Static Motion Research Articles

Comparison of flow instabilities under static condition and marine motion conditions based on experiments

An experimental investigation was performed on two-phase flow instability with twin parallel rectangular channels under static condition and marine motion conditions. Marine motion conditions include inclination, fluctuation and rolling. The maximum inclination angle is 45°, maximum amplitude and acceleration of fluctuation are 0.8m and 1.9m2/s, respectively; maximum amplitude and angular acceleration of rolling are 30° and 0.5rad/s2, respectively. Test thermal parameters are 3–8MPa for pressure, 300–700kg/m2s for mass velocity, and 15–90°C for inlet subcooling in this experiment. Comparisons have been made on four aspects: (1) general observation of flow oscillation; (2) period of flow oscillation; (3) flow instability boundary heat flux; (4) flow instability zone under static condition and motion conditions. Contrary to what is observed under static condition, the flow oscillation under motion conditions is actually the superposition of thermal-induced oscillation and motion-induced oscillation. But further comparison indicates that the influence of marine motion conditions on flow stability is very limited. In general, the period of oscillation, flow instability boundary heat flux and distribution of instability zone are much more affected by thermal parameters than the motion conditions and the point to point comparison shows that the differences of boundary heat flux brought by motion is no more than ±5%. Finally, an empirical formula considering a pressure correction is correlated based on experimental data, which is applicable for the prediction of the instability boundary under both static and motion conditions.

A Video Saliency Detection Model in Compressed Domain

Saliency detection is widely used to extract regions of interest in images for various image processing applications. Recently, many saliency detection models have been proposed for video in uncompressed (pixel) domain. However, video over Internet is always stored in compressed domains, such as MPEG2, H.264, and MPEG4 Visual. In this paper, we propose a novel video saliency detection model based on feature contrast in compressed domain. Four types of features including luminance, color, texture, and motion are extracted from the discrete cosine transform coefficients and motion vectors in video bitstream. The static saliency map of unpredicted frames (I frames) is calculated on the basis of luminance, color, and texture features, while the motion saliency map of predicted frames (P and B frames) is computed by motion feature. A new fusion method is designed to combine the static saliency and motion saliency maps to get the final saliency map for each video frame. Due to the directly derived features in compressed domain, the proposed model can predict the salient regions efficiently for video frames. Experimental results on a public database show superior performance of the proposed video saliency detection model in compressed domain.

Learning Representations of Animated Motion Sequences—A Neural Model

AbstractThe detection and categorization of animate motions is a crucial task underlying social interaction and perceptual decision making. Neural representations of perceived animate objects are partially located in the primate cortical region STS, which is a region that receives convergent input from intermediate‐level form and motion representations. Populations of STS cells exist which are selectively responsive to specific animated motion sequences, such as walkers. It is still unclear how and to what extent form and motion information contribute to the generation of such representations and what kind of mechanisms are involved in the learning processes. The article develops a cortical model architecture for the unsupervised learning of animated motion sequence representations. We demonstrate how the model automatically selects significant motion patterns as well as meaningful static form prototypes characterized by a high degree of articulation. Such key poses are selectively reinforced during learning through a cross talk between the motion and form processing streams. Furthermore, we show how sequence‐selective representations are learned in STS by fusing static form and motion input from the segregated bottom‐up driving input streams. Cells in STS, in turn, feed their activities recurrently to their input sites along top‐down signal pathways. We show how such learned feedback connections enable predictions about future input as anticipation generated by sequence‐selective STS cells. Network simulations demonstrate the computational capacity of the proposed model by reproducing several experimental findings from neurosciences and by accounting for recent behavioral data.

Accurate Human Navigation Using Wearable Monocular Visual and Inertial Sensors

This paper presents a novel visual-inertial integration system for human navigation in free-living environments, where the measurements from wearable inertial and monocular visual sensors are integrated. The preestimated orientation, obtained from magnet, angular rate, and gravity sensors, is used to estimate the translation based on the data from the visual and inertial sensors. This has a significant effect on the performance of the fusion sensing strategy and makes the fusion procedure much easier, because the gravitational acceleration can be correctly removed from the accelerometer measurements before the fusion procedure, where a linear Kalman filter is selected as the fusion estimator. Furthermore, the use of preestimated orientation can help to eliminate erroneous point matches based on the properties of the pure camera translation and thus the computational requirements can be significantly reduced compared with the RANdom SAmple Consensus algorithm. In addition, an adaptive-frame rate single camera is selected to not only avoid motion blur based on the angular velocity and acceleration after compensation, but also to make an effect called visual zero-velocity update for the static motion. Thus, it can recover a more accurate baseline and meanwhile reduce the computational requirements. In particular, an absolute scale factor, which is usually lost in monocular camera tracking, can be obtained by introducing it into the estimator. Simulation and experimental results are presented for different environments with different types of movement and the results from a Pioneer robot are used to demonstrate the accuracy of the proposed method.

Analytical Method of the Performance of the Rotational INS based on the Spatial Accumulation of the Inertial Instrument Biases

Rotational inertial navigation system (INS) make the biases accumulate averagely to the directions of the navigation coordinate frame by rotating the inertial measurement unit, and eliminate the influence of the biases using the integration of the navigation computation, so that the precision of the INS can be improved effectively. According to the error suppression principle of the rotational INS, this work analyzes the accumulation of the biases in the navigation frame space per unit time by approximately discretizing the IMU rotation path, in order to compare the performance of the rotation modulation schemes with different angular motion statuses. By analyzing the constant angular rate rotation scheme, the linearly varied angular rate rotation schemes and the sine angular rate rotation scheme, the conclusion can be drawn that with the extension of the varying angular rate process, the spatial accumulation of the biases increase, which decreases the error suppression effect of rotation modulation. The conclusion was verified by the simulation of navigation errors. Therefore, the design principle of the rotation modulation schemes is reached that the angular rate should be kept constant in the single-axis rotation modulation and the dual-axis alternate rotation modulation

Nanometer Resolution Self‐Powered Static and Dynamic Motion Sensor Based on Micro‐Grated Triboelectrification

A one-dimensional displacement and speed sensing technology that consists of a pair of micro-grating structures and utilizes the coupling between the triboelectric effect and electrostatic induction is demonstrated. Its distinct advantages, including being self-powered, high resolution, large dynamic range, and long detecting distance, show extensive potential applications in automation, manufacturing, process control, and portable devices.

Quasidynamic calibration of stroboscopic scanning white light interferometer with a transfer standard

A stroboscopic scanning white light interferometer (SSWLI) can characterize both static features and motion in micro(nano)electromechanical system devices. SSWLI measurement results should be linked to the meter definition to be comparable and unambiguous. This traceability is achieved by careful error characterization and calibration of the interferometer. The main challenge in vertical scale calibration is to have a reference device with reproducible out-of-plane movement. A piezo-scanned flexure guided stage with capacitive sensor feedback was attached to a mirror and an Invar steel holder with a reference plane—forming a transfer standard that was calibrated by laser interferometry with 2.3 nm uncertainty. The moving mirror vertical position was then measured with the SSWLI, relative to the reference plane, between successive mirror position steppings. A light-emitting diode pulsed at 100 Hz with 0.5% duty cycle synchronized to the CCD camera and a halogen light source were used. Inside the scanned 14 μm range, the measured SSWLI scale amplification coefficient error was 0.12% with 4.5 nm repeatability of the steps. For SWLI measurements using a halogen lamp, the corresponding results were 0.05% and 6.7 nm. The presented methodology should permit accurate traceable calibration of the vertical scale of any SWLI.

Experimental Aeroelastic Response for a Freeplay Control Surface in Buffeting Flow

A partial control surface is constructed near the midspan of a NACA 0012 airfoil model with and without freeplay gaps. Static and dynamic control surface pitch motion measurements were performed in wind-tunnel tests at higher angles of attack including buffet or von Kármán vortex street flows. Two typical angles of attack, and 40 deg, and four freplay gaps in the pitch stiffness, , 0.5, 0.75, and 1.0 deg, are considered in the tests. This study has measured the static and dynamic responses of the flap pitch motion (with and without freeplay gaps) induced by the buffeting flow. Also, the buffeting frequency has been determined from the measured flap pitch responses. The buffet flow occurs at large angles of attack, and this leads to a larger preload from the aerodynamic forces and a larger static pitch equilibrium position. In this case, there is no limit cycle oscillations of the flap pitch motion induced by the freeplay gap to be found. Because the flap pitch motions are around the upper boundary of the freeplay gap, the dynamic pitch response has only a small change with different freeplay gaps. Buffeting flow excitation leads to a large dynamic response when the buffeting frequency is close to the flap natural frequency.

INFLUENCE OF THE STATIC IMAGES THAT EVOKE ILLUSORY MOTION PERCEPTION ON THE EYE MOVEMENTS AND THE BODY SWAY

Previous studies suggested that eye movements might be one of the factors that static images evoke illusory motion perception. The influence that visual information gives to posture control is also...

Investigating the neural regions involved in the storage of dynamic and static motion after effect using TMS

Investigating the neural regions involved in the storage of dynamic and static motion after effect using TMS

Three-dimensional comparison of static and dynamic scapular motion tracking techniques

The shoulder is complex and comprised of many moving parts. Accurately measuring shoulder rhythm is difficult. To classify shoulder rhythm and identify pathological movement, static measures have been the preferred method. However, dynamic measures are also used and can be less burdensome to obtain. The purpose of this paper was to determine how closely dynamic measures represent static measures using the same acromion marker cluster scapular tracking technique. Five shoulder angles were assessed for 24 participants using dynamic and static tracking techniques during humeral elevation in three planes (frontal, scapular, sagittal). ANOVAs were used to identify where significant differences existed for the factors of plane, elevation angle, and tracking technique (static, dynamic raising, dynamic lowering). All factors were significantly different for all shoulder angles (p<0.001), except for elevation plane in scapulothoracic protraction/retraction (p=0.955). Tracking techniques were influential (p<0.001), but the grouped mean differences fell below a clinically relevant 5° benchmark. There was large variation in mean differences of the techniques across individuals. While population averages are similar, individual static and dynamic shoulder assessments may be different. Caution should be taken when dynamic shoulder assessments are performed on individuals, as they may not reflect those obtained in static scapular motion tracking.

The influence of the intermolecular surface forces on the static deflection and pull-in instability of the micro/nano cantilever gyroscopes

In this paper, the effects of van der Waals and Casimir forces on the static deflection and pull-in instability of a micro/nano cantilever gyroscope with proof mass at its end are investigated. The micro/nano gyroscope is subjected to coupled bending motions which are related by base rotation and nonlinearities due to the geometry and the inertial terms. It is actuated and detected by capacitance plates which are placed on the proof mass. The extended Hamilton principle is used to find the equations governing the static behavior of the clamp-free micro/nano gyroscopes under electrostatic, Casimir and van der Waals forces. The equations of static motion are discritized by Galerkin’s decomposition method. The nonlinear equilibrium equations are solved analytically using homotopy perturbation method (HPM). The static response of the micro/nano gyroscopes to variations in the DC voltage across the drive and sense electrodes is obtained and the effects of different parameters on pull-in instability are investigated. The presented results can be used for accurate estimations of the instability and performance of the micro/nano gyroscopes.

Detection of Laminar Flow Separation and Transition on a NACA-0012 Airfoil Using Surface Hot-Films

A method for mapping the separation and transition of flow over a slowly pitching airfoil with high angular resolution is presented. An array of surface-mounted hot-film sensors is used to record simultaneous corresponding voltages. The method makes use of windowed correlation and spectral signatures of hot-film sensor voltages in synchronization with a servo-motor controlling airfoil pitch angle. Results are given for a NACA-0012 airfoil at three airspeeds at pitch angles of less than 6 deg. The airspeeds correspond to a region of known aeroelastic instability; they are situated between chord Reynolds numbers of 50,000 and 130,000. Tests in static and quasi-static pitch motion schedules were conducted. The quasi-static airfoil was sinusoidally pitching at 0.025 Hz between −6 deg and +6 deg (corresponding to a half-chord based reduced frequency between 0.0011 and 0.0020) and the detected separation and transition agreed very well with the static case. These results constitute a verification of the method used and provide insight into the size and location of the laminar separation bubble at transitional Reynolds numbers.

A heuristic model of stone comminution in shock wave lithotripsy

A heuristic model is presented to describe the overall progression of stone comminution in shock wave lithotripsy (SWL), accounting for the effects of shock wave dose and the average peak pressure, P+(avg), incident on the stone during the treatment. The model is developed through adaptation of the Weibull theory for brittle fracture, incorporating threshold values in dose and P+(avg) that are required to initiate fragmentation. The model is validated against experimental data of stone comminution from two stone types (hard and soft BegoStone) obtained at various positions in lithotripter fields produced by two shock wave sources of different beam width and pulse profile both in water and in 1,3-butanediol (which suppresses cavitation). Subsequently, the model is used to assess the performance of a newly developed acoustic lens for electromagnetic lithotripters in comparison with its original counterpart both under static and simulated respiratory motion. The results have demonstrated the predictive value of this heuristic model in elucidating the physical basis for improved performance of the new lens. The model also provides a rationale for the selection of SWL treatment protocols to achieve effective stone comminution without elevating the risk of tissue injury.

Towards a general method for estimating the unbalanced magnetic pull in mixed eccentricities motion including sufficiently large eccentricities in a hydropower generator and their validation against EM simulations

Electromagnetic (EM) analysis of hydropower generators is common practice but rotor whirling is little studied. This paper suggests a novel semi-analytical method for estimating the steady state unbalanced magnetic pull (UMP) when the rotor centre is undergoing mixed eccentricities motion. The ability to estimate the UMP for mixed eccentricities motion in finite element method (FEM)-based modelling software packages is rare. The proposed methodology in its formulation takes advantage of the fact that a purely dynamic eccentricity motion including non-synchronous whirling and a purely static eccentricity motion can be more amenable to implement in existing FEM-based EM modelling software products for UMP estimation. After these initial separate UMP results are obtained, the proposed method can be applied for virtually any mixed eccentricities motion cases up to sufficiently large eccentricities for quick analysis instead of running the mixed eccentricities simulations directly in a FEM-based software package. Good agreement between the UMP from the actual EM mixed eccentricities motion simulations in a commercial FEM-based software package and the UMP estimations by the novel method is made for a wide range of eccentricities that may commonly occur in practice. A modified feature selective validation (FSV) method, the FSV-UPC, is applied to assess the similarities and the differences in the UMP computations.

Effects of head orientation on the perceived tilt of a static line and 3D global motion.

Effects of head orientation on the perceived tilt of a static line and 3D global motion.

Sounding the gallery: video and the rise of art-music

Introduction 1 Composing with Technology: The Artist-Composer 2 Silent Music and Static Motion: The Audio-Visual History of Video 3 Towards the Spatial: Music, Art and the Audiovisual Environment 4 The Rise of Video Art-Music: 1963-1970 5 Interactivity, Mirrored Spaces and the Closed-Circuit Feed: Performing Video Epilogue: Towards the Twenty First Century Index

Accurate Estimation of Human Body Orientation From RGB-D Sensors

Accurate estimation of human body orientation can significantly enhance the analysis of human behavior, which is a fundamental task in the field of computer vision. However, existing orientation estimation methods cannot handle the various body poses and appearances. In this paper, we propose an innovative RGB-D-based orientation estimation method to address these challenges. By utilizing the RGB-D information, which can be real time acquired by RGB-D sensors, our method is robust to cluttered environment, illumination change and partial occlusions. Specifically, efficient static and motion cue extraction methods are proposed based on the RGB-D superpixels to reduce the noise of depth data. Since it is hard to discriminate all the 360 (°) orientation using static cues or motion cues independently, we propose to utilize a dynamic Bayesian network system (DBNS) to effectively employ the complementary nature of both static and motion cues. In order to verify our proposed method, we build a RGB-D-based human body orientation dataset that covers a wide diversity of poses and appearances. Our intensive experimental evaluations on this dataset demonstrate the effectiveness and efficiency of the proposed method.

Common (and multiple) neural substrates for static and dynamic motion after-effects: A rTMS investigation

IntroductionProlonged exposure to directional motion (adaptation) biases the perceived direction of subsequently presented test stimuli towards the opposite direction with respect to that of adaptation (i.e., motion after-effect; MAE). Different neural populations seem to be involved in the generation of the MAE, depending on the spatiotemporal characteristics of both adapting and test stimuli. Although the tuning mechanisms of the neural populations involved in the MAE have been psychophysically identified, the specific loci along the motion processing hierarchy where the different types of MAE take place is still debated. MethodIn this study, by using repetitive transcranial magnetic stimulation (rTMS) delivered during the inter-stimulus interval (ISI) between adapting and test patterns, we investigated the cortical locus of processing of static MAE (sMAE) and dynamic MAE (dMAE). ResultsResults showed that rTMS over V2/V3 or V5/MT decreased the perceived duration of both sMAE and dMAE, although rTMS over V2/V3 decreased mainly the perceived duration of sMAE. ConclusionssMAE and dMAE rely on the same cortical structures present at intermediate and low-levels of motion processing, although low-level visual areas (e.g., V2/V3) show a prevalence of neurons responsible for sMAE.

A saliency-driven robotic head with bio-inspired saccadic behaviors for social robotics

This paper presents a robotic head for social robots to attend to scene saliency with bio-inspired saccadic behaviors. Scene saliency is determined by measuring low-level static scene information, motion, and object prior knowledge. Towards the extracted saliency spots, the designed robotic head is able to turn gazes in a saccadic manner while obeying eye---head coordination laws with the proposed control scheme. The results of the simulation study and actual applications show the effectiveness of the proposed method in discovering of scene saliency and human-like head motion. The proposed techniques could possibly be applied to social robots to improve social sense and user experience in human---robot interaction.