Search Results (91)

Ferronickel slag and ground granulated blast-furnace slag (GGBFS) are solid waste by-products from the metallurgical industry. When incorporated into concrete, they help promote resource utilization, reduce hydration heat, and lower both solid waste emissions and the carbon footprint. To facilitate the application of ferronickel slag–GGBFS concrete in 3D printing, this study examines how aggregate size and nozzle diameter affect its performance. The investigation involves in situ printing, rheological characterization, mechanical testing, and scanning electron microscopy (SEM) analysis. Results indicate that excessively large average aggregate size negatively impacts the smooth extrusion of concrete strips, resulting in a cross-sectional width that exceeds the preset dimension. Excessively small average aggregate size results in insufficient yield stress, leading to a narrow cross-section of the extruded strip that fails to meet printing specifications. The extrusion performance is closely related to both the average aggregate size and nozzle diameter, which can significantly influence the normal extrusion stability and print quality of 3D printed concrete strips. The thixotropic performance improves with an increase in the aggregate size. Both compressive and flexural strengths improve with increasing aggregate size but decrease with an increase in the printing nozzle size. Anisotropy in mechanical behavior decreases progressively as both parameters mentioned increase. By examining the cracks and pores at the interlayer interface, this study elucidates the influence mechanism of aggregate size as well as printing nozzle parameters on the mechanical properties of 3D printed ferronickel slag–GGBFS concrete. This study also recommends the following ranges. When the maximum aggregate size exceeds 50% of the nozzle diameter, smooth extrusion is not achievable. If it falls between 30% and 50%, extrusion is possible but shaping remains unstable. When it is below 30%, both stable extrusion and good shaping can be achieved. Full article

This paper proposes a miniaturized design for a terahertz tri-mirror compact antenna test range (CATR) system, composed of a square-aperture paraboloid primary mirror with a side length of 0.2 m and two shaped mirrors with circular apertures of 0.06 m and 0.07 m in diameter. The design first employs the cross-polarization cancelation method based on beam mode expansion to determine the geometric configuration of the system, thereby enabling the structure to exhibit low cross-polarization characteristics. Subsequently, the shaped mirrors, with beamforming and wave-front control capabilities, are synthesized using dynamic ray tracing based on geometric optics (GO) and the dual-paraboloid expansion method. Finally, the strong edge diffraction effects induced by the small-aperture primary mirror are suppressed by optimizing the desired quiet-zone (QZ) field width, adjusting the feed-edge taper, and incorporating rolled-edge structures on the primary mirror. Numerical simulation results indicate that within the 100–500 GHz frequency band, the system’s cross-polarization level is below −40 dB, while the amplitude and phase ripples of the co-polarization in the QZ are, respectively, less than 1.6 dB and 10°, and the QZ usage ratio exceeds 70%. The designed CATR was manufactured and tested. The results show that at 183 GHz and 275 GHz, the measured co-polarization amplitude and phase ripples in the system’s QZ are within 1.8 dB and 15°, respectively. While these values deviate slightly from simulations, they still meet the CATR evaluation criteria, which specify QZ co-polarization amplitude ripple < 2 dB and phase ripple < 20°. The overall physical structure sizes of the system are 0.61 m × 0.2 m × 0.66 m. The proposed miniaturized terahertz tri-mirror CATR design methodology not only enhances the QZ characteristics but also significantly reduces the spatial footprint of the entire system, demonstrating significant potential for practical engineering applications. Full article

Tire shape prediction presents significant engineering challenges due to the complex behavior of cord-rubber composites during manufacturing processes. Fabric cord components undergo thermal shrinkage and permanent deformation that substantially influence final tire dimensions, creating discrepancies between mold geometry and cured tire shape. While Post-Cure Inflation (PCI) helps control these dimensional changes, accurate prediction methods remain essential for reliable performance forecasting. This study addresses this challenge through a systematic experimental characterization of fabric cord behavior under manufacturing conditions. Thermal shrinkage and permanent set were quantified under various combinations of in-mold strain and PCI force, with distinct patterns identified for different cord materials (PET and nylon). Based on these experimental findings, a comprehensive finite element analysis methodology was developed to predict cured tire shape. Validation against 65 tire profiles demonstrated remarkable improvements over conventional approaches, with dimensional error reductions of 54.2% for the outer diameter and 49.5% for the section width. Profile and footprint predictions also showed significantly enhanced accuracy, particularly in capturing geometric features critical for tire–road contact characteristics. The proposed methodology enables more precise tire design optimization, improved performance prediction, and reduced prototype iterations, ultimately enhancing both product development efficiency and final tire performance. Full article

Background and Objectives: Graft impingement against the intercondylar notch has been identified as a significant contributor to graft deterioration and suboptimal outcomes following anterior cruciate ligament (ACL) reconstruction. This study aimed to (1) identify the optimal combination of tunnel positions that minimizes impingement between the ACL graft and femoral intercondylar notch. Materials and Methods: Three-dimensional models of nine normal knees were reconstructed using computed tomography scans obtained at four knee flexion angles (0°, 45°, 90°, and 120°). Virtual ACL grafts with diameters of 7 mm and 9 mm were modeled as cylinders. Nine graft configurations were investigated by varying femoral and tibial footprint locations (anteromedial, central, and posterolateral) in all possible combinations. For each configuration, impingement volume was quantified by measuring the overlap between the intercondylar notch and the virtual graft using Boolean operators in 3D simulation software. The effects of graft diameter, footprint location, and knee flexion angle on impingement volume were analyzed. Results: Maximum impingement volumes were observed at 0° knee extension, with significant reductions at 45° flexion (p < 0.01) and negligible impingement at 90° and 120° flexion. The 9 mm diameter grafts demonstrated significantly greater impingement volumes than 7 mm grafts (p < 0.01). Impingement volumes increased progressively as footprint locations shifted from posterolateral to anteromedial positions in both femoral and tibial components. However, statistically significant differences in impingement volume across footprint locations were observed only for tibial positioning (p < 0.001), not for femoral positioning (p > 0.05). The femoral anteromedial-tibial anteromedial configuration exhibited the highest impingement volume (577.8 ± 171.3 mm³ for 9 mm grafts), while the femoral posterolateral-tibial posterolateral configuration showed the lowest (73.5 ± 85.6 mm³). Conclusions: Tunnel position, graft diameter, and knee flexion angle significantly influence impingement risk in ACL reconstruction. Tibial tunnel position appears more critical than femoral position in minimizing graft impingement. Posterolateral positioning of tunnels, particularly on the tibial side, may reduce impingement volume. Clinical Relevance: This study provides quantitative evidence to guide surgeons in optimizing tunnel placement and graft selection for anatomical single-bundle ACL reconstruction, potentially reducing the risk of graft deterioration and failure due to mechanical impingement. Full article

With the widespread application of ozone technology in agricultural plant protection, developing an ozonated water atomizer that integrates efficient mixing and precise spraying has been recognized as a significant challenge. Swirling flow is considered a method to enhance hydrodynamics and mass transfer in gas–liquid mixing. This study innovatively combines an axial nozzle with a swirling mixing chamber, utilizing the negative pressure generated by the high-speed central airflow at the nozzle throat as the driving force for swirling mixing and initial atomization, completing mass transfer and preliminary atomization before the formation of the mist, thereby improving gas–liquid contact and mass transfer efficiency. Through numerical simulations, the impact of geometric parameters at key locations on the internal flow of the atomizer was analyzed. The optimized inlet diameter of the atomizer was found to be 9 mm, with a throat length of 3 mm and a self-priming hole diameter of 1.5 mm. Experimental results on droplet size and ozone droplet concentration verified that at the optimal spraying pressure of 0.6 MPa, a concentration of up to 3.73 mg·L⁻¹ with an average droplet size of 102 µm, evenly distributed, could be generated at a distance of 40 cm from the target. This work provides a technological framework for advancing precision ozone-based plant protection, aligning with global efforts to reduce agrochemical footprints through innovative application systems. It offers theoretical guidance and data support for the development and design of high-efficiency ozone atomizers in agricultural applications, aiming to minimize the use of agricultural chemicals and promote the growth of green plant protection technologies. Full article

A laser-based selective wax ablation method using a 532 nm Nd:YAG laser was developed to improve the foliar uptake efficiency of agrochemicals in citrus leaves. In contrast to conventional applications that suffer major losses, our approach exposes up to 80% of the underlying epidermis (within the irradiated footprint) with no visible tissue damage, thereby substantially enhancing substance penetration. Efficacy was confirmed using two indicators: (1) A fluorescent glucose analog (2-NBDG) exhibited a radial expansion velocity reaching 0.0105 mm/min in treated areas, enabling rapid phloem transport across an 8 cm distance within just three minutes—an 11,280% improvement over untreated controls. (2) Laser-induced breakdown spectroscopy (LIBS) demonstrated a threefold increase in zinc (Zn) uptake (and over fivefold compared to untreated leaves) when using a Zn-based foliar fertilizer. To assess processing efficiency, we quantified the ablation footprint by combining single-pulse laser shots in a 1 cm-diameter region and found that 23.4% of the total area was fully exposed. This selective, non-invasive approach enables precise targeting, potentially reducing fertilizer and pesticide usage while improving crop health. Beyond citrus, it is readily adaptable to other crops, with integration into orchard or greenhouse spraying systems as a promising path for scale-up. Such versatility highlights the technique’s potential to optimize efficacy, cut input costs, and diminish environmental impact in modern precision agriculture. Full article

Micropiles are a new type of retaining structure widely used in slope engineering due to their small footprint, low vibration and noise emissions, and simple construction process. This study aims to investigate the dynamic response and failure mechanisms of micropiles used in retaining accumulation landslides under seismic loading through shaking table tests and numerical simulation. The failure process, observed phenomena, and bending moments of micropiles in the test were discussed, and the shear force distribution of micropiles was thoroughly analyzed based on numerical simulation. The findings reveal that the natural frequency of the entire landslide system exhibits a gradual decrease and tends to stabilize under sustained earthquake excitation. The bending moment of micropiles follows an “S” shape, with a larger magnitude at the top and a smaller one at the bottom. Additionally, the shear force distribution exhibits a “W-shaped” pattern. Damage to micropiles mainly includes the flexural shear combination failure at the load-bearing section (which occurs within 1.4–3.6 times the pile diameter above the sliding surface) and the shear failure near the sliding surface. This study provides significant insights into the strengthening mechanisms of micropiles under seismic action and offers valuable guidance for the design of slope support. Full article

There is a growing demand for sustainable solutions in civil engineering concerning the carbon footprint of cementitious composites. Alkali-Activated Binders (AAB) are materials with great potential to replace ordinary Portland cement (OPC), with similar strength levels and lower environmental impact. Despite their improved environmental performance, their durability remains a gap in the literature, influenced by aspects of mechanical behavior, physical properties, and microstructure. This paper aims to assess the impact of steel slag aggregates and curing temperature of a proposed AAB based concrete formulation by characterizing fresh state, mechanical behavior, and microstructure. The proposed AAB is composed of fly ash (FA) and basic oxygen furnace (BOF) steel slag (SS) as precursors, sodium silicate and sodium hydroxide solution as activators, in total replacement of OPC, using baosteel slag short flow (BSSF) SS as aggregate in comparison with natural aggregate. The concrete formulation was designed to achieve a high-performance concrete (HPC) and a self-compacting concrete (SCC) behavior. Mechanical characterization encompassed hardened (compressive strength and Young’s modulus), fresh state (J-ring, slump flow, and T50), and durability tests (scanning electronic microscopy, water penetration under pressure, and chloride ion penetration). The compressive strength (64.1 ± 3.6 MPa) achieves the requirements of HPC, while the fresh state results fulfill the SCC requirements as well, with a spread diameter from 550 mm to 650 mm (SF-1 class). However, the flow time ranges from 3.5 s to 13.8 s. There was evidence of high chloride penetrability, affected by the lower electrical resistance inherent to the material. Otherwise, there was a low water penetration under pressure (3.5 cm), which indicates a well-consolidated microstructure with low connected porosity. Therefore, the durability assessment demonstrated a divergence in the results. These results indicate that the current durability tests of cementitious materials are not feasible for AAB, requiring adapted procedures for AAB composite characterization. Full article

The renewal of underground infrastructure is an emerging challenge for most municipalities in the United States. As compared to trenchless cured-in-place pipes (CIPPs), excavation technologies (ETs) have adverse impacts on the environment. Due to its lower ecological impact, trenchless technology is preferred in comparison to conventional pipe replacement. The selection of the most appropriate method depends on factors such as the existing sewer network, traffic disruption, soil conditions, and environmental safety. Recent concerns pertaining to environmental impact have increased the demand for reduced carbon footprints. The objectives of this paper are the following: (1) to present a comprehensive review on the achievements achieved over the years in understanding the factors influencing environmental emissions from the use of CIPP and ETs and (2) to analyze and compare the environmental emissions produced from CIPPs and ETs for 8-inch-, 10-inch-, and 12-inch-diameter pipes. Published papers from 1990 through 2024 have been included, which reported emissions from both alternatives. A comparison of total environmental emissions produced from both the processes is presented. The literature review and analysis suggest that higher emissions are a result of higher fuel consumption, material use, and input allocation. The emissions of pipeline renewal methods were evaluated using USEPA’s TRACI 2.1 methodology within SimaPro software. The analysis showed that CIPP renewal greatly reduced carbon emissions when compared with ET. CIPPs exhibited approximately 70% less ecological impact, 75% less impact on human health, and 60% less depletion of resources. CIPPs reduced carbon emissions by 78–100% in comparison to ETs. The recycling materials used in CIPPs potentially reduce the environmental impact by 10%, making them highly sustainable. The installation phase should therefore be carefully analyzed for factors like the pipe material and the pipes’ external diameter in view of achieving the greatest sustainability of these methods, as these characteristics affect emissions. It can be inferred that the comparison of the emissions of both alternatives is extremely vital for sustainable underground infrastructure development. Full article

Although UAV height is precisely determined using GNSS, the vertical distance between the UAV and the sea surface should be subtracted to obtain the sea surface height (SSH). This distance can be measured using nadir-looking LiDAR or GNSS reflectometry (GNSS-R); thus, these two methods are examined in this study through three two-minute UAV experimental flights. The measurements of the flight-averaged SSHs made with both approaches were in good agreement with the reference SSH determined from a GNSS buoy, with differences of 0.03 m (LiDAR) and 0.05 m (GNSS-R), although the standard deviation (SD) for GNSS-R (1.72 m) was significantly larger than that for LiDAR (0.20 m). Each 4 Hz GNSS-R measurement was subject to errors caused by surface waves, though over 16 GNSS reflection points within a 70 m diameter footprint were used; these errors were, however, removed in the temporal mean. Extending the footprint diameter to 230 m with stronger data quality controls resulted in a smaller error (0.02 m) and SD (0.79 m). Meanwhile, LiDAR measured the flat-surface SSH at the nadir only, which inherently filtered out slant reflections, resulting in a lower SD. However, this filter reduces data acquisition rates, especially when the UAV attitude tilts. Full article

The aim of this article is to analyse the global environmental impact of wind farms, i.e., the effects on human health and the local ecosystem. Compared to conventional energy sources, wind turbines emit significantly fewer greenhouse gases, which helps to mitigate global warming. During the life cycle of a wind farm, 86% of CO₂ emissions are generated by the extraction of raw materials and the manufacture of wind turbine components. The water consumption of wind farms is extremely low. In the operational phase, it is 4 L/MWh, and in the life cycle, one water footprint is only 670 L/MWh. However, wind farms occupy a relatively large total area of 0.345 ± 0.224 km²/MW of installed capacity on average. For this reason, wind farms will occupy more than 10% of the land area in some EU countries by 2030. The impact of wind farms on human health is mainly reflected in noise and shadow flicker, which can cause insomnia, headaches and various other problems. Ice flying off the rotor blades is not mentioned as a problem. On a positive note, the use of wind turbines instead of conventionally operated power plants helps to reduce the emission of particulate matter 2.5 microns or less in diameter (PM 2.5), which are a major problem for human health. In addition, the non-carcinogenic toxicity potential of wind turbines for humans over the entire life cycle is one of the lowest for energy plants. Wind farms can have a relatively large impact on the ecological system and biodiversity. The destruction of animal migration routes and habitats, the death of birds and bats in collisions with wind farms and the negative effects of wind farm noise on wildlife are examples of these impacts. The installation of a wind turbine at sea generates a lot of noise, which can have a significant impact on some marine animals. For this reason, planners should include noise mitigation measures when selecting the site for the future wind farm. The end of a wind turbine’s service life is not a major environmental issue. Most components of a wind turbine can be easily recycled and the biggest challenge is the rotor blades due to the composite materials used. Full article

Miniature steerable instruments have the potential to reduce the invasiveness of therapeutic interventions and enable new treatment options. Traditional ways of driving such instruments rely on extrinsic systems due to the challenge of miniaturizing and embedding intrinsic actuators that are powerful enough near the instrument tip or within the instrument shaft. This work introduces a method to amplify the output force of fluidic actuators by connecting their outputs in parallel but distributing them serially in currently underutilized space along the device’s long axis. It is shown that this new approach makes it possible to realize a significant force amplification within the same instrument diameter, producing a $380\%$ higher static force and a further driving motion of the steerable bending segment 55.6° than an actuator representing the current state of the art, all while occupying a similar footprint. Full article

This study focuses on the application of neural networks to optimize 3D printing parameters in order to reduce particulate matter (PM) emissions and enhance sustainability. This research identifies key parameters, such as head temperature, bed temperature, print speed, nozzle diameter, and cooling, that significantly impact particle matter emissions. Quantitative analysis reveals that higher head temperatures (225 °C), faster print speeds (50 mm/s), and larger nozzle diameters (0.8 mm) result in elevated PM emissions, while lower settings (head temperature at 190 °C, print speed at 30 mm/s, nozzle diameter of 0.4 mm) help minimize these emissions. Using multilayer perceptron (MLP) neural networks, predictive models with an accuracy of up to 95.6% were developed, allowing for a precise optimization of 3D printing processes. The MLP 7-19-6 model showed a strong correlation (0.956) between input parameters and emissions, offering a robust tool for reducing the environmental footprint of additive manufacturing. By optimizing 3D printing settings, this study contributes to more sustainable practices by lowering harmful emissions. These findings are crucial for advancing sustainable development goals by providing actionable strategies for minimizing health risks and promoting eco-friendly manufacturing processes. Ultimately, this research supports the transition to greener technologies in the field of additive manufacturing. Full article

This paper introduces a novel design for a liquid-deployed Piezoelectric Micromachined Ultrasonic Transducer (PMUT). This design was specifically developed to resonate at a lower ultrasonic frequency than a PMUT with a circular, fully clamped diaphragm with the same diameter. Furthermore, the novel design was also optimised to enhance its ultrasonic radiation reception capabilities. These parametric enhancements were necessary to develop a PMUT device that could form part of an eventual microscale sensory device used for the Structural Health Monitoring (SHM) of reinforced concrete (RC) structures. Through these two enhancements, an eventual microscale sensor can be made smaller, thus taking up a smaller die footprint and also be able to be deployed further apart from each other. Eventually, this would reduce the developed distributed sensor system’s cost. The innovative design employed a configuration where the diaphragm was only pinned at particular points along its circumference. This paper presents results from Finite Element Modelling (FEM), as well as experimental work that was conducted to develop and test this novel PMUT. The experimental work presented involved both laser vibrometry and ultrasonic radiation lab work. The results show that when compared to a clamped diaphragm design, the novel device managed to achieve the required reduction in resonant frequency and presented an enhanced sensitivity to incoming ultrasonic radiation. Full article

In Japan, the number of power wheelchair users is increasing as the country becomes an aging society. This trend is expected to continue in the future. Electric wheelchairs currently on the market include (1) bar-handle-type power wheelchairs for older users and (2) joystick-type power wheelchairs that change direction by operating a joystick. When such electric wheelchairs are used outdoors, the problem is curb-climbing at the boundary between the roadway and the sidewalk. It would be difficult for a wheelchair with a small front wheel diameter of 200 mm to overcome a curb height of 50 mm. Therefore, users are forced to take a detour or drive on the street to avoid the curb step. One of the most effective ways to solve this problem is to increase the wheel diameter. However, larger wheels make it more difficult for users to get in and out of the wheelchair. In addition, there are problems such as an increased footprint when turning, which makes the wheelchairs difficult to use on narrow streets. In this paper, using a joystick-type six-wheel electric wheelchair as an example, we examined the mechanism by which an electric wheelchair can overcome curb climbing and consider improvements to the chassis with a method that does not rely on increasing the wheel diameter. As a result, it became possible to overcome a curb of 96 mm in height with a front-wheel diameter of 200 mm. Full article