bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability and Synthesis Issues of Robust Control With Fuzzy Logic Fusion
Authors: Chen Zheng , Hope Tony , Sadek Hassan , Smith Graham 
Published: February 2021

Abstract
Non-linearity and uncertainty are two major issues which trouble the control system design. During past decades, many non-linear control approaches and robust control approaches have been developed to tackle these issues. This paper discusses an alternative approach for designing a control system for a dynamic process with some kind of non-linearity and uncertainties. This approach embeds fuzzy-logic-based inference mechanism into a linear robust control framework to achieve a robust property within the whole operating region of a dynamic process. In this paper, firstly, a T-S type global model of a non-linear process which engages the format suitable for robust system analysis and synthesis is presented. Based on the assumption that the control system developed hires the same fuzzy logic inference mechanism for controller fusion, a stability condition for the fuzzy-logic-based control system has been achieved and an approach of robust stability synthesis via linear matrix inequalities (LMI) discussed. The simulation results of a design example (an end milling process control) show that robust stability and satisfactory performance have been reached.
Electromagnetic Levitation: A Nonlinear Analysis Approach
Authors: Ciocirlan Bogdan O. , Marghitu Dan B. , Beale David G. , Overfelt Ruel A. 
Published: February 2021

Abstract
In this paper, a nonlinear dynamics approach for analyzing the time evolution of an electromagnetically levitated droplet is proposed. The analysis was performed on the experimental data acquired from a levitation instrument developed by Space Power Institute at Auburn University. Several nonlinear dynamics tools were applied in order to reveal whether the time evolution of the droplet is deterministic (periodic, quasiperiodic or chaotic) or random. Quantities characterizing time series data such as the attractor dimension or the largest Lyapunov exponent were computed. It was mainly found that the underlying dynamics of the molten droplet is in fact chaotic.
On Time Domain Identification and Sensitivity Analysis Using Orthogonal Functions
Authors: Pacheco Ricardo P. , Steffen Valder 
Published: February 2021

Abstract
Orthogonal functions can be integrated using a so-called operational matrix. This characteristic transforms a set of second order differential equations into algebraic equations which are easily solved. In the case of mechanical systems the unknown parameters can be determined from these algebraic equations. For this purpose, the input and output signals have to be expanded in time orthogonal functions. This technique can be also applied for sensitivity analysis. In this paper Fourier series, Legendre polynomials, Jacobi polynomials, Chebyshev series, Block-Pulse functions and Walsh functions are used to expand the signals as time functions.
A Nonlinear Observer for Synchronization of Chaotic Systems
Authors: Walker David M. , Mees Alistair I. 
Published: February 2021

Abstract
We present a method for the design of nonlinear observers of continuous time chaotic systems. We argue that the synchronization of chaotic systems can usefully be viewed as an observer problem. The method incorporates output feedback, and Lyapunov stability arguments are used to give conditions on whether synchronization is possible.
Nonlinear Feedback Law for Tracking Control of DC-Actuated Robots
Authors: Beji L. , Pascal M. 
Published: February 2021

Abstract
In this paper, a nonlinear feedback law for tracking control of robots is proposed. The dynamic of actuators and only position measurements are taking into account to design the control law. The stability results are obtained from the passivity property of the system, and using singular perturbations techniques. Simulation tests are performed on a three degrees-of-freedom serial robot to illustrate our control law.
An Overview of Some Non-Traditional Neural-Network Training Strategies for Seismic-Response Suppression of Building Structures
Authors: Liut Daniel A. , Matheu Enrique E. , Mook Dean T. , Singh Mahendra P. 
Published: February 2021

Abstract
Two novel methods to generate efficient control laws for neural-network controllers used to reduce the response of buildings under seismic-induced ground excitations are discussed. The training schemes do not rely on the emulation of the structure to be controlled. The proposed controller has a feedback structure, utilizing a limited set of response quantities. A shear building actuated at its top by a tuned-mass damper is utilized to demonstrate the effectiveness of the controller. The building model includes hysteretic characteristics. For training purposes, an ensemble of synthetically generated ground-motion time histories, with appropriate site spectrum characteristics, have been used. The performance of the trained controller is then evaluated for three different historic ground-acceleration records that do not belong to the training set of time histories. The numerical simulations show the effectiveness of the proposed scheme with modest control requirements.
Nonlinear Model Reference Adaptive Control for Limit Cycle Oscillations
Authors: Ko Jeonghwan , Akella Maruthi R. , Junkins John L. , Strganac Thomas W. , Kurdila Andrew J. 
Published: February 2021

Abstract
Recently derived structured model reference adaptive control (MRAC) method is employed for the active suppression of limit cycle oscillations for a typical wing section with structural nonlinearity. The structured MRAC takes advantage of the specific structure of governing equations for the general mechanical systems. The adaptive control method is implemented and tested in wind tunnel experiment to validate the performance. For comparison, results obtained with adaptive feedback linearization are also presented.
Nonlinear Control Methods for High Energy Limit Cycle Oscillations
Authors: Strganac Thomas , Junkins John , Ko J. , Kurdila Andrew J. 
Published: February 2021

Abstract
Limit cycle oscillations, as they manifest in high performance fighter aircraft, remain an area of scrutiny by the aerospace industry and military. Tools for the simulation and prediction of the onset for limit cycle oscillations have matured significantly over the years. Suprisingly, less progress has been made in the derivation of active control methodologies for these inherently nonlinear dynamic phenomena. Even in the cases where it is known that limit cycle oscillation may be observed in particular flight regimes, and active control methodologies are employed to attenuate response, there are very few analytical results that study the stability of the closed loop system. In part, this may be attributed to the difficulty in characterizing the nature of the contributing nonlinear structural and nonlinear aerodynamic interactions that account for the motion. This paper reviews recent progress made by the authors in the derivation, development and implementation of nonlinear control methodologies for a class of low speed flutter problems. Both analytical and experimental results are summarized. Directions for future study, and in particular technical barriers that must be overcome, are summarized in the paper.
Distributed Versus Concentrated Flexibility in Shape Control of Lifting Surfaces: The “Belt-Rib” Structural Concept
Authors: Campanile Lucio Flavio , Sachau Delf 
Published: February 2021

Abstract
The “mechatronic” way of dealing with the issue of structure geometry control, based on mechanical systems with hinges, bearing and discrete actuators, cannot easily cope with the strict requirements of aircraft design.
In this paper a “structronic” concept for airfoils with variable camber is presented, in which the desired geometry changes are achieved through structural flexibility and no moveable parts are needed.
A short introduction to the “structronic” approach to structure adaptation in general and to airfoil shape control in particular opens the paper, with some emphasis on the role of solid-state actuators. The description of the new structural concept (the belt-rib concept) follows, with the application to the case of a landing flap with variable camber.
Some results of FEM simulations as well as of experimental tests on different prototypes — one of them equipped with shape memory wires as actuators — are also included in the paper. The results provide a first feasibility proof of the new concept and encourage further work.
An Improved Fuzzy Integration Control Method Without Quantification
Authors: Zhang Weiguo , Duan Fuhai , Zhao Zhong , Yang Xiangzhong 
Published: February 2021

Abstract
In this paper, dynamic inversion method is used to decouple a multivariable system. Then by canceling traditional fuzzy quantification operation and based on analytical optimal correction function and on-line interpolation, two improved design methods for fuzzy controllers are provided. A class of nonlinear PID controllers is formed when traditional PI controllers are joined after the improved fuzzy controllers immediately. Both methods can essentially remove the system’s steady-state errors and flutter phenomenon, which are caused by the fuzzy quantification errors and regulating dead bands in the traditional fuzzy control system. Finally, by combining the improved fuzzy control methods with the dynamic inversion method, a kind of dynamic decoupling fuzzy integration control method for multivariable systems is constructed. The integration control system designed by this method possesses not only excellent decoupling results and better control performance, but also stronger adaptability to the parameter changes in the system. In addition, an example and its simulation results are also provided.
On- Versus Off-Bike Power Training in Professional Cyclists: A Randomized Controlled Trial
Authors: Valenzuela Pedro L. , Gil-Cabrera Jaime , Talavera Eduardo , Alejo Lidia B. , Montalvo-Pérez Almudena , Rincón-Castanedo Cecilia , Rodríguez-Hernández Iván , Lucia Alejandro , Barranco-Gil David 
Published: February 2021

Purpose: To compare the effectiveness of resistance power training (RPT, training with the individualized load and repetitions that maximize power output) and cycling power training (CPT, short sprint training) in professional cyclists. Methods: The participants (20 [2] y, peak oxygen uptake 78.0 [4.4] mL·kg−1·min−1) were randomly assigned to perform CPT (n = 8) or RPT (n = 10) in addition to their usual training regime for 7 weeks (2 sessions/wk). The training loads were continuously registered using the session rating of perceived exertion. The outcomes included endurance performance (8-min time trial and incremental test), as well as measures of muscle strength/power (1-repetition maximum and mean maximum propulsive power on the squat, hip thrust, and lunge exercises) and body composition (assessed by dual-energy X-ray absorptiometry). Results: No between-group differences were found for training loads or for any outcome (P > .05). Both interventions resulted in increased time-trial performance, as well as in improvements in other endurance-related outcomes (ie, ventilatory threshold, respiratory compensation point; P < .05). A significant or quasi-significant increase (P = .068 and .047 for CPT and RPT, respectively) in bone mineral content was observed after both interventions. A significant reduction in fat mass (P = .017), along with a trend (P = .059) toward a reduced body mass, was observed after RPT, but not CPT (P = .076 for the group × time interaction effect). Significant benefits (P < .05) were also observed for most strength-related outcomes after RPT, but not CPT. Conclusion: CPT and RPT are both effective strategies for the improvement of endurance performance and bone health in professional cyclists, although the latter tends to result in greater improvements in body composition and muscle strength/power.
Metal-induced stress in survivor plants following the end-Permian collapse of land ecosystems
Authors: Chu Daoliang , Corso Jacopo Dal , Shu Wenchao , Song Haijun , Wignall Paul B. , Grasby Stephen E. , Schootbrugge Bas van de , Zong Keqing , Wu Yuyang , Tong Jinnan 
Published: February 2021

AbstractTeratological spores and pollen are widespread in sediments that record the Permian-Triassic mass extinction. The malformations are thought to be the result of extreme environmental conditions at that time, but the mutagenic agents and the precise timing of the events remain unclear. We examined the abundance of teratological sporomorphs and metal concentrations in a Permian-Triassic tropical peatland succession of southwestern China. We find a significant peak of spore tetrads of lycopsid plants (as much as 19% of all sporomorphs) coeval with increases in Cu and Hg concentrations above the main terrestrial extinction interval, which marks the loss of Permian Gigantopteris forests, increased wildfire activity, and the disappearance of coal beds. Thus, in tropical peatlands, mutagenesis affected only surviving plants. Mutagenesis was likely caused by metal toxicity, linked to increased Hg and Cu loading, but was not itself a direct cause of the terrestrial crisis.
Apatite nanoparticles in 3.46–2.46 Ga iron formations: Evidence for phosphorus-rich hydrothermal plumes on early Earth
Authors: Rasmussen Birger , Muhling Janet R. , Suvorova Alexandra , Fischer Woodward W. 
Published: February 2021

AbstractPhosphorus is an essential nutrient that is thought to have regulated primary productivity in global oceans after the advent of oxygenic photosynthesis. The prime source of seawater phosphorus is regarded to be continental weathering of phosphate minerals. Ancient seawater phosphorus concentrations have been constrained using the phosphorus content of iron-rich chemical sediments—banded iron formations (BIFs); however, the removal processes and depositional phases remain unclear. Here we report that nanometer-sized apatite crystals (&lt;500 nm) are ubiquitous in 3.46–2.46 Ga BIFs and cherts from the Kaapvaal (South Africa) and Yilgarn, and Pilbara (Western Australia) cratons. The apatite is uniformly dispersed in a chemical sediment comprising greenalite nanoparticles, which were encased in very early diagenetic silica cement that limited compaction and chemical reactions. The lack of organic carbon (below detection; &lt;0.3 wt%) and absence of primary iron oxides implies that the phosphorus was not derived from the degradation of organic matter or seawater scavenging by oxide particles. Instead, the occurrence of apatite in sediments derived from hydrothermally sourced Fe2+ and SiO2(aq) suggests that phosphorus too was derived from vent plumes. Today, seawater P is rapidly removed from vent fluids due to scavenging by oxidized Fe2+. However, prior to the Great Oxidation Event (2.45–2.32 Ga), dissolved phosphorus released during anoxic alteration of seafloor basalts escaped the iron-oxidation trap. Our results point to the existence of a submarine hydrothermal flux of dissolved phosphorus that supplied nutrients to the early anoxic oceans. High amounts of seawater P may help to explain why phosphorus is ubiquitous in cell biology—it was not limiting during the origin and early evolution of life.
Recalibrating Rodinian rifting in the northwestern United States
Authors: Brennan Daniel T. , Li Zheng-Xiang , Rankenburg Kai , Evans Noreen , Link Paul K. , Nordsvan Adam R. , Kirkland Christopher L. , Mahoney J. Brian , Johnson Tim , McDonald Bradley J. 
Published: February 2021

Abstract
A lack of precise age constraints for Neoproterozoic strata in the northwestern United States (Washington State), including the Buffalo Hump Formation (BHF), has resulted in conflicting interpretations of Rodinia amalgamation and breakup processes. Previous detrital zircon (DZ) studies identified a youngest ca. 1.1 Ga DZ age population in the BHF, interpreted to reflect mostly first-cycle sourcing of unidentified but proximal magmatic rocks intruded during the amalgamation of Rodinia at ca. 1.0 Ga. Alternatively, the ca. 1.1 Ga DZ population has been suggested to represent a distal source with deposition occurring during the early phases of Rodinia rifting, more than 250 m.y. after zircon crystallization. We combined conventional laser-ablation split-stream analyses of U-Pb/Lu-Hf isotopes in zircon with a method of rapid (8 s per spot) U-Pb analysis to evaluate these opposing models. Our study of ∼2000 DZ grains from the BHF identified for the first time a minor (∼1%) yet significant ca. 760 Ma population, which constrains the maximum depositional age. This new geochronology implies that the BHF records early rift deposition during the breakup of Rodinia and correlates with sedimentary rocks found in other late Tonian basins of southwestern Laurentia.
Is the Eastern Denali fault still active?
Authors: Choi Minhee , Eaton David W. , Enkelmann Eva 
Published: February 2021

AbstractThe Denali fault, a transcurrent fault system that extends from northwestern Canada across Alaska toward the Bering Sea, is partitioned into segments that exhibit variable levels of historical seismicity. A pair of earthquakes (M 6.2 and 6.3) on 1 May 2017, in proximity to the Eastern Denali fault (EDF), exhibited source mechanisms and stress conditions inconsistent with expectations for strike-slip fault activation. Precise relocation of ∼1500 aftershocks revealed distinct fault strands that are oblique to the EDF. Calculated patterns of Coulomb stress show that the first earthquake likely triggered the second one. The EDF parallels the Fairweather transform, which separates the obliquely colliding Yakutat microplate from North America. In our model, inboard transfer of stress is deforming and shortening the mountainous region between the EDF and the Fairweather transform. This is supported by historical seismicity concentrated southwest of the EDF, suggesting that it now represents a structural boundary that controls regional deformation but is no longer an active fault.
Absence of relationship between serum cortisol and critical illness in premature infants
Authors: Prelipcean Irina , Wynn James Lawrence , Thompson Lindsay , Burchfield David James , James-Woodley Laurence , Chase Philip B , Barnes Christopher P , Bernier Angelina 
Published: February 2021

BackgroundInadequate cortisol production in response to critical illness in extremely preterm infants may exacerbate poor outcomes. Despite commonly measuring cortisol concentration and administering hydrocortisone for presumed adrenal insufficiency, the relationship between serum cortisol concentration and illness severity remains unclear in this unique population.ObjectiveTo determine the relationship between cortisol concentrations and illness severity as measured by the Score for Neonatal Acute Physiology II, neonatal Sequential Organ Failure Assessment and Vasoactive-Inotropic Score in premature infants.Design/MethodsThis retrospective, single-center cohort study included preterm infants born <30 weeks gestational age admitted to a level IV neonatal intensive care unit (NICU) between June 2011 and July 2018, who had a serum cortisol obtained for clinical indications before 36 weeks PMA. Demographic data were collected on infants and mothers. Nine clinical variables were identified a priori that could potentially modify cortisol concentration including critical illness. Univariate and multivariable analyses determined the relationship between cortisol concentration and each of these variables.ResultsA total of 224 preterm infants with pretreatment serum cortisol concentration met criteria for inclusion. The median (IQR) gestational age at birth was 25 weeks (24, 26) and at cortisol measurement was 26 weeks (25, 28). The median cortisol was 13.3 ug/dL. Non-survivors had the highest values. Cortisol concentration did not correlate with any of the selected illness severity scores.Conclusion(s)Cortisol concentrations in extremely preterm infants did not correlate with illness severity regardless of gestational age. Further studies are needed to identify clinically useful mediators of adrenal dysfunction and to guide clinical management.
Statin use and clinical outcomes in patients with COVID-19: An updated systematic review and meta-analysis
Authors: Pal Rimesh , Banerjee Mainak , Yadav Urmila , Bhattacharjee Sukrita 
Published: February 2021

AbstractPurposeObservations studies have shown that prior use of statins is associated with a reduced risk of adverse clinical outcomes in patients with COVID-19. However, the available data are limited, inconsistent and conflicting. Besides, no randomised controlled trial exists in this regard. Hence, the present meta-analysis was conducted to provide an updated summary and collate the effect of statin use on clinical outcomes in COVID-19 using unadjusted and adjusted risk estimates.MethodsPubMed, Scopus and Web of Science databases were systematically searched using appropriate keywords till December 18 2020, to identify observational studies reporting clinical outcomes in COVID-19 patients using statins versus those not using statins. Prior and in-hospital use of statins were considered. Study quality was assessed using the Newcastle-Ottawa Scale. Unadjusted and adjusted pooled odds ratio (OR) with 95% CIs were calculated.ResultsWe included 14 observational studies pooling data retrieved from 19 988 patients with COVID-19. All the studies were of high/moderate quality. Pooled analysis of unadjusted data showed that statin use was not associated with improved clinical outcomes (OR 1.02; 95% CI 0.69 to 1.50, p=0.94, I2=94%, random-effects model). However, on pooling adjusted risk estimates, the use of statin was found to significantly reduce the risk of adverse outcomes (OR 0.51; 95% CI 0.41 to 0.63, p&lt;0.0005, I2=0%, fixed-effects model).ConclusionsStatin use is associated with improved clinical outcomes in patients with COVID-19. Individuals with multiple comorbidities on statin therapy should be encouraged to continue the drug amid the ongoing pandemic.
Human cytomegalovirus infection is associated with stroke in women: the US National Health and Nutrition Examination Survey 1999–2004
Authors: Zhen Juanying , Zeng Minyan , Zheng Xiaodan , Qiu Hongyan , Cheung Bernard Man Yung , Xu Aimin , Wu Jun , Li Chao 
Published: February 2021

AbstractBackgroundIncreasing evidence indicated that infection factors play important roles in stroke development. Human cytomegalovirus (HCMV) infection was positively associated with atherosclerosis and hypertension which are stroke risk factors. Therefore, we aimed to explore the relationship between HCMV infection and stroke using the data of US National Health and Nutrition Examination Survey (NHANES).MethodsWe analysed data on 2844 men and 3257 women in the NHANES 1999–2004. We included participants aged 20–49 years who had valid data on HCMV infection and stroke.Results54.1% of participants had serological evidence of HCMV infection and 0.8% of them had a previous diagnosis of stroke. There were ethnic differences in the prevalence of HCMV seropositivity (p&lt;0.001). There was no significant association between HCMV seropositivity and stroke in men in any of the models. In women, HCMV seropositivity was associated with stroke before adjustment (OR=3.45, 95% CI 1.09 to 10.95, p=0.036). After adjusting for race/ethnicity, the association remained significant (OR=4.40, 95% CI 1.37 to 14.09, p=0.014). After further adjustment for body mass index, diabetes, hypercholesterolaemia, hypertension, alcohol consumption, smoking and physical activity, the association still existed (OR=3.58, 95% CI 1.14 to 11.25, p=0.030). The association was significant consistently in adjusted model for age (OR=3.39, 95% CI 1.08 to 10.64, p=0.037).ConclusionsWe found a strong association between HCMV and stroke in women from the nationally representative population-based survey. This provide additional motivation for undertaking the difficult challenge to reduce the prevalence of stroke.