Mitigation of Through-Wall Distortions of Frontal Radar Images using Denoising Autoencoders

Radar images of humans and other concealed objects are considerably distorted by attenuation, refraction and multipath clutter in indoor through-wall environments. While several methods have been proposed for removing target independent static and dynamic clutter, there still remain considerable challenges in mitigating target dependent clutter especially when the knowledge of the exact propagation characteristics or analytical framework is unavailable. In this work we focus on mitigating wall effects using a machine learning based solution -- denoising autoencoders -- that does not require prior information of the wall parameters or room geometry. Instead, the method relies on the availability of a large volume of training radar images gathered in through-wall conditions and the corresponding clean images captured in line-of-sight conditions. During the training phase, the autoencoder learns how to denoise the corrupted through-wall images in order to resemble the free space images. We have validated the performance of the proposed solution for both static and dynamic human subjects. The frontal radar images of static targets are obtained by processing wideband planar array measurement data with two-dimensional array and range processing. The frontal radar images of dynamic targets are simulated using narrowband planar array data processed with two-dimensional array and Doppler processing. In both simulation and measurement processes, we incorporate considerable diversity in the target and propagation conditions. Our experimental results, from both simulation and measurement data, show that the denoised images are considerably more similar to the free-space images when compared to the original through-wall images

Representation of Radar Micro-Dopplers Using Customized Dictionaries

Human motions give rise to frequency modulations, known as micro-Dopplers, to continuous wave radar signals. Micro-Doppler signals have been extensively researched for the classification of different types of human motions as well as to distinguish humans from other moving targets. However, there are two main scenarios where the performance of existing algorithms deteriorates significantly—one, when the channel consists of multiple moving targets resulting in distorted signatures, and two, when the systems conditions during the training stage deviate significantly from the conditions during the test stage. In this chapter, it is demonstrated that both of these limitations can be overcome by representing the radar data through customized dictionaries, fine-tuned to provide sparser representations of the data, than traditional data-independent dictionaries such as Fourier or wavelets. The performances of the algorithms are evaluated with both simulated and measured radar data gathered from moving humans in indoor line-of-sight conditions

Radar simulation of human activities in non line-of-sight environments

textThe capability to detect, track and monitor human activities behind building walls and other non-line-of-sight environments is an important component of security and surveillance operations. Over the years, both ultrawideband and Doppler based radar techniques have been researched and developed for tracking humans behind walls. In particular, Doppler radars capture some interesting features of the human radar returns called microDopplers that arise from the dynamic movements of the different body parts. All the current research efforts have focused on building hardware sensors with very specific capabilities. This dissertation focuses on developing a physics based Doppler radar simulator to generate the dynamic signatures of complex human motions in nonline-of-sight environments. The simulation model incorporates dynamic human motion, electromagnetic scattering mechanisms, channel propagation effects and radar sensor parameters. Detailed, feature-by-feature analyses of the resulting radar signatures are carried out to enhance our fundamental understanding of human sensing using radar. First, a methodology for simulating the radar returns from complex human motions in free space is presented. For this purpose, computer animation data from motion capture technologies are exploited to describe the human movements. Next, a fast, simple, primitive-based electromagnetic model is used to simulate the human body. The microDopplers of several human motions such as walking, running, crawling and jumping are generated by integrating the animation models of humans with the electromagnetic model of the human body. Next, a methodology for generating the microDoppler radar signatures of humans moving behind walls is presented. This involves combining wall propagation functions derived from the finite-difference time-domain (FDTD) simulation with the free space radar simulations of humans. The resulting hybrid simulator of the human and wall is used to investigate the effects of both homogeneous and inhomogeneous walls on human microDopplers. The results are further corroborated by basic point-scatterer analysis of different wall effects. The wall studies are followed by an analysis of the effects of flat grounds on human radar signatures. The ground effect is modeled using the method of images and a ground reflection coefficient. A suitable Doppler radar testbed is developed in the laboratory for simulation validation. Measured data of different human activities are collected in both line-of-sight and through-wall environments and the resulting microDoppler signatures are compared with the simulation results. The human microDopplers are best observed in the joint timefrequency space. Hence, suitable joint time-frequency transforms are investigated for improving the display and the readability of both simulated and measured spectrograms. Finally, two new Doppler radar paradigms are considered. First, a scenario is considered where multiple, spatially distributed Doppler radars are used to measure the microDopplers of a moving human from different viewing angles. The possibility of using these microDoppler data for estimating the positions of different point scatterers on the human body is investigated. Second, a scenario is considered where multiple Doppler radars are collocated in a two-dimensional (2-D) array configuration. The possibility of generating frontal images of human movements using joint Doppler and 2-D spatial beamforming is considered. The performance of this concept is compared with that of conventional 2-D array processing without Doppler processing.Electrical and Computer Engineerin

Is adding intra-articular steroid in total knee arthroplasty cocktail obligatory?

Background: The patients can undergo total knee replacement surgery either under general anaesthesia, combined spinal and epidural anaesthesia, nerve root block, spinal combined with intra-articular knee cocktail. There is an ongoing debate amongst Arthroplasty surgeons whether to include steroid in the cocktail or not. The aim of this study is to assess whether there is an added benefit of including steroid in the intraarticular mixture.Methods: This prospective study was conducted at Sri Ramachandra Institute of Higher education, Chennai between December 2017 to December 2018. The study was conducted in the Arthroplasty unit, Department of Orthopaedics. SRIHER ethics committee clearance was obtained prior to the start of the study. The inclusion criteria were patients who underwent total knee replacement surgery under combined spinal and intra-articular knee cocktail. Patients were divided into two groups based on the use of steroid in the intra-articular mixture. Patients were evaluated using Visual analogue scale, opioids usage as primary endpoint while any joint infection within six months of the surgery and knee society score at 1 month and 6 months as the secondary endpoint.Results: The mean visual analogue score for the 0 pod for the group I and group II were 2.3 and 2.4 respectively. There was no case of infection in both groups.Conclusions: There is no fringe benefit of adding steroid to the knee cocktail. So it is not obligatory to add steroid in intra-articular total knee arthroplasty cocktail

Characterization of Non-volatile Particulate Matter in Pressurized Premixed Laminar Jet-A Flames Via Thermophoretic Sampling

Production and subsequent emissions of non-volatile particulate matter (nvPM) pose a challenge for both optical diagnostics and physical probing, especially at conditions relevant to practical combustors. Key to enabling nvPM mitigation is in-situ optical measurements, particularly laser induced incandescence (LII). However, interpreting the LII signals is challenging. To quantitatively use LII in gas turbines, their measurements must be calibrated and validated against physical nvPM samples. The preferred approach for extracting these physical samples is in-situ thermophoretic soot sampling followed by transmission electron microscope (TEM) imaging. This thesis work deals with the design of a multi-probe thermophoretic soot sampling system capable of extracting nvPM samples in laminar, rich flames of prevaporized jet-A/air premixtures at elevated pressures. The flames under investigation were observed to exhibit thermal-diffusive instabilities, that are responsible for the flame to form corrugated structures. Moreover, these instabilities cause the corrugated flame to exhibit spatio-temporal variations, which exacerbate the challenges in implementing diagnostics. For the soot sampler, a significantly larger sampling time of 125 ms was required to obtain sufficient soot deposition on the TEM grids, which can enhance the extent of restructuring in the deposited soot particles. Visualization of the data through the TEM revealed (i) a wide range of soot particle size varying between 10 – 250 nm; (ii) presence of non-soot organic matters that include (1) fibers, (2) sharp contrasted mineral-like structures, and (3) uniform and porous spherical structures with varying contrast; and (iii) the dominant morphological characteristics of the flame generated soot particles that are indicative of its chemically reactive nature and restructuring. Furthermore, the quantitative results show (i) increasing soot particle size with pressure, and (ii) an increasing-decreasing trend for the mean soot particle size with height above the burner. While the effect of pressure is explained by the enhanced extent of graphitization and maturity in the nanostructures of soot particles at elevated pressures; the dependence on height can be explained through particle agglomeration for the initial increase in size with height, followed by oxidation of the particles respectively. However, considering the range of tested HAB when compared to the flame length, the possibility for inconclusive variation stems from preheat temperature variations and restructuring effectsM.S

Estimation of the seismic response of buildings and the effect of different scaling methods for ground motion

The Seismic design code of Canada is changing rapidly to accommodate the needs of the future generation of buildings for management of earthquake hazard mitigation. In this context the recent advancement in Earthquake Technology and Structural Engineering has emphasized on the need for a better methodology and in-depth investigation into the area of structural performance evaluation in order to ensure that structures designed for the areas of high and moderate seismic hazard to the expected standards and meet the objective of life safety and collapse prevention in a real life scenario. In order to ensure the above performance objectives for a building structure, it is necessary to estimate its capacity with respect to the demand, and the dynamic response corresponding to the design levels of earthquakes. The research carried out here aims to investigate: (i) the earthquake demand and capacity profiles of a set of set of moment frame buildings designed according to the latest version of the National Building Code of Canada, and (ii) the effect of scaling and spectral matching techniques commonly applied to ground motions on the seismic demand parameters determined using the dynamic time history analysis. A set of buildings with steel moment resisting frames of 5, 10, 15, 20 stories in height and located in Vancouver area of Canada have been considered in this study. An extensive review has been conducted to determine the existing methods for performance-based design and the techniques available to selecting and scaling suite of earthquake records to perform a fully non-linear dynamic analysis in time domain. Based on that, a range of scaling techniques including linear scaling techniques, and spectral matching technique have been considered for an ensemble of recorded ground motion time histories. In addition a set of artificially generated spectrum-compatible earthquake records are also considered. The static pushover analysis has been carried out and the corresponding capacity curves have been obtained and interpreted with commonly used performance-based design methods. It is observed that all the methods considered here confirm that the existing design based on the code procedure is adequate and conservative. The pushover curves are also compared to the results obtained from the Time history analysis to determine the performance achievements of the buildings. The interstory drift obtained from the time history analysis using different scaling methods show a uniform and consistent pattern of deformation in low rise to medium rise frames whereas dispersion greater dispersion of the results has been observed in tall buildings. Other response quantities such as the lateral drift, base shear and bending moment show similar patterns. Based on the results from the research it is suggested to use the artificial records if site specific real ground motion records are unavailable. The scope for further research lies in exploring ways to the possibility of new scaling techniques that can control the dispersion in the response more effectivel

Pesticides handling practices among potato growers in Kavrepalanchok, Nepal

The rate of pesticide application in the agricultural field is surging. Farmers are getting exposed to pesticide hazards from the misuse and unsafe handling of pesticides. The study was conducted among 101 potato growers in Kaverpalanchok district of Nepal in 2018. The objective of the study was to assess the knowledge, status, and pesticide handling practices among potato growers. Around 94% farmers applied pesticides against early and late blight. Only 5% growers treated seed before potato sowing. About 93 and 73% farmers sprayed pesticides 2-10 times/season into the field and spent 2-6 hours/pesticide spray respectively. More than 2/3rd growers did not read the pesticide labels, and nearly 95% growers received information on pesticide applications from agrovet rather than authorized government bodies. Only 13% farmers had received Integrated Pest Management (IPM) training. However, 1/4th of them had practiced IPM techniques. The majority of the growers used masks, rubber boots, and long-sleeved clothes during pesticide handling. Nearly 2/3rd growers threw pesticide containers anywhere in the environment. Concerned authorities should provide IPM training, skill-building programs on pesticide handling and awareness on waiting period and environmental hazards to avoid pesticide risk

Radar Enhanced Multi-Armed Bandit for Rapid Beam Selection in Millimeter Wave Communications

Multi-arm bandit (MAB) algorithms have been used to learn optimal beams for millimeter wave communication systems. Here, the complexity of learning the optimal beam linearly scales with the number of beams, leading to high latency when there are a large number of beams. In this work, we propose to integrate radar with communication to enhance the MAB learning performance by searching only those beams where the radar detects a scatterer. Further, we use radar to distinguish the beams that show mobile targets from those which indicate the presence of static clutter, thereby reducing the number of beams to scan. Simulations show that our proposed radar-enhanced MAB reduces the exploration time by searching only the beams with distinct radar mobile targets resulting in improved throughput.Comment: 5 pages, 6 figure

Functional and radiological analysis of posterior lumbar interbody fusion in spondylolisthesis

Background:Spondylolisthesis is present in 5% of the adult population with clinical evidence of low back pain. These patients are treated initially by conservative measures, failing of which surgical intervention is mandatory. Majority of patients with varying degree of slip and disability ultimately require surgical intervention. In this study we are trying to analyse the functional outcome following posterior lumbar interbody fusion in spondylolisthesis.Methods: Posterior lumbar interbody fusion using pedicle screw and rods with cage was performed on 25 patients. 6 months follow-up was completed in 25 patients who were then reviewed at regular intervals. Out of the 25 patients, 17(68%) were females and 8(32%) were males. The mean age of the patients was 40.64 years. Out of 25 patients, 14 patients had listhesis at L4 – L5 level and another 11 at L5 – S1 level. 21(84%) were Isthmic variant and 4 (16%) were Degenerative spondylolisthesis.Results:The mean follow up period in this study of 25 patients is 19 months. Out of 25 patients, there was mean improvement of 18.96 in the Oswestry scoring index. The Visual analogue scale score showed a mean improvement of 6.48. Radiologically, the percentage of slip was decreased by a mean of 8.40%. One patient had a cage extrusion with no neurological deficit.Conclusions:The pedicle screw with rod and cage system is easy to use and provides the anatomic restoration of the isthmus in isthmic spondylolisthesis or restoring the stability after laminectomy/discectomy in degenerative spondylolisthesis. From our study, we strongly believe that this technique is very useful in low grade degenerative and isthmic spondylolisthesis