京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19314号 / 工博第4111号 / 新制||工||1634(附属図書館) / 32316 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 陰山 洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

In this dissertation, we study the existence and nonexistence of positive radial solutions for classes of quasilinear elliptic equations and systems in a ball with Dirichlet boundary conditions. Our nonlinearities are asymptotically p-linear at infinity and are allowed to be singular at zero with non-positone structure, which have not been considered in the literature. In the one parameter single equation problem, we are able to show the existence of a positive radial solution with precise lower bound estimate for a certain range of the parameter. We also extend the study to a class of asymptotically p-linear system with two parameters and in the presence of singularities. We establish the existence of a positive solution with a precise lower bound estimate when the product of the parameters is in a certain range. Necessary and sufficient conditions for the existence of a positive solution are also obtained for both the single equation and system under additional assumptions. Our approach is based on the Schauder Fixed Point Theorem.

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Background: E-Commerce is a type of commerce that has become increasingly important worldwide in the last 20 years. Especially the Covid-19 pandemic has once again strongly catalyzed this development. However, there are still difficulties in implementing and conducting E- Commerce, especially in developing countries such as Nigeria. Much research has been done to determine what challenges companies face when implementing E-Commerce solutions in Nigeria. However, overcoming these challenges still needs to be elucidated by research. Purpose: This study aims to discover what challenges exist for E-Commerce companies in Nigeria and what solutions could help overcome them. By identifying these challenges and solutions, our study aims to provide a deeper insight into the E-Commerce world of the developing country Nigeria and thus show companies how they can deal with these issues. Method: We conducted a qualitative study using a grounded theory approach. Semi-structured interviews with experts, E-Commerce-, logistic- and FinTech-companies provided insights into the E-Commerce landscape of Nigeria. Conclusion: The study revealed that there are still many challenges in the E-Commerce sector in Nigeria. However, there are many solutions to the issues, especially in terms of E-Commerce awareness, logistics, and sustainability, which ultimately underlines the potential of E-Commerce in Nigeria.

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