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The core idea of this study is developing a reliable method to manually guide robots in the physical cooperation scenarios, having human safety in priority. To this end, a safe human–robot cooperation algorithm in the presence of physical intentional interactions without employing force and vision sensors is developed. The physical interaction is recognized and controlled through available common sensors. Contact occurrence and its position are investigated by using online external torque vector obtained by residual based observer. Then, the force vector is estimated and employed in the suggested controller for manually guiding the robot. To completely handle the cooperation phase, four guiding scenarios based on actual conditions are recommended. Performance of the proposed controller-observer method during manipulation has been validated through multiple experiments on a KUKA LBR iiwa.

It is so important to consider the passive defense problem in any places there have been attacks by varies kinds of military threats and terrorists. It is certain that social security is related to overcoming on these perils and protection from country. Vital facilities are one of examples that should be protected. Vital facilities include roads, bridges, transmission lines, and telecom and media network. With attention to the intense dependent to export and transmit of oil and gas and with consideration of this point that many places are full of gas and oil resource, the protection of these lines is very important. In recent years, occurrence of varies kinds of terrorist accidents in relation to important structures in all the world causes that the explosion loads have special attention. Explosion can generate much damage with vibration in vast soil media. Thus, it is important to predict the dynamic impact load and its treatment response. With attention to regardable development of numerical methods in recent decades, it is possible to investigate the explosion effects on surface and underground structures. In this research, the newest applied method modeling of the explosion phenomenon has been investigated and comprehensive information has been earned. In this investigation, problem of explosion wave’s propagation effects on buried pipes simulated by ABAQUS/CAE 6.10-1 was studied based on the finite element method. Surface explosion effects on gas buried pipe lines and their dynamic response have been investigated depending on properties and their characteristics. The variation of buried pipe depth effects and variation effects in soil properties around pipe in different cases has been considered, and the results are here. The results showed that in buried pipes under surface explosions, displacements, major stresses, and strains decrease in clay, dense, and loose sands with increase of buried depth. These results obtain that because of increase of closuring of pipes in soil when internal friction angle increases for a kind of soil, the stress on pipe rim will decrease also. It was also observed that the pipe performance in clay and loose sands is better than that in compacted sand, respectively.

Atrial fibrillation (AF) can alter intra-cardiac flow and cardiac output that subsequently affects aortic flow circulation. These changes may become more significant where they occur concomitantly with ageing. Aortic ageing is accompanied with morphological changes such as dilation, lengthening, and arch unfolding. While the recognition of AF mechanism has been the subject of numerous studies, less focus has been devoted to the aortic circulation during the AF and there is a lack of such investigation at different ages. The current work aims to address the present gap. First, we analyse aortic flow distribution in three configurations, which attribute to young, middle and old people, using geometries constructed via clinical data. We then introduce two transient inlet flow conditions representative of key AF-associated defects. Results demonstrate that both AF and ageing negatively affect flow circulation. The main consequence of concomitant occurrence is enhancement of endothelial cell activation potential (ECAP) throughout the vascular domain, mainly at aortic arch and descending thoracic aorta, which is consistent with some clinical observations. The outcome of the current study suggests that AF exacerbates the vascular defects occurred due to the ageing, which increases the possibility of cardiovascular diseases per se. Supplementary Information The online version contains supplementary material available at (10.1007/s10439-021-02744-9).

Herein, the synthesis of a novel highly-oxidized carbon nanotubes (OMWCNT) modified by the Emeraldine salt (ES)-based polyaniline (PANI) nanofibers (NFs) was carried out. The zinc doped OMWCNT-PANI particles were synthesized to achieve novel nanoparticles, enhancing the thermal/mechanical hallmarks and features of the epoxy nano-composite coatings. Various characterization methods were utilized to affirm the triumphant deposition of the Zn-linked PANI nanofibers on the OMWCNT network. The DMTA, TGA, and Raman examinations were applied to delineate the prepared nano-composite films' thermal/mechanical characteristics. The results disclosed that the inclusion of 0.15 wt% of OMWCNT-PANI-Zn into the epoxy matrix has a substantial efficacy on the thermomechanical properties. That is to say, the Tg, storage modulus, cross-linking density, and tensile strength increased about 10.5°C, 17%, 205%, and 137%, respectively, compared with the Neat/EP coating. Additionally, the remaining weight of 14% for OMWCNT-PANI-Zn/EP at 600°C evidenced the significant epoxy composite thermal stability enhancement.

Manipulation and secure transportation of loads by robotic manipulators along predetermined paths is still an open challenge in the robotics field. In this article, the problem of pushing and driving an object on a surface employing a robot to reach a specific destination is considered under a-priori unknown friction conditions. For this purpose, the equations of motion are derived according to the limit surface conceptualization of friction force. Although friction parameters may be considered locally constant, nonetheless they gradually vary over large surfaces. The friction term is thus faced with a slowly time-varying indeterminacy and needs an online estimation scheme. By defining a mission consisting of pushing an object via a robot to find a path among obstacles, an optimum path is firstly planned then a non-linear model predictive controller is used to track the desired path. In order to alleviate the indeterminacy due to friction, the corresponding terms in the equations of motion are set as a disturbance which is estimated by a purposely designed observer and then eliminated in a feedforward manner. There is also no need to perform preliminary offline tests.

Ultrasonic wavefield imaging with a non-contact technology can provide detailed information about the health status of an inspected structure. However, high spatial resolution, often necessary for accurate damage quantification, typically demands a long scanning time. In this work, we investigate a novel methodology to acquire high-resolution wavefields with a reduced number of measurement points to minimize the acquisition time. Such methodology is based on the combination of compressive sensing and convolutional neural networks to recover high spatial frequency information from low-resolution images. A data set was built from 652 wavefield images acquired with a laser Doppler vibrometer describing guided ultrasonic wave propagation in eight different structures, with and without various simulated defects. Out of those 652 images, 326 cases without defect and 326 cases with defect were used as a training database for the convolutional neural network. In addition, 273 wavefield images were used as a testing database to validate the proposed methodology. For quantitative evaluation, two image quality metrics were calculated and compared to those achieved with different recovery methods or by training the convolutional neural network with non-wavefield images data set. The results demonstrate the capability of the technique for enhancing image resolution and quality, as well as similarity to the wavefield acquired on the full high-resolution grid of scan points, while reducing the number of measurement points down to 10% of the number of scan points for a full grid.

PURPOSE: We aimed to investigate the spatial O(3) indices (SOMO35: annual sum of maximum daily 8-h ozone means over 35 ppb, AOT40: the accumulated exposure over an hourly threshold of 40 ppb during daylight hours between 8:00 and 20:00 in the growing seasons of plants) in Tehran (2019–2020). METHODS: The data of ambient O(3) concentrations, measured at twenty-three regulatory ambient air quality monitoring stations (AQMSs) in Tehran, were obtained. RESULTS: The annual mean O(3) concentrations were found to be 15.8–25.7 ppb; the highest and lowest annual mean concentration of ambient O(3) were observed in Shahrdari 22 and Shahr-e-Rey stations, respectively. Spatial distribution of exposure to O(3) across Tehran was in the range of 1.36–1.64; the highest O(3) concentrations were observed in the northern, west and south-western parts of Tehran, while the central and south areas of Tehran city experienced low to moderate concentrations. The indices of SOMO35, AOT40f and AOT40v across AQMSs in Tehran was in the range of 1830–6437 ppb. Days, 10,613–39,505 ppb.h and 4979–16,804 ppb.h, respectively. For Tehran city, the indices of SOMO35 and AOT40f were 4138 ppb. days and 27,556 ppb.h respectively. Our results revealed that the value of SOMO35 across AQMSs of Tehran was higher than the recommended target value of 3000 ppb. days. CONCLUSIONS: To reduce O(3) pollution and its effects on both human and plants health, the governmental organizations should take appropriate sustainable control policies. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40201-020-00552-2) contains supplementary material, which is available to authorized users.

Purpose This computational fluid dynamics study investigates the necessity of incorporating heart failure severity in the preoperative planning of left ventricular assist device (LVAD) configurations, as it is often omitted from studies on LVAD performance. Methods A parametric study was conducted examining a common range of LVAD to aortic root flow ratios (LVAD/AR-FR). A normal aortic root waveform was scaled by 5–30% in increments of 5% to represent the common range of flow pumped by the left ventricle for different levels of heart failure. A constant flow rate from the cannula compensated for the severity of heart failure in order to maintain normal total aortic flow rate. Results The results show that LVAD/AR-FR can have a significant but irregular impact on the perfusion and shear stress-related haemodynamic parameters of the subclavian and carotid arteries. Furthermore, it is found that a larger portion of the flow is directed towards the thoracic aorta at the expense of the carotid and subclavian arteries, regardless of LVAD/AR-FR. Conclusion The irregular behaviour found in the subclavian and carotid arteries highlights the necessity of including the LVAD/AR-FR in the preoperative planning of an LVAD configuration, in order to accurately improve the effects on the cardiovascular system post implantation.

The study aimed to assess the effect of interprofessional education on practice and the impact of participants’ self-efficacy on interprofessional collaboration. The study was a quasi-experimental ...

An extensive study of capillary flow of fluids with various viscosities in straight and periodically constricted microchannels with different surface wettability is presented. Capillary filling speed in hydrophilic, less hydrophilic, and hydrophobic microchannels were experimentally monitored and compared with the Washburn theoretical model. For all liquids, a linear relationship was found between the square of propagation distance and time, which is expected for Newtonian fluids. Experimental results indicated slower velocity compared to the theoretical prediction due to simplifications of the Washburn model. Capillary filling speed of fluids into long-fluororinated chain silane modified channels confirmed the expected lyophobic nature of the coating (i.e., not favorable for either hydrophilic or hydrophobic liquids). Presence of the precursor film ahead of the three-phase contact line in the microscopic level was demonstrated. White light and fluorescent images confirmed the presence of precursor film and capillary evaporation at the interface. Evaporation enhanced the deviation between experimental and theoretical results due to continuous wettability alteration of penetrating fluid.

Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) enable higher efficiency, higher power density, and smaller passive components resulting in lighter, smaller and more efficient electrical systems as opposed to conventional Silicon (Si) based devices. This paper investigates the detailed benefits of using GaN devices in transportation electrification applications. The material properties of GaN including the applications of GaN HEMTs at different switch ratings are presented. The challenges currently facing the transportation industry are introduced and possible solutions are presented. A detailed review of the use of GaN in the Electric Vehicle (EV) powertrain is discussed. The implementation of GaN devices in aircraft, ships, rail vehicles and heavy-duty vehicles is briefly covered. Future trends of GaN devices in terms of cost, voltage level, gate driver design, thermal management and packaging are investigated.

Atrial fibrillation (AF) is the most common type of arrhythmia, which undermines cardiac function. Atrial fibrillation is a multi-facet malady and it may occur as a result of other diseases or it may trigger other problems. One of the main complications of AF is stroke due to the possibility of clot formation inside the atrium. However, the possibility of stroke occurrence due to the AF and the location from which an embolus dispatches are subject of debate. Another hypothesis about the embolus formation during AF is thrombus formation in aorta and carotid arteries, embolus detachment and its movement. To investigate the possibility of the latter postulation, the current work suggests a parametric study to quantify the sensitivity of aortic flow to four common AF traits including lack of atrial kick, atrial remodelling, left ventricle systolic dysfunction, and high frequency fibrillation. The simulation was carried out by coupling several in-house codes and ANSYS-CFX module. The results reveal that AF traits lower flow rate at left ventricular outflow tract, which in general lowers blood perfusion to systemic, cerebral and coronary circulations. Consequently, it leads to endothelial cell activation potential (ECAP) increase and variation of flow structure that both suggest predisposed areas to atherogenesis and thrombus formation in different regions in ascending aorta, aortic arch and descending thoracic aorta. Electronic supplementary material The online version of this article (10.1007/s10439-020-02448-6) contains supplementary material, which is available to authorized users.

This paper provides an update and overview of the Center for Remote Sensing of Ice Sheets (CReSIS) radars and platforms, including representative results from these systems. CReSIS radar systems operate over a frequency range of 14–38 GHz. Each radar system's specific frequency band is driven by the required depth of signal penetration, measurement resolution, allocated frequency spectra, and antenna operating frequencies (often influenced by aircraft integration). We also highlight recent system advancements and future work, including (1) increasing system bandwidth; (2) miniaturizing radar hardware; and (3) increasing sensitivity. For platform development, we are developing smaller, easier to operate and less expensive unmanned aerial systems. Next-generation platforms will further expand accessibility to scientists with vertical takeoff and landing capabilities.

Slippage occurrence has an important roll in stable and robust object grasping and manipulation. However, in majority of prior research on soft finger manipulation, presence of the slippage between fingers and objects has been ignored. In this paper which is a continuation of our prior work, a revised and more general method for dynamic modeling of planar slippage is presented using the concept of friction limit surface. Friction limit surface is utilized to relate contact sliding motions to contact frictional force and moment in a planar contact. In this method, different states of planar contact are replaced with a second-order differential equation. As an example of the proposed method application, dynamic modeling and slippage analysis of object manipulation on a horizontal plane using a three-link soft finger is studied. Then, a controller is designed to reduce and remove the undesired slippage which occurs between the soft finger and object and simultaneously move the object on a predefined desired path. Numerical simulations reveal the acceptable performance of the proposed method and the designed controller.

Biosensors are favored devices for the fast and cost-effective detection of biological species without the need for laboratories. Microfluidic integration with biosensors has advanced their capabilities in selectivity, sensitivity, controllability, and conducting multiple binding assays simultaneously. Despite all the improvements, their design and fabrication are still challenging and time-consuming. The current study aims to enhance microfluidic-integrated biosensors’ performance. Three different functional designs are presented with both active (with the help of electroosmotic flow) and passive (geometry optimization) methods. For validation and further studies, these solutions are applied to an experimental setup for DNA hybridization. The numerical results for the original case have been validated with the experimental data from previous literature. Convection, diffusion, migration, and hybridization of DNA strands during the hybridization process have been simulated with finite element method (FEM) in 3D. Based on the results, increasing the velocity on top of the functionalized surface, by reducing the thickness of the microchamber in that area, would increase the speed of surface coverage by up to 62%. An active flow control with the help of electric field would increase this speed by 32%. In addition, other essential parameters in the fabrication of the microchamber, such as changes in pressure and bulk concentration, have been studied. The suggested designs are simple, applicable and cost-effective, and would not add extra challenges to the fabrication process. Overall, the effect of the geometry of the microchamber on the time and effectiveness of biosensors is inevitable. More studies on the geometry optimization of the microchamber and position of the electrodes using machine learning methods would be beneficial in future works.

In this letter, we extend our recent results on prediction of the older people's perceived difficulty of verbal communication during a humanoid-mediated storytelling experiment to the case of a longitudinal conversation that was conducted over a four-week period and included a battery of conversational topics. For this purpose, we used our model that estimates the older people's perceived difficulty by mapping their prefrontal cortex (PFC) activity during the verbal communication onto fine-grained cluster spaces of a working memory (WM) task that induces loads on human's PFC through modulation of its difficulty level. This enables us to differentially quantify the observed changes in PFC activity during the conversation based on the difficulty level of the WM task. We show that such a quantification forms a reliable basis for learning the PFC activation patterns in response to conversational contents. Our results indicate the ability of our model to predict the older people's perceived difficulty of a wide range of humanoid-mediated tele-conversations, regardless of their type, topic, and duration.

Approximating distributions over complicated manifolds, such as natural images, are conceptually attractive. The deep latent variable model, trained using variational autoencoders and generative adversarial networks, is now a key technique for representation learning. However, it is difficult to unify these two models for exact latent-variable inference and parallelize both reconstruction and sampling, partly due to the regularization under the latent variables, to match a simple explicit prior distribution. These approaches are prone to be oversimplified, and can only characterize a few modes of the true distribution. Based on the recently proposed Wasserstein autoencoder (WAE) with a new regularization as an optimal transport. The paper proposes a stacked Wasserstein autoencoder (SWAE) to learn a deep latent variable model. SWAE is a hierarchical model, which relaxes the optimal transport constraints at two stages. At the first stage, the SWAE flexibly learns a representation distribution, i.e., the encoded prior; and at the second stage, the encoded representation distribution is approximated with a latent variable model under the regularization encouraging the latent distribution to match the explicit prior. This model allows us to generate natural textual outputs as well as perform manipulations in the latent space to induce changes in the output space. Both quantitative and qualitative results demonstrate the superior performance of SWAE compared with the state-of-the-art approaches in terms of faithful reconstruction and generation quality., Comment: arXiv admin note: text overlap with arXiv:1902.05581

This paper examines the effect of mediated hugs that are achieved with a huggable communication medium on the brain activities of users during conversations. We measured their brain activit...

This paper addresses the problem of executing multiple prioritized tasks for robot manipulators with compliant behavior in the remaining null space. A novel controller–observer is proposed to ensure accurate accomplishment of various tasks based on a predefined hierarchy using a new priority assignment approach. Force control, position control and orientation control are considered. Moreover, a compliant behavior is imposed in the null space to handle physical interaction without using joint torque measurements. Asymptotic stability of the task space error and external torque estimation error during executing multiple tasks are shown. The performance of the proposed approach is evaluated on a 7R light weight robot arm by several case studies.

Mechanical energy harvesters are designed to capture the ambient energy and transform it into usable electrical energy. Power harvesting from mechanical vibrations is the fundamental step toward providing self-powered smart systems in the developing wireless and portable electronic devices marketplace. This paper presents a new design and an analytical model for the development of a composite energy harvester by using piezoelectric stacks. The in-plane polarization of the piezoelectric elements and the flexible electrode design using piezoelectric stacks are introduced to maximize the electrical voltage/charge output. The presented model is applicable to composite beams with structural strain rate damping and embedded piezoelectric stacks. The steady state vibration response of the composite harvester subjected to a harmonic base motion is obtained and electrical outputs are analytically derived. Moreover, a parametric study for the composite energy harvester with different embedded piezoelectric stacks number, length and thickness under the excitation in a wide frequency domain has been done. Finally, the new design is compared to a conventional unimorph harvester with identical geometrical and material properties to demonstrate the potential significant improvement in the electrical charge and voltage outputs.

Viscosity reduction is necessary for economical heavy oil production. Dilution of heavy oil with light hydrocarbons is one of the extraction methods as an alternative to the thermal processes. However, in-situ upgrading of heavy oil leads to asphaltene deposition, which causes pore clogging and prevents diluted oil to drain in the direction of production well. Understanding the asphaltene precipitation and deposition mechanism on hydrophilic and hydrophobic porous media improves the efficiency of the solvent-based extraction methods and accuracy of solvent selection in both experiment and simulation. In this work, two different patterns of microfluidic platforms were used to study asphaltene deposition in porous media. Porous media were treated with a silane to evaluate the effect of wettability alteration on asphaltene deposition. Quantitative analysis of the detection point of asphaltene deposition showed faster precipitation from n-pentane in comparison with n-decane as heavier solvent. Helium Ion Microscopy (HIM) analysis was performed on precipitated asphaltene to evaluate the effect of different solvents on the structure of asphaltene precipitates. Moreover, a high-resolution Total Internal Reflection Fluorescence (TIRF) microscopy was used to identify the morphology of precipitated asphaltenes and results compared with HIM analysis. It was found that precipitated asphaltene with n-decane had larger asphaltene particles but fine precipitates from n-pentane led to higher aggregation and flocculation. Formation damage and pore blockage of deposited asphaltene from n-pentane was noticeably higher than n-decane.

In this work, a microfluidic platform along with X-ray computerized tomography were employed to analyze diffusive mass transfer of a low viscosity solvent (hexane) into a high viscosity hydrocarbon (bitumen). T-shaped microfluidic channels were fabricated to measure the diffusion coefficient in significantly shorter times and lower sample volume compared with traditional methods. Semitransparent nature of bitumen facilitates the application of light transmission imaging during the time and relating intensities to solvent concentration. Diffusion mass transfer was studied with respect to Fickian and Single-File mass transfer mechanisms and corresponding equation was applied to calculate both constant and concentration dependent diffusion coefficients. The accuracy of Fickian mass transfer mechanism was confirmed with calculating values of fitting parameter (i.e. nw) in addition to superimposition of data for both techniques. The optimum values of constant diffusion coefficient for T-shaped microchannel and X-ray technique were 2 × 10−10 and 1.8 × 10−10 m2·s−1, respectively. Concentration dependent diffusion coefficients ranged from 1 × 10−12 to 3.6 × 10−10 m2·s−1 for the experiments that reveal constant mutual diffusion coefficient assumption can result in significantly high errors particularly at low and high solvent mass fractions.

This paper presents the free vibration analysis of a non-uniform cone beam with nonlinearly varying axial functionally graded material (FGM) properties. Based on the Adomian decomposition method and a proposed modified mathematical procedure, the vibration mode shapes and natural frequencies of a nonlinearly tapered FGM beam are analytically derived. Several vibration analyses for uniform and non-uniform FGM structures are presented and the results are compared with the existing ones to prove the effectiveness and accuracy of the proposed methodology. Additionally, vibration analysis of exponentially and trigonometrically tapered beams with nonlinearly axial varying FGM properties considering different geometry and material taper ratios was studied and presented. Based on this analytical model, ideal structural design can be efficiently achieved for many engineering applications, such as stability enhancement and energy harvesting.

The paper presents a numerical analysis of pressuremeter test in unsaturated cohesive soils. In practice, pressuremeter is commonly expanded up to 10–15% cavity strains. At these strains, limit pressure is not usually reached, and its value is estimated by extrapolation. Accordingly, authors suggest using cavity pressure at 10% strain (P10) for the interpretation of pressuremeter test rather than limit pressure. At this strain, it is also assured that plastic strain occurs around the cavity, which is crucial for the interpretations. In unsaturated soils, the moisture at which a soil is tested has a noticeable influence on the pressuremeter cavity pressure, and consequently, on the magnitude of P10. In this paper, unsaturated soil behaviour has been captured by Barcelona basic model (BBM), and the influence of each BBM parameter on the P10 value is explored. Next, relative weight analysis technique is performed to investigate the relative importance of BBM parameters in prediction of P10. Artificial intelligence technique of genetic programming is used to develop a relationship to predict the P10 value in unsaturated soils from BBM parameters. Finally, the application of the proposed equation is shown through illustrative examples.

Due to a rapid increase in urbanisation, accurate wind microclimate assessment is of crucial importance. Evaluating wind flows around buildings is part of the planning application process in the design of new developments. In this study, computational fluid dynamics (CFD) simulations are carried out for a case study, representing the East Village in the London Olympic Park. Following a validation test against experimental data for a simpler urban configuration, the key input parameters, including appropriate boundary conditions, mesh setting and type of turbulence model, are selected for the Olympic Park model. All the simulations are conducted using the commercial code STARCCM+ under steady-state conditions with the Reynolds-averaged Navier–Stokes (RANS) method. The turbulence is modelled using different common variants of eddy-viscosity models (EVMs) including standard k-ε, realizable k-ε and standard and shear stress transport (SST) k-ω. The results demonstrate that standard and realisable k-ε models correlate very well with the experimental data, while some discrepancies are found with standard and SST k-ω. Following the determination of areas of high velocity, appropriate tree planting is proposed to overcome the effect of corner and downwash acceleration. With the optimised arrangement of trees and using specific types of tree (e.g., birch), wind speeds at the pedestrian level are reduced by 3.5, 25 and 66% in three main regions of interest. Moreover, we investigate the effects of tree heights. The obtained results illustrate that the wind velocity reduces when the crowns of the trees are located closer to the buildings and the ground. Our high-resolution CFD simulation and results offer a quantitative tool for wind microclimate assessment and optimised design and arrangement of trees around buildings to improve pedestrian comfort.

Purpose/objectives The aim of the study was to assess the professional behavior of dental residents through Professionalism Mini-Evaluation Exercise (P-MEX). Methods This was a descriptive-analytical study. Content validity of P-MEX form was investigated for use in the context of dentistry. A total of 24-item version of P-MEX consisted of doctor-patient relationship skills (n = 7), reflective skills (n = 5), time management (n = 3), and interprofessional relationship skills (n = 9) was used in the present study. Residents in different dental specialties (n = 56) were evaluated by trained raters (448 times). Data were analyzed by descriptive (mean, SD) and analytical tests (Pearson, ANOVA, and post hoc test (Bonferroni)). Results Validity of P-MEX was approved in the field of dentistry. The mean score of professional behavior in residents were reported 2.79 ± 0.24, with minimum and maximum scores of 2.17 and 3.62, respectively. The residents' professional behavior in the domain of reflective skills and doctor-patient relationship skills were lower than the other domains. Conclusion(s) The results showed that the scores of professional behavior among dental residents were classified in the below expectation level and their scores have followed a downward trend from the second year. Therefore, planning for training and continuous assessment of professional behavior among residents in the faculty of dentistry should be considered.

This research identifies the feasibility of training an artificial neural network (ANN) autopilot, using supervised learning techniques, including an imitation learning framework known as the data aggregation set (DAgger) algorithm. The ANN autopilot aims to mimic a unified guidance, navigation & control (GNC) system to fly a fixed-wing UAS. Utilizing high-fidelity nonlinear 6-DOF aircraft simulations, it is shown that several modifications in existing imitation learning techniques must be considered. DAgger algorithm when applied sequentially to augment data along the desired flight trajectory to train the ANN autopilot is unable to generalize across turning and straight-line maneuvers, and hence cannot learn to fly stably, eventually terminating the simulation. Monte-Carlo methods when incorporated into the DAgger algorithm allow for sampling of random data along the desired flight trajectory, proved to be effective to train the ANN autopilot to fly indefinitely with acceptable tracking errors, however undesirable low frequency oscillations were observed in control input and aircraft states. The oscillatory behavior is dealt with by introducing a time-based moving window along the trajectory for data addition in conjunction with the standard DAgger algorithm. Different variations of DAgger algorithms are tested and compared using closed-loop 6-DOF flight simulations. 3D trajectory tracking and stability in aircraft states are evaluated with evidence supporting the idea that an ANN autopilot can behave as a unified GNC system and fly a fixed-wing UAS.

This study investigated the laminar convective heat transfer and fluid flow of Al2O3 nanofluid in a counter flow double-pipe heat exchanger equipped with overlapped twisted tape inserts in both inner and outer tubes. Two models of the same (co-swirling twisted tapes) and opposite (counter-swirling twisted tapes) angular directions for the stationary twisted tapes were considered. The computational fluid dynamic simulations were conducted through varying the design parameters, including the angular direction of twisted tape inserts, nanofluid volume concentration, and Reynolds number. It was found that inserting the overlapped twisted tapes in the heat exchanger significantly increases the thermal performance as well as the friction factor compared with the plain heat exchanger. The results indicate that models of co-swirling twisted tapes and counter-swirling twisted tapes increase the average Nusselt number by almost 35.2&ndash, 66.2% and 42.1&ndash, 68.7% over the Reynolds number ranging 250&ndash, 1000, respectively. To assess the interplay between heat transfer enhancement and pressure loss penalty, the dimensionless number of performance evaluation criterion was calculated for all the captured configurations. Ultimately, the highest value of performance evaluation criterion is equal to 1.40 and 1.26 at inner and outer tubes at the Reynolds number of 1000 and the volume fraction of 3% in the case of counter-swirling twisted tapes model.

Recent advances in guiding and localizing light at the nanoscale exposed the enormous potential of ultrascaled plasmonic devices. In this context, the decay of surface plasmons to hot carriers triggers a variety of applications in boosting the efficiency of energy-harvesting, photocatalysis, and photodetection. However, a detailed understanding of plasmonic hot carrier generation and, particularly, the transfer at metal-semiconductor interfaces is still elusive. In this paper, we introduce a monolithic metal-semiconductor (Al-Ge) heterostructure device, providing a platform to examine surface plasmon decay and hot electron transfer at an atomically sharp Schottky nanojunction. The gated metal-semiconductor heterojunction device features electrostatic control of the Schottky barrier height at the Al-Ge interface, enabling hot electron filtering. The ability of momentum matching and to control the energy distribution of plasmon-driven hot electron injection is demonstrated by controlling the interband electron transfer in Ge, leading to negative differential resistance.

International audience; Investigating group-IV-based photonic components is a very active area of research with extensive interest in developing complementary metal-oxide-semiconductor (CMOS) compatible light sources. However, due to the indirect band gap of these materials, effective light-emitting diodes and lasers based on pure Ge or Si cannot be realized. In this context, there is considerable interest in developing group-IV based Raman lasers. Nevertheless, the low quantum yield of stimulated Raman scattering in Si and Ge requires large device footprints and high lasing thresholds. Consequently, the fabrication of integrated, energy-efficient Raman lasers is challenging. Here, we report the systematic investigation of stimulated Raman scattering (SRS) in Ge nanowires (NWs) and axial Al-Ge-Al NW heterostructures with Ge segments that come into contact with self-aligned Al leads with abrupt metal–semiconductor interfaces. Depending on their geometry, these quasi-one-dimensional (1D) heterostructures can reassemble into Ge nanowires, Ge nanodots, or Ge nanodiscs, which are monolithically integrated within monocrystalline Al (c-Al) mirrors that promote both optical confinement and effective heat dissipation. Optical mode resonances in these nanocavities support in SRS thresholds as low as 60 kW/cm$^2$. Most notably, our findings provide a platform for elucidating the high potential of future monolithically integrated, nanoscale low-power group-IV-based Raman lasers.

Congenital heart disease (CHD) is the most common birth defect globally and coarctation of the aorta (CoA) is one of the commoner CHD conditions, affecting around 1/1800 live births. CoA is considered a CHD of critical severity. Unfortunately, the prognosis for a child born in a low and lower-middle income country (LLMICs) with CoA is far worse than in a high-income country. Reduced diagnostic and interventional capacities of specialists in these regions lead to delayed diagnosis and treatment, which in turn lead to more cases presenting at an advanced stage. Computational fluid dynamics (CFD) is an important tool in this context since it can provide additional diagnostic data in the form of hemodynamic parameters. It also provides an in silico framework, both to test potential procedures and to assess the risk of further complications arising post-repair. Although this concept is already in practice in high income countries, the clinical infrastructure in LLMICs can be sparse, and access to advanced imaging modalities such as phase contrast magnetic resonance imaging (PC-MRI) is limited, if not impossible. In this study, a pipeline was developed in conjunction with clinicians at the Red Cross War Memorial Children’s Hospital, Cape Town and was applied to perform a patient-specific CFD study of CoA. The pipeline uses data acquired from CT angiography and Doppler transthoracic echocardiography (both much more clinically available than MRI in LLMICs), while segmentation is conducted via SimVascular and simulation is realized using OpenFOAM. The reduction in cost through use of open-source software and the use of broadly available imaging modalities makes the methodology clinically feasible and repeatable within resource-constrained environments. The project identifies the key role of Doppler echocardiography, despite its disadvantages, as an intrinsic component of the pipeline if it is to be used routinely in LLMICs.

Traditional path-planning algorithms are entirely reliant on a priori information to function, meaning user interaction is always required. This rigidity constrains the functionality of Unmanned Aerial Systems in search, rescue, and reconnaissance missions. A new adaptive scalable and intelligent path-planning algorithm is developed based on biological evolution and metaheuristic methods that can operate independently of predefined waypoints using an energy constraint cost function to optimize scalability of number of Unmanned Aerial Systems search pathways in dynamically unknown areas. To demonstrate the capabilities of the proposed optimization techniques, several simulations are performed for various number of agents attempting to track both static and dynamic targets which remain unknown to all agents until they are within a range of UAS. Results show that the agents are able to find the desired targets without any a priori information.

An in-house unmanned aerial system (UAS) is designed, analyzed and manufactured to support high-sensitivity and low-frequency ice penetrating radars to be used for research in the polar region. A 55 MHz antenna will be secured onto the wings. The UAS, called Astrid, is designed based on previous research experience that provided information on the significant effects of the polar atmospheric conditions (e.g. wind shear, gusts, etc.) on UAS performance. In addition to the adverse weather conditions, post flight test analysis showed that pusher engines on UASs cause significant changes to the aerodynamic forces and moments generated by the horizontal tail. This is primarily due to the turbulent nature of the propwash slipstreams flowing over the empennage and variation of their turbulency with changes in engine RPM. Based on this information, a wing configuration with a stabilizing polyhedral is selected. Astrid UAS also features a pusher engine with a twin boom, high-horizontal tail offset from the zero-lift plane. A dynamic model for Astrid UAS is developed using Advanced Aircraft Analysis (AAA), a program used to estimate aircraft stability and control derivatives. These derivatives are used to create a linear time-invariant system used for modal analysis. The dynamic model of the aircraft was used to investigate its handling qualities. Astrid's maiden flight test was successfully conducted in October 2019 and the longitudinal dynamic model is validated in subsequent flight tests.

In this paper, the propwash phenomenon for pusher configuration unmanned aerial systems (UASs) is studied. The SkyHunter UAS has the propeller placed aft of the fuselage and in front of the horizontal tail with no offset from the zero lift plane. Thus, the propeller slipstream directly flows over the horizontal tail affecting its aerodynamics. To validate the physics based model developed for propwash impacts and to quantify the effects of propwash, the SkyHunter UAS was equipped with an extra pitot tube. The first pitot tube was placed at the nose of the aircraft where the air is undisturbed and it was measuring the aircraft's velocity. The second pitot tube was placed at different locations on the horizontal tail and three flight tests were conducted. Flight test data showed that the current configuration of the SkyHunter: (A) has large variations in the horizontal tail dynamic pressure ratio along the span of the horizontal tail. (B) had the dynamic pressure ratio higher than 1.7 in two of the three investigated locations along the span of the horizontal tail. This suggests that the theoretical estimate of the dynamic pressure ratio (which is 0.93) may be an under estimation. (C) The dynamic pressure ratio varied with time during flight. A change in the horizontal tail dynamic pressure ratio directly leads to a shift in the location of the aerodynamic center of an aircraft as well as changes in the stability and control derivatives of an aircraft. The implication of these changes in small UASs can be significant since they affect the aircraft longitudinal stability, trim elevator, and flight characteristics. In order to mitigate such changes during flight, a redesign was made to the original empennage design where is an offset was added between the zero lift plane and the aerodynamic center of the horizontal tail. This redesign intends to move the horizontal tail above (and away from) the propeller slipstream. Manufacturing of the redesigned horizontal tail was completed recently and it was flight tested. Flight test data from the new design show that the new design successfully mitigates the effects of the propwash.

The combination of Moore's law and Dennard's scaling rules have constituted the fundamental guidelines for the silicon-based semiconductor industry for decades. Furthermore, the enormous growth of global data volume has pushed the demand for complex and densely packed devices. In recent years, it has become clear that wired interconnects impose increasingly severe speed and power limitations onto integrated circuits as scaling slows toward a halt. To overcome these limitations, there is a clear need for optical data processing. Despite significant progress in the development of silicon photonics, light sources remain challenging owing to the indirect bandgap of group IV materials. It is therefore highly desirable to develop new concepts for a silicon light source that meets efficiency and footprint requirements similar to their electronic counterparts. Here, we demonstrate an electrically driven and tunable silicon light source by matching the resonant modes of a silver nanocavity with the hot luminescence spectrum of an avalanching p-n junction. The cavity significantly enhances phonon-assisted recombination of hot carriers by tailoring the local density of states at the size-tunable resonance. Such tunable nanoscale emitter may be of great interest for short-reach communications, microdisplays or lab-on-chip applications.

This work presents an analytical model for the development of a piezoelectric energy harvester with general nonlinear geometry and functionally graded material (FGM) properties based on Adomian decomposition method. The model is applied to geometrically and materially non-uniform beams with structural strain rate damping and surface bonded piezoelectric layers to derive the dynamic response of the smart structure to base motion excitations and efficiently harvesting the subsequent vibrational energy. Firstly, the steady state vibration response of the smart non-uniform FGM beam subjected to a harmonic base motion is obtained and then electromechanical outputs of the piezoelectric patches are analytically derived. Furthermore, a comprehensive parametric study for bimorph piezoelectric energy harvesters with different nonlinearly tapered geometry and FGM properties in a wide frequency range has been done. Considering the same volume of the harvester, it is demonstrated that the novel non-uniform FGM design can significantly increase the electrical output of the harvester by more than 19.76 times compared to the traditional uniform homogenous design. With the presented methodology, optimum structural design for piezoelectric energy harvesters with respect to the operation frequency domain can be effectively achieved.

In this paper, we present a brief overview of the state of the art in radar systems for ice and snow measurements. Emphasis is given to the instrumentation developed at the University of Kansas for multi-band data retrieval at frequencies ranging from 14 MHz to 38 GHz, which is operated onboard manned and unmanned aircraft. The information collected with these systems is used to estimate parameters such as ice thickness, ice surface and bedrock topography, snow cover thickness on sea ice, and annual snow accumulation. We give a summary of recent field programs (including operations out of Punta Arenas, Chile), present sample results, and discuss recent collaborations with Chilean institutions.

Vibration and stability analysis of nonlinearly tapered cone beams coupled with a piezoelectric layer under compressive axial load is conducted using a new semi-theoretical model based on the Adomian decomposition method and a modified mathematical procedure. The method is applied to tapered structures with perfectly surface-bonded piezoelectric layers and general boundary conditions to analytically derive the natural frequencies and mode shape functions for flutter and buckling analysis. Furthermore, from the optimum structural design perspective, the effects of follower force, geometrical tapering ratio, boundary condition, and applied voltage on piezoelectric layers on the structural stability are thoroughly studied and presented. Simulation results show that the stability of the beam can be noticeably enhanced by the external voltage because of a pair of tensile loads locally induced by the piezoelectric effect. Moreover, for certain boundary conditions and applied voltages, the nonlinear tapered design has much greater buckling and flutter capacities than does the uniform beam. Consequently, the ideal structural design for effective stability enhancement can be reached efficiently.

This paper presents an analytical approach for the development of a new wideband piezoelectric energy harvesting system. The proposed model is based on Adomian decomposition method to derive the dynamic response of the general non-uniform smart structures under external environmental excitations over a wide frequency domain efficiently harvesting the subsequent vibrational energy. The steady-state response of a nonlinearly tapered piezoelectric harvester subjected to harmonic base motion is obtained, and the higher potential electromechanical outputs compared with traditional uniform harvester are analytically derived. Afterward, a group of nonlinearly tapered cantilevers with the same volume and length but different taper ratios and surface bonded piezoelectric layers are assembled together in order to build a broadband piezoelectric energy harvester. Through numerical studies, it is proven that with the proposed non-uniform configuration, the new energy harvester design can function effectively and efficiently with high voltage output over a wide frequency range. The designed wideband harvester can automatically activate one of the non-uniform bimorphs to resonate at particular ambient vibration frequencies and eventually reach the maximum electromechanical output. Based on the proposed theoretical model, an optimum structural design for the wideband piezoelectric energy harvester in the required operational frequency range can be efficiently achieved.

In this paper, two new approaches for handling multiple tasks in redundant manipulators based on predefined allocated priorities are proposed. The first approach is an integrated scheme which emplo...

Numerical simulation is performed to evaluate the privilege of inserting stationary or rotating twisted tape inside a tube as a heat transfer enhancement technique. The main emphasis of this work is placed on understanding the effect of pitch distance on the hydrothermal performance of such a system. The obtained results are validated with published experimental findings. The results of numerical study shows that the heat transfer, pressure drop and total energy consumption are increased by inserting a twisted tape inside a tube. Under the stationary condition, decreasing the pitch distance results in higher Nusselt number together with more friction factor. As the twisted tape starts to rotate (RTT1 case), both Nusselt number and friction factor are further increased. However, decreasing the pitch distance from L/2 to L/6 exhibits a marginal impact on the Nusselt number and friction factor. Further increase in the angular velocity (RTT3 case), although improved the average Nusselt number, comes at the expense of much more friction factor as well as energy consumption. Considering performance evaluation criterion (PEC) as a metric to assess the interaction between heat transfer and energy consumption, it is found that rotating twisted tape is beneficial at lower Reynolds number. Among the design parameters analysed in this research, the highest PEC number of 1.5 corresponds to the case of stationary twisted tape at Reynolds number of 1000 and twisted tape pitch of L/6.

This paper focuses on the dynamic modeling of a cylindrical shell equipped with piezoceramic sensors and actuators, as well as the design of a broad band multi-input and multi-output linear quadratic Gaussian controller for the suppression of vibrations. The optimal locations of actuators are derived by Genetic Algorithm (GA) to effectively control the specific structural modes of the cylinder. The dynamic model is derived based on the Sanders shell theory and the energy approach for both the cylinder and the piezoelectric transducers, all of which reflect the piezoelectric effect. The natural vibration characteristics of the cylindrical shell are investigated both theoretically and experimentally. The theoretical predictions are in good agreement with the experimental results. Then, the broad band multi-input and multi-output linear quadratic Gaussian controller was designed and applied to the test article. An active vibration control experiment is carried out on the cylindrical shell and the digital control system is used to implement the proposed control algorithm. The experimental results show that vibrations of the cylindrical shell can be suppressed by the piezoceramic sensors and actuators along with the proposed controller. The optimal location of the actuators makes the proposed control system more efficient than other configurations.

A turboprop transport Flight Data Recorder data indicates that attempt to recover from the stalled conditions has failed, even though the pitch angle is continuously pushed nose-down in accordance with the published stall-recovery technique. The present study is to examine the reasons for the angle of attack being increased in the first place and not being reduced after stall, even though the longitudinal control is set to nose-down. Fuzzy Logic models are used to preserve nonlinear and unsteady aerodynamic effects. It is found that the increasing angle of attack is initially caused by the nose-up pitching moment due to inertial coupling. In the subsequent nose-down control attempt for stall recovery, the stall angles of attack are still increasingly higher because the pitch rate relative to the rotating axes stays mostly positive. The present simulation study is based on a new method to be called “Fuzzy-Logic Dynamic Inversion,” where desired dynamics with reduced Euler angles and angular rates are specified; while the required control inputs in elevator, aileron and rudder are determined, all through Fuzzy Logic models. Results in elevator, aileron and rudder controls are illustrated to demonstrate the possibility of stall recovery and accident prevention. It is shown that if at the first sign of stall in icing and crosswind flight conditions, and the landing is aborted, stall recovery is possible by applying proper control inputs simultaneously about three control axes to reduce the moments of inertial coupling and the roll and pitch angles.

In this research, an organo-metallic complex based on zinc ions (Znq2), which can be used in organic light-emitting diodes, was investigated. Nanoparticles of ZnO were produced and added to the Znq2 complex. By means of x-ray diffraction, the structure of Znq2 complex and ZnO nanoparticles and the energy levels of them were determined from cyclic-voltammetry analysis. From thermal gravimetric studies, it was found that the complexes have a high thermal stability in the air atmosphere. The purity of samples was confirmed by Fourier transform infrared spectroscopy. The maximum intensity of the photoluminescence spectrum of Znq2 occurred at 565 nm and showed a blue shift to 511 nm by adding ZnO nanoparticles to the Znq2 complex. The optical and electrical properties of the Znq2 and the mixture of Znq2 and ZnO nano powders were studied in order to find any possible applications in organic light emitting devices.

In this paper, the Intelligent Impedance Control based Wavelet Neural Network (IIC-WNN) is introduced as a noble adaptive variable impedance approach to enhance the efficiency of tracking the desired force and interaction with varying unknown (in terms of unknown stiffness and unknown geometric) environment. In the proposed method, a systematic online adaptation mechanism using the wavelet neural network is presented to adapt the impedance parameter according to a variable environment. Using the introduced adaptive law, the robot would be able to track the desired force on the moving environment with the unknown stiffness. Unlike the general impedance control which the position and stiffness of the environment need to be available and known for choosing the impedance parameters, the proposed structure for the impedance equation leads to adapt the impedance parameters according to the interaction environment. In addition, the stability conditions and adaptation laws using Lyapunov’s method for the variable impedance are given to guarantee the force tracking and stability of the closed-loop system. Finally, various numerical and experimental results verify the performance of the proposed adaptive approach. The experimental results strongly prove that the presented method has a better force tracking performance than the general impedance with constant parameters.

One of the main challenges faced by the structural health monitoring community is acquiring and processing huge sets of acoustic wavefield data collected from sensors, such as scanning laser Doppler vibrometers or ultrasonic scanners. In fact, extracting information that allows the estimation of the damage condition of a structure can be a time-consuming process. This paper presents a damage detection and localization technique based on a compressive sensing algorithm, which significantly allows us to reduce the acquisition time without losing in detection accuracy. The proposed technique exploits the sparsity of the wavefield in different representation domains, such as those spanned by wave atoms, curvelets, and Fourier exponentials to recover the full wavefield and, at the same time, to infer the damage location, based on comparison between the wavefield reconstructions produced by the different representation domains. The procedure is applied to three different setups related to an aluminum plate with a notch, a glass fiber reinforced polymer plate with a notch, and a composite plate with a delamination. The results show that the technique can be applied in a variety of structural components to reduce acquisition time and achieve high performance in defect detection and localization by removing up to 80% of the Nyquist sampling grid.

In this work, aminotrimethylene phosphonic acid (ATMP) functionalized graphene oxide (GO) was used for the construction of an epoxy composite coating with superior thermal and mechanical properties. The successful synthesis of the GO-ATMP and GO-ATMP-Zn nano-hybrids was confirmed using FT-IR, XRD, and UV–visible techniques. The TGA test proved the excellent thermal stability of the GO-ATMP-Zn nanoparticle, revealing only 30% weight loss until 600 °C. The prepared nanoparticles were incorporated into the epoxy matrix and characterized via FT-IR and Raman spectroscopy. The results proved that the GO-ATMP-Zn nanoparticles did not negatively affect the curing process and resulted in a less hydrophilic surface (86° water contact angle) than the unfilled coating (68° water contact angle). The DMTA analysis proved the increase of storage modulus (E') and Tg in GO-ATMP-Zn nanocomposite. 0.15% wt. of GO-ATMP-Zn could diminish the thermal decomposition of the epoxy matrix by about 15.7% (at 600 °C), due to its chemical nature and good dispersion in the nanocomposite. Moreover, the flame resistance of the GO-ATMP-Zn/EP nanocomposite was improved significantly compared with the unfilled epoxy coating. The tensile strength tests demonstrated 70% and 74% improvements in the tensile strength (TS) and elongation at break, respectively.

Multi-walled carbon nanotubes (MWCNTs), which are one of the most favorable large aspect ratio hollow-cylindrical nanomaterials, have been considered for numerous advanced applications due to their exceptional thermal-mechanical and electrical characteristics. However, because of the high surface area and being susceptible to agglomeration, they suffered from low dispersion ability. Thus, functionalization with organic and inorganic materials is one of the promising solutions to their limitations. Due to the presence of sp2-bonded carbon atoms, they have no functionalities. One way to generate carboxylic functionalities on MWCNTs is their oxidation. Herein, this study reports the synthesis of a novel highly-oxidized multi-walled carbon nanotube (O-MWCNT) particles modified by the polyaniline (PANI) nanofibers and their performance in the epoxy-based nanocomposites for achieving passive/active anti-corrosion system with efficacious self-healing potency and barrier anti-corrosion characteristic. The O-MWCNT-PANI nanocomposite was then modified by the zinc metal cations to accomplish a smart self-healing anti-corrosion system. The total resistance of about 4000 ohm.cm2 was achieved in the extract with O-MWCNT-PANI-Zn, while the blank sample showed a resistance of about 1200 ohm.cm2 after three hours of immersion time. The most noticeable enhancement of the dual active-barrier protection was obtained in the scratched coatings with modified nano-inhibitors. The more log|Z|10 mHz values were reached, including 4.82 ohm.cm2 and 5.06 ohm.cm2, in O-MWCNT-PANI/EP and O-MWCNT-PANI-Zn/EP, respectively.

Although visual servoing has been considered as a solution to increase dexterity and intelligence of the robotic systems specially in unstructured environments, some prominent deficiencies are preventing it from practical employment. Trajectory planning is a solution to overcome the shortcomings of visual servoing and makes it practical for industrial applications. In this paper, a new trajectory planning technique is developed to perform image-based visual servoing (IBVS) tasks for a 4 DOFs robotic manipulator system. In this method, the camera’s velocity screw is parameterized using time-based profiles. The parameters of the velocity profile are then determined such that the velocity profile takes the robot to its desired position. This is done by minimizing the errors between the initial and desired features. A depth estimation technique is proposed to provide the trajectory planning algorithm with an accurate initial depth. This algorithm is tested and validated via the experiment on a 4 DOFs Denso robot in an eye-in-hand configuration. Experimental results demonstrate that the proposed method provides with a reliable visual servoing algorithm by overcoming the IBVS drawbacks such as surpassing the system limits and causing instability of the system in fulfilling the tasks which require a 180° rotation of the camera about its center.