Investigation of Bipolar Electrochemically Exfoliated Graphene for Supercapacitor Applications

Developing a reliable, simple, cost-efficient and eco-friendly method for scale-up production of high-quality graphene-based materials is essential for the broad applications of graphene. Up to now, various manufacturing methods have been employed for synthesizing high quality graphene, however aggregation and restacking has been a major issue and the majority of commercially available graphene products are actually graphite microplates. In this study, bipolar electrochemistry techniques have been used to exfoliate and deposit graphene nanosheets in a single-step process to enable high performance device application. In the first part of this study, bipolar electrochemistry concept is utilized to design a single-step and controllable process for simultaneously exfoliating a graphite source and depositing both graphene oxide (GO) and reduced graphene oxide (rGO) layers on conductive substrates. The electrochemical performance of the fabricated graphene-based materials as the electrode for supercapacitors has been investigated. Areal capacitance of 1.932 mF cm-2 for the rGO, and 0.404 mF cm-2 for GO at a scan rate of 2 mV s-1 were achieved. Moreover, a cut-off frequency of 1820 Hz was obtained, which is a promising characteristic for AC filtering applications. Although the physicochemical characteristics of produced graphene have been evaluated in the first part, the exfoliation and deposition mechanisms were still unclear. In the second part of this dissertation, a novel modified BPE system with an electrically connected graphite-platinum couple acting as the bipolar electrode has been designed in order to decouple and investigate the contribution of anodic/cathodic exfoliation and deposition of graphene in the BPE process. Electron microscopy and infrared spectroscopy results indicate that both anodic and cathodic exfoliation of graphene could take place regardless of the type of polarization; however, the morphology and deposition rate highly depend on the polarization. Furthermore, the graphene fabricated by anodic exfoliation was found to show higher levels of oxidation compared to the graphene produced by cathodic exfoliation. In the last part of this study, for the first time, a vertically aligned graphene layer was deposited on a micro-sized interdigitated gold current collector by a modified bipolar electrochemistry method. Both time domain and frequency domain electrochemical performance of on-chip micro-supercapacitors (MSCs) were evaluated. An areal capacity of 640.9 μF cm-2 at a scan rate of 2 mV s-1 and 239.31 μF cm-2 at discharge current density of 25 μA cm-2 was delivered with an excellent cyclability. Most importantly, the MSC exhibited a very fast response (cut-off frequency of 3486 Hz) and very close to ideal performance (phase angle reached -83.2°) at low frequencies. For the first time, this dissertation reported the modified BPE method as a novel approach for three in one exfoliation, deposition and reduction of high-quality graphene with vertically aligned and porous structure. The unique design of the BPE cell enabled the author to study the BPE mechanisms and measure the bipolar current for the first time. The method could successfully be employed to fabricate fast response microsupercapacitors based on vertically aligned graphene nanosheets

Information Sharing for Customized Dynamic Visual Analytics: A Framework

Supply chain activities generate massive amount of data by several actors such as, suppliers, manufacturers, warehouses, distributers, and wholesalers. Visual analytics (VA) plays a key role in knowledge discovery and insight generation from this data and helps various players to enhance their operational and strategic decision making. This is more essential for Fast moving consumer goods (FMCG) industry, given the size of the industry and its sensitivity to the diverse market uncertainties. In this paper, we present a PhD research plan that responds to the requirements of a FMCG supply chain VA system by means of a comprehensive framework. In this regard, the information flow throughout the supply chain is a significant factor for developing a reliable and efficient VA solution and a proper information flow throughout the supply chain can be enhanced with the help of the framework consisting of modules including Data Generation, Data Integration and Management, Data Analytics, Data Visualization, and Data-driven decision making. The aim of the study is to explore the development of a VA framework that acts as a guideline for supply chain players to improve their analytical capabilities.publishedVersio

Social media advertising: The role of personalization in Performance expectancy and customer purchase intention

Dissertation presented as the partial requirement for obtaining a Master's degree in Statistics and Information Management, specialization in Marketing Research and CRMSocial media is being widely used as a platform to manage marketing and advertising activities. Organizations are always having a challenge in how they can design social media advertising by spending a lot of time, money, and resources on social media ads to successfully fascinate customers and motivate them to purchase their brands. This study aims to evaluate the impact of personalization on purchase intention and also investigating the role of personalization moderating the relation between Performance expectancy and customer purchase intention. The conceptual model will be based on the extending Unified Theory of Acceptance and Use of Technology (UTAUT2). This study will be expected to provide several theoretical and practical rules on how personalization can successfully impact customer purchase intention over social media platforms

FOOD (IN) SECURITY OF PROTRACTED REFUGEES: A GLOBAL CRISIS

Abstract In their journey towards, resettlement, integration or repatriation, protracted refugees face adverse challenges meeting their basic needs and rights. The relationship between nutrition and health, establishing links between a lack of certain nutrients and growth, physical health, and mental health, indicates the need to understand factors that influence healthy eating and food insecurity. Considering the Sustainable Development Goal of Zero hunger by 2030, it is crucial to investigate both nutrition and food security as an essential component of global health. This research investigates the barriers and facilitators of food security for protracted refugee households. A mixed method analysis was used to identify the relationship between food security of protracted refugees and socioeconomic and sociocultural factors. The quantitative approach, using a sociodemographic and food security questionnaire and logistic regression procedure, sought to capture the prevalence of household food insecurity and its relation with sociodemographic variables (including: age of household breadwinner, number of household members, family types, status in the host country) and socioeconomic variables (including: income, employment status, home/land/cattle ownership). Through qualitative in-depth interviews with Afghan refugee households, the complexity of experience surrounding households food security was examined, specifically by assessing quality of life, perceptions of a balanced meal, food environments (pre- and post-migration), and the push and pull factors of migration associated with food security. In the reintegration country, Pakistan, approximately 85% of the protracted refugee families experienced degrees of household food insecurity, with 52.2% falling under the severe food insecurity category. Food insecurity was significantly associated with the respondents’ gender and the family’s employment status. However, length of residency in Pakistan was not associated with food security status. In the resettlement country, Canada, more than 93% of refugee households were food insecure, with a majority being moderately food insecure (65.3%). Food insecurity was found to be associated with low levels of education and in cases where social assistance was the main source of income. Qualitative data revealed that regardless of the length of protracted status for Afghan refugees, food insecurity remained a consistent condition for refugee families in the reintegration country. Qualitative data underscored that all refugees, regardless of their transitory country, experienced chronic food insecurity in the transitory ountry and, despite improvements in the living conditions in the country of resettlement, food insecurity persisted in Canada. The finding of this research demonstrates, much like their refugee status, that food insecurity is a prolonged and critical situation facing Afghan refugees, despite processes of integration or resettlement in different countries. These findings also illuminate the risk for food insecurity following repatriation to Afghanistan

The Impact of Ocean Freight Rate Fluctuation on Wheat Flow

The global economy is increasingly defined by access to international markets, with reduced barriers to trade between many countries. Continued reduction in the costs of moving products both within a country and around the world is crucial for modern business to remain competitive. International trade in grain is no different, and presents its own unique challenges for study in a Canadian context. Ocean freight rates for grain have recently been very unstable. After a long period of low freight rates, capacity became limited in 2003 and 2004 more than tripling freights rates. Although freight rates have subsequently declined, the increasing dominance of containerized ocean traffic may perpetuate the recent instability in bulk freight rates. The impact of ocean freight rates on Canada’s competitiveness in the grain markets is poorly understood. The theory for the flow of commodities over space has been well studied in the context of trade and while there have been a number of studies concerning the spatial nature of grain handling and transportation in Canada. However, to date there has been minimal effort to analyze ocean freight transportation prices and their impact on wheat flows from Canada. The purpose of this study is to analyze the impact of ocean freight rates on international competitiveness of Canadian wheat. To analyze the impact of ocean freight rates on Canada’s competitiveness a spatial, product-differentiated, equilibrium model of international wheat market is developed in this research that allows for two way trade and explains the linkages among the various locations of production and consumption. The model incorporates changes in ocean freight rates and the geographical distances with non-homogeneous wheat originated from different wheat exporters. The model is used to examine the potential impact of changes in freight rates on Canada and other main players in world wheat market. The model is a tool to compare the price and quantity changes and compare the comparative advantages and disadvantages that are created by changes in wedges due to freight rate fluctuation. The result implies that shorter geographical distances and lower freight rates do not necessarily result in increasing export to the regions with lower per unit freight rates. This is why before any decision making, it is reasonable to adopt such a tool that is capable of measuring the reactions to price changes that are associated with freight rates considering different demand and supply parameters

High-current anode phenomena in vacuum arcs

The goal of the work is to investigate the high-current anode phenomena using spectroscopic methods as well as electrical measurements. Different current waveforms and vacuum interrupter properties on the formation of high-current anode phenomena are investigated. Optical emission spectroscopy combined with high-speed camera imaging is used to investigate the temporal and spatial distribution of different species during discharge modes. The ground state density of Cr I before and after current zero is calculated. A new electric arc model based on the existence diagram is proposed

Partially-Observable Security Games for Automating Attack-Defense Analysis

Network systems often contain vulnerabilities that remain unfixed in a network for various reasons, such as the lack of a patch or knowledge to fix them. With the presence of such residual vulnerabilities, the network administrator should properly react to the malicious activities or proactively prevent them, by applying suitable countermeasures that minimize the likelihood of an attack by the attacker. In this paper, we propose a stochastic game-theoretic approach for analyzing network security and synthesizing defense strategies to protect a network. To support analysis under partial observation, where some of the attacker's activities are unobservable or undetectable by the defender, we construct a one-sided partially observable security game and transform it into a perfect game for further analysis. We prove that this transformation is sound for a sub-class of security games and a subset of properties specified in the logic rPATL. We implement a prototype that fully automates our approach, and evaluate it by conducting experiments on a real-life network

Symbolic Abstract Heaps for Polymorphic Information-flow Guard Inference (Extended Version)

In the realm of sound object-oriented program analyses for information-flow control, very few approaches adopt flow-sensitive abstractions of the heap that enable a precise modeling of implicit flows. To tackle this challenge, we advance a new symbolic abstraction approach for modeling the heap in Java-like programs. We use a store-less representation that is parameterized with a family of relations among references to offer various levels of precision based on user preferences. This enables us to automatically infer polymorphic information-flow guards for methods via a co-reachability analysis of a symbolic finite-state system. We instantiate the heap abstraction with three different families of relations. We prove the soundness of our approach and compare the precision and scalability obtained with each instantiated heap domain by using the IFSpec benchmarks and real-life applications