High gear ratio mechanical transmissions for actuators: Simplified models for efficiency under opposing and aiding loads

Planetary gear drives are widely employed in electrical and hydraulic actuation systems, to adapt a high speed, low torque motor to a low speed, high torque user, within strict weight and volume constraints. During the early design phases of these devices, accurate yet simple simulation models are required to evaluate the performance of a given configuration of the device. Similar models are also useful within diagnostic and health monitoring analyses of existing machines, as a discrepancy between the actual behaviour of the physical system and that predicted by its digital twin may be the effect of a damage. This work compares different models available in literature for the efficiency of high gear ratio mechanical transmissions; the models are applied to multiple arrangements common for planetary drives, and the results in form of an efficiency map for the transmissions are compared and discussed. The simulations provide different levels of detail, and require different levels of knowledge about the specific architecture of the system. All of them are able to deal with dry friction; additionally, the different behaviour of the transmission under the effect loads aligned in the same direction of speed or in the opposite one is accounted for

Gray matter reduction in high-risk subjects, recently diagnosed and chronic patients with schizophrenia: A revised coordinate-based meta-analysis

INTRODUCTION: Characterizing neuroanatomical markers of different stages of schizophrenia (SZ) to assess of how the disorder develops is extremely important for the clinical practice. It still remains uncertain how abnormalities are formed as SZ progresses. OBJECTIVES: We reviewed and analyzed 113 voxel based morphometry studies on people at risk of or with schizophrenia to assess GM alterations at different stages of the disorder and to functionally characterize these GM variations. METHODS: We performed a meta-analysis of voxel-based morphometry studies of genetic and clinical high-risk subjects (g-/c-HR), recently diagnosed (RDSZ) and chronic SZ patients (ChSZ). We quantified gray matter (GM) changes associated with these four conditions and compared them with contrast and conjunctional data. We performed the behavioral analysis and networks decomposition of alterations to obtain their functional characterization. RESULTS: Compared to previous investigations, results reveal a robust cortical-subcortical, left-to-right homotopic progression of GM loss. The right anterior cingulate is the only altered region in all conditions. Contrast analyses show left-lateralized insular, amygdalar and parahippocampal GM reduction in RDSZ, which appears bilateral in ChSZ. An overlap between RDSZ and ChSZ is observed in the left insula, amygdala, precentral and inferior frontal gyri. Functional decomposition shows involvement of the salience network, with an enlargement of the sensorimotor network in RDSZ and the thalamus-basal nuclei network in ChSZ. [Figure: see text] CONCLUSIONS: These results can help the research on diagnostic and neuroimaging biomarkers of SZ staging, as well as on the identification of new therapeutics neuroanotomic targets that could be addressed with focused magnetic or non-invasive electric stimulation. DISCLOSURE: No significant relationships

Time perception and the experience of agency in meditation and hypnosis

Mindfulness meditation and hypnosis are related in opposing ways to awareness of intentions. The cold control theory of hypnosis proposes that hypnotic responding involves the experience of involuntariness while performing an actually intentional action. Hypnosis therefore relies upon inaccurate metacognition about intentional actions and experiences. Mindfulness meditation centrally involves awareness of intentions and is associated with improved metacognitive access to intentions. Therefore, mindfulness meditators and highly hypnotizable people may lie at opposite ends of a spectrum with regard to metacognitive access to intention‐related information. Here we review the theoretical background and evidence for differences in the metacognition of intentions in these groups, as revealed by chronometric measures of the awareness of voluntary action: the timing of an intention to move (Libet's “W” judgments) and the compressed perception of time between an intentional action and its outcome (“intentional binding”). We review these measures and critically evaluate their proposed connection to the experience of volition and sense of agency

Residual strength evaluation of Notre Dame surviving masonry after the fire

An impressive fire devastated the cathedral of Notre Dame in Paris, one of the symbols of European architecture. The flames spread from the scaffolding embracing the base of the spire on the cathedral roof. The fire blazed up in the church during the religious celebration on April 15th at 6:45 p.m. The fire enveloped abruptly the roof and the spire erected by Viollet-le-Duc in 1860. The collapse took place about 80 min around 8 p.m [1–3]. Today, the clamor is all around, the silence is in the heart. At the time of the present paper, the causes of the catastrophe are still wrapped in a dense smoke, like the one generated by the burning “forest”– as the roof structure was called. This is the figure of the disaster. The Cathedral's inferno devastated a world treasure, prompting an outpouring of collective sorrow and soul-searching over whether to recreate the destroyed oak-framed roofing and spire or adapt the cathedral to the 21st century. In the present paper, a computer-based fire simulation model based on Computational Fluid Dynamics (CFD) was used to determine the spread of fire and smokes into the structure of the roof and, at the same time, an original evaluation of the residual strength taking into account the fire effect and the water saturation in the limestone after the extinguishing was estimated. The residual strength ratio (RSR) and the compressive strength (CS) evolution are carefully evaluated for the injured structures. An estimation of the residual effective strength of the masonry walls of the Cathedral is proposed

COMPLIANT LEGS IN BIPED ROBOTS FOR RUNNING OPTIMIZATION

Bipedal robotic locomotion is one of the most complex robotic research field, in which many aspects must be studied (i.e., dynamic balance, interaction with different terrains, walking cycle, running cycle, etc.). In this paper, compliant legs are implemented in a virtual biped robot in order to increase walking and running performances. The virtual model has been presented in other works and it is optimised and validated in this paper. Several simulations have been made implementing different values of stiffness in the legs of the virtual robot. A comparison between compliant and no compliant legs has been performed presenting innovative results. The conceived idea of the biped robot with compliant legs allows to increase the locomotion performances of bipedal robots and can be used to design innovative personal vehicles and exoskeletons in the next future