Influence of Variable Side-Stay Geometry on the Shimmy Dynamics of an Aircraft Dual-Wheel Main Landing Gear

Commercial aircraft are designed to fly but also need to operate safely and efficiently as vehicles on the ground. During taxiing, take-off, and landing the landing gear must operate reliably over a wide range of forward velocities and vertical loads. Specifically, it must maintain straight rolling under a wide variety of operating conditions. It is well known, however, that under certain conditions the wheels of the landing gear may display unwanted oscillations, referred to as shimmy oscillations, during ground maneuvers. Such oscillations are highly unwanted from a safety and a ride-comfort perspective. In this paper we conduct a study into the occurrence of shimmy oscillations in a main landing gear (MLG) of a typical midsize passenger aircraft. Such a gear is characterized by a main strut attached to the wing spar with a side-stay that connects the main strut to an attachment point closer to the fuselage center line. Nonlinear equations of motion are developed for the specific case of a two-wheeled MLG configuration and allow for large angle deflections within the geometrical framework of the system. The dynamics of the MLG are expressed in terms of three degrees of freedom: torsional motion, in-plane motion, and out-of-plane motion (with respect to the side-stay plane). These are modeled by oscillators that are coupled directly through the geometric configuration of the system as well as through the tire/ground interface, which is modeled here by the von Schlippe stretched string approximation of the tire dynamics. The mathematical model is fully parameterized and parameters are chosen to represent a generic (rather than a specific) landing gear. In particular, the positions of the attachment points are fully parameterized so that any orientation of the side-stay plane can be considered. The occurrence of shimmy oscillations is studied by means of a two-parameter bifurcation analysis of the system in terms of the forward velocity of the aircraft and the vertical force acting on the gear. The effect of a changing side-stay plane orientation angle on the bifurcation diagram is investigated. We present a consistent picture that captures the transition of the two-parameter bifurcation diagram as a function of this angle, with a considerable complexity of regions of different types of shimmy oscillations for intermediate and realistic side-stay plane orientations. In particular, we find a region of tristability in which stable torsional, in-plane, and out-of-plane shimmy oscillations coexist

Weaning at Anglo-Saxon raunds: Implications for changing breastfeeding practice in britain over two millennia.

This study investigated stable-isotope ratio evidence of weaning for the late Anglo-Saxon population of Raunds Furnells, Northamptonshire, UK. δ(15) N and δ(13) C values in rib collagen were obtained for individuals of different ages to assess the weaning age of infants within the population. A peak in δ(15) N values at about 2-year-old, followed by a decline in δ(15) N values until age three, indicates a change in diet at that age. This change in nitrogen isotope ratios corresponds with the mortality profile from the site, as well as with archaeological and documentary evidence on attitudes towards juveniles in the Anglo-Saxon period. The pattern of δ(13) C values was less clear. Comparison of the predicted age of weaning to published data from sites dating from the Iron Age to the 19th century in Britain reveals a pattern of changing weaning practices over time, with increasingly earlier commencement and shorter periods of complementary feeding in more recent periods. Such a change has implications for the interpretation of socioeconomic changes during this period of British history, since earlier weaning is associated with decreased birth spacing, and could thus have contributed to population growth. Am J Phys Anthropol 151:604-612, 2013. © 2013 Wiley Periodicals, Inc

BGS Groundhog® desktop Geoscientific Information System external user manual

BGS Groundhog is a software platform developed by the British Geological Survey (BGS) for the management and display of subsurface geological information. There are two main components; 1. BGS Groundhog Web 2. BGS Groundhog Desktop GSIS This user manual relates specifically to the Desktop GSIS component of the platform. The software is available under the UK’s Open Government Licence, which means the software is free to use, exploit and re-distribute for academic, personal, research or commercial purposes, subject to the terms of the UK’s Open Government Licence. Groundhog Desktop is intended as a basic GeoScientific Information System (GSIS*) – a software tool which facilitates the collation, display, filtering and editing of a range of data relevant to subsurface interpretation and modelling. It has been developed by the Modelling Systems software development team, with help and advice being provided by Holger Kessler, Steve Mathers and Ricky Terrington. This manual provides information on the use of the software for external clients

Observation of Muon Neutrino Disappearance with the MINOS Detectors in the NuMI Neutrino Beam

This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current ν_μ interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27×10^(20) 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336±14 events. The data are consistent with ν_μ disappearance via oscillations with Δm_(32)^2|=2.74_(-0.26)^(+0.44)×10^(-3)  eV^2 and sin^2(2θ_(23))>0.87 (68% C.L.)

First observations of separated atmospheric ν_μ and ν̅ _μ events in the MINOS detector

The complete 5.4 kton MINOS far detector has been taking data since the beginning of August 2003 at a depth of 2070 meters water-equivalent in the Soudan mine, Minnesota. This paper presents the first MINOS observations of ν_μ and ν̅ _μ charged-current atmospheric neutrino interactions based on an exposure of 418 days. The ratio of upward- to downward-going events in the data is compared to the Monte Carlo expectation in the absence of neutrino oscillations, giving R^(data)_(up/down/R^(MC)_(up/down) = 0:62^(+0.19)_(0:14)(stat.) ± 0.02(sys.). An extended maximum likelihood analysis of the observed L/E distributions excludes the null hypothesis of no neutrino oscillations at the 98% confidence level. Using the curvature of the observed muons in the 1.3 T MINOS magnetic field ν_μ and ν̅ _μ interactions are separated. The ratio of ν̅ _μ to ν_μ events in the data is compared to the Monte Carlo expectation assuming neutrinos and antineutrinos oscillate in the same manner, giving R^(data)_(ν_μ/ν̅ _μ) / R^(MC)_(ν_μ/ν̅ _μ) = 0.96^(+0:38)_(0.27)(stat.) ± 0.15(sys.), where the errors are the statistical and systematic uncertainties. Although the statistics are limited, this is the first direct observation of atmospheric neutrino interactions separately for ν_μ and ν̅ _μ

Pengembangan Media Pembelajaran Virtual dan Interaktif untuk Mensimulasikan Instalasi Jaringan Listrik di SMK 2 Surakarta

Pembelajaran instalasi listrik di SMK sering menjadi masalah karena harus tersedianya peralatan yang harus selalu membeli perangkat nyata namun setelah itu perangkat yang digunakan untuk pembelajaran tidak digunakan kembali dan juga yang penting adalah ternyata cara pembelajaran seperti ini kurang efektif karena biasanya dilakukan secara berkelompok. Pada saat pembelajaran dilakukan secara berkelompok maka ada siswa yang hanya mengandalkan hasil kerja rekan-rekannya dan ada yang tidak memperhatikan terhadap pelajaran yang diberikan akhirnya tidak menerima manfaat dari pembelajaran tersebut. Untuk itu dikembangkan sebuah media interaktif yang ditujukan untuk mensimulasikan rangkaian listrik sederhana sehingga bisa dicoba secara langsung oleh masing-masing siswa secara menarik dan interaktif sehingga setiap siswa akan menjadi senang belajar instalasi listrik dan mendapat manfaat serta bisa menyerap materi yang diinginkan

Strut-Braced Wing Modelling with a Reduced Order Beam Model

In recent years there has been much interest in the study of strut-braced wings, as they potentially offer the opportunity to design lightweight wings with increased wingspan. This work includes NASA’s development of a strut-based configuration as part of the Subsonic Ultra Green Aircraft Research (SUGAR) project. Optimisation strategies, based on linear structural models have been proposed to size such a wing. Here, a simple sizing study is conducted on the SUGAR planform using empirical formula and a linear Nastran structural model. The resulting wing is then analysed using a novel nonlinear structural solver to assess the effect of including geometric nonlinearities on the predicted wing response. It is shown that for the maximum stress levels considered geometric nonlinearity has only a slight effect on the deflections of the sized wingmodel.<br/