Browsing by Subject "Vibration"

Now showing 1 - 10 of 10
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    Directional Rumble Strips for Reducing Wrong-Way-Driving Freeway Entries
    (Center for Transportation Studies, University of Minnesota, 2019-07) Luo, Albert C; Guo, Chuan; Xing, Siyuan; Xu, Yeyin; Guo, Siyu; Liu, Chuanping
    This report presents evaluation results of directional rumble strips (DRS) designed to deter wrong-way (WW) freeway entries. Mathematical models have been built to identify high-risk locations of WWD. Based on the model, one off-ramp, exit 41 northbound on I-70 was found to have a WW entry probability of 55%. 96 hours of video data were recorded at the chosen off-ramp. Then one pattern of DRS (D3) was implemented on the chosen location with the help of the Illinois Department of Transportation (IDOT). Sound and vibration data were recorded and compared between RW and WW directions for speed ranging from 15 mph to 30 mph. Another 96 hours of video data were recorded after the implementation. The analysis of before and after implementation data showed that the DRS cannot reduce the probability of WWD, but it can warn WW drivers and reduce their speed, which will significantly reduce WWD accidents.
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    Directional Rumble Strips for Reducing Wrong-Way-Driving Freeway Entries
    (Center for Transportation Studies, University of Minnesota, 2018-02) Zhou, Huaguo; Xue, Chennan; Yang, Lingling; Luo, Albert
    This report presents the evaluation results of five types of directional rumble strips (DRS) based on extensive field tests conducted at the National Center for Asphalt Technology (NCAT) in Auburn, Alabama. The ultimate goal of this study is to develop a low-cost safety countermeasure by capturing a driver’s attention through elevated invehicle sound and vibration for wrong-way (WW) driving while providing normal sound and vibration levels for right-way (RW) driving. Tests of sound and vibration generated by different DRS were performed with full-size passenger vehicles for six categories of speed: 10, 15, 20, 25, 35, and 45 mph. For each type of DRS concept design, three initial tests were performed with vehicles traveling on normal pavement (ambient condition), followed by three to five tests on the DRS in both WW and RW directions. The study identified three final design patterns (C, D Configuration 3, and E.1) that can generate elevated sound and vibration for WW drivers. The field test results also showed that speed had a significant impact on sound and vibration. Considering that travelling speed will be different on DRS by WW and RW drivers, additional speed studies were conducted to estimate the WW and RW driving speeds at the proposed DRS implementation spots on off-ramps. Based on the results, recommendations were developed to implement the final three DRS designs on off-ramps that can achieve the maximum safety benefits by alerting WW drivers through in-vehicle elevated sound and vibration.
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    Field Implementation of Direction Rumble Strips for Deterring Wrong-Way Entries
    (Center for Transportation Studies, University of Minnesota, 2019-07) Zhou, Huaguo; Xue, Chennan
    This report presents the field implementation results of three directional rumble strip (DRS) patterns designed to deter wrong-way (WW) freeway entries. Southbound off-ramps at Exits 208 and 284 on I-65 in Alabama were selected for implementation because they were ranked as high-risk locations by a network screening tool developed by Auburn University. Three patterns (D3, C, and E.1) were recommended for field implementation based on the results of a previous project. Pattern D3 was installed at the off-ramp terminal near the stop bar or yield line. Pattern C was implemented at the segment between the terminal and ramp curve. Pattern E.1 was placed on the tangent part before the ramp curve. WW incident and traffic speed data before and after the implementation were collected using cameras and magnetic sensors, respectively. Field driving tests were conducted to collect sound and vibration data at various speed categories for both RW and WW directions. Before and after studies evaluated the effectiveness of the DRS patterns in reducing wrong way driving (WWD) incidents and traffic speeds on off-ramps. Sound and vibration analyses quantified the differences between right way (RW) and WW drivers’ perceptions. Results showed that the number of WWD incidents and average driving distances were significantly reduced after implementing all of the DRS. The results confirmed that WWDs can perceive elevated sound and vibrations when passing the DRS. The DRS can also reduce the 85th percentile, mean, and standard deviations of off-ramp traffic speeds. A general guideline was developed for implementing different DRS to deter WW freeway entries.
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    Ground Vibration Test Time Domain Data
    (2014-09-03) Gupta, Abhineet
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    Ground Vibration Test with Hammer
    (2014-07-24) Moreno, Claudia
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    Ground Vibration Test with Shaker
    (2014-07-24) Moreno, Claudia
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    Monitoring and Assessment Program for Wabasha County Bridge
    (1998-09) Fick, Damon R.; Schultz, Arturo E.; Bergson, Paul M.; Galambos, Theodore V.
    A 143-m (470-foot) span steel truss bridge, the Wabasha County Bridge crosses the Mississippi River at Wabasha, Minn. In November 1996, the Minnesota Department of Transportation (Mn/DOT) implemented a retrofit strategy to mitigate perceptible vibrations in several truss members at moderate and strong wind gusts. In this strategy, Mn/DOT installed a "central cord" of tubular members, halfway between top and bottom cords, to reduce the effective length of the truss members, thereby increasing the natural frequencies of vibration and reducing the amplitude of vibration and the associated strains. This report documents the monitoring and assessment program used to investigate the dynamic response and efficacy of the retrofit strategy for the Wabasha Country Bridge. Researchers determined amplitudes and frequencies of the vibration for the longest diagonal member. The measured frequencies are larger than those estimated before the retrofit and have resulted in reduced strains and displacements from vibration. Maximum strain levels at the quarter point of the member are estimated to be small after the retrofit, with peak values corresponding to 8.6 MPa (1.2 ksi).
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    Perception and Mechanical Properties of the Pacinian Corpuscle
    (2020-05) Held, Tiffany
    The sense of touch is processed by the somatosensory system in which mechanoreceptors are the sensory neurons that translate mechanical stimuli into neural impulses by using specialized mechanoreceptive end organs. Pacinian corpuscles (PCs), located primarily in the hairless skin of the hands and feet, are the mechanoreceptor responsible for sensing low--amplitude, high--frequency vibrations (80-1000 Hz). In this thesis, I explored how vibrotactile perception is mediated by the PCs using a combination of computational modeling, benchtop experiments on donor tissue, and psychophysical tests. There are several mechanical models of the PC, and the first part of this thesis demonstrated that a multiphysics model of a single PC contained enough details to recapitulate the trend of observed discriminability of human subjects. We showed that discriminability of sinusoidal vibrations increases as the frequency difference between the pairs increase, and we found that complex waveforms with two frequency components were more difficult to discriminate and did not follow a discernible trend. Next, we investigated the effect that Dupuytren disease (DD) has on vibrotactile perception at frequencies within the PC's range. Dupuytren disease is a progressive hand disorder in which growth and densitification of fibrous tissue in the palms eventually causes the affected fingers to bend irreversibly. DD usually presents clinically after the age of 50, affects about 3 per 10,000 adults, and is associated with alterations to the size and the internal structure of PCs. By measuring vibrotactile sensitivity in healthy and DD subjects, we found that women are more sensitive to high--frequency vibrations than men and that men with DD may exhibit reduced sensitivity compared to men without DD. We also found that, for patients in which DD presents unilaterally, the finger with DD is less sensitive than the corresponding finger on the unaffected hand. These data may serve as a useful reference to future DD researchers and may facilitate development of novel diagnostic or prognostic protocols. Finally, we designed a system to measure the viscoelastic properties of the PC and tested isolated human cadaveric PCs from donors with and without DD to better understand how the mechanoreceptor's viscoelastic properties affect vibrotactile perception.
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    Vibrational Spectroscopy on the Silicon Hydride Mode: Probing Ultrafast Dynamics in Small Molecules to Macromolecular Polymer Systems
    (2019-06) Olson, Courtney Marie
    This thesis describes Fourier transform infrared (FTIR) and two-dimensional infrared (2D-IR) spectroscopy applied to small molecule silanes (trimethoxysilane and triphenylsilane) and polydimethylsiloxane (PDMS). 2D-IR spectroscopy gives information about the dynamics that the vibrational probe is sensitive to and the heterogeneous and homogeneous contributions to the linear FTIR lineshape. The vibrational probe used for all the studies in this thesis is the silicon hydride stretch due to being present in the small molecule silanes and in PDMS. The studies presented show how the silicon hydride mode was first characterized in small molecules to understand the probe more. Then, the probe was utilized in polymer systems to study more complex motions to make the connection between the ultrafast dynamics of polymers to the macroscopic properties. The first study involved studying the solvation dynamics of two small molecule silanes in three neat solvents using FTIR and 2D-IR spectroscopies along with molecular dynamics simulations. The two different molecules exhibited different degrees of vibrational solvatochromism, and the differences was found to be a result of higher mode polarization with more electron withdrawing ligands using density functional theory calculations. The solvent dynamics were found to be dominated by their interactions with neighboring solvent molecules rather than with the solute. Next, FTIR and 2D-IR spectroscopies were used to study PDMS cross-linked films and siloxane oligomers without solvent and swollen or dissolved in various solvents. There is an absence of vibrational solvatochromism in these systems, which was shown by 2D-IR spectroscopy to be due to the heterogeneity. The silicon hydride mode in the cross-linked, solvent-free PDMS film exhibited spectral diffusion, which must be due to the polymer structural motions. However, once the solvent penetrates the network, the dynamics become a convolution of the solvent and polymer motions due to the motions being of similar timescale. In the last study discussed, FTIR and 2D-IR spectroscopies were used to study the ultrafast structural dynamics of PDMS thin films with various physical and chemical changes done to the polymer, which included elevated curing temperature, increased cross-linker agent concentration, compression, and cooling near the glass transition temperature. The FTIR spectra were found to be relatively insensitive to all of these perturbations, which 2D-IR spectroscopy revealed was caused by the overwhelming heterogeneity. There is clearly a disconnect between the microscopic and macroscopic behavior in this polymer due to having only slight differences in the heterogeneous and homogeneous dynamics.