Direction Of Relative Motion Research Articles

Multidigit tactile perception II:perceptual weighting during integration follows a leading-finger priority.

When we run our hand across a surface, each finger typically repeats the sensory stimulation that the leading finger has already experienced. Because of this redundancy, the leading finger may attract more attention and contribute more strongly when tactile signals are integrated across fingers to form an overall percept. To test this hypothesis, we re-analyzed data collected in a previous study (Arslanova I, Takamuku S, Gomi H, Haggard P, J Neurophysiol 128: 418-433, 2022), where two probes were moved in different directions on two different fingerpads and participants reported the probes' average direction. Here, we evaluate the relative contribution of each finger to the percept and examine whether multidigit integration gives priority to the leading finger. Although the hand actually remained static in these experiments, a "functional leading finger" could be defined with reference to the average direction of the stimuli and the direction of hand-object relative motion that this implied. When participants averaged the motion direction across fingers of the same hand, the leading finger received a higher weighting than the nonleading finger, even though this biased estimate of average direction. Importantly, this bias disappeared when averaging motion direction across the two hands. Both the reported average direction and its systematic relation to the difference between the individual stimulus directions were explained by a model of motion integration in which the sensory weighting of stimuli depends on the directions of the applied stimuli. Our finding supports the hypothesis that the leading finger, which often receives novel information in natural hand-object interactions, is prioritized in forming our tactile perception.NEW & NOTEWORTHY The capacity of the tactile system to process multiple simultaneous stimuli is restricted. One solution could be to prioritize input from more informative sources. Here, we show that sensory weighting accorded to each finger during multidigit touch is biased in a direction-dependent manner when different motions are delivered to the fingers of the same hand. We argue that tactile inputs are weighted based on purely geometric information to prioritize "novel" information from the leading finger.

A versatile semi-active magnetorheological inerter with energy harvesting and active control capabilities

Semi-active devices typically adjust the system’s damping coefficient to control vibration, offering advantages such as excellent performance and low power consumption. However, the output force of the traditional variable damping (VD) device can only be opposite to the relative motion direction of the device’s two terminals, which limits the vibration control performance. This paper introduces a versatile semi-active magnetorheological (MR) inerter with three operating modes, the VD, energy harvesting, and active control modes, to break through the performance bottleneck of traditional semi-active devices. The MR inerter combines two MR dampers and a flywheel, acting as the controllable units and energy sink. The built prototype is tested, and its parameters are identified. When the innovative semi-active inerter works with a corresponding control strategy to regulate the current in two MR dampers, it can achieve vibration energy storage and release. The harvested energy can help to reduce the high dependency of the semi-active output force on external inputs. The proposed semi-active inerter has excellent potential in the future applications.

Feature-Specific Salience Maps in Human Cortex.

Priority map theory is a leading framework for understanding how various aspects of stimulus displays and task demands guide visual attention. Per this theory, the visual system computes a priority map, which is a representation of visual space indexing the relative importance, or priority, of locations in the environment. Priority is computed based on both salience, defined based on image-computable properties; and relevance, defined by an individual's current goals, and is used to direct attention to the highest-priority locations for further processing. Computational theories suggest that priority maps identify salient locations based on individual feature dimensions (e.g., color, motion), which are integrated into an aggregate priority map. While widely accepted, a core assumption of this framework, the existence of independent feature dimension maps in visual cortex, remains untested. Here, we tested the hypothesis that retinotopic regions selective for specific feature dimensions (color or motion) in human cortex act as neural feature dimension maps, indexing salient locations based on their preferred feature. We used fMRI activation patterns to reconstruct spatial maps while male and female human participants viewed stimuli with salient regions defined by relative color or motion direction. Activation in reconstructed spatial maps was localized to the salient stimulus position in the display. Moreover, the strength of the stimulus representation was strongest in the ROI selective for the salience-defining feature. Together, these results suggest that feature-selective extrastriate visual regions highlight salient locations based on local feature contrast within their preferred feature dimensions, supporting their role as neural feature dimension maps.SIGNIFICANCE STATEMENT Identifying salient information is important for navigating the world. For example, it is critical to detect a quickly approaching car when crossing the street. Leading models of computer vision and visual search rely on compartmentalized salience computations based on individual features; however, there has been no direct empirical demonstration identifying neural regions as responsible for performing these dissociable operations. Here, we provide evidence of a critical double dissociation that neural activation patterns from color-selective regions prioritize the location of color-defined salience while minimally representing motion-defined salience, whereas motion-selective regions show the complementary result. These findings reveal that specialized cortical regions act as neural "feature dimension maps" that are used to index salient locations based on specific features to guide attention.

A general geometric transformation model for line-scan image registration

A reasonable geometric transformation model is the key to image registration. When the relative motion direction between the line-scan camera and the object is strictly parallel to the planar object, it is possible to align the image by using the eight-parameter geometric transformation model of the line-scan image. However, it will be invalid when the relative motion direction is arbitrary. Therefore, a new general geometric transformation model of line-scan images is proposed for line-scan image registration in this paper. Considering the different initial poses and motion directions of the line-scan camera, the proposed model is established based on the imaging model of the line-scan camera. In order to acquire line-scan images to verify the proposed model, a line-scan image acquisition system was built. The method based on feature points is used to register the line-scan images. The experimental results show that the proposed geometric transformation model can align the line-scan image collected under arbitrary relative motion direction, not just the parallel case. Besides, the statistical errors of the image feature point coordinates are the best performance after registration. The accuracy of the registration results is better than that of other existing geometric transformation models, which verifies the correctness and generality of the geometric transformation model of the line-scan camera proposed in this paper.

Self-adaptive retro-reflective Doppler cloak based on planar space-time modulated metasurfaces

As engineered electromagnetic covers based on (space-) time modulated metamaterials and metasurfaces, Doppler cloaks are able to compensate the Doppler effect induced by the motion of a scatterer, making it appear as if it were at rest to a detecting radar system. Perfect Doppler compensation can be theoretically always achieved for any relative velocity and motion direction of the cloaked scatterer with respect to the detecting system. However, the motion can be still detected from the cross section variation of the Doppler cloaked scatterer, especially under oblique incidence illumination. The challenge is, therefore, to have a proper Doppler compensation and maintain the amount of scattered energy toward the detection system as much constant as possible with respect to the illumination angle. In this Letter, we propose the design of self-adaptive retro-reflective planar Doppler cloak composed of a pair of space-time modulated metasurfaces: the first metasurface focuses the incident field in a specific location on the second metasurface, which is designed for enabling retro-reflection and Doppler frequency shift compensation. Here, the self-adaptive Doppler cloak is applied to a metallic planar reflector, moving toward its normal direction, and illuminated by an oblique plane wave. We demonstrate that the proposed Doppler cloak can perform frequency conversion and simultaneously maintain the radar cross section of the reflector as much stable as possible within an angular range of about 60° centered at the normal direction. The self-adaptive Doppler cloak may enhance the undetectability of cloaked moving objects.

AUV Path Planning in Dynamic Environment Based on Improved Artificial Potential Field Method Based on Visibility Graph

In order to solve the forced shaking problem of the Autonomous Underwater Vehicle (AUV) facing dynamic obstacles in the path planning when the Artificial Potential Field Method is used, a method of removing the shaking state based on a favorable path is proposed, and on this basis, Visibility Graph Method is used to optimize the path of the AUV to avoid dynamic obstacles. By judging the relative motion direction of AUV and dynamic obstacle, the moving direction of AUV is adjusted based on Visibility Graph Method when it is far away from the obstacle. When it is close to the obstacle, the direction conducive to approaching the target point is selected as the favorable forward direction to bypass the obstacle. The simulation results show that the dynamic obstacle avoidance path optimization method based on the Visibility Graph Method reduces the number of moving steps by about 19% compared with the traditional method when dealing with a single dynamic obstacle, and can be applied in complex environments with multiple dynamic obstacles.

Friction-induced planar vibration of two rigid plates

The dynamical model for friction-induced vibration of two rigid circular plates in point contact is studied in this paper. Besides the rotational motion in the circumferential direction that is normally regarded as the principal direction of relative motion, the two-dimensional translational motion is also considered for both rigid plates. The coupling of the translational motion and the rotational motion causes the direction of relative motion and friction force to shift from the circumferential direction and vary during vibration (in relation to the situation in which translational motion is absent), thereby greatly increasing the complexity of the dynamics of the friction-excited system. The system dynamics comprises two distinct states of motion, i.e., slip and stick, and the friction force during sticking is a reaction force enforcing the constraint of zero relative velocity, which cannot be explicitly expressed as a function of state variables, therefore the values of state variables and friction force in the state of stick cannot be directly obtained from the integration of equations of motion. To address this problem, two different methods are proposed and the accuracy and efficiency of the two numerical methods are subsequently examined. Both the linear stability and the nonlinear steady-state responses of the system are investigated. The numerical study demonstrates that the coupling of the translational motion and the rotational motion of the two rigid plates greatly expands the ranges of operating parameters for dynamic instability compared with those of the situation where the two rigid plates undergo only rotational motion, and results in rich bifurcation behaviours. Therefore this study underlies the necessity to take into account the oscillations of components that seem not to be in the principal direction of relative motion in the research of friction-induced vibration of mechanical systems.

Analysis of Aerobics Auxiliary Training Based on Deep Learning

With the in-depth integration of information technology and subject teaching, it is also an inevitable trend to apply modern information technology to aerobics teaching. In this paper, the N-best algorithm is used in the video and real-time camera in aerobics, so that the human posture parameters in a single-frame image can be estimated. By using the relative position and motion direction of each part of the human body to describe the characteristics of aerobics, the Laplace scoring method is used to reduce the dimension of the data, and the discriminant human motion feature vector with a strong local topological structure is obtained. Finally, the iterative self-organizing data analysis technology (ISODATA algorithm) is used to dynamically determine the keyframe. In the aerobics video keyframe extraction experiments, the ST-FMP model improves the recognition accuracy of nondeterministic body parts of the flexible hybrid articulated human model (FMP) by about 15 percentage points and achieves 81% keyframe extraction accuracy, which is better than the keyframe algorithms of KFE and motion block. The proposed algorithm is sensitive to human motion features and human pose and is suitable for motion video annotation review.

Study of typical electric two‐wheelers pre-crash scenarios using K-medoids clustering methodology based on video recordings in China

Crash safety of electric two-wheelers (ETWs) has been one of the most important safety issues in China due to their high proportion of involvement in traffic accidents. Automated Emergency Braking (AEB) systems have proven to be effective in reducing the number of fatalities and injuries in traffic accidents. Providing test scenarios is one of the fundamental tasks required for establishing a set of AEB test programs for ETWs. Compared to traditional in-depth accident data, accident data accompanied with video recordings provide more accurate accident information prior to a crash as both the traffic environment and the crash process can be observed from the video. In this study, a set of typical AEB test scenarios for ETWs was developed using accident data with video information. Video recordings of 630 car-to-ETW crashes in China from 2010 to 2021 were selected from the VRU Traffic Accident database with Video (VRU-TRAVi). A K-medoids11See Section 2.3 Cluster Analysis. cluster analysis was carried out based on variables including the collision time, visual obstruction, motion of the car and ETW before the collision, relative motion direction between the car and ETW, and the ETW type. The velocity information of cars and ETWs was also accounted for in each clustering scenario. Seven typical pre-crash scenarios were obtained, including five electric-scooter (E-scooter) scenarios (representing two scenarios where the ETWs are approaching the car from the left side, two scenarios where the ETWs are approaching the car in the same direction and another scenario where the ETWs are approaching the car in the opposite direction) and two electric-bike (E-bike) scenarios where the E-bikes are approaching the car in the perpendicular direction. Both E-bike scenarios are consistent with the E-scooter scenario except for the ETW type and velocity range; therefore, by combining the E-bike and E-scooter scenarios, five ETW scenarios were finally recommended as AEB test scenarios. By comparing with typical scenarios extracted based on the China In-Depth Accident Study (CIDAS) data and the China New Car Assessment Program (C-NCAP) test scenarios, the results show that future AEB test scenarios for ETWs should focus on scenarios with visual obstructions and scenarios where either the car or the ETW is turning, with a velocity range of 15–30 km/h for ETWs.

Understanding WiFi Signal Frequency Features for Position-Independent Gesture Sensing

Recent years have witnessed rapid development in the research area of WiFi sensing, which senses human activities in a contactless and non-intrusive manner. One major issue that hinders real-world deployment of these systems is position dependence, i.e., once the human target changes location and orientation, the sensing performance degrades significantly. Existing machine learning based methods aim to solve this problem by either generating high-dimensional features or transfer learning the environment knowledge. However, these methods require significant training effort and yet acquire limited improvement. In this paper, we start by understanding and analyzing the Doppler frequency shift in WiFi sensing. We then develop a WiFi frequency model to quantify the relationship between signal frequency and target position, motion direction and speed for human activities. Based on this theoretical model, we prove that the commonly-used movement speed and motion direction features are position dependent, and further identify movement fragments and relative motion direction changes as two position-independent features. Building upon the frequency model and the position-independent features, we design a suite of position-independent gestures and develop the gesture recognition system accordingly. Evaluation results show that under various conditions (i.e., different locations, orientations, environments, and persons), our system achieves more than 96 percent recognition accuracy without any training, significantly outperforming state-of-the-art machine learning based solutions.

The change in the wetting regime of a nanodroplet on a substrate with varying wettability: A molecular dynamics investigation

The effect of the triple-phase contact line (TPCL) on the wetting phenomenon has been extensively discussed during the past decade. Numerous attempts have also been made to quantify its characteristics based on thermodynamic or mechanical definitions. In this research, molecular dynamics simulation was used to define the term “vicinity of the TPCL” and its effect on the hydrophilic and hydrophobic behaviors of a water nanodroplet. A nanodroplet was placed on a substrate that was modified in a stepwise manner by growing a patch of heterogeneity from either the center of the substrate or from the sides. The relative direction of motion of the TPCL and the patch determined the pathway that the nanodroplet chooses in order to change its wetting regime from hydrophilic to hydrophobic and vice versa. A gradual change occurs when the TPCL and the heterogeneity move in the same direction, and an abrupt change takes place otherwise. In addition to the insights into the wetting phenomenon, the width of the TPCL is also discussed. The obtained data suggest that the effective width of the TPCL, δ, is different inside the perimeter of the nanodroplet from outside of it. Moreover, the value of δ for the abrupt pathway is twice as large as the gradual one. In conclusion, the width, or vicinity, of the TPCL depends on the type of the pathway and the configuration of the substrate-patch system and cannot be treated similarly in both cases.

Examination of an averaging method for estimating repulsion and attraction interactions in moving groups.

Groups of animals coordinate remarkable, coherent, movement patterns during periods of collective motion. Such movement patterns include the toroidal mills seen in fish shoals, highly aligned parallel motion like that of flocks of migrating birds, and the swarming of insects. Since the 1970's a wide range of collective motion models have been studied that prescribe rules of interaction between individuals, and that are capable of generating emergent patterns that are visually similar to those seen in real animal group. This does not necessarily mean that real animals apply exactly the same interactions as those prescribed in models. In more recent work, researchers have sought to infer the rules of interaction of real animals directly from tracking data, by using a number of techniques, including averaging methods. In one of the simplest formulations, the averaging methods determine the mean changes in the components of the velocity of an individual over time as a function of the relative coordinates of group mates. The averaging methods can also be used to estimate other closely related quantities including the mean relative direction of motion of group mates as a function of their relative coordinates. Since these methods for extracting interaction rules and related quantities from trajectory data are relatively new, the accuracy of these methods has had limited inspection. In this paper, we examine the ability of an averaging method to reveal prescribed rules of interaction from data generated by two individual based models for collective motion. Our work suggests that an averaging method can capture the qualitative features of underlying interactions from trajectory data alone, including repulsion and attraction effects evident in changes in speed and direction of motion, and the presence of a blind zone. However, our work also illustrates that the output from a simple averaging method can be affected by emergent group level patterns of movement, and the sizes of the regions over which repulsion and attraction effects are apparent can be distorted depending on how individuals combine interactions with multiple group mates.

Directional optimal reciprocal collision avoidance

A great amount of effort has been devoted to the study on self-separation assurance approach for civil aviation in the airspace with increasing density. In this article, the Optimal Reciprocal Collision Avoidance (ORCA) algorithm is modified to make it work for autonomous and decentralized collision avoidance for civil aircraft. Without considering the direction selectivity of collision-free maneuver, aircraft may select the relative parallel trajectories by deploying the ORCA algorithm in both decentralized and centralized way. As a result, the collision tends to be postponed to the next time horizon because civil aircraft need to return to original trajectories. Simultaneously, the unified rules can hardly be integrated into the approach due to the lack of direction selectivity for collision-free navigation. The process of separation assurance will be disorderly when multiple aircraft are involved. To solve the problem mentioned above, a new algorithm called Directional Optimal Reciprocal Collision Avoidance (DORCA) is proposed. The DORCA algorithm employs a vector rotation mode to construct the forbidden Velocity Obstacle (VO) set in order to improve the computation efficiency. In addition, the direction selectivity of maneuver is achieved through constructing the direction-constrained VO set according to the direction of relative motion in velocity space. Direction selectivity of the algorithm enables the process of collision avoidance to comply with the unified rules. A number of encounter scenarios are conducted to confirm the validity and feasibility of the proposed DORCA algorithm. In all scenarios tested, the direction selectivity of collision-free maneuver can be successfully integrated into the DORCA algorithm, and the algorithm is more efficient than the ORCA algorithm for collision avoidance in decentralized way.

Spitzer + VLTI-GRAVITY Measure the Lens Mass of a Nearby Microlensing Event

Abstract We report the lens mass and distance measurements of the nearby microlensing event TCP J05074264+2447555 (Kojima-1). We measure the microlens parallax vector using Spitzer and ground-based light curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this determination with the angular Einstein radius measured by VLTI-GRAVITY observations, we find that the lens is a star with mass at a distance D L = 429 ± 21 pc. We find that the blended light basically all comes from the lens. The lens-source proper motion is , so with currently available adaptive-optics instruments, the lens and source can be resolved in 2021. This is the first microlensing event whose lens mass is unambiguously measured by interferometry + satellite-parallax observations, which opens a new window for mass measurements of isolated objects such as stellar-mass black holes.

Kilonova Emission from Black Hole–Neutron Star Mergers. I. Viewing-angle-dependent Lightcurves

Abstract In this paper, we explore the viewing angle effect on black hole–neutron star (BH–NS) merger kilonova lightcurves. We extrapolate the fitting formulae for the mass and velocity of dynamical ejecta across a wide mass ratio range validated with 66 simulations and use them in kilonova lightcurve calculations. The calculated peak luminosity of a BH–NS merger kilonova is typically about a few times 1041 erg s−1, which is always ≲4.5 × 1041 erg s−1. This corresponds to AB absolute magnitudes fainter than ∼−15 mag in the optical and ∼−16 mag in the infrared. The dynamical ejecta usually contribute to the majority of the kilonova emission, as its projected photosphere area is much larger than that of the disk wind outflows. The fitted blackbody temperature and the observed multiband lightcurve shape are insensitive to the line of sight. The peak time of the observed multiband lightcurves, affected by the light-propagation effect, is related to the relative motion direction between the dynamical ejecta and the observer. The predicted peak luminosity, which changes with the projected photosphere area, only varies by a factor of ∼(2–3) (or by ∼1 mag) for different viewing angles. When taking the short-duration gamma-ray burst afterglow into account, for an on-axis geometry, the kilonova emission is usually outshone by the afterglow emission and can only be observed in the redder bands, especially in the K band at late times. Compared with GW 170817/AT 2017gfo, BH–NS merger kilonovae are optically dim but possibly infrared bright, and have lower fitting temperature at the same epoch after the merger.

Phonon-Induced Ratchet Motion of a Water Nanodroplet on a Supported Black Phosphorene.

Phonons are not supposed to carry any physical momentum as lattice vibrational modes; thus, it is believed no mass transport could be induced by phonons. In this Letter, we show that a ratchet motion of a water nanodroplet could be induced on a two-dimensional puckered lattice like black phosphorene (BP) by exciting its flexural phonons through a moving substrate. The water nanodroplet exhibits a forward motion along the armchair or a backward motion along the zigzag directions on a BP lattice that is supported on a substrate possessing a relative armchair or zigzag forward motion with BP. Through the analysis of the structure and vibrational density states of BP, it is found that in-plane lattice displacement asymmetry and the in-plane vibration asymmetry are induced by the excited flexural phonons, which determine the water nanodroplet motion as an anisotropic Brownian motor. Simulations of the nanodroplet motion as functions of the substrate relative motion speed and direction and also the substrate coupling strength with BP are performed. Results of the nanodroplet ratchet motion exhibit good agreement with the theoretical predications from calculating the Brownian motor asymmetry. Our findings reveal a promising mass transport strategy and a further understanding of phonon-related interactions in crystalline solids.

Clustering algorithm based on analytic hierarchy process in LTE-V2V

As a hot area of urban transportation, the development of internet of vehicles and related technologies has received widespread attention. This paper proposes an analytic hierarchy process clustering algorithm (AHP-CA) based on the analytic hierarchy process in the LTE vehicle self-organizing network in the scenario of urban two-direction road intersections. The AHP-CA algorithm introduces the average distance between vehicles, normalizes the average relative speed, and uses the average relative motion direction as the vehicle eigenvalue for the clustering index. The analytic hierarchy process (Analytic Hierarchy Process, AHP) is used to determine the weights of different vehicle feature values, and the appropriate nodes are selected as cluster heads by combining the weights. The simulation results verify the stability of the cluster head under different vehicle speeds and communication distances.

Velocity Estimation From a Single Linear Motion Blurred Image Using Discrete Cosine Transform

There is a growing trend to use a digital camera as an instrument to measure velocity instead of a regular sensor approach. This paper introduces a new proposal for estimating kinematic quantities, namely, the angle and the relative speed, from a single motion blur image using the discrete cosine transform (DCT). Motion blur is a common phenomenon present in images due to the relative movement between the camera and the objects, during sensor exposure to light. Today, this source of kinematic data is mostly dismissed. The introduced technique focuses on cases where the camera moves at a constant linear velocity while the background remains unchanged. 2250 motion blur pictures were shot for the angle experiments and 500 for the speed estimation experiments, in a light and distance controlled environment, using a belt motor slider driven at angles between 0° and 90° and 10 preset speeds. The DCT Hough and DCT Radon results were compared to discrete Fourier transform (DFT) Hough and DFT Radon algorithms for angle estimation. The mean absolute error of the DCT Radon method for direction estimation was 4.66°. In addition, the mean relative error for speed estimation of the DCT Pseudocepstrum was 5.15%. The innovative DCT frequency analysis proposals were more accurate than all competitors evaluated for the reconstruction of the point spread function that enables calculation of relative velocity and motion direction. These results demonstrate that cameras as an instrument can be used to measure velocity even using a single linear motion blur degraded image.

Characteristics analysis of rotor-rolling bearing coupled system with fit looseness fault and its verification

Outer ring of bearing fit looseness fault is a common fault. Scratch often appears in the inner surface of pedestal. The fit looseness fault mechanism is not clear. For rotor-rolling bearing system with fit looseness fault between rotor-bearing outer ring and pedestal, a rotor coupling dynamic model that the interaction of bearing outer ring and pedestal are considered. This model is different from the universal rubbing model, where the directions of relative motion between rotor and stator are not considered. Numerical integration method is used to obtain the response of the system where the rotor is established by FEM and the bearing outer ring and pedestal are established by lumped mass model. Firstly, modal test results and simulation results were used to verify the correctness of this model. Secondly, the role of tightening torque between bearing outer ring and pedestal is considered, and the response characteristics of bearing and rotor are analyzed when fit looseness fault is considered. Finally, comparing the simulation results with test results, the waveform and spectrum are similar, which verifies the correctness of the fit looseness model. The fit looseness fault characteristics are that the acceleration after noise reduction shows periodic impact, up and down asymmetry, multiple frequencies appear. A method by increasing tightening torque is put forward to control the vibration caused by fit looseness fault.

The Researches on Vehicle-borne Speed and Direction Detection Method Based on Binocular Image Matching

In order to realize accurate perception of vehicle speed and direction, a method for perceiving vehicle speed and direction accurately is proposed, which is based on road surface information images captured by two parallel vehicle-borne imaging devices. The interval time between two imaging devices is controlled accurately, so the overlapping road surface information images can be obtained. The relative motion distance and direction is calculated by image matching. The vehicle speed and direction can be calculated based on the calibration parameters and interval time. The experimental results show that the proposed method has high reliability and accuracy.