Records with Subject: Modelling and Simulations
Showing records 1 to 25 of 5563. [First] Page: 1 2 3 4 5 Last
Accelerating Discovery in Consumer Product Design
Brian T. Gettelfinger
July 9, 2024 (v1)
Keywords: Consumer Products, Design, Modelling
At Procter and Gamble, innovation is based on a framework of Irresistible Superiority [1] that utilizes five complementary components – Products, Packages, Communication, Retail Execution, and Value. Increasing-ly, the computational techniques heavily leveraged with-in the Process Systems Engineering community are play-ing a leading role in delivering these five vectors, and they become increasingly valuable as we aim to deliver products in more exploratory consumer spaces – where combining high-volume data, advanced modeling, and quantified uncertainty will allow us to discover and deliv-er better products faster than ever before...
Model Diagnostics for Equation-Oriented Models: Roadblocks and the Path Forward
Andrew Lee, Robert B. Parker, Sarah Poon, Dan Gunter, Alexander W. Dowling, Bethany Nicholson
July 9, 2024 (v1)
Keywords: Education, Modelling and Simulations, Optimization, Pyomo, Simulation
Equation-Oriented (EO) modeling techniques have been gaining popularity as an alternative for simulating and optimizing process systems due to their flexibility and ability to leverage state-of-the-art solvers inaccessible to many procedural modeling approaches. Despite these advantages, adopting EO modeling tools remains challenging due to the significant learning curve and effort required to build and solve models. Many techniques are available to help diagnose problems with EO process models and reduce the effort required to create and use them. However, these techniques still need to be integrated into EO modeling environments, and many modelers are unaware of sophisticated EO diagnostic tools. To survey the availability of model diagnostic tools and common workflows, the U.S. Department of Energy’s Institute for the Design of Advanced Energy Systems (IDAES) has conducted user experience interviews of users of the IDAES Integrated Platform (IDAES-IP) for process modeling. The inter... [more]
Jacobian-based Model Diagnostics and Application to Equation Oriented Modeling of a Carbon Capture System
Douglas A. Allan, Anca Ostace, Andrew Lee, Brandon Paul, Anuja Deshpande, Miguel A. Zamarripa, Joshua C. Morgan, Benjamin P. Omell
July 9, 2024 (v1)
Equation-oriented (EO) modeling has the potential to enable the effective design and optimization of the operation of advanced energy systems. However, advanced modeling of energy systems results in a large number of variables and non-linear equations, and it can be difficult to search through these to identify the culprit(s) responsible for convergence issues. The Institute for the Design of Advanced Energy Systems Integrated Platform (IDAES-IP) contains a tool to identify poorly scaled constraints and variables by searching for rows and columns of the Jacobian matrix with small L2-norms so they can be rescaled. A further singular value decomposition can be performed to identify degenerate sets of equations and remaining scaling issues. This work presents an EO model of a flowsheet developed for post-combustion carbon capture using a monoethanolamine (MEA) solvent system as a case study. The IDAES diagnostics tools were successfully applied to this flowsheet to identify problems to im... [more]
Internally Heated Crackers for Decarbonization and Optimization of Ethylene Production
Edwin A. Rodriguez-Gil, Rakesh Agrawal
July 9, 2024 (v1)
Keywords: Computational Fluid Dynamics, Cracking, Decarbonization, Ethylene, Net-Zero, Process Optimization, Reactor Design
Ethylene is a crucial precursor for a diverse spectrum of products and services. As global production exceeds 150 million tons annually and is projected to surpass 255 million tons by 2035, the imperative for sustainable and efficient ethylene production becomes increasingly clear. Despite Externally Heated Crackers (EHCs) dominating ethylene production for over a century, they face intrinsic limitations that necessitate transformative solutions, including intense radial thermal gradients, high metal demand, and substantial CO2 emissions. This study employs a robust combination of Computational Fluid Dynamics (CFD) coupled with detailed chemical kinetics to rigorously assess selected configurations of Internally Heated Crackers (IHCs) against the leading EHC designs. Our findings reveal that IHCs exhibit the potential to enhance ethylene output by a factor of 1.66 when compared to EHCs of the same length, diameter, and surface temperature. These results herald a promising era for devel... [more]
Model assessment for Design of Future Manufacturing systems using Digital Twins: A case study on a single-scale pharmaceutical manufacturing unit
Prem Jagadeesan, Shweta Singh
July 9, 2024 (v1)
Keywords: Dynamic Modelling, Identifiability, Sloppiness, Stability, System Identification
Designing a digital twin will be crucial in developing automation-based future manufacturing systems. The design of digital twins involves data-driven modelling of individual manufacturing units and interactions between the various entities. The goals of future manufacturing units such as zero waste at the plant scale can be formulated as a model-based optimal control problem by identifying the necessary state, control inputs, and manipulated variables. The fundamental assumption of any model-based control scheme is the availability of a “reasonable model”, and hence, assessing the goodness of the model in terms of stability and sensitivity around the optimal parameter value becomes imperative. This work analyses the data-driven model of an acetaminophen production plant obtained from SINDy, a nonlinear system identification algorithm using sparse identification techniques. Initially, we linearize the system around optimal parameter values and use local stability analysis to assess the... [more]
Industrial Biosolids from Waste to Energy: Development of Robust Model for Optimal Conversion Route – Case Study
Hesan Elfaki, Dhabia M. Al-Mohannadi
July 9, 2024 (v1)
Keywords: Biosolids, Energy, Simulation, Utilization
Utilizing sustainable energy sources is crucial for expanding the range of solutions available to meet the growing energy demand and reducing reliance on environmentally damaging and depleting conventional fuels. Biosolids, a type of biomass, are generated as secondary effluent during wastewater treatment process in municipal and industrial sites. These solids possess the potential to serve as a sustainable energy source due to their richness of carbon. For an extended period, biosolids have been landfilled, even though it can be considered a wasteful use of a precious resource and a possible mean for contamination to the food supply chain. This has served as an extra impetus to investigate the potential for harnessing the capabilities of these substances. While many research studies have looked at different ways to put biomass waste to use, very little has been written on biosolids, especially those derived from industrial sources. This research assesses the feasibility of transformin... [more]
Constraint Formulations for Bayesian Optimization of Process Simulations: General Approach and Application to Post-Combustion Carbon Capture
Clinton M. Duewall, Mahmoud M. El-Halwagi
July 9, 2024 (v1)
Keywords: Carbon Capture, Derivative Free Optimization, Global optimization, Process Simulation, Surrogate Modeling
Some of the most highly trusted and ubiquitous process simulators have solution methods that are incompatible with algorithms designed for equation-oriented optimization. The natively unconstrained Efficient Global Optimization (EGO) algorithm approximates a black-box simulation with kriging surrogate models to convert the simulation results into a reduced-order model more suitable for optimization. This work evaluates several established constraint-handling approaches for EGO to compare their accuracy, computational efficiency, and reliability using an example simulation of an amine post-combustion carbon capture process. While each approach returned a feasible operating point in the number of iterations provided, none of them effectively converged to a solution, exploring the search space without effectively exploiting promising regions. Using the product of expected improvement and probability of feasibility as next point selection criteria resulted in the best solution value and re... [more]
Design and Optimization of a Multipurpose Zero Liquid Discharge Desalination Plant
Dev Barochia, Hasan Nikkhah, Burcu Beykal
July 9, 2024 (v1)
Keywords: Aspen Plus, Data-driven optimization, Desalination, Multicomponent Analysis, Zero liquid discharge
We study the design and optimization of a multicomponent seawater desalination process with zero liquid discharge (ZLD). The designed process is highly integrated with multiple sub processing units that include humidification-dehumidification, Lithium Bromide absorption chiller, multi-effect evaporators, mechanical vapor compression, and crystallization. Aspen Plus software with E-NRTL and SOLIDS thermodynamic packages are used for modeling and simulation of desalination and crystallization units, respectively. In addition to this, we use data-driven optimization to find the best operating condition (i.e., the temperature of the last effect evaporator) that minimizes the overall energy consumption of the designed plant with an output constraint imposed on the mass fraction of salts going to the ZLD system should be greater than 20 wt.% to achieve the ZLD goal. We use a local sample-based data-driven optimizer, Nonlinear Optimization with the Mesh Adaptive Direct Search (NOMAD) algorith... [more]
The design and operational space of syngas production via integrated direct air capture with gaseous CO2 electrolysis
Hussain M. Almajed, Omar J. Guerra, Ana Somoza-Tornos, Wilson A. Smith, Bri-Mathias Hodge
July 9, 2024 (v1)
Keywords: Aspen Plus, Carbon Dioxide Capture, Modelling and Simulations, Syngas, Technoeconomic Analysis
The overarching goal of limiting the increase in global temperature to = 2.0° C likely requires both decarbonization and defossilization efforts. Direct air capture (DAC) and CO2 electrolysis stand out as promising technologies for capturing and utilizing atmospheric CO2. In this effort, we explore the details of designing and operating an integrated DAC-electrolysis process by examining some key parameters for economic feasibility. We evaluate the gross profit and net income to find the most appropriate capacity factor, average electricity price, syngas sale price, and CO2 taxes. Additionally, we study an optimistic scenario of CO2 electrolysis and perform a sensitivity analysis of the CO2 capture price to elucidate the impact of design decisions on the economic feasibility. Our findings underscore the necessity of design improvements of the CO2 electrolysis and DAC processes to achieve reasonable capacity factor and average electricity price limits. Notably, CO2 taxes and tax credits... [more]
Modeling the Maximization of Waste Heat Use in a Liquid Solvent Direct Air Capture Plant Through Hydrogen Production
Erick O. Arwa, Kristen R. Schell
July 9, 2024 (v1)
Keywords: Climate change, Direct air capture, Hydrogen, Negative emission technologies, PEM
Direct air capture (DAC) of carbon dioxide is a promising technology to enable climate change mitigation. The liquid solvent DAC (LSDAC) process is one of the leading technologies being piloted. However, LSDAC uses a high-temperature regeneration process which requires a lot of thermal energy. Although current LSDAC designs incorporate pre-heat cyclones and a heat recovery steam generator to enable heat recovery, these do not maximize the use of the heat in the products of calcination. In this paper, a linear optimization model is developed to minimize energy cost in a LSDAC that is powered by renewable energy and natural gas. First, the material flow network is modified to include a heat exchanger (HX) and water supply to a proton exchange membrane (PEM) electrolyser. Mass and energy balance constraints are then developed to include the water flow as well as the energy balance at the PEM and the HX. Results show that about 911 tonnes of hydrogen could be produced over 336 hours of ope... [more]
Graph-Based Representations and Applications to Process Simulation
Yoel R. Cortés-Peña, Victor M. Zavala
July 9, 2024 (v1)
Keywords: Distillation, Flowsheet Convergence, Graph-Theory, Liquid Extraction, Process simulation
Rapid and robust convergence of a process flowsheet is critical to enable large-scale simulations that address core scientific questions related to process design, optimization, and sustainability. However, due to the highly coupled and nonlinear nature of chemical processes, efficiently solving a flowsheet remains a challenge. In this work, we show that graph representations of the underlying physical phenomena in unit operations may help identify potential avenues to systematically reformulate the network of equations and enable more robust topology-based convergence of flowsheets. To this end, we developed graph abstractions of the governing equations of vapor-liquid and liquid-liquid equilibrium separation equipment. These graph abstractions consist of a mesh of interconnected variable nodes and equation nodes that are systematically generated through PhenomeNode, a new open-source library in Python developed in this study. We show that partitioning the graph into separate mass, en... [more]
Towards the Development of Digital Twin for Pharmaceutical Manufacturing
Katherine Raudenbush, Nikola Malinov, Jayanth V. Reddy, Chaoying Ding, Huayu Tian, Marianthi Ierapetritou
July 9, 2024 (v1)
Keywords: Biopharmaceutical manufacturing, Digital twin, Pharmaceutical manufacturing, Process Modeling
Pharma 4.0 has continued to advance as the industry develops advances in process analytical technologies, automation, and digit-ization. Digital twins which transform on-line process measure-ments into meaningful outputs in real-time are being developed to seize the opportunity made possible with this shift. Digital twins can be used for improved process optimization on a range of scales, from determining optimal metabolite concentrations in upstream bioreactors to considering economic and environmental impacts of process decisions. In this paper, we explore the current uses of digital twins in solid-based pharmaceutical space and the bio-pharmaceutical manufacturing. Applications cover scale up of upstream processes, product quality control, and consideration of continuous systems. We also describe the intersection of digital twins in flow sheet modeling, sensitivity analysis and optimization, and design space evaluation. Finally, areas requiring further im-provement for industry adop... [more]
Heat and Mass Transfer Characteristics of Oily Sludge Thermal Desorption
Kai Li, Ao Cai, Yijun Tang, Xianyong Zhang
June 21, 2024 (v1)
Keywords: energy distribution, heat transfer, liquid evaporation, process simulation
Oily sludge is a loose material containing solid and multiple liquid components. Thermal desorption is an efficient method of disposing of liquids from oily sludge. Most existing studies have mainly discussed the effect of some external process parameters on thermal desorption, with little discussion on the heat transfer characteristics and the variation in the wet component mass of oily sludge under heating. Small-scale experiments have been performed to measure the rise in temperature and liquid phase content change of the sludge during heating. The temperature rise rate increases with material density and increases faster during the initial heating stage, while it slows down as the liquid phase evaporates. The adhesive shear stress is determined by measuring the pulling force of the test rod, which decreases with decreasing water content and increases significantly with decreasing oil phase content. Heat transfer and energy distribution models have been developed to calculate the ri... [more]
Effects of the PMMA Molecular Weight on the Thermal and Thermo-Oxidative Decomposition as the First Chemical Stage of Flaming Ignition
Antonio Galgano, Colomba Di Blasi
June 21, 2024 (v1)
Keywords: decomposition kinetics, Modelling, molecular weight, piloted ignition, PMMA, spontaneous ignition
The piloted and the spontaneous ignition of low and high molecular weight (LMW and HMW) polymethyl methacrylate are simulated using a one-dimensional condensed-gas phase model for constant heat fluxes in the range of 25−150 kW/m2. Purely thermal (nitrogen) and thermo-oxidative (air) decomposition is considered, described by a single and four-step kinetics for the low and high molecular weight polymer, respectively. Different optical properties are also examined. The same trends of the ignition time and other ignition parameters are always observed. Due to a more significant role of the chemical kinetics, the effects of the sample molecular weight and reaction atmosphere are higher at low heat fluxes. Times are shorter for the black HMW samples and thermo-oxidative kinetics. For piloted ignition, factors are around 2.8−1.6, whereas for thermal decomposition, they are 1.3−1.2. The corresponding figures are 1.8−1.3 and 1.3−1.1, in the same order, for the spontaneous ignition. Overall, the... [more]
Autonomous Hydrodistillation with a Digital Twin for Efficient and Climate Neutral Manufacturing of Phytochemicals
Alexander Uhl, Larissa Knierim, Theresa Höß, Marcel Flemming, Axel Schmidt, Jochen Strube
June 21, 2024 (v1)
Keywords: autonomous operation, climate neutrality, digital twin, green technology, hydrodistillation, natural products, phytochemicals, process analytical technology, Renewable and Sustainable Energy
Hydrodistillation is traditionally a green technology for the manufacturing of natural products that are volatile. As well as acknowledged process intensification methods such as microwave support for energy efficiency to move towards climate neutral operation, digital twins combined with process analytical technology for advanced process control enables reliable operation of an optimal operation point regarding lowest cost of goods, as well as lowest global warming potential equivalent. A novel process control enabled by digital twin technology has shown to reduce the ecological footprint of the extraction by up to 46.5%, while reducing the cost of extraction by 22.4%. Additionally, skilled operator time is reduced, and the sustainable plant material is utilized most efficiently. The approach is ready to apply, but broad industrialization seems to be held back by unclear business cases and lack of comprehension of decision makers. This is in drastic contrast to the political demand fo... [more]
Numerical Reservoir Simulation of Supercritical Multi-Source and Multi-Component Steam Injection for Offshore Heavy Oil Development
Qiang Fu, Zhouyuan Zhu, Junjian Li, Hongmei Jiao, Shuoliang Wang, Huiyun Wen, Yongfei Liu
June 21, 2024 (v1)
Keywords: mineral dissolution, offshore heavy oil development, pyrolysis reaction, supercritical multi-source and multi-component steam, thermal reservoir simulation
We present the workflow for numerical reservoir simulation of supercritical multi-source and multi-component steam injection for offshore heavy oil development. We have developed unique techniques in a commercial reservoir simulator to implement the thermal properties of supercritical multi-source and multi-component steam, the pyrolysis chemical reactions, the temperature-dependent relative permeability, and the process of partially dissolving the sandstone rock to enhance the matrix permeability in a commercial reservoir simulator. Simulations are conducted on the type pattern reservoir model, which represents one of the heavy oil fields in CNOOC’s Bohai Bay oil field. Simulation input parameters are calibrated based on laboratory experiments conducted for supercritical multi-source and multi-component steam injection. Simulation results have shown clear improvements in injecting supercritical multi-source and multi-component steam in offshore heavy oil reservoirs compared to the nor... [more]
Digital Twin Enabled Process Development, Optimization and Control in Lyophilization for Enhanced Biopharmaceutical Production
Alex Juckers, Petra Knerr, Frank Harms, Jochen Strube
June 21, 2024 (v1)
Keywords: Advanced Process Control, controlled nucleation, digital twin, lyophilization, Process Analytical Technology, process modeling, process optimization, Quality by Design
Digital twins have emerged as a powerful concept for real-time monitoring and analysis, facilitating Quality by Design integration into biopharmaceutical manufacturing. Traditionally, lyophilization processes are developed through trial-and-error, incorporating high security margins and inflexible process set points. Digital twins enable the integration of adaptable operating conditions and implementation of automation through Advanced Process Control (APC) with Process Analytical Technology (PAT) and validated physicochemical models that rely on heat and mass transfer principles, allowing us to overcome the challenges imposed by the lyophilization process. In this study, a digital twin for freeze-drying processes is developed and experimentally validated. Using the digital twin, primary drying conditions were optimized for controlled nucleation and annealing methods by carrying out a few laboratory tests beforehand. By incorporating PAT and modeling, the digital twin accurately predic... [more]
One-Dimensional Numerical Simulation on Removal of CO2 Hydrate Blockage around Wellbore by N2 Injection
Tao Liao, Liang Yuan, Wei Li, Jingyu Kan, Wei Luo, Xiaoqin Xiong, Nan Li
June 21, 2024 (v1)
Keywords: CO2 hydrate, depressurization, hydrate blockage, hydrate dissociation, N2 injection
CO2 sequestration in sediments as solid hydrate is considered a potential way to capture and store anthropogenic CO2. When CO2 hydrate is formed in front of CO2 migration, the injection channel will be blocked, and the removal of hydrate blockage becomes the first problem that must be faced. This work proposed an N2 injection method to remove CO2 hydrate blockage. Based on numerical simulation, a study was conducted using TOUGH+MIXHYD v.1.0 to confirm the feasibility of N2 injection and compare it to depressurization. The spatial and temporal distribution characteristics of pressure, temperature, hydrate saturation, and gas saturation were investigated. Under the combined effects of temperature, pressure, and gas composition, secondary CO2-N2 hydrate can form far from the injection point, causing an increase in local temperature and hydrate saturation. The rate of CO2 hydrate dissociation using direct depressurization is significantly slower compared to N2 injection methods. As the pre... [more]
Study on the Behavior and State of Viscous Fractured Leakage Bridging and Plugging Slurry during the Pump-In and Pressurization Process
Yanhui Wu, Cheng Han, Yi Huang, Wandong Zhang, Ming Luo, Peng Xu, Qinglin Liu
June 21, 2024 (v1)
Keywords: Computational Fluid Dynamics, fracture leakage, particle sedimentation, pumping–squeezing
Clarifying the process of bridging and plugging slurry during pumping and squeezing can effectively improve the efficiency and accuracy of fractured leakage treatment while minimizing impacts on safety and the environment. In this paper, computational fluid dynamics (CFD) numerical simulation and experimentation (hydrostatic settling method) are combined to evaluate the dynamic settlement process of different types of plugging slurry through sedimentation changes, sedimentation volume, sedimentation velocity and sedimentation height for factors such as viscosity, particle size, density and concentration of plugging slurry. The formula of particle sedimentation velocity is combined to obtain the following: When the viscosity of plugging slurry is more than 30 mPa·s, the particle diameter is 1.5 mm (particle size is half the fracture width), and the particle density is 2.0−2.6 g/cm3; it shows good dispersion and plugging performance under pumping pressure and while holding and squeezing... [more]
Simulation Study on the Prediction of Macroscale Young’s Modulus Based on the Mesoscale Characteristics of Tight Glutenite Reservoirs
Fengchao Xiao, Shicheng Zhang, Xiaolun Yan, Xuechen Li, Xinfang Ma, Cong Xiao
June 21, 2024 (v1)
Keywords: glutenite, gravel characteristics, meso-mechanics, numerical simulation
To obtain the macroscale Young’s modulus of glutenite under gravel inclusions, a numerical simulation of macroscale Young’s modulus prediction based on the mesoscale characteristics of glutenite was carried out. Firstly, the micron indentation test was used to obtain the meso-mechanical parameters of gravel and matrix in glutenite to ensure the reasonableness of the numerical simulation parameter settings; secondly, a two-dimensional glutenite physical model generation method based on the secondary development of Python was put forward; and then, the macroscale Young’s modulus variation rule of glutenite under different gravel sizes, particle size ratios, and content characteristics were analyzed using the finite element method (FEM). The results show that Young’s modulus of gravel is larger than Young’s modulus of the matrix, and Young’s modulus of different gravel and matrix has some differences. The gravel content is the main controlling factor affecting the macroscale Young’s modul... [more]
The Impact of Discrete Element Method Parameters on Realistic Representation of Spherical Particles in a Packed Bed
Zahra Ghasemi Monfared, J. Gunnar I. Hellström, Kentaro Umeki
June 21, 2024 (v1)
Keywords: discrete element method, packed bed, rolling friction, sub-steps, void fraction, wall effect
Packed bed reactors play a crucial role in various industrial applications. This paper utilizes the Discrete Element Method (DEM), an efficient numerical technique for simulating the behavior of packed beds of particles as discrete phases. The focus is on generating densely packed particle beds. To ensure the model accuracy, specific DEM parameters were studied, including sub-step and rolling resistance. The analysis of the packed bed model extended to a detailed exploration of void fraction distribution along radial and vertical directions, considering the impact of wall interactions. Three different samples, spanning particle sizes from 0.3 mm to 6 mm, were used. Results indicated that the number of sub-steps significantly influences void fraction precision, a key criterion for comparing simulations with experimental results. Additionally, the study found that both loosely and densely packed beds of particles could be accurately represented by incorporating appropriate values for rol... [more]
A Numerical Simulation Study into the Effect of Longitudinal and Transverse Pitch on Deposition of Zhundong Coal Ash on Tube Bundles
Zipeng Guo, Jianbo Li, Yintang Liang, Xiaofei Long, Xiaofeng Lu, Dongke Zhang
June 21, 2024 (v1)
Keywords: ash deposition, CFD modeling, heat flux, particle trajectories, tube bundles, Zhundong coal ash
In this paper, the dynamic deposition behavior of Na-enriching Zhundong coal ash on tube bundles with varying longitudinal and transverse pitches was numerically studied. By using a modified critical viscosity model, an improved CFD deposition model has been established and key parameters, including deposit mass and morphology, particle trajectories and impaction and sticking probabilities, as well as the heat flux distribution, have been analyzed. The results show that the ash deposited on tubes in the first row is, respectively, 1.74 and 3.80 times higher than that on the second and third rows, proving that ash deposition in the downstream is lessened. As the longitudinal pitch increased from 1.50 D to 2.50 D, deposit mass in the downstream increased two times, suggesting that an increase in longitudinal pitch would aggravate ash deposition. The effect of transverse pitch, however, with the least deposit propensity at St/D = 1.75, is non-linear due to the joint effect of adjacent tub... [more]
Numerical Simulation of Mold Slag Entrapment Behavior in Nonoriented Silicon Steel Production Process
Wenjie Huo, Caijun Zhang, Yanchao Zhang, Xuekai Li
June 21, 2024 (v1)
Keywords: immersion depth, nonoriented silicon steel, nozzle angle, numerical simulation, slag drawing speed, slag entrapment behavior
This paper is based on the surface defects of casting billets in the production process of nonoriented silicon steel plates at a steel plant in North China. Taking the parameters of a slab mold in the nonoriented silicon steel production process as a prototype, the flow field characteristics of the mold under the same section, different drawing speed and immersion depth were systematically studied by using a LES (large eddy simulation) and VOF (volume of fluid) coupling algorithm. The results show that under the current conditions, when the critical slag entrapment speed increases from 1.0 m/min to 1.2 m/min, the nozzle insertion depth increases linearly with the critical slag entrapment speed, while when the nozzle insertion depth exceeds 130 mm, the increasing effect of further increasing the nozzle insertion depth on the critical slag entrapment speed begins to decrease. When the drawing speed of continuous casting is kept constant at 1.4 m/min, the abnormal fluctuation height of th... [more]
Stochastic Modeling and Simulation of Filament Aggregation in Alzheimer’s Disease
Vaghawan Prasad Ojha, Shantia Yarahmadian, Madhav Om
June 21, 2024 (v1)
Keywords: AD, Alzheimer’s, chemical reaction, Gillespie algorithm, stochastic modeling
Alzheimer’s disease has been a serious problem for humankind, one without a promising cure for a long time now, and researchers around the world have been working to better understand this disease mathematically, biologically and computationally so that a better cure can be developed and finally humanity can get some relief from this disease. In this study, we try to understand the progression of Alzheimer’s disease by modeling the progression of amyloid-beta aggregation, leading to the formation of filaments using the stochastic method. In a noble approach, we treat the progression of filaments as a random chemical reaction process and apply the Monte Carlo simulation of the kinetics to simulate the progression of filaments of lengths up to 8. By modeling the progression of disease as a progression of filaments and treating this process as a stochastic process, we aim to understand the inherent randomness and complex spatial−temporal features and the convergence of filament propagatio... [more]
Simulation Analysis of the Characteristics of Layered Cores during Pulse Decay Tests
Haobo Chen, Yongqian Liu, Pengda Cheng, Xinguang Zhu, Guofeng Han
June 21, 2024 (v1)
Keywords: layered cores, low permeability, pulse decay testing, simulation analysis
The permeability of low-permeability cores is generally measured using a pulse decay method. The core of low-permeability rocks, such as shale, often has a layered structure. The applicability of pulse decay testing for layered cores is not clear. In this study, the performance of the pulse decay method on layered cores was comprehensively investigated. Numerical simulations were conducted to investigate the influence of the interlayer permeability ratio, storativity ratio, layer thickness, interlayer location, and number of layers on the pulse decay pressure and pressure derivative curves, as well as the permeability obtained from pulse decay testing. The results revealed that the pressure curves of layered cores exhibit distinct differences from those of homogeneous cores if the upstream permeability is larger than the downstream one. The pressure derivative curve shows more inclined or horizontal straight-line segments than in the homogeneous case. The shapes of the pressure and pre... [more]
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