Waste Materials and Management: Lessons from the Flint Water Crisis in Michigan and Blast Furnace Slag Usage in Indiana

Two aspects of solid waste management were investigated for this thesis. The first effort focused on better understanding solid waste management before, during, and after the large-scale 2015 drinking water lead crisis in Flint, Michigan. When large drinking water systems are unable to deliver safe water, the provision of emergency water supplies becomes a necessity. The author investigated waste management challenges associated with the large-scale drinking water disaster. In October 2015, more than 90,000 people were directed not to use their lead contaminated water, but instead use emergency drinking water and in-home filters. Discussions with organizations that responded to the incident as well as a review of scintific literature and records were conducted. Results demonstrated that public and private partnerships enabled the water distribution and waste collection/recycling activities. Millions of water bottles were supplied to the community, but the actual amounts may have been less than the estimates for community water needs. During January 2016, the recycling participation rate increased from 13% to 27%. Water bottle and faucet filter recycling was encouraged by the establishment of drop-off locations and the curbside pickup program was expanded. Tens of thousands of filters were donated to the community, but government records found only about 2,600 filters were recycled. Points of distribution (PODs) were established to provide emergency supplies, increase waste management efficiency, but were relocated months after the initial response because their initial locations were not optimal. A lack of formal material flow tracking entering and leaving Flint inhibited a better understanding of waste management activities. Communities seeking to better prepare for large-scale emergencies should: pre-identify the roles of waste management organizations, setup a procedure for documenting emergency water supply materials entering and exiting the community, determine POD locations, draft public notifications about waste management activities, and centralize all data archiving. The goal of second Chapter was to better understand the factors that can influence chemical leaching from air cooled blast furnace slag (ACBFS) for Indiana Department of Transportation (INDOT) projects. In July 2016 a green seepage with a sulfurous smell oozed from Ind. 49 and caused a Fire Chief and a police officer in hospital for breathing problems. To deal with a leaching problem lasting more than ten months at one site, a project was constructed, but INDOT spent more than $500,000 to remove slag several years later because of reoccurring problem. A literature review of government documents, peer-review, and trade industry literature was conducted. A visit to an ACBFS storage facility and steel mill that generated the ACBFS was also completed. ACBFS handling and testing procedures at the storage facility and those prescribed by INDOT were also reviewed. The project team also contacted other state transportation agencies (IL, MD, MI, NY, and OH) to determine the degree they incorporated ACBFS into their projects and to determine if product performance tests were required. Results showed that changes to INDOT test methods and acceptance criteria are warranted. Indiana Test Method (ITM) 212 should be revised to extend the test duration, pH acceptance criterion, and add additional material acceptance criteria. Unbound ACBFS should be avoided for construction applications 1) where ground water could contact the material, 2) near environmentally sensitive and populated areas, 3) where a drainage system is not present. Additional work to improve the ability of INDOT to detect ACBFS that would cause short- or long-term chemical leaching problems could include 1) evaluating and optimizing stockpile sampling practices for representative sampling, 2) modifying ITM 212 to better predict worst-case leaching conditions and leachate quality, 3) conduct a head-to-head comparison of bench-scale and field-scale leaching results

Post-transient relaxation in graphene after an intense laser pulse

High intensity laser pulses were recently shown to induce a population inverted transient state in graphene [T. Li et al. Phys. Rev. Lett. 108, 167401 (2012)]. Using a combination of hydrodynamic arguments and a kinetic theory we determine the post-transient state relaxation of hot, dense, population inverted electrons towards equilibrium. The cooling rate and charge-imbalance relaxation rate are determined from the Boltzmann-equation including electron-phonon scattering. We show that the relaxation of the population inversion, driven by inter-band scattering processes, is much slower than the relaxation of the electron temperature, which is determined by intra-band scattering processes. This insight may be of relevance for the application of graphene as an optical gain medium.Comment: 10 pages, 4 figures, submitted as contribution of the IMPACT Special Topics series of the EP

Receiver design for SPAD-based VLC systems under Poisson-Gaussian mixed noise model

Single-photon avalanche diode (SPAD) is a promising photosensor because of its high sensitivity to optical signals in weak illuminance environment. Recently, it has drawn much attention from researchers in visible light communications (VLC). However, existing literature only deals with the simplified channel model, which only considers the effects of Poisson noise introduced by SPAD, but neglects other noise sources. Specifically, when an analog SPAD detector is applied, there exists Gaussian thermal noise generated by the transimpedance amplifier (TIA) and the digital-to-analog converter (D/A). Therefore, in this paper, we propose an SPAD-based VLC system with pulse-amplitude-modulation (PAM) under Poisson-Gaussian mixed noise model, where Gaussian-distributed thermal noise at the receiver is also investigated. The closed-form conditional likelihood of received signals is derived using the Laplace transform and the saddle-point approximation method, and the corresponding quasi-maximum-likelihood (quasi-ML) detector is proposed. Furthermore, the Poisson-Gaussian-distributed signals are converted to Gaussian variables with the aid of the generalized Anscombe transform (GAT), leading to an equivalent additive white Gaussian noise (AWGN) channel, and a hard-decision-based detector is invoked. Simulation results demonstrate that, the proposed GAT-based detector can reduce the computational complexity with marginal performance loss compared with the proposed quasi-ML detector, and both detectors are capable of accurately demodulating the SPAD-based PAM signals

Simple Anosov representations of closed surface groups

We introduce and study \emph{simple Anosov representations} of closed hyperbolic surface groups, analogous to Minsky's \emph{primitive stable representations} of free groups. We prove that the set of simple Anosov representations into $\mathrm{SL}(d,\mathbb{C})$ with $d \geqslant 4$ strictly contains the set of Anosov representations. As a consequence, we construct domains of discontinuity for the mapping class group action on character varieties which contain non-discrete representations

Index Modulation-Aided OFDM for Visible Light Communications

Index modulation-aided orthogonal frequency-division multiplexing(IM-OFDM) is a promising modulation technique to achieve high spectral and energy efficiency. In this chapter, the conventional optical OFDM schemes are firstly reviewed, followed by the principles of IM-OFDM. The application of IM-OFDM in visible light communication (VLC) systems is introduced, and its performance is compared with conventional optical OFDM, which verifies its superiority. Finally, the challenges and opportunities of IM-OFDM are discussed for the VLC applications