Tracking individuals in areas such as dense urban environments and building interiors is desirable for numerous critical applications, but has been problematic mainly because of the unreliability or unavailability of GPS in many locations of interest. To date, tracking applications that utilize inertial sensors within smart devices have had varied degrees of success: accuracy typically dips below that of standard GPS within minutes and depends strongly on the quality of the sensors in the device, as well as the location that the device is carried on the body. In this paper we present a sensor module that interfaces with modern smart devices and which utilizes a low-cost, commercial-off-the-shelf, 9-axis IMU and pressure sensor to provide an advanced pedestrian dead reckoning solution. The sensor module is designed to communicate with the smart device (e.g., iOS, Android or Windows) via the audio jack and is intended for use as a beltmounted pedestrian tracker. In addition to describing the device hardware and functionality, we present our approach to processing the sensor module data streams to determine a user’s position. Results using the prototype sensor module in operationally relevant scenarios is presented and discussed.
Crude oil spills in the marine environment result in spatially variable slicks, with up to 90% of the oil contained in less than 10% of the slick area. Rapid slick containment and cleanup is in the interest of all stakeholders and can be best accomplished by focusing efforts on the thickest regions of the slick. An instrument for estimating oil slick thickness would expedite the cleanup process and offers the potential to minimize a spills’ environmental impact. In this work, we have experimented using infrared (IR) spectroscopy and pattern recognition algorithms to discriminate thin and thick regions of an oil slick. Fourier transform-IR (FT-IR) spectra of five crude oils and one refined oil at varying thicknesses on water were collected at short standoff in a laboratory setting. The strong C-H stretching absorbances near 3000 cm-1 and 1500 cm-1 proved most useful for discriminating oil thickness. Several techniques for signal representation and discrimination were explored in attempt to classify spectra as thin or thick, where “thick” was defined as greater than a predetermined thickness threshold. Although a discrimination approach using Principal Component Analysis and artificial neural networks was most efficient, a template matching approach provided slightly better performance. Thick oil slicks were determined with 95% probability of detection (Pd) and 5% probability of false alarm (Pfa) when the oil was contained in the template matching database (88% Pd with 15% Pfa when the oil was not in the database). The system’s overall performance varied with the predetermined thickness threshold, with 100 μm producing the best results.
Detection of explosive hazards is a critical component of enabling and improving operational mobility and protection of US Forces. The Autonomous Mine Detection System (AMDS) developed by the US Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate (NVESD) is addressing this challenge for dismounted soldiers. Under the AMDS program, ARA has developed a vapor sampling system that enhances the detection of explosive residues using commercial-off-the-shelf (COTS) sensors. The Explosives Hazard Trace Detection (EHTD) payload is designed for plug-and-play installation and operation on small robotic platforms, addressing critical Army needs for more safely detecting concealed or exposed explosives in areas such as culverts, walls and vehicles. In this paper, we describe the development, robotic integration and performance of the explosive vapor sampling system, which consists of a sampling “head,” a vapor transport tube and an extendable “boom.” The sampling head and transport tube are integrated with the boom, allowing samples to be collected from targeted surfaces up to 7-ft away from the robotic platform. During sample collection, an IR lamp in the sampling head is used to heat a suspected object/surface and the vapors are drawn through the heated vapor transport tube to an ion mobility spectrometer (IMS) for detection. The EHTD payload is capable of quickly (less than 30 seconds) detecting explosives such as TNT, PETN, and RDX at nanogram levels on common surfaces (brick, concrete, wood, glass, etc.).
Surface-enhanced Raman scattering has been measured for solutions of 2,4-dinitrotoluene (2,4-DNT), trinitrotoluene (TNT), and hexahydro-1,3,5-trinitro-s-triazine (RDX) adsorbed onto metal foils, island films, coated microspheres, and colloids. The wavelength selectivity of the method was also investigated for lasers which potentially may be used in a field instrument. Preliminary room temperature vapor-phase SERS detection of 2,4-DNT adsorbed on gold foil has been achieved. The results demonstrate the potential of SERS as a detector of buried landmines when coupled to compact man- portable Raman instrumentation.
Two fluorescence sensors that are much simpler and less expensive than conventional laser based devices have been developed. The sensors are designed to be deployed in cone penetrometers, utilizing a mercury lamp in the cone for excitation of either a down-hole filter- photomultiplier combination or an up-hole multichannel spectrometer for detecting emission. Both sensors are demonstrated to be useful for rapid, in situ detection of fuels at concentrations ranging to below 100 ppm (a typical action level for cleanup) in soil.
The intensity of surface enhanced Raman scattering (SERS) from benzoic acid and benzoic acid derivatives on mildly roughened, thermally evaporated Ag films shows a strong dependence on the rate at which the Ag film was deposited. Slowly deposited Ag films give a superior SERS response, by up to a factor of 10, to quickly deposited films, with films deposited at an intermediate rate yielding intermediate results. Careful examination using STM indicates that little distinction can be made between the differently prepared films in terms of surface roughness. By contrast TEM measurements reveal that the average metal grain dimension in slowly deposited Ag films is about 3-4 times greater than that in their quickly deposited counterparts. On the premise that the fundamental excitation of importance to the enhancement mechanism is the surface plasmon polariton (SPP) it is argued that the contrast in Raman scattering efficiency is due to differences in elastic grain boundary scattering of SPPs (leading to different degrees of internal SPP damping), rather than differences in the interaction of SPPs with surface inhomogeneities. Corollary data on elastic SPP-photon scattering obtained in a related experiment are also presented.
The importance of techniques to sense and monitor the environment are becoming increasingly more important with the intensifying presence of groundwater and soil contaminations. Our research and development effort is aimed at producing a commercial, low cost, field portable instrument for the field screening/in situ monitoring of contamination from organic solvents based on the principle of combining spectroscopic, electrochemical, and fiber optic techniques. Some of the advantages of this technique for monitoring a contamination site are cost, small size of sampling probe, real-time analysis, the capability of sensing in adverse environments, and the ability of using a central detection facility. The technique has an
advantage over current integrating fiber optic chemical sensing methods in that the sensing only takes place when the electrochemical device is turned on. This should enable long-term monitoring of a site to be accomplished with only one probe/instrument system.
Surface-enhanced Raman spectroscopy is being evaluated for use as an advanced method for detecting
organic contaminants in groundwater during field-screening of environmental samples. The SERS technique
offers attractive and unique capabilities for detecting a wide range of organic contaminants in aqueous
environments at ppm to ppb levels. An inexpensive computer-controlled portable spectrometer system coupled
to a fiberoptic probe has been developed for rapid on-site and in situ determination of organic contamination
in groundwater. Applications of recent advances in substrate fabrication for use with environmental samples
are discussed, and critical issues pertaining to substrate durability, repeatability, sensitivity, selectivity and
universality are addressed.
Conventional Raman spectroscopy is often limited by its low sensitivity due to the
inherently weak Raman cross section of organic chemicals. A relatively new detection
technique, Surface-Enhanced Raman Scattering (SERS) spectroscopy is based on recent
experimental observations, which have indicated enhancement of the Raman scattering
efficiency by factors of up to 106 when a compound is adsorbed on rough metallic surfaces
that have submicron-scale protrusions. In this report we discuss the development of the
SERS technique as a tool for monitoring hazardous chemical emissions and its application
to in situ remote sensing.