Change In Position Research Articles

How do gender stereotypes about leadership positions change in the face of a crisis?

How do gender stereotypes about leadership positions change in the face of a crisis?

Nonlinear soliton spiral induces coupled multimode dynamics in multi-stable dissipative metamaterials

With the robust and self-trapped properties, recent advances about soliton dynamics in multi-stable mechanical metamaterials have led to many innovative techniques from signal processing to robotics. This work proposes a multi-stable mechanical metamaterial driven by nonlinear dissipative solitons, in which the coupling and decoupling of multiple locomotion modes can be achieved. Based on a cylinder network with asymmetric energy landscape, the uniform field model of Landau theory is developed. During the theoretical calculation, the analytical solutions of several dissipative solitons are derived, which allow multiple special behaviors of solitary waves, such as wave velocity gaps, directional propagation and spiral phase transition. By incorporating such effects into robotic designs, a variety of complex movements can be achieved by a single structure, including hopping, rolling, rotating, swinging, bending and translational components. In particular, as excitation positions change, the mechanical metamaterial can flexibly switch multiple locomotion modes without changing configurations, e.g., spinning and spin-less, straight and oblique as well as coupled multimode movements. This work wishes to provide some new inspirations for the applications of nonlinear elastic wave metamaterials and phase transition theory in robotics.

Characteristics and Presentation of Orthostatic Hypertension in Community-Dwelling Older Adults

Abstract Background Standing poses a hemodynamic challenge for the cardiovascular system, regulated by neurohumoral reflexes. In 2023, an elevated blood pressure response upon standing was officially defined as a minimum 20 mmHg increase in systolic pressure during position changes, distinguishing Orthostatic Hypertension (OHT) as a condition where blood pressure exceeds 140 mmHg when standing. This new definition underscores the importance of understanding the implications of OHT on individuals' health and quality of life. Methods Retrospective study of the Technology Research for Independent Living (TRIL) Clinic at St. James’s Hospital, from August 2007 to May 2009. The population included healthy community-dwelling adults aged 60 and older. This study aimed to profile individuals with OHT, understand the predictors of this condition, and explore its association with biopsychosocial variables. Results In a study of 442 participants (67.7% female, mean age 72.7), we identified a prevalence rate of 12.9% for an exaggerated orthostatic pressor response and observed OHT in 6.1% of participants at the 120-second mark after standing. Additionally, significant associations were discovered between OHT and conditions such as heart failure, stroke, and the use of certain medications such as SSRI and ACE inhibitors. Conclusion The results of this study highlight the potential health consequences of OHT among older adults, particularly in those with pre-existing cardiovascular conditions. Further research is needed to explore this lesser-known but significant orthostatic disorder.

A Multi-Sensor Fusion Underwater Localization Method Based on Unscented Kalman Filter on Manifolds.

In recent years, the simplified computation of position and velocity changes in nonlinear systems using Lie groups and Lie algebra has been widely used in the study of robot localization systems. The unscented Kalman filter (UKF) can effectively deal with nonlinear systems through the unscented transformation, and in order to more accurately describe the robot localization system, the UKF method based on Lie groups has been studied successively. The computational complexity of the UKF on Lie groups is high, and in order to simplify its computation, the Lie groups are applied to the manifold, which efficiently handles the state and uncertainty and ensures that the system maintains the geometric constraints and computational simplicity during the updating process. In this paper, a multi-sensor fusion localization method based on an unscented Kalman filter on manifolds (UKF-M) is investigated. Firstly, a system model and a multi-sensor model are established based on an Autonomous Underwater Vehicle (AUV), and a corresponding UKF-M is designed for the system. Secondly, the multi-sensor fusion method is designed, and the fusion method is applied to the UKF-M. Finally, the proposed method is validated using an underwater cave dataset. The experiments demonstrate that the proposed method is suitable for underwater environments and can significantly correct the cumulative error in the trajectory estimation to achieve accurate underwater localization.

Semi-analytical Monte Carlo simulation of underwater target echoes from a small UAV-based oceanic lidar

Small unmanned airborne oceanic lidars are becoming increasingly popular for ocean surveys. They typically weigh less than 10 kg and can be mounted on commonly used commercial drones, making them easier to use than traditional large oceanic lidars, which typically weigh up to 80 kg and can only be carried on manned aircraft. Unmanned airborne oceanic lidars typically fly at lower altitudes and use higher laser emission frequencies, making them suitable for detecting underwater targets. However, most of the existing LiDAR underwater echo simulation models are designed for flat terrain and assume that the target fills the LiDAR receiving field of view, and there are few studies on the echoes of suspended targets smaller than the field of view range. Therefore, we combined ray tracing and semi-analytical Monte Carlo to model the laser echo energy of the underwater target. The study investigated the energy change of the target echo in the direction of deviation from the laser outgoing direction, and the impact of absorption and scattering coefficients on it. The difference in echo energy between different fields of view for extended and non-extended targets and the effect of water quality on it were explored. The echo waveforms of the target under different tilt angles were simulated, and it was found that the target echo pattern will be tilted with the change of tilt angle and offset position.

Local slope tolerance model for optical surfaces with distortion as the evaluation criterion

Ultra-precision imaging systems support cutting-edge scientific exploration and technological innovation. The continuous development of optical freeform and aspheric surface technology offers new possibilities for high-performance optical systems but also presents significant manufacturing challenges. In this paper, we derive and discuss in detail the impact of surface manufacturing errors on the image point positions of optical systems. The analysis reveals that among the manufacturing errors, the surface slope error is the primary factor driving positional changes in image points. Based on these insights, a local slope tolerance model using distortion as the evaluation criterion is proposed. This model specifies the slope error requirements at each point on the surface, ensuring the optical system's distortion meets the acceptable threshold during manufacturing. The model’s effectiveness is validated through an off-axis three-mirror freeform optical system and a Cassegrain aspheric optical system.

UAV Autonomous Navigation Based on Deep Reinforcement Learning in Highly Dynamic and High-Density Environments

Autonomous navigation of Unmanned Aerial Vehicles (UAVs) based on deep reinforcement learning (DRL) has made great progress. However, most studies assume relatively simple task scenarios and do not consider the impact of complex task scenarios on UAV flight performance. This paper proposes a DRL-based autonomous navigation algorithm for UAVs, which enables autonomous path planning for UAVs in high-density and highly dynamic environments. This algorithm proposes a state space representation method that contains position information and angle information by analyzing the impact of UAV position changes and angle changes on navigation performance in complex environments. In addition, a dynamic reward function is constructed based on a non-sparse reward function to balance the agent’s conservative behavior and exploratory behavior during the model training process. The results of multiple comparative experiments show that the proposed algorithm not only has the best autonomous navigation performance but also has the optimal flight efficiency in complex environments.

Impact of Diluents on Flame Stability With Blends of Natural Gas and Hydrogen

Abstract Two potential decarbonization pathways for natural gas (NG)-fueled gas turbine engines include blending hydrogen (H2) into NG and postcombustion carbon capture. H2 blending changes several combustion properties, including flame speed and stretch sensitivity. The use of post-combustion carbon capture systems is typically facilitated by the implementation of exhaust gas recirculation (EGR), where exhaust gases are injected into the inlet of the engine, increasing carbon dioxide (CO2) concentration at the outlet and, hence, increasing the efficiency of carbon capture technologies. In this work, we explore the impact of H2 blending and EGR on the stability of a swirl-stabilized, central-piloted flame. Mixtures of NG and H2 are tested at a range of different diluent compositions, with oxygen varied from 21% to 15% by volume in the oxidizer. In all cases, a constant adiabatic flame temperature is maintained to mimic the operation of a gas turbine at a given turbine inlet temperature. A variable-length combustor is used for testing, where combustor length is varied to understand the dynamic stability characteristics of the system. Results show that EGR and H2 work in opposition to each other, where higher levels of EGR result in poor flame holding and higher levels of H2 result in better flame holding. Increasing H2 generally increases the amplitude of thermoacoustic instability at each condition, a result of the change in flame position in this particular combustor. Importantly, H2 can be added to NG to improve flame holding without significantly decreasing CO2 levels in the products, showing that H2 blending can be a method for counteracting combustor operability issues that arise from high levels of EGR necessary to improve the efficiency of typical carbon capture systems.

An exploratory study of nursing tasks that induce physical and mental stress among hospital nurses

BackgroundNursing tasks are major contributing factors of nurses' stress. Identifying these stress-inducing tasks by hospital and department is the first step in devising practical strategies to address this issue. ObjectivesThis study aimed to develop a nursing task list by categorizing nursing tasks and identifying the ones that induced physical and mental stress among hospital nurses. MethodsThis descriptive exploratory study was conducted. In the first phase, the nursing task list was formulated based on a literature review and an expert content validity verification. In the second phase, the stress-inducing (both physical and mental) nursing tasks in different departments at two types of hospitals were investigated from 775 nurses. The data were analyzed using descriptive statistics, t-test, χ2 test and ANOVA performed using SPSS/WIN 26.0. ResultsThe nursing task of “exercise and position change” was identified to cause the highest physical stress across all five departments in both advanced general hospitals and general hospitals. Similarly, the nursing task “explanation of patients' condition upon request from the patients' family members” induced the greatest mental stress in both advanced general hospitals and general hospitals. Finally, “substitution for physicians: prescription” was identified as the greatest mental stress-inducing nursing task in general hospitals. ConclusionBased on a nursing task list developed, we determined which nursing tasks induce physical and mental stress in different departments at two types of hospitals. This foundational work will be crucial for exploring practical strategies to relieve nurses' stress.

Robust optical picometrology through data diversity

Topologically structured light contains deeply subwavelength features, such as phase singularities, and the scattering of such light can therefore be sensitive to the geometry or movement of scattering objects at such scales. Indeed, it has been shown recently that single-shot optical measurements can yield positional precision better than 100 pm (less than one five-thousandth of the wavelength λ) via a deep-learning-enabled analysis of scattering patterns. Measurement performance, and the extent to which it can be sustained, are constrained by the quality and depth of neural network training data and the stability of the experimental apparatus. Here, we show that a neural network can be trained through exposure to an extended envelope of instrumental/ambient noise conditions to robustly quantify picometric displacements of a target against orders-of-magnitude larger background fluctuations, to maintain precision and accuracy of 100–150 pm in optical measurements (at λ = 488 nm) of nanowire positional change. This capability opens up a range of application opportunities, for example in the optical study of nanostructural dynamics, stiction, material fatigue, and phase transitions.

Cardiac Output Directly Influences Intracardiac Air After Venous Air Embolism: An Echocardiographic Model Comparing Position Change on Intracardiac Air Bubble Clearance.

Venous air embolism (VAE) can cause significant morbidity and mortality. Prevention and management of VAE include cessation of air entrainment, positioning changes, and hemodynamic support. The degree to which position change and cardiac output (CO) moderate resolution of intracardiac air has not been rigorously studied using contemporary transesophageal echocardiography (TEE). This observational cohort-type study aimed to identify the effect of supine vs sitting positioning on the movement and resolution of intracardiac air. In 20 patients undergoing seated neurosurgery, central venous air aspiration catheters were placed through the median basilic vein. TEE was used to estimate the time required for clearance of agitated microbubbles from the right atrium and ventricle in both the supine and sitting position. Estimates of CO were also obtained echocardiographically in each position. Average clearance time was faster in the sitting vs the supine position with no significant difference in CO. A negative correlation between CO and right atrial clearance time across all patients was demonstrated with a Pearson coefficient of -0.4 (95% CI -0.07, -0.65) with P = .02. During VAE, both patient position and CO can significantly affect how bubbles move through intracardiac chambers. However, augmenting CO during VAE may be clinically more feasible, efficient, and productive than changing positioning-especially during crises unless the changing in position is intended to halt the entrainment of air. Further TEE studies of intravascular air movement affected by other position changes (lateral, reverse Trendelenburg) and vasopressors should be considered.

Effect of toroidal mode coupling on explosive dynamics of m/n = 3/1 double tearing mode

The CLT code was used to quantitatively study the impact of toroidal mode coupling on the explosive dynamics of the m/n = 3/1 double tearing mode. The focus of this study was on explosive reconnection processes, in which the energy bursts and the main mode no longer dominates when the separation between two rational surfaces is relatively large in the medium range. The development of higher m and n modes is facilitated by a relatively large separation between two rational surfaces, a small q min (the minimum value of the safety factor), or low resistivity. The relationships between the higher m and n mode development, explosive reconnection rate, and position exchange of 3/1 islands are summarized for the first time. Separation plays a more important role than q min in enhancing the development of higher m and n modes. At a relatively large separation, the good development of higher m and n modes greatly reduces the reconnection rate and suppresses the development of the main mode, resulting in the main mode not being able to develop sufficiently large to generate the position changes of 3/1 islands.

Numerical investigation and rapid prediction of the erosion rate of gate valve in gas-solid flow

Gate valves are essential control components in pneumatic conveying systems and often experience erosion on their sealing structures due to impacts from solid particles. The erosion leads to a degradation of the sealing effectiveness and, in severe cases, system malfunction. To address this issue, a numerical model based on computational fluid dynamics (CFD) is developed for the simplified two-dimensional gate valve. The two-way Euler-Lagrange method is utilized to investigate the characteristics of gas-solid two-phase flow and erosion rate. The simulation procedure is verified by comparing the simulation results with experimental data. Results show that the sealing surface separates the free shear layer above the cavity and a low-velocity zone is created on the sealing surface. The particles moving at the downstream bottom are the main particles that impact the sealing surface. The erosion results show that the maximum erosion rate occurs near the top of the sealing surface. And the low-velocity zone reduces the erosion rate within that region. Particle diameter, gas velocity, and valve opening have an important effect on erosion on the sealing surface. The erosion rate increases as the valve opening decreases. The value of the maximum erosion rate increases with particle diameter and gas velocity, and its position changes. Finally, based on the established numerical model, a prediction model for the sealing surface erosion rate is constructed using the surrogate model approach.

The preliminary study of the effects of individual musculoskeletally stable position in the treatment of temporomandibular disorders

BackgroundTemporomandibular Disorders (TMD) is the dysfunction of group of muscles and bones in the joint area, the main symptoms of TMD are the pain of the chewing muscles and (or) the temporomandibular joints, mandibular movement disorders and joint noise. This study was designed to explore the therapeutic effects following Individual Musculoskeletally Stable (IMS) position stabilization splint therapy for TMD patients using Fricton index, cone beam computed tomography (CBCT) and surface-Electromyogram (sEMG).MethodsIn this study, we enrolled 31 TMD patients (ranging from 18 to 26 years old, including 7 males and 24 females), first Fricton index was used to evaluate the clinical curative effect of TMD with the treatment of IMS stabilization splint; then CBCT was used to observe the TMJ condylar position changes of TMD before and after the treatment of IMS stabilization splint; finally sEMG was used to observe the changes of electromyography of anterior temporalis (AT) and masseter muscles (MM) of TMD before and after the treatment of IMS stabilization splint.ResultsThe course of treatment was 6–8 months, with an average of 7.6 months. After the IMS stabilization splint treatment, TMD symptoms relieved, especially in pain, mandibular movement disorder, but still slightly inferior in the treatment of joint noise. And there was a statistically significant difference in the anterior and inner joint space, the condyle had the tendency of moving forward and outward. AT presented reduction significantly of EMG value at rest position after treatment.ConclusionsIMS stabilization splint is a therapeutic reversible treatment for TMD, especially for pain and mandibular movement disorder; it produces effects of forward and outward condylar movement and elimination of the masticatory muscles antagonism.

Effect of filament positions on the properties of core yarns produced by embeddable and locatable spinning

To investigate the impact of positional changes of the strand and filament on the performance of embeddable and locatable spun (ELS) core yarns, various parameters were set for ELS systems to produce different yarns. The experiment involved controlling the distance between the strand and filament, as well as the distance between strands. The yarns were then subjected to systematic testing and analysis to evaluate their hairiness, dryness, strength, and abrasion resistance. The experimental results revealed some significant findings. Firstly, increasing the strand spacing from 1 mm to 5 mm led to a consecutive reduction (most by 33.3%) in hairiness for 3 mm distance. Secondly, when the strand spacing was set at 3 mm, the yarn strength increased by 6.8%. Furthermore, by maintaining a fixed strand spacing, increasing the distance between the filament and strand resulted in further reduction of yarn hairiness and improved overall yarn strength. Regarding abrasion resistance, the best performance was observed at a strand spacing of 2 mm. Additionally, the overall abrasion resistance of yarns with increasing strand spacing was superior to that of yarns with varying filament positions. Understanding the relationship between filament positions and yarn properties holds practical significance for the advancement of high-performance composite yarns.

An on-machine measurement and calibration method for incident laser error in dual-swing laser heads

The dual-swing laser head is essential for five-axis laser machining, yet its precision is greatly affected by the incident laser beam. Any positional or angular deviation in the laser can cause the focus spot position of the head to change continuously during rotation, thereby severely compromise the manufacturing performance of the head. However, the current calibration methods for the incident beam of dual-swing laser heads have issues with low accuracy and insufficient engineering applicability. This paper proposes an on-machine measurement and calibration method for incident laser error in dual-swing laser heads. An error model for the incident beam with a dual-swing laser head was established, from which the law of spot position changes caused by incident beam errors during the head's rotation was derived. Subsequently, following this law, a precision calibration method for the laser head's incident beam error was proposed, based on the theory of optical image height. Afterwards, an on-machine error measurement system was established on the dual-swing laser head, and the calibration method was verified through experiments. The results show that the use of this calibration method can improve the accuracy of the incident beam for dual-swing laser head to 0.071 mm, which is approximately 3–4 times better than traditional calibration methods, thereby significantly enhancing the manufacturing precision of the laser head.

Sense of embodiment with synchronized avatar during walking in mixed reality.

Gait guidance systems that synchronize the gait rhythm with an avatar in a mixed reality (MR) environment are attracting attention owing to their rehabilitation applications. More effective gait guidance can be achieved by changing body sensations for the sense of embodiment (SoE), which refers to the feeling of owning, controlling, and being inside a body in MR. This study investigated full-body synchronous motion between a human and a virtual avatar to enhance the SoE in walking with actual position changes in the real world. The full-body motion and gait rhythm were measured using body-worn inertial measurement units and a visual avatar was provided through a transparent head-mounted display. The results showed that the SoE of the participants was enhanced under higher synchronization conditions. In addition, questionnaire results showed that the SoE in the synchronous condition was significantly higher than that in the asynchronous condition, and the SoE in the self-avatar condition was significantly higher than that in the other-avatar condition. This indicates that a higher synchronization level with the appearance of an avatar leads to a stronger SoE in the human perception mechanism, which is important for potential application in medical or other fields.

The causes of changes in student positioning in group discussions using Polya’s problem-solving and <i>commognitive</i> approaches

This study aims to describe the causes of changes in student positioning during group discussions utilizing Polya’s problem-solving method and commognitive principles. The subjects of the study are mathematics education students from STKIP Taman Siswa Bima. Two groups were selected from 30 participants, each consisting of three individuals representing the roles of expert, facilitator, and novice. The research approach employed was qualitative exploratory. The findings indicate that changes in positioning were due to role shifts among group members, where group 1 changed from an initial positioning of EP1FP1NP1 to F’P1E’P1NP1, incorporating complete stages of Polya’s problem-solving process and commognitive components. Group 2 transitioned from EP2FP2NP2 to F’P2FP2NP2, reflecting an incomplete application of Polya’s problem-solving stages and commognitive components. Future research recommendations include examining how changes in student positioning occur in algebra problem-solving discussions using Polya’s problem-solving strategies and commognitive components, with a focus on individual student problem-solving within groups.

A Two-Scale Texture Modelling of AA1050 Aluminum Alloy after Accumulative Roll-Bonding (ARB)

Texture evolution during accumulative roll-bonding (ARB) is complicated because of the change in the through-thickness position that results from repeated cutting–stacking and roll-bonding. In this study, a macro–micro two-scale modeling was carried out to investigate the behaviors of texture evolution during ARB. The finite element method (FEM) was used to predict the strain history at a macro-scale, while a crystal plasticity FEM was used to reproduce the texture at a micro-scale. The texture evolution along three different cutting–stacking paths was traced and investigated. The patterns of texture transition between the rolling-type, shear-type, and random-type textures were studied by using area fractions of texture components, the distribution of textures, and the distribution of crystal rotation angles.

Effect of Positional Changes on Cerebral Perfusion in Parkinson's Disease Patients With Orthostatic Hypotension.

Orthostatic hypotension (OH) is one of the most common autonomic dysfunctions in Parkinson's disease (PD) patients. However, many patients with OH are asymptomatic. Conversely, orthostatic dizziness (OD) is not always associated with OH. We investigated the effects of positional changes on cerebral perfusion in patients with PD and OH. We enrolled 42 patients, comprising 31 PD patients and 11 healthy controls. All the subjects underwent the following clinical assessments: the OH questionnaire, head-up tilt test (HUTT) with transcranial Doppler (TCD), near-infrared spectroscopy, measurement of the change in oxygenated hemoglobin (ΔHboxy) during the squat-to-stand test (SST), measurement of the time derivative of total hemoglobin (DHbtot), and time taken to reach the peak (peak time [PT]) of DHbtot after restanding. The mean flow velocity change (ΔMFV) in the TCD during the HUTT failed to differentiate between the PD-OH(+) and PD-OH(-) groups. The change in oxygenated hemoglobin ΔHboxy was greater in the PD-OH(+) group, which persisted for 9 min until the end of the HUTT only in the left hemisphere. During SST, PT was significantly delayed in the left hemisphere in PD-OH(+) patients. Although TCD demonstrated no significant difference in ΔMFV, the parameters measured by near-infrared spectroscopy, such as ΔHboxy during HUTT and PT during the SST, significantly increased ΔHboxy or delayed PT in the left hemisphere of PD-OH(+). Positional changes have a detrimental effect on cerebral hemodynamics in patients with PD and OH, especially in the left hemisphere.