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REFLECTIONS ON SYSTEMIC PROBLEMS AND SOLUTIONS

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Journal of Systems Science and Systems Engineering 2017年第3期26卷 265-268页

作者： Stuart A. Umpleby Department of Management The George Washington University Washington DC20052 USA

This special issue of JSSSE contains papers presented at a conference at the University of Sichuan in Chengdu, China, in October, 2015. The papers provide an indication of how the fields of systems science and cybernetics have evolved in recent decades. This preface briefly describes the context in which systems science and cybernetics have evolved.

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A novel near-infrared light responsive 4D printed nanoarchitecture with dynamically and remotely controllable transformation

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Nano Research 2019年第6期12卷 1381-1388页

作者： Haitao Cui Shida Miao Timothy Esworthy Se-jun Lee Xuan Zhou Sung Yun Hann Thomas J.Webster Brent T.Harris Lijie Grace Zhang Department of Mechanical and Aerospace Engineering The George Washington UniversityWashingtonDC 20052USA Department of Chemical Engineering Northeastern UniversityBostonMA 02115USA Department of Neurology and Pathology Georgetown UniversityWashingtonDC 20007USA Departments of Electrical and Computer Engineering The George Washington UniversityWashingtonDC 20052USA Department of Biomedical Engineering The George Washington UniversityWashingtonDC 20052USA Department of Medicine The George Washington UniversityWashingtonDC 20052USA

Four-dimensional (4D) printing is an emerging and highly innovative additive manufacturing process by which to fabricate pre-designed,self-assembly structures with the ability to transform over ***,one of the critical challenges of 4D printing is the lack of advanced 4D printing systems that not only meet all the essential requirements of shape change but also possess smart,dynamic capabilities to spatiotemporally and instantly control the shape-transformation ***,we present a facile 4D printing platform which incorporates nanomaterials into the conventional stimuli-responsive polymer,allowing the 4D printed object to achieve a dynamic and remote controlled,on-time and position shape transformation.A proof-of-concept 4D printed brain model was created using near-infrared light (NIR) responsive nanocomposite to evaluate the capacity for controllable 4D transformation,and the feasibility of photothermal stimulation for modulating neural stem cell *** novel 4D printing strategy can not only be used to create dynamic 3D patterned biological structures that can spatiotemporally control their shapes or behaviors of transformation under a human benign stimulus (NIR),but can also provide a potential method for building complex self-morphing objects for widespread applications.

关键词： near-infrared light responsive four-dimensional (4D) printing dynamically and remotely controllable graphene brain neural stem cell

Interpretation of thermal dependence of magnetic aftereffect for magnetic nanocomposite with slow decay rates

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International Journal of Smart and Nano Materials 2013年第2期4卷 91-101页

作者： Shuo Gu Yi Jin Gary R.Kahler Ming Zhang Peijie Chen Mohammadreza Ghahremani Edward Della Torre Lawrence H.Bennett Department of Electrical and Computer Engineering The George Washington UniversityWashington DC 20052 USA Department of Chemistry The George Washington UniversityWashington DC 20052USA

A new experimental characterization is presented of time-,field-,and temperature-dependent dynamic effects in magnetization of a nanocomposite which displays slow *** and temperature variations of irreversible susceptibility,χirr,decay coefficient,S,fluctuation field,hf,and activation volume,V,have been calculated for the nanocomposite sample(Co_(80)Ni_(20))using a recently developed modified Preisach–Arrhenius(MPA)*** sample is composed of non-interacting nanoparticles having negligible reversible ***-Arrhenius behavior is observed in both the maximum decay coefficient,Smax,and the fluctuation field,hf,as a function of temperature *** peak of both temperature curves are identical and occur at a critical temperature Tk of∼50 K,which agrees with our experimental *** on the effect of a temperature-dependent chemical potential on energy barrier,hf is studied for T

关键词： magnetic aftereffect fluctuation field numerical modeling Co_(80)Ni_(20)nanocomposite

Nanoindentation in elastoplastic materials:insights from numerical simulations

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International Journal of Smart and Nano Materials 2010年第2期1卷 95-114页

作者： Steven W.Moore Majid T.Manzari Yin-Lin Shen Department of Mechanical and Aerospace Engineering The George Washington UniversityWashingtonDC 20052USA Department of Civil and Environmental Engineering The George Washington UniversityWashingtonDC 20052USA

Finite element simulations of nanoindentation were performed on an elastoplastic material using Berkovich and conical indenters to investigate the effects of geometry on the load-displacement response of the *** Berkovich indenter,widely used in nanoindentation experiments,is typically simplified to a theoretically equivalent 70.3°conical indenter for numerical simulations,which allows for a less computationally intensive two-dimensional(2D)axisymmetric *** studies into the validity of this equivalence assumption for indentations in elastoplastic materials have varying *** 2D and 3D finite element simulations,the present study investigates the response of elastoplastic materials,obeying a combined isotropic and kinematic hardening,to indentation with conical and Berkovich *** show that there is a clear difference in the load-displacement response of the selected material to the two *** Berkovich geometry is found to produce a more localized pattern of contact stresses and plastic strains,leading to a smaller mobilized force for the same magnitude of *** further validate the numerical simulations,experimental results of nanoindentation into an aluminium specimen were compared to elastoplastic finite element simulation *** suggest that machining-induced residual stresses have likely affected the experimental results.

关键词： nanoindentation finite element analysis elastoplasticity tip geometry

Quantifying Information via Shannon Entropy in Spatially Structured Optical Beams

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Research 2021年第1期2021卷 780-788页

作者： Maria Solyanik-Gorgone Jiachi Ye Mario Miscuglio Andrei Afanasev Alan E.Willner Volker J.Sorger Department of Electrical and Computer Engineering The George Washington UniversityWashingtonDC 20052USA Department of Physics The George Washington UniversityWashingtonDC 20052USA Department of Electrical Engineering at University of Southern California Los AngelesCalifornia 90089USA

While information is ubiquitously generated,shared,and analyzed in a modern-day life,there is still some controversy around the ways to assess the amount and quality of information inside a noisy optical channel.A number of theoretical approaches based on,e.g.,conditional Shannon entropy and Fisher information have been developed,along with some experimental *** of these approaches are limited to a certain alphabet,while others tend to fall short when considering optical beams with a nontrivial structure,such as Hermite-Gauss,Laguerre-Gauss,and other modes with a nontrivial ***,we propose a new definition of the classical Shannon information via the Wigner distribution function,while respecting the Heisenberg *** this definition,we calculate the amount of information in Gaussian,Hermite-Gaussian,and LaguerreGaussian laser modes in juxtaposition and experimentally validate it by reconstruction of the Wigner distribution function from the intensity distribution of structured laser *** experimentally demonstrate the technique that allows to infer field structure of the laser beams in singular optics to assess the amount of contained *** the generality,this approach of defining information via analyzing the beam complexity is applicable to laser modes of any topology that can be described by well-behaved *** Shannon information,defined in this way,is detached from a particular alphabet,i.e.,communication scheme,and scales with the structural complexity of the *** a synergy between the Wigner distribution function encompassing the information in both real and reciprocal space and information being a measure of disorder can contribute into future coherent detection algorithms and remote sensing.

关键词： distribution Spatial complexity

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Simulation of collisions between buckyballs and graphene sheets

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International Journal of Smart and Nano Materials 2012年第1期3卷 14-22页

作者： Zhen Zhang Xianqiao Wang Jiaoyan Li Department of Mechanical and Aerospace Engineering The George Washington UniversityWashingtonDC 20052USA

The phenomena of buckyball-graphene collisions were investigated by classical molecular dynamics(MD)simulation using the empirical Tersoff *** cases were investigated:collisions between a buckyball and a single-layer graphene;collisions between a nano-onion(a double-layer concentric spherical nanostructure:a C_(60) in a C_(320))and a single-layer graphene;collisions between a nano-onion and a double-layer *** impact velocity of the buckyball or nano-onion ranged from 4.37 km/s to 15.31 km/*** results for the buckyball-graphene collisions show that the buckyball bounces back when the impact velocity is less than 8.75 km/s,sticks to the graphene when the impact velocity is between 8.75 km/s and 12.03 km/s,and breaks when the impact velocity is greater than 12.03 km/*** phenomena are observed for the other two cases.A single buckyball can never go through a single-layer graphene intact;however,the inner structure(C_(60))of a nano-onion can penetrate through a single-layer graphene without any *** energy evolution during the whole simulation process was also studied.

关键词： graphene buckyball nano-onion collisions Tersoff potential

A censored-Poisson model based approach to the analysis of RNA-seq data

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Quantitative Biology 2020年第2期8卷 155-171页

作者： Xing Chen Yinglei Lai Department of Statistics The George Washington UniversityWashingtonDC 20052USA

Background:With the recent advance of sequencing technology,the collction of RNA expression(RNA-seq)data has been growing ***-seq data are statistically count-type *** distribution is a basic probability distribution for modeling count-type *** Poisson regression models,various experimental factors,GC content as well as alternative splicing isoforms can be flexibly considered in RNA-seq data *** to the biochemical and technical limitations of sequencing technology,the biases among RNA-seq data have been ***:In this study,an artificial censoring approach has been proposed to an isoform-specific Poisson regression model for analy zing RNA-seq *** expression values can be grouped(censored)into one probability category,and high expression values can also be grouped(censored)into another probability *** have implemented the related Newton-Raphson numeric computing procedure to achieve the maximum likelihood estimation for our censored-Poisson regression *** related mathematical simplifications have been derived for the consideration of stable and convenient numerical ***:The advantages of our artificial censoring approach have been demonstrated in both simulation studies and application analysis of experimental ***:Our proposed artificial censoring approach allows us to focus on the majority of *** the extreme values(tails)of data are artificially censored,more efficient analysis results can be obtained,even from relatively simple Poisson regression *** proposed artificial censoring approach can certainly be considered for other well-developed models or methods for RNA-seq data analysis.

关键词： RNA-seq Poisson models censored distribution

Micromorphic theory:a gateway to nano world

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International Journal of Smart and Nano Materials 2010年第2期1卷 115-135页

作者： Xianqiao Wang James D.Lee Department of Mechanical and Aerospace Engineering The George Washington UniversityWashingtonDC 20052USA

Micromorphic theory(MMT)envisions a material body as a continuous collection of deformable particles;each possesses finite size and inner *** is considered as the most successful top-down formulation of a two-level continuum model,in which the deformation is expressed as a sum of macroscopic continuous deformation and internal microscopic deformation of the inner *** this work,the kinematics including the objective Eringen tensors is *** laws are derived by requiring the energy equation to be form-invariant under the generalized Galilean *** concept of material force and the balance law of pseudomomentum are generalized for *** axiomatic approach is demonstrated in the formulation of constitutive equations for a generalized micromorphic thermoviscoelastic solid,generalized micromorphic fluid,micromorphic plasticity,and micromorphic electromagnetic-thermoelastic *** of MMT in micro/nanoscale are discussed.

关键词： micromorphic theory Eringen tensors constitutive theory generalized micromorphic solid/fluid electromagnetic-thermoelastic coupling micro/nanomechanics

Emerging electrochemical processes for materials recovery from wastewater: Mechanisms and prospects

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Frontiers of Environmental Science & Engineering 2020年第5期14卷 157-170页

作者： Lingchen Kong Xitong Liu Department of Civil and Environmental Engineering The George Washington University80022nd St NWWashingtonDC 20052USA

Recovering valuable materials from waste streams is critical to the transition to a circular economy with reduced environmental damages caused by resource extraction *** and industrial wastewaters contain a variety of materials,such as nutrients(nitrogen and phosphorus),lithium,and rare earth elements,which can be recovered as value-added *** to their modularity,convenient operation and control,and the non-requirement of chemical dosage,electrochemical technologies offer a great promise for resource recovery in small-scale,decentralized ***,we review three emerging electrochemical technologies for materials recovery applications:electrosorption based on carbonaceous and intercalation electrodes,electrochemical redox processes,and electrochemically induced *** highlight the mechanisms for achieving selective materials recovery in these *** also present an overview of the advantages and limitations of these technologies,as well as the key challenges that need to be overcome for their deployment in real-world systems to achieve cost-effective and sustainable materials recovery.

关键词： Materials recovery Electrosorption Capacitive deionization Redox processes Electrochemical precipitation