Process Control Applications in Microbial Fuel Cells(MFC)

abstract: Microbial fuel cells(MFC) use micro-organisms called anode-respiring bacteria(ARB) to convert chemical energy into electrical energy. This process can not only treat wastewater but can also produce useful byproduct hydrogen peroxide(H2O2). Process variables like anode potential and pH play important role in the MFC operation and the focus of this dissertation are pH and potential control problems. Most of the adaptive pH control solutions use signal-based-norms as cost functions, but their strong dependency on excitation signal properties makes them sensitive to noise, disturbances, and modeling errors. System-based-norm( H-infinity) cost functions provide a viable alternative for the adaptation as they are less susceptible to the signal properties. Two variants of adaptive pH control algorithms that use approximate H-infinity frequency loop-shaping (FLS) cost metrics are proposed in this dissertation. A pH neutralization process with high retention time is studied using lab scale experiments and the experimental setup is used as a basis to develop a first-principles model. The analysis of such a model shows that only the gain of the process varies significantly with operating conditions and with buffering capacity. Consequently, the adaptation of the controller gain (single parameter) is sufficient to compensate for the variation in process gain and the focus of the proposed algorithms is the adaptation of the PI controller gain. Computer simulations and lab-scale experiments are used to study tracking, disturbance rejection and adaptation performance of these algorithms under different excitation conditions. Results show the proposed algorithm produces optimum that is less dependent on the excitation as compared to a commonly used L2 cost function based algorithm and tracks set-points reasonably well under practical conditions. The proposed direct pH control algorithm is integrated with the combined activated sludge anaerobic digestion model (CASADM) of an MFC and it is shown pH control improves its performance. Analytical grade potentiostats are commonly used in MFC potential control, but, their high cost (>$6000) and large size, make them nonviable for the field usage. This dissertation proposes an alternate low-cost($200) portable potentiostat solution. This potentiostat is tested using a ferricyanide reactor and results show it produces performance close to an analytical grade potentiostat.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Restriction of Macrophage infection During HIV and SIV infection: The Role of Antibodies and Coreceptor Use Plasticity in Enforcing Cd4-Dependent Entry and Shaping Tropism in Vivo

The pathogenesis of HIV and SIV infection is determined to a large extent by adaptations of the virus that enable it to infect different cell types and either destroy these cells, or establish long-term reservoirs of viral replication. CD4+ T cells are the predominant targets of HIV and SIV infection in vivo, although some variants of these viruses have the ability to efficiently infect macrophages, which express exceedingly low levels of CD4. I sought to understand the selective forces that normally favor CD4+ T cell infection while restricting macrophage infection in vivo. To investigate these forces, I examined viral envelope glycoprotein (Env) variants that emerged during an in vivo SIV infection model in which extensive tissue macrophage infection was observed in experimentally CD4+ T cell-depleted rhesus macaques. I found that plasma-derived viral Envs from these animals had a remarkable ability to mediate entry into cells expressing CCR5 but lacking CD4, a phenotypic hallmark of macrophage-tropic viruses. These CD4-independent Env variants were highly sensitive to neutralization by anti-Env antibodies, as well as to control SIV+ plasma. However, plasma from CD4+ T cell-depleted animals could not neutralize CD4-independent Envs. This suggests that CD4+ T cells enforce CD4-dependent SIV entry by supporting the production of anti-Env antibodies that normally prevent the emergence of macrophage-tropic virus. In further studies, I asked whether other forces might restrict the emergence of CD4-independent Envs in vivo by examining entry coreceptor use by these Envs. Despite the ability of CD4-independent Envs to mediate robust entry in the presence of high cell surface levels of rhesus macaque CCR5, they were impaired in their use of human CCR5, rhesus macaque GPR15, and low levels of rhesus macaque CCR5. These phenotypes indicated that CD4-independent entry is accompanied by reduced plasticity in coreceptor usage, possibly restricting the virus in its range of potential target cells in vivo. Future studies will examine whether antibody-mediated enforcement of CD4 tropism and coreceptor usage are selective pressures that also explain the conservation of CD4-dependent entry during HIV-1 infection. It is possible that these forces can be manipulated to reshape viral tropism and eliminate HIV-1 macrophage reservoirs

Design of a Fractional Order CRONE and PID Controllers for Nonlinear Systems using Multimodel Approach

This paper deals with the output regulation of nonlinear control systems in order to guarantee desired performances in the presence of plant parameters variations. The proposed control law structures are based on the fractional order PI (FOPI) and the CRONE control schemes. By introducing the multimodel approach in the closed-loop system, the presented design methodology of fractional PID control and the CRONE control guarantees desired transients. Then, the multimodel approach is used to analyze the closed-loop system properties and to get explicit expressions for evaluation of the controller parameters. The tuning of the controller parameters is based on a constrained optimization algorithm. Simulation examples are presented to show the effectiveness of the proposed method

Control of feedback for assistive listening devices

Acoustic feedback refers to the undesired acoustic coupling between the loudspeaker and microphone in hearing aids. This feedback channel poses limitations to the normal operation of hearing aids under varying acoustic scenarios. This work makes contributions to improve the performance of adaptive feedback cancellation techniques and speech quality in hearing aids. For this purpose a two microphone approach is proposed and analysed; and probe signal injection methods are also investigated and improved upon

3 sampled-data control of nonlinear systems

This chapter provides some of the main ideas resulting from recent developments in sampled-data control of nonlinear systems. We have tried to bring the basic parts of the new developments within the comfortable grasp of graduate students. Instead of presenting the more general results that are available in the literature, we opted to present their less general versions that are easier to understand and whose proofs are easier to follow. We note that some of the proofs we present have not appeared in the literature in this simplified form. Hence, we believe that this chapter will serve as an important reference for students and researchers that are willing to learn about this area of research

Opinion Behavior Analysis in Social Networks Under the Influence of Coopetitive Media

Both interpersonal communication and media contact are important information sources and play a significant role in shaping public opinions of large populations. In this paper, we investigate how the opinion-forming process evolves over social networks under the media influence. In addition to being affected by the opinions of their connected peers, the media cooperate and/or compete mutually with each other. Networks with mixed cooperative and competitive interactions are said to be coopetitive . In this endeavor, a novel mathematical model of opinion dynamics is introduced, which captures the information diffusion process under consideration, makes use of the community-based network structure, and takes into account personalized biases among individuals in social networks. By employing port-Hamiltonian system theory to analyze the modeled opinion dynamics, we predict how public opinions evolve in the long run through social entities and find applications in political strategy science. A key technical observation is that as a result of the port-Hamiltonian formulation, the mathematical passivity property of individuals’ self-dynamics facilitates the convergence analysis of opinion evolution. We explain how to steer public opinions towards consensus, polarity, or neutrality, and investigate how an autocratic media coalition might emerge regardless of public views. We also assess the role of interpersonal communication and media exposure, which in itself is an essential topic in mathematical sociology

Protein Nanoparticles as Vaccine Platforms for Human and Zoonotic Viruses

Vaccines are one of the most effective medical interventions, playing a pivotal role in treating infectious diseases. Although traditional vaccines comprise killed, inactivated, or liveattenuated pathogens that have resulted in protective immune responses, the negative consequences of their administration have been well appreciated. Modern vaccines have evolved to contain purified antigenic subunits, epitopes, or antigen-encoding mRNAs, rendering them relatively safe. However, reduced humoral and cellular responses pose major challenges to these subunit vaccines. Protein nanoparticle (PNP)-based vaccines have garnered substantial interest in recent years for their ability to present a repetitive array of antigens for improving immunogenicity and enhancing protective responses. Discovery and characterisation of naturally occurring PNPs from various living organisms such as bacteria, archaea, viruses, insects, and eukaryotes, as well as computationally designed structures and approaches to link antigens to the PNPs, have paved the way for unprecedented advances in the field of vaccine technology. In this review, we focus on some of the widely used naturally occurring and optimally designed PNPs for their suitability as promising vaccine platforms for displaying native-like antigens from human viral pathogens for protective immune responses. Such platforms hold great promise in combating emerging and re-emerging infectious viral diseases and enhancing vaccine efficacy and safety