Alternative approach for teaching multibody dynamics

The paper presents an alternative method, the Implicit Constraint Approach (ICA), for developing the equations of motion to describe a system of connected bodies typified by mechanisms and robotic devices. By its simplicity of description and implementation compared to conventional methods, the ICA engages students more in the physics (rather than the mathematics) of the system under study. The ICA enables the direct formation of all needed equations by using only the dynamic equilibrium conditions (in the Newton or Lagrange form). Unlike current approaches, no auxiliary algebraic constraint equations are required. Thus the descriptive equations are ordinary differential equation (ODEs) rather than differential-algebraic equations (DAEs). This leads to simpler mathematics and a broader range of potentially useful numerical integration methods. Examples are provided which illustrate the use of the ICA. The more involved examples employ a general purpose computer program that uses the ICA to provide the kinematics and forces for a planar mechanism of arbitrary complexity

Teacher 2020. On the Road to Entrepreneurial Fluency in Teacher Education

No abstract available

Using a 2-D Simulation Program to Support Interactive Learning of 3-D Vehicle Dynamics

The author has developed an undergraduate course to introduce students to the basic principles of land vehicle dynamics. Many students, though they are intrinsically interested in the subject, have difficulty grasping the physical principles needed to enable a sufficient understanding of the subject to support their aspirations of making informed vehicle design decisions. An intriguing potentially useful fact is that the computer gaming world has developed widely available very sophisticated vehicle computer models with realistic human driver interfaces. However, while very entertaining, these computer games are not suitable for helping undergraduate engineering students understand the basic principles needed for land vehicle design. Therefore, as part of this course, the students develop their own dynamic models of vehicles (using Working Model 2D) starting with simplified quarter-vehicle suspension systems and working up to a steerable four-wheel drive vehicle traveling over a rough road. The innovation from an instructional standpoint is that students can get a good understanding of some three-dimensional effects, and thus the design principles derivable from this understanding, through employing a fairly simple to program and use widely available 2-D dynamic simulator software. The paper outlines the methodology for incorporating 3-D effects for land vehicle problems, and this methodology is illustrated with some specific examples

Simplified Explanation of Pneumatic Tire Behavior

This paper develops a simple model for the behavior of a pneumatic tire when vertically loaded. The model is based on the behavior of a thick-skinned spherical membrane (like a basketball) being compressed between two flat plates. The model is reasonably accurate for bicycle, motorcycle, truck, general purpose, and early model automobile tires which all have a circular cross-section. However modern automobile tires have a wide aspect ratio when unloaded, have unloaded line contact with the ground across the tread width, and have relatively stiff sidewalls that contribute to the tire’s load carrying capability (and in the case of run-flat tires can totally support the car’s weight). Thus the analysis in this paper is quantitatively representative for tires of initially round cross-section, like a typical motorcycle tire, but provides only a qualitative idea of the tire support mechanism for modern automobile tires

Using Off-campus Student-designed Experiments to Aid in Student Learning

In an upper level undergraduate elective course in vehicle dynamics, the author has developed some off-campus experimental-based assignments that involve the students (in pairs) designing the experiments and providing their own measuring tools and test vehicle to get results that they can compare with their calculated predictions. The students are free to design their own procedure or do some investigation and use an industry-standard approach. The students typically find that their experimental results vary considerably from their predictions. While this can be due to simple student implementation errors, it is typically a result of more complex issues. This leads to some deep learning (and a little frustration) for the students as they look into why their results, which they have clearly observed, should differ so much from those predicted by standard machine design and dynamics formulae they have previously used without question. Students must dig into and understand the assumptions behind the standard formulas and also the assumptions they made in designing and executing their experiments. (Texts and Internet articles are often misleading on this subject so students also get an appreciation for the nuances of interpreting what someone has written.) To balance the frustration factor associated with the “reality” of the assignment, there is a fun factor in testing using real vehicles (in various states of conforming to the original manufacturers’ specifications) that pushes the students further in the assignment than they would go with a typical campus lab experiment. The paper describes two of the experiments providing some sample student approaches with examples of experiment-calculation discrepancies and their likely causes

The APM Galaxy Survey:- V. Catalogues of Galaxy Clusters

We describe the construction of catalogues of galaxy clusters from the APM Galaxy survey using an automated algorithm based on Abell-like selection criteria. We investigate the effects of varying several parameters in our selection algorithm, including the magnitude range, and radius from the cluster centre used to estimate the cluster richnesses. We quantify the accuracy of the photometric distance estimates by comparing with measured redshifts, and we investigate the stability and completeness of the resulting catalogues. We find that the angular correlation functions for different cluster catalogues are in good agreement with one another, and are also consistent with the observed amplitude of the spatial correlation function of rich clusters.Comment: 14 pages, PostScript, including 15 figures, submitted to MNRAS. Also available from ftp://ftp-astro.physics.ox.ac.uk/pub/gbd/papers/apm5.ps.g

Automatic skin segmentation for gesture recognition combining region and support vector machine active learning

Skin segmentation is the cornerstone of many applications such as gesture recognition, face detection, and objectionable image filtering. In this paper, we attempt to address the skin segmentation problem for gesture recognition. Initially, given a gesture video sequence, a generic skin model is applied to the first couple of frames to automatically collect the training data. Then, an SVM classifier based on active learning is used to identify the skin pixels. Finally, the results are improved by incorporating region segmentation. The proposed algorithm is fully automatic and adaptive to different signers. We have tested our approach on the ECHO database. Comparing with other existing algorithms, our method could achieve better performance

Statement of George W. Sutherland

Reminiscences of an early Colfax, Washington, resident, chiefly about a company of volunteers formed to protect the Palouse country during the 1877 Nez Perce War, as recorded by Jerome Peltier.https://dc.ewu.edu/spc_pubs/1014/thumbnail.jp

High Resolution Gas-phase Silicon 2p Core-level Spectroscopy Using Synchrotron Radiation

High resolution (0.05 eV) Si 2p pre-edge photoabsorption spectra of SiH{dollar}\sb4{dollar}, SiD{dollar}\sb4{dollar}, Si{dollar}\sb2{dollar}H{dollar}\sb6{dollar} and Si{dollar}\sb3{dollar}H{dollar}\sb8{dollar} show a large number of peaks due to Si 2p {dollar}\to{dollar} Rydberg transitions, along with rich vibrational structure. The SiD{dollar}\sb4{dollar} spectrum has been very useful in distinguishing between Rydberg states and vibrational excitations. The spectra of Si{dollar}\sb2{dollar}H{dollar}\sb6{dollar} and Si{dollar}\sb3{dollar}H{dollar}\sb8{dollar} are very similar to each other, exhibiting excitation of asymmetric Si-H vibrations.;The Si L- and K-edge XANES spectra of Si(OCH{dollar}\sb3)\sb{lcub}\rm X{rcub}{dollar}(CH{dollar}\sb3)\sb{lcub}\rm 4-X{rcub}{dollar} (X = 0-4) are reported and the two end members of the series, Si(OCH{dollar}\sb3)\sb4{dollar} and Si(CH{dollar}\sb3)\sb4{dollar}, are compared to the spectra of SiO{dollar}\sb2{dollar} and SiC. The L-edge spectra of gaseous Si(OCH{dollar}\sb3)\sb4{dollar} and solid SiO{dollar}\sb2{dollar} are qualitatively identical, while the L-edge spectra of Si(CH{dollar}\sb3)\sb4{dollar} and SiC show strong similarities. MX-X{dollar}\alpha{dollar} calculations for the two species Si(OCH{dollar}\sb3)\sb4{dollar} were used to assign the various spectra for both compounds. Assignments for SiO{dollar}\sb2{dollar} are based upon a molecular orbital interpretation of the electronic structure of this compound.;High resolution ({dollar}\sim{dollar}0.1 eV) Si 2p gas-phase photoelectron spectra of 24 compounds are reported: SiH{dollar}\sb{lcub}\rm X{rcub}{dollar}D{dollar}\sb{lcub}\rm 4-X{rcub}{dollar}; Si(CH{dollar}\sb3)\sb{lcub}\rm X{rcub}{dollar}(OCH{dollar}\sb3)\sb{lcub}\rm 4-X{rcub}{dollar}; Si(CH{dollar}\sb3)\sb{lcub}\rm X{rcub}{dollar} (N(CH{dollar}\sb3)\sb2\rbrack\sb{lcub}\rm 4-X{rcub}{dollar}; SiH{dollar}\sb{lcub}\rm X{rcub}{dollar} (Si(CH{dollar}\sb3)\sb3\rbrack\sb{lcub}\rm 4-X{rcub}{dollar}; (X = 0-4), and SiH{dollar}\sb3{dollar}-CH{dollar}\sb3{dollar}, SiH{dollar}\sb3{dollar}-SiH{dollar}\sb3{dollar}, SiH{dollar}\sb3{dollar}-SiH{dollar}\sb2{dollar}-SiH{dollar}\sb3{dollar}, Si(CH{dollar}\sb3)\sb3{dollar}-Si(CH{dollar}\sb3)\sb3{dollar}, Ge (Si(CH{dollar}\sb3)\sb3\rbrack\sb4{dollar} and (Si(CH{dollar}\sb3)\sb2\rbrack\sb6{dollar}. Vibrational excitations have been resolved in the spectra of SiH{dollar}\sb{lcub}\rm X{rcub}{dollar}D{dollar}\sb{lcub}\rm 4-X{rcub}{dollar}, SiH{dollar}\sb3{dollar}-CH{dollar}\sb3{dollar}, SiH{dollar}\sb3{dollar}-SiH{dollar}\sb3{dollar} and SiH{dollar}\sb3{dollar}-SiH{dollar}\sb2{dollar}-SiH{dollar}\sb3{dollar}. For the compounds {dollar}\rm SiH\sb{lcub}X{rcub}D\sb{lcub}4-X{rcub}{dollar} and SiH{dollar}\sb3{dollar}-CH{dollar}\sb3{dollar} the vibrational structure is dominated by the Si-H, Si-D or Si-C symmetric vibrational mode. Conversely, the spectra of SiH{dollar}\sb3{dollar}-SiH{dollar}\sb3{dollar} and SiH{dollar}\sb3{dollar}-SiH{dollar}\sb2{dollar}-SiH{dollar}\sb3{dollar} are dominated by the asymmetric Si-H bending vibrations--the first example of this in core-level photoelectron spectroscopy. In the remaining compounds the vibrational effects are not resolved; however, the peak widths increase in the order Si(CH{dollar}\sb3)\sb4\u3c{dollar} Si (Si(CH{dollar}\sb3)\sb3\rbrack\sb4\u3c{dollar} Si (N(CH{dollar}\sb3)\sb2\rbrack\sb4\u3c{dollar} Si(OCH{dollar}\sb3)\sb4\u3c{dollar} SiF{dollar}\sb4{dollar} indicating that the vibrational manifold increases analogously.;The valence photoelectron spectra of Si(CH{dollar}\sb3)\sb4{dollar}, Si(CH{dollar}\sb3)\sb3{dollar}-Si(CH{dollar}\sb3)\sb3{dollar}, Si (Si(CH{dollar}\sb3)\sb3\rbrack\sb4{dollar}, Ge (Si(CH{dollar}\sb3)\sb3\rbrack\sb4{dollar} and (Si(CH{dollar}\sb3)\sb2\rbrack\sb6{dollar} are reported at four different photon energies, 21.2, 100, 120 and 135 eV