9,264 research outputs found
Energy and position resolution of a CdZnTe gamma-ray detector with orthogonal coplanar anodes
We report on the simulation, construction and performance of prototype CZT imaging detectors employing orthogonal coplanar anodes. These detectors employ a novel electrode geometry with non-collecting anode strips in 1D and collecting anode pixels, interconnected in rows, in the orthogonal dimensions. These detectors retain the spectroscopic and detection efficiency advantages of single carried charge sensing devices as well as the principal advantage of conventional strip detectors with orthogonal anode and cathode strips, i.e. an N X N array of imagin pixels are realized with only 2N electronic channels. Charge signals induced on the various electrodes of a prototype detector with 8 X 8 unit cells are in good agreement with the simulations. The position resolution is about 1 mm in the direction perpendicular to the pixel lines while it is of the order of 100 micrometers in the other direction. Energy resolutions of 0.9 percent at 662 keV, 2.6 percent at 122 keV and 5.7 percent at 60 keV have been obtained at room temperature
Generating Information-Diverse Microwave Speckle Patterns Inside a Room at a Single Frequency With a Dynamic Metasurface Aperture
We demonstrate that dynamic metasurface apertures (DMAs) are capable of generating a multitude of highly uncorrelated speckle patterns in a typical residential environment at a single frequency. We use a DMA implemented as an electrically-large cavity excited by a single port and loaded with many individually-addressable tunable metamaterial radiators. We placed such a DMA in one corner of a plywood-walled L-shape room transmitting microwave signals at 19 GHz as we changed the tuning states of the metamaterial radiators. In another corner, in the non-line-of-sight of the DMA, we conducted a scan of the field generated by the DMA. For comparison, we also performed a similar test where the DMA was replaced by a simple dipole antenna with fixed pattern but generating a signal that spanned 19-24 GHz. Using singular value decomposition of the scanned data, we demonstrate that the DMA can generate a multitude of highly uncorrelated speckle patterns at a single frequency. In contrast, a dipole antenna with a fixed pattern can only generate such a highly uncorrelated set of patterns when operating over a large bandwidth. The experimental results of this paper suggest that DMAs can be used to capture a diversity of information at a single frequency which can be used for single frequency computational imaging systems, NLOS motion detection, gesture recognition systems, and more
Standardized field testing of assistant robots in a Mars-like environment
Controlled testing on standard tasks and within standard environments can provide meaningful performance comparisons between robots of heterogeneous design. But because they must perform practical tasks in unstructured, and therefore non-standard, environments, the benefits of this approach have barely begun to accrue for field robots. This work describes a desert trial of six student prototypes of astronaut-support robots using a set of standardized engineering tests developed by the US National Institute of Standards and Technology (NIST), along with three operational tests in natural Mars-like terrain. The results suggest that standards developed for emergency response robots are also applicable to the astronaut support domain, yielding useful insights into the differences in capabilities between robots and real design improvements. The exercise shows the value of combining repeatable engineering tests with task-specific application-testing in the field
Crowd Counting Through Walls Using WiFi
Counting the number of people inside a building, from outside and without
entering the building, is crucial for many applications. In this paper, we are
interested in counting the total number of people walking inside a building (or
in general behind walls), using readily-deployable WiFi transceivers that are
installed outside the building, and only based on WiFi RSSI measurements. The
key observation of the paper is that the inter-event times, corresponding to
the dip events of the received signal, are fairly robust to the attenuation
through walls (for instance as compared to the exact dip values). We then
propose a methodology that can extract the total number of people from the
inter-event times. More specifically, we first show how to characterize the
wireless received power measurements as a superposition of renewal-type
processes. By borrowing theories from the renewal-process literature, we then
show how the probability mass function of the inter-event times carries vital
information on the number of people. We validate our framework with 44
experiments in five different areas on our campus (3 classrooms, a conference
room, and a hallway), using only one WiFi transmitter and receiver installed
outside of the building, and for up to and including 20 people. Our experiments
further include areas with different wall materials, such as concrete, plaster,
and wood, to validate the robustness of the proposed approach. Overall, our
results show that our approach can estimate the total number of people behind
the walls with a high accuracy while minimizing the need for prior
calibrations.Comment: 10 pages, 14 figure
Short-range passive radar for small private airports surveillance
This paper investigates the effectiveness of a passive radar for enhancing the security level in small airports and private runways. Specifically WiFi transmissions are parasitically exploited to perform detection and localization of non-cooperative targets that can be occupying the runway and the surrounding areas. Targets of interest include light/ultralight aircrafts, vehicles, people and even animals that may intrude onto the runways either intentionally or accidentally. The experimental results obtained by means of an experimental setup developed at SAPIENZA University of Rome prove the successful applicability of the proposed approach for small airports surveillance. © 2016 EuMA
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