Flight Measurements Research Articles

Robust multiple sensor localization via semidefinite relaxation in wireless sensor networks with anchor position uncertainty

Sensor localization is an important step of wireless sensor network (WSN) before conducting a common surveillance task. We propose a robust multiple sensor cooperative localization method against the uncertainty of anchor position estimate based on Time of Flight (TOF) measurements. A key feature is that it makes no statistic assumption on the anchor position uncertainties, which are often difficult to obtain, and only assumes that the error modulus of anchor position is upper bounded. The Maximum likelihood (ML) problem is formulated, where both the TOF measurements between anchors and sensors and the measurements among sensors are utilized in a cooperative way. The semidefinite relaxation technique is provided to transform the nonconvex ML problem into a convex one. The Cramer–Rao lower bounds with and without anchor position uncertainties are also derived. The simulation and experimental results show that our method can yield a good estimate compared to other localization methods.

Enhancing sensitivity to rotations with quantum solitonic currents

We study a gas of attracting bosons confined in a ring shape potential pierced by an artificial magnetic field. Because of attractive interactions, quantum analogs of bright solitons are formed. As a genuine quantum-many-body feature, we demonstrate that angular momentum fractionalization occurs and that such an effect manifests on time of flight measurements. As a consequence, the matter-wave current in our system can react to very small changes of rotation or other artificial gauge fields. We worked out a protocol to entangle such quantum solitonic currents, allowing us to operate rotation sensors and gyroscopes to Heisenberg-limited sensitivity. Therefore, we demonstrate that the specific coherence and entanglement properties of the system can induce an enhancement of sensitivity to an external rotation.

Estimation of sulfuric acid concentration using ambient ion composition and concentration data obtained with atmospheric pressure interface time-of-flight ion mass spectrometer

Abstract. Sulfuric acid (H2SO4, SA) is the key compound in atmospheric new particle formation. Therefore, it is crucial to observe its concentration with sensitive instrumentation, such as chemical ionisation (CI) inlets coupled to atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometers. However, there are environmental conditions for which and physical reasons why chemical ionisation cannot be used, for example in certain remote places or during flight measurements with limitations regarding chemicals. Here, we propose a theoretical method to estimate the SA concentration based on ambient ion composition and concentration measurements that are achieved by APi-TOF alone. We derive a theoretical expression to estimate the SA concentration and validate it with accurate CI-APi-TOF observations. Our validation shows that the developed estimate works well during daytime in a boreal forest (R2=0.85); however, it underestimates the SA concentration in, e.g. the Antarctic atmosphere during new particle formation events where the dominating pathway for nucleation involves sulfuric acid and a base (R2=0.48).

Indoor Positioning of Low-Cost Narrowband IoT Nodes: Evaluation of a TDoA Approach in a Retail Environment.

The localization of internet of things (IoT) nodes in indoor scenarios with strong multipath channel components is challenging. All methods using radio signals, such as received signal strength (RSS) or angle of arrival (AoA), are inherently prone to multipath fading. Especially for time of flight (ToF) measurements, the low available transmit bandwidth of the used transceiver hardware is problematic. In our previous work on this topic we showed that wideband signal generation on narrowband low-power transceiver chips is feasible without any changes to existing hardware. Together with a fixed wideband receiving anchor infrastructure, this facilitates time difference of arrival (TDoA) and AoA measurements and allows for localization of the fully asynchronously transmitting nodes. In this paper, we present a measurement campaign using a receiver infrastructure based on software-defined radio (SDR) platforms. This proves the actual usability of the proposed method within the limitations of the bandwidth available in the ISM band at . We use the results to analyze the effects of possible anchor placement schemes and scenario geometries. We further demonstrate how this node-to-infrastructure-based localization scheme can be supported by additional node-to-node RSS measurements using a simple clustering approach. In the considered scenario, an overall positioning root-mean-square error (RMSE) of is achieved.

Airborne GNSS-R Polarimetric Multiincidence Data Analysis for Surface Soil Moisture Estimation Over an Agricultural Site

The objective of this study is to propose a mapping of surface soil moisture ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SSM</i> ) using airborne measurements based on the GLObal Navigation Satellite System Reflectometry Instrument (GLORI), a polarimetric instrument. GNSS-R measurements were acquired at the agricultural Urgell site in Spain in July 2021. In situ measurements describing the soil moisture and roughness and the vegetation cover leaf area index were then obtained simultaneously with flight measurements. An analysis of observable copolarization (right-right) reflectivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\rm{\Gamma }}}_{RR}$</tex-math></inline-formula> and the cross-polarization (right-left) reflectivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\ {\Gamma }_{RL}$</tex-math></inline-formula> behaviors as a function of incidence angle is proposed, as is normalization of the reflectivity function of the incidence angle. The sensitivity of reflectivities is then proposed as a function of surface soil moisture. An empirical model with two variables, soil moisture and the normalized difference vegetation index ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NDVI</i> ), based on the principle of the tau-omega model is then considered for the inversion of GNSS-R reflectivity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\Gamma }_{RL}\ $</tex-math></inline-formula> and estimation of soil moisture. This model is calibrated and validated by a threefold cross-validation approach. A mapping of SSM at 100 m resolution is created with data from the studied site and three acquired flights.

Computation of static disturbances experienced by a launch vehicle during the flight

During its course from a launch site to an intended orbit, a launch vehicle faces an adverse environment and withstand a plethora of disturbances. The set of disturbance forces acting on each stage of the vehicle depends on the configuration of that stage. Different methodologies are used to predict the magnitude of static disturbances before the flight. To ensure the launch success, performance of a flight control system is validated using a high fidelity six degrees of freedom simulation testbed, in the presence of predicted magnitude of these disturbances. Magnitude experienced by the launch vehicle during its maiden flight, might vary from the predicted set. Actual magnitude of these disturbances is known only after the flight in post-flight exercise of matching launch vehicle dynamics using ground simulations. Correct information of the magnitude of these disturbances is of significant importance for subsequent developmental flights. Control power plant sizing, preflight actuator biasing to nullify lift-off disturbance and autopilot integrator limit setting are all dependent on the exact knowledge of these sources of disturbances. Flight data measurements of a launch vehicle offer a rich galore of information in this regard. This paper presents an analytical technique which uses flight measurements to compute static disturbances experienced during the flight by a launch vehicle. The main sources of steady disturbances considered in this paper are center of gravity, thrust-line offset and thrust misalignment.

Flight Measurement System for Airship Propeller Based on Tube-type Strain Gauge Balance

Flight Measurement System for Airship Propeller Based on Tube-type Strain Gauge Balance

Bipolar 1,8-naphthalimides showing high electron mobility and red AIE-active TADF for OLED applications.

Aiming to design bipolar organic semiconductors with high electron mobility and efficient red thermally activated delayed fluorescence (TADF), three donor-acceptor compounds were designed and synthesized selecting 1,8-naphthalimide as an acceptor and phenoxazine, 3,7-di-tert-butylphenothiazine or 2,7-di-tert-butyldimethyl-9,10-dihydroacridine as donor moieties. Aggregation induced emission enhancement was detected for the compounds causing efficient TADF in the solid-state. Photoluminescence quantum yields up to 77% were observed for the films of the compounds doped in a host. The compounds exhibited small singlet-triplet splitting (0.03-0.05 eV), and high reverse intersystem crossing rates of 2.08 × 105-1.13 × 106 s-1. The compounds were characterized by satisfactory hole and electron-injecting properties with ionization potentials of 5.72-5.83 eV and electron affinities of 2.79-2.91 eV. Bipolar charge transport was revealed by time of flight measurements. Electron transport with low dispersity and mobilities exceeding 2 × 10-3 cm2 V-1 s-1 was observed at an electric field of 4.6 × 105 V cm-1. The compounds were used as emitters in red electroluminescent devices, which showed maximum external quantum efficiencies up to 8.2%. Utilization of host-guest systems as light-emitting materials with hosts preferably transporting holes and TADF guests which preferably transport electrons allowed maximum efficiencies to be achieved at a practical brightness of 700-2200 cd m-2. DFT calculations of the geometry, electronic structure, absorption and photoluminescence spectra of all compounds were carried out to prove the conclusions drawn from the experiment. The results of the calculations clearly show that the first excited state for all compounds is the intramolecular charge transfer state. Quantitative analysis of the separation degree of electronic density during excitation allows the observed dependence of the blue shift value in the absorption and emission spectra on the increasing polarity of the solvent to be explained.

Complex Fuzzy Assessment of Green Flight Activity Investments for Sustainable Aviation Industry

The aviation industry harms the environment mainly via the creation of carbon emissions. Hence, action needs to be taken to ensure the environmental sustainability of the aviation industry such as the recycling of waste products, effective waste management and the introduction of energy efficiency measures. However, at the same time, the implementation of improvements to remediate such problems leads to the creation of additional costs for aviation companies. Companies thus need to conduct comprehensive priority analyses regarding the optimum strategy for the sustainability of the aviation industry. However, there is a very limited number of studies in the literature that focused on which approach should be prioritized. Accordingly, this study aimed at the assessment of the viability of investing in so-called green flight measures in the aviation industry, for which a completely original decision-making model was created. Firstly, the various strategic priorities were weighted and the impact-relation directions between them illustrated aimed at the identification of potential influences by means of a multi stepwise weight assessment ratio analysis (M-SWARA) methodology that incorporates bipolar q-rung orthopair fuzzy sets (q-ROFSs) and golden cut. Secondly, the various flight activities are ranked, and the potential impacts of these activities determined in terms of the strategic priorities of a sustainable aviation industry employing q-ROF as the elimination and choice translating reality (ELECTRE) technique. All the calculations were also computed with intuitionistic fuzzy sets (IFSs) and Pythagorean fuzzy sets (PFSs) aimed at verifying the validity of the findings. The analysis concluded that while energy efficiency comprises the most important factor in terms of strategic priority investment for the circular economy-based aviation industry, emergency response makes up the most crucial activity in the industry. Operational efficiency must be prioritized to decrease the amount of fuel consumed, in connection with which flight routes should be planned according to current weather conditions, which would serve to shorten flight times and, thus, help to increase energy efficiency. Such an approach would make a positive contribution to minimizing carbon emissions aimed at ensuring the sustainability of the aviation industry.

A Method for Calculating Atmospheric Radiation Produced by Relativistic Electron Precipitation

AbstractRadiation safety in the Earth's atmosphere is of particular importance to our living environment, especially at aviation altitudes. Aviation radiation has been long known to originate primarily from the galactic and solar system: galactic cosmic rays and solar energetic protons. Recent flight measurements by the Automated Radiation Measurements for Aerospace Safety experiment have uncovered another potential source for aviation radiation: Relativistic Electron Precipitation (REP) from the Van Allen radiation belts. REP can induce radiation at aviation altitudes through bremsstrahlung X‐ray production, which carries radiation down to the stratosphere and even the troposphere. In this study, using a suite of physics‐based Monte Carlo models, we characterize the effective radiation dose produced at altitudes between ground and low‐Earth‐orbit by relativistic precipitation electrons with energies between 100 keV and 10 MeV. We produce a lookup table of atmospheric radiation production that calculates the expected radiation dose for a given precipitation flux, spectrum, and pitch angle distribution. This lookup table provides results that are consistent with X‐ray measurements during radiation belt precipitation by balloon‐borne instruments in the stratosphere, and can be directly used to convert space‐borne measurements of precipitation fluxes into aviation radiation. This study represents our first attempt toward better understanding of REP's role in the atmospheric high‐altitude radiation environment.

Comparison of ICON/MIGHTI and TIMED/TIDI Neutral Wind Measurements in the Lower Thermosphere.

This study cross-compares ICON/MIGHTI and Thermosphere, Ionosphere, Mesosphere Energetics & Dynamics (TIMED)/TIMED Doppler Interferometer (TIDI) MLT region neutral winds from middle Northern Hemisphere to low Southern Hemisphere latitudes. We utilized MIGHTI level-2.2 (v4) and TIDI level-3 (v11) neutral winds from January 2020 to November 2020 and found their conjunctions using a space-time window of LST ± 15 min, latitude ± 4°, and longitude ± 4° around each TIDI wind measurement. Due to the nature of their orbital geometry, frequent conjunctions occurred between MIGHTI and TIDI. These conjunctions are spread in longitudes and they occur at approximately fixed LSTs and latitudes, which allows us to compare their observed diurnal variability. MIGHTI and TIDI wind observations agree well (except on the TIDI coldside during forward flight) and show similar large amplitude longitudinal variations that can reach more than 100 m/s. MIGHTI and TIDI zonal and meridional winds show moderate correlations of 0.60 and 0.55, respectively. The slopes of regression fits for zonal and meridional winds are 0.92 and 0.91, respectively. The root mean square differences in zonal and meridional winds are 56 and 66 m/s, respectively. We found that TIDI coldside measurements in forward flight show a systematic bias and this behavior is repetitive as the instrument pointing direction is changed by the periodic TIMED yaw maneuver. The nature of this systematic bias suggests that the TIDI zero-wind references (at least for the coldside telescopes) need revision. This investigation can provide guidance toward improving the TIDI data analysis. In addition, the results of this study act as a validation of MIGHTI MLT winds.

Modelling and Validation of a Guided Acoustic Wave Temperature Monitoring System.

The computer modelling of condition monitoring sensors can aide in their development, improve their performance, and allow for the analysis of sensor impact on component operation. This article details the development of a COMSOL model for a guided wave-based temperature monitoring system, with a view to using the technology in the future for the temperature monitoring of nozzle guide vanes, found in the hot section of aeroengines. The model is based on an experimental test system that acts as a method of validation for the model. Piezoelectric wedge transducers were used to excite the Lamb wave mode in an aluminium plate, which was temperature controlled using a hot plate. Time of flight measurements were carried out in MATLAB and used to calculate group velocity. The results were compared to theoretical wave velocities extracted from dispersion curves. The assembly and validation of such a model can aide in the future development of guided wave based sensor systems, and the methods provided can act as a guide for building similar COMSOL models. The results show that the model is in good agreement with the experimental equivalent, which is also in line with theoretical predictions.

DEVELOPMENT OF AN OPEN-SOURCE OBJECT FLIGHT SPEED MEASURING SETUP FOR INDOOR MEASUREMENTS

Time of flight measurement is an important procedure for indoor object flight speed measurement applications. Measuring a fast-moving object is very difficult such as military and sport shooting. Today, there is a requirement for measuring high-speed objects using a cost-effective solution. The speed detection processing requires two referencing points from flight start to end. The difference between these two points and time parameters leads to calculating speed. In-flight speed detection applications mostly an object is thrown by a launcher and measurements are conducted in a linear horizontal measurement line. The terminals of this line are refer to these two points. There are light-based solutions such as infra-red (IR) sensors, fast cameras for indoor speed measurement. However, commercial solutions based on sensors or fast cameras are expensive options and these solutions are not easily affordable for research facilities and laboratories with low-budget. In this study, an object flight speed detection setup is demonstrated for indoor measurements. The results show that is possible to use a microcontroller (MCU) with two IR sensor for calculating the flight speed with low-cost and high accuracy.

Multi-dimensional radio frequency interference framework for characterizing radio astronomy observatories

Radio frequency interference (RFI) has historically plagued radio astronomy, worsening with the rapid spread of electronics and increasing telescope sensitivity. We present a multi-dimensional probabilistic framework for characterizing the RFI environment around a radio astronomy site that uses data from the telescope observations themselves. We apply the framework to about 1500 h of commissioning data (∼200 TB) from the MeerKAT radio telescope; producing a six-dimensional array that yields both average RFI occupancy as well as distributions around the mean as a function of key variables (time of day, frequency, baseline, azimuth, and elevation). This allows for automated alerting for significant new sources of RFI and monitoring of RFI trends. Our results provide the first detailed view of the MeerKAT RFI environment at high sensitivity. As expected, in the MeerKAT L-band, we find that the major RFI contributors are from the global positioning system satellites, flight distance measurement equipment, and the global system for mobile communications. Beyond characterizing RFI environments, our approach allows observers access to the prior probability of RFI in any combination of tracked variables, allowing for more efficient observation planning and data flagging.

Approaches, challenges and recent advances in automated bee counting devices: A review

AbstractFor nearly 100 years, electronic bee counters have been developed using various technologies to track the foraging activity of mostly honey bee colonies. These counters should enable remote monitoring of the hives without disturbing natural flight behaviour while generating precise scientific data. However, there are few counters on the market that are able to fulfil this task. One main challenge is the lack of standardised methods to validate a counter's precision, as validation is crucial to categorise and judge the data produced by the counter, especially for scientific purposes. Another challenge is the interpretation of flight data to measure the effects of environmental or anthropogenic sources. Nevertheless, recent developments in the field are promising. This review describes the historic development of automated bee flight measurements and critically compares validation methods to encourage their improvement. To increase the comparability of future analyses of bee counters, current advances in data interpretation are also presented.

In-situ monitoring and ex-situ elasticity mapping of laser induced metal melting pool using ultrasound: Numerical and experimental approaches

This study presents novel in-situ monitoring of the melting pool behavior and ex-situ inspection of the heat-affected softening in gallium metal using an ultrasonic technique. In the laser welding and laser melting additive manufacturing process, understanding the melting pool's behavior is necessary but challenging. Optical, thermal, and radiational imaging methods provide valuable information but are limited due to the lack of depth and material properties information. An ultrasonic time of flight measurement monitoring technique is numerically and experimentally used to study the behavior of laser-induced melting pools, including phase transition, pool initialization and growth, and solidification in real-time. Besides, a dynamic bulk modulus elastography scan was demonstrated to visualize the laser-heating induced mechanical property reduction as an ex-situ inspection process which can be an in-situ process in the future. The laser softened area had a drop in the elasticity resembling a melt pool's shape. With the continuous development, the unique technique would be suitable and helpful to be used as a diagnostic tool to monitor laser welding, laser melting-based additive manufacturing, and other melt-solidify processing systems.

Influence of Chemical Kinetics Models on Plasma Generation in Hypersonic Flight

The accuracy and sensitivity of plasma generation predicted by several different chemical kinetics models is investigated in the context of weakly ionized hypersonic flowfields around the Radio Attenuation Measurement (RAM-C) vehicle. A computational fluid dynamics analysis is used to examine 13 independent trajectory points along the RAM-C II flight, and an assessment of the chemistry models is made by comparing results to available flight measurements. The limitations of making such comparisons with the raw flight data are established in detail, including the inherent shortcomings associated with interpolating the flight data to assess a single trajectory point. Two separate geometries are evaluated in this study, as the initial RAM-C geometry was altered during flight after its nose cap was pyrotechnically ejected. The blunter post-ejection geometry generates more electrons in the stagnation region. In general, good agreement is found between each chemistry model and flight data from both the electrostatic probe and reflectometer stations above 56 km. An expected sizable gap exists between the simulations and reflectometer data at lower altitudes. The impact of forward reaction rates, equilibrium constants, and number of species varies considerably based on altitude, velocity, and position along the body.

MEMS microphone intensity array for cabin noise measurements

Aircraft cabin noise measurements in flight are used toto quantify the noise level, and to identify the entry point of acoustic energy into the cabin. Sound intensity probes are the state-of-the-art measurement technique for this task. During measurements, additional sound absorbing material is used to ease the rather harsh acoustic measurement environment inside the cabin. In order to decrease the expensive in-flight measurement time, an intensity array approach was chosen. This intensity probe consists of 512 MEMS-Microphones. Depending on the frequency, these microphones can be combined as an array of hundreds of 3D- intensity probes. The acoustic velocity is estimated using a high order 3D finite difference stencil. At low frequencies, a larger spacing is used to reduce the requirement of accurate phase match of the microphone sensors. Measurements were conducted in the ground-based Dornier 728 cabin noise simulation as well as in-flight.

Operational noise optimization of aircraft approaches - Initial findings

As the pilots slow the aircraft down and extend flaps and landing gear in preparation for landing the characteristics of the aircraft as a noise source changes. In the OPNOP project, the possibility to use this variation in noise generation to minimize noise at a specified location is examined. Such analysis requires an increased understanding about aircraft noise generation as the aircraft changes configuration and speed during the approach, where theoretical models available can be overly simplistic and of little use for this purpose. Using flight data from 113 actual Airbus A321 flights, and corresponding noise measurements on the ground, this study reports on the initial findings forming the foundation on which further analysis will be conducted. Intermediary findings relate to: a comparison between models and actual measurements, the distance variability to the runway for various flap selections and extension of the landing gear as well as a comparison between flight data and on-ground noise measurements. Captured data suggest that it should be possible to use speed and configuration recommendations to reduce noise over selected approach areas. Future research will include scenario generation and incorporate flight data from an earlier study to increase validity.

Investigation of Photoexcitation Energy Impact on Electron Mobility in Single Crystalline CdTe.

The exceptional electronic properties of cadmium telluride (CdTe) allow the material to be used in a wide range of high energy radiation detection applications. Understanding the mechanisms of local carrier scattering is of fundamental importance to understand the charge transport in the material. Here, we investigate the effect of photoexcitation on electron transport properties in chlorine doped single crystalline cadmium telluride (SC-CdTe:Cl). For this purpose time of flight measurements were performed on SC-CdTe:Cl in order to study the electron drift mobility in the low injection regime. Measurements were made at the temperature intervals of 80 to 300 K, for an applied electric field between 270 and 1600 V/cm and for wavelengths of 532, 355 and 213 nm. We have found that the electron drift mobility was affected by the excitation energy for temperatures below 200 K. In addition, the measurements revealed that it is possible to determine impurity and shallow trap concentration by this method. The method proves to be extremely sensitive in measuring very low impurity levels and in identifying dominant scattering mechanisms.