Frenet force analysis in performance evaluation of railroad vehicle systems

A data-driven science approach, based on integrating nonlinear multibody system (MBS) formulations and new geometric concepts, is used in this paper to compare the performance of two widely used railroad bogies: the three-piece bogie and the Y25 bogie. MBS algorithms are used to solve the bogie nonlinear differential/algebraic equations (DAEs) to determine the bogie motion trajectories. To have a better understanding of the bogie dynamic behavior, a distinction is made between the geometry of actual motion trajectories (AMT) and the track geometry. The AMT curves are described using the motion-dependent Frenet-Euler angles, referred to as Frenet bank, curvature, and vertical development angles, which differ from their counterparts used in the description of the track geometry. In particular, the Frenet bank angle defines the super-elevation of the AMT curve osculating plane, referred to as the motion plane, distinguishing this Frenet super-elevation from the fixed-in-time track super-elevation. The paper explains the difference between the lateral track plane force balance used in practice to determine the balance speed and the Frenet force balance which is based on recorded motion trajectories. Computer simulations of bogies travelling on a track, consisting of tangent, spiral, and curve sections are performed with particular attention given to the deviations of the AMT curves from the track centerline. The results obtained in this study demonstrate the dependence of the AMT curve geometry on the wheelset forward motion, highlighting the limitations of tests performed using roller test rigs which do not allow longitudinal wheelset motion

Analysis of the backward bending modes in damped rotating beams

[EN] This article presents a study of the backward bending mode of a simply supported rotating Rayleigh beam with internal damping. The study analyses the natural frequency behaviour of the backward mode according to the internal viscous damping ratio, the slenderness of the beam and its spin speed. To date, the behaviour of the natural frequency of the backward mode is known to be a monotonically decreasing function with spin speed due to gyroscopic effects. In this article, however, it is shown that this behaviour of the natural frequency may not hold for certain damping and slenderness conditions, and reaches a minimum value (concave function) from which it begins to increase. Accordingly, the analytical expression of the spin speed for which the natural frequency of the backward mode attains the minimum value has been obtained. In addition, the internal damping ratio and slenderness intervals associated with such behaviour have been also provided.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors gratefully acknowledge the financial support of Ministerio de Ciencia, Innovacion y Universidades Agencia Estatal de Investigacion and the European Regional Development Fund (project TRA2017-84701-R), as well as Generalitat Valenciana (project Prometeo/2016/007) and European Commission through the project 'RUN2Rail - Innovative RUNning gear soluTiOns for new dependable, sustainable, intelligent and comfortable RAIL vehicles' (Horizon 2020 Shift2Rail JU call 2017, grant number 777564)Martínez Casas, J.; Denia Guzmán, FD.; Fayos Sancho, J.; Nadal, E.; Giner Navarro, J. (2019). Analysis of the backward bending modes in damped rotating beams. Advances in Mechanical Engineering. 11(4):1-13. https://doi.org/10.1177/1687814019840474S113114Zorzi, E. S., & Nelson, H. D. (1977). Finite Element Simulation of Rotor-Bearing Systems With Internal Damping. Journal of Engineering for Power, 99(1), 71-76. doi:10.1115/1.3446254Ku, D.-M. (1998). FINITE ELEMENT ANALYSIS OF WHIRL SPEEDS FOR ROTOR-BEARING SYSTEMS WITH INTERNAL DAMPING. Mechanical Systems and Signal Processing, 12(5), 599-610. doi:10.1006/mssp.1998.0159Dimentberg, M. F. (2005). Vibration of a rotating shaft with randomly varying internal damping. Journal of Sound and Vibration, 285(3), 759-765. doi:10.1016/j.jsv.2004.11.025Vatta, F., & Vigliani, A. (2008). Internal damping in rotating shafts. Mechanism and Machine Theory, 43(11), 1376-1384. doi:10.1016/j.mechmachtheory.2007.12.009Rosales, M. B., & Filipich, C. P. (1993). Dynamic Stability of a Spinning Beam Carrying an Axial Dead Load. Journal of Sound and Vibration, 163(2), 283-294. doi:10.1006/jsvi.1993.1165Mazzei, A. J., & Scott, R. A. (2003). Effects of internal viscous damping on the stability of a rotating shaft driven through a universal joint. Journal of Sound and Vibration, 265(4), 863-885. doi:10.1016/s0022-460x(02)01256-7Ehrich, F. F. (1964). Shaft Whirl Induced by Rotor Internal Damping. Journal of Applied Mechanics, 31(2), 279-282. doi:10.1115/1.3629598Vance, J. M., & Lee, J. (1974). Stability of High Speed Rotors With Internal Friction. Journal of Engineering for Industry, 96(3), 960-968. doi:10.1115/1.3438468Vila, P., Baeza, L., Martínez-Casas, J., & Carballeira, J. (2014). Rail corrugation growth accounting for the flexibility and rotation of the wheel set and the non-Hertzian and non-steady-state effects at contact patch. Vehicle System Dynamics, 52(sup1), 92-108. doi:10.1080/00423114.2014.881513Glocker, C., Cataldi-Spinola, E., & Leine, R. I. (2009). Curve squealing of trains: Measurement, modelling and simulation. Journal of Sound and Vibration, 324(1-2), 365-386. doi:10.1016/j.jsv.2009.01.048Bauer, H. F. (1980). Vibration of a rotating uniform beam, part I: Orientation in the axis of rotation. Journal of Sound and Vibration, 72(2), 177-189. doi:10.1016/0022-460x(80)90651-3Shiau, T. N., & Hwang, J. L. (1993). Generalized Polynomial Expansion Method for the Dynamic Analysis of Rotor-Bearing Systems. Journal of Engineering for Gas Turbines and Power, 115(2), 209-217. doi:10.1115/1.2906696Hili, M. A., Fakhfakh, T., & Haddar, M. (2006). Vibration analysis of a rotating flexible shaft–disk system. Journal of Engineering Mathematics, 57(4), 351-363. doi:10.1007/s10665-006-9060-3Young, T. H., Shiau, T. N., & Kuo, Z. H. (2007). Dynamic stability of rotor-bearing systems subjected to random axial forces. Journal of Sound and Vibration, 305(3), 467-480. doi:10.1016/j.jsv.2007.04.016Wang, J., Hurskainen, V.-V., Matikainen, M. K., Sopanen, J., & Mikkola, A. (2017). On the dynamic analysis of rotating shafts using nonlinear superelement and absolute nodal coordinate formulations. Advances in Mechanical Engineering, 9(11), 168781401773267. doi:10.1177/1687814017732672Lee, C.-W. (1993). Vibration Analysis of Rotors. Solid Mechanics and Its Applications. doi:10.1007/978-94-015-8173-8Genta, G. (1999). Vibration of Structures and Machines. doi:10.1007/978-1-4612-1450-2Cheng, C. C., & Lin, J. K. (2003). Modelling a rotating shaft subjected to a high-speed moving force. Journal of Sound and Vibration, 261(5), 955-965. doi:10.1016/s0022-460x(02)01374-

Control and optimization of semi-passively actuated multibody systems

The controlled multibody systems are under the consideration. At the lecture special emphasis is put on the study of underactuated and overactuated systems having different type of actuators (external powered drives, unpowered spring-damper like drives, etc.). Several questions are addressed about the role of inherent dynamics, and how much multibody system should be governed by external powered drives and how much by the systems inherent dynamics. The lecture consists of the following parts: introduction to the subject in question; mathematical statement of the optimal control problems that are suitable for modelling of controlled motion and optimization of semi-passively controlled multibody systems with different degrees of actuation; description of the methodology and the numerical algorithms for solution of control and optimization problems for semi-passively actuated multibody systems. The solutions of several optimal control problems for different kind of semi-passively actuated multibody systems are presented. Namely, the energy-optimal control of planar semi-passively controlled three-link manipulator robot, the energy-optimal control of closed-loop chain semi-passively actuated SCARA-like robot; optimization of the hydraulic and pneumatic drives of the multibody system modelled the human locomotor apparatus with above-knee prostheses, and others. Future perspectives in area of control and optimization problems of the semi-passively actuated multibody systems are discussed

Pre-processing Agilent microarray data

<p>Abstract</p> <p>Background</p> <p>Pre-processing methods for two-sample long oligonucleotide arrays, specifically the Agilent technology, have not been extensively studied. The goal of this study is to quantify some of the sources of error that affect measurement of expression using Agilent arrays and to compare Agilent's Feature Extraction software with pre-processing methods that have become the standard for normalization of cDNA arrays. These include log transformation followed by loess normalization with or without background subtraction and often a between array scale normalization procedure. The larger goal is to define best study design and pre-processing practices for Agilent arrays, and we offer some suggestions.</p> <p>Results</p> <p>Simple loess normalization without background subtraction produced the lowest variability. However, without background subtraction, fold changes were biased towards zero, particularly at low intensities. ROC analysis of a spike-in experiment showed that differentially expressed genes are most reliably detected when background is not subtracted. Loess normalization and no background subtraction yielded an AUC of 99.7% compared with 88.8% for Agilent processed fold changes. All methods performed well when error was taken into account by t- or z-statistics, AUCs ≥ 99.8%. A substantial proportion of genes showed dye effects, 43% (99%<it>CI </it>: 39%, 47%). However, these effects were generally small regardless of the pre-processing method.</p> <p>Conclusion</p> <p>Simple loess normalization without background subtraction resulted in low variance fold changes that more reliably ranked gene expression than the other methods. While t-statistics and other measures that take variation into account, including Agilent's z-statistic, can also be used to reliably select differentially expressed genes, fold changes are a standard measure of differential expression for exploratory work, cross platform comparison, and biological interpretation and can not be entirely replaced. Although dye effects are small for most genes, many array features are affected. Therefore, an experimental design that incorporates dye swaps or a common reference could be valuable.</p

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Background: Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. // Methods: We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung's disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. // Findings: We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung's disease) from 264 hospitals (89 in high-income countries, 166 in middle-income countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in low-income countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. // Interpretation: Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between low-income, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030