Phase Change Research Articles

Thermal performance analysis of a lithium-ion cell using the novel fins and the phase change material

The battery thermal management system (BTMS) plays a key role in keeping the electric vehicle battery temperature within thermal safety limits. A poorly designed BTMS may reduce the operational life of the battery. The present work aims to maintain the battery temperature below the threshold limit using the triangular and elliptical-shaped novel fins and the phase change material (PCM). Multiple arrays of these fins were fitted along the cell height in the annulus space between the cell sleeve and the casing such that the tip of the fins touches the casing. The individual and the combined performance of the fins and the PCM was assessed through temperature measurements using the thermocouples and the thermal camera at various power inputs of 30, 50 and 70 W. At 70 W, the cell operation was extended by a maximum of 250 %, 270 % and 280 % for the cell with PCM, with PCM and triangular fins and PCM with elliptical fins, respectively. The lowest extension in cell operation by 10 % was observed for the triangular fins alone at 70 W. This demonstrates the significant influence of the PCM on the cell performance. The temperature contours using the thermal camera showed that for all power settings, the peak temperature occurs at the cell center. The present studies demonstrate a significant potential for BTMS application in the combined system of elliptical fins with PCM.

The role of cavity shapes in improving the performance of a heat sink incorporating nano-enhanced phase change material

Improving the cooling performance of heat sink is critical for providing better thermal management to compact electronic devices. Thus, analyzing various cavity shapes for a heat sink containing Nano-enhanced Phase Change Material is of utmost necessity. The present study focuses on a two-dimensional conjugate heat propagation in a Heat sink with Rectangular (HRC), Trapezoidal (HTC), and Wavy (HWC) cavities. Various cavity shapes are examined to identify the ideal shape for a heat sink containing nano-enhanced Phase Change Material (Ne-PCM). The copper oxide (CuO) nanoparticle enhanced paraffin is considered as Ne-PCM. The analysis encompasses identification of the potent cavity shape, its optimum geometric parameters, the dominant mode of heat transfer and ultimately the desirable thermophysical properties of the Ne-PCM. Among HRC, HTC, and HWC, the heat sink with HRC performs the best by maintaining the lowest base temperature. The HTC, has a better initial performance than the HRC, though HTC has low PCM content. Nevertheless, as time progresses, HTC fails to inhibit the base temperature rise. In contrast, due to increased contact surface area, PCM in HWC experiences a stronger opposing viscous force. Consequently, HWC has conduction-dominated heat transfer and the slowest melting of PCM that elevates the base temperature, accumulating heat near cavity walls. Shortening the relative pitch distance and elongating the relative height of the HRC further lowers the base temperature of the heat sink. Notably, the heat transfer mode analysis reveals that in the cavity with maximum height, heat diffusion dominates convective heat transfer. Heat diffusion increases away from the cavity walls towards the middle of the cavity. Ultimately, it is noted that a denser PCM with high thermal conductivity and low viscosity effectively maintains a low heat sink base temperature. A denser PCM imparts more sensible and latent heat absorption capability and maintains a lower base temperature. On complete melting, the convective heat transfer is much higher in a denser PCM. A PCM with higher thermal conductivity marginally lowers the base temperature with a small increase in PCM melting rate.

Forms and Migration Mechanisms of Phosphorus in the Ice, Water, and Sediments of Cold and Arid Lakes.

Phosphorus (P) is a crucial nutrient in lake ecosystems and organic phosphorus (Po) is a significant component. However, the distribution characteristics and migration behaviour of Po in ice-water-sediment systems under freezing and thawing conditions in cold and arid regions remain unclear. This study aims to investigate the forms of Po and its contribution to endogenous P pollution. We selected three lakes (Dai, Hu, and Wu Lake) and employed phosphorus nuclear magnetic resonance (31P-NMR) techniques to analyse the following: (1) The total phosphorus (TP) content, which was the highest in the water from Dai Lake (0.16 mg/L), with substantial seasonal variation observed in Wu Lake, where P content was four times higher in summer than in winter because of farmland drainage. (2) Eutrophication analysis, which indicated that Dai Lake had significantly higher eutrophication levels than Wu Lake, with P being the controlling factor in Dai Lake and both N and P in Wu Lake. The proportion of Po in the TP content was 90%, 70%, and 55% for Wu, Dai, and Hu Lake, respectively, indicating that Po was the main component of eutrophic lakes. (3) 31P-NMR, which revealed that orthophosphate (Ortho-P) and monoester phosphate (Mon-P) were the main P components in the winter, with a higher P content in Dai Lake. Ortho-P has a higher content in ice, indicating that inorganic phosphorus (Pi) migration is the main factor in ice-water media. Mon-P showed multiple peaks in Dai Lake, indicating a complex composition of adenosine monophosphate and glucose-1-phosphate. (4) The ice-water phase change simulation experiments, which showed that phosphate was the least repelled in ice, while pyrophosphate (Pyro-P) and macromolecular P were more repelled. Adding sediment enhanced the migration of P but did not change the repulsion of macromolecular P, suggesting the molecular structure as the main influencing factor. These results provide important scientific evidence for the quantitative analysis of Po pollution in lake water environments, aiding in P load reduction and risk prevention and control.

Analysis of power generation considering design and finishing materials of thermoelectric energy harvesting blocks

A thermoelectric-generator-based energy-harvesting block capable of continuously generating electricity 24 h a day using solar radiation and waste heat from a building exterior was proposed. The energy-harvesting block consists of a thermoelectric generator and a phase change material. This study aims to investigate the amount of power generated according to various designs and types of finishing materials for energy-harvesting blocks to increase the amount of power generated by small energy-harvesting blocks. It consists of a single-layer energy-harvesting block that removes the thermal resistor, and a double-layer energy-harvesting block that enlarges the area to increase radiation and convection. Four types of energy harvesting blocks applied with black coating were manufactured to increase the insolation absorption rate, and the temperature and open circuit voltage were measured. Among the four types of energy-harvesting blocks, the black-coated double-layer energy-harvesting block produced the maximum power generation of 0.0601 Wh/day. The black coating has a significant influence on the inflow of solar radiation and the amount of power generated, and the double-layer energy-harvesting block is a suitable design to maximize the amount of power generated.

Integration of photo/magnetic responsive composite phase change materials with polyurethane sponge for sustainable and efficient cleanup of crude oil spills

The efficient remediation of viscous oil spills is still a global challenge in practice due to the poor fluidity caused by their high viscosity. The adsorbents with in situ heating characteristics are regard as potential candidate for rapid and efficient crude oil spills cleanup. Although solar-assisted heating is the cleanest and most energy-efficient way, the great variation of sunlight intensity with the season and location is an obstacle to its practical application. To promote oil adsorption and enhance energy utilization efficiency, we constructed a novel adsorbent with simultaneous photo/magnetic-thermal response, and importantly phase change materials (PCMs) as thermal energy storage unit were introduced into the adsorbents. The Co/CNTs with high graphitization as efficient sunlight absorbers can significantly improve the photothermal conversion capacity of the adsorbent, resulting in rapid oil adsorption under solar illumination. Besides, benefiting from the superior magnetic response of Co particles encapsulated in the carbon skeleton, the adsorbent also enables efficient oil adsorption under alternating magnetic field. Most importantly, thanks to the cross-connected network structure of CNTs derived from the carbonization of ZIF-67, the PEG was well anchored in the Co/CNTs particles, which allows the adsorbent to store thermal energy and release heat for sustained cleanup of the oil spills when the energy input is insufficient. The adsorbent integrates with superior photo/magnetic-thermal conversion and thermal storage functions provides an innovative solution for efficient and energy-saving remediation of crude oil spills and breaks new grounds of PCMs applications.

Transient thermal management of laser systems using Plate-Fin phase change heat Exchangers: Experimental and computational study

To mitigate transient thermal shocks in lasers and reduce thermal stresses caused by temperature fluctuations, the use of phase change materials (PCMs) in thermal management systems is a viable solution. This study proposes an innovative two-dimensional transient heat transfer model specifically designed for plate-fin phase change heat exchangers (PFPCHEs). The model meticulously simulates the complex heat transfer phenomena within the heat exchanger, including fluid convection, solid thermal conduction, and the phase change processes of PCM. The convective heat transfer coefficient between fluid and plate is calculated using the Wieting correlation. An advanced pulse-mode experimental test platform was constructed to validate the model, dynamically monitoring and recording outlet temperatures and heat exchange performance for stringent experimental comparison. The research explores the impact of key operating parameters such as initial temperature, flow rate, and inlet temperature of the cooling cycle on the performance of the heat exchanger, providing valuable design and control strategies for transient thermal management of laser systems. The experimental results confirm that the model accurately predicts the dynamic response characteristics and temperature distribution of PFPCHEs under multi-cycle pulse loads, with 96% of the predictions within a 10% error margin. A significant finding is that the initial temperature has negligible influence on the heat transfer characteristics when it is below the solid phase temperature of the PCM. Moreover, by meticulously adjusting the flow rate and inlet temperature of cooling cycle, it is possible to effectively maintain the stability of the outlet temperature throughout the entire pulse cycle. This is crucial for minimizing temperature fluctuations within the thermal management system and extending the service life of electronic components.

Improved phase change performance of ultrasonic-assisted melting: A visualized experimental study

To address the non-constant heat sources and fluctuating user heat loads of renewable energy utilization, ultrasonic-assisted solid-liquid phase change technology with a faster thermal response was proposed for balancing supply and demand. In this study, an ultrasonic field due to its sound flow and cavitation effect was introduced to enhance phase change heat transfer in pure paraffin. The effectiveness of ultrasonic-assisted melting in achieving faster thermal response was experimentally proved. A visual experimental system was established to test the solid-liquid phase change performance of a cavity under varying ultrasonic power and heat sources. Melting interfaces were shot and binarized, while temperature evolutions of paraffin were obtained and compared. Meanwhile, melting endothermicity was also assessed and performed. The experimental results demonstrated that higher ultrasonic power correlated with increased efficiency. The dumbbell-shaped phase interface observed with ultrasonic assistance reflected significant advantages in enhancing overall heat transfer, particularly in the severely underperforming bottom paraffin region. The provision of ultrasonic field decreased melting time by 59.72 % and increased temperature response rate by 161.70 % with a 60 W ultrasonic power compared to no initiating vibration. Ultrasonic-assisted melting also could achieve enhancement of 151.90 % on melting endothermic rate, offering valuable potentiality in notably short heat absorption/thermal storage processing.

Machine learning boiling prediction: From autonomous vision of flow visualization data to performance parameter theoretical modeling

Flow boiling is a highly efficient configuration for meeting the high heat dissipation demands of thermal management systems. However, the complex physics of two-phase flow has hindered its broader application, especially in terms of quantifying visual information. Recent advancements in machine learning vision tools have revolutionized the analysis of phase change phenomena by enabling the digitalization of physically meaningful features such as void fraction, vapor-liquid interfacial behaviors, and liquid-solid wall wetting front areas en masse. In this study, we systematically investigate two-phase models that compute void fractions, heat transfer coefficients, and critical heat flux using live bubble data streams under microgravity. The collected empirical bubble data is used to supplement and validate traditional control-volume-based theoretical modeling approaches. Void fraction data is first validated with analytical frameworks. This is followed by void fractions and wetting front areas being used to improve correlations predicting heat transfer coefficients. This work showcases the potential of using a new machine learning-based strategy to accelerate scientific formula discovery through the extraction of multi-level and physically meaningful features.

Phase change heat storage and enhanced heat transfer based on metal foam under unsteady rotation conditions

Phase change heat storage technology is an essential method for balancing supply and demand in solar energy heat utilization. In this study, a numerical model of the phase change heat storage process is built to explore the impact of non-constant rotation, with and without metal foam. Subsequently, an investigation into the influence of metal foam pore density and porosity on heat storage performance is conducted, with a focus on Taguchi design for statistical analysis. The research delves into the effects of foam parameters on heat storage rate, temperature response, heat storage time, and heat storage properties. Findings reveal significant resolidification in the melting process of this thermal storage structure without metal foam, due to periodic rotation speed hindrance in transferring heat to the outside. Taguchi design results underscore the greater influence of porosity on the melting time and average heat storage rate compared to pore density. Specifically, a reduction in melting time by 62.21 % and 30.49 %, and an increase in average heat storage rate by 237.56 % and 51.19 % is observed when pore density and porosity are 40 PPI and 0.97, compared with the ones with porosities of 0.99 and 0.98, demonstrating minimal impact on total heat absorption.

Electron iso-density surfaces provide a thermodynamically consistent representation of atomic and molecular surfaces

The surface area of atoms and molecules plays a crucial role in shaping many physiochemical properties of materials. Despite its fundamental importance, precisely defining atomic and molecular surfaces has long been a puzzle. Among the available definitions, a straightforward and elegant approach by Bader describes a molecular surface as an iso-density surface beyond which the electron density drops below a certain cut-off. However, so far neither this theory nor a decisive value for the density cut-off have been amenable to experimental verification due to the limitations of conventional experimental methods. In the present study, we employ a state-of-the-art experimental method based on the recently developed concept of thermodynamically effective (TE) surfaces to tackle this longstanding problem. By studying a set of 104 molecules, a close to perfect agreement between quantum chemical evaluations of iso-density surfaces contoured at a cut-off density of 0.0016 a.u. and experimental results obtained via thermodynamic phase change data is demonstrated, with a mean unsigned percentage deviation of 1.6% and a correlation coefficient of 0.995. Accordingly, we suggest the iso-density surface contoured at an electron density value of 0.0016 a.u. as a representation of the surface of atoms and molecules.

Influence of the foam-fin structure on the thermal performance of a coupled phase change liquid cooling module

Effective thermal management is key to ensuring the reliable operation of high power electronic equipment. In this study, the strategy of phase transition and liquid cooling coupling applied to transient high power electronic equipment has been examined. In order to improve the performance of the phase changing material (PCM) in temperature control, the effects of the coupling structure have been addressed with a consideration of fin, copper foam (CF), graphite foam (GF), fin-copper foam (FCF) and fin-graphite foam (FGF) structures in heat dissipation. In this study, pure paraffin wax (PPW) was used as phase change material to prepare heat sinks based on the above five structures. The experimental study investigates the impact of different thermal conductivity strategies on temperature control characteristics, with a focus on cold capacity recovery and the combined phase change and liquid cooling, using pure paraffin wax module as a reference. The results have revealed that the fin-foam coupling structure delivers a better PCM performance than the single fin or foam structure. Operating at a heating power of 10 W, 15 W and 20 W, the temperature control time of the FGF structure was increased by 13.6 %∼14.6 % relative to the GF structure. At 15 °C with flow rates of 1 L/min, 1.5 L/min, 2 L/min liquid cooling conditions, the cooling capacity recovery time was reduced by 18.8 %, 17.2 %, 19.7 %, respectively. In the phase-change liquid-cooling coupling temperature control experiment, the final temperature increase in the FGF system was 11.7 °C -15.2 °C lower than that of the GF system under the same water temperature and volume flow for a 50 W heat source. The incorporation of fins also enhanced the thermal conductivity strengthening capability of the copper foam and reduced the cold recovery time. Based on the comprehensive evaluation, the FGF structure demonstrates superior temperature control performance and cold recovery characteristics of PCM, making it an optimal strengthening method. Following closely are the FCF, GF, Fin and CF structures. Compared to pure paraffin modules, these five modules exhibit varying degrees of improvement in temperature control and cold capacity recovery efficiency. This study provides guidance for optimizing heat sink design based on PCM in electronic applications.

Double emulsion templates for efficient production of phase change microcapsules

The utilization of phase change materials (PCMs) in thermal storage technology exhibits great potential for various applications in thermal management and latent heat storage systems. However, leakage of organic PCMs hinders its practical application. Encapsulation of PCMs in microcapsules with polymer shells can prevent PCM leakage while improving heat transfer and stability. In this study, shell monomers were introduced as an immiscible third phase into the traditional o/w two-phase emulsion system, and the formed three-phase complex emulsion was dynamically reconfigured to exhibit a core–shell encapsulated conformation induced by interfacial tension, resulting in the formation of a thermodynamically stable double emulsion. Microcapsules with 1,6-hexanediol diacrylate (HDDA) shells were successfully prepared using this double emulsion as a template. The emulsion configuration is of significant advantage in promoting stable encapsulation of the phase change material in the shell material, resulting in fast and efficient encapsulation and improved utilization of the phase change material. Phase change microcapsules with different phase change temperatures were prepared and characterized using n-octadecane (C18), methyl stearate (Mes), n-eicosane (C20) and n-docosane (C22) as phase change materials, respectively. Results show that the prepared microcapsules are spherically integrated, with smooth surfaces and obvious core–shell structures, and the enthalpies of phase transition of C18, Mes, C20 and C22 microcapsules are as high as 171.86, 122.37, 165.77 and 178.69 J/g, respectively. These microcapsules exhibit excellent thermal stability and durability and the encapsulation efficiencies exceed 99.7 % at different phase change temperatures. Furthermore, the potential applications of PCM microcapsules in the field of temperature regulation were also demonstrated. This double-emulsion template method provides a straightforward, rapid and scalable approach for the mass production of microcapsules with different core–shell compositions.

Experimental and numerical estimation of thermal conductivity of bio-based building composite materials with an enhanced thermal capacity

The paper tackles the important problem of estimating and predicting the thermal conductivity of bio-based building materials that can help decarbonize the building sector. Knowledge and the possibility to optimize their insulating properties is the first criterion for determining the ability of their use in the building sector. The novel yet not well-studied hemp shives and magnesium binder composites with improved thermal mass by microencapsulated phase change material (PCM) were considered. The samples of composites without PCM having different densities as well as with different amounts of microencapsulated PCM and the same density were manufactured and tested experimentally in different states, i.e., dry and after conditioning at relative humidity (RH) of 50, 75, and 90 %, and in the case of samples with PCM also at different average measurement temperatures selected with respect to the phase change range of the PCM. A novel method of predicting bio-based composites' effective thermal conductivity tensor was also developed. The method is based on the numerical solution of the heat conduction equation at the micro-scale considering real composite microstructure. The method was tuned using micro-computed tomography (μCT) data with the microstructure of composites without PCM and then applied to predict the thermal conductivities of composites with PCM, utilizing computational domains with an artificially distributed PCM in the binder. The experimental testing of composites without PCM revealed an apparent effect of increasing thermal conductivity with rising sample density and RH applied during conditioning. With an increase in density from 394 to 576 kg/m3, their thermal conductivities varied from 0.105 to 0.159 W/m/K for the dry state and from 0.157 to 0.241 W/m/K for RH 90 %. A similar effect of sample state and RH was observed for composites with microencapsulated PCM, which had the highest thermal conductivity, equal to 0.265 W/m/K, for the lowest PCM amount and RH 90 %. Moreover, a decrease in composites' effective thermal conductivity with an increase in PCM fraction was observed, except for the lowest PCM fraction, for which it increased. It also rose with increasing the average measurement temperature. The developed micro-scale-based numerical method allowed for predicting the thermal conductivities of composites with accuracies below 4.1 and 7.2 % for composites without and with PCM, respectively, except for the composite with the lowest amount of PCM, which behaved differently. Thus, its suitability for designing and optimizing bio-based composites was shown.

Simulation of boost path and phase control method in supercritical CO2 pipeline commissioning process

CO2 pipeline can be applied to Enhanced Oil Recovery (EOR) projects and CO2 geological storage projects, and has high engineering application value. However, pipeline transportation of CO2 is a high-risk link in CO2 storage projects. The phase state commonly used to transport CO2 is a supercritical state with both gaseous and liquid characteristics, and there are also great challenges in the field of pipeline transportation. The existing researches have carried out a lot of exploration and application development in the heat transfer, phase change, transient and special conditions of supercritical CO2 pipeline operation.In this paper, the modeling and exploration of the commissioning process before the formal operation of the supercritical CO2 pipeline are carried out, and the boost path of the supercritical CO2 pipeline in the phase diagram under different working conditions is obtained. The model developed in this paper is based on the sensitivity analysis of the effects of variables such as ground temperature, filling pressure speed, and whether to perform pressure-stabilizing leak detection operations. The step-up path in the phase diagram of the CO2 pipeline commissioning process and the adjustment control method are obtained. And the critical temperature of each working condition that cannot avoid phase transition, thus contributing to the existing knowledge system in this field.

Effects of Freeze–Thaw Cycles and the Prefreezing Water Content on the Soil Pore Size Distribution

Volumetric changes induced by soil moisture phase changes can lead to pore system redistribution in freezing and thawing soil, which in turn affects soil strength and stability. The prefreezing water content and the number of freeze–thaw cycles (FTCs) affecting key factors of soil pore changes, and they determine the volumetric change magnitude and frequency during ice–water phase transitions. This study aims to reveal the effect of the prefreezing water content and the number of freeze–thaw cycles on the pore size distribution (PSD) of black soil, meadow soil and chernozem, which account for the largest arable land area in Heilongjiang Province, China. In situ soil samples with different prefreezing water contents were subjected to 1, 2, 3, 5, 10, and 20 FTCs, and then nuclear magnetic resonance (NMR) was used to quantify the PSD. It was shown that the pore sizes of the three soil types spanned multiple orders of magnitude, ranging from 0.001 to 100 μm overall. The inflection point of the cumulative porosity curves of all three soils occurred near 0.1 μm. For black soil and chernozem with high prefreezing water contents, when the number of FTCs reached 10 or 20, the soil self-weight led to thaw settlement, which reduced the difference in the total porosity of the soils with varying moisture contents. The initial FTC exerts the most significant influence on the pore structure. The impact of the prefreezing water content on soil pore structure diminishes as the number of FTCs increases. The plant root residues rendered meadow soil less sensitive to water content differences after the first FTCs but also limited the development of macropores during the late freeze–thaw period. The prefreezing water content alters the distribution of soil moisture before freezing and has a greater influence on the pore distribution of frozen-thawed soils compared to the cumulative effect of multiple FTCs.

Melting and heat management of phase change material using smart ternary-hybrid coolant

This research investigates the effectiveness of using a smart ternary-hybrid nanofluid to enhance the melting rate and convective behavior of electrically conducting tin (Sn) in a rectangular enclosure under the influence of a uniform magnetic field. The enclosure has adiabatic vertical walls with hot and cold temperatures on the bottom and top walls. The finite element method (FEM) is used to solve the governing equations with appropriate boundary conditions using Galerkin's weighted residual approach. The study focuses on applying tin as the phase change material (PCM), with the highest temperature of 508 K, the lowest temperature of 503 K, and the melting interface temperature of 505 K. To enhance the heat transfer performance, tin-based ternary (graphene (G), silicon carbide (SiC), and nickel (Ni)) hybrid smart coolant is applied into the system. To investigate the mechanism of the melting and convective thermal transfer process, the results of the present study are reported with time for various values of the magnetic field (Ha) and solid concentration of ternary hybrid nanoparticle (ϕ). This study represents the streamlines, isothermal lines, melting interface, melting fraction, and heat transfer for the above-mentioned parameters. The results show that increasing the magnetic field reduces the rate of thermal transport by 38.96 % at t = 4000s. However, at a particular time of 2500s, increasing the solid volume fraction of nanoparticles enhances the melting fraction by approximately 8.34 %. Two regression equations are derived for the Nusselt number and melting fraction, with multiple response variables. This article improves understanding of natural convective heat transport during phase change processes for various coolants in different engineering applications.

Operando electrical biasing TEM experiments of Ge-rich GST thin films with FIB sample preparation

Ge-Sb-Te (GST) ternary alloy is the core material for phase-change memory (PCM). Compared with Ge2Sb2Te5 (GST-225), Ge-rich GST (GGST) has a higher crystallization temperature (about 400°C) and thereby an improved thermal stability. In this paper, we propose a methodology dedicated to studying the phase changes by operando transmission electron microscopy (TEM). The methodology combines focused ion beam (FIB) specimen preparation and injection of electrical pulses for in-situ studies. We show how the microstructure is correlated to the electrical switching dynamics in GGST nanobridges. The electrical pulse modification, the electrochemical migration, local current density, void formation and the corresponding switching mechanism are discussed.

Proposals for Incorporating the Reversal in Single-Case ABAB Designs Data Analysis

One of the commonly used single-case experimental designs (SCEDs) in education research is the ABAB design, commonly referred to as reversal design. This design is applicable when the studied behavior is reversible (i.e., reverses to baseline levels when the intervention is withdrawn) and it allows for a within-unit replication of the “basic effect”, that is, a comparison between two adjacent conditions (with and without an active intervention). Methodologically, one of its strengths is to provide three phase change moments to demonstrate experimental control. However, the withdrawal of the intervention (i.e., the comparison between the first intervention phase and the second baseline phase) has not received sufficient attention in the SCED literature. The aim of the current text is to propose quantifications that enable using the information from the withdrawal. Specifically, the quantifications allow for assessing the degree to which withdrawing the intervention leads to initial baseline levels as well as incorporating the reversal in an overall effect size. The proposals are illustrated with several real educational science data sets, including both within-unit analysis and replication of the ABAB design across units, and representing different degrees of reversal of the target behavior when the intervention is withdrawn.

CRYOMOVE: Cold chain real-time management of vaccine delivery using PCM and deep learning

Vaccines are temperature-sensitive biological products that can become ineffective or even hazardous if exposed to temperatures outside the recommended range. Therefore, it is crucial to maintain the cold chain during the transportation and storage of vaccines in order to ensure that they arrive at their destination in optimal condition. Vaccines are typically transported and stored in containers lined with Phase Change Material (PCM) to maintain a specific temperature range (usually lower than the ambient temperature). Firstly, we have simulated the melting of PCM at three distinct external temperatures using ANSYS Fluent software in order to forecast the Melt Fraction (MF) vs. time curve for each of these temperatures. The external temperature consistently undergoes dynamic changes. Running a simulation each time the temperature shifts is impractical due to its time and data-intensive nature. Consequently, we adopted a more efficient approach by training a simple Artificial Neural Network (ANN) based on simulation data. This ANN is designed to learn and predict the MF versus time curve for any given external temperature. Real-time temperature data from the vaccine box is transmitted to the cloud. Subsequently, the machine learning model operates on the cloud to predict the remaining time for the PCM to melt. This predictive analysis is performed recursively every 10 min to account for dynamic fluctuations in external temperatures, providing continuous updates on the time remaining for PCM meltdown. This is then conveyed to the cold chain managers to take preventive measures if the external conditions are harsh and there is a chance for vaccines to get ruined because of the temperature. This same approach can be extended to other applications beyond vaccine delivery such as food storage and transportation, pharmaceuticals, and more.

Investigating phase changes in cyanide-containing organic compounds with high melting points based on Quantitative Structure-Property Relationship modelling

Cyanide-containing organic compounds exhibit heat-resistant properties due to their high melting points, which can exceed 250 °C. These compounds find widespread applications in various industries. To predict their thermal decomposition temperatures, a straightforward model is introduced in this study. Unlike complex descriptors and computer codes, this model relies on structural parameters specific to cyanide-containing organic compounds. The investigation revealed that certain structural variables significantly influence the onset decomposition temperature. Among these, the number and type of rings play a crucial role. The model was developed and tested using a dataset of 77 experimental thermal decomposition onset temperatures for cyanide-containing organic compounds. For training and test sets comprising 62 and 15 compounds, respectively, the predicted values demonstrated good agreement with experimental data. Specifically, the coefficient of determination (R2) was 0.922 for the training set and 0.897 for the test set. The root mean square deviation (RMSD) and average absolute deviation (AAD) were 14.37 and 17.11 K for the training set, and 11.10 and 13.80 K for the test set. Furthermore, the proposed model outperformed a more complex existing model when applied to 13 cyanide-containing organic compounds. Additionally, this method can be utilized for designing cyanide-containing organic compounds with desired decomposition temperatures.