| 1. |
- Osman, Ahmed M. Shahat
(författare)
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Smart Cities and Big Data Analytics : A Data-Driven Decision-Making Perspective
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The phenomenon of digitalization has led to the emergence of a new term—big data. Big data refers to the vast volumes of digital data characterized by its volume, velocity, variety, veracity, and value. The accumulation of enormous amounts of digital data has encouraged academics to develop appropriate technologies and algorithms to manage and analyze these data in order to leverage the embedded relationships within the data to support decision-making. This approach has revolutionized the organizational strategies of most business areas by digitally transforming business operations and decision-making processes.A “smart city” is a new concept that depends primarily on digitization and big data analysis. The aim of a smart city is to tackle the challenges of ever-increasing urbanization by utilizing atypical approaches. The utilization of big data analysis in smart cities has been investigated thoroughly in the literature from various aspects, such as those related to recommended technologies and the domains of applications. A smart city is a compound system with multi-domain attributes in which the citizens represent key participants in decision-making. However, harnessing big data analysis to support decision-making in the smart city context is rarely approached in academia. The infrequency of this type of research was sufficient to motivate this interesting research. Two research questions drive this thesis: RQ1: What are the challenges of utilizing big data analytics (BDA) to enable decision-making in smart cities? RQ2: What are the design principles of the BDA framework in the context of smart cities? To address these research questions, numerous research methods were applied, including a systematic literature review, design science research, use case, and case study. In addition, internationally acknowledged information systems databases were searched to collect quality scholarly articles and conference proceedings: ACM Digital Library, IEEE, SCOPUS, Springer Link, INSPEC, INSPEC, and Web of Science. A freely published dataset for experimental purposes on Yelp (www.yelp.com) was used for the use case experiment. Lastly, the case study was based on data from a national Egyptian digital transformation project called Nafeza.The research findings revealed the need to introduce an inventive framework for exploiting big data analysis in smart city applications. The main contribution of this research is the proposal of a novel framework for utilizing big data analytics in smart cities. The proposed framework, the Smart Cities Data Analytics Panel (SCDAP), is a domain-independent big data analysis framework. It compiles the relevant design principles mentioned in the literature, particularly those that are distinctive to smart cities. The design principles of SCDAP are founded on the literature review, use case, and case study methodologies and are the main contribution of this research.As the four papers that formed the foundation of this thesis combine theoretical and practical research, the contributions of this research can be of direct benefit to academic researchers in this field and practitioners of smart city projects.
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| 2. |
- Abbas Ahmed M Gadeh EL Dum, Nagat
(författare)
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Immunomodulation of cytokine and chemokine production in animal models of neuroinflammatory and neurodegenerative disorders
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Experimental autoimmune neuritis (EAN) is a CD4+ T cell-mediated autoimmune disease of the peripheral nervous system (PNS) that can be actively induced in susceptible animal species and strains by active immunization with heterogeneous peripheral nerve myelin or its component P2 or PO proteins or their peptides emulsified in Freund's complete adjuvant. EAN represents an animal model for studying the immunopathogenesis and therapy of Guillain-Barré syndrome (GBS ) which is a major inflammatory demyelinating disease of the PNS in humans. The close clinical, histopathological, and electrophysiological similarities between EAN and GBS make EAN an especially suitable model, capable of offering insights into the pathophysiology of GBS. EAN is also considered to represent a general model for studying CD4+-mediated autoimmune diseases. Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia in the Western world. It is characterised neuropathologically by the deposition of extracellular amyeloid plaques containing aggregates of the amyloid protein beta (A-beta) peptide, as well as by intracellular aggregation of neurofibrillary tangles and selective neuronal loss accompanied by cerebrovascular amyloidosis. The mechanism of AD has not been completely defined. The inflammatory cytokines have been implicated as mediators in response to brain injury in AD. A-beta precursor protein APP transgenic mice (Tg2576) are one of the most widely used animal model for A-beta plaques in cortical regions of the brain, which over-expresses human APP with the Swedish double mutation. Peak numbers of macrophage inflammatory protein (MIP)- 1 alpha-positive cells in the sciatic nerve were seen on day 14 post-immunization (p.i.), which coincided with the development of severe clinical signs. Administration of an anti-MIP-1 alpha antibody suppressed clinical signs of EAN and inhibited inflammation and demyelination in the sciatic nerve. Peak numbers of monocyte chemotactic protein (MCP)-1-positive cells in the sciatic nerve were detected on day 7 p.i. (i.e., tile onset of clinical EAN). Administration of an anti-MCP-1 antibody caused a delay of onset of EAR The numbers of MIP-2-positive cells reached a maximum on day 21 p.i. Anti-MIP-2 antibody failed to suppress clinical signs of EAN and inflammation and demyelination in the sciatic nerve. EAN was strongly suppressed by Rolipram administered twice daily intraperitoneally from day 9 p.i., after onset of clinical EAN, to day 18 p.i., over 10 days. This clinical effect was associated with dose-dependent downregulation of interferon (IFN)-gamma and the chemokines MIP-1alpha, MIP-2 and MCP-1 as well as up-regulated interleukin (IL)-4 production in sciatic nerve sections from Rolipram-treated EAN rats at the maximum of clinical EAN, i.e., on day 14 p.i. These findings suggest that Rolipram could be useful in certain T cell-dependent autoimmune diseases and inflammatory neuropathies. ABR-215062, which is a new synthetic immunomodulatory compound derived from Linomide, administered daily subcutaneously from the day of inoculation strongly suppressed EAN in a dose-dependent manner. ABR215062 reduced the incidence of EAN, ameliorated clinical signs, and inhibited PO peptide 180-199-specific T and B cell responses and also decreased inflammation and demyelination in the peripheral nerves. The suppression of clinical EAN is associated with inhibition of the inflammatory cytokines IFN-gamma and tumor necrosis factor-alpha as well as the enhancement of the anti-inflammatory cytokine IL-4 in peripheral nerve tissues. The suppressive effects of ABR-215062 on EAN are quite similar to those of Linomide on EAN. These findings suggest that ABR-215062 could be useful in certain T cell-mediated autoimmune diseases. To elucidate the mechanisms involved in A-beta-mediated inflammation, we used immunocytochemistry and in situ hybridization to study the potential role of the cytokines interferon-gamma (IFN-gamma), interleukin (IL)-12 and IL-4 in transgenic mice Tg2576. Cytokine and cytokine mRNA expression was detected in brain sections from cortical regions at various postnatal ages ranging from 3 to 19 months. High levels of IFN-gamma and IL-12 mRNA expression, as well as their protein production appeared early at 9 months and peaked at 17-19 months in Tg2576 mice. Significantly increased transcripts of IFN-gamma and IL-12 genes were found in the reactive microglia. and astrocytes surrounding AP deposits. Both findings indicate a role for the pro-inflammatory cytokines IFN-gamma and IL-12 in early disease development and are consistent with microglial activation related to AP formation. In contrast, transcription and production of IL-4 in brain sections was almost undetectable in transgenic mice up to post-natal ages of 17-19 months. These results suggest a major pro-inflammatory role for IL-12 and IFN- gamma in Tg2576 transgenic mice that may provide the association between AP plaque formation, microglial and astrocyte activation in these animals. These observations call for further studies on the potential role of anti-inflammatory therapeutic strategies for AD.
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| 3. |
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| 4. |
- Ahmed, Hesham M., 1981-
(författare)
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Investigations of the Kinetics of Reduction and Reduction/Carburization of NiO-WO3 Precursors.
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Kinetic studies of reduction of the mixtures of NiO and WO3 having different Ni/(Ni+W) molar ratios in flowing hydrogen gas were investigated by means of Thermo Gravimetric Analysis (TGA), Fluidized Bed (FB) technique as well as Thermal diffusivity measurements under isothermal conditions. In the case of TGA, the reaction progress was monitored by mass loss, while evolved gas analysis by a gas chromatograph was the indicator of the reaction progress in the case of FB. The results indicate that the reduction reaction proceeds through three consecutive steps, viz. NiO-WO3 Ni-WO3 Ni-WO2 Ni-W The present results show that the fluidized bed technique can be successfully utilized in bulk production of intermetallics containing W and a transition metal (or a composite material) wherein the process conditions would have a strong impact on the particle size of the end product. During the investigations, it was found that there was a delay in the reaction during the hydrogen reduction of NiO-WO3 mixed oxides in a fluidized bed reactor. In order to understand the same, a theoretical model was developed to estimate the apparent reaction rate constant for the reduction reaction from the intrinsic chemical reaction rate constant. Appropriate differential mass balance equations based on intrinsic chemical reaction rate constants and thermodynamic equilibria were developed. The proposed model was successfully applied in predicting the overall reaction kinetics of a fluidized bed reactor. This model is also suitable for scale-up calculations. SEM images showed that the particle size of the final product was dependent on the Ni/(Ni+W) molar ratio; smaller particles were formed at higher nickel contents. X-ray diffractions of the reduced precursors exhibited slight shift of Ni peaks from the standard one indicating the dissolution of W into Ni. A new method for studying kinetics of the hydrogen reduction of NiO-WO3 precursors was developed in which the reaction progress was monitored by following the change of thermal diffusivity of the precursors. Activation energies of reduction as well as sintering were calculated. This method is considered unique as it provides information regarding the physical changes like sintering, change of porosity and agglomeration along with the chemical changes occurring during the gas/solid reaction. As a continuation of the kinetic studies, Ni-W-C ternary carbides were synthesized by simultaneous reduction–carburization of Ni-W-O system using H2-CH4 gas mixtures by TGA. The results showed that the reduction of the oxide mixture was complete before the carburization took place. The nascent particles of the metals formed by reduction could react with the gas mixture with well-defined carbon potential to form a uniform product of Ni-W-C. The above-mentioned experiments were conducted in such a way to ensure that the reaction was controlled by the chemical reaction. The activation energies of the reduction as well as carburization processes at different stages were calculated accordingly. The present dissertation demonstrates the potential of the investigations of gas/solid reactions towards tailoring the process towards materials with optimized properties as for example introduction of interstitials. The present process design is extremely environment-friendly with reduced number of unit processes and the product being H2O.
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| 5. |
- El-Bahrawy, Ahmed M. A., 1958
(författare)
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Guided Elastic Waves along Periodically Corrugated Structures
- 1994
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present thesis consider time-harmonic surface and guided elastic waves propagating along periodically corrugated structures. The problems discussed deal with various configurations where the surfaces are sinusoidally - singly or doubly - periodic, and the interest is focused on investigating the roots of the dispersion relations and in particular the stopband and cross-over resonances. In all cases the results are presented for varying frequencies, corrugation heights, and, when relevant, angles of propagation. The analyses and results may be applicable in a variety of fields: ultrasonic nondestructive testing and evaluation of materials, ultrasonic devices, mode converters and energy transformation, filters, etc. Firstly, we consider the two-dimensional problem of the periodically corrugated parallel plate with traction-free surfaces. Using the technique based on the Rayleigh hypothesis (also called a modal approach) the dispersion relation for the symmetric Rayleigh-Lamb modes is obtained. The symmetric sinusoidally corrugated plate is studied numerically and the behaviour of the three lowest modes in both stopbands and passbands is closely investigated. The existence and behaviour of surface waves along an infinite, periodically corrugated, cylindrical cavity with traction-free boundary in an elastic medium is next investigated. The dispersion relation is derived by use of both the modal and the formally exact null- field approaches to demonstrate the equivalence of the two techniques. The sinusoidally corrugated cavity is studied numerically, and the dispersion relation is solved for roots on the physical Riemann sheet for the first three modes and on some of the nonphysical sheets for the axially symmetric one. The three-dimensional geometry of a, on both surfaces, double corrugated layer on a half-space is then considered. The dispersion relation for the full problem is derived using the null-field approach. The stopband and passband structure of the physical modes are investigated numerically for two different doubly sinusoidally corrugated geometries. First the Rayleigh-like surface waves that exist when there is no layer are investigated for varying frequency, corrugations heights, and angle of propagation. Afterwards, with the layer present, some of the lowest Love and Rayleigh-Lamb-like waves are studied. In the last part of the thesis the excitation of generalized Rayleigh waves by a time- harmonic source located below the infinite, doubly periodically corrugated free boundary of an elastic half-space is studied. The full elastodynamic equations are solved using the null-field approach, and the contribution of the surface waves to the total displacement field is obtained for the sinusoidally corrugated geometry with equal periods of corrugation. For different corrugation heights and frequencies and both a vertical and an arbitrarily directed horizontal point force, numerical results are presented for the angular dependence of the surface field far away from the source where the generalised Rayleigh mode contribution dominates.
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| 6. |
- El-Zohry, Ahmed M.
(författare)
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Exploring Organic Dyes for Grätzel Cells Using Time-Resolved Spectroscopy
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Grätzel cells or Dye-Sensitized Solar Cells (DSSCs) are considered one of the most promising methods to convert the sun's energy into electricity due to their low cost and simple technology of production. The Grätzel cell is based on a photosensitizer adsorbed on a low band gap semiconductor. The photosensitizer can be a metal complex or an organic dye. Organic dyes can be produced on a large scale resulting in cheaper dyes than complexes based on rare elements. However, the performance of Grätzel cells based on metal-free, organic dyes is not high enough yet. The dye's performance depends primarily on the electron dynamics. The electron dynamics in Grätzel cells includes electron injection, recombination, and regeneration. Different deactivation processes affect the electron dynamics and the cells’ performance.In this thesis, the electron dynamics was explored by various time-resolved spectroscopic techniques, namely time-correlated single photon counting, streak camera, and femtosecond transient absorption. Using these techniques, new deactivation processes for organic dyes used in DSSCs were uncovered. These processes include photoisomerization, and quenching through complexation with the electrolyte. These deactivation processes affect the performance of organic dyes in Grätzel cells, and should be avoided. For instance, the photoisomerization can compete with the electron injection and produce isomers with unknown performance. Photoisomerization as a general phenomenon in DSSC dyes has not been shown before, but is shown to occur in several organic dyes, among them D149, D102, L0 and L0Br. In addition, D149 forms ground state complexes with the standard iodide/triiodide electrolyte, which directly affect the electron dynamics on TiO2. Also, new dyes were designed with the aim of using ferrocene(s) as intramolecular regenerators, and their dynamics was studied by transient absorption.This thesis provides deeper insights into some deactivation processes of organic dyes used in DSSCs. New rules for the design of organic dyes, based on these insights, can further improve the efficiency of DSSCs.
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| 7. |
- Hedström, Axel, 1989-
(författare)
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Empirical Studies on Economic and Financial Spillovers : Asymmetric Risk and Dependence Modeling
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Financial assets are volatile, and volatility becomes more intense in terms of size and rate of recurrence when markets are uncertain and growing rapidly. The fact that the recurrence rate increased during crisis periods, such as the IT bubble in the early 2000 and the global financial crisis that started in 2007, is a key finding in the literature. Estimating these results requires modeling a time series that can consider volatility clustering. However, the prominent model in finance and economics estimates that the average volatility increases when uncertainty increases. This modeling process needs to consider the asymmetry that financial assets and economic outcomes, such as gross domestic product (GDP) exhibit, which tend to fall drastically in a short period and increase steadily over a long period. To model these different behaviors, one must consider the asymmetric nature of the return, for example, when a stock has extremely low or extremely high returns in a day. To model this behavior, I used several methods in settings that could better explain what happens during market periods when there is higher uncertainty. The general finding is that correlations are higher when returns are in the lower quantiles, called the left tails. Thus, financial assets are positively correlated, especially during periods of increased uncertainty. It is not only clustering that one would try to explain, but another issue is the prediction of one asset’s effect on another. The effect of one asset on another asset is called the spillover effect. We tried to distinguish between events that happen during the same time that affect all assets. These events are called systematic risk, and the effects that one asset has on another asset is called systemic risk. Explaining the systemic risk typically has higher priority from a policy perspective, as systemic risk can be a driver for risk transmission from one asset to another, creating a chain of risk or a spiral of risk. Hence, the approaches I used can model that chain of risk and predict risk transmission while controlling for external factors that increase uncertainty. The results of this research show the connection between energy assets and renewable energy stocks in Papers 1 and 2. For instance, we found that there is a possibility of adjusting the European carbon emission cap and that renewable energy stocks positively correlate with energy commodities in the tails. Thus, renewable energy stocks follow a macroeconomic cycle. The findings of Paper 3 show the systemic and systematic nature of cross-country spillovers between emerging and developed financial markets, and that the spillover is time-varying with increasing spillovers in crisis periods. Paper 4 examines the Nordic banking sector. The results show that banks’ spillover to their local markets is due to their systemic importance and the strength of the spillover is related to the bank’s characteristics. In the final Paper, I studied the upside and downside movement asymmetry of stocks and found that betting on upside volatility is better than a portfolio perspective but comes at the cost of increased pricing errors. The empirical findings of this thesis significantly contribute to policymakers and institutional investors in portfolio diversification and risk management.
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| 8. |
- Lind, Thérèse, 1989-
(författare)
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Financial literacy, motivated reasoning, and gender : essays in behavioral economics
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- I wrote this thesis to create a better understanding of how individual characteristics influence our feelings, our behavior and our way of interpreting information. My focus is on financial behavior and financial information, however I also consider a political context. I investigate the (usually) enabling abilities of financial literacy and numeracy. I also consider impediments such as stereotype threat and motivated reasoning, which can prevent people from engaging in certain behaviors or from interpreting information objectively. Both processes stem from valued beliefs and psychological foundations, consequently peoples’ efforts, decisions, and evaluations are based on them.The first essay, “Competence, confidence, and gender: The role of perceived and actual financial literacy in household finance,” broadens our understanding of the benefits of financial competence. I contrast perceived and actual levels of financial literacy, and consider the role of numeracy and cognitive reflective ability. I conclude that perceived and actual levels of financial literacy positively affect behavior and wellbeing; however, perceived financial literacy more so than actual financial literacy. No such effect is observed for numeric ability and cognitive reflection. Furthermore, women are more anxious about financial matters even though they tend to engage more frequently in the considered financial behaviors.The second essay, “Threatening finance? Examining the gender gap in financial literacy,” continues my exploration of the relationship between gender and financial literacy. In a series of studies, I investigate whether the observed gender gap in financial literacy can be identified in nonnumerical contexts, if it can be associated with confidence in financial matters, and if it can be attributed to stereotype threat, which posits that inbuilt prejudices about gender and finance undermine women’s performance of tasks that involve finance. The results show that the observed gender gap in financial literacy is robust even in nonnumerical financial contexts and suggest that a stereotype threat for women in the financial domain might be present. The gender gap in financial literacy could not be attributed to a difference in (displayed) confidence.In the third essay, “Preferences for lump-sum over divided payment structures,” I investigate whether or not people display systematic preferences for lump–sum or divided payment structures and how these preferences differ in gain (benefit) and loss (payment) situations. I investigate what happens when payments belong to a single underlying event, such as when people can choose to pay immediately or in installments. I also examine whether or not individual differences in time preferences, risk preferences, numeracy, and financial literacy are associated with preferences for one payment structure or the other. The aggregate results show a tendency for people to prefer obtaining and paying money in lump sums. I find no systematic indication that the considered individual differences play a role in this type of decision.The fourth essay, “Motivated reasoning when assessing the effect of refugee intake,” inquires into differences in worldview ideology, whether people identify as nationally or globally oriented, hinder them from objectively interpreting information. I use an experiment to find out if people display motivated reasoning when interpreting numerical information about the effects of refugees on the crime rate. Our results show evidence of motivated reasoning along the lines of worldview ideology. However, individuals with higher numeric ability were less likely to engage in motivated reasoning, leading to the conclusion that motivated reasoning is more likely to be driven by feelings and emotional cues than by deliberate analytical processes.
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| 9. |
- Lång, Elisabeth, 1983-
(författare)
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Short- and Long-Term Influences of Education, Health Indicators, and Crime on Labor Market Outcomes : Five Essays in Empirical Labor Economics
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this thesis is to improve the understanding of how several individual characteristics, namely education (years of schooling), health indicators (height, weight, smoking, alcohol consumption, and exercise), criminal behavior, and crime victimization, influence labor market outcomes in the short and long run. The first part of the thesis consists of three studies in which I adopt a within-twin-pair difference approach to analyze how education, health indicators, and earnings are associated with each other over the life cycle. The second part of the thesis includes two studies in which I use field experiments in order to test the employability of exoffenders and crime victims.The first essay, Learning for life?, describes an analysis of the education premium in earnings and health-related behaviors throughout adulthood among twins. The results show that the education premium in earnings, net of genetic inheritance, is rather small over the life cycle but increases with the level of education. The results also show that the education premium in health-related behaviors is mainly concentrated on smoking habits. The influences of education on earnings and health-related behaviors seem to work independently of each other, and there are no signs that health-related behaviors influence the education premium in earnings or vice versa.The second essay, Blowing up money?, details an analysis of the association between smoking and earnings in two different historical social contexts in Sweden: the 1970s and the 2000s. I also consider possible differences in this association in the short and long run as well as between the sexes. The results show that the earnings penalty for smoking is much stronger in the 2000s as compared to the 1970s (for both sexes) and that it is larger in the long run as compared to the short run (for men).The third essay, Two by two, inch by inch, describes an analysis of the height premium among Swedish twins. The results show that the height premium is relatively constant over the life cycle and that it is larger below median height for men and above median height for young women. The estimates are similar for monozygotic and dizygotic twins, indicating that environmentally and genetically induced height differences are similarly associated with earnings over the life cycle.The fourth essay, The employability of ex-offenders, published in IZA Journal of Labor Policy (2017), 6:6, details an analysis of whether male and female exoffenders are discriminated against when applying for jobs in the Swedish labor market. The results show that employers do discriminate against exoffenders but that the degree of discrimination varies across occupations. Discrimination against ex-offenders is pronounced in female-dominated and high-skilled occupations. The magnitude of discrimination against exoffenders does not vary by applicants’ sex.The fifth essay, Victimized twice?, describes an analysis of whether male and female crime victims are discriminated against when applying for jobs in the Swedish labor market. This study is the first to consider potential hiring discrimination against crime victims. The results show that employers do discriminate against crime victims. The discrimination varies with the sex of the crime victim and occupational characteristics and is concentrated among high-skilled jobs for female crime victims and among femaledominated jobs for male crime victims.
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| 10. |
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