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Sensor Technology
Published in Stephen Horan, Introduction to PCM Telemetering Systems, 2018
Typical digital clocks are used in time-of-flight measurements that can measure elapsed time or distance. Measuring the elapsed time between the reception of a start pulse and a stop pulse produces the time-of-flight measurement. These pulses can be generated, for example, in a laser rangefinding device by having the start pulse generated when the laser pulse is emitted and the stop pulse when the return pulse is received. The sensor determines the distance by measuring the elapsed time, multiplying it by the speed of light, and dividing the result by two. This technique can have a dynamic range in excess of 1000. Often, the resolution error is dominated by the widths of the pulses and not the clocking circuitry. The heart of these time-of-flight converters is a high accuracy clock circuit that produces a result proportional to the flight time.
Location and Position Estimation in Wireless Sensor Networks
Published in Shafiullah Khan, Al-Sakib Khan Pathan, Nabil Ali Alrajeh, Wireless Sensor Networks, 2016
Muhammad Farooq-i-Azam, Muhammad Naeem Ayyaz
It is to be noted that for the one-way ToA technique to work, the receiver must know the time of transmission of the signal. In the case of an RF signal, the transmitting node can embed this information in the beacon signal that it sends to the receiver. However, RF signals travel at a very high speed, which is almost equal to the speed of light, that is, 3 × 108 m/s. Their use in distance estimation using time of flight requires extremely accurate and stable clocks and highly precise hardware for time measurement. For example, if sensor nodes are located 10 m apart and an RF signal is used for ranging, then the time taken by the signal to travel from the transmitting node to the receiving node is given as follows: t=d/v=10/3×108=3.33×10−8=33.3nanoseconds
Robot Vision
Published in Bogdan M. Wilamowski, J. David Irwin, Control and Mechatronics, 2018
Laser time-of-flight range instruments either measure the time it takes for a short pulse of laser light to beam to and be reflected back from a point on the surface of an object or the phase shift encountered by a modulated continuous laser beam during the round trip. Since light travels at approximately 30 cm/ns (10−9 s), sub-centimeter accuracy range measurement require time to be measured with approximately ±10 ps (10−12 s) accuracy using the first approach. With both approaches, averaging over a number of cycles can be used to reduce range error, but at the cost of increased measurement time.
Detection of new phytochemical compounds from Vassobia breviflora (Sendtn.) Hunz: antioxidant, cytotoxic, and antibacterial activity of the hexane extract
Published in Journal of Toxicology and Environmental Health, Part A, 2023
Altevir Rossato Viana, Bruna Godoy Noro, Daniel Santos, Katianne Wolf, Yasmin Sudatti Das Neves, Rafael Noal Moresco, Aline Ferreira Ourique, Erico Marlon Moraes Flores, Cristiano Rodrigo Bohn Rhoden, Luciana Maria Fontanari Krause, Bruno Stefanello Vizzotto
For the phytochemical detection, 20 μl hexane extract was diluted in 1.5 ml acetonitrile (ACN): H2O (1:1) with 0.1% formic acid. The bioactive compounds were identified by electrospray ionization with high-resolution time-of-flight mass spectrometry. (ESI-TOF-MS, Xevo G2 Q-ToF, Waters, USA). Mass spectra were acquired from 50 to 1000 Da and ESI-TOF-MS detection was performed in positive ion mode with a capillary voltage of 2kV, cone voltage of 20 V, and extractor cone voltage of 3 V. The gas and gas cone flow rates were 500 L/hr and 10 L/hr, respectively. The dissolution temperature was set at 500°C and the source temperature at 150°C. As for the negative ion mode with a capillary voltage of 2.5 kV, a cone voltage of 40 V, and an extractor cone voltage of 4 V. The desolvation gas and cone gas flow rates were 200 L/hr and 10 L/hr, respectively. The desolvation temperature was set to 450°C and source temperature was set to 150°C (Boeira et al. 2020). System control and data acquisition were performed using MassLynx Software V 4.1. The mass instrument was calibrated to increase accuracy and precision.
Mapping of aeolian deposits of an industrial site in the arid region using the TIR bands of ASTER and study of physicochemical characters and stabilization of sand erosion
Published in Geomatics, Natural Hazards and Risk, 2022
Rajendran Sankaran, Nabil Zouari, Fadhil N. Sadooni, Zulfa Ali Al Disi, Abdulaziz Al-Jabri, Hamad Al-Saad Al-Kuwari
In addition to the above, the samples were studied for sand stabilization using isolated ureolytic bacteria strains at the Department of Biology and Environmental Microbiology, Qatar University. The isolation of ureolytic bacterial strains by adding 2 g of each soil sample to 20 ml of urea culture media. The cultures were incubated for 72 h in a shaker set at 30 °C and 200 rpm. Then, 3 successive enrichment cultures were performed using the initial culture: 2 ml per 20 ml. For the purification of the ureolytic bacterial strains, the strains were performed using the streak plate method until pure strains were obtained. The identification of the bacterial strains was performed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The determination of bacterial growth and urease activity was studied from the cultures performed using 20 g L−1 urea after 3 days of incubation using the phenol-hypochlorite method as described by Burbank et al. (2012) and Bibi et al. (2018). Further, the strains were inculcated in urea media supplemented with calcium chloride, and then incubated in a shaker set at 200 rpm and 30 °C for 5 days. At the end of the incubation period the precipitations were obtained by centrifugation at 5000 rpm for 10 min. The recovered precipitates were washed three times with distilled water to remove any residuals before air drying at 40 °C. The characterization of minerals formed by the isolates was studied using X-Ray diffraction (XRD) analyses.
Spectroscopy of astrophysically relevant ions in traps
Published in Molecular Physics, 2020
In the 1985 experiment, radiation from the second harmonic of an Nd:YAG laser was used to produce carbon clusters from a rotating graphite disk. The neutral molecules were ionised in a helium expansion and detected via time-of-flight mass spectrometry. The results showed a distribution where, for mass-to-charge ratios (m/z) of greater than 480, only species containing an even number of carbon atoms were observed. Moreover, a slightly enhanced peak at , and also one at , was seen. These ‘clusters’ are now known as fullerenes, an allotrope of carbon in addition to the previously identified graphite and diamond. It was immediately recognised that this may have implications for the DIB enigma and, in 1987, Kroto highlighted the astrophysical importance of the singly charged cation C, writing ‘The present observations indicate that C might survive in the general interstellar medium (probably as the ion C) protected by its unique ability to survive processes so drastic that, most if not all, other known molecules are destroyed’ [68]. This conjecture was subsequently shown to be correct.