Natural Motion Research Articles

Portable markerless hand motion capture system for determining the grasps performed in activities of daily living

ABSTRACT Upper-limb prostheses are either too expensive for many consumers or have a greatly simplified choice of actions. This research aims to enable an improvement to the quality of life for recipients of these devices by providing an understanding of how we use our hands in modern everyday life. To achieve this a taxonomy of grasps used in activities of daily living has been created. A portable motion capture system was developed to collect data. Thirteen participants’ hand movements were recorded (totalling 62 hours and 10 minutes of data). From these data, 38 and 22 grasps were observed from the left and right hands, respectively. The portable system effectively captured natural hand motions, which formed an updated taxonomy of grasps.

Research on the progress of neurorehabilitation

With the intensification of global aging problems, the incidence of central nervous system diseases such as stroke is getting higher and higher. At the same time, the number of disabled people has also increased. Amputation and neurological diseases are important causes of disability, and neurorehabilitation is an important method for restoring the nervous function and autonomous movement ability of the disabled. At present, neurorehabilitation methods commonly used in clinical treatment mainly include: wearing prosthetic limbs, functional electrical stimulation (FES) therapy, rehabilitation robots, and so on. The prosthetic limb refers to an artificial device used to replace the function of a lost limb. Many advanced technologies are being used to improve the motion control of prosthetics to achieve natural movement. FES is a technique that can improve physiological function or treat diseases by stimulating nerves or tissues through current, and has become one of the important means to promote nerve regeneration and restore motor function. Rehabilitation robots are the equipment that uses mechanical devices and advanced control technology to assist rehabilitation treatment and functional recovery. This article mainly discusses the current research progresses of prosthetic limbs, EFS and rehabilitation robots, so as to promote the development of neurorehabilitation.

Contrariety and Complementarity: Reading Spinoza’s Intersubjective Holism of Ideas with Aristotle’s Two Accounts of Motion

Do minds and ideas connect, interact, or even depend on each other, and if so, how exactly do they connect and interact? How to conceive of the mode and process of minds and ideas being in a network and connected in some way, that is, being intersubjective or social? Martin Lenz’s study Socializing Minds (2022) convincingly shows that, contrary to widespread opinion in philosophy of mind, at least some early modern philosophers, here Spinoza, Locke, and Hume, actually give a positive answer to the first question and present models that respond to the second question, thus, addressing what Lenz proposes to call ‘the contact problem’ and repudiating the idea that mentalism is necessarily bound to individualism. In this comment, I focus on a detail in Lenz’s reconstruction of Spinoza’s ‘metaphysical model’ of intersubjectivity of minds, namely the Aristotelian physical dynamism that would underlie Spinoza’s idea of the interaction of minds. While I agree that Spinoza’s model of the interaction of minds refers to the Aristotelian conception of motion, I argue that the guiding principle in natural motion is best understood not only in terms of contrariety but also in terms of complementarity. A closer reading of Aristotle’s theory of motion (kinēsis, metabolē) identifies two approaches to natural motion, one based on contrary principles, the other on complementary principles or powers (dynameis; potentiae). I suggest conceiving them as two sources for modelling natural motion and thus as two resources for a kinetic modelling of intersubjectivity and sociality. Admittedly, my proposal goes beyond Spinoza’s model of ideas in contact, and probably beyond Lenz's interpretation of that model, but it might enrich the imagination of the socialising of minds and ideas from a kinetic point of view, which, at least as I understand it, is precisely what Spinoza and Lenz thrive on.

Human-network regions as effective geographic units for disease mitigation

Susceptibility to infectious diseases such as COVID-19 depends on how those diseases spread. Many studies have examined the decrease in COVID-19 spread due to reduction in travel. However, less is known about how much functional geographic regions, which capture natural movements and social interactions, limit the spread of COVID-19. To determine boundaries between functional regions, we apply community-detection algorithms to large networks of mobility and social-media connections to construct geographic regions that reflect natural human movement and relationships at the county level in the coterminous United States. We measure COVID-19 case counts, case rates, and case-rate variations across adjacent counties and examine how often COVID-19 crosses the boundaries of these functional regions. We find that regions that we construct using GPS-trace networks and especially commute networks have the lowest COVID-19 case rates along the boundaries, so these regions may reflect natural partitions in COVID-19 transmission. Conversely, regions that we construct from geolocated Facebook friendships and Twitter connections yield less effective partitions. Our analysis reveals that regions that are derived from movement flows are more appropriate geographic units than states for making policy decisions about opening areas for activity, assessing vulnerability of populations, and allocating resources. Our insights are also relevant for policy decisions and public messaging in future emergency situations.

Characterizing ramp events in floating offshore wind power through a fully coupled electrical-mechanical mathematical model

Floating Offshore Wind Turbines (FOWTs) exhibit a noteworthy nonlinear low-frequency dynamic response during rated and higher wind-wave scenarios, leading to a substantial exacerbation of its power characteristics, power stability, and wind energy forecast reliability. This study develops a fully coupled FOWT model to investigate the impact of wind and wave loads on wind power ramp events (WPREs), which integrates mechanical and electrical factors, including a spar buoy FOWT with generator, converter, and aero-hydro-servo-elastic (AHSE) dynamics. Results indicate that the floating structure enables periodic and significant WPREs of FOWTs, as wave load and platform natural motion causing low and ultra-low frequency response. In contrast to bottom-fixed offshore wind turbines (OWT), FOWTs exhibit a supplementary decline in rated power output ranging from 7.9 % to 40.5 % during WPREs. Moreover, ramp peak mainly depends on the aerodynamic loads, but become sensitive to wave loads characterized by wave heights over 2.52 m. FOWT power performance is highly unstable within the rated wind speed range, under WPREs within ultra short time period, resulting in failure to meet grid standards, emphasizing the external need for targeted power compensation and power signal processing. Overall, this study highlights the importance of pitch motion and wave load impact for WPRE study of FOWTs.

Best Practices for Research in Virtual and Augmented Reality in Dermatology

Virtual reality (VR) and augmented reality (AR) technologies have advanced rapidly in recent years. These cutting-edge technologies provide dermatology researchers, educators, proceduralists, and patients with opportunities in new scientific horizons. VR is a technology that facilitates immersive human experiences by allowing users to connect with various simulated environments through natural head and hand movements, whereas AR supplements a user's perception of their real environment with virtual elements. Despite technological advancements, there is limited literature on the methodological steps for conducting rigorous VR and AR research in dermatology. Effective storyboarding, user-driven design, and interdisciplinary teamwork play a central role in ensuring that VR/AR applications meet the specific needs of dermatology clinical and research teams. We present a step-by-step approach for their design, team composition, and evaluation in dermatology research, medical education, procedures, and habit formation strategies. We also discuss current VR and AR dermatology applications and the importance of ethical and safety considerations in deploying this new technology.

Touch‐Enabled Self‐Powered Elastomeric Keypad for Mapping Human Input and an Emergency Alert via Triboelectric Effect

The demand for smart, flexible electronics and wearable devices has been increasing rapidly, thereby making the user comfortable by bridging the gap between humans and machines. Herein, groundbreaking research in the field of wearable triboelectric nanogenerators (TENGs) and their innovative applications are presented by exploring a novel silicone elastomer‐based TENG. Different approaches involve the creation of wearable flexion and ring sensors for harvesting biomechanical energy from the natural finger joint motions and for sensing finger movements, wherein the silicone film acts as triboelectric negative material and human skin acts as the positive material. Additionally, the article describes the development of a touch keypad comprising 12 silicone film‐based TENG devices arranged in a 3 × 4 keypad array. Each keypress results in triboelectrification, converting mechanical energy into electrical power. Integrating an Arduino microcontroller and a graphical user interface provides user‐friendly and interactive functionality for recognizing and visualizing keypresses. Most notably, the article introduces the novel concept of an emergency alarm system, the “global emergency tracker system,” employing the 12‐keypad array. Users can trigger security alerts by pressing specific key patterns, such as “SOS” or “911.” This work showcases the potential of TENGs in wearable technology, human–machine interfaces, and security systems, pushing the boundaries of energy harvesting and practical applications in diverse fields. The combination of materials, device designs, and applications highlights the innovative nature of this research, promising advancements in sustainable energy generation and personal safety.

Leyenes: A gaze-based text entry method using linear smooth pursuit and target speed

Gaze-based writing is one of the most widespread eye tracking applications for human–computer interaction. While eye tracking communication has traditionally been employed as an assistive technology, declining prices of eye trackers now make it a feasible alternative to keyboards or touchscreens in many contexts (for example, the interaction with public info points). In this paper we propose Leyenes, a text entry method based on smooth pursuit, a natural eye movement that occurs when the gaze follows a moving target. Our approach requires no explicit calibration by the user, allowing for more spontaneous interaction and enabling eye input even when calibration is difficult to achieve or maintain. To the best of our knowledge, Leyenes is the first text entry technique based on smooth pursuit that considers both (approximate) gaze speed and position and employs a linear interface instead of the more common circular layouts. The results of the user study we conducted show that the proposed solution is slow but robust, with a very low error rate, which makes it particularly suitable for extemporaneous writing of short text.

Astrotheology: The natural interface between hyperspace and the Trinity

Over the past few decades, physicists are seeking a unifying theory that could encapsulate the theories of general relativity and quantum mechanics, our understanding of the very big and the infinitesimal small, into one all-inclusive theory. This quest led to a renewed interest in the proposal of hyperspace, which states that the structure of space and time are folded into one another, creating multiple dimensions. The author believes that the biblical confession about the resurrected Christ could be beneficial to science and theology in this respect. Biblical testimony provides insight into the apparent natural and effortless movement of Christ between the different dimensions in nature. Astrotheology, as a nexus between the different disciplines, is well equipped to describe themeaning and implications of the resurrection with regard to the fabric of space-time. The author opines that it could facilitate as a natural interface between hyperspaceand the Trinity. This proposal aims to accentuate, from a scriptural point of view, that reality indeed comprises more than four dimensions and that astrotheology could make a significant epistemological contribution in the dialogue about hyperspace and God’s agency in creation.

ADVANCED ANALYSIS TOOLS FOR THE EUROPEAN GROUND MOTION SERVICE DATA

Abstract. This paper is focused on Advanced Differential Interferometric SAR (A-DInSAR). In the first part, the paper describes the European Ground Motion Service (EGMS), a new service of the Copernicus Land Monitoring Service. The EGMS provides consistent, regular, standardized, harmonized and reliable information regarding natural and anthropogenic ground motion over Europe. It is derived from A-DInSAR analysis of Copernicus Sentinel-1 data. The EGMS includes three main products: Basic, i.e. basic deformation maps delivered for individual and consistent frames of image stacks; Calibrated, i.e. deformation map integrated into a reference Global Navigation Satellite System network; and Ortho, which includes the East-West and Up-Down deformation, obtained by combining the ascending and descending results. The second part of the paper describes examples of data analysis. The first one is a clustering of PSI results, which highlights the so-called Active Deformation Areas (ADAs). The second one is an automatic classification of the ADAs. The third analysis concerns the differential deformation maps, which are useful to highlight areas where high deformation gradients occur. Such gradients are often associated to damages in buildings and infrastructures.

Linking microbiome and stress hormone responses in wild tropical treefrogs across continuous and fragmented forests

The amphibian skin microbiome is an important component of anti-pathogen defense, but the impact of environmental change on the link between microbiome composition and host stress remains unclear. In this study, we used radiotelemetry and host translocation to track microbiome composition and function, pathogen infection, and host stress over time across natural movement paths for the forest-associated treefrog, Boana faber. We found a negative correlation between cortisol levels and putative microbiome function for frogs translocated to forest fragments, indicating strong integration of host stress response and anti-pathogen potential of the microbiome. Additionally, we observed a capacity for resilience (resistance to structural change and functional loss) in the amphibian skin microbiome, with maintenance of putative pathogen-inhibitory function despite major temporal shifts in microbiome composition. Although microbiome community composition did not return to baseline during the study period, the rate of microbiome change indicated that forest fragmentation had more pronounced effects on microbiome composition than translocation alone. Our findings reveal associations between stress hormones and host microbiome defenses, with implications for resilience of amphibians and their associated microbes facing accelerated tropical deforestation.

Simplified Physical Model‐based Balance‐preserving Motion Re‐targeting for Physical Simulation

AbstractIn this study, we propose a novel motion re‐targeting framework that provides natural motions of target robot character models similar to the given source motions of a different skeletal structure. The natural target motion requires satisfying kinematic constraints to show a similar motion to the source motion although the kinematical structure between the source and the target character models differ from each other. Simultaneously, the target motion should maintain physically plausible features such as keeping the balance of the target character model. To handle the issue, we utilize a simple physics model (an inverted‐pendulum‐on‐a‐cart model) during the motion re‐targeting process. By interpreting the source motion's balancing property via the pendulum model, the target motion inherits the balancing property of the source motion. The inheritance is derived by performing the motion analysis to extract the necessary parameters for re‐targeting the pendulum model's motion pattern and parameter learning to estimate the suitable parameters for the target character model. Based on the simple physics inheritance, the proposed framework provides balance‐preserving target motions, even applicable to the full‐body physics simulation or a real robot control. We validate the framework by experimenting with motion re‐targeting from animal character and human character source models to the quadruped‐ and humanoid‐type target models with Muaythai punching, kicking and walking motions. We also implement comparisons with the existing methods to clarify the enhancement.

Synchronous and Fully Steerable Active Particle Systems for Enhanced Mimicking of Collective Motion in Nature.

The collective motion observed in living active matter, such as fish schools and bird flocks, is characterized by its dynamic and complex nature, involving various moving states and transitions. By tailoring physical interactions or incorporating information exchange capabilities, inanimate active particles can exhibit similar behavior. However, the lack of synchronous and arbitrary control over individual particles hinders their use as a test system for the study of more intricate collective motions in living species. Herein, a novel optical feedback control system that enables the mimicry of collective motion observed in living objects using active particles is proposed. This system allows for the experimental investigation of the velocity alignment, a seminal model of collective motion (known as the Vicsek model), in a microscale perturbed environment with controllable and realistic conditions. The spontaneous formation of different moving states and dynamic transitions between these states is observed. Additionally, the high robustness of the active-particle group at the critical density under the influence of different perturbations is quantitatively validated. These findings support the effectiveness of velocity alignment in real perturbed environments, thereby providing a versatile platform for fundamental studies on collective motion and the development of innovative swarm microrobotics.

Monitoring of the Surface Water Regime of the Sava River Alluvium in Serbia Using Geographic Information System (GIS) Techniques

In the spacious inundation area on the left bank of the lower course of the Sava River in Serbia, there is an abandoned meander Special Nature Reserve, “Obedska bara”, which represents a very important floodplain in this part of Europe. This area is characterized by an exceptional wealth of biodiversity with a significant presence of rare and endangered species of national and international importance. Hydrological conditions in the mentioned area were analyzed from the aspect of surface water movement in nature and conditions altered by human factors (after the construction of the road network, canals, etc.). The movement of surface water, i.e., the filling and emptying of the investigated area, parallel to the water level of the Sava River, is shown using a digital terrain model. Our simulation of the change in surface water level within the studied area included the display of underwater areas, both with the formation of a flood wave (i.e., increasing water level of the Sava) and with the outflow of water from the pond when the water level in the Sava was reduced in both scenarios (natural and conditions altered by human factors). GIS and terrain digitalization were used for geospatial and hydrological analyses and, based on this, maps that display endangered areas could be made. The obtained results show that the largest human impact was recorded at the water level of the Sava River 74 m above sea level. The aforementioned water regime changes were shown to negatively affect dominant vegetation, such as pedunculate oak and ash.

Facilitating question identification through natural intensity eyebrow movements in virtual avatars

In conversation, recognizing social actions (similar to ‘speech acts’) early is important to quickly understand the speaker’s intended message and to provide a fast response. Fast turns are typical for fundamental social actions like questions, since a long gap can indicate a dispreferred response. In multimodal face-to-face interaction, visual signals may contribute to this fast dynamic. The face is an important source of visual signalling, and previous research found that prevalent facial signals such as eyebrow movements facilitate the rapid recognition of questions. We aimed to investigate whether early eyebrow movements with natural movement intensities facilitate question identification, and whether specific intensities are more helpful in detecting questions. Participants were instructed to view videos of avatars where the presence of eyebrow movements (eyebrow frown or raise vs. no eyebrow movement) was manipulated, and to indicate whether the utterance in the video was a question or statement. Results showed higher accuracies for questions with eyebrow frowns, and faster response times for questions with eyebrow frowns and eyebrow raises. No additional effect was observed for the specific movement intensity. This suggests that eyebrow movements that are representative of naturalistic multimodal behaviour facilitate question recognition.

A New Method to Evaluate Pressure Distribution Using a 3D-Printed C2-C3 Cervical Spine Model with an Embedded Sensor Array

Cervical degenerative disc diseases such as myelopathy and radiculopathy often require conventional treatments like artificial cervical disc replacement or anterior cervical discectomy and fusion (ACDF). When designing a medical device, like the stand-alone cage, there are many design inputs to consider. However, the precise biomechanics of the force between the vertebrae and implanted devices under certain conditions require further investigation. In this study, a new method was developed to evaluate the pressure between the vertebrae and implanted devices by embedding a sensor array into a 3D-printed C2-C3 cervical spine. The 3D-printed cervical spine model was subjected to a range of axial loads while under flexion, extension, bending and compression conditions. Cables were used for the application of a preload and a robotic arm was used to recreate the natural spine motions (flexion, extension, and bending). To verify and predict the total pressure between the vertebrae and the implanted devices, a 3D finite element (FE) numerical mathematical model was developed. A preload was represented by applying 22 N of force on each of the anterior tubercles for the C2 vertebra. The results of this study suggest that the sensor is useful in identifying static pressure. The pressure with the robot arm was verified from the FE results under all conditions. This study indicates that the sensor array has promising potential to reduce the trial and error with implants for various surgical procedures, including multi-level artificial cervical disk replacement and ACDF, which may help clinicians to reduce pain, suffering, and costly follow-up procedures.

Contributed Session II: The relationship between temporal summation at detection threshold and fixational eye movements.

We studied the relationship between the threshold temporal summation of increment pulses and fixational eye-movements. Six participants completed a 2AFC increment detection task. Stimuli were 0.16 x 2.2 arcmin increments of 543 nm light presented via an AOSLO with a 60 Hz frame rate. Stimuli for temporal integration were two single frame presentations with a 16 ms (consecutive frames), 33 ms, 100 ms, or 300 ms inter-stimulus interval (ISI). Data were also collected for increments presented on a single frame. Stimuli were presented in either world-fixed coordinates (natural retinal image motion) or were stabilised on the retina. There were large differences in overall sensitivity across individuals, but the time-course of performance change with ISI was similar across participants. Thresholds for ISI=33 ms were close to performance with two consecutive frames, suggesting complete summation of light energy; whereas thresholds for ISI=300 ms were closer to the single-frame case, suggesting limited summation; and thresholds for ISI=100 ms were intermediate, suggesting residual summation. The effect of ISI on threshold was similar for stabilised stimuli and natural viewing, but there was a small trend towards lower thresholds for stabilised stimuli at short ISI and vice-versa at long ISI. We plan to present our results in the context of an ideal observer calculation that may clarify how the initial visual encoding, including temporal summation within cones, shapes performance.

Toward an Ecology of Disentanglement

Abstract The relationship between nature and culture is a major theme in the philosophical discourse on the Anthropocene. The best-known movements within Anthropocene thinking are ecomodernism and posthumanism. Both movements distance themselves from the idea that nature and culture are strictly separate domains. In the Anthropocene, this separation no longer appears tenable; nature and culture have become inextricably entangled. The world consists exclusively of hybrids, compositions of both human and nonhuman entities. Ecomodernists and posthumanists are of one mind in their criticism of the traditional nature movement, which believes that it can return to a past when nature and culture were still distinct entities and there was such a thing as “pristine” nature. I will argue that denying the possibility of any decoupling between humans and nonhumans will result in the latter being severely curtailed in their freedom to autonomously shape their own lives, and I will therefore argue for what I like to call an “ecology of disentanglement.”

EarSet: A Multi-Modal Dataset for Studying the Impact of Head and Facial Movements on In-Ear PPG Signals

Photoplethysmography (PPG) is a simple, yet powerful technique to study blood volume changes by measuring light intensity variations. However, PPG is severely affected by motion artifacts, which hinder its trustworthiness. This problem is pressing in earables since head movements and facial expressions cause skin and tissue displacements around and inside the ear. Understanding such artifacts is fundamental to the success of earables for accurate cardiovascular health monitoring. However, the lack of in-ear PPG datasets prevents the research community from tackling this challenge. In this work, we report on the design of an ear tip featuring a 3-channels PPG and a co-located 6-axis motion sensor. This, enables sensing PPG data at multiple wavelengths and the corresponding motion signature from both ears. Leveraging our device, we collected a multi-modal dataset from 30 participants while performing 16 natural motions, including both head/face and full body movements. This unique dataset will greatly support research towards making in-ear vital signs sensing more accurate and robust, thus unlocking the full potential of the next-generation PPG-equipped earables.

Chewing Analysis by Means of Electromagnetic Articulography: Current Developments and New Possibilities

Chewing is a complex procedure that involves sensory feedback and motor impulses controlled by the trigeminal system in the brainstem. The analysis of mandibular movement is a first approximation to understanding these mechanisms. Several recording methods have been tested to achieve this. Video, ultrasound, the use of external markers and kinesiographs are examples of recording systems used in research. Electromagnetic articulography is an alternative method to those previously mentioned. It consists of the use of electromagnetic fields and receiver coils. The receiver coils are placed on the points of interest and the 3D coordinates of movement are saved in binary files. In the Oral Physiology Laboratory of the Dental Sciences Research Center (Centro de Investigación en Ciencias Odontológicas—CICO), in the Faculty of Dentistry at the Universidad de La Frontera (Temuco, Chile) several research studies have been carried out using the AG501 3D EMA articulograph (Carstens Medizinelektronik, Lenglern, Germany). With this device, they developed a series of protocols to record mandibular movement and obtain new information, such as the 3D Posselt polygon, the area of each polygon, individualized masticatory cycles and speed and acceleration profiles. Other investigations have analyzed these parameters, but separately. The AG501 allows for holistic analysis of all these data without altering natural movement. A limitation of this technology is the interference generated by its metallic elements. The aim of the present work is to show the developed methods used to record mandibular movement in the CICO, using the AG501 and compare them with others used in several research studies.