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Symmetry-aware recursive image similarity exploration for materials microscopy

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npj Computational Materials 2021年第1期7卷 1508-1521页

作者： Tri N.M.Nguyen Yichen Guo Shuyu Qin Kylie S.Frew Ruijuan Xu Joshua C.Agar Department of Materials Science and Engineering Lehigh UniversityBethlehemPA 18015USA Department of Computer Science and Engineering Lehigh UniversityBethlehemPA 18015USA Department of Mechanical Engineering Lehigh UniversityBethlehemPA 18015USA Department of Applied Physics Stanford UniversityStanfordCA 94305USA

In pursuit of scientific discovery,vast collections of unstructured structural and functional images are acquired;however,only an infinitesimally small fraction of this data is rigorously analyzed,with an even smaller fraction ever being *** method to accelerate scientific discovery is to extract more insight from costly scientific experiments already ***,data from scientific experiments tend only to be accessible by the originator who knows the experiments and ***,there are no robust methods to search unstructured databases of images to deduce correlations and ***,we develop a machine learning approach to create image similarity projections to search unstructured image *** improve these projections,we develop and train a model to include symmetry-aware *** an exemplar,we use a set of 25,133 piezoresponse force microscopy images collected on diverse materials systems over five *** demonstrate how this tool can be used for interactive recursive image searching and exploration,highlighting structural similarities at various length *** tool justifies continued investment in federated scientific databases with standardized metadata schemas where the combination of filtering and recursive interactive searching can uncover synthesis-structure-property *** provide a customizable open-source package(https://***/m3-learning/Recursive_Symmetry_Aware_Materials_Microstructure_Explorer)of this interactive tool for researchers to use with their data.

关键词： interactive image similarity

Modelling and control of a spatial dynamic cable

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Acta Mechanica Sinica 2019年第4期35卷 866-878页

作者： Bo Tian Subhrajit Bhattacharya Department of Mechanical Engineering and Mechanics Lehigh University Bethlehem PA 18015 USA

We study the problem of dynamically controlling the shape of a cable that is fixed at one end and attached to an actuated robot at another end. This problem is relevant to unmanned aerial vehicles (UAVs) tethered to a base. While rotorcrafts, such as quadcopters, are agile and versatile in their applications and have been widely used in scientific, industrial and military applications, one of the biggest challenges with such UAVs is their limited battery life that make the flight time for a typical UAVs limited to twenty to thirty minutes for most practical purposes. A solution to this problem lies in the use of cables that tether the UAV to a power outlet for constant power supply. However, the cable needs to be controlled effectively in order to avoid obstacles or other UAVs. In this paper, we develop methods for controlling the shape of a cable using actuation at one end. We propose a discrete model for the spatial cable and derive the equations governing the cable dynamics for both force controlled system and position controlled system. We design a controller to control the shape of the cable to attain the desired shape and perform simulations under different conditions. Finally, we propose a quasi-static model for the spatial cable and discuss the stability of this system and the proposed controller.

关键词： Lagrangian mechanics Discrete model of cable Control of under-actuated systems

How territoriality affects the density of an egg predator： Habitat renovation and reintroduction as a method of conserving two endangered desert spring fish

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Current Zoology 2014年第4期60卷 527-533页

作者： Timothy PACIOREK Layla AL-SHAER Murray ITZKOWITZ Department of Biological Sciences Lehigh University Bethlehem PA 18015 USA

Conservation of endangered sympatric species must be carefully executed to ensure that the protection of one species does not negatively impact the survival of another. Critically endangered Pecos gambusia Gambusia nobilis and Leon Springs pupfish Cyprinodon bovinus, which are endemic to a threatened desert spring habitat, exemplify one such scenario. Recently, this habitat has been expanded, and captively bred C. bovinus were released to repopulate an area historically known to contain this species. A previous study suggested that G. nobilis are detrimental to C. bovinus populations, due to their tendency to congregate near spawning pairs and feed on their eggs. Whether G. nobilis are attracted to territorial C. bovinus, regardless of spawning behavior, remains unclear. To determine this, the number of G. nobilis in occupied and unoccupied breeding territories of both wild and captively bred C. bovinus was measured. Gambusia nobilis densities were similar between unoccupied and occupied territorial sites, suggesting that they do not show a preference for C. bovinus territories. Regardless of habitat location or prior captivity, territorial C. bovinus significantly excluded G. nobilis within their direct vicinity （5 cm）, but not from their entire territory. Decreased G. nobilis density within the habitat may allow C. bovinus to defend their breeding territories more readily during the summer spawning season. This study provides empirical evidence of captively raised individuals behaving similarly to wild indi- viduals upon reintroduction to their natural habitat and support for conservation methods that focus on common limiting factors between endangered species [Current Zoology 60 （4）： 527-533, 2014].

关键词： Pupfish Gambusia Habitat Conservation Territory Density

Population differentiation at a regional scale in spadefoot toads： contributions of distance and divergent selective environments

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Current Zoology 2016年第2期62卷 193-206页

作者： Amber M. RICE Michael A. MCQUILLAN Heidi A. SEEARS Joanna A. WARREN Department of Biological Sciences Lehigh University BethLehem PA 18015 USA

The causes of population differentiation can provide insight into the origins of early barriers to gene flow. Two key drivers of population differentiation are geographic distance and local adaptation to divergent selective environments. When reproductive isolation arises because some populations of a species are under selection to avoid hybridization while others are not, population differentiation and even speciation can result. Spadefoot toad populations Spea multiplicata that are sympatric with a congener have undergone reinforcement. This reinforcement has resulted not only in increased reproductive isolation from the congener, but also in the evolution of reproductive isolation from nearby and distant conspecific allopatric populations. We used multiple approaches to evaluate the contributions of geographic distance and divergent selective environments to population structure across this regional scale in S. multiplicata, based on genotypes from six nuclear microsatellite markers. We compared groups of populations varying in both geographic location and in the presence of a congener. Hierarchical F-statistics and results from cluster analyses and discriminant analyses of principal components all indicate that geographic distance is the stronger contributor to genetic differentiation among S. multiplicata populations at a regional scale. However, we found evidence that adaptation to divergent selective environments also contributes to population structure. Our findings highlight how variation in the balance of evolutionary forces acting across a species＇ range can lead to variation in the relative contributions of geographic distance and local adaptation to population differentiation across different spatial scales.

关键词： cascade reinforcement character displacement reproductive isolation spatial scale Spea multipficata speciation

DPCM-based vibration sensor data compression and its effect on structural system identification

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Earthquake Engineering and Engineering Vibration 2005年第1期4卷 153-163页

作者：张云峰李健 Department of Civil & Environmental Engineering Lehigh University Bethlehem PA 18015 USAAssistantProfessor Department of Civil & Environmental Engineering Lehigh University Bethlehem PA 18015 USA Graduate Researcher

Due to the large scale and complexity of civil infrastructures, structural health monitoring typically requires a substantial number of sensors, which consequently generate huge volumes of sensor data. Innovative sensor data compression techniques are highly desired to facilitate efficient data storage and remote retrieval of sensor data. This paper presents a vibration sensor data compression algorithm based on the Differential Pulse Code Modulation (DPCM) method and the consideration of effects of signal distortion due to lossy data compression on structural system identification. The DPCM system concerned consists of two primary components: linear predictor and quantizer. For the DPCM system considered in this study, the Least Square method is used to derive the linear predictor coefficients and Jayant quantizer is used for scalar quantization. A 5-DOF model structure is used as the prototype structure in numerical study. Numerical simulation was carried out to study the performance of the proposed DPCM-based data compression algorithm as well as its effect on the accuracy of structural identification including modal parameters and second order structural parameters such as stiffness and damping coefficients. It is found that the DPCM-based sensor data compression method is capable of reducing the raw sensor data size to a significant extent while having a minor effect on the modal parameters as well as second order structural parameters identified from reconstructed sensor data.

关键词： data compression instrumentation linear predictor modal parameters sensor system identification vibration

Ductility demands on buckling-restrained braced frames under earthquake loading

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Earthquake Engineering and Engineering Vibration 2003年第2期2卷 255-268页

作者： Larry A.Fahnestock Richard Sause James M.Ricles Le-Wu Lu Department of Civil and Environmental Engineering ATLSS CenterLehigh UniversityBethlehemPennsylvaniaUSA Graduate Research Assistant Department of Civil and Environmental Engineering ATLSS CenterLehigh UniversityBethlehemPennsylvaniaUSA Professor

Accurate estimates of ductility demands on buckling-restrained braced frames(BRBFs)are crucial to performance-based design of *** analytical study on the seismic behavior of BRBFs has been conducted at the ATLSS Center,lehigh university to prepare for an upcoming experimental *** analysis program DRAIN-2DX was used to model a one-bay,four-story prototype BRBF including material and geometric *** buckling- restrained brace(BRB)model incorporates both isotropic and kinematic *** static pushover and time- history analyses were performed on the prototype *** objectives for the BRBs were defined and used to evaluate the time-history analysis *** emphasis was placed on global ductility demands and ductility demands on the *** demands were compared with anticipated ductility *** analysis results,along with results from similar previous studies,are used to evaluate the BRBF design provisions that have been recommended for codification in the United *** results show that BRB maximum ductility demands can be as high as 20 to *** demands significantly exceed those anticipated by the BRBF recommended *** from the static pushover and time- history analyses are used to demonstrate why the ductility demands exceed those anticipated by the recommended provisions. The BRB qualification testing protocol contained in the BRBF recommended provisions is shown to be inadequate because it requires only a maximum ductility demand of at most *** to the testing protocol are recommended.

关键词： buildings buckling-restrained braced frames buckling-restrained braces structural response seismic response ductility demand seismic codes and standards

Solutions to Some Open Problems in Fluid Dynamics

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Chinese Annals of Mathematics,Series B 2008年第2期29卷 179-198页

作者： Linghai ZHANG Department of Mathematics Lehigh University 14 East Packer Avenue Bethlehem Pennsylvania 18015

Let u=u（x,t,uo）represent the global solution of the initial value problem for the one-dimensional fluid dynamics equation ut-εuxxt＋δux＋γHuxx＋βuxxx＋f（u）x=αuxx,u（x,0）=uo（x）, whereα〉0,β〉0,γ〉0,δ〉0 andε〉0 are *** equation may be viewed as a one-dimensional reduction of n-dimensional incompressible Navier-Stokes equations. The nonlinear function satisfies the conditions f（0）=0,｜f（u）｜→∞as ｜u｜→∞,and f∈C^1（R）,and there exist the following limits Lo=lim sup/u→o f（u）/u^3 and L∞=lim sup/u→∞ f（u）/u^5 Suppose that the initial function u0∈L^I（R）∩H^2（R）.By using energy estimates,Fourier transform,Plancherel＇s identity,upper limit estimate,lower limit estimate and the results of the linear problem vt-εv（xxt）＋δvx＋γHv（xx）＋βv（xxx）=αv（xx）,v（x,0）=vo（x）, the author justifies the following limits（with sharp rates of decay） lim t→∞[（1＋t）^（m＋1/2）∫｜uxm（x,t）｜^2dx]=1/2π（π/2α）^（1/2）m!!/（4α）^m[∫R uo（x）dx]^2, if∫R uo（x）dx≠0, where 0!!=1,1!!=1 and m!!=1·3…（2m-3）…（2m-1）.Moreover lim t→∞[（1＋t）^（m＋3/2）∫R｜uxm（x,t）｜^2dx]=1/2π（x/2α）^（1/2）（m＋1）!!/（4α）^（m＋1）[∫Rρo（x）dx]^2, if the initial function uo（x）=ρo′（x）,for some functionρo∈C^1（R）∩L^1（R）and∫Rρo（x）dx≠0.

关键词： Exact limits Sharp rates of decay Fluid dynamics equation Global smooth solutions

Neuron-neuron attraction shapes morphology and activity of tissue engineered brain constructs

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Neural Regeneration Research 2022年第12期17卷 2655-2656页

作者： Yevgeny Berdichevsky Department of Bioengineering Department of Electrical and Computer EngineeringLehigh UniversityBethlehemPAUSA

The propensity of neuronal stem cells to aggregate is well *** of differentiated neurons,particularly those of the brain regions such as the cortex,has been reported more recently(Hasan et al.,2019;Ming et al.,2020).However,the tendency of these cells to aggregate may play a significant role in the brain’s response to injury,and may also be important in developing regenerative therapies to treat brain *** types of injury,including stroke and trauma,result in formation of liquid-filled cavities in the brain(Kazim et al.,2011;Moreau et al.,2012).Cavities are also produced by resection surgery in patients suffering from epilepsy or by surgical brain tumor *** cavitation represents a loss of neural circuitry and therefore leads to deficits in function and behavior.

关键词： al. epilepsy Neuron

Explicit Traveling Wave Solutions to Nonlinear Evolution Equations

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Chinese Annals of Mathematics,Series B 2011年第6期32卷 929-964页

作者： Linghai ZHANG Department of Mathematics Lehigh University 14 East Packer Avenue Bethlehem Pennsylvania 18015 USA

First of all,some technical tools are *** the author studies explicit traveling wave solutions to nonlinear dispersive wave equations,nonlinear dissipative dispersive wave equations,nonlinear convection equations,nonl... 详细信息

关键词： Explicit traveling wave solutions Nonlinear partial differential eauations Reduction of order