Simulated Wind Research Articles

Advancing moisture management in activewear: a novel dynamic testing approach for dynamic breathability of sportswear

This study presents a novel dynamic hot plate test for examining the exothermic and endothermic behaviors of textiles, emphasizing the dynamic conditions akin to physical activities. The method surpasses previous standards, for example ISO 16533 and the dynamic hot plate test developed by Naylor, by integrating sweating and wind simulations, thus offering a more precise assessment of fabric performance and physical sensation while wearing activewear. The investigation involved five fabric samples made from four different fiber types: 100% Merino wool, 100% polyester, 100% cotton, and 100% viscose.. The experimental setup, consisting of a 90-minute test with relaxation, activity, and drying phases, highlighted significant fabric-specific responses. Notably, polyester exhibited the highest heat loss rate at 388 W/m² during the activity phase, underscoring its potential for moisture management and cooling. Conversely, Merino wool showed the lowest heat loss rate at 212 W/m², suggesting a more stable microclimate. The dynamic conditions induced marked changes in microclimate temperature, humidity, and fabric surface temperatures, particularly noticeable when wind was introduced. These findings emphasized the importance of dynamic testing in evaluating activewear fabrics, suggesting that materials such as polyester offer excellent cooling and moisture management, whereas natural fibers such as Merino wool may enhance wearer comfort by maintaining a more consistent microclimate. This research contributes to refining fabric performance testing standards by emphasizing the significance of real-world dynamic conditions.

Characterizing Model Uncertainties in Simulated Coast-to-Offshore Wind over the Northeast U.S. Using Multi-platform Measurements from the TCAP Field Campaign

Numerical weather prediction models, such as the Weather Research and Forecasting model, are widely used to provide estimates of the offshore wind energy resource owing to their large spatial coverage compared to available observations. Nevertheless, spatiotemporal distribution of model biases is highly dependent on factors including model configuration, location, and the interplay of multiscale physical processes. Here we focus on the characterization of model uncertainties in simulated coast-to-offshore winds over the northeast United States by varying sea surface temperature (SST) forcings and surface layer (SL) and planetary boundary layer (PBL) parameterizations, as well as identifying biases that may be directly passed from initial and boundary conditions. Multiple measurements, including aircraft data collected during the U.S. Department of Energy's Two-Column Aerosol Project experiment, are used to constrain the model results, and facilitate quantitative comparisons. Our analysis indicates that while SST forcing has notable impacts on simulated air temperature and moisture within PBL, the modeled winds are in general more sensitive to the choices of SL and PBL physics than to SST. The model’s forcing data not only controls the vertical dependence of wind speed errors, but also alters regional variability in the wind speed’s spatial correlation, which underscores the impact of initial and boundary conditions on simulated winds. Coastal and offshore near-surface wind speed biases tend to exhibit much higher similarity in winter than in summer due to the presence of much stronger and more persistent synoptic wind conditions. This study highlights the importance of accurate atmospheric forcing and parameterization choices in improving wind forecasts and suggests the potential for extrapolating coastal wind biases to offshore locations, aiding wind energy forecasting and informing the third Wind Forecast Improvement Project.

A Laboratory Study of Plasma Charging Inside Lava Tubes on the Lunar Surface

Abstract The electrostatic charging environment inside lunar lava tubes was investigated in laboratory experiments using a glass tube exposed to a simulated solar wind flow. A conducting surface was attached at the entrance of the tube and biased to various negative potentials to study the electron shielding effect on the charging conditions inside the tube. The electrical potential at the bottom of the glass tube was measured using a planar probe. It is shown that the bottom surface potential is positive and increases with the increasing ion beam energy, as well as with the increasing depth inside the tube, as a result of electron Debye shielding at the entrance and along the length of the tube due to the electron thermal motion. It is found that the bottom tube potential does not approach the ion kinetic energy even when the solar wind electrons are nearly fully shielded from entering the tube. We show that ion-generated secondary electrons from the sidewall of the tube partially neutralize the buildup of positive charges at the bottom of the tube. Our results provide insights into the plasma charging environment inside lunar lava tubes that may be used as natural habitats for future human exploration on the surface of the Moon.

Icarus 3.0: Dynamic heliosphere modelling

Space weather predictions are necessary to avoid damage caused by intense geomagnetic storms. Such strong storms are usually caused by a co-rotating interaction region (CIR) passing at Earth or by the arrival of strong coronal mass ejections (CMEs). To mitigate the damage, the effect of propagating CMEs in the solar wind must be estimated accurately at Earth and other locations. Modelling solar wind accurately is crucial for space weather predictions, as it is the medium for CME propagation. The Icarus heliospheric modelling tool is upgraded to handle dynamic inner heliospheric driving instead of using steady boundary conditions. The ideal magnetohydrodynamic (MHD) solver and the automated grid-adaptivity are adjusted to the latest MPI-AMRVAC version. This new combination allows us to model the solar heliosphere more accurately. The inner boundary conditions, prescribed at 0.1 AU for the heliospheric model, are updated time-dependently throughout the simulation. The coronal model (r<0.1 AU) is computed repeatedly for selected magnetograms, and the r=0.1 AU radial boundary prescription is provided to the heliospheric modelling tool. The particle sampling within MPI-AMRVAC is extended to handle stretched spherical grid information. It is well suited for tracing solar wind plasma conditions at the locations of planets and satellites in the heliosphere. The solar wind obtained in the simulation is dynamic and shows significant variations throughout the evolution. When comparing the results with the observations, the dynamic solar wind results are more accurate than previous results obtained with purely steady boundary driving. The CMEs propagated through the dynamic solar wind background produce more similar signatures in the time-series data than in the steady solar wind. Dynamic boundary driving in Icarus results in a more self-consistent solar wind evolution in the inner heliosphere. The upgraded particle sampling allows for a very versatile sampling of the solution at the spatio-temporally varying locations of satellites. The obtained space weather modelling tool for dynamic solar wind and CME simulations is better suited for space weather forecasting than a steady solar wind model.

Super Typhoons Simulation: A Comparison of WRF and Empirical Parameterized Models for High Wind Speeds

As extreme forms of tropical cyclones (TCs), typhoons pose significant threats to both human society and the natural environment. To better understand and predict their behavior, scientists have relied on numerical simulations. Current typhoon modeling primarily falls into two categories: (1) complex simulations based on fluid dynamics and thermodynamics, and (2) empirical parameterized models. Most comparative studies on these models have focused on wind speed below 50 m/s, with fewer studies addressing high wind speed (above 50 m/s). In this study, we design and compare four different simulation approaches to model two super typhoons: Typhoon Surigae (2102) and Typhoon Nepartak (1601). These approaches include: (1) The Weather Research and Forecasting (WRF) model simulation driven by NCEP Final Operational Global Analysis data (FNL), (2) WRF simulation driven by the fifth generation of the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data (ERA5), (3) the empirical parameterized Holland model, and (4) the empirical parameterized Jelesnianski model. The simulated wind fields were compared with the measured wind data from The Soil Moisture Active Passive (SMAP) platform, and the resulting wind fields were then used as inputs for the Simulating WAves Nearshore (SWAN) model to simulate typhoon-induced waves. Our findings are as follows: (1) for high wind speeds, the performance of the empirical models surpasses that of the WRF simulations; (2) using more accurate driving wind data improves the WRF model’s performance in simulating typhoon wind speeds, and WRF simulations excel in representing wind fields in the outer regions of the typhoon; (3) careful adjustment of the maximum wind speed radius parameter is essential for improving the accuracy of the empirical models.

Validity of the Diabetic Wound Assessment Learning Tool.

The development of the Diabetic Wound Assessment Learning Tool (DiWALT) has previously been described. However, an examination of its application to a larger, more heterogeneous group of participants is lacking. In order to allow for a more robust assessment of the psychometric properties of the DiWALT, we applied it to a broader group of participants. We built validity evidence for the tool by assessing 74 clinician participants' during two simulated wound care scenarios: Two assessors independently rated each participant using our tool, with a total of five raters providing scores. We evaluated validity evidence using generalizability theory analyses and by comparing performance scores across the three experience levels using ANOVA. The tool differentiated between novices and the other two groups well (p < 0.01) but not between intermediates and experts (p = 0.34). Our generalizability coefficient was 0.87, and our phi coefficient was 0.87. The accumulated validity evidence suggests our tool can be used to assess novice clinicians' competence in initial diabetic wound management during simulated cases. Further work is required to clarify the DiWALT's performance in a broader universe of generalisation and to examine evidence for its extrapolation and implications inferences.

Efficient wind farm layout optimization with the FLOWERS AEP model and analytic gradients

Wind farm layout optimization (WFLO) studies often aim to maximize the annual energy production (AEP) of a wind farm by choosing an arrangement of turbines that minimizes wake interactions. One way to reduce the cost of WFLO studies is by using more computationally efficient AEP models. The cost of standard AEP modeling approaches, based on the numerical integration of low-fidelity engineering wake models, scales poorly with the number of simulated discrete wind conditions. A second way to reduce cost when using a gradient-based algorithm is to supply exact gradient information instead of finite-difference estimates. However, analytical functions for the derivatives of AEP with respect to turbine positions are not always available in the conventional modeling approach. FLOWERS is a computationally inexpensive, analytical model for wind farm AEP that is specifically developed for WFLO applications. In this paper, we analyze the performance of the FLOWERS AEP model with analytic gradients in a layout optimization study compared with a reference optimization framework across three wind farm case studies. We find that the FLOWERS-based approach reduces computation time by a factor of 50–4000 and improves optimal AEP by about 0.3% with less than half of the variability in AEP across instances with randomized initial conditions. We also find the optimal layouts to be insensitive to model parameter tuning, making FLOWERS-based layout optimization a streamlined, user-friendly approach.

Future Derecho Potential in the United States

Abstract This study uses high-resolution, convection-permitting, dynamically downscaled regional climate simulation output to assess how long-lived, convectively induced, extratropical windstorms known as derechos may change across the CONUS during the twenty-first century. Three 15-yr epochs including a historical period (1990–2005) and two separate late-twenty-first-century periods (2085–2100) employing intermediate (RCP4.5) and pessimistic (RCP8.5) greenhouse gas concentration scenarios are evaluated. A mesoscale convective system (MCS) identification and tracking tool catalogs derecho candidates across epochs using simulated radar reflectivity and maximum 10-m wind speed as a proxy for near-surface severe wind gusts. Results indicate that MCS-based windstorms, including derechos, are more frequent, widespread, and intense in both future climate scenarios examined for most regions of the central and eastern CONUS. Increases are suggested across all parts of the year, with significant changes in populations concentrated during the early spring and summer months, suggesting the potential for a longer, more extreme MCS windstorm season. This research provides insights for forecasters, emergency managers, and wind-vulnerable stakeholders on how these events may change across the twenty-first century so that they may mitigate, adapt to, and become resilient against severe convective storm perils. Significance Statement Long-lived, thunderstorm-induced, damaging wind events known as derechos may increase across most portions of the central and eastern United States in the future, with projections indicating a near doubling or tripling of annual cases in the Midwest, eastern Great Plains, and Mississippi and Ohio Valley regions by the end of the twenty-first century. Modeling projections suggest that future derechos could generally be longer-lived, more expansive, and capable of producing more severe wind gusts and damage, which will ultimately increase risk to life, infrastructure, and wind-sensitive industries affected by these extreme thunderstorm events.

A simplified statistical model for regional offshore typhoon wind risk assessment

The accuracy of typhoon wind risk assessment methods is of great significance for offshore or coastline areas. Due to the practical limitations of typhoon measurement, it is common to perform Monte-Carlo simulation (MCS) to extrapolate such data to thousands of years to estimate the extreme wind speed. However, there are technical limitations for engineering applications of this technique, and the computational costs are significant for assessment on a regional level. For the preliminary typhoon risk assessment for a region, a simplified statistical method (SSM) is proposed in this paper. In the proposed method, the extreme wind speed is estimated with the extended “Improved Method of Independent Storms” (XIMIS) method, based on simulated wind field results using the best track typhoon data, i.e., the historical typhoon record information. The results of the simplified statistical method are validated by comparison with local code wind speeds and with full track MCS results in the Northwest Pacific basin using the best track database of the Joint Typhoon Warning Center (JTWC). Finally, the proposed SSM method is used to produce a wind map for typhoon risk assessment in offshore and coastal regions of southeast China, with high efficiency and acceptable accuracy.

ВЛИЯНИЕ СУЛЬФАТИАЗОЛА СЕРЕБРА НА ЗАЖИВЛЕНИЕ КОЖНЫХ РАН, ОБРАЗУЮЩИХСЯ ПРИ ПРОРЕЗЫВАНИИ СПИЦАМИ АППАРАТОВ НАРУЖНОЙ ФИКСАЦИИ

The study of the healing mechanisms of skin wounds resulting from damage to the skin by transosseous needles of external fixation devices in the treatment of osteoarticular pathology with the aim of further targeted correction of these processes is one of the urgent tasks of modern traumatology and orthopedics. The effect of silver sulfathiazole, recommended for the prevention of infectious complications, on the healing of this type of wound has not been studied previously. The aim of the study was to investigate the effect of silver sulfathiazole on the healing of skin wounds formed during the cutting of external fixation devices by pins. The experimental study was performed on 35 sexually mature male Wistar rats. Modeling of a skin wound formed during the cutting of external fixation devices by pins was carried out in sterile operating room conditions, under drug anesthesia of animals that underwent transosseous osteosynthesis of the femur using an original design of the external fixation device. By tractional movement of the proximal pin with a dosed stretching of the supports at a rate of 1 mm in 4 steps, tension and cutting of the skin were carried out for 10 days (the distraction period), then the device was in a static position for 15 days (the period of fixation of the limb in the device), after which the device was dismantled and observation was carried out for another 30 days. The animals were divided into 2 groups. In the control group, the simulated wound healed under natural healing conditions; in the experimental group, silver sulfathiazole applications were performed twice daily during the distraction period. Skin wounds were examined using light microscopy and morphometry after 10 days of distraction, 15 days of fixation, and 30 days after the apparatus was removed. The thickness of the epidermis, dermis, and the numerical density of the sebaceous glands and hair follicles were measured on digital images of histological preparations stained with hematoxylin and eosin. The volume density of elastic fibers was determined on preparations stained with orcein according to Tenzer-Unn. The obtained quantitative data were subjected to statistical analysis. The study showed that the formation of a skin wound with transosseous pins is accompanied by tissue tension. Healing of this type of wound occurs with a delay in epithelialization and an increase in the duration of the inflammatory phase. This affects the mechanisms of extracellular matrix synthesis and leads to the formation of scar tissue in the area of damage. The use of silver sulfathiazole applications promotes accelerated wound closure by epithelium, a reduction in the period of inflammation, normalization of elastin synthesis, and a decrease in cicatricial changes in the skin regenerate.

Large Eddy Simulation of Flow Around Twin Tower Buildings in Tandem Arrangements with Upstream Corner Modification

The aerodynamic performance of twin tall buildings immersed in the atmospheric boundary layer was numerically investigated by adopting the spatial-averaged large eddy simulation (LES) method. This study focused on the effects of corner cutting and chamfering. The buildings were both square and sectional with a width-to-height ratio of 1:6, and were arranged in a tandem configuration with a spacing ratio of 2.0. The corner-cutting and chamfering measures were only applied to the upstream cylinder, with a corner modification rate of 10%. To generate the turbulent inflow boundary condition (IBC) for LES, steady-state equilibrium IBC expressions were introduced into the vortex method, which were implemented in the commercial code Ansys Fluent. The present simulation method and solution parameters were first verified by comparing the simulated wind field and the wind pressure distribution on a single tall building with those of the wind tunnel test. The influences of the corner-cutting and chamfering measures on the wind load of the tandem buildings were then comparatively studied concerning the statistical values of their aerodynamic force coefficients and wind pressure coefficients. The influence mechanism was analyzed based on the simulated time-averaged flow field and the instantaneous vortex structure around the buildings. The results indicated that upstream corner-cutting and chamfering measures can induce a diffusion angle shift in the separated shear flow from the leading edge of the upstream building, thus affecting the separation and reattachment of the separated upstream flow on the downstream building. Among the measures studied, upstream corner cutting is more effective in reducing wind pressure and aerodynamic force coefficients.

Towards advanced forecasting of solar energetic particle events with the PARASOL model

Gradual solar energetic particle (SEP) events are generally attributed to the particle acceleration in shock waves driven by coronal mass ejections (CMEs). Space-weather effects of such events are important, so there has been continuous effort to develop models able to forecast their various characteristics. Here we present the first version of a new such model with the primary goal to address energetic storm particle (ESP) events. The model, PARASOL, is built upon the PArticle Radiation Asset Directed at Interplanetary Space Exploration (PARADISE) test-particle simulation model of SEP transport, but includes a semi-analytical description of an inner (i.e., near the shock) part of the foreshock region. The semi-analytical foreshock description is constructed using simulations with the SOLar Particle Acceleration in Coronal Shocks (SOLPACS) model, which simulates proton acceleration self-consistently coupled with Alfvén wave generation upstream of the shock, and subsequent fitting of the simulation results with suitable analytical functions. PARASOL requires input of solar wind and shock magnetohydrodynamic (MHD) parameters. We evaluate the performance of PARASOL by simulating the 12 July 2012 SEP event, using the EUropean Heliospheric FORecasting Information Asset (EUHFORIA) MHD simulation of the solar wind and CME in this event. The PARASOL simulation has reproduced the observed ESP event ($E\lesssim 5$~MeV) in the close vicinity of the shock within one order of magnitude in intensity.

Droughts in Wind and Solar Power: Assessing Climate Model Simulations for a Net‐Zero Energy Future

AbstractUnderstanding and predicting “droughts” in wind and solar power availability can help the electric grid operator planning and operation toward deep renewable penetration. We assess climate models' ability to simulate these droughts at different horizontal resolutions, ∼100 and ∼25 km, over Western North America and Texas. We find that these power droughts are associated with the high/low pressure systems. The simulated wind and solar power variabilities and their corresponding droughts during historical periods are more sensitive to the model bias than to the model resolution. Future climate simulations reveal varied future change of these droughts across different regions. Although model resolution does not affect the simulation of historical droughts, it does impact the simulated future changes. This suggests that regional response to future warming can vary considerably in high‐ and low‐resolution models. These insights have important implications for adapting power system planning and operations to the changing climate.

Influence of tropical cyclone moving speeds on the attenuation effect of Holland surface wind and storm surge simulation in Guangdong Province, China

The Holland wind model remains limitations on the accurate surface wind estimation of tropical cyclone (TC) and the storm surge modelling. This study investigates the influence of TC moving speeds on the attenuation effect of Holland surface wind and proposes a weakening factor to correct Holland surface wind. Then the corrected surface wind fields are combined with ERA5 to produce the improved hybrid surface wind fields to simulate total water levels. The significant linear correlation (R2 = 0.54) between TC moving speeds and the weakening factor shows that the slower the TC moves, the greater attenuation rate the surface wind speeds need. The improved Hybrid wind fields (Hybrid_f) have the best agreement with ground observations, with the Skills and RMSEs in the range of 0.65-0.93 and 2.3-6.9 m/s. The total water levels of storm surge simulated by the Hybrid_f have the best agreement with gauge measurements, with the Skills and RMSEs in the range of 0.72-0.99 and 0.16-0.51 m. In particular, the improved surface wind fields for TCs with slower movement substantially mitigate the severe reduction of water levels. These findings offer valuable insights for optimizing the surface wind fields to improve storm surge modeling and other applications.

Plasma and Flow Simulation of the Ion Wind in a Surface Barrier Discharge Used for Gas Conversion Benchmarked by Schlieren Imaging

Surface dielectric barrier discharges (sDBD) are efficient and scalable plasma sources for plasma-based gas conversion. One prominent feature of an sDBD is the generation of an ion wind, which exerts a force on the neutrals, thus leading to an efficient mixing of plasma and a passing gas stream. This becomes apparent by the creation of upstream and downstream vortices in the vicinity of the plasma. In this study, these vortices are generated by high voltage burst pulses consisting of two half cycles of an almost sinusoidal voltage shape. The vortices are monitored by Schlieren imaging diagnostic to benchmark and connect two simulations of the sDBD: a plasma model simulating a streamer for 25 ns starting from the electrode and propagating along a dielectric surface followed by a decay. The streamer is the source of electrical charges accelerated as ion wind by the applied electric field from the sDBD power supply. A second flow simulation models this ion wind as a time-averaged thrust acting on the passing gas stream. The conversion of the time-resolved forces from the nanosecond plasma simulation into the steady state thrust in the flow simulation indicates that the force from the plasma lasts much longer than the actual streamer propagation phase. This is explained by the fact that the charges in the streamer channel remain present for almost 100 ns, and the voltage from the power supply lasts for a few microseconds being applied to the electrode so that ions in the streamer channel are still accelerated even after a streamer stops to propagate after a few ns. The thrust generated during the streamer phase, including the relaxation phase, agrees well with predictions from flow simulation. Additionally, properly converting the time-resolved forces from the plasma simulation into a time-averaged thrust for the flow simulation yields exactly the synthetic Schlieren images as measured in the experiments.

Global Simulation of the Solar Wind: A Comparison with Parker Solar Probe Observations during 2018–2022

Global magnetohydrodynamic (MHD) models play an important role in the infrastructure of space weather forecasting. Validating such models commonly utilizes in situ solar wind measurements made near the Earth’s orbit. The purpose of this study is to test the performance of G3DMHD (a data driven, time-dependent, 3D MHD model of the solar wind) with Parker Solar Probe (PSP) measurements. Since its launch in 2018 August, PSP has traversed the inner heliosphere at different radial distances sunward of the Earth (the closest approach ∼13.3 R ⊙), thus providing a good opportunity to study evolution of the solar wind and to validate heliospheric models of the solar wind. The G3DMHD model simulation is driven by a sequence of maps of the photospheric field extrapolated to the assumed source surface (2.5 R ⊙) using the potential field model from 2018 to 2022, which covers the first 15 PSP orbits. The Pearson correlation coefficient (cc) and the mean absolute scaled error (MASE) are used as the metrics to evaluate the model performance. It is found that the model performs better for both magnetic intensity (cc = 0.75; MASE = 0.60) and the solar wind density (cc = 0.73; MASE = 0.50) than for the solar wind speed (cc = 0.15; MASE = 1.29) and temperature (cc = 0.28; MASE = 1.14). This is due primarily to lack of accurate boundary conditions. The well-known underestimate of the magnetic field in solar minimum years is also present. Assuming that the radial magnetic field becomes uniformly distributed with latitude at or below 18 R ⊙ (the inner boundary of the computation domain), the agreement in the magnetic intensity significantly improves (cc = 0.83; MASE = 0.49).

Impact of solar-wind turbulence on a planetary bow shock

Context. The interaction of the solar-wind plasma with a magnetized planet generates a bow-shaped shock ahead of the wind. Over recent decades, near-Earth spacecraft observations have provided insights into the physics of the bow shock, and the findings suggest that solar-wind intrinsic turbulence influences the bow shock dynamics. On the other hand, theoretical studies, primarily based on global numerical simulations, have not yet investigated the global three-dimensional (3D) interaction between a turbulent solar wind and a planetary magnetosphere. This paper addresses this gap for the first time by presenting an investigation of the global dynamics of this interaction that provides new perspectives on the underlying physical processes. Aims. We use the newly developed numerical code MENURA to examine how the turbulent nature of the solar wind influences the 3D structure and dynamics of magnetized planetary environments, such as those of Mercury, Earth, and magnetized Earth-like exoplanets. Methods. We used the hybrid particle-in-cell code MENURA to conduct 3D simulations of the turbulent solar wind and its interaction with an Earth-like magnetized planet through global numerical simulations of the magnetosphere and its surroundings. MENURA runs in parallel on graphics processing units, enabling efficient and self-consistent modeling of turbulence. Results. By comparison with a case in which the solar wind is laminar, we show that solar-wind turbulence globally influences the shape and dynamics of the bow shock, the magnetosheath structures, and the ion foreshock dynamics. Also, a turbulent solar wind disrupts the coherence of foreshock fluctuations, induces large fluctuations on the quasi-perpendicular surface of the bow shock, facilitates the formation of bubble-like structures near the nose of the bow shock, and modifies the properties of the magnetosheath region. Conclusions. The turbulent nature of the solar wind impacts the 3D shape and dynamics of the bow shock, magnetosheath, and ion foreshock region. This influence should be taken into account when studying solar-wind-planet interactions in both observations and simulations. We discuss the relevance of our findings for current and future missions launched into the heliosphere.

Reconstruction of Historical Site-Scale Dust Optical Depth (DOD) Time Series from Surface Dust Records and Satellite Retrievals in Northern China: Application to the Evaluation of DOD in CMIP6 Historical Simulations

Abstract The biases generated by state-of-the-art climate models in simulating dust optical depth (DOD) remain to be detailed. Here, a site-scale DOD dataset in March–August over northern China (NC) during 1980–2001 was reconstructed using the empirical relationship between MODIS-retrieved DOD and dust-event frequencies during 2001–21. Then, through the combined use of MODIS-based and reconstructed DOD, we evaluated the reproducibility of DOD from 10 models participating in phase 6 of the Coupled Model Intercomparison Project (CMIP6) for the historical period (1980–2001 and 2002–14) and under different Shared Socioeconomic Pathways (SSPs) during 2015–21. The results demonstrate that CMIP6 models and multimodel ensemble mean (MEM) are capable of capturing the spatial pattern of DOD, but with considerable uncertainty and intermodel variability in magnitude. Regionally averaged DOD is underestimated by 56.09% during 1980–2001 and overestimated by 30.97% during 2002–14 in MEM over NC. Simultaneously, the intermodel standard deviations are greater than MEM during 2002–14, suggesting large discrepancies among individual models. Very few models accurately capture the trends in DOD, which can mainly be attributed to the different trends in simulated wind speed (WS), soil moisture, and vegetation cover, and their contributions to dust evolution. Under four SSPs, despite the best correlation between SSP1-2.6-modeled and MODIS DOD over Gobi Desert (GD), overestimation of DOD is still observed. More models under SSP1-2.6 capture the positive DOD trend, mainly attributable to positive changes in simulated WS over GD.

Investigation of the Durability of a Water Electrolysis Cell with Iridium Fiber Anode Against Voltage Fluctuations Simulating Wind Power

Introduction Water electrolysis is the core technology for successfully transferring renewable energy to hydrogen energy. Our group have been focusing on wind power and PEM water electrolyzer. For aiming at hydrogen production through the water electrolysis directly using fluctuating wind power, the durability against voltage fluctuations has been studied1,2. So far, we have developed an accelerated potential fluctuation protocol based on voltage fluctuations of the actual wind power located in Hibikinada, Japan. Long-term durability of a water electrolysis cell equivalent to 320 days was evaluated using a membrane electrode assembly (MEA) with IrO2 anode and Pt/KB cathode. As a result, we have found that the current loss during the durability test is mostly recovered after the rest time, which enhances the removal of generated gasses remained in catalyst layers. On the other hand, a certain amount of irreversible current loss has also been found. That was caused by the partially peeled off catalyst layer due to increase in the internal pressure within the catalyst layer by remained gases.Besides the durability study, development of new anode catalysts has been tried in our group. Iridium fibers are one of our developed catalysts. Since the requirement of high porosity in the catalyst layers is expected for avoiding the stagnation of gases based on our durability study, adapting the Iridium fiber catalyst is aimed in order to improve the durability of a water electrolysis cell in this study. Experimental Iridium fibers were synthesized by electrospinning a solution containing IrCl3∙xH2O, ethanol, dimethylformamide, and polyvinylpyrrolidone with a slightly modified heat treatments from the original method3. When the electrospun Iridium fiber precursor was heated at 500°C for 2 hours with heating rate of 3°C/min in the air atmosphere, Iridium fibers shown in Figure 1 were obtained. After the ball-milling process, Iridium fibers were spray printed within the area of 1 cm2 square to get 0.5 g Ir /cm2 on Nafion117 membrane as an anode. Commercially available 46% Pt/KB was similarly spray printed on the other side to get 0.3 g Pt/cm2. The resulting MEA was assembled into a JARI holder, and the electrochemical properties were evaluated by flowing 5 cc/min of water at 80°C to the anode and cathode. A durability test was performed using an accelerated potential fluctuation protocol with an upper potential limit of 2.3 V developed in our previous study1. In this protocol, one set of voltage fluctuation corresponds to 48 hours, and then 80 sets were performed. AC impedance and I-V performance were evaluated after every set, and each overvoltage was separately analyzed. Results and Discussion When the current at 2.0 V was monitored during the durability test, the large current drop was observed from the 1st set to the 5th set during the durability test. Based on the separated overvoltage analysis, the activation overvoltage and diffusion overvoltage increased simultaneously. Rather slow drop was observed for a standard MEA with IrO2 in our previous study2. The result suggests that generated gas is more easily stagnated in the catalysts layer with Iridium fiber anode, which is not our expectation. Therefore, the anode structure was evaluated by FIB-SEM. As a result, inter-fiber pores were covered by extra Nafion ionomer, leading to reduced mass transfer within the catalyst layer. However, the current loss was mostly recovered after the 100 h rest time after 40 sets and 80 sets of potential fluctuations. The recovery was 95% and 93% after 40 sets and 80 sets, respectively, for a standard MEA. In contrast, for MEA with Ir fibers, the complete recovery of the current was obtained, which suggesting higher resistance to the internal pressure derived by gas stagnation within the catalyst layer. References Y. Honsho et. al., J. Power Sources, 564, pp.232826, 2023.T. Hoshii et. al., ECS Trans., 112(4), pp.451, 2023.Y.-B. Cho et. al., ACS Appl. Mater. Interfaces, 10, pp.541, 2018. Figure 1

Study on the Influence of Wind Load on the Safety of Magnetic Adsorption Wall-Climbing Inspection Robot for Gantry Crane

The maintenance of the surface of steel structures is crucial for ensuring the quality of shipbuilding cranes. Various types of wall-climbing robots have been proposed for inspecting diverse structures, including ships and offshore installations. Given that these robots often operate in outdoor environments, their performance is significantly influenced by wind conditions. Consequently, understanding the impact of wind loads on these robots is essential for developing structurally sound designs. In this study, SolidWorks software was utilized to model both the wall-climbing robot and crane, while numerical simulations were conducted to investigate the aerodynamic performance of the magnetic wall-climbing inspection robot under wind load. Subsequently, a MATLAB program was developed to simulate both the time history and spectrum of wind speed affecting the wall-climbing inspection robot. The resulting wind speed time-history curve was analyzed using a time-history analysis method to simulate wind pressure effects. Finally, modal analysis was performed to determine the natural frequency and vibration modes of the frame in order to ensure dynamic stability for the robot. The analysis revealed that wind pressure predominantly concentrates on the front section of the vehicle body, with significant eddy currents observed on its windward side, leeward side, and top surface. Following optimization efforts on the robot’s structure resulted in a reduction in vortex formation; consequently, compared to pre-optimization conditions during pulsating wind simulations, there was a 99.19% decrease in induced vibration displacement within the optimized inspection robot body. Modal analysis indicated substantial differences between the first six non-rigid natural frequencies of this vehicle body and those associated with its servo motor frequencies—indicating no risk of resonance occurring. This study employs finite element analysis techniques to assess stability under varying wind loads while verifying structural safety for this wall-climbing inspection robot.