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Diagnostics of discharge and reactive species generation in cold argon plasma jets
No full textTypically driven by applying a high-voltage electric field to a working gas (such as noble gases Ar or He), atmospheric pressure plasma jets (APPJs) are capable of generating energetic particles in the open air environment, including electrons, metastable atoms, and reactive oxygen and nitrogen species (RONS) such as O, OH, NO, and O3. These reactive species can be conveniently transported with the plume extended from the nozzle and interact with target surfaces, for example, biological tissue, achieving significant treatment effects with minimal thermal damage. Therefore, due to their versatility, non-thermal APPJs have become a valuable tool for a wide range of applications in both research and industry. In this thesis, we focus on two relatively long-lived reactive species, O(1S) and NO, both of which play important roles in biomedical applications. We aim to understand how they are generated in APPJs and to provide insight into how to precisely control their production. The kHz AC and pulsed Ar jets are used. Diagnostic techniques, mainly including optical emission spectroscopy (OES), laser-induced fluorescence (LIF) and iCCD imaging, are established and employed in this work. O(1S) generation is characterized by the green emission at 557.7 nm in an AC Ar plasma jet. Spectral analysis utilizing continuum emission and line ratios is employed to track changes in electron density and electron temperature under different conditions in the downstream region. Two discharge regimes are presented: diffuse discharge and DAF (diffuse and filamentary) discharge, each exhibiting two distinct branches of the green emission intensity, with the finding that the intense and diffuse green plume only forms when the downstream electron density is approximately lower than 1 x 10^20 /m^3 and the electron temperature is lower than 1.1 eV.NO production is explored in a pulsed Ar plasma jet operating in the ambient air, with LIF to measure the absolute density of the ground state NO that is on the order of 10^19/ m^3, and OES to estimate the emission intensity of the excited state NO. Both the temporal evolution and spatial distribution of NO in the plasma plume are examined. The chemical processes related to NO generation are analyzed, with the variations in discharge power, gas flow rate, and gas admixture, to identify the dominant reactions in this plasma source. The quenching characteristics of the excited state NO are utilized to probe its quenching rate and the derived concentrations of some important quenchers, such as air and water vapor. With the help of the total quenching rate of the excited state NO, accessed by the decay of LIF signals, an estimation of the gas phase air and H2O concentrations in the plume of a plasma jet is presented. The spatial distributions of air fraction and water vapor concentration are visualized for a freely expanding plasma jet in ambient air, the jet with a glass target and a water target. The influence of a water target on discharge morphology, ionization wave propagation, and NO generation (both in space and in time) is comprehensively investigated for the same pulsed Ar plasma jet by using demineralized water as a substrate, with a glass target and a freely expanding jet as references. The enhancements of ground state NO density and excited state NO emission intensity are confirmed due to the presence of water and attributed to the role of OH in the chemical reactions. Four different water configurations---normal demineralized water, heated demineralized water, saline water and grounded demineralized water are compared to explore the effect of the water condition on the discharge behavior and NO formation. To conclude, we have established a diagnostic platform involving LIF, OES, and iCCD imaging to characterize plasma properties and critical species (O and NO) in kHz cold Ar plasma jets. Our primary focus is on controlling the production of O(1S) and NO, for which optimal generation conditions are investigated. Moreover, the influence of liquid targets on the plasma itself and the resultant species formation has been elucidated, offering significant insights for liquid-containing object treatments
Particle-resolved CFD study of liquid axial penetration and lateral spreading in an ordered trickle bed reactor
No full textTrickle bed reactors are frequently applied in the chemical process industries for gas-liquid-solid contacting. The performance of these reactors is sensitively influenced by the hydrodynamics. This study focuses on investigating the complex interaction between the gas and liquid phases in these reactors. Specifically, the effects of inlet liquid flux, surface wettability, and gas velocity on lateral spreading and axial penetration of the liquid are explored. An ordered trickle bed is used to reduce the effects of the configuration of the particles on these parameters. Using Direct Numerical Simulation (DNS), we determined that the lateral spreading and axial penetration are enhanced with an increased liquid flux, as expected. Interestingly, the initial liquid inertia, represented by the liquid jet velocity, has limited influence on both lateral spreading and axial penetration in the ordered bed, while the gravitational force is the dominant factor for the axial penetration. Furthermore, the contact angle has minimal impact on lateral spreading, indicating the presence of an additional force restricting spreading. Notably, the gas velocity is identified as a crucial factor influencing lateral spreading, as high velocities prevent the capillary forces from spreading the liquid. These insights in the contributing forces on the spreading behaviour in trickle bed reactors facilitate an improved reactor design and optimization.</p
Immunomodulatory topographies regulate myofibroblast differentiation and influence fibrous encapsulation of glaucoma drainage devices
No full textElevated intraocular pressure (IOP) is the primary driver of glaucoma, and lowering IOP remains essential for preventing vision loss. Glaucoma drainage devices (GDDs) help reduce IOP but often fail due to fibrosis. This study identifies surface micro topographies capable of modulating the fibrotic response to GDDs both in vitro and in vivo. Using the TopoChip high-throughput platform (2176 topographies), we fabricated poly(styrene-block-isobutylene-block-styrene) SIBS based micro topographies and screened them for their effects on human Tenon fibroblast adhesion and transdifferentiation, as well as primary macrophage attachment and cytokine expression. These screens revealed micro topographies that differentially regulate fibroblast and macrophage behaviour, enabling the selection of three candidate designs for in vivo evaluation. When incorporated into glaucoma shunts implanted in rabbits, these micro topographies produced distinct tissue responses compared with smooth controls, including differences in collagen deposition and density at the implant interface. Overall, this work demonstrates that engineered micro topographies can modulate wound healing around GDDs and provides a foundation for design-driven strategies to improve implant performance. Future studies will focus on long-term implantation to optimize therapeutic outcomes.</p
Uncovering Subpopulations in Extracellular Vesicles via Multiplexed Spectral PAINT Super-Resolution Microscopy
No full textExtracellular vesicles (EVs) are attracting growing interest in nanomedicine as nature’s own nanocarriers. EV characterization remains challenging, due to complexity and heterogeneity. As such, there is a growing need for experimental techniques that can probe with molecular specificity at the single-particle level. We present a fluidic and super-resolution imaging platform that employs spectral point accumulation for imaging in nanoscale topography (sPAINT) to perform multiplexed imaging of individual EVs derived from prostate cancer (PC3) cells. By combined analysis of the solvatochromic dye Nile Red and fluorescent lectin probes, we can map glycosylation patterns and membrane polarity at the single-particle level, two rather unexplored properties of EVs. Our results reveal pronounced inter- and intraparticle heterogeneity, with polarity signatures consistent with ordered lipid domains. This multiplexed single-molecule imaging strategy enables truly multiparametric EV analysis, allowing the identification of subpopulations that remain indistinguishable in bulk or single-marker approaches.</p
A GaN-Based All-Solid-State Impedance-Matched Marx Generator With High Repetition Rates
No full textIn this paper, a novel all-solid-state impedance-matched Marx generator (IMG) is proposed that offers fast recharge times and, thus, high repetition rates with little impact on the output rise time. The topology consists of an inverted buck converter combined with a Marx generator. The proposed topology is primarily suitable for the generation of pulses with short pulse widths (e.g., 100nsto500ns) and high repetition rates (e.g., higher than 1kHz). Previous studies have shown that, for certain applications, such as air purification, shorter pulse rise times result in higher yields. Therefore, the proposed generator is optimized for a short output rise time through accurate stage timing and the utilization of an impedance-matched layout. Finally, a prototype capable of generating 4.65kV, 95A pulses has been realized to validate the proposed topology. Results show that the generator can achieve a 10kHz repetition rate when generating 100ns full-load output pulses with an output voltage rise time of 8.57ns. In addition, two iterations of the proposed IMG have been built to further improve the output rise time and enhance robustness against electromagnetic interference (EMI)
Applying the Refined Kano Model to Enhance Youth Housing Toward User-Centered Sustainability:Insights from Three Cases in Taipei
No full textThe development of youth housing is a top priority in Taiwan to address housing justice concerns. However, planners often neglect real user needs, particularly those related to sustainability. This paper employs the refined Kano model to identify priority features for youth housing under sustainable development. Data from 327 participants, aged between 20 and 40 years, residing in Taipei City, forms the basis of this study. The findings reveal priority features for youth housing: durability and well-being emerge as high value-added features for customer satisfaction, while safety and security, well-optimized layouts, cleanliness, and maintenance should be provided as critical features. Moreover, accessibility and mobility, along with maximizing usable units, are potential features for youth housing planning. This paper assesses three cases in Taipei City based on the results of refined Kano models, revealing their strengths and improvement areas, notably in Case Alpha, where insufficient priority features hinder resident satisfaction. Resident feedback highlights concern about spatial efficiency, material durability, maintenance, and community space. Further research is needed to evaluate the quality of features, especially priority ones, to ensure long-term living quality. This study can offer valuable insights for architects, policymakers, housing developers, and researchers to enhance user-centered planning, improve existing housing quality, and design better living spaces under sustainable development principles.</p
Unlocking zero-cost flexibility in office buildings with adaptive comfort heating strategy and thermal mass utilization
No full textThe growing share of renewable energy introduces significant variability and uncertainty in the electricity grid, increasing the need for demand-side flexibility. Buildings with controllable assets represent a promising source of flexibility. This study explores adaptive comfort heating strategies to unlock cost-free flexibility in the thermal mass of office buildings while maintaining comfort. A twofold methodology is proposed: a measurement study assessing the impact of adaptive setpoint adjustments on thermal comfort, and a simulation-based framework quantifying flexibility under diverse design and control strategies. The framework couples building simulations with a penalty-aware controller to optimize battery and heat pump operation in response to dynamic electricity prices or CO2 intensity using mixed-integer linear programming. Applying the methodology to a 2511 m2 Dutch office building shows that thermal mass delivers load shifting comparable to that of a 200 kWh battery. Analysis of eight variations of the case study, differing in layout, insulation, and window-to-wall ratio, further confirms these findings. Thermal mass provides 17.2 to 19.7 Wh/m2 of daily average shiftable electricity depending on comfort constraints, while the battery contributes 19.4 to 23.3 Wh/m2 under price-based and 10.7 to 16.1 Wh/m2 under CO2-based optimization. The battery’s high investment cost and embodied CO2 limit its economic and environmental benefits compared to rooftop PV and cost-free thermal mass. Results also highlight the strong influence of window-to-wall ratio and office layout on potential shiftable electricity. Overall, adaptive comfort control strategies enable office buildings to provide cost-free flexibility that, when aggregated, can support renewable integration, balancing services, and grid resilience
A Bidirectional Transformerless Voltage Regulator for Single/Three Phase Applications Based on Direct AC-AC Converter
No full textIn this paper, a novel AC-AC voltage regulator topology is proposed for single-phase and three-phase applications. The proposed structure provides a common ground between the input and output, eliminating the need for a transformer in series compensators. This results in significant reductions in size, weight, cost, and electrical complexity typically associated with transformers. The topology supports bidirectional power flow, enabling both power injection and absorption. Depending on the selected switching pattern, the converter can operate in buck, boost, or buck-boost modes, either in phase or out of phase with the input voltage, allowing flexible control of the output voltage relative to the input. The proposed structure offers continuous input and output currents, requires a low number of passive and active components, and operates without commutation issues or the need for snubber circuits. A comprehensive analysis of the converter's operation, switching patterns, interval-based behavior, gain and stress characteristics, and its extension to three-phase systems is presented. The simulation and experimental results of a prototype up to 2 kW validate the theoretical analysis
Quadratic optimization for sustainable agriculture:A study of mixed cropping systems
No full textMixed cropping systems present a promising solution to conventional agriculture by combining multiple crops within a single field, thereby increasing biodiversity and soil health. However, these systems also pose new operational planning challenges regarding crop assignment and scheduling. To address this issue, we propose a novel decision problem in which crops must be assigned to different farms and fields over time, considering crop interactions, farm characteristics, growth conditions, and customer locations. We formulate this as a mixed-integer quadratically constrained optimization model and propose two column generation-based approaches that substantially outperform commercial solvers in both solution feasibility and quality for realistic-sized problems. Our computational experiments reveal that higher levels of crop compatibility promote more localized crop production with shorter transportation distances while maintaining yield benefits through beneficial crop interactions. Moreover, we observe that certain crops act primarily as ’yield catalyst’ crops, which create value by enhancing the overall productivity in the system. These findings provide practical guidelines for the implementation of mixed cropping systems, highlighting the importance of evaluating both direct revenues and companion planting benefits in agricultural planning. This research lays the groundwork for future work on sustainable agricultural innovation through mixed cropping systems.</p