Silicon is widely used within energy, electro-mechanical, environmental devices by nanostructural control. As silicon parts constitute structural components whose size is ever decreasing, it is ...critical to understand the mechanical properties of single crystal silicon from precise measurements of load and displacement using microscopic sample in sub-micron and macroscopic scales. Here, the mechanical properties of single crystal silicon were precisely evaluated by bending tests at room temperature using microcantilever beam specimens having a several micron size. The microcantilever beam specimens were prepared using a focused ion beam technique, followed by loading the tip of the specimens. The smaller specimens deformed nonlinearly and then fractured. The unloaded specimen after nonlinear deformation showed permanent strain and many dislocations close to the region where high tensile stress was applied. This means that the nonlinear stress–strain relationship in the very high bending stress is determined by plastic deformation controlled by dislocation despite occurring at room temperature. The bending strength increased with a decrease in specimen size, and the smallest specimens had close to ideal strength. The size of the region where the dislocations accumulated in high density corresponded to the flaw size estimated from the fracture mechanics. This means that the bending strength of the microcantilever beam specimens of silicon is dominated by newly generated defects resulting from dislocations; in other words, the size effect of bending strength of silicon at the micrometer scale is controlled by the accumulation of newly formed dislocations because the dense dislocation region should be lower in a smaller-sized specimen.
Accomplishing motor function requires multimodal information, such as visual and haptic feedback, which induces a sense of ownership (SoO) over one's own body part. In this study, we developed a ...visual-haptic human machine interface that combines three different types of feedback (visual, haptic, and kinesthetic) in the context of passive hand-grasping motion and aimed to generate SoO over a virtual hand. We tested two conditions, both conditions the three set of feedback were synchronous, the first condition was in-phase, and the second condition was in antiphase. In both conditions, we utilized passive visual feedback (pre-recorded video of a real hand displayed), haptic feedback (balloon inflated and deflated), and kinesthetic feedback (finger movement following the balloon curvature). To quantify the SoO, the participants' reaction time was measured in response to a sense of threat. We found that most participants had a shorter reaction time under anti-phase condition, indicating that synchronous anti-phase of the multimodal system was better than in-phase condition for inducing a SoO of the virtual hand. We conclude that stronger haptic feedback has a key role in the SoO in accordance with visual information. Because the virtual hand is closing and the high pressure from the balloon against the hand creates the sensation of grasping and closing the hand, it appeared as though the person was closing his/her hand at the perceptual level.
Understanding the brain is important in the fields of science, medicine, and engineering. A promising approach to better understand the brain is through computing models. These models were adjusted ...to reproduce data collected from the brain. One of the most commonly used types of data in neuroscience comes from electroencephalography (EEG), which records the tiny voltages generated when neurons in the brain are activated. In this study, we propose a model based on complex networks of weakly connected dynamical systems (Hindmarsh-Rose neurons or Kuramoto oscillators), set to operate in a dynamic regime recognized as Collective Almost Synchronization (CAS). Our model not only successfully reproduces EEG data from both healthy and epileptic EEG signals, but it also predicts EEG features, the Hurst exponent, and the power spectrum. The proposed model is able to forecast EEG signals 5.76 s in the future. The average forecasting error was 9.22%. The random Kuramoto model produced the outstanding result for forecasting seizure EEG with an error of 11.21%.
In this study, we investigated the underlying mechanisms of a motor system that affects skills and strategies of expert dart throwers. Eight experts participated in our experiment and each subject ...performed 42 throws. Kinematics of the shoulder, elbow, wrist, and dart were recorded by six high-speed cameras (200 Hz). The vertical error curve over time was calculated based on both hand and dart trajectories to clarify their relationship and interaction, which could attribute to their skills. Moreover, the kinematics of the dart (speed and direction) and angular kinematics of the elbow and wrist at the time of release were investigated to elucidate which parameters constitute the throwing strategies of experts. Experimental results showed that expert's throwing can be classified into two strategies, i.e., reducing timing sensitivity and reducing timing error. These strategies were derived from the spatial and temporal controls of the hand trajectory. Moreover, we confirmed that the speed of the dart and angular acceleration of the wrist joint at the time of release were highly correlated with the time-window for successful release. These results imply that the two strategies are characterized not only by a spatiotemporal relationship between the hand and dart trajectories, but also by relationships with release kinematic parameters of the proximal joint and the dart. Understanding characteristics which lead to strategies of skilled throwers would provide effective training methodology for beginners.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Event-related desynchronization/synchronization (ERD/S) is an electroencephalogram (EEG) feature widely used as control signals for Brain-Computer Interfaces (BCIs). Nevertheless, the underlying ...neural mechanisms and functions of ERD/S are largely unknown, thus investigating them is crucial to improve the reliability of ERD/S-based BCIs. This study aimed to identify Motor Imagery (MI) conditions that enhance ERD/S. We investigated following three questions: 1) whether target-directed MI affects ERD/S, 2) whether MI with sound imagery affects ERD/S, and 3) whether ERD/S has a body part dependency of MI. Nine participants took part in the experiments of four MI conditions; they were asked to imagine right foot dorsiflexion (F), right foot dorsiflexion and the sound of a bass drum when the sole touched the floor (FS), right leg extension (L), and right leg extension directed toward a soccer ball (LT). Statistical comparison revealed that there were significant differences between conditions L and LT in beta-band ERD and conditions F and L in beta-band ERS. These results suggest that mental rehearsal of target-directed lower limb movement without real sensory stimuli can enhance beta-band ERD; furthermore, MI of foot dorsiflexion induces significantly larger beta-band ERS than that of leg extension. These findings could be exploited for the training of BCIs such as powered prosthetics for disabled person and neurorehabilitation system for stroke patients.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Regional cerebral activity related to attention may be more useful as an evaluation index for attention levels than conventional task performance score-based methods. We therefore researched whether ...the quantitative evaluation of attention using regional cerebral activity, measured using near-infrared spectroscopy (NIRS), was appropriate. NIRS signals during the continuous performance test (CPT), which is well known as an attention test, were measured and analyzed. We confirmed activities in the regions that may be associated with the right-side anterior cingulate cortex (ACC), and on the estimated dorsolateral prefrontal cortex (DLPFC). Furthermore, there was a high correlation between activity on the DLPFC related to executive function and the performance score. Our study using cerebral activity could not quantify attention, but it opened the possibility of quantifying levels of executive function.
In post-stroke rehabilitation, positive use of affected limbs in daily life is important to improve affected upper-limb function. Several studies have quantitatively evaluated the amount of ...upper-limb activity, but few have measured finger usage. In this study, we used a ring-shaped wearable device to measure upper-limb and finger usage simultaneously in hospitalized patients with hemiplegic stroke and investigated the association between finger usage and general clinical evaluation.
Twenty patients with hemiplegic stroke in an inpatient hospital participated in this study. All patients wore a ring-shaped wearable device on both hands for 9 h on the day of the intervention, and their finger and upper-limb usage were recorded. For the rehabilitation outcome assessments, the Fugl-Meyer Assessment of the Upper Extremity (FMA-UE), Simple Test for Evaluating Hand Function (STEF), Action Research Arm Test (ARAT), Motor Activity Log-14 (MAL), and Functional Independence Measure Motor (FIM-m) were performed and evaluated on the same day as the intervention.
Finger usage of the affected hand was moderately correlated with STEF (Formula: see text, Formula: see text) and STEF ratio (Formula: see text, Formula: see text). The finger-usage ratio was moderately correlated with FMA-UE (Formula: see text, Formula: see text) and ARAT (Formula: see text, Formula: see text), and strongly correlated with STEF (Formula: see text, Formula: see text) and STEF ratio (Formula: see text, Formula: see text). The upper-limb usage of the affected side was moderately correlated with FMA-UE (Formula: see text, Formula: see text), STEF (Formula: see text, Formula: see text) and STEF ratio (Formula: see text, Formula: see text), and strongly correlated with ARAT (Formula: see text, Formula: see text). The upper-limb usage ratio was moderately correlated with ARAT (Formula: see text, Formula: see text) and STEF (Formula: see text, Formula: see text), and strongly correlated with the STEF ratio (Formula: see text, Formula: see text). By contrast, there was no correlation between MAL and any of the measurements.
This measurement technique provided useful information that was not biased by the subjectivity of the patients and therapists.
Many motion sensor-based applications have been developed in recent years because they provide useful information about daily activities and current health status of users. However, most of these ...applications require knowledge of sensor positions. Therefore, this research focused on the problem of detecting sensor positions. We collected standing-still and walking sensor data at various body positions from ten subjects. The offset values were removed by subtracting the sensor data of standing-still phase from the walking data for each axis of each sensor unit. Our hierarchical classification technique is based on optimizing local classifiers. Many common features are computed, and informative features are selected for specific classifications. In this approach, local classifiers such as arm-side and hand-side discriminations yielded F1-scores of 0.99 and 1.00, correspondingly. Overall, the proposed method achieved an F1-score of 0.81 and 0.84 using accelerometers and gyroscopes, respectively. Furthermore, we also discuss contributive features and parameter tuning in this analysis.
The purpose of the study was to clarify the exothermic chemical reaction mechanisms in Ti/Si multilayered nanofilms under mechanical loading. We conducted in situ compression experiments of ...truncated-cone specimens of polycrystalline-Ti/amorphous-Si multilayered nanofilms (bilayer thickness of ~ 34 nm) deposited by electron beam evaporation within a scanning electron microscope. The true stress increased almost linearly with increasing true strain and the tangent modulus began to decrease at ~ 3 GPa. Transmission electron microscopy of the deformed specimens confirmed that each layer was plastically compressed in the stacking direction and expanded in the in-plane direction, resulting in an increase in the Ti/Si interface area. Selected-area electron diffraction analysis revealed that a new crystal structure, proposed to be Ti5Si4 and/or TiSi, was generated on the Ti/Si interface and within the Ti layer. In addition, the volume of the specimens decreased with increasing strain, supporting the hypothesis of a chemical reaction occurring. The chemical reaction was induced at the new reactive Ti/Si interface by the partial fracture of preexisting compound layers due to tensile stresses in the in-plane direction, and/or induced by diffusion-induced mixing through the thinned compound layers. These findings present the possibility of controlling the chemical reaction by local mechanical loading. The observed exothermic reaction can be used for various applications, such as local heating in large-scale micro- and nanodevices.
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