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•Large-scale graded HEA component is fabricated by high-throughput LPBF.•Crack free samples were successfully fabricated with high Al content.•Dual phase structure induced by the ...chemical segregation can inhibit hot tearing.
It is of great significance to explore the chemical compositions, which have not been hitherto examined for their suitability for additive manufacturing (AM), so as to broaden AM’s material library. Since solidification cracking is a major impediment in AM of alloys, especially high entropy alloys (HEAs), a detailed study on the cracking issue during AM is imperative. Keeping this in mind, a customized laser powder bed fusion (LPBF) setup is utilized to fabricate a compositionally graded AlxCoCrFeNi (x = 0.04–0.75) HEA, using the equiatomic AlCoCrFeNi and CoCrFeNi powders as feedstock, to examine the compositional range that enables crack-free fabrication. Experimental results show that when x ≤ 0.7, crack-free fabrication is possible. This compositional range exceeds the threshold reported in the recent literature. Microstructural characterization reveals a constant dual phase structure throughout the gradient, which is induced by the chemical segregation. Further analysis shows that both utilizing AlCoCrFeNi powder as Al source and the segregation contribute to the enhanced printability. The results suggest that the dual phase structure introduced by chemical segregation can effectively inhibit the initiation and propagation of hot tearing problem in metal additive manufacturing.
With the development and utilization of three-dimensional (3D) intraoral scanning (IOS) technology, the morphological characteristics of teeth were quantitatively assessed. In this research, we aimed ...to explore the prevalence of dental caries in relation to each measurable morphological indicator of the tooth body via 3D intraoral scanning techniques.
A hospital-based single-centre study was conducted at our hospital from Dec. 2021 to Apr. 2023. A total of 53 patients were involved in the study, providing complete morphological data for 79 teeth. Each patient completed an oral hygiene routine questionnaire and underwent examination by an experienced dentist to evaluate caries conditions before undergoing 3D intraoral scanning to obtain a digital dental model. Geomagic Studio 2014 was used to extract oral morphological data from the models. The acquired data were entered, cleaned and edited using Excel 2016 and subsequently exported to SPSS version 25.0 for analysis. Chi-square analysis and logistic regression analyses were employed to test the associations.
Among the participants, 33 (61.1%) were female, with a mean age of 26.52 ± 10.83 years. Significant associations were found between dental caries and the vertical distance between the distal tip and the gum (OR 14.02; 95% CI 1.80-109.07; P = 0.012), the distal lateral horizontal distance of occlusion (OR 0.40; 95% CI 0.18-0.90; P = 0.026), and the mesial horizontal distance of occlusion (OR 2.20; 95% CI 1.12-4.31; P = 0.021). The Hosmer-Lemeshow test indicated a P value of 0.33.
The vertical distance between the distal tip and the gum, the distal lateral horizontal distance of the occlusion and the mesial horizontal distance of the occlusion were the influencing factors for dental caries (identified as independent risk factors). We hypothesize that these factors may be associated with the physiological curvature of teeth and the role of chewing grooves in plaque formation over time. However, further studies involving larger population samples and more detailed age stratification are still needed.
Three-dimensional ultrasound imaging is a promising medical imaging technology because of its ease of use and improved accuracy in diagnosis. However, its high computational complexity and resulting ...high power consumption has precluded its use in hand-held applications. In this paper, we present a separable beamforming method that greatly reduces computational complexity. Our method is based on decomposing the delay term in a way that minimizes the root-mean-square error caused by the decomposition. We analyze tradeoffs between the approximation error caused by the decomposition and computational complexity. Then, we present enhancements to the Sonic Millip3De hardware accelerator for ultrasound beamforming to implement separable beamforming. Using hardware synthesis targeting standard cells in 45 nm, we show that the proposed method allows us to boost the Sonic Millip3De frame rate from 1-2 Hz to 32 Hz while maintaining power consumption at 15 W. We validate image quality of our method using cyst phantom simulations in Field II. Our evaluation demonstrates that the proposed separable beamforming method can produce 3-D images with high quality that are comparable to those generated by non-separable beamforming.
This paper aims to find a forecasting model based on the comparative study of wavelet- ARIMA and EMD-ARIMA models and residual-based model selection technique for temperature time series. Time series ...analysis is essential in studying temperature data for investigating the variation and predicting the future trend, in which we can control the changes and make good decisions. And most important is to understand the trend in the series with time. This study applied hybridized models of wavelet transform and empirical mode decomposition with seasonal autoregressive integrated moving average (SARIMA), which combines two models to get better accuracy, for forecasting daily average temperature time series data in the central region of Eritrea, Asmara. Daily data was collected for 30 years, from January 1, 1991, to December 31, 2020. The study compares WT-SARIMA and EMD-SARIMA models to find a well fit and better forecasting model. Model selection techniques are essential for time series analysis to determine which model best fits our data. AIC and BIC are the most used methods in model selection. This paper uses an additional method based on the residual series. In estimating accurate parameters, the structure of the residual sequence had a lot of connection, in which a stationary residual depict an accurate estimation. From this perspective, a nonstationarity measurement of the residual series is used for model selection. The relative performance is based on the predictive capability of sample forecasts assessed. The results indicate that the hybridized wavelet-SARIMA model is more effective than the other models, and MATLAB soft-wire is used for this analysis.
Cyst nematodes are one of the major groups of plant-parasitic nematode, responsible for considerable crop losses worldwide. Improving genetic resources, and therefore resistant cultivars, is an ...ongoing focus of many pest management strategies. One of the major bottlenecks in identifying the plant genes that impact the infection, and thus the yield, is phenotyping. The current available screening method is slow, has unidimensional quantification of infection limiting the range of scorable parameters, and does not account for phenotypic variation of the host. The ever-evolving field of computer vision may be the solution for both the above-mentioned issues. To utilise these tools, a specialised imaging platform is required to take consistent images of nematode infection in quick succession.
Here, we describe an open-source, easy to adopt, imaging hardware and trait analysis software method based on a pre-existing nematode infection screening method in axenic culture. A cost-effective, easy-to-build and -use, 3D-printed imaging device was developed to acquire images of the root system of Arabidopsis thaliana infected with the cyst nematode Heterodera schachtii, replacing costly microscopy equipment. Coupling the output of this device to simple analysis scripts allowed the measurement of some key traits such as nematode number and size from collected images, in a semi-automated manner. Additionally, we used this combined solution to quantify an additional trait, root area before infection, and showed both the confounding relationship of this trait on nematode infection and a method to account for it.
Taken together, this manuscript provides a low-cost and open-source method for nematode phenotyping that includes the biologically relevant nematode size as a scorable parameter, and a method to account for phenotypic variation of the host. Together these tools highlight great potential in aiding our understanding of nematode parasitism.
Multi-material additive manufacturing holds immense potential for performance and functionality enhancement. Past research efforts primarily focused on the horizontal interface (perpendicular to the ...sample build direction) during the laser-powder bed fusion (LPBF) of multi-materials, whereas a few studies demonstrated that the vertical interface (parallel to the sample build direction) is in fact the main obstacle towards high-integrity multi-material fabrication in a three-dimensional space. In this work, facilitated by our own patented powder spreading device, we explored the mechanisms behind defect formation along both the horizontal and vertical interfaces during the LPBF production of 316L stainless steel and K220 copper multi-materials. High-fidelity fluid dynamics simulations were also conducted to rationalise the experimental observations. A practical process parameter optimisation approach is also proposed at the end, with the aim of mitigating those large defects currently occurring near the vertical interface.
Retrograde tracers based on viral vectors are powerful tools for the imaging and manipulation of upstream neural networks projecting to a specific brain region, and they play important roles in ...structural and functional studies of neural circuits. However, currently reported retrograde viral tracers have many limitations, such as brain area selectivity or the inability to retrograde label genetically defined brain-wide projection neurons. To overcome these limitations, a new retrograde tracing method, AAV-PHP.eB assisted retrograde tracing systems (PARTS) based on rabies virus, was established through brain-wide TVA-dependent targeting using an AAV-PHP.eB that efficiently crosses the blood-brain barrier in C57BL/6 J mice, and complementation of EnvA-pseudotyped defective rabies virus that specifically recognizes the TVA receptor. Furthermore, combined with Cre transgenic mice, cell-type-specific PARTS (cPARTS) was developed, which can retrograde label genetically defined brain-wide projection neurons. Our research provides new tools and technical support for the analysis of neural circuits.
While there is considerable interest in additive manufacturing of alloys and their resulting properties, the ‘bottom up’ approach of fabricating components—point by point, line by line, and layer by ...layer, offers a new tool for micro- and meso‑ structure control that has not yet been fully exploited by alloy designers. The mesostructures, which can be manipulated either through the choice of the processing parameters when prealloyed powders are used, or by using mixed powders (‘in situ alloying’), can be used to improve the overall mechanical performance of the printed part. Whilst the microstructures can be tailored to enhance strength, the mesostructures can be designed to improve the fracture toughness and other damage tolerance properties. These aspects are highlighted in this viewpoint paper.
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In this study, bamboo powder (BP), bamboo parenchyma cells (PCs), and bamboo fibers (BFs) were used as precursors to prepare activated carbon by ZnCl2 one-step activation to investigate the ...differences in the pore structures of the three. The results showed that BFs-based activated carbon had a higher specific surface area (2129 m2/g). Subsequently, the activation reaction paths of the BFs-based activated carbon preparation process were analyzed and explored by TGA, XRD, TG-MS-FTIR, EA, and other analytical methods, and the reaction mechanism was inferred. The results showed that the main reaction below 220 °C was the breaking of molecular bonds of oxygen-containing functional groups on hemicellulose, and the pyrolysis by-products at this stage were dominated by small molecules such as H2O, CO2, CH4, CH3OH, and HCHO. The pyrolysis of cellulose and the activation reaction of ZnCl2 were the main reactions between 220 °C and 650 °C. ZnCl2 was a strong dehydrating agent that can form ZnOCl2·2 H2O with intramolecular water molecules, and gradually decompose to form ZnO with the increase in temperature, the main gaseous products in this temperature interval were mainly H2O, CO, CO2, C3H4, and CH4. Above 650 °C, pyrolysis was basically completed and continued to shift to the aromatic structure, with the gaseous products mainly being H2, H2O, CO2, CH4, CO, C3H4, and a small amount of CH3OH and HCHO.
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•The reaction mechanism in the activation of bamboo fibers by ZnCl2 was studied.•The staged pyrolysis process of BFACs was analyzed and summarized.•220°C-650 °C as the main stage of activation.•The gases produced in each pyrolysis stage were analyzed using TG-MS-FTIR.•Possible reactions in the activation of bamboo fibers by ZnCl2 were proposed.
Microstructural heterogeneity is a feature of common occurrence in alloys additively manufactured using techniques such as laser powder bed fusion (LPBF). Additionally, chemical heterogeneities can ...arise both at micro- and meso-scales, especially when powder mixtures are used. While such chemical heterogeneities are considered undesirable hitherto, recent studies show that they may be beneficial in tailoring for the desired mechanical property combinations. In this study, we fabricated a graded alloy coupon with the mixed powders of the CoCrMo alloy and elemental Ni and investigated the microstructural and mesoscopic chemical heterogeneities in it. Chemical heterogeneities, which are either rich in Ni or CoCrMo, were observed due to the incomplete mixing of the powders. Banded patterns, with alternating layers that are enriched with different chemical species, were also observed. Distinct stacking fault energies between these chemical heterogeneities result in distinct deformation mechanisms; while planar slip and strain-induced martensitic transformation occur in the CoCrMo-rich heterogeneities, homogenous deformation associated with the wavy slip occurs in the Ni-rich ones. Detailed mechanical property characterizations show that the microscale chemical segregation not only strengthens the matrix but also improves the work hardening ability of the bulk material through kinematic hardening mechanism. These findings substantiate the key design principles for exploiting chemical segregations that form during in situ alloying for simultaneous enhancement of the strength and ductility in AM alloys.
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