Pseudo 2D Research Articles

Effects of pressure and particle size on bubble behaviors in a pseudo 2D pressured fluidized bed with Geldart A/B, B and D particles

Bubble behaviors of three types of particles from Geldart A/B, B and D groups were comprehensively investigated in a pseudo 2D pressurized fluidized bed via digital image analysis. Based on the analysis of a large quantity of experimental data, the effects of pressure and particle size on the spatial distribution of bubbles, bubble diameter, rise velocity, bubble fraction and flow regimes were obtained. Results show that bubbles are smaller and uniformly dispersed throughout the bed of Geldart A/B particles, while they become densely populated and grow into much larger sizes in the bed of Geldart B particles. A single peak of large bubbles in the center and emptying of bubble near the walls is formed in the bed of Geldart D particles due to the preferable rising path of bubbles towards the center and the significant coalescence of bubbles. Bubble diameter decreases with increasing pressure, and the effect of pressure is more pronounced on Geldart D particles. Bubble rise velocity increases with the increasing particle size and decreases as pressure rises. Large bubbles/slugs hardly appear in the bed of Geldart A/B particles, while they are clearly visible in the bed of Geldart B and D particles. The flow regime transition from slugging to fast fluidization shifts to the lower gas velocity for Geldart D particles compared with Geldart B particles.

Parameter sensitivity analysis of an electrochemical-thermal model for energy-storage lithium-ion batteries

The lithium-ion batteries used for energy storage have the characteristics of large volume, high capacity, and long cycle life. Understanding the influence of physical parameters on electric potential and temperature is of critical importance for the design and operation of battery management systems. Here we developed an electrochemical-thermal coupled model that is composed of lithium-ion battery Pseudo-2D (P2D) model and heat transfer equations. A sensitivity analysis is carried out to illuminate the influence of various electrochemical parameters on battery capacity, terminal voltage, temperature curve and other technical indicators for a LiFePO4 battery with the capacity of 117Ah. The sensitivity matrices of the parameters under different C-rates and depth of discharge regions are organized, and a new five segments sensitivity analysis method is proposed in this study, which is helpful to reduce the sensitivity variance caused by the change of capacity during the discharging process. The parameters which have the greatest impact on battery capacity, voltage, and temperature are sorted out and illustrated. Furthermore, the influence rules of electrochemical parameters on the capacity and temperature-related technical indicators have also been summarized.

Parametrization of a Doyle-Fuller-Newman (DFN) Model for a Commercial 37Ah Li-Ion Battery and Validation with Incremental Capacity Analysis

Physico-chemical modeling is considered as a very interesting way of simulating the behavior of a Li-ion battery cell by linking its internal state to its performance and aging. However, an accurate parametrization of such models is necessary for a truly representative outcome. In the case of commercial batteries, the parametrization procedure is hardly ever entirely undergone, leaving room for parameters tweaking and inaccurate simulation results. In the framework of this work, over 70% of the parameters were measured for a Samsung SDI 37Ah Li-ion prismatic battery (NMC111/Graphite) for PHEV (Plug-in Hybrid Electric Vehicle) applications. A Doyle-Fuller-Newman (DFN) Pseudo 2D model is chosen based on the work of Dufour et al.1. The major electrochemical characterization technics and measurement results for every component in the cell will be presented. The cells were opened in the ante-mortem procedure2, materials were identified, geometrical parameters were measured and samples were taken for coin-cell experiments. A small portion of the electrolyte was recovered and studied to conclude that it was made of EC-DMC-EMC at 1:1:2 portions. A similar solution was synthetized in order to conduct ionic conductivity measurements at temperatures ranging from -30 to 60°C. Samples from the separator were taken for both effective ionic conductivity and porosity measurements. The tortuosity of the electrodes was calculated via an EIS (Electrochemical Impedance Spectroscopy) with a blocking-electrodes configuration, and finally the diffusion factor in the active particles was estimated via GITT (Galvanostatic Intermittent Titration Technique) experiments. A very slow current regime was used to lithiate and de-lithiate the active materials in a half-cell experiment for electrode balancing purposes. The model was compiled using COMSOL Multiphysics 5.5, and results were compared to validation experiments conducted on the full-setup prismatic cell. The charge curve was validated under different current and power regimes at 25°C, and the Incremental Capacity (IC) curve showed a reasonable accuracy. With this in hand, the following step would be to couple this performance model to an aging model and to compare the evolution of the IC peaks with the experimental aging.

J-upscaling in two-dimensional solid-state NMR spectroscopy

The direct measurement of homonuclear scalar couplings (J) in solids, which serve as important parameters for the elucidation of molecular structure/ characterization of materials, is difficult due to the inherent broadening of spectral lines in the solid-state NMR. The earlier reported J-measurements in solid-state NMR are based on 1D/ pseudo 2D spin echo modulation techniques, which rely on computing the J-values by fitting the spin-echo modulations to appropriate mathematical functions, and may involve expertise in the area. On the other hand, the present study demonstrates two simple 2D-NMR methods: J-upscaled mechanism uniform cross-peak double quantum filtered COSY (JS-UC2QFCOSY) and its selective refocusing variant JS2-UC2QFCOSY that allow an easy quantification of scalar couplings, which have been exemplified for unambiguous measurement of JCC values in 13C3-alanine and 13C6-histidine.2HCl samples. These versatile experimental approaches are expected to be highly useful in structural characterizations of organic solids and other materials.

Multi-scale thermal modeling, experimental validation, and thermal characterization of a high-power lithium-ion cell for automobile application

Detailed thermal analysis of individual cell types used to power electric propulsion systems is rarely performed. Nano structured lithium-iron-phosphate or LFP cathodes show great promise in automobile application due to stable discharge profile and excellent safety features. This study is aimed at thermal characterization of a commercially favored lithium-ion cell under variable loads and operating conditions. An innovative reduced order electrochemical-thermal coupled model is developed using multi-scale multi-domain (MSMD) approach. A pseudo 2D (1D + 1D) electrochemical heat generation model is dynamically coupled to a 3D heat transport model. 3D cell domain is discretized using finite element (FE) mesh. Six representative discretization elements are selected for coupling. Electrochemical model is solved using a C-based code for each of the six elements. Model is validated using experimentally measured data and found to be in good agreement. Reduced order coupled model adequately captures temporal as well as spatial variations in cell temperature with sufficiently moderate computational expense. Simulation results show that lower operating temperatures and higher applied currents erode cell capacity. Optimum operating temperature window for the selected cell is found between 10 °C and 50 °C.

Geothermal reservoir depth of Seulawah Agam volcano estimated from 1D magnetotelluric

SeulawahAgam has planned to construct a geothermal power plant with an estimated 275 MW by the government to replace fossil energy. This study used a magnetotelluric (MT) survey to investigate the primary geothermal system, such as heat sources, reservoirs, or faults, which are responsible for regulating the surface manifestation. The regional volcano and fault of the Seulimum segments were traversed by 26 MT stations. The 1D Inversion was conducted toward the overall MT data using the Occam inversion algorithm from IP2Win MT. This Inversion was performed to acquire characteristics of the geothermal system based on resistivity parameters against the depth. The 1D model distribution was combined and converted into pseudo 2D, which could depict the subsurface conditions. Based on the data analysis, the cross-section model revealed that the volcanic sediment layer near the surface had a resistivity of 57-98 Om. In the depth of 4-8 km in profile one, and 0.2-2 km, in profile 2, coverage of clay CAP rocks was found with impermeable properties, where the resistivity was low (<10 Om). Afterward, the reservoir layer was characterized by resistivity ranging from 94 to 188 Om located at 1-3 km depth, where this anomaly could be seen across all measuring tracks. Meanwhile, the region beneath the reservoir was estimated to be a heat source with a depth range of 2-5 km, as evidenced by a high resistivity of more than >1000 Om. The pseudo-2D results could provide an initial model of SeulawahAgam's geothermal system.

A modified pseudo 2D physically-based model for double-gate TFETs: Role of precise calculations of drain and source depletion regions

In this current study, a modified pseudo two-dimensional (2-D) semi-analytical model for double gate tunnel FETs (DG-TFETs) is introduced. The main regions in the DG-TFET structure are the channel and the depletion regions inside the source and the drain. In such regions, the 2-D Poisson's equation is solved by adjusting suitable boundary conditions. The source and the drain depletion region lengths are calculated precisely by an iterative technique resulting in an accurate prediction of the electrostatic potential. According to the obtained 2-D electrostatic potential, the energy band diagram could be extracted and, consequently, the minimum tunneling width is calculated. Accordingly, the model of drain current is introduced by applying Kane's tunneling model. Further, the source depletion charge and the channel charge are derived, and the terminal capacitance components are then extracted. A comparison between the proposed model and SILVACO TCAD simulations shows a satisfactory agreement that confirms the validation of the presented model robustness.

Air preheating potential with high Opaque Ventilated Façade under natural and forced convection

Opaque ventilated façades (OVF) are increasingly used in building envelope because of their positive impact on building energy efficiency. Usually, air flow is driven by natural ventilation. Recently, there were some attempts to drive air flow mechanically to preheat or precool air in combination with HVAC, Heat pump or Latent Heat Thermal Energy Storage (LHTES) systems. In this framework, an experimental real-scale module of an OVF was built (1.9 m width and 3.5 m height). In this study, OVF is tested during autumn under natural and under forced convection by means of ventilator placed at cavity outlet. Inlet air flowrate are changed from day to day or during the day. For each test, temperature, air velocity, air flow rate and thermal flux are monitored at different locations of OVF. Their analysis shows that collector efficiency and amount of collected energy depend mainly on cavity air flow rate. The measurements are compared to simulation results obtained from two thermal models describing OVF: Trnsys Type 1230 and home-developed pseudo 2D. A good agreement is found for air temperature at cavity outlet while differences are observed in opaque layers due to modelling assumptions. Last, sensitivity analysis on two design parameters is carried out.

Conditions for High Rate, High Capacity Li-Ion Convection Cells through Dimensional Analysis

Improved performance of Li-ion cells for applications, such as, electric vehicles, renewable energy storage, and grid load leveling, calls for both high energy and rate capability. An implied high capacity under high rate cell (dis)charge is presently very difficult or unachievable in closed Li-ion cells. A common limitation under such demands is electrolyte transport and frequently Li-ion salt bulk diffusion in particular. The limitation leads to salt concentration variation and depletion in the cathode. A convection cell with in-operation electrolyte flow can significantly mitigate this limitation under quantitatively defined ranges of conditions, as published recently.1 This finding emerged from the addition of convection to a DUALFOIL-based pseudo 2D Li-ion cell model to create LIONSIMBA+c and dimensional analysis of input electrolyte transport properties, dimensions, and operational parameters. With cell performance output expressed as %capacity accessed, inputs combined into dimensionless groups explain the balance of migration versus diffusion and convection and allow for collapse of myriad output data points into families of curves for analysis.Here, we elaborate on the LIONSIMBA+c result analysis including the dimensionless groups that describe Li-ion cell capacity limitations with and without flow. Full material working capacity is achievable with low current or fast electrolyte transport – diffusion or convection. Notably, flow serves as an operational throttle for obtaining desirable transport. With discharge rate increase or sluggish transport, deliverable capacity drops precipitously and asymptotically approaches reduced levels, particularly when there is low initial Li-ion salt amount. A material balance explains the reduced capacity values at high rate. The accessible discharge time and thus capacity is gated by the time that migration depletes Li-ion salt in the cathode. We also examine the corresponding common electrolyte concentration profile behavior under different parameter combinations with similar dimensionless group values. Reference Gao, M. J. Orella, T. J. Carney, Y Román-Leshkov, J. Drake, and F. R. Brushett, J. Electrochem. Soc. 167 140551 (2020).

Study on gas hydrate targets in the Danube Paleo-Delta with a dual polarization controlled-source electromagnetic system

The Black Sea is known to have extensive direct and indirect indicators of methane hydrates. Since the resistivity of the seafloor increases significantly in the presence of gas hydrates or free gas, marine controlled-source electromagnetics (CSEM) is a suitable method for the investigation of hydrates. We have collected CSEM data in a channel-levee system of the Danube paleo-delta (Bulgarian sector) at water depths of about 1500 m. The working area is within the gas hydrates stability zone and seismics suggests the presence of gas hydrates. The CSEM data were acquired with stationary receivers and a novel mobile, dual polarization transmitter system, and interpreted in terms of rotational invariants by means of 1-D inversions at common midpoints (CMP) to generate pseudo 2D resistivity sections. The inversion results reveal two resistive layers at shallow depths of 60–120 mbsf and greater depths of 270–400 mbsf. A comparison with seismics shows a good correlation of the shallow layer with high amplitude reflections and a velocity anomaly. The deeper layer can be tied to the current bottom simulating reflector (BSR). The comparison to a second CSEM experiment, which was conducted by the BGR (Federal Institute for Geosciences and Natural Resources, Germany) shows a good agreement of the derived sections down to a depth of about 350 m. Based on salinity and porosity models derived from boreholes in the Black Sea, we apply Archie's law to estimate potential gas hydrate saturations of up to 23% for the shallow resistor and up to 7% for the deeper layer. Differences are evident at depths greater than 450 m, where we see a conductive layer not evident in the BGR section. This deeper conductor could be evidence for increasing salinities of pore fluids at greater depths, which were previously found in DSDP drilling cores.

Estimation of Grouped Parameters Using Tanks-in-Series Lithium-Ion Battery Model

Parameter estimation is critical for efficient Battery Management System (BMS) performance. The accuracy and predictability of a model depends on the precision of its parameters. Moreover, model parameters tend to change with battery aging. Efficient BMS performance requires accurate tracking and updating of relevant parameters as the battery ages. Estimating parameters for electrochemical models is challenging due to the complexity of the governing equations, and the possibility of degeneracy, with multiple sets of parameter values that give the same accuracy for fitting charge/discharge data. Parameter estimation of various lithium-ion battery systems has been attempted with different model types, including equivalent circuit model2, single particle model3 and pseudo 2D (P2D) model.4,5 Estimation approaches reported in literature, such as, GA6, heuristic algorithms7, etc., are difficult to implement in real-time due to computational complexity. In the past, we proposed and implemented reformulated p2D models for real-time parameter estimation.8,9 While the reformulated models are computationally inexpensive, the large set of parameters and resulting likelihood of degeneracy introduce substantial complexity. Recently, we proposed lithium-ion Tanks-in-Series battery model10. This model is generated by systematic volume-averaging of the p2D model that enables efficient and real-time simulation with reduced set of parameters.In this presentation, we propose to estimate non-dimensional grouped parameters using non-dimensional Tanks-in-Series battery model. The grouping of parameters further reduces the number of parameters that needs to be estimated. This also reduces the computational effort required to perform optimization. The non-dimensional model captures resistances offered due to transport, reaction kinetics, and ohmic drop in electrolyte based on the non-dimensional grouped parameters that absorb constitutive expressions and parameters, such as electrolyte diffusivity, ionic conductivity, reaction rate constants and solid phase diffusivity. The estimation is performed on experimental charge/discharge data obtained from cylindrical cells having NCA and NMC cathode chemistries. The accuracy of the estimated parameters is validated using experimental cycling data obtained at different c-rates by calculating the error in voltage-time curves between the model prediction using estimated parameters and the experimental data. Acknowledgements The authors acknowledge funding from the U.S. Department of Energy Office of Electricity Energy Storage Program through Sandia National Laboratories, under the guidance of Dr. Imre Gyuk, and the Texas Materials Institute at The University of Texas at Austin. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy National Nuclear Security Administration under contract DE-NA-0003525. SAND2020-14131 A References V. Ramadesigan, P. W. C. Northrop, S. De, S. Santhanagopalan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 159, R31–R45 (2012).Y. Hu, S. Yurkovich, Y. Guezennec, and B. J. Yurkovich, Control Eng. Pract., 17, 1190–1201 (2009).A. P. Schmidt, M. Bitzer, Á. W. Imre, and L. Guzzella, IFAC Proc. Vol., 43, 198–203 (2010).J. C. Forman, S. J. Moura, J. L. Stein, and H. K. Fathy, in 5th Annual Dynamic Systems and Control Conference,, p. 1–8 (2012).S. Santhanagopalan, Q. Guo, and R. E. White, J. Electrochem. Soc., 154, 198–206 (2007).A. Jokar, B. Rajabloo, M. Désilets, and M. Lacroix, J. Electrochem. Soc., 163, A2876–A2886 (2016).J. Li, L. Zou, F. Tian, X. Dong, Z. Zou, and H. Yang, J. Electrochem. Soc., 163, A1646–A1652 (2016).V. Boovaragavan, S. Harinipriya, and V. R. Subramanian, J. Power Sources, 183, 361–365 (2008).V. Ramadesigan, K. Chen, N. A. Burns, V. Boovaragavan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 158, A1048–A1054 (2011).A. Subramaniam, S. Kolluri, C. D. Parke, M. Pathak, S. Santhanagopalan, and V. R. Subramanian, J. Electrochem. Soc., 167, 013534-013534–18 (2020).

Analyzing and mitigating battery ageing by self-heating through a coupled thermal-electrochemical model of cylindrical Li-ion cells

An integrated battery model is constructed by coupling a three-dimensional electrochemical model with a two-dimensional axisymmetric heat transfer model, and implemented for simulation of the thermal behavior in a 21,700-type cylindrical cell, comprising a graphite/LiNi0.8Co0.15Al0.05O2 chemistry. The electrochemical model is based on the disassembled battery structure and considers the temperature-dependent ageing kinetics induced by solid electrolyte interphase (SEI) formation and metallic Li plating. Compared with a classic pseudo-2D (P2D) model, the proposed model provides better fitting results for both battery electrochemical and thermal properties. The simulation results show battery surface temperatures can reach up to 80 °C and 110 °C for discharge rates of 3C and 4C, respectively. By applying appropriate cooling liquids, this surface temperature increase can be efficiently controlled and the core temperature will be correspondingly reduced, while the internal temperature gradient remains the same. It is primarily the improvement of thermal conductivity in radial direction which can reduce differences between core and surface temperature. Moreover, the model is able to characterize accelerated ageing kinetics caused by battery self-heating during operation. The results show that the capacity of the investigated battery decreases to 80% after 500 cycles, which is in good agreement with commercial specifications.

Cross-flow plate reactor for ethanol steam reforming: A theoretical study

In this contribution, a theoretical study of ethanol steam reforming (ESR) over a Pd-based catalyst in a plate microreactor is carried out. ESR is convectively heated by means of a flue gas stream flowing through contiguous plates in a cross-flow configuration.To describe the performance of the reactor under steady-state adiabatic operation a pseudo homogeneous 2D model is considered. The influence of the main operating variables and the different flue gas feed arrangements on the performance of the reformer has been analysed with the aim of accomplishing a total hydrogen production of 1 kWth.The results show that the cross-flow plate reactor is a promising design to carry out the ESR under operating and design conditions that favour thermal homogeneity (high heat transfer) and a high enough residence time of the reactants in the reforming side.

Understanding Deviations between Spatially Resolved and Homogenized Cathode Models of Lithium‐Ion Batteries

Porous electrode models are essential for inexpensively predicting the performance and lifetime of lithium‐ion batteries. Physics‐based models range from microscopic 3D models, which spatially resolve the microstructural characteristics of all phases in porous electrodes, to reduced and computationally effective models, which do not resolve the microstructure. The homogenized Newman model, also known as the pseudo‐2D (P2D) model, is well established and widely used. However, the necessary simplification shows its weaknesses, especially for high charge and discharge rates, and these lead to significant differences in comparison with the microscopic 3D model. Herein, the validity of the homogenized Newman model is investigated with respect to variations of the microstructural characteristics of a porous cathode. The effects of 1) a homogenized conductive additive; 2) non‐spherical particle geometries; and 3) overlapping particles on charge/discharge curves are analyzed. The result is a better understanding of the validity limits of P2D models. These new insights about the individual influences of the simplifications will be used to improve the homogenized model. The simulation of complex cathode structures, where several homogenization assumptions are violated, shows that the improved homogenized model reaches a very high accuracy, and, thus, overcomes the existing limitations of the P2D model approach.

Modeling and Optimization of Multi-functional Ammonia Slip Catalysts for Diesel Exhaust Aftertreatment

Ammonia slip catalysts (ASC) are used downstream of the NH3-selective catalytic NOx reduction (SCR) system, to minimize ammonia slip from transport sector SCR units. The ASC may consist of an SCR active layer for NOx control, a layer with oxidation functionality for ammonia conversion, or a combination thereof, either as individual layers or as a single mixed layer. Mathematical models of such systems involve flow and mass transfer in the monolithic channels as well as coupled reaction/diffusion processes in the catalytic layers. In this work, we develop a single-channel 1D-1D (pseudo 2D) steady-state tank-in-series mathematical model for monolithic ammonia slip catalysts with up to two layers. Kinetics of relevant reactions over the Cu-Beta zeolite and the Pt/TiO2 layer, including SCR, ammonia oxidation, and the formation of N2O, were derived based on an extensive flow reactor study. The model was validated based on experiments using four different small-scale ASC monoliths, showing good agreement between the model predictions and the experimental results. Comparison of ten ASC configurations for the oxidation of 200 ppm NH3 at 300 °C shows that configurations with a pure layer of NH3 oxidation catalyst generate undesirable high N2O and NOx levels. The best ASC configurations feature fast diffusion in the catalytic layers (a high effective diffusion coefficient), a thin top layer loading with some ammonia oxidation catalyst, and a mixed layer of ammonia oxidation catalyst and the SCR catalyst to limit the formation of N2O and NOx.

Unusual porous crystals via catenation of 1D ladders: unprecedented mixture effects on the adsorption of xylene isomers in a SCSC mode

The pseudo 2D open-channel crystals formed via catenation of 1D ladders show unusual mixture effects on the adsorption of o-, m-, and p-xylene isomers in a SCSC mode, and are a practical template for structural determination of small hydrocarbons.

Parameter Estimation of Lithium-Ion Battery Models Using a Novel Tanks-in-Series Approach

Lithium-ion batteries play a vital role in electric vehicles and energy storage systems. In order to monitor, predict and control the performance of lithium-ion batteries, advanced Battery Management Systems (BMS) are key. Intensive efforts are being pursued to develop electrochemical model-based battery management systems (BMS).1 The accuracy and predictability of a model depends on the precision of its parameters. Precise parameter estimation is critical for efficient BMS performance. Moreover, model parameters tend to change with battery aging. Efficient BMS performance requires the accurate tracking and update of relevant parameters.Estimating parameters for electrochemical models is challenging due to the complexity of the governing equations, and the possibility of degeneracy, with multiple sets of parameter values that give the same accuracy for fitting charge/discharge data. Parameter estimation of various lithium-ion battery systems has been attempted with different model types, including equivalent circuit model2, single particle model3 and pseudo 2D (P2D) model.4,5 Literature approaches to estimate parameters using GA6, heuristic algorithms7 etc., are difficult to implement in real-time due to computational complexity. In the past, we proposed and implemented reformulated p2D models for real-time parameter estimation.8,9 While the reformulated models are computationally inexpensive, the large set of parameters and resulting likelihood of degeneracy introduce substantial complexity.In this presentation, we propose to estimate parameters of the recently published Tanks-in-Series model10. This model is generated by systematic volume-averaging of the p2D model that enables efficient and real-time simulation. The number of parameters to be estimated in the tank model can be reduced by grouping the transport, design and kinetic parameters. The estimation is performed on experimental charge/discharge data for cylindrical cells. The accuracy of the estimated parameters is validated by using a dynamic charging profile (FUDS cycle test) and measuring the error in voltage-time curves. Acknowledgements The authors acknowledge funding from the Department of Energy, Office of Electricity, Energy Storage Program. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525 and the Texas Materials Institute at The University of Texas at Austin. References V. Ramadesigan, P. W. C. Northrop, S. De, S. Santhanagopalan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 159, R31–R45 (2012).Y. Hu, S. Yurkovich, Y. Guezennec, and B. J. Yurkovich, Control Eng. Pract., 17, 1190–1201 (2009).A. P. Schmidt, M. Bitzer, Á. W. Imre, and L. Guzzella, IFAC Proc. Vol., 43, 198–203 (2010).J. C. Forman, S. J. Moura, J. L. Stein, and H. K. Fathy, in 5th Annual Dynamic Systems and Control Conference,, p. 1–8 (2012).S. Santhanagopalan, Q. Guo, and R. E. White, J. Electrochem. Soc., 154, 198–206 (2007).A. Jokar, B. Rajabloo, M. Désilets, and M. Lacroix, J. Electrochem. Soc., 163, A2876–A2886 (2016).J. Li, L. Zou, F. Tian, X. Dong, Z. Zou, and H. Yang, J. Electrochem. Soc., 163, A1646–A1652 (2016).V. Boovaragavan, S. Harinipriya, and V. R. Subramanian, J. Power Sources, 183, 361–365 (2008).V. Ramadesigan, K. Chen, N. A. Burns, V. Boovaragavan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 158, A1048–A1054 (2011).A. Subramaniam, S. Kolluri, C. D. Parke, M. Pathak, S. Santhanagopalan, and V. R. Subramanian, J. Electrochem. Soc., 167, 013534-013534–18 (2020).

Hardware-friendly architecture for a pseudo 2D weighted median filter based on sparse-window approach

Stereo matching, which is conventionally used for three-dimensional (3D) information acquisition through cameras, is the most actively studied subject in computer vision. To obtain sophisticated 3D information, refining the disparity map in stereo vision is important. The weighted median filter (WMF) is extensively used to eliminate outliers in post-processing. To this end, various studies have implemented WMFs in hardware for real-time processing. Among them, the separable weighted median filter (sWMF) vertically and horizontally separates a two-dimensional WMF into two one-dimensional WMFs to reduce hardware resource usage. Herein, we propose a hardware architecture that can reduce the hardware resource usage of the sWMF by applying the sparse-window approach, which is a method of creating a window by selecting pixels sparsely. This approach makes it possible to reduce drastically the number of elements to be computed. Although the proposed architecture has an insignificant disparity error rate, similar to that of the sWMF, it saves 33% slice lookup tables (LUTs) and 69% slice registers when using a window size of 37 × 37 pixels as the synthesis result on the Xilinx XC7K325T FPGA. When a window size of 49 × 13 pixels with the best performance is used, the proposed architecture uses 7335 slice LUTs, 4126 slice registers, and 21 block RAMs. The proposed architecture operates at frequencies of up to 167.95 MHz; hence, it can operate in real time. The proposed WMF architecture is suitable for application in embedded systems and low-resource environments as it is hardware-friendly.

CFD-DEM simulation of gas-solid flow of wet particles in a fluidized bed with immersed tubes

In an intensified fluidized bed processing of wet particles, it is often to use heat transfer immersed tubes to maintain reasonable temperature distribution. The wet particles could adhere to the immersed tubes, which hinders the normal fluidization. We studied the gas-solid flow in a pseudo 2D fluidized bed of wet particles with the presence of immersed tubes, by using CFD-DEM simulation with the hysteretic contact model. The gas-solid flow characteristics around the immersed tubes and the effects of immersed tubes, adhesive force and fluidization velocity on the fluidization of wet particles are analyzed. With the increase of the adhesive force the agglomeration mainly occurs near the bed wall and the channeling mainly appears in the middle of the bed. The immersed tubes can cause the particles to accumulate on the upper surface of the tubes. Also, it can break the bubbles and agglomerates when the fluidization velocity is high. As the fluidization becomes poor, the particle agglomeration becomes more obvious and coordination number increases. The local poor fluidization zone is observed mainly in the gaps between the wall and the immersed tubes.

Single and ensemble response of colloidal ellipsoids to a nearby ac electrode

Anisotropic colloids can be used as building blocks for fabricating assemblies with complex microstructure and function. External electric fields are one key tool used to assemble such colloidal structures. Herein, we utilized a parallel plate electrode geometry to drive motion of micrometer scale ellipsoidal colloids. The response of pseudo 2D layers of ellipsoids with systematically altered aspect ratios was measured as a function of electric field strength and frequency. We found there to be a weak dependence of ellipsoid ensemble structure on aspect ratio. Namely, regions of aggregation and separation were only slightly dependent on particle aspect ratio. We found that ellipsoids with a smaller aspect ratio tended to align with the electric field, while high aspect ratio ellipsoids did not in response to an electric field of the magnitude and time scale used herein. In addition, we found the kinetics of aggregation of colloids to be very similar regardless of aspect ratio. Complementary experiments utilizing these data demonstrated long-lasting deposition of ellipsoids in energetically unfavorable orientations, which is being used as a model system for the measurement of light scattered from an evanescent wave by an ellipsoid.