Search Results (99)

Maximum aerobic capacity (MAC) helps in physical work capacity evaluation. In practice, the construction jobs are designed using the standard treadmill or ergometer MAC value, which is inappropriate and leads to injuries. According to NIOSH, the average oxygen consumption during an 8 h day is recommended to be no more than 33% of the exercise-specific MAC. Therefore, there is a necessity for construction activity-specific MAC exercise protocols and estimation models. The aim of the study is to develop MAC estimation models for common construction activities such as walking, carrying, lifting, and combined (carrying, dragging, hammering, lifting, and wrenching) using the submaximal exercise test mode. Ten male participants performed all four activities at three different intensities for five minutes each. The oxygen uptake and heart rate were recorded for each trial. This study shows that the average MAC value for walking, carrying, lifting, and combined activities is 0.779 gpm (2.95 L/m), 0.674 gpm (2.55 L/m), 0.745 gpm (2.82 L/m), and 0.608 gpm (2.30 L/m), respectively. The MAC value of combined construction activities is significantly lower than walking (28%), carrying (11%), and lifting (22%). The study recommends using a construction activity-specific exercise protocol for evaluating jobs or workers to prevent a mismatch between job demands and worker capabilities. Full article

Titanium alloy TC4 countersunk head bolts (CHB) are widely used in spacecraft structures, but the research on CHB does not receive enough attention at present. There are still some more opportunities worthy of in-depth research, such as insufficient research on CHB of high-strength fasteners for aerospace applications, an insufficient combination of CHB simulation tests with real working conditions, and inspection and testing methods. In this study, through the combination of finite element simulation and experiments, the working conditions of the CHB connection structure bearing tensile load and CHB screwing were analyzed, and the requirements of the CHB connection structure and installation of CHB were optimized. Based on the single-bolt tensile simulation, the working conditions of multi-bolt connection structures under eccentric load and single-bolt composite laminate connection structures under tensile load were analyzed. Meanwhile, the structure of CHB was further optimized, and the simulation analysis model of the CHB tightening process was established. The research shows that the larger fixing bolt countersunk angle θ₁ and the smaller countersunk fillet radius r, the better the ultimate bearing capacity of the connection structure will be. When the countersunk bevel angle of pressure plate θ₂ was greater than or less than 100°, the clamping force–angle slope will decrease, while when θ₂ was smaller, it will have a greater influence on the slope. The coaxiality Φ had little influence on the slope around the allowable tolerance range (0.3 mm), but the influence on the slope becomes greater when it exceeds the tolerance range. The research results provide a reference and basis for the layout of CHB and the use of composite materials in aerospace connection structures. Full article

Mycobacterium tuberculosis (TB) antigen-based skin tests, known as TB-specific skin tests (TBSTs), have been recommended by the World Health Organization (WHO) to test for TB infection (TBI). In light of these new recommendations, we conducted a situational analysis and market assessment to evaluate the utility of testing for TBI in general and of the new TBSTs in South Africa. We found the following barriers to acceptability of testing for TBI overall, regardless of the test: the perceived high prevalence of TBI; prior experiences of poor TB preventive treatment (TPT) uptake, which has led to the removal of TBI tests from the current TPT guidelines; and a poor sensitivity of previous TBI tests in people living with HIV (PLHIV). In addition, further barriers to the new TBSTs in particular were as follows: patient level barriers linked to repeat visits; the need for cold chains; and the need for a strong laboratory system, which reduces the need for point-of-care options. TBI testing was thought to be potentially useful to determine the eligibility for TPT in these use cases: healthcare workers, pregnant women living with HIV and prisoners. One other use case was in the TB diagnoses of children, where it was thought that a positive immunological test (TST/IgRA/TBST) could indicate a TB contact and serve as a ‘rule in’ test to strengthen the evidence for TB disease as a cause. Full article

Magnetic levitation actuators (MLAs) are frequently employed in photolithography, precise positioning and transportation. The actuator, which consists of racetrack coils and one-dimensional 3 Halbach arrays, has the capacity to calculate the wrench model in real time. However, the high computational demands of the high-dimensional wrench model will result in a prolonged control cycle. Based on a levitation plane composed of three groups of magnetic levitation actuators, this paper proposes a wrench model considering six dimensions to calculate the output current required by the actuator in real time. This method simplifies the expression form of the formula and directly calculates the expression of the current conversion matrix, thereby enabling the system’s computing speed to reach 3 KHz. The system’s step response and trajectory-tracking performance were simulated and compared under the models with and without angular consideration. It has been demonstrated that when rotation angles are incorporated into the magnetic levitation plane, the wrench model considering angles achieves better performance than the wrench model without rotation angles. Full article

Introduction: Tuberculosis (TB) remains a public health concern, and people at risk for TB are hesitant to seek care. The first South African National TB prevalence survey, conducted in 2017–2019, found that most participants with TB symptoms did not seek care for TB. In 2022, an estimated 23% of people with TB in South Africa were undiagnosed, contributing to the country’s burden of “missing” TB cases. This study explores health-seeking behaviour among people with TB (PwTB) in South Africa, focussing on barriers and facilitators to care-seeking and the quantification of TB-related stigma from a patient and community perspective. Methods: We conducted a mixed-method study in the City of Johannesburg (COJ) Metropolitan Municipality from February to March 2022. PwTB aged 18 and older initiating TB treatment for microbiologically confirmed pulmonary TB were recruited from three primary healthcare facilities in the COJ. After providing written informed consent, they participated in a one-time, in-depth, face-to-face interview. The interviews were digitally recorded and conducted by trained facilitators. We used thematic analysis with deductive approaches to develop themes. We used the Van Rie TB stigma assessment scale to quantify perceived stigma. Results: We interviewed 23 PwTB with an overall median age of 39 years and 14 (61%) males. Patient-level barriers to accessing TB care included visiting traditional healers and pharmacists before their TB diagnosis; wrong or missed diagnosis by private doctors; work commitments; scarcity of resources to attend the clinic or walk long distances; perceived and experienced stigma; and a lack of TB knowledge. Facility-level barriers included long clinic queues and uncertainty about where to receive TB care in the clinic. Facilitators for TB care-seeking included being in contact with someone who had TB, receiving encouragement from family, or having knowledge about TB transmission and early diagnosis. The overall median total stigma score among 21 PwTB was 53 (IQR: 46–63), with median community and patient stigma scores of 25 (IQR: 22–30) and 31 (IQR: 21–36), respectively. Conclusions: We found important considerations for the TB programme to improve the uptake of services. Since PwTB consult elsewhere before visiting a facility for TB care, TB programmes could establish private–public partnerships. TB programmes could also increase TB awareness in the community, especially among males, and mobile clinics could be considered to assist with TB case detection and treatment provision. Applying behavioural design techniques and co-designing interventions with patients and providers could improve TB health-seeking behaviours. Full article

This paper deals with static stability in planar grasps of an object by multiple fingers. Differently from previous research, we focus on the case that each finger has redundant links and joints. Based on contact constraints between the object and fingers, the relationships among displacements of object’s pose, contact positions, and joint positions are formulated. Using the constraints, the redundant joints are reduced to independent parameters. The relationship between the displacement and reaction torque of each joint is modeled as a linear spring, and potential energy of the grasp is formulated. Not only for frictionless sliding contact but also for pure rolling contact, we derive stable conditions on the contact positions and joint positions. Based on the conditions, partially differentiating the potential energy, a wrench (force and moment) vector and a stiffness matrix applied to the object by each finger are derived. Summing up the wrenches and matrices of all the fingers, we obtain a wrench vector and a stiffness matrix of the grasp, and we evaluate the grasp stability. Because of our analytical formulation, grasp parameters such as local curvatures at contact points, joint stiffnesses, etc., are explicitly included in the derived matrices. Partially differentiating the wrenches and matrices by the grasp parameters, we clarify effects of the parameters on the stability. Moreover, the difference between the frictionless sliding contact and pure rolling contact is derived in the wrench vector and the stiffness matrix. Using numerical examples, we validate our analysis. Full article

The interaction between equine hooves and various ground surfaces is a critical factor for injury prevention and performance in modern equestrian sports. Accurate measurement of surface grip is essential for evaluating the effectiveness of different hoof protection systems. This study introduces the Vienna Grip Tester (VGT), a novel sensor-based device developed to quantify rotational resistance—an important parameter for assessing hoof–surface interaction. The VGT utilizes a torque wrench and spring-loaded mechanism to simulate lateral hoof movements under a standardized vertical load (~700 N), enabling objective grip measurements across different conditions. Twenty combinations of hoof protection (barefoot, traditional iron shoe, and two glue-on models) and surfaces (sand, sand with fiber at 25 °C and −18 °C, frozen sand, and turf) were tested, yielding 305 torque measurements. Statistical analysis (repeated-measures ANOVA with Bonferroni correction) revealed significant differences in grip among surface types and hoof protection systems. Frozen surfaces (SDAF (31 ± 8.9 Nm and SDF 33 ± 8.7 Nm, p < 0.001) exhibited the highest grip, while dry sand (SDA (18.3 ± 3.3 Nm, p < 0.001) showed the lowest. Glue-on shoes (glue-on grip, 26 ± 10 Nm; glue-on, 25 ± 10 Nm) consistently provided superior grip compared to traditional or unshod hooves (bare hoof, 21 ± 7 Nm). These results validate the VGT as a reliable and practical tool for measuring hoof–surface grip, with potential applications in injury prevention, hoof protection development, and surface optimization in equestrian sports. Full article

Bolt connections are a critical component in steel structure design. After a period of operation, bolts in steel structures may experience loosening due to prolonged external forces or fatigue, posing a potential threat to overall structural safety. Currently, the practical method for detecting loose bolts in steel structures typically involves contact-based assessment, specifically using a torque wrench for testing. However, given the numerous bolts in a connection design, this contact-based evaluation method is inefficient for large-scale bridge bolt connection areas and is extremely time-consuming. To address this issue, this preliminary study explores the use of infrared thermography to assess bolt temperature changes during connection behavior and further evaluate bolt tightness. The analysis method integrates advanced image processing and time series analysis techniques to identify abnormal temperature distribution and temperature gradients in the connection area, establishing quantifiable indicators for bolt temperature status. Full article

In this paper, we present the design and control of a novel aerial vehicle inspired by the biomechanics of a rabbit named “Flybbit”. Flybbit consists of two main components, namely a movable “Ears” part and a rigid “Body” part, forming a composite flying system with five controllable degrees of freedom (DOFs). The “Ears” part is equipped with two tiltable motors paired with optional-sized propellers, enabling additional thrust generation and flight stability maintenance, and the “Body” part incorporates four fixed motors, analogous to a rabbit’s limbs, to provide the primary propulsion. To fully exploit the actuation capability, we derive the system dynamics and introduce a dynamic control allocation method with an adaptive strategy to mitigate actuator saturation during complex combined maneuvers. Furthermore, we analyze the differential flatness property and develop a nonlinear inverse dynamics controller enhanced with hybrid external wrench estimation, enabling accurate trajectory tracking in five DOFs. Flybbit supports both manual operation via RC and autonomous flight via onboard computation. Comprehensive simulations and real-world experiments validate the proposed design and control framework. Full article

Controlling legged robots to run at high speeds or to traverse complex terrains remains challenging due to the difficulty of handling the interaction between the robot and the ground. Impedance control and model predictive control are widely used to account for ground reaction forces (GRFs) during dynamic locomotion. This paper introduces a model predictive impedance control (MPIC) method that combines the advantages of both strategies and applies it to a quadruped robot. The proposed approach reformulates MPIC within the single rigid body model (SRBM) framework and derives linear inequality constraints for the equivalent wrench, allowing explicit consideration of GRF limits while retaining compliant behavior against ground impacts and external disturbances. Furthermore, a novel optimized gait pattern based on a simplified dynamic model is introduced to minimize the effect of GRFs on the robot. The resulting gait improves stability compared to conventional gait patterns while maintaining a similar level of energy efficiency. The proposed method is validated through various simulations under diverse conditions. The results demonstrate that it enables the quadruped robot to run at a speed of 12 m/s while maintaining stability against repeated lateral disturbances. Full article

The scope of this paper is the development of a cost-effective wireless torque measurement system for vehicle drivetrain shafts. The prototype integrates strain gauges, an HX711 conditioner, a Wemos D1 Mini ESP8266, and a rechargeable battery directly on the rotating shaft, forming a self-contained sensor node. Calibration against a certified dynamometric wrench confirmed an operating span of ±5–50 N·m. Within this range, the device achieved a mean absolute error of 0.559 N·m. It also maintained precision better than ±2.5 N·m at 95% confidence, while real-time data were transmitted via Wi-Fi. The total component cost is below EUR 30 based on current prices. The novelty of this proof-of-concept implementation demonstrates that reliable, IoT-enabled torque sensing can be realized with low-cost, readily available parts. The paper details assembly, calibration, and deployment procedures, providing a transparent pathway for replication. By aligning with Industry 4.0 requirements for smart, connected equipment, the proposed torque measurement system offers an affordable solution for process monitoring and predictive maintenance in automotive and industrial settings. Full article

Background and Objective: Match analysis plays a vital role in forming the scientific foundation of training and guiding strategic decision-making in wrestling. By objectively evaluating athletes’ technical and tactical performances, coaches and athletes can optimize preparation and in-match strategies. This study aimed to analyze the technical and tactical characteristics of medal matches in Greco-Roman (GR), Freestyle (FS), and Women’s Wrestling (WW) at the 2024 European Wrestling Championships. Methods: A total of 54 elite-level matches (18 from each style), held in Bucharest between 12 and 18 February, 2024, were retrospectively analyzed. Three expert observers evaluated the matches using video footage from the United World Wrestling (UWW) archive. Descriptive statistics were performed using SPSS 25.0. Results: Across 301 recorded actions, 2-point techniques (52.16%) and 1-point techniques (43.85%) were dominant; only 3.99% were 4-point actions. GR primarily utilized body lock and gut wrench; FS favored single-leg attacks and leg lace. In WW, the scores were obtained from techniques applied in the par terre position with a high frequency (60.8%). Most victories in all styles occurred by points rather than technical superiority or falls. Conclusion: The findings reveal a strategic preference for low-risk, controlled techniques in high-level matches. These insights can inform evidence-based training and match preparation for future championships. Full article

The Karak Wadi Al Fayha Fault (KWF) is a major NW-trending intraplate wrench fault system extending over 325 km from Western Karak in Jordan to Wadi Al Fayha in Saudi Arabia. Structurally linked to the Precambrian Najd Fault System, the KWF has been previously mapped using field observations, gravity, magnetic, and reflection seismic methods. However, these approaches lacked the vertical resolution necessary to characterize its shallow structure, leaving its influence on recent deposits and surface topography poorly understood. This study employs reflection seismic sections integrated with a Digital Elevation Model to refine terrain analysis and enhance fault mechanism solutions for determining the regional stress field pattern. Our results provide compelling evidence of the KWF’s upward propagation into the surface, as demonstrated by deformation of the uppermost Cretaceous and Cenozoic successions, distinct geomorphic features in the Digital Elevation Model, alignment of earthquake epicenters along the fault, and active landslides associated with its movement. We suggest that the reactivation of the KWF has been influenced by changing stress fields from the Late Cretaceous (Turonian) to the present. The Northwestern Arabian plate has undergone multiple tectonic stress transitions, including WNW–ESE compression associated with the Syrian Arc Fold-Belt system (Turonian–Plio-Pleistocene) and subsequent NNE–SSW extension linked to Red Sea rifting (Neogene–present). The analysis of fault mechanism solutions suggests that the latest fault movements result from the continued activity of the Irbid Rift event (Eocene) and the Dead Sea Transform Fault since the Miocene. Full article

The flow rate through hydraulic resistance increases with the pressure drop across it, but this correlation is no longer valid under cavitation conditions. This study investigates choked flow in calibrated screw-in orifices, widely used for control and damping in fluid power components. An experimental campaign was conducted on orifices with diameters ranging from 1 to 0.4 mm at various upstream pressures using hydraulic oil. A computational fluid dynamics (CFD) model was developed and validated against experiments, then used to analyze the effects of geometric parameters such as edge chamfers, hex wrench sockets, and length-to-diameter ratio. From CFD results, an analytical correlation between flow rate and pressure drop was derived, incorporating flow saturation effects. The study revealed that under saturation conditions, flow rate is largely unaffected by geometry, except for the ideal case of a perfectly sharp-edged orifice, which is rarely encountered. Even minimal chamfers of a few hundredths of a millimeter make the restrictor non-ideal. The derived correlation can be integrated into lumped parameter models of fluid power components to account for choked flow. Full article

Traditional tendon-driven continuum robot (TDCR) models based on Cosserat rod theory often assume that tendon tension is a continuous wrench along the backbone. However, this assumption overlooks critical factors, including the discrete arrangement of disks, the segmented configuration of tensioned tendons, and the friction between tendons and guide holes. Additionally, tendon forces are not continuous but discrete, concentrated wrenches, with the frictional force magnitude and direction varying based on the TDCR’s bending configuration. We propose a TDCR modeling method that integrates Cosserat rod theory with a finite element approach to address these limitations. We construct a Cosserat rod model for the robot’s backbone, discretize the tendon geometry using the finite element method (FEM), and incorporate friction modeling between tendons and guide holes. Furthermore, we introduce an algorithm to determine the direction of friction forces, enhancing modeling accuracy. This approach results in a more realistic and comprehensive mathematical representation of TDCR behavior. Numerical simulations under various tendon-routing scenarios are conducted and compared with classical TDCR models. The results indicate that our friction-inclusive model improves accuracy, yielding an average configuration deviation of only 0.3% across different tendon routings. Experimental validation further confirms the model’s accuracy and robustness. Full article