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A Study on Refractive Index Sensors Based on Optical Micro-Ring Resonators

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photonic Sensors 2017年第3期7卷 217-225页

作者： georgios N. TSIGARIDAS Department of physics School of Applied Mathematical and Physical Sciences National Technical University of Athens Zografou Campus GR-15780 Zografou Athens Greece

In this work, the behavior of refractive index sensors based on optical micro-ring resonators is studied in detail. Using a result of waveguide perturbation theory in combination with numerical simulations, the optimum design parameters of the system, maximizing the sensitivity of the sensor, are determined. It is found that, when optimally designed, the sensor can detect relative refractive index changes of the order of △n/n≈3×10^-4, assuming that the experimental setup can detect relative wavelength shifts of the order of △λ/λ≈3×10^-5. The behavior of the system as bio-sensor has also been examined. It is found that, when optimally designed, the system can detect refractive index changes of the order of △n≈ 10^-3 for a layer thickness of t=- 10 nm, and changes in the layer thickness of the order of △t≈0.24 nm, for a refractive index change of △n=0.05.

关键词： Optical micro-ring resonators refractive index sensors bio-sensors nano-photonic sensors

Model Reference Adaptive Control for Networked Distributed Systems with Strong Interconnections and Communication Delays

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Journal of Systems Science & Complexity 2018年第1期31卷 38-68页

作者： LYMpEROpOULOS georgios IOANNOU petros Department of Electrical Engineering University of Southern California

In recent years, networked distributed control systems（NDCS） have received research attention. Two of the main challenges that such systems face are possible delays in the communication network and the effect of strong interconnections between agents. This paper considers an NDCS that has delays in the communication network, as well as strong interconnections between its agents. The control objective is to make each agent track efficiently a reference model by attenuating the effect of strong interconnections via feedback based on the delayed information. First, the authors assume that each agent knows its own dynamics, as well as the interconnection parameters, but receives information about the states of its neighbors with some communication delay. The authors propose a distributed control scheme and prove that if the interconnections can be weakened and if the communication delays are small enough, then the proposed scheme guarantees that the tracking error of each agent is bounded with a bound that depends on the size of the weakened interconnections and delays, and reduces to zero as these uncertainties reduce to zero. The authors then consider a more realistic situation where the interconnections between agents are unknown despite the cooperation and sharing of state information. For this case the authors propose a distributed adaptive control scheme and prove that the proposed scheme guarantees that the tracking errors are bounded and small in the mean square sense with respect to the size of the weakened interconnections and delays, provided the weakened interconnections and time delays are small enough. The authors then consider the case that each agent knows neither its dynamics nor the interconnection matrices. For this case the authors propose a distributed adaptive control scheme and prove that the proposed scheme guarantees that the tracking errors are bounded and small in the mean square sense provided the weakened interconnections and time delays are

关键词： Adaptive control network distributed control delay systems

A systematic review of teleophthalmological studies in Europe

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International Journal of Ophthalmology(English edition) 2018年第2期11卷 314-325页

作者： georgios Labiris Eirini-Kanella panagiotopoulou Vassilios p.Kozoboli Department of Ophthalmology University Hospital of AlexandroupolisDraganaAlexandroupolis 68 100Greece Eye Institute of Thrace Alexandroupolis 68100Greece

A systematic review of the recent literature regarding a series of ocular diseases involved in European telemedicine projects was performed based on the pub Med, Google Scholar and Springer databases in June 2017. Literature review returned 44 eligible studies; among them, emergency ophthalmology, diabetic retinopathy, glaucoma, age-related macular disease, cataract and retinopathy of prematurity. The majority of studies indicate teleophthalmology as a valid, reliable and cost-efficient method for care-provision in ophthalmology patients which delivers comparable outcomes to the traditional examination methods.

关键词： teleophthalmology telemedicine Europe glaucoma cataract diabetic retinopathy

physics-informed machine learning for the COVID-19 pandemic: Adherence to social distancing and short-term predictions for eight countries

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Quantitative Biology 2022年第2期10卷 139-149页

作者： georgios D.Barmparis Giorgos p.Tsironis Institute of Theoretical and Computational physics and Department of physics University of CreteHeraklion 71003Greece

Background:The analysis of COVID-19 infection data through the eye of physics-inspired Artificial Intelligence leads to a clearer understanding of the infection dynamics and assists in predicting future *** spreading of the pandemic during the first half of 2020 was curtailed to a larger or lesser extent through social distancing measures imposed by most *** the context of the standard Susceptible-Infected-Recovered(SIR)model,changes in social distancing enter through time-dependent infection ***:In this work we use machine learning and the infection dynamical equations of SIR to extract from the infection data the degree of social distancing and,through it,assess the effectiveness of the imposed ***:Quantitative machine learning analysis is applied to eight countries with infection data from the first viral *** find as two extremes Greece and USA where the measures were successful and unsuccessful,respectively,in limiting *** physics-based neural network approach is employed to the second wave of the infection,and by training the network with the new data,we extract the time-dependent infection rate and make short-term predictions with a week-long or even longer *** algorithmic approach is applied to all eight countries with good short-term *** data for Greece is analyzed in more detail from August to December ***:The model captures the essential spreading dynamics and gives useful projections for the spreading,both in the short-term but also for a more intermediate horizon,based on specific social distancing measures that are extracted directly from the data.

关键词： COVID-19 physics-informed machine learning SIR time-dependent infection rate short-term predictions

particle paths of Lagrangian Velocity Distribution Simulating the Spiral Arms of Galaxy M51

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Journal of Thermal Science 2008年第1期17卷 61-63页

作者： georgios H.Vatistas Department of Mechanical and Industrial Engineering Concordia UniversityMontrealQuebecCanada H3G 1M8

Galaxies are huge families of stars held together by their own gravities. The system M51 is a spiral galaxy. It possesses billions of stars. The range of the spiral arms extends hundred thousand light years. The present study is in an attempt in using the particle paths of the Lagrangian flow field to simulate the spiral arms of Galaxy M51. The Lagrangian flow field is introduced. The initial locations of fluid particles in the space between two concen- tric cylinders are ftrst specified. Then a linear velocity distribution of the fluid particles is used with different an- gle rotations of the particles to obtain the particle paths in the Lagrangian diagram. For simulating the spiral arms of Galaxy M51, the Lagrangian M51 diagram is developed. The particle paths of the Lagrangian M51 diagram agree quite well with the spiral arms of Galaxy M51.

关键词： Lagrangian flow field particle path Dimensionless normalization Spiral arms Galaxy M51

Hepatocellular carcinoma and metabolic syndrome: The times are changing and so should we

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World Journal of Gastroenterology 2019年第29期25卷 3842-3848页

作者： georgios Tsoulfas Department of Surgery Aristotle University of Thessaloniki

Although hepatocellular carcinoma (HCC) is as prevalent as ever as a cancerrelated mortality, and some would even argue that it is increasing, the pattern of its etiologies has been changing. Specifically, the domination of viral hepatitis C virus is being overcome, partly because of the emergence of the antiviral treatments, and partly because of the significant increase, especially in developed countries, of the combination of obesity, diabetes, metabolic syndrome, nonalcoholic fatty liver disease and non-alcoholic steatohepatitis. This editorial will explore the interconnection of this group of diseases and how they are linked to HCC. More importantly, it will argue that this shift in HCC etiology essentially means that we have to change how we approach the treatment of HCC, by changing our focus (and resources) to earlier stages of the disease development in order to prevent the appearance and progression of HCC.

关键词： Hepatocellular carcinoma Diabetes Obesity Steatosis Non-alcoholic fatty liver disease Body-mass index Non-alcoholic steatohepatitis

Cross-polarized GpR Imaging of Fracture Flow Channeling

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Journal of Earth Science 2015年第6期26卷 776-784页

作者： georgios p.Tsoflias Christopher perll Matthew Baker Matthew W.Becker Department of Geology the University of Kansas Chesapeake Energy Marathon Oil Corporation California State University Long Beach

Ground penetrating radar（GpR） can be used to image fractures and monitor fluid flow in the subsurface. Conventional GpR imaging uses single-polarization, co-polarized acquisition. We examine the use of cross-polarized GpR signals for imaging flow channeling in a discrete horizontal fracture. Numerical modeling（FDTD） demonstrates that when the fracture channel is oriented at an oblique angle to the survey line, depolarization of the GpR signal results in scattered energy along the cross-polarized components. When the channel is oriented parallel or orthogonal to the survey line, all scattered energy is captured by the co-polarized components and no signal is present in the cross-polarized orientation. Multipolarization, time-lapse 3D GpR field data were acquired at the Altona Flat Rock test site in New York State. The GpR surveys were conducted during background fresh fracture water conditions and during a natural gradient saline tracer test which was used to highlight flow channels along a sub-horizontal fracture. Amplitude analysis of the cross-polarized data reveals flow channeling that is in agreement with the co-polarized GpR images and with independent hydraulic tests. This investigation demonstrates that cross-polarized components of GpR signals can be used to enhance imaging of flow channels in fractured media.

关键词： GpR single-polarization cross-polarized data rapid flow saline tracer fractured rock.

Risk of colorectal neoplasm in patients with acromegaly: A meta-analysis

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World Journal of Gastroenterology 2008年第22期14卷 3484-3489页

作者： Theodoros Rokkas Dimitrios pistiolas panos Sechopoulos georgios Margantinis georgios Koukoulis Gastroenterology Clinic Henry Dunant Hospital 107 Messogion Ave. Athens 11526 Greece

AIM: To examine the risk of colorectal neoplasm in acromegalic patients by meta-analyzing all relevant controlled studies. METHODS: Extensive English language medical literature searches for human studies, up to December 2007, were performed using suitable keywords. pooled estimates [odds ratio (OR) with 95% confidence intervals (CI)] were obtained using either the fixed or random-effects model as appropriate. Heterogeneity between studies was evaluated with the Cochran Q test whereas the likelihood of publication bias was assessed by constructing funnel plots. Their symmetry was estimated by the adjusted rank correlation test. RESULTS: For hyperplastic polyps the pooled ORs with 95% CI were 3.557 (2.587-4.891) by fixed effects model and 3.703 (2.565-5.347) by random effects model. The Z test values for overall effect were 7.81 and 6.984, respectively (p pooled ORs with 95% CI were 2.486 (1.908-3.238) (fixed effects model) and 2.537 (1.914-3.364) (random effects model). The Z test values were 6.747 and 6.472, respectively (p pooled OR with 95% CI was identical for both fixed and random effects model (OR, 4.351; 95% CI, 1.533-12.354; Z = 2.762, p = 0.006]. There was no significant heterogeneity and no publication bias in all the above meta-analyses. CONCLUSION: Acromegaly is associated with an increased risk of colorectal neoplasm.

关键词： Acromegaly Colon cancer Colon polyps Colon neoplasia Meta-analysis

Anion effect on Li/Na/K hybrid electrolytes for Graphite//NCA(LiNi_(0.8)Co_(0.15)Al_(0.05)O_(2))Li-ion batteries

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Journal of Energy Chemistry 2022年第1期31卷 451-462,I0012页

作者： Aiman Jrondi georgios Nikiforidis Meriem Anouti Laboratoire pCM2E Universite de ToursFaculte des sciences et technologiePare de Grandmont37200 ToursFrance LE STUDIUM Institute for Advanced Studies 45000 OrleansFrance

The electrolyte is an essential component of a battery system since it is responsible for the conduction of ions between the *** the quest for cheaper alternatives to common organic electrolytes for lithium-ion batteries(LIB),we formulated hybrid electrolytes comprising a mixture of Na,K,and Li alkaline salts with ethylene carbonate(EC),ethyl methyl carbonate(EMC),and lithium hexafluorophosphate(LipF_(6)),giving a total salt concentration of 1.5 M;we determined their physicochemical properties and investigated their electrochemical behavior on a nickel cobalt aluminum oxide(NCA)cathode and graphite(Gr)*** electrolytes demonstrated a melting transition peak(T_(m)).eutectic behavior,and ionic conductivities(-13 mS cm^(-1))close to those of a commercial LIB electrolyte(SE,EC/EMC+1 M LipF_(6))and activation energies of ca.3 kJ mol^(-1).The half-cell coin cells revealed high coulombic efficiency(99%),specific capacity(175 mAh g^(-1) at C/10),and capacity retention(92% for NaCF_(3)SO_(3))for the NCA cathode and a moderate performance(coulombic efficiency of 98%for 20 cycles)on the graphite anode after the formation of the SEI *** hybrid electrolytes were cycled at 25℃ in a Gr//NCA cell yielding specific capacities of ca.225 mAh g^(-1) at a C/5 rate,corroborating that the anion plays a key role and highlighting their potential for energy storage applications.

关键词： Hybrid electrolyte Alkali salts NCA//Li cell Li-ion battery