On the use of the l(2)-norm for texture analysis of polarimetric SAR data

In this paper, the use of the l2-norm, or Span, of the scattering vectors is suggested for texture analysis of polarimetric synthetic aperture radar (SAR) data, with the benefits that we need neither an analysis of the polarimetric channels separately nor a filtering of the data to analyze the statistics. Based on the product model, the distribution of the l2-norm is studied. Closed expressions of the probability density functions under the assumptions of several texture distributions are provided. To utilize the statistical properties of the l2-norm, quantities including normalized moments and log-cumulants are derived, along with corresponding estimators and estimation variances. Results on both simulated and real SAR data show that the use of statistics based on the l2-norm brings advantages in several aspects with respect to the normalized intensity moments and matrix variate log-cumulants.Peer ReviewedPostprint (published version

Assistive Multi-Purpose Mobility Device with Folding Temporary Seat

Crutches and canes are widely used to provide stability and support while walking. Many users, particularly the elderly, have limited endurance. The goal of this project was to design and build a device that can be used as a forearm crutch or a cane and integrates the ability for the user to rest comfortably and safely in a seated position. A first generation multi-purpose device was successfully designed and manufactured that includes a foldable seat and two folding support legs attached to the main shaft that forms a base of support when deployed. The prototype successfully supported a 205 lb. seated user on carpeted floor. Student testers reported that folding the device into a seat was very intuitive. Future prototypes would increase load limit, especially on low friction surfaces

Statistical modeling of polarimetric SAR data: a survey and challenges

Knowledge of the exact statistical properties of the signal plays an important role in the applications of Polarimetric Synthetic Aperture Radar (PolSAR) data. In the last three decades, a considerable research effort has been devoted to finding accurate statistical models for PolSAR data, and a number of distributions have been proposed. In order to see the differences of various models and to make a comparison among them, a survey is provided in this paper. Texture models, which could capture the non-Gaussian behavior observed in high resolution data, and yet keep a compact mathematical form, are mainly explained. Probability density functions for the single look data and the multilook data are reviewed, as well as the advantages and applicable context of those models. As a summary, challenges in the area of statistical analysis of PolSAR data are also discussed.Peer ReviewedPostprint (published version

Cost Analysis for the MS4 Permits

Stormwater runoff is the number one pollutant of water bodies in the United States. As runoff flows over impervious surfaces, it picks up pollutants and discharges directly to nearby water bodies such as lakes or rivers. The United States Environmental Protection Agency regulates stormwater runoff pollution through the Municipal Separate Storm Sewer System, or MS4, permit. Currently, Massachusetts stormwater is regulated through a 2003 MS4 permit. However, a new permit is anticipated to be issued in 2014. The goal of our project was to estimate the cost of implementing the new upcoming permit. We found the estimated cost of implementing the upcoming new permit for four case study towns with different population, area, and impervious surface area

Higher order statistics for texture analysis and physical interpretation of polarimetric SAR data

The logarithmic cumulants (log-cumulants for short) of the second and third orders are widely used in the statistical analysis of polarimetric synthetic aperture radar (PolSAR) data. However, both the product model and the finite mixture model may produce the same values of these statistics, which means that the use of these log-cumulants is not enough to determine the statistical model of the data. In this letter, it is demonstrated that the log-cumulants of higher orders can help to distinguish the concept of texture from that of mixture, providing a physical insight into the data statistics. A tool called log-cumulant cube, which helps to visualize this difference, is proposed by considering texture distributions from the Pearson's family. Results on both simulated and real SAR data show that the use of higher order statistics is useful when it comes to the texture analysis of PolSAR data.Peer ReviewedPostprint (author's final draft

Hydrogen Supply Infrastructure Network Planning Approach towards Chicken-egg Conundrum

In the early commercialization stage of hydrogen fuel cell vehicles (HFCVs), reasonable hydrogen supply infrastructure (HSI) planning decisions is a premise for promoting the popularization of HFCVs. However, there is a strong causality between HFCVs and hydrogen refueling stations (HRSs): the planning decisions of HRSs could affect the hydrogen refueling demand of HFCVs, and the growth of demand would in turn stimulate the further investment in HRSs, which is also known as the ``chicken and egg'' conundrum. Meanwhile, the hydrogen demand is uncertain with insufficient prior knowledge, and thus there is a decision-dependent uncertainty (DDU) in the planning issue. This poses great challenges to solving the optimization problem. To this end, this work establishes a multi-network HSI planning model coordinating hydrogen, power, and transportation networks. Then, to reflect the causal relationship between HFCVs and HRSs effectively without sufficient historical data, a distributionally robust optimization framework with decision-dependent uncertainty is developed. The uncertainty of hydrogen demand is modeled as a Wasserstein ambiguity set with a decision-dependent empirical probability distribution. Subsequently, to reduce the computational complexity caused by the introduction of a large number of scenarios and high-dimensional nonlinear constraints, we developed an improved distribution shaping method and techniques of scenario and variable reduction to derive the solvable form with less computing burden. Finally, the simulation results demonstrate that this method can reduce costs by at least 10.4% compared with traditional methods and will be more effective in large-scale HSI planning issues. Further, we put forward effective suggestions for the policymakers and investors to formulate relevant policies and decisions

Comparative genomics reveals intraspecific divergence of Acidithiobacillus ferrooxidans: insights from evolutionary adaptation

Acidithiobacillus ferrooxidans serves as a model chemolithoautotrophic organism in extremely acidic environments, which has attracted much attention due to its unique metabolism and strong adaptability. However, little was known about the divergences along the evolutionary process based on whole genomes. Herein, we isolated six strains of A. ferrooxidans from mining areas in China and Zambia, and used comparative genomics to investigate the intra-species divergences. The results indicated that A. ferrooxidans diverged into three groups from a common ancestor, and the pan-genome is ‘open’. The ancestral reconstruction of A. ferrooxidans indicated that genome sizes experienced a trend of increase in the very earliest days before a decreasing tendency during the evolutionary process, suggesting that both gene gain and gene loss played crucial roles in A. ferrooxidans genome flexibility. Meanwhile, 23 single-copy orthologous groups (OGs) were under positive selection. The differences of rusticyanin (Rus) sequences (the key protein in the iron oxidation pathway) and type IV secretion system (T4SS) composition in the A. ferrooxidans were both related to their group divergences, which contributed to their intraspecific diversity. This study improved our understanding of the divergent evolution and environmental adaptation of A. ferrooxidans at the genome level in extreme conditions, which provided theoretical support for the survival mechanism of living creatures at the extreme

Serum CHI3L1 as a biomarker of interstitial lung disease in rheumatoid arthritis

BackgroundInterstitial lung disease (ILD) is a relatively prevalent extra-articular manifestation of rheumatoid arthritis (RA) and contributes to significant morbidity and mortality. This study aimed to analyze the association between chitinase-3 like-protein-1(CHI3L1) and the presence of RA-ILD.MethodsA total of 239 RA patients fulfilling the American Rheumatism Association (ACR) 1987 revised criteria were enrolled and subclassified as RA-ILD and RA-nILD based on the results of high-resolution computed tomography scans (HRCT) of the chest. The disease activity of RA was assessed by Disease Activity Score for 28 joints (DAS28) and categorized as high, moderate, low, and remission. Chemiluminescence immunoassays were applied to determine the serum levels of CHI3L1. Univariate analysis was performed and the receiver operating characteristics (ROC) curves were plotted to evaluate the correlation between RA-ILD and CHI3L1.ResultsAmong the eligible RA patients studied, 60 (25.1%) patients were diagnosed with RA-ILD. Compared with RA-nILD, RA patients with ILD had significantly higher median age (median [IQR], 68.00 [62.00-71.75] vs 53.00 [40.00-63.00], p<0.001) and a higher proportion of males (21 (35.0%) vs 30 (16.8%), p=0.003). Notably, differences in DAS28 scores between the two groups were not observed. The serum level of CHI3L1 was significantly higher in RA-ILD patients (median [IQR], 69.69 [44.51-128.66] ng/ml vs 32.19 [21.63-56.99] ng/ml, p<0.001). Furthermore, the areas under the curve (AUC) of CHI3L1 attained 0.74 (95% confidence interval [CI], 0.68-0.81, p<0.001) in terms of identifying patients with RA-ILD from those without ILD. Similar trends were seen across the spectrum of disease activity based on DAS28-ESR.ConclusionOur findings of elevated serum CHI3L1 levels in RA-ILD patients suggest its possible role as a biomarker to detect RA-ILD noninvasively