Pressure Variation Research Articles

Seepage–Deformation Coupling Analysis of a Core Wall Rockfill Dam Subject to Rapid Fluctuations in the Reservoir Water Level

Core wall rockfill dams are susceptible to cracking at the dam’s crest, as well as collapse and settlement of the rockfill during storage and operation periods, particularly due to rapid fluctuations in the water level in pumped storage power stations. Most studies on the impact of fluctuations in the reservoir’s water level on dam deformation have considered fluctuations of less than 5 m/d, while pumped storage power stations experience much larger fluctuations. Additionally, the seepage and stress fields within the dam’s rock and soil interact and influence each other. Few studies have used the coupling theory of seepage and stress to analyze seepage and deformation in core wall rockfill dams. To address these issues, a finite element model using seepage–stress coupling theory was utilized to investigate the variations in the phreatic line, earth pressure, and deformation of a core wall rockfill dam due to rapid fluctuations in the reservoir’s water level. Additionally, the results of the finite element simulation were compared with and analyzed alongside safety monitoring data. The results indicated that, upon a sudden decrease in the reservoir’s water level, there was a lag in the decline of the phreatic line in Rockfill I, which created a large hydraulic gradient, resulting in a reverse seepage field on the dam’s slope surface and generating a drag force directed upstream. Consequently, a significant concentration of stress occurred on one-third of the upstream slope surface of the dam and the seepage curtain, and the increase in horizontal displacement was substantially greater than the increase in settlement from one-third of the rockfill’s height to the dam’s foundation. The deformation was more sensitive to the lowest water level of the reservoir rather than to the fastest rate of decline. Sudden rises in the reservoir’s water level result in decreased horizontal displacements and settlement of the dam. Amid rapid fluctuations of the reservoir’s water level, changes in the vertical earth pressure were more pronounced at the bottom of the core wall than in its midsection. Compared with the core wall, variations in the vertical earth pressure in the upstream and downstream filter layers were minor at similar elevations. A peak horizontal displacement of 6.5 mm was noted at one-third the height of Rockfill I, with the greatest increase in settlement of 3.5 mm at the dam’s crest. To ensure a project’s safety, it is crucial to control the elevation of the lowest point during a sudden drop in the reservoir’s level and to carefully monitor for cracks or voids within approximately one-third of the dam’s height in Rockfill I and at the dam crest. This study’s results provide a scientific basis for assessing core wall rockfill dams’ health and securing long-term safety at pumped storage power facilities.

Role of Hyperbaric Oxygen Therapy in Traumatic Brain Injury: A Systematic Review of Randomized Controlled Trials

Abstract Background Traumatic brain injury (TBI) is a significant public health concern. Standard care involves conservative management and pharmacological and surgical interventions. Hyperbaric oxygen therapy (HBOT) has emerged as a potential treatment for TBI, with varied findings in the literature. Our systematic review aims to comprehensively assess the efficacy and safety of HBOT in TBI management, addressing existing knowledge gaps and providing insights for clinical practice and future research. Methods A systematic literature search was performed in PubMed, SCOPUS, Central Cochrane Registry of Controlled Trials (The Cochrane Library), and ScienceDirect databases for the role of HBOT in TBI. We included studies involving randomized controlled trials (RCTs). Quasi-randomized controlled studies, prospective, retrospective observational studies, case series, case reports, letters, editorials, comments, animal studies, and studies from non-English literature were excluded. Results After identifying 306 articles, we narrowed it to 8 for qualitative synthesis. The studies were categorized into subgroups: those on patients with an acute history of cerebral injury and those with a history of mild TBI. The combined RCTs involved 651 patients (326 in the first subgroup, 325 in the second). Despite a uniform HBOT session duration of 60 minutes, variations in compression, decompression phases, and pressure used (1.5ATA to 2.5ATA) hindered meta-analysis comparability. Outcome measures differed, complicating comparisons. Overall, HBOT appears beneficial in the first group and less so in the second. Complications are primarily pulmonary, which include dyspnea, cyanosis, hyperoxic pneumonia, and increased fraction of inspired oxygen requirement. Conclusion Our study encountered challenges in reaching definitive conclusions due to outcome variability among the included studies. Despite mixed results, HBOT shows potential benefits for acute TBI patients. Conversely, our findings suggest the limited efficacy of HBOT for chronic traumatic brain injury patients. Further research is crucial, particularly exploring diverse HBOT treatment protocols to establish optimal pressure levels and the required number of sessions for effective outcomes

Current Evidence for a New Surgical Technique for Scleral Fixation: The Implantation of a Carlevale Lens, a Systematic Review.

Background: The Carlevale lens (FIL SSF, Soleko IOL Division, Italy) is a new lens for suture-less scleral fixation. This paper aimed to systematically review articles on this lens, the surgical techniques used for its implantation, complications and outcomes. Methods: This systematic review was performed following the PRISMA guidelines. The search string used was "Carlevale" AND "scleral fixation" from inception until March 2024. For completeness, either case-control studies, case reports or case series written in English were included. The authors used the Newcastle-Ottawa scale for the case-control studies and the JBI Critical Appraisal Checklist for case reports and case series. Results: Twenty-nine articles were included. Scleral fixation with Carlevale lens can be performed by creating scleral flaps or, alternatively, by using scleral pockets. The two sclerotomies must be diametrically opposed, and are preferably created by 25-gauge trocars. A pars plana vitrectomy should be performed every time, and the design of the lens should be suitable for self-anchoring to the sclera; the most accredited strategy to achieve this is to avoid scleral sutures. There were only a few intraoperative and postoperative complications reported; vitreous hemorrhages were the most frequent intraoperative events, while the most relevant postoperative complications were vitreous hemorrhages, cystoid macular oedema and transient variations in the intraocular pressure. Excellent results have been obtained in terms of BCVA, IOL centration and stability, mean intraocular pressure, postoperative spherical equivalent, separation between anterior and posterior chamber and the distance of the IOL from anterior chamber structures. Conclusions: The foldable hydrophilic design of the Carlevale lens has shown good effectiveness, IOL stability and few intra and post-operative complications.

Study of wellbore instability in shale formation considering the effect of hydration on strength weakening

Shale formations often contain a high proportion of clay minerals, which, upon contact with drilling fluid, undergo hydration expansion. This leads to wellbore instability, a problem that poses significant challenges globally. This study aims to investigate the variation of mechanical properties of shale with respect to hydration time. We employ an empirical model that relates shale strength parameters to the time of drilling through geological formations. Additionally, we consider both shear failure along the wellbore boundary and shear sliding along bedding planes in the analysis. We establish a predictive model for wellbore instability in shale formations. The model quantitatively analyzes the variation of wellbore collapse pressure with drilling time. The research findings indicate that, when the influence of bedding is considered, both the wellbore collapse pressure and the optimal well trajectory undergo significant changes, in addition, for some wellbore trajectories, the collapse pressure can increase by more than 30%. Therefore, it is essential to account for the influence of bedding in wellbore stability analysis in shale formations. As the bedding dip angle changes, both the numerical values and distribution range of wellbore collapse pressure and the optimal well trajectory change noticeably. Changes in bedding dip direction, however, do not affect the numerical values of collapse pressure but do influence the distribution region of the optimal well trajectory. Thus, in wellbore trajectory design within shale formations, it is crucial to determine the orientation of bedding and adjust the well trajectory accordingly to enhance wellbore stability. Furthermore, shale hydration does not impact the optimal well trajectory for a block, but with prolonged hydration, the minimum drilling fluid density required to maintain wellbore stability gradually increases. This suggests that hydration intensifies the weakening effect on bedding plane strength. The research results are helpful to understand the effect of hydration on shale wellbore stability and ensure shale wellbore stability during drilling cycle.

Simulation of heat and pressure transfer in concentric heat exchangers for small industrial scale

Abstract A Heat exchanger is a tool in industry which aims to transfer energy from hot fluid to cold fluid. The amount of heat transferred is an important parameter of the design and performance of heat exchangers. Concentric tube is a type of heat exchanger that is widely used in industries such as material processing and food preparation. One way to get the value of heat transfered before manufacturing a heat exchanger is to carry out computational fluid dynamic simulations. This simulation will make it easier for us to understand the heat transfer phenomenon that occurs from hot fluid to cold fluid. The aim of this study is to calculate how much heat transfer and pressure drop there is in a laboratory scale cocentric tube type heat exchanger. We also get a picture of the pressure drop that occurs due to fluid friction with the inner pipe walls. Experiments and simulations carried out in this study will then be validated. Variations in flow rate on the tube and shell sides are applied. the greater the flow rate, the greater the transfer of heat. The same trend is shown by variations in pressure. The greater the pressure, the greater the pressure drop that occurs. In this study, the pressure drop from the heat exchanger inlet to the heat exchanger outlet was 0.015%.

Continental and oceanic AAM contributions to Chandler Wobble with the amplitude attenuation from 2012 to 2022

We reconstructed the Chandler Wobble (CW) from 1962 to 2022 by combining the Eigen-oscillator excited by geophysical fluids of atmospheric and oceanic angular momentums (AAM and OAM). The mass and motion terms for the AAM are further divided with respect to the land and ocean domains. Particular attention is placed on the time span from 2012 to 2022 in relation to the observable reduction in the amplitude of the CW. Our research indicates that the main contributor to the CW induced by AAM is the mass term (i.e., the pressure variations over land). Moreover, the phase of the AAM-induced CW remains relatively stable during the interval of 1962–2022. In contrast, the phase of the OAM-induced CW exhibits a periodic variation with a cycle of approximately 20 years. This cyclic variation would modulate the overall amplitude of the CW. The noticeable amplitude deduction over the past ten years can be attributed to the evolution of the CW driven by AAM and OAM, toward a state of cancellation. These findings further reveal that the variation in the phase difference between the CW forced by AAM and OAM, may be indicative of changes in the interaction between the solid Earth, atmosphere, and ocean.

Research on hydraulic variable pressure pumped compressed air energy storage system

Abstract To cope with the problems of large pressure variation, large throttling loss of the existing pumped compressed air energy storage system, a new hydraulic variable pressure pumped compressed air energy storage system is proposed in this paper. The key components include a variable-speed pump turbine, a hydraulic potential energy transfer device and a water-gas compatible tank. For the proposed system, a thermodynamic model is established. And its correctness is verified by comparing it with measured data. Then, the charging and discharging simulation is carried out. Finally, the variation process of each key parameter of the system is revealed. It is found that the energy efficiency of the system is high, reaching 58.2%, and the energy density is 0.36 kW·h/m3. Through the hydraulic potential energy transfer device, the pressure variation of 2.2 MPa in the tank is converted into the head variation of about 60 m (0.6 MPa) at the variable-speed pump turbine, which improves the operating efficiency of the hydraulic machinery. This technology can provide support for the development of energy storage technology.

Community science approach reveals temporal and eutrophication-related spatial patterns in bladderwrack-associated invertebrate fauna

Coastal zones are affected by a variety of anthropogenic drivers. While scientific assessments of the large-scale impacts are often insufficient due to limited resources, community science approaches (i.e. engaging voluntary participation by the general public in scientific research) may allow studying processes on larger geographic and/or temporal scales. In this study, a community science campaign was launched to assess geographic and temporal patterns in subtidal bladderwrack (Fucus vesiculosus) -associated invertebrate fauna along the coastal eutrophication gradient of the Finnish Baltic Sea coast in 2020–2021. The data collected by the community scientists were quality-controlled and generally similar to scientist-collected data. However, most taxa had somewhat lower abundances than data collected with another, more established sampling method. The community composition of fauna differed between areas with varying eutrophication status, and the total abundances of fauna were highest in the areas with the lowest eutrophication impacts. The data also revealed spatial and temporal patterns of individual taxa. For example, the abundance of blue mussel (Mytilus edulis) was highest in less eutrophied areas, while the abundance of non-indigenous Harris mud crab (Rhithropanopeus harrisii) was highest in the areas with moderate eutrophication impacts. A two-fold increase in the abundance of isopods that graze on bladderwrack was observed between the study years, indicating a sizeable temporal variation in bladderwrack grazing pressure. The study provides novel information on bladderwrack-associated invertebrate fauna and the applicability of using community science in marine subtidal research. The results suggest that community science is an effective approach to assessing subtidal community-level patterns, and its continued use is recommended to complement data collection across large spatial and temporal scales in marine key habitats.

Study of boundary layer characteristics during the landfalling of a Nisarga cyclone

One of the most important parameters in meteorology is the mean wind profile in the tropical cyclone boundary layer. The vertical profile of wind speed and wind direction were measured during the period of the Nisarga cyclone from May 31st, 2020, to June 5th, 2020, using the newly installed Phased Array Doppler Sodar system at the Center for Space and Atmospheric Science (CSAS), Sanjay Ghodawat University, Kolhapur (16.74° N, 74.37° E; near India's western coast). Our analysis revealed that the maximum mean wind speed was 17 m/s on June 3, 2020, at 10:00 IST. It also shows the change in wind direction from southwest to southeast on June 2 and 3, 2020. Daily high-resolution reanalysis data in the domain, 0–25°N, 65–110°E, during the period from May 31st to June 5th, 2020, revealed the variation of the atmospheric pressure of the Nisarga cyclone from 1000 to 1008 hPa, sea surface temperature (SST) between 30 °C and 31 °C, outgoing longwave radiation (OLR) between 100 and 240 Wm-2, wind speed between 3 and 15 m/s, and low values of vertical wind shear (VWS) were observed to the north of Nisarga track. These observations may provide more insights for the study of boundary layer turbulence during cyclonic activities.

Quantitative Assessment of Factors Contributing to Variations in Sea Surface pCO2 in the Pacific Sector of the Arctic Ocean

AbstractTo quantitatively assess seasonal variations in the partial pressure of carbon dioxide (pCO2) in the Pacific sector of the Arctic Ocean (Canada Basin and Chukchi Sea) in 2021, water temperature, salinity, chlorophyll‐a, pCO2, dissolved inorganic carbon (DIC), total alkalinity (TA), and nutrients were measured. During summer 2021, surface water pCO2 in our study area (315 ± 41 μatm) was undersaturated with respect to the atmosphere (404 ± 4 μatm), and the ocean was a sink for atmospheric CO2 (−10.5 ± 11.0 mmol C m−2 day−1). Using DIC, TA, and nutrients in the temperature minimum layer, we estimated the under‐ice pCO2 in the water during the previous winter and calculated changes in pCO2 (δpCO2) due to temperature changes, freshwater inflow, biological activity, and other factors (gas exchange and advection) from winter to summer. In the Chukchi Sea, biological activity and temperature changes had significant impacts on pCO2, whereas in the Canada Basin, the influx of freshwater caused a significant decrease in pCO2. Our results suggested that different types of freshwaters had different effects on pCO2, with sea ice meltwater having a greater effect on reducing pCO2 than river water or snowmelt water. We therefore emphasize the importance of freshwater type and proportion, as well as freshwater supply, for prediction of future pCO2 changes.

Study on the influence of intermediate airshafts on the aerodynamic effect of urban rapid rail transit

This study explores how intermediate airshafts affect the aerodynamics of urban rapid transit trains in tunnels. It employs a three-dimensional turbulence model to simulate train-tunnel interactions, specifically examining airshafts’ impact on transient pressure variations along surfaces. The model’s accuracy and reliability are confirmed by comparing results with full-scale experimental data. The results show that airshafts effectively mitigate peak tunnel wall pressures, with the lowest peak overpressure observed at the airshaft location. With the airshaft-reflected expansion wave arriving ahead of the train, the pressure between the train front and tunnel wall decreases compared to scenarios without airshafts. Similar transient pressure changes at the tunnel entrance and rear half suggest the emergence of a “secondary compression wave” due to the train’s transit.

The structural, magnetic, optoelectronic, and mechanical characteristics of NaGeX3 perovskites under pressure for soler-cell applications

This study examines the physical properties of germanium-based halide perovskite through Density Functional Theory (DFT) computations. The physical, optical, mechanical, and magnetic properties of NaGeX3 (X = Cl, Br, and I) were examined with the effects of hydrostatic pressure applied externally. The compounds were subjected to pressure variations ranging from 0 to 5 GPa. The results indicate a decrease in the band gap from the infrared to the visible spectrum. For NaGeCl3, NaGeBr3, and NaGeI3 the band gap decreased from 0.766 eV, 0.497 eV, and 0.400 eV to 0 eV, respectively, indicating the metallic behavior. The mechanical properties of NaGeX3 (X = Cl, Br, and I) demonstrate that for all three compounds, Bulk Modulus (B), Shear Modulus (G), Young’s Modulus (E), Poisson’s ratio (ν), and Pugh’s ratio B/G all increase with increasing pressure. It demonstrates that all these NaGeX3 (X = Cl, Br, I) compounds are ductile in nature. The compounds are determined to be diamagnetic based on their magnetic property investigation, which reveals no notable changes in behavior up to 5 GPa of rising pressure. To gain a better understanding of the properties of the material when incident light strikes its surface, researchers also looked in at optical absorption, reflectivity, dielectric constants, refractive index, conductivity, and loss functions. Pressure-induced NaGeX3 perovskite compounds, where X = Cl, Br, and I, show an increase in dielectric constant as pressure rises, suggesting a decrease in charge carrier recombination rates and a possibility for higher optoelectronic device efficiency. For all NaGeX3 compounds (where X = Cl, Br, and I), the maximum absorption coefficient peaks are located around 3 eV, indicating that increasing pressure increases optical conductivity. Additionally, they have significantly low reflectance throughout the visible spectrum and very narrow band gap, which indicates significant absorption and the possibility of effective Near-Infrared (NIR) Sensors, photodetector etc applications.

Recommendations on setup in simulating atmospheric gravity waves under conventionally neutral boundary layer conditions

Wind farm-induced atmospheric gravity waves have been the subject of recent research as they can impact wind farm performance. Pressure variations associated with gravity waves can contribute to the global blockage effect and wind farm wake recovery. Therefore, accurate numerical simulation of flow fields, where wind-farm-induced gravity waves may be produced, is important. Three main considerations in such simulations are the overall domain size, the use of Rayleigh damping near domain boundaries to dampen gravity waves, and advection damping at the inlet to prevent spurious oscillations. Often these considerations are treated ad hoc rather than systematically. This work aims to test and extend the systematic modelling of internal gravity waves proposed in a preliminary investigation to modelling of both internal and trapped gravity waves. The preliminary study identifies the length scales to set the domain and damping layer sizes and the time scale to configure the Rayleigh damping coefficient but under linearly stratified conditions. Large eddy simulations of flow through a wind farm canopy are performed under conventionally neutral boundary layer (CNBL) conditions to test the validity of proposed setups for CNBL conditions. Background atmospheric parameters, such as Froude number (Fr), inversion height (Hi ), and inversion layer Froude number (Fri ) control most of the atmospheric gravity wave characteristics. We validated for CBNL conditions that the effective wavelengths of the internal gravity waves are the correct length scale to configure the domain size and damping layer thickness. Likewise, the optimum damping coefficient to dampen the internal gravity waves relates to the free atmosphere’s buoyancy frequency or buoyant perturbations’ time scale. We infer that the damping coefficient in the inversion layer may relate to the inversion buoyancy frequency to effectively dampen the trapped gravity waves. Moreover, the advection damping length is linked to the horizontal wavelength of the trapped gravity waves in the inversion layer to prevent spurious waves at the inlet by retaining wave energy accumulation.

Beam-induced backgrounds measured in the ATLAS detector during local gas injection into the LHC beam vacuum

Inelastic beam-gas collisions at the Large Hadron Collider (LHC), within a few hundred metres of the ATLAS experiment, are known to give the dominant contribution to beam backgrounds. These are monitored by ATLAS with a dedicated Beam Conditions Monitor (BCM) and with the rate of fake jets in the calorimeters. These two methods are complementary since the BCM probes backgrounds just around the beam pipe while fake jets are observed at radii of up to several metres. In order to quantify the correlation between the residual gas density in the LHC beam vacuum and the experimental backgrounds recorded by ATLAS, several dedicated tests were performed during LHC Run 2. Local pressure bumps, with a gas density several orders of magnitude higher than during normal operation, were introduced at different locations. The changes of beam-related backgrounds, seen in ATLAS, are correlated with the local pressure variation. In addition the rates of beam-gas events are estimated from the pressure measurements and pressure bump profiles obtained from calculations. Using these rates, the efficiency of the ATLAS beam background monitors to detect beam-gas events is derived as a function of distance from the interaction point. These efficiencies and characteristic distributions of fake jets from the beam backgrounds are found to be in good agreement with results of beam-gas simulations performed with the Fluka Monte Carlo programme.

Cavitational Erosion Behavior of a Biodegradable Alloy from the Zn-Mg System for Biomedical Applications

Zinc and magnesium are known to be biocompatible metals. For this reason, current technologies seek to build parts to be implanted in various places to help the human body. Among these are those in the blood circulatory system, such as the stars and valves at the heart, which aim to increase the life span of the hydrodynamic shocks of the blood circulatory system, in order to prevent heart attacks, respectively the bursting of various vessels that can be life-threatening. Studies in the field of flow show that even in the human body there are manifestations of cavitational type, as a result of pressure variations, with decrease below that of vaporization and then increase. Starting from these findings, the paper presents the results of the cavitation tests, carried out on the bicocompatiobil ZnMg alloy, created in Politehnica University of Bucharest laboratories. The objective is a new and future one that will lead to the realization of valves for the heart, or stars, that can withstand the shocks produced by the implosions of the cavitational bubbles in the blood. For this purpose, microstructural investigations are performed, mechanical properties are analysed and the behavior and resistance to erosion generated by vibrating cavitation are studied, according to the reference standard ASTM G32-2016. The results, compared to those of pure zinc, show that this alloy is a solution for building biocompatible components that can serve cardiac people, in order to reduce the harmful effects of the blood circulatory system.

Suppression mechanism of transient pressure during the turbine runaway of an ultra-high head pump-turbine

Abstract Pressure fluctuation (PF) is a serious issue in transitions of the ultra-high head (UHH) pump-turbines (PTs). To explore the mechanism and control method of PF, the turbine runaway process (TRP) of an UHH PT was simulated using the one- and three-dimensional coupled method. The study suggested that the local backflow (BF) near the high-pressure (HP) inlet of the impeller blocked the impeller channel and induced water hammer. The local BF near the HP inlet of the impeller were closely related to the ratio of rotational speed to PT head. To suppress the BF this study proposed an improved impeller channel with 5 degree spread angle in meridian plane. The study found that the increase of rotational speed and transient pressure variations induced by water hammer could be suppressed successfully by using the improved impeller. The study provided important reference for the design and optimization of the UHH PTs.

Physiological mechanisms behind respiratory variations in right atrial pressure in pulmonary hypertension

Impaired respiratory variation of right atrial pressure (RAP) in severe pulmonary hypertension (PH) suggests difficulty tolerating increased preload during inspiration. Our study explores whether this impairment links to specific factors: right ventricular (RV) diastolic function, elevated RV afterload, systolic RV function, or RV-pulmonary arterial (PA) coupling. We retrospectively evaluated respiratory RAP variation in all participants enrolled in the EXERTION study. Impaired respiratory variation was defined as end-expiratory RAP − end-inspiratory RAP ≤ 2 mm Hg. RV function and afterload were evaluated using conductance catheterization. Impaired diastolic RV function was defined as end-diastolic elastance (Eed) ≥ median (0.19 mm Hg/mL). Seventy-five patients were included; PH was diagnosed in 57 patients and invasively excluded in 18 patients. Of the 75 patients, 31 (41%) had impaired RAP variation, which was linked with impaired RV systolic function and RV-PA coupling and increased tricuspid regurgitation and Eed as compared to patients with preserved RAP variation. In backward regression, RAP variation associated only with Eed. RAP variation but not simple RAP identified impaired diastolic RV function (area under the receiver operating characteristic curve [95% confidence interval]: 0.712 [0.592, 0.832] and 0.496 [0.358, 0.634], respectively). During exercise, patients with impaired RAP variation experienced greater RV dilatation and reduced diastolic reserve and cardiac output/index compared with patients with preserved RAP variation. Preserved RAP variation was associated with a better prognosis than impaired RAP variation based on the 2022 European Society of Cardiology/European Respiratory Society risk score (chi-square P = 0.025) and survival free from clinical worsening (91% vs 71% at 1 year and 79% vs 50% at 2 years [log-rank P = 0.020]; hazard ratio: 0.397 [95% confidence interval: 0.178, 0.884]). Subgroup analyses in patients with group 1 and group 4 PH demonstrated consistent findings with those observed in the overall study cohort. Respiratory RAP variations reflect RV diastolic function, are independent of RV-PA coupling or tricuspid regurgitation, are associated with exercise-induced haemodynamic changes, and are prognostic in PH.Trial registration. NCT04663217.

The Effect of Pressure Variations on the Electronic Structure, Phonon, and Superconducting Properties of Yttrium Hydrogen Selenide Compound

The Effect of Pressure Variations on the Electronic Structure, Phonon, and Superconducting Properties of Yttrium Hydrogen Selenide Compound

A novel investigation into strain-induced changes in the physical properties and solar cell performances of lead-free Ca3NCl3 perovskite

The first-principle calculations were employed to analyze the structural, thermodynamic, electronic, optical, and mechanical properties of calcium-based halide perovskites, Ca3NCl3, under pressure variations from +6 % to −6%. The Ca3NCl3 materials are thermodynamically and dynamically stable, as indicated by the negative final enthalpy values obtained under pressures ranging from −6% to +6 %. The charge density maps confirm the existence of both ionic and covalent bonding features. The unstressed Ca3NCl3 has a direct bandgap of 1.66 eV with PBE functions, 2.32 eV with HSE functions and 1.48 eV with spin-orbit coupling (SOC) at the Γ point. When subjected to compressive strain, the bandgap reduces to 1.37 eV(PBE), 1.93 eV(HSE) and 1.08 eV(SOC) at −6% strain, causing a redshift in absorption coefficient peaks. Conversely, under tensile strain, the bandgap slightly rises to 1.92 eV(PBE), 2.60 eV(HSE) and 1.73 eV(SOC) at +6 % strain, resulting in a blueshift in absorption coefficient peaks. The Ca3NCl3 materials show enhanced optical absorption, loss function, conductivity, dielectric function, refractive index and reflectivity under applied pressure, making them more appropriate for use in solar absorbers, surgical tools, and optoelectronic devices. The investigation of the mechanical properties reveals that the Ca3NCl3 perovskite is mechanically stable. Moreover, with rising pressure (tensile to compressive), elastic constants, elastic moduli, ductility, machinability index, bulk modulus, shear modulus, pugh's ratio, young modulus and anisotropy all rise. The photovoltaic (PV) performance of novel cell configurations, featuring Ca3NCl3 as an absorber and CdS as an Electron Transport Layer (ETL), was systematically studied using the SCAPS-1D simulator. This structure achieved a maximum power conversion efficiency (PCE) of 20.88 %, with a current density (JSC) of 19.184 mAcm−2, a voltage (VOC) of 1.22 V, and a fill factor (FF) of 89.06. The valuable findings from our simulations will aid in the experimental design of an efficient Ca3NCl3-based new inorganic perovskite solar cell in the near future.

Magnetopause MHD surface wave theory: progress & challenges

Sharp boundaries are a key feature of space plasma environments universally, with their wave-like motion (driven by pressure variations or flow shears) playing a key role in mass, momentum, and energy transfer. This review summarises magnetohydrodynamic surface wave theory with particular reference to Earth’s magnetopause, due to its mediation of the solar-terrestrial interaction. Basic analytic theory of propagating and standing surface waves within simple models are presented, highlighting many of the typically-used assumptions. We raise several conceptual challenges to understanding the nature of surface waves within a complex environment such as a magnetosphere, including the effects of magnetic topology and curvilinear geometry, plasma inhomogeneity, finite boundary width, the presence of multiple boundaries, turbulent driving, and wave nonlinearity. Approaches to gain physical insight into these challenges are suggested. We also discuss how global simulations have proven a fruitful tool in studying surface waves in more representative environments than analytic theory allows. Finally, we highlight strong interdisciplinary links with solar physics which might help the magnetospheric community. Ultimately several upcoming missions provide motivation for advancing magnetopause surface wave theory towards understanding their global role in filtering, accumulating, and guiding turbulent solar wind driving.