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Swedish transport administration initiated this Master Thesis project and the aim was to compare regulations for the design of high-speed railways from three European countries: France, Germany and Spain. The reason why this is of interest for the Swedish transport administration is the design of the first Swedish high-speed railway, called Ostlänken. Therefore, a literature study of the regulations and other literature regarding high-speed railway has been carried out. A basic description of railway components, slab track and ballasted tracks is presented. Ballasted embankments usually consist of a trackbed layer (ballast onto subballast), and the ultimate thickness of this layer is discussed, as there are a number of methods available to calculate the appropriate thickness, with a number of different design parameters. These design methods results in different trackbed thickness and choosing the “wrong” method might lead to an overestimation or underestimation of the trackbed layer. Constructing a ballastless railway line means that the ballast is replaced by another material, usually a slab made of reinforced concrete or asphalt, and the rail is cast onto this slab. Countries design their slab using different methods. Germany has constructed high-speed railway lines with a slab track solution, generally slabs with low flexible stiffness. France has until recently constructed their high-speed line ballasted but is now developing a new slab track technique, called NBT (New Ballastless Track) and Spain uses various methods. It is difficult to compare the regulations, however, there are some factors that at least begin to explain the differences between the countries: the frost hazard, the inherent ground quality, purpose with the railway (mixed traffic, solely passenger traffic, etc.), design parameters (life, axle load, etc.). Furthermore, the settlement requirements, soil classification and bearing capacity are factors that varies from country to country, but the origin for this variation is harder to detect.

Most aircraft accidents are caused by technical problems or weather-related issues. One cause of weather-related incidents is inlight icing, which can induce negative performance characteristics and endanger the operation of an airplane. Various researchers investigating the problem of inlight icing have proposed ice-phobic coatings as one viable solution. For this purpose, it is critical to study the behavior of a droplet impact on different types of surfaces. As an alternative to physical testing, three-dimensional numerical simulation using computational fluid dynamics offers a promising strategy for evaluating the effects of surface characteristics. Using the volume of fluid method, three simulations of high-speed droplet impact on superhydrophobic surfaces with and without micro-scale roughness elements, were generated. The simulations showed that, for the roughness configurations considered, the superhydrophobic surfaces with micro-scale roughness elements were significantly less effective at repelling the droplet than the smooth superhydrophobic surfaces.

Ten subjects were randomly assigned to train one arm with ballistic movements (BT), whereas the other arm trained with ballistic and heavy resistance movements (BT+HRT). The training program consisted of three training sessions per week, over a ten week period. The BT arm executed ten sets of six maximal ballistic elbow extension actions (10% MVC), whereas the BT+HRT arm executed five sets of six repetitions of maximal ballistic actions followed by five sets of five to eight repetitions of heavy resistance elbow extension actions. After training, evoked twitch contractile properties, ballistic, 1 RM, and isometric MVC measures were analyzed. Incorporated with all performance measures were EMG recordings of the agonist (AG) triceps and antagonist (ANT) biceps. Muscle biopsies of triceps were also taken to determine muscle fibre type composition, and fibre area. The BT+HRT arm demonstrated a significant decrease in the percent population of type IIb fibres (22% to 18. 8%). Furthermore, the BT+HRT arm produced hypertrophy, type IIa (6184 to 7086 μm²) and IIb (5714 to 6734 μm²) fibre areas increased, whereas type I fibre areas (3503 to 3828 μm²) did not significantly increase, after training. In contrast, the BT arm and control arm did not display fibre transformation or hypertrophy after training. Triceps evoked twitch peak torque increased for only the BT+HRT arm (12.5 to 13.8 N·m). Furthermore, the 1 RM increased significantly in the BT+HRT arm (~24%) but did not change significantly in the BT arm. However, ballistic and isometric MVC PT values increased similarly in both the BT (19.6 to 23.5 N·m; 45.4 to 52.6 N·m) and the BT+HRT (19.6 to 23.6 N·m; 49.6 to 56.0 N·m) arms. The EMG results corresponded to the performance results in that triceps AEMG in the 1 RM test tended to increased more after HRT (0.71 to 1.01 mV) than only BT (0.72 to 0.81 mV), but in the ballistic (HRT= 0.63 to 0.79 mV; BT= 0. 62 to 0. 73 mV) and isometric MVC performance measures (HRT= 0.80 to 0.84 mV; BT= 0.80 to 0.87 mV), the AEMG results were similar. Supplementary HRT caused muscle hypertrophy, particularly of the type II fibres, but did not promote improvement in ballistic performance with loads equal to or less than 10% of maximal isometric force. / Thesis / Master of Science (MS)

High-speed rail (HSR) in most industrialized countries in Europe and Asia have proven profitable and increase GDP in primary, secondary and tertiary station locations, balance greenhouse gas emissions, maintain safety and temporal standards, and assuage traffic concerns of growing populations. The Metroliner’s short completion timeline and ability to demonstrate a successful product prior to appropriating or obligating funds propelled America’s passenger rail industry forward in congruence with establishing the Office of High-Speed Ground Transportation in 1965. However, the US’ rotating bipartisan political structure hinders hyper-expensive 20-year-long projects, as shown in California, Florida, and the Northeast Corridor (NEC). In contrast to this, China’s centralized government, dense city centers, and politically motivated expansion led to construction of the world’s largest HSR network with 37,900 kilometers of tracks in 2021 and 70,000 kilometers expected by 2035. While HSR in the US may be profitable in the NEC, governmental structure, infrastructure density, and high temporal and financial costs reduce plausibility for HSR despite proven positive effects.

This work investigates steady deformations, measured spectra of quasi-static ring deformations, natural frequencies, vibration modes, parametric instabilities, and nonlinear dynamics of high-speed planetary gears with an elastically deformable ring gear and equally-spaced planets. An analytical dynamic model is developed with rigid sun, carrier, and planets coupled to an elastic continuum ring. Coriolis and centripetal acceleration effects resulting from carrier and ring gear rotation are included. Steady deformations and measured spectra of the ring deflections are examined with a quasi-static model reduced from the dynamic one. The steady deformations calculated from the analytical model agree well with those from a finite element/contact mechanics (FE/CM) model. The spectra of ring deflections measured by sensors fixed to the rotating ring, space-fixed ground, and the rotating carrier are much different. Planet mesh phasing significantly affects the measured spectra. Simple rules are derived to explain the spectra for all three sensor locations for in-phase and out-of-phase systems. A floating central member eliminates spectral content near certain mesh frequency harmonics for out-of-phase systems. Natural frequencies and vibration modes are calculated from the analytical dynamic model, and they compare well with those from a FE/CM model. Planetary gears have structured modal properties due to cyclic symmetry, but these modal properties are different for spinning systems with gyroscopic effects and stationary systems without gyroscopic effects. Vibration modes for stationary systems are real-valued standing wave modes, while those for spinning systems are complex-valued traveling wave modes. Stationary planetary gears have exactly four types of modes: rotational, translational, planet, and purely ring modes. Each type has distinctive modal properties. Planet modes may not exist or have one or more subtypes depending on the number of planets. Rotational, translational, and planet modes persist with gyroscopic effects included, but purely ring modes evolve into rotational or one subtype of planet modes. Translational and certain subtypes of planet modes are degenerate with multiplicity two for stationary systems. These modes split into two different subtypes of translational or planet modes when gyroscopic effects are included. Parametric instabilities of planetary gears are examined with the analytical dynamic model subject to time-varying mesh stiffness excitations. With the method of multiple scales, closed-form expressions for the instability boundaries are derived and verified with numerical results from Floquet theory. An instability suppression rule is identified with the modal structure of spinning planetary gears with gyroscopic effects. Each mode is associated with a phase index such that the gear mesh deflections between different planets have unique phase relations. The suppression rule depends on only the modal phase index and planet mesh phasing parameters (gear tooth numbers and the number of planets). Numerical integration of the analytical model with time-varying mesh stiffnesses and tooth separation nonlinearity gives dynamic responses, and they compare well with those from a FE/CM model. Closed-form solutions for primary, subharmonic, superharmonic, and second harmonic resonances are derived with a perturbation analysis. These analytical results agree well with the results from numerical integration. The analytical solutions show suppression of certain resonances as a result of planet mesh phasing. The tooth separation conditions are analytically determined. The influence of the gyroscopic effects on dynamic response is examined numerically and analytically. / Doctor of Philosophy / Planetary gears in aerospace applications have thin ring gears for reducing weight. These lightweight ring gears deform elastically when transmitting power. At high speed, Coriolis and centripetal accelerations of planetary gears become significant. This work develops an analytical planetary gear model that takes account of an elastically deformable ring gear and speed-dependent gyroscopic (i.e., Coriolis) and centripetal effects. Steady deformations, measured spectra of quasi-static ring deformations, natural frequencies, vibration modes, parametric instabilities, and dynamic responses of planetary gears with equally-spaced planets are investigated with the analytical model. Steady deformations refer to quasi-static deflections that result from applied torques and centripetal acceleration effects. These steady deformations vary because of periodically changing mesh interactions. Such variation leads to cyclic stress that reduces system fatigue lives. This work evaluates planetary gear steady deformations with the analytical model and studies the effects of system parameters on the steady deformations. Ring deflections measured by sensors fixed to the rotating ring gear (e.g., a strain gauge), space-fixed ground (e.g., a displacement probe), and the rotating carrier have much different spectra. The planet mesh phasing, which is determined by gear tooth numbers and the number of planets, significantly influences these spectra. Simple rules are derived that govern the occurrence of spectral content in all the three measurements. Understanding these spectra is of practical significance to planetary gear engineers and researchers. Planetary gears have highly structured modal properties due to cyclic symmetry. Vibration modes are classified into rotational, translational, and planet modes in terms of the motion of central members (sun and carrier). The central members have only rotation for a rotational mode, only translation for a translational mode, and no motion for a planet mode. Translational modes have two subtypes, rotational modes have only one subtype, and planet modes may not exist or have one or more subtypes depending on the number of planets. For each subtype of modes, all planets have the same motion with a unique phase relation between different planets and the elastic ring gear has unique deformations. Understanding this modal structure is important for modal testing and resonant mode identification in dynamic responses. Sun-planet and ring-planet mesh interactions change periodically with mesh frequency. These mesh interactions are modeled as time-varying stiffnesses that parametrically excite the planetary gear system. Parametric instabilities, in general, occur when the mesh frequency or one of its harmonics is near twice a natural frequency or combinations of two natural frequencies. Closed-form expressions for parametric instability boundaries that bound the instability region are determined from the analytical model. Certain parametric instabilities are suppressed as a result of planet mesh phasing. Near resonances, vibration can become large enough that meshing teeth lose contact. The analytical model is extended to include the tooth separation nonlinearity. Closed-form approximations for dynamic responses near resonances are determined from the analytical model, and these analytical results compare well with those from numerical simulations of the analytical model. Tooth separation conditions are analytically determined. The influences of planet mesh phasing and Coriolis acceleration on dynamic responses near resonances are investigated numerically and analytically.

Design for prevention of aeroelastic instability (that is, the critical speeds leading to aeroelastic instability lie outside the operating range) is an integral part of the wing design process. Availability of the sensitivity derivatives of the various critical speeds with respect to shape parameters of the wing could be very useful to a designer in the initial design phase, when several design changes are made and the shape of the final configuration is not yet frozen. These derivatives are also indispensable for a gradient-based optimization with aeroelastic constraints. In this study, flutter characteristic of a typical section in subsonic compressible flow is examined using a state-space unsteady aerodynamic representation. The sensitivity of the flutter speed of the typical section with respect to its mass and stiffness parameters, namely, mass ratio, static unbalance, radius of gyration, bending frequency and torsional frequency is calculated analytically. A strip-theory formulation is newly developed to represent the unsteady aerodynamic forces on a wing. This is coupled with an equivalent plate structural model based on a Rayleigh-Ritz formulation and the aeroelastic equations are solved as an eigenvalue problem to determine the critical speed of the wing. The sensitivity of divergence and flutter speeds to shape parameters, namely, aspect ratio, area, taper ratio and sweep angle are computed analytically. The aeroelastic equations are also integrated with respect to time using the Wilson-θ method at different values of freest ream speed, to observe the aeroelastic phenomena in real time. of divergence and flutter speeds to shape parameters, namely, aspect ratio, area, taper ratio and sweep angle are computed analytically. The aeroelastic equations are also integrated with respect to time using the Wilson-B method at different values of freest ream speed, to observe the aeroelastic phenomena in real time. Flutter analysis of the wing is also carried out using a lifting-surface subsonic kernel function aerodynamic theory (FAST) and an equivalent plate structural model The flutter speed is obtained using a <i>V-g</i> type of solution. The novel method of automatic differentiation using ADIFOR is implemented to generate exact derivatives of the flutter speed with respect to shape and modal parameters of the wing. Finite element modeling of the wing is done using NASTRAN so that wing structures made of spars and ribs and top and bottom wing skins could be analyzed. The free vibration modes of the wing obtained from NASTRAN are input into FAST to compute the flutter speed. The derivatives of flutter speed with respect to shape parameters are computed using a combination of central difference scheme and ADIFOR and the sensitivity to modal parameters is calculated using ADIFOR. An equivalent plate model which incorporates first-order shear deformation theory is then examined so it can be used to model thick wings, where shear deformations are important. The sensitivity of natural frequencies to changes in shape parameters is obtained using ADIFOR. A simple optimization effort is made towards obtaining a minimum weight design of the wing, subject to flutter constraints, lift requirement constraints for level flight and side constraints on the planform parameters of the wing using the IMSL subroutine NCONG, which uses successive quadratic programming. / Ph. D.

The adjustable-pitch setting on an axial-flow fan is the most common method of controlling airflow for primary coal mine ventilation. With this method, the fan operates at a constant speed dictated by its motor design. The angles of the blades are adjusted to change the amount of airflow and pressure to meet ventilation requirements. Typically, the fan does not operate at its optimum efficiency, which only occurs in a narrow band of air pressures and quantities. The use of variable frequency drives (VFDs), which control fan speed, provides a solution to this problem. VFDs are already used in various similar applications such as pumping and building ventilation. New technology now enables efficient VFD operation in medium voltage (2,300 – 6,900 V) fan applications. The primary benefit of a variable frequency drive is that it allows motors to operate at reduced speeds, and thus at a lower power, without a loss of torque. VFDs also allow for efficient operation over the entire life of the fan. The technical considerations of using a VFD are presented in this work, along with a method for choosing and modeling a variable speed fan to achieve maximum energy savings. As a part of this research, a spreadsheet program was developed that will calculate the optimum fan operating speed based on given fan data and specified operating conditions. A representative room and pillar coal mine is modeled to illustrate the selection and modeling process and as an example of the economic implications of using a VFD. The use of VFDs is shown to potentially yield large energy savings by increasing the fan efficiency over the life of the mine. Although there are definite power savings while using variable speed fans, the magnitude of these savings is specific to an individual mine and the operating conditions encountered. The determination of whether the use of VFDs is economically feasible requires analysis for the specific mine and its operating conditions. This work provides the background and a method for such an evaluation. / Master of Science

This study conducted a series of tests on a shock mitigating seat designed for high speed craft using various input excitations to better understand the relationship between various seat and operational conditions, and the response of the seat. A seat model of the test seat is used for a parametric study of various spring, damping and operational configurations. A seat shake rig is implemented to simulate motions of multiple high-speed craft as well as various defined inputs. At each test input the occupant weight and suspension preload is varied and the response is analyzed to find changes in acceleration, which is representative of the changes in force and displacement. By representing the seat as a based-excitation two-degree-of-freedom system, we develop the equations of motion and model them in Simulink to analyze the effects of various spring rates and damping coefficients. Based on the results it is found that an increase in occupant mass results in a decrease in observed acceleration. Increasing suspension preload is found to be detrimental to the mitigating abilities of the seat, changing the dynamics to those similar of a rigid-mounted seat. An analysis of the defined inputs resulted in confirming various seat characteristics. The analysis of the Simulink model revealed that increasing the spring rate results in an increase in acceleration. An increase in damping coefficient resulted in an increase in acceleration and ride harshness. / Master of Science

The Available Bit Rate (ABR) service class for the Asynchronous Transfer Mode (ATM) protocol was originally designed to manage data traffic. ABR flow control makes no guarantees concerning cell transfer delay or cell delay variation. A closed-loop feedback mechanism is used for traffic management. To use this class of service for video transport, the video source will accept feedback from the network and adapt its source rate based on this status information. The objective of this research is to assess the ability of the ATM ABR service class to deliver Moving Picture Experts Group version 1 (MPEG-1) video. Three approaches to source-level control are compared: (i) arbitrary loss or no control method, (ii) selective discard of MPEG B-pictures, and (iii) selective discard of MPEG B- and P-pictures. Performance is evaluated based on end-to-end delay, congested queue occupancy levels, network utilization, and jitter. A description of the investigation, assumptions, limitations, and results of the simulation study are included. / Master of Science