Search Results (706)

This paper presents the design, simulation, fabrication, and characterization of a novel large-scan-range electrothermal micromirror integrated with a pair of position sensors. Note that the micromirror and the sensors can be manufactured within a single MEMS process flow. Thanks to the precise control of the fabrication of the grid-based large-size Al/SiO₂ bimorph actuators, the maximum piston displacement and optical scan angle of the micromirror reach 370 μm and 36° at only 6 Vdc, respectively. Furthermore, the working principle of the sensors is deeply investigated, where the motion of the micromirror is reflected by monitoring the temperature variation-induced resistance change of the thermistors on the substrate during the synchronous movement of the mirror plate and the heaters. The results show that the full-range motion of the micromirror can be recognized by the sensors with sensitivities of 0.3 mV/μm in the piston displacement sensing and 2.1 mV/° in the tip-tilt sensing, respectively. The demonstrated large-scan-range micromirror that can be monitored by position sensors has a promising prospect for the MEMS Fourier transform spectrometers (FTS) systems. Full article

Food adulteration which is economically motivated (i.e., food fraud) is an incentive for the development and application of new and fast detection methods/instruments. An example of a fast method that is extremely environmentally friendly is near-infrared spectroscopy (NIRS). Therefore, the goal of this research was to examine the potential of its application in monitoring the adulteration of blended sunflower/olive oils and to compare two types of NIRS instruments, one of which is a portable micro-device, which could be used to assess the purity of olive oil anywhere and would be extremely useful to inspection services. Both NIR devices (benchtop and portable) enable absorbance monitoring in the wavelength range from 900 to 1700 nm. Extra virgin oils (EVOOs) and “ordinary” olive oils (OOs) from large and small producers were investigated, which were diluted with sunflower oil in proportions of 1–15%. However, with the appearance of different salad oils that have a defined share of EVOO stated on the label (usually 10%), the possibilities of the recognition and manipulation in these proportions were tested; therefore, EVOO was also added to sunflower oil in proportions of 1–15%. The composition of fatty acids, color parameters, and total dissolved substances and conductivity for pure and “adulterated” oils were monitored. Standard tools of multivariate analysis were applied, such as (i) analysis of main components for the qualitative classification of oil and (ii) partial regression using the least square method for quantitative prediction of the proportion of impurities and fatty acids. Qualitative models proved successful in classifying (100%) the investigated oils, regardless of whether the added thinner was olive or sunflower oil. Developed quantitative models relating measured parameters with the NIR scans, resulted in values of R² ≥ 0.95 and was reliable (RPD > 8) for fatty acid composition prediction and for predicting the percentage of the added share of impurity oils, while color attributes were less successfully predicted with the portable NIR device (RPD in the range of 2–4.2). Although with the portable device, the prediction potentials remained at a qualitative level (e.g., color parameters), it is important to emphasize that both devices were tested not only with EVOO but also with OO and regardless of whether proportions of 1–15% sunflower oil were added to EVOO and OO or EVOO and OO in the same proportions to sunflower oil. Full article

In this article, the sol–gel method was used as a synthesis method, which shows the physicochemical nature of the synthesis of a new complex material, ferrite Li_0.5MnFe_1.5O₄. The structure and composition of the synthesized ferrite were determined by X-ray phase analysis. According to analysis indicators, it was found that our compound is a single-phase, spinel-structured, and syngony-cubic type of compound. The microstructure of the compound and the quantitative composition of the elements contained within it were analyzed under a scanning electron microscope (SEM). Under a scanning electron microscope, microsystems were taken from different parts of Li_0.5MnFe_1.5O₄-type crystallite; the elemental composition of crystals was analyzed; and the general type of surface layer of complex ferrite was shown. As a result, given the fact that the compound consists of a single phase, the clarity of its construction was determined by the topography and chemical composition of the compound. As a result, it was found that the newly synthesized complex ferrites correspond to the formula Li_0.5MnFe_1.5O₄. The particles of the formed compounds have a large size (between 50.0 μm or 20.0 μm and 10.0 μm). Electrophysical measurements were carried out on an LCR-800 unit at intervals of 293–483 K and at frequencies of 1.5 and 10 kHz. An increase in frequency to 10 kHz led to a decrease in the value ε in the range of the studied temperature (293–483 K). Full article

Drone lidar has the potential to provide detailed measurements of vertical forest structure throughout large areas, but a systematic evaluation of unsampled forest structure in comparison to independent reference data has not been performed. Here, we used ray tracing on a high-resolution voxel grid to quantify sampling variation in a temperate mountain forest in the southwest Czech Republic. We decoupled the impact of pulse density and scan-angle range on the likelihood of generating a return using spatially and temporally coincident TLS data. We show three ways that a return can fail to be generated in the presence of vegetation: first, voxels could be searched without producing a return, even when vegetation is present; second, voxels could be shadowed (occluded) by other material in the beam path, preventing a pulse from searching a given voxel; and third, some voxels were unsearched because no pulse was fired in that direction. We found that all three types existed, and that the proportion of each of them varied with pulse density and scan-angle range throughout the canopy height profile. Across the entire data set, 98.1% of voxels known to contain vegetation from a combination of coincident drone lidar and TLS data were searched by high-density drone lidar, and 81.8% of voxels that were occupied by vegetation generated at least one return. By decoupling the impacts of pulse density and scan angle range, we found that sampling completeness was more sensitive to pulse density than to scan-angle range. There are important differences in the causes of sampling variation that change with pulse density, scan-angle range, and canopy height. Our findings demonstrate the value of ray tracing to quantifying sampling completeness in drone lidar. Full article

Copper is an essential element in living organisms and is crucial in marine ecosystems. However, excessive concentrations can lead to seawater pollution and pose a risk of toxicity to marine organisms, as it is a heavy metal. In addition, it can enter the human body through the food chain, potentially endangering human health. Consequently, there is increasing focus on the rapid and highly sensitive detection of copper ions (Cu²⁺). We prepared a graphite carbon electrode modified with graphitised multi-walled carbon nanotubes/copper(II) ion carrier IV (GMWCNT/copper(II) ion carrier IV/glassy carbon electrode (GCE)) using a drop-coating method. Scanning electron microscopy (SEM) analysis revealed that the composite material film possessed a large surface area. Incorporating this composite material significantly enhanced the adsorption capacity for ions on the electrode surface and greatly improved conductivity. Differential pulse anodic stripping voltammetry (DPASV) was employed to quantify copper levels in seawater. Under optimal experimental conditions, a strong linear relationship was observed between the Cu²⁺ response peak current and its concentration within a range of 50–500 µg L⁻¹, with a correlation coefficient of 0.996. The GMWCNT/copper(II) ion carrier IV/GCE exhibited excellent stability and reproducibility, achieving a low detection limit for Cu²⁺ at 0.74 µg L⁻¹ when applied to copper detection in seawater. Furthermore, spiked recovery rates ranging from 98.6% to 102.8% demonstrated the method’s high sensitivity, convenient operation, and practical value for real-world applications in detecting Cu²⁺ levels in seawater. Full article

The monolithic integration of gallium phosphide (GaP), with its green band gap, high refractive index, large optical non-linearity, and broad transmission range on silicon (Si) substrates, is crucial for Si-based optoelectronics and integrated photonics. However, material mismatches, including thermal expansion mismatch and polar/non-polar interfaces, cause defects such as stacking faults, microtwins, and anti-phase domains in GaP, adversely affecting its electronic properties. Our paper presents a structural and defect analysis using scanning transmission electron microscopy, high-resolution transmission electron microscopy, and scanning nanobeam electron diffraction of epitaxial GaP islands grown on Si nanotips embedded in SiO₂. The Si nanotips were fabricated on 200 mm n-type Si (001) wafers using a CMOS-compatible pilot line, and GaP islands were grown selectively on the tips via gas-source molecular-beam epitaxy. Two sets of samples were investigated: GaP islands nucleated on open Si nanotips and islands nucleated within self-organized nanocavities on top of the nanotips. Our results reveal that in both cases, the GaP islands align with the Si lattice without dislocations due to lattice mismatch. Defects in GaP islands are limited to microtwins and stacking faults. When GaP nucleates in the nanocavities, most defects are trapped, resulting in defect-free GaP islands. Our findings demonstrate an effective approach to mitigate defects in epitaxial GaP on Si nanotip wafers fabricated by CMOS-compatible processes. Full article

Cadmium (Cd) and zinc (Zn) in seawater enter the human body through the food chain. Combined toxicity tests indicated that high concentrations of Cd(II) and low concentrations of Zn(II) had a synergistic effect on humans. Thus, there is an urgent need to prepare a sensor for rapid and simultaneous detection of Cd(II) and Zn(II) in seawater. Herein, a reduced graphene oxide/carboxylated multi-walled carbon nanotube (rGO/MWCNT-COOH)-modified glassy carbon electrode was prepared in the experiments using the dropping method. The synthesis of various materials achieved the purpose of expanding the surface area, and scanning electron microscopy was used to observe the structure of the composite membrane. Moreover, the large number of functional groups on the surface of the composite membrane can also increase the adsorption of ions. For the determination of trace cadmium (II) and zinc (II) in seawater, the method used was differential pulse voltammetry (DPV). The results show that the peak current, which was obtained in the range of 5–400 μg/L for Cd(II) and Zn(II), has a linear relationship with concentration, corresponding to the detection limits of 0.8 μg/L for Cd(II) and 0.98 μg/L for Zn(II). The modified electrode was used to determine the Cd(II) and Zn(II) content in the coastal seawater of the Maowei Sea, and the recovery rate was between 95.8 and 98.2% for Cd(II) and 96.7~99.4% for Zn(II), which provided a novel approach of detection to define trace Cd(II) and Zn(II) in seawater. Full article

The model organism Neurospora crassa has been cultivated in laboratories since the 1920s and its saprotrophic lifestyle has been established for decades. However, beyond their role as saprotrophs, fungi engage in intricate relationships with plants, showcasing diverse connections ranging from mutualistic to pathogenic. Although N. crassa has been extensively investigated under laboratory conditions, its ecological characteristics remain largely unknown. In contrast, Brachypodium distachyon, a sweet grass closely related to significant crops, demonstrates remarkable ecological flexibility and participates in a variety of fungal interactions, encompassing both mutualistic and harmful associations. Through a comprehensive microscopic analysis using electron, fluorescence, and confocal laser scanning microscopy, we discovered a novel endophytic interaction between N. crassa and B. distachyon roots, where fungal hyphae not only thrive in the apoplastic space and vascular bundle but also may colonize plant root cells. This new and so far hidden trait of one of the most important fungal model organisms greatly enhances our view of N. crassa, opening new perspectives concerning the fungus‘ ecological role. In addition, we present a new tool for studying plant–fungus interspecies communication, combining two well-established model systems, which improves our possibilities of experimental design on the molecular level. Full article

The paper presents a novel small-footprint varactor diode-based reconfigurable reflectarray (RRA) design and investigates its power reflection efficiency theoretically and experimentally in a real-life indoor environment. The surface is designed to operate at 865.5 MHz and is intended for simultaneous use with other wireless power transfer (WPT) efficiency-improving techniques that have been recently reported in the literature. To the best of the authors’ knowledge, no RRA intended to improve the performance of antenna-based WPT systems operating in the sub-GHz range has been designed and studied both theoretically and experimentally so far. The proposed RRA is a two-layer structure. The top layer contains electronically tunable phase shifters for the local phase control of an incoming electromagnetic wave, while the other one is fully covered by metal to reduce the phase shifter size and RRA’s backscattering. Each phase shifter is a pair of diode-loaded 8-shaped metallic patches. Extensive numerical studies are conducted to ascertain a suitable set of RRA unit cell parameters that ensure both adequate phase agility and reflection uniformity for a given varactor parameter. The RRA design parameter finding procedure followed in this paper comprises several steps. First, the phase and amplitude responses of a virtual infinite double periodic RRA are computed using full-wave solver Ansys HFSS. Once the design parameters are found for a given set of physical constraints, the phase curve of the corresponding finite array is retrieved to estimate the side lobe level due to the finiteness of the RRA aperture. Then, a diode reactance combination is found for several different RRA reflection angles, and the corresponding RRA radiation pattern is computed. The numerical results show that the side lobe level and the deviation of the peak reflected power angles from the desired ones are more sensitive to the reflection coefficient magnitude uniformity than to the phase agility. Furthermore, it is found that for scanning angles less than 50°, satisfactory reflection efficiency can be achieved by using the classical reactance profile synthesis approach employing the generalized geometrical optics (GGO) approximation, which is in accord with the findings of other studies. Additionally, for large reflection angles, an alternative synthesis approach relying on the Floquet mode amplitude optimization is utilized to verify the maximum achievable efficiency of the proposed RRA at large angles. A prototype consisting of 36 elements is fabricated and measured to verify the proposed reflectarray design experimentally. The initial diode voltage combination is found by applying the GGO-based phase profile synthesis method to the experimentally obtained phase curve. Then, the voltage combination is optimized in real time based on power measurement. Finally, the radiation pattern of the prototype is acquired using a pair of identical 4-director printed Yagi antennas with a gain of 9.17 dBi and compared with the simulated. The calculated results are consistent with the measured ones. However, some discrepancies attributed to the adverse effects of biasing lines are observed. Full article

To explore the size, morphology, and distribution patterns of internal pore defects in WE43 magnesium alloy formed by laser powder bed fusion (LPBF), as well as their impact on its mechanical properties, computer tomography (CT), metallographic microscopy, and scanning electron microscopy were used to observe the material’s microstructure and the morphology of tensile test fractures. The study revealed that a large number of randomly distributed non-circular pore defects exist internally in the LPBF-formed WE43 magnesium alloy, with a defect volume fraction of 0.16%. Approximately 80% of the defects had equivalent diameters concentrated in the range of 10∼40 μm, and 56.2% of the defects had sphericity values between 0.65∼0.7 μm, with the maximum defect equivalent diameter being 122 μm. There were a few spherical pores around 20 μm in diameter in the specimens, and unfused powder particles were found in pore defects near the edges of the parts. Under the test conditions, the fusion pool structure of LPBF-formed WE43 magnesium alloy resembled a semi-elliptical shape with a height of around 66 μm, capable of fusion three layers of powder material in a single pass. Columnar grains formed at the edge of individual fusion pools, while the central area exhibited equiaxed grains. The “scale-like pattern” formed by overlapping fusion pool structures resulted in the microstructure of LPBF-formed WE43 magnesium alloy mainly consisting of fine equiaxed grains with a size of 2.5 μm and columnar grains distributed in a band-like manner. Full article

This study focuses on the growth of Cu₂O/CuO nanowires by one-step thermal oxidation using a flexible copper mesh at oxidation temperatures in the range of 300 to 600 °C in a controlled atmosphere of mixed-flow Ar and O₂ gases. Thermal oxidation is one of the simplest used methods to obtain nanowires on a metal surface, offering advantages such as low production costs and the ability to produce metal oxides on a large scale without the use of hazardous chemical compounds. The growth of metal oxides on a conductive substrate, forming metal/oxide structures, has proven to be an effective method for enhancing charge-transfer efficiency. The as-synthesized Cu/Cu₂O/CuO (Nw) electrodes were structurally and morphologically characterized using techniques such as XRD and SEM/EDX analysis to investigate the structure modification and morphologies of the materials. The supercapacitor properties of the as-developed Cu/Cu₂O/CuO (Nw) electrodes were then examined using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) measurements, and electrochemical impedance spectroscopy (EIS). The CV curves show that the Cu/Cu₂O/CuO (Nw) structure acts as a positive electrode, and, at a scan rate of 5 mV s ⁻¹, the highest capacitance values reached 26.158 mF cm⁻² for the electrode oxidized at a temperature of 300 °C. The assessment of the flexibility of the electrodes was performed at various bending angles, including 0°, 45°, 90°, 135°, and 180°. The GCD analysis revealed a maximum specific capacitance of 21.198 mF cm⁻² at a low power density of 0.5 mA cm⁻² for the oxidation temperature of 300 °C. The cycle life assessment of the all of the as-obtained Cu/Cu₂O/CuO (Nw) electrodes over 500 cycles was performed by GCD analysis, which confirmed their electrochemical stability. Full article

Ni-rich Li(Ni_xCo_yMn_z)O₂ (x ≥ 0.8)-layered oxide materials are highly promising as cathode materials for high-energy-density lithium-ion batteries in electric and hybrid vehicles. However, their tendency to undergo side reactions with electrolytes and their structural instability during cyclic lithiation/delithiation impairs their electrochemical cycling performance, posing challenges for large-scale applications. This paper explores the application of an Al₂O₃ coating using an atomic layer deposition (ALD) system on Ni-enriched Li(Ni_0.8Co_0.1Mn_0.1)O₂ (NCM811) cathode material. Characterization techniques, including X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, were used to assess the impact of alumina coating on the morphology and crystal structure of NCM811. The results confirmed that an ultrathin Al₂O₃ coating was achieved without altering the microstructure and lattice structure of NCM811. The alumina-coated NCM811 exhibited improved cycling stability and capacity retention in the voltage range of 2.8–4.5 V at a 1 C rate. Specifically, the capacity retention of the modified NCM811 was 5%, 9.11%, and 11.28% higher than the pristine material at operating voltages of 4.3, 4.4, and 4.5 V, respectively. This enhanced performance is attributed to reduced electrode–electrolyte interaction, leading to fewer side reactions and improved structural stability. Thus, NCM811@Al₂O₃ with this coating process emerges as a highly attractive candidate for high-capacity lithium-ion battery cathode materials. Full article

High-intensity anthropogenic activities have greatly altered the estuarine-shelf depositional processes of sediments, and the intensity and frequency of the impacts of human interventions have far exceeded the natural development of estuarine systems. Since the reform and opening up, human activities such as dams, sand mining, channel dredging, and reclamation have already caused anomalous changes in the dynamical–sedimentary–geomorphological processes of the Lingdingyang Estuary (LE). Analyzing the impact of high-intensity anthropogenic activities on sedimentary processes and the hydrodynamic environment through sedimentary records can provide a scientific basis for predicting the evolution of the estuary and the sustainable development of the Guangdong–Hongkong–Macao Greater Bay Area. The aims of this study are to reveal the impact of varying intensity human activities across different periods on depositional pattern and conduct a preliminary investigation into the spatial differences in sedimentary characteristic attributed to human activities. Two cores (LD11 and LD13) located in the LE were selected for continuous scanning of high-resolution XRF, grain size, and ²¹⁰Pb_ex dating tests, and scrutinized with the previous studies of the historical process of human activities in the LE. The results show the following: (1) The abrupt alterations in ²¹⁰Pb_ex, geochemical indices, and grain size in LD13 happened in close proximity to the 95 cm layer, suggesting a shift in the sedimentary environment during 1994. (2) In the context of the continuous reduction in water and sediment flux into the LE after 1994, the large-scale and high-intensity human activities like sand mining, channel dredging, and reclamation are responsible for the sedimentation rate increase rather than decrease, the coarsening of sediment fractions, the frequent fluctuations in Zr/Rb, Zr/Al, Sr/Fe, and Sr/Al ratios, and the increase in anomalous extremes. (3) Sedimentary records found in locations varying in anthropogenic intensities differ greatly. Compared with the nearshore siltation area, the grain size composition in the channel area is noticeably coarser and exhibits a wider range of grain size variations. The ²¹⁰Pb_ex is strongly perturbed and the vertical distribution is disturbed; the phenomenon of multiple inversions from the surface downwards is shown, making it impossible to carry out sedimentation rate and dating analysis, and the geochemical indicators have changed drastically without any obvious pattern. The evidence of the human activities can be retrieved in the sedimentary record of the estuary and provide a different angle to examine the impacts of the human activities. Full article

This study investigates the effects of process parameters in the powder bed fusion–laser beam (PBF-LB) process on IN939 samples. The parameters examined include laser power (160, 180, and 200 W), laser scanning speed (400, 800, and 1200 mm/s), and hatch distance (50, 80, and 110 μm). The study focuses on how these parameters affect surface roughness, relative density, defect formation, and the microstructure of the samples. Surface roughness analysis revealed that the average surface roughness (Sa) values of the sample ranged from 4.6 μm to 9.5 μm, while the average height difference (Sz) varied from 78.7 μm to 176.7 μm. Furthermore, increasing the hatch distance from 50 μm to 110 μm while maintaining constant laser power and scanning speed led to a decrease in surface roughness. Relative density analysis indicated that the highest relative density was 99.35%, and the lowest was 93.56%. Additionally, the average porosity values were calculated, with the lowest being 0.06% and the highest reaching 9.18%. Although some samples had identical average porosity values, they differed in porosity/mm² and average Feret size. Variations in relative density and average porosity were noted in samples with the same volumetric energy density (VED) due to different process parameters. High VED led to large, irregular pores in several samples. Microcracks, less than 50 μm in length, were present, indicating solidification cracks. The microstructural analysis of the XZ planes revealed arc-shaped melt pools, columnar elongated grains aligned with the build direction, and cellular structures with columnar dendrites. This study provides insights for optimizing PBF-LB process parameters to enhance the quality of IN939 components. Full article

This study addresses the environmental and health hazards posed by Pb(II) and iodine, two significant contaminants. The objective was to explore the adsorption of these substances from aqueous solutions using biochar derived from the leaf midribs of the date palm through a slow pyrolysis process. The pyrolysis was conducted in two stages within a vacuum furnace: initially at 300 °C for 1 h followed by overnight cooling, and then at 600 °C with a similar cooling process. The resulting biochar was characterized for its microstructural features and functional groups using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. It exhibited a porous structure with large numbers of pores (20 to 50 μm in size) and functional groups including O-H, C-H, and C=C, which are integral to its adsorption capabilities. For the adsorption studies, a 100 ppm Pb(II) ion solution was treated with varying amounts of biochar (20, 40, 60, and 80 mg) for 24 h. In parallel, iodine adsorption was tested, with biochar quantities ranging from 0.1 to 0.4 g/50 mL. Both treatments were followed by filtration and analysis using atomic absorption spectroscopy to determine the remaining concentrations of Pb(II) and iodine. The study also explored the effect of varying incubation periods (up to 30 h) on iodine adsorption. The results were significant; 100% adsorption of Pb(II) was achieved with the addition of 60 mg of biochar per 10 mL of solution. In contrast, for iodine, a maximum adsorption of 39.7% was observed with 30 mg or 40 mg of biochar per 50 mL. These findings demonstrate the potential of date palm-derived biochar as an effective and sustainable material for the removal of Pb(II) and iodine from contaminated water, offering valuable insights for environmental remediation strategies. Full article