Rock Mass Characterization by UAV and Close-Range Photogrammetry: A Multiscale Approach Applied along the Vallone dell’Elva Road (Italy)

Geostructural rock mass surveys and the collection of data related to discontinues provide the basis for the characterization of rock masses and the study of their stability conditions. This paper describes a multiscale approach that was carried out using both non-contact techniques and traditional support techniques to survey certain geometrical features of discontinuities, such as their orientation, spacing, and useful persistence. This information is useful in identifying the possible kinematics and stability conditions. These techniques are extremely useful in the case study of the Elva valley road (Northern Italy), in which instability phenomena are spread across 9 km in an overhanging rocky mass. A multiscale approach was applied, obtaining digital surface models (DSMs) at three different scales: large-scale DSM of the entire road, a medium-scale DSM to assess portions of the slope, and a small-scale DSM to assess single discontinuities. The georeferenced point cloud and consequent DSMs of the slopes were obtained using an unmanned aerial vehicle (UAV) and terrestrial photogrammetric technique, allowing topographic and rapid traditional geostructural surveys. This technique allowed us to take measurements along the entire road, obtaining geometrical data for the discontinuities that are statistically representative of the rock mass and useful in defining the possible kinematic mechanisms and volumes of potentially detachable blocks. The main purpose of this study was to analyse how the geostructural features of a rock mass can affect the stability slope conditions at different scales in order to identify road sectors susceptible to different potential failure mechanisms using only kinematic analysis.

Totimorphic assemblies from neutrally stable units

Inspired by the quest for shape-shifting structures in a range of applications, we show how to create morphable structural materials using a neutrally stable unit cell as a building block. This unit cell is a self-stressed hinged structure with a one-parameter family of morphing motions that are all energetically equivalent. However, unlike kinematic mechanisms, the unit cell is not infinitely floppy and instead exhibits a tunable mechanical response akin to that of an ideal rigid-plastic material. Theory and simulations allow us to explore the properties of planar and spatial assemblies of neutrally stable elements, and solve the inverse problem of designing assemblies that can morph from one given shape into another. Simple experimental prototypes of these assemblies corroborate our theoretical results and show that the addition of switchable hinges allows us to create load-bearing structures. Altogether, totimorphs pave the way for structural materials whose geometry and deformation response can be controlled independently and at multiple scales.

Data-driven dictionary design–based sparse classification method for intelligent fault diagnosis of planet bearings

Planet bearings have remained as the challenging components for health monitoring and diagnostics in the planetary transmission systems of helicopters and wind turbines, due to their intricate kinematic mechanisms, strong modulations, and heavy interferences from gear vibrations. To address intelligent diagnostics of planet bearings, this article presents a data-driven dictionary design–based sparse classification (DDD-SC) approach. DDD-SC is free of detecting the weak frequency features and can achieve reliable fault recognition performances for planet bearings without establishing any explicit classifiers. In the first step, DDD-SC implements the data-driven dictionary design with an overlapping segmentation strategy, which leverages the self-similarity features of planet bearing data and constructs the category-specific dictionaries with strong representation power. In the second step, DDD-SC implements the sparsity-based intelligent diagnosis with the sparse representation–based classification criterion and differentiates various planet bearing health states based on minimal sparse reconstruction errors. The effectiveness and superiority of DDD-SC for intelligent planet bearing fault diagnosis have been demonstrated with an experimental planetary transmission system. The extensive diagnosis results show that DDD-SC can achieve the highest diagnosis accuracy, strongest anti-noise performance, and lowest computation costs in comparison with three classical sparse representation–based classification and two advanced deep learning methods.

Depth-dependent inversion of normal faults: Structural analysis of the Penobscot 3D seismic volume, offshore Nova Scotia

<p>The inversion of rift-related faults on passive margins through kinematic reactivation is documented globally. Such structures form an integral part in petroleum systems, provide essential constraints on the kinematic and structural evolution of rifts and passive margins, and can be used as global markers for far-field stresses. Despite the importance of inverted normal faults, the controls on their kinematic evolution, as well as existence and interactions within fault populations are often poorly constrained. Here, we present new structural interpretation and kinematic modelling of an inverted relay ramp structure located offshore Nova Scotia, Canada. This structure is imaged on the Penobscot 3D seismic reflection survey down to ~3.5 s TWTT, and is constrained by two exploration wells. We map two major normal faults that display evidence for inversion in their lower portions (reverse faulting and low-amplitude folding), below ~2.5 s TWTT, though retain a normal offset in upper sections. The wider fault population is dominated by ~ENE-WSW striking normal faults that dip both north and south, while both of the two major faults dip approximately south and are associated with antithetic and synthetic faults. This kinematic dichotomy along the major faults is important as inversion such as this may go unrecognised if seismic data does not image the full depth of a structure. To accommodate such depth-dependent inversion, if both horizons co-existed during inversion, a reduction in volume of the sedimentary package is required between the normal and reverse segments of the fault. In this study, we explore possible kinematic mechanisms to explain inversion structure and the mechanisms accommodating the volumetric changes/ or mass movements required using fault restoration and strain modelling. Our results favour a poly-phase deformation history that can be reconciled with other inversion structures on related passive-margin segments, suggesting these could be widespread processes.</p>

Duty Factor Reflects Lower Limb Kinematics of Running

The aim was to identify the differences in lower limb kinematics used by high (DFhigh) and low (DFlow) duty factor (DF) runners, particularly their sagittal plane (hip, knee, and ankle) joint angles and pelvis and foot segment angles during stance. Fifty-nine runners were divided in two DF groups based on their mean DF measured across a range of speeds. Temporal characteristics and whole-body three-dimensional kinematics of the running step were recorded from treadmill runs at 8, 10, 12, 14, 16, and 18 km/h. Across speeds, DFhigh runners, which limit vertical displacement of the COM and promote forward propulsion, exhibited more lower limb flexion than DFlow during the ground contact time and were rearfoot strikers. On the contrary, DFlow runners used a more extended lower limb than DFhigh due to a stiffer leg and were midfoot and forefoot strikers. Therefore, two different lower limb kinematic mechanisms are involved in running and the one of an individual is reflected by the DF.

Design of a Close Power Loop Test Bench for Contra-Rotating Propellers

The aim of the research is to develop an azimuthing contra-rotating propeller for commercial applications with a power of 2000 kW. The thruster system is designed especially to be installed on high speed crafts (HSCs) for passenger transport with a cruising speed of about 35–40 knots. The topic is very useful because the azimuth thruster solutions currently do not find commercial applications in naval units for passenger transport. The latter are heavy, not very efficient from a hydrodynamic point of view and suitable for maximum cruising speed of about 18–20 knots. The study is interesting because among the advantages that these solutions provide are the possibility of transmitting very high torques and to guarantee a much longer life cycle. In more detail, the propulsion is realized by using a C-drive configuration, with a first mechanical transmission realized by using bevel gears mounted in a frame inside the hull, and a second transmission realized by bevel gears housed in a profiled hull at the lower end of a support structure. In the profiled hull will be installed the shafts of the propellers, in a contra-rotating configuration. In order to optimize the system before its industrial use, a close power loop test bench has been studied and designed to test high power transmissions. The test configuration allows to implement a back-to-back connection between two identical azimuthing contra-rotating propellers. Moreover, the particular test bench allows to size the electric motor simply based on the dissipated power by the kinematic mechanisms. Since the efficiency of these systems are very high, it is not necessary to use large electric motors, thus managing to contain the operating costs of the testing phase. The most significant disadvantage is the need to have two identical transmissions with consequent increase in installation costs. Through the back-to-back test bench it was possible to study the increase in efficiency compared to traditional systems.

Parallel Architectures for Humanoid Robots

The structure of humanoid robots can be inspired to human anatomy and operation with open challenges in mechanical performance that can be achieved by using parallel kinematic mechanisms. Parallel mechanisms can be identified in human anatomy with operations that can be used for designing parallel mechanisms in the structure of humanoid robots. Design issues are outlined as requirements and performance for parallel mechanisms in humanoid structures. The example of LARMbot humanoid design is presented as from direct authors’ experience to show an example of the feasibility and efficiency of using parallel mechanisms in humanoid structures. This work is an extension of a paper presented at ISRM 2019 conference (International Symposium on Robotics and Mechatronics).

A STUDY OF HIGH LIFT AERODYNAMIC DEVICES ON COMMERCIAL AIRCRAFTS

Aerodynamic performance of aircraft wings vary with flight path conditions and depend on efficiency of high lift systems. In this work, a study on high lift devices and mechanisms that aim to increase maximum lift coefficient and reduce drag on commercial aircraft wings is discussed. Typically, such extensions are provided to main airfoil along span wise direction of wing and can increase lift coefficient by more than 100% during operation. Increasing the no of trailing edge flaps in chord wise direction could result in 100% increment in lift coefficient at a given angle of attack but leading edge slats improve lift by delaying the flow separation near stall angle of attack. Different combinations of trailing edge flaps used by Airbus, Boeing and McDonnel Douglas manufacturers are explained along with kinematic mechanisms to deploy them. The surface pressure distribution for 30P30N airfoil is evaluated using 2D vortex panel method and effects of chord wise boundary layer flow transitions on aerodynamic lift generation is discussed. The results showed better agreements with experiment data for high Reynolds number (9 million) flow conditions near stall angle of attack.

Sonations in Migratory and Non-migratory Fork-tailed Flycatchers (Tyrannus savana)

Synopsis Sonations are sounds that animals produce with structures other than the vocal apparatus for communication. In birds, many sonations are usually produced with modified flight feathers through diverse kinematic mechanisms. For instance, aeroelastic fluttering of feathers produces tonal sound when airflow exceeds a threshold velocity and induces flight feathers to oscillate at a constant frequency. The Fork-tailed flycatcher (Tyrannus savana) is a Neotropical bird with both migratory and year-round resident subspecies that differ in the shape of the outer primary feathers of their wings. By integrating behavioral observations, audio recordings, and high-speed videos, we find that male Fork-tailed flycatchers produce sonations with their outer primary feathers P8-10, and possibly P7. These sounds are produced during different behavioral contexts including: the pre-dawn display, intraspecific territorial disputes, when attacking potential nest predators, and when escaping. By placing feathers in a wind tunnel, we elicited flutter at frequencies that matched the acoustic signature of sounds recorded in the wild, indicating that the kinematic mechanism responsible for sound production is aeroelastic flutter. Video of wild birds indicated that sonations were produced during the downstroke. Finally, the feathers of migratory (T.s.savana) and year-round resident (T.s.monachus) Fork-tailed flycatchers flutter in feather locations that differ in shape between the subspecies, and these shape differences between the subspecies result in sounds produced at different frequencies.