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Natural Frequencies of Layered Beams Using a Continuous Variation Model
No full textThis work involves the determination of the bending natural frequencies of beams whose properties vary along the length. Of interest are beams with different materials and varying cross-sections, which are layered in cells. These can be uniform or not, leading to a configuration of stacked cells of distinct materials and size. Here the focus is on cases with two, or three cells, and shape variations that include smooth (tapering) and sudden (block type) change in cross-sectional area. Euler-Bernoulli theory is employed. The variations are modeled using approximations to unit step functions, here logistic functions. The approach leads to a single differential equation with variable coefficients. A forced motion strategy is employed in which resonances are monitored to determine the natural frequencies. Forcing frequencies are changed until large motions and sign changes are observed. Solutions are obtained using MAPLE®’s differential equation solvers. The overall strategy avoids the cumbersome and lengthy Transfer Matrix method. Pin-pin and clamp-clamp boundary conditions are treated. Accuracy is partially assessed using a Rayleigh-Ritz method and, for completeness, FEM. Results indicate that the forced motion approach works well for a two-cell beam, three-cell beam and a beam with a sinusoidal profile. For example, in the case of a uniform two-cell beam, with pin-pin boundary conditions, results differ less than 1 %
Electrical breakdown of polypropylene filled with natural clay as nanomaterial
No full textThis study presents the breakdown behavior of polypropylene filled with a various concentrations of nano-size natural clay. The concentrations of natural clay by weight were 0 %, 2 %and 6 % in polypropylene. For different concentrations of natural clay each specimen was subjected to a sinusoidal voltage waveform at power frequency with a certain ramp rate to a level where a breakdown occurred. The rms voltage at the breakdown was considered as the breakdown voltage of the sample. The mean dielectric strength improved about 3.5 % for the nanocomposite with 2 % of natural clay concentration in the host polypropylene. However, the improvement on the mean dielectric strength of the nanocomposite with 6 %concentration of natural clay appeared to be little more than 1 % when compared with 2 % concentration of natural clay in the host. This implies that there exits an optimum concentration of nanosize natural clay in polypropylene. Also observed was the increase of the dielectric strength of the materials with the increase of the ramp rate of the applied voltage
Self-Study Appendices
No full textThis is a single PDF file of all appendices to the Self-Study Report as submitted with the final version
2015 Program Audit Form
No full textProgram Audit Form summarizes the visit team\u27s initial assessment of each program being considered for accreditation and/or extension of accreditation by ABET
Injury Sources for Second Row Occupants in Frontal Crashes Considering Age and Restraint Condition Influence
No full textThe current study examined field data in order to document injury rates, injured body regions, and injury sources for persons seated in the second row of passenger vehicles. It was also intended to identify whether these varied with respect to age and restraint use in vehicles manufactured in recent years. Data from the 2007-2012 National Automotive Sampling System (NASS/CDS) was used to describe occupantsseated in the second row of vehicles in frontal crashes. Injury plots, comparison of means and logistic regression analysis were used to seek factors associated with increased risk of injury. Restraint use reduced the risk of AIS ≥ 2 injury from approximately 1.8% to 5.8% overall. Seventy nine percent of the occupants in the weighted data set used either a lap and shoulder belt or child restraint system. The most frequently indicated injury source for persons with a MAIS ≥ 2 was “seat, back support”, across restraint conditions and for all but the youngest occupants. The factors most strongly associated with injury risk in the crash dataset were the velocity difference (delta V) and age, which had significant association with injury risk in restrained occupants of the second row. These data suggest that prevention of injurious contact with the back of the front seat may be an important factor in efforts to reduce the injury rate in second row passengers regardless of age and restraint condition
2014-2015 Annual Report
Get PDFThis document highlights the programs and events, such as workshops and weekly meetings conducted by the Center for Excellence in Teaching and Learning. Details and attendance are provided
Efficient high-order methods for solving fractional differential equations of order α ∈ (0, 1) using fast convolution and applications in wave propagation
Get PDFIn this work we develop a means to rapidly and accurately compute the Caputo fractional derivative of a function, using fast convolution. The key element to this approach is the compression of the fractional kernel into a sum of M decaying exponentials, where M is minimal. Specifically, after N time steps we find M= O (log N) leading to a scheme with O (N log N) complexity. We illustrate our method by solving the fractional differential equation representing the Kelvin-Voigt model of viscoelasticity, and the partial differential equations that model the propagation of electromagnetic pulses in the Cole-Cole model of induced dielectric polarization
Electrospinning and Characterization of Polyvinyl Alchohol Nanofibers with Gold Nanoparticles
No full textPure polyvinyl alcohol (PVOH or PVA) and composite PVOH and gold nanofibers were electrospun to form nonwoven mats. Aqueous solutions of the PVOH and gold nanoparticles were blended at various concentrations to achieve viscous solutions suitable for the electrospinning process. The concentrations were varied to obtain sub-micron and nanoscale fiber mats. Fiber mat morphology was analyzed using scanning electron microscopy (SEM). Gold nanoparticle content was verified using thermal gravimetric analysis (TGA) and Transmission Electron Microscopy (TEM). Gold nanoparticle size was measured using TEM and verified using Ultraviolet-Visible (UV-Vis) spectroscopy. The bulk chemistry and surface chemistry was analyzed using Fourier Transform Infra-red (FTIR) spectroscopy and contact angle analysis. The fiber morphology, chemical compositions and contact angle data show that these electrospun materials are suitable for applications including biosensing, biomedical and tissue engineering
A Method for Measuring the Néel Relaxation Time in a Frozen Ferrofluid
No full textWe report a novel method of determining the average Néel relaxation time and its temperature dependence by calculating derivatives of the measured time dependence of temperature for a frozen ferrofluid exposed to an alternating magnetic field. The ferrofluid, composed of dextran-coated Fe3O4 nanoparticles (diameter 13.7 nm ± 4.7 nm), was synthesized via wet chemical precipitation and characterized by x-ray diffraction and transmission electron microscopy. An alternating magnetic field of constant amplitude (H0=20H0=20 kA/m) driven at frequencies of 171 kHz, 232 kHz, and 343 kHz was used to determine the temperature dependent magnetic energy absorption rate in the temperature range from 160 K to 210 K. We found that the specific absorption rate of the ferrofluid decreased monotonically with temperature over this range at the given frequencies. From these measured data, we determined the temperature dependence of the Néel relaxation time and estimate a room-temperature magnetocrystalline anisotropy constant of 40 kJ/m3, in agreement with previously published results