OuluREPO University of Oulu repository
Not a member yet
54977 research outputs found
Sort by
The geopolitics and biopolitics of governing cross-border mobilities in the Covid-19 pandemic: Rationalities, technologies, and subjectivities
No full textModeling and temporal analysis of electrical impedance spectroscopy responses of Rosa chinensis under powdery mildew stress
No full textAbstract
Under the intensifying impact of global climate change, the frequency of plant disease outbreaks is steadily increasing, posing significant challenges to healthy cultivation and precision management. To enable early diagnosis of plant disease stress, this study used two rose (Rosa chinensis) varieties, ’Red Cap’ and ’Carefree Wonder’ were used to conduct powdery mildew stress experiment. Throughout the stress period, leaf electrical impedance spectroscopy (EIS), physiological parameters, and ultrastructural observations, were collected. A novel lumped equivalent circuit model was proposed, incorporating plant cell electrophysiological properties. The model developed for both rose varieties-featuring Constant Phase Elements (CPE) and Warburg elements (W), successfully characterized the resistive properties of the leaf tissue, including the extracellular resistance (R1), cell membrane resistance (R2), intracellular resistance (R3), and vacuole interior resistance (R4). Model parameters R1 and R3 were significantly correlated with the above physiological indicators, and showed significant differences 3 to 11 days earlier than traditional physiological parameters, demonstrating strong potential for early detection of cellular damage. Overall, this study demonstrates that EIS technology can dynamically reflect electrical property changes in plant tissues under biotic stress, effectively overcoming the lag limitations of conventional physiological measurements, providing a promising tool for early disease diagnosis and resistance screening.Abstract
Under the intensifying impact of global climate change, the frequency of plant disease outbreaks is steadily increasing, posing significant challenges to healthy cultivation and precision management. To enable early diagnosis of plant disease stress, this study used two rose (Rosa chinensis) varieties, ’Red Cap’ and ’Carefree Wonder’ were used to conduct powdery mildew stress experiment. Throughout the stress period, leaf electrical impedance spectroscopy (EIS), physiological parameters, and ultrastructural observations, were collected. A novel lumped equivalent circuit model was proposed, incorporating plant cell electrophysiological properties. The model developed for both rose varieties-featuring Constant Phase Elements (CPE) and Warburg elements (W), successfully characterized the resistive properties of the leaf tissue, including the extracellular resistance (R1), cell membrane resistance (R2), intracellular resistance (R3), and vacuole interior resistance (R4). Model parameters R1 and R3 were significantly correlated with the above physiological indicators, and showed significant differences 3 to 11 days earlier than traditional physiological parameters, demonstrating strong potential for early detection of cellular damage. Overall, this study demonstrates that EIS technology can dynamically reflect electrical property changes in plant tissues under biotic stress, effectively overcoming the lag limitations of conventional physiological measurements, providing a promising tool for early disease diagnosis and resistance screening
Joint content popularity and audience retention-aware live streaming over RSMA edge networks
No full textAbstract
The exponential growth of high-quality live streaming services over cellular networks, particularly in heterogeneous environments facilitated by 6G, has underscored the need for novel wireless communication. To address this challenge, Rate Splitting Multiple Access (RSMA) has emerged as a promising interference management scheme in advanced cellular networks. This paper considers such a potential environment where the impacts of content popularity and audience retention are jointly investigated to maximize the average video resolution of live streaming services over RSMA edge networks. The complex problem is modeled as a Markov Decision Process and subsequently addressed using an appropriate reinforcement learning framework leveraging the Deep Deterministic Policy Gradient (DDPG) technique, named DDPG-BARMAS. Simulation results demonstrate that the proposed DDPG-BARMAS method significantly outperforms existing algorithms in terms of video resolution improvement, highlighting its potential as a robust solution for future wireless live-streaming services.Abstract
The exponential growth of high-quality live streaming services over cellular networks, particularly in heterogeneous environments facilitated by 6G, has underscored the need for novel wireless communication. To address this challenge, Rate Splitting Multiple Access (RSMA) has emerged as a promising interference management scheme in advanced cellular networks. This paper considers such a potential environment where the impacts of content popularity and audience retention are jointly investigated to maximize the average video resolution of live streaming services over RSMA edge networks. The complex problem is modeled as a Markov Decision Process and subsequently addressed using an appropriate reinforcement learning framework leveraging the Deep Deterministic Policy Gradient (DDPG) technique, named DDPG-BARMAS. Simulation results demonstrate that the proposed DDPG-BARMAS method significantly outperforms existing algorithms in terms of video resolution improvement, highlighting its potential as a robust solution for future wireless live-streaming services
Integration of direct air capture with Allam cycle: Innovative pathway in negative emission technologies
No full textAbstract
The advancement of negative emission technologies (NETs) is crucial for addressing climate change by reducing atmospheric carbon dioxide levels. This study presents a comprehensive evaluation of a High Temperature Direct Air Capture (HT-DAC) system integrated with a supercritical CO2 (S-CO2) cycle, representing a significant advancement in carbon capture, energy optimization, and NET systems. Given to significant energy demands of HT-DAC, the primary objective of this research is to address the process’s energy intensity by focusing on the development of a more efficient power island. Specifically, this study investigates the energy demands of the Air Separation Unit (ASU) to minimize energy consumption and improve the overall efficiency of the Allam cycle when coupled with the ASU. Additionally, the study examines the thermal integration of the system using pinch analysis to assess the impact of this innovative power island on energy efficiency. Key results indicate that the proposed system is capable of capturing 0.99 million tons of CO2 per year directly from the air, achieving a capture efficiency of 75 %. The specific energy requirement for the process is initially 3.19 kWh per kg of captured CO2, which is reduced to 2.21 kWh/kgCO2 following process optimization and heat integration. Through this optimization, hot and cold utility demands are reduced by 69.7 % and 36.9 %, respectively, while 110.1 MW of heat is recovered through the design of heat exchangers network, resulting in an 9.66 % reduction in overall energy demand compared to the base case. Furthermore, the integration of captured and regenerated CO2 (135.1 tons per hour with a purity of 98.1 mol%) offers substantial potential for synthetic fuel production and underground storage.Abstract
The advancement of negative emission technologies (NETs) is crucial for addressing climate change by reducing atmospheric carbon dioxide levels. This study presents a comprehensive evaluation of a High Temperature Direct Air Capture (HT-DAC) system integrated with a supercritical CO2 (S-CO2) cycle, representing a significant advancement in carbon capture, energy optimization, and NET systems. Given to significant energy demands of HT-DAC, the primary objective of this research is to address the process’s energy intensity by focusing on the development of a more efficient power island. Specifically, this study investigates the energy demands of the Air Separation Unit (ASU) to minimize energy consumption and improve the overall efficiency of the Allam cycle when coupled with the ASU. Additionally, the study examines the thermal integration of the system using pinch analysis to assess the impact of this innovative power island on energy efficiency. Key results indicate that the proposed system is capable of capturing 0.99 million tons of CO2 per year directly from the air, achieving a capture efficiency of 75 %. The specific energy requirement for the process is initially 3.19 kWh per kg of captured CO2, which is reduced to 2.21 kWh/kgCO2 following process optimization and heat integration. Through this optimization, hot and cold utility demands are reduced by 69.7 % and 36.9 %, respectively, while 110.1 MW of heat is recovered through the design of heat exchangers network, resulting in an 9.66 % reduction in overall energy demand compared to the base case. Furthermore, the integration of captured and regenerated CO2 (135.1 tons per hour with a purity of 98.1 mol%) offers substantial potential for synthetic fuel production and underground storage
Linearization Techniques for Bipolar Transistor Transconductance Stage
No full textAbstract
Conventional BJT differential pairs have a relatively small input voltage dynamic range. This paper reviews and compares several linearization techniques, which are used to expand the input transconductance (gm) stage’s dynamic range. Two techniques are emphasized: The first one is the multi-tanh principle, and the other one is based on classical emitter degeneration. The main concept of multi-tanh is that individual nonlinear gm functions can be divided along the input voltage axis to obtain a function with higher linearity. This modification expands the linearity and results in a wider operating dynamic range. Emitter degeneration is an elementary technique used to increase stability and lessen thermal runaway. Adding an emitter resistor creates negative feedback, this keeps the transistor’s operation stable. Simulation results are provided for both, and the layout is presented for the emitter degeneration circuit. Both circuits are designed using state-of-the art SiGe BiCMOS technology provided by IHP.Abstract
Conventional BJT differential pairs have a relatively small input voltage dynamic range. This paper reviews and compares several linearization techniques, which are used to expand the input transconductance (gm) stage’s dynamic range. Two techniques are emphasized: The first one is the multi-tanh principle, and the other one is based on classical emitter degeneration. The main concept of multi-tanh is that individual nonlinear gm functions can be divided along the input voltage axis to obtain a function with higher linearity. This modification expands the linearity and results in a wider operating dynamic range. Emitter degeneration is an elementary technique used to increase stability and lessen thermal runaway. Adding an emitter resistor creates negative feedback, this keeps the transistor’s operation stable. Simulation results are provided for both, and the layout is presented for the emitter degeneration circuit. Both circuits are designed using state-of-the art SiGe BiCMOS technology provided by IHP
The maturity of circular economy in sparsely populated areas and the regional development of circular economy
No full textAbstract
The Earth's ever-growing population, accelerating depletion of finite natural resources, loss of biodiversity, and increasing greenhouse gas emissions are driving a shift from the unsustainable traditional linear economic system towards a cyclical, more sustainable circular economy. At the core of the circular economy is reducing waste generation and using waste as resources, using cleaner energy sources and increasing energy efficiency, ecosystem thinking, and continuous value creation. This article studied the regional maturity of circular economy in sparsely populated case areas and the development of the regional circular economy. Key findings were the cornerstones of circular economy, and the framework based on them, and the process chart of regional circular economy development. The developed framework and process model contribute to innovation in how circular economy practices are implemented regionally. These findings also provide transferable insights for sparsely populated areas globally navigating the ongoing economic restructuring.Abstract
The Earth's ever-growing population, accelerating depletion of finite natural resources, loss of biodiversity, and increasing greenhouse gas emissions are driving a shift from the unsustainable traditional linear economic system towards a cyclical, more sustainable circular economy. At the core of the circular economy is reducing waste generation and using waste as resources, using cleaner energy sources and increasing energy efficiency, ecosystem thinking, and continuous value creation. This article studied the regional maturity of circular economy in sparsely populated case areas and the development of the regional circular economy. Key findings were the cornerstones of circular economy, and the framework based on them, and the process chart of regional circular economy development. The developed framework and process model contribute to innovation in how circular economy practices are implemented regionally. These findings also provide transferable insights for sparsely populated areas globally navigating the ongoing economic restructuring
Glucose-assisted core-shell C-MoO2@C-MoS2 microspheres for boosting lithium-ion diffusion kinetics
No full textAbstract
Molybdenum-based materials, such as MoO2 and MoS2, have gathered significant attention in lithium-ion battery research because of their high theoretical specific capacity. However, their practical use is constrained by inherent low conductivity and structural degradation that occurs in the lithiation/delithiation processes. Herein, uniform core-shell C-MoO2@C-MoS2 microspheres with a diameter of ca. 1.2 μm were successfully fabricated through synchronous reduction and sulfidation of MoO3, using an economical glucose as carbon resource, co-reductant, and structure directing agents. In-situ XRD analysis reveals the excellent reversibility and structural stability of C-MoO2@C-MoS2 during the charge-discharge cycle. Moreover, the unique core-shell structure also endows C-MoO2@C-MoS2 with a high reversible lithium storage capacity (377 mAh·g−1 after 550 cycles at 0.1 A g−1, coulombic efficiency >99.5 %), low charge-transfer resistance (52.4 Ω), and a high Li+ diffusion kinetics (DLi+ = 3.89 × 10−11 cm2 s−1). Notably, C-MoO2@C-MoS2 contributes significantly to the interlayer capacitance, accounting for 69 % at 1.0 mV s−1. This study offers a novel and straightforward approach for constructing core-shell structured composites with potential applications in new energy technologies.Abstract
Molybdenum-based materials, such as MoO2 and MoS2, have gathered significant attention in lithium-ion battery research because of their high theoretical specific capacity. However, their practical use is constrained by inherent low conductivity and structural degradation that occurs in the lithiation/delithiation processes. Herein, uniform core-shell C-MoO2@C-MoS2 microspheres with a diameter of ca. 1.2 μm were successfully fabricated through synchronous reduction and sulfidation of MoO3, using an economical glucose as carbon resource, co-reductant, and structure directing agents. In-situ XRD analysis reveals the excellent reversibility and structural stability of C-MoO2@C-MoS2 during the charge-discharge cycle. Moreover, the unique core-shell structure also endows C-MoO2@C-MoS2 with a high reversible lithium storage capacity (377 mAh·g−1 after 550 cycles at 0.1 A g−1, coulombic efficiency >99.5 %), low charge-transfer resistance (52.4 Ω), and a high Li+ diffusion kinetics (DLi+ = 3.89 × 10−11 cm2 s−1). Notably, C-MoO2@C-MoS2 contributes significantly to the interlayer capacitance, accounting for 69 % at 1.0 mV s−1. This study offers a novel and straightforward approach for constructing core-shell structured composites with potential applications in new energy technologies
Synergistic adsorption and photocatalytic removal of hexavalent chromium and direct red 23 dye using porous magnetic hydroxyapatite-metakaolin geopolymer granules doped with TiO₂
No full textAbstract
This study presents a novel approach to addressing challenges of photocatalysy by TiO₂ powder and the adsorption of anionic pollutants by geopolymers (GP) through the development of granules based on hydroxyapatite-geopolymer (HAP-MK-GP) materials. The synthesized HAP-MK-GP/Fe₃O₄-TiO₂ granules exhibit promising physicochemical properties, including a high porosity of 0.25 cm³/g, a specific surface area of 106.59 m²/g, notable magnetic behavior (saturation magnetization of 18.89 emu/g), and strong mechanical integrity (compressive strength of 1.63 MPa).
The adsorption kinetics and equilibrium data for Direct Red 23 (DR23) dye and hexavalent chromium (Cr(VI)) conformed to the Langmuir isotherm and pseudo-second-order kinetic models, indicating monolayer adsorption on a homogeneous surface. The maximum adsorption capacities were determined as 15.23 mg/g for DR23 and 36.06 mg/g for Cr(VI) under the following conditions: pH of 3, temperature of 21°C, adsorbent dosages of 4 g/L for DR23 and 2 g/L for Cr(VI), and initial pollutant concentrations of 100 mg/L.
Under UV irradiation, the granules demonstrated high photocatalytic efficiency for DR23 degradation, achieving removal rates exceeding 95% under optimized conditions: pH of 3, temperature of 21°C, 4 g/L of dose, and [DR23]0 of 50 mg/L. Electron paramagnetic resonance (EPR) confirmed the generation of reactive radicals (•OH and O₂•⁻), crucial for photocatalytic activity. Chemical oxygen demand (COD) and total organic carbon (TOC) analyses corroborated the significant mineralization of DR23 dye. These findings underscore the potential of HAP-MK-GP/Fe₃O₄-TiO₂ granules as a highly efficient dual-function photocatalyst-adsorbent material for wastewater treatment applications.Abstract
This study presents a novel approach to addressing challenges of photocatalysy by TiO₂ powder and the adsorption of anionic pollutants by geopolymers (GP) through the development of granules based on hydroxyapatite-geopolymer (HAP-MK-GP) materials. The synthesized HAP-MK-GP/Fe₃O₄-TiO₂ granules exhibit promising physicochemical properties, including a high porosity of 0.25 cm³/g, a specific surface area of 106.59 m²/g, notable magnetic behavior (saturation magnetization of 18.89 emu/g), and strong mechanical integrity (compressive strength of 1.63 MPa).
The adsorption kinetics and equilibrium data for Direct Red 23 (DR23) dye and hexavalent chromium (Cr(VI)) conformed to the Langmuir isotherm and pseudo-second-order kinetic models, indicating monolayer adsorption on a homogeneous surface. The maximum adsorption capacities were determined as 15.23 mg/g for DR23 and 36.06 mg/g for Cr(VI) under the following conditions: pH of 3, temperature of 21°C, adsorbent dosages of 4 g/L for DR23 and 2 g/L for Cr(VI), and initial pollutant concentrations of 100 mg/L.
Under UV irradiation, the granules demonstrated high photocatalytic efficiency for DR23 degradation, achieving removal rates exceeding 95% under optimized conditions: pH of 3, temperature of 21°C, 4 g/L of dose, and [DR23]0 of 50 mg/L. Electron paramagnetic resonance (EPR) confirmed the generation of reactive radicals (•OH and O₂•⁻), crucial for photocatalytic activity. Chemical oxygen demand (COD) and total organic carbon (TOC) analyses corroborated the significant mineralization of DR23 dye. These findings underscore the potential of HAP-MK-GP/Fe₃O₄-TiO₂ granules as a highly efficient dual-function photocatalyst-adsorbent material for wastewater treatment applications
Marketing agility in underdog entrepreneurship: A qualitative assessment in post-conflict Sub-Saharan African context
No full textAbstract
Extant entrepreneurship literature lacks specific research on how underdog entrepreneurs survive and strive in post-conflict environments. This study seeks to explore the role of marketing agility as an essential capability to survive and exploit business opportunities in post-conflict Sub-Saharan Africa, where institutional voids and volatility coexist. The empirical research design comprises of multiple case studies of sixteen underdog (war-affected) entrepreneurs in Liberia and Sierra Leon; both countries which went through civil war and violent internal strife in recent past. The study findings reveal that marketing agility and its dimensions, i.e., robustness, responsiveness, and proactiveness, are critical for underdog entrepreneur’s business’s survival. Finally, the findings also show that institutional context, volatility, and individual experiences of entrepreneurs tend to influence the manifestation of this marketing agility.Abstract
Extant entrepreneurship literature lacks specific research on how underdog entrepreneurs survive and strive in post-conflict environments. This study seeks to explore the role of marketing agility as an essential capability to survive and exploit business opportunities in post-conflict Sub-Saharan Africa, where institutional voids and volatility coexist. The empirical research design comprises of multiple case studies of sixteen underdog (war-affected) entrepreneurs in Liberia and Sierra Leon; both countries which went through civil war and violent internal strife in recent past. The study findings reveal that marketing agility and its dimensions, i.e., robustness, responsiveness, and proactiveness, are critical for underdog entrepreneur’s business’s survival. Finally, the findings also show that institutional context, volatility, and individual experiences of entrepreneurs tend to influence the manifestation of this marketing agility
