Simultaneous Motion Research Articles

Machining of Smooth Optical Surfaces by Ultraprecision Milling with Compensated Feeding Mechanisms

Waviness tends to be generated on cut surfaces even when an ultraprecision milling machine with a single-crystal diamond tool is used. The present study deals with the reduction of waviness by controlling the feeding mechanisms of the milling machine. A machining experiment on a spherical surface of a mirror element in a mirror array showed that the machined surface exhibited periodic waviness with a height of 30 nm and a wavelength of 300 μm. To investigate the reason for such waviness, a slope was machined under simultaneous multiaxis motion control of the feeding mechanisms of the milling machine. This proved that the interpolation errors of the encoders used in the milling machine produce the waviness on the machined surface when machining is carried out under simultaneous multiaxis motion control. To reduce such interpolation errors, the positioning accuracy of the machine stages was measured using a laser interferometer. On the basis of the measured results, the feeding mechanisms were compensated such that the positioning errors including the interpolation errors were corrected. Using the machine with the compensated feeding system, a mirror element was shaped. Consequently, waviness was reduced and the surface smoothness was less than 10 nm, demonstrating that such compensation can produce superior optical surfaces.

Possible causes of electrical resistivity distribution inhomogeneity in Czochralski grown single crystal silicon

Electrical resistivity distribution maps have been constructed for single crystal silicon wafers cut out of different parts of Czochralski grown ingots. The general inhomogeneity of the wafers has proven to be relatively high, the resistivity scatter reaching 1–3 %. Two electrical resistivity distribution inhomogeneity types have been revealed: azimuthal and radial. Experiments have been carried out for crystal growth from transparent simulating fluids with hydrodynamic and thermophysical parameters close to those for Czochralski growth of silicon single crystals. We show that a possible cause of azimuthal electrical resistivity distribution inhomogeneity is the swirl-like structure of the melt under the crystallization front (CF), while a possible cause of radial electrical resistivity distribution inhomogeneity is the CF curvature. In a specific range of the Grashof, Marangoni and Reynolds numbers which depend on the ratio of melt height and growing crystal radius, a system of well-developed radially oriented swirls may emerge under the rotating CF. In the absence of such swirls the melt is displaced from under the crystallization front in a homogeneous manner to form thermal and concentration boundary layers which are homogeneous in azimuthal direction but have clear radial inhomogeneity. Once swirls emerge the melt is displaced from the center to the periphery, and simultaneous fluid motion in azimuthal direction occurs. The overall melt motion becomes helical as a result. The number of swirls (two to ten) agrees with the number of azimuthally directed electrical resistivity distribution inhomogeneities observed in the experiments. Comparison of numerical simulation results in a wide range of Prandtl numbers with the experimental data suggests that the phenomena observed in transparent fluids are universal and can be used for theoretical interpretation of imperfections in silicon single crystals.

Running ground reaction forces across footwear conditions are predicted from the motion of two body mass components.

Although running shoes alter foot-ground reaction forces, particularly during impact, how they do so is incompletely understood. Here, we hypothesized that footwear effects on running ground reaction force-time patterns can be accurately predicted from the motion of two components of the body's mass (mb): the contacting lower-limb (m1 = 0.08mb) and the remainder (m2 = 0.92mb). Simultaneous motion and vertical ground reaction force-time data were acquired at 1,000 Hz from eight uninstructed subjects running on a force-instrumented treadmill at 4.0 and 7.0 m/s under four footwear conditions: barefoot, minimal sole, thin sole, and thick sole. Vertical ground reaction force-time patterns were generated from the two-mass model using body mass and footfall-specific measures of contact time, aerial time, and lower-limb impact deceleration. Model force-time patterns generated using the empirical inputs acquired for each footfall matched the measured patterns closely across the four footwear conditions at both protocol speeds (r2 = 0.96 ± 0.004; root mean squared error = 0.17 ± 0.01 body-weight units; n = 275 total footfalls). Foot landing angles (θF) were inversely related to footwear thickness; more positive or plantar-flexed landing angles coincided with longer-impact durations and force-time patterns lacking distinct rising-edge force peaks. Our results support three conclusions: 1) running ground reaction force-time patterns across footwear conditions can be accurately predicted using our two-mass, two-impulse model, 2) impact forces, regardless of foot strike mechanics, can be accurately quantified from lower-limb motion and a fixed anatomical mass (0.08mb), and 3) runners maintain similar loading rates (ΔFvertical/Δtime) across footwear conditions by altering foot strike angle to regulate the duration of impact. NEW & NOTEWORTHY Here, we validate a two-mass, two-impulse model of running vertical ground reaction forces across four footwear thickness conditions (barefoot, minimal, thin, thick). Our model allows the impact portion of the impulse to be extracted from measured total ground reaction force-time patterns using motion data from the ankle. The gait adjustments observed across footwear conditions revealed that runners maintained similar loading rates across footwear conditions by altering foot strike angles to regulate the duration of impact.

Attention to a threat-related feature does not interfere with concurrent attentive feature selection.

Visual features associated with a task and those that predict noxious events both prompt selectively heightened visuocortical responses. Conflicting views exist regarding how the competition between a task-related and a threat-related feature is resolved when they co-occur in time and space. Utilizing aversive classical Pavlovian conditioning, we investigated the visuocortical representation of two simultaneously presented, fully overlapping visual stimuli. Isoluminant red and green random dot kinematogram (RDK) stimuli were flickered at distinct tagging frequencies (8.57Hz, 12Hz) to elicit distinguishable steady-state visual evoked potentials (ssVEPs). Occasional coherent motion events prompted a motor response (task) or predicted a noxious noise (threat). These events occurred either in the green (task cue), the red (threat cue), or in both RDKs simultaneously. In the initial habituation phase, participants responded to coherent motion of the green RDK with a key press, but no loud noise was presented at any time. Here, selective amplification was seen for the task-relevant (green) RDK, and interference was observed when both RDKs simultaneously showed coherent motion. Upon pairing the threat cue with the noxious noise in the subsequent acquisition phase, the threat cue-evoked ssVEP (red RDK) was also amplified, but this amplification did not interact with amplification of the task cue or alter the behavioral or visuocortical interference effect observed during simultaneous coherent motion. Although competing feature conjunctions resulted in interference in the visual cortex, the acquisition of a bias toward an individual threat-related feature did not result in additional cost effects.

Evaluation of the Crustal Features of the Gulf of Aqaba Deduced from Geophysical Data

The Gulf of Aqaba is considered as an interesting rift system. Therefore, it is important to understand the crustal features and thickness variation along the Gulf; to be able to evaluate the effect of tectonic activities in shaping the Gulf. The obtained data were used to estimate the reliable empirical relations between the Bouguer anomalies (ΔgB) and crustal thickness (Hc) in the Gulf of Aqaba. This equation was used to calculate the depth reliefs to the Moho boundary. The output map of the Moho relief and the corresponding crustal thickness were constructed for the Gulf of Aqaba. The depth from sea level down to the Moho discontinuity in the Gulf of Aqaba varies between about 37 km in the northern deep and abruptly changes to about 28 km at the southern area, Tiran Strait. Below the central part of the gulf, a Moho depth of about 34 km is obtained. The Red Sea crust is thinner than that of the Dead Sea rift; indicating the presence of a mantel upwelling that is related to the spreading of the sea floor. The asymmetry of crustal thickness between the eastern and western borders of the Gulf of Aqaba could be attributed to simultaneous strike-slip motion. The relative displacement between the two borders is observed clearly through the sea floor and Moho discontinuity. The displacement is nearly equivalent to 0.18° (i.e. about 20.4 km) and is assumed to be achieved in about 4.08 to 3.4 million years, according to the estimated rate of the transform motion along the Gulf of Aqaba (Dead Sea transform) that is about 0.5 to 0.6 cm/y.

Allosteric response to ligand binding: Molecular dynamics study of the N-terminal domains in IP 3 receptor.

Inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) is a huge tetrameric intracellular Ca2+ channel that mediates cytoplasmic Ca2+ signaling. The structural basis of the gating in IP3R has been studied by X-ray crystallography and cryo-electron microscopy, focusing on the domain rearrangements triggered by IP3 binding. Here, we conducted molecular dynamics (MD) simulations of the three N-terminal domains of IP3R responsible for IP3 binding (IBC/SD; two domains of the IP3 binding core, IBCβ and IBCα, and suppressor domain, SD) as a model system to study the initial gating stage. The response upon removal of IP3 from the IP3-bound form of IBC/SD was traced in MD trajectories. The two IBC domains showed an immediate response of opening after removal of IP3, and SD showed a simultaneous opening motion indicating a tight dynamic coupling with IBC. However, when IBC remained in a more closed form, the dynamic coupling broke and SD exhibited a more amplified closing motion independently of IBC. This amplified SD motion was caused by the break of connection between SD and IBCβ at the hinge region, but was suppressed in the native tetrameric state. The analyses using Motion Tree and the linear response theory clarified that in the open form, SD and IBCα moved collectively relative to IBCβ with a response upon IP3 binding within the linear regime, whereas in the closed form, such collectiveness disappeared. These results suggest that the regulation of dynamics via the domain arrangement and multimerization is requisite for large-scale allosteric communication in IP3R gating machinery.

Investigation of Internal Target Volumes Using Device and Deviceless Four-dimensional Respiratory Monitoring Systems for Moving Targets in Four-dimensional Computed Tomography Acquisition.

Aims and Objectives:The influence of target motion on the reconstructed internal target volume (ITV) for device-based (DB) external surrogate system and Smart deviceless (DL) 4-dimensional (4D) system were compared in a controlled phantom experiment. The volumetric changes in reconstructed ITVs from the average intensity projection (AveIP) images using DB method (Anzai Respiratory Gating System, ANZAI MEDICAL CO., LTD, Japan) and DL method (Smart deviceless 4D system by GE Medical Systems (Chicago, USA)) with the theoretical true volume (ITVth) for moving target with the increasing target motion in anterior-posterior (A-P), lateral (left-right [L-R]) and inferior-superior (S-I) directions were assessed.Materials and Methods:4D computed tomography (4DCT) of CIRS dynamic phantom (Computerized Imaging Reference Systems Inc., Norfolk, VA, USA) with 2.5 cm diameter spherical target of volume 8.2 cc programmed to move in a cos4(x) motion pattern placed in the lung volume were acquired for various target motion pattern using DB and DL method of gating. AveIP images of 10 phase binned image sets were generated and ITVs were delineated.Results:The maximum absolute percent differences between ITVave and ITVth for DL and DB methods were 15.91% and 4.94 % respectively for target motion of 5 mm in AP with 15 mm S-I direction. When the S-I motion was decreased to 10 mm, the observed % difference of the ITVs were also decreased to 12.5% and 0.3% for DL and DB method. When the lateral [L-R] motion was varied from 0 mm to 5 mm for S-I motion of 5 mm to 15 mm, the differences in the ITVs were significant (P = 0.004) with the maximum absolute percent difference of 18.61% and 4.94 % for DL and DB gating. With the simultaneous motion of the target in all the 3 directions, the difference in the reconstructed ITVs were statistically significant for DL method (P = 0.0002) and insignificant for DB method (P = 0.06) with an average increase of 10% in ITVDL against 2% in the ITVDB. The difference in ITVDL was significant for the target motion above 3 mm in A-P and L-R directions for S-I movement of above 10 mm (P = 0.0002). However, for low excursions of the target movement, no significant difference in the ITVs were observed (P > 0.06). In general, ITVDBs were closer to the ITVth (within 7.8%) than ITVDL (18.61%).Conclusion:The results showed that the DL method is an effective way of image sorting in 4D acquisition for smaller target excursion. When the target motion exceeds 3 mm in A-P and L-R directions with S-I more than 10 mm, DB method is the choice due to its accuracy in reproducing the absolute target volume.

Real-time simultaneous shim and motion measurement and correction in glycoCEST MRI using double volumetric navigators (DvNavs).

CEST MRI allows for indirect detection of molecules with exchangeable protons, measured as a reduction in water signal because of continuous transfer of saturated protons. CEST requires saturation pulses on the order of a second, as well as repeated acquisitions at different offset frequencies. The resulting extended scan time makes CEST susceptible to subject motion, which introduces field inhomogeneity, shifting offset frequencies and causing distortions in CEST spectra that resemble true CEST effects. This is a particular problem for molecules that resonate close to water, such as hydroxyl group in glycogen. To address this, a technique for real-time measurement and correction of motion and field inhomogeneity is proposed. A CEST sequence was modified to include double volumetric navigators (DvNavs) for real-time simultaneous motion and shim correction. Phantom tests were conducted to investigate the effects of motion and shim changes on CEST quantification and to validate the accuracy of DvNav motion and shim estimates. To evaluate DvNav shim and motion correction in vivo, acquisitions including 5 experimental conditions were performed in the calf muscle of 2 volunteers. Phantom data show that DvNav-CEST accurately estimates frequency and linear gradient changes because of motion and corrects resulting image distortions. In addition, DvNav-CEST improves CEST quantification in vivo in the presence of motion. The proposed technique allows for real-time simultaneous motion and shim correction with no additional scanning time, enabling accurate CEST quantification even in the presence of motion and field inhomogeneity.

Effect of simultaneous three-angular motion on the performance of an air–water–oil separator under offshore operation

A three-dimensional (3D) multiphase Eulerian computational fluid dynamics (CFD) model was developed to investigate the effect of a simultaneous three-angular motion (roll, yaw and pitch) on the performance of an air-water-oil separator. The dynamic mesh method with a 3D rotational matrix was used to simulate the three-phase separator under simultaneous three-angular motion. The pressures at water and oil outlets were adjusted by a user-defined function based on a proportional control algorithm. The CFD model was validated against experimental free oscillations of an immiscible two-fluid system under a pitching motion. The simultaneous three-angular motion with an amplitude 2° and a period of 8 s showed an oil purity of 98% and an oil recovery of 99%, which were comparable to those of the onshore separator. However, the 4° simultaneous three-angular motion deteriorated the oil recovery to 92% and the water purity to 75%. As the separation performance of the pitching motion was similar to that of the simultaneous three-angular motion, the performance of the three-phase separator can be tested simply by the pitching motion.

Simultaneous motion monitoring and truth-in-delivery analysis imaging framework for MR-guided radiotherapy

Intrafraction motion (i.e. motion occurring during a treatment session) can play a pivotal role in the success of abdominal and thoracic radiation therapy. Hybrid magnetic resonance-guided radiotherapy (MR-gRT) systems have the potential to control for intrafraction motion. Recently, we introduced an MRI sequence capable of acquiring real-time cine imaging in two orthogonal planes (SOPI). We extend SOPI here to permit dynamic updating of slice positions in one-plane while keeping the other plane position fixed. In this implementation, cine images from the static plane are used for motion monitoring and as image navigators to sort stepped images in the other plane, producing dynamic 4D image volumes for use in dose reconstruction. A custom 3D-printed target, designed to mimic the pancreas and duodenum and filled with radiochromic FXG gel, was interfaced to the dynamic motion phantom. 4D-SOPI was acquired in a dynamic motion phantom driven by an actual patient respiratory waveform displaying amplitude/frequency variations and drifting and in a healthy volunteer. Unique 4D-MRI epochs were reconstructed from a time series of phantom motion. Dose from a static 4 cm × 15 cm field was calculated on each 4D respiratory phase bin and epoch image, scaled by the time spent in each bin, and then rigidly accumulated. The phantom was then positioned on an Elekta MR-Linac and irradiated while moving. Following irradiation, actual dose deposited to the FXG gel was determined by applying a R1 versus dose calibration curve to R1 maps of the phantom. The 4D-SOPI cine images produced a respiratory motion navigator that was highly correlated with the actual phantom motion (CC = 0.9981). The mean difference between the accumulated and measured dose inside the target was 4.4% of the maximum prescribed dose. These initial results demonstrate that 4D-SOPI is a promising imaging framework enabling simultaneous real-time motion monitoring and truth-in-delivery analysis for integrated MR-gRT systems.

A Fully Coupled Computational Fluid Dynamics Method for Analysis of Semi-Submersible Floating Offshore Wind Turbines Under Wind-Wave Excitation Conditions Based on OC5 Data

Accurate prediction of the time-dependent system dynamic responses of floating offshore wind turbines (FOWTs) under aero-hydro-coupled conditions is a challenge. This paper presents a numerical modeling tool using commercial computational fluid dynamics software, STAR-CCM+(V12.02.010), to perform a fully coupled dynamic analysis of the DeepCwind semi-submersible floating platform with the National Renewable Engineering Lab (NREL) 5-MW baseline wind turbine model under combined wind–wave excitation environment conditions. Free-decay tests for rigid-body degrees of freedom (DOF) in still water and hydrodynamic tests for a regular wave are performed to validate the numerical model by inputting gross system parameters supported in the Offshore Code Comparison, Collaboration, Continued, with Correlations (OC5) project. A full-configuration FOWT simulation, with the simultaneous motion of the rotating blade due to 6-DOF platform dynamics, was performed. A relatively heavy load on the hub and blade was observed for the FOWT compared with the onshore wind turbine, leading to a 7.8% increase in the thrust curve; a 10% decrease in the power curve was also observed for the floating-type turbines, which could be attributed to the smaller project area and relative wind speed required for the rotor to receive wind power when the platform pitches. Finally, the tower-blade interference effects, blade-tip vortices, turbulent wakes, and shedding vortices in the fluid domain with relatively complex unsteady flow conditions were observed and investigated in detail.

A Modified Cooperative A* Algorithm for the Simultaneous Motion of Multiple Microparts on a "Smart Platform" with Electrostatic Fields.

In this article, a method for microparts parallel manipulation with electrostatic forces, applied by conductive electrodes embedded on a Programmable “Smart Platform”, is introduced. The design of the platform and the layout of the electrodes underneath the rectangular microparts with respect to the platform’s geometry are presented. The electrostatic phenomena that result to the electrostatic forces applied to the microparts by the activated electrodes of the “Smart Platform” are studied in detail. Algorithms for the activation of the platform’s electrodes for the motion of the rectangular microparts are introduced and their motion is simulated. The Configuration-Space (C-Space) of the microparts on the “Smart Platform” is defined taking into account the static obstacles that are placed on the platform and the rest of moving microparts. Considering the layout of the platform, the activation algorithms, the motion and the C-Space of the microparts, a modified A* algorithm is proposed and the best path for every moving rectangular micropart on the “Smart Platform”, is computed with respect to time. Simulated experiments are presented to demonstrate the effectiveness of the proposed approach and the results are discussed.

Asynchronous earthquake strong motion and RC bridges response

Abstract The dynamic response of long structures (e.g., bridges) is sensitive to the spatial variability of strong ground motion (asynchronous motion). Ground motion differences increase from point to point with increasing foundation distance. This latter is due to two physical phenomena: soil-wave interaction, that causes the loss of coherence and local amplification; wave traveling with finite velocity, that causes signals time lag. This ground motion variability produces a different structural demand compared to the synchronous one, which is the only one considered by designers in the majority of cases. A few codes consider this type of actions, therefore further research efforts are necessary. In this study, asynchronous ground motions are generated by means of a new generation procedure implemented in the software GAS 2.0 using as input the simultaneous strong motion records from the April 6th, 2009, L'Aquila (Italy) at the seismic stations AQA and AQV, located in the Aterno River valley. These records are used to calibrate the generation model and to produce sets of asynchronous earthquake sampling. The asynchronous earthquake sets are applied on a typical highway reinforced concrete bridge to study its dynamic response considering two different configurations: non-isolated with traditional supports and isolated bridge with lead rubber bearings. The bridge is placed in two positions along the wave propagation direction: a position near one recording station and a position between the two stations to consider local soil effects. The response parameters investigated are the maximum relative displacements of soil and deck. The results show that there is an important variation of relative displacement along the direction of wave propagation due to asynchronous motion with effects that designer should consider for the structural details design of isolated and non-isolated bridges.

Numerical prediction methodology for tow orientation on irregular mandrels with constant cross-sections

Because of the decisive role of tow orientation in braided fabric on the mechanical performance of composite, having an accurate tow orientation prediction method for each specific mandrel shape is a cornerstone for applying circular braiding technology. This work presents a numerical method to predict the tow orientation on an irregular, constant cross-section mandrel. In this numerical method, the cross-section of the mandrel is approximated by a series of line segments, and then the surface meshes of the mandrel are generated in STL format. A set of kinematic equations, which was deduced from the simultaneous motion relationship between the translation of the take-up device and the rotation of the spools, was used to calculate the sequence of the deposition points located on the edges of surface mesh for the approximated tow orientation. Braiding experiments for various process parameters were conducted on a mandrel with a specially designed cross-section manufactured using a three-dimensional printer and the angle of the braiding tow was measured. The influence of translation speed, shape of cross-section and convergence region length on braiding angle were analysed via a comparison of the simulation results and the experimental data. Two types of variation of the braiding angles in the braided fabric and its influence factors are also discussed in detail. It was shown that the numerical method, which can rapidly predict the braiding angle for an irregular, constant cross-section mandrel, is beneficial for optimizing the process parameters for hollow composite component manufacture.

Design and Evaluation of Passive Shoulder Joint Tracking Module for Upper-Limb Rehabilitation Robots.

As the number of people suffering from shoulder movement disabilities increases, there is a rising demand for shoulder rehabilitation. The natural motion of the shoulder joint [glenohumeral (GH) joint] includes not only three-degrees-of-freedom (DOF) rotation but also three-DOF translation of the joint center due to simultaneous motion of the shoulder girdle. If the motion of the shoulder girdle is restricted, then the arm cannot be raised above a certain posture. This paper presents a passive shoulder joint tracking device that allows three-DOF translation of the shoulder joint while compensating for gravity. The single-DOF vertical tracker with a constant-force spring compensates for the gross weight of the user's arm, the upper limb rehabilitation device, and the tracker itself while allowing vertical tracking motion. The two-DOF horizontal tracker consists of two linear guides arranged perpendicular to each other. The tracker freely follows the shoulder joint in the horizontal plane. The effect of using the passive shoulder joint tracking device was evaluated by means of experiments by combining two popular commercial upper limb rehabilitation apparatuses with the proposed tracker. Nineteen subjects (8 healthy persons and 11 patients with shoulder impairments) participated in the evaluation study. The movement of the GH joint and the interactive force between the subject and the commercial rehabilitation device were analyzed when subjects made the following shoulder movements: flexion/extension and abduction/adduction. The improved tracker allowed a greater range of motion and reduced interaction. The tracker can be combined with existing commercial rehabilitation devices for more natural shoulder movement during rehabilitation tasks.

Influence of Interference Effects of the Rotor on the Launch Dynamics of Gliding Unmanned Aerial Vehicle

A mathematical model of the gliding unmanned aerial vehicle (UAV) motion is performed taking into account the interference effect of the main rotor on the UAV. Calculated values are presented for the interference addition to the aerodynamic coefficients of forces and moments on the UAV path section close to the carrier. The problems of stabilization and control are solved, providing stability of the UAV motion at the launch with due account of the aerodynamic interference and the effect of short-term upper stage engine operation, as well as a safe distance between the carrier and the UAV during their simultaneous motion.

A Wearable Detector for Simultaneous Finger Joint Motion Measurement.

This paper presents a wearable and stretchable detector for simultaneous finger joint motion measurement, providing the feasible technical solutions to solve the problems existing in the current devices. The sensor array installed in the detector consists of 14 custom-made bending sensors and an inertial measurement unit with high accuracy. The glove support for a sensor array, which is made of three silicone materials with different elasticity, not only overcomesthedrawbacks of cloth support, but also addresses the compatibility between the stretch substrate and the inelastic sensing components. Besides, two-section electrical connection avoids the problems caused by the external wires in traditional solutions to enhance the durability of glove. The experiment results indicated that the wearable detector offers a good user experience by exerting a small force on fingers. The device also shows a strong durability as it worked properly after tens of thousands of bending. The measurement tests on a single sensor demonstrated that two kinds of sensors are both with high accuracy. Besides, the hand goniometric system has an excellent performance in terms of hand motion detection. The measurement error of the device in subjects with different hand sizes is within a reasonable range. The good properties of the sensory detector allow it to be applied in clinical applications.

Vision-based dynamic target trajectory and ego-motion estimation using incremental light bundle adjustment

This paper presents a vision-based, computationally efficient method for simultaneous robot motion estimation and dynamic target tracking while operating in GPS-denied unknown or uncertain environments. While numerous vision-based approaches are able to achieve simultaneous ego-motion estimation along with detection and tracking of moving objects, many of them require performing a bundle adjustment optimization, which involves the estimation of the 3D points observed in the process. One of the main concerns in robotics applications is the computational effort required to sustain extended operation. Considering applications for which the primary interest is highly accurate online navigation rather than mapping, the number of involved variables can be considerably reduced by avoiding the explicit 3D structure reconstruction and consequently save processing time. We take advantage of the light bundle adjustment method, which allows for ego-motion calculation without the need for 3D points online reconstruction, and thus, to significantly reduce computational time compared to bundle adjustment. The proposed method integrates the target tracking problem into the light bundle adjustment framework, yielding a simultaneous ego-motion estimation and tracking process, in which the target is the only explicitly online reconstructed 3D point. Our approach is compared to bundle adjustment with target tracking in terms of accuracy and computational complexity, using simulated aerial scenarios and real-imagery experiments.

Математична модель функціонування бункера шнекового транспортера-подрібнювача

Шнекові транспортери широко застосовуються в аграрній сфері виробництва для переміщення, змішування, дозування продуктів тощо. Удосконалення існуючих конструкцій шнекових транспортерів і обгрунтування їх раціональних параметрів і режимів роботи дозволяє розширити функціональні можливості технологічних операцій і підвищити продуктивність роботи механізмів загалом. На основі аналізу існуючих гвинтових механізмів запропоновано шнековий транспортер-подрібнювач коренеплодів з комбінованим робочим органом. Він виконаний у вигляді шнекового конвеєра, який встановлено в напрямній трубі, яка має завантажувальний бункер. На внутрішній стороні витків шнека закріплено ножі-подрібнювачі. Наведено результати аналітичних досліджень технологічного процесу переміщення коренеплодів в об’ємному просторі бункера. Розроблено математичну модель функціонального процесу роботи бункера залежно від вхідних і вихідних потоків коренеплодів. Результати досліджень є подальшим кроком з розробки методики обгрунтування параметрів шнекових механізмів. Ключові слова: коренеплоди, завантажувальна горловина, запас коренеплодів, вивантажувальна горловина, споживання запасу, маса коренеплодів

A Fault Model with Two Asperities of Different Areas and Strengths

A fault with two asperities with different areas and strengths is considered. The fault is treated as a dynamical system with two state variables (the slip deficits of the asperities) and four dynamic modes, for which complete analytical solutions are provided. The seismic events generated by the fault can be discriminated in terms of a variable related with the difference between the slip deficits of the asperities at the beginning of the interseismic interval preceding the event. The effect of the difference between the asperity areas on several features of the model, such as the force rates on the asperities, the slip duration and amplitude, the occurrence of events involving the simultaneous motion of the asperities and the radiation of elastic waves, is discussed. As an application, the $$M_w$$ 8.0 2007 Pisco, Peru, earthquake is considered: it is modelled as a two-mode event due to the consecutive failure of two asperities, one almost twice as large as the other. The source function and final seismic moment predicted by the model are found to be in good agreement with observations.