Maximum Flux Research Articles

Numerical simulation research on thermal insulation performance of composite heat-insulation zone structure in hydrothermal high-temperature mine

In hydrothermal high-temperature abnormal mines, the composite heat-insulation zone structure, formed through a combination of guniting and grouting, serves to mitigate heat dissipation from the surrounding rock into the airflow. To comprehensively understand the thermal insulation performance of the composite heat-insulation zone structure, this study employs numerical simulation to analyze the following aspects: the variation in the temperature field within the surrounding rock of the roadway without insulation, the influence of structural parameters of the composite heat-insulation zone on temperature distribution in the surrounding rock of the roadway, and the thermal insulation effectiveness of the composite heat-insulation zone with varying structures. The findings indicate that the temperature distribution within the surrounding rock of the roadway lacking a heat-insulation zone is relatively uniform. However, as ventilation time extends, the heat regulation zone within the surrounding rock gradually extends deeper, ultimately forming an elliptical cooling area. The composite heat-insulation zone structure effectively mitigates heat transfer from deeper surrounding rock to the roadway wall, consequently altering the scope of the roadway's heat regulation zone. Enhancing the thermal insulation performance of the composite heat-insulation zone structure can be achieved by increasing the thickness of the thermal insulation layer, adjusting grouting rate and depth, and reducing the thermal conductivity of insulation materials. The thermal insulation effectiveness of the thermal insulation layer surpasses that of the grouting layer, with its performance primarily influenced by the thermal conductivity of the materials used. Simulation results demonstrate that the composite heat-insulation zone structure reduces the maximum heat flux on the roadway wall from 47.4 to 37.7 W/m2, resulting in a 20% reduction in heat transfer from deeper surrounding rock. These findings offer valuable insights for implementing thermal insulation techniques in hydrothermal high-temperature anomaly mines.

Coolability of a Corium Pool in a Debris Bed: Impact of Debris Size, Steam, and Liquid Flow Rate; Tilting Angle; and Pressure on Critical Heat Flux—First Numerical Evaluations

In case of a severe accident in a light water reactor, a debris bed may form in the core and possibly melt, as happened in Three Mile Island Unit 2. Knowledge about the coolability of such a molten pool surrounded by debris is crucial to investigate the possibility of stabilizing a part of the fuel inside the vessel. In particular, it is of primary interest to determine the maximum size of a molten pool surrounded by debris that may be stabilized under water. A key parameter is the maximum heat flux [critical heat flux (CHF)] that may be extracted from the pool boundary by water flowing within the debris bed. A facility was built at IRSN to determine the CHF under various conditions. A heated copper surface simulates the boundary of the pool and is placed in contact with a debris bed (monodisperse steel balls), under water. In this article, we first complete previous experimental work with steam and liquid flow rates, ball diameter, tilting angle of the heated surface, and pressure up to 2.5 bar absolute. A general CHF correlation depending on the tilting angle and the steam flow rate is derived, and an example of the use of this correlation to evaluate the maximum mass of the corium pool that can be stabilized under water is given, for some typical reactor conditions. In the last part of the article, the accuracy of the ASTEC code is evaluated based on first calculations intending to reproduce the experimental impact of liquid and steam flow rates.

Design and fabrication of PPTA-braid-reinforced PFA/GE hollow fiber composite membranes

Due to the effects of the rapid development of modern society and fresh water resource pollution, water shortage has further accelerated, which is becoming a very urgent problem. Herein, the poly (p-phenylene terephthalamide)-(PPTA-) braid-reinforced (PBR) poly(tetrafluoroethylene-co-perfluoropropylvinylether)/graphene (PFA/GE) hollow fiber composite membranes (HFCMs) were prepared by dipping coating-thermal sintering coupling technique with a green process. GE is an emerging type of two-dimensional functional nanoparticle with a tunable passageway for oil molecules. The influences of the GE concentration in the casting solution on the structure and performance of the PBR−PFA/GE HFCMs were investigated. The results showed that the addition of GE produced a finger-like pore structure suitable for oil channels. Meanwhile, the roughness and contact angle of the composite membrane increased accordingly, and the water contact angle increased from 115° to 120°. The permeation fluxes of kerosene also increased obviously with the increase of GE contents, and the maximum flux of M-3 reached as high as 217.66 L·m−2·h−1. The application of the lubricating oil flux test under working conditions of 60–150 °C has demonstrated the high-temperature oil permeability resistance of the composite membrane. Even after long-term use, its separation efficiency for water-in-oil emulsions still remains above 99.5 %. In addition, the membrane separation-efficiency both up to 99.9 % for activated carbon and silica dioxide (SiO2) in kerosene. Overall, the PBR-PFA/GE HFCMs with excellent lipophilicity presented great potential for oily wastewater treatment at high temperatures.

Biological Production of Distinct Carbon Pools Drives Particle Export Efficiency in the Southern Ocean

AbstractWe use observations from the Southern Ocean (SO) biogeochemical profiling float array to quantify the meridional pattern of particle export efficiency (PEeff) during the austral productive season. Float estimates reveal a pronounced latitudinal gradient of PEeff, which is quantitatively supported by a compilation of existing ship‐based measurements. Relying on complementary float‐based estimates of distinct carbon pools produced through biological activity, we find that PEeff peaks near the region of maximum particulate inorganic carbon sinking flux in the polar antarctic zone, where net primary production (NPP) is the lowest. Regions characterized by intermediate NPP and low PEeff, primarily in the subtropical and seasonal ice zones, are generally associated with a higher fraction of dissolved organic carbon production. Our study reveals the critical role of distinct biogenic carbon pool production in driving the latitudinal pattern of PEeff in the SO.

Modeling and analysis of a novel 6-DOF magnetic levitation system with experimental verification

To improve the uniformity of magnetic flux and increase the stroke of the magnetic levitation system, this paper designs a novel 6-DOF magnetic levitation system and proposes an improved novel Halbach array. First, a repulsive passive magnetic bearing is utilized to provide levitation force, leading to a noticeable reduction in levitation power consumption. Then, a magnetic circuit model for the magnetic levitation system is established, and the improved novel Halbach array is optimized based on this model. Next, the stable levitation model and measurement model for the system are established, and the magnetic field distribution and magnetic bearing stiffness are analyzed. Results indicated an increase of 0.1[Formula: see text]T in the maximum magnetic flux density, accompanied by an improvement in the uniformity of magnetic flux. Additionally, there is an enhancement of 10% in magnetic bearing stiffness. Finally, a prototype of the system is constructed, and the stable levitation simulation and experiment of the actuator are conducted with this system. The maximum levitation absolute displacement error obtained by simulation is about 655[Formula: see text]nm, and the experimental results exhibited a maximum levitation absolute displacement error of approximately 750 nm for the system, confirming the effectiveness of the proposed modeling method.

Analysis of vacuum operation on hydrogen separation from H2/H2O mixture via Pd membrane using Taguchi method, response surface methodology, and multivariate adaptive regression splines

The influence of vacuum pressure applied on H2 separation from a palladium membrane is explored in this study. Three factors with three levels are considered, including the membrane chamber temperature with levels 320 °C, 350 °C, and 380 °C; the retentate-side total pressure with levels 1, 2, and 3 atm; and the permeation-side vacuum pressure with levels 0, 25, and 50 kPa. The Taguchi, response surface methodology (RSM), and multivariate adaptive regression splines (MARS) methods are employed to analyze the effects of the three parameters on hydrogen separation and predict their optimal combination. The retentate-side total pressure exhibits the highest impact on H2 permeation, following the permeation-side vacuum pressure and then the membrane chamber temperature. The maximum H2 flux is 0.226 mol∙s−1∙m−2, with H2 recovery of 91 % obtained at the optimal conditions with a temperature of 380 °C, a total pressure of 3 atm, and a vacuum pressure of 50 kPa. The improvement in H2 flux reaches 21.6 % compared with the case without the imposed vacuum pressure at the same temperature and total pressure. This result shows the imposed vacuum pressure is an efficient way to enhance H2 permeation. The maximum relative errors between the experimental data and the predictions from the Taguchi, RSM, and MARS methods are 6.74 %, 3.37 %, and 8.08 %, respectively. The RSM method presents higher accuracy than Taguchi and MARS, perhaps due to a more precise analysis of the interaction terms. The smaller amount of input data and ignoring the temperature effect in MARS could be the reason for the lower accuracy. Nevertheless, the MARS method still demonstrates acceptable results. The cost of the Taguchi method is lower than that of the RSM method since it requires fewer experimental cases. In a word, the choice of the prediction method depends on the desired accuracy and the experimental cost.

Experimental Study of Partial Open Side Effect on Natural Convection in a Porous Cavity

This research provides information on the heat transfer in the cavity by natural convection which has a partially open side with a ratio (A = 1, 0.75, 0.5, 0.25) to the surroundings for cooling. It is filled with porous media (glass beads) and saturated with air. The bottom wall was heated with a constant heat flux (q = 1500, 3000, 4500, 6000) W/m2 while the top and other walls of the cavity were well insulated. The porous media had small porosity (0.418), a range of Rayleigh number Ra (57.6-1470). The distribution of temperatures, the local Nusselt number, and the average Nusselt number were all extracted from the testing rig's temperature data. It is clear that the fluid flow and heat transfer are affected by heat flux and the ratio of partially open side. Observed that, the greatest temperature values at maximum heat flux (q) and minimum open ratio (A). Thus, the temperature rising at all values of the constant heat flux and the enhancement of the local Nusselt number at (q = 6000) W/m2 about (5.47%, 3.85%, 1.76%) for (A = 1, 0.75, 0.5) respectively, when compared with (A = 0.25). The enhancement of the average Nusselt number at (q = 6000) W/m2 is about (7.28%, 4.55%, 2.27%) for (A = 1, 0.75, 0.5) respectively, compared with (A = 0.25).

Optimized preparation route for polyamide top-coated forward osmosis membrane for enhanced water flux using industrial wastewater as feed.

The forward osmosis (FO) process has recently gained significant interest in treating wastewater, brackish/seawater and concentrating feedstocks for various operations, including desalination. The study investigates the effect of different synthesis conditions of the polyamide-based thin-film composite (TFC) FO membranes on the membranes' final performance. Taguchi statistical analyses were used to fabricate and optimize the polyamide TFC FO membrane. The process parameters as factors were the amount of polyethersulfone (PES), polyethylene glycol 400 (PEG-400), polyvinyl pyrrolidone (PVP), m-phenylenediamine (MPD), and trimesoyl chloride (TMC), and TMC reaction-time (RT). The Taguchi method was adopted to investigate the optimal conditions and the significance of individual factors using an L16 (45) orthogonal array. Another Taguchi analysis (Taguchi 2) was adopted to investigate the influence of other important parameters like optimal conditions for MPD, TMC, and TMC reaction-time factors using an L9 (33) orthogonal array. Confirmation tests validated a maximum water flux of 46.4 ± 2.32 L/m2·h with a specific combination of control factors for membrane synthesis: PES/PEG/PVP/MPD/TMC/TMC RT-16/7/0.5/1/0.05/30. These tests demonstrated a high-water flux of 7.05 ± 0.35 L/m2·h when exposed to industrial wastewater (secondary effluent) as the feed solution (FS) and fertilizer as the draw solution (DS) in the FO process. The R2 values were more than 90%. The experimental validation confirmed the models' predictive ability with different FSs, including industrial wastewater.

What can be learnt from UHECR anisotropies observations

Context. Various signals of anisotropy of the ultra-high-energy cosmic rays (UHECRs) have recently been reported, whether at large angular scales, with a dipole modulation in right ascension observed in the data of the Pierre Auger observatory (Auger), as discussed in the first paper accompanying the present one, or at intermediate angular scales, with flux excesses identified in specific directions by Auger and the Telescope Array (TA) Collaborations. Aims. We investigated the implications of the current data regarding these intermediate scale anisotropies, and examined to what extent they can be used to shed light on the origin of UHECRs, and constrain the astrophysical and/or physical parameters of the viable source scenarios. We also investigated what could be learnt from the study of the evolution of the various UHECR anisotropy signals, and discussed the expected benefit of an increased exposure of the UHECR sky using future observatories. Methods. We simulated realistic UHECR sky maps for a wide range of astrophysical scenarios satisfying the current observational constraints, with the assumption that the UHECR source distribution follows that of the galaxies in the Universe, also implementing possible biases towards specific classes of sources. In each case, several scenarios were explored with different UHECR source compositions and spectra, a range of source densities and different models of the Galactic magnetic field. We also implemented the Auger sky coverage, and explored various levels of statistics. For each scenario, we produced 300 independent datasets on which we applied similar analyses as those recently used by the Auger Collaboration, searching for flux excesses through either blind or targeted searches and quantifying correlations with predefined source catalogues through a likelihood analysis. Results. We find the following. First, with reasonable choices of the parameters, the investigated astrophysical scenarios can easily account for the significance of the anisotropies reported by Auger, even with large source densities. Second, the direction in which the maximum flux excess is found in the Auger data differs from the region where it is found in most of our simulated datasets, although an angular distance as large as that between the Auger direction and the direction expected from the simulated models at infinite statistics, of the order of ∼20°, occurs in ∼25% of the cases. Third, for datasets simulated with the same underlying astrophysical scenario, and thus the same actual UHECR sources, the significance with which the isotropy hypothesis is rejected through the Auger likelihood analysis can be largest either when ‘all galaxies’ or when only ‘starburst’ galaxies are used to model the signal, depending on which model is used to model the Galactic magnetic field and the resulting deflections. Fourth, the study of the energy evolution of the anisotropy patterns can be very instructive and provide new astrophysical insight about the origin of the UHECRs. Fifth, the direction in which the most significant flux excess is found in the Auger dataset above 8 EeV appears to essentially disappear in the dataset above 32 EeV, and, conversely, the maximum excess at high energy has a much reduced significance in the lower energy dataset. Sixth, both of these appear to be very uncommon in the simulated datasets, which could point to a failure of some generic assumption in the investigated astrophysical scenarios, such as the dominance of one type of source with essentially the same composition and spectrum in the observed UHECR flux above the ankle. Seventh, given the currently observed level of anisotropy signals, a meaningful measurement of their energy evolution, say from 10 EeV to the highest energies, will require a significant increase in statistics and a new generation of UHECR observatories.

Study of the Accuracy of the Ronen Method at Material Interfaces

The Ronen Method (RM) is a nonlinear iterative scheme that demands successive resolutions of the diffusion equation, where local diffusion constants are modified to reproduce more accurate estimates of the neutron currents by a transport operator. The methodology is currently formulated using the formalism of the collision probability method for evaluation of the current. The RM was recently tested on a complete suite of one-dimensional (1-D) multigroup benchmark problems. Small differences in the flux (less than 2%) were reported at material interfaces and close to the vacuum boundary with respect to the reference solution from transport. This work investigates first a possible numerical equivalence between transport and diffusion in some representative 1-D problems from the same benchmark test suite. The equivalence is sought with optimal diffusion coefficients computed using reference transport solutions that allow for adjusting the diffusion model. The RM, which attempts to obtain such equivalent diffusion coefficients without knowing the reference solution, is then compared to the optimal coefficients. The accuracy of the flux distribution at material interfaces is investigated for different approximations of the vacuum boundary and by decreasing progressively the RM convergence tolerance set in the iterative scheme. Using tighter convergence criteria, the RM calculates more accurate flux distributions at all material interfaces, regardless of the value of the diffusion coefficient and the extrapolated distance set at the beginning of the iterative scheme. Maximum flux deviations are remarkably reduced when the RM convergence tolerance is set to eight or more significant digits, leading to improvements in the flux deviation of two orders in magnitude and providing numerical proof for equivalence with transport in the tested configurations.

STONKS: Quasi-real time XMM-Newton transient detection system

Over recent decades, astronomy has entered the era of massive data and real-time surveys. This is improving the study of transient objects -- although they still contain some of the most poorly understood phenomena in astrophysics, as it is inherently more difficult to obtain data to constrain the proposed models. In order to help detect these objects in their brightest state and build synergies with multi-wavelength real-time surveys, we have built a quasi-real time automatic transient detection system for the XMM-Newton pipeline: the Search for Transient Objects in New detections using Known Sources (STONKS) pipeline. STONKS detects long-term X-ray transient events by automatically comparing new XMM-Newton detections to any available archival X-ray data at this position, sending out an alert if the variability between observations (defined as the ratio between the maximum flux and the minimum flux or upper limit) is over 5. This required an initial careful cross-correlation and flux calibration of various X-ray catalogs from different observatories ( XMM-Newton Chandra Swift ROSAT, and eROSITA). A Bayesian framework was put into place to solve any ambiguous associations. We also systematically computed the XMM-Newton upper limits at the position of any X-ray source covered by the XMM-Newton observational footprint, even without any XMM-Newton counterpart. The behavior of STONKS was then tested on all 483 observations performed with imaging mode in 2021. Over the 2021 testing run, STONKS provided a daily alert rate of 0.7$^ $ alerts per day, about 80<!PCT!> of them corresponding to serendipitous sources. Among the detected variable serendipitous sources, there are: several highly variable active galactic nuclei (AGNs) and flaring stars, as well as new X-ray binary and ultra-luminous X-ray source candidates, some of which are present here. STONKS also detected targeted tidal disruption events, ensuring its ability to detect other serendipitous events. As a byproduct of our method, the archival multi-instrument catalog contains about one million X-ray sources, with 15<!PCT!> of them involving several catalogs and 60<!PCT!> of them having XMM-Newton (pointed or slew) upper limits. STONKS demonstrates a great potential for revealing future serendipitous transient X-ray sources, providing the community with the ability to follow-up on these objects a few days after their detection with the goal of obtaining a better understanding of their nature. The underlying multi-instrument archival X-ray catalog will be made available to the community and kept up to date with future X-ray data releases.

About the Possible Solar Nature of the ~200 yr (de Vries/Suess) and ~2000–2500 yr (Hallstadt) Cycles and Their Influences on the Earth’s Climate: The Role of Solar-Triggered Tectonic Processes in General “Sun–Climate” Relationship

(1) Introduction: The subject of the present study concerns the analysis of the existence and long time evolution of the solar ~200 yr (de Vries/Suess) and ~2400 yr (Hallstadt) cycles during the recent part of the Wurm ice epoch and the Holocene, as well as their forcing on the regional East European climate during the last two calendar millennia. The results obtained here are compared with those from our previous studies, as well as with the results obtained by other authors and with other types of data. A possible scenario of solar activity changes during the 21st century, as well as different possible mechanisms of solar–climatic relationships, is discussed. (2) Data and methods: Two types of indirect (historical) data series for solar activity were used: (a) the international radiocarbon tree ring series (INTCAL13) for the last 13,900 years; (b) the Schove series of the calendar years of minima and maxima and the magnitudes of 156 quasi 11 yr sunspot Schwabe–Wolf cycles since 296 AD and up to the sunspot cycle with number 24 (SC24) in the Zurich series; (c) manuscript messages about extreme meteorological and climatic events (Danube and Black Sea near-coast water freezing), extreme summer droughts, etc., in Bulgaria and adjacent territories since 296 and up to 1899 AD, when the Bulgarian meteorological dataset was started. A time series analysis and χ2-test were used. (3) Results and analysis: The amplitude modulation of the 200 yr solar cycle by the 2400 yr (Hallstadt) cycle was confirmed. Two groups of extremely cold winters (ECWs) during the last ~1700 years were established. Both groups without exclusion are concentrated near 11 yr sunspot cycle extremes. The number of ECWs near sunspot cycle minima is about 2 times greater than that of ECWs near sunspot cycle maxima. This result is in agreement with our earlier studies for the instrumental epoch since 1899 AD. The driest “spring-summer-early autumn” seasons in Bulgaria and adjacent territories occur near the initial and middle phases of the grand solar minima of the Oort–Dalton type, which relate to the downward phases and minima of the 200 yr Suess cycle. (4) Discussion: The above results confirm the effect of the Sun’s forcing on climate. However, it cannot be explained by the standard hypothesis for total solar irradiation (TSI) variations. That is why another hypothesis is suggested by the author. The mechanism considered by Svensmark for galactic cosmic ray (GCR) forcing on aerosol nuclei was taken into account. However, in the hypothesis suggested here, the forcing of solar X-ray flux changes (including solar flares) on the low ionosphere (the D-layer) and following interactions with the Earth’s lithosphere due to the terrestrial electric current systems play a key role for aerosol nuclei and cloud generation and dynamics during sunspot maxima epochs. The GCR flux maximum absorption layer at heights of 35–40 km replaces the ionosphere D-layer role during the sunspot minima epochs.

Numerical investigation of droplet impact and heat transfer on hot substrates under an electric field

In this study, the effects of the electric field on the impact dynamics and heat transfer of a single droplet impinging on hot substrates in the film evaporation regime were numerically investigated with phase-field method. According to the simulation results, many fancy impact behaviors of the droplets under a vertical electric field were observed. A strong electric field was found to induce upward pinch-off or even tiny jet phenomena on the hydrophilic substrates. In contrast, the bouncing droplet on hydrophobic substrate would be vertically stretched before leaving the substrates. The maximum spreading ratio of impacting droplets was always inversely proportional to the applied electric field intensity. Correlations of the maximum spreading for the charged condition were proposed by considering the effects of the electric force. In addition, the total heat transfer from hot substrates to the impacting droplet was verified as closely related to the maximum spreading area, spreading time, and instantaneous local heat flux. However, the broken droplets from the induced tiny jet would eventually fall back to disturb the sessile droplet, enhancing the droplet cooling efficiency. The modified heat transfer model of impacting droplets under the effect of an electric field on hydrophilic substrates was established. Finally, the surface charge distribution and electric force loading of the impacting droplets were also discussed. This work delved deep into the underlings of droplet spreading heat transfer under an electric field, and the main findings promised to advance high-efficiency cooling technology.

High-Redshift Quasars at z ≥ 3: Radio Variability and MPS/GPS Candidates

We present a study of the radio variability of bright, S1.4≥100 mJy, high-redshift quasars at z≥3 on timescales of up to 30–40 yrs. The study involved simultaneous RATAN-600 measurements at the frequencies of 2.3, 4.7, 8.2, 11.2, and 22.3 GHz in 2017–2020. In addition, data from the literature were used. We have found that the variability index, VS, which quantifies the normalized difference between the maximum and minimum flux density while accounting for measurement uncertainties, ranges from 0.02 to 0.96 for the quasars. Approximately half of the objects in the sample exhibit a variability index within the range from 0.25 to 0.50, which is comparable to that observed in blazars at lower redshifts. The distribution of VS at 22.3 GHz is significantly different from that at 2.3–11.2 GHz, which may be attributed to the fact that a compact AGN core dominates at the source’s rest frame frequencies greater than 45 GHz, leading to higher variability indices obtained at 22.3 GHz (the VS distribution peaks around 0.4) compared to the lower frequencies (the VS distribution at 2.3 and 4.7 GHz peaks around 0.1–0.2). Several source groups with distinctive variability characteristics were found using the cluster analysis of quasars. We propose seven new candidates for gigahertz-peaked spectrum (GPS) sources and five new megahertz-peaked spectrum (MPS) sources based on their spectrum shape and variability features. Only 6 out of the 23 sources previously reported as GPS demonstrate a low variability level typical of classical GPS sources (VS<0.25) at 4.7–22.3 GHz. When excluding the highly variable peaked-spectrum blazars, we expect no more than 20% of the sources in the sample to be GPS candidates and no more than 10% to be MPS candidates.

Re-entry rocket basic flow characteristics and thermal environment of different retro-propulsion modes

During the supersonic re-entry of multi-nozzle heavy rockets into the atmosphere, the basic flow state becomes increasingly complex due to the coupling effect between the retro-propulsion plumes and the freestream. A numerical method using the hybrid Reynolds-Averaged Navier-Stokes and Large Eddy Simulation (RES) method and discrete coordinate method is developed to accurately estimate the thermal environment. In addition, finite rate chemical kinetics is used to calculate the afterburning reactions. The numerical results agree well with wind tunnel data, which confirms the validity and accuracy of the numerical method. Computations are conducted for the heavy carrier rocket re-entry from 53.1 km to 39.5 km altitude with 180° angle of attack by using three different Supersonic Retro-Propulsion (SRP) modes. The numerical results reveal that these three SRP flow fields are all Short Penetration Models (SPM). As the re-entry altitudes decrease, both the plume-plume interaction and the plume-freestream interaction become weaker. The highest temperatures in the plume shear layers of the three SRP modes increase by 8.36%, 7.33% and 6.92% respectively after considering afterburning reactions, and all occur at a re-entry altitude of 39.5 km. As the rocket re-enters the atmosphere, the maximum heat flux on the rocket base plate of three SRP modes stabilizes at 290, 170 and 200 kW/m2 respectively, but the maximum heat flux on the side wall increases significantly. When the altitude declines to 39.5 km, the extreme heat flux of the three modes increase by 84.16%, 49.45% and 62.97% respectively compared to that at 53.1 km.

Color constancy mechanisms in virtual reality environments.

Prior research has demonstrated high levels of color constancy in real-world scenarios featuring single light sources, extensive fields of view, and prolonged adaptation periods. However, exploring the specific cues humans rely on becomes challenging, if not unfeasible, with actual objects and lighting conditions. To circumvent these obstacles, we employed virtual reality technology to craft immersive, realistic settings that can be manipulated in real time. We designed forest and office scenes illuminated by five colors. Participants selected a test object most resembling a previously shown achromatic reference. To study color constancy mechanisms, we modified scenes to neutralize three contributors: local surround (placing a uniform-colored leaf under test objects), maximum flux (keeping the brightest object constant), and spatial mean (maintaining a neutral average light reflectance), employing two methods for the latter: changing object reflectances or introducing new elements. We found that color constancy was high in conditions with all cues present, aligning with past research. However, removing individual cues led to varied impacts on constancy. Local surrounds significantly reduced performance, especially under green illumination, showing strong interaction between greenish light and rose-colored contexts. In contrast, the maximum flux mechanism barely affected performance, challenging assumptions used in white balancing algorithms. The spatial mean experiment showed disparate effects: Adding objects slightly impacted performance, while changing reflectances nearly eliminated constancy, suggesting human color constancy relies more on scene interpretation than pixel-based calculations.

Core Optimization for Extending the Graphite Irradiation Lifespan in a Small Modular Thorium-Based Molten Salt Reactor

The lifespan of core graphite under neutron irradiation in a commercial molten salt reactor (MSR) has an important influence on its economy. Flattening the fast neutron flux (≥0.05 MeV) distribution in the core is the main method to extend the graphite irradiation lifespan. In this paper, the effects of the key parameters of MSRs on fast neutron flux distribution, including volume fraction (VF) of fuel salt, pitch of hexagonal fuel assembly, core zoning, and layout of control rod assemblies, were studied. The fast neutron flux distribution in a regular hexagon fuel assembly was first analyzed by varying VF and pitch. It was demonstrated that changing VF is more effective in reducing the fast neutron flux in both global and local graphite blocks. Flattening the fast neutron flux distribution of a commercial MSR core was then carried out by zoning the core into two regions under different VFs. Considering both the fast neutron flux distribution and burnup depth, an optimized core was obtained. The fast neutron flux distribution of the optimized core was further flattened by the rational arrangement of control rod channels. The calculation results show that the final optimized core could reduce the maximum fast neutron flux of the graphite blocks by about 30% and result in a more negative temperature reactivity coefficient, while slightly decreasing the burnup and maintaining a fully acceptable core temperature distribution.

Selective transmembrane transport of iodide based on electrochemically induced iodide-trap BiOI/MWCNTs/PVA composite membrane

An electrochemically induced bismuth iodine oxide/multiwalled carbon nanotubes/polyvinyl alcohol (BiOI/MWCNTs/PVA) composite membrane electrode with iodide ion trap (I−-trap) was fabricated by prerelease of I− under reduction potential. The I−-trap BiOI/MWCNTs/PVA composite membrane with unique lattice confinement structures was used for the selective extraction of I− in an electrochemically switched ion permselective (ESIP) process. In the ESIP system, the direct uptake and release of I− were realized by applying a cell voltage-pulse potential (CV-PP) coupling circuit on the membranes to switch the oxidation/reduction state. The I−-trap BiOI/MWCNTs/PVA composite membrane exhibited a maximum flux of 8.32 mg·m−2·min−1 and superior electrochemical stability. The separation factors of I−/Br−, I−/Cl−, I−/NO3−, and I−/SO42−in the mixed solutions were 2.67, 3.71, 3.82, and 6.70 respectively. Therefore, such a novel I−-trap BiOI/MWCNTs/PVA composite membrane could be used in the ESIP system for the selective extraction of I− ions from low concentration solutions.

Two Shell-burning White Dwarfs in Symbiotics of the Small Magellanic Cloud

SMC3 and Lin358 are super-soft X-ray sources (SSS) in symbiotics of the Small Magellanic Cloud. They have been observed as SSS for over 30 yr. We present new observations done in 2014, 2021 and in 2023 with XMM-Newton, NICER, and Chandra. Lin358 is modeled with an effective temperature around 200,000 K, and a maximum flux value around 8.25 × 10−13 erg cm−2 s−1 in 2021. An observation close to periastron revealed hardening of the source. SMC3 is known to undergo an X-ray obscuration approximately every 4.5 yr; we measured the peak X-ray flux of 4.12 × 10−13 in 2014 with the Chandra Low Energy Transmission Grating. Models indicate an effective temperature of about 500,000 K, consistent with previous findings, and increasing luminosity excursion between maxima and minima. We suggest that with such high effective temperature, indicative of steady shell burning, the possibility these systems are on the path to type Ia supernova is worth considering.

Synergism induced intensification for the recovery of phenolic compounds using polymer inclusion membranes containing binary mixed carriers

The separation and recovery of phenolic compounds from wastewater have both economic and practical significance. In this study, polymer inclusion membranes (PIMs) were developed using binary mixed carriers containing trioctylmethylammonium chloride (Aliquat 336) and tributyl phosphate (TBP), and poly(vinyl) chloride (PVC) as the base polymer for the recovery of phenolic compounds from aqueous solutions. The use of mixed carriers Aliquat 336 + TBP enhanced the extractability and transport efficiency of phenol, indicating the presence of synergism. The optimal results of this work showed that the maximum of transport fluxes (JSmax or -JMmax) increased from 0.097 (h−1) using the PIM composed of 40 wt% PVC and 60 wt% Aliquat 336, to 0.143 (h−1) using the PIM composed of 40 wt% PVC + 40 wt% Aliquat 336 + 20 wt% TBP. The addition of TBP eliminated the retention of the extracted Aliquat 336-phenol complexes in the membrane by forming an adduct with extracted species. The extraction/stripping efficiencies of 93.5%/83.8% and the permeability coefficient of 5.88 μm s−1 were obtained. The PIM containing synergistic mixed carriers could be recycled at least 15 times.