Specific Configuration Research Articles

Comparative analysis of performance of different types of Tesla valves

Abstract The Tesla valve is a valve with no moving parts. Its special configuration also allows the pressure drop of fluid passing through the Tesla valve from the reverse inlet to be much greater than the pressure drop of fluid passing through the Tesla valve from the forward inlet. Therefore, the Tesla valve has a certain degree of single pilot connectivity and pressure reduction capability. This article selected 8 common types of Tesla valves, By using numerical calculation method through Fluent simulation, the differences of resistance coefficient, pressure drop and Di value of 8 types of single-stage Tesla valves under three different working conditions were compared. In order to explore the performance of 8 kinds of Tesla valves under the three working conditions. At the same time, the relationship between the flow state and the structure of each part of the fluid before and after passing through the distributary pipe is analyzed. The simulation results show that due to the different structure of various Tesla valves, the flow rate, pressure and turbulent kinetic energy of the fluid inside the valve also have different changes. At the same time, there are many similarities in the flow state of some Tesla valves with similar structural types. Finally, according to the calculation results, the advantages and disadvantages of various types of Tesla valves and their applications are analyzed.

Macapá, a Brazilian equatorial magnetometer station: installation, data availability, and methods for temperature correction

Abstract. In the last 60 years, the largest displacement of the magnetic equator (by about 1100 km northwards) occurred in the Brazilian longitudinal sector. The magnetic equator passed by Tatuoca magnetic observatory (TTB) in northern Brazil in 2012 and continues to move northward. Due to the horizontal geomagnetic field geometry at the magnetic equator, enhanced electric currents in the ionosphere are produced – the so-called equatorial electrojet (EEJ). The magnetic effect of the EEJ is observed in the range of ±3° from the magnetic equator, where magnetic observatories record an amplified daily variation of the H component. In order to track the spatial and temporal variation of this phenomena, a new magnetometer station was installed in Macapá (MAA), which is about 350 km northwest of TTB. In this paper, we present the setup and data analysis of MAA station from November 2019 until September 2021. Because of its special configuration, we develop a method for temperature correction of the vector magnetometer data.

From single tube to multi-channel configuration: Constructing nanofiltration membranes with superior adhesion strength on the ceramic support by interfacial polymerization

Ceramic membranes with multi-channel configurations exhibit superior mechanical strength, high packing density, and high separation efficiency, making them more suitable for industrial applications than single tube and hollow fiber membranes. However, the preparation of thin-film composite (TFC) membranes on multi-channel ceramic supports remains a challenge because of the poor compatibility between organic and inorganic materials and their special configuration. In this study, nanofiltration membranes with a stabilized structure supported by 19-channel ceramic membranes were successfully prepared with improved adhesion strength and dynamic interfacial polymerization. TFC membranes with different channels exhibited uniform microstructure and stable performance. Specifically, polyethyleneimine, which served as a polymerization reactant, can be tightly wound on the surface of ceramic membranes via hydrogen bonding and van der Waals forces during interfacial polymerization. Owing to the enhanced cross-linked network interactions between the support and separation layers, the adhesion strength was significantly improved. Consequently, the optimized membranes maintained excellent rejection to MgCl2 of ∼94 % after the back-flush test under the pressure of 4 bar. Additionally, the multi-channel TFC membranes exhibited stable performance, with a pure water permeance of ∼14.9 LMH/bar and a molecular weight cut-off of 450 Da. When filtering sunset yellow for 10 h, the prepared membranes exhibited stable permeance and excellent rejection performance.

Pt Ternary Alloy with Rare Earth Metal - Pt5Ce-Co Intermetallic Nanoparticles as Highly Active Catalyst for Oxygen Reduction Reaction in PEMFCs

Alloying with rare earth elements is an important direction of exploring in Pt-based alloy design in oxygen reduction reaction (ORR), due to its special electronic configurations. Here we reported a ternary intermetallic alloy Pt5Ce-Co/C. The electronic valence state of Pt alloys was modified by the unique 4f orbital and the contraction effect of Ce, plus the additional active sites provided by the Co incorporation, optimizing the adsorption energy of the reaction intermediates, and effectively improving the electrocatalytic performance. The Pt5Ce-Co/C achieved 2.8 A∙mgPt -1 of mass activity in ORR catalysis, which can maintain 1.4 A∙mgPt -1 after 30k of accelerated stress test (AST). For membrane electrode assembly test, Pt5Ce-Co/C shows an initial mass activity of 724 mA∙mgPt -1, and a current density of 1876 mA∙cm-2 at 0.7 V under heavy-duty vehicle testing. This work provides an avenue to design advanced PGM ternary alloys by incorporating rare-earth metals to promote the catalyst performance.

Causal technological model for predicting void fraction and energy consumption in material extrusion process of polylactic acid

The rapid expansion of Additive Manufacturing (AM) technologies within the framework of Industry 4.0 raises important questions about their sustainability. Specifically, the widespread use of Material Extrusion (MEx) processes for polymeric materials necessitates a thorough evaluation of the possible balance between performance efficiency and sustainability, highlighting the need for further research into optimizing process parameters to ensure high product quality and reduced energy consumption. The present work focuses on Fused Filament Fabrication (FFF) technology, investigating the relationship between sustainability and print quality. A causal technology model is proposed to elucidate this relationship, underlining the impact of process parameters on defect generation and energy use. A real-time monitoring system for energy consumption measurements was employed to create an energy model that accounts for each component of the CreatBot F430 printer. An image analysis procedure was performed on a special configuration of the HIROX RH-2000 digital microscope to determine the void fraction of each sample. An experimental campaign was conducted, producing single-layer samples in polylactic acid (PLA) following a full factorial plan with four process parameters. A void fraction of up to 18 % was observed, with energy consumption per sample ranging between 638 J and 8843 J. Statistical analysis was performed to assess the impact of each process parameter and to determine operational ranges through the Response Surfaces Method. These results showed good agreement with the predicted conditions, demonstrating the model's effectiveness in supporting decision-making processes in technology selection.

Temperature impact on acoustic wave reflection in quasi-collinear acousto-optic devices.

Quasi-collinear geometry is a special configuration of acousto-optic (AO) diffraction that applies the acoustic wave reflection from the AO cell input optical face and provides an extremely large interaction length for achieving abnormally high spectral resolution of AO tunable filters. As a result, it becomes possible to implement the multifrequency diffraction which has found important applications for laser pulse shaping. The operation of quasi-collinear AO devices in the multifrequency diffraction regimen is accompanied by the appearance of the longitudinal and transverse temperature gradients in the crystal, mainly due to the acoustic power absorption. Temperature changes the AO cell material stiffness moduli, affecting the characteristics of the incident and reflected acoustic waves (propagation velocities and walk-off angles), and the reflection condition in general. On the example of paratellurite crystal is shown that the AO cell heating near the reflecting facet leads to a deviation of the reflected acoustic beam propagation direction from that specified during the AO cell manufacturing. The deviation magnitude depends on the reflection geometry choice and, in the paratellurite, may exceed several degrees, which adversely affects the AO diffraction characteristics, reducing the AO interaction efficiency and distorting the transmission function shape. The reflected beam deviation may be compensated by means of choosing the angle between the AO cell reflecting face and the piezoelectric transducer face, taking into account the operating AO device thermal regimen.

A mixed-dimensional formulation for the simulation of slender structures immersed in an incompressible flow

We consider the simulation of slender structures immersed in a three-dimensional (3D) flow. By exploiting the special geometric configuration of the slender structures, this particular problem can be modeled by mixed-dimensional coupled equations. Taking advantage of the slenderness of the structure and thus considering 3D/1D coupled problems raise several challenges and difficulties. From a mathematical point of view, these include defining well-posed trace operators of co-dimension two. On the computational standpoint, the non-standard mathematical formulation makes it difficult to ensure the accuracy of the solutions obtained with the mixed-dimensional discrete formulation as compared to a fully resolved one. Here we proposed to circumvent theses issues by imposing the fluid–structure coupling conditions on the 2D fluid–structure interface but in a reduced way still taking advantage of the 1D dynamic of the slender structure. We consider the Navier–Stokes equations for the fluid and a Timoshenko beam model for the structure. We complement these models with a mixed-dimensional version of the fluid–structure interface conditions, based on the projection of kinematic coupling conditions on a finite-dimensional Fourier space on each beam cross section. Furthermore, we develop a discrete fictitious domain formulation within the framework of the finite element method, establish the energy stability of the scheme, provide extensive numerical evidence of the accuracy of the discrete formulation, notably with respect to a fully resolved (ALE based) model and a standard reduced modeling approach.

Bioinspired Nanocomposite Dry Adhesives Applicable Over a Wide Temperature Range

AbstractBioinspired structural adhesives have shown great potential in the field of industrial manipulation and locomotion. However, such adhesives usually perform great adhesion performance at room temperature, reliable adhesion under high‐temperature conditions remains a major challenge and is rarely investigated, which severely limits the applications of current bioinspired adhesives. Here, a bioinspired adhesive structure based on fluororubber (FKM) and nanofillers is proposed. The adhesive structure has a “suction cup‐shaped” tip that mimics the special structural configuration of the adhesive setae of Dytiscus lapponicus, and the ability to regulate the structural modulus by adjusting the content of nanofillers, as well as exhibiting strong and contamination‐free adhesion (>350 kPa) with high adhesive efficiency (up to 77.7) in a wide temperature range (from room temperature to high temperatures (>200 °C)). Moreover, the adhesion performance can be enhanced by precisely regulating the structural modulus, and the enhancement mechanism is demonstrated based on the cohesive zone theory. The proposed adhesion strategy expands the application areas of dry adhesives from room‐ to high‐temperature conditions, especially for the pick‐up and transfer of thin and fragile materials that require high‐temperature operation, opening an avenue for the development of devices and systems based on dry adhesives.

Time Optimal Altitude-Hold Flight Mode Transition Strategy for a Class of Ducted Fan Tail Sitter UAV

For special tail sitter configurations such as the ducted fan tail sitter unmanned aerial vehicle (UAV), the widely used trajectory planning methodology based on differential flatness might not be applicable due to complex aerodynamic coupling effects. As a result, the flight mode transition remains a challenging task. In this paper, we address the time optimal altitude-hold flight mode transition issue for a class of ducted fan tail sitter UAV. The foundation of the framework is the dynamic transition corridor in which the limitation of jerk is particularly considered, aiming to thoroughly reflect the dynamic feature of aggressive maneuvers. Based on this, we propose a time optimal strategy to generate feasible altitude-hold transition trajectories. Simultaneous, by fully utilizing the manifestation of time optimal altitude-hold flight behavior revealed by the transition corridor, we try to tackle the time optimal altitude-hold transition by means of a novel model-free control scheme. Comparative simulations show that both of the transition strategies achieve satisfactory performance on time optimal altitude-hold transition in the absence of disturbance, while the model-free control scheme exhibits better robustness under external disturbance.

Massive twistor worldline in electromagnetic fields

We study the (ambi-)twistor model for spinning particles interacting via electromagnetic field, as a toy model for studying classical dynamics of gravitating bodies including effects of both spins to all orders. We compute the momentum kick and spin kick up to one-loop order and show precisely how they are encoded in the classical eikonal. The all-orders-in-spin effects are encoded as a dynamical implementation of the Newman-Janis shift, and we find that the expansion in both spins can be resummed to simple expressions in special kinematic configurations, at least up to one-loop order. We confirm that the classical eikonal can be understood as the generator of canonical transformations that map the in-states of a scattering process to the out-states. We also remark that cut contributions for converting worldline propagators from time-symmetric to retarded amount to the iterated action of the leading eikonal at one-loop order.

Tuning Iron Active Sites of FeOOH via Al3+ and Heteroatom Doping-Induced Asymmetric Oxygen Vacancy Electronic Structure for Efficient Alkaline Water Splitting.

Oxygen evolution reaction is the essential anodic reaction for water splitting. Designing tunable electronic structures to overcome its slow kinetics is an effective strategy. Herein, the molecular ammonium iron sulfate dodecahydrate is employed as the precursor to synthesize the C, N, S triatomic co-doped Fe(Al)OOH on Ni foam (C,N,S-Fe(Al)OOH-NF) with asymmetric electronic structure. Both in situ oxygen vacancies and their special electronic configuration enable the electron transfer between the d-p orbitals and get the increase of OER activity. Density functional theory calculation further indicates the effect of electronic structure on catalytic activity and stability at the oxygen vacancies. In alkaline solution, the catalyst C,N,S-Fe(Al)OOH-NF shows good catalytic activity and stability for water splitting. For OER, the overpotential of 10 mAcm-2 is 264mV, the tafel slope is 46.4 mVdec-1, the HER overpotential of 10 mAcm-2 is 188mV, the tafel slope is 59.3 mVdec-1. The stability of the catalyst can maintain ≈100h. This work has extraordinary implications for understanding the mechanistic relationship between electronic structure and catalytic activity for designing friendly metal (oxy)hydroxide catalysts.

Theoretical study of Jahn Teller effect on ion diffusion in trigonal prismatic 1H-MnO2

The trigonal prismatic MnO6 is a basic structural unit of Mn-based compound which has been seldom explored in theoretical and experimental studies. In this paper, the diffusion potential energy surfaces of Li+, Na+, K+, Mg2+, Al3+, and NH4+ ion in trigonal prismatic 1H-MnO2 are presented, which give an intuitionistic picture of the Jahn-Teller effect on the diffusion process. Based on the nudged elastic band method, it is found that the diffusion of ions in trigonal prismatic MnO2 is accompanied by consecutive structural distortion. The low diffusion barriers indicate trigonal prismatic MnO2 is a fast ion conductor. Band structure calculations show the semimetal characteristic of the intercalated compound, which is fit for high electrochemical performance. The details of the diffusion process are also highlighted. Our theoretical study provides an in-depth understanding and research on the fundamentals of the diffusion process in the special configuration in MnO2 and helps to develop novel high-performance electrodes.

Advanced computer architecture optimization for machine learning/deep learning

Abstract The recent progress in Machine Learning (Géron, 2022) and particularly Deep Learning (Goodfellow, 2016) models exposed the limitations of traditional computer architectures. Modern algorithms demonstrate highly increased computational demands and data requirements that most existing architectures cannot handle efficiently. These demands result in training speed, inference latency, and power consumption bottlenecks, which is why advanced methods of computer architecture optimization are required to enable the development of ML/DL-dedicated efficient hardware platforms (Engineers, 2019). The optimization of computer architecture for applications of ML/DL becomes critical, due to the tremendous demand for efficient execution of complex computations by Neural Networks (Goodfellow, 2016). This paper reviewed the numerous approaches and methods utilized to optimize computer architecture for ML/DL workloads. The following sections contain substantial discussion concerning the hardware-level optimizations, enhancements of traditional software frameworks and their unique versions, and innovative explorations of architectures. In particular, we discussed hardware including specialized accelerators, which can improve the performance and efficiency of a computation system using various techniques, specifically describing accelerators like CPUs (multicore) (Hennessy, 2017), GPUs (Hwu, 2015) and TPUs (Contributors, 2017), parallelism in multicore architectures, data movement in hardware systems, especially techniques such as caching and sparsity, compression, and quantization, other special techniques and configurations, such as using specialized data formats, and measurement sparsity. Moreover, this paper provided a comprehensive analysis of current trends in software frameworks, Data Movement optimization strategies (A.Bienz, 2021), sparsity, quantization and compression methods, using ML for architecture exploration, and, DVFS (Hennessy, 2017),, which provides strategies for maximizing hardware utilization and power consumption during training, machine learning, dynamic voltage, and frequency scaling, runtime systems. Finally, the paper discussed research opportunity directions and the possibilities of computer architecture optimization influence in various industrial and academic areas of ML/DL technologies. The objective of implementing these optimization techniques is to largely minimize the current gap between the computational needs of ML/DL algorithms and the current hardware’s capability. This will lead to significant improvements in training times, enable real-time inference for various applications, and ultimately unlock the full potential of cutting-edge machine learning algorithms.

Symmetric optical multipass matrix systems and the general rapid design methodology

We proposed an original type of multipass cell named symmetric optical multipass matrix system (SMMS), in which the same matrix patterns of various sizes can be formed on both sides. According to its special symmetric configurations, the SMMS design problem is modeled as a variant of the classical traveling salesman problem, which can be rapidly solved by evolutionary optimization algorithms. Two sets of 3-mirror SMMSs are designed, analyzed and built, which show superior characteristics of high stability, desirable beam quality and adjustable optical path lengths. Additionally, they can support simultaneous detection of multiple species with multi-laser channels. The proposed method is further extended to design a 4-mirror SMMS, which verifies the universality and robustness of the design methodology. The experimental observations are in consistent with the theoretical calculations. The newly proposed SMMSs have a broad application prospect in trace gas measurement.

Contributions of the extended ELISE and BATMAN Upgrade test facilities to the roadmap towards ITER NBI

ITER’s NBI systems are a first of its kind system with very challenging targets for the RF-driven ion source and the acceleration stage. In a step ladder approach, the ion source test facilities BATMAN Upgrade (BUG) and ELISE support the activities carried out at the Neutral Beam Test Facility, Padua, which is equipped with the ion source facility SPIDER and with MITICA being equivalent to the ITER Heating Neutral Beam injector (HNB), capable of operating at the full power and pulse length of the ITER HNBs. The contributions of the prototype ion source at BUG (1/8 scale) and the size scaling experiment ELISE (1/2 size ITER source) to the roadmap are manifold: for hydrogen operation the ion source performance is demonstrated in several sequential 1000 s pulses, whereas long pulse deuterium operation is limited by the heat load of the co-extracted electrons on the extraction grid. Measures like special magnetic filter field configurations or biasing of surfaces and improved Cs management are identified. Both facilities have recently been extended to full steady state compatibility and very first insights of the ion source performance with steady state extraction compared to the previously used beam blips (10 s extraction every 150 s) are already gained. A pulse length of 400 s, as required for the first deuterium campaigns at ITER, seems to be feasible soon, whereas the one hour pulse imposes the highest challenge to overcome. Investigations on beam divergence revealed a divergence at the upper limit of the acceptable value for the HNB. Measurements on the beam uniformity on the scale of beamlet groups and grid segments at ELISE demonstrated a uniformity of better than the required 90%. BUG and ELISE gave input to recent implementations at SPIDER; MITICA and ITER’s NBI. Still open points and challenges are addressed, for which a continuation of the step ladder approach is essential.

Breaking scaling relation of single-atom site via energy storage-release effect from adjacent carbon vacancy for low-temperature-resistant Fenton-like catalysis

To realize efficient antibiotics degradation in low-temperature water, single-atom FeN4 sites are engineered near carbon vacancies in a porous catalyst (PCvFe1-5) via thermal-etching and pyrolysis. The high-specific-surface-area (2202.80 m2 g−1) carbon support and dispersive Fe atoms co-enrich sulfamethoxazole and peroxymonosulfate to enhance the reactant collision frequency. Carbon vacancies allow the catalyst to deform for storing the peroxymonosulfate adsorption energies at FeN4 sites, which are subsequently released to facilitate -SO4H desorption for rapid site regeneration. This breaks the scaling relation suffered by single-atom sites, thereby reducing the thermodynamic energy barrier. Consequently, a low-temperature-resistant Fenton-like system with ultralow activation energy of 9.06 kJ mol−1 is constructed for sulfamethoxazole degradation. The normalized kinetic rate constant at 2 ℃ exceeds that of reported catalysts working at 25/30 ℃ by 1–2 orders of magnitude. Moreover, due to the special site configuration, PCvFe1-5 degrades sulfamethoxazole via both long-range catalyst-mediated electron transfer and short-range direct collision oxidation.

Rational design of precious tetrametallic single-cluster catalysts for electrocatalytic nitrate reduction reaction

Single cluster catalysts (SCCs) with high metal loading can exhibit extraordinary catalytic activity in electrocatalytic reactions, but the rational design of active sites remains a challenge. Herein, we proposed a series of SCCs with pyramid-shaped precious tetrametallic clusters anchored on g-CN monolayer (M4/g-CN) as efficient catalysts for the electrochemical reduction of nitrate to ammonia (NO3RR). By means of first-principle computations, the stability, catalytic mechanism and activity, as well as selectivity of these SCCs are systematically investigated. The calculation results show that most SCCs (Ru4/g-CN, Rh4/g-CN, Pd4/g-CN, Os4/g-CN, Ir4/g-CN, Pt4/g-CN) are thermodynamically stable due to the strong binding energy and significant charge transfer behavior between tetrametallic clusters and g-CN support. More important, the volcano curve between limiting potentials and adsorption free energy of NO3‾ can be established, in which Ir4/g-CN can exhibit optimal NO3RR activity due to its location of volcano top. Further analysis of electronic structures reveals that the special pyramid configuration can significantly promote the enrichment of charge on active site and elevate its d-band center, and thus facilitates the NO3RR. This finding pours new vigor into the development of the SCCs family.

Ductile design of single-pier steel and concrete hybrid coupled walls with hinged base and corner components

The seismic behaviour of hybrid coupled walls (HCWs) made of a single reinforced concrete (RC) wall connected to two steel side columns through steel links, named as single-pier HCWs (SP-HCWs), is studied through nonlinear finite element simulations. The design concept is that the steel links are intended to work as dissipative elements while the steel side columns and the RC wall should remain elastic. Given that previous studies highlighted difficulties in avoiding damage at the base of the RC wall due to the concentration of bending moment, this study focuses on a special configuration providing very limited damage at the base of the RC wall that could be rapidly and economically repaired. The original scheme of SP-HCW with fixed base is modified introducing a hinged connection combined with vertical steel elements, called corner components. A ductile design methodology is proposed and applied for proportioning 54 case studies with different building heights, coupling ratios, height-to-length ratios of the RC wall, in addition to different base conditions (fixed base, hinged base with corner components designed as non-dissipative elements, hinged base with corner components designed as dissipative elements). Results of nonlinear finite element analyses validate the design methodology and highlight the potentialities of the proposed solutions, showing the benefits of a hinged base with corner components.

Analysis and improvement of gas flow behaviour at the inlet duct of an industrial HRSG boiler through CFD modelling

This work analyses and improves the distribution of the flow of flue gases along the inlet duct of two industrial Heat Recovery Steam Generation (HRSG) boilers. The inlet duct connection with the boiler casing presents a special configuration, being axial for one boiler and radial for the other. The study was carried out using a 3D Computational Fluid Dynamics (CFD) modelling. The flow uniformity improvement is studied considering the introduction of baffles, perforated plates and the Part Elimination and Lattice Search (PELS) method. The Root Mean Square (RMS) axial velocity is used to determine uniform flow distribution. Its value must be equal to or below 0.2 m/s. Nevertheless, the pressure drop in the boiler must not increase by 1 mbar as compared to the standard case. After analysing the 3D CFD modelling results, our conclusion is that, in an axial configuration, the PELS method and a perforated plate (TAD44A65) located at the inlet of the recovery zone can improve the fluid flow uniformity to 40 %. For the radial configuration, only a perforated plate (TAD44A65) located at the inlet of the recovery zone improves fluid flow uniformity to 43 %.

Stochastic evaluation of quasi-zero stiffness magnetic spring using a reluctance-corrected analytical model

—In state of the art high-precision motion systems, which utilize magnetic levitation, a quasi-zero stiffness gravity compensation is one of the essentials to improve dynamic performance, eliminate position dependency and thus simplify controller design. Special configurations of permanent magnets, such as Halbach magnet arrays, can realize magnetic levitation as a form of magnetic spring. However, unlike conventional permanent magnet machines with large stiffness, the quasi-zero stiffness magnetic spring requires higher modeling accuracy for force estimation, which is affected by the nonlinear reluctance effect of permanent magnets. In this study, we propose an accurate magnetic modeling method for the quasi-zero stiffness magnetic spring. By correcting the reluctance effect of magnets, the proposed magnetic model achieves superior accuracy estimating levitation force and stiffness to the conventional surface current model. Using the reluctance-corrected magnetic model, tolerance analysis was performed to identify dominant geometric parameters affecting the uncertainty of the Halbach array magnetic spring performance. A Monte-Carlo simulation was used to estimate the overall tolerance of magnetic forces and stiffness. The experimental results fit in the tolerances.