample of 122 schools in three regions in a German state, 75 school leaders and their teams participated in a 3-year program using multiple approaches; the rest served as the control group. The multiple approaches covered the school leaders’ (a) professional development, comprising (i) a professional development program, (ii) individual coaching series, and (b) support for them, including (iii) school consultancy and (iv) additional financial resources. The quality of the interventions (regarding both the process and didactic qualities, as well as outcome qualities) and how the quality of both the school leadership and the schools changes over time as a consequence of these interventions are analyzed. The study’s results show a highly positive assessment of the quality and advantages of the multiple approaches and their benefits for the quality of school leadership and further aspects of the school. The regression analyses demonstrate that positively perceived outcome qualities of the interventions are associated with improvements in numerous dimensions of school quality. Full article
(This article belongs to the Special Issue Transforming Educational Leadership)
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30 pages, 3291 KiB  
Review
Advances in Modeling Approaches for Oral Drug Delivery: Artificial Intelligence, Physiologically-Based Pharmacokinetics, and First-Principles Models
by Yehuda Arav
Pharmaceutics 2024, 16(8), 978; https://doi.org/10.3390/pharmaceutics16080978 - 24 Jul 2024
Viewed by 568
Abstract
Oral drug absorption is the primary route for drug administration. However, this process hinges on multiple factors, including the drug’s physicochemical properties, formulation characteristics, and gastrointestinal physiology. Given its intricacy and the exorbitant costs associated with experimentation, the trial-and-error method proves prohibitively expensive. [...] Read more.
Oral drug absorption is the primary route for drug administration. However, this process hinges on multiple factors, including the drug’s physicochemical properties, formulation characteristics, and gastrointestinal physiology. Given its intricacy and the exorbitant costs associated with experimentation, the trial-and-error method proves prohibitively expensive. Theoretical models have emerged as a cost-effective alternative by assimilating data from diverse experiments and theoretical considerations. These models fall into three categories: (i) data-driven models, encompassing classical pharmacokinetics, quantitative-structure models (QSAR), and machine/deep learning; (ii) mechanism-based models, which include quasi-equilibrium, steady-state, and physiologically-based pharmacokinetics models; and (iii) first principles models, including molecular dynamics and continuum models. This review provides an overview of recent modeling endeavors across these categories while evaluating their respective advantages and limitations. Additionally, a primer on partial differential equations and their numerical solutions is included in the appendix, recognizing their utility in modeling physiological systems despite their mathematical complexity limiting widespread application in this field. Full article
(This article belongs to the Special Issue Mathematical Modeling in Drug Delivery)
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19 pages, 1789 KiB  
Article
Development and Effectiveness Evaluation of 360-Degree Virtual Reality-Based Educational Intervention for Adult Patients Undergoing Colonoscopy
by Minju Gwag and Jaeyong Yoo
Healthcare 2024, 12(14), 1448; https://doi.org/10.3390/healthcare12141448 - 20 Jul 2024
Viewed by 850
Abstract
Providing patients with accurate and organized information about colonoscopy, while reducing anxiety, is critical to the procedure’s success. This study evaluated the impact of an immersive 360° virtual reality (VR)-based educational intervention for first-time adult colonoscopy patients regarding anxiety, attitudes, knowledge, compliance with [...] Read more.
Providing patients with accurate and organized information about colonoscopy, while reducing anxiety, is critical to the procedure’s success. This study evaluated the impact of an immersive 360° virtual reality (VR)-based educational intervention for first-time adult colonoscopy patients regarding anxiety, attitudes, knowledge, compliance with bowel preparation, and bowel cleanliness. A quasi-experimental design with a non-equivalent control group and non-synchronized pretest–post-test clinical trial was conducted with 40 patients in the experimental group and 40 in the control group. The 360° VR intervention included two sessions: precautions before colonoscopy and the colonoscopy process. The control group received education through individual verbal explanations with written materials. The findings indicated that the VR intervention significantly improved patients’ colonoscopy-related anxiety, attitudes, adherence to bowel preparation instructions, and bowel cleanliness. Utilizing 360° VR as an educational tool has the potential to enhance the effectiveness of educational programs by providing realistic information and engaging patients. These findings suggest that 360° VR has the capacity to enhance screening rates and clinical outcomes by reducing negative perceptions associated with colonoscopy. Furthermore, the application of this method can extend to diverse diagnostic testing-related nursing situations in clinical settings. Full article
(This article belongs to the Section Nursing)
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20 pages, 3067 KiB  
Article
Properties of Z1 and Z2 Deep-Level Defects in n-Type Epitaxial and High-Purity Semi-Insulating 4H-SiC
by Paweł Kamiński, Roman Kozłowski, Jarosław Żelazko, Kinga Kościewicz and Tymoteusz Ciuk
Crystals 2024, 14(6), 536; https://doi.org/10.3390/cryst14060536 - 7 Jun 2024
Viewed by 621
Abstract
For the first time, the Z1 and Z2 defects with closely spaced energy levels having negative-U properties are revealed in high-purity semi-insulating (HPSI) 4H-SiC using Laplace-transform photoinduced transient spectroscopy (LPITS). In this material, after switching off the optical [...] Read more.
For the first time, the Z1 and Z2 defects with closely spaced energy levels having negative-U properties are revealed in high-purity semi-insulating (HPSI) 4H-SiC using Laplace-transform photoinduced transient spectroscopy (LPITS). In this material, after switching off the optical trap-filling pulse, either the one-electron or the two-electron thermally stimulated emission from these defects is observed at temperatures 300–400 K. It is found that the former corresponds to the Z10/+ and Z20/+ transitions with the activation energies of 514 and 432 meV, respectively, and the latter is associated with the Z1−/+ and Z2−/+ transitions with the activation energies of 592 meV and 650 meV, respectively. The Z1 and Z2 defect concentrations are found to increase from 2.1 × 1013 to 2.2 × 1014 cm−3 and from 1.2 × 1013 to 2.7 × 1014 cm−3, respectively, after the heat treatment of HPSI 4H-SiC samples at 1400 °C for 3 h in Ar ambience. Using the electrical trap-filling pulse, only the thermal two-electron emission from each defect was observed in the epitaxial 4H-SiC through Laplace-transform deep level transient spectroscopy (LDLTS). The activation energies for this process from the Z1 and Z2 defects are 587 and 645 meV, respectively, and the defect concentrations are found to be 6.03 × 1011 and 2.64 × 1012 cm−3, respectively. It is postulated that the Z1 and Z2 defects are the nearest-neighbor divacancies involving the carbon and silicon vacancies located at mixed, hexagonal (h), and quasi-cubic (k) lattice sites. Full article
(This article belongs to the Special Issue Wide Bandgap Semiconductor: GaN and SiC Material and Device)
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17 pages, 6705 KiB  
Article
Five-Year Evaluation of the PROA-NEN Pediatric Antimicrobial Stewardship Program in a Spanish Tertiary Hospital
by Aurora Fernández-Polo, Susana Melendo-Perez, Nieves Larrosa Escartin, Natalia Mendoza-Palomar, Marie Antoinette Frick, Pere Soler-Palacin and on behalf of the PROA-NEN Working Group
Antibiotics 2024, 13(6), 511; https://doi.org/10.3390/antibiotics13060511 - 30 May 2024
Viewed by 806
Abstract
Introduction: Actions to reduce and optimize antimicrobial use are crucial in the management of infectious diseases to counteract the emergence of short- and long-term resistance. This is particularly important for pediatric patients due to the increasing incidence of serious infections caused by resistant [...] Read more.
Introduction: Actions to reduce and optimize antimicrobial use are crucial in the management of infectious diseases to counteract the emergence of short- and long-term resistance. This is particularly important for pediatric patients due to the increasing incidence of serious infections caused by resistant bacteria in this population. The aim of this study was to evaluate the impact of a pediatric antimicrobial stewardship program (PROA-NEN) implemented in a Spanish tertiary hospital by assessing the use of systemic antimicrobials, clinical indicators, antimicrobial resistance, and costs. Methods: In this quasi-experimental, single-center study, we included pediatric patients (0–18 years) admitted to specialized pediatric medical and surgical units, as well as pediatric and neonatal intensive care units, from January 2015 to December 2019. The impact of the PROA-NEN program was assessed using process (consumption trends and prescription quality) and outcome indicators (clinical and microbiological). Antibiotic prescription quality was determined using quarterly point prevalence cross-sectional analyses. Results: Total antimicrobial consumption decreased during the initial three years of the PROA-NEN program, followed by a slight rebound in 2019. This decrease was particularly evident in intensive care and surgical units. Antibiotic use, according to the WHO Access, Watch and Reserve (AWaRe) classification, remained stable during the study period. The overall rate of appropriate prescription was 83.2%, with a significant increase over the study period. Clinical indicators did not substantially change over the study period. Direct antimicrobial expenses decreased by 27.3% from 2015 to 2019. Conclusions: The PROA-NEN program was associated with reduced antimicrobial consumption, improved appropriate use, and decreased costs without compromising clinical and/or microbiological outcomes in patients. Full article
(This article belongs to the Section Antibiotics Use and Antimicrobial Stewardship)
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17 pages, 3601 KiB  
Article
Simulation and Diagnosis of Physical Precipitation Process of Local Severe Convective Rainstorm in Ningbo
by Tingting Lu, Yeyi Ding, Zan Liu, Fan Wu, Guoqiang Xue, Chengming Zhang and Yuan Fu
Atmosphere 2024, 15(6), 658; https://doi.org/10.3390/atmos15060658 - 30 May 2024
Viewed by 411
Abstract
On 31 July 2021, Ningbo, an eastern coast city in China, experienced a severe convective rainstorm, characterized by intense short-duration precipitation extremes with a maximum rainfall rate of 130 mm h−1. In this research, we first analyzed this rainstorm using Doppler [...] Read more.
On 31 July 2021, Ningbo, an eastern coast city in China, experienced a severe convective rainstorm, characterized by intense short-duration precipitation extremes with a maximum rainfall rate of 130 mm h−1. In this research, we first analyzed this rainstorm using Doppler radar and precipitation observation and then conducted high-resolution simulation for it. A three-dimensional precipitation diagnostic equation is introduced to quantitatively analyze the microphysical processes during the rainstorm. It is shown that this rainstorm was triggered and developed locally in central Ningbo under favorable large-scale quasi-geostrophic conditions and local conditions. In the early stage, the precipitation increase is mainly driven by the strong convergence of water vapor, and a noticeable increase in both the intensity and spatial extent of uplift promotes the upward transportation of water vapor. As the water vapor flux and associated convergence weaken in the later stage, the precipitation reduces accordingly. Cloud microphysical processes are also important in the entire precipitation process. The early stage updraft supports the escalations in raindrops, with the notable fluctuations in raindrop concentrations directly linked to variations in ground precipitation intensity. The behavior of graupel particles is intricately connected to their melting as they fall below the zero-degree layer. Although cloud water and snow exhibit changes during this period, the magnitudes of these adjustments are considerably less pronounced than those in raindrops and graupels, highlighting the differentiated response of various condensates to the convective dynamics. These results can help deepen the understanding of local severe rainstorms and provide valuable scientific references for practical forecasting. Full article
(This article belongs to the Special Issue Characteristics of Extreme Climate Events over China)
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18 pages, 6269 KiB  
Article
The Influence of Sudden Stratospheric Warming on the Development of Ionospheric Storms: The Alma-Ata Ground-Based Ionosonde Observations
by Galina Gordiyenko, Artur Yakovets, Yuriy Litvinov and Alexey Andreev
Atmosphere 2024, 15(6), 626; https://doi.org/10.3390/atmos15060626 - 23 May 2024
Viewed by 543
Abstract
This paper examines the response of the ionosphere to the impact of two moderate geomagnetic storms observed on January 17 and 26–27, 2013, under conditions of strong sudden stratospheric warming. The study uses data from ground-based ionosonde measurements at the Alma-Ata ionospheric station [...] Read more.
This paper examines the response of the ionosphere to the impact of two moderate geomagnetic storms observed on January 17 and 26–27, 2013, under conditions of strong sudden stratospheric warming. The study uses data from ground-based ionosonde measurements at the Alma-Ata ionospheric station (43.25 N, 76.92 E) combined with optical observation data (The Spectral Airglow Temperature Imager (SATI)). Ionosonde data showed that the geomagnetic storms under consideration do not generate ionospheric storms but demonstrate some unusual types of diurnal foF2 variations with large (up to 60%) deviations in foF2 from median values observed during the night/morning periods on 13–15 and 20–23 January, which do not have any relation to solar or geomagnetic activity. Wave-like disturbances in ΔfoF2, Δh’F, and daily averaged foF2 values with a quasi-period of 5–8 days and peak-to-peak amplitude from about 1 MHz to 2 MHz (~from 20% to ~40%) and ~40 km are observed during the period 9–28 January, after registration of the occurrence of the major SSW event on 6–7 January. The observed variations in the OH emission rate are found to be quite similar to those observed in the ionospheric parameters that assume a community of processes in the stratosphere/mesosphere/ionosphere system. The study shows that the F region of the ionosphere is influenced by processes in the lower ionosphere, in this case by processes associated with sudden stratospheric warming SSW-2013, which led to modification of the structure of the ionosphere and compensation of processes associated with the development of the ionospheric storms. Full article
(This article belongs to the Special Issue Effect of Solar Activities to the Earth's Atmosphere)
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14 pages, 4499 KiB  
Article
Symmetries in Collisions as Explored through the Harmonic Oscillator
by Martin Freer and Miriam Davies
Symmetry 2024, 16(2), 231; https://doi.org/10.3390/sym16020231 - 14 Feb 2024
Viewed by 975
Abstract
The present study explores the symmetries associated with the cluster structure of light nuclei and draws the connection between solutions of the Schrödinger equation for the harmonic oscillator and the quasi-crystalline arrangements of α-particles, which gives rise to a series of collective behaviors. [...] Read more.
The present study explores the symmetries associated with the cluster structure of light nuclei and draws the connection between solutions of the Schrödinger equation for the harmonic oscillator and the quasi-crystalline arrangements of α-particles, which gives rise to a series of collective behaviors. The double-center harmonic oscillator is used to formulate the collisions of two nuclei described by harmonic oscillator solutions and traces out the evolution of the cluster structure in the dynamics of the collision process and demonstrates that the symmetries are preserved in this process. The connection between this study and stellar nucleosynthesis is described. Full article
(This article belongs to the Special Issue Role of Symmetries in Nuclear Physics)
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27 pages, 13530 KiB  
Article
Approximation of a Convective-Event-Monitoring System Using GOES-R Data and Ensemble ML Models
by Rodrigo Dávila-Ortiz, José Noel Carbajal-Pérez, Juan Alberto Velázquez-Zapata and José Tuxpan-Vargas
Remote Sens. 2024, 16(4), 675; https://doi.org/10.3390/rs16040675 - 14 Feb 2024
Viewed by 1182
Abstract
The presence of deep convective clouds is directly related to potential convective hazards, such as lightning strikes, hail, severe storms, flash floods, and tornadoes. On the other hand, Mexico has a limited and heterogeneous network of instruments that allow for efficient and reliable [...] Read more.
The presence of deep convective clouds is directly related to potential convective hazards, such as lightning strikes, hail, severe storms, flash floods, and tornadoes. On the other hand, Mexico has a limited and heterogeneous network of instruments that allow for efficient and reliable monitoring and forecasting of such events. In this study, a quasi-real-time framework for deep convective cloud identification and modeling based on machine learning (ML) models was developed. Eight different ML models and model assembly approaches were fed with Interest Fields estimated from Advanced Baseline Imager (ABI) sensor data on the Geostationary Operational Environmental Satellite-R Series (GOES-R) for one region in central Mexico and another in northeastern Mexico, both selected for their intense convective activity and high levels of vulnerability to severe weather. The results indicate that a simple approach such as Logistic Regression (LR) or Random Forest (RF) can be a good alternative for the identification and simulation of deep convective clouds in both study areas, with a probability of detection of (POD) ≈ 0.84 for Los Mochis and POD of ≈ 0.72 for Mexico City. Similarly, the false alarm ratio (FAR) ≈ 0.2 and FAR ≈ 0.4 values were obtained for Los Mochis and Mexico City, respectively. Finally, a post-processing filter based on lightning incidence (Lightning Filter) was applied with data from the Geostationary Lightning Mapper (GLM) of the GOES-16 satellite, showed great potential to improve the probability of detection (POD) of the ML models. This work sets a precedent for the implementation of an early-warning system for hazards associated with intense convective activity in Mexico. Full article
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18 pages, 7069 KiB  
Article
Impact of Electrode Distance in a Quasi-Uniform Model Electrode System on Lightning Impulse Breakdown Voltage in Various Insulating Liquids
by Wiktor Kunikowski, Pawel Rozga, Bartlomiej Pasternak, Jakub Staniewski, Filip Stuchala and Konrad Strzelecki
Energies 2024, 17(4), 782; https://doi.org/10.3390/en17040782 - 6 Feb 2024
Cited by 1 | Viewed by 882
Abstract
This study presents findings on the influence of gap length distance on the lightning impulse breakdown voltage of three dielectric liquids of different chemical origins. The liquids were tested in a model electrode system with a quasi-uniform electric field distribution and a pressboard [...] Read more.
This study presents findings on the influence of gap length distance on the lightning impulse breakdown voltage of three dielectric liquids of different chemical origins. The liquids were tested in a model electrode system with a quasi-uniform electric field distribution and a pressboard plate placed on the grounded electrode. The experimental studies were supported using calculations and simulations to show the individual relationships between the lightning impulse breakdown voltage and gap distance, which represent the so-called volume effect of the most stressed liquid. The results of the experiment, which involved four considered gap distances of 2, 4, 6, and 8 mm, show that a dynamic increase in lightning impulse breakdown voltage with an increase in gap distance is associated with mineral oil and bio-based hydrocarbons. However, similar trends were not observed for synthetic ester. Calculations that allowed us to assess the impact of gap length distance on lightning impulse breakdown voltage support the observations from the experimental studies. The curves obtained in this field can be considered in the process of designing insulating systems for transformers. Full article
(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)
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12 pages, 6202 KiB  
Article
Hydride-Induced Responses in the Mechanical Behavior of Zircaloy-4 Sheets
by Hsiao-Ming Tung and Tai-Cheng Chen
Metals 2024, 14(2), 177; https://doi.org/10.3390/met14020177 - 1 Feb 2024
Viewed by 1049
Abstract
This study aimed to investigate the impact of hydrogen content, up to 1217 ppm, on the mechanical properties of Zircaloy-4, with a particular focus on the formation and impact of hydrides. Tensile specimens were tested across a range of temperatures and hydrogen concentrations. [...] Read more.
This study aimed to investigate the impact of hydrogen content, up to 1217 ppm, on the mechanical properties of Zircaloy-4, with a particular focus on the formation and impact of hydrides. Tensile specimens were tested across a range of temperatures and hydrogen concentrations. The results revealed a pronounced ductile-to-brittle transition associated with hydride formation. When the hydrogen content in the specimens ranged between 700 and 850 ppm, a ductile-to-brittle transition was observed at temperatures of 25 °C, 50 °C, and 75 °C. At 25 °C, the ultimate tensile strength (UTS) of Zircaloy-4 linearly increased as the hydrogen concentration rose from 0 to 1217 ppm H. However, at higher temperatures, the behavior of UTS became more complex, especially in the hydrogen concentration ranges of 500–850 ppm H. Elongation (EL) in the hydrided specimens was affected by both temperature and hydrogen concentration. As hydrogen concentration increased, there was a noticeable decline in uniform EL, while non-uniform EL showed even more significant reductions. Scanning electron microscopy (SEM) analysis of the fracture surfaces revealed that quasi-cleavage features became evident when the hydrogen content reached 850 ppm H, across all tested temperatures. These findings not only provide a quantitative assessment of the safety implications of Zircaloy-4 in nuclear reactor applications but also highlight the importance of the hydrogen charging process and mechanical testing in understanding its mechanical behavior. Full article
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14 pages, 4222 KiB  
Article
The Domain and Structural Characteristics of Ferroelectric Copolymers Based on Vinylidene Fluoride Copolymer with Tetrafluoroethylene Composition (94/6)
by Valentin V. Kochervinskii, Evgeniya L. Buryanskaya, Alexey S. Osipkov, Dmitriy S. Ryzhenko, Dmitry A. Kiselev, Boris V. Lokshin, Aleksandra I. Zvyagina and Gayane A. Kirakosyan
Polymers 2024, 16(2), 233; https://doi.org/10.3390/polym16020233 - 15 Jan 2024
Cited by 2 | Viewed by 1124
Abstract
This paper presents data on the macroscopic polarization of copolymer films of vinylidene fluoride with tetrafluoroethylene obtained with a modified apparatus assembled according to the Sawyer–Tower Circuit. The kinetics of the polarization process were analyzed taking into consideration the contributions of both bound [...] Read more.
This paper presents data on the macroscopic polarization of copolymer films of vinylidene fluoride with tetrafluoroethylene obtained with a modified apparatus assembled according to the Sawyer–Tower Circuit. The kinetics of the polarization process were analyzed taking into consideration the contributions of both bound and quasi-free (impurity) charges. It was shown that an “abnormal” decrease in conductivity was observed in fields near the coercive fields. This could be associated with the appearance of deep traps of the impurity charge carriers formed by the polar planes of β-phase crystals. The conductivity data obtained from the charge and current responses differed. It was concluded that chain segments contributing to polarization with sufficiently low fields were present in the amorphous phase. A comparison showed that the average size of β-phase crystals (crystals of X-ray diffraction reflection width) was almost one order of magnitude lower than the domain size obtained using piezoresponse force microscopy (PFM). The analysis of the fast-stage dielectric response before and after polarization indicated that as the external polarizing field increased in the ferroelectric polymer chains, conformational transitions occurred according to the T3GT3G → (-TT-)n и TGTG → (-TT-)n types. This was accompanied by an increase in the effective dipole moment in the amorphous phase chains. The analysis of the IR spectroscopy data obtained in transmission and ATR modes revealed a difference in the conformational states of the chains in the core and surface parts of the film. Full article
(This article belongs to the Special Issue Stimuli-Responsive Polymers)
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