Chemical detection of explosives in soil for locating buried landmines.

Trinitrotoluene (TNT) is a highly explosive nitroaromatic compound that is used for military and terrorist activities such as the development of improvised explosive devices (IEDs), landmines and is the main charge or explosive in most of the anti-personal and anti-vehicle mines. Different chemicals/ contaminants associated with TNT in soils near buried land mines comprise the microbial transformation products of TNT (2-amino-4,6-dinitrotoluene [2-Am-DNT] and 4-amino-2,6-dinitrotoluene [4-Am-DNT]), manufacturing impurities of TNT (2,4-DNT, 2,6-DNT, and 1,3-DNB), and TNT. Time, cost, and casualties associated with demining have necessitated the demand for improved detection techniques with reduced false positives by directly detecting the explosive material, rather than casing material of mines. Different analytical methods used to detect trace level of explosives in soil include ion mobility mass spectrometry, gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS) that require samples to be collected from hazardous sites to laboratories. This is extremely unsafe, time consuming, involve large and expensive instrumentation cost and specially trained staff. Thus, detecting chemical signatures of these nitroaromatics in soil infected with these chemicals due to leaked TNT mines can provide location of landmines/ landmine prone zones to aide humanitarian demining process. This paper illustrates soil analysis for explosives and selected contaminants by Raman spectroscopy as a chemical, nondestructive, remote sensing method. As with advancement of Raman-based standoff detection techniques, field-portable instruments and UAV deployable probes, this technique can be effectively employed in detecting buried landmines based on specific chemical signatures of target analyte. In this present study, TNT-based nitroaromatic was assessed in contaminated soil samples using Raman spectroscopy, where uncontaminated soil was used as background and matrix for spiking target contaminants at different concentrations

Fuzzy logic, edge enabled underwater video surveillance through partially wireless optical communication.

Underwater surveillance is inherently tricky to achieve. Even in the clearest waters, the visibility tends to be in the range of tens of meters. Normally, tethered Remotely Operated Vehicles (ROVs) with underwater cameras are used for underwater imaging at closer ranges. Currently, detailed visible light imaging can be achieved utilising green laser technology, and this is limited to close ranges due to the inherent properties of light attenuation in water. The alternative is to utilise sonar based imaging which is capable of visualising distances, however, this technique is vulnerable to noise that interferes with the operating frequency, rendering the applications somewhat limited. The emergence of high data-rate, wireless, optical communication could allow for dense placement of short-range imaging equipment to monitor areas of strategic interest to extend the range, however, there needs to be a reliable method of wirelessly communicating this data to the sea surface regardless of the localised environmental conditions that may interfere with a visible light transmission. This paper proposes a fuzzy logic, edge computing enabled routing algorithm for optical networks that utilises a wired connection among source nodes to "pass" video data around among themselves to decide which seafloor node is best placed to transmit the data according to relative local turbidity, light intensity and sea-life activity, the main factors that hamper a well-considered wireless optical network. From there, a selected node can theoretically transmit the data from the source to the sea-surface through the wireless optical relay network implemented above. This mechanism shows promise in improving link reliability and throughput compared to alternative systems

A simulation into the physical and network layers of optical communication network for the subsea video surveillance of illicit activity.

Criminal activity is increasingly entering the ocean subsurface with acts such as illegal fishing and narco-submarining becoming points of contention. This among other illicit acts taking place in this domain imply a need for surveillance to render these activities apparent. However, subsurface Underwater Sensor Networking which is central to the surveillance is still generations behind terrestrial networking, therefore it is still challenging to monitor for subsurface activities. This is since the current signal transmission standard, acoustic communication, is limited in practical bandwidth and thus channel data-rate, this is, however, caveated with omni-directional propagation and supreme range rendering it reliable but incapable of carrying video or other data intensive sensor information. There is, however, an emerging technology based on optical (visible light) communication that can accommodate surveillance applications with superior data rates and energy savings. This investigation demonstrates how theoretically it is possible to achieve a network of underwater channels capable of sustaining a multimedia feed for monitoring subsurface activity using modern optical communication when in compared to an acoustic network. In addition, a simple topology was investigated that shows how the range limitations of this signaling can be extended by adding floating relay nodes. Through simulations in Network Simulator 3 (NS-3)/Aquasim-NG software it is shown that Visible Light wireless communication in visible light networks have a channel capacity high enough to carry out monitoring in strategic areas, referencing, optical modems that are available in the market. This implies that data-rates of 10 Mb/s are possible for the real-time video surveillance

Nile red-dye based analysis of synthetic fibres for forensic applications.

Forensic evaluation of crime scenes normally involves examination of textile fibers, to find out the association between an individual and a crime scene, or between a suspect and a victim. The forensic samples normally include a mix of various types, sizes (micro to nano - scale) and shapes of natural and synthetic fibers, which are very difficult to differentiate/identify. Various sophisticated analytical instruments are being used to carry out the examination of these fibers. They involve various microscopy and spectroscopy based techniques, most of which are very complex and highly sensitive. Further, they may require a series of sample preparation steps to get high selectivity and are highly time consuming. Here we report a fluorescence microscopy based synthetic (plastic) fiber detection method using Nile Red (NR) dye, which provides high selectivity for synthetic fibers. The methodology involves the use of NR dye which selectively stains the fibers collected on filter papers following separation from samples/soils and water. The selectivity of NR towards the fibers is due to their non-polar property. Binding with NR makes the fibers fluoresce when viewed under a fluorescence microscope. This selectivity of NR for fibers makes the identification of fibers lot easier and less timeconsuming in forensic samples when compared to the more commonly used optical microscopy (where the presence of naturally-occurring substances of similar size can result in more errors). The paper will discuss optimisation of various parameters and method validation for detection of synthetic fibers and microplastics from soil samples. As an example, our method has shown to provide distinct clarity for the analysis of microfibers. The potential for the application of the method for faster forensics analysis will be discussed

Theoretical design and analysis of a sensing system for high pressure and temperature measurement in subsea underwater applications.

The theoretical design and analysis of a metal coated hybrid sensing system of Fibre Bragg Grating (FBG) and Extrinsic Fabry-Perot Interferometer (EFPI) cavity for high pressure high temperature (HPHT) measurement in subsea underwater applications is reported. The FBG and EFPI are used to measure temperature and pressure respectively. An opto-mechanical model that assesses the measurement of HPHT for subsea underwater applications with hybrid sensing system was developed. In this model, coating of the sensor with metallic materials is studied. The model combines both optical and structural analyses for developing an optimal sensor system design. The optical analysis is carried out to obtain the spectral response of the sensor while the structural analysis is used to obtain the change in optical properties of the sensor due to photo-elastic effect. Analytical results showed that the temperature sensitivity of the hybrid sensor with double layer metal coated FBG increased to 23.89 pm/ {deg}C when compared with single metal coated FBG of 13.95 pm/ {deg}C from previous study and the associated pressure range measured up to 5000 Psi. Furthermore, the proposed sensor design has shown good linearity. While the single coated FBG sensor shows little sensitivity, the sensitivity increases with thickness for double metal coating

Design optimization of Cassegrain telescope for remote explosive trace detection.

The past three years have seen a global increase in explosive-based terror attacks. The widespread use of improvised explosives and anti-personnel landmines have caused thousands of civilian casualties across the world. Current scenario of globalized civilization threat from terror drives the need to improve the performance and capabilities of standoff explosive trace detection devices to be able to anticipate the threat from a safe distance to prevent explosions and save human lives. In recent years, laser-induced breakdown spectroscopy (LIBS) is an emerging approach for material or elemental investigations. All the principle elements on the surface are detectable in a single measurement using LIBS and hence, a standoff LIBS based method has been used to remotely detect explosive traces from several to tens of metres distance. The most important component of LIBS based standoff explosive trace detection system is the telescope which enables remote identification of chemical constituents of the explosives. However, in a compact LIBS system where Cassegrain telescope serves the purpose of laser beam delivery and light collection, need a design optimization of the telescope system. This paper reports design optimization of a Cassegrain telescope to detect explosives remotely for LIBS system. A design optimization of Schmidt corrector plate was carried out for Nd:YAG laser. Effect of different design parameters was investigated to eliminate spherical aberration in the system. Effect of different laser wavelengths on the Schmidt corrector design was also investigated for the standoff LIBS system

Optical fibre-based sensors for oil and gas applications.

Oil and gas (O&G) explorations moving into deeper zones for enhanced oil and gas recovery are causing serious safety concerns across the world. The sensing of critical multiple parameters like high pressure, high temperature (HPHT), chemicals, etc., are required at longer distances in real-time. Traditional electrical sensors operate less effectively under these extreme environmental conditions and are susceptible to electromagnetic interference (EMI). Hence, there is a growing demand for improved sensors with enhanced measurement capabilities and also sensors that generates reliable data for enhanced oil and gas production. In addition to enhanced oil and gas recovery, the sensing technology should also be capable of monitoring the well bore integrity and safety. The sensing requirements of the O&G industry for improved sensing in deeper zones include increased transmission length, improved spatial coverage and integration of multiple sensors with multimodal sensing capability. This imposes problems like signal attenuation, crosstalks and cross sensitivities. Optical fibre-based sensors are expected to provide superior sensing capabilities compared to electrical sensors. This review paper covers a detailed review of different fibre-optic sensing technologies to identify a feasible sensing solution for the O&G industry

Multimodal, software defined networking for subsea sensing and monitoring.

The prevalence of oceanic industry and ocean borne interests has given rise to the concept of the Underwater Internet of Things as a vector for automation and data analytics in an environment hostile to anthropomorphic activity. Through the Internet of Underwater Things, it is theorised that sensors along the ocean floor or otherwise can be densely connected to the internet through wireless acoustic or optical links. However, both technologies have significant disadvantages that prevent either becoming a dominant technology. This project proposes a wireless software defined multimodal network infrastructure, that is proven using channel modelling and power analysis calculations, to be capable of robustly transmitting sensor data from source to sink by managing each technology according to its optimal environment. It was found that it is achievable to populate an opto-acoustic network in such a way that Successful Delivery Ratio becomes 90%-100% in clear water whilst achieving a 17% saving in overall energy consumption in a network mounted on a pipeline at 200 m depth when compared to a stand-alone equivalent acoustic network

Generalized small-signal modelling of dual active bridge DC/DC converter

this paper presents a novel generalised approach of the small-signal modelling of dual active bridge (DAB) DC/DC converter. The adopted analysis is based on a per-unit fundamental frequency representation of the DAB. The outcome of the proposed modelling approach is a small signal, linearised, state-space DAB model; which is considered as a main building block for future control applications. The developed small signal DAB model includes all possible degrees of freedom affecting the performance of the DAB; this includes the voltage conversion ratio to allow the study of all DAB operation modes (i.e.: unity-gain and buck/boost modes.). Furthermore, since triple phase shift control (TPS) is used in this development work, the proposed model incorporates phase shift in addition to duty ratios. This feature allows for bridge voltage regulation, which is essential for efficient DAB operation in the case of buck/boost operation. Another key achievement is that the proposed small signal modelling methodology can be applied to any bidirectional DC-DC converter regardless of ratings, parameter values and number of ports. Extensive simulation is carried out to verify the proposed analysis