Search Results (23,614)

The simulations presented here are based on the observational data of lightning electric currents associated with the eruption of the Hunga Tonga volcano in January 2022. The response of the lithosphere (Earth)–atmosphere–ionosphere–magnetosphere system to unprecedented lightning currents is theoretically investigated at low frequencies, including ultra low frequency (ULF), extremely low frequency (ELF), and very low frequency (VLF) ranges. The electric current source due to lightning near the location of the Hunga Tonga volcano eruption has a wide-band frequency spectrum determined in this paper based on a data-driven approach. The spectrum is monotonous in the VLF range but has many significant details at the lower frequencies (ULF, ELF). The decreasing amplitude tendency is maintained at frequencies exceeding 0.1 Hz. The density of effective lightning current in the ULF range reaches the value of the order of 10⁻⁷ A/m². A combined dynamic/quasi-stationary method has been developed to simulate ULF penetration through the lithosphere (Earth)–atmosphere–ionosphere–magnetosphere system. This method is suitable for the ULF range down to 10⁻⁴ Hz. The electromagnetic field is determined from the dynamics in the ionosphere and from a quasi-stationary approach in the atmosphere, considering not only the electric component but also the magnetic one. An analytical/numerical method has been developed to investigate the excitation of the global Schumann resonator and the eigenmodes of the coupled Schumann and ionospheric Alfvén resonators in the ELF range and the eigenmodes of the Earth–ionosphere waveguide in the VLF range. A complex dispersion equation for the corresponding disturbances is derived. It is shown that oscillations at the first resonance frequency in the Schumann resonator can simultaneously cause noticeable excitation of the local ionospheric Alfvén resonator, whose parameters depend on the angle between the geomagnetic field and the vertical direction. VLF propagation is possible over distances of 3000–10,000 km in the waveguide Earth–ionosphere. The results of simulations are compared with the published experimental data. Full article

This paper proposes a three-stage op amp based on the SOI (silicon-on-insulator) process, which achieves a low offset voltage and temperature coefficient across a wide temperature range from −40 °C to 250 °C. It can be used in aerospace, oil and gas exploration, automotive electronics, nuclear industry, and in other fields where the ability of electronic devices to withstand high-temperature environments is strongly required. By utilizing a SC (Switched Capacitor) notch filter, the op amp achieves low input offset in a power-efficient manner. The circuit features a multi-path nested Miller compensation structure, consisting of a low-speed channel and a high-speed channel, which switch according to the input signal frequency. The input-stage operational amplifier is a fully differential, rail-to-rail design, utilizing tail current control to reduce the impact of common-mode voltage on the transconductance of the input stage. The two-stage operational amplifier uses both cascode and Miller compensation, minimizing the influence of the feedforward signal path and improving the amplifier’s response speed. The prototype op amp is fabricated in a 0.15 µm SOI process and draws 0.3 mA from a 5 V supply. The circuit occupies a chip area of 0.76 mm². The measured open-loop gain exceeds 140 dB, with a 3 dB bandwidth greater than 100 kHz. The amplifier demonstrates stable performance across a wide temperature range from −40 °C to 250 °C, and exhibits an excellent input offset of approximately 20 µV at room temperature and an offset voltage temperature coefficient of 0.7uV/°C in the full temperature range. Full article

Most mosquito surveillance programs rely on traps baited with carbon dioxide (CO₂) to attract host-seeking mosquitoes. The source of CO₂, traditionally dry ice or gas cylinders, poses operational challenges, especially in remote locations. CO₂ production from citric acid and sodium bicarbonate (NaHCO₃) using low-cost intravenous fluid bags (‘acid traps’) was evaluated in laboratory experiments. Field trials then compared the efficacy of these acid traps with dry ice traps. Using a 2 × 2 Latin square style design, trapping locations were established at two sites in Sydney, New South Wales, Australia (one urban and another peri-urban), to assess trap performance in diverse environments. The laboratory results showed CO₂ production of sufficient amount and duration for overnight mosquito capture. Whilst field experiments showed that dry ice traps captured more mosquitoes (up to 59%) than acid traps, numbers were similar in the urban environment. At both sites, species composition was similar, with Culex quinquefasciatus, Aedes notoscriptus, and Aedes vigilax predominantly collected, and these are known species of pest and public health concern. Further modifications to the acid traps could further improve CO₂ output and trap efficiency. Full article

The hybrid FEM-DBCI numerical method is proposed for the computation of coupling factors between time-harmonic magnetic fields and human bodies. Characteristics are highlighted which make FEM-DBCI very suitable to perform such computations. Several coil geometries are considered (circular coils) at low frequency. A simplified model of the human body is assumed as suggested by IEC standards. Details of the method are highlighted, and numerical results are also provided. Full article

A nuclear electromagnetic pulse (NEMP) is the fourth effect of a nuclear explosion, characterized by a strong electromagnetic field that can instantly damage electronic devices. To investigate the spatial field value distribution characteristics of the source region of low-altitude NEMPs, this study employed a finite-difference time-domain (FDTD) method based on a rotating ellipsoidal hyperbolic coordinate system. Due to intense field variations near the explosion center, non-uniform grids were employed for both spatial and temporal steps, and an OpenMP parallel algorithm was utilized to enhance computational efficiency. Analysis focused on the following two scenarios: varying angles at a constant distance and varying distances at a constant angle, considering both transverse magnetic (TM) and transverse electric (TE) waves. The results indicate that the spatial field value distribution characteristics differ between the two wave types. For TM waves, the electric and magnetic fields share the same polarity, but their waveform polarities are opposite above and below the explosion center. A TE wave is exactly the opposite. Compared with a TM wave, a TE wave has stronger peak electromagnetic fields but narrower pulse widths and lower overall energy. This research provides significant support for the development of nuclear explosion detection technology and offers theoretical foundations for the protection of surrounding environmental facilities. Full article

Precise photogrammetric mapping of preharvest conditions in an apple orchard can help determine the exact position and volume of single apple fruits. This can help estimate upcoming yields and prevent losses through spatially precise cultivation measures. These parameters also are the basis for effective storage management decisions, post-harvest. These spatial orchard characteristics can be determined by low-cost drone technology with a consumer grade red-green-blue (RGB) sensor. Flights were conducted in a specified setting to enhance the signal-to-noise ratio of the orchard imagery. Two different altitudes of 7.5 m and 10 m were tested to estimate the optimum performance. A multi-seasonal field campaign was conducted on an apple orchard in Brandenburg, Germany. The test site consisted of an area of 0.5 ha with 1334 trees, including the varieties ‘Gala’ and ‘Jonaprince’. Four rows of trees were tested each season, consisting of 14 blocks with eight trees each. Ripe apples were detected by their color and structure from a photogrammetrically created three-dimensional point cloud with an automatic algorithm. The detection included the position, number, volume and mass of apples for all blocks over the orchard. Results show that the identification of ripe apple fruit is possible in RGB point clouds. Model coefficients of determination ranged from 0.41 for data captured at an altitude of 7.5 m for 2018 to 0.40 and 0.53 for data from a 10 m altitude, for 2018 and 2020, respectively. Model performance was weaker for the last captured tree rows because data coverage was lower. The model underestimated the number of apples per block, which is reasonable, as leaves cover some of the fruits. However, a good relationship to the yield mass per block was found when the estimated apple volume per block was combined with a mean apple density per variety. Overall, coefficients of determination of 0.56 (for the 7.5 m altitude flight) and 0.76 (for the 10 m flights) were achieved. Therefore, we conclude that mapping at an altitude of 10 m performs better than 7.5 m, in the context of low-altitude UAV flights for the estimation of ripe apple parameters directly from 3D RGB dense point clouds. Full article

The application of cyclones can be traced back to 100 years ago. Salt, an important carrier of energy exchange in the human body, is one of the essential substances. Currently, salt surface impurities are mostly removed manually, resulting in low sorting efficiency. Cyclones, as important physical separation equipment, are widely used in separating different substances. This paper focuses on using cyclones for salt decontamination. However, due to the limitations of the cyclone’s structure, ensuring grading accuracy is challenging. The flow field, as the main power source in the cyclone grading process, significantly impacts the grading effect. The overflow pipe, where fine particles exit, has a significant effect on the internal flow field. To explore the impact of the overflow pipe structure on the cyclone’s internal flow field, five overflow pipe structures were designed and numerically analyzed. The results indicate that the improved overflow tube structure has higher static pressure than the conventional linear structure. Type 2 (Parabolic) has the highest tangential velocity, which is 27.7 percentage points higher than that of the conventional cyclone, while Type 3 (hyperbola) has the lowest axial velocity(minimum value is only 0.3 m/s) and turbulence intensity(minimum value of the cone segment is only 0.2), resulting in longer particle residence time in the cyclone for better separation. Additionally, vortices are effectively avoided, improving the stability of the flow field to some extent. The obtained data provide a theoretical basis and support for the structural design of new cyclones. Full article

This paper investigated the optimization of the hardness and oscillation mode of flexible hydrofoils using bidirectional fluid–structure interaction (FSI) to address the issue of insufficient guidance in engineering applications. A two-dimensional flexible symmetric hydrofoil model of NACA0012 with a chord length of 1 m was constructed for this research. The hydrodynamic characteristics of low-frequency flexible hydrofoils with varying hardness and oscillation modes were analyzed through numerical simulation. The results indicated that the flexible hydrofoil with a Shore hardness of D50 exhibited the most optimal hydrodynamic performance under low-frequency conditions across the five groups of hardness tests. Among the three commonly utilized oscillation modes, the inboard oscillation mode demonstrated the most favorable performance. The hydrodynamic performance of the flexible hydrofoil surpassed that of the rigid hydrofoil in both inward and outward oscillation motions; however, it was inferior in pure pitching motions. Comparative analysis of the vortex structure and velocity distribution in the flow field revealed that the inward oscillation motion effectively enhanced the kinetic energy of the wake vortex and slowed down vortex dissipation, thereby improving the overall flow velocity. These findings provide theoretical support for the study of flexible hydrofoils and contribute to their advancement in pumping applications under actual ultra-low head conditions. Full article

The genome sequence of Pantoea agglomerans UADEC20 is presented, which is a strain isolated from agricultural fields in northeast Mexico. The genome was assembled into 13 scaffolds, constituting a total chromosome size of 4.2 Mbp, with two of the scaffolds representing closed plasmids. The strain exhibits activity in phosphate solubilization and exopolysaccharide (EPS) production and secretion; therefore, we explored its biotechnological potential via its genome sequencing and annotation. Genomic analyses showed that a total of 57 and 58 coding sequences (CDSs) related to phosphate solubilization and EPS production were identified within its genome, in addition to a reduced number of CDSs related to drug resistance and phages. The comprehensive set of genes supporting phosphate solubilization, EPS synthesis, and secretion, along with its low virulence and antibiotic resistance levels, justify further research for its potential biotechnological application and possible use as a plant growth-promoting agent in the field. These findings suggest a unique genetic background in the P. agglomerans UADEC20 strain. Full article

Fluidic oscillators have emerged as a prominent topic of research in the field of flow control, owing to their broad sweep range and enhanced control efficiency. However, the underlying mechanisms governing the operation of fluidic oscillators remain poorly understood, and the effect of oscillation frequency on flow control performance has yet to be conclusively determined. In this study, a novel fluidic oscillator is proposed that achieves frequency decoupling by replacing the conventional feedback channel with synthetic jets, thereby enabling modulation of oscillation frequency at a constant momentum coefficient. When applied to a high-lift airfoil, results show that at a momentum coefficient of 14.1%, the lift coefficient increase achieved under F⁺ = 1 control outperforms that under F⁺ = 10 by more than 0.3. This finding suggests the presence of an optimal frequency for fluidic oscillators, which maximizes their flow control effectiveness. Notably, this optimal frequency is unaffected by variations in the momentum coefficient. A deeper analysis of the fluidic oscillator’s working principle reveals that periodic oscillations dominate the turbulent kinetic energy and Reynolds shear stress, driving enhanced chordwise momentum exchange. This increased energy transfer strengthens the boundary layer’s resistance to separation, effectively mitigating flow detachment and improving lift enhancement. Finally, the periodic flow field on the surface of the high-lift airfoil under fluidic oscillator control was examined. It was observed that, at low frequencies, the fluidic oscillator effectively controls the shedding of separation vortices, ensuring that the frequency of vortex shedding aligns with the oscillation frequency of the fluidic oscillator. This alignment likely contributes to the superior lift enhancement observed under low-frequency conditions. Full article

It has long been debated whether gamma-ray bursts (GRBs) could serve as potential sources of ultra-high-energy cosmic rays (UHECRs). In this study, we consider GRBs as sources of UHECR injection with an injection index of $\alpha =2$ and propagate them through the extragalactic magnetic field within the framework of CRPropa 3. The baryon loading factor $f_{CR}$ is taken into account to quantify the rate of UHECR energy injection. In the benchmark case with a jet opening angle of ${\theta }_j=1$ and $f_{CR}=1$, we find that both high- and low-luminosity populations contribute to less than 10% of the UHECR spectrum. The most constrained scenario suggests $f_{CR}\le 15$, indicating that GRBs are less efficient in producing the all-sky UHECR intensity. The high-energy diffuse neutrinos and gamma rays resulting from interactions between UHECRs from GRBs and extragalactic background photons do not dominate the observations of Fermi-LAT or IceCube. Full article

Unmanned Aerial Vehicles (UAVs) are increasingly gaining popularity, and their consistent prevalence in various applications such as surveillance, search and rescue, and environmental monitoring requires the development of specialized policies for UAV traffic management. Integrating this novel aerial traffic into existing airspace frameworks presents unique challenges, particularly regarding safety and security. Consequently, there is an urgent need for robust contingency management systems, such as Anti-UAV technologies, to ensure safe air traffic. This survey paper critically examines the recent advancements in ground-to-air vision-based Anti-UAV detection and tracking methodologies, addressing the many challenges inherent in UAV detection and tracking. Our study examines recent UAV detection and tracking algorithms, outlining their operational principles, advantages, and disadvantages. Publicly available datasets specifically designed for Anti-UAV research are also thoroughly reviewed, providing insights into their characteristics and suitability. Furthermore, this survey explores the various Anti-UAV systems being developed and deployed globally, evaluating their effectiveness in facilitating the integration of small UAVs into low-altitude airspace. The study aims to provide researchers with a well-rounded understanding of the field by synthesizing current research trends, identifying key technological gaps, and highlighting promising directions for future research and development in Anti-UAV technologies. Full article

The multi-sublattice ferrimagnet Co₂FeO₂BO₃, a prominent example of lanthanide-free magnets, was the subject of element-selective studies using X-ray magnetic circular dichroism (XMCD) observations at the L- and K- X-ray absorption edges. Research findings indicate that the distinct magnetic characteristics of Co₂FeO₂BO₃, namely its remarkable high coercivity (which surpasses 7 Tesla at low temperatures), originate from an atypical arrangement of magnetic ions in the crystal structure (sp.gr. Pbam). The antiferromagnetic nature of the Co²⁺-O-Fe³⁺ exchange interaction was confirmed by identifying the spin and orbital contributions to the total magnetization from Co (m_L = 0.27 ± 0.1 μ_B/ion and m^eff_S = 0.53 ± 0.1 μ_B/ion) and Fe (m_L = 0.05 ± 0.1 μ_B/ion and m^eff_S = 0.80 ± 0.1 μ_B/ion) ions through element-selective XMCD analysis. Additionally, the research explicitly revealed that the strong magnetic anisotropy is a result of the significant unquenched orbital magnetic moment of Co, a feature that is also present in the related compound Co₃O₂BO₃. A complex magnetic structure in Co₂FeO₂BO₃, with infinite Co²⁺O₆ layers in the bc-plane and strong antiferromagnetic coupling through Fe³⁺ ions, is suggested by element-selective hysteresis data, which revealed that Co²⁺ ions contribute both antiferromagnetic and ferromagnetic components to the total magnetization. The findings underline the suitability of Co₂FeO₂BO₃ for applications in extreme environments, such as low temperatures and high magnetic fields, where its unique magnetic topology and anisotropy can be harnessed for advanced technologies, including materials for space exploration and quantum devices. This XMCD study opens the door to the production of novel high-coercivity, lanthanide-free magnetic materials by showing that targeted substitution at specific crystallographic sites can significantly enhance the magnetic properties of such materials. Full article

Bioinspired composites for thermal energy storage have gained much attention all over the world. Bioinspired structures have several advantages as the skeleton for preparing thermal energy storage materials, including preventing leakage and improving thermal conductivity. Phase change materials (PCMs) play an important role in the development of energy storage materials because of their stable chemical/thermal properties and high latent heat storage capacity. However, their applications have been compromised, owing to low thermal conductivity and leakage. The plant-derived scaffolds (i.e., wood-derived SiC/Carbon) in the composites can not only provide higher thermal conductivity but also prevent leakage. In this paper, we review recent progress in the preparation, microstructures, properties and applications of bioinspired composites for thermal energy storage. Two methods are generally used for producing bioinspired composites, including the direct introduction of biomass-derived templates and the imitation of biological structures templates. Some of the key technologies for introducing PCMs into templates involves melting, vacuum impregnation, physical mixing, etc. Continuous and orderly channels inside the skeleton can improve the overall thermal conductivity, and the thermal conductivity of composites with biomass-derived, porous, silicon carbide skeleton can reach as high as 116 W/m*K. In addition, the tightly aligned microporous structure can cover the PCM well, resulting in good leakage resistance after up to 2500 hot and cold cycles. Currently, bioinspired composites for thermal energy storage hold the greatest promise for large-scale applications in the fields of building energy conservation and solar energy conversion/storage. This review provides guidance on the preparation methods, performance improvements and applications for the future research strategies of bioinspired composites for thermal energy storage. Full article

Considering that fungi display a great morphological, ecological, metabolic, and phylogenetic diversity, their taxonomic identification is extremely important because it helps us establish important information about each species and its possible biochemical and ecological roles. Traditionally, the identification of fungi at the species level has been carried out with molecular tools such as DNA sequencing, but it still represents a huge challenge today due to the heterogeneity of the fungal kingdom, making the task of identification a complex and difficult process. Biotyping, a type of chemotaxonomy, has been developed in the field of the identification/differentiation and classification of micro-fungi through tools such as mass spectrometry (MS). Here, two endophytic strains isolated from two different hosts were cultivated and studied regarding their morphology and molecular biology. Morphology analysis determined the strains as Diaporthe, and the molecular analysis results grouped them as D. melongenae. We sought a faster and less complex way of differentiating these fungal strains of interest through an MS chemical profile and MS/MS data using a low-resolution mass spectrometer. Additionally, we linked this information with the structure of compounds previously isolated in the genus Diaporthe. Studies conducted using this technique allowed us to propose the structure of distinctive molecules that are unique to each strain and share compounds common to this genus (13 compounds in total). In addition, this is the first report of secondary metabolites in D. melongenae. The dataset demonstrates that the two strains under investigation can be distinguished via mass spectrometry, suggesting host affinity; both exhibits pronounced differences in their chemical profiles across all culture media and incubation periods with the parameters described herein. Full article