Position Variables Research Articles

The Intra-Examiner Variability in and Accuracy of Traditional Manual Diagnostics of Benign Paroxysmal Positional Vertigo: A Prospective Observational Cohort Study

Background/Objectives: Accurate head positioning is essential for diagnostics of benign paroxysmal positional vertigo (BPPV). This study aimed to quantify the head angles and angular velocities during traditional manual BPPV diagnostics in patients with positional vertigo. Methods: A prospective, observational cohort study was conducted at a tertiary university hospital outpatient clinic. One trained examiner performed the Supine Roll Test (SRT) and the Dix–Hallpike test (DHT) on 198 adults with positional vertigo. The primary outcomes included head angle variability and accuracy and angular velocity variability. The secondary outcomes examined the relationship between the head angle accuracy and participant-reported limitations. Results: The absolute variability for all head angles ranged from ±8.7° to ±11.0°. The yaw axis head angles during the DHT, particularly on the left side, had the highest relative variability (left DHT: coefficient of variance 0.29). Systematic errors included the yaw axis head angles undershooting the target (90°) by 19.7–23.8° during the SRT and the pitch axis head angles undershooting the target (120°) by 7.8–8.7° during the DHT. The left-sided yaw axis in the DHT was undershot by 11.8°, while the right-sided DHT angle was slightly overshot (2.5°). Right-sided yaw axis angles in the SRT and DHT were more accurate than the left-sided ones (right SRT: 19.9°; left SRT: 23.9°; p < 0.0001) (right DHT: 7.0°; left DHT: 13.2°; p < 0.0001). The regression analysis found no association between the participant-reported limitations and head angle accuracy. Conclusions: This study highlights the substantial variability and inaccuracies in head positioning during traditional manual BPPV diagnostics, supporting the relevance of a guidance system to improve BPPV diagnostics. Level of evidence: III. Trial registration: ClinicalTrials.gov identifier: NCT05846711.

In vivo kinematics during step ascent: Changes to the knee associated with osteoarthritis

BackgroundStair climbing is a kinematically demanding activity, essential for maintaining independence and quality of life, yet is often impaired in patients with knee osteoarthritis (OA). The purpose of this study was to examine differences in kinematics of a step-up movement between participants with osteoarthritis and asymptomatic controls. MethodsThirty participants with end-stage OA awaiting total knee arthroplasty (TKA) and twenty-eight sex and age-similar asymptomatic participants were recruited. Participants performed a step-up task which was imaged via single-plane fluoroscopy. 3-dimensional prosthesis computer-aided design models were registered to the fluoroscopy, yielding in-vivo kinematic data. Kinematic variables of position, displacement, and rate-of-change in six degrees of freedom were compared between the two groups. ResultsOA knees exhibited significantly different kinematics to asymptomatic knees during step-up. Knees with OA demonstrated a reduced terminal extension angle, inferior translation and increased internal rotation throughout the movement compared to asymptomatic. OA participants exhibited more variability in kinematic parameters compared to asymptomatic controls, reflecting the heterogeneity within OA pathology. ConclusionThe findings of this study indicate that knee kinematics, particularly rotation, differ significantly between OA and asymptomatic knees during step-up. Optimising rotational profiles in OA knee management could help optimise patient function and inform rehabilitation and surgical protocols.

The Effect of Managerial Humour on Counterproductive Work Behaviours in Sport Service Providers

The purpose of this study is to examine the effect of managerial humor on counterproductive work behaviors in sport organizations. Another aim of the study is to examine whether managerial humor and counterproductive work behaviors vary according to gender, age, marital status, and position variables. The study was prepared using the relational survey model and conducted on a voluntary basis. The questionnaire technique was used as a data collection tool in the study. In the study, coaches, facility supervisors and counseling staff in sports service companies located in the European side of Istanbul constitute the population and 322 personnel selected by convenience sampling method from this population constitute the sample. In addition to the personal information form, the perceived manager humor scale and the counterproductive work behavior scale were used in the study. The analysis of the study was transferred to the SPSS 25.0 package program, and after the Kolmogorov-Smirnov normality test, it was determined that the data did not show normal distribution. Reliability analysis was performed to determine the reliability levels of the total and subdimensions of the scales used in our study, and "Chronbach's Alpha Coefficient" was obtained. As a statistical analysis, Mann Whitney U, Kruskal Wallis and Spearman correlation analyses were applied to the research group. According to the results of the research, excessive use of humor in sports companies can cause counterproductive work behaviors by damaging business efficiency. In particular, sarcastic humor and rejectionist humor can cause problems between individuals by causing business productivity. Keywords: Behavior, Humor, Sports Businesses

How Does an Expert Artist Create Artwork? Skills and Strategies of an Expert Calligrapher Utilizing Ecological Constraints

How does an artist utilize ecological constraints to create artwork? What physical skills support this creative process? This paper presents three studies examining the bottom-up creative process of an expert calligrapher over 16 trials, analyzing the same case from different perspectives. The first study focuses on the calligrapher’s writing posture. It reveals that the calligrapher synchronized trunk and brush tip movements, flexibly altering whole-body coordination patterns depending on character forms. The second study investigates the modification process of the 17 characters written on the paper. The calligrapher progressively adjusted the form and layout of characters by establishing coordinative structures among the variables of character form and position, thus effectively utilizing the margins of the paper. The third study examines the calligrapher’s gaze searches. It shows that these searches allowed accurate adjustments of character shapes and layout by flexibly changing gaze direction distribution depending on the position of the paper and characters relative to the body. Collectively, the three studies demonstrate that the expert calligrapher’s key skill is the flexibility to make bottom-up adjustments to characters’ form and layout by actively utilizing the ecological constraints of the paper. This skill is supported by flexible gaze searches and a writing posture involving whole-body coordination.

Evaluation of an improved picket fence style test for routine MLC positional QA.

The aim was to develop and evaluate an EPID-based MLC positional test that addresses known weaknesses of the picket fence test and has sufficient accuracy so that the AAPM MPPG 8.b. MLC position action limit of±0.5mm can be implemented. Weaknesses and inaccuracies in the picket fence test were identified and a new test plan and analysis algorithm named stakitt was developed. Stakitt was evaluated for repeatability and for sensitivity on the Varian TrueBeam linac with both Millennium MLC and HDMLC and on a Varian Clinac with Millennium MLC. Sensitivity was tested via deliberate introduction of errors into the test plan of magnitude:±0.1,±0.5,±1.0 and±1.5mm. Measured sensitivity was compared to published sensitivity of the picket fence test. Additionally, a use case was presented based on results from a TrueBeam linac to highlight the effect of MLC backlash on MLC positions at non-zero gantry angles. Repeatability was observed to within 0.04mm (3 SD) with the TrueBeams being more repeatable than the Clinac. The deliberately introduced errors were accurately measured to within 0.28mm and were comparable to the traditional picket fence. Reduced accuracy was recorded for the HDMLC small leaves, which was attributed to an apparent variation in measured leaf width across the range of travel, which impacted the measurement of the leaf tip position. The clinical use case demonstrated variability in MLC leaf positions between gantry 90° and gantry 270° that were of the magnitude of the MLC backlash. The stakitt test addresses the weaknesses of the picket fence test and has accuracy appropriate for implementation of a±0.5mm action limit. However, such an action limit may not be currently practical at non-zero gantry angles due to the impact of MLC leaf backlash.

Economic, cultural, and social inequalities in potentially inappropriate medication: A nationwide survey- and register-based study in Denmark.

Potentially inappropriate medication (PIM) is associated with negative health outcomes and can serve as an indicator of treatment quality. Previous studies have identified social inequality in treatment but often relied on narrow understandings of social position or failed to account for mediation by differential disease risk among social groups. Understanding how social position influences PIM exposure is crucial for improving the targeting of treatment quality and addressing health disparities. This study investigates the association between social position and PIM, considering the mediation effect of long-term conditions. This cross-sectional study utilized data from the 2017 Danish National Health Survey, including 177,495 individuals aged 18 or older. Data were linked to national registers on individual-level. PIM was defined from the STOPP/START criteria and social position was assessed through indicators of economic, cultural, and social capital (from Bourdieu's Capital Theory). We analyzed odds ratios (ORs) and prevalence proportion differences (PPDs) for PIM using logistic regression, negative binomial regression, and generalized structural equation modeling. The models were adjusted for age and sex and analyzed separately for indicators of under- (START) and overtreatment (STOPP). The mediation analysis was conducted to separate direct and indirect effects via long-term conditions. Overall, 14.7% of participants were exposed to one or more PIMs, with START PIMs being more prevalent (12.5%) than STOPP PIMs (3.1%). All variables for social position except health education were associated with PIM in a dose-response pattern. Individuals with lower wealth (OR: 1.85 [95% CI 1.77, 1.94]), lower income (OR: 1.78 [95% CI 1.69, 1.87]), and lower education level (OR: 1.66 [95% CI 1.56, 1.76]) exhibited the strongest associations with PIM. Similar associations were observed for immigrants, people with low social support, and people with limited social networks. The association with PIM remained significant for most variables after accounting for mediation by long-term conditions. The disparities were predominantly related to overtreatment and did not relate to the number of PIMs. The study's main limitation is the risk of reverse causation due to the complex nature of social position and medical treatment. The findings highlight significant social inequalities in PIM exposure, driven by both economic, cultural, and social capital despite a universal healthcare system. Understanding the social determinants of PIM can inform policies to reduce inappropriate medication use and improve healthcare quality and equity.

Segment Anything Model for fetal head-pubic symphysis segmentation in intrapartum ultrasound image analysis

The Angle of Progression (AoP), determined by the contour delineations of the pubic symphysis and fetal head (PSFH) in intrapartum ultrasound (US) images, is crucial for predicting delivery mode and significantly influences labor outcomes. However, automating AoP measurement based on PSFH segmentation remains challenging due to poor foreground-background contrast, blurred boundaries, and anatomical variability in shapes, sizes, and positions during labor. We propose a novel Segment Anything Model (SAM) framework, AoP-SAM, designed to enhance the PSFH segmentation, AoP measurement and outcome prediction, tackling the challenges of small target segmentation and accurate boundary segmentation. It synergistically combines CNNs and Transformers within a cooperative encoder to process complex spatial relationships and contextual information to segment the PSFH. In this encoder, we devise a multi-scale CNN branch to capture intrinsic local details, which compensates for the defects of the Transformer branch in extracting local features. Further, a cross-branch attention module is applied to improve prediction by fostering the effective information exchange and integration between two branches. Evaluations on the benchmark dataset demonstrate that our method achieves state-of-the-art (SOTA) performance. Specifically, in the PSFH segmentation task, the AoP measurement task, and the AoP classification task, we achieved a DSC of 0.8745 on the PS structure, a ΔAoP of 7.6743°, and an F1-score of 0.7719, respectively. Compared to the second-ranking method, these results represent improvements of 2.5%, 6.3%, and 1.1%. Our study presents a framework for intrapartum biometry, offering significant advancements in labor monitoring and delivery mode prediction in clinical settings. Future efforts will focus on optimizing AoP-SAM for resource-constrained environments, highlighting its potential for lightweight adaptation. https://github.com/maskoffs/AoP-SAM.

Synchronization of networked mechanical systems without velocity information

AbstractThis paper studies the synchronization problem in a network of interconnected mechanical systems where the velocity information of the interacting agents is unavailable. To achieve this, a distributed law related to the kinetic and potential energies of the considered system is proposed. Specifically, by introducing an auxiliary system and a distributed filter, it is shown that the proposed algorithm enables the synchronization of the considered system by merely using the local position measurements. Moreover, it is also shown that, compared with the existing literature, the derived synchronization conditions are irrelevant to the eigenvalues of Laplacian matrix, thus circumventing the global information of the underlying system. Moreover, on condition that the absolute position information is available, it is also shown that apart from the synchronization of agents, the discrepancy between the position variable of the original system and that of the auxiliary variable tends to zero eventually. Finally, a concrete example and some comparisons are conducted to support the formulated setup and the obtained theoretical results.

Psychological mood patterns among Jordanian handball players

The purpose of this study was to identify the prevailing mood patterns amongst handball players in Jordan. Therefore, this descriptive study was conducted on a sample consisting of (76) male handball players participating in the 2022/2023 Jordanian Handball League championship. The list of mood patterns for athletes was used as a data collection tool along with the following three statistical methods: Arithmetic mean, Standard deviations, and Two-Way ANOVA. The study results showed that the personal flexibility pattern emerged in first place with a high level and an arithmetic average of (2.3728). The cease operations pattern emerged second with a high level and an arithmetic average of (2.2556). The excitement operations pattern emerged third with a high level and an arithmetic average of (2.2257). Results relatively exhibited that there were no statistically significant differences in the level of mood patterns according to the variable of experience and player position amongst handball players. The researchers suggested a number of recommendations including, raising the awareness of handball players on psychological importance; in addition to mood preparation prior to the competitions. It is advised that players take courses and educational workshops that can be offered to athletes to enhance their psychological and physical performance Especially courses in regard to the excitement operations pattern, which obtained the lowest order among the three mood patterns.

Identifying successful football teams in the European player transfer network

This paper considers the European transfer market for professional football players as a network to study the relation between a team’s position in this network and performance in its domestic league. Our analysis is centered on eight top European leagues. The market in each season is represented as a weighted directed network capturing the transfers of players to or from the teams in these leagues, and we also consider the cumulative network over the past 28 years. We find that the overall structure of this transfer market network has properties commonly observed in real-world networks, such as a skewed degree distribution, high clustering, and small-world characteristics. To assess football teams we first construct a measure of within-league performance that is comparable across leagues. Regression analysis is used to relate league performance with both the network position and level of engagement of the team in the transfer market, under two complimentary setups. Network position variables include, e.g., betweenness centrality, closeness centrality and node clustering coefficient, whereas market engagement variables capture a team’s activity in the transfer market, e.g., total number of player transfers and total paid for players. For the season snapshots, the number of transfers correspond to weighted in- and out-degree. Our analysis first corroborates several recent findings relating aspects of market engagement with teams’ league performance. A higher number of incoming transfers indicates worse performance and better resourced teams perform better. Then, and across specifications, we find that network position variables remain salient even when engagement variables are already considered. This substantiates the notion in the existing literature that a high degree corresponds to better team performance and suggests that network aspects of trading strategy may affect a team’s success in their respective domestic league (or vice versa). In this sense, the approach and findings presented in this paper may in the future guide team’s player acquisition policies.

Mechanical properties and damage mechanism of SMAHC laminates

Abstract The combination of smart materials and composite materials to achieve lightweight and intelligent structures has been an important research direction in recent years. In this paper, a three-dimensional woven hybrid shape memory alloy (SMA actuator) is modularly implanted into a composite laminate to prepare a SMA hybrid composite (SMAHC) laminate. The orthogonal test was designed with the three variables of SMA actuator modular implantation position, SMA pre-strain and SMA number. According to the orthogonal test results and finite element results, the influence of the three variables on the stiffness before heating, the stiffness change rate after heating and the strength of SMAHC laminates was studied. According to the test index, the influence of the three variables on the results was further evaluated. The results show that the implantation position has the greatest influence on the mechanical properties of SMAHC laminates, followed by SMA pre-strain, and the number of SMA has the least influence. The location and form of damage of SMAHC laminates are further summarized, and the bending damage mechanism of SMAHC laminates is analyzed.

Time evolutions of information entropies in a one-dimensional Vlasov–Poisson system

A one-dimensional Vlasov–Poisson system is considered to elucidate how the information entropies of the probability distribution functions of the electron position and velocity variables evolve in the Landau damping process. Considering the initial condition given by the Maxwellian velocity distribution with the spatial density perturbation in the form of the cosine function of the position, we derive linear and quasilinear analytical solutions that accurately describe both early and late time behaviors of the distribution function and the electric field. The validity of these solutions is confirmed by comparison with numerical simulations based on contour dynamics. Using the quasilinear analytical solution, the time evolutions of the velocity distribution function and its kurtosis indicating deviation from the Gaussian distribution are evaluated with the accuracy of the squared perturbation amplitude. We also determine the time evolutions of the information entropies of the electron position and velocity variables and their mutual information. We further consider Coulomb collisions that relax the state in the late-time limit in the collisionless process to the thermal equilibrium state. In this collisional relaxation process, the mutual information of the position and velocity variables decreases to zero, while the total information entropy of the phase-space distribution function increases by the decrease in the mutual information and demonstrates the validity of Boltzmann's H-theorem.

PENGEMBANGAN KENDALI TERBANG BERBASIS SLIDING MODE CONTROL DENGAN ELIMINASI CHATTERING PADA QUADROTOR UNTUK MENGATASI GANGGUAN ANGIN TAK TENTU DI KAWASAN JAWA BARAT

Quadrotors are intrinsically unstable. If there is a sudden wind disturbance, this wind disturbance will be amplified so that the quadrotor's attitude becomes uncontrollable. West Java is one of the regions in Indonesia that has quite high wind disturbances. The recorded daily wind disturbance reached 6.99 m/s with a maximum value of 9.95 m/s. In this research, a control system based on the sliding mode control (SMC) algorithm is used. The advantage of this control algorithm is its ability to compensate for uncertain disturbances. This research investigates the implementation of the SMC control into a quadrotor by incorporating random wind disturbance aspects into the model. The research was carried out numerically with simulations using MATLAB/Simulink, with the position variables being the main focus. Quadrotor equipped with SMC has a lower mean error value for the desired position relative to the real position. This shows that the SMC control algorithm that has been created is able to properly overcome random wind disturbances that occur in the West Java area.

Observations of Sea Ice Edge Position in the Barents and Greenland Seas: Temporal Variability and Long‐Term Changes

AbstractSea ice edges play an essential role in the Earth's climate and weather systems through active atmosphere‐ice‐ocean interactions. However, our understanding of the observed positions of sea ice edges remains limited. The present study investigated, on seasonal and longer timescales from 1979 to 2023, the variability in sea ice edge positions in the Barents and Greenland Seas. We objectively derived the positions of sea ice edges based on satellite‐derived sea ice concentration gridded on a 25‐km resolution. In the Barents Sea, warm, narrow currents flow eastward along the northern and southern rims of the Central Bank. Until the mid‐2000s, sea ice edges fluctuated between these currents interannually during December–June, depending on the surface wind direction. However, after the mid‐2000s, the sea ice edges were mostly positioned near the northern current or farther to the north. Furthermore, sea ice edges during October–March were identified frequently near the warm current flowing along the continental slope in the northern Barents Sea after the mid‐2000s. In the Greenland Sea, sea ice edges were typically positioned near the East Greenland Current (EGC) throughout the year until 2006. However, sea ice edges in summer were located far to the west of the EGC after 2006. These observations suggest that the geographical relationship between sea ice edges and ocean currents has changed due to global warming.

Psychological distress, work environment quality, and motivation levels among nurses working in Saudi Arabia.

A favorable clinical environment and nurse motivation are both essential for achieving high-quality patient outcomes and organizational performance in healthcare systems, which can be highly distressing for nurses. The purpose of this study was thus to determine the associations among and influences of psychological distress, work environment quality, and motivation on one another. This was a cross-sectional, descriptive-correlational study conducted with a total sample of 204 nurses in two public tertiary hospitals. We used an online survey to collect nurses' responses, which comprised the Kessler Psychological Distress Scale-6, Brief Nurses' Practice Environment Scale, and Multidimensional Work Motivation Scale. We ran the necessary statistical analyses in SPSS version 28. We found that nurses' psychological distress, work environment quality, and motivation were moderate. A significant, positive, and moderate relationship existed between psychological distress and work environment quality, while nurses' educational level was statistically different with their motivation level. In the regression, only the nationality, current position, and work environment variables significantly influenced psychological distress. The hospital type also significantly influenced work environment quality. No variable was found to influence nurses' motivation level, though. We concluded that nurses' work environment quality and motivation are interconnected with the psychological stress they experience at work. Monitoring nurses' work environment quality, motivation levels, and psychological distress is thus vital to ensure better patient care.

The influence of lumbar vertebra and cage related factors on cage-endplate contact after lumbar interbody fusion: An in-vitro experimental study

Lumbar interbody fusion (LIF) using interbody cages is an established treatment for lumbar degenerative disc disease, but fusion results are known to be affected by risk factors such as bone mineral density (BMD), endplate geometry and cage position. At present, direct measurement of endplate-cage contact variables that affect LIF have not been fully identified. The aim of this study was to use cadaveric experiments to investigate the dependency between BMD, endplate geometry, cage parameters like type, orientation, position, and contact variables like stress and area. One vertebral body specimen from each of the five lumbar positions was harvested from five male donors. The lower half of each vertebra was potted and placed in a material testing machine (Instron 8874). A spinal cage was clamped to the machine then lowered to bring it into contact against the superior endplate. A lockable ball-joint was used to rotate the cage such that its inferior surface was congruent with the local endplate surface. A pressure sensor (Tekscan) was placed between the cage and endplate to record contact area and the peak and average contact pressures. Axial compression of 400 N was performed for five positions using a straight cage, and in one anterior position using a curved cage. The linear mixed model was utilised to perform data analyses for experimental results with statistical significance set at p < 0.05. The results indicated two trends toward significance for contact area, one for volumetric BMD (vBMD) of the vertebra (p = 0.081), and another for predicted contact area (p = 0.057). Peak contact pressure correlated significantly with vBMD (p = 0.041), and there was a trend between average contact pressure and lateral position of cage (p = 0.051). In addition, predicted contact area correlated significantly with cage orientation (p < 0.001). These results indicated that high vBMD of vertebra and a medially positioned cage led to higher contact pressures. Logically, low vBMD of vertebra and transverse cage orientation increased the contact area between the cage and endplate. In conclusion, the study identified significant influence of vBMD of vertebra, cage position and orientation on cage-endplate contact which may help to inform cage selection and design for LIF.

Quantifying uncertainty in time perception: A modified reproduction method.

In time perception research, we typically measure how an observer perceives time intervals by collecting data from multiple trials with a single estimate recorded on each. However, this gives us limited information about the observer's uncertainty for each estimate, which we usually measure from the variability across trials. Our study tested the potential of a modified reproduction task to provide a duration estimate as well as a measure of uncertainty on a single-trial basis. Participants were instructed to press and hold a key to temporally bracket the end of a learned duration (0.6-4 s) as narrowly as possible. Therefore, we expected the bracket's length to indicate the level of uncertainty. We compared this method to a conventional reproduction task. Taking the mid-point of the bracket as the duration estimate, we found that both methods produced equivalent data. Critically, the bracket length predicted reproduction variability, indicating that a single bracket obtained in an individual trial could potentially provide as much information as multiple reproductions. Additionally, relative variability in bracket start and end positions suggests a combination of additive and multiplicative noise components. Our findings highlight the bracket method as a more efficient and nuanced approach to measure time estimates and their associated uncertainty, expanding the methodological toolkit and opening new avenues in time perception research.

An accessible digital imaging workflow for multiplexed quantitative analysis of adult eye phenotypes in Drosophila melanogaster.

The compound eye of Drosophila melanogaster has long been a model for studying genetics, development, neurodegeneration, and heterochromatin. Imaging and morphometry of adult Drosophila and other insects is hampered by the low throughput, narrow focal plane, and small image sensors typical of stereomicroscope cameras. When data collection is distributed among many individuals or extended time periods, these limitations are compounded by inter-operator variability in lighting, sample positioning, focus, and post-acquisition processing. To address these limitations we developed a method for multiplexed quantitative analysis of adult Drosophila melanogaster phenotypes. Efficient data collection and analysis of up to 60 adult flies in a single image with standardized conditions eliminates inter-operator variability and enables precise quantitative comparison of morphology. Semi-automated data analysis using ImageJ and R reduces image manipulations, facilitates reproducibility, and supports emerging automated segmentation methods, as well as a wide range of graphical and statistical tools. These methods also serve as a low-cost hands-on introduction to imaging, data visualization, and statistical analysis for students and trainees.

Decoherence of a charged Brownian particle in a magnetic field: an analysis of the roles of coupling via position and momentum variables

Abstract The study of decoherence plays a key role in our understanding of the transition from the quantum to the classical world. Typically, one considers a system coupled to an external bath which forms a model for an open quantum system. While most of the studies pertain to a position coupling between the system and the environment, some involve a momentum coupling, giving rise to an anomalous diffusive model. Here we have gone beyond existing studies and analyzed the non-Markovian master equation, involving the quantum Langevin dynamics of a harmonically oscillating charged Brownian particle in the presence of a magnetic field and coupled to Ohmic (s = 1), sub-Ohmic (s &lt; 1) and super-Ohmic (s &gt; 1) heat baths via both position and momentum couplings. The presence of both position and momentum couplings leads to a stronger interaction with the environment, resulting in a faster loss of coherence compared to a situation where only position coupling is present. The rate of decoherence can be tuned by controlling the relative strengths of the position and momentum coupling parameters. In addition, the magnetic field results in the slowing down of the loss of information from the system, irrespective of the nature of coupling between the system and the bath. A faster decoherence rate is observed for higher values of the Ohmicity parameter ‘s’. Our results can be experimentally verified by designing a suitable ion trap setup.

Investigating and exploiting the impact of variability in resonator parameters on the vibration attenuation in locally resonant metamaterials.

Locally resonant metamaterials (LRMs) have recently emerged in the search for lightweight noise and vibration solutions. These materials have the ability to create stop bands, which arise from the sub-wavelength addition of identical resonators to a host structure and result in strong vibration attenuation. However, their manufacturing inevitably introduces variability such that the system as-manufactured often deviates significantly from the original as-designed. This can reduce attenuation performance, but may also broaden the attenuation band. This work focuses on the impact of variability within tolerance ranges in resonator properties on the vibration attenuation in metamaterial beams. Following a qualitative pre-study, two non-intrusive uncertainty propagation approaches are applied to find the upper and lower bounds of three performance metrics, by evaluating deterministic metamaterial models with uncertain parameters defined as interval variables. A global search approach is used and compared with a machine learning (ML)-based uncertainty propagation approach which significantly reduces the required number of simulations. Variability in resonator stiffnesses and masses is found to have the highest impact. Variability in the resonator positions only has a comparable impact for less deep sub-wavelength designs. The broadening potential of varying resonator properties is exploited in broadband optimization and the robustness of the optimized metamaterial is assessed.This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 2)'.