Top Value Research Articles

Efficient All‐Polymer Solar Cells Enabled by a Novel Medium Bandgap Guest Acceptor

Comprehensive SummaryNear‐infrared (NIR)‐absorbing polymerized small molecule acceptors (PSMAs) based on a Y‐series backbone (such as PY‐IT) have been widely developed to fabricate efficient all‐polymer solar cells (all‐PSCs). However, medium‐bandgap PSMAs are often overlooked, while they as the third component can be expected to boost power conversion efficiencies (PCEs) of all‐PSCs, mainly due to their up‐shifted lowest unoccupied molecular orbital (LUMO) energy level, complimentary absorption, and diverse intermolecular interaction compared to the NIR‐absorbing host acceptor. Herein, an IDIC‐series medium‐bandgap PSMA (P‐ITTC) is developed and introduced as the third component into D18/PY‐IT host, which can not only form complementary absorption and cascade energy level, but also finely optimize active layer morphology. Therefore, compared to the D18/PY‐IT based parental all‐PSCs, the ternary all‐PSCs based on D18/PY‐IT:P‐ITTC obtain an increased exciton dissociation, charge transport, carrier lifetime, as well as suppressed charge recombination and energy loss. As a result, the ternary all‐PSCs achieve a high PCE of 17.64% with a photovoltage of 0.96 V, both of which are among the top values in layer‐by‐layer typed all‐PSCs. This work provides a method for the design and selection of the medium‐bandgap third component to fabricate efficient all‐PSCs.

The Chemistry of Levulinic Acid: Its Potential in the Production of Biomass‐based Chemicals

Biomass has been identified as the ultimate sustainable resource for all carbon‐based consumer products of the chemical industries in the future. Its catalytic conversion leads to the formation of various platform chemicals that could partially or even fully replace the fossil‐based building blocks that have been currently used in synthetic chemical processes. Among these compounds, levulinic acid (LA) has been recognized as a member of the "Top Value Added Chemicals from Biomass" and has attracted significant attention since the seminal paper reported by Werpy and Petersen in 2004. This review summarizes the properties, recent advances, and developments in the chemistry of levulinic acid. The production of LA from both plant and animal‐based carbohydrate feedstocks via 5‐hydroxymethylfurfural or furfuryl alcohol is discussed from a mechanistic perspective, highlighting intrinsic molecular‐level limitations to LA formation. The efficiencies of recently developed catalytic systems are also summarized and compared. Furthermore, the conversion of LA into high‐value‐added downstream chemicals, including its role in the synthesis of complex molecular structures, is overviewed. This section discussed the reactions of LA in the points of view of its various transformations on carbonyl‐, carboxy‐, methyl‐, and methylene functional groups. The reactions of these functionalities with C‐ ,N‐, O‐, and S‐nucleophiles, alcohols, amines, organometallic reagents, oxygen etc. were thematically summarized. Our review also outlooks to highlight the challenges and opportunities associated with the extensive research area of organic chemistry of levulinic acid.

Individuals' top values and health behavior engagement: results of a National US Survey.

Although linked with subjective wellbeing, little research has examined relations of values with health behaviors and health. Because values are principles that guide behavior across situations, this exploratory retrospective study examined how individuals' highest value relates to their health behaviors and health. Participants were 3865 (aged 18-89 years) adults who completed the Health Information National Trends Survey (HINTS), a nationally-representative survey administered by the US National Cancer Institute. HINTS 5 Cycle 4 data were collected early in 2020. Participants selected the value most important to them in their day-to-day life from a set of seven values. Five categories of health-related measures were assessed in relation to values: substance use, physical activity, cancer screening, general health, and coping. Top values were safety of family (29.9%), happiness (20.9%), and autonomy (14.1%). Findings indicated that some top values, such as health and religion, were associated favorably with some health behaviors, while other top values, such as happiness or autonomy, were in some instances associated with poorer health behaviors. These results, while exploratory, suggest that individuals' highest value may be meaningfully related to their health behaviors and self-reported health status. Future research into values and health appears warranted.

Experimental study on the compression and shear deformation evolution of coal pillar dam samples

To understand the mechanical properties and deformation failure patterns of coal pillar dams in gently inclined coal seam mine underground reservoirs, compression-shear coupling tests with variable angles were conducted on coal pillar dam samples under different saturation states. The digital image correlation (DIC) technique was utilized to obtain the deformation patterns of the displacement field throughout the compression-shear failure process of the samples. Numerical simulations were used to perform a comparative analysis and validation of the experimental results. The results indicated that the load-bearing capacity of the coal pillar dam samples decreased by 12.8–17.4% under water-saturated conditions. For every 5° increase in the inclination angle, the load-bearing capacity of the coal pillar dam samples decreased by an average of 3.53%. The normal stress and shear stress on the shear surface of the saturated samples were both lower than those of the natural samples, and both exhibited a linear variation with increasing inclination angle. The deformation evolution of the coal pillar dam samples under different test conditions exhibited similarity. The initial positive and negative displacement extremities in the horizontal direction were located at the lower right and upper left corners of the samples, respectively. Ultimately, the displacement field of the samples showed a pattern of smaller displacements at the top and larger displacements at the bottom, with negative values at the top and positive values at the bottom, distributed along the direction of the sample’s bedding. The saturated state and the increase in inclination both had a weakening effect on the load-bearing performance of the samples but had a relatively small impact on the differences in the displacement field deformation patterns. The research results can provide a reference for the study of the stability of coal pillar dams under similar conditions.

PENGARUH CUSTOMER RELATIONSHIP, STRATEGIC SUPPLIER, INFORMATION SHARING & POSTPONEMENT TERHADAP ORGANIZATIONAL PERFORMANCE YANG DIMEDIASI INBOUND DAN OUTBOUND INNOVATION

Technological advancements and the growth of e-commerce have increased the complexity of supply chain management, making it more vulnerable to disruptions. The COVID-19 pandemic has highlighted this vulnerability, leading organizations to reassess traditional risk management approaches and emphasize collaborative partnerships to enhance supply chain value. This study aims to evaluate the impact of Customer Relationship (CR), Quality of Information Sharing (QIS), Strategic Supplier Partnership (SSP), Postponement (P), Top Management Knowledge Value (TMKV), and Knowledge Sharing Practice (KSP) on Organizational Performance (OP), with Inbound and Outbound Open Innovation (IOI and OOI) as mediating variables. Data was collected from 164 professionals in Jakarta using the Purposive Sampling method through online questionnaires on Google Forms. Data analysis was conducted using the Partial Least Squares Structural Equation Modeling (PLS-SEM) method. The results of the study show that all independent variables positively affect organizational performance, although not all of these effects are significant. This indicates that effective integration between Supply Chain Management strategies and Open Innovation can improve organizational performance. TMKV has a significant positive impact on KSP, KSP also has a significant positive impact on IOI, IOI has a significant positive impact on OP, and KSP mediated by IOI is proven to have a significant positive effect in supporting OP, while OOI mediation is not proven. This study is not intended to generalize a theory due to the limitations in sample size, industry, and geographical area.

Acoustic characterization of the Municipal Museum Abade Pedrosa

The 2016 interventions concerning the rehabilitation of the Municipal Museum Abade Pedrosa in Santo Tirso, Portugal were analyzed to verify in what way acoustics interferes in the museum enjoyment. In situ measurements were done in every exhibition room: Reverberation Time, RASTI and the Equivalent Sound Level (LAeq). RT[500, 1k, 2k Hz] values were between 2.5 and 3.9 s. The RASTI mean values varied between 0.44 and 0.55 s. LAeq values of background noise reached a top value of 43 dB(A) in the 1000 Hz frequency band and a global value of 57 dB(A) in every room. A multicriteria analysis was carried out to globally characterize the museum in a simple and perceptive way, with an algorithm that ranks all the different rooms, in which they were generally classified as "bad". A comparison of these values was done with similar studies in other museums: Soares dos Reis (Porto), Serralves (Porto) and other international museums, being possible to verify that the Municipal Museum Abade Pedrosa has worse acoustic values compared to those other museums. It was also suggested possible improvements that could contribute for the acoustic correction of the space, with a predictable cost of about 27000 €.

High-Performing Flexible Mg3Bi2 Thin-Film Thermoelectrics.

With the advances in bulk Mg3Bi2, there is increasing interest in pursuing whether Mg3Bi2 can be fabricated into flexible thin films for wearable electronics to expand the practical applications. However, the development of fabrication processes for flexible Mg3Bi2 thin films and the effective enhancement of their thermoelectric performance remain underexplored. Here, magnetron sputtering and ex-situ annealing techniques is used to fabricate flexible Mg3Bi2 thermoelectric thin films with a power factor of up to 1.59 µW cm-1 K-2 at 60°C, ranking as the top value among all reported n-type Mg3Bi2 thin films. Extensive characterizations show that ex-situ annealing, and optimized sputtering processes allow precise control over film thickness. These techniques ensure high adhesion of the films to various substrates, resulting in excellent flexibility, with <10% performance degradation after 500 bending cycles with a radius of 5mm. Furthermore, for the first time, flexible thermoelectric devices are fabricated with both p-type and n-type Mg3Bi2 legs, which achieve an output power of 0.17 nW and a power density of 1.67 µW cm-2 at a very low temperature difference of 2.5°C, highlighting the practical application potential of the device.

An Ultrasensitive Bi2O2Se/In2S3 Photodetector with Low Detection Limit and Fast Response toward High-Precision Unmanned Driving.

The machine vision utilized in unmanned driving systems must possess the ability to accurately perceive scenes under low-light illumination conditions. To achieve this, photodetectors with low detection limits and a fast response are essential. Current systems rely on avalanche diodes or lidars, which come with the drawbacks of increased energy consumption and complexity. Here, we present an ultrasensitive photodetector based on a two-dimensional (2D) Bi2O2Se/In2S3 heterostructure, incorporating a homotype unilateral depletion band design. This innovative architecture effectively modulates the transport of both free and photoexcited carriers, suppressing the dark current and facilitating the rapid and efficient separation of photocarriers. Owing to these features, this device exhibits a responsivity of 144 A/W, a specific detectivity of 1.2 × 1014 Jones, and a light on/off ratio of 1.1 × 105. These metrics rank among the top values reported for state-of-the-art 2D devices. Moreover, this device also demonstrates a fast response time of 170/296 μs and a low noise equivalent power of 0.57 fW/Hz1/2, attributes that endow it with ultraweak light imaging capabilities. Furthermore, we have successfully integrated this device into an unmanned driving system, providing a perspective on the design and fabrication of future optoelectronic devices.

Proton conductivity and dielectric studies on chitosan/polyvinyl alcohol blend electrolytes: Synergistic improvements with ionic liquid and graphene oxide

This study investigates the impact of ionic liquid, 1-methylimidazolium tetrafluoroborate (IL) and graphene oxide (GO) on the performance of chitosan/polyvinyl alcohol (CS/PVA)-based composite electrolytes. Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirm the successful incorporation of IL and GO, affecting the structural and morphological properties of the electrolytes. Thermogravimetric analysis (TGA) reveals enhanced thermal stability in GO-doped samples, with increased residual weight at high temperatures, while IL addition leads to higher initial weight loss due to its hygroscopic nature. Ionic conductivity measurements demonstrate that the CS/PVA/IL-GO(4.0) composite achieves the highest proton conductivity of 1.76 × 10−3 S/m at 300 K and 1 MHz, surpassing other samples and aligning with top values reported in literature. Dielectric studies show a significant increase in dielectric constant to 9.55 × 104 at 300 K and 20 Hz for CS/PVA/IL-GO(4.0), attributed to enhanced dipole alignment and polarization effects. The loss tangent analysis indicates the shortest relaxation time of 2.07 × 10−4 s for CS/PVA/IL-GO(4.0), correlating with its superior proton conductivity. These findings highlight the potential of CS/PVA/IL-GO electrolytes for advanced energy storage and conversion applications, suggesting further research into GO dispersion and long-term stability for optimized performance in practical devices.

Optimizing Drone-Based IoT Base Stations in 6G Networks Using the Quasi-opposition-Based Lemurs Optimization Algorithm

The rapid evolution and integration of next-generation Internet-of-things (NG-IoT) applications present new complexities for sixth-generation (6G) mobile communication networks, including the need for extensive connectivity, increased network capacity, and ultralow-latency communications. While ultradense networking, characterized by deploying numerous base stations, offers a potential solution, practical and financial constraints limit its feasibility. Drone-based stations (DBSs) emerge as a flexible alternative, but their optimal positioning remains a critical challenge due to finite energy sources and potential signal degradation. This study introduces a new quasi-opposition-based lemurs optimizer (QOBLO) to address the optimal placement of DBSs in NG-IoT networks. QOBLO combines lemur foraging behaviour with quasi-opposition-based learning to enhance exploration and exploitation in the optimization process. The performance of QOBLO was evaluated across three scenarios and compared with other swarm intelligence algorithms using metrics such as Friedman’s ranking test (FRT) and the Wilcoxon signed-rank test (WSRT). Rigorous simulations emulated real-world conditions and varying network demands, testing QOBLO's adaptability and robustness. Results indicate that QOBLO significantly outperforms other algorithms, achieving a top FRT value of 1.234 and demonstrating superior p values in the WSRT. These findings highlight QOBLO's capability to enhance connectivity, coverage, and energy efficiency in 6G environments. The primary contribution of this research is the development of QOBLO, a scalable and efficient method for optimizing DBS deployment. This new approach improves network performance in complex NG-IoT applications, offering a robust solution to the challenges of 6G networks and ensuring enhanced reliability and sustainability of future communication infrastructures.

Long-term mulched drip irrigation facilitates soil organic carbon stabilization and the dominance of microbial stochastic assembly processes

Mulched drip irrigation (MDI) is generally accepted as a method to decrease soil salinization and improve crop yields in arid and semi-arid regions. However, there remain gaps in how MDI drives soil organic carbon (SOC) dynamic microbial assembly processes with time, and the mediating role of microorganisms remains unclear. In this study, we investigated the aforementioned issues across soil profiles in cotton fields with different years of MDI. The results showed that MDI did not cause the differences in SOC, particular organic carbon (POC), and mineral-associated organic carbon (MOC) in soil layers. The POC and MOC contents had a parabola relationship with time, and showed an opposite trend in soil. After 15 years of MDI, the ratio of MOC/SOC increased to a peak value of 50 % and 52 % in topsoil and subsoil, respectively; the ratio of POC/SOC decreased to valley values of 50 % and 48 %, respectively (P < 0.05). Long-term MDI reduced the differences in oxidase between soil layers but accelerated SOC loss by increasing polyphenol oxidase activity (P < 0.05). Compared with that of other years, with 10 years of MDI, bacterial Shannon diversity decreased to a valley value, and fungal Shannon diversity reached to a top value in subsoil (P < 0.05). In general, stochastic processes were mainly controlled by dispersal limitation, and undominated processes dominated microbial assembly; however, there was a close relationship between bacterial communities and organic carbon fractions. The high percentage of positive linkages among microorganisms indicated that long-term MDI was beneficial for carbon fixation. Additionally, a decrease of fungal oligotroph/copiotroph ratio, the relative abundance of Ascomycota and Basidiomycota was beneficial for the accumulation of SOC and POC in topsoil (P < 0.05). In conclusion, long-term MDI is useful for the fixation of organic carbon via improving soil POC content and strengthening linkages within community assemblies.

Effect of flow patterns on recovery of invertases from Saccharomyces cerevisiae using polyethylene glycol/magnesium sulfate system in microchannels

The use of microdevices in extraction processes in aqueous two-phase systems (ATPS) has been studied for years in the literature. However, the effects of flow patterns still need to be adequately explored, especially for real samples. In this sense, the present study investigated the performance of microdevices in the recovery and partial purification of invertases with varying flow patterns. The invertases from Saccharomyces cerevisiae and the polyethylene glycol 1500/magnesium sulfate system were used in the experiments. Beyond the flow pattern, the study sought to maximize recovery and purification factor (PF) values by varying other operating conditions, including residence time, volumetric ratio, and channel diameter. It was observed that the short slug and long slug patterns showed better separation performance than the parallel pattern regardless of residence time and volumetric ratio. Increasing the residence time from 15 to 35 min increased the top recovery and PF values by two times, indicating that S. cerevisiae invertase partition is slow to the top phase. The maximum values of recovery (57.01 % ± 2.67 %) and PF (4.16 ± 0.06) were reached in the condition with long slug pattern, 35 min of operation, volumetric ratio of 2:1, and a channel diameter of 0.51 mm. The present study provides valuable information for integrating microdevices in a protocol for purifying invertase from S. cerevisiae and other proteins in real systems.

Field investigation on thermal comfort of metro passengers in hot summer and warm winter zone of China: A case study in Guangzhou

In the hot summer and warm winter zone of China, the metro thermal environments and passengers’ thermal comfort were rarely examined, influencing factors such as commuter hours and individual factors were less discussed, and understanding them was beneficial for improving human thermal comfort and saving energy. In this study, a field study was undertaken in Guangzhou located in the region during the summer of 2023. Four metro stations and three metro lines were selected, a total of 1481 valid questionnaires were gathered. The results revealed that the metro thermal environment was highly commendable during the hot summer months, with a thermal acceptability vote (TAV) ranging from 81 % to 89 % across the entrance (ET), concourse (CC), platform (PF), and carriage (CR). Furthermore, the upper limit of the 80 % acceptance range for operative temperature (Top) was 29.11 °C in the ET, 27.82 °C in the CC, 29.13 °C in the PF, and 28.44 °C in the CR. These temperatures exceed the actual mean Top values in these locations, indicating there is a significant potential for energy savings in metro environments. The upper limits of Top values for passengers with low, medium and high metabolic rates are 30.34 °C, 28.92 °C, and 28.25 °C, respectively. Thermal sensation votes (TSVs) fell well within the comfort zone specified in ISO 7730 (−0.7 < PMV < 0.7) during both peak and off-peak hours. No difference was found in TSVs between the two genders and among the different ages.

Relationship between serum uric acid, nocturnal hypertension and risk for preeclampsia in high-risk pregnancies.

To analyze the possible association between serum uric acid (SUA) and nocturnal hypertension and to evaluate the ability of these variables (alone or in combination) to predict preeclampsia (PE) we conducted a historical cohort study in 532 high-risk pregnancies. Women were divided according to SUA values and nocturnal blood pressure (BP) into four groups: 1- normal SUA and nocturnal normotension; 2- high SUA and nocturnal normotension; 3- normal SUA and nocturnal hypertension and 4- high SUA and nocturnal hypertension. High SUA was defined by the top quartile values and nocturnal hypertension as BP ≥ 120/70 mmHg, using ambulatory blood pressure monitoring (ABPM), during nocturnal rest. Risks for PE were compared using logistic regression. SUA had a weak but significant correlation with daytime systolic ABPM (r = 0.11, p = 0.014), daytime diastolic ABPM (r = 0.13, p = 0.004), nighttime systolic ABPM (r = 0.16, p < 0.001) and nighttime diastolic ABPM (r = 0.18, p < 0.001). Also, all ABPM values were higher in women with high SUA. The absolute risk of PE increased through groups: 6.5%, 13.1%, 31.2%, and 47.9% for groups 1, 2, 3, and 4, respectively, p < 0.001. Compared with Group 1, Group 3 (OR 6.29 95%CI 3.41-11.60), but not Group 2 (OR 2.15 95%CI 0.88-5.24), had statistically significant higher risk for PE. Group 4 (women with both, high SUA and nocturnal hypertension) had the highest risk (OR 13.11 95%CI 6.69-25.70). Risks remained statistically significant after the adjustment for relevant variables. In conclusion, the combination of SUA > 4 mg/dL and nocturnal BP > 120/70 mmHg implies a very high risk to developed PE.

Autonomy ranks as highest importance to dermatology physician assistants in Pennsylvania with highest compensations

Introduction: By exploring the relationship between compensation and job values, this research letter aims to contribute to the existing literature on health care professional compensation and job satisfaction, particularly within the context of dermatology physician assistants (PAs). Objectives: The authors aim to answer the question, “Does annual salary compensation correlate with any reported job values among dermatology PAs in Pennsylvania?” Method: This research letter presents a postsurvey analysis of a salary survey conducted among the members of the Pennsylvania Dermatology Physician Assistants (PDPA). The data used in this analysis were obtained from the previously published salary survey conducted by the PDPA. The survey asked participants to rank the factors most important in selecting a dermatology position. Results: Dermatology PAs in Pennsylvania who earned the highest income in a given year reported job autonomy as a top value [rs (79)=−0.2208, P=0.048]. Discussion: Schedule flexibility may allow PAs to be more productive in seeing more patients and, therefore, result in higher compensations. PAs with freedom, independence, and discretion may feel respected and valued. This could result in positive effects on productivity and, as a downstream result, higher compensation.

Evaluating Lean Combustion Cycle Stability and Emissions in Spark Ignition Engines with Gasoline, Ethanol, and Methanol Blends

Abstract Fuels for vehicles account for a large portion of the world’s total energy demand, which in turn leads to increased carbon emissions. Ethanol and methanol are a fuel with a simple carbon chain and OH- bonds. It has similar properties to gasoline, and ethanol can be made from the fermentation of plant carbohydrates, called bioethanol. The advantage of using bioethanol is that it contributes to carbon neutrality. This paper will investigate the use of three manually blended gasoline ethanol and methanol (GEM) fuels in a spark ignition engine to address cycle-to-cycle variation (CCV), knock potential, and emissions with lean blend conditions. In the experiments conducted, the air-fuel ratio was conditioned lean by utilizing an electronic control unit to adjust the injector spray duration. This experiment provides results that there is a potential for mild knocking on the use of alcohol fuel with lean fuel mixture conditions at engine speed 4000 RPM, while at engine speed 6000 RPM and 8000 RPM the use of GEM tends to be stable, but in the CCV results the increase in COV (coefficient of variation) value using GEM fuel tends to be more sloping, especially with the addition of more methanol. Emission results from the use of GEM produce top emission CO2 value obtained by the E5M15 mixture at λ=1.2 and an engine speed of 8000 RPM, with a value of 13.75% and then peak CO2 emissions at a value of λ = 1.2 whereas in the use of pure gasoline peak CO2 is at a value of λ = 1.1.

Efficient and Stable Air-Processed Organic Solar Cells Enabled by an Antioxidant Additive.

Current high-efficiency organic solar cells (OSCs) are generally fabricated in an inert atmosphere that limits their real-world scalable manufacturing, while the efficiencies of air-processed OSCs lag far behind. The impacts of ambient factors on solar cell fabrication remain unclear. In this work, the effects of ambient factors on cell fabrication are systematically investigated, and it is unveiled that the oxidation and doping of organic light absorbers are the dominant reasons causing cell degradation when fabricated in air. To address this issue, a new strategy for fabricating high-performance air-processed OSCs by introducing an antioxidant additive (4-bromophenylhydrazine, BPH) into the precursor solutions, is developed. BPH can effectively inhibit oxygen infiltration from the ambient to the photoactive layer and suppress trap formation caused by oxidation. Compared with conventional air-processed OSCs, this strategy remarkably increases the cell power conversion efficiency (PCE) from 16.7% to 19.3% (independently certified as 19.2%), representing the top value of air-processed OSCs. Furthermore, BPH significantly improves the operational stability of the cells in air by two times with a T80 lifetime of over 500 h. This study highlights the potential of using antioxidant additives to fabricate high-efficiency and stable OSCs in air, significantly promoting the industrialization of OSCs.

The effects of 3D printing designs on PLA polymer flexural and fatigue strength

This study assessed the comprehensive assessment of flexural and fatigue strength of the three-dimensional (3D)-printed polylactic acid (PLA) samples across diverse printing designs and parameters. The experiment framework included a diverse array of printing parameters: layer heights, first layer thicknesses, infill densities, top/bottom infill patterns, extruder temperatures, perimeters, and types of solid layer top and bottom. Our findings suggest that there is an interplay between these parameters and the mechanical properties of PLA specimens. Notably, the fatigue strength of PLA printing specimens is more significantly influenced (0.44%) by an increase in the thickness of the first layer compared to flexural strength (87%). The rate of increase in bending strength is lower in cases of layer height (3.55%) and initial layer height (0.44%) in contrast with other factors. Specimens with an initial layer thickness of 0.4 mm reached the highest number of cycles until failure, recording 21 022 cycles. Furthermore, the study identifies the infill pattern’s impact on strength, highlighting that the line infill pattern type case has the highest bending strength of 75.97 MPa and surpasses the honeycomb pattern in bending strength. Compared to the Honeycomb pattern, the rectilinear design has 2.1% higher bending strength. The number of cycles to failure of the rectilinear pattern is greater than those of the honeycomb pattern. In comparison to other patterns, the Rectilinear Top/Bottom infill pattern has a higher interest rate of 27.5% for bending strength and 200.83% for fatigue strength. Additionally, greater bending and flexural strength are obtained by raising the solid layer top, bottom, and perimeter values, respectively. In comparison to the other temperatures, the bending strength and fatigue strength are highest at 200 °C. Therefore, the first layer height of 0.4 mm, the top/bottom rectilinear infill pattern, the extruder temperature of 200 °C, the perimeter value of 3, the solid layer/top value of 3, and the solid layer/bottom value of 3 are the optimal values for the part subjected to at the same time bending strength combined with fatigue strength. This comprehensive study may provide a broader and deeper understanding of individual and combined effects on an overview of the bending and fatigue strength in connection to printing design and printing parameters, as well as the ideal optimal parameters for 3D printing with the PLA material. Manufacturers and designers can use the recommended parameters to optimize the strength of their printed parts, considering both bending and fatigue performance.

EVALUATING MODEL ROBUSTNESS FOR DEFECT IDENTIFICATION AND CLASSIFICATION IN COMPOSITE AEROSTRUCTURE MATERIAL

Abstract Aircraft structures are required to have a high level of quality to satisfy their need for light weight, efficient flight, and withstanding high loads over their lifespan. These aerostructures are typically made from composite material due to their good tensile strength and resistance to compression. To ensure their structural integrity, the composite material requires inspection for common flaws such as porosity, delaminations, voids, foreign object debris, and other defects. Ultrasonic testing (UT) is a popular non-destructive inspection (NDI) technique used for effectively evaluating composite material. Current inspection methods rely heavily on human experience and are extremely time consuming. Therefore, there is a need for the development of techniques to reduce the manual inspection time. This work compares the performance of different deep learning-based methods in the identification and classification of defects. Deep learning has shown great promise in numerous fields, and we show its effectiveness in the evaluation of composite aerostructure material. The methods developed here are both highly reliable with a top recall value of 98.64% as well as extremely efficient requiring an average of 4 seconds during the inferencing stage to evaluate new composites. Finally, we investigate model robustness to concept drift by measuring its performance over time.

Comparison of the microhardness of lowviscosity bulk-fill composite resins

The aim of this study is to compare the microhardness of five different low-viscosity bulk-fill composites. The bulk-fill composites used in the study; Estelite Bulk-fill flow (EBF), Filtek Bulk-fill (FBF), SureFil SDR flow (SDR), Tetric EvoFlow Bulk fill (TEFBF), X-tra Base (XBF). Cylindrical molds with a diameter of 5 mm and a height of 4 mm were used for the Vicker's Micro Hardness (VMH) test. Bulk-fill composite resins were placed in these molds at once. The polymerization of the composites was achieved for 20 seconds with the LED light curing. A total of 50 composite discs were prepared (n=10). Then the microhardness of the top and bottom surfaces was measured using MVK-H1 Microhardness Tester (Akashi Co, Tokyo, Japan. Depth of polymerization of each sample was recorded. Data were analyzed by using the Kruskal Wallis H and Mann Whitney-U tests. The bottom and top surface hardness values of the XBF composite samples (43.82±0.95 MPa, 47.87±0.59 MPa) were statistically significantly higher than the other bulk-fill composite samples (p&lt;0.001). The bottom and top surface hardness values of the FBF composite (27.85±0.56 MPa, 22.05±1.40 MPa) were found to be statistically lower than other bulk-fill composite samples (p&lt;0.001). Among the low-viscosity bulk-fill composites used in the study, except for FBF, the VMH values of the others were found to be above 0.80, and it was observed that they reached sufficient microhardness.