MECHANISTIC CHARACTERIZATION OF RUBBERIZED ASPHALT MIXTURE AND DESIGN USING FULL SCALE TIRE-PAVEMENT FINITE ELEMENT MODELING

Rubberized half-warm mix asphalt (HWMA) is being considered as one of the promising and sustainable solutions to the current environmental and economic crisis of asphalt industry. A fully mechanistic characterization and performance analysis of this mixture subjected to realistic loading and temperature conditions is necessary before its application in a practical pavement structure. The objective of this research is to characterize the viscoelastic properties of rubberized HWMA at different temperatures and to develop and validate a finite element model of a tire-pavement structure. In this research, a generalized Maxwell model is chosen to represent the time dependent stress-strain behavior of rubberized HWMA. The dynamic modulus test results are used to calculate the viscoelastic model parameters and the resilient modulus test results are used to calculate the elastic modulus of the mixture. A finite element model is developed to conduct numerical experiment of dynamic modulus test. The model parameters are fine-tuned by comparing the finite element simulation results and the laboratory dynamic modulus experimental results. Results show that the viscoelstic model represents the actual rubberized HWMA behavior well in the high loading frequency range and shows deviation in low frequency range indicating that another model or a modification to the existing model is required to represent the behavior of rubberized HWMA for a wide range of loading frequency. The same procedure is followed to calibrate model parameters for neat hot mix asphalt (HMA), warm mix asphalt (WMA) and HWMA mixtures to compare the differences in model predictions and to use in full scale modeling. In addition to the material model, the mechanistic behavior of flexible pavement under realistic loading and boundary condition requires accurate representation of the vehicular load on the pavement. The load from the tire in this study is modeled using both a moving distributed load and rolling tire in contact with pavement in 2- and 3-dimensional simulation domains to understand the relative accuracy of various combinations of simplified and complex modeling techniques and their central processing unit (CPU) cost. The contact pressure and length, which are critical for accurately predicting the pavement performance, are calibrated by matching the pressure distribution exerted at the top of the pavement, especially for 2D simulations. Temperature dependency of pavement materials is considered by incorporating model parameters from low to high range temperatures. The computed longitudinal strain and vertical stress are compared with the measured field data found in the literature. The results show that the values computed with the viscoelastic material model in 3D simulation domain agree well with the measured data. Fatigue and rutting performance of rubberized and neat HWMA pavements is evaluated using the 3D rolling tire-pavement model. Results of neat binder mix have better fatigue resistance compared to the rubberized mixture. Similarly, the effect of layer thickness, pavement temperature and traffic speed are also computed to gain further insights into the applicability of various asphalt mixtures. Finally, the 3D pavement-rolling tire model seems to be a promising tool for obtaining valuable information about mechanistic behavior of various geometric and material combinations for economical design

Design and Assembly of High-Temperature Signal Conditioning System on LTCC with Silicon Carbide CMOS Circuits

The objective of the work described in this dissertation paper is to develop a prototype electronic module on a low-temperature co-fired ceramic (LTCC) material. The electronic module would perform signal conditioning of sensor signals (thermocouples) operating under extreme conditions for applications like gas turbines to collect data on the health of the turbine blades during operation so that the turbines do not require shutdown for inspection to determine if maintenance is required. The collected data can indicate when such shutdowns, which cost $1M per day, should be scheduled and maintenance actually performed. The circuits for the signal conditioning system within the prototype module must survive the extreme temperature, pressure, and centrifugal force, or G-force, present in these settings. Multiple fabrication runs on different integrated silicon carbide (SiC) process technologies have been carried out to meet the system requirements. The key circuits described in this dissertation are - two-stage op amp topologies and voltage reference, which are designed and fabricated in a new SiC CMOS process. The SiC two-stage op amp with PFET differential input pair showed 48.9 dB of DC gain at 500oC. The voltage reference is the first in SiC CMOS technology to employ an op amp-based topology. The op amp circuit in the voltage reference is a two-stage with NFET differential input pair that uses the indirect compensation technique for the first time in the SiC CMOS process to provide 42.5 dB gain at 350oC. The designed prototype module implemented with these circuits was verified to provide signal conditioning and signal transmission at 300oC. The signal transmission circuit on the module was also verified to operate with a resonant inductive wireless power transfer method at a frequency of 11.8 MHz for the first time. A second prototype module was also developed with the previously fabricated 1.2 µm SiC CMOS process. The second module was successfully tested (with wired power supply) to operate at 440oC inside a probe-station and also verified for the first time to sustain signal transmission (34.65 MHz) capability inside a spin-rig at a rotational speed of 10,920 rpm. All designed modules have dimensions of (length) 68.5 mm by (width) 34.3 mm to conform to the physical size requirements of the gas turbine blade

UV Dynamics of Different Ring Molecules Studied by Ultrafast Electron Diffraction

Understanding natural light-induced phenomena requires a direct viewing of atomic motion during structural evolution, which, in turn, facilitates controlling and manipulating these light-induced processes. Ultrafast Electron Diffraction (UED) is a structure-sensitive technique that can probe electronic and nuclear dynamics at sub-angstrom spatial and femtosecond time scales. UED has become a vital tool for studying photo-induced molecular dynamics and underlying science. Organic ring systems are prevalent in biology, materials, and pharmaceuticals. Their synthesis and transformation are fundamental in synthetic chemistry, influencing various fields. We used UV photons to photo-excite different cyclic molecules and investigated their photo-dynamics using gas phase UED. The photochemical transformation of quadricyclane involves an ultrafast process in which a highly strained three-membered ring is converted into less strained five and six-membered rings. The isomerization of quadricyclane into norbornadiene has recently garnered considerable attention, particularly within its application as a Molecular Solar Energy Storage (MOST) system. The UV-induced reaction probed by MeV-UED displays simultaneous electronic and nuclear dynamics. Comparison of experimental data with simulations reveals a substantial structural change as the molecule crosses the conical intersection. The analysis also suggests the involvement of a dissociation channel in addition to QD to NB isomerization in photodynamics. Cis stilbene has been serving as a model system for exploring photoisomerization and photocyclization. While the dynamics of the first excited state have been extensively investigated, higher excited states remain less explored. We employed MeV-UED to examine the dynamics following ionization due to the absorption of two UV photons. The experimental data precisely captures the oscillations of the cis-stilbene cation and agrees well with theoretical predictions. Pentamethyl-cyclopentadiene (PMCP) is a small polyene molecule, and investigating its photoreaction can provide valuable insights into reaction mechanisms, which can be applied to studying other complex polyenes. Using our KeV-UED setup, we initiated the photoreaction by pumping with 266nm photon and probed by 90KeV electron beam. The preliminary analysis of this data shows a good pump-probe signal and structural change in the molecule

A Game-Theoretic Drone-as-a-Service Composition for Delivery

We propose a novel game-theoretic approach for drone service composition considering recharging constraints. We design a non-cooperative game model for drone services. We propose a non-cooperative game algorithm for the selection and composition of optimal drone services. We conduct several experiments on a real drone dataset to demonstrate the efficiency of our proposed approach.Comment: 5 pages, 3 figures. This is an accepted paper and it is going to appear in the Proceedings of the 2020 IEEE International Conference on Web Services (IEEE ICWS 2020) affiliated with the 2020 IEEE World Congress on Services (IEEE SERVICES 2020), Beijing, Chin

Effect of antioxidants on lipid oxidation in herring (Clupea harengus) co-product silage during its production, heat-treatment and storage

Provided high product quality, ensilaging can be used to valorize fish filleting co-products into a silage suitable for food applications. However, a documented challenge for products from hemoglobin-rich fish raw materials is the high susceptibility to lipid oxidation, calling for stabilization by antioxidants. In a comparison among different rosemary-containing antioxidants and isoascorbic acid, we here found that the commercial mixture Duralox MANC-213 (MANC) provided the best protection against peroxide value and 2-thiobarbituric acid reactive substances (TBARS) development during ensilaging of herring filleting co-products (0-7 days, 22 degrees C), and also during subsequent heat-treatment (30 min, 85 degrees C). Increasing MANC concentration from 0.25 and 0.75 to 1.25% lowered TBARS values from 43.53 and 25.12 to 18.04 mu mole TBARS/Kg silage, respectively, after 7 days of ensilaging. During storage at 4 degrees C/22 degrees C in presence of MANC, 1.25% provided the highest protection with 87-90% and 66-73% lower TBARS, at 4 degrees C and 22 degrees C, respectively, at 6 months compared to the controls. At this time point, heat-treated silages had lower protein degree of hydrolysis and free amino acids values than the non-heat-treated one. Regardless of antioxidant addition, total volatile basic nitrogen (TVB-N) formation still increased during the storage, but, overall, TVB-N values in silages were below the acceptable limit of 30 mg TVB-N/100 g fish for human consumption. Together with lipid oxidation data, this suggest that herring silage produced in presence of antioxidants can be used both for high quality feed and food applications