Complex Relative Motion Research Articles

A Link Planning and DDoS Attack Detection in SDN Based Integrated Space-Terrestrial Networks

It is expected that 5G networks would require both great dependability and stability as fundamental requirements. The introduction of a satellite component into LTE (long term evolution) networks has emerged as an attractive solution for meeting these requirements. This will enable the provision of backup interoperability to essential base stations and the routing of traffic away from crowded locations. During peak hours, the demand for their terrestrial links must be increased or even adopted in the case of anticipated breakdown or repair. Integrated spaceterrestrial networks have shown to be an advantageous design due to its broad coverage and high precision. Designing a network routing plan is not a straightforward process when the complex relative motion of low-earth-orbit (LEO) satellites and unmanned aircraft systems (UAS) is considered (UAS). To be more explicit, the major difficulty is discovering how to locate acceptable connections in timevarying network settings to offer reliable and effective UAS data transmission. This study begins with a motion analysis of satellites and UASs to discover which access satellites are most suited for usage with UASs. This is done in order to resolve the aforementioned problem. In order to provide an effective and reliable intersatellite link (ISL) deployment between access satellites, double exponential smoothing (DES) is afterwards proposed as an alternative to traditional routing. This is required to guarantee the timely delivery of UAS data. The simulation results demonstrate that the proposed DES approach is both feasible and effective. A time series-based method known as DES is used to compute the port information in an adjustable manner, and an algorithm known as SVM (Support Vector Machine) is utilized to determine if a Distributed Denial of Service (DDoS) attack has really occurred. Experiments that are typical demonstrate that the UAS may greatly reduce the controller's workload while maintaining dependable detection accuracy.

An Efficient Approach for Coherent Integration Detection of High-speed Maneuvering Targets with Arbitrary-Order Doppler Frequency Migrations

In radar detection applications, high-speed maneuvering targets (HSMTs) are commonly encountered. Given the range cell migration (RCM) and arbitrary-order Doppler frequency migrations (DFMs) induced by the complex relative motions between the HSMT and radar, they usually present a great challenge for target detections. In addition, the complex Doppler ambiguity will further aggravate the difficulty in focusing of HSMT. To address these issues, an efficient approach for coherent integration detection of HSMTs is proposed. First, inspired by the symmetrical feature of range frequency, a new range frequency reversal transform is introduced to correct complex arbitrary-order DFMs simultaneously. After that, by exploiting the advantage of range-azimuth joint processing, a modified two-dimensional scaled Fourier transform is developed to remove the residual RCM and a well-focused result is thus achieved. Furthermore, a discrimination procedure is proposed to remove the spurious peak for cross terms of targets with the same parameters. The proposed method has an extremely low computational cost and does not need to know the target motion order a priori because the operations of multidimensional search and parameter estimation are avoided. It also handles complex arbitrary-order DFMs, blind speed sidelobe, and complex Doppler center blur and spectrum ambiguity. The experiments using real data also validate the performance of the proposed method.

Co-generation of Collision-Free Shapes for Arbitrary One-Parametric Motion

Mechanical assemblies can exhibit complex relative motions, during which collisions between moving parts and their surroundings must be avoided. To define feasible design spaces for each part's shape, "maximal" collision-free pointsets can be computed using configuration space modeling techniques such as Minkowski operations and sweep/unsweep. For example, for a pair of parts undergoing a given relative motion, to make the problem well-posed, the geometry of one part (chosen arbitrarily) must be fixed to compute the maximal shape of the other part by an unsweep operation. Making such arbitrary choices in a multi-component assembly can place unnecessary restrictions on the design space. A broader family of collision-free pairs of parts can be explored, if fixing the geometry of a component is not required. In this paper, we formalize this family of collision-free shapes and introduce a generic method for generating a broad subset of them. Our procedure, which is an extension of the unsweep, allows for co-generation of a pair of geometries which are modified incrementally and simultaneously to avoid collision. We demonstrate the effectiveness and scalability of our procedure in both 2D and 3D by generating a variety of collision-free shapes. Notably, we show that our approach can automatically generate freeform cam and follower profiles, gear teeth, and screw threads, starting from colliding blocks of materials, solely from a specification of relative motion and without the use of any feature-informed heuristics. Moreover, our approach provides continuous measures of collision that can be incorporated into standard gradient-descent design optimization, allowing for simultaneous collision-free and physics-informed co-design of mechanical parts for assembly.

Features of mathematical modeling transmission parameters of drilling rigs with planetary gears

The features of the approach to the mathematical modeling of power transmission parameters of drilling rigs (DR), which include gear planetary gear mechanisms in the kinematic structure, are considered. At the same time, the modeling features consist in the special properties of the kinematics and dynamics of planetary gears, as well as the presence of elements of complex relative motion in them. This circumstance requires a thorough analysis of the parameters at the design stage, which should be based on the use of available and promising methods of mathematical modeling with the possibility of using modern mathematical apparatus and numerical methods of calculations. In order to solve this problem, the authors proposed a method for mathematical modeling of mechanical processes in the transmissions of DR with planetary gears. This makes it possible, based on the results of theoretical studies, to predict the optimal parameters of the power transmission of DR.

A Modified Keystone Transform Matched Filtering Method for Space-Moving Target Detection

High speed, high maneuverability, and weak space-moving targets (SMTs) are major threats for space-borne radar (SBR) systems. First, the severe range migration (RM) and Doppler extension are induced by complex relative motion between the radar platform and non-cooperative moving targets, making moving target detection (MTD), and parameter estimation particularly difficult. Apart from this challenge, Doppler ambiguity and Doppler aliasing arise from the limited pulse repetition frequency (PRF) of a SBR system to ensure an adequate coverage rate, which may make the existing MTD algorithms deteriorate dramatically. To address these issues, we focus on the detection of high speed and high maneuverability targets based on the modified keystone transform matched filtering (MKTMF), whose Doppler frequency exceeds PRF as well as spans multiple PRFs. The proposed method is suitable for the weak MTD under a low signal-to-noise ratio (SNR) case since the nonlinear operation is not involved. Finally, some numerical results and real data results are provided to validate the superiority of the proposed method.

A Motion Information Acquisition Algorithm of Multiantenna SAR Installed on Flexible and Discontinuous Structure Based on Distributed POS

Airborne multi-antenna SAR urgently needs the high-precision motion information of each antenna to realize high-precision imaging. Distributed Position and Orientation System (POS) is an important way to solve this problem based on transfer alignment. Because multiple antennas are usually installed on the flexible and discontinuous structure, there are complex and time-varying relative motions between different antennas. This relative motion will lead to the decline of transfer alignment accuracy, and directly affects the imaging accuracy of SAR. To solve this problem, a motion information acquisition algorithm of multi-antenna SAR installed on flexible and discontinuous structure based on distributed POS is given. Firstly, the gyroscopes and accelerometers of the distributed POS are used to calculate the relative attitude between nodes, which is applicable to both continuous and discontinuous structure. Secondly, combining the smooth estimation and the distributed filter, a distributed smoothing algorithm including forward filter and backward smoothing is proposed to calculate the high-precision and smoothed motion data of each sub-node. The forward filter obtains the motion parameters of each sub-node through transfer alignment based on the above relative attitude data. The backward smoothing further improves the motion information accuracy of sub-node by using the measurement data at all time and sharing the data of all nodes. Through the flight imaging test of multi-antenna SAR installed on a flexible and discontinuous platform, it is shown that the proposed algorithm can significantly improve the accuracy of the sub-node motion data, in which the errors of position, velocity and attitude are reduced by 58.9%, 61.9% and 71.2% respectively. Based on this motion data, SAR achieves better imaging focusing effect.

A Convolutional Neural Network Particle Filter for UUV Target State Estimation

The challenges facing unmanned underwater vehicle (UUV) target state estimation are observation uncertainty, the unpredictability of the target motion model, and the complex relative motion of the moving target to the observer. Aiming at the above problems, a convolutional neural network particle filter (CNNPF) is proposed and applied to UUV target state estimation using forward-looking sonar. First, we design a target state prediction network based on convolutional neural network (CNN) to describe the nonlinear measurement and non-Markov target motion process models. Then, a target state prediction dataset is established for the prediction network to build the state space of UUV target state estimation and extract target motion features from the nonsequential measurements. Moreover, particles are sampled from the observations with disturbed time series to approximate the non-Gaussian distribution of measurements. The sampling particles in the target measured state space are mapped to target predictive state space through the prediction network. Convolutional and pooling layers impart invariance to the prediction network and improve its adaptability to uncertain measurement. Finally, the predicted states of particles are used to estimate the target states. The statistical experiment, simulation cases, and hardware-in-the-loop experiment proved the applicability and performance of the CNNPF.

Motion Processing Deficits in Children With Cerebral Visual Impairment and Good Visual Acuity.

PurposeWe sought to characterize neural motion processing deficits in children with cerebral visual impairment (CVI) who have good visual acuity using an objective, quantifiable method (steady-state visual evoked potentials [SSVEPs]).MethodsWe recorded SSVEPs in response to three types of visual motion – absolute motion and more complex relative and rotary motion, comparing them to form-related vernier and contour responses. We studied a group of 31 children with CVI diagnosed via detailed clinical examinations and 28 age-matched healthy controls.ResultsUsing measurements made at the appropriate response harmonics of the stimulation frequency, we found significant deficits in cerebral processing of relative and rotary motion but not of absolute motion in children with CVI compared with healthy controls. Vernier acuity, in keeping with good recognition acuity in both groups, was not different, nor were contour-related form responses.ConclusionsDeficits for complex motion but relative sparing of elementary motion and form-related signals suggests preferential damage to extra-striate visual motion areas in children with CVI. The fact that these preferential losses occur in the absence of significant acuity loss indicates that they are not secondary to reduced visual acuity, but rather are an independent vulnerability in CVI. These results corroborate parental and caregivers’ reports of difficulties with tasks that involve motion perception in children with CVI.

Three-dimensional multi-finger caging for capturing convex objects in the space

Multi-finger caging offers an adaptive and robust object grasping approach, but caging objects in the space is complicated and difficult due to the complex relative motion between the object and the multi-fingered mechanism, and the high degrees of freedom of fingers. In this paper, an integrative three-dimensional multi-finger caging algorithm for tumbling targets in the space is presented. The main core of the proposed algorithm is the “leader-follower” mode: (1) in order to realize the synchronous motion of the tumbling target, the leading finger of the multi-fingered mechanism is selected and its base joint is controlled to track the caging point of the target using the model predictive control strategy; (2) to simplify the degrees of freedom, the leading finger adjusts its joint angles to resemble its shape as closely as possible with the caging edge based on One Way Distance, then possible configurations of other following fingers are determined according to structural constraints of the multi-fingered mechanism; and (3) the effective caging configuration is determined according to the derived multi-finger caging conditions. The main advantages of this work are (1) the simple task mode – “leader-follower” mode can significantly simplify the calculation burden of caging configuration design; (2) the adaptivity and robustness for tumbling targets with different shapes benefited from the flexibility of the caging configuration. The proposed algorithm is applied in the capture of a dysfunctional satellite with solar panels and a discarded upper stage rocket, respectively. The simulation results show that the proposed algorithm can find the effective caging configuration efficiently.

Parametric Approach for Satellite Relative Orbit Designs and Constellations

This paper proposes a dynamics solution that creates an identical constellation pattern of multiple satellites with the parameterization of relative motion dynamics. The parameterization illustrates that the complexity of relative motion dynamics is interpreted by a Ptolemaic model of an epicycle and deferent system. All possible relative orbits can be represented by a hypo-epi curve or a deformed curve on the x-y plane and a simple z-axis harmonic oscillator motion. The designed relative orbits are used to create identical constellation patterns of multiple satellites, called parametric constellations in this study, by closed-form formulas and satellite phasing rules obtained from the geometrical relationship and periodic conditions. In conclusion, the resulting solution contributes to solving technical dynamics and tracking problems by simply designing complex relative motions in free space.

Focusing Challenges of Ships With Oscillatory Motions and Long Coherent Processing Interval

Ship motions during long coherent processing interval (CPI) have six degrees of freedom, and the oscillatory motions are roughly periodical. The traditional ship imaging methods usually use a short time interval to form an image, while the image quality may suffer from low resolution, poor signal-to-noise ratio (SNR), and scatter scintillation. Using a longer CPI to generate an image may improve the quality but, however, largely increase the focusing difficulty. In this article, we investigate the focusing challenges of oscillatory ships with long CPI. Through analyzing the relative motion between the radar and the ship, the properties of wavenumber domain support (WDS) and point spreading function (PSF) of oscillatory ship imaging are studied. It is illustrated that the WDS is a 3-D sparse curved surface generated by the complex relative motion, with a time-variant energy density, nonparallel spectrum boundaries, and a complex structure. The PSF of an oscillatory ship may have a 3-D resolution but also multiple high-level sidelobes. The relationship between the WDS and the nonideal PSF is illustrated with the projection slice theorem (PST). Moreover, it is discussed that the scatterers distributed on a 3-D ship cannot be focused uniformly on a 2-D imaging plane (IP) due to the variation of the slant-range plane (SRP). The projection relationships of the resolutions and focusing positions between the SRP and the IP are also derived. Simulation results are presented to validate the analyses throughout this article.

Intra-swarm migration of size-variable robotic modules utilizing the Brazil nut effect

In this work, we apply physical granular segregation phenomena to the problem of intra-swarm module migration in a robotic swarm. These segregation phenomena allow for complex relative motion between interacting particles on the basis of differing physical properties. In particular, the Brazil nut effect is one such phenomenon that causes segregation of particles based on relative size difference. We simulated size-variable modules in order to take advantage of this effect and induce intra-swarm module migration. Intra-swarm module migration refers to the movement of the modules within the confines of the swarm, relative to each other, as well as the swarm container. We introduced two methods to produce different kinds of module movement. The first of these, called the flashlight method, induced movement of an individual module relative to its neighbours. The second, called the zone method, induced an orientation-aligned global module motion within the swarm. In this work, we evaluate the effects of different parameters on the nature of the movements induced by these methods.

A Novel Blind Motion Blur Restoration Algorithm for Text Images

Text images captured by the surveillance system or hand-hold cameras often suffer from motion blur due to the complex relative motion between the camera and the target during the exposure time. The accuracy of the kernel estimation and the effective priors for clear text images are two important keys in blind motion deblurring. A novel blind motion deblurring algorithm is proposed for text images in a complex scene. A criterion for selecting informative edges and an L 0 constraint are combined to improve the accuracy of the kernel estimation. Then, a fast non-blind deconvolution scheme is applied to accelerate the algorithm. Experimental results on text images show that the proposed method can achieve high-quality results with low computational complexity.

On the Nature of the Compact Sources in IRAS 16293–2422 Seen at Centimeter to Submillimeter Wavelengths

We present multi-epoch continuum observations of the Class 0 protostellar system IRAS 16293–2422 taken with the Very Large Array (VLA) at multiple wavelengths between 7 mm and 15 cm (41 GHz down to 2 GHz), as well as single-epoch Atacama Large Millimeter/submillimeter Array continuum observations covering the range from 0.4 to 1.3 mm (700 GHz down to 230 GHz). The new VLA observations confirm that source A2 is a protostar driving episodic mass ejections, and reveal the complex relative motion between A2 and A1. The spectrum of component B can be described by a single power law (Sν ∝ ν2.28) over the entire range from 3 to 700 GHz (10 cm down to 0.4 mm), suggesting that the emission is entirely dominated by dust even at λ = 10 cm. Finally, the size of source B appears to increase with frequency up to 41 GHz, remaining roughly constant (at 039 ≡ 55 au) at higher frequencies. We interpret this as evidence that source B is a dusty structure of finite size that becomes increasingly optically thick at higher frequencies until, in the millimeter regime, the source becomes entirely optically thick. The lack of excess free–free emission at long wavelengths, combined with the absence of high-velocity molecular emission, indicates that source B does not drive a powerful outflow, and might indicate that source B is at a particularly early stage of its evolution.

A deeper understanding on the motion behaviors of wire during ultrasonic wedge-wedge bonding process

AbstractUltrasonic wire bonding is a dominating interconnection technique that has been applied in packaging industry for decades. The phenomena at the wire/substrate interface and the wire/tool interface, however, are not clear yet. Specifically, the motion behaviors of the wire during the bonding process have to be deeply understood. In this project, the relative motion amplitudes at the wire/tool interface and the self-cleaning efficiency at the wire/substrate interface are investigated via the analysis of an artificially coated layer. For each experiment, a thin layer made of a specific material was coated onto the surface of a 400 μm wire by physical vapor deposition. The change of thicknesses of the layer was observed by a scanning electron microscope after the bonding process. The results indicated a complex relative motion behavior at the wire/tool interface. The relative motion amplitude at the fillets contact regions is higher than that at the other contact perimeter regions while the amplitude at the central area is the lowest. The insignificant influence of a 200 nm aluminum oxide layer on the bonding quality demonstrated the high self-cleaning efficiency of the wedge-wedge bonding process.

A complex relative motion between hairpin loop 2 and transmembrane domain 5 in the glutamate transporter GLT-1

Excitatory amino acid transporter 2, also known as glial glutamate transporter type 1 (GLT-1), plays an important role in maintaining suitable synaptic glutamate concentrations. Reentrant helical hairpin loop (HP) 2, as the extracellular gate, has been shown to participate in the binding of substrate and ions. Several residues in transmembrane domain (TM) 5 have been shown to be involved in the construction of the transport pathway. However, the spatial relationship between HP2 and TM5 during the recycling of glutamate has not yet been clarified. We introduced cysteine residue pairs in HP2 and TM5 of cysteine-less-GLT-1 by using site-directed mutagenesis in order to assess the proximity of HP2 and TM5. A significant decrease in substrate uptake was seen in the I283C/S443C and S287C/S443C mutants when the oxidative cross-linking agent copper(II) (1,10-phenanthroline)3 (CuPh) was used. The inhibitory effect of CuPh on the transport activity of the S287/S443C mutant was increased after the application of glutamate or potassium. In contrast, an apparent protection of the transport activity of the I283C/S443C mutant was observed after glutamate or potassium addition. The membrane-impermeable sulfhydryl reagent (2-trimethylammonium) methanethiosulfonate (MTSET) was used to detect the aqueous permeability of each single mutant. The aqueous permeability of the I283C mutant was identical to that of the S443C mutant. The sensitivity of I283C and S443C to MTSET was attenuated by glutamate and potassium. All these data indicate that there is a complex relative motion between TM5 and HP2 during the transport cycle.

Spatial Vibration and Its Numerical Analytical Method of Four-high Rolling Mills

The rolls in contemporary four-high mills cannot be maintained parallel during the rolling process. Therefore, four-high rolling mill vibrations take place in six degree of freedom (DOF) leading to spatial behaviors involving vertical, horizontal, axial, torsional, cross and swinging vibration modes resulting in complex relative motions between the rolls. Two numerical methods, modified Riccati-transfer matrix method (Riccati-TMM) and finite element method (FEM), are presented to analyze a spatial vibration characteristic of two four-high rolling mills with different stability. The natural frequency and mode shape of four-high rolling mills are obtained, and the clearance has a great effect on natural frequency and mode shape. In addition, field testing experiment is also conducted to measure natural frequency by power spectrum analysis of rolling mill vibration. Experimental results basically agree with those calculated by Riccati-TMM and FEM, which means that the Riccati-TMM and the FEM can be used for analysis of spatial vibration of four-high rolling mill. Meanwhile, the spatial vibration shows more compound vibration behaviors and the negative effect of horizontal, vertical, cross and swinging vibration modes are effectively controlled after redesign of rolling mill. These advantages have a great significance for the rolling mill to be operated with a much higher rolling speed and improved yield of products.

Spatial Vibration Characteristics of Four-High Rolling Mills

The contemporary four-high mills are unstable and four-high rolling mill vibrations take place in six DOF leading to spatial behaviors involving vertical, horizontal, axial, reverse, cross and swinging vibration modes resulting in complex relative motions between the rolls. In this paper, a spatial vibration characteristic analysis of two four-high rolling mills with different stability will be presented based on the transfer matrix method (TMM) and Finite Element Method (FEM). The natural frequency and mode shape of four-high rolling mill are obtained. Vibration experimental results will be presented to prove the validity of the spatial vibration of rolling mill.

Learning Relative Motion Concepts in Immersive and Non-immersive Virtual Environments

The focus of the current study is to understand which unique features of an immersive virtual reality environment have the potential to improve learning relative motion concepts. Thirty-seven undergraduate students learned relative motion concepts using computer simulation either in immersive virtual environment (IVE) or non-immersive desktop virtual environment (DVE) conditions. Our results show that after the simulation activities, both IVE and DVE groups exhibited a significant shift toward a scientific understanding in their conceptual models and epistemological beliefs about the nature of relative motion, and also a significant improvement on relative motion problem-solving tests. In addition, we analyzed students’ performance on one-dimensional and two-dimensional questions in the relative motion problem-solving test separately and found that after training in the simulation, the IVE group performed significantly better than the DVE group on solving two-dimensional relative motion problems. We suggest that egocentric encoding of the scene in IVE (where the learner constitutes a part of a scene they are immersed in), as compared to allocentric encoding on a computer screen in DVE (where the learner is looking at the scene from “outside”), is more beneficial than DVE for studying more complex (two-dimensional) relative motion problems. Overall, our findings suggest that such aspects of virtual realities as immersivity, first-hand experience, and the possibility of changing different frames of reference can facilitate understanding abstract scientific phenomena and help in displacing intuitive misconceptions with more accurate mental models.

Spatial vibration of rolling mills

The analysis of rolling mill vibrations is usually limited to simple planar or low DOF vibrations. In reality, however, rolling mill vibrations take place in six DOF leading to spatial behaviors involving vertical, horizontal, axial, reverse, cross and swinging vibration modes resulting in complex relative motions between the rolls. In this paper, a complete spatial vibration characteristic analysis will be presented based on the modified Riccati-overall transfer matrix method. The proposed methodology will be applied to two distinct mill configurations, namely two high-stiffness mills with and without clearance in the chocks. Coupled vibration characteristics of cross and sway motions will be presented along with the complex mode shape analysis of the mills. Experimental results will be presented to prove the validity of the proposed method for spatial vibration analysis.