Experiments on magnetic interference for a portable airborne magnetometry system using a hybrid unmanned aerial vehicle (UAV)

Using unmanned aerial vehicles (UAVs) for airborne magnetometry offers not only improved access and rapid sampling but also reduced logistics costs. More importantly, the UAV-borne aeromagnetometry can be performed at low altitudes, which makes it possible to resolve fine features otherwise only evident in ground surveys. Developing such a UAV-borne aeromagnetometry system is challenging owing to strong magnetic interference introduced by onboard electric and electronic components. An experiment concerning the static magnetic interference of the UAV was conducted to assess the severity of the interference of a hybrid vertical take-off and landing (VTOL) UAV. The results of the static experiment show that the wing area is highly magnetic due to the proximity to servomotors and motors, whereas the area along the longitudinal axis of the UAV has a relatively smaller magnetic signature. Assisted by the static experiment and aerodynamic simulations, we first proposed a front-mounting solution with two compact magnetometers. Subsequently, two dynamic experiments were conducted with the setup to assess the dynamic interference of the system. The results of the dynamic experiments reveal that the strongest source of in-flight magnetic interference is the current-carrying cables connecting the battery to the flight controller and that this effect is most influential during pitch maneuvers of the aircraft.

Experiments on magnetic interference for a portable airborne magnetometry system using a hybrid unmanned aerial vehicle (UAV)

Airborne magnetic surveys are an important and efficient tool for mapping the subsurface, providing insights e.g. into mineral deposits. Compared to traditional ground methods, airborne magnetic surveys offer great advantages with improved access and rapid sampling. But the cost and hassle of transporting and operating a conventional manned airborne magnetic survey system are strong impediments for its wider use. In addition, the conventional airborne systems are challenged by the need for low-altitude (≤ 80 m) surveying to detect small-scale subsurface features evident in ground surveys. Portable and compact airborne magnetic survey systems using unmanned aerial vehicles (UAVs) can not only bridge the gap between conventional airborne magnetic surveys and ground magnetic surveys but also complement magnetic surveys to fit broader geophysical applications. Therefore, developing high-quality, stable, and portable UAV-borne survey systems is of high interest to the geophysical exploration community. However, developing such a system is challenging owing to strong magnetic interference introduced by onboard electric engines and other onboard electronic devices. As a result, tests concerning the static and dynamic magnetic interference of a UAV are critical to assess the severity of the interference and can help to improve the design of the system at the early stage of development. A static experiment and two dynamic experiments were conducted to understand the characterization of the magnetic interference of our hybrid vertical take-off and landing (VTOL) UAV. The results of the static experiment show that the wing area is highly magnetic due to the proximity to servomotors and motors, but the area along the longitudinal axis of the UAV is relatively magnetically quiet. To reduce the magnetic signature, the highly-magnetic servomotors on the wings were replaced with less magnetic servomotors of a brush-less type. Assisted by aerodynamic simulations, we further designed a front-mounting solution for two compact magnetometers. Two dynamic experiments were conducted with this setup to understand the dynamic interference of the UAV in operation. The results of the dynamic experiments reveal that the strongest source of in-flight magnetic interference is mainly due to the cables connecting the battery to the flight controller and that this effect is most influential during pitch maneuvers of the aircraft.

Experimental Research on the Characteristics of Thermal Bow in an Aeroengine HP Spool

During the cooling process after shut down for aeroengines, internal hot air rises and cold air drops due to natural convection, which makes uneven temperature distribution in the casing and creates temperature difference in radial and axial directions, causing uneven deformation of rotor. Once aeroengine starts after a little time of cooling, thermal bow forms more easily, causing excessive vibration. In some cases, the thermal bow can be so severe that the engine will be unable to start. Based on the rotor for one certain type of aeroengine, the paper describes an experiment of thermal bow failure, which is divided into a static one and a dynamic one, both having simulated the uneven temperature field. Firstly, the static experiment measures temperature difference and deformation of rotor in different temperature environments and dissimilar cold blowing conditions. Results show temperature difference of each cross section increases with the growth of casing temperature. And cold blowing can quickly and effectively eliminate uneven temperature distribution and structural deformation. Secondly, the dynamic experiment produces the results that the vibration amplitude increases obviously when rotating frequency approaches critical speeds (2365r/min and 2892r/min). As the cooling time increases, the amplitude decreases until normal, which is the most important feature different from that in failure of initial mass imbalance. Thermal bow mainly influences the fundamental frequency vibration. Cold blowing can quickly and effectively reduce vibration amplitude. The conclusions obtained from the dynamic experiments are consistent with the known regulations from engineering experience.

DEFORMATION RESPONSE OF POLYDIMETHYLSILOXANE SUBSTRATES SUBJECTED TO UNIAXIAL QUASI-STATIC LOADING

To investigate cellular response of cardiomyocytes to substrate mechanics, biocompatible material with stiffness in physiological range is needed. PDMS based material is used for construction of microfluidic organ on chip devices for cell culture due to ease of device preparation, bonding, and possibility of surface functionalization. However it has stiffness orders of magnitude out of physiological range. Therefore, we adapted recently available protocol aiming to prepare substrates which offer stiffness in physiological range 5−100kPa using various mixtures of Sylgard. An in-house developed loading device with single micron position tracking accuracy and sub-micron position sensitivity was adapted for this experimental campaign. All batches of the samples were subjected to uniaxial loading. During quasi-static experiment the samples were compressed to minimally 40% deformation. The results are represented in the form of stress-strain curves calculated from the acquired force and displacement data and elastic moduli are estimated.

Dollars do not determine detection: Monetary value associated with unexpected objects does not affect the likelihood of inattentional blindness

Conscious perception often fails when an object appears unexpectedly and our attention is focused elsewhere (inattentional blindness). Although various factors have been identified that modulate the likelihood of this failure of awareness, it is not clear whether the monetary reward value associated with an object can affect whether or not this object is detected under conditions of inattention. We hypothesised that unexpectedly appearing objects that contain a feature linked to high value, as established via reward learning in a previous task, would subsequently be detected more frequently than objects containing a feature linked to low value. A total of 537 participants first learned the association between a perceptual feature (colour) and subsequent reward values (high, low, or none reward). Afterwards, participants were randomly assigned to a static (Experiment 1) or dynamic (Experiment 2) inattentional blindness task including an unexpected object associated with high, low, or none reward. However, no significant effect of the previously learned value on the subsequent likelihood of detection was observed. We speculate that artificial monetary value, which is known to affect attentional capture, is not strong enough to determine whether or not an object is consciously perceived.

Static Experiment and Finite Element Analysis of a Multitower Cable-Stayed Bridge with a New Stiffening System

Based on the stiffness limitations of the midtower in multitower cable-stayed bridges, a new stiffening system (tie-down cables) is proposed in this paper. The sag effects and wind-induced responses can be reduced with the proposed system because tie-down cables are short and aesthetic compared with traditional stiffening cables. The results show that the stiffening effect of tie-down cables is better than that of traditional stiffening cables in controlling the displacement and internal force of the bridge based on a static experiment and finite element analysis. Therefore, the proposed system can greatly improve the overall stiffness of a bridge, and its stiffening effect is better than that of traditional stiffening cables in controlling the displacement and internal force. The results provide a reference for the application of such systems in practical engineering.