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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

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

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

An accurate model for the thin film flow

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Acta Mechanica Sinica 2008年第4期24卷 375-380页

作者： Hamid Ait Abderahmane georgios H.Vatistas Department of Mechanical and Industrial Engineering Concordia University 1455 de Maisonneuve Blvd West Montreal OC H3G 1M8 Canada

This paper deals with the linear stability of a liquid film flowing down an inclined plane. The Navier-Stokes equations were reduced into four evolution equations that describe the development of the film depth, the flow rate, the free surface velocity, and the wall shear stress, using the Karman-Polhausen boundary layer integral method. Thus, we were able to determine the stability threshold and approach well the critical wave number for long waves. The obtained results were found to be in good agreement with the experiments of Liu et al.

关键词： Liquid film Linear stability Flow model

On the refracted patterns produced by liquid vortices

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Acta Mechanica Sinica 2007年第1期23卷 11-15页

作者： Yasser Aboelkassem georgios H.Vatistas McGill University MontrealQCH3A-2K6Canada Concordia University MontrealQCH3G 1M8Canada

A theoretical analysis of the refracted shadows produced by steady and time-decaying liquid vortices under uniform illumination from above is given in this article. An expression for the induced shadow intensity is derived and found to be a function of the vortex＇s free surface profile, i.e., function of the static pressure distribution. The patterns for different focusing depth are given and compared with previous visualization results from the literature. The phenomenon is examined and illustrated as a bench mark case by using both steady and time-decaying algebraic vortex models. However, this study can be extended to check the feasibility of recovering the main flow properties by analyzing the luminous image intensity of the refracted patterns. The present analysis is valid only when the swirl velocity is order of magnitude higher than the meridional flow components and the vorticity is concentrated within the core region and of intense conditions.

关键词： Fluid dynamics - Vortices - Dark shadows Intensity - Time decay

Strength, deformability and permeability of kakiritic rocks from the Gotthard base tunnel

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第9期15卷 2224-2237页

作者： Martin Vogelhuber Erich Pimentel georgios Anagnostou ETH Zurich ZurichSwitzerland

The 57-km long,new Gotthard Base Tunnel(GBT)crosses over a 1.1-km long stretch containing kakirites,*** rocks which,depending on the degree of tectonisation,may exhibit severe squeezing behaviour upon tunnel *** tunnel stretch was already identified as a key problem in the early planning phase,necessitating intensive geological exploration and laboratory investigations over a 14-year period,including research and development in experimental *** laboratory investigations for the GBT provided not only a considerable amount of data about the geotechnical parameters of the kakirites,but also valuable information about their basic behaviour and the adequacy of various testing techniques for this type of ***,by using specially designed testing equipment and procedures,it was shown that,(1)conventional rock mechanics triaxial tests cannot provide reliable results for kakirites;(2)the kakirites obey the principle of effective stress in Terzaghi’s classical form and consequently it is indispensable to measure the pore pressure during triaxial testing,analogously to the consolidated drained(CD)and consolidated undrained(CU)tests in soil mechanics;(3)the effects of a possible loss of water and desaturation during sampling,transport,storage and preparation of specimens can be successfully mitigated by subjecting the specimens to flow-through before the actual triaxial testing;and,(4)CD tests on partially saturated specimens that are obtained by means of flow-through can provide reliable and reproducible *** saves a significant amount of time,allows a greater number of tests to be performed,and allows results to be obtained more quickly,which is particularly important for decision-making during tunnel advance.

关键词： Squeezing Pore pressure Triaxial testing

Surgical treatment of hepatic metastases from colorectal cancer

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World Journal of Gastrointestinal Oncology 2011年第1期3卷 1-9页

作者： georgios Tsoulfas Manousos georgios Pramateftakis Ioannis Kanellos Department of Surgery Aristoteleion University of ThessalonikiThessaloniki 54622Greece

Colorectal carcinoma is one of the most frequent cancers in Western societies with an incidence of around 700 per million *** half of the patients develop metastases from the primary tumor and liver is the primary metastatic *** survival rates after hepatectomy for metastatic colorectal cancer have been reported in the last few years and these may be the result of a variety of factors,such as advances in systemic chemotherapy,radiographic imaging techniques that permit more accurate determination of the extent and location of the metastatic burden,local ablation methods,and in surgical techniques of hepatic *** have led to a more aggressive approach towards liver metastatic disease,resulting in longer *** goal of this paper is to review the role of various forms of surgery in the treatment of hepatic metastases from colorectal cancer.

关键词： Hepatic metastases Colorectal cancer Liver resection

An integrated multi-criteria analysis for assessing sustainability of agricultural production at regional level

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Information Processing in Agriculture 2020年第2期7卷 223-232页

作者： georgios Bartzas Kostas Komnitsas School of Mining and Metallurgical Engineering National Technical University of AthensZografos CampusAthens 15780Greece School of Mineral Resources Engineering Technical University of CreteChaniaCrete 73100Greece

Assessment of agricultural production sustainability is a multi-dimensional task that involves the quantification of various economic,social and environmental indicators at different scales and uncertainty *** this context,a particularly challenging approach is proposed involving the appropriate selection of the most representative criteria that ensure economic viability,eco-friendliness and social development,in order to overcome the limitations of other methodological approaches that are often vague and *** this study,a holistic methodology that integrates life cycle analysis(LCA),environmental risk assessment(ERA)along with on-site farm and regional surveys using the multi-criteria environment of the Analytical Hierarchy Process(AHP)is designed for the identification of the most sustainable agricultural management practices at regional *** on a set of 13 representative sub-criteria,the proposed approach was applied to Pistacia vera *** in Aegina island,Greece,where narrow range of resources is available,groundwater supply is scarce and of poor ***,three alternative scenarios,*** scenario representing the current production(BL)as well as Composting(CO)and Biochar Use(BU)scenarios aiming at sustainability improvement were *** of multi-criteria and sensitivity analyses suggest that the optimal sustainable management scenario is CΟ,which involves on-site composting of organic solid waste,mainly produced at farm site,and subsequent application in the *** proposed methodology shows significant potential as a valuable multi-criteria tool that can be easily adapted at regional level to assist decision makers such as farmers and their associations,policy makers,local and regional authorities to efficiently explore a range of alternative farm management practices and thus identify pathways toward sustainability.

关键词： Sustainability Multi-criteria analysis LCA AHP Pistacia vera L. Sensitivity analysis