Signal Generation for FMCW Ultra-Wideband Radar

One of the greatest concerns facing the planet earth today is global warming. Globally the temperatures have risen and this has caused rise in sea level. Since a large percentage of the population lives near the coast sea level rise could have potentially catastrophic consequences. One of the largest uncertainties in projections of sea level rise is the changes of mass-balance of the ice sheets of Greenland and Antarctica. To predict the rise in sea level we need accurate measurements of mass-balance. One of the methods of determining mass-balance is through surface ice elevation measurements. In order to measure surface ice elevation, map near surface internal layers and measure the thickness of snow over sea ice Ultra-Wideband (UWB) Frequency-Modulated Continuous-Wave Radars are being developed at CReSIS. FMCW radars are low-cost low-power solution to obtain very fine range resolution. However, nonlinearities present in the transmit frequency sweep of the FMCW radar can deteriorate the range resolution. The main objective of the thesis was to produce an ultra linear transmit chirp signal for UWB Radars. This was done by using the Voltage-Controlled-Oscillator (VCO) in a Phase-Locked Loop configuration. To check the linearity of the chirp beat frequency was generated using delay line as a synthetic target and captured on the oscilloscope. This beat signal data were further analyzed for linearity and we found that the frequency response of the beat signal was a focused Sinc wave as opposed to a smeared signal in case of nonlinear chirp. Also the phase of the beat signal data was linear with respect to time

An ultra-wideband, microwave radar for measuring snow thickness on sea ice and mapping near-surface internal layers in polar firn

This is the published version. Copyright 2013 International Glaciological SocietySea ice is generally covered with snow, which can vary in thickness from a few centimeters to >1 m. Snow cover acts as a thermal insulator modulating the heat exchange between the ocean and the atmosphere, and it impacts sea-ice growth rates and overall thickness, a key indicator of climate change in polar regions. Snow depth is required to estimate sea-ice thickness using freeboard measurements made with satellite altimeters. The snow cover also acts as a mechanical load that depresses ice freeboard (snow and ice above sea level). Freeboard depression can result in flooding of the snow/ice interface and the formation of a thick slush layer, particularly in the Antarctic sea-ice cover. The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an ultra-wideband, microwave radar capable of operation on long-endurance aircraft to characterize the thickness of snow over sea ice. The low-power, 100mW signal is swept from 2 to 8GHz allowing the air/snow and snow/ ice interfaces to be mapped with 5 cm range resolution in snow; this is an improvement over the original system that worked from 2 to 6.5 GHz. From 2009 to 2012, CReSIS successfully operated the radar on the NASA P-3B and DC-8 aircraft to collect data on snow-covered sea ice in the Arctic and Antarctic for NASA Operation IceBridge. The radar was found capable of snow depth retrievals ranging from 10cm to >1 m. We also demonstrated that this radar can be used to map near-surface internal layers in polar firn with fine range resolution. Here we describe the instrument design, characteristics and performance of the radar

Correlation analysis for energy losses, waiting times and durations of type I edge-localized modes in the Joint European Torus

Several important ELM control techniques are in large part motivated by the empirically observed inverse relationship between average ELM energy loss and ELM frequency in a plasma. However, to ensure a reliable effect on the energy released by the ELMs, it is important that this relation is verified for individual ELM events. Therefore, in this work the relation between ELM energy loss (W-ELM) and waiting time (Delta t(ELM)) is investigated for individual ELMs in a set of ITER-like wall plasmas in JET. A comparison is made with the results from a set of carbon-wall and nitrogen-seeded ITER-like wall JET plasmas. It is found that the correlation between W-ELM and Delta t(ELM) for individual ELMs varies from strongly positive to zero. Furthermore, the effect of the extended collapse phase often accompanying ELMs from unseeded JET ILW plasmas and referred to as the slow transport event (STE) is studied on the distribution of ELM durations, and on the correlation between W-ELM and Delta t(ELM). A high correlation between W-ELM and Delta t(ELM), comparable to CW plasmas is only found in nitrogen-seeded ILW plasmas. Finally, a regression analysis is performed using plasma engineering parameters as predictors for determining the region of the plasma operational space with a high correlation between W-ELM and Delta t(ELM)

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Meta-analysis comparing percutaneous coronary intervention with coronary artery bypass grafting for non-ST elevation acute coronary syndrome in patients with multivessel or left main disease

OBJECTIVES: Outcomes of patients presenting with non-ST-elevation acute coronary syndrome (NSTE-ACS) with multivessel coronary disease (MVD) and/or unprotected left main coronary artery disease (CAD) revascularized with percutaneous coronary intervention(PCI) or coronary artery bypass grafting(CABG) is not well defined. DESIGN: MEDLINE/PubMed and EMBASE/Ovid were queried for studies that investigated PCI vs. CABG in this disease subset. The primary outcome was major cardiac adverse events (MACE) at 30 days and long-term follow-up (3 to 5 years). RESULTS: The final analysis included 9 studies with a total of 9299 patients. No significant difference was observed between PCI and CABGin30 days MACE (risk ratio [RR] 0.96; 95% confidence interval [CI] 0.38-2.39, all-cause mortality, myocardial infarction, and stroke. A meta-regression analysis revealed patients with a history of PCI had higher risk of MACE with PCI as compared with CABG. At long-term follow-up, PCI compared with CABG was associated with higher risk of MACE (RR 1.52; 95% CI 1.28-1.81), myocardial infarction, and repeat revascularization, while no difference was observed in the risk of stroke and all-cause mortality. CONCLUSION: In patients with NSTE-ACS and MVD and/or unprotected left main CAD, no differences were observed in the clinical outcomes between PCI and CABG at 30 days follow-up. With long-term follow-up, PCI was associated with a higher risk of MACE