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Exploiting a metal wire grating in total internal reflection geometry to achieve achromatic polarization conversion

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Photonics Research 2017年第4期5卷 299-304页

作者： XUDONG LIU XUEQUAN CHEN EDWARD P.J.PARROTT emma pickwell-macpherson Department of Electronic Engineering Chinese University of Hong Kong

We demonstrate how a metal wire grating can work as a 45° polarization converter, a quarter-wave retarder, and a half-wave retarder over a broadband terahertz range when set up in total internal reflection geometry. Classical electromagnetic theory is applied to understand the mechanism, and equations to calculate the polarization state of reflected light are derived. We use a metal grating with a period of 20 μm and width of 10 μm on a fused silica surface: linearly polarized terahertz light incident from fused silica with a supercritical incident angle of 52° is totally reflected by the metal grating and air. The polarization of the terahertz light is rotated by 45°, 90°, and circularly polarized by simply rotating the wire grating. The performance is achromatic over the measured range of 0.1–0.7 THz and comparable to commercial visible light wave retarders.

关键词： THz

RECENT DEVELOPMENTS OF TERAHERTZ TECHNOLOGY IN BIOMEDICINE

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Journal of Innovative Optical Health Sciences 2008年第1期1卷 29-44页

作者： emma pickwell-macpherson SHENGYANG HUANG KANIS WAI CHI KAN YIWEN SUN YUAN TING ZHANG Joint Research Centre for Biomedical Engineering Department of Electronic Engineering The Chinese University of Hong Kong†Institute of Biomedical and Health Engineering Shenzhen Institute of Advanced Technology Chinese Academy of Sciences China Key Laboratory for Biomedical Informatics and Health Engineering Chinese Academy of Science China

Terahertz technology is continually evolving and much progress has been made in recent *** new applications are being discovered and new ways to implement terahertz imaging *** this review,we limit our discussion to biomedical applications of terahertz imaging such as cancer detection,genetic sensing and molecular *** discussion of the development of new terahertz techniques is also focused on those that may accelerate the progress of terahertz imaging and spectroscopy in biomedicine.

关键词： spectroscopy. terahertz limit

Robust and accurate terahertz time-domain spectroscopic ellipsometry

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Photonics Research 2018年第8期6卷 768-775页

作者： XUEQUAN CHEN EDWARD P.J.PARROTT ZHE HUANG HAU-PING CHAN emma pickwell-macpherson Department of Electronic Engineering The Chinese University of Hong Kong School of Science Zhejiang University of Science and Technology Department of Electronic Engineering City University of Hong Kong Department of Physics and Astronomy Warwick University

In this work, we show how fiber-based terahertz systems can be robustly configured for accurate terahertz ellipsometry. To this end, we explain how our algorithms can be successfully applied to achieve accurate spectroscopic ellipsometry with a high tolerance on the imperfect polarizer extinction ratio and pulse shift errors. Highly accurate characterization of transparent, absorptive, and conductive samples comprehensively demonstrates the versatility of our algorithms. The improved accuracy we achieve is a fundamental breakthrough for reflectionbased measurements and overcomes the hurdle of phase uncertainty.

关键词：光纤太赫兹椭偏仪通讯技术发展现状

Calibration method to improve the accuracy of THz imaging and spectroscopy in reflection geometry

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Photonics Research 2016年第3期4卷 29-35页

作者： Shuting Fan Edward P.J.Parrott Benjamin S.Y.Ung emma pickwell-macpherson Department of Electric and Computer Engineering Hong Kong University of Science and Technology Department of Electronic Engineering The Chinese University of Hong Kong

We introduce a novel method to accurately extract the optical parameters in terahertz reflection imaging. Our method builds on standard self-referencing methods using the reflected signal from the bottom of the imaging window material to further compensate for time-dependent system fluctuations and position-dependent variation in the window thickness. Our proposed method not only improves the accuracy, but also simplifies the imaging procedure and reduces measurement times.

关键词： Calibration method to improve the accuracy of THz imaging and spectroscopy in reflection geometry THz

A promising diagnostic method:Terahertz pulsed imaging and spectroscopy

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World Journal of Radiology 2011年第3期3卷 55-65页

作者： Ming Yiu Sy Yi-Xiang J Wang Anil T Ahuja emma pickwell-macpherson Department of Electronic Engineering The Chinese University of Hong Kong Department of Imaging and Interventional Radiology The Chinese University of Hong Kong Department of Electronic and Computer Engineering Hong Kong University of Science and Technology

The terahertz band lies between the microwave and infrared regions of the electromagnetic *** radiation has very low photon energy and thus it does not pose any ionization hazard for biological *** is strongly attenuated by water and very sensitive to water *** absorption spectra due to intermolecular vibrations in this region have been found in different biological *** unique features make tera-hertz imaging very attractive for medical applications in order to provide complimentary information to existing imaging *** has been an increasing interest in terahertz imaging and spectroscopy of biologically related applications within the last few years and more and more terahertz spectra are being *** paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques,and a number of applications such as molecular spectroscopy,tissue characterization and skin imaging are discussed.

关键词： Biomedical Imaging Spectroscopy Terahertz

Interconnection Gridlock Threatens Transition to Renewable Energy

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Engineering 2024年第5期36卷 3-5页

作者： emma Hiolski Senior Technology Writer

In October 2023,the International Energy Agency(IEA)released a report identifying inadequate grid infrastructure as a key threat to meeting the climate goals laid out by the Paris Agreement[1],the landmark 2015 international treaty in which 196 parties agreed to limit global warming to well below 2℃ above preindustrial levels[2].Importantly,funding for the treaty’s calledfor transition from fossil fuels to clean energy has accelerated[3],with recently legislated massive governmental subsidies and other incentives(e.g.,the Inflation Reduction Act[4])aimed specifically at promoting renewable ***,a commensurate surge in investment in electrical grids has not materialized;instead,it has stagnated for the past decade at around 300 billion USD per year worldwide[1].

关键词： Transition instead massive

Modern internet search analytics and thyroidectomy:What are patients asking?

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World Journal of Otorhinolaryngology-Head and Neck Surgery 2024年第1期10卷 49-58页

作者： Neeraj Suresh Christian Fritz emma De Ravin Karthik Rajasekaran Department of Otorhinolaryngology–Head&Neck Surgery University of PennsylvaniaPhiladelphiaPennsylvaniaUSA Perelman School of Medicine at the University of Pennsylvania PhiladelphiaPennsylvaniaUSA Leonard Davis Institute of Health Economics University of PennsylvaniaPhiladelphiaPennsylvaniaUSA

Objectives:Thyroidectomy is among the most commonly performed head and neck surgeries,however,limited existing information is available on topics of interest and concern to *** Design:***:***:A search engine optimization tool was utilized to extract metadata on Google‐suggested questions that“People Also Ask”(PAA)pertaining to“thyroidectomy”and“thyroid surgery.”These questions were categorized by Rothwell criteria and topics of *** Journal of the American Medical Association(JAMA)benchmark criteria enabled quality ***:A total of 250 PAA questions were ***‐oriented PAA questions describing what to expect during and after the surgery on topics such as postoperative management,risks or complications of surgery,and technical details were significantly less popular among the“thyroid surgery”group(P<0.001,P=0.005,and P<0.001,respectively).PAA questions about scarring and hypocalcemia were nearly threefold more popular than those related to pain(335 and 319 vs.113 combined search engine response page count,respectively).The overall JAMA quality score remained low(2.50±1.07),despite an increasing number of patients searching for“thyroidectomy”(r(77)=0.30,P=0.007).Conclusions:Patients searching for the nonspecific term“thyroid surgery”received a curated collection of PAA questions that were significantly less likely to educate them on what to expect during and after surgery,as compared to patients with higher health literacy who search with the term“thyroidectomy.”This suggests that the content of PAA questions differs based on the presumed health literacy of the internet user.

关键词： information quality online health education search analytics thyroid surgery thyroidectomy

Extreme Weather Disruptions and Emergency Preparedness Among Older Adults in Ohio: An Eight-County Assessment

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International Journal of Disaster Risk Science 2024年第2期15卷 213-225页

作者： Smitha Rao Fiona C.Doherty Anthony Traver Marisa Sheldon emma Sakulich Holly Dabelko‑Schoeny College of Social Work The Ohio State UniversityColumbusOH 43210USA Age Friendly Innovation Center College of Social WorkThe Ohio State UniversityColumbusOH 43210USA College of Public Health The Ohio State UniversityColumbusOH 43210USA

The disproportionate risks and impacts of climate change and extreme weather on older adults are increasingly evident. While especially true in disaster-prone areas, human-caused climate change introduces an element of uncertainty even in previously identified “safe” regions such as the Midwestern United States. Using a cumulative disadvantage and vulnerability-informed framework and descriptive statistics from multiple data sources, this article provides an overview of climate impacts, vulnerabilities, and county-level characteristics, focusing on older adults living in Central Ohio. A comparative multiple-case study methodology was used to triangulate regionally representative primary and secondary data sources to examine state and county-level measures of vulnerability, emergency preparedness, and disruptions caused by extreme weather among older adults across eight counties in Central Ohio. Seventy-eight percent of older adults in the sample reported being prepared for emergencies per Federal Emergency Management Agency guidelines. Older adults in Union County reported the highest rates of preparedness, while those in Fayette County reported the lowest. County-level rates of disruption of life activities by extreme weather ranged widely. Among the most rural in the region, Fayette County emerged as uniquely disadvantaged, with the lowest median income, the most vulnerable across multiple social vulnerability dimensions, and the most reported disruptions to life activities from extreme weather. County profiles offer a snapshot of existing vulnerabilities, socioeconomic conditions, special needs, preparedness, and current disruptions among older adults in the region and can inform resource mobilization across community and policy contexts.

关键词： Disaster preparedness Extreme weather Midwestern United States Older adults Regional assessment Social vulnerability

Methane cracking in molten tin for hydrogen and carbon production—a comparison with homogeneous gas phase process

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Frontiers of Chemical Science and Engineering 2024年第7期18卷 155-166页

作者： emmanuel Busillo Benedetta de Caprariis Maria Paola Bracciale Vittoria Cosentino Martina Damizia Gaetano Iaquaniello emma Palo Paolo De Filippis Chemical Engineering Department Sapienza University of RomeRome 00184Italy NextChem S.p.A. Rome 00156Italy

Methane cracking is considered a bridge technology between gray and green hydrogen production *** this work an experimental study of methane cracking in molten tin is *** tests were conducted in a quartz reactor(i.d.=1.5 cm,L=20 cm)with capillary injection,varying temperature(950–1070°C),inlet methane flow rate(30–60 mL·min^(-1))and tin height(0–20 cm).The influence of the residence time in the tin and in the headspace on methane conversion and on carbon morphology was *** conversions obtained in tin and in the empty reactor were measured and compared with results of detailed kinetic simulations(CRECK).Furthermore,an expression of a global kinetic constant for methane conversion in tin was also *** highest conversion(65%at Q0=30 mL·min^(-1) and t=1070°C)is obtained for homogeneous gas phase reaction due to the long residence time(70 s),the presence of tin leads to a sharp decrease of residence time(1 s),obtaining a conversion of 35%at 1070°C,thus meaning that tin owns a role in the *** characterization(scanning electron microscopy,Raman)reported a change in carbon toward sheet-like structures and an increase of the carbon structural order in the presence of molten tin media.

关键词： methane cracking molten media H2 production carbon morphology