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STUDY OF TWO-PHASE VOID FRACTION IN A RECTANGULAR CHANNEL USING CAPACITANCE SENSOR
No full textTwo-phase liquid-gas flow has many applications in the nuclear industry, including active heat exchangers, reactor core designs, secondary steam generators, and two-phase flow loop balance of the plant. The void fraction is a crucial parameter to determine the pressure drop, flow regimes and liquid levels inside the nuclear reactor core. For the past forty years, void fraction has been studied by many researchers by different measurement techniques. Each method has positive and negative attributes. In this study, after extensive literature reviews, the author has chosen a capacitance type void fraction sensor over other void fraction measuring techniques. The principal concept of a capacitance type void fraction sensor lies in the change in permittivity of a two-phase mixture that is caused by the change in void fraction. The capacitance is a proportional function of the permittivity of the dielectric. Capacitance is largest for all liquid, smallest for all gas and in between for a mixture. The first part of this research is to construct a self-made capacitance sensor and an unique vertical, air-water flow calibration loop. The sensor consists of rectangular acrylic duct made of four side plates with dimensions 6 inches x 4 inches x 0.2 inches (length x width x thickness) and one square base with the edge of 5 inches. Eighteen fully threaded copper screws served as electrodes are attached to two opposite plates of the sensor. The capacitance is measured by eighteen electrodes. A guard electrode is placed in between two measuring electrodes to minimize edge effects and stray capacitance. Vertical two-phase flow is generated with porous xiv plugs machined on the bottom surface of the test section. Capacitance signals are recorded by a high-speed capacitance meter that can measure small capacitance in the order of pF. Data was collected covering a wide range of void fractions, from approximately 0.0 to 1.0. Flow regimes encountered included bubble, slug and annular flow. The second part of this research is to build a finite element model (FEM) to simulate experimental environment for the evaluation of the capacitance. The FEM was built by Finite Element Heat Transfer (FEHT). The FEM consists of 6,256 triangular nodes. The measured capacitances for two boundary cases: empty test-section and filled with water are 8.31 pF and 29.97 pF, respectively. The FEM predicted capacitances for two boundary cases within 90% accuracy. Both simulation and experiment show a similar trend that capacitance monotonically decreases with void fraction. A third objective of this study is to create a new mathematical model capable of accurately predicting two-phase void fraction using only the channel geometry, liquid and vapor mass flow rates, and the properties of the working fluid. The predicted void fraction is validated by void fraction data collected using an in-house capacitance sensor and a unique vertical, air-water flow calibration loop. Compared to measured void fraction data, the new mathematical model has a better performance than commonly used models such as Lockhart Martinelli model, Rouhani-Axelsson model, Wallis model and homogeneous model
Estimation of Queue Length and Greenlight Duration at Signalized Intersection Using Collaborative Perception and Machine Learning Methods in V2X Environments
No full textConnected and Autonomous Vehicles (CAVs) utilize ecodriving systems for efficient fuel consumption while traversing signalized intersections. Applications such as Green Light Optimal Speed Advisory (GLOSA), Eco Arrival and Departure, and other Eco-Driving support these objectives. Estimating the accurate signal phase timing durations with real-time evaluation of queue lengths, queue clearance timings, and other traffic flow parameters play a crucial role in enabling energy-efficient maneuvering through intersections. To enable the dynamic processing of traffic flow, this research focuses on utilizing collaborative perception through Vehicle-to-Everything (V2X) communication to estimate queue lengths and broadcast estimated green light durations through enhanced SPAT messages. In our approach, Road Side Units collaborate with CAVs through perception data sharing to calculate green light duration at signalized intersections, enabling efficient traffic flow through optimized broadcasting of timing information. The study features a random forest algorithm with geo-spatial and corridor enhancements. Our model is trained on corridor specific data from Metro Detroit area, capturing individual intersection geometry and signal timing plans. Results reveal our system efficiently determines duration of green light based on vehicle distribution along the lanes leading to the intersection, queue length and traffic flow parameters. This efficiency is maintained under different traffic volumes and queue lengths with improved performance
Learn How to Design High-Quality Qualitative Educational Research! - A Workshop for Disciplinary STEM Faculty by Disciplinary STEM Faculty
No full textThe purpose of this workshop-designed for instructional and disciplinary STEM faculty interested in learning about qualitative research-is to (1) introduce participants to high-quality qualitative research design and (2) practice this design process alongside disciplinary STEM faculty to expand their STEM education research abilities and network. We will do so using the ProQual approach, a methodologically unencumbered and widely accessible way of thinking about qualitative research design that was deployed and refined over the last three years as part of the NSF-funded ProQual Institute for Research Methods [1]. This workshop will be conducted by ProQual Institute alumni, who are culturally sensitive to the challenges faced by disciplinary STEM faculty. Leveraging a propagation model of effecting academic change [2], the workshop leaders will serve as a community of practice to help participants move their educational research ideas forward during and after the workshop. In doing so, we strive to further FIE\u27s mission to create a collaborative, supportive, and inclusive community of educational researchers
Gelatin-reduced graphene oxide-azithromycin biocomposite coating on baghdadite scaffolds
No full textA critical bone tissue engineering (BTE) strategy is fabricating porous scaffolds using simple and straightforward techniques. However, all porous structures share a common drawback, reduced strength due to porosity. Furthermore, bone scaffolds are vulnerable to bacterial infections when implanted, especially in compromised bone conditions. In this study, baghdadite (BAGH) scaffolds were developed and coated with gelatin (Gel)-reduced graphene oxide (RGO)-azithromycin (AZM) with suitable porosity (75–80%) and pore size (600–800 μm) using the space holder method, combined with a dip coating process in a low vacuum condition. The outcomes revealed that incorporating the Gel-RGO layer increased the compressive strength from 0.8 to 2.9 MPa for the Gel-RGO-AZM scaffolds. The scaffolds coated with Gel-RGO-AZM demonstrated improved bioactivity compared to their uncoated counterparts, showcasing the ability to generate hydroxyapatite (HA)-like crystals after a 28-day soaking period in simulated body fluid (SBF). In vitro studies validated the antimicrobial effectiveness of co-released RGO and AZM from Gel-RGO-AZM coated scaffolds against E. coli and S. aureus bacteria. Moreover, the coated scaffolds exhibited significantly improved cellular responses. In conclusion, the research results show that the developed BAGH scaffolds coated with Gel-RGO-AZM are promising materials for BTE, offering enhanced compressive strength, bioactivity, biocompatibility, and antibacterial performance
Impact dynamics of compound droplets on low-temperature copper plates
No full textDimethyl silicone oil–water compound droplets were generated using the injection technique and freely dropped on low-temperature (Tw = -13 °C) copper plates. The effects of impact height and water volume fraction α on the impact dynamics of the compound droplets were investigated. The different morphologies of compound droplets impinging on an ambient temperature (Tw = 25 °C) and the low-temperature copper metal plates were analyzed. It was seen that relative to the ambient temperature plate, the droplet impacting the low-temperature copper plate did not display Corona splashing. Moreover, the lower temperature plate slowed down the speed of the droplet impact spreading and jetting processes. Under the condition of an identical impact height, three water volume fractions were tested, and the jet height was observed to decrease as α gradually increased. Additionally, the spreading diameters of both the internal and external droplets increase with the impact height for a specific value of α
Sepiolite-based PDA-PAM hydrogels with enhanced interfacial adhesion capability
No full textElastic and dense connective tissues exhibit exceptional tensile strength and fatigue resistance, enabling them to withstand continuous stretching and cyclic loading. The endeavor to replicate these remarkable mechanical properties in artificial bionic robots or engineered tissues is still a challenge. Our study reveals that the toughness of the body\u27s elastic connective tissues is due to the orderly arrangement of collagen fibers. These fibers, 20 to 100 nanometers in diameter, act as a crucial buffer, reducing tension and fatigue impact. Inspired by that, we design and fabricate a sepiolite-based polydopamine-acrylamide (S-PDA-PAM) hydrogel, which mimics the structure of human tissue. The results demonstrate that, through mechanical training, the sepiolite composite hydrogel exhibits a higher adhesive fatigue threshold. Aligned sepiolite nanofibers reinforce and prevent polymer chain debonding, functioning as a rigid matrix. This structural reinforcement greatly increases the energy barrier against fatigue crack propagation, significantly raising the interfacial fatigue threshold. This boost in fatigue resistance gives the composite material exceptional mechanical resilience, similar to natural tissues
Pilot plant study on manganese bioleaching using biomass decomposition products as a nutrient source and electrolysis for oxide precipitation
No full textManganese leaching was carried out on a small pilot scale with 110 kg of ore using manganese-reducing organisms and fermentative organisms with biomass (Typha latifolia) as the source of nutrition. This study was carried out without externally supplied chemical reagents and with minimal capital investment. The process involves fermentative organisms to ferment biomass from T. latifolia and generate organic acids. Manganese-reducing organisms and organic acids reduced and dissolved manganese from pyrolusite ore. Manganese was precipitated from the manganese-bearing solution using an electrolytic oxidation technique. A manganese concentration above 500 mg/L and negligible dissolved iron was achieved at a flow rate of 30 L/day, maintaining a pH range of 4 to 5, and a redox potential between 0.10 and 0.46 V. Manganese oxide was produced at a rate of 12 g/day, with a purity of 90 %. Amorphous manganese oxide was deposited on the cathode, while crystalline manganese oxide formed on the anode
Research progress of bio-asphalt towards green pavement development: Preparation, properties, and mechanism
No full textBio-asphalt is a binder that is derived from bio-oil, which is extracted from fast pyrolysis or hydrothermal liquefaction of biomass and petroleum asphalt under specific conditions or by adding other external agents to bio-oil under defined conditions. Due to its renewable and eco-friendly characteristics, bio-asphalt has immense potential to substitute petroleum asphalt and reduce the environmental impact of road construction. This paper provides a comprehensive review of research progress on bio-asphalt, including the preparation and composition of bio-oil, the preparation process and properties of bio-asphalt, modified bio-asphalt, and its modification mechanisms. Future research directions for the development of bio-asphalt are also proposed. The review indicates that most types of bio-oil can improve the low-temperature and fatigue properties of virgin asphalt but may have adverse effects on the high-temperature performance and aging resistance. To improve the performance of bio-asphalt, modifiers such as polymers, rock asphalt, montmorillonite, and nano-clay materials are used to modify bio-asphalt. The majority of existing research is focused on physical modification, with relatively little attention given to chemical and composite modifications. Future studies should focus on the preparation process and classification of bio-oil, the development of efficient modifiers, and the mechanisms of composite-modified bio-asphalt to enhance its quality and increase its proportion of substitution for petroleum asphalt
Toward understanding the surface morphology and microscopic mechanical properties of asphalt after experiencing tensile and compressive stress
No full textLoad-induced stress is a one of the major causes of asphalt pavement failure. It is, therefore, necessary to understand the changes in stress on the microscopic mechanical properties of asphalt in improving pavement design. While much research been carried out concerning effects brought about by tensile, the effects that compressive stress would have on the microscopic mechanical properties of asphalt remains less explored. In the current study, a custom-designed tension–compression device was developed and atomic force microscopy (AFM), complemented by molecular dynamics (MD) simulations, to investigate the microscopic properties of asphalt in both undeformed and deformed states. The findings reveal that asphalt exhibits significantly weaker compressive strength compared to tensile strength. Under tensile stress, the various components in asphalt align loosely in the direction of tension, while asphaltenes are affected the least. These changes in apparent morphology reflect different migration rates of the various components. Under compressive stress, the asphalt surface is more compact, and this reduces the area of the “bee” structure. Under varying stress conditions, asphalt exhibits a smoothing of the rough region with an associated loss in adhesion. Specifically, increased tensile strain leads to smoother topography and increased adhesion, while increasing compressive strain has the opposite effect. These results provide valuable theoretical insights for the design and maintenance of more durable asphalt pavements
Mechatronics Design and Control of a Hybrid Flying-Ground Robot for Long-Endurance Mobility
No full textThis paper presents the design and control of a novel hybrid robot capable of both aerial and ground locomotion, aimed at enhancing long-endurance mobility in challenging environments. The robot integrates mechatronic systems to seamlessly transition between flying and ground modes, offering versatility in diverse operational scenarios such as search and rescue, environmental monitoring, and industrial inspection. Key design features include a lightweight yet robust frame, energy-efficient propulsion systems, and a dual-mode navigation algorithm that optimizes energy consumption by prioritizing ground mobility when aerial performance is unnecessary. Simulation results demonstrate the effective design in both modes. By reducing the energy demands of aerial locomotion and maximizing the efficiency of ground-based travel, this approach contributes to sustainability efforts, reducing the overall environmental impact of robotic operations. This hybrid design promises a new avenue for autonomous systems where endurance, versatility, and sustainability are critical factors