Detection and identification of toxic environmental gases have assumed paramount importance precisely in the defense, industrial and civilian security sector. Numerous methods have been developed for the sensing of toxic gases in the environment ever since surface acoustic wave (SAW) technology came into existence. Such SAW sensors called electronic nose (E-Nose) sensor use the frequency response of a delay line/resonator. SAW device is focused and given importance. The selective coating between input and output interdigital transducers (IDTs) in the SAW device is responsible for corresponding changes in operating frequency of the device for a specific gas/vapour absorbed from the environment. A suitable combination of well-designed SAW delay lines with selective coatings not only help to improve sensor sensitivity and selectivity but also leads to the minimization of false frequency alarms in the E-Nose sensor. This article presents a comprehensive review of design, development, simulation and modelling of a SAW sensor for potential sensing of toxic environmental gases.
The Open Skies Treaty has been a peace-building instrument between North American and European nations for over two decades. This agreement is based on the possibility for each country-signatory of the Treaty to independently conduct observation flights and obtain aerial imagery data of the territories of other Treaty States-Parties. This imagery data was originally acquired only using traditional photographic film cameras. Together with the rapid development and advancement of digital sensor technologies, the logical step forward was to amend the Treaty provisions to allow for the use of these types of sensors during observation missions. This paper describes this transition process and highlights a number of technical problems which needed to be addressed by experts working within the Open Skies Consultative Commission workgroups.
The brake linkage of a hoisting machine is a very important component determining the safety of the hoisting machine’s entire braking system. It is subject to weekly inspections. However, an efficiency test of brake performance is carried out every 6 months. Once every 3 years, a test must be carried out by an appraiser who pays particular attention to the executive and control components of the brakes as well as the strain - brake system and brake release components. The legal provisions regulating the testing of braking system linkages are not precise. So far, the control has been based on random measurement of strains using electrical resistance strain gauges stuck to the surface of the linkage. A new method for measuring the strains of the linkage has been proposed in the work. It is based on fibre optic strain sensors with Fibre Bragg Gratings (FBG). They are mounted using specially designed and tested holders for mounting on the brake linkage. They provide quick assembly and the measurement of strain in the direction parallel to the axis of the linkage. The structure of the holder also allows for the measurement in 4 positions turned every 90 relative to one another. Such a measurement enables a comprehensive analysis of strains and stresses in the brake linkage. In the work, it was shown that there is a complex state of strain and stress in the brake linkage. The previous procedures for linkage testing are inadequate in relation to this condition. An experimental and numerical method was proposed to assess the state of linkage stress. It should constitute the basis for the decision of the appraiser to allow the linkage for further use. The method proposed in the work also allows for continuous measurements of linkage strains as well as dynamic braking tests.
Beamforming is an advanced signal processing technique used in sensor arrays for directional signal transmission or reception. The paper deals with a system based on an ultrasound transmitter and an array of receivers, to determine the distance to an obstacle by measuring the time of flight and – using the phase beamforming technique to process the output signals of receivers for finding the direction from which the reflected signal is received – locates the obstacle. The embedded beam-former interacts with a PID-based line follower robot to improve performance of the line follower navigation algorithm by detecting and avoiding obstacles. The PID (proportional-integral-derivative) algorithm is also typically used to control industrial processes. It calculates the difference between a measured value and a desired set of points, then attempts to minimize the error by adjusting the output. The overall navigation system combines a PID-based trajectory follower with a spatial-temporal filter (beamformer) that uses the output of an array of sensors to extract signals received from an obstacle in a particular direction in order to guide an autonomous vehicle or a robot along a safe path.
The paper presents a method of measuring the angle of rotation and twist using a tilted fibre Bragg grating (TFBG) periodic structure with a tilt angle of 6◦, written into a single-mode optical fibre. It has been shown that the rotation of the sensor by 180◦ causes a change in the transmission coefficient from 0.5 to 0.84 at a wavelength of 1541.2 nm. As a result of measurements it was determined that the highest sensitivity can be obtained for angles from 30◦ to 70◦ in relation to the basic orientation. The change in the transmission spectrum occurs for cladding modes that change their intensity with the change in the polarization of light propagating through the grating. The same structure can also be used to measure the twist angle. The possibility of obtaining a TFBG twist by 200◦ over a length of 10 mm has been proved. This makes it possible to monitor both the angle of rotation and the twist of an optical fibre with the fabricated TFBG.