Search Results (23)

Thermoplastic starch (TPS) is a biodegradable polymer from renewable sources, but its limited mechanical and thermal properties restrict wider industrial use compared to petroleum-based plastics. In this study, TPS-based biocomposites were developed and optimized by incorporating agricultural and mineral Residues: coffee husks (CH), potassium feldspar (PF), and Bahia Beige marble (BB) as reinforcements. Mechanical, thermal, and morphological characterizations were carried out, and a simplex–lattice mixture design was applied to optimize the formulations. The 70/20/5/5 (TPS/CH/PF/BB, wt.%) composition achieved the highest tensile strength (2.0 MPa) and elastic modulus (70.2 MPa), while the 90/0/5/5 formulation showed superior impact resistance. FTIR and SEM analyses confirmed effective filler dispersion and strong matrix–filler interactions. Scheffé polynomial models (R² > 87%) accurately predicted performance, highlighting the reliability of the statistical approach. From a sustainability perspective, this work demonstrates that upcycling coffee husks and mineral residues into TPS-based biocomposites contributes to waste reduction, landfill diversion, and the development of cost-effective biodegradable materials. The proposed systems offer potential for eco-friendly packaging and agricultural applications, reducing dependence on fossil-based plastics and mitigating the environmental footprint of polymer industries. Statistical optimization further enhances efficiency by minimizing experimental waste. Moreover, this research supports circular economy strategies and provides scalable, sustainable solutions for waste valorization. Full article

Background: Dental caries is a prevalent dental problem affecting primary and permanent teeth. Early demineralization of enamel lesions can be reversed through remineralization. Many studies have focused on caries prevention and disease progression arrest using silver diamine fluoride (SDF). No in vitro studies have compared the remineralization effects of different 38% SDF solutions on artificially demineralized enamel lesions. This study aimed to compare the remineralization potential of three commercial 38% silver diamine fluoride formulations on artificial enamel lesions in primary teeth using a pH cycling model. The hypothesis was as follows: different commercial SDF formulations would exhibit varying remineralization effects, as measured by surface microhardness, due to potential differences in their compositions. Materials and Methods: In this study, 75 primary molars were randomized into five groups (N = 15): I: baseline, II: SDF Riva Star Aqua^® 38%, III: Riva Star^® 38%, IV: SDF Advantage Arrest^® 38%, and V: control. Artificial caries were created by submerging teeth in 10 mL of demineralization solution (pH 4.5) for three days in a light-resistant container, ensuring distinct visual changes in the enamel as per the International Caries Detection and Assessment System (ICDAS level 2). After pH cycling, all samples underwent a standardized Vickers microhardness test (VMHT) with a 50 g load for 15 s. Data were analyzed using one-way ANOVA and Tukey’s post hoc test, with a significance level set at p ≤ 0.05. Results: The one-way ANOVA test indicated a significant difference in microhardness among the groups (SDF Riva Star Aqua, SDF Riva Star, and SDF Advantage Arrest), with an F-value of 167.73 and p < 0.001. The post hoc Scheffé test showed that SDF Riva Star Aqua and SDF Riva Star were not significantly different (p = 0.388). However, SDF Advantage Arrest had a significantly higher mean microhardness compared to both groups (p < 0.001). Overall, these results show that SDF Advantage Arrest leads to greater microhardness than SDF Riva Star Aqua or SDF Riva Star. Conclusions: SDF Advantage Arrest showed superior performance among the SDF-treated groups, significantly increasing microhardness compared to SDF Riva Star Aqua and SDF Riva Star. This suggests that SDF Advantage Arrest offers enhanced remineralization and structural strengthening, making it the most effective option for managing demineralized primary teeth. Future research should investigate the long-term performance and mechanisms of these treatments to optimize clinical protocols for preserving primary tooth integrity. Full article

Classroom management is an essential yet frequently under-practiced competency in undergraduate teacher education, with important implications for sustainable teacher preparation. This study investigated whether pre-service teachers who feel more capable of managing classrooms also engage more deeply with simulation-based training. Fifty-seven Korean pre-service teachers (15 men, 42 women), all undergraduate students enrolled in a secondary teacher education program at a college of education, completed a five-item classroom-management-efficacy scale, then experienced a 15 min branching simulation that required choosing recognition, punishment, or aggression strategies in response to a disrespectful virtual student. Interest was assessed immediately afterwards with a 24-item instrument covering the four phases of the interest-development model (triggered situational, maintained situational, emerging individual, and well-developed individual). A post-test comparative design and MANOVA revealed that efficacy level had a significant multivariate effect on overall interest (Wilks Λ = 0.78, p = 0.029, partial η² = 0.12). Scheffe contrasts showed that high-efficacy participants outscored their low-efficacy peers on maintained situational and emerging individual interest, p < 0.05, and surpassed the middle-efficacy group in three of the four phases. Repeated measures ANOVA confirmed a general decline from situational to individual interest across all groups (F (3, 52) = 9.23, p < 0.01), underscoring the difficulty of converting short-term curiosity into lasting commitment. These findings position classroom-management efficacy as a key moderator of engagement and support the use of adaptive simulations as sustainable tools for teacher education. By tailoring challenge levels and feedback to participants’ efficacy, guided simulations can foster deeper engagement and promote individualized growth—helping build resilient and well-prepared educators. Full article

As a renewable energy source and potential substitute for fossil fuels, biodiesel plays an increasingly important role in both energy security and environmental protection. Accurate thermal conductivity data of biodiesels and their mixture with diesel are critical to engine design to achieve high combustion efficiency. This study measured the thermal conductivity of binary mixtures of heptane and biodiesel components, specifically methyl myristate, methyl laurate, and methyl caprate, over a temperature range of 298.15–328.15 K, using the two-wire 3ω method. Based on the experimental data, the effect of mass fraction, temperature, and carbon chain length of the fatty acid ester on the thermal conductivity was analyzed. The second-order Scheffé polynomial model, Flippov equation, Jamieson equation, and Chen equation were used to correlate the experimental data and compare to find a better one. The Flippov equation shows the lowest absolute average relative deviation of 0.80% for the binary mixtures of heptane with methyl myristate, methyl laurate, and methyl caprate. Full article

A mixture experiment is one where the response depends only on the relative proportions of the ingredients present in the mixture. Different regression models are used to analyze mixture experiments, such as the Scheffé model, the Slack Variable model, and models with inverse terms. Models with inverse terms are worthy of consideration in certain applications. These models have been analyzed considering their fit quality, but not their numerical stability. This article analyzes the numerical stability of the model with inverse terms and the use of pseudo components. Likewise, a criterion is defined for the selection of the regression model with inverse terms, based on the quality of fit and numerical stability. Full article

This research explores how variations in laser powder bed fusion (LPBF) parameters—laser power (P), scanning speed (v), and base plate preheating temperature (ϑ_p)—affect the mechanical properties of the EOS Co-Cr SP2 dental alloy. A central composite design (CCD) was used to optimize the process parameters. Mechanical testing focused on crucial properties for dental applications, including yield strength (Rp_0.2), elongation (ε), toughness (KV_a), and flexural strength (R_ms). Microstructural analysis was conducted using light and electron microscopy, while XRD identified microstructural phases. Statistical analysis (ANOVA, Scheffé post hoc test, α = 0.05) revealed significant effects of P, v, and ϑ_p on the mechanical properties. Response surface models (RSMs) were developed, and optimal parameters were determined to achieve maximum toughness and flexural strength. Maximum values were obtained with laser power above 205 W and base plate preheating at 310 °C. The mathematical model predicted toughness values with less than 5% deviation from experimental results, indicating high accuracy. Full article

This study aimed to confirm the mediating effects of symptom experiences on the relationship between the body image and quality of life of hemodialysis patients. Data were collected from 153 patients who were diagnosed with ESRD at a tertiary general hospital and receiving regular hemodialysis in Korea. The data were collected between 20 July and 11 August 2023. The following statistical analyses were conducted: t-test, ANOVA, Scheffé test, Pearson’s correlation coefficient analysis, and Hayes’ Process Macro Model 4 (to test the mediating effect). The factors influencing quality of life were body image (β = 0.46, p < 0.001), monthly family income (over KRW 3 million) (β = 0.22, p = 0.002), and symptom experiences (β = −0.20, p = 0.001). The mediation analysis indicated that the symptom experiences mediated the relationship between body image and quality of life. Based on the results, education, counseling, and symptom management programs that can improve body image and reduce symptom experience should be developed, and customized programs that reflect the characteristics of a target population, such as economic level, should be developed and provided. Full article

Materials that generate structural color may be promising alternatives to dyes and pigments due to their relative long-term stability and environmentally benign properties. Liquid crystal (LC) mixtures of cholesteryl esters demonstrate structural color due to light reflected from the helical structure of the self-assembled molecules. The apparent color depends on the pitch length of the liquid crystal. While a wide range of colors have been achieved with such LC formulations, the nature of the pitch–concentration relationship has been difficult to define. In this work, various machine learning approaches to predict the reflected wavelength, i.e., the position of the selective reflection band, based on LC composition are compared to a Scheffe cubic model. The neural network regression model had a higher root mean squared error (RMSE) than the Scheffe cubic model with improved predictions for formulations not included in the dataset. Decision tree regression provided the best overall performance with the lowest RMSE and predicted position of the selective reflection band within 0.8% of the measured values for LC formulations not included in the dataset. The predicted values using the decision tree were over two-fold more accurate than the Scheffe cubic model. These results demonstrate the utility of machine learning models for predicting physical properties of LC formulations. Full article

The main factor in the turnover of new nurses in Korea is burnout, and a high turnover rate can lead to discontinuation in the nursing profession, due to failure to adapt to the organization. This study aimed to examine the mediating influences of an exchange relationship with the preceptor on the relationship between burnout and job retention intention among new nurses in Korea. Data were collected from 210 new nurses in three general hospitals from 2 May to 30 June 2023. The following statistical analysis were conducted: t-test, ANOVA, the Scheffé test, Pearson’s correlation coefficient analysis, and Hayes Process Macro Model 4 (to test the mediating effect). Burnout was negatively associated with job retention intention (r = −0.54, p < 0.001) and the exchange relationship with the preceptor (r = −0.29, p = 0.001). The exchange relationship with the preceptor was positively associated with job retention intention (r = 0.38, p < 0.001). Furthermore, the mediation analysis indicated that the exchange relationship with the preceptor mediated the relationship between burnout and job retention intention. According to the results, the impact of burnout on the job retention intention was mediated by the exchange relationship with the preceptor. Therefore, to increase the job retention intention of new nurses, developing programs to enhance the exchange relationship with the preceptor are recommended. Full article

Today, the concepts of “epistemological belief” (EB) and “locus of control” (LOC) have become important in education. It is considerable to investigate these concepts on teacher candidates who are the teachers of the future. This study aimed to examine the LOC and EB of social studies teacher candidates. The research, which adopted a survey model, was conducted with five hundred and fifty social studies teacher candidates studying at seven state universities in Turkey. The Locus of Control Scale and the Epistemological Belief Scale were used to collect research data. Descriptive statistics, independent samples t-test, one-way analysis of variance (ANOVA), the Scheffe test, and correlation analysis were employed in the data analysis process. When evaluating the research results, it was determined that female teacher candidates have a higher external LOC. No significant difference was observed in social studies teacher candidates’ LOC regarding their parents’ educational grade level. It was observed that there was a significant difference in the EB of social studies teacher candidates regarding gender. It was revealed that female teacher candidates had underdeveloped/immature EB. No significant difference was found in the EB of social studies teacher candidates based on their parents’ educational levels or grade. It was observed that there is a weak but positive significant relationship between the social studies teacher candidates’ LOC and EB and their sub-scales. Full article

Phaleria macrocarpa (Scheff.) Boerl. or ‘Mahkota Dewa’ is a popular plant found in Malaysia as it is a valuable source of phytochemicals and therapeutic properties. Drying is an essential step in the storage of P. macrocarpa fruits at an industrial level to ensure their availability for a prolonged shelf life as well as preserving their bioactive compounds. Hence, this study evaluates the effect of different temperatures on the drying kinetics, extraction yield, phenolics, flavonoids, and antioxidant activity of P. macrocarpa fruits. The oven-drying process was carried out in this study at temperatures of 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C. Six thin-layer drying models (i.e., Lewis, Page, Henderson and Pabis, two-term exponential, Logarithmic, and Midilli and Kucuk models) were evaluated to study the behaviour of oven-dried P. macrocarpa fruits based on the coefficient of determination ($R^2$), root mean square error ($RMSE$), and chi-square (${\chi }^2$). The quality of the oven-dried P. macrocarpa fruits was determined based on their extraction yield, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity (2,2-diphenyl-1-picrylhydrazyl) using ultrasound-assisted extraction. The results showed that the time for moisture removal correspondingly increased in the oven-dried P. macrocarpa fruits. Apparently, the Midilli and Kucuk model is the most appropriate model to describe the drying process. The range of effective moisture diffusivity was 1.22 × ${10}^{-8}$ to 4.86 × ${10}^{-8}$ ${\mathrm{m}}^2/\mathrm{s}$, and the activation energy was 32.33 kJ/mol. The oven-dried P. macrocarpa fruits resulted in the highest extraction yield (33.99 ± 0.05%), TPC (55.39 ± 0.03 mg GAE/g), TFC (15.47 ± 0.00 mg RE/g), and DPPH inhibition activity (84.49 ± 0.02%) at 60 °C based on the significant difference (p < 0.05). A strong correlation was seen between the antioxidant activity, TPC, and TFC in the oven-dried P. macrocarpa fruits. The current study suggests that the oven-drying method improved the TPC, TFC, and antioxidant activity of the P. macrocarpa fruits, which can be used to produce functional ingredients in foods and nutraceuticals. Full article

To test the impact of FFF filaments, printing parameters, thermoforming foils, repeated thermoforming cycles, and type of jaw on the dimensional stability of FFF models for aligners and to compare them with plaster models, FFF models (maxilla, n = 48; mandible, n = 48) from two filaments (SIMPLEX aligner and Renfert PLA HT, both Renfert GmbH) were fabricated using four printing parameters (one, two, or three loops; four loops acted as the default) and conventional plaster models (n = 12) based on a young, female dentition. All models were thermoformed under pressure three times in total using two different thermoforming foils, namely 0.75 mm × 125 mm Ø aligner foil (CA Pro+ Clear Aligner, Scheu Dental) and 1.0 mm × 125 mm Ø Duran foil (Duran+, Scheu Dental). Aligner foil was heated at 220 °C for 25 s and Duran foil at 220 °C for 30 s. All models were scanned after fabrication as well as after each thermoforming cycle. The obtained STL datasets were analyzed using the local best-fit method (GOM Inspect Pro, Carl Zeiss Metrology GmbH). Data were analyzed using a Kolmogorov–Smirnov-test, a one-way ANOVA with post-hoc Scheffé, and a t-test (p < 0.05). The dimensional stability of the models was most strongly affected by the printing parameters (number of loops; η_p² = 0.768, p < 0.001) followed by the thermoforming foil used (η_p² = 0.663, p < 0.001) as well as the type of model (η_p² = 0.588, p < 0.001). In addition, various interactions showed an influence on the dimensional stability (η_p² = 0.041–0.386, p < 0.035). SIMPLEX maxillary models (default; four loops), thermoformed using aligner foil, showed higher deformation stability than did plaster models. These initial FFF models provide comparable precision to plaster models, but the dimensional stability of the FFF models, in contrast to that of plaster models, decreases with increasing numbers of thermoforming cycles. Full article

This study is a descriptive survey aiming to examine the general characteristics, emotional labor, anger, and work engagement of mental health specialists at mental health welfare centers and determine their effects on work-life balance (WLB). A total of 193 mental health specialists from 21 mental health welfare centers at metropolitan cities U and B were enrolled. A self-report and anonymous online questionnaire was used to collect data from 11 March to 1 April 2021. The collected data were analyzed using the t-test, analysis of variance, Scheffé test, Pearson’s correlation coefficients, and multiple regressions using SPSS Windows (Ver 25.0). We found that WLB is significantly negatively correlated with emotional labor (r = −0.47, p < 0.001), anger (r = −0.32, p < 0.001), and work engagement (r = 0.37, p < 0.001). The regression model confirmed that the male sex (β = 0.35, p = 0.002), moderate perceived health (β = −0.31, p = 0.003), poor perceived health (β = −0.35, p = 0.020), 1–3 years of career experience at a mental health welfare center (β = 0.27, p = 0.043), level of attentiveness required in emotional labor (β = −0.23, p = 0.014), and vigor of work engagement (β = 0.15, p = 0.005) were predictors of WLB, and these factors explained 43.1% of the variance. Supportive work policies and environments that promote perceived health, reduce emotional labor, and stimulate work engagement are needed to help mental health specialists at mental health welfare centers maintain a good WLB and enjoy a higher quality of life. Full article

Nurses often have a heavy workload and struggle to maintain a good quality of life (QOL). The aim of this study was to explore the relationship between perceived stresses and sleep disturbance, and quality of life among Korean clinical nurses. A cross-sectional design was used to examine these relationships among 200 clinical nurses at three hospitals in South Korea. Standardized instruments were used, including the Perceived Stress Scale (PSS), Insomnia Severity Index (ISI), Eating Behavior Questionnaire (DEBQ), and the WHOQoL-BREF questionnaire. The data were analyzed using descriptive statistics, the t-test, ANOVA, the Scheffe test, Pearson’s correlation coefficient, and multiple regression analysis using SPSS/WIN 24.0 program. Multiple regression analysis showed that clinical nurses who had a subjective health status (β = 0.29, p = 0.001), perceived stress (β = −0.32, p < 0.001), and sleep disturbance (β = −0.21, p = 0.001) were more likely to have a higher quality of life. The explanatory power of the regression model was statistically significant at 36.7%. Multiple regression analysis showed that clinical nurses who had better subjective health status, lower perceived stress, and fewer sleep disturbances were more likely to have a higher quality of life. Full article

Pervious concrete provides a tailored surface course with high permeability properties which permit the easy flow of water through a larger interconnected porous structure to prevent flooding hazards. This paper reports the modeling of the flexural properties of quarry dust (QD) and sawdust ash (SDA) blended green pervious concrete for sustainable road pavement construction using Scheffe’s (5,2) optimization approach. The simplex mixture design method was adapted to formulate the mixture proportion to eliminate the set-backs encountered in empirical or trials and the error design approach, which consume more time and resources to design with experimental runs required to evaluate the response function. For the laboratory evaluation exercise, a maximum flexural strength of 3.703 N/mm² was obtained with a mix proportion of 0.435:0.95:0.1:1.55:0.05 for water, cement, QD, coarse aggregate and SDA, respectively. Moreover, the minimal flexural strength response of 2.504 N/mm² was obtained with a mix ratio of 0.6:0.75:0.3:4.1:0.25 for water, cement, QD, coarse aggregate and SDA, respectively. The test of the appropriateness of the developed model was statistically verified using the Student’ t-test and an analysis of variance (ANOVA), and was confirmed to be acceptable based on computational outcomes at the 95% confidence interval. Furthermore, the scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) were used to evaluate the morphological and mineralogical behavior of green prior concrete samples with various additive mixture compositions. The addition of QD and SDA, on the other hand, aided the creation of porous microstructures in the concrete matrix due to fabric changes in the concrete mixture, potentially aided by the formation of cementitious compounds such as calcium aluminate hydrate and calcium silicate hydrate. Full article