A collision study is performed to compare the interference rejection characteristics of two spread spectrum receivers, one employing a sliding correlator and the other using a more sophisticated matched filter design. The testing involves using two similar transmitters, one acting a the jammer, to test the collision dynamics of each receiver. Packet data from both transmitters contain identical spreading codes. Data from the testing is analyzed and the receivers' jamming margin, capture, and process gain qualities are compared as to which system best optimizes a one-way channel. Motivation for the collision study stems from researching a one-way communication link for the Interactive Video Data Service ( IVDS ) project currently being developed by the Center for Wireless Telecommunications ( CWT ) at Virginia Tech. A novel retransmission technique has previously been developed which discusses the probability of packet collisions on the channel and uses a computer program to simulate the channel model. This thesis will provide more information as to what happens in packet collisions as well as determine which receiver type offers the greatest interference rejection. / Master of Science

The demands for an increase in productivity and reduced assembly costs require engineers to automate solutions that replace manual labor. This work concentrated on a common assembly primitive, threaded fastener insertion, in an effort to determine the nature of contact between a bolt and nut during thread mating. The assembly problem was initially simplified as a two-dimensional analysis to gain an understanding about how contacts between the bolt and nut change during counter-clockwise motion. Tessellated solid models were used during three-dimensional collision analysis in such a way that the approximate location of the contact point was enumerated. The advent of a second contact point presented a more constrained contact state since we are interested in maintaining both contacts; thus the bolt rotated about a vector defined by the initial two contact points until a third contact location was found. By analyzing the depth of intersection of the bolt into the nut as well as the vertical movement of the origin of the bolt reference frame, we determined that there are three types of contacts states present: unstable two-point, quasi-stable two-point, stable three point. Though the unstable case remains to be deciphered, the parametric equations derived in this work can be used without modification to create a full spectrum of maps at any point in the history of a threaded assembly problem. We investigated 81 potential orientations, each of which has its own set of contact points. From this exhaustive examination, we are capable of detailing a contact state history and, from this, have the potential to develop a constraint network. / Master of Science

Contact is one of the most challenging nonlinearities to solve in solid mechanics. In traditional linear finite element analysis, the contact surface is only C^0 continuous, as a result, the normal to the contact surface is not continuous. The normal contact force is directed along the normal in the direction of the contact surface, and therefore, the contact force is discontinuous. This issue is tackled in linear finite element analysis using various surface smoothing techniques, however, a better solution is to use isogeometric analysis where the solution space is spanned by smooth spline basis functions. Unfortunately, spline-based isogeometric contact analysis still has limited applicability to industrial computer aided design (CAD) representations. Building analysis suitable mesh from the industrial CAD representations has been a major bottleneck of the computer aided engineering workflow. One promising alternative field of study, intended to address this challenge, is called the immersed finite element method. In this method, the original CAD domain is immersed in a rectilinear grid called the background mesh. This cuts down the model preparation and the mesh generation time from the original CAD domain, but the method suffers from limited accuracy issues. In this dissertation, the original CAD domain is immersed in an envelope domain which can be of arbitrary topological and geometric complexity and can approximate none, some or all of the features of the original CAD domain. Therefore, the method, called the flex representation method, is much more flexible than the traditional immersed finite element method. Within the framework of the flex representation method, a robust and accurate contact search algorithm is developed, that efficiently computes the collision points between the contacting surfaces in a discrete setting. With this information at hand, a penalty based formulation is derived to enforce the contact constraint weakly for multibody and self-contact problems. In addition, the contact algorithm is used to solve various proof-of-concept academic problems and some real world industrial problems to demonstrate the validity and robustness of the algorithms.

<p> Water drops at their boiling point were projected through a steam atmosphere to strike a surface which was varied in temperature from 300 to 900 degrees Fahrenheit. A high-speed motion picture study of the collision process showed that, except at low surface temperatures, the drop flattened out on impact and rebounded in a state of oscillation. Measurements of the change in drop diameter on collision indicated that the amount of evaporation due to heat transfer from the surface was extremely small except when the drop extensively wetted the surface. Solution of a mathematical model of the initial impact dynamics and models of heat transfer through a vapour film beneath the drop and by direct liquid-surface contact confirmed experimental observations. </p> / Thesis / Doctor of Philosophy (PhD)

A search for the Higgs boson produced with large transverse momentum and decaying as H -&gt; bb is presented, using the 80 fb^{-1} from the dataset collected by the ATLAS detector at sqrt{s}=13 TeV. The Higgs boson is reconstructed as a large-R jet with two b-tagged variable radius track-jets. The work focuses on a peculiar event topology in which the Higgs is produced in association with another Large-R jet. Considering events with reconstructed pT above 480 GeV and with a reconstructed mass from 70-230 GeV, a signal significance of 1.6 sigma for the Higgs and of 5 sigma for the V (Z boson + W boson) is observed. Furthermore, the new Full Run2 analysis is presented, using 136 fb^{-1} from the dataset collected by the ATLAS detector at sqrt{s}=13 TeV. The strategy up to the computation of the expected sensitivity for the Higgs boson is presented in this thesis. The validation of the background modeling is described in details, including tests on data. A preliminary extraction of the Z boson signal is performed and the measured signal strength corresponds to muZ = 0.82 +/- 0.09.

Nowadays, more and more flexible and efficient processes are required in modern industrial applications. In this field, robots are a key technoligy. In this paper a application is considered, where a 6-axis-industrial robot has to pick-and-place objects time efficiently in a constantly changing environment. Therefore, a concept for automated motion planning is presented, which is composed of two steps which are path planning and trajectory generation. In this paper suitable and established model-based methods are analyzed and chosen. Eventually, the suitability of the presented concept for the considered task is shown by implementing the concept in Matlab and applying it to a 6-axis articulated robot arm.

This thesis is to study the optimisation problems in autonomous vehicles, especially the modelling and optimisation of collision avoidance, and to develop some optimisation algorithms based on genetic algorithms and neural networks to operate autonomous vehicles without any collision. Autonomous vehicles, also called self-driving vehicles or driverless vehicles are completely robotised driving frameworks to allow the vehicle to react to outside conditions within a bunch of calculations to play out the undertakings. This thesis summarised artificial intelligence and optimisation techniques for autonomous driving systems in the literature. The optimisation problems related to autonomous vehicles are categorised into four groups: lane change, motion planner, collision avoidance, and artificial intelligence. A chart had been developed to summarise those research and related optimisation methods to help future researchers in the selection of optimisation methods Collision Avoidance is one of streamlining issues in autonomous vehicles. Several sensors had been used to identify position and dangers and collision avoidance algorithms had been developed to analyse the dangers and to use vehicles to avoid a collision. In this thesis, the current research on collision avoidance has been reviewed and some challenges and future works were presented to select the research direction of this thesis, the aim of this research will be the development of optimisation methods to avoid collisions in a predefined environment. The contributions of this thesis are that (1) a simulation model had been developed using Matlab for collision avoidance and serval scenarios were proposed and experimented with. The sensors are used as the inputs to determine collision in the learning preparation of the algorithm; (2) a neural network was used for collision avoidance of autonomous vehicles; (3) a new method was proposed with the combination of genetic algorithm and neural network. In the proposed frame, the neural network is used for decision making and a genetic algorithm is used for the training of the neural network. The results and experimentation show that the proposed strategies are well in the designed environment.

This paper is an investigation into the effect of the bat support conditions on the collision between a baseball and a baseball bat. Bat performance is tested using both machines and human subjects. For the machine tests, a baseball is fired from an air-cannon at a stationary bat, where the bat is either allowed to rotate only or is completely unrestricted after impact. The initial and rebound ball speeds are measured for a range of impact locations. For the human tests, a person swings the bat and hits the ball off of a tee. The bat speed prior to impact and the ball speed after impact are measured. The results for each method of testing are compared, and the final ball speed is found to be independent of the bat support condition.

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