Search Results (53)

This study analyzes the design and performance of artificial lighting in a classroom setting, focusing on the balance between photopic and melanopic illuminance to optimize both visual comfort and circadian well-being. A three-dimensional simulated room model is used to evaluate three luminaires with different spatial distribution curves and two white LEDs, cool (CCT 6487 K) and warm (CCT 2268 K). The assessment includes an analysis of photopic and melanopic illuminance at the corneal plane, E_v and mEDI, respectively, with particular emphasis on the impact of the luminaires’ spatial distribution and the spectral characteristics of the light. The results indicate that a Lambertian spatial distribution of light achieves the best balance between illuminance uniformity and visual comfort. Illuminance uniformity is calculated on the horizontal work plane at 0.80 m, in line with the nature of visual tasks in classroom settings, making it the optimal solution for the simulated scenario. The cool LED provides greater melanopic stimulation, which is ideal for cognitive activation in the morning. Conversely, the warm LED creates a more relaxing atmosphere with lower melanopic values, making it better suited for the evening. Furthermore, this study proposes a dynamic lighting system that adjusts the correlated color temperature throughout the day by modifying the spectral power distribution of the light to accommodate both visual and biological needs. This research highlights the importance of integrating photopic and melanopic lighting considerations in luminaire design, offering practical insights for creating flexible and health-promoting environments in real-world settings. Full article

Background/Objectives: The prevalence of myopia is increasing globally, including in Spain. The early detection of ocular biometric parameters associated with myopia development is crucial for implementing control strategies. This study aims to describe the normative biometric values in a Spanish school-aged population and compare them with previously established reference data. Methods: A cross-sectional, observational, and analytical study was conducted on 558 students aged 6 to 12 years from the Educare Valdefuentes School in Madrid. Ocular biometric parameters, including axial length (AL), corneal curvature (CR), anterior chamber depth (ACD), crystalline lens thickness (LT), corneal thickness (CCT), and posterior vitreous depth (PVD), were measured using IOLMaster 700. The axial length/corneal radius (AL/CR) ratio was calculated. Percentile growth curves were generated, and the results were statistically analyzed using IBM SPSS 29. Results: AL significantly increased with age (p < 0.001), and boys had longer AL than girls. The AL/CR ratio showed a moderate correlation with myopia risk (ρ = 0.647, p < 0.001). Compared to previous European studies, no significant differences were found, except for minor variations in AL and CR. Conclusions: These percentile-based biometric values provide a useful reference for monitoring ocular growth and assessing myopia risk in Spanish children. The AL/CR ratio remains a strong predictor of myopia development, supporting its role in early detection strategies. Full article

The continuous cooling transformation (CCT) curves of undercooled austenite serve as crucial references for obtaining desired microstructures and properties in metallic materials (particularly deformed metals) through heat treatment. In this study, static and dynamic CCT curves were constructed for experimental steels micro-doped with rare earth element Ce by combining temperature-dilatometric curves recorded after austenitization at 900 °C with microstructural characterization and microhardness measurements. Comparative analyses were conducted on the microstructures and microhardness of three experimental steels with varying Ce contents subjected to sizing (reducing) diameter deformation at 850 °C and 950 °C. The CCT experimental results revealed that the microhardness of the tested steels increased with cooling rates. Notably, dynamic CCT specimens cooled at 50 °C/s to room temperature following superheated deformation exhibited 56.7 HV5 higher microhardness than static CCT specimens, accompanied by increased martensite content. The reduction of deformation temperature from 950 °C to 850 °C resulted in the expansion of the bainitic phase region. The incorporation of trace Ce elements demonstrated a significant enhancement in the microhardness of 30MnNbRE steel. This research proposes an effective processing route for improving strength-toughness combination in microalloyed oil well tubes: introducing trace Ce additions followed by sizing (reducing) diameter deformation at 950 °C and subsequent ultra-fast cooling at 50 °C/s to room temperature. This methodology facilitates the production of high-strength/toughness steels containing abundant martensitic microstructures. Full article

The aim of this work is to perform a detailed dilatometric analysis of the decomposition of austenite during the cooling process using experimentally derived continuous cooling transformation (CCT) diagrams for two specific tool steels, X153CrMoV12 Bohdan Bolzano, Bratislava, Slovakia and 100MnCrW4. The dilatometric curves were compared with metallographic evaluations using scanning electron microscopy (SEM). In addition, hardness measurements were performed to obtain additional information about the mechanical properties of the materials. All experimental work was performed using a DIL 805A. The accuracy of the resulting CCT diagrams was verified by comparing them with those calculated with the JMatPro software v12.4. The cooling rates ranged from 20 °C/s to 0.01 °C/s, depending on the specific type of steel tested. The novelty of this research is the combination of experimental and simulation methods to analyze the influence of alloying elements on the kinetics of phase transformations in tool steels. It was found that one of the most significant factors affecting the CCT diagrams is the weight percentage of alloying elements in the steels. These results clearly show that increasing the weight percentage of the content of alloying elements has a significant impact on the accuracy of the simulation results derived from the JMatPro software. Full article

Background: The purpose of this study is the evaluation of imaging findings of acute-phase cardiac CT (cCT) in stroke patients with large vessel occlusion (LVO) to identify potential cardioembolic sources (CES) in patients without intracardiac thrombi and atrial fibrillation (AF). Material and Methods: This retrospective study included 315 patients with LVO who underwent cCT imaging in the acute stroke setting. The images were analysed for 15 imaging findings following the established minor and major cardioembolic risk factors. The final stroke aetiology was determined using the TOAST classification through interdisciplinary consensus following a thorough clinical evaluation. Multivariate regression analysis was performed to identify imaging findings associated with CES. Results: A cardioembolic aetiology was identified on cardiac CT in 211 cases (70%). After adjustment for AF and intracardiac thrombi, the multivariate regression analysis revealed significant associations with left ventricular dilation (adjusted odds-ratio (AOR) 32.4; 95% CI 3.0–349; p = 0.004), visible interatrial right-to-left shunt (AOR 30.8; 95% CI 2.7–341.3; p = 0.006), valve implants (AOR 24.5; 95% CI 2.2–270.9; p = 0.009), aortic arch atheroma grade > II (AOR 6.9; 95% CI 1.5–32.8; p = 0.015) and post-ischaemic myocardial scars (AOR 6.3, 95% CI 1.2–34.1; p = 0.032) as independent risk factors for a cardioembolic aetiology. The combined model achieved an area under the ROC curve of 0.83. Conclusions: In patients with LVO without AF and intracardiac thrombi as a cause, the presence of left ventricular dilatation, interatrial right-to-left shunts, valve implants, post-ischaemic myocardial scarring and advanced aortic arch atheroma (grade > 2) in particular is significantly associated with a cardioembolic cause of stroke and should be add-on evaluated in acute-phase cCT. Further investigations are warranted to confirm these associations. Full article

In order to gain insight into the changes of the organization and hardness of 500 MPa steel-grade low-temperature-resistant steel bars (HRB500DW) for liquefied nature gas (LNG) storage tanks during the continuous cooling phase transformation process, the effects of different rolling temperatures and cooling speeds on the organization of the phase change law, microstructure and hardness were studied. The results show that the critical phase transformation points A_C1 and A_C3 of the test steel were 702 and 880 °C, respectively. The organization of the test steel was polygonal ferrite and pearlite when the cooling rate was 1–2 °C/s. At a cooling speed of 5 °C/s, a small amount of bainite started to be produced in the region of a large deformation of rolling, and at 15 °C/s, some slate martensite started to be produced. At a cooling speed of 10 to 25 °C/s, the organization was mainly bainite. At a cooling rate of 40 °C/s, continuous pre-eutectic reticulated ferrite was formed at the austenite grain boundaries, reducing material properties. As the cooling speed increased, the hardness of the matrix organization of the test bars increased. The lower initial rolling temperature led to the expansion of the martensitic transformation zone. For rebar producers, the initial rolling temperature of 1050 °C was better than the initial rolling temperature of 1000 °C. Full article

Background/Objectives: Out-of-hospital cardiac arrests (OHCAs) are common, with return of spontaneous circulation (ROSC) achieved in approximately 25% of patients. However, it remains unknown whether post-ROSC care delivered by a pre-hospital critical care team (CCT) improves patient outcomes. We therefore aimed to investigate this in OHCA patients admitted to our intensive care unit (ICU). Methods: In this retrospective observational study, consecutive adults with ROSC after non-traumatic OHCA admitted to our ICU between 1 September 2019 and 31 August 2022 were included. We compared patients who received post-ROSC care from a CCT to those who received standard care. The primary outcome was a good neurological outcome on hospital discharge (defined as Cerebral Performance Category 1–2). Descriptive statistics, Area Under the Receiver Operating Characteristic Curve (AUC) values, and adjusted Odds Ratios (ORs) are reported. We constructed multivariable logistic regression models that adjusted for the component variables of the MIRACLE2 score. Results: We included 126 OHCAs (median age 63 years, 69% male), which were largely witnessed (82%), involved bystander cardiopulmonary resuscitation (87%), and had an initial shockable rhythm (61%). The prevalence of good neurological outcomes was higher in patients who received post-ROSC care from a pre-hospital CCT (37% vs. 17%, p = 0.012). The MIRACLE2 score was a strong predictor of good neurological outcomes (AUC 0.932), and in our multivariable analysis, good neurological outcome was associated with both CCT presence post-ROSC (aOR 3.77, 95% CI 1.02–13.89) and the delivery of PHEA (aOR 4.10, 95% CI 1.10–15.27, p = 0.035). Furthermore, in patients meeting the Utstein criteria (n = 69), good neurological outcomes were also more prevalent with CCT presence post-ROSC (62% vs. 29%, p < 0.001). Conclusions: We found that post-ROSC care delivered by a pre-hospital CCT was associated with good neurological outcomes on hospital discharge. Full article

42CrMo4-type steel grades are widely used in a great variety of components that require ad hoc mechanical properties. However, due to the dimensions of large components and the previous thermomechanical treatments, the presence of heterogeneities in the chemical compositions are expected to impact those mechanical properties. In the present work, a detailed analysis of phase transformation behavior upon cooling was carried out through a dilatometry test on samples of 42CrMo4 belonging to a component that has a non-homogeneous chemical distribution. The analysis of the dilatation signals and the quantitative metallography shows a rather complex behavior depending on the cooling rate as well as on the region of observation. Two different phase transformation models based on Li’s approach were applied to the present composition to determine the CCT curve as well as the fraction of the microconstituents. An extensive discussion was carried out on some aspects about Kirkaldy-based approaches that need to be improved so as to attain more reliable quantitative results when modeling phase transformations in heterogenous systems. Full article

Low-alloy wear-resistant steel often requires the addition of trace alloy elements to enhance its performance while also considering the cost-effectiveness of production. In order to comparatively analyze the strengthening mechanisms of Mo and Cr elements and further explore economically feasible production processes, we designed two types of low-alloy wear-resistant steels, based on C-Mn series wear-resistant steels, with individually added Mo and Cr elements, comparing and investigating the roles of the alloying elements Mo and Cr in low-alloy wear-resistant steels. Utilizing JMatPro software to calculate Continuous Cooling Transformation (CCT) curves, conducting thermal simulation quenching experiments using a Gleeble-3800 thermal simulator, and employing equipment such as a metallographic microscope, transmission electron microscope, and tensile testing machine, this study comparatively investigated the influence of Mo and Cr on the microstructural transformation and mechanical properties of low-alloy wear-resistant steels under different cooling rates. The results indicate that the addition of the Mo element in low-alloy wear-resistant steel can effectively suppress the transformation of ferrite and pearlite, reduce the martensitic transformation temperature, and lower the critical cooling rate for complete martensitic transformation, thereby promoting martensitic transformation. Adding Cr elements can reduce the austenite transformation zone, decrease the rate of austenite formation, and promote the occurrence of low-temperature phase transformation. Additionally, Mo has a better effect on improving the toughness of low-temperature impact, and Cr has a more significant improvement in strength and hardness. The critical cooling rates of C-Mn-Mo steel and C-Mn-Cr steel for complete martensitic transition are 13 °C/s and 24 °C/s, respectively. With the increase in the cooling rate, the martensitic tissues of the two experimental steels gradually refined, and the characteristics of the slats gradually appeared. In comparison, the C-Mn-Mo steel displays a higher dislocation density, accompanied by dislocation entanglement phenomena, and contains a small amount of residual austenite, while granular ε-carbides are clearly precipitated in the C-Mn-Cr steel. The C-Mn-Mo steel achieves its best performance at a cooling rate of 25 °C/s, whereas the C-Mn-Cr steel only needs to increase the cooling rate to 35 °C/s to attain a similar comprehensive performance to the C-Mn-Mo steel. Full article

Purpose: This study aimed to employ the incremental digital image correlation (DIC) method to obtain displacement and strain field data of the cornea from Corvis ST (CVS) sequences and access the performance of embedding these biomechanical data with machine learning models to distinguish forme fruste keratoconus (FFKC) from normal corneas. Methods: 100 subjects were categorized into normal (N = 50) and FFKC (N = 50) groups. Image sequences depicting the horizontal cross-section of the human cornea under air puff were captured using the Corvis ST tonometer. The high-speed evolution of full-field corneal displacement, strain, velocity, and strain rate was reconstructed utilizing the incremental DIC approach. Maximum (max-) and average (ave-) values of full-field displacement V, shear strain γxy, velocity VR, and shear strain rate γxyR were determined over time, generating eight evolution curves denoting max-V, max-γxy, max-VR, max-γxyR, ave-V, ave-γxy, ave-VR, and ave-γxyR, respectively. These evolution data were inputted into two machine learning (ML) models, specifically Naïve Bayes (NB) and Random Forest (RF) models, which were subsequently employed to construct a voting classifier. The performance of the models in diagnosing FFKC from normal corneas was compared to existing CVS parameters. Results: The Normal group and the FFKC group each included 50 eyes. The FFKC group did not differ from healthy controls for age (p = 0.26) and gender (p = 0.36) at baseline, but they had significantly lower bIOP (p < 0.001) and thinner central cornea thickness (CCT) (p < 0.001). The results demonstrated that the proposed voting ensemble model yielded the highest performance with an AUC of 1.00, followed by the RF model with an AUC of 0.99. Radius and A2 Time emerged as the best-performing CVS parameters with AUC values of 0.948 and 0.938, respectively. Nonetheless, no existing Corvis ST parameters outperformed the ML models. A progressive enhancement in performance of the ML models was observed with incremental time points during the corneal deformation. Conclusion: This study represents the first instance where displacement and strain data following incremental DIC analysis of Corvis ST images were integrated with machine learning models to effectively differentiate FFKC corneas from normal ones, achieving superior accuracy compared to existing CVS parameters. Considering biomechanical responses of the inner cornea and their temporal pattern changes may significantly improve the early detection of keratoconus. Full article

This article presents research results on the share of coal in the energy mix and the impact of clean coal technologies on Poland’s energy mix. Two mathematical models were utilised: the Boltzmann sigmoidal curve and a supervised machine learning model that employs multiple regressions. Eight explanatory variables were incorporated into the model, the influence of which on the explained variable was confirmed by Student’s t-test. The constructed models were verified using ex post errors and the Durbin–Watson and Shapiro–Wilk statistical tests. It was observed that the share of coal in the mix decreased more dynamically after 2015 compared to previous years. Furthermore, a simulation was conducted using the machine learning model, which confirmed the hypothesis on the influence of clean coal technologies on the level of coal share in the Poland energy production structure. As shown by the analysis and simulation, coal could be maintained in the energy mixes of EU countries, and even if the negative aspects of using this fuel were limited—primarily the emission of harmful substances—its share could even increase. It was noted that this share could be higher by 22% assuming a return to the interest in CCT levels from before 2015 and the reduction in CO₂ emissions using membrane techniques proposed by the authors. Clean coal technologies would enable diversification of the energy mix, which is an important aspect of energy security. They would also enable the gradual introduction of renewable energy sources or other energy sources, which would facilitate the transition stage on the way to a sustainable energy mix. Full article

The CCT/TRiC complex is a type II chaperonin that undergoes ATP-driven conformational changes during its functional cycle. Structural studies have provided valuable insights into the mechanism of this process, but real-time dynamics analyses of mammalian type II chaperonins are still scarce. We used diffracted X-ray tracking (DXT) to investigate the intramolecular dynamics of the CCT complex. We focused on three surface-exposed loop regions of the CCT1 subunit: the loop regions of the equatorial domain (E domain), the E and intermediate domain (I domain) juncture near the ATP-binding region, and the apical domain (A domain). Our results showed that the CCT1 subunit predominantly displayed rotational motion, with larger mean square displacement (MSD) values for twist (χ) angles compared with tilt (θ) angles. Nucleotide binding had a significant impact on the dynamics. In the absence of nucleotides, the region between the E and I domain juncture could act as a pivotal axis, allowing for greater motion of the E domain and A domain. In the presence of nucleotides, the nucleotides could wedge into the ATP-binding region, weakening the role of the region between the E and I domain juncture as the rotational axis and causing the CCT complex to adopt a more compact structure. This led to less expanded MSD curves for the E domain and A domain compared with nucleotide-absent conditions. This change may help to stabilize the functional conformation during substrate binding. This study is the first to use DXT to probe the real-time molecular dynamics of mammalian type II chaperonins at the millisecond level. Our findings provide new insights into the complex dynamics of chaperonins and their role in the functional folding cycle. Full article

Continuous cooling transformation (CCT) diagrams of base metals are common in welding. They can be built using physical or numerical simulations, each with advantages and limitations. However, those are not usual for weld metal, considering its variable composition due to the dilution of the weld into the base metal. Wire Arc Additive Manufacturing (WAAM) is a distinctive case in which the interest in materials comparable with weld composition raises attention to estimating their mechanical properties. Notwithstanding, this concept is still not used in WAAM. Therefore, the aim of this work was to address a methodology to raise MC-CCT (Multiple Cycle Continuous Cooling Transformation) diagrams for WAAM by combining physical and numerical simulations. A high-strength low-alloy steel (HSLA) feedstock (a combination of a wire and a shielding gas) was used as a case study. To keep CCT as representative as possible, the typical multiple thermal cycles for additive manufacturing thin walls were determined and replicated in physical simulations (Gleeble dilatometry). The start and end transformations were determined by the differential linear variation approach for each thermal cycle. Microstructure analyses and hardness were used to characterise the product after the multiple cycles. The same CCT diagram was raised by a commercial numerical simulation package to determine the shape of the transformation curves. A range of austenitic grain sizes was scanned for the curve position matching the experimental results. Combining the experimental data and numerically simulated curves made estimating the final CCT diagram possible. Full article

In this paper, the progress of the test methods and characterization approaches of aluminum alloys hardenability was reviewed in detail. The test method mainly included the traditional end-quenching method and the modified method. While the characterization approaches of alloy hardenability consist mainly of ageing hardness curves, solid solution conductivity curves, ageing tensile curves, time temperature transformation (TTT) curves, time temperature properties (TTP) curves, continuous cooling transformation (CCT) curves, and advanced theoretical derivation method have appeared in recent years. The hardenability testing equipment for different tested samples with different material natures, engineering applications properties, and measurement sizes was introduced. Meanwhile, the improvement programmed proposed for shortcomings in the traditional hardenability testing process and the current deficiencies during the overall hardenability testing process were also presented. In addition, the influence factors from the view of composition design applied to the hardenability behaviors of Aluminum alloys were summarized. Among them, the combined addition of micro-alloying elements is considered to be a better method for improving the hardenability of high-strength aluminum alloys. Full article

The paper deals with the dilatometric study of high-alloy martensitic tool steel with the designation M398 (BÖHLER), which is produced by the powder metallurgy process. These materials are used to produce screws for injection molding machines in the plastic industry. Increasing the life cycle of these screws leads to significant economic savings. This contribution focuses on creating the CCT diagram of the investigated powder steel in the range of cooling rates from 100 to 0.01 °C/s. JMatPro^® API v7.0 simulation software was used to compare the experimentally measured CCT diagram. The measured dilatation curves were confronted with a microstructural analysis, which was evaluated using a scanning electron microscope (SEM). The M398 material contains a large number of carbide particles that occur in the form of M₇C₃ and MC and are based on Cr and V. EDS analysis was used to evaluate the distribution of selected chemical elements. A comparison of the surface hardness of all samples in relation to the given cooling rates was also carried out. Subsequently, the nanoindentation properties of the formed individual phases as well as the carbides, where the nanohardness and reduced modulus of elasticity (carbides and matrix) were evaluated. Full article