•Prandtl-Ishlinskii hysteresis model can provide better performance.•The feedback controller reduces the hysteresis non-linearity.•Fuzzy logic controller can minimize the low amplitude vibration.
The ...piezoelectric actuators are widely used to realize high precise motion with fractional force and torque in both linear and rotary joints of the micro-systems. The control system plays a major role on overall dynamics including positioning and tracking objectives in piezoelectric actuator based micro-systems. The piezoelectric actuator inherently has its own non-linear behaviour such as hysteresis, creep, thermal drift and vibration which deteriorates overall performances including stability of the developed systems. This article reviews the various efforts for solving the major issues such as hysteresis and creep. It has been inferred that generalized control solution is not appropriate for all kind of piezoelectric actuators. Hence it has been observed that appropriate control strategies has to be implemented for reducing tracking error, position error and non-linear characteristic of piezoelectric actuator namely hysteresis and creep.
Carbon Nanotubes (CNTs) and nano Zero-Valent Iron (nZVI) particles, as well as two nanocomposites based on these novel nanomaterials, were employed as nano-adsorbents for the removal of hexavalent ...chromium, selenium and cobalt, from aqueous solutions. Nanomaterials characterization included the determination of their point of zero charge and particle size distribution. CNTs were further analyzed using scanning electron microscopy, thermogravimetric analysis and Raman spectroscopy to determine their morphology and structural properties. Batch experiments were carried out to investigate the removal efficiency and the possible competitive interactions among metal ions. Adsorption was found to be the main removal mechanism, except for Cr(VI) treatment by nZVI, where reduction was the predominant mechanism. The removal efficiency was estimated in decreasing order as CNTs-nZVI > nZVI > CNTs > CNTs-nZVI* independently upon the tested heavy metal. In the case of competitive adsorption, Cr(VI) exhibited the highest affinity for every adsorbent. The preferable Cr(VI) removal was also observed using binary systems of the tested metals by means of the CNTs-nZVI nanocomposite. Single species adsorption was better described by the non-linear Sips model, whilst competitive adsorption followed the modified Langmuir model. The CNTs-nZVI nanocomposite was tested for its reusability, and showed high adsorption efficiency (the qmax values decreased less than 50% with respect to the first use) even after three cycles of use.
•CNTs-nZVI composite performances are strictly related to the manufacturing process.•The used nano-adsorbents showed remarkable selectivity towards Cr(VI).•CNTs-nZVI composite can be re-used after three cycles of metals recovery.
The current article deals with the nonlinear free vibration of nanocomposite circular plates reinforced with graphene platelets (GPL). The functionally graded (FG) plate is considered over a three ...parameter non-linear elastic foundation. In this research, three types of gradings are assumed for reinforcing the plate by GPLs. The Halpin-Tsai micromechanical rule is exploited to obtain the elastic modulus of the plate. The first order shear deformation plate theory associated with the nonlinear strain-displacement relations are applied to extract the governing motion equations. The generalized differential quadrature (GDQ) method is implemented to solve the equations of motion in the plate domain. Furthermore, an iterative displacement control technique associated with the weighted residual technique are used to linearize the present problem and obtain the linear and nonlinear frequencies. After examining the validation study, some parametric studies are tabulated and plotted to recognize the effects of the boundary condition, distribution types of GPL, GPL weight fraction, geometrical parameters, and elastic foundation parameters on the linear and non-linear free vibration behaviour of structure. It is shown that maximum frequencies of the plate belong to the FG-X case and the minimum ones are obtained in FG-O type.
The global movement for ecosystem restoration has gained momentum in response to the Bonn Challenge (2010) and the UN Decade on Ecosystem Restoration (UNDER, 2021–2030). While several science‐based ...guidelines exist to aid in achieving successful restoration outcomes, significant variation remains in the outcomes of restoration projects. Some of this disparity can be attributed to unexpected responses of ecosystem components to planned interventions.
Given the complex nature of ecosystems, we propose that concepts from Complex Systems Science (CSS) that are linked to non‐linearity, such as regime shifts, ecological resilience and ecological feedbacks, should be employed to help explain this variation in restoration outcomes from an ecological perspective.
Our framework, Explore Before You Restore, illustrates how these concepts impact restoration outcomes by influencing degradation and recovery trajectories. Additionally, we propose incorporating CSS concepts into the typical restoration project cycle through a CSS assessment phase and suggest that the need for such assessment is explicitly included in the guidelines to improve restoration outcomes.
To facilitate this inclusion and make it workable by practitioners, we describe indicators and methods available for restoration teams to answer key questions that should make up such CSS assessment. In doing so, we identify key outstanding science and policy tasks that are needed to further operationalize CSS assessment in restoration.
Synthesis and applications. By illustrating how key Complex Systems Science (CSS) concepts linked to non‐linear threshold behaviour can impact restoration outcomes through influencing recovery trajectories, our framework Explore Before You Restore demonstrates the need to incorporate Complex Systems thinking in ecosystem restoration. We argue that inclusion of CSS assessment into restoration project cycles, and more broadly, into international restoration guidelines, may significantly improve restoration outcomes.
o
El movimiento global para la restauración de ecosistemas ha cobrado impulso en respuesta al Desafío de Bonn (2010) y el Decenio de las Naciones Unidas sobre la Restauración de Ecosistemas (UNDER, 2021–2030). Aunque existen varias pautas con base científica para ayudar a lograr resultados satisfactorios en la restauración ecológica, sigue habiendo una variación significativa en los resultados de los proyectos de restauración. Parte de esta disparidad puede atribuirse a respuestas inesperadas de los componentes del ecosistema a las intervenciones hechas/realizadas.
Dada la naturaleza compleja de los ecosistemas, proponemos que se empleen conceptos de la Teoría de los Sistemas Complejos (TSC) que enfatizan la no‐linealidad, como por ejemplo, los cambios de régimen, la resiliencia ecológica y las retroalimentaciones ecológicas, para ayudar a explicar la variación en los resultados de la restauración desde una perspectiva ecológica.
Nuestro marco teórico, Explora Antes de Restaurar, ilustra cómo estos conceptos influyen en las trayectorias de degradación y recuperación ecológicas. Proponemos incorporar los conceptos de la TSC en el ciclo típico de planificación, ejecución y adaptación de los proyectos para mejorar los resultados de la restauración ecológica.
Para facilitar esta inclusión y hacerla útil y viable para los profesionales y ejecutores de proyectos de restauración, describimos los indicadores y métodos disponibles para que los equipos de restauración respondan a las preguntas clave que deberían formar parte de dicha evaluación de la TSC. Al hacerlo, identificamos las principales tareas científicas y políticas pendientes que son necesarias para operacionalizar aún más la evaluación de la TSC en la restauración.
Síntesis y aplicaciones. Nuestro marco teórico Explora Antes de Restaurar demuestra la necesidad de incorporar el pensamiento de la Teoría de Sistemas Complejos en la restauración de ecosistemas. La inclusión de la evaluación de la TSC en los ciclos de elaboración y ejecución de proyectos de restauración, y de manera más amplia, en las pautas internacionales de restauración, podría mejorar significativamente los resultados de la restauración ecológica.
Abstrato
O movimento global para a restauração de ecossistemas ganhou força em resposta ao Desafio de Bonn (2010) e à Década da ONU para a Restauração de Ecossistemas (UNDER, 2021–2030). Embora existam várias diretrizes baseadas na ciência para auxiliar na obtenção de resultados bem‐sucedidos na restauração, ainda existe uma variação significativa nos resultados de projetos de restauração. Parte dessa disparidade pode ser atribuída a respostas inesperadas de componentes do ecossistema às intervenções planejadas.
Dada a natureza complexa dos ecossistemas, propomos que conceitos da Ciência de Sistemas Complexos (CSS) vinculados à não linearidade, como mudanças de regime, resiliência ecológica e feedbacks ecológicos, devam ser utilizados para ajudar a explicar essa variação nos resultados da restauração do ponto de vista ecológico.
Nossa proposta e modelo, Explore Antes de Restaurar, ilustra como esses conceitos impactam os resultados da restauração, influenciando as trajetórias de degradação e recuperação. Além disso, propomos a incorporação de conceitos de CSS no ciclo típico de projetos de restauração por meio de uma fase de avaliação de CSS, e sugerimos que a necessidade dessa avaliação seja explicitamente incluída nas diretrizes para melhorar os resultados da restauração.
Para facilitar essa inclusão e torná‐la viável para os profissionais da área, descrevemos indicadores e métodos disponíveis para equipes de restauração responderem a perguntas‐chave que devem compor essa avaliação de CSS. Ao fazer isso, identificamos tarefas científicas e políticas essenciais que são necessárias para operacionalizar ainda mais a avaliação de CSS na restauração.
Síntese e aplicações. Ao ilustrar como conceitos‐chave de CSS vinculados ao comportamento não linear podem impactar os resultados da restauração ao influenciar trajetórias de recuperação, nossa proposta de modelo Explore Antes de Restaurar demonstra a necessidade de incorporar uma mentalidade de Sistemas Complexos na restauração de ecossistemas. Argumentamos que a inclusão da avaliação de CSS nos ciclos de projetos de restauração e, de forma mais ampla, nas diretrizes internacionais de restauração, pode melhorar significativamente os resultados da restauração.
Abstrakt
Die weltweite Bewegung zur Wiederherstellung von Ökosystemen hat an Dynamik gewonnen als Reaktion auf die Bonner Herausforderung (2010) und das UN‐Jahrzehnt für die Wiederherstellung von Ökosystemen (UNDER, 2021–2030). Obwohl mehrere wissenschaftsbasierte Leitlinien existieren, um erfolgreiche Wiederherstellungsergebnisse zu erzielen, bleibt eine erhebliche Variation in den Ergebnissen von Wiederherstellungsprojekten bestehen. Ein Teil dieser Diskrepanz kann auf unerwartete Reaktionen der Ökosystemkomponenten auf geplante Interventionen zurückgeführt werden.
Angesichts der komplexen Natur von Ökosystemen schlagen wir vor, Konzepte aus der Komplexen Systemwissenschaft (CSS), die mit Nichtlinearität verbunden sind, wie Regimewechsel, ökologische Resilienz und ökologische Rückkopplungen, einzusetzen, um diese Variation in den Ergebnissen der Wiederherstellung aus ökologischer Sicht zu erklären.
Unser Rahmen, ‘Erkunden Sie bevor Sie wiederherstellen’, veranschaulicht, wie diese Konzepte die Ergebnisse der Wiederherstellung beeinflussen, indem sie Degradations‐ und Erholungstrajektorien beeinflussen. Darüber hinaus schlagen wir vor, CSS‐Konzepte in den typischen Wiederherstellungsprojektzyklus durch eine CSS‐Bewertungsphase zu integrieren, und schlagen vor, dass die Notwendigkeit einer solchen Bewertung explizit in die Leitlinien aufgenommen wird, um die Wiederherstellungsergebnisse zu verbessern.
Um diese Integration zu erleichtern und für Praktiker umsetzbar zu machen, beschreiben wir Indikatoren und Methoden, die für Restaurationsteams verfügbar sind, um Schlüsselfragen zu beantworten, die diese CSS‐Bewertung ausmachen sollten. Auf diese Weise ermitteln wir ausstehende hervorragende wissenschaftliche und politische Aufgaben die erforderlich sind um die CSS‐Bewertung in der Wiederherstellung weiter zu operationalisieren.
Synthese und Anwendungen. Indem wir veranschaulichen, wie sich CSS‐Schlüsselkonzepte die mit nichtlinearem Schwellenverhalten verbunden sind auf die Wiederherstellungsergebnisse auswirken können durch Beeinflussung von Erholungstrajektorien, verdeutlicht unser Rahmen „Erkunden Sie bevor Sie wiederherstellen“ die Notwendigkeit einer Integration des komplexen Systemdenkens in die Ökosystem‐Restaurierung. Wir argumentieren, dass die Einbeziehung der CSS‐Bewertung in die Zyklen des Restaurierungsprojekts, im weiteren Sinne in internationale Restaurationsrichtlinien, die Wiederherstellungsergebnisse signifikant verbessern kann.
Abstrait
Le mouvement mondial pour la restauration des écosystèmes a pris de l'ampleur grâce au Défi de Bonn (2010) et à la Décennie des Nations Unies pour la Restauration des Écosystèmes (UNDER, 2021–2030). Bien qu'il existe plusieurs directives basées sur des approches scientifiques pour des projets de restauration réussis, une variation significative persiste dans les résultats des projets de restauration, qui s'explique en partie par des réponses inattendues des composants de l'écosystème aux interventions planifiées.
Compte tenu de la nature complexe des écosystèmes, nous proposons que des concepts de la Science des Systèmes Complexes (CSS) liés à la non‐linéarité, tels que les changements de régime, la résilience écologique et les rétroactions écologiques, soient utilisés pour aider à expliquer cette variation dans les résultats de restauration d'un point de vue écologique.
Notre cadre, Explore Before You Restore, illustre comment ces concepts impactent les résultats de restauration en influençant les trajectoires
The light output produced by light ions ( Z≤4) in CsI(Tl) crystals is studied over a wide range of detected energies (E≤300MeV). Energy-light calibration data sets are obtained with the 10 cm ...crystals in the recently upgraded High-Resolution Array (HiRA10). We use proton recoil data from 40,48Ca + CH2 at 28 MeV/u, 56.6 MeV/u, 39 MeV/u and 139.8 MeV/u and data from a dedicated experiment with direct low-energy beams. We also use the punch through points of p, d, and t particles from 40,48Ca + 58,64Ni, 112,124Sn collisions reactions at 139.8 MeV/u. Non-linearities, arising in particular from Tl doping and light collection effects in the CsI crystals, are found to significantly affect the light output and therefore the calibration of the detector response for light charged particles, especially the hydrogen isotopes. A new empirical parametrization of the hydrogen light output, L(E,Z=1,A), is proposed to account for the observed effects. Results are found to be consistent for all 48 CsI(Tl) crystals in a cluster of 12 HiRA10 telescopes.
The paper investigates the cyclic response of soft cellular materials undergoing repeated local instabilities. Our focus is mainly on the coupling between material non-linearities, geometric ...non-linearity as well as defects induced by 3D printing. Two paradigmatic lattices (triangular and hexagonal), each with its own distinct deformation mode and defect sensitivity, are examined, and the emergence of as-built material and geometric defects in the form of microporosity, strut thickness reduction, and nodal dispersion is studied via computed tomography and optical analyses. Experiments are carried out on the base material and lattice specimens for given cycling strains and cycle ratios. Numerical models are developed to understand the individual role of the main constitutive aspects of the base material, e.g. damage, creep, and visco-elasticity, as well as to assess the role of defects in each architecture. The results show that the activation of local buckling combined with the engagement of material non-linearities has multiple outcomes. It leads to local storage of inelastic strain, which in turn perturbs the lattice geometry after the second cycle and severely impacts the subsequent response, e.g. softening; it reduces the tangent modulus at zero strain; and it also decreases the maximum and minimum cyclic stresses. The detriment is further fueled by geometric deviations caused by 3D printing. Furthermore, a theoretical model is presented to obtain stress bound estimates of the stabilized response, hence offering guidelines for the design of 3D printed soft metamaterials under cycling loading. The paper concludes with a systematic discussion on the coupled role of non-linearities (material and geometry) and defects, and on the accuracy of the numerical and theoretical models herein presented.
•The cyclic engagement of elastic instability is investigated in elastomeric lattices.•The role of as-built material and geometric defects in the cyclic response is quantified.•The interaction between defects, material and geometric non-linearity is unveiled.•A theoretical model is presented to predict stress bounds of the stabilized response.
•Temporal heterogeneity exists in the associations between metro ridership and the built environment.•Built environment variables have non-linear and threshold effects on metro ridership.•Distance to ...the city center and population density are strong predictors of metro ridership in the morning peak hour.•Employment density, enterprise density, and road density are strong predictors in the evening peak hour.•Critical TOD planning parameters are identified.
The metro is the backbone of the transport system in many cities. Analyzing the built-environment correlates of metro ridership is crucial for transit-oriented development (TOD) planning and practice. Although numerous studies went along this line, they have rarely considered the non-linearity and temporal heterogeneity in the association of metro ridership with the built environment. After collecting transit smart card data, geo-data, and mobile phone signal data, this study adopts the random forest model to reveal the complex association of hourly metro ridership in November 2019 in Chengdu (China) with the built environment in three times of day (i.e., morning peak, noon off-peak, and evening peak hours). Notably, the contribution of several variables, such as the number of station entrances/overpasses and parking density, has rarely been considered in the literature. The results confirm the presence of non-linearity and temporal heterogeneity in the aforementioned association. Access to the city center and population density are strong predictors of metro ridership in the morning peak hour, whereas employment density, enterprise density, and road density are strong predictors in the evening peak hour. There are great differences in the correlates of metro ridership in different periods. Critical TOD planning parameters are also identified from the partial dependence plots obtained from random forest modeling.
•We established a threshold model for data from REC by source in U.S.•Nonlinear relationship b/w REC by source and GDP.•The effect of REC on GDP depends REC by source used.•Effect is positive if U.S. ...use REC by source above a threshold.•Effect is negative if U.S. use REC by source below a threshold.
With the climate challenges and the depletion of fossil resources, the renewable energy option seems to be a wise choice; this renews the debate on the relationship between renewable energy sources consumption and economic growth. This study relies on a threshold effects regression model to explore and evaluate the non-linear relationship between the series in the United States during the period 1984Q1–2021Q3. Using the threshold detection method proposed by Hansen and Seo (2002), the results of this method show that the renewable energy sources consumption/GDP relationship is non-linear. They also reveal, for all the different sources, an optimal renewable energy sources consumption/GDP threshold of 5.535; 2.715; 1.988 and 8.925% for BIO, GEO, Solar and HPower, respectively. The results indicate the presence of mixed directions of causality between the renewable energy sources consumption and GDP, using the Threshold Vector Error Correction model (TVECM). The findings of this paper suggest that if the United States aim to realize positive economic growth from their investment to renewable energy, they need to surpass a certain threshold of renewable energy sources consumption.
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The main focus of this research is on improving the performance of dynamic systems with actuator non‐linearities and time‐varying disturbances. To this end, using the concept of finite‐time ...stability, a novel observer is presented to estimate the disturbances in systems with input non‐linearities. Then, introducing an innovative sliding manifold, a robust observer‐based technique is derived to guarantee the finite‐time stability of the sliding surface. Hence, the closed‐loop system would be stable in the presence of hard non‐linearities and time‐varying disturbances. The performance of the proposed approach was assessed in using a simulation study of two numerical examples. The obtained results and comparison with a conventional method confirmed the benefits of the suggested approach.
Clinical prediction models provide risk estimates for the presence of disease (diagnosis) or an event in the future course of disease (prognosis) for individual patients. Although publications that ...present and evaluate such models are becoming more frequent, the methodology is often suboptimal. We propose that seven steps should be considered in developing prediction models: (i) consideration of the research question and initial data inspection; (ii) coding of predictors; (iii) model specification; (iv) model estimation; (v) evaluation of model performance; (vi) internal validation; and (vii) model presentation. The validity of a prediction model is ideally assessed in fully independent data, where we propose four key measures to evaluate model performance: calibration-in-the-large, or the model intercept (A); calibration slope (B); discrimination, with a concordance statistic (C); and clinical usefulness, with decision-curve analysis (D). As an application, we develop and validate prediction models for 30-day mortality in patients with an acute myocardial infarction. This illustrates the usefulness of the proposed framework to strengthen the methodological rigour and quality for prediction models in cardiovascular research.
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