bluuebunny/crossref_metadata_2025 huggingface dataset:
Material and Microslip Damping in a Rotor Taking Gravity and Anisotropic Bearings Into Account
Authors: Wettergren Håkan L.
Published: February 2021

The paper is concerned with material and microslip damping in a rotor. The horizontal rotor is carried by anisotropic bearings, which means that the shaft feels three different frequencies, the rotational frequency and the difference and the sum of the rotational and vibrational frequencies. When material damping is studied these three frequencies lead to three different equivalent viscous damping constants and the dissipated energy can be solved analytically.

The rotor slot wedges in a turbine generator are used as an example of microslip damping. In this case the damping is non-linear and the results are obtained through numerical simulations.

The results show that these two different internal damping sources give both similarities and dissimilarities. The sign change and different magnitude of the dissipated energy running sub- or supercritical are the same. However the dissipated energy for material damping is not affected by gravity which microslip damping is.
A Nonlinear Tennis Racket Model With Modal Damping
Authors: Poggi Marc , Berlioz Alain , Dufour Régis
Published: February 2021

This article presents a model for predicting the response of a tennis racket under impact stress. Parameter identification and basic phenomena analysis are performed with mechanical models and experiments carried out on the frame, the ball, natural gut and aramid fiber string beds, and impacts of the ball on string beds supported by a rigid frame. The composite frame is modeled with beam finite elements and the string bed with a specific element able to take into account the nonlinear behavior arising from the string material and from the hardening geometric phenomenon. The frame is linear and is reduced with a dynamic condensation method and a modal basis enables the damping to be introduced by experimental modal damping ratios. Then experimental serves validate the predicted impact response of the tennis racket.
Velocity Jumps Induced by C0-Constraints
Authors: Glocker Christoph
Published: February 2021

Impacts in rigid body dynamics are characterized by the occurrence of impulsive forces leading to instantaneous changes in the velocities of the system. Such velocity jumps are usually associated with collisions of the bodies between each other or in interaction with the environment. Besides the collisions, there are other sources for velocity jumps, such as the restriction of a dynamic system to C0-submanifolds. This case will be discussed in the paper by an example. It will be shown that velocity jumps may occur, and that they may be interpreted as ordinary collisions at a priori unknown locations of the rigid body system. A solution method, based on a time scaling procedure, is proposed. This leads to equations, similar to those of classical dynamics, whereas the displacements are fixed. It will further be shown that any velocity jump which preserves kinetic energy may be interpreted as a reflection when the kinetic metric is used. This provides an alternative method to compute the post-impact velocities by a direct evaluation of the reflection law.
Impacts With Friction: Theory and Experiments
Authors: Pfeiffer Friedrich
Published: February 2021

Various models for impacts with friction have been proposed, the most successful ones taking into consideration a compression and an expansion phase in normal and tangential direction. Impulses are stored during compression and released with frictional losses during expansion. Stick-slip and detachment phenomena during the impact can be considered by complementarity rules.

A corresponding model for impacts with friction is presented and verified by measurements with an impact machine. In addition, some industry applications confirm the theory.
A Time Stepping Algorithm for Mechanical Systems With Unilateral Contacts
Authors: Stiegelmeyr Andreas , Pfeiffer Friedrich
Published: February 2021

The paper deals with a method to solve mechanical systems with unilateral contacts, numerically. The algorithm is based on a discretisation schema which fulfils the normal constraints on the position level. This prohibits drift phenomena and thus improves the numerical stability. Finally, the algorithm is applied to a roller coaster vehicle with 24 wheel–rail–contacts.
Identification of Impact Damping of Two Elastic Bodies
Authors: Hu Haiyan , Jin Dongping
Published: February 2021

The contact force of two impacting elastic bodies is widely modeled as the parallel combination of a nonlinear spring and a nonlinear dashpot. The restoring force of the nonlinear spring can be determined according to the Hertzian contact law in elasticity, while the model and corresponding parameters of the nonlinear damping force have to be identified through experiments. The current approaches of damping identification are based on the measured time histories of both contact force and relative approaching velocity of two impacting bodies. In this paper, a new technique is presented for the damping identification on the basis of measured time history of the contact force only. Hence, the tough problem of measuring the relative approaching velocity of two impacting bodies just before impact is removed. The efficacy test of the new technique is given in the paper through an example of identifying the impact damping of a pair of clamped beams.
A Note in Non-Intermittent Contact Problems of a Special Class of Ultrasonic Motors
Authors: Sattel Thomas , Hagedorn Peter
Published: February 2021

Contact problems play a key-role in ultrasonic motors. Our aim is the formulation of a contact model for stationary and non-stationary stator-rotor contact problems for a special class of non-intermittent ultrasonic motors. With the models proposed up to now, a detailed analysis of dynamic contact problems is only possible in a very limited manner. The simple contact model presented here can be used for numerical simulations and parameter studies and is verified by experimental studies carried out in our lab. First simulations show that, depending on the friction law, momentary perturbations can lead to self-excited vibrations in the rotor.
Stability and Synthesis Issues of Robust Control With Fuzzy Logic Fusion
Authors: Chen Zheng , Hope Tony , Sadek Hassan , Smith Graham
Published: February 2021

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

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

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

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.
Structural Damage Detection Using Modal Norms
Authors: Gawronski Wodek , Sawicki Jerzy T.
Published: February 2021

A modal H2 norm is used to detect structural damages. The norm is determined for each sensor location, and for modal modes of interest. The sensor norm detects the damage location, the modal norm detect the most damaged mode.
Nonlinear Feedback Law for Tracking Control of DC-Actuated Robots
Authors: Beji L. , Pascal M.
Published: February 2021

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

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

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

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

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

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.
Atmospheric pressure plasma reduction of copper oxide to copper metal
Authors: Lee Joyce , Williams Thomas S. , Hicks Robert F.
Published: February 2021

Copper oxide films were reduced to copper with an atmospheric pressure argon and hydrogen plasma at temperatures between 25 and 300 °C. A 50-nm-thick CuO layer on a Cu-coated Si wafer, 200 mm in diameter, was fully reduced by the plasma in 200 s at 200 °C. The activation energy for the reaction was found to be 3.7 kcal/mol. X-ray photoelectron spectroscopy confirmed that the copper oxide was reduced to metallic copper. Cross-sectional scanning electron microscopy revealed that voids appeared between the oxide and the base metal layer when the CuO was thicker than 20 nm. These voids remained at the interface after reduction of the copper oxide back to copper metal.
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

Teratological 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

Phosphorus 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 (<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; <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

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

The 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

Background

Inadequate 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.

Objective

To 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/Methods

This 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.

Results

A 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

Purpose

Observations 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.

Methods

PubMed, 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.

Results

We 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<0.0005, I2=0%, fixed-effects model).

Conclusions

Statin 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

Background

Increasing 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).

Methods

We 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.

Results

54.1% 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<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).

Conclusions

We 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.
Study of risk factors for intraoperative hypothermia during pediatric burn surgery
Authors: Hu Yaoqin , Tian Yangfan , Zhang Manqing , Zhao Jialian , Shu Qiang
Published: February 2021

Background

Intraoperative hypothermia (core temperature <36.0°C) is common during the perioperative period and can result in adverse consequences, especially in children. We aimed to determine the incidence of intraoperative hypothermia and its risk factors in pediatric patients during burn surgery.

Methods

In the present study we enrolled 197 pediatric patients with burn injury undergoing surgical debridement and skin grafting. Factors, such as total burn surface area (TBSA), were collected and analyzed to identify the potential risk factors for intraoperative hypothermia.

Results

The incidence of intraoperative hypothermia among all patients was 17.8%. Compared with patients with normothermia, children with hypothermia were associated with larger TBSA (25% vs 15%, p<0.001) and with less intraoperative active warming (34.28% vs 54.93%, p<0.05). In addition, compared with patients with moderate-degree burn, patients with severe and extremely severe burn were associated with much higher risk of intraoperative hypothermia [severe: odds ratio (OR)=3.805, 95% confidence interval (CI)=1.396-10.368, p=0.009; extremely severe: OR=6.933, 95% CI=2.604-18.462, p<0.001]. TBSA was the only independent risk factor that emerged as being strongly associated with intraoperative hypothermia (OR=1.068, p=0.001) and could be used to predict the occurrence of hypothermia when combined with other factors. TBSA for predicting intraoperative hypothermia by receiver operating characteristic (ROC) curve analysis showed a good predictive ability with an area under the ROC curve of 0.758.

Conclusion

TBSA is an important risk factor for intraoperative hypothermia in pediatric patients with burn.
Early Environmental Upheaval and the Risk for Schizophrenia
Authors: Paquin Vincent , Lapierre Mylène , Veru Franz , King Suzanne
Published: February 2021

Why does prenatal exposure to wars, natural disasters, urbanicity, or winter increase the risk for schizophrenia? Research from the last two decades has provided rich insight about the underlying chains of causation at play during environmental upheaval, from conception to early infancy. In this review, we appraise the evidence linking schizophrenia spectrum disorder to prenatal maternal stress, obstetric complications, early infections, and maternal nutrition and other lifestyle factors. We discuss putative mechanisms, including the maternal stress system, perinatal hypoxia, and maternal–offspring immune activation. We propose that gene–environment interactions, timing during development, and sex differentiate the neuropsychiatric outcomes. Future research should pursue the translation of animal studies to humans and the longitudinal associations between early exposures, intermediate phenotypes, and psychiatric disorders. Finally, to paint a comprehensive model of risk and to harness targets for prevention, we argue that risk factors should be situated within the individual's personal ecosystem.
Entre el Mercado y el Leviatán
Authors: Fuentes Fernando , Ponce Carlos
Published: February 2021

La crisis económica mundial, generada por la pandemia del Covid, ha disparado en muchos países, incluido Chile, la idea de que se requiere más Estado para ayudar a quienes no han recibido lo que merecen, tanto en la forma de oportunidades como de acceso a bienes y servicios que la sociedad ofrece. Es imposible desarrollar en este espacio un análisisexhaustivo de un tópico tan complejo. Más importante aún, la naturaleza del tema excede a la Economía y, por lo tanto, un tratamiento adecuado requiere de un análisis multidisciplinario. Aceptando estas limitaciones, el objetivo del presente artículo es exponer la complejidad de esta idea y alertar de que la misma, considerada como acertada en forma literal, puede resultar perniciosa para alcanzar el desarrollo humano. Continuar leyendo...
Consulta pública anteproyecto de ley sobre empleo público
Authors: Abarzúa Eduardo , Egaña Rodrigo , Paris Enrique
Published: February 2021

Ante el reciente llamado del gobierno a participar en una consulta ciudadana respecto del anteproyecto de ley en materia de empleo público, es pertinente preguntarse por la trascendencia del hecho tanto desde el punto de vista de las propuestas y su originalidad, como del método utilizado. En materia de reforma y modernización del Estado, el empleo público es posiblemente uno de sus mayores desafíos, especialmente si se pretende remodelar el sistema para adecuarlo a las exigencias que enfrenta la administración del Estado de servir de mejor forma a la ciudadanía y atraer el talento necesario para hacerlo con eficiencia y eficacia. Continuar leyendo...
Frame-Based and Mask-Based Stereotactic Radiosurgery: The Patient Experience, Compared
Authors: Pavlica Matthew , Dawley Troy , Goenka Anuj , Schulder Michael
Published: February 2021

Introduction: Noninvasive frameless modalities have become increasingly utilized for stereotactic radiosurgery (SRS) for benign and malignant pathologies. There is minimal comparison in the literature of frame-based (FB) and mask-based (MB) SRS. With the dual capabilities of the Elekta Gamma Knife® Icon™, we sought to compare patient perceptions of FB and MB SRS with respect to comfort and pain and to examine effects of lesion type on the patient experience of SRS. Methods: Over a 1-year period, patients who underwent single fraction, fractionated or hypofractionated FB or MB Gamma Knife SRS at our institution were given an 8-question survey about their experience with the procedure immediately after treatment was completed. Descriptive statistics were applied. Results: A total of 117 patients completed the survey with 65 FB and 52 MB SRS treatments. Mean pain for FB SRS (5.64 ± 2.55) was significantly greater than mean pain for MB SRS (0.92 ± 2.24; t114 = 10.46, p < 0.001). Patient comfort during the procedure was also higher for those having MB SRS (p < 0.001). Mixed results were obtained when investigating if benign versus malignant diagnosis affected patient experience of SRS. For the purposes of this study, malignant diagnoses were almost entirely metastatic lesions. Diagnosis played no role on pain levels when all patients were analyzed together. The treatment technique had no effect on patient comfort in patients with benign diagnoses, while patients with malignant diagnoses treated with MB SRS were more likely to be comfortable (p < 0.001). Among patient’s receiving FB treatments, diagnosis played no role on patient comfort. When only MB treatments were analyzed, patients were more likely to be comfortable if they had a malignant lesion (p < 0.01). Conclusions: Patients treated with MB SRS experience the procedure as more comfortable and less painful compared to those treated using a FB modality. Overall, this difference was not affected by a benign versus a malignant diagnosis and the treatment type is more indicative of the patient experience during SRS. A more homogenous sample between modalities and diagnoses and further follow-up with the patient’s input on their experience would be beneficial.
Optimal generation for wind-thermal power plant systems with multiple fuel sources
Authors: Vinh Phan Nguyen , Dinh Bach Hoang , Phan Van-Duc , Nguyen Hung Duc , Nguyen Thang Trung
Published: February 2021

In this paper, the combined wind and thermal power plant systems are operated optimally to reduce the total fossil fuel cost (TFFC) of all thermal power plants and supply enough power energy to loads. The objective of reducing TFFC is implemented by using antlion algorithm (ALA), particle swarm optimization (PSO) and Cuckoo search algorithm (CSA). The best method is then determined based on the obtained TFFC from the three methods as dealing with two study cases. Two systems with eleven units including one wind power plant (WPP) and ten thermal power plants are optimally operated. The two systems have the same characteristic of MFSs but the valve loading effects (VLEs) on thermal power plants are only considered in the second system. The comparisons of TFFC from the two systems indicate that CSA is more powerful than ALA and PSO. Furthermore, CSA is also superior to the two methods in terms of faster search process. Consequently, CSA is a powerful method for the problem of optimal generation for wind-thermal power plant systems with consideration of MFSs from thermal power plants.
Power dissipation analysis of PV module under partial shading
Authors: Yu Byunggyu , Ko Seok-Cheol
Published: February 2021

Photovoltaic (PV) generation has been growing dramatically over the last years and it ranges from small, rooftop-mounted or building integrated systems, to large utility scale power stations. Especially for rooftop-mounted PV system, PV modules are serially connected to match with PV inverter input voltage specification. For serially connected PV system, shading is a problem since the shaded PV module reduces the output whole string of PV modules. The excess power from the unshaded PV module is dissipated in the shaded PV module. In this paper, power dissipation of PV module under partial shading is analyzed with circuit analysis for series connected PV modules. The specific current and voltage operating point of the shaded PV module are analyzed under shading. PSIM simulation tool is used to verify the power dissipation analysis. When there is no bypass diode and three solar modules are connected in series, upto 39.1% of the total maximum PV power is dissipated in the shaded PV module. On the other hand, when the bypass is attached, 0.3% of the total maximum power is generated as a loss in the shaded PV module. The proposed analysis technique of shaded PV module could be used in PV system performance analysis, especially for maximum power point tracking (MPPT) performance.
Modeling and simulation of a 3-ф induction motor based on two types of WFA
Authors: Ali Ahmed J. , Khalaf Laith A. , Ahmed Ahmed H.
Published: February 2021

This paper has been proposed to simulate the transient model of 3-Ф cage rotor induction motor based on winding function approach (WFA). According to this method the motor is assumed to be consist of an electrical circuits on both stator and rotor. The magneto motive forces (MMF) that have been generated by these circuits play a role for coupling them together. Then mutual and self-inductances will be easily computed using WFA. Two types of WFA have been used to build and simulate the model of the induction motor. In the one part type, it’s assumed that the coupling MMF between stator and rotor have a non-sinusoidal shapes according to the actual windings distribution over the motor slots. While in second part type the generated MMF in are assumed to have sinusoidal waveform. The suggested models may be used to simulate the dynamic as well as steady state performance of a faulty and non-faulty motor. A simulation of the suggested models that consists of m-rotor bars and n-stator phases multiple coupled circuit-based has been performed using matlab m.file and the results of the motor current have been proved in its nonlinear way by using WFA.
Online instrument systems in reality for remote wiring and measurement of electronic in e-learning from LabVIEW+NI ELVIS II vs embedded system+web services
Authors: Ouatik Fahd , Raoufi Mustapha , Ouatik Farouk , Skouri Mohammed
Published: February 2021

Recently The prestigious universities of the world strive and aim to computerize their distance education service and more specifically the remote practical work, which allows students to manipulate electronic experiments via the web, for to solve a set of problems: pedagogical, management, security, restriction by time and place and the problems the overcrowding of students in universities. This paper will describe the E@SLab system developed by the university Cadi Ayyad member of the e-live project funded by EU in the frame of ERASMUS+E@SLab is based on the latest technologies of development and respects educational and pedagogical standards. E@SLab offers 2 versions different of remote laboratory: first version (s1) is an embedded system its part software is node js+Ubuntu and the part hardware a card pcduino or raspebery. The second version (s2) is based on LABview and its hardware part is the NI ELVIS II pedagogical map. In this paper, we will compare and discuss the architecture, performance of the 2 versions of E@SLAB and review other famous approaches NetLab, VISIR, for comparing with E@SLab with the intention show its singularity.
Speech emotion recognition based on SVM and KNN classifications fusion
Authors: Al Dujaili Mohammed Jawad , Ebrahimi-Moghadam Abbas , Fatlawi Ahmed
Published: February 2021

Recognizing the sense of speech is one of the most active research topics in speech processing and in human-computer interaction programs. Despite a wide range of studies in this scope, there is still a long gap among the natural feelings of humans and the perception of the computer. In general, a sensory recognition system from speech can be divided into three main sections: attribute extraction, feature selection, and classification. In this paper, features of fundamental frequency (FEZ) (F0), energy (E), zero-crossing rate (ZCR), fourier parameter (FP), and various combinations of them are extracted from the data vector, Then, the principal component analysis (PCA) algorithm is used to reduce the number of features. To evaluate the system performance. The fusion of each emotional state will be performed later using support vector machine (SVM), K-nearest neighbor (KNN), In terms of comparison, similar experiments have been performed on the emotional speech of the German language, English language, and significant results were obtained by these comparisons.
Restoration for blurred noisy images based on guided filtering and inverse filter
Authors: Altaie Rusul H.
Published: February 2021

The development of complex life leads into a need using images in several fields, because these images degraded during capturing the image from mobiles, cameras and persons who do not have sufficient experience in capturing images. It was important using techniques differently to improve images and human perception as image enhancement and image restoration etc. In this paper, restoration noisy blurred images by guided filter and inverse filtering can be used for enhancing images from different types of degradation was proposed. In the color images denoising process, it was very significant for improving the edge and texture information. Eliminating noise can be enhanced by the image quality. In this article, at first, The color images were taken. Then, random noise and blur were added to the images. Then, the noisy blurred image passed to the guided filtering to get on denoised image. Finally, an inverse filter applied to the blurred image by convolution an image with a mask and getting on the enhanced image. The results of this research illustrated good outcomes compared with other methods for removing noise and blur based on PSNR measure. Also, it enhanced the image and retained the edge details in the denoising process. PSNR and SSIM measures were more sensitive to Gaussian noise than blur.
Visual, navigation and communication aid for visually impaired person
Authors: Saha Sagor , Shakal Farhan Hossain , Mahmood Mufrath
Published: February 2021

The loss of vision restrained the visually impaired people from performing their daily task. This issue has impeded their free-movement and turned them into dependent a person. People in this sector did not face technologies revamping their situations. With the advent of computer vision, artificial intelligence, the situation improved to a great extent. The propounded design is an implementation of a wearable device which is capable of performing a lot of features. It is employed to provide visual instinct by recognizing objects, identifying the face of choices. The device runs a pre-trained model to classify common objects from household items to automobiles items. Optical character recognition and Google translate were executed to read any text from image and convert speech of the user to text respectively. Besides, the user can search for an interesting topic by the command in the form of speech. Additionally, ultrasonic sensors were kept fixed at three positions to sense the obstacle during navigation. The display attached help in communication with deaf person and GPS and GSM module aid in tracing the user. All these features run by voice commands which are passed through the microphone of any earphone. The visual input is received through the camera and the computation task is processed in the raspberry pi board. However, the device seemed to be effective during the test and validation.