scholarly journals Variation of Signal Reflection on Electrodes of Silicon Mach-Zehnder Modulators: Influence of Nanoscale Variation and Mitigation Strategies

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 499
Author(s):  
Zhaobang Zeng ◽  
Ding Ding ◽  
Qianyi Gao ◽  
Nan Yang ◽  
Peiyan Zhao ◽  
...  
Keyword(s):  
Correlation Coefficients ◽  
Critical Issue ◽  
Microwave Signal ◽  
Mitigation Strategies ◽  
Electrode Impedance ◽  
Signal Attenuation ◽  
Electro Optic ◽  
High Bit Rates ◽  
Design Bias ◽  
Fabrication Variation

Driving signal reflection on traveling wave electrodes (TWEs) is a critical issue in Mach–Zehnder modulators. Fabrication variation often causes a random variation in the electrode impedance and the signal reflection, which induces modulation characteristics variation. The variation of reflection could be intertwined with the variation of other electrode characteristics, such as microwave signal attenuation, resulting in complexity. Here, we characterize the (partial) correlation coefficients between the reflection and modulation characteristics at different bit rates. Decreasing correlation at higher bit rates is observed. Device physics analysis shows how the observed variation can be related to nanoscale variation of material properties, particularly in the embedded diode responsible for electro-optic modulation. We develop a detailed theory to analyze two variation modes of the diode (P-i-N diode or overlapping P/N regions), which reveal insight beyond simplistic diode models. Microwave signal attenuation tends to reduce the correlation with on-electrode reflection, particularly at high bit rates. The theory shows the relative importance of conductor-induced attenuation and “dielectric”-induced attenuation, with different dependence on the frequency and fabrication variation. Strategies on how to mitigate the effect of variation for better fabrication tolerance are discussed by considering three key factors: pre-shift in structural design, bias condition, and fabrication control accuracy.

Impacts Conflict over Place Change

2020 ◽  
Author(s):  
Bob McKercher ◽  
Bruce Prideaux
Keyword(s):  
Large Scale ◽  
Critical Issue ◽  
Social Impacts ◽  
Social Consequences ◽  
Mitigation Strategies ◽  
Tourism Impacts ◽  
Community Attitudes ◽  
Relevant Today ◽  
Critical Issues ◽  
First Editions

Concerns about unsustainable tourism practices have been a subject of academic inquiry since the earliest days of tourism scholarship. Indeed, it seems that a majority of the papers published in the first editions of Annals of Tourism Research documented adverse social and cultural impacts of tourism. As McKercher and Prideaux (2014: 21) noted: “Wenkman (1975) documented the adverse environmental impacts of tourism on Hawaii. UNESCO (1976) published a literature review of the adverse social consequences of tourism. Rodenburg (1980) condemned large scale tourism in Bali and argued that small, community based tourism is preferred. Farrell (1979) documented adverse host-guest interactions. Jafari (1974) wrote a lengthy article documenting explicitly focusing on the costs, and not benefits of tourism.” Since then, a range of topics has emerged with the sophistication of the research evolving as our understanding of the causes of impacts and possible mitigation strategies have matured. Yet, to a large extent, many of the critical issues remain unresolved, in spite of the emergence of sustainable tourism as a dominant paradigm, as discussed in the next chapter. Hundreds, if not thousands of academic papers have been published examining the impacts of tourism on host communities (Nunkoo, Smith and Ramkissoon, 2013). Deery, Jago and Fredline (2012: 65), though, note that much of this work is derivative, leading them to conclude “research into the social impacts of tourism appears to be in a state of ‘arrested development,’ [where] there is a sense that the advances in understanding the impacts of tourists on host communities is incremental at best, or potentially circular.” The reasons are manifold. Far too much of this research is descriptive in nature, and is typified by a ‘fill in the blank study – Understanding social impacts/community attitudes of tourism in ___________ destination.’ Many papers as well use the same metrics to measure attitudes, and therefore, unsurprisingly, come to the same conclusions. A third issue is that much of this research is of the self-fulfilling prophecy kind, where if one structures the study to look for adverse impacts, they can be found. A fourth and more critical issue is the lack of theoretical basis for most of the research, something identified by Ap (1990) 30 years ago that is still relevant today. This chapter explores some of the challenges in the conceptual discussion of tourism impacts. It begins with quest for theory and then reviews the founda- tional models by Doxey (1975) and Budowski (1976) that framed unsustainable practices within a conflict paradigm. It then looks at such issues as impacts as a function of place change.

Intraoperative Monitoring of Heparin: Comparison of Activated Coagulation Time and Whole Blood Heparin Measurements by Different Point-of-Care Devices with Heparin Concentration by Laboratory-Performed Plasma Anti-Xa Assay

2019 ◽  
Vol 50 (4) ◽  
pp. 348-356 ◽  
Author(s):  
Thomas Z Thompson ◽  
Rebecca L Kunak ◽  
Natasha M Savage ◽  
Shvetank Agarwal ◽  
Jennifer Chazelle ◽  
...  
Keyword(s):  
Point Of Care ◽  
Correlation Coefficients ◽  
Critical Issue ◽  
Poor Correlation ◽  
Surgical Interventions ◽  
Additional Information ◽  
Parallel Testing ◽  
Heparin Concentration ◽  
Angioplasty And Stenting ◽  
Activated Coagulation Time

AbstractBackgroundCardiac surgical interventions, extracorporeal membrane oxygenation, transcutaneous coronary-artery angioplasty, and stenting are carried out while patients are being treated with the anticoagulation drug heparin. Monitoring the level and reversal of heparinization during and at the conclusion of medical and surgical procedures is a critical issue in patient care.MethodsWe performed parallel testing of the ACCRIVA Hemochron Signature Elite ACT+ and Hemochron Response analyzer, iSTAT platform, and 2 Hepcon Hemostasis Management System (HMS) Plus analyzers for monitoring intraoperative heparin treatment. Laboratory anti-Xa assay was used as the criterion standard for heparin measurement.ResultsPoor correlation between the 2 Hemochron analyzers was identified at 0.78. Correlation between the analyzers on the i-STAT platform was 0.97. Regression analysis revealed that i-STAT values were generally lower, by 43 seconds, than Hemochron values. The correlation between Hepcon and i-STAT activated clotting time (ACT) results was 0.94. The i-STAT ACT results were generally 23 seconds lower than the Hepcon ACT values. Correlation coefficients on comparing Hepcon ACT and i-STAT ACT using laboratory anti-Xa assay were 0.83 and 0.87, respectively. The correlation between Hepcon heparin concentration and anti-Xa results was 0.85.ConclusionsACT monitoring with iSTAT offers good correlation between instruments and with the Hepcon ACT. Hepcon occupies a specific niche in cardiac operating departments because of its ability to provide additional information regarding heparin concentration; however, lack of suitable proficiency testing may impair its use. The iSTAT is a more reliable platform for broader, hospital-wide application.

scholarly journals Millimeter-wave and microwave signal generation by low-bandwidth electro-optic phase modulation

2006 ◽  
Vol 14 (21) ◽  
pp. 9617 ◽  
Author(s):  
Víctor Torres-Company ◽  
Mercedes Fernández-Alonso ◽  
Jesús Lancis ◽  
Juan C. Barreiro ◽  
Pedro Andrés
Keyword(s):  
Millimeter Wave ◽  
Phase Modulation ◽  
Microwave Signal ◽  
Signal Generation ◽  
Electro Optic ◽  
Microwave Signal Generation

scholarly journals Prediction of source contributions to urban background PM10 concentrations in European cities: a case study for an episode in December 2016 – Part.1 The country contributions

2019 ◽  
Author(s):  
Matthieu Pommier ◽  
Hilde Fagerli ◽  
Michael Schulz ◽  
Alvaro Valdebenito ◽  
Richard Kranenburg ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Total Concentration ◽  
Large Fraction ◽  
Correlation Coefficients ◽  
Grid Cell ◽  
Primary Component ◽  
Mitigation Strategies ◽  
Grid Cells ◽  
European Cities ◽  
The Impact

Abstract. A large fraction of the urban population in Europe is exposed to particulate matter levels above the WHO guideline. To make more effective mitigation strategies, it is important to understand the influence on particulate matter (PM) from pollutants emitted in different European nations. In this study, we evaluate a source apportionment forecasting system aimed to assess the domestic and transboundary contributions to PM in major European cities for an episode in December 2016. The system is composed of two models (EMEP/MSC-W rv4.15 and LOTOS-EUROS v2.0) which allows to consider differences in the source attribution. We also compared the PM10 concentrations and both models present satisfactory agreement in the 4day-forecasts of the surface concentrations, since the hourly concentrations can be highly correlated with in-situ observations. The correlation coefficients reach values up to 0.58 for LOTOS-EUROS and 0.50 for EMEP for the urban stations; and 0.58 for LOTOS-EUROS and 0.72 for EMEP for the rural stations. However, the models under-predict the highest hourly concentrations measured by the urban stations (mean underestimation by 36 %), predictable with the relatively coarse model resolution used (0.25° longitude × 0.125° latitude). For the source receptor calculations, the EMEP/MSC-W model uses a scenario having reduced anthropogenic emissions and then it is compared to a reference run where no changes are applied. Different percentages (5 %, 15 % and 50 %) in the reduced emissions were used to test the robustness of the methodology. The impact of the different ways to define the urban area for the studied cities was also investigated (i.e. 1 model grid cell, 9 grid cells and the grid cells covering the definition given by the Global Administrative Area – GADM). We found that by combining the use of the 15 % factor and of a larger domain for the city edges (9 grid cells or GADM), it helps to reduce the impact of non-linearity on the chemistry which is seen in the mismatch between the total concentration and the sum of the concentrations from different calculated sources. Even limited, this non-linearity is observed in the NO3−, NH4+ and H2O concentrations, which is related to gas-aerosol partitioning of the species. The use of a 15 % factor and of a larger city domain also gives a better agreement in the determination of the main country contributors between both country source receptor calculations. During the studied episode, dominated by the influence of the domestic emissions for the 34 European cities investigated and occurring from December 01st to 09th 2016, the two models agree 68 % of the time (on hourly resolution) on the country, having been the dominant contributor to PM10 concentrations. 75 % of the hourly predicted PM10 concentrations by both models, have the same top 5 main country contributors. Better results are found in the determination the dominant country contributor for the primary component (70 % for POM and 80 % for EC) than for the secondary inorganic aerosols (50 %).

MATHEMATICAL MODEL FOR THE PREDICTION OF MICROWAVE SIGNAL ATTENUATION DUE TO DUSTSTORM

2009 ◽  
Vol 6 ◽  
pp. 139-153 ◽  
Author(s):  
Zain Elabdin Omer Elshaikh ◽  
Md. Rafiqul Islam ◽  
Othman O. Khalifa ◽  
Hany Essam Abd-El-Raouf
Keyword(s):  
Mathematical Model ◽  
Microwave Signal ◽  
Signal Attenuation

scholarly journals LB-10. Rapid Assessments of Non-Pharmaceutical Intervention Uptake and Population Mobility Patterns Elucidate SARS-Cov-2 Transmission Dynamics

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S848-S848
Author(s):  
Amy Wesolowski ◽  
Dustin Gibson ◽  
Smisha Agarwal ◽  
Anastasia Lambrou ◽  
Gregory Kirk ◽  
...  
Keyword(s):  
Public Transportation ◽  
Panel Member ◽  
Correlation Coefficients ◽  
Grocery Store ◽  
Mitigation Strategies ◽  
Population Mobility ◽  
Mobility Patterns ◽  
Research Support ◽  
Pairwise Correlation ◽  
Significant Relationships

Abstract Background Current mitigation strategies for SARS-CoV-2 rely on population-wide adoption of non-pharmaceutical interventions (NPIs). Monitoring NPI adoption, mobility patterns and their association with SARS-CoV-2 infection can provide key information for public health agencies and be used to calibrate transmission models. Methods We used an online panel to accrue representative samples from Florida, Illinois, and Maryland (n=3,009, approximately 1,000 per state) from July 15–31, 2020 and capture socio-demographically and geographically resolved information about NPI adoption and mobility in the prior 2 weeks. Logistic regression was used to identify correlates of self-reported SARS-CoV-2 infection in the prior 2 weeks. Results Overall, 96% reported traveling outside their home in the prior 2 weeks, the most common reason being to visit a grocery store/pharmacy (92%), followed by visiting friends/family (61%), and visiting a place of worship (23%); 22% reporting public transportation use. In total, 44% of respondents reported always practicing social distancing and 40% reported always using a mask indoors and outdoors. Overall, 74 (2.5%) reported testing positive for SARS-CoV-2 in the prior 2 weeks, with strong dose-response relationships between several forms of movement frequency and SARS-CoV-2 positivity. Variables capturing mobility were all highly correlated with one another, suggesting there are clusters of individuals who engage in multiple activities (Figure); 41% of positive cases engaged in all forms of mobility captured compared to 1% of those who did not test positive within the prior 2 weeks. Patterns of mobility and NPI uptake did not significantly differ by state; however, there were significant relationships with age, race/ethnicity, and gender. In multivariable models including adjustment for NPIs, significant relationships remained with public transportation, visiting a place of worship, and participating in outdoor group fitness activities. Figure. Heatmap depicting pairwise Spearman correlation coefficients between survey responses. Pairwise correlation coefficients are displayed in the boxes at intersection of any two variables. Questions were asked with respect activities in the prior 2 weeks. Conclusion NPI adoption and mobility did not vary across these three states with variable policies and SARS-CoV-2 positivity rates. Rather, associations with recent positivity appear to be driven largely by mobility patterns and engagement in activities where NPI use may be challenging or inconsistent. Disclosures Shruti Mehta, PhD, MPH, Gilead Sciences (Other Financial or Material Support, Speaker) Sunil Solomon, MD, PhD, MPH, Abbott Diagnostics (Grant/Research Support)Gilead Sciences (Grant/Research Support, Advisor or Review Panel member)

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