S. Nag

Ultrawideband through-wall radar for detecting the motion of people in real time

Law enforcement officers and search-and-rescue workers often face the difficult task of determining the locations of people inside a building or obscured by smoke and debris. To address this problem, Time Domain Corporation (TDC) has developed a real-time, hand-held radar to detect the motion of persons in range and azimuth through non-metallic walls. This radar is a time modulated ultra-wide band (TM-UWB) impulse radar that generates a two-dimensional (2D) representation of moving targets in real time. The intentional transmit power emitted from the radar is comparable to the FCC Part 15, Class B limits. It has the following benefits: (1) covertness because of its ultra-low power noise-like signal, (2) high resolution at low radio frequencies for penetrating building materials, (3) reduced range ambiguities and clutter fold-over because of pseudo-random time modulation, and (4) clutter rejection because of the ultra-wide bandwidth of the signal. In this paper, an outline of the key parameters of the TDC prototype radar RadarVision2000 (RV2000) and a brief description of the algorithm that generates a motion map showing the range and direction of the moving people are presented. Some typical radar images of multiple targets for a variety of building materials and cluttered environment obtained using the prototype are shown. Finally, the paper presents some preliminary results for resolving the targets in the elevation plane along with a processing technique for reducing the intensity of multi-path responses in the images.

Elemental partitioning between α and β phases in the Ti–5Al–5Mo–5V–3Cr–0.5Fe (Ti-5553) alloy

Using atom probe tomography, the partitioning of alloying elements between α and β in the alloy Ti metal-5553 (Ti–5Al–5Mo–5V–3Cr–0.5Fe) has been investigated as a function of heat-treatment. It has been shown that β-solutionizing followed by step-quenching to a higher temperature (700°C) or slow-cooling leads to substantial partitioning of the alloying elements, including an enrichment of slow-diffusing Mo at the α/β interfaces. In contrast, it was found that the combination of β-solutionizing, quenching to room temperature and aging at 400°C leads to rather limited partitioning of these alloying elements.

A standoff, focused-beam land mine radar

This paper describes a standoff, focused-beam, ground-penetrating radar (GPR) for detecting buried antipersonnel (AP) mines. The radar features a 1 to 6 GHz, pulsed stepped-frequency microwave source with hardware range gate, an ultrawide bandwidth feed antenna, and an offset parabolic reflector. A focused-beam, created by feeding the reflector from an offset position, reduces the surface clutter and improves the detection of buried mines. A processing technique based on spectral analysis (Prony method) is developed in an attempt to reduce surface clutter. Tests conducted at the Fort A.P. Hill countermine test lanes showed excellent detection capability for both metallic and nonmetallic mines.

Influence of Seeding and Bath Conditions in Hydrothermal Growth of Very Thin (∼20 nm) Single-Crystalline Rutile TiO2 Nanorod Films

New seeding conditions have been examined for the hydrothermal growth of single-crystalline rutile TiO₂ nanorods. Rutile nanorods of ∼20 nm diameter are grown from seed layers consisting of either (A) TiO₂ or MnOOH nanocrystals deposited from suspension, or (B) a continuous sheet of TiO₂. These seed layers are more effective for seeding the growth of rutile nanorods compared to the use of bare F-SnO₂ substrates. The TiO₂ sheet seeding allows lower concentration of titanium alkoxide precursor relative to previously reported procedures, but fusion of the resulting TiO₂ nanorods into bundles occurs at higher precursor concentration and/or longer growth duration. Performance of polymer-oxide solar cells prepared using these nanorods shows a dependence on the extent of bundling as well as rod height.

Laser deposited biocompatible Ca–P coatings on Ti–6Al–4V: Microstructural evolution and thermal modeling

A high intensity continuous wave diode pumped ytterbium laser source was used to deposit Ca-P coatings on a Ti-6Al-4V biocompatible alloy in order to generate a physically textured surface, enhancing osseointegration. Scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and energy dispersive spectroscopy (EDS) studies were coupled with X-ray and micro diffraction work to determine the structure, composition, and phases present in various zones of a sample prepared across the coating/substrate interaction zone. Three-dimensional thermal modeling was also carried out to determine the cooling rate and maximum temperature experienced by different regions of the substrate. Combining these results provide us with valuable insights regarding the thermo-physical as well as chemical interactions that take place across the coating-substrate interface.

Corrosion resistance and in vitro response of laser-deposited Ti-Nb-Zr-Ta alloys for orthopedic implant applications

While direct metal deposition of metallic powders, via laser deposition, to form near-net shape orthopedic implants is an upcoming and highly promising technology, the corrosion resistance and biocompatibility of such novel metallic biomaterials is relatively unknown and warrants careful investigation. This article presents the results of some initial studies on the corrosion resistance and in vitro response of laser-deposited Ti-Nb-Zr-Ta alloys. These new generation beta titanium alloys are promising due to their low elastic modulus as well as due the fact that they comprise of completely biocompatible alloying elements. The results indicate that the corrosion resistance of these laser-deposited alloys is comparable and in some cases even better than the currently used commercially-pure (CP) titanium (Grade 2) and Ti-6Al-4V ELI alloys. The in vitro studies indicate that the Ti-Nb-Zr-Ta alloys exhibit comparable cell proliferation but enhanced cell differentiation properties as compared with Ti-6Al-4V ELI.

Covert situational awareness with handheld ultrawideband short-pulse radar

Law enforcement and emergency services all face the difficult task of determining the locations of people within a building. A handheld radar able to detect motion through walls and other obstructions has been developed to fill this need. This paper describes the attributes and difficulties of the radar design and includes test results of the radars performance. This discussion begins by summarizing key user requirements and the electromagnetic losses of typical building materials. Ultra-wideband (UWB) short pulse radars are well suited for a handheld sensor primarily because of their inherit time isolation in high clutter environments and their capability to achieve high resolution at low spectral center frequencies. There are also constraints that complicate the system design. Using a technique referred to as time-modulation allows the radars to reject range ambiguities and enhances electromagnetic compatibility with similar radars and ambient systems. An outline of the specifications of the radar developed and a process diagram on how it generates a motion map showing range and direction of the people moving within structures is included. Images are then presented to illustrate its performance. The images include adults, child, and a dog. The test results also include data showing the radars performance through a variety of building materials.

Comparison of the crystallization behavior of Fe-Si-B-Cu and Fe-Si-B-Cu-Nb-based amorphous soft magnetic alloys

The role of the solute elements, copper, and niobium, on the different stages of de-vitrification or crystallization of two amorphous soft magnetic alloys, Fe73.5Si13.5B9Nb3Cu1, also referred to as FINEMET, and a Fe76.5Si13.5B9Cu1 alloy, a model composition without Nb, has been investigated in detail by coupling atom probe tomography and transmission electron microscopy. The effects of copper clustering and niobium pile-up at the propagating interface between the α-Fe3Si nanocrystals and the amorphous matrix, on the nucleation and growth kinetics have been addressed. The results demonstrate that while Cu clustering takes place in both alloys in the early stages, the added presence of Nb in FINEMET severely restricts the diffusivity of solute elements such as Cu, Si, and B. Therefore, the kinetics of solute partitioning and mobility of the nanocrystal/amorphous matrix interface is substantially slower in FINEMET as compared to the Fe76.5Si13.5B9Cu1 alloy. Consequently, the presence of Nb limits the growth rate of the α-Fe3Si nanocrystals in FINEMET and results in the activation of a larger no. of nucleation sites, leading to a substantially more refined microstructure as compared to the Fe76.5Si13.5B9Cu1 alloy.

Evolution of a honeycomb network of precipitates in a hot-rolled commercial Mg–Y–Nd–Zr alloy

Coupled processes of dynamic recovery and precipitation, occurring during hot-rolling and subsequent aging, lead to the formation of a unique honeycomb network of precipitates in commercial Mg–Y–Nd–Zr or WE43 alloy. The honeycomb network is developed on the (0 0 0 1)Mg basal planes and consisted of fine Nd-rich β 1 platelets lying on all three planes presumably decorating recovery-generated dislocation subcell boundaries. Three variants of β 1 platelets are connected by Y-rich precipitates at the nodes of the hexagonal honeycomb network.

Radar images of penetrable targets generated from ramp profile functions

Images can be generated for penetrable targets from their scattered fields when the time dependence of the incident electromagnetic (EM) wave takes the form of a ramp function. Previous researchers have developed these concepts for conducting targets. This paper focuses attention on penetrable targets. Ramp response signatures of the targets for cases where the dielectric constant of the target is greater than and also less than that of the ambient medium are included. The latter case can be applied as a signature of antipersonnel mines. The results contained herein are based on: (1) scattering measurements in The Ohio State University ElectroScience Laboratory compact range; (2) scattering computation using an eigenfunction solution and a method of moments solution; and (3) a very limited set of measurements generated from a buried land mine using the ElectroScience Laboratory ground penetrating radar. The targets presented in this paper include metallic and dielectric spheres and actual land mines.