Simplified Conditions Research Articles

Effects of the Seal Wire on the Nonlinear Dynamics of the Aircraft Engine Turbine Blades

Abstract Complicated systems made of multiple components are known to be difficult to model, considering their solutions can change dramatically even with the slightest variations in conditions. Aircraft engines contain such complicated systems, and some components in aircraft engines' turbines can cause significant changes in the system's overall response. Hence, this study is focused on investigating the behavior of a turbine blade of an aircraft engine and the effects of the contact between the blade and the seal wire on the dynamics of the blade-disk system. The investigation is performed via various numerical simulations in time and frequency domains. One sector of the bladed disk is modeled using the finite element method with the lock plate and the seal wire imposing cyclic symmetry boundary conditions in the static, modal, and frequency domain forced response analyses. In time domain analyses, the cyclic symmetry is replaced with simplified displacement restricting boundary conditions. The time domain analysis contains steady-state forced responses of the system. The results show that contact with the seal wire is not a major source of nonlinearity and damping. The contacts with the lock plate contribute more to the vibration damping than the seal wire. However, compared to the contacts at the root of the blade, both components remain less significant with regard to frictional damping and nonlinearity.

Frictional boundary condition for lattice Boltzmann modelling of dense granular flows

Hydrodynamic approaches that treat granular materials as a continuum via the homogenization of discrete flow properties have become viable options for efficient predictions of bulk flow behaviours. However, simplified boundary conditions in computational fluid dynamics are often adopted, which have difficulty in describing the complex stick–slip phenomenon at the boundaries. This paper extends the lattice Boltzmann method for granular flow simulations by incorporating a novel frictional boundary condition. The wall slip velocity is first calculated based on the shear rate limited by the Coulomb friction, followed by the reconstruction of unknown density distribution functions through a modified bounce-back scheme. Validation is performed against a unique plane Couette flow configuration, and the analytical solutions for the flow velocity profile and the wall slip velocity, as functions of the friction coefficient, are reproduced by the numerical model. The transition between no-slip and partial-slip regimes is captured well, but the convergence rate drops from second order to first order when slip occurs. The rheological parameters and the basal friction coefficient are calibrated further against the discrete element simulation of a square granular column collapsing over a horizontal bottom plane. It is found that the calibrated continuum model can predict other granular column collapses with different initial aspect ratios and slope inclination angles, including the basal slip and the complex internal flow structures, without any further adjustments to the model parameters. This highlights the generalization ability of the numerical model, which has a wide range of application in granular flow predictions and controls.

Investigating hygrothermal bending behavior of FG nanobeams via local/nonlocal stress gradient theory of elasticity with general boundary conditions

The bending response of functionally graded (FG) nanobeams under hygrothermal loading was investigated to emphasize the different scenarios that arise when using simplified and original boundary conditions. The governing equations were derived by using the principle of virtual work on the basis of the local/nonlocal stress gradient theory of elasticity. A Wolfram language code in Mathematica was written by the authors to develop a numerical investigation for different values of the material gradient index, the gradient length parameter, the nonlocal parameter, and considering two distinct types of thermal loading, that is, uniform temperature rise and heat conduction across the thickness of FG nanobeam cross-section.

Streamlining efficient and selective synthesis of benzoxanthenones and xanthenes with dual catalysts on a single support

Using two catalysts on a single support can improve reaction efficiency, higher yields, improved selectivity, and simplified reaction conditions, making it a valuable approach for industrial transformation. Herein, we describe the development of a novel and effective heterogeneous catalyst, WCl6/CuCl2, supported on graphitic carbon nitride (W/Cu@g-C3N4), which was synthesized under hydrothermal conditions. The structure and morphology properties of the W/Cu@g-C3N4 were characterized using various spectroscopic techniques, including FTIR, XRD, TEM, TGA, EDX, and SEM. The W/Cu@g-C3N4 support material enabled the rapid and efficient synthesis of benzoxanthenones and xanthenes derivatives in high yields under mild reaction conditions and short reaction times. The W/Cu@g-C3N4 catalyst was also found to be easily recyclable, and its catalytic performance did not significantly decrease after five times use. The findings suggest that W/Cu@g-C3N4 is a promising chemical synthesis catalyst with significant implications for sustainable and cost-effective organic synthesis.

Coevolutionary stability of host-symbiont systems with mixed-mode transmission

The coevolution of hosts and symbionts based on virulence and mode of transmission is a complex and diverse biological phenomenon. We introduced a conceptual model to study the stable coexistence and coevolution of an obligate symbiont (mutualist or parasite) with mixed-mode transmission and its host. Using an age-structured Leslie model for the host, we demonstrated how the obligate symbiont could modify the host’s life history traits (survival and fecundity) and the long-term growth rate of the infected lineage. When the symbiont is vertically transmitted, we found that the host and its symbiont could maximize the infected lineage’s evolutionary success (multi-level selection). Our model showed that symbionts’ effect on host longevity and reproduction might differ, even be opposing, and their net effect might often be counterintuitive. The evolutionary stability of the ecologically stable coexistence was analyzed in the framework of coevolutionary dynamics. Moreover, we found conditions for the ecological and evolutionary stability of the resident host-symbiont pair, which does not allow invasion by rare mutants (each mutant dies out by ecological selection). We concluded that, within the context of our simplified model conditions, a host-symbiont system with mixed-mode transmission is evolutionarily stable unconditionally only if the host can maximize the Malthusian parameters of the infected and non-infected lineages using the same strategy. Finally, we performed a game-theoretical analysis of our selection situation and compared two stability definitions.

Testing a tine weeder with artificial weeds in the controlled conditions of a soil bin

AbstractFarmers adjust physical weed control (PWC) tools to optimize performance based on soil conditions, as well as the size and species of weeds and crop. These many variables make PWC field research challenging. Research in controlled conditions would reduce variability and allow more rapid testing of PWC tools. To this end, we constructed a soil bin with a mobile tool carriage inside of a heated glasshouse. The soil bin was 2 m wide by 12 m long by 1 m high. The mobile tool carriage can operate PWC tools at 0.4–19.0 km h−1. Research methods were developed using a tine weeding tool and artificial weeds (AWs). The tine weeder offered uniform soil disturbance and, based on observation, has both uprooting and burial modes of action. Tine speed, angle and depth were evaluated in replicated soil bin and field experiments. Efficacy using AWs in soil bin was similar to efficacy based on surrogate and a real weed in one field experiment, but much greater than values measured in a second field experiment. Despite this inconsistency, we think that the simplified conditions of the soil bin system may be useful to test and prioritize tool settings or adjustments for field studies.

In situ crosslinked electrospun gelatin matrix with unoxidized tannic acid through stable hydrogen bonding

AbstractThis study aims to comprehend the mechanism of in situ crosslinking of gelatin (Gel) with tannic acid (TA) in an unoxidized environment due to TA's biocompatibility, hydroxyl group abundance, and non‐covalent bonding capability. The crosslinking of gelatin in an unoxidized medium offers advantages over oxidized, including enhanced biocompatibility and simplified reaction conditions. In this study, 20% (w/v) gelatin was crosslinked with varying TA percentages at 45°C, followed by electrospinning to obtain fibrous mats using acetic acid (AA) as the solvent. Increasing TA content resulted in a transition from nanoscale to microscale fiber diameter, indicating increased intermolecular and intramolecular hydrogen bonding. The tensile strength of Gel/TA‐5% was 5.6 MPa, surpassing the Gel/TA‐18% sample, suggesting fewer grafting and branching reactions within TA itself. The stability of the gelatin matrix was evaluated through fiber degradation rates within the initial 7‐day period, with percentages of 25%, 38%, 50%, and 85% observed for 18%, 15%, 10%, and 5% TA concentrations, respectively. The swelling percentage of fibrous mats in a buffer solution of pH 7.4 was highest for Gel/TA‐5% at approximately 290%. At lower TA concentrations, the crosslinking density is constrained; hence, progressive fiber disassembly at pH 7.4 improves the TA release, resulting in greater antibacterial efficacy in the first 4 h. Thus, electrospun fibers from in situ crosslinked gelatin with TA in an unoxidized medium holds promise for applications such as drug delivery and wound dressing, owing to the improved properties and enhanced release capabilities of the resulting gelatin‐based fibers

Biomechanics of abdominal aortic aneurysm in the framework of Windkessel effect and fully-developed inflow velocity via two-way non-linear FSI

Abdominal aortic aneurysm (AAA) is a pathological condition characterised by localised dilation of the infrarenal aorta, which can be fatal if rupture occurs. Current diagnostic criteria for repair are not patient-specific, but computational modelling may help to predict the potential growth and risk of AAA rupture accurately. This paper highlights how important using the Windkessel effect and fully-developed inflow velocity framework for the biomechanical analysis of AAA is; in other words, this research investigates how different boundary conditions in modelling methods affect the ability to correctly represent the biomechanics of AAA with complex non-linear parameters using a two-way fluid–structure interaction (FSI) technique. Time-averaged wall shear stress (TAWSS) is highly sensitive to boundary conditions, so unrealistic or simplified boundary conditions can lead to very different TAWSS results. This study also revealed that the use of outflow 3-element Windkessel boundary conditions on pulsatile pressure affects the flow pattern and increases the flow recirculation period. By accounting for the Windkessel effect and preventing backflow in numerical studies of AAA, the maximum displacement found in the distal branches can also be reduced. Models assuming plug velocity profiles overestimate peak wall stress by approximately 20% compared with models using fully developed parabolic inlet velocity profiles. This study incorporated a three-layer anisotropic material model and non-Newtonian fluid properties into the simulation, providing a more realistic representation of the effect of boundary condition selection on AAA mechanics. The results summarised from the parametric study could contribute to better prediction of AAA growth and rupture risk, and have important implications for the development of improved treatment strategies for AAA patients.

A Simplified Lattice Boltzmann Boundary Conditions for Gas Transport in Self-Affine Microchannels with an Inherent Roughness of in a Tight Reservoir

A simplified method of determining lattice Boltzmann boundary conditions based on self-affine microchannels with an inherent roughness in a tight reservoir is presented in this paper to address nonlinear efficiency problems in fluid simulation. This approach effectively combines the influence of rough surfaces in the simulation of the flow field, the description of L-fractal theory applied to rough surfaces, and a generalized lattice Boltzmann method with equivalent composite slip boundary conditions for inherent roughness. The numerical simulations of gas slippage in a two-dimensional plate model and rough surfaces to induce gas vortex reflux flow are also successfully carried out, and the results are in good agreement with the simulation results, which establishes the reliability and flexibility of the proposed simplified method of rough surfaces. The effects of relative average height and fractal dimensions of the rough surfaces under exact boundary conditions and equivalent coarsened ones are investigated from three perspectives, namely those of the average lattice velocity, the lattice velocity at average height position at the outlet, and the coefficient of variation for lattice velocity at average height position. It was found that the roughness effect on gas flow behavior was more obvious when it was associated with the enhanced rarefaction effect. In addition, the area of gas seepage was reduced, and the gas flow resistance was increased. When the fractal dimension of the wall was about 1.20, it has the greatest impact on the fluid flow law. In addition, excessive roughness of the wall surface tends to lead to vortex backflow of the gas in the region adjacent to the wall, which greatly reduces its flow velocity. For gas flow in the nanoscale seepage space, wall roughness hindered gas migration rate by 84.7%. For pores larger than 200 nm, the effects of wall roughness on gas flow are generally negligible.

Public service in wartime

The article is devoted to the organization of activities of public authorities under martial law. The normative legal acts adopted during the war regarding the peculiarities of the organization of labor relations of public servants and the activities of military administrations and their officials have been analyzed. The simplified procedure for admission to the civil service and the flexibility of the legislation in terms of civil service are highlighted. The opinion of scientists regarding the possibility of forming a personnel reserve and the formation of appropriate professional specialized lists of potential candidates for filling positions in the civil service was analyzed, taking into account the professional training of the specialist, his practical experience in the past, as well as the immediate place of work. Reservations were expressed regarding simplified conditions for appointment to civil service positions, which in a certain way violated the basic principles of civil service, namely stability, and professionalism. At the same time, the urgency of restoring the personnel reserve of the civil service was emphasized.The special administrative and legal status of regional military administrations is characterized, because, in addition to the specifics of formation and termination of activity, they are endowed with additional powers to introduce and ensure the implementation of measures of the legal regime and receive double subordination depending on the powers they exercise.It has been found that local self-government bodies (village, settlement, city council; its executive bodies and chairman) will continue to exercise the powers assigned to them by the Law of Ukraine «On Local Self-Government in Ukraine». There are no restrictions on such powers upon the introduction of martial law. Power decisions at the local level remain with local self government bodies, except for those where the military administrations of settlements are conducted.

A Simulation Framework for Electrochemical Processes with Electrolyte Flow

Software tools for simulating electrochemical processes (e.g. COMSOL Multiphysics, ELSYCA) are mostly of commercial type. Besides, three-dimensional simulations in complex cell geometries are known to become resource-expensive, as typically thin concentration boundary layers need to be resolved. This work presents a simulation framework for electrochemical processes based on the open source platform OpenFOAM. The finite volume method used and combined with domain decomposition is able to efficiently benefit from multi-core computer architectures. Our framework takes into account electrolyte flow, which is well known to affect mass transfer, and allows to consider multi-species electrolytes and forcing of the electrolyte. The stability and fast convergence of the method presented is found to rely on the linearization of the Butler-Volmer condition in the iterative solver. The framework is validated against an analytical solution valid for simplified conditions and an electrodeposition process at a conically shaped electrode in an external magnetic field. The latter exhibits transient departure of the concentration boundary layer from the cathode, and excellent agreement with COMSOL simulation results is found.

Lagrangian approach and shape gradient for inverse problem of breaking line identification in solid: contact with adhesion

A class of inverse identification problems constrained by variational inequalities is studied with respect to its shape differentiability. The specific problem appearing in failure analysis describes elastic bodies with a breaking line subject to simplified adhesive contact conditions between its faces. Based on the Lagrange multiplier approach and smooth Lavrentiev penalization, a semi-analytic formula for the shape gradient of the Lagrangian linearized on the solution is proved, which contains both primal and adjoint states. It is used for the descent direction in a gradient algorithm for identification of an optimal shape of the breaking line from boundary measurements. The theoretical result is supported by numerical simulation tests of destructive testing in 2D configuration with and without contact.

Developing a Biomechanical Testing Setup of the Pelvis-Part II: Experimental Testing.

Biomechanical testbench emulating the physiological loading of the pelvis is crucial in developing reconstructive implants for fragility fractures of the pelvis. Additionally, it will help understand the influence of the common daily loading on the pelvic ring. However, most reported experimental studies were mainly comparative with simplified loading and boundary conditions. In Part I of our study, we described the concept of the computational experiment design to design and construct a biomechanical testbench emulating the gait movement of the pelvis. The 57 muscles and joints' contact forces were reduced to four force actuators and one support, producing a similar stress distribution. The experimental setup is explained in this paper and some experimental results are presented. In addition, a series of repeatability and reproducibility tests were conducted to assess the test stand capabilities of replicating the gait physiological loading. The calculated stresses and the experimentally recorded strains showed that the pelvic ring response to the loading always follows the loaded leg side during the gait cycle. Furthermore, the experimental results of the pelvis displacement and strain at selected locations match the numerical ones. The developed test stand and the concept of computational experiment design behind it provide guidelines on how to design biomechanical testing equipment with physiological relevance.

Magnetic Resonance Velocimetry Measurements of Internal Blade Cooling Flow and Computational Fluid Dynamic Validation by Data Matching With the Experimental Data

Abstract The optimal Reynolds-averaged Navier–Stokes (RANS) turbulence model to be used in a Computational Fluid Dynamics (CFD) simulation varies depending on the application. Conventionally, the model is selected from benchmark tests and experience, but its performance is difficult to predict. For this reason, this study presents a cost-effective CFD validation routine, which uses three-dimensional experimental velocity data obtained in replicas of the specific flow system. Magnetic Resonance Velocimetry is used as the measurement technique. Since the objective is only the validation of the turbulence model, the experiment and the simulation are performed with simplified flow conditions, hence stationary isothermal isovolumetric flow without inertial forces. The routine applies a data-matching routine to align the two three-dimensional data sets before they are interpolated on a common grid. Various error metrics are presented, which provide the degree of the CFD modeling error and indicate its source. For demonstration, the validation routine is used to evaluate RANS-CFD results of a three-pass internal cooling system of a high-pressure turbine airfoil used in a small industrial gas turbine. The simulations are performed with the eddy-viscosity-based turbulence model k–ω shear stress transport (SST), the Reynolds-stress Speziale, Sarkar and Gatski (SSG), and baseline-Explicit algebraic Reynolds stress model turbulence (BSL-EARSM) models. The results indicate strong local errors in the examined turbulence models. None of the models performed well enough, underlining that every RANS-CFD application needs to be validated.

A study of the thermal performance prediction of embedded pipes in protection engineering based on multiple regression analysis

There are currently a large number of information equipment and similar devices that generate a significant amount of residual heat that must be eliminated through protection engineering. The ground heat exchanger can be useful in the treatment of residual heat due to their high efficiency and adequate concealment. In order to eliminate internal waste heat, the heat exchanger are laid within the inner surface of the surrounding soil at engineering entrances. In this study, the numerical heat transfer model of embedded pipes in protection engineering is developed based on the finite element software COMSOL. In addition, a total of eleven independent variables representing influencing factors of embedded pipe heat transfer were taken into account. The average heat transfer rate per meter, the heat exchanger effectiveness, and the total thermal resistance in the first 20 days of embedded pipe heat transfer were taken into account as dependent variables. Accordingly, a single factor regression model was developed in order to investigate the correlation between the three dependent variables and each independent variable, and the independent variables that had no significant influence on the dependent variables were removed. Then, the orthogonal experiment tables of 10 factor 5 level, 7 factor 5 level, and 4 factor 5 level were established based on the three dependent variables and independent variables, respectively. According to the experimental groups in the three tables, the step-by-step method in multiple regression analysis was employed in order to obtain the prediction formula of the average heat transfer rate per meter, the heat exchanger effectiveness, and the total thermal resistance in the first 20 days of embedded pipe heat transfer. At the same time, the influence degree of each independent variable on the dependent variables is obtained. Three evaluation indexes were selected to analyze the error of prediction results and numerical solutions. It was found that the prediction model was accurate overall. Furthermore, the prediction formula is compared to the analytical solution, and the results obtained by the two methods are comparable. The predictive solution is superior to the analytical solution because of the fewer simplified conditions and a lot of numerical simulation. These results indicate that, it is worth noting that the analysis of the influence of each factor and the predictive solution have a certain reference value for the future application of embedded pipes.

High-resolution Observations of H i in the IC 63 Reflection Nebula

Photodissociation regions (PDRs), where the (far-)ultraviolet light from hot young stars interact with the gas in surrounding molecular clouds, provide laboratories for understanding the nature and role of feedback by star formation on the interstellar medium. While the general nature of PDRs is well understood—at least under simplified conditions—the detailed dynamics and chemistry of these regions, including gas clumping, evolution over time, etc., can be very complex. We present interferometric observations of the 21 cm atomic hydrogen line, combined with [C ii] 158 μm observations, toward the nearby reflection nebula IC 63. We find a clumpy H i structure in the PDR, and a ring morphology for the H i emission at the tip of IC 63. We further unveil kinematic substructure, of the order of 1 km s−1, in the PDR layers and several legs that will disperse IC 63 in <0.5 Myr. We find that the dynamics in the PDR explain the observed clumpy H i distribution and lack of a well-defined H i/H2 transition front. However, it is currently not possible to conclude whether H i self-absorption and nonequilibrium chemistry also contribute to this clumpy morphology and missing H i/H2 transition front.

Memristor bridge synapse for better artificial neuron perceptron

In artificial neural networks, the fourth passive element memristor can be utilized as an electronic synapse that serves as the interface between neurons. The artificial neuron composed of the memristor bridge synapse not only has the characteristics of low power consumption and high integration but also has a more simplified circuit and weight change conditions. Particularly, it has the ability of bionic intelligent information processing. This paper established two novel synaptic structures on the basis of memristor bridges (type 1 and type 2) and then synthetically analyzed how to realize the artificial neuron perceptron. Herein, the artificial synapses (type 1 and type 2) have the following characteristics: continuous changes in synaptic weights (positive, negative, and zero) and memory properties. Among them, the type 2 memristor bridge has the advantage of a wider range of weight updates for the synaptic circuit, which can realize the function of the artificial neuron perceptron with less error. This work lays the foundation for the future exploitation of artificial intelligence.

Synergistically enhancing the electrical conductivity of carbon fibre reinforced polymers by vertical graphene and silver nanowires

Increasing the electrical conductivity of carbon fibre reinforced polymers (CFRPs) holds great promises for a range of applications, such as removing the need for metallic meshes in the protection against electromagnetic interference and lightning strikes. Herein, a hybrid method of improving the electrical conductivity of CFRPs by functionalizing carbon fibres with vertical graphene (VG) and modifying the matrix with silver nanowires (AgNWs) is introduced. The results revealed that the hybrid method increased the through-thickness and the in-plane electrical conductivities by almost 38 times and 39%, respectively, without adversely affecting mechanical properties. Finite element modelling revealed that the unprecedented synergy is due to the significant reduction in the contact resistance between carbon fibres by the combination of VGs on the fibres and the AgNWs in the matrix. Computational modelling showed that the electrical conductivity increase can reduce the joule heat density by around one thousand times under simplified lightning strike conditions.

Body Mechanics, Optimality, and Sensory Feedback in the Human Control of Complex Objects.

Humans are adept at a wide variety of motor skills, including the handling of complex objects and using tools. Advances to understand the control of voluntary goal-directed movements have focused on simple behaviors such as reaching, uncoupled to any additional object dynamics. Under these simplified conditions, basic elements of motor control, such as the roles of body mechanics, objective functions, and sensory feedback, have been characterized. However, these elements have mostly been examined in isolation, and the interactions between these elements have received less attention. This study examined a task with internal dynamics, inspired by the daily skill of transporting a cup of coffee, with additional expected or unexpected perturbations to probe the structure of the controller. Using optimal feedback control (OFC) as the basis, it proved necessary to endow the model of the body with mechanical impedance to generate the kinematic features observed in the human experimental data. The addition of mechanical impedance revealed that simulated movements were no longer sensitively dependent on the objective function, a highly debated cornerstone of optimal control. Further, feedforward replay of the control inputs was similarly successful in coping with perturbations as when feedback, or sensory information, was included. These findings suggest that when the control model incorporates a representation of the mechanical properties of the limb, that is, embodies its dynamics, the specific objective function and sensory feedback become less critical, and complex interactions with dynamic objects can be successfully managed.

Nanotomography Investigation of 3D Printed Batteries with a Water-in-Salt Gel Polymer Electrolyte

3D printing, also known as additive manufacturing, has emerged as a promising strategy to design and fabricate future energy storage devices. Although significant progress has been reported, current 3D printed battery designs are still limited by the choice of the electrolyte, such as ceramic or conventional toxic organic electrolytes. Here, we incorporated the latest developments in aqueous batteries into a novel 3D printable battery that can be fabricated directly in an ambient environment that is also more environmentally friendly. Specifically, a gel polymer electrolyte with a water-in-salt concept was introduced in our 3D-printed batteries. Combining their advantages, the resulting 3D printable batteries show promise for much simplified processing conditions. The structural, (electro-)chemical, and morphological evolution batteries are being investigated by synchrotron X-ray nanotomography and electrochemical analysis. Overall, our research explores the possibility of an easier and more environmentally friendly way to build 3D printable, customizable batteries for future technologies.