38,767 research outputs found
Towards the development of a smart flying sensor: illustration in the field of precision agriculture
Sensing is an important element to quantify productivity, product quality and to make decisions. Applications, such as mapping, surveillance, exploration and precision agriculture, require a reliable platform for remote sensing. This paper presents the first steps towards the development of a smart flying sensor based on an unmanned aerial vehicle (UAV). The concept of smart remote sensing is illustrated and its performance tested for the task of mapping the volume of grain inside a trailer during forage harvesting. Novelty lies in: (1) the development of a position-estimation method with time delay compensation based on inertial measurement unit (IMU) sensors and image processing; (2) a method to build a 3D map using information obtained from a regular camera; and (3) the design and implementation of a path-following control algorithm using model predictive control (MPC). Experimental results on a lab-scale system validate the effectiveness of the proposed methodology
Automated single-cell motility analysis on a chip using lensfree microscopy.
Quantitative cell motility studies are necessary for understanding biophysical processes, developing models for cell locomotion and for drug discovery. Such studies are typically performed by controlling environmental conditions around a lens-based microscope, requiring costly instruments while still remaining limited in field-of-view. Here we present a compact cell monitoring platform utilizing a wide-field (24 mm(2)) lensless holographic microscope that enables automated single-cell tracking of large populations that is compatible with a standard laboratory incubator. We used this platform to track NIH 3T3 cells on polyacrylamide gels over 20 hrs. We report that, over an order of magnitude of stiffness values, collagen IV surfaces lead to enhanced motility compared to fibronectin, in agreement with biological uses of these structural proteins. The increased throughput associated with lensfree on-chip imaging enables higher statistical significance in observed cell behavior and may facilitate rapid screening of drugs and genes that affect cell motility
Control and ultrasonic actuation of a gas-liquid interface in a microfluidic chip
This article describes the design and manufacturing of a microfluidic chip,
allowing for the actuation of a gas-liquid interface and of the neighboring
fluid. A first way to control the interface motion is to apply a pressure
difference across it. In this case, the efficiency of three different
micro-geometries at anchoring the interface is compared. Also, the critical
pressures needed to move the interface are measured and compared to theoretical
result. A second way to control the interface motion is by ultrasonic
excitation. When the excitation is weak, the interface exhibits traveling
waves, which follow a dispersion equation. At stronger ultrasonic levels,
standing waves appear on the interface, with frequencies that are half integer
multiple of the excitation frequency. An associated microstreaming flow field
observed in the vicinity of the interface is characterized. The meniscus and
associated streaming flow have the potential to transport particles and mix
reagents
Experimental investigation of some aspects of insect-like flapping flight aerodynamics for application to micro air vehicles
Insect-like flapping flight offers a power-efficient and highly manoeuvrable basis for micro air vehicles for indoor applications. Some aspects of the aerodynamics associated with the sweeping phase of insect wing kinematics are examined by making particle image velocimetry measurements on a rotating wing immersed in a tank of seeded water. The work is motivated by the paucity of data with quantified error on insect-like flapping flight, and aims to fill this gap by providing a detailed description of the experimental setup, quantifying the uncertainties in the measurements and explaining the results. The experiments are carried out at two Reynolds numbers-500 and 15,000-accounting for scales pertaining to many insects and future flapping-wing micro air vehicles, respectively. The results from the experiments are used to describe prominent flow features, and Reynolds number-related differences are highlighted. In particular, the behaviour of the leading-edge vortex at these Reynolds numbers is studied and the presence of Kelvin-Helmholtz instability observed at the higher Reynolds number in computational fluid dynamics calculations is also verified
3D Microfluidic model for evaluating immunotherapy efficacy by tracking dendritic cell behaviour toward tumor cells
Immunotherapy efficacy relies on the crosstalk within the tumor microenvironment between cancer and dendritic cells (DCs) resulting in the induction of a potent and effective antitumor response. DCs have the specific role of recognizing cancer cells, taking up tumor antigens (Ags) and then migrating to lymph nodes for Ag (cross)-presentation to naïve T cells. Interferon-α-conditioned DCs (IFN-DCs) exhibit marked phagocytic activity and the special ability of inducing Ag-specific T-cell response. Here, we have developed a novel microfluidic platform recreating tightly interconnected cancer and immune systems with specific 3D environmental properties, for tracking human DC behaviour toward tumor cells. By combining our microfluidic platform with advanced microscopy and a revised cell tracking analysis algorithm, it was possible to evaluate the guided efficient motion of IFN-DCs toward drug-treated cancer cells and the succeeding phagocytosis events. Overall, this platform allowed the dissection of IFN-DC-cancer cell interactions within 3D tumor spaces, with the discovery of major underlying factors such as CXCR4 involvement and underscored its potential as an innovative tool to assess the efficacy of immunotherapeutic approaches
Decentralized collaborative transport of fabrics using micro-UAVs
Small unmanned aerial vehicles (UAVs) have generally little capacity to carry
payloads. Through collaboration, the UAVs can increase their joint payload
capacity and carry more significant loads. For maximum flexibility to dynamic
and unstructured environments and task demands, we propose a fully
decentralized control infrastructure based on a swarm-specific scripting
language, Buzz. In this paper, we describe the control infrastructure and use
it to compare two algorithms for collaborative transport: field potentials and
spring-damper. We test the performance of our approach with a fleet of
micro-UAVs, demonstrating the potential of decentralized control for
collaborative transport.Comment: Submitted to 2019 International Conference on Robotics and Automation
(ICRA). 6 page
On the trade-off between electrical power consumption and flight performance in fixed-wing UAV autopilots
This paper sets out a study of the autopilot design for fixed wing Unmanned Aerial Vehicles (UAVs) taking into account the aircraft stability, as well as the power consumption as a function of the selected control strategy. To provide some generality to the outcomes of this study, construction of a reference small-UAV model, based on averaging the main aircraft defining parameters, is proposed. Using such a reference model of small, fixed-wing UAVs, different control strategies are assessed, especially with a view towards enlarging the controllers' sampling time. A beneficial consequence of this sample time enlargement is that the clock rate of the UAV autopilots may be proportionally reduced. This reduction in turn leads directly to decreased electrical power consumption. Such energy saving becomes proportionally relevant as the size and power of the UAV decrease, with benefits of lengthening battery life and, therefore, the flight endurance. Additionally, through the averaged model, which is derived from both published data and computations made from actual data captured from real UAVs, it is shown that behavior predictions beyond that of any particular UAV model may be extrapolated.Peer ReviewedPostprint (author's final draft
Solitonic State in Microscopic Dynamic Failures
Onset of permanent deformation in crystalline materials under a sharp
indenter tip is accompanied by nucleation and propagation of defects. By
measuring the spatio-temporal strain field nearthe indenter tip during
indentation tests, we demonstrate that the dynamic strain history at the moment
of a displacement burst carries characteristics of formation and interaction of
local excitations, or solitons. We show that dynamic propagation of multiple
solitons is followed by a short time interval where the propagating fronts can
accelerate suddenly. As a result of such abrupt local accelerations, duration
of the fast-slip phase of a failure event is shortened. Our results show that
formation and annihilation of solitons mediate the microscopic fast weakening
phase, during which extreme acceleration and collision of solitons lead to
non-Newtonian behavior and Lorentz contraction, i.e., shortening of solitons
characteristic length. The results open new horizons for understanding dynamic
material response during failure and, more generally, complexity of earthquake
sources
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