Search Results (90)

Previously, we proposed a navigation method based on image processing to move to the front of a pallet that can be detected in the field of view. We also proposed an image-processing method to estimate the inclination angle when the pallet is inclined at a pitch with respect to the running surface, such as a pallet loaded on a truck. In this study, we improved the robustness of the existing method so that the series of operations from approach to fork insertion can be realized stably without being affected by the environment. Furthermore, a series of operations from approach to fork insertion was realized by an automatic forklift (Autonomous Guided Forklift, AGF) in an indoor laboratory space simulating a warehouse. Full article

Most existing depth-averaged granular flow theories assume that dry, cohesionless granular materials are incompressible, with the void ratio among grains remaining spatially and temporally invariant. However, recent large-scale experiments showed that the pore space among grains varies both spatially and temporally. This study, therefore, incorporates the effects of granular dilatancy to perform analytical and numerical investigations of granular flows down inclined planes. A high-resolution shock-capturing scheme is employed to numerically solve the compressible depth-averaged equations for temporal and spatial evolution of the flow thickness and depth-averaged velocity, as well as depth-averaged volume fraction. Additionally, a traveling wave solution is constructed. The comparison between analytical and numerical solutions confirms the accuracy of the numerical solution and also reveals that the gradient of the solids volume fraction, induced by granular dilatancy, results in a gentler slope of the granular front, in agreement with experimental observations. Furthermore, this numerical framework is applied to investigate granular flows transitioning from an inclined plane onto a horizontal run-out pad. The numerical solution shows that the incorporation of granular dilatancy causes the shock wave to propagate upstream more rapidly. As a result, the position and morphology of the mass deposit exhibit closer alignment with experimental data. Full article

Background: This paper concerns the study of forces acting on the upper ankle joint of a human in static and quasi-dynamic positions. This paper aimed to determine the pressure forces on the axis of the upper ankle joint in the position of the body tilting forward and backward, as well as in a neutral position. Methods: A model with designated centres of gravity (including and excluding the weight of the platform imitating the foot) and the point of gravity imitating the proximal insertion of the triceps surae and tibialis anterior muscles was developed for this study. The forces and the weight of the tilted object were measured using dynamometers. A method for determining the arms of gravitational forces and the angle of inclination of an object is presented. The function describing the distribution of gravitational loading along its tilting part was described. Next, all measurements and calculations were referred to the human body. Results: Measurements of muscle force, body gravity, the arms of these forces, and the angles of the object’s inclination on the axis of rotation are presented. A methodology for determining the pressure force on the human upper ankle joint axis is presented. The distribution of the value of the pressure force and its components from the maximal forward, through the vertical body position, up to the maximal backward position of the body tilt, is provided. Conclusions: The ankle joint pressure force is the vector sum of the force of gravity and the force of the muscle counteracting the body tilt. This force is the smallest in the vertical body position and increases with the body tilt. It reaches 5.23 times the weight of the tilting part of the body when the body is tilted to its maximum forward position, and 3.57 times the weight when the body tilts backward. Regardless of the direction of the body tilt, the joint pressure vector always runs through the axis of the upper ankle joint. Full article

In the development of tight gas reservoirs in Chuanzhong BJC Gas Field of the Sichuan Basin, running horizontal casing in ultra-long open-hole section faces challenges. These include large friction prediction errors and high casing buckling risks. These challenges significantly impede both the efficiency and safety of field development. Traditional static segmented friction models fail to accurately predict friction coefficients. The reason is that they cannot track dynamic changes in wellbore inclination, azimuth, and dogleg severity in real time. To address this bottleneck, this study develops a technical system termed AI-based dynamic friction inversion-segmented process optimization. Clustering algorithms are used to divide regions. These regions have low, medium, and high friction characteristics. The simulated annealing algorithm dynamically corrects friction coefficients. Meanwhile, the segmented processes of float collars and drilling fluid density are optimized. Verification was conducted on well J108-2H, which features an open-hole section of 4060.9 m and a horizontal-to-vertical ratio (HD/TVD) of 1.88. Results show that this system significantly reduces the mean absolute percentage error of friction coefficient prediction. It also greatly improves the accuracy of casing running feasibility assessment. As a result, the casing in well J108-2H was run smoothly and efficiently. The research results provide an innovative solution for the safe and efficient development of ultra-long open-hole sections in unconventional gas reservoirs. Full article

One of the most common malocclusions encountered in everyday practice by orthodontists is skeletal Class II malocclusion, namely a protrusion of the maxilla, a retrusion of the mandible or a combination of both. To correct it, many clinicians use functional devices that guide the mandible into a more forward position. This stimulates bone growth, correcting the skeletal discrepancy. Controversy exists as to whether these appliances accelerate the growth rate, helping the mandible reach its final size earlier, or whether the growth of the mandible is observed as a positive response to the stimuli. This study examined whether the protrusion of the mandible in rats accelerates the growth rate or increases the overall growth of the mandible in the long run. Relapse was also assessed by removing the appliance prior to the end of the experiment. Seventy-two four-week-old Wistar rats were used. The treatment group, which consisted of 36 rats, had a device fitted on their upper incisors that led to a protrusion of their mandible. The device, a bite-jumping appliance, consisted of an iron-cast inclined plane and was fitted for 24 h a day, inducing a 3.5 mm anterior protrusion and 3 mm inferior displacement of the mandible. The control group consisted of 36 rats that were fed the same soft diet as the treatment group. Both groups were divided into three subgroups. The first was sacrificed 30 days after the onset of the experiment, the second at 60 days, and the last subgroup had the appliance removed for 30 days and was sacrificed 90 days after the onset of the experiment. At the beginning of the experiment, as well as at each time interval prior to the sacrifice of the animals, the appliances were removed, and cone beam-computed tomography was performed on every animal. Linear measurements were made on each 3D scan, measuring the growth of the mandible. Measurements of mandibular growth were higher compared to the control group. For instance, Gonion-Menton was 1.18 mm higher on month 2 compared to month 1 in the control group, whereas the same measurement marked a 1.82 mm difference in the experimental group. Condylion–Menton on the same intervals marked a 0.84 mm difference in the control, whereas a 1.35 mm difference was noted in the experimental group. Given the results, true mandibular growth is achieved using functional appliances for Class II malocclusion correction in rats. Full article

Classifying human locomotor activities from wearable sensor data is an important high-level component of control schemes for many wearable robotic exoskeletons. In this study, we evaluated three machine learning models for classifying activity type (walking, running, jumping), speed, and surface incline using input data from body-worn inertial measurement units (IMUs) and e-textile insole pressure sensors. The IMUs were positioned on segments of the lower limb and pelvis during lab-based data collection from 16 healthy participants (11 men, 5 women), who walked and ran on a treadmill at a range of preset speeds and inclines. Logistic Regression (LR), Random Forest (RF), and Light Gradient-Boosting Machine (LGBM) models were trained, tuned, and scored on a validation data set (n = 14), and then evaluated on a test set (n = 2). The LGBM model consistently outperformed the other two, predicting activity and speed well, but not incline. Further analysis showed that LGBM performed equally well with data from a limited number of IMUs, and that speed prediction was challenged by inclusion of abnormally fast walking and slow running trials. Gyroscope data was most important to model performance. Overall, LGBM models show promise for implementing locomotor activity prediction from lower-limb-mounted IMU data recorded at different anatomical locations. Full article

Monte Carlo simulations of induced extensive air showers (EASs) by ultra-high-energy cosmic rays are widely used in comparison with measured events at experiments to estimate the main cosmic ray characteristics, such as mass, energy, and arrival direction. However, these simulations are computationally expensive, with running time scaling proportionally with the number of radio antennas included. The AugerPrime upgrade of the Pierre Auger Observatory will feature an array of 1660 radio antennas. As a result, simulating a single EAS using the full detector array will take weeks on a single CPU thread. To reduce the simulation time, detectors are commonly pre-selected based on their proximity to the shower core, using a selection ellipse based on the Cherenkov radiation footprint scaled by a fixed constant factor. While effective, this approach often includes many noisy antennas at high zenith angles, reducing computational efficiency. In this paper, we introduce an optimal method for selecting candidate detectors with high predicted signal-to-noise ratio for proton and iron primary cosmic rays, replacing the constant scaling factor with a function of the zenith angle. This approach significantly reduces simulation time—by more than 50% per CPU thread for the heaviest, most inclined showers—without compromising signal quality. Full article

This study empirically examines how Big4 audit firms mediate the relationship between family-controlled enterprises and their earnings management practices. Analyzing a dataset of 61 non-financial family-listed companies listed on the Indonesia Stock Exchange from 2017 through 2019 reveals that family-controlled businesses and Big4 auditors are associated with lower earnings management, resulting in improved financial reporting quality. The study also shows that family-owned enterprises are more inclined to hire a higher-quality auditing firm for their financial statement assessments. Moreover, our results suggest that Big4 auditors partially mediate the relationship between family businesses and their earnings management practices. The additional tests conducted in this study highlight the significant role of family-run firms and Big4 auditors in curbing earnings management, primarily when corporate management is prone to decrease reported earnings. Robustness tests validate the reliability of the conclusions drawn from the primary findings. Our study shows that family managers align their goals with the firm and shareholders, enhancing company financial reporting integrity. Our finding also emphasizes the crucial role of Big4 auditors in minimizing intra-family agency conflicts in family firms, promoting transparency, and aligning family managers’ interests with external stakeholders. Full article

Determining the friction coefficients for uniform flows over very rough bottoms is a long-standing problem in open-channel hydraulics and river engineering. This experimental study presents measurements of the surface deformation as well as Darcy–Weisbach and Manning friction coefficients for steady, turbulent (6058 $\le \mathcal{R}e\le$ 28,502), and subcritical flows (0.14 $\le \mathcal{F}r\le$ 0.52) over large roughness elements, where $\mathcal{F}r$ and $\mathcal{R}e$ denote the Froude and Reynolds numbers, respectively. The experiments were conducted in a rectangular, inclined flume with a train of half-cylinders mounted on the bed, with radii in the range 20 mm $\le a\le$ 50 mm. These obstacles yield a relative submergence 1.45 $\le h_N/a\le$ 4.41 and a constant spacing ratio $e/a=12.8$ across all experimental runs, where $h_N$ and e denote the normal flow depth and the center-to-center spacing between cylinders, respectively. The relative amplitude of the surface profiles, ($\Delta h/a$), was analyzed and found to correlate strongly with $h_N/a$, $\mathcal{R}e$ and $\mathcal{F}r$. The results reveal very high values of the Darcy friction factor, f, which follows scaling laws of the form ${f\propto (h_N/a)}^{\widehat{n}}$, with $\widehat{n}<0$, independent of a, and ${f\propto \mathcal{R}e}^{\beta }$, where $\beta <0$ is closely linked to a. Scaling relationships for the Manning roughness coefficient, (n), were also investigated and are reported herein. Full article

This study examined the differences in physiological, metabolic and running dynamics responses between level and inclined treadmill protocols and their implications for accurately determining training intensities. Twenty-three healthy, active adults (18 male and 5 female) from 25 to 59 years old (age: 42.7 years, height: 1.77 m, body mass: 71.9 kg, $V{O}_{2max}$: 54.3 mL·${\mathrm{kg}}^{-1}$·${\min }^{-1}$) completed both protocols. Physiological markers (gas exchange threshold (GET), respiratory compensation point (RCP), $V{O}_{2max}$), metabolic variables (HR, $V{O}_2$, $VC{O}_2$, RER, VE, speed) and running dynamic variables (running economy (RE), stride length (SL), ground contact time (GCT), cadence) were measured and matched for the external work rate at each stage. The data were analyzed using one-way repeated measures ANOVA with Tukey’s post hoc procedure. No significant differences were observed in the physiological markers for the inclined and flat protocols across all the intensities. However, the metabolic variables showed significant differences (p = 0.0333 to <0.0001) between the inclined and flat protocols at higher intensities. The RE was consistently improved in the flat protocol compared with the inclined protocol, with significant differences observed at the high-intensity stages (p = 0.0232 to <0.0001). While the physiological markers remained unaffected, metabolic responses and running kinematics differed significantly between the protocols. These results highlight that training intensity zones derived from inclined protocols may not be appropriate for flat terrain training, underlining the importance of testing specificity in athlete preparation. Full article

Nowadays, lumbar supports are applied when designing tractor seats to address the issue of tractor operators’ lumbar discomfort. This research aimed to investigate the effect of lumbar support on ride comfort using various lumbar support thicknesses and running velocities based on body pressure distribution measures and subjective comfort evaluations. The repeated measures ANOVA results revealed that the lumbar support thickness (p < 0.05) and running velocity (p < 0.05) had a prominent, main effect on the pressure distribution indexes, and the interaction effect between them was also significant (p < 0.05). As the lumbar support thickness increased, the degree of comfort at the waist, thigh, elbow, and for the overall body first increased and then decreased, while shoulder comfort was reduced continuously. There was an obvious relationship between the outcome of the subjective comfort assessment and the pressure distribution indexes. The 3 cm thick lumbar support did not enhance ride comfort significantly, whereas the 9 cm thick lumbar support imposed excessive pressure on the lumbar spine, thus leading to an excessive forward inclination of the lumbar spine and increased tiredness. Most tractor operators selected the 6 cm thick lumbar support. This research provides insights from practical applications that may be useful for the design and assessment of tractor seats, based on body pressure distribution, to increase overall ride comfort and reduce operator fatigue. Full article

Inflation across the globe after the COVID-19 pandemic has shown some persistence and followed an upward trend well above inflation targets and beyond normal historical movements. The Saudi inflation rate followed similar patterns of global trends, surging significantly and persisting well above the pre-pandemic levels. This paper examines determinants of inflation in Saudi Arabia, considering internal and external factors, and evaluates whether inflation responds to common global shocks or is largely influenced by macroeconomic variabilities within the economy. Findings and analyses in this paper are based on both conventional Auto Regressive Distributive Lag (ARDL) and non-linear ARDL (NARDL) models using quarterly level data to capture short-run dynamics and long-run relationships between inflation rate and examined macroeconomics variables, namely oil prices real effective exchange rate, money supply, and government spending. Reported results reveal an asymmetrical relationship between oil price fluctuations and inflation rate volatilities in Saudi Arabia. Inclines in oil prices lead to higher inflation, while the decline in oil prices does not alleviate inflationary pressures, and these results are consistent both in the short-run and the long run. The influence of pass-through real effective exchange rate is also evident in transmitting global shocks to local consumer prices in the long run, where a depreciation in real effective exchange rate results in a higher cost of imported goods, exerting additional stresses on local inflation. For factors within the economy, findings indicate a substantial long-term inflationary effect of money supply on the inflation rate in Saudi Arabia, where a one percent increase in the money supply led to more than one-third increase in inflation in the long run. On the other hand, while the influence of government spending on inflation was statistically significant, its impact is less pronounced in explaining the inflation rate’s variations. The analysis reveals that the evaluated variables exert a stronger influence on inflation in the long run. This underscores the critical need for policymakers to consider the cumulative effects of these determinants when formulating effective long-term inflation stabilization policies. Full article

Ski mountaineering (Skimo) combines mountain climbing and skiing, with ascents on skis or by carrying them, followed by ski descents. Despite its popularity, the literature lacks integrated biomechanical analyses during indoor training, limiting evidence-based recommendations for training, injury prevention, and performance improvement in this sport. This study analyzed four Skimo athletes during uphill walking and running on a 9° inclined treadmill at 7 km/h and 8 km/h. Kinematics was assessed by an optoelectronic system, and surface electromyography recorded the muscular activity of twelve bilateral muscles (Erector Spinae, Rectus Abdominis, Rectus Femoris, Biceps Femoris, Tibialis Anterior, Gastrocnemius Lateralis). Rectus Femoris and Biceps Femoris co-activation supported knee stability during the load support phase, especially while running. Running at 8 km/h was the most demanding condition, with increased knee flexion throughout the task cycle. Switching from 7 to 8 km/h reduced the maximum extension and increased the maximum flexion of both hip and knee and required the Gastrocnemius’ recruitment in the swing phase. Regardless of task and speed, Rectus Abdominis and Erector Spinae played a key role in stabilizing the trunk. This study provided a biomechanical characterization of two motor gestures typical in Skimo, highlighting how task typology and velocity could influence kinematics and muscle activation. Full article

Treadmill running simulates various conditions, including flat, uphill, and downhill gradients, making it useful for training and rehabilitation. This study aimed to examine how incline and decline treadmill running affect local dynamic stability of individual running movement components that cooperatively contribute to achieving the running tasks. Principal component analysis (PCA) was used to decompose movement components, termed principal movements (PMs), from kinematic marker data collected from 19 healthy recreational runners (9 females and 10 males, 23.6 ± 3.7 years) during treadmill running at 10 km/h across different gradients (−6, −3, 0, +3, +6 degrees). The largest Lyapunov exponent (LyE) of individual PM positions (higher LyE = greater instability) was analyzed using repeated-measures ANOVA to assess treadmill gradient effects across PMs. The results showed that the effects of treadmill gradient appear in PM₃, which corresponds to the mid-stance phase of the gait cycle. Specifically, decline treadmill running significantly decreased local dynamic stability (greater LyE) compared to equivalent incline conditions (p ≤ 0.005). These findings suggest that decline treadmill running should be used cautiously in rehabilitation settings due to its potential to reduce an ability to control and respond to small perturbations, thereby increasing the risk of instability during the weight-bearing support phase of gait. Full article

This study presents numerical and experimental investigations on an oscillating water column (OWC) wave energy device integrated into a sloping breakwater. Regular waves were generated in a physical wave tank to investigate the hydrodynamic performance and extraction efficiency of the small-scale nested OWC device. Simultaneously, to complement various scenarios, numerical simulations were conducted using the open-source computational fluid dynamics platform OpenFOAM. The volume of fluid (VOF) method was employed to capture the complex evolution of the air–water interface, and an artificial source term (Forchheimer flow region) was introduced into the Navier–Stokes equations to replace the power take-off (PTO) system. By analyzing wave reflection properties, energy absorption efficiency, and wave run-up, the hydrodynamic characteristics of the inclined OWC device were explored. The comparison between the numerical and experimental results indicate a good consistence. A smaller front wall draft broadens the high-efficiency frequency bandwidth. For relatively long waves, increasing the air chamber width enhances energy conversion efficiency and reduces wave run-up. The optimal configuration was achieved with the following dimensionless parameters: front wall draft $a/h=1/3$, air chamber width $d_1/h=2/9$, and slope $i=2$. Due to the sloped structure, when compared with a vertical OWC, long waves can more easily enter the chamber. This causes the efficient frequency bandwidth to shift towards the low frequency range, allowing more wave energy to be converted into pneumatic energy. As a result, wave run-up is reduced, enhancing the protective function of the breakwater. Full article