Search Results (100)

Large steel frame support structures may encounter multiple-hazard coupling effects, such as earthquakes and wind loads, during their service period, and their combined damage effects are often significantly greater than those under single-hazard conditions. This study focuses on a single case example of large steel frame support structures, adopts a one-way CFD (Computational Fluid Dynamics)-to-structure loading analysis method to quantify the distribution of wind drag coefficients influenced under shielding effects, and reveals the response amplification and transition behavior under earthquake–wind load coupling effects through a systematic parametric analysis. The results demonstrate that within the simulated wind speed range (10–30 m/s), the drag coefficient of the structure is insensitive to the Reynolds number. The drag coefficient of the first row of members remains stable at approximately 1.25, whereas those of the second and subsequent rows are concentrated in the 0.6–0.8 range and decrease progressively along the wind direction. This pattern challenges the conventional design assumption of using a unified drag coefficient. Based on the analyzed cases, under earthquake–wind coupling effects, the structural amplitude amplification effect demonstrates significant load-dominant transition characteristics—when the earthquake acceleration is low (0.05 g), the wind load-induced amplitude amplification effect is pronounced, reaching 206.3%. As the earthquake intensity increases, the amplification effect stabilizes at approximately 9%. This study identifies structural drag coefficients for considering shielding effects, reveals the coupling mechanism between earthquakes and wind loads, and provides theoretical support for the multihazard performance-based design of temporary large-scale spatial structures. It should be noted that the findings and the proposed load-dominance transition characteristics are primarily applicable to temporary large-scale spatial frame structures operating within a service wind speed range of 10 to 30 m/s. Full article

To address the demand for a micro-power supply for vehicle suspension control, a novel harvester is proposed to recover vortex-induced vibration energy in the wake of a shock absorber. A suspension dynamic model was established to simulate the spring compression process and identify the wind-shielding condition. The spring-shock absorber assembly was then simplified as a stepped cylinder with two cross-sections. Flow-field analysis showed that the size, shape, and rising angle of the wake vortices were affected by the bluff-body geometry, Reynolds number, and boundary conditions. The downwash motion was found to directly influence vortex development, and two new vortex-connection modes were identified. These results provided guidance for harvester optimization. A two-way fluid–structure interaction model was developed to describe the electromechanical conversion behavior of the proposed harvester under flow excitation. Numerical results showed that the output voltage increased with vehicle speed. An average peak voltage of 1.82 V was obtained when the piezoelectric patches were installed two larger-cylinder diameters downstream. The optimal patch length was 120 mm, and further increasing the length did not significantly improve the harvesting performance. Finally, a full-scale prototype was tested, and the measured voltage agreed well with the simulation results. The proposed harvester can therefore serve as a potential micro-power source for low-power suspension electronics. Full article

Near-surface air temperature measurements are sensitive to solar radiation and ambient longwave irradiance, which can introduce measurement errors of approximately 1 °C. This study presents the design and experimental validation of a high-accuracy naturally ventilated radiation shield that operates without mechanical aspiration. Computational fluid dynamics (CFD) simulations were used to optimize a bowl–cover airflow-guiding structure and shading configuration, thereby enhancing air exchange around the sensing probe and reducing radiation-induced heating. A coupled multi-parameter simulation framework was further developed to evaluate the sensitivity of radiation error to wind speed, scattered radiation, altitude, and other environmental factors. Field intercomparison experiments were conducted using a Model 076B radiation shield as the reference and a Model 41003 radiation shield for comparison. Results show that the proposed shield exhibits a mean uncorrected radiation error of 0.12 °C, which is significantly lower than that of the 41003 shield (0.59 °C). In addition, a multilayer perceptron (MLP)-based radiation error correction model was developed using environmental parameters as inputs, achieving a root mean square error (RMSE) of 0.051 °C and a mean absolute error (MAE) of 0.043 °C. After correction, the correlation coefficient between Pt100 probe measurements and reference values reaches 0.999, demonstrating the potential of the proposed approach for high-accuracy near-surface air temperature observations. Full article

Ice accretion on arctic vessels and offshore platforms poses serious threats to navigation and operational safety. Existing research has primarily focused on isolated structures. This study employs a combined approach of numerical simulation and experimental validation. It systematically investigates the icing characteristics of tandem twin-cylinders in wake flow fields. This configuration is common yet rarely studied in real marine environments. The model employs two identical cylinders arranged in tandem. It examines the effects of wind speed, distance, diameter, and wind direction angle on ice accretion morphology and distribution. Validation was conducted through wind tunnel tests at 5 m/s wind speed and 2.0 g/m³ liquid water content. Results demonstrate a significant shielding effect from the upstream cylinder wake. As wind speed increases, the ice mass difference between upstream and downstream cylinders widens. Ice mass shows a nonlinear relationship with distance. Minimum ice accretion on the downstream cylinder occurs at 350–450 mm distance. This results from wake pattern transition. The shielding effect exhibits strong nonlinear dependence on wind direction angle. A deviation of 8.2° increases total ice mass by 242.5%. Multivariable analysis confirms these nonlinear mechanisms persist under coupled distance–wind speed variations. This study provides the first systematic revelation of twin-cylinder icing mechanisms in wake flow fields. It offers a validated predictive tool for anti-icing design of arctic marine structures. Full article

As a common large-scale civil engineering structure, cable-supported photovoltaic (PV) arrays are typically designed with a 25-year service life, with their primary structural system composed of beam-column frames, pre-tensioned cables and modules. Cable-supported photovoltaic arrays are susceptible to large-amplitude wind-induced vibrations (WIV), threatening structural safety and serviceability. This study investigates interference effects on an eight-row array that employs aeroelastic wind tunnel tests, focusing on how tilt angle and sag-to-span ratio influence vibration characteristics and interference mechanisms. Results show coupled vertical–torsional vibrations with amplitudes increasing with wind speed and that are more intense under wind suction than under wind pressure. Reducing tilt angle and sag-to-span ratio effectively suppresses vibrations and raises critical flutter speed. For interference effects, mean response demonstrates clear shielding with amplitudes decreasing leeward. In contrast, fluctuating response behavior depends on tilt angle: 5° tilt angle produces a shielding effect, while 25° tilt angle causes an amplification effect with periodic fluctuations. The 25° tilt angle shows greater sensitivity to wind speed, evidenced by decreasing interference coefficients from the second to eighth windward rows with increasing wind speed. Although reducing the sag-to-span ratio most effectively suppresses vibrations in the first windward row and consequently affects downstream interference coefficients, it does not alter the fundamental trends governed by tilt angle. Full article

Wind is one of the main environmental loads acting on temporary scaffolding structures, yet current design codes apply simplified assumptions regarding its distribution. This study presents full-scale measurements of wind velocities on 10 façade scaffolds located across Poland, representing various building geometries and exposure conditions. Each scaffold was instrumented with five two-dimensional ultrasonic anemometers and one three-dimensional rooftop reference anemometer. Data were analysed in 10 min averages, divided into 30° directional sectors and compared with the normative model defined in EN 12811-1 using the site factor $c_s$. The results reveal strong spatial variability of wind action across scaffold surfaces, with measured local velocities ranging from 20% to 140% of the reference values. The parallel flow component exhibited substantial scatter, while the perpendicular component was strongly damped by façade shielding and protective netting. For most mid-façade positions, measured values corresponded to $c_s=0.25–0.5$, whereas corner and edge locations frequently exceeded $c_s=1.0$. The findings demonstrate that the uniform site factors assumed in current standards do not capture the aerodynamic complexity of real scaffolds, especially under oblique or high-intensity wind conditions. The presented dataset provides a unique experimental basis for improving scaffold wind load modelling and developing position-specific design provisions. Full article

Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation technique extensively utilized in neuroscience and clinical medicine; however, its underlying mechanisms require further elucidation. Due to ethical safety considerations, low cost, and physiological similarities to humans, rodent models have become the primary subjects for TMS animal studies. Nevertheless, existing TMS coils designed for rodents face several limitations, including size constraints that complicate coil fabrication, insufficient stimulation intensity, suboptimal focality, and difficulty in adapting coils to practical experimental scenarios. Currently, many studies have attempted to address these issues through various methods, such as adding magnetic nanoparticles, constraining current distribution, and incorporating electric field shielding devices. Integrating the above methods, this study designs a small arc-shaped TMS coil for the frontoparietal region of rats using the inverse boundary element method, which reduces the coil’s interference with experimental observations. Compared with traditional geometrically scaled-down human coil circular and figure-of-eight coils, this coil achieves a 79.78% and 57.14% reduction in half-value volume, respectively, thus significantly improving the focusing of stimulation. Meanwhile, by adding current density constraints while minimizing the impact on the stimulation effect, the minimum wire spacing was increased from 0.39 mm to 1.02 mm, ensuring the feasibility of the coil winding. Finally, coil winding was completed using 0.05 mm × 120 Litz wire with a 3D-printed housing, which proves the practicality of the proposed design method. Full article

Meeting the International Maritime Organization’s (IMO) 2050 targets for reducing greenhouse gas (GHG) emissions requires cost-effective solutions that minimize wind resistance without compromising safety, particularly for medium-sized multipurpose vessels (MPVs), which have been underrepresented in prior research. This study numerically evaluates 20 bow-mounted NaviScreen configurations using a coupled high-fidelity computational fluid dynamics (CFD) and finite element analysis (FEA) approach. Key design variables—including contact angle (35–50°), lower-edge height (1.2–2.0 m), and horn position (3.2–5.3 m)—were systematically varied. The sloped Type-15 shield reduced aerodynamic resistance by 17.1% in headwinds and 24.5% at a 30° yaw, lowering total hull resistance by up to 8.9%. Nonlinear FEA under combined dead weight, wind loads, and Korean Register (KR) green-water pressure revealed local buckling risks, which were mitigated by adding carling stiffeners and increasing plate thickness from 6 mm to 8 mm. The reinforced design satisfied KR yield limits, ABS buckling factors (>1.0), and NORSOK displacement criteria (L/100), confirming structural robustness. This dual-framework approach demonstrates the viability of NaviScreens as passive aerodynamic devices that enhance fuel efficiency and reduce GHG emissions, aligning with global efforts to address climate change by targeting not only CO2 but also other harmful emissions (e.g., NOx, SOx) regulated under MARPOL. The study delivers a validated CFD-FEA workflow to optimize performance and safety, offering shipbuilders a scalable solution for MPVs and related vessel classes to meet IMO’s GHG reduction goals. Full article

The jet fan system is a widely adopted form of longitudinal ventilation due to its cost-effectiveness, operational flexibility, and high reliability. However, in large-section highway tunnels with a low height-to-span ratio, the limited clearance between the tunnel ceiling and surrounding structural boundaries imposes significant constraints on improving ventilation performance by adjusting the installation height or pitch angle of the jet fan. To address this limitation, this study proposes a deflector shield system to enhance the aerodynamic efficiency of jet fans. A total of thirteen test cases, including a control group, three deflector plate quantities, and four deflector pitch angles, were tested in a full-scale field test conducted in a large-section tunnel. The objective of this study was to evaluate the influence of the number and pitch angle of deflector plates on tunnel ventilation efficiency and to identify the optimal parameter combination for application in large-section tunnels. The results show that static pressure along the tunnel initially rises with distance from the fan, peaks, and then declines sharply. The pressure rise coefficient is significantly enhanced under several configurations, particularly with four deflector plates at 8° and 10° pitches, and with five plates at 4° to 10° pitches. When the number of deflector plates is five, a sharp drop in average wind speed is observed 15 m downstream of the fan, and extensive low-velocity regions appear further downstream. In contrast, the configurations with four deflector plates at 8° and 10° exhibit better wind speed uniformity in the downstream flow field. Considering both the pressure rise coefficient and wind speed uniformity, the optimal ventilation performance of the jet fan system is achieved with four deflector plates at a pitch angle of 8°. Full article

Oil prices are volatile. How does this affect Japanese and South Korean firms? Since they import almost all of their oil, oil price increases may harm their economies. To investigate these issues, this paper examines how oil prices affect sectoral stock returns. Using Hamilton’s method to decompose oil price changes into portions driven by global demand and by oil supply, the results indicate that many sectors in both countries benefit from increases in global aggregate demand that raise oil prices. Many industrial firms in Japan that produce advanced products also benefit from supply-driven oil price changes. The finding that many firms benefit from higher oil prices indicates that blanket subsidies to compensate for oil price increases are unnecessary. Targeted subsidies would be more economical and eco-friendly. Many sectors in Japan and Korea that produce for the domestic economy are harmed by oil price increases. Large oil price swings will continue due to wars, tariffs, geopolitical events, and climate change. These will whipsaw sectors in both countries. To shield their economies from oil price changes, Japan and Korea should invest in technologies to improve wind, solar, and hydro power and should facilitate intra-regional trade in renewables. They should also encourage individual sectors such as airlines, cosmetics, agriculture, hotels, semiconductors, and automobiles to reduce their exposure to fossil fuels and to choose environmentally friendly production methods. In addition, both countries should expedite their targets for achieving carbon neutrality. This paper considers ways to achieve these goals. Full article

Smart cities are widely regarded as a promising solution to urbanization challenges; however, environmental aspects such as outdoor thermal comfort and urban heat island are often less addressed than social and economic dimensions of sustainability. To address this gap, we developed and evaluated an affordable, scalable, and cost-effective weather station platform, consisting of a centralized server and portable edge devices to facilitate urban heat island and outdoor thermal comfort studies. This edge device is designed in accordance with the ISO 7726 (1998) standards and further enhanced with a positioning system. The device can regularly log parameters such as air temperature, relative humidity, globe temperature, wind speed, and geographical coordinates. Strategic selection of components allowed for a low-cost device that can perform data manipulation, pre-processing, store the data, and exchange data with a centralized server via the internet. The centralized server facilitates scalability, processing, storage, and live monitoring of data acquisition processes. The edge devices’ electrical and shielding design was evaluated against a commercial weather station, showing Mean Absolute Error and Root Mean Square Error values of 0.1 and 0.33, respectively, for air temperature. Further, empirical test campaigns were conducted under two scenarios: “stop-and-go” and “on-the-move”. These tests provided an insight into transition and response times required for urban heat island and thermal comfort studies, and evaluated the platform’s overall performance, validating it for nuanced human-scale thermal comfort, urban heat island, and bio-meteorological studies. Full article

Optically pumped magnetometers (OPMs) are a promising magnetoencephalography (MEG) technology for the non-invasive measurement of human electrophysiological signals. Prior work developed biplanar background field-nulling coils necessary for OPM operation, but these were expensive to produce and required tedious error-prone manual winding of >1 km of copper wire. Here, we developed a precise and reproducible manufacturing process by fabricating these coils on two-layer printed circuit boards (PCBs). Building on open-source software (bfieldtools), we developed a pipeline to determine the optimal current loops of 1.5 × 1.5 m² biplanar nulling coils, connected these loops into a continuous conducting path across PCB layers, and printed them as pairs of 1.5 × 0.75 m² PCBs, which were soldered and mounted on an aluminum frame. Our coils achieved efficiencies of 1.3–7.1 nT/mA, similar to or higher than previous designs. We reduced the largest background field component from 21 to 2 nT, enabling OPMs in a lightly shielded room to record somatosensory evoked fields (SEFs) comparable to SQUID-MEG. Our coil system is cheaper than commercial alternatives and is available as an open-source package opmcoils, thus enabling more affordable background field nulling for OPM-MEG and realizing its potential as an accessible sensor technology for human neuroscience. Full article

This study examines the impact of surrounding buildings and wind incidence angles on the aerodynamic loads of a high-rise building with a 1:1 base–edges and a 1:6 base–height ratio. CFD simulations were conducted using OpenFOAM with the classic RANS $k-ϵ$ turbulence model, validated against experimental data from Tokyo Polytechnic University. The aerodynamic coefficients were analyzed for wind angles of $\theta$ = 0°, 15°, 30°, and 45°, varying with the adjacent building height. Additionally, topology optimization via the Bi-directional Evolutionary Structural Optimization (BESO) method was applied to determine the optimal bracing system under wind-induced loads. The results indicate that surrounding buildings significantly modify the aerodynamic response, particularly for asymmetric wind angles, where torsional effects become more pronounced. A shielding effect was observed, reducing drag and base moment but with a lesser influence on lift. The topology optimization results show that material distribution is directly influenced by aerodynamic coefficients, with “X” bracing patterns in case of low torsion and an additional member when torsional effects increase. This study highlights the importance of wind engineering in high-rise structural design and urban planning, emphasizing the necessity of specific wind assessments for accurate load predictions in dense urban environments. Full article

The thermal protection system of a re-entry vehicle requires a high-heat-resistant heat shield to protect the spacecraft. Most of the ablative materials developed so far have high heat resistance but have technical issues such as long production times. In this study, we propose a new ablative material (LATS/PEEK) consisting of PEEK and carbon felt as a material that can solve these problems. PEEK has excellent properties such as a short production time and its ability to be produced using 3D printer technology. In addition, PEEK can be molded with a variety of fusion bonding methods, so it is possible to mold the heat shield and structural components as a single structure. However, heating tests conducted in previous research have confirmed the expansion phenomenon of CF/PEEK produced by 3D printers. The expansion of the ablative material is undesirable because it changes the aerodynamic characteristics during re-entry flight. Therefore, the purpose of this research is to clarify the mechanism of the expansion phenomenon of the ablative material based on PEEK resin. Therefore, we conducted thermal gravimetric analysis (TGA) and thermomechanical analysis (TMA) and concluded that the expansion phenomenon during the heating test was caused by the pressure increase inside the ablative material due to pyrolysis gas. Based on this mechanism, we developed a new 3D LATS/PEEK with a structure that can actively release pyrolysis gas, and we conducted a heating test using an arc-heating wind tunnel. As a result, it was found that 3D LATS/PEEK had less expansion and deformation during the heating test than CF/PEEK manufactured using a 3D printer. Full article

This study examines how urban morphology, road configurations, and meteorological factors shape fine particulate matter (PM_2.5) dispersion in high-density urban environments, addressing a gap in block-level air quality analysis. While previous research has focused on individual street canyons, this study highlights the broader influence of building arrangement and height. Integrating computational fluid dynamics (CFD) simulations with interpretable machine learning (ML) models quantifies PM_2.5 concentrations across various urban configurations. CFD simulations were conducted on different road layouts, block height configurations, and aspect ratio (AR) levels. The resulting dataset trained five ML models with Extreme Gradient Boosting (XGBoost), achieving the highest accuracy (91–95%). Findings show that road-specific mitigation strategies must be tailored. In loop-road networks, centrally elevated buildings enhance ventilation, while in grid-road networks, taller perimeter buildings shield inner blocks from arterial emissions. Additionally, this study identifies a threshold effect of AR, where values exceeding 2.5 improve PM_2.5 dispersion under high wind velocity. This underscores the need for wind-sensitive designs, including optimized wind corridors and building alignments, particularly in high-density areas. The integration of ML with CFD enhances predictive accuracy, supporting data-driven urban planning strategies to optimize road layouts, zoning regulations, and aerodynamic interventions for improved air quality. Full article