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Probabilistic fragility analysis:A tool for assessing design rules of RC buildings

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Earthquake Engineering and Engineering Vibration 2008年第1期7卷 45-56页

作者： nikos D Lagaros Institute of Structural Analysis&Seismic Research National Technical University of AthensGreece Lecturer

In this work, fragility analysis is performed to assess two groups of reinforced concrete structures. The first group of structures is composed of buildings that implement three common design practices; namely, fully infilled, weak ground story and short columns. The three design practices are applied during the design process of a reinforced concrete building. The structures of the second group vary according to the value of the behavioral factors used to define the seismic forces as specified in design procedures. Most seismic design codes belong to the class of prescriptive procedures where if certain constraints are fulfilled, the structure is considered safe. Prescriptive design procedures express the ability of the structure to absorb energy through inelastic deformation using the behavior factor. The basic objective of this work is to assess both groups of structures with reference to the limit-state probability of exceedance. Thus, four limit state fragility curves are developed on the basis of nonlinear static analysis for both groups of structures. Moreover, the 95% confidence intervals of the fragility curves are also calculated, taking into account two types of random variables that influence structural capacity and seismic demand.

关键词： probabilistic fragility analysis design practice behavior factor Monte Carlo simulation method

pH-responsive AIE-active Polyethylene-based Block Copolymers

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Chinese Journal of Polymer Science 2019年第9期37卷 930-935页

作者： Yu Jiang nikos Hadjichristidis Physical Sciences and Engineering Division KAUST Catalysis Center Polymer Synthesis Laboratory King Abdullah University of Science and Technology (KAUST)

A novel synthetic strategy towards pH-responsive aggregation-induced emission (AIE)-active tetraphenylethene (TPE)- functionalized polyethylene-based block copolymers is presented. Tris(3-(4-(l,2,2-triphenylvinyl)phenoxy)propyl)borane was used to initiate the polyhomologation of dimethylsulfoxonium methylide to afford well-defined a-TPE-ω-OH linear polyethylenes (PE). The terminal hydroxyl groups were transformed to atom transfer radical polymerization (ATRP) initiating sites by esterification with bromoisobutyryl bromide, followed by polymerization of rert-butyl acrylate (tBA) to provide TPE-PE-b-PtBA block copolymers. After hydrolysis of the rBu group to COOH group, the corresponding pH-responsive TPE-PE-b-PAA block copolymers were obtained. All synthesized block copolymers revealed AIE behavior either in solution or bulk. Due to the pH-responsivity of PAA chains, the aggregation state at different pH and consequently the fluorescence intensity changed. Also, the synthesized block copolymers exhibited ion-specificity fluorescence properties.

关键词： Polyhomologation ATRP Polyethylene-b-poly(acrylic acid) AIE pH-responsivity Ion-specificity

Investigation of proper modeling of very dense granular flows in the recirculation system of CFBs

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Particuology 2012年第6期10卷 699-709页

作者： Aristeidis Nikolopoulos nikos Nikolopoulos nikos Varveris Sotirios Karellas Panagiotis Grammelis Emmanuel Kakaras Laboratory of Steam Boilers and Thermal Plants Thermal Engineering SectorSchool of Mechanical EngineeringNTUAAthensGreece Centre for Research and Technology Hellas Institute for Solid Fuels Technology and ApplicationsAthens Gr-15310Greece

The aim of this paper is the development of new models and] or the improvement of existing numerical models, used for simulating granular flow in CFB （circulating fluidized bed） recirculation systems. Most recent models follow the TFM （two-fluid model） methodology, but they cannot effectively simulate the inter-particle friction forces in the recirculation system, because the respective stress tensor does not incorporate compressibility of flow due to change of effective particle density. As a consequence, the induced normal and shear stresses are not modeled appropriately during the flow of the granular phase in the CFB recirculation system. The failure of conventional models, such as that of yon MisesJCoulomb, is mainly caused by false approximation of the yield criterion which is not applicable to the CFB recirculation system. The present work adopts an alternative yield function, used for the first time in TFM Eulerian modeling. The proposed model is based on the Pitman-Schaeffer-Gray-Stiles yield criterion. Both the temporal deformation of the solid granular phase and the repose angle that the granular phase forms are more accurately simulated by this model. The numerical results of the proposed model agree well with experimental data, implying that frictional forces are efficiently simulated by the new model.

关键词： Euler-EulerCFBRepose angleFull-loop simulationGranular viscosityYield criterion

Guest Editorial:Special Section on Battery Energy Storage Systems for Net-zero Power Systems and Markets

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Journal of Modern Power Systems and Clean Energy 2024年第2期12卷 321-322页

作者： Pierluigi Mancarella nikos Hatziargyriou Chongqing Kang The University of Melbourne MelbourneAustralia The University of Manchester ManchesterUK National Technical University of Athens(NTUA) AthensGreece Tsinghua University BeijingChina IEEE

Battery energy storage technologies have witnessed both dramatic cost reduction and technical evolution in recent *** is leading to widespread deployment of battery energy storage systems(BESSs)worldwide,particularly to support operation of power grids with already deep penetration of *** the development of new battery technologies with different power-to-energy ratios and for various engineering applications,BESSs could play a strategic role towards a net-zero energy *** opportunities are emerging for BESSs to participate in several markets,provide different grid services,and perform“value stacking”,eventually allowing development of new business cases and improved BESS *** configurations that are“behind the meter”,“in front of the meter”,hybrid plants co-located with renewables,and so forth,are only some of the exciting propositions that are being seen in different countries and at different scales,from highly distributed(virtual power plants),to neighbourhood-level(community batteries),to utility scale.

关键词： Battery battery eventually

Optical RAM and integrated optical memories:a survey

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Light(Science & Applications) 2020年第1期9卷 1117-1132页

作者： Theoni Alexoudi George Theodore Kanellos nikos Pleros Department of Informatics Aristotle University of ThessalonikiThessalonikiGreece Department of Electrical&Electronic Engineering University of BristolBristolUK

The remarkable achievements in the area of integrated optical memories and optical random access memories(RAMs)together with the rapid adoption of optical interconnects in the Datacom and Computercom industries introduce a new perspective for information storage directly in the optical domain,enabling fast access times,increased bandwidth and transparent cooperation with optical interconnect *** article reviews state-of-the-art integrated optical memory technologies and optical RAM cell demonstrations describing the physical mechanisms of several key devices along with their performance metrics in terms of their energy,speed and *** applications are outlined,concluding with the scaling challenges to be addressed toward allowing light to serve as both a datacarrying and data-storage medium.

关键词： RAM transparent scaling

Taking central nervous system regenerative therapies to the clinic: curing rodents versus nonhuman primates versus humans

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Neural Regeneration Research 2020年第3期15卷 425-437页

作者： Magdalini Tsintou Kyriakos Dalamagkas nikos Makris Departments of Psychiatry and Neurology Services Center for Neural Systems InvestigationsCenter for Morphometric AnalysisAthinoula A.Martinos Center for Biomedical ImagingMassachusetts General HospitalHarvard Medical SchoolBostonMAUSA Department of Psychiatry Psychiatry Neuroimaging LaboratoryBrigham and Women’s HospitalHarvard Medical SchoolBostonMAUSA University College of London Division of Surgery&Interventional Science Center for Nanotechnology&Regenerative MedicineUniversity College LondonLondonUK Department of Physical Medicine and Rehabilitation The University of Texas Health Science Center at HoustonHoustonTXUSA The Institute for Rehabilitation and Research Memorial Hermann Research Center The Institute for Rehabilitation and Research Memorial Hermann HospitalHoustonTXUSA Department of Anatomy&Neurobiology Boston University School of MedicineBostonMAUSA

The central nervous system is known to have limited regenerative *** only does this halt the human body’s reparative processes after central nervous system lesions,but it also impedes the establishment of effective and safe therapeutic options for such *** the high prevalence of stroke and spinal cord injury in the general population,these conditions remain incurable and place a heavy burden on patients’families and on society more *** and neural engineering are diverse biomedical fields that attempt reparative treatments,utilizing stem cells-based strategies,biologically active molecules,nanotechnology,exosomes and highly tunable biodegradable systems(e.g.,certain hydrogels).Although there are studies demonstrating promising preclinical results,safe clinical translation has not yet been accomplished.A key gap in clinical translation is the absence of an ideal animal or ex vivo model that can perfectly simulate the human microenvironment,and also correspond to all the complex pathophysiological and neuroanatomical factors that affect functional outcomes in humans after central nervous system *** an ideal model does not currently exist,but it seems that the nonhuman primate model is uniquely qualified for this role,given its close resemblance to *** review considers some regenerative therapies for central nervous system repair that hold promise for future clinical *** addition,it attempts to uncover some of the main reasons why clinical translation might fail without the implementation of nonhuman primate models in the research pipeline.

关键词： animal models central nervous system regeneration clinical translation exosomes hydrogels neural tissue engineering nonhuman primates spinal cord injury stem cells stroke

The interaction of electric vehicles with the power grid-Challenges and solutions

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iEnergy 2023年第4期2卷 254-255页

作者： nikos Hatziargyriou School of Electrical and Computer Engineering National Technical University of AthensZografosAthens

One quarter of the green house gas(GHG)emissions is attributed to the transport *** the world moves to a low-carbon economy,electrification and efficiency improvements of transport has become one of the primary policy... 详细信息

关键词： attributed interaction expanding

Neural network analysis of overturning response under near-fault type excitation

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Earthquake Engineering and Engineering Vibration 2005年第2期4卷 213-228页

作者： nikos Gerolymos Marios Apostolou George Gazetas School of Civil Engineering National Technical UniversityAthensGreece Post-doctoralResearch Engineer School of Civil Engineering National Technical UniversityAthensGreece Ph.D.Student School of Civil Engineering National Technical UniversityAthensGreece Professor

Under strong seismic excitation, a rigid block will uplift from its support and undergo rocking oscillations which may lead to （complete） overturning. Numerical and analytical solutions to this highly nonlinear vibration problem are first highlighted in the paper and then utilized to demonstrate how sensitive the overturning behavior is not only to the intensity and frequency content of the base motion, but also to thc presence of strong pulses, to their detailed sequence, and even to their asymnletry. Five idealised pulses capable of representing ＂rupture-directivity＂ and ＂fling＂ affected ground motions near the fault, are utilized to this end ： the one-cycle sinus, the one-cycle cosinus, the Ricker wavelet, the truncated （T）-Ricker wavelet, and the rectangular pulse ＂Overturning-Acceleration Amplification＂ and ＂Rotation＂ spectra are introduced and presented. Artificial neural network modeling is then developed as an alternative numerical solution. The neural network analysis leads to closed-form expressions for predicting the overturning failure or survival of a rigid block, as a function of its geometric properties and the characteristics of the excitation time history. The capability of the developed neural network modeling is validated through comparisons with the numerical solution. The derived analytical expressions could also serve as a tool for assessing the destructiveness of near-fault ground motions, for structures sensitive to rocking with foundation uplift.

关键词： overturning uplifting pulse near-fault moti neural network rocking spectrum Kocaeli records

Overview of Gait Synthesis for the Humanoid COMAN

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Journal of Bionic Engineering 2017年第1期14卷 15-25页

作者： Chengxu Zhou Xin Wang Zhibin Li nikos Tsagarakis Department of Advanced Robotics lstituto Italiano di Tecnologia Via Morego 30 16163 Genova Italy Shenzhen Academy of Aerospace Technology Shenzhen 518057 China School of Informatics University of Edinburgh 10 Crichton St Edinburgh EH8 9AB UK

This paper focuses on the developments of a generic gait synthesis for the humanoid robot COMAN. Relying on the essential Gait Pattern Generator （GPG）, the proposed synthesis offers enhanced versatilities for the locomotion under different purposes, and also provides the data storage and communication mechanisms among different modules. As an outcome, we are able to augment new abilities for COMAN by integrating new control modules and software tools at a cost of very few modifications. Moreover, foot placement optimization is introduced to the GPG to optimize the gait parameter references in order to meet the robot＇s natural dynamics and kinematics, which enhances the synthesis＇s robustness while it＇s being implemented on real robots. We have also presented a practical approach to generate pelvis motion from CoM references using a simplified three-point-mass model, as well as a straightforward but effective idea for the state estimation using the sensory feedback. Three physical experiments were studied in an increasing complexity to demonstrate the effectiveness and successful implementation of the proposed gait synthesis on a real humanoid system.

关键词： humanoid robots bipedal locomotion gait synthesis dynamic walking