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Development and comparative lifecycle assessment of various LDPE and HDPE production processes based on CO2 capture and utilization
Get PDFLow-density polyethylene (LDPE) and high-density polyethylene (HDPE) are some of the most commonly used materials worldwide. These polymers are typically produced through the polymerization of ethylene which is conventionally produced through the energy-intensive steam cracking of naphtha or ethane. However, the conventional production process for LDPE and HDPE results in significant greenhouse gas emissions (1.92 and 1.86 kg CO2/kg of polymer, respectively).
Hence, this work focuses on the design of alternative pathways based on CO2 capture and utilization (CCU) for polymer production. The proposed pathways for CCU-polymers are based on the conversion of CO2 to methanol, followed by the methanol-to-olefins (MTO) process to produce mainly ethylene, and consequently LDPE and HDPE from ethylene. The process design and simulation of the entire pathway are conducted in AspenPlus, while the life cycle assessment (LCA) is done through OpenLCA.
The LCA results showed that the CCU-MTO pathway is an environmentally attractive option, particularly in regions where renewable (low-carbon) electricity is more prominent, such as Quebec and Ontario, where negative CO2 emissions are achieved. This makes polymer production via the proposed method suitable for the permanent mitigation of CO2
Fault Tree Analysis of Safety-Critical Systems via Statistical Model Checking
Get PDFThe design of safety-critical systems have become more and more complex in recent years. As a result, identifying the sources of failure and mitigating their effects on the system are of great importance. In this context, several methods have been proposed. One of the widely-used approaches for reliability analysis of systems is fault tree analysis (FTA).
The traditional methods of FTA that are based on paper and pencil proof or simulation can be drastically time-consuming and highly prone to error, especially when analyzing complex systems with redundant architectures.
In this work, we propose a statistical model checking (SMC) based approach for FTA of safety critical systems that can mitigate the above-mentioned problems regarding the traditional FTA methods. In our approach, the FT gates are modelled using the priced timed automata (PTA) formalism, and then the full fault tree model is created by the parallel composition of the models of each gate.
Furthermore, in our method, the FT models take into account both the power consumption and failure rates of the system components. With this, it becomes possible to determine when the power source will run out of power and then the mission time of the system can be determined. As a result, the FTA time period can be restricted to the system’s mission time and the resources can be used more efficiently.
Our proposed approach is also able to perform a formal assessment of the FT model. This evaluation includes a criticality analysis to identify the fault tree’s critical elements that have the greatest impact on the probability of system failure. The critical FT components are then subjected to various risk mitigation techniques based on component redundancy, such as triple modular redundancy (TMR) and quintuple modular redundancy (QMR)
Removal of Nutrients from Water Using Biosurfactant Micellar Enhanced Ultrafiltration
Get PDFRemoving nutrients, e.g., ammonia, nitrate and, phosphate (NH4+, NO3-, PO43-) from wastewater, has been a great challenge. Various studies have been undertaken for metal and nutrient removal from wastewater using physical and chemical treatment techniques and synthetic surfactants. However, there have been very few studies on treatment incorporating biodegradable biosurfactants which are the candidates to enhance nutrient removal from wastewater. Either a microbial-derived biosurfactant (rhamnolipid) or a yeast-derived biosurfactant (sophorolipid) or both can be used for this removal process based on their efficiency with Micellar Enhanced Ultrafiltration (MEUF). In the MEUF process, surfactant micelles, aggregates of surfactant monomers, can bind cations and anions when oppositely charged. The MEUF system works by rejecting micelles containing cations and anions with larger diameters than the pore size of the ultrafiltration membrane. The MEUF process can be incorporated in this proposed study to increase the efficiency of metal removal and lower costs by reducing pore pressure compared to reverse osmosis (RO) and nanofiltration (NF). The micelle-containing metal cations will be removed, and it is possible to recover the biosurfactant from the filtration system. Different parameters, e.g., surface tension, critical micelle concentration (CMC), pH, and temperature, were examined during the experimentation. The overall efficiency of the process was estimated based on the ion concentration of the final filtrate. The experimental results demonstrate that the elimination rate for NH4+, PO43-, and NO3- is around 80-90% at higher temperatures and biosurfactant concentrations. Removal rates varied from 60 to 70% at lower pH and initial ionic concentrations. However, one of the system's significant disadvantages is the reduction in membrane permeate flux produced by various experiment conditions, one being membrane fouling. The optimum conditions that deliver the most excellent nutrient removal were determined. The generated results can further be used for metal and nutrient removal from eutrophic lakes, wastewater treatment plants (WWTP), and industrial effluents in future work
Accuracy Improvement of Industrial Robot Using PID Controller Based on Back-propagation Neural Networks
Get PDFNowadays, industrial robots are widely used in many fields. With the wide range of applications, the accuracy of robots has become an issue of concern. In some path following tasks, the accuracy of existing robots does not yet meet the industry standard. In this research, the accuracy of the robot is enhanced by using position-based visual servoing. The purpose of this research is to propose a novel dynamic path tracking (DPT) method to solve the aforementioned accuracy problem. This method uses the C-Track from Creaform to measure the end-effector of the robot M-20iA from Fanuc and to use the visual information to guide the robot to follow the desired path. First, a stereo binocular camera C-Track provides the real-time pose information of the end-effector. To remove the noise transmitted from the camera, the research uses a robust Kalman filter (RKF) to improve the performance of the standard Kalman filter under disturbance by correcting the state variable error covariance (P). Then, the Fanuc robot M-20iA uses position-based visual servoing (PBVS) strategy to correct the position and orientation of the end-effector, which is implemented through dynamic path modification (DPM) function, in conjunction with real-time data acquired by C-Track. Next, adaptive neuro-PID (ANPID) control is developed as the PBVS scheme for DPM correction. Such control strategy has a strong adaptive and self-learning capability, which enables online tuning of the PID controller parameters, resulting in better performance in robot control. Finally, extensive experiment tests have been carried out and the results show that the the accuracy of path following reaches ±0.08mm and ±0.04deg, compared with the accuracy ±0.2mm and ±0.1deg achieved by conventional PID controller
COVID-19 Crisis and Parameters for Sustainable Entrepreneurship
Get PDFPURPOSE: Entrepreneurship and sustainability have been debated for the last decade, urging the deployment of an effective entrepreneurial ecosystem. COVID-19 has posed a new challenge to emerging entrepreneurs in all sectors, and they have reduced their commitment to entrepreneurial sustainability and innovation. The commitment to sustainability is essential to keep the relationship between start-up growth and socio-economic capital.
DESIGN/METHODOLOGY/APPROACH: This commentary paper explores entrepreneurial sustainability through the lens of the COVID-19 crisis.
FINDINGS: This paper outlines the impact of the COVID-19 crisis on entrepreneurial activity and explores relationships between sustainability and socio-economic development.
ORIGINALITY/VALUE: The COVID-19 pandemic has brought an opportunity to review the entrepreneurial eco-system to reset the scope of entrepreneurship sustainability. It has signaled that sustainability should be determined by temporal construal theory concerning radical solutions
An urban political ecology of flood control and population relocation in Ouagadougou - Burkina Faso
Get PDFGlobally, the number of people at risk from flooding has been increasing since 2000, with the population from the South being more vulnerable. Millions of households are displaced by disasters every year. In 2009, the city of Ouagadougou in Burkina Faso experienced its most disastrous flood ever recorded. As a response, the government designed a permanent relocation plan in Yagma, a village located outside the city of Ouagadougou. The relocation plan disrupted the livelihoods of the households that were affected by the flood, leading many of them to return and rebuild their houses in flood prone areas. This paper contributes to a body of literature analyzing the heritage of postcolonialism on the flood vulnerability on the poorer communities in Ouagadougou. Using a political ecology frame, the thesis attempts to understand how the government of Burkina Faso and flood victims understand land and belongings, and how that understanding shaped the relocation program. After interviewing flood victims and government officials, an analysis revealed that contrasting views are at work. A perspective based on technical calculations and a neo-colonialist vision of development, on the one hand, and a grounded perspective based on relationships to the land and each other, on the other
Understanding Geographical Patterns of Scientific Collaboration in the field of Artificial Intelligence
Get PDFThe role of geographical proximity in facilitating inter-regional or inter-organizational collaborations has been studied thoroughly in recent years. However, the effect of geographical proximity on forming scientific collaborations at the individual level has not been addressed so far. Using co-publication data of AI researchers from 2000 to 2019, first, the effect of geographical proximity on the chance of future scientific collaboration among researchers was studied. The logit regression and machine learning classification results show that geographical distance is an essential impediment to scientific collaboration at the individual level despite the tremendous improvements in transportation and communication technologies during recent decades. Second, the interplay between geographical proximity and network proximity was examined to see whether network proximity can substitute geographical proximity in encouraging long-distance scientific collaborations. The results show that the effect of network proximity on the likelihood of scientific collaboration increases with geographical distance, implying that network proximity acts as a substitute for geographical proximity. Therefore, policies aiming at encouraging long-distance collaborations could positively affect scientific collaboration and future knowledge production
A Comprehensive Heat Transfer Analysis for Thermoplastic Composites Made by Automated Fiber Placement Using Hot Gas Torch
Get PDFThermoplastic composites bring many benefits in terms of mechanical properties and manufacturing. Possibility of healing and recycling and proper strength are some of these desirable characteristics. Automated fiber placement (AFP) process can be used to manufacture both thermoplastic and thermoset composite structures. However, manufacturing of thermoplastic composite structures with free edges using AFP process faces a big challenge. These structures such as flat laminates deform, and these undesirable deformations occur even during the manufacturing process of unidirectional laminates. The distortion of thermoplastic structures with free edges is mainly caused by development of temperature gradients and residual stresses. To investigate the temperature gradients and residual stresses, accurate heat transfer models need to be developed. In this study a two-dimensional transient heat transfer model was developed for thermoplastic structures manufactured by AFP process with a hot gas torch. The accuracy of heat transfer model for AFP process using hot gas torch is highly dependent upon the accuracy of hot gas/air and convection coefficient distributions in the vicinity of the substrate (thermal inputs). Therefore, mathematical models for both thermal inputs were developed in this study. Inter-layer thermal contact resistance and temperature dependencies of the material properties were considered, and the heat transfer model was validated by experimental results. Furthermore, a heat transfer model was developed to include the effects of time between each pass. Then, using the validated heat transfer models and considering temperature histories and the time between each pass, the development of temperature gradients was investigated for various types of mandrels
Essays on entrepreneurial actions in uncertain and resource-constrained situations
Get PDFThis dissertation consists of three essays that study entrepreneurial actions in uncertain and resource-constrained situations by focusing on effectuation, bricolage, and bootstrapping literature. The first essay fills some important gaps in the literature on antecedents of effectuation. It does so by introducing three non-economic antecedents of effectuation and scrutinizes the impact of perceived disruptiveness of the business idea, entrepreneurs’ motivation, and their ambiguity tolerance (indicators of innovators) with regard to taking effectual processes. 75 hand-collected responses from nascent ventures that are active in Montreal, Canada, and 200 responses via Qualtrics from new ventures operating across Canada form the sample of the first essay. The results are consistent in both samples and show the significant impact of perceived disruptiveness of the product/service and autonomous type of motivation on using effectuation.
The second essay starts a new dialogue in the literature of effectuation/causation and focuses on the performance of entrepreneurs rather than firms. It addresses the questions about whether entrepreneurs can cognitively recognize when effectual/causal approaches are likely to yield better performance and execute them. Based on a sample of 200 entrepreneurs in Canada, the second essay studies the effect of openness to change, optimism, ambition, and team size on the entrepreneurs’ capability of choosing and fulfilling the best approach (effectuation vs causation) at different levels of product/service disruptiveness.
The third essay is meant to obviate some limitations regarding entrepreneurial approaches to overcome resource scarcity (bricolage, effectuation, and bootstrapping), namely, the considerable amount of overlap among approaches, unclear boundaries between what entrepreneurs do and how they do it, different antecedents of the approaches, and the multidimensional nature of them. To obviate the mentioned limitations, the third essay makes two major contributions to the literature. First, it introduces four distinct, single-dimensional, and easily measurable innovative courses of action that entrepreneurs undertake to overcome resource scarcity. Second, to stress the differences among the courses of action and to stimulate empirical studies in the future, it elaborates on process-related, organizational, environmental, and individual factors that affect the decision of entrepreneurs on prioritizing some innovative courses of action over others to overcome resource scarcity
Melting Glaciers and Rising Seas: Indigenous Digital Art in the Arctic and Pacific Islands
Get PDFThis thesis analyzes two works: Rise: From One Island to Another (2018), a video-poem by Marshallese artist Kathy Jetñil-Kijiner and Kalaaleq artist Aka Niviâna, and Arkhticós Doloros (2019), a poem and performance by Kalaaleq artist Jessie Kleemann. The 350.org production of Rise: From One Island to Another (Rise) demonstrates how climate change is affecting Indigenous communities in Kalaallit Nunaat (“Greenland”) and Aelon Kein Ad (“Marshall Islands”), focusing on glacial melt and severity of floods due to rising sea levels. Arkhticós Doloros presents Kleemann’s personal engagement with melting glaciers in Kalaallit Nunaat. These works are part of a growing movement of Black, Indigenous, and People of Colour (BIPOC) artists who highlight how discourses around the anthropocene— the era in which human activity has significantly altered the environment and climate—do not fully account for the relationship between colonialism and climate change. Indigenous scholars, such as Kyle Whyte (Potawatomi) and Zoe Todd (Métis), argue for a decolonization of the anthropocene that is rooted in Indigenous ways of knowing about the land, waters, and relationships with human and non-human life. Aligned with these scholars, this thesis argues that Rise and Arkhticós Doloros call attention to the need for a decolonization of the anthropocene by advocating for Indigenous communities’ knowledges and experiences. Drawing on Hupa/Yurok/Karuk scholar Cutcha Risling Baldy and Diné scholar Melanie K. Yazzie’s notion of radical relationality—an Indigenous feminist framework that considers decolonization by establishing relationships with and through the waterways—this thesis considers Kalaallit and Marshallese artists’ relationships with and through melting glaciers and rising seas