Engineering Commons^™

Evaluation Of A Threshold-Based Model Of The Elevated-Temperature Fatique Of Impact-Damaged Γ-Tial, Trevor S. Harding, J. Wayne Jones

Materials Engineering

Step-loading fatigue tests have been conducted on two γ-TiAl alloys with differing microstructures following quasi-static indentations intended to simulate assembly-related impact damage to low-pressure turbine blades. Fatigue tests were conducted at 600 °C using computer-controlled servohydraulic loading at a frequency of 20 Hz. Reasonably good agreement was achieved between the fatigue data and calculated fatigue strength based on the fatigue threshold and measured impact severity. In certain cases, the fatigue threshold model fails to completely describe the data. These discrepancies may be related to residual stresses, variations in crack-shape morphology, and small-crack effects. Residual stresses could not be directly measured, …

A Theory Of Volumetric Growth For Compressible Elastic Biological Materials, Stephen M. Klisch, Timothy J. Van Dyke, Anne Hoger

Mechanical Engineering

A general theory of volumetric growth for compressible elastic materials is presented. The authors derive a complete set of governing equations in the present configuration for an elastic material undergoing a continuous growth process. In particular, they obtain two constitutive restrictions from a work-energy principle. First, the authors show that a growing elastic material behaves as a Green-elastic material. Second, they obtain an expression that relates the stress power due to growth to the rate of energy change due to growth. Then, the governing equations for a small increment of growth are derived from the more general theory. The equations …

Statistics Of Sdf-System Estimate Of Roof Displacement For Pushover Analysis Of Buildings, Anil K. Chopra, Rakesh K. Goel, Chatpan Chintanapakdee

Civil and Environmental Engineering

Investigated in this report is the basic premise that the roof displacement of a multistory building can be determined from the deformation of an SDF system. For this purpose, the response of both systems is determined rigorously by nonlinear response history analysis, without introducing any of the approximations underlying the simplified methods for estimating the deformation of an SDF system (see, e.g., FEMA-273 or ATC-40 guidelines). The statistics of the SDF-system estimate of roof displacement are presented for a variety of building frames and six SAC buildings subjected to ground motion ensembles.

Two sets of structural systems and ground motions …

Determination Of Thickness Of Smooth Geomembranes, Nazli Yesiller, Arif Cekic

Civil and Environmental Engineering

Tests were conducted to determine thickness of smooth, nonreinforced geomembranes using three methods: mechanical (according to ASTM and European standards), ultrasonic, and magnetic methods. The mechanical method is the standard procedure used for determining thickness of geomembranes. The ultrasonic and magnetic methods are not commonly used for geomembranes; however, they are used for testing other materials such as metals. Tests were conducted on 15 geomembranes representing five types of polymers (HDPE, LLDPE, PVC, PP, and EPDM). The results of the testing program indicated that the level of pressures applied affected the thickness measurements in mechanical tests. While the low pressures …

Evaluation Of Drip And Microsprayer Irrigation Systems In California's Central Valley, Charles M. Burt

BioResource and Agricultural Engineering

No abstract provided.

Evaporation Estimates For Irrigated Agriculture In California, Charles M. Burt, Daniel J. Howes, Andrew Mutziger

BioResource and Agricultural Engineering

All California irrigation districts that receive either federal or state water are now required to prepare Water Conservation Plans. For the first time in the history of most districts, they are developing an elementary water balance. The term "elementary" should be emphasized, because there are significant weaknesses in our knowledge of subsurface flows and some components of Evapotranspiration (ET). Irrigation districts generally use published "typical" values of ET for their water balance computations.

Ultrasonic Pulse Velocity In Concrete Using Direct And Indirect Transmission, Ismail Ozgur Yaman, Gokhan Inci, Nazli Yesiller, Haluk M. Aktan

Civil and Environmental Engineering

The relationship between velocities of ultrasonic stress waves transmitted along direct and indirect paths was investigated. Tests were conducted on plain concrete slabs of dimensions 1000 x 1500 mm, with a thickness of 250 mm. Direct ultrasonic wave transmission tests were conducted between top and bottom surfaces of the slabs and indirect tests were conducted along the slab surface. A test procedure, described in BS 1881 to determine indirect wave velocities, was refined by defining the number and spacing of transducers. Comparisons were made between direct and indirect wave velocity measurements using statistical analysis. The statistical analysis revealed that direct …

Sampling Switch Having An Independent "On" Impedance, Adrian K. Ong, Vladimir I. Prodanov, Maurice J. Tarsia

Electrical Engineering

A sampling device for sampling an input signal in response to a pulse train of a sample signal. The sampling device includes a sampling transistor for creating samples in response to the sample signal. The sampling transistor has an impedance corresponding with the difference between the gate to source voltage and the threshold voltage of the sampling transistor. The sampling device also includes a control device for generating a control signal. The control device includes a bootstrap reference voltage source for providing a reference voltage in response to the sample signal, and a control circuit for generating the control circuit …

A Java-Applet-Based Three-Phase Power System Harmonics Simulator, Taufik, Linda Kakinami

Electrical Engineering

This paper presents the development of a Java applet to simulate three-phase power system when harmonics is being introduced. The applet-based makes the simulator a very useful visual tool in understanding how harmonics affects the shape of sinusoidal waveform and thus the quality of power resulted thereof. The use of Java applet also enables the simulator to be run through internet via web-browser, and hence improves its availability and accessibility. The skeleton of the simulator will first be described. Then, discussion on how to operate the simulator follows which includes an example with snapshots to demonstrate the execution of the …

The Current State Of Research On Academic Dishonesty Among Engineering Students, Trevor S. Harding, Donald D. Carpenter, Susan M. Montgomery, Nicholas H. Steneck

Materials Engineering

Academic dishonesty, or cheating, has become a serious problem at colleges and universities. This is particularly true of engineering students who, are among the most likely to cheat in college. The present paper reviews the literature as a basis of broadly understanding academic dishonesty. This discussion focuses on three primary issues: (1) perceptions of and attitudes towards cheating, (2) reasons for student cheating, and (3) methods of promoting academic integrity. A current research project being developed by the authors is also discussed. The premise of this research is that students are constantly making ethical judgements between the pressure to cheat …

Siptool: The 'Signal And Image Processing Tool' An Engaging Learning Environment, Fred W. Depiero

Electrical Engineering

The ‘Signal and Image Processing Tool’ is a multimedia software environment for demonstrating and developing Signal & Image Processing techniques. It has been used at Cal Poly for three years. A key feature is extensibility via C/C++ programming. The tool has a minimal learning curve, making it amenable for weekly student projects. The software distribution includes multimedia demonstrations ready for classroom or laboratory use. SIPTool programming assignments strengthen the skills needed for life-long learning by requiring students to translate mathematical expressions into a standard programming language, to create an integrated processing system (as opposed to simply using canned processing routines).

Automatic Compact Disc Transfer For Quality Assurance Testing, Ravi P. Ramachandran, John Chen, Linda M. Head, John L. Schmalzel, Hampton C. Gabler

Mechanical Engineering

The purpose of this project was to design, build and test a low cost prototype that transfers compact discs (CDs) from a spindle to a computer based testing station. This will speed up the CD production/testing interface and eliminate the need for manual operation. Along with a heavy product design technical component, the project included a real life educational experience for the four students who got credit for a one year advanced senior project. Various designs were considered and the optimal design (based on cost and performance) was prototyped.

A Cmos Agc-Less If Strip For Bluetooth, Vladimir I. Prodanov, George Palaskas, Jack Glas, Vito Boccuzzi

Electrical Engineering

This paper presents an IF chain suitable for Low-IF fully-integrated GFSK receivers. The circuit performs amplification and channel selection (including image rejection). A five-pole Gm-C polyphase filter forms the core of the IF strip. The filter is current driven and has transimpedance gain of ≃ 120 kΩ. The filter is architectured so that GFSK signals with dynamic range exceeding 50dB can be decoded without the need of any automatic gain control. This AGC-less IF strip was fabricated in standard 0.25 µm CMOS process. It draws 6.2 mA from a 2.5 V supply and has better than 4.8 nA rms input …

Hfco2 Laves Phase Intermetallics - Part Ii: Elastic And Mechanical Properties As A Function Of Composition, Katherine C. Chen, Fuming Chu, Paul G. Kotula, Dan Thoma

Materials Engineering

In efforts to establish and understand structure–property relationships in Laves phase intermetallics, elastic and mechanical properties are studied as a function of composition in the C15 HfCo₂ system. Elastic constants and Debye temperatures are determined by resonant ultrasound spectroscopy (RUS) at room temperature. A maximum near the stoichiometric Laves composition is revealed with the Young's modulus, bulk modulus, and Poisson's ratio. In addition, a slight drop in shear modulus is found with Co-rich compositions, and the Debye temperature increases with Co-content. Room temperature Vickers indentation is performed to assess the microhardness and fracture toughness of the HfCo₂ alloys. …

Hfco2 Laves Phas Intermetallics - Part I: Solubility Limits And Defect Mechanisms, Katherine C. Chen, Eric J. Peterson, Dan J. Thoma

Materials Engineering

Solubility limits and constitutional defects in Laves phase intermetallics are investigated with the C15 HfCo₂ system. Several binary alloy compositions based on HfCo₂ are characterized by optical and scanning electron microscopy (SEM), electron microprobe analysis (EPMA), X-ray diffraction (XRD), and density measurements. Rietveld refinements of XRD scans are used to determine lattice constants, anisotropic strain parameters, and atomic occupancies. Compositional trends are compared against predicted or calculated trends due to an anti-site substitution or vacancy defect mechanism. Geometric models and atomic size factors are used to establish solubility limits and to give insight into defect mechanisms. Results from …

Compressive Behavior Of Concrete With Vitrified Soil Aggregate, Shane M. Palmquist, Daniel C. Jansen, Christopher W. Swan

Civil and Environmental Engineering

The compressive behavior of portland cement concrete with vitrified soil coarse aggregate is the focus of this paper. A total of 10 batches of concrete were examined at four different coarse aggregate volume fractions with three different combinations of vitrified and natural coarse aggregates. For comparison purposes, the ratios of cement, water, and fine aggregates were held constant. The stress-strain curves, modulus of elasticity, compressive strength, and Poisson's ratio are examined as a function of coarse aggregate content. Results show a decrease in compressive strength as the volume fraction of vitrified soil aggregate increased. Moduli of elasticity for concrete with …

Evaluation Of Geomembranes Using An Ultrasonic Method, Nazli Yesiller, Sevil Sungur

Civil and Environmental Engineering

An ultrasonic testing procedure was developed to evaluate geomembranes. The pulse-echo inspection technique was used on the surface of geomembranes without disturbing the material. The equipment required consists of a P-wave transducer, a pulser-receiver, and a signal acquisition system. Travel time of ultrasonic waves and waveform energy are measured to evaluate the condition of geomembranes. Laboratory tests were conducted to assess the effectiveness of the method. Defects that simulate installation damage and various in-service degradation conditions were induced on samples. The defects were identified with the ultrasonic method at a success rate higher than 98%. Changes in the thickness or …

Watershed Management Technique To Control Sediment Yield In Agriculturally Dominated Areas, John W. Nicklow, Misgana K. Muleta

Civil and Environmental Engineering

Non-point source pollution is recognized internationally as a critical environmental problem. In Illinois, soil erosion from agricultural lands is the major source of such pollution. The erosion process, which has been accelerated by human activity, tends to reduce crop productivity and leads to subsequent problems from deposition on farmlands and in water bodies. Comprehensive watershed management, however, can be used to protect these natural resources. In this study, a discrete time optimal control methodology and computational model are developed for determining land use and management alternatives that minimize sediment yield from agriculturally-dominated watersheds. The solution methodology is based on an …

Simplified Analysis Of Asymmetric Structures With Supplemental Damping, Rakesh K. Goel

Civil and Environmental Engineering

This study investigated the effects of neglecting off‐diagonal terms of the transformed damping matrix on the seismic response of non‐proportionally damped asymmetric‐plan systems with the specific aim of identifying the range of system parameters for which this simplification can be used without introducing significant errors in the response. For this purpose, a procedure is presented in which modal damping ratios computed by neglecting off‐diagonal terms of the transformed damping matrix are used in the traditional modal analysis. The effects of the simplification are evaluated first by comparing the aforementioned modal damping ratios with the apparent damping ratios obtained from the …

Rapid Appraisal Process And Benchmarking, Charles M. Burt, Stuart W. Styles

BioResource and Agricultural Engineering

This WORD document [Rapid Appraisal Process (RAP) and Benchmarking] provides an explanation of the Rapid Appraisal Process (RAP), as well as a brief explanation of Benchmarking and the data that must be collected for both endeavors. This document also provides an explanation the EXCEL documents that are used by persons during the RAP. An EXCEL spreadsheet (with 12 internal worksheets) is provided twice:
1. Rapid Appraisal and Benchmarking BLANK.xls
2. Rapid Appraisal and Benchmarking EXAMPLE.xls
As the names suggest, the EXAMPLE has data in it so that users can examine an example before entering data in a blank spreadsheet.

Proceso De Evaluación Rápido (Rap) Y Comparación Con El Patrón De Referencia (Benchmarking): Explicación Y Herramientas, Charles M. Burt

BioResource and Agricultural Engineering

Este documento WORD [RAP Documento en Español] provee una explicación del Proceso De Evaluación Rápido (RAP), como también una breve explicación de la Comparación con el Patrón de Referencia como también de los datos que deben ser recolectados para ambos esfuerzos. Este documento también provee una explicación de los archivos en EXCEL que son usados durante el RAP. Una planilla de cálculo en EXCEL (con 13 hojas de trabajo internas) es provista dos veces:

1. RAP en Español – EN BLANCO.xls

2. RAP en Español – EJEMPLO.xls

Como lo sugieren sus nombres, el EJEMPLO tiene datos previamente ingresados de manera …

Shock Layer Instability Near The Newtonian Limit Of Hypervelocity Flows, H. G. Hornung, P. Lemieux

Mechanical Engineering

The curved bow shock in hypersonic flow over a blunt body generates a shear layer with smoothly distributed vorticity. The vorticity magnitude is approximately proportional to the density ratio across the shock, which may be very large in hypervelocity flow, making the shear layer unstable. A computational study of the instability reveals that two distinct nonlinear growth mechanisms occur in such flows: First, the vortical structures formed in the layer move supersonically with respect to the flow beneath them and form shock waves that reflect from the body and reinforce the structures. Second, the structures deform the bow shock, forming …

The Demise Of Aerospace, Part 2. We Doubt It., John H. Mcmasters, Russell M. Cummings

Aerospace Engineering

No abstract provided.

Microwave Modulation Of A Quantum-Well Laser With And Without External Optical Injection, Xiaomin Jin, Shun-Lien Chuang

Electrical Engineering

We compare three microwave modulation methods experimentally and theoretically using a semiconductor quantum-well (QW) Fabry–Perot test laser: 1) direct microwave current modulation of the test laser (electrical modulation); 2) optical modulation by an external single-wavelength pump laser with a modulated optical injection power; and 3) electrical modulation of the test laser that is injection locked by an external single-wavelength pump laser with a constant injection power. This is the first direct comparison of the three modulation methods on the same QW laser, to the best of our knowledge. The bandwidth of optical absorption modulation is 7.7 GHz, which is 1.45 …

Removing Barriers To High-Strength Concrete In Boston, Daniel C. Jansen, Herman Protze

Civil and Environmental Engineering

No abstract provided.

The Foundation Series On Corrosion: Integrating Science, Math, Engineering & Technology In A Lab Setting, Linda Vanasupa, Heather Smith, Blair London, Katherine C. Chen, David Niebuhr, Lanny Griffin, Jeff Jones

Materials Engineering

We have developed a laboratory module focusing on the subject of corrosion. The module itself is designed to be completed in one three-hour session. It consists of three parts: I. The Impact of Corrosion Media, II. The Impact of Corroding Materials, III. The Impact of Anode/Cathode Sizes. Our objectives in developing this module were to address the need for clear bridges between math, science and technology in the engineering curriculum and to provide a means of faculty development primarily at community colleges. As a result, it was designed to allow the engineering student to experience the synergy of science, math …

Asee Student Chapters: From Student Members To Faculty, Jennifer Kadlowec, Kurt Degoede, Trevor S. Harding, Christian Lorenz

Materials Engineering

The University of Michigan Student Chapter of the American Society for Engineering Education has grown from a small core group of founding members, who organized panel discussions for the graduate student community, into a flourishing student organization, which continues to grow in membership and events. The purpose of this paper is to promote graduate student chapters of the ASEE and demonstrate the positive impact that student member participation has had, particularly for those who have recently entered academia. Many events and activities of the University of Michigan Student Chapter of the American Society for Engineering Education (UM-ASEE Student Chapter) will …

Useful Approaches To Preventing Academic Dishonesty In The Classroom, Trevor S. Harding

Materials Engineering

Over the past three decades, academic dishonesty (a.k.a. cheating) has become an increasingly common occurrence among college-aged students, and engineering students are known to be among the most frequent culprits. At most universities, cheating is dealt with after the fact. Few institutions go beyond drafting an academic integrity policy to prevent cheating before it happens. The same situation exists in the classroom. The majority of college professors report doing little or nothing to reduce the frequency of cheating in their classes, usually because of a lack of awareness of its occurrence. And when cheating is observed, faculty overwhelmingly choose to …

On The Frequency And Causes Of Academic Dishonesty Among Engineering Students, Trevor S. Harding

Materials Engineering

According to studies of self-reported academic dishonesty conducted over time, cheating among college students has been on the increase since at least the 1940’s. This is especially true for engineering students who are now among the most likely to cheat compared to other disciplines. This paper will present a synopsis of the literature on academic dishonesty. In addition, the results of a pilot study on cheating among engineering students conducted at a small mid-western private engineering school are described. Engineering students in an introductory engineering materials course were asked to complete a survey on their perceptions of cheating; therefore, all …

Greasing The Tenure Track 2, David Braun

Electrical Engineering

Some new faculty must balance the competing demands of the desire to teach effectively while maintaining a heavy teaching load. Oh, and, by the way, along the way to the tenure hurdle, research, professional development, and service duties may distract from family, friends, and real life. Based on the author’s participation in the NSF's New Century Scholars (NCS) Workshop at Stanford University as both a scholar (1999) and, subsequently, as a senior scholar (2000), this paper summarizes six useful tips for tenure-track faculty. This second paper in the series by NCS senior scholars provides the perspective of an engineering educator …