The US Army’s future operating concept will rely heavily on sensors, nano-electronics and photonics technologies to rapidly develop situational understanding in challenging and complex environments. Recent technology breakthroughs in integrated 3D multiscale semiconductor modeling (from atoms-to-sensors), combined with ARL’s Open Campus business model for collaborative research provide a unique opportunity to accelerate the adoption of new technology for reduced size, weight, power, and cost of Army equipment. This paper presents recent research efforts on multi-scale modeling at the US Army Research Laboratory (ARL) and proposes the establishment of a modeling consortium or center for semiconductor materials modeling. ARL’s proposed Center for Semiconductor Materials Modeling brings together government, academia, and industry in a collaborative fashion to continuously push semiconductor research forward for the mutual benefit of all Army partners.
Acoustic sensors are being employed on airborne platforms, such as Persistent Threat Detection System (PTDS) and
Persistent Ground Surveillance System (PGSS), for source localization. Under certain atmospheric conditions, airborne
sensors offer a distinct advantage over ground sensors. Among other factors, the performance of airborne sensors is
affected by refraction of sound signals due to vertical gradients in temperature and wind velocity. A comprehensive
experiment in source localization with an aerostat-mounted acoustic system was conducted in summer of 2010 at Yuma
Proving Ground (YPG). Acoustic sources on the ground consisted of one-pound TNT denotations and small arms
firings. The height of the aerostat was approximately 1 km above the ground. In this paper, horizontal, azimuthal, and
elevation errors in source localization and their statistics are studied in detail. Initially, straight-line propagation is
assumed; then refraction corrections are introduced to improve source localization and decrease the errors. The
corrections are based on a recently developed theory [Ostashev, et. al, JASA 2008] which accounts for sound refraction
due to vertical profiles of temperature and wind velocity. During the 2010 YPG field test, the vertical profiles were
measured only up to a height of approximately 100 m. Therefore, the European Center for Medium-range Weather
Forecasts (ECMWF) is used to generate the profiles for July of 2010.
Acoustic sensors are being employed on airborne platforms, such as Persistent Threat Detection System (PTDS)
and Persistent Ground Surveillance System (PGSS), for source localization. Under certain atmospheric conditions,
airborne sensors oer a distinct advantage over ground sensors. The performance of both ground and
airborne sensors is aected by environmental factors, such as atmospheric turbulence and wind and temperature
proles. For airborne sensors, the eects of refraction must be accounted for in order to determine the
source coordinates. Such a method for ground-to-air applications has been developed and is further rened here.
Ideally, knowledge of the exact atmospheric proles will allow for the most accurate mitigation of refractive
eects. However, acoustic sensors deployed in theater are rarely supported by atmospheric sensing systems that
retrieve real-time temperature and wind elds. Atmospheric conditions evolve through seasons, time of day,
and are strongly location dependent. Therefore, the development of an atmospheric proles database based on
a long time series climatological assessment will provide knowledge for use in physics-based bearing estimation
algorithms, where otherwise no correction would have been performed. Long term atmospheric data sets from
weather modeling systems are used for a climatological assessment of the refraction corrections and localization
errors over selected sites.
In nonlinear acoustic detection experiments involving a buried inert VS 2.2 anti-tank landmine, airborne sound at two closely spaced primary frequencies f1 and f2 couple into the ground and interact nonlinearly with the soil-top pressure plate interface. Scattering generates soil vibration at the surface at the combination frequencies | m f1 +- n f2 | , where m and n are integers. The normal component of the particle velocity at the soil surface has been measured with a laser Doppler velocimeter (LDV) and with a geophone by Sabatier et. al. [SPIE Proceedings Vol. 4742, (695-700), 2002; Vol. 5089, (476-486), 2003] at the gravel lane test site. Spatial profiles of the particle velocity measured for both primary components and for various combination frequencies indicate that the modal structure of the mine is playing an important role. Here, an experimental modal analysis is performed on a VS 1.6 inert anti-tank mine that is resting on sand but is not buried. Five top-plate mode shapes are described. The mine is then buried in dry finely sifted natural loess soil and excited at f1 = 120 Hz and f2 = 130 Hz. Spatial profiles at the primary components and the nonlinearly generated f1 - (f2 - f1) component are characterized by a single peak. For the 2f1+f2 and 2f2 + f1 components, the doubly peaked profiles can be attributed to the familiar mode shape of a timpani drum (that is shifted lower in frequency due to soil mass loading). Other nonlinear profiles appear to be due to a mixture of modes. This material is based upon work supported by the U. S. Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate under Contract DAAB15-02-C-0024.
Recent work in acoustic landmine detection has shown that many landmines exhibit a multi-mode vibration pattern. To fully map the vibration pattern of these modes requires spatial resolutions on the order of millimeters. An optical technique that lends itself to such vibration sensing is an electronic speckle pattern interferometer (ESPI). In this work the double-pulse ESPI system has been used for the vibration measurement of the ground surface. The principle of method is based on recording two specklegrams of the object with two laser pulses synchronized with the vibration peak and the vibration valley respectively. The 2D vibration amplitude spatial distribution is obtained by subtracting two specklegrams and processing the received correlation fringe pattern. The experimental setup uses a mechanical shaker to excite vibrations in the ground to significantly increase the vibration amplitudes at the spot of interest and a laser Doppler vibrometer to detect the resonant frequency of the mine. Experimental results are presented from laboratory experiments. The spatial maps of the vibrating ground over buried antitank and antipersonnel landmines are studied. The effect of the vibration of a granular material like sand on the speckle decorrelation is discussed. This material is based upon work supported by the U. S. Army Communications-Electronics Command Night Vision and Electronic Sensors Directorate under Contract DAAB15-02-C-0024.
An acoustics-based system has recently proved successful at detecting buried land mines. The present paper describes the use of this land mine detection system to discern shapes of buried objects. Steel plate targets of three shapes were used: circle, square, and equilateral triangle, each buried in sand with their major surface horizontal. In each case, for certain frequency bands, when a color-scaled spatial distribution of particle velocity amplitude is displayed in real time, the target shape is clearly visible. Calculations are made using a simplistic theoretical model in an effort to understand the frequency dependence of the experimental result. For each target, wave scattering is crudely mimicked by calculating the radiant pattern in an infinite fluid from a simple source distribution of the same shape as the target and visualizing its interference with plane incident wave. Limited qualitative understanding of experimental result is obtained with this crude mode, but the need for a more realistic scattering calculation is indicated.