Reverse Mode Research Articles

Study of polymer-stabilized cholesteric liquid crystals for reflective displays in active matrix driving

This paper attempts to explore the feasibility of using cholesteric liquid crystals (CLCs) for reflective displays in active matrix (AM) driving. The study focuses on reverse mode polymer-stabilized cholesteric liquid crystals (PSCLCs) to overcome the inherent bistability of CLCs and achieve faster response times for switching between bright and dark states. Key parameters such as cell gap, monomer concentration, polymerization temperature, and different monomer types and liquid crystal hosts are systematically investigated to optimize the electro-optical properties of the liquid crystals for active matrix driving. The research demonstrates that PSCLCs can operate within a 15 V driving voltage range while maintaining a good bright-dark state contrast ratio (>10) and a response time of less than 42 ms. This suggests significant potential for their application in dynamic reflective display technologies.

Learning Force Field Parameters from Differentiable Particle-Field Molecular Dynamics.

We develop ∂-HylleraasMD (∂-HyMD), a fully end-to-end differentiable molecular dynamics software based on the Hamiltonian hybrid particle-field formalism, and use it to establish a protocol for automated optimization of force field parameters. ∂-HyMD is templated on the recently released HylleraaasMD software, while using the JAX autodiff framework as the main engine for the differentiable dynamics. ∂-HyMD exploits an embarrassingly parallel optimization algorithm by spawning independent simulations, whose trajectories are simultaneously processed by reverse mode automatic differentiation to calculate the gradient of the loss function, which is in turn used for iterative optimization of the force-field parameters. We show that parallel organization facilitates the convergence of the minimization procedure, avoiding the known memory and numerical stability issues of differentiable molecular dynamics approaches. We showcase the effectiveness of our implementation by producing a library of force field parameters for standard phospholipids, with either zwitterionic or anionic heads and with saturated or unsaturated tails. Compared to the all-atom reference, the force field obtained by ∂-HyMD yields better density profiles than the parameters derived from previously utilized gradient-free optimization procedures. Moreover, ∂-HyMD models can predict with good accuracy properties not included in the learning objective, such as lateral pressure profiles, and are transferable to other systems, including triglycerides.

Direct design of ground-state probabilistic logic using many-body interactions for probabilistic computing

In this work, an innovative design model aimed at enhancing the efficacy of ground-state probabilistic logic with a binary energy landscape (GSPL-BEL) is presented. This model enables the direct conversion of conventional CMOS-based logic circuits into corresponding probabilistic graphical representations based on a given truth table. Compared to the conventional approach of solving the configuration of Ising model-basic probabilistic gates through linear programming, our model directly provides configuration parameters with embedded many-body interactions. For larger-scale probabilistic logic circuits, the GSPL-BEL model can fully utilize the dimensions of many-body interactions, achieving minimal node overhead while ensuring the simplest binary energy landscape and circumventing additional logic synthesis steps. To validate its effectiveness, hardware implementations of probabilistic logic gates were conducted. Probabilistic bits were introduced as Ising cells, and cascaded conventional XNOR gates along with passive resistor networks were precisely designed to realize many-body interactions. HSPICE circuit simulation results demonstrate that the probabilistic logic circuits designed based on this model can successfully operate in free, forward, and reverse modes, exhibiting the simplest binary probability distributions. For a 2-bit × 2-bit integer factorizer involving many-body interactions, compared to the logic synthesis approach, the GSPL-BEL model significantly reduces the number of consumed nodes, the solution space (in the free-run mode), and the number of energy levels from 12, 4096, and 9–8, 256, and 2, respectively. Our findings demonstrate the significant potential of the GSPL-BEL model in optimizing the structure and performance of probabilistic logic circuits, offering a new robust tool for the design and implementation of future probabilistic computing systems.

Hydrodynamics of standing-and-walking on the water surface by dolphins using collaborative movements of the body and fins

To break the application scenario limitations of traditional bionic underwater robots and open up the way of information docking between underwater and water surface, a systematic study was conducted on the cross-medium standing-and-walking (SAW) behavior of dolphins under the collaborative movements of the body, caudal, and pectoral fins. A three-dimensional physical model of the biomimetic dolphin robot was established, a collaborative movement law of the body, caudal, and pectoral fins was proposed, and the SAW behavior under two modes, Homologous and Reverse modes, was realized. The mapping relationship between the robot's kinematic parameters and hydrodynamic performance parameters was analyzed, the respective advantages of the two vertical walking modes were compared, and the SAW mechanism of the two modes was revealed physically with the help of the evolution law of the flow field around the robot. The results show that the biomimetic dolphin robot can realize cross-medium SAW behavior through the collaborative movements of the body, caudal pectoral fins. It is worth noting that the Hom mode has a superior walking speed, which can reach up to 0.27 m/s, an increase in 83.3% compared to the Rev mode under the same conditions, while the Rev mode has better walking stability, with a minimum fluctuation rate of 2.59%, a 30.8% improvement compared to the Hom mode. This research provides a novel idea for enhancing the surface operation capability of traditional biomimetic underwater robots and provides an important fluid mechanics theoretical basis for the design of new generation of cross-medium dolphin robots.

A generalized prediction model for complete performance investigation of pump operated as turbine in microhydro applications using novel approach for improving sustainability

Centrifugal pumps operated in reverse mode (popularly called pump as turbines (PATs)) are well-established as green energy converters, mainly used in microhydro applications due to their lower capital cost. However, the appropriate selection of the pump for reverse-mode application is a critical issue due to the unavailability of its characteristic curve in turbine mode. Therefore, various researchers have proposed models to predict PAT parameters from pump characteristics based on diverse approaches. Still, researchers are striving to develop a prediction model, which can predict the head and flow rates for the PAT with less than ±20 % deviation for both. This work proposed a novel approach to predict the characteristics of PAT with the integration of ensemble regression modelling for Best Efficiency Point (BEP) and from it, by polynomial equations complete characteristics curve. The data from in-house experiments and open literature are used to develop the proposed model excluding the data of four pumps, which are typically used for validation of it. The predicted parameters of PAT from pump characteristics show good agreement for four selected PATs with <10 % maximum deviation. Compared to the literature prediction models, it shows a lower deviation for the same four PATs. A case study based on the field data is carried out to justify the applicability of the proposed model. By using this model selected pump when operated in PAT will produce higher power and generate more revenue compared to literature models, resulting in the economical utilization of resources and improving sustainability. Though the savings are lower, it will be significant for a large number of PAT applications.

LC-MS/MS of Dexamethasone in Rabbit Vitreous Liquid Delivered through Novel Self-nanoemulsifying Drug Delivery Systems

Background: Dexamethasone (DEX), delivered through newly developed selfnanoemulsifying drug delivery systems, which is administered to rabbit eyes, has been presented. The instrumental parameters of the multiple LC-MS/MS methods in the literature are modified according to rabbit vitreous liquid and current laboratory conditions. Methods: Quick optimization of the chromatographic and mass spectrometric parameters was done by inspecting the available literature for the analysis of DEX by LC-MS/MS from biological matrices. Chromatographic separation was achieved in the reverse mode using C18 (50x2.1mm, 5μm) as a stationary phase and acetonitrile and water with ammonium acetate as a mobile phase in gradient elution. Quantitation was done in multiple reaction monitoring (MRM) mode by following the transition of m/z 393 &gt; m/z 373 in positive ion mode. The method was also validated in terms of selectivity, within-day accuracy and precision, linearity, and limit of detection (LOD). The extraction of DEX from rabbit vitreous liquid samples was carried out by protein precipitation using acetonitrile: water (70:30, v/v). Results: DEX and beclomethasone (IS) were successfully separated and detected under optimized experimental settings. The method was selective for DEX and linear in the range of 0.5 and 250 ng/ml. The lower limit of quantification (LLOQ) was determined to be 0.238 ng/ml. The percent relative standard deviation (RSD) and recovery (%) of the low, medium, and high calibration levels were below 10% and within the range of 111%-114%, respectively. RSD (%) and recovery (%) of the LLOQ were below 17% and 82%, respectively. The validated method was successfully applied for the determination of pharmacokinetic properties of newly formulated dexamethasone selfnanoemulsifying drug delivery systems (DEXSNEDDS) used to administer DEX intravitreally to the rabbit. Conclusion: LC-MS/MS conditions for the analysis of LC-MS/MS were determined by examining relevant literature for accomplishing simple and practical optimization of the experimental parameters, followed by method validation and analysis of rabbit vitreous liqiud. As conclusion, pharmacokinetic data of DEXSNEDDS has been obtained in the most accurate, sensitive, economical and rational way possible.

Experimental investigation of bidirectional series resonant DC-DC converter in different operating modes

This paper presents a study of bidirectional series resonant DC/DC converter. The main operating modes of the converter with phase-shift control technique are observed. An experimental survey with a laboratory model of such type of converter working over the resonant frequency is made. The functionality of the studied device operating in a wide area of loading is demonstrated with waveforms of the main parameters. The conducted measurements are used to build the experimental output characteristics of the converter. A similarity of the experimental results with the theoretical are denoted, and the ability to achieve current source characteristics for the whole range of loading is proven. The possibility of the studied converter for operation both in forward and reverse modes of energy flow is proved, which positions the device as an appropriate variant for implementation in the storage system control area.

Two Steps Non-Enzymatic Synthesis of Molnupiravir, which is Free from Mutagenic Impurity and Analytical Method Development for Estimation of Genotoxic Impurity (Hydroxylamine Hydrochloride Content) by using RP-HPLC Technique

Genotoxic impurity free Molnupiravir was synthesised by a novel and an elegant non-enzymatic method, which is simple operationally and ecologically. The genotoxic raw material, Hydroxylamine, was used in the initial stages of synthesis to get the mutagenic impurity free Molnupiravir. A new and sensitive HPLC method was developed and validated for the determination of hydroxylamine in Molnupiravir drug substance according to ICH guidelines. The HPLC method was developed and optimized on Zorbax SB C18 150×4.6mm, 3.5µm column with oven temperature maintained at 40°C. 1.0 mL of Orthophosphoric acid in 1000 mL water was selected as mobile phase in isocratic reverse phase mode. Chromatographic parameters are flow rate: 0.8 ml/min, wavelength detection: 252 nm, injection volume: 10µl and run time: 20 min. Based on the validation data; the method was found to be specific, sensitive, accurate and precise. This method can be used as a good quality control tool for quantification of hydroxylamine at the low level. The experimental data was deliberated in detail in this research paper.

Reverse mode LCPG films with self-assembly support of gel networks

ABSTRACT Liquid crystal physical gels (LCPG) with a 3D network structure show considerable promise as novel functional materials with a great impact on scientific and practical applications. LCPGs are not characterised by high hardness and high strength, but this mild nature is capable of forming dynamic supramolecular structures with the self-assembly ability of various non-covalent bonds such as hydrogen bonding, π-π stacking, and van der Waals forces. In addition to anisotropic changes under optical and electrical stimulation, it enables to be one of the candidates for display devices. When the isotropic-anisotropic transition temperature of LCPG solution (TIA) is higher than the sol-gel transition temperature of gel molecules (TSG), the gelation can anchor the orientation of liquid crystal molecules to achieve the alteration of transparency and scattering of the film. In this paper, reverse mode LCPG films with high contrast, low driving voltage, and excellent cycle life were prepared using oriented liquid crystal cassettes and LCPG solutions, it also focused on the effects of chiral compounds (S)-octan-2-yl 4-((4-(hexyloxy)benzoyl)oxy)benzoate (S811) and gel 1,3:2,4-bis-0-(3,4-dimethylbenzylidene)sorbitol (DMDBS) content on electro-optical properties of LCPG films as well as the different functions of TIA and TSG on film orientation.

Inverse analysis of granular flows using differentiable graph neural network simulator

Inverse problems in granular flows, such as landslides and debris flows, involve estimating material parameters or boundary conditions based on a target runout profile. Traditional high-fidelity simulators for these inverse problems are computationally expensive, restricting the number of possible simulations. These simulators are also non-differentiable, making efficient gradient-based optimization methods for high-dimensional spaces inapplicable. Machine learning-based surrogate models offer computational efficiency and differentiability. However, they often struggle to generalize beyond their training data due to relying on low-dimensional input–output mappings that fail to capture the complete physics of granular flows. We propose a novel differentiable graph neural network simulator (GNS) that combines reverse mode automatic differentiation of graph neural networks with gradient-based optimization for solving inverse problems. GNS learns the dynamics of granular flow by representing the system as a graph and predicts the evolution of the graph at the next timestep, given the current state. The differentiable GNS demonstrates optimization capabilities beyond the training data. We demonstrate the effectiveness of our method for inverse estimation across single and multi-parameter optimization problems, including evaluating material properties and boundary conditions for a target runout distance and designing baffle locations to limit a landslide runout. Our proposed differentiable GNS framework solves inverse problems with orders of magnitude faster convergence than the conventional gradient-based optimization approach using finite difference.

Investigation into the impact of bulk defects in the drift layer on the electrical properties of GaN-based trench Schottky barrier diodes

Using numerical simulation tools, this work systematically investigates the impact of bulk defects in the drift layer on GaN-based trench metal–insulator–semiconductor barrier-controlled Schottky rectifiers. Investigations show that in forward conduction, the acceptor-type defects significantly increase the on-resistance (R on.sp). When the device is in reverse blocking mode, donor-type defects tend to weaken the charge-coupling effect, leading to early breakdown of the device, while acceptor-type defects show the opposite feature. In addition, our report identifies that the reverse blocking effect is significantly impacted when the defects are located in the region with maximum electric field magnitude. We also find that the acceptor-type traps generate a remarkable charging/discharging effect, which will destabilize the dynamic forward conduction process. Hence, we numerically prove that bulk defects should be avoided in actual power diodes.

Naltrindole attenuates irreversible Hypercontracture during Myocardial Ischemia by a Novel Mechanism and elicits robust cardioprotective effects in Myocardial Ischemia/Reperfusion Injury

Introduction: Previous studies have shown that naltrindole (NTI) produced robust cardioprotective effects (e.g.~80% reduction of infarct size) in both ex-vivo (2.5-5μM) and in-vivo (3.75-7.5 mg/kg) rat myocardial ischemia-reperfusion (MIR) injury models. We recently showed that NTI 100-200μM attenuated phorbol 12-myristate 13-acetate (PMA) induced polymorphonuclear leukocytes (PMNs) superoxide (SO) release by a novel mechanism of action (MOA) devoid of opioid receptors. We hypothesize NTI’s novel MOA is a reduction of intracellular calcium (Ca2+). To test this hypothesis, we conducted PMN SO release and isolated perfused MIR assays using KB-R7943(KB). KB is known to reduce intracellular Ca2+ via inhibition of reverse mode Na+/Ca2+ exchanger and therefore should attenuate PMN SO release, myocardial ischemic hypercontracture, infarct size, and left ventricular end diastolic pressure (LVEDP). Methods: PMNs and hearts isolated from anesthetized male Sprague Dawley (SD) rats (~400g SO release assay, ~300g for perfused hearts). PMN SO release was stimulated using PMA (100nM) ± NTI 10-200 μM, KB 5-20 μM, or vehicle (0.5% DMSO; controls) and measured spectrophotometrically as a change in absorbance @ 550nm over 390 secs and cell viability was determined using 0.2% Trypan blue exclusion. We then infused NTI 1.25-5μM, KB 10-20μM, or naloxone (NX; negative control) 10μM for 5 min into perfused hearts, just prior to global I (30min)/R(45min). Cardiac LV function was measured via a pressure transducer and infarct size using 1% triphenyltetrazolium chloride staining in MIR assay. Data were analyzed using ANOVA and Fischers post-hoc analysis, with p&lt;0.05 considered statistically significant. Results: PMN SO release assay: KB 10 μM, KB 20 μM, NTI 100 μM (~3.75 mg/kg), and NTI 200 μM(~7.5 mg/kg) significantly attenuated PMA induced PMN SO release by ~40% (KB 10μM, n=7, p&lt;0.05), ~50% ((KB 20μM, n=7, p&lt;0.05), ~30% (NTI 100 μM, n=7, p&lt;0.05), 75% (NTI 200μM, n=7, p&lt;0.05) respectively when compared to untreated control (n=10). MIR assay: NTI 5μM, 2.5μM, 1.25μM and KB 20 μM reduced infarct size (4.8±3%, n=5, p&lt;0.05), (6.8±0.8%, n=6, p&lt;0.05), (12.2±3%, n=5), and (2.9±2%, n=5, p&lt;0.05) respectively compared to vehicle (14.1±2%, n=9) and NX 10μM controls (18±3%, n=3). NTI 5 μM and KB 20 μM had significantly improved LVEDP to (32.4±11%, n=5, p&lt;0.05) and (22.8±4%, n=5, p&lt;0.05) respectively compared to vehicle control (72.4±6%, n=9) and NX 10μM controls(54.2±8%, n=3) Conclusion: NTI and KB showed concentration-dependent effects on reducing PMN SO release. Both NTI (2.5μM, 5μM) and KB (20μM) reduced infarct size and improved LVEDP. The novel MOA of NTI is most likely mediated via a reduction in intracellular Ca2+ and subsequent hypercontracture during myocardial ischemia. The infarct reducing effect of NTI can benefit patients who will undergo elective PCI, CABG, and transplants. Funding: This study was funded by the Philadelphia College of Osteopathic Medicine, Department of Biomedical Sciences, Division of Research, and the Center for Chronic Diseases of Aging and Young Therapeutics, LLC. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Stress-Induced Proteasome Sub-Cellular Translocation in Cardiomyocytes Causes Altered Intracellular Calcium Handling and Arrhythmias.

The ubiquitin-proteasome system (UPS) is an essential mechanism responsible for the selective degradation of substrate proteins via their conjugation with ubiquitin. Since cardiomyocytes have very limited self-renewal capacity, as they are prone to protein damage due to constant mechanical and metabolic stress, the UPS has a key role in cardiac physiology and pathophysiology. While altered proteasomal activity contributes to a variety of cardiac pathologies, such as heart failure and ischemia/reperfusion injury (IRI), the environmental cues affecting its activity are still unknown, and they are the focus of this work. Following a recent study by Ciechanover's group showing that amino acid (AA) starvation in cultured cancer cell lines modulates proteasome intracellular localization and activity, we tested two hypotheses in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs, CMs): (i) AA starvation causes proteasome translocation in CMs, similarly to the observation in cultured cancer cell lines; (ii) manipulation of subcellular proteasomal compartmentalization is associated with electrophysiological abnormalities in the form of arrhythmias, mediated via altered intracellular Ca2+ handling. The major findings are: (i) starving CMs to AAs results in proteasome translocation from the nucleus to the cytoplasm, while supplementation with the aromatic amino acids tyrosine (Y), tryptophan (W) and phenylalanine (F) (YWF) inhibits the proteasome recruitment; (ii) AA-deficient treatments cause arrhythmias; (iii) the arrhythmias observed upon nuclear proteasome sequestration(-AA+YWF) are blocked by KB-R7943, an inhibitor of the reverse mode of the sodium-calcium exchanger NCX; (iv) the retrograde perfusion of isolated rat hearts with AA starvation media is associated with arrhythmias. Collectively, our novel findings describe a newly identified mechanism linking the UPS to arrhythmia generation in CMs and whole hearts.

Inhibition of the Sodium-Calcium Exchanger Reverse Mode Activity Reduces Alcohol Consumption in Rats.

Excessive and uncontrolled consumption of alcohol can cause alcohol use disorder (AUD), but its pharmacological mechanisms are not fully understood. Inhibiting the reverse mode activity of the sodium-calcium exchanger (NCX) can reduce the risk of alcohol withdrawal seizures, suggesting that NCX could play a role in controlling alcohol consumption. Here, we investigated how two potent inhibitors of NCX reverse mode activity, SN-6 (NCX1) and KB-R7943 (NCX3), affect voluntary alcohol consumption in adult male and female rats using the intermittent alcohol access two-bottle choice paradigm. Initially, animals were trained to drink 7.5% ethanol and water for four weeks before administering SN-6 and KB-R7934. Afterward, their alcohol intake, preference, and water intake were recorded 2 and 24 h after exposure to water and 7.5% ethanol. SN-6 significantly reduced alcohol consumption by 48% in male and 36% in female rats without affecting their water intake. Additionally, SN-6 significantly reduced alcohol preference in females by 27%. However, KB-R7943 reduced alcohol consumption by 42% in female rats and did not affect alcohol preference or water intake. These findings suggest that alcohol exposure increased NCX reverse activity, and targeting NCX1 could be an effective strategy for reducing alcohol consumption in subjects susceptible to withdrawal seizures.

A novel multi-port high-gain bidirectional DC–DC converter for energy storage system integration with DC microgrids

Bidirectional converters have often been used in numerous applications like DC microgrids, renewable energy, hybrid energy storage systems, electric vehicles, etc. The paper proposes a novel multi-port high-gain (NMPHG) bidirectional DC–DC converter that supports DC microgrid (DC-MG) applications. The main contributions of the proposed converter are high step-up/step-down conversion gain, multiple input ports, lower switch voltage stress, and lower component count owing to the single converter with multiple input ports for DC microgrid applications. The detailed operational principle, analysis, and design considerations of proposed NMPHG bidirectional DC–DC converters are discussed. Furthermore, the loss analysis, detailed comparison with similar works, and efficiency analysis with non-modalities during forward power flow (LV to HV) and reverse power flow (HV to LV) modes are presented. The efficiency of the proposed converter is found to be 93.8% in forward power flow and 92.9% in reverse power flow modes at rated power. Finally, a hardware prototype of the proposed NMPHG bidirectional DC–DC converters is implemented with 100 W in FPF mode and 200 W in RPF mode with a TMS320F28335 processor and validated with theoretical counterparts.

The effect of the four-tentacled collaboration on the self-propelled performance of squid robot

This study conducts a numerical investigation of the self-propelled performance of a bio-inspired squid robot equipped with four rigid tentacles, exploring three sets of collaborative modes. Leveraging the open-source platform OpenFOAM, we develop a self-propulsion module incorporating the dynamic overset grid technique to manipulate the complex motion of rigid tentacles. The driving system of a single tentacle is simplified into a two-link mechanism, where the phase difference between the links effectively emulates the oscillatory pattern of fish-like locomotion. The interaction of four tentacles gives rise to three distinct driving modes: reverse, homologous, and interlace modes. The results indicate that the homologous mode follows the hydrodynamic characteristics of fish-like waves, the interlace mode can cause the robot to deviate from the initial path, and the reverse mode outperforms the other two modes, exhibiting a higher ultimate cruising speed. Regardless of the propulsion process, the cruising performance of the robot is significantly influenced by the maximum amplitude angle θmax. An increase in θmax also contributes to an elevation in the instantaneous longitudinal force coefficient CFx, with the most pronounced impact observed in the homologous mode. The disparity among the three modes is also evident in the periodic pressure variation and flow field evolution patterns. The vortex distribution during steady-state moments systematically reveals the collaborative effects among the tentacles in different modes on the self-propulsion performance.

Exploring the Effectiveness of Reverse Engineering Pedagogy in a Culture-Oriented STEAM Course: from Heritage to Creativity

This research innovatively combines culture-based Culture-STEAM (C-STEAM) with Reverse Engineering pedagogy, aiming to explore the effectiveness of C-STEAM Reverse Engineering Teaching Mode on students’ Creative Thinking, Cultural Competence and Engineering Thinking. The study was conducted in an STEAM course of 90 undergraduate students major in Educational Technology. Based on the observation of the pilot study (Study 1), we refined the research design and accessed its efficacy through quasi-experimental design in the formal study (Study2). The results indicate that the experimental group outperformed the control group in aspects of Creative Thinking. Such as the Rationality, Concreteness, Generate Precise Ideas and Improve Idea. Both the experimental and control groups exhibited significant improvement in terms of the Value, Accuracy, and Logicality of Creative Thinking, overall Cultural Competence, Cultural Understanding, Cultural Identity, and Engineering Thinking. However, the two groups of students did not show significant progress in Generate Diverse Ideas, Flexibility and Evaluate Idea within Creative Thinking, as well as Cultural Practice within Cultural Competence. The study underscores the value of the C-STEAM Reverse Engineering Teaching Mode, particularly in enhancing students’ Creative Thinking, Cultural Competence, and Engineering Thinking, which provides a reference example for teachers to cultivate students’ ability. This study makes up for the gaps in C-STEAM related teaching mode innovation and explores possible directions for the future development of STEAM education. Nevertheless, it necessitates further refinement exploration of its internal mechanism.

Exploration of Reverse Assessment Mode Design for Engineering Courses Based on OBE Concept

Exploration of Reverse Assessment Mode Design for Engineering Courses Based on OBE Concept

Development of single point prediction model using artificial neural network and experimental validation for pump as turbine applications

This paper proposed a new approach based on artificial neural networks (ANNs) to select the most appropriate centrifugal pumps for reverse operation i.e. pump as turbines (PAT), by predicting parameters at Best Efficiency Point from pump mode data. Both, exhaustive experimental data of 49 pumps (specific speeds 9−104) collected from open literature and by in-house experimentation data, considered input data-set as pump and target data-set as PAT are used for training the ANN models with two different training functions: Levenberg–Marquardt and Bayesian regularisation. The proposed ANN prediction model shows a deviation lower than 10% compared to the respective experimental value. Additionally, the trained ANN model tested with four pumps (not included in training data sets of proposed models) shows maximum absolute deviation in head number, flow number, and efficiency within the 10%, 7%, and 6% range, respectively, compared to the experimental values. Furthermore, the efficiency of reverse mode evaluated for variation in rotational speed shows a maximum of 3.3% (within 5%) absolute deviation compared to respective experimental results. Overall, the ANNs based prediction model of PAT parameters is recommended compared to conventional models available in the literature as it gives superior results (less than 10% deviation) for practical application.

Numerical investigation of axial force of a centrifugal pump in the reverse mode

This paper numerically investigates the hydraulic performance and axial force of a low specific speed centrifugal pump in the turbine mode using the k - ω SST model. Numerical results are validated against the experimental data in the literature and a good agreement is observed. Results show that the rotation factor increases by flowrate, since the head, which is directly proportional to the transferred circumferential momentum, increases by the flowrate in the turbine mode. Moreover, values of rotation factors on both sides varies in radial direction due to geometrical parameters and, they reduce where larger axial gaps are present. Additionally, the pressure distributions on the hub and shroud sides are correlated with rotation factors on these areas. Interestingly, the axial position of the impeller plays an important role in the axial force of the PAT. By applying impeller movement of 5 mm from its original position, the point of zero axial force has shifted to higher flowrates and the maximum axial force is reduced 50%. Finally, with 10 mm movement of the impeller, the axial force exhibits distinct behavior so that its direction is preserved and, the returned magnitude is almost constant in the working range by 60% decrease in the maximum axial force.