Effective Index Research Articles

Quantitative Measures of Engagement in History Classes: Analyzing the Efficacy of Interactive Pedagogies

This study aimed to evaluate the impact of interactive pedagogy on student engagement and knowledge retention. A quantitative method was used. The sample was 500 students from three high schools. The Engagement measurement instrument and Knowledge Retention Test were used to measure engagement and knowledge retention metrics. Data collection was conducted over one semester. Data analysis used descriptive statistics, inferential, ANOVA, and Effectiveness Index. The results of this study confirmed that classroom activity engagement reached 88.32%, and history knowledge retention reached 80.30%, indicating the success of the pedagogical intervention. The Effectiveness Index of student engagement and knowledge retention was 35.70%.

SGIR-Tree: Integrating R-Tree Spatial Indexing as Subgraphs in Graph Database Management Systems

Efficient spatial query processing in Graph Database Management Systems (GDBMSs) has become increasingly important owing to the prevalence of spatial graph data. However, current GDBMSs lack effective spatial indexing, causing performance issues with complex spatial graph queries. This study proposes a spatial index called Subgraph Integrated R-Tree (SGIR-Tree) for efficient spatial query processing in GDBMSs. The SGIR-Tree integrates the hierarchical R-Tree structure with the graph structure of GDBMSs by converting R-Tree elements into graph components like nodes and edges. The Minimum Bounding Rectangle (MBR) information of spatial objects and R-Tree nodes is stored as properties of these graph elements, and the leaf nodes are directly connected to the spatial nodes. This approach combines the efficiency of spatial indexing with the flexibility of graph databases, thereby allowing spatial query results to be directly utilized in graph traversal. Experiments using OpenStreetMap datasets demonstrate that the SGIR-Tree outperforms the previous approaches in terms of query overhead and index overhead. The results are expected to improve spatial graph data processing in various fields, including location-based service and urban planning, significantly advancing spatial data management in GDBMSs.

Construction and Comparison of Machine-Learning Forecast Models of Albacore Thunnus alalunga Fishing Grounds in the South Pacific Ocean

The traditional methods for predicting the distribution of albacore (Thunnus alalunga) fishing grounds have low performance and accuracy. Uneven sampling can result in unreasonable evaluation indicators. To address these issues, three methods, equi-frequency, K-means clustering algorithm, and 1-R split, were applied to discretize the catch per unit effort (CPUE) of albacore in the South Pacific from 2016 to 2021 and partition the fishing grounds into abundance levels. Eight machine learning models were used to predict the fishing grounds. In addition to the traditional evaluation index based on confusion matrix, top-k index was also used to evaluate the accuracy of fishery abundance predictions. The results showed that (1) When sampling is unbalanced, the reported accuracy does not fully represent the actual performance of the model in predicting the abundance of albacore in the fishing ground. F1 value can be used as the index of the model effect and stability. (2) In binary classification, the quartile stacking algorithm has the best stacking performance, with F1 0.89. (3) The top-1 prediction accuracy of three-category fishery forecasting is the highest at 0.74, and the top-1 prediction accuracy of five-category fishery forecasting is the highest at 0.54. (4) The top-k accuracy of classification of fisheries with multiple abundance using K-means is significantly better than that of equal frequency discretization (p < 0.001). The top-k evaluation index was used to predict the fishing grounds of albacore across multiple abundance levels for the first time in this study, which is significant for pioneering a new method for this application and which provides a demonstration of the development of artificial intelligence techniques for fisheries in the future.

Using a Claim-Support-Question (CSQ) Technique in Teaching and Learning English Reading for the 3rd Year English Education Students at the Department of Foreign Languages, Faculty of Education, National University of Laos

The main purposes of this study were to: 1) examine the efficiency index of reading lesson plans; 2) investigate the effectiveness index of learning reading outcomes; and 3) to study the 3rd year English education students’ satisfaction towards the teaching and learning of reading using a CSQ technique. The research instruments include four lesson plans, a pre-posttest which consists of 21 items, an observation form, and the satisfaction questionnaire, which consists of 22 items. The target group of the study was the 3rd year English education students at the Faculty of Education, National University of Laos, with a total of 28 students (23 female). The data obtained were analysed using a computer program to find the mean ( ), standard deviation (S.D), percentage (%), efficiency index (E1/E2) and effectiveness index (E.I). The findings reveal that: The efficiency index of the reading lesson plans through using a CSQ technique for the 3rd year English education students was 82.05/88.44, which is higher than the criteria of 80/80. The effectiveness index of reading learning performance through using a CSQ technique was 6699, which was equal to 66.99%, which is higher than the criteria .05 (55%). The 3rd year English education students’ satisfaction towards teaching and learning reading through using a critical thinking technique (CSQ) was at a high level ( = 4.29, S.D = 0.77).

Compressed Point Cloud Quality Index by Combining Global Appearance and Local Details

In recent years, many standardized algorithms for point cloud compression (PCC) has been developed and achieved remarkable compression ratios. To provide guidance for rate-distortion optimization and codec evaluation, point cloud quality assessment (PCQA) has become a critical problem for PCC. Therefore, in order to achieve a more consistent correlation with human visual perception of a compressed point cloud, we propose a full-reference PCQA algorithm tailored for static point clouds in this article, which can jointly measure geometry and attribute deformations. Specifically, we assume that the quality decision of compressed point clouds is determined by both global appearance (e.g., density, contrast, and complexity) and local details (e.g., gradient and hole). Motivated by the nature of compression distortions and the properties of the human visual system, we derive perceptually effective features for the above two categories, such as content complexity, luminance/geometry gradient, and hole probability. Through systematically incorporating measurements of variations in the local and global characteristics, we derive an effective quality index for the input compressed point clouds. Extensive experiments and analyses conducted on popular PCQA databases show the superiority of the proposed method in evaluating compression distortions. Subsequent investigations validate the efficacy of different components within the model design.

Characterization of Water Bodies through Hydro-Physical Indices and Anthropogenic Effects in the Eastern Northeast of Brazil

Brazil, despite possessing the largest renewable freshwater reserves in the world (8.65 trillion m3 annually), faces growing challenges in water management due to increasing demand. Agriculture, responsible for 68.4% of water consumption, is one of the main drivers of this demand, especially in the São Francisco River Basin, where irrigation accounts for 81% of total water withdrawals. Water bodies play a crucial role in sustaining ecosystems and supporting life, particularly along the East-West axis of Alagoas, a water-rich region in the ENEB. This study aimed to map and quantify the spatiotemporal variations of water bodies in the ENEB region and assess the impacts of human activities using MODIS satellite data, applying hydrological indices such as NDWI, MNDWI, and AWEI. Between 2003 and 2022, significant variations in the extent of water bodies were observed, with reductions of up to 100 km2 during dry periods and expansions of up to 300 km2 during wet seasons compared to dry periods. AWEI and MNDWI proved to be the most effective indices for detecting water bodies with MODIS data, providing accurate insights into water dynamics. Additionally, the MapBiomas Rios dataset, despite being resampled from a 30 m to a 500 m resolution, offered the most accurate representation of water bodies due to its methodology for data acquisition. Changes in albedo and surface temperature were also detected, highlighting the influence of climate change on the region’s water resources. These findings are crucial for guiding the sustainable management of water resources, not only in Alagoas but also in other regions of Brazil and similar semi-arid areas around the world. The study demonstrates the hydrological variability in the state of Alagoas, indicating the need for adaptive strategies to mitigate the impacts of climate change and anthropogenic pressures, supporting the need for informed decision-making in water resource management at both local and national levels.

High birefringent slotted core slotted cladding porous core PCF for THz waveguide

A novel design featuring a porous core photonic crystal fiber (PC-PCF) is proposed in this paper for terahertz (THz) waveguide application. This work uses finite element method (FEM) and a boundary condition related to perfectly matched layer (PML) for analyzing the guiding properties. This methodology is supported by a fiber type featuring a slotted core and slotted cladding, utilizing Zeonex as the material. It offers high birefringence valued at 0.0978, small confinement loss of 10−14 dB/cm, a meager amount of effective material loss (EML) valued at 0.011697 dB/cm and a very high core power fraction (CPF) of 67.156%. Additionally, it shows a flattened pattern of dispersion measuring 0.4 ± 0.2 ps/THz/cm at an extensive frequency range of 0.5 THz to 2 THz. Other significant waveguide properties: effective refractive index, numerical aperture (NA), V-parameter, effective area, spot size, and beam divergence of the suggested fiber are numerically analyzed and conferred thoroughly. Regarding its mode of operation, the proposed fiber primarily functions in multimode, but it can also operate in single mode for higher porosity levels and lower core diameters. This unique characteristic renders the proposed PC-PCF structure well-suited for a broad range of applications, offering versatility as to its mode of operation.

Thermal Comfort Conditions and Mortality in Brazil.

Conventional temperature-based approaches often overlook the intricate nature of thermal stress experienced by individuals. To address this limitation, climatologists have developed thermal indices-composite measures designed to reflect the complex interaction of meteorological factors influencing human perception of temperature. Our study focuses on Brazil, estimating the association between thermal comfort conditions and mortality related to respiratory and circulatory diseases. We examined four distinct thermal indices: the discomfort index (DI), net effective temperature (NET), humidex (H), and heat index (HI). Analyzing a comprehensive dataset of 2,872,084 deaths from 2003 to 2017, we found significant variation in relative risk (RR) based on health outcomes, exposure lag, percentile of exposure, sex/age groups, and specific thermal indices. For example, under high exposure conditions (99th percentile), we observed that the shorter lags (3, 5, 7, and 10) had the most robust effects on all-cause mortality. For example, under lag 3, the pooled national results for the overall population (all ages and sexes) indicate an increased risk of all-cause mortality, with an RR of 1.17 (95% CI: 1.13; 1.122) for DI, 1.15 (95% CI: 1.12; 1.17) for H, 1.15 (95% CI: 1.09; 1.21) for HI, and 1.18 (95% CI: 1.13; 1.22) for NET. At low exposure levels (1st percentile), all four distinct thermal indices were linked to an increase in all-cause mortality across most sex and age subgroups. Specifically, for lag 20, we observed an estimated RR of 1.19 (95% CI: 1.14; 1.23) for DI, 1.12 (95% CI: 1.08; 1.16) for H, 1.17 (95% CI: 1.12; 1.22) for HI, and 1.18 (95% CI: 1.14; 1.23) for NET. These findings have important implications for policymakers, guiding the development of measures to minimize climate change's impact on public health in Brazil.

Impact of concrete durability improvement on building life cycle carbon emissions: a case study of residential buildings in Northwest China.

Building carbon emissions (CE) have become the focus of the current topic, but there is still no mature typical building life cycle theory method from the perspective of building materials, and the research on the relationship between building durability and building life cycle is still insufficient. To this end, this study established a detailed calculation method for building carbon emissions (CE) and divided the building life cycle (BLC) into three stages: manufacturing, use, and demolition according to the result analysis. In addition, a durability improvement and carbon reduction scheme of "partition, resistance, and repair" is proposed, and the carbon emission reduction index of effectiveness index is proposed. The proposed method is applied to the case of residential buildings in Northwest China. The main conclusions are as follows: the CE of residential buildings are more dependent on the use stage. If the centralized heating system is adopted, the CE in the operation stage account for 80-90%. If the air conditioning refrigeration and heating system is adopted, the CE in the operation stage account for about 50%. Using the method of improving the durability of buildings to extend the service life of buildings is very significant for building carbon reduction (RC); the effectiveness index proposed in this paper includes key indicators such as total CE, service life, and building area. Compared with the traditional index, the effectiveness index is more accurate and comprehensive. CR is the focus of green building, but the impact of economy needs to be considered in practical engineering. In the future research, durability, CE, and economy need to be considered comprehensively for careful study.

The Curative Hypolipidemic Effect, Antioxidant Activity, and Atherogenic Indexes of Methanolic Extract of Arbutus Pavarii Leaves

The aim of the study was to investigate the antioxidant activity and curative effect of (MEAPL) and its role in the treatment of hypercholesterolemia in male albino rats. The effect of (MEAPL) against hypercholesterolemia in rats was analyzed via examination of various types of parameters, (LDL), (HDL), (TC), and (TG), also liver enzymes (ALT, AST, G-GT, LDH, and ALP) besides proteins and MDA. Antioxidant enzymes (SOD, GR, GPx, and CAT), were measured in control and (HFD). We have found that the level of TC, LDL, TG, and liver enzymes were increased but the level of HDL decreased in HFD rats compared with control. Lipid peroxidation was determined by the level of MDA, which increased in HFD compared with control while antioxidant enzymes SOD, GR, GPx, and CAT were decreased. The results obtained revealed that MEAPL has a healing effect against hypercholesterolemia compared with the reference standard agent ˝Atorvastatin˝ and standard antioxidant vitamin C.

Dez River Araphid/Bi-raphid diatoms for nano-optic applications

Micro and nano-silica structure technology is sumptuous and has empirical intricacies, so employing natural nanostructures can be inexpensive and more environmentally friendly. This green capacity can be the starting point of engineering and nanotechnology studies. Diatoms are good candidates for these structures, abundant in water and soil. They are types of algae with silicate frustules that may have periodic structures. Diatoms have a high potential to be used as sensors. They are very similar to photonic crystals.In this article, for the first time, some Araphid and Bi-raphid diatoms of the Dez River have been reported, and some of their optical characteristics have been investigated. The studied Dez-river Bi-raphid diatom shows no photonic band gap. Its periodic structure shows a maximum reflectance at λ=600nm, which seems to be an appropriate wavelength for the effective refractive index guiding mechanism through a siliceous defect. The studied Araphid diatoms show that the PBG waveguiding mechanism is achieved at the wavelength of about λ=690nm, too. This structure can be used as a narrow-band filter with a more than %95 efficiency for the mentioned wavelength. So the extraordinary structure of the Dez River Araphid and Bi-raphid diatoms can overtake the boundaries of the most advanced lithography techniques without spending time and money.

Could Diffusion Indexes Have Forecasted the Great Depression?

ABSTRACTWas the Depression forecastable? In this paper, we test how effective diffusion indexes are in forecasting the deepest recession in US history: the Great Depression. In a seminal paper, Moore considered the effectiveness of diffusion indexes, though retrospectively and not out‐of‐sample. We reconstruct Moore's diffusion indexes for this historical period and make our own comparable indexes for out‐of‐sample predictions. We find that diffusion indexes, including the horizon‐specific ones we produce, can nowcast turning points fairly well. Forecasting remains difficult, but our results suggest that the initial downturn in 1929 may be forecastable months before the Great Crash. This is a novel result, as previous authors had generally found the Depression was not forecastable.

Novel inhalable nano-based/microparticles for enhanced sustained pulmonary delivery of remdesivir - A patient malleable treatment for coronaviruses infection: In vitro aerosolization, cytotoxicity assays and antiviral activity studies

Remdesivir (RDV) is an antiviral used in potential treatment of SARS-COV-2 infection during the COVID-19 pandemic worldwide. However, it is still limited to IV administration for hospitalized patients. Therefore, we report herein successful development of RDV-loaded nanosuspensions (NS) using polycaprolactone and pluronic® F127, for the first time. The optimized RDV-NS was further loaded into inhalable nano-based/microparticles (OLN-microparticles) via co-spray drying with hyaluronic acid and mannitol. OLN-microparticles exhibited high yield value ∼80.56 %, with satisfactory entrapment efficiency and drug loading percent ∼97.27 ± 1.84 % and 3.92 ± 0.07 %, respectively. Carr's index was equal to 22.7 ± 11.67 % indicating good flowability properties. Scanning electron microscopic analysis showed spherical-shaped particles. Transmission electron microscope demonstrated grape-shaped clumps surface porosity. OLN-microparticles exhibited excellent aerodynamic features including; emitted fraction ∼97.46 ± 1.70 %, respirable particle fraction 53.77 ± 0.2 %, effective inhalation index 72.39 ± 1.40 %, and mass median aerodynamic diameter 2.25 ± 0.01 μm. Compared to plain RDV, OLN-microparticles showed significantly enhanced sustained release (p < 0.0001) with 1.5 and 1.9 fold increase at 24 and 48 h, respectively in Gamble's solution. OLN-microparticles also showed favorable cytotoxic profile with CC50 ∼ 252.0 μg/mL, inhibitory concentration (IC50) 13.08 μg/mL, and safety index (SI) 19.26 which is 1.3 fold higher compared to plain RDV. The Optimal release profile of OLN-microparticles enabled controlled and sustained release with enhanced cellular uptake. Hence, OLN-microparticles represented an efficient alternative form of dry powder for inhalation for deep and targeted pulmonary delivery of RDV, outweighing limitations accompanied with IV administration. It can provide self-administered and malleable access of treatment for SARS-COV-2 infected patients.

Measurement of the effective refractive index of silicon-on-insulator waveguide using Mach–Zehnder interferometers

We propose and demonstrate an accurate method of measuring the effective refractive index of silicon-on-insulator waveguides. By conducting the combined analysis to the troughs’ wavelength in spectra of Mach–Zehnder interferometers on chip. The wavelength-dependent and temperature-dependent effective refractive index of the fabricated waveguides are measured experimentally, and obtained the thermo-optic coefficient of silicon-on-insulator waveguides is about 2×10−4 /℃ in the 1550 nm communication band. The maximum measurement error for effective and group refractive index respectively are 1.5×10−5 and 1.5×10−3 obtained by numerical simulation. And an improved method for taking value of the free spectral range was discussed to obtain a more accurate group refractive index. It proves a fast and lost-cost measurement way to evaluate key optical parameters of waveguide, which can indicate the quality of fabrication process and optimize photonic components.

Correlations between intraoperative and postoperative echocardiographic measurements in patients undergoing aortic bioprosthetic valve replacement: a prospective observational study.

Patient-prosthesis mismatch (PPM) should be avoided during surgical aortic valve replacement because PPM would worsen the mortality and morbidity. Diagnosis of PPM could be made using various parameters measured by intraoperative transesophageal echocardiography. However, few studies have examined which parameters correlate most accurately between intraoperative and postoperative values. This single-center prospective observational study analyzed 46 patients who underwent surgical aortic valve replacement (SAVR). Echocardiography was performed at the following 3-time points: preoperatively, intraoperatively, and 1month postoperatively. The correlation between intraoperative and postoperative measurement values, including peak velocity (PV), mean pressure gradient (MPG), effective orifice area (EOA), and effective orifice area index (EOAI), were assessed using Pearson's correlation coefficient. Moreover, to evaluate whether a multivariable linear regression model with intraoperative and postoperative stroke volume added as an explanatory variable improves the correlation, the multiple correlation coefficients were calculated. PV, MPG, EOA, and EOAI measured intraoperatively and 1month postoperatively were significantly correlated. The r values of each measurement were 0.35, 0.344, 0.411 and 0.323, respectively. The multivariable linear regression model showed that the multiple correlation coefficients for MG and EOA were 0.491 and 0.663, respectively. Intraoperative and postoperative PV, MPG, EOA, and EOAI were significantly correlated in patients undergoing SAVR with a bioprosthetic valve. The r value for EOA was 0.441, the largest among the measured values. Adjustment for stroke volume improved the strength of the correlation. Intraoperative evaluation of prosthetic valve function was considered most appropriate using EOA. University Hospital Medical Information Network Clinical Trials Registry, registration number UMIN000046164, https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000052695 .

Uniaxial compressive stress-strain behavior of steel fiber reinforced geopolymer concrete confined by stirrups: Experimental study and analytical model

The compressive stress-strain relationship of confined steel fiber reinforced geopolymer concrete (SFRGC) is a basis for its structural nonlinear analysis and engineering design. This paper presents an experimental study on the stress-strain behavior of stirrup confined-SFRGC under uniaxial compression, with emphasis on the effects of stirrup spacing, stirrup strength and steel fiber (SF) volume fraction. The failure modes, stress-strain curves, energy absorption capacity and post-peak ductility were analyzed. The results demonstrated that due to the stirrup constraint and SF fiber crack-bridging effects, the integrity of specimens was significantly improved, showing notable ductile failure mode. The stress-strain behavior of core SFRGC was notably affected by the constraint level of stirrups, however, the effect of SF was mainly reflected in post-peak stress-strain branches. Reducing the stirrup spacing, improving the stirrup strength, and increasing the SF content can effectively enhance the strength and deformation characteristics of confined-SFRGC, as well as ductility. Moreover, synergetic effect of SF and stirrups on improving the deformation capacity of SFRGC was observed, whereas the peak stress and corresponding strain changed insignificantly with the SF content. In addition, the stirrups can reach yield around the peak stress point. Based on the analysis of test results, formulae for characterizing the peak stress, peak strain, elastic modulus as well as stress-strain responses of confined-SFRGC were proposed, with the effective confinement index of stirrups and fiber reinforcing factor introduced. The model predicted curves were in great agreement with the test curves.

An intervention study of poly-victimization among rural left-behind children based on the theoretical framework of planned behavior

BackgroundPoly-victimization (PV) not only threatens physical and mental health but also causes a range of social problems. Left-behind children in rural areas are more likely to experience PV problems. However, there have been fewer studies on PV among rural children, and even fewer intervention studies.ObjectiveThe difference-in-differences method was employed to analyze the impact of intervention measures, based on the theory of planned behavior, on PV among left-behind children in rural areas.MethodsThe study subjects were left-behind children from six middle schools in two cities in southern China, who completed the baseline survey from 2020 to 2021. They were divided into a control group and an intervention group, each consisting of 228 cases, based on their schools. Before and after the intervention, the Self-made victimization-related knowledge, attitude, and practice questionnaire, Poly-victimization scale, and Middle school students’ coping style scale were used to evaluate the victimization-related KAP(knowledge, attitude, and practice), victimization occurrence, and coping styles of left-behind children, respectively. Stata 15.0 was used to establish a difference-in-differences regression model to analyze the impact of the intervention measures on poly-victimization and coping styles.ResultsMixed Anova revealed that after the intervention, the KAP scores of the intervention group were significantly higher than those of the control group (p < 0.05). After the intervention, the incidence of child victimization in the intervention group dropped to 9.60% (n = 22), lower than in the baseline survey, with a statistically significant difference (p < 0.01). The incidence of PV among children in the intervention group was lower than that in the control group, with the difference being statistically significant (p < 0.01). The net reduction in the incidence of PV among children was 21.20%. After the intervention, the protection rate for preventing PV among children was 73.33%, and the effect index was 3.75. The intervention improved children’s coping styles, problem-solving, and help-seeking, while reducing negative coping styles such as avoidance and venting, with the differences being statistically significant (p < 0.05).ConclusionIntervention measures based on the theory of planned behavior reduce the occurrence of PV among left-behind children, and the intervention effects on different types of victimization are also different.

Performance Characterization of the Field Aged Asphalt Pavement Materials at Mortar Scale: Testing Method Optimization and Rheology Analysis

Performance evaluation at the asphalt mortar scale offers increased sensitivity to aging and is less affected by extraction processes comparated to asphalt mixture. Despite these benefits, there is currently a lack of standardized methods for directly processing mortar samples obtained from field mixtures. This study aims to improve and validate a manufacturing procedure for aged mortar specimens derived from field aging cores, and to evaluate the field damage level of asphalt paving materials at the mortar scale. A novel approach was developed that incorporates warm sieving, compaction, coring, and cutting to manufacture mortar specimens suitable for Dynamic Shear Rheometer (DSR) tests. This study selected mortar specimens with different service ages and conducted rheological tests, including frequency sweep tests and modified Multiple Stress Creep Recovery (MSCR) tests, to assess their rheological performance. And the significance test of all the indcies were conducted to select suitable indcies.The results show the proposed aged mortar manufacture approach can prepare eligible mortar specimens for rheology tests. The rheology test results show that several indices can distinguish different mortar types and service ages, and the indices of surface layer mortar follow a linear relationship with service age. The linear viscoelastic zone (LVE), representative shear modulus (G0), and unrecovered creep compliance at 1.6kPa (Jnr1.6) and 3.2kPa (Jnr3.2) are identified as effective indices for evaluating the behavior of field aged mortar because of their effectiveness, lower variability, and better distinction.

Novel Orange-Emitting YPO4:Sm3+/Polymer Nanocomposite Phosphor Films for LED Applications.

A polymer based nanocomposite (NC) material embedded with highly luminescent nanopowders could be promising for replacing traditional luminescent materials from a technological pointof view.In this study, we have successfully obtained YPO4: Sm3+ /Polymer nanocomposite phosphor films by embedding YPO4: Sm3+ luminescent nanoparticles (NPs) for orange-light emitting diode (LED) applications. These luminescent NPs were synthesized using the sol gel method in different polymer matrices i.e. polystyrene (PS) and poly (methyl methacrylate) (PMMA) by using direct solution mixing. The structural, morphological, and photoluminescence characteristics of the nano-phosphors and resulting NC films were examined and discussed. The emission spectra of YPO4: Sm3+ (x at.%) nano-phosphors under near-UV excitation at 404nm were dominated by orange emission attributed to 6H5/2 4F7/2 (601nm) luminescence of Sm3+ ions. The optimum doping concentration of activator Sm3+ in YPO4 matrix was found to be 5 at.%. When the doping concentration of Sm3+ was higher than 5 at.%, concentration quenching occurred. The incorporation of YPO4: Sm3+ NPs into polymer matrices indicated that the NCs retained the original luminescence properties of the luminescent NPs, although a decrease in their emission intensity was observed for the NC films, attributable to a polymer matrix effect, which dominated in PS matrix. The fluorescence decay times of NPs in the NC films were measured and compared to those of proper YPO4: Sm3+ nano-phosphors. A decrease in decay time in NC film was observed due the effective refractive index effect. Temperature-dependent photoluminescence (TDPL) of PMMA NC film was studied in 100-400K range, investigating the thermal stability of the film. Additionally, CIE coordinates confirmed the red-orange light emission of the prepared phosphors and NC films. The obtained results indicate that the synthesized polymer-nanophosphor NC films are promising candidates for orange-LED applications.

Investigation into the shear effect of torsion extrusion process

Torsion extrusion (TE) is a severe plastic deformation (SPD) technique with the potential to be used for the preparation of large bulk materials with enhanced mechanical properties. Shear deformation is the key factor for SPD to enhance the materials properties. However, it is not clear by far that what shear strains are dominant in torsion extrusion process and how they distribute in the extruded materials. These issues are crucial to the working parameters design of the torsion extrusion process for maximizing the shear effect. To this end, a plasticine billet with two colors was applied as experimental material, and the material flow pattern was revealed by measuring the twisted bicolor interfaces. The torsion extrusion was implemented using a die with a wavy cross-sectional bearing segment (W-TE), which is able to prevent the circumferential sliding of the materials against the die. Flow velocities were re-built according to the bicolor interfaces at each section in a cylindrical system. Strain rates and shear strains induced by torsion deformation along the radius of the material were formulated based on the velocity field and Eulerian variable derivatives, from which the dominant shear strain can be recognized. A shear effect index (SEI) was proposed to evaluate the contribution of the shear strains induced by torsion, and the distribution of SEI was analyzed. Furthermore, the W-TE experiments on the as-cast TiB2/2026 Al composite were carried out to demonstrate the positive correlation between the shear effect and the microstructural improvement, and finite element simulation for such experiments showed the consistency of the simulated deformation patterns with the plasticine measured ones. The evaluation method and the experimental results deepened the understanding to the shear effect of torsion extrusion process.