Engineering Commons^™

Plastic Solder Paste Stencil For Surface Mount Technology, Christopher K. Wong, Daniel Waldorf

Industrial and Manufacturing Engineering

Solder paste masks or stencils are an integral part of the manufacturing process for surface mount PCBs. This study examines the feasibility of a process for rapid creation of a solder paste stencil using thermoplastic material. CNC laser cutting of the stencil geometry is replacing traditional use of chemical etching on metal sheets to produce stencils. Laser cutting has been used to improve process speed, accuracy, and cost. This research attempts to continue to simplify and reduce costs in the stencil making process by proposing as the stencil material a common thermoplastic that can be cut easily and quickly using …

Global Projects Prepare Wpi Students For The 21st Century, William W. Durgin, Donald N. Zwiep

Office of the Provost Scholarship

The WPI project based curriculum, which emphasizes discovery based learning are an alternative to the traditional information transfer process, has proved successful in delivering global engineering education. More than 25% of the learning process of the students is integrated into two formal projects, the Major Qualifying Project (MQP) which is designed as a capstone for professional technical competence and the Interactive Qualifying Project (IQP) which relates science and technology to societal concerns and student needs. Both the MQP and IQP may be completed on- or off-campus. Currently, over 50% of the graduating class will have completed one of the projects …

Effect Of Foreign Object Damage On The Fatigue Strength Of An Xd™ Γ-Tial Alloy, Trevor S. Harding, J. Wayne Jones

Materials Engineering

High cycle fatigue has become the leading cause of failure in gas turbine engine blades in recent years [1]. The majority of these failures were associated with surface damage such as foreign object damage (FOD). Therefore, the ability of a material to resist impact damage and the subsequent fatigue propagation of any cracks that may result has become a crucial design consideration. Substantial research has been conducted on the effects of simulated FOD in conventional turbine blade materials where the formation of cracks at the impact site was not a common occurrence [2, 3 and 4]. However, impacts of more …

Direct Displacement-Based Design Using Inelastic Design Spectrum, Rakesh K. Goel, Anil K. Chopra

Civil and Environmental Engineering

No abstract provided.

Lip Feature Extraction Towards An Automatic Speechreading System, Xiaozheng Zhang, Russell M. Mersereau

Electrical Engineering

The use of color information can significantly improve efficiency and robustness of lip feature extraction capability over purely grayscale-based methods. Edge information provides another useful tool in characterizing lip boundaries. In this paper we present a method of integrating both types of information to address the problem of lip feature extraction for the purpose of speechreading. We first examine various color models and view hue as an effective descriptor to characterize the lips due to its invariance to luminance and human skin color, and its discriminative properties. We use prominent red hue as an indicator to locate the position of …

Irrigation District Service In The Western United States, Charles M. Burt, Stuart W. Styles

BioResource and Agricultural Engineering

Data were obtained from 61 agricultural districts within the Mid-Pacific Region of the U.S. Bureau of Reclamation regarding the level of water delivery service provided to users, water pricing, associated characteristics, and plans for modernization. A flexibility index was developed and used by the writers to characterize the degree of water delivery flexibility provided by each district. The flexibility index provides a rating of 3–15 (15 being the highest value) based upon the frequency, rate, and duration of irrigation water delivery service to farmers. The data show that 42% of the districts received a flexibility score of 12 or greater, …

The Effect Of Anisotrophy On The Potential Distribution In Biological Tissues And Its Impact On Nerve Excitation Simulations, Robert B. Szlavik, Hubert De Bruin

Biomedical Engineering

Presents a finite difference solution of the potential distribution associated with electrical current stimulation in an anisotropic in-homogeneous tissue environment and compare it to the isotropic case. The results demonstrate that there can be significant errors associated with the assumption of isotropic tissue properties in calculating the potential distribution along an axon in nerve excitation simulations. These errors can have a significant impact on predicted nerve fiber recruitment patterns when evaluating the efficacy of specific surface or intramuscular stimulus electrode configurations. The results of this study also suggest when a more comprehensive tissue model should be implemented in an electrode …

Relative Intensity Noise Characteristics Of Injection-Locked Semiconductor Lasers, Xiaomin Jin, Shun-Lien Chuang

Electrical Engineering

An experimental and theoretical study of relative intensity noise (RIN) spectra of side-mode injection-locked Fabry–Perot semiconductor lasers is reported. It is shown that the injection-locking technique effectively increases the relaxation oscillation frequency from 4.5 GHz (free-running mode) to 12 GHz (injection-locked mode) and enhances relaxation peaks of the slave laser RIN spectra. Results from our theoretical model, which include the key parameters for semiconductor quantum-well lasers, such as the linewidth enhancement factor, the nonlinear gain saturation coefficients, and optical confinement factor, show good agreement with our experimental results.

Stability And Heat Transfer Characteristics Of Condensate Fluid Layers In Reduced Gravity, James C. Hermanson, Andreas N. Alexandrou, William W. Durgin, Peder C. Pedersen, Jeffrey S. Allen

Office of the Provost Scholarship

The focus of this ground-based program is the study of film condensation phenomena under variable, reduced-gravity conditions. Experimental tests, combined with numerical modeling, are employed to gain an improved understanding of the fundamental fluid physics responsible for condensate film growth, film instability and the resulting interfacial motion under variable gravity, and the corresponding implications for heat transfer. There has been relatively little research on the mechanisms operative at the film interface between condensed liquid and its vapor under reduced gravity conditions. Of particular interest are the stability characteristics of the condensate layer, and how they differ from those of films …

Thermally Treated Coal Tar Contaminated Soil As A Concrete Aggregate, Katherine E. Leblanc, John L. Durant, Christopher Swan, Michael J. Weaver, Daniel C. Jansen

Civil and Environmental Engineering

The current practice of landfilling thermally treated and untreated coal tar-contaminated soil is expensive, and it is a waste of a potentially useful material and landfill space. A less expensive and possibly more practical alternative is to use coal tar-contaminated soil as an aggregate in concrete. Because little work has been done in this area, the present study was undertaken to evaluate the effects of coal tar-contamination and thermal treatment on the physical properties of soil and the strength of concrete containing contaminated soil as an aggregate. Also assessed was the leachability of coal tar constituents (specifically, polycyclic aromatic hydrocarbons …

Field Case Histories For Spt-Based In Situ Liquefaction Potential Evaluation, K. Onder Cetin, Raymond B. Seed, Robb E.S. Moss, Armen Der Kiureghian, Kohji Tokimatsu, Leslie F. Harder, Jr., Robert E. Kayen

Civil and Environmental Engineering

This report provides documentation of the field performance case histories and site response analyses described in the report entitled "SPT-Based Probabilistic and Deterministic Assessment of Seismic Soil Liquefaction Initiation Hazard," by Cetin, et al. (2000).

Table 3-5, taken from that report, summarizes the interpreted field performance case histories from the original database of Seed et al. (1984) that were found to conform to the standards of Data Classes A, B or C, and so were used in the studies of Cetin et al. Table 3-7, also taken from that report, summarizes the cases that were deleted from the overall database …

Benchmarking Irrigation, Charles M. Burt

BioResource and Agricultural Engineering

A few performance indicators (e.g., “efficiency”) have been included in irrigation jargon for many decades. However, at the Rome meeting we will have a comprehensive discussion on irrigation benchmarking. It will be easy to fall into a discussion of definitions and specifics. Prior to that, it might be helpful to consider the following aspects that will help to set the stage for the details:

Direct Stochastic Equivalent Linearization Of Sdof Smart Mechanical System, L. Duval, Mohammad N. Noori, S. Seelecke

Office of the Dean (CENG) Scholarship

The first and second moments of response variables for SDOF system with pseudoelastic material are obtained by a direct linearization procedure. This procedure is an adaptation of well-known statistical linearization methods, and provides concise, model-independent linearization coefficients. The method can be applied to systems that incorporate any SMA hysteresis model having a differential constitutive equation, and can be used for zero and non-zero mean random vibration. This implementation eliminates the effort of deriving linearization coefficients for new SMA hysteresis model. In this paper the complete statistical response of SDOF system containing a mass and a bar made of SMA is …

A Technique For Analyzing Radiation From Conformal Antennas Mounted On Arbitrarily-Shaped Conducting Bodies, Dean Arakaki, Douglas H. Werner, Raj Mittra

Electrical Engineering

This paper presents an efficient method to solve the problem of radiation from conformal aperture and microstrip antennas mounted on arbitrarily shaped conducting bodies. The method, based on the surface equivalence and reciprocity principles, uses a combination of the finite difference time domain (FDTD) and method of moments (MoM) techniques to substantially improve the computational efficiency of the radiation pattern calculation. When the geometry and location of the radiating element are modified, only a small portion of the overall analysis requires re-simulation. This leads to a significant improvement in computational efficiency over presently used techniques, and can substantially improve the …

Wavelet-Based Approach For Structural Damage Detection, Z. Hou, Mohammad N. Noori, R. St. Amand

Office of the Dean (CENG) Scholarship

A wavelet-based approach is proposed for structural damage detection and health monitoring. Characteristics of representative vibration signals under the wavelet transformation are examined. The methodology is then applied to simulation data generated from a simple structural model subjected to a harmonic excitation. The model consists of multiple breakable springs, some of which may suffer irreversible damage when the response exceeds a threshold value or the number of cycles of motion is accumulated beyond their fatigue life. In cases of either abrupt or accumulative damages, occurrence of damage and the moment when it occurs can be clearly determined in the details …

The Effect Of Impact Damage On The Room-Temperature Fatigue Behavior Of Γ-Tial, Trevor S. Harding, J. Wayne Jones

Materials Engineering

The relationship between impact damage and the fatigue behavior of γ-TiAl has been examined. Axial fatigue specimens fabricated from cast Ti-47.9Al-2.0Cr-1.9Nb (to be referred to as 48-2-2) and Ti-47.3Al-2.2Nb-0.5Mn-0.4W-0.4Mo-0.23Si (to be referred to as WMS) alloys were damaged by impact under controlled conditions with a 60 deg wedge-shaped indenter to simulate assembly-related damage in low-pressure turbine blades. The level of damage produced was quantified and found to correlate well with the peak load of the impact event. The WMS alloy exhibited a greater resistance to impact damage due to its higher yield strength and lamellar microstructure. A measure of the …

Implementing An Engineering Teaching Development Program For Graduate Student Instructors, Sara Soderstrom, Christian Lorenz, Michael Keinath, Trevor S. Harding

Materials Engineering

The Engineering Teaching Development Project (ETDP), a pilot program started by the student chapter of ASEE at the University of Michigan, is a multi-component program designed to improve the long-term teaching skills of graduate student instructors (GSIs) in the College of Engineering. The first component of the ETDP is college-wide pedagogical workshop series. These workshops are conducted by nationally recognized engineering educators invited by the ASEE student chapter. The topics of these workshops include cooperative learning, diversity in the classroom, and classroom assessment techniques. These workshops offer a means of continual improvement for all of the educators in the university, …

Supplemental Viscous Damping Effects On Seismic Demands Of Linear Elastic Systems, Linda M. Tam, Rakesh K. Goel

Civil and Environmental Engineering

The objective of this study is to examine the effects of viscous supplemental damping on response quantities of asymmetric-plan structures responding in a linearly elastic fashion. The response quantities which will be investigated include: element deformations, base shears, and base torques. These response quantities will be normalized, evaluated, and then analyzed.

It is shown that supplemental damping is indeed effective in reducing element deformations and base torques. In some cases, supplemental damping is also effective in reducing base shears. In order to achieve the largest reduction in flexible element deformation, it is recommended that all fluid viscous dampers be placed …

Desiccation And Cracking Behavior Of Three Compacted Landfill Liner Soils, N. Yesiller, C. J. Miller, G. Inci, K. Yaldo

Civil and Environmental Engineering

Tests were conducted to investigate desiccation cracking of three compacted liner soils obtained from local landfills in southeast Michigan. The soils had low plasticity with varying fines content. Large-scale samples of the soils were subjected to wetting and drying cycles. Surficial dimensions of cracks and suction in the soils were monitored. Surficial dimensions of cracks were quantified using the crack intensity factor (CIF), which is the ratio of the surface area of cracks to the total surface area of a soil. All of the soils were subjected to a compaction–dry cycle (i.e. soils were allowed to dry after compaction) and …

Product Flexibility In Selecting Manufacturing Planning And Control Strategy, Emine Persentili, Sema E. Alptekin

Industrial and Manufacturing Engineering

The manufacturing systems capable of producing several products simultaneously are frequently subject to changes in product types due to demand fluctuations. In such systems a product flexible manufacturing planning and control (MPC) strategy is needed to change from one product type to another with minimum deterioration to system performance levels. The objective of this research is to develop a systematic analysis and evaluation approach in order to compare the MRP-push and JIT-pull strategies quantitatively based on a product flexibility measure. A new product flexibility measure is developed based on the sensitivity to change concept and presented together with the implementation …

A Method For Reducing The Variation In "On" Resistance Of A Mos Sampling Switch, A. K. Ong, Vladimir I. Prodanov, M. Tarsia

Electrical Engineering

Variation in the “on” resistance of a MOS sampling switch can introduce distortion into the front end of a switched-capacitor filter or analog-to-digital converter. We review three methods commonly used to linearize the resistance of a MOS switch and propose a new technique that addresses their limitations. A practical method for implementation is also suggested.

V-I Converters With Transconductance Proportional To Bias Current In Any Technology, Vladimir I. Prodanov

Electrical Engineering

In this paper we discuss circuits comprised of multiple differential pairs driven in parallel. We show that high linearity and linear with bias current tunability are intrinsic properties of any equidistant-offset multi-pair circuit. We argue that these two properties could potentially allow us to implement designs of analog filters, multipliers and other circuits that are (in first-order) technology independent. Simulations results are provided in support of presented simple intuitive explanation.

Operator Split Technique Applied To Random Vibration Of Smart Sdof Mechanical Systems, L. Duval, Mohammad N. Noori, M. A. Savi

Office of the Dean (CENG) Scholarship

A significant amount of research in the last few years has greatly advanced the field of structural control through the use of smart materials. Smart materials have the ability to change shape, stiffness, natural frequency, damping and other mechanical characteristics in response to environmental condition changes. One of he new class of materials with promising applications in structural and mechanical systems are Shape Memory Alloys (SMAs). However, there are few studies where the random response of mechanical systems containing shape memory components has been conducted. Such study is important to verify the feasibility on the use of SMAs in structural …

Modified Testing Procedure For The Two Parameter Fracture Model For Concrete, Daniel C. Jansen, W. Jason Weiss, Stefan H.F. Schleuchardt

Civil and Environmental Engineering

No abstract provided.

Ultrasonic Monitoring Method And System For Wake Turbulence Useful At Runways, Hamid Johari, William W. Durgin

Office of the Provost Scholarship

Two techniques for detecting vortices and their associated circulation are disclosed. The first is termed a closed path configuration, and the second is termed the dual path configuration. These techniques are useable for the detection of wake turbulence especially in the vicinity of airport runways, which results from wing tip vortices generated by aircraft during take-off and landing. The systems are similar in that they use ultrasonic measurement techniques to determine the circulation about defined areas. The circulation is reflective of the vorticity associated with trailing vortices, which are manifest within the area.

Control Of Earthquake Induced Vibrations In Asymmetric Buildings Using Passive Damping, Rakesh K. Goel

Civil and Environmental Engineering

This paper summarizes the results of a recent investigation on the dynamic response of asymmetric-plan buildings with supplemental viscous damping to harmonic ground motion using modal analysis techniques. It is shown that most modal parameters, except modal damping ratios and dynamic amplification factors, are affected very little by the plan-wise distribution of supplemental damping in the practical range of system parameters. The first modal damping ratio increases while the second decreases as CSD moves from right to left of the system plan, and their values increase with larger plan-wise spread of the supplemental damping. Trends for the dynamic amplification factors …

Application Of Inelastic Design Spectrum To Capacity-Demand Diagram Methods, Anil K. Chopra, Rakesh K. Goel

Civil and Environmental Engineering

An improved capacity-demand-diagram method that uses the well-known constant-ductility design spectrum for the demand diagram is developed and illustrated by examples. This method estimates the deformation of inelastic SDF systems consistent with the selected inelastic design spectrum, while retaining the attraction of graphical implementation of the ATC-40 Nonlinear Static Procedure.

Problems Of Irrigation In Developing Countries: Discussion, Plusquellec Herve, Charles M. Burt

BioResource and Agricultural Engineering

No abstract provided.

Preliminary Design Of An Electrodynamic Balance For Single Particle Analysis, C. Bobcowski, J. Costa, S. Shaw, R. Zucal, J. Schmalzel, R. Ordonez, John Chen

Mechanical Engineering

An electrodynamic chamber (EDC) is a device that controls the electrodynamic field surrounding a single particle. By suspending the particle at a fixed point in space, various measurements can be made to determine thermodynamic properties of the particle. This paper describes the preliminary engineering development of an EDC for combustion research at Rowan University.

Steady State Operating Characteristics Of Hybrid Loaded Resonant Power Converter, Taufik

Electrical Engineering

No abstract provided.