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Dowla, Farid

Publications and source records attributed to Dowla, Farid.

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

GPR Imaging for Deeply Buried Objects: A Comparative Study Based on Compositing of Scanning Frequencies and a Chirp Excitation Function

Compositing of ground penetrating radar (GPR) scans of differing frequencies have been found to produce cleaner images at depth using the Gaussian mixture model (GMM) feature of the expectation-maximization (EM) algorithm. GPR scans at various heights (“Stand Off”), as well as ground-based scans, have been studied. In this paper, we compare the GPR response from a chirp excitation function-based radar with the response from the EM GMM algorithm compositing process, using the same mix of frequencies. A chirp excitation pulse was found to be effective in delineating the defined buried object, but the resulting image is less sharp than the GMM EM method.

58 GEOSCIENCES↗
DOE OSTI2018

Compositing "Stand Off" Ground Penetrating Radar Scans of Differing Frequencies.

Methods have been developed to combine signals of various frequencies in a manner to produce clearer images in the presence of noise. Ground Penetrating Radar (GPR) scans at various frequencies are no exception. Methods using an optimization problem solver, the Expectation-Maximization (EM) Algorithm, define weights used to perform the task of combining GPR scans. In this paper, we explore using the Gaussian Mixture Model (GMM) feature of the EM Algorithm on GPR scans taken at various heights above ground ("Stand Off' GPR). This method demonstrates the same measured improvement toward producing a cleaner image as GPR scans taken at ground level using the same EM Algorithm method.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Design Considerations for Secure Wireless Sensor Communication Systems in Harsh Electromagnetic Environments of Nuclear Reactor Facilities

Wireless sensors can potentially play a significant role in safety, efficiency, and reliability of the instrumentation and control process in current and next generation nuclear power reactors. While conventional narrowband wireless sensors have shown a certain level of success in some nuclear power plants (NPPs), the radio frequency (RF) propagation challenges posed by the heavy metallic and cluttered environment of NPPs has prevented their widespread use in such operations. Furthermore, these challenges include RF wave propagation in harsh (reflective, absorptive, cluttered) environments, data security issues, and RF interference to and from other devices in the vicinity of a nuclear reactor core. In this paper, first we address how ultrawideband (UWB) RF technology can complement the narrowband (i.e., WiFi) solutions that have been used in some NPPs by providing an alternative solution in addressing the signal propagation issues in such electromagnetically harsh environments. Second, we discuss and present the UWB software simulation results on multipath harsh environments, and then address the data security issues. In the final sections of the paper, we present the experimental results of using UWB signaling in a representative harsh environment conducted at the Massachusetts Institute of Technology research reactor site. We plan to develop the UWB communications hardware based on the results of this paper and report on its performance in the field with emphasis on the security aspects of the system in a subsequent paper.

42 ENGINEERING↗
DOE OSTI2017

Compositing Ground Penetrating Radar Scans of Differing Frequencies for Better Depth Perception

Methods developed to reduce interference in a noisy environment, be it radar target responses or effective communications in the presence of noise for mobile phone users, are vital in delivering a clear usable signal. The methods used to render a cleaner signal can also be used to combine signals of various frequencies. Ground Penetrating Radar (GPR) scans over the same area are no exception. This paper explores using an optimization problem solver, the Expectation Maximization (EM) Algorithm, to define the weights to use to combine multiple GPR scans at different frequencies over the same target area. This approach exploits the Gaussian Mixture Model (GMM) feature of the EM algorithm to produce a cleaner image at depth. Our method demonstrates a measured improvement toward producing a cleaner image.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

Secure passive RFID tag with seal

A secure passive RFID tag system comprises at least one base station and at least one passive RFID tag. The tag includes a fiber optic cable with the cable ends sealed within the tag and the middle portion forming an external loop. The loop may be secured to at least portions of an object. The tag transmits and receives an optical signal through the fiber optic cable, and the cable is configured to be damaged or broken in response to removal or tampering attempts, wherein the optical signal is significantly altered if the cable is damaged or broken. The tag transmits the optical signal in response to receiving a radio signal from the base station and compares the transmitted optical signal to the received optical signal. If the transmitted optical signal and the received optical signal are identical, the tag transmits an affirmative radio signal to the base station.

36 MATERIALS SCIENCE↗
DOE OSTI2017

A robust wireless communication system for electromagnetically harsh environments of nuclear facilities - 155

Wireless sensors could play a significant role in safety, efficiency, and reliability of instrumentation and control process in current and next generation nuclear power reactors. While conventional narrowband wireless sensors have successfully been used in numerous industrial applications, the RF propagation challenges posed by the heavy metallic and cluttered environment of Nuclear Power Plants (NPPs) has prevented their use in such operations. These challenges include: RF propagation in harsh (reflective, absorptive, cluttered) environments, data security issues, and RF interference to and from other devices in a nuclear reactor. In this introductory paper, first we address how Ultra-wideband (UWB) technology can provide a viable solution for the signal propagation issues in such electromagnetically harsh environments. Second, we present a novel UWB remote powering scheme that allows for battery-free operation of sensors to increase their lifetime. We finalize the paper by presenting the experimental results of using UWB signaling in a representative harsh environment conducted at MIT research reactor. We plan to address the security issues through an innovative UWB communications scheme for sensor data communications in a subsequent paper. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2017

Transmit-reference methods in software defined radio platforms for communication in harsh propagation environments and systems thereof

A method for adaptive Radio Frequency (RF) jamming according to one embodiment includes dynamically monitoring a RF spectrum; detecting any undesired signals in real time from the RF spectrum; and sending a directional countermeasure signal to jam the undesired signals. A method for adaptive Radio Frequency (RF) communications according to another embodiment includes transmitting a data pulse in a RF spectrum; and transmitting a reference pulse separated by a predetermined period of time from the data pulse; wherein the data pulse is modulated with data, wherein the reference pulse is unmodulated. A method for adaptive Radio Frequency (RF) communications according to yet another embodiment includes receiving a data pulse in a RF spectrum; and receiving a reference pulse separated in time from the data pulse, wherein the data pulse is modulated with data, wherein the reference pulse is unmodulated; and demodulating the pulses.

42 ENGINEERING↗
DOE OSTI2016

Secure RFID tag or sensor with self-destruction mechanism upon tampering

A circuit board anti-tamper mechanism comprises a circuit board having a frangible portion, a trigger having a trigger spring, a trigger arming mechanism actuated by the trigger wherein the trigger arming mechanism is initially non-actuated, a force producing mechanism, a latch providing mechanical communication between the trigger arming mechanism and the force producing mechanism, wherein the latch initially retains the force producing mechanism in a refracted position. Arming pressure applied to the trigger sufficient to overcome the trigger spring force will actuate the trigger arming mechanism, causing the anti-tamper mechanism to be armed. Subsequent tampering with the anti-tamper mechanism results in a decrease of pressure on the trigger below the trigger spring force, thereby causing the trigger arming mechanism to actuate the latch, thereby releasing the force producing mechanism to apply force to the frangible portion of the circuit board, thereby breaking the circuit board.

42 ENGINEERING↗
DOE OSTI2016

Secure optionally passive RFID tag or sensor with external power source and data logging

A secure optionally passive RFID tag or sensor system comprises a passive RFID tag having means for receiving radio signals from at least one base station and for transmitting radio signals to at least one base station, where the tag is capable of being powered exclusively by received radio energy, and an external power and data logging device having at least one battery and electronic circuitry including a digital memory configured for storing and recalling data. The external power and data logging device has a means for powering the tag, and also has a means.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2015

Scoping Study on Developing Alternatives to Radionuclide-based Logging Technologies

Subsurface devices utilizing radioisotopes, 241 Am and 137 Cs, are critical for reservoir characterization and related completion and production decisions. Being small, mobile and used widely worldwide, these sources can pose radiological dispersal device (RDD) security risks. The security concerns have been exacerbated by recent stolen or missing source incidents, existence of a black-market on sources in general, and attempts at their malevolent use. Consequently, in addition to decades-long industry effort to develop non-nuclear and nuclear-based alternative logging technologies, governments, international agencies, and national labs are actively assessing measures and technologies to mitigate risks of such sources. Risk mitigation efforts include enhanced regulations, source-use guidelines, research and development on electronic tracking of sources, and continued exploration of alternative technologies by both the petroleum industry and U S Department of Energy (DOE). In recent years, the petroleum industry has continued to explore new nuclear-based and nonnuclear alternative techniques and several DOE-sponsored reports have been prepared on the topic. However, there has been no significant synergy between the industry and DOE efforts in developing alternatives.

02 PETROLEUM↗
NASA NTRS2012

GPR Imaging for Deeply Buried Objects: A Comparative Study Based on FDTD Models and Field Experiments

Conventional use of Ground Penetrating Radar (GPR) is hampered by variations in background environmental conditions, such as water content in soil, resulting in poor repeatability of results over long periods of time when the radar pulse characteristics are kept the same. Target objects types might include voids, tunnels, unexploded ordinance, etc. The long-term objective of this work is to develop methods that would extend the use of GPR under various environmental and soil conditions provided an optimal set of radar parameters (such as frequency, bandwidth, and sensor configuration) are adaptively employed based on the ground conditions. Towards that objective, developing Finite Difference Time Domain (FDTD) GPR models, verified by experimental results, would allow us to develop analytical and experimental techniques to control radar parameters to obtain consistent GPR images with changing ground conditions. Reported here is an attempt at developing 20 and 3D FDTD models of buried targets verified by two different radar systems capable of operating over different soil conditions. Experimental radar data employed were from a custom designed high-frequency (200 MHz) multi-static sensor platform capable of producing 3-D images, and longer wavelength (25 MHz) COTS radar (Pulse EKKO 100) capable of producing 2-D images. Our results indicate different types of radar can produce consistent images.

Tilley, roger↗