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Characterization of multi-scale ionospheric irregularities using ground-based and space-based GNSS observations

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Satellite Navigation 2021年第1期2卷 192-212页

作者： YuXiang Peng Wayne A Scales michael D Hartinger Zhonghua Xu Shane coyle Center for Space Science and Engineering research Virginia TechBlacksburgVA 24061USA Bradley Department of Electrical and computer Engineering Virginia TechBlacksburgVA 24061USA Space Science Institute BoulderCO 80301USA National Institute of Aerospace HamptonVA 23666USA Center for Space Science and Engineering research Virginia TechBlacksburgVA 24061USA.

Ionospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). How-ever, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite ionospheric monitoring has been undertaken for decades, these irregularities in multiple spatial and temporal scales are still not fully understood. This paper reviews Virginia Tech’s recent studies on multi-scale ionospheric irregularities using ground-based and space-based GNSS observations. First, the relevant background of ionospheric irregularities and their impact on GNSS signals is reviewed. Next, three topics of ground-based observations of ionospheric irregulari-ties for which GNSS and other ground-based techniques are used simultaneously are reviewed. Both passive and active measurements in high-latitude regions are covered. Modelling and observations in mid-latitude regions are considered as well. Emphasis is placed on the increased capability of assessing the multi-scale nature of ionospheric irregularities using other traditional techniques (e.g., radar, magnetometer, high frequency receivers) as well as GNSS observations (e.g., Total-Electron-content or TEC, scintillation). Besides ground-based observations, recent advances in GNSS space-based ionospheric measurements are briefly reviewed. Finally, a new space-based ionospheric observa-tion technique using GNSS-based spacecraft formation flying and a differential TEC method is demonstrated using the newly developed Virginia Tech Formation Flying Testbed (VTFFTB). Based on multi-constellation multi-band GNSS, the VTFFTB has been developed into a hardware-in-the-loop simulation testbed with external high-fidelity global ionospheric model(s) for 3-satellite formation flying, which can potentially be used for new multi-scale ionospheric measurement mission design.

关键词： GNSS Ionospheric irregularities remote sensing Active experiment Spacecraft formation flying

Efficient recovery of Structured Sparse Signals via Approximate Message Passing with Structured Spike and Slab Prior

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China communications 2018年第6期15卷 1-17页

作者： Xiangming Meng Sheng Wu michael riis ANDersen Jiang Zhu Zuyao Ni Huawei Technologies co.Ltd. Shanghai 201206China Tsinghua Space Center Tsinghua UniversityBeijing 100084China Department of computer Science Aalto University P.O.Box 15400FI-00076Finland Ocean college Zhejiang UniversityZhoushan 316021China

Due to limited volume, weight and power consumption, micro-satellite has to reduce data transmission and storage capacity by image compression when performs earth observation missions. However, the quality of images may be unsatisfied. This paper considers the problem of recovering sparse signals by exploiting their unknown sparsity pattern. To model structured sparsity, the prior co.relation of the support is encoded by imposing a transformed Gaussian process on the spike and slab probabilities. Then, an efficient approximate message-passing algorithm with structured spike and slab prior is derived for posterior inference, which, combined with a fast direct method, reduces the computational complexity significantly. Further, a unified scheme is developed to learn the hyperparameters using expectation maximization(EM) and Bethe free energy optimization. Simulation results on both synthetic and real data demonstrate the superiority of the proposed algorithm.

关键词： compressed sensing structuredsparsity spike and slab prior approximate message passing expectation propagation

A decision framework for identifying models to estimate forest ecosystem services gains from restoration

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Forest Ecosystems 2016年第2期3卷 126-137页

作者： Zachary L. Christin Kenneth J. Bagstad michael A. Verdone Earth Economics 107 N Tacoma Ave Tacoma WA 98403 USA. U.S. Geological Survey Geosciences & Environmental Change Science Center Box 25046 MS 980 Denver CO 80225 USA. International Union for the conservation of Nature 1630 Connecticut Ave. NW #300 Washington DC 20009 USA.

restoring degraded forests and agricultural lands has become a global conservation priority. A growing number of tools can quantify ecosystem service tradeoffs associated with forest restoration. This evolving ＂tools landscape＂ presents a dilemma： more tools are available, but selecting appropriate tools has become more challenging. We present a restoration Ecosystem Service Tool Selector （rESTS） framework that describes key characteristics of 13 ecosystem service assessment tools. Analysts enter information about their decision context, services to be analyzed, and desired outputs. Tools are filtered and presented based on five evaluative criteria： scalability, cost, time requirements, handling of uncertainty, and applicability to benefit-cost analysis. rESTS uses a spreadsheet interface but a web-based interface is planned. Given the rapid evolution of ecosystem services science, rESTS provides an adaptable framework to guide forest restoration decision makers toward tools that can help quantify ecosystem services in support of restoration.

关键词： Decision support Ecosystem services Forest restoration Modeling Valuation comparative toolsassessment

Quantifying spatiotemporal variability in occupant exposure to an indoor airborne contaminant with an uncertain source location

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Building Simulation 2023年第6期16卷 889-913页

作者： John E.Castellini Jr Cary A.Faulkner Wangda Zuo michael D.Sohn Department of Mechanical Engineering University of Colorado BoulderUCB 427BoulderCO80309USA Department Architectural Engineering The Pennsylvania State UniversityUniversity ParkPA16802USA National renewable Energy National Laboratory GoldenCO80401USA Energy Analysis and Environmental Impacts Division Lawrence Berkeley National Laboratory1 Cyclotron RoadBerkeleyCA94720USA

Well-mixed zone models are often employed to compute indoor air quality and occupant *** effective,a potential downside to assuming instantaneous,perfect mixing is underpredicting exposures to high intermittent concentrations within a *** such cases are of concern,more spatially resolved models,like computational-fluid dynamics methods,are used for some or all of the ***,these models have higher computational costs and require more input information.A preferred compromise would be to continue with a multi-zone modeling approach for all rooms,but with a better assessment of the spatial variability within a *** do so,we present a quantitative method for estimating a room’s spatiotemporal variability,based on influential room *** proposed method disaggregates variability into the variability in a room’s average concentration,and the spatial variability within the room relative to that *** enables a detailed assessment of how variability in particular room parameters impacts the uncertain occupant *** demonstrate the utility of this method,we simulate contaminant dispersion for a variety of possible source *** compute breathing-zone exposure during the releasing(source is active)and decaying(source is removed)*** CFD methods,we found after a 30 minutes release the average standard deviation in the spatial distribution of exposure was approximately 28%of the source average exposure,whereas variability in the different average exposures was lower,only 10%of the total *** also find that although uncertainty in the source location leads to variability in the average magnitude of transient exposure,it does not have a particularly large influence on the spatial distribution during the decaying period,or on the average contaminant removal *** systematically characterizing a room’s average concentration,its variability,and the spatial variability within the room important insights can be gain

关键词： uncertainty variability airborne contaminant spatiotemporal variability well-mixed heterogeneity

Modeling the dose-response rate/associations between VO2max and self-reported Physical Activity Questionnaire in children and adolescents

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Journal of Sport and Health Science 2020年第1期9卷 90-95页

作者： Alan M.Nevill michael J.Duncan Gavin Sandercock Faculty of Education Health and WellbeingUniversity of WolverhamptonWalsall CampusWalsallWS13BDUK Faculty of Health and Life Sciences Coventry UniversityCoventryCV15FBUK School of Biological Sciences University of EssexColchesterCO43SQUK

Background'. This study sought to explore the dose—response rate/association between aerobic fitness (VC)2max) and self-reported physical activity(PA) and to assess whether this association varies by sex, age, and weight ***. VO2max was assessed using the 20・m shuttle・run test. PA was assessed using the Physical Activity Questionnaire (PAQ) for Adolescents(aged > 11 years, PAQ-A) or for Children (aged rs, PAQ-C). The associations between V02raax and PAQ were analyzed using analysisof covariance (ANcoVA), adopting PAQ and PAQ2 as covariates but allowing the intercepts and slope parameters of PAQ and PAQ2 tovary with the categorical variables sex, age group, and weight ***: ANcoVA identified a curvilinear association between VO2max and PAQ, with positive linear PAQ terms that varied for both sex andweight status but with a negative PAQ2 term of —0.39 (95% confidence interval (CI): —0.57 to —0.21) that was common for all groups in regardto age, sex, and weight status. These curvilinear (inverted U) associations suggest that the benefits of increasing PA (same dose) on VO2max isgreater when children report lower levels of PA compared to children who report higher levels of PA. These dose-response rates were alsosteeper for boys and were steeper for lean children compared to overweight/obese ***'. Health practitioners should be aware that enco.raging greater PA (same dose) in inactive and underweight children will result ingreater gains in V02max (response) compared with their active and overweight/obese counterparts.

关键词： Aerobic fitness Curvilinear association Sex Slope parameters Weight status

Nitrogen enhanced drainage of co2 rich coal seams for mining

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International Journal of Mining Science and Technology 2017年第5期27卷 755-761页

作者： Luke D.connell regina Sander michael Camilleri Deasy Heryanto Zhejun Pan Nicholas Lupton CSIrO Energy ClaytonVictoria 3169Australia

coal seams with high co_2 gas contents can be difficult to drain gas for outburst management. coal has a high affinity for co_2 with adsorption capacities typically twice that of CH_4. This paper presents an analysis of nitrogen injection into coal to enhance drainage of high co_2 gas contents. core flooding experiments were conducted where nitrogen was injected into coal core samples from two Australian coal mining basins with initial co_2 gas contents and pressures that could be encountered during underground mining. Nitrogen effectively displaced the co_2 with mass balance analysis finding there was only approximately 6%–7% of the original co_2 gas content residual at the end of the core flood. Using a modified version of the SIMED II reservoir simulator, the core flooding experiments were history matched to determine the nitrogen and methane sorption times. It was found that a triple porosity model(a simple extension of the Warren and root dual porosity model) was required to accurately describe the core flood observations. The estimated model properties were then used in reservoir simulation studies comparing enhanced drainage with conventional drainage with underground in seam boreholes. For the cases considered, underground in seam boreholes were found to provide shorter drainage lead times than enhanced drainage to meet a safe gas content for outburst management.

关键词： Gas drainage High co2 ECBM reservoir simulation

The aggressive invasion of exotic reptiles in Florida with a focus on prominent species： A review

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Current Zoology 2011年第5期57卷 599-612页

作者： richard ENGEMAN Elliott JAcoBSON michael L. AVErY Walter E. MESHAKA, Jr. USDA/APHIS/Wildlife Services/National Wildlife research Ctr 4101 LaPorte Ave. Fort Collins CO 80521-2154 USA college of Veterinary Medicine University of Florida Gainesville FL 32610 USA USDA/APHIS/Wildlife Services/National Wildlife research Ctr 2820 East University Ave. Gainesville FL 32641 USA The State Museum of Pennsylvania 300 North Street Harrisburg Pennsylvania 17120 USA

Florida, along with Hawaii, has among the two worst invasive species problems in the USA, and the state is espe-cially susceptible to establishment by alien reptiles. Besides the large numbers of established non-native reptile species in Florida, many of these species present novel difficulties for management, or have other characteristics making effective management ex-tremely challenging. Moreover, initiation of management action requires more than recognition by experts that a potentially harmful species has become established. It also requires the political will along with concomitant resources and appropriate per-sonnel to develop effective methods and apply them. We review the situation in Florida, including assessment of risk for estab- lishment, and we use a subset of prominent species to illustrate in more detail the array of invasive reptile species circumstances in Florida, including routes of introduction, impacts, and potential and implemented management actions. These examples not only highlight the severity of the invasive reptile problems in the state, but they also show the diversity in resolve and response towards them and the motivating factors [Current Zoology 57 （5）： 599-612, 2011].

关键词： Argentine black and white tegus Biophysical ecology Burmese pythons control Green and spiny-tailed iguanas,Invasive species Nile monitors Northern curlytail lizards

The Structure of Ammonium D,L-Tartrate

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Chinese Journal of Structural Chemistry 2001年第6期20卷 470-472页

作者： NIE Jing-Jing XU Duan-Jun WU Jing-Yun CHIANG michael Yen-Nan Department of Chemistry Zhejiang University Department of Chemistry National Sun Yat-Sen University

The single crystals of the title compound NH4+C4H5O6- (C4H9NO6, Mr = 167.1) were obtained from a hot aqueous solution containing L-glutamine and D,L-tartaric acid in mole ratio1:1.5. The crystal belongs to monoclinic space group P21/c with a = 7.646(2), b = 7.804(2), c = 11.502(3)? ?= 102.26(2)o, V = 670.7(3)?, Z = 4, F(000) = 352, Dc = 1.655 ***-3, m(MoKa) = 0.16 mm-1, r = 0.035, wr = 0.094 for 1028 observed reflections (I>2s(I)). The enatiomeric anions of the tartrate with both (2S,3S)- and (2r,3r)-configuration co-exist in the unit cell. The carbon skeleton assumes a coplanar arrangement with a torsion angle of 181.5o. The three- dimensional H-bonding network exists in the crystal. While tartrate groups link each other by H-bonds between carboxyl and hydroxyl groups, the ammonium cations insert between the tartrate groups to form a sandwich-like crystal structure.

关键词： crystal structure ammonium tartrate H-bonding hydrolysis glutamine

Endoscopic retrograde cholangiopancreatography and liver biopsy in the evaluation of elevated liver function tests after liver transplantation

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World Journal of Hepatology 2021年第1期13卷 132-143页

作者： Augustin Attwell Samuel Han michael Kriss Department of Medicine University of Colorado-DenverDenverCO 80203United States Department of Medicine Ohio State University Wexler Medical SchoolColumbusOH 43210United States Department of Medicine University of Colorado Medical SchoolAuroraCO 80045United States

BACKGrOUND Abnormal liver function tests(LFTs)in post-liver transplant(LT)patients pose a challenge in the timing and selection of diagnostic *** are little data regarding the accuracy of endoscopic retrograde cholangiopancreatography(ErCP)and liver biopsy(LB)in diagnosing post-transplant *** To evaluate the diagnostic performance of ErCP and LB in patients with nonvascular post-LT *** This single-center retrospective study evaluated patients undergoing both ErCP and LB for evaluation of elevated LFTs within 6 mo of LT from 2000 to *** operating characteristics including accuracy,sensitivity and specificity for various diagnoses were calculated for ErCP and *** r factor(ratio of alkaline phosphatase to alanine aminotransferase)was also calculated for each *** Of the 1284 patients who underwent LT,91 patients(74.7%males,mean age of 51)were *** strictures(AS,24.2%),acute cellular rejection(ACr,11%)and concurrent AS/ACr(14.3%)were the most common *** carried an accuracy of 79.1%(95%CI:69.3-86.9),LB had an accuracy of 93.4%(95%CI:86.2-97.5),and the combination of the two had an accuracy of 100%(95%CI:96-100).There was no difference between patients with AS and ACr in mean r factor(AS:1.9 vs ACr:1.1,P=0.24).Adverse events did not differ between the two tests(ErCP:3.1%vs LB:1.1%,P=0.31).coNCLUSION In patients with abnormal LFTs after LT without vascular complications,the combination of LB and ErCP carries low risk and improves diagnostic accuracy over either test alone.

关键词： Liver transplantation Endoscopic retrograde cholangiopancreatography Liver biopsy Abnormal liver tests Acute cellular rejection Anastomotic biliary stricture