Constant Conditions Research Articles

Effect of gradient metal foam on phase change heat storage process under constant rotation condition: A numerical study

Effect of gradient metal foam on phase change heat storage process under constant rotation condition: A numerical study

The discrete unified gas kinetic scheme with constant Neumann boundary condition for flow and heat transfer

The discrete unified gas kinetic scheme with constant Neumann boundary condition for flow and heat transfer

Revealing the Adsorptive Capacity of Cultivated Calcareous Soil Profiles for Humic Acid

ABSTRACT Research on the adsorption of organic matter to soils is important for scientists investigating carbon sequestration and its effects on climate change. Limited studies were carried out to test the capacity of calcareous soils to adsorb organic carbon. The main aim of this work was to find the maximum capacity of calcareous croplands to store organic carbon. An adsorption experiment was performed onto soil samples with different concentrations of humic acid (HA) under constant pH and ionic strength conditions. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms were fitted to the adsorption data, and model parameters were obtained. The results indicated that Langmuir and Temkin isotherms described the adsorption data better than the Freundlich isotherm. The maximum capacity of organic carbon adsorbed was 0.8 g/kg in the soil samples of this study. Deep layers had more capacity (17–34%) to adsorb organic matter than topsoils. The free energy of adsorption (E) derived from Dubinin–Radushkevich isotherm ranged from 0.26 to 1.06 kJ/mol (less than 8 kJ/mol), indicating that the physisorption process occurred. Due to the negligible HA desorption, the whole mechanism was irreversible.

ESTUDO DO DESENVOLVIMENTO ABSOLUTO DOS JUVENIS DO CARANGUEJO VIOLINISTA MINUCA RAPAX (SMITH, 1870) (DECAPODA: OCYPODIDAE), CULTIVADO EM CONDIÇÕES LABORATORIAIS

ABSTRACT This study observed the growth of juvenile Minuca rapax crabs reared in the laboratory up to the 10th juvenile instar. Juveniles were obtained after larval rearing and a total of 50 specimens were used for growth analysis, by measuring the width (L.C.) and length of the cephalothorax (C.C.). The crabs were kept individually in plastic containers containing sandy substrate and filtered seawater, without aeration and under constant conditions of salinity 30, temperature 26°C, pH 8.0 and photoperiod (12:12 h/light:dark). Newly hatched Artemia nauplii were used exclusively as food. The crabs reached the 10th juvenile instar after 184 days of cultivation, showing a reduction in survival rate over successive molts. The growth of M. rapax was continuous, with a strong positive correlation between C.C. and L.C., indicating a linear increase in these variables. A variation was also observed in the duration of the inter-moulting period of the respective instars. The average duration was shorter for the initial instars (4.9 ± 2.8) and extended throughout development, with the highest values in the most advanced instars (16.2 ± 7) days. The ratio between C.C. and L.C. showed a reduction as the juveniles grew, indicating that there was a change in the morphology of the cephalothorax during growth. The availability and type of food, as well as rearing conditions, can be determining factors in the growth of estuarine crab species in the laboratory. Keywords: Fiddler crab, development, juvenile, neotropical species.

Does Temperature Tolerance Increase in Long-Term Domesticated Frankliniella occidentalis Under Constant Temperature?

The wide distribution of Frankliniella occidentalis is largely due to its extreme temperature adaptability. In current studies, most scholars consider environmental changes to be the main factor affecting insect temperature adaptation. However, our previous studies have shown that the adaptability of F. occidentalis to extreme temperature conditions can be strengthened through domestication. In this study, the population of F. occidentalis raised in the laboratory for a long time (2008–2022) under relatively constant temperature and humidity conditions was used as the experimental material. Over 14 years, changes in temperature tolerance after the same high- and low-temperature stress were evaluated by comparing the survival data of the 2010 population, 2016 population (more than 100 generations), and 2022 population (more than 200 generations). The survival data and LT50 values demonstrated significant stage- and sex-specific differences in thermal tolerance: The cold tolerance of F. occidentalis improved significantly, with LT50 decreasing from −12.5 °C (P2010) to −13.4 °C (P2022) for females and −11.5 °C to −13.0 °C for males. Notably, male adults showed higher survival rates than females at −14 °C and −15 °C. Meanwhile, heat tolerance increased most markedly in 2nd instar larvae (ΔLT50 = +4.1 °C). These findings indicate an environment-independent evolutionary pathway within the population, providing a new research direction for insect population evolution.

Research on Centrifugal Pump Speed Measurement Based on Vibration Measurement.

Traditional rotational speed measurement methods, such as invasive sensors and visual recognition technologies, are often constrained by physical wear and environmental limitations. This paper introduces a non-invasive rotational speed measurement approach based on vibration signal frequency spectrum analysis. The proposed method utilizes the Zoom-FFT algorithm to process vibration signals collected during pump operation, enabling the precise identification of the dominant frequency and its correlation with the pump shaft frequency for accurate speed calculation. The experimental results obtained from a centrifugal pump under varying operating conditions demonstrate the following: At a constant rotational speed, flow variations have a minimal impact on the measurement accuracy, with errors ≤0.04%. Under constant flow conditions, the speed calculation accuracy achieves an error rate of 0.27% across different speeds. Compared to traditional methods, the proposed approach exhibits superior reliability and accuracy. This non-invasive method minimizes physical wear and reduces dependency on environmental factors, offering an effective solution for mechanical equipment monitoring and fault diagnosis.

Functional response of two native species Typhlodromus khosrovensis and Euseius amissibilis (Acari: Phytoseiidae) feeding on eggs of Tetranychus urticae (Acari: Tetranychidae)

Typhlodromus (Anthoseius) khosrovensis and Euseius amissibilis are two native phytoseiidae species in different parts of Tehran city, Iran, which were recorded from white mulberry trees, for the first time. The studies about the predator-prey dynamics of native phytoseiids are rare. Thus, this investigation aimed to determine the predatory efficiency of both species against eggs of Tetranychus urticae. Under constant conditions (27 °C, 65% RH, and a photoperiod of 16:8 h L/ D), six egg prey densities (2, 4, 8, 16, 32, and 64) were separately offered to each predator to record its predation rates for 24h. According to the results, T. khosrovensis, and E. amissibilis represented a type II functional response. In T. khosrovensis, the attack rate coefficient (α) was 0.0213 h<sup>-1</sup>, and the handling time (T<sub>h</sub>) was 2.8013 h. These values in E. amissibilis were recorded as 0.0204 h<sup>-1</sup> and 2.3018 h, respectively. The maximum attack rate (T/T<sub>h</sub>) on eggs of T. urticae was estimated to be 8.57 h<sup>-1</sup> for T. khosrovensis, and 9.98 h<sup>-1</sup> for E. amissibilis. Therefore, both native predators illustrated a highly efficient biological control against eggs of T. urticae, although field studies are needed to show their ability as promising predators on mulberry trees in the future.

Hydrocracking of Various Vacuum Residues

The residue conversion processes, coking, visbreaking, and fluid catalytic cracking (FCC), have demonstrated that feedstock quality is the single factor that most affects process performance. While, for the FCC, it is known that the heavy oil conversion at a maximum gasoline yield point can vary between 50 and 85 wt. %, for the vacuum residue hydrocracking, no reports have appeared yet to reveal the dependence of conversion on the quality of vacuum residue being hydrocracked. In order to search for such a dependence, eight vacuum residues derived from medium, heavy, and extra heavy crude oils have been hydrocracked in a laboratory unit at different reaction temperatures. The current study has witnessed that the vacuum residue hydrocracking obeys the same rule as that of the other residue conversion processes, confirming that the feedstock quality has a great influence on the process performance. A conversion variation between 45 and 85 wt. % can be observed when the sediment content in the hydrocracked atmospheric residue is within the acceptable limit, guaranteeing the planned cycle length. An intercriteria analysis was performed, and it revealed that the vacuum residue conversion has negative consonances with the contents of nitrogen and metals. Correlations were developed which predict the conversion at constant operating conditions within the uncertainty of conversion measurement of 1.7 wt. % and correlation coefficient of 0.964. The conversion at constant hydrocracked atmospheric residue (HCAR) sediment content was predicted with a correlation coefficient of 0.985. The correlations developed in this work disclosed that the higher the contents of metals, nitrogen, and asphaltenes, and the lower the content of sulfur, the lower the conversion in the hydrocracking process is. It was also shown that vacuum residues, which have the same reactivity (the same conversion at identical operating conditions), can indicate significant difference in the conversion at the same HCAR sediment content due to their diverse propensity to form sediments in the process of hydrocracking.

Circadian rhythms are more resilient to pacemaker neuron disruption in female Drosophila.

The circadian system regulates the timing of multiple molecular, physiological, metabolic, and behavioral phenomena. In Drosophila, as in other species, most of the research on how the timekeeping system in the brain controls the timing of behavioral outputs has been conducted in males, or sex has not been included as a biological variable. A critical set of circadian pacemaker neurons in Drosophila release the neuropeptide pigment-dispersing factor (PDF), which functions as a key output factor in the network with complex effects on other clock neurons. Lack of Pdf or its receptor, PdfR, results in most flies displaying arrhythmicity in activity-rest cycles under constant conditions. However, our results show that female circadian rhythms are less affected by mutations in both Pdf and PdfR. CRISPR-Cas9-mediated mutagenesis of Pdf, specifically in ventral lateral neurons (LNvs), also has a greater effect on male rhythms. We tested the influence of M-cells on the circadian network and showed that speeding up the molecular clock specifically in M-cells led to sexually dimorphic phenotypes, with a more pronounced effect on male rhythmic behavior. Our results suggest that the female circadian system is more resilient to manipulations of M-cells and the PDF pathway, suggesting that circadian timekeeping is more distributed across the clock neuron network in females.

Energy efficient cascade connected Peltier sensor based air conditioner using liquid coolant heat exchanging methodology and internet of things

This paper presents an energy-efficient air conditioning system integrating cascaded Peltier TEC1-12715 thermoelectric sensors and Internet of Things (IoT) technology. The prototype employs a liquid coolant heat exchanging methodology using ethanol which enhances thermal conductivity and minimizes environmental impact. An ESP32 microcontroller, paired with the Blynk platform, facilitates real-time temperature monitoring and remote control for smart operation. The system maintains a consistent indoor temperature of 21 °C in a 49 square feet room, achieving this setpoint in 24 min under constant power conditions, regardless of external temperature variations. Operating with a maximum power consumption of 570 watts per hour, the unit provides heating and cooling functionalities while delivering an energy savings of up to 0.45 units compared to a 0.75–ton conventional system. Comparative analysis with traditional air conditioning highlights its improved efficiency, suitability for small-scale smart home applications. This innovative approach demonstrates the potential of combining thermoelectric cooling with IoT and alternative coolants for sustainable climate control solutions.

Analytical Study of Atmospheric Pollution Dispersion with Distance Dependent Wind and Constant Removal Dynamics

This study presents an analytical investigation into the dispersion of atmospheric pollutants under the influence of a spatially varying wind velocity and a constant pollutant removal rate. A one-dimensional, steady-state mathematical model is developed, wherein the wind velocity increases linearly with distance from the pollution source, and pollutant removal is modeled through a constant rate sink term representing scavenging processes such as chemical reactions, dry and wet deposition, and precipitation. The governing advection reaction equation is solved exactly, yielding an explicit expression for the pollutant concentration as a function of distance. Parametric analysis reveals that both increasing wind gradients and higher removal rates significantly reduce pollutant concentrations downwind. Specifically, when wind acceleration is present (i.e., non-zero wind gradient), pollutants disperse more rapidly than under constant wind conditions. Additionally, higher removal rates amplify the decay of concentration profiles, particularly in combination with accelerated wind. These findings emphasize the nonlinear interplay between transport and loss mechanisms, offering practical insights for air quality management, urban planning, and the strategic siting of emission sources.

Endogenous regulation of behavior and reproductive physiology in a resident passerine songbird†.

Seasonal timing of reproductive events requires the interaction of the circannual clock and environmental cues. Many avian species exhibit robust circannual rhythms in controlled environments. However, the molecular changes preceding changes in physiology and behavior are poorly understood. The spotted munia (Lonchura punctulata) is an ideal experimental animal to investigate this question as it shows a strong annual cyclicity under prolonged captive conditions. In the current experiment, birds (18 males + 18 females) were maintained under equinox photoperiod (12L:12D, L = light, ~1.86W/m2; D = dark, <0.00014W/m2) with constant temperature (22 ± 2°C) and humidity (58 ± 2%) for ~10months. Based on gonadal status, we identified pre-breeding, breeding, and onset of regression phases and measured body weight, histological changes, active and sleep behavior, and hypothalamic gene expressions. Body fattening, gonadal recrudescence, and organ-specific lipid accumulation were observed during the breeding phase. Increased allopreening behavior coupled with reduced sleep suggested increased social interaction and nighttime vigilance during the reproductive period. The elevated hypothalamic Gonadotropin-Releasing Hormone expression, plasma testosterone, and corticosterone levels during the pre-breeding phase prepared the birds for upcoming reproductive processes. Overall, our data provide evidence of endogenous molecular changes under constant environmental conditions that might inform conserved mechanisms across species.

Estimating the Intra-Puparial Period of Chrysomya nigripes Aubertin Using Morphology and Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) Spectroscopy.

Chrysomya nigripes Aubertin, 1932, is a species of Calliphoridae widely distributed in Southeast Asia, with studies and case reports confirming the value of this species in estimating the minimum postmortem interval (PMImin). However, data on the growth and development of this species' intra-puparial age are not yet complete. Here, we investigated the intra-puparial morphological changes of C. nigripes at seven temperatures, ranging from 16 °C to 34 °C. We also investigated the potential value of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) coupled with chemometric methods for the intra-puparial age estimation of C. nigripes at 19 °C, 25 °C, and 31 °C. The spectral data within the wavenumber range of 1800-900 cm-1, collected from the second thoracic segment of all puparia, were processed. Through this procedure, the mean values of ATR-FTIR spectra of C. nigripes of puparia at each intra-puparial age under various constant temperature conditions were obtained. The results showed that at 16 °C, C. nigripes could not complete its developmental process, while it could do so at the remaining six constant temperatures. With an increase in temperature, the average duration of the intra-puparial period was reduced from the longest at 19 °C of 192 ± 0 h to 77.3 ± 4.6 h at 34 °C. The intra-puparial morphological changes were divided into 12 sub-stages, and the development of the compound eyes, mouthparts, antennae, thorax, legs, wings, and abdomen were divided into 6-8 sub-stages. The Partial Least Squares Discriminant Analysis (PLS-DA) classification model predicted better results compared to the Random Forest (RF) classification model, with an accuracy of 58.3%, 77.8%, and 100% at 19 °C, 25 °C, and 31 °C, respectively. In this study, each sub-stage of the C. nigripes pupa and the time range of structure emergence were recorded, and it was concluded that the spectral trends were time-dependent. Thus, ATR-FTIR combined with chemometrics could also be used as a tool to assist in estimating the intra-puparial stage of C. nigripes and provide a reference value for PMImin.

The Impact of Airflow and Multisensory Feedback on Immersion and Cybersickness in a VR Surfing Simulation.

Virtual Reality (VR) systems have increasingly leveraged multisensory feedback to enrich user experience and mitigate cybersickness. With a similar goal in focus, this paper presents an in-depth exploration of integrating airflow with visual and kinesthetic cues in a VR surfing simulation. Utilizing a custom-designed airflow system and a physical surfboard mounted on a 6-Degree of Freedom (DoF) motion platform, we present two studies that evaluate the effect of the different feedback modalities. The first study assesses the impact of variable airflow, which dynamically adjusts to the user's speed (wind speed) in VR, compared to constant airflow conditions, under both active and passive user engagement scenarios. Results demonstrate that variable airflow significantly enhances immersion and reduces cybersickness, particularly when users are actively engaged in the simulation. The second study evaluates the individual and combined effects of vision, motion, and airflow on acceleration perception, user immersion, and cybersickness, revealing that the integration of all feedback modalities yields the most immersive and comfortable VR experience. This study underscores the importance of synchronized multisensory feedback in dynamic VR environments and provides valuable insights for the design of more immersive and realistic virtual simulations, particularly in aquatic, interactive, and motion-intensive scenarios.

Thermal and CFD Analysis of Evaporator Fins for Efficient Two-Phase Vapor Cooling in Aerospace Systems

The enhancement of heat transfer through secondary fin areas offers a significant advantage in designing and developing compact heat exchangers, where size and weight constraints are critical, particularly in aerospace applications. This study aims to improve the performance of compact heat exchangers by optimizing the heat transfer coefficient. Offset fins are selected over conventional fin configurations due to their superior performance. The fin geometry, with dimensions of 1 × 49, is modeled in a mathematical domain and analyzed using the commercial computational tool ANSYS Fluent. A two-phase flow model is adopted, considering refrigerant R134a. Thermal simulations are conducted under constant heat flux conditions on the wall, with two different mass fluxes (G). Three key parameters, vapor quality, heat transfer coefficient, and pressure drop, are computed. The computational results are validated against experimental data from the literature, showing a deviation of approximately 6%. The total heat load of the evaporator is estimated to be 2.35 kW. The proposed model bridges the gap between theoretical simulations and practical applications, demonstrating significant potential for improving the thermal management of aerospace systems. Also, this work contributes to developing efficient, compact heat exchangers for diverse engineering applications.

Distributed Virtual Inertia Control Strategy for Multi-Virtual Synchronous Machine Parallel System Based on Neighbor Communication.

As a typical grid-forming control method, virtual synchronous generator (VSG) control enhances system inertia but introduces frequency oscillation issues. This problem becomes particularly severe in multi-VSG parallel systems when inconsistent virtual inertia exists among power sources, significantly compromising the security and stability of power system operation. Virtual inertia control can directly regulate the rate of change of frequency (RoCoF) under constant torque difference conditions to suppress frequency oscillations, offering faster response characteristics. Therefore, this paper proposes a distributed virtual inertia control strategy for multi-VSG parallel systems. First, a small-signal model of the multi-machine parallel system is established, and its small-signal stability is demonstrated. Second, a neighbor-communication-based distributed virtual inertia coordination control method is proposed. Through neighbor information exchange and local decision-making, this method enables dynamic adjustment of each unit's virtual inertia, driving frequency synchronization among all units in the system. This effectively suppresses post-disturbance frequency oscillations and enhances the dynamic performance of low-inertia power systems. Furthermore, the stability of the proposed control strategy is rigorously proven through the construction of a Lyapunov energy function. Finally, MATLAB/Simulink simulations verify that the proposed virtual inertia control strategy can effectively mitigate frequency oscillations while reducing their settling time.

Effect of Mechanical Vapour Ejector System on Thermal Performance of Multipurpose Processing Vat during the Manufacture of Khoa

This study evaluated the effect of a Mechanical Vapour Ejector System (MVES) on the thermal performance of a Multipurpose Processing Vat (MPV) during the manufacture of khoa. The investigation was aimed to intensify the process of heat transfer and improve the thermal performance of multipurpose processing vat used for manufacturing various traditional dairy products. The MVES employed MPV was tested under varying air flow rates, steam pressures, and scraper speeds, while maintaining constant feed conditions. Results showed a significant (p&lt;0.05) improvement in evaporation rate (by 17.5%) and overall heat transfer co-efficient, particularly during the concentration stage. Additionally, steam and power consumption were reduced by 12.7% and 10.1%, respectively. The proximate composition of the khoa and its sensory evaluation also indicated enhanced quality in the khoa produced with MVES. These findings suggest that the MVES-integrated MPV is an efficient and energy-saving system for traditional dairy processing.

Autonomous Artificial Molecular Motors and Pumps

AbstractOver the past decade there has been a tremendous development of systems capable to autonomously convert energy, in particular light and chemical, into directed motion at the nanoscale. These nanoscopic devices are called molecular motors. The autonomous operation of artificial molecular motors and pumps under constant experimental conditions represents a key achievement to their implementation into more sophisticated networks. Nonetheless, the principles behind successful autonomous operation are only recently being rationalized. Within this review we focus on the fundamental aspects that enable the autonomous operation of molecular motors exploiting light and chemical energy. We also compare the mechanisms of operation with these two energy sources and highlight the common ground of these systems as well as their differences and specificities by discussing a selection of recent examples in the two classes. Finally, we provide a perspective view on future advances in this exciting research area.

An experimental study on effect of curvatures of upstream tube on thermal performance of downstream tube in cross-flow of air

Heat transfer on a straight tube in the wake of a tube of same diameter with different curvatures was investigated in cross-flow of air at Reynolds number of 35,000. The straight tube was given constant heat flux condition and placed at different spacing ratios of 2.0, 2.25, 2.5, 3.0, 3.5, and 4.0, from the curved tubes at blockage ratio of 0.1. Four different curvatures ratios 0.5, 1.0, 1.5 and 2.0, on curved tubes were given which were aligned with the mainstream as concave and convex profiles forming different combinations of curvature ratios and spacing ratios to analyse their thermal performance. The study shows a paramount advantage of enhanced thermal performance using curved tube combinations over straight tube combinations and identifies a Reynolds number-based inflection point describing “Heat Promoter” as upstream segment of the tube. The results illustrate that concave curved combination with curvature ratio 1.0 at spacing ratio 2.5 exhibited highest thermal performance with 2.36 times enhanced heat transfer.

External Vibration-Assisted Carbon Dioxide Sequestration in Heavy Oil Reservoirs: The Influences of Frequency and Cavity Distribution

This study investigates the effect of external vibration stimulation on CO2 dissolution behavior in heavy oil reservoirs, focusing on the influence of vibration frequency and cavity distribution within porous media. Experiments reveal that 5 Hz vibration significantly enhances CO2 dissolution, while higher frequencies (10 Hz and 20 Hz) hinder the process. A more homogeneous and extensive distribution of oil-depleted cavities further improves dissolution rates, particularly in post-gas flooding scenarios. The dissolution process, observed under constant pressure conditions, is categorized into three stages: cavity filling, fast dissolution, and slow dissolution. Vibration stimulation effectively enhances the fast dissolution stage but has a minimal impact on the slow dissolution stage. Intermittent vibration shows mixed effects, improving dissolution at 100% oil saturation but reducing rates at 90% saturation due to cavity-induced flow disruptions. These findings demonstrate the potential of vibration-stimulated CO2 dissolution (VS-CO2 dissolution) as a novel technique for enhancing CO2 storage and heavy oil recovery in reservoirs. This study provides critical insights for optimizing vibration frequency and cavity distribution, paving the way for improved field applications of this innovative technology.