Basic Modes Research Articles

TD-DFT calculation, equilibrium and kinetic adsorption study of removal of rose bengal dye by poly vinyl alcohol as a synthetic polymer adsorbent hybrid blend

Spectrophotometric study of the efficacy of the synthetic polymer such as polyvinyl alcohol in the removal of the dye Rose Bengal (RO) was examined. Different contact times, starting dye concentrations, adsorbent doses, dye solution temperatures, and pH values were tested. Density functional theory (DFT) with functional B3LYP and Hartree-Fock (HF) were used to investigate the optimal geometries, vibrational wavenumbers, vibrational band intensities, and atomic charges of 9VC. The researchers contrasted theoretical predictions for the basic vibrational modes with actual measurements. Using the functional B3LYP of DFT, we analyzed the hybrid organic dye (PVA+RO)HB such as the shape of geometry, electronic configuration, the capacity of polarizability, and second-order hyperpolarizability. The time-dependent density functional theory (TD- DFT), linked to a variety of hybrid functionals, was used in order to conduct research on the electronic absorption spectrum. Good agreement was found between the correlation coefficient values obtained from the Langmuir and Freundlich isotherm models, which were used to characterize the adsorption equilibrium. Pseudo-first-order kinetics was the best fit for the data on RO adsorption onto PVA. The values of enthalpy change and free energy change are negative and these confirm that our study concluded the exothermic and adsorption mechanism was spontaneous, respectively. The adsorption capacity was found to increase with increasing temperature. So, the kinetic parameters were evaluated from the temperature dependence of the adsorption capacity using the method of least squares.

Study on resonance of multi-degree-of-freedom structure based on modal orthogonal basis

Resonance of multi-degree-of-freedom system or structure is a basic and important concept in structural vibration theory, but it lacks a complete and rigorous definition. In order to establish an accurate concept of structural resonance, based on the concept of single-degree-of-freedom system resonance and modal orthogonality, this paper discusses the necessary conditions of system resonance by analyzing the displacement response of multi-degree-of-freedom vibration system, that is, while ensuring that the vibration frequency of the system (a certain natural frequency) is equal to the excitation frequency, its displacement response should also present the corresponding modal shape. An example of simply supported beam is used to illustrate its rationality. At the same time, the theoretical method of pure modal resonance of multi-degree-of-freedom system is given by rational allocation of excitation force. The pure modal resonance of multi-degree-of-freedom system or structure can be realized, which can be used to accurately identify the modal parameters of the structure. It is of great theoretical significance and engineering application value to discriminate the concept of multi-degree-of-freedom system or structure resonance.

A Discontinuous Galerkin Finite Element Method with Physical Modal Basis for the Neutron Transport Equation on Arbitrary Polygonal Meshes

The deterministic methods are efficient for solving the neutron transport equation (NTE), but suffer from discretization errors. The increasingly complex geometric models make spatial discretization errors the primary source of discretization errors. Considering that spatial discretization errors come from inaccurate geometric shape descriptions and low-accuracy numerical schemes, this paper develops a Discontinuous Galerkin Finite Element Method for the NTE on unstructured polygonal meshes to reduce spatial discretization errors. In this method, the physical modal basis is adopted to handle the polygonal mesh and to achieve high-order accuracy in a uniform and efficient way. The numerical results of various fixed-source and k-eigenvalue benchmarks demonstrate that the method developed in this paper can give accurate solutions on polygonal meshes with high convergence rates.

An Empirical Model of Ionospheric Total Electron Content Based on Tide‐Like Signature Modeling

AbstractAccurate modeling of the total electron content (TEC) benefits scientific research and practical application. In this study, the global ionospheric maps from the Center for Orbit Determination of Europe (CODE) covering the years 2000–2021 are utilized to develop an empirical model of TEC by superposing the tide‐like components in the ionosphere. The tide‐like components, including the migrating and non‐migrating ones, are first derived from the daily CODE TEC data. Then, the sine and cosine components of a tide‐like signature are separately decomposed into the basic modes as a function of the modified inclination latitude with the principle component analysis, and the temporal evolution is regressed to the solar radiation dependence and interannual variation. As such, the climatological behavior of tidal amplitudes and phases could be well parameterized, and the developed model is capable of reproducing the global TEC patterns. The modeled TEC agrees well with the CODE input data with zero systematic error and a low root mean square error of 3.849 TECu, demonstrating a good model performance. This developed model, associated with the parametric tide‐like signatures, could serve as a background for future investigations of the ionospheric responses to the forcing from below or above.

Assessment of Existing Masonry Resistance Using Partial Factors Approaches and Field Measurements

The vast majority of existing structures in Croatia, as well as in other European countries, are made of unreinforced masonry. The seemingly ideal building material presents a great challenge for engineers in earthquake-prone zones. Given that structural failure can have significant consequences in terms of loss of human lives as well as financial losses, a comprehensive structural reliability assessment is needed. Old existing masonry structures often do not have design documentation, and even when they do, the initial mechanical properties have almost certainly degraded over time. That is why in situ testing is of great importance, but masonry is also characterized by a large scattering of results. After recent severe earthquakes in Croatia, more than ever, there is a need for a more reliable assessment of existing masonry structures. This paper presents reliability approaches for resistance evaluation of existing masonry in a real case study where basic failure modes of the masonry were observed. First, the data recommended in standards were used, followed by the updated data obtained from the flat-jack test. Finally, the design value method (DVM) and the adjusted partial factor method (APFM) were used. These methods align with Eurocode standards for new structures but are also adaptable for the assessment of existing structures. Differences in the results between the existing and the new version of the standard were observed, as well as an increase in the obtained resistances with an increase in the complexity of the methods used. Also, the influence of in situ testing proved to be an important factor in the analysis.

Performance of Solar Steel Distillation with Using Different Types of Parameters and Material

Abstract: There is almost no water left on earth that is safe to drink without purification after 20-25 years from today. This is a seemingly bold statement, but it is unfortunately true. Only 1% of Earth's water is in afresh, liquid state, and nearly al of this is poluted by both diseases andtoxic chemicals. For this reason, purification ofwater supplies is extremely important. Keeping these things in mind, we have devised a model which wil convert the dirty/saline water into pure/potable water using the renewable source of energy (i.e. solar energy). The basic modes of the heat transfer involved are radiation, convection and conduction. The results are obtained by evaporation of the dirty/saline water and fetching it out as pure/drinkable water. The designed model produces 1.5 litres of pure waterfrom 14 litres of dirty water during six hours. The eficiency of plant is 64.37%. The TDS(Total Dissolved Solids) in the pure water is 81ppm.

On the Spatiotemporal Pattern Formation in Nonlinear Coupled Reaction–Diffusion Systems

Nonlinear coupled reaction–diffusion (NCRD) systems have played a crucial role in the emergence of spatiotemporal patterns across various scientific and engineering domains. The NCRD systems considered in this study encompass various models, such as linear, Gray–Scott, Brusselator, isothermal chemical, and Schnakenberg, with the aim of capturing the spatiotemporal patterns they generate. These models cover a diverse range of intricate spatiotemporal patterns found in nature, including spots, spot replication, stripes, hexagons, and more. A mixed-type modal discontinuous Galerkin approach is employed for solving one- and two-dimensional NCRD systems. This approach introduces a mathematical formulation to handle the occurrence of second-order derivatives in diffusion terms. For spatial discretization, hierarchical modal basis functions premised on orthogonal scaled Legendre polynomials are used. Moreover, a novel reaction term treatment is proposed for the NCRD systems, demonstrating an intrinsic feature of the new DG scheme and preventing erroneous solutions due to extremely nonlinear reaction terms. The proposed approach reduces the NCRD systems into a framework of ordinary differential equations in time, which are addressed by an explicit third-order TVD Runge–Kutta algorithm. The spatiotemporal patterns generated with the present approach are comparable to those found in the literature. This approach can readily be expanded to handle large multi-dimensional problems that appear as model equations in developed biological and chemical applications.

A multi-scale model-order reduction strategy for vibration analysis of coupled structures with local inhomogeneities

Although the wave finite-element method (WFEM) is an efficient numerical technique to analyze wave propagation characteristics and forced response of waveguides at medium and high frequencies, its application to large-scale and complex structures is still a challenge. In this paper, we introduce a model-order reduction (MOR) strategy for the WFEM to rapidly investigate the dynamics of coupled elastic systems involving one-dimensional waveguides with local inhomogeneities, such as steel bridges, fuselages and pipeline systems. The proposed method combines the advantages of mode-based component mode synthesis (CMS) and wave-based WFEM. A reduced modal basis is first established to describe the internal degrees of freedom using CMS. Subsequently, a reduced solution subspace considering the contribution of propagating and evanescent waves is constructed by the duality of Bloch’s formulations for the waveguide part, while wave scattering characteristics of the coupled element are used to quantify the influence of fixed-interface modes determined by CMS. Structural dynamic response can be then efficiently calculated using a dynamic stiffness matrix method. The performance of the MOR method in dispersion analysis and forced-response calculation is elaborately illustrated via an example of a steel beam with a diaphragm. The influence of the diaphragm on structural dynamic response is explained from the perspective of wave-propagation characteristics. Finally, the method is applied to a real steel–concrete composite girder, and the effects of the number and thickness of diaphragms on the vibration of each plate of the girder are discussed to provide some suggestions on vibration control.

Investigations and analysis of current modes and emission properties of emitters with different tip shapes for ionic liquid electrospray thrusters

High-precision ionic liquid electrospray thrusters (ILETs) can be used for space exploration missions such as orbital control, attitude adjustment or drag-free control. A micro-newton thrust can be generated by the emitter, which is the most critical part of the thruster. The study was conducted on an ionic liquid electrospray thruster with active propellant feed subsystems. In order to investigate the effect of emitter tip shape on the emission properties of the thruster, four types of emitters have been proposed and fabricated, namely flat emitter, unilateral emitter, bilateral emitter, and tapered emitter. It is found that the basic current modes of the four emitters are similar, but the magnitude of voltages for current mode transitions are different. The voltages of current mode transitions under the unilateral emitter are significantly larger than those of the other three kinds of emitters. Furthermore, the processes to establish and cease emission of ILETs with capillary emitters were first studied based on startup delay and end-up delay. Mathematical models were established to calculate the startup delay and end-up delay of the four emitters. The calculated results agree well with the experiments over 95 % by creatively adding a shape coefficient in the models. Finally, the stable emission regions based on beam currents and current noises of the four emitters were analyzed and demonstrated. As a result, the tapered emitter has the largest stable emission region, while the unilateral has the advantage of maintaining steady emission at extremely low flow rate and voltage. Overall, the emission performance of the tapered emitter is the best, while the bilateral emitter is slightly inferior, both significantly superior to the other two kinds of emitters. However, the bilateral emitter with a uniform profile could be produced in large quantities quickly and cheaply, which is suitable for upcoming massive space exploration missions.

Conceptual typologies of learning communities for master’s course students using a publications exemplar: a comparative institutional analysis

ABSTRACT With an increased emphasis being placed on the importance of postgraduate students publishing articles in international journals, many students may feel a need to organise learning communities with faculty members or their peers to support this aspirational activity. Most research in this area is related to doctoral students, but places relatively little focus on master ones. This study aims to conceptualise possible patterns for the formation of such learning communities through a comparative institutional analysis, based on a qualitative game theoretic discussion. We propose four basic learning community modes: individual (i.e. one-on-one consultancy by faculty staff reviewing individual student drafts); lecture (i.e. writing lectures led by a faculty staff member); peer collaboration (i.e. only students working together on their drafts); and, solo (i.e. individual students working on their own manuscripts without structured support). This is one of a small number of attempts to formalise and provide an analytical model of possible types of coordination between faculty members and master’s course students regarding learning community activities. Our analysis indicates that the most efficient strategy for students reaching the point of successful submission is to have faculty members support them by facilitating groups of student authors and providing feedback on their drafts.

Bring memristive in-memory computing into general-purpose machine learning: A perspective

In-memory computing (IMC) using emerging nonvolatile devices has received considerable attention due to its great potential for accelerating artificial neural networks and machine learning tasks. As the basic concept and operation modes of IMC are now well established, there is growing interest in employing its wide and general application. In this perspective, the path that leads memristive IMC to general-purpose machine learning is discussed in detail. First, we reviewed the development timeline of machine learning algorithms that employ memristive devices, such as resistive random-access memory and phase-change memory. Then we summarized two typical aspects of realizing IMC-based general-purpose machine learning. One involves a heterogeneous computing system for algorithmic completeness. The other is to obtain the configurable precision techniques for the compromise of the precision-efficiency dilemma. Finally, the major directions and challenges of memristive IMC-based general-purpose machine learning are proposed from a cross-level design perspective.

On the Question of the Sign of Size Effects in the Elastic Behavior of Foams

Due to their good ratio of stiffness and strength to weight, foam materials find use in lightweight engineering. Though, in many applications like structural bending or tension, the scale separation between macroscopic structure and the foam’s mesostructure like cells size, is relatively weak and the mechanical properties of the foam appear to be size dependent. Positive as well as negative size effects have been observed for certain basic tests of foams, i.e., the material appears either to be more compliant or stiffer than would be expected from larger specimens. Performing tests with sufficiently small specimens is challenging as any disturbances from damage of cell walls during sample preparation or from loading devices must be avoided. Correspondingly, the number of respective data in literature is relatively low and the results are partly contradictory.In order to avoid the problems from sample preparation or bearings, the present study employs virtual tests with CT data of real medium-density ceramic foams. A number of samples of different size is “cut” from the resulting voxel data. Subsequently, the apparent elastic properties of each virtual sample are “measured” directly by a free vibrational analysis using finite cell method, thereby avoiding any disturbances from load application or bearings. The results exhibit a large scatter of the apparent moduli per sample size, but with a clear negative size effect in all investigated basic modes of deformation (bending, torsion, uniaxial). Finally, the results are compared qualitatively and quantitatively to available experimental data from literature, yielding common trends as well as open questions.

A modal decomposition approach to topological wave propagation

The design of valley-Hall topological insulators is typically informed by analyzing the primitive unit cell, using the Berry curvature of the Bloch-eigenmodes to predict energy localization on the domain boundary, or the dispersion diagram of the semi-infinite lattice to predict the group velocity of topological waves. However, practical systems are finite in size and the propagating topological wave is composed of a finite bandwidth as guaranteed by the Fourier uncertainty principle. Hence, the propagation predicted by the ideally infinite lattice for a given frequency deviate from practical topological systems driven by finite bandwidth wave packets. In this work, we demonstrate that the propagating topological waves in valley Hall lattices can be interpreted using the linear degenerate modal basis. We show that a small subset of closely spaced modes comprise the topological waves, which enables the construction of analytical reduced-order models that accurately capture the topological wave. This result is related to the sparse density of the modal spectrum inside the topological band gap, which allows for the energy to be carried nearly completely by a narrow band of spectrally isolated eigenmodes that are spatially localized along the domain boundary. This result is then employed to refine group velocity predictions of propagating topological waves with respect to input signal bandwidth and frequency by matching the modal spectrum to the supercell dispersion diagram describing the semi-infinite system. Moreover, we utilize the damped modal spectrum to characterize variations in wave group velocity in damped topological lattices and predict edge-to-bulk transitions. Hence, this work establishes a framework for accurately characterizing undamped and damped topological wave propagation in quantum valley Hall systems using the machinery of classical dynamics.

Power Management of Renewable-Grid Integrated Smart e-Mobility System for Light Electric Vehicles

This work proposes an architecture that integrates renewable energy sources or photovoltaic (PV) systems with the dc-link of utility and acts as primary and secondary energy sources to the electric vehicle (EV) load. The proposed architecture contains the dc-link cascaded single-stage conventional H-bridge, which superimposes a dual boost interleaved (DBI) topology with a series-series resonant (SSR) converter system. Further, the SSR side contains a wireless charging system followed by the diode bridge rectifier and a Li-ion battery as an EV load. It is challenging to integrate the above system with reduced power stages. Moreover, achieving power control in an integrated single-stage system makes it more complex. Therefore, this work includes a fundamental operation and analysis of the proposed architecture. A system-level power management scheme is also provided to control the proposed system. This power management scheme includes four basic power modes that comply with different system conditions during its operation. Furthermore, the essential of the power management scheme is to ensure that the utility should support the charging structure during excess or shortage of power flow between PV and EV load. Finally, the proposed architecture has been validated using MATLAB simulation and a 1.2kW hardware prototype.

Le détachement paradoxal en la Présence de l’Infini

The Presence of the Infinite in human existence may be considered as mystery. If so, then believers endorse three a priori. Firstly, human person, as finite, has the intuition of the Infinite that opens the way to an existential positioning in front of the Infinite. Secondly, the intuition of the Infinite gives birth to an idea of the Infinite, and eventually to the desire of the Infinite (the desire to be United with such Infinite). Thirdly, the idea of the Infinite allows believers to develop a fragmentary understanding of the ultimate ground for being and existence. The Infinite is thus unknowable by human (finite) beings. Being in the Presence of the Infinite then becomes a paradox that requires detachment. Being detached is being absolutely centered on God rather than any other existential concern. It requires two basic modes of detachment : the detachment from language and conceptual knowledge, on one hand, and the detachment of the self in relation with the Infinite, on the other hand. Being attached is considering God as a being who is alongside innumerable beings. Detachment rather allows believers to avoid the interpretative trap of the objectification of God.

SBFEM with reduced modal basis for hydrodynamic bearings

AbstractThe numerical effort of transient rotordynamic simulations is often dominated by the computation of nonlinear hydrodynamic bearing forces. These forces are described by the Reynolds equation and need to be computed at every time step. Usually, numerical models, analytical approximations, or look‐up table techniques are employed, depending on the desired tradeoff between accuracy and computational cost. In recent studies, a semi‐analytical approach based on the scaled boundary finite element method (SBFEM) has been developed as an efficient alternative to these methods. The partial differential equation is transformed into a system of ordinary differential equations, leading to an eigenvalue problem. Here, the numerical effort can be further decreased by means of a modal reduction, which is investigated in this study. The shaft eccentricity determines the smoothness of the hydrodynamic pressure field and is identified as an adequate indicator as to what subset of eigenvalues and eigenvectors should be considered in the solution.

Leading basic modes of spontaneous activity drive individual functional connectivity organization in the resting human brain

Spontaneous activity of the human brain provides a window to explore intrinsic principles of functional organization. However, most studies have focused on interregional functional connectivity. The principles underlying rich repertoires of instantaneous activity remain largely unknown. We apply a recently proposed eigen-microstate analysis to three resting-state functional MRI datasets to identify basic modes that represent fundamental activity patterns that coexist over time. We identify five leading basic modes that dominate activity fluctuations. Each mode exhibits a distinct functional system-dependent coactivation pattern and corresponds to specific cognitive profiles. In particular, the spatial pattern of the first leading basis mode shows the separation of activity between the default-mode and primary and attention regions. Based on theoretical modelling, we further reconstruct individual functional connectivity as the weighted superposition of coactivation patterns corresponding to these leading basic modes. Moreover, these leading basic modes capture sleep deprivation-induced changes in brain activity and interregional connectivity, primarily involving the default-mode and task-positive regions. Our findings reveal a dominant set of basic modes of spontaneous activity that reflect multiplexed interregional coordination and drive conventional functional connectivity, furthering the understanding of the functional significance of spontaneous brain activity.

Linear and Nonlinear Modes and Data Signatures in Dynamic Systems Biology Models

The particulars of stimulus–response experiments performed on dynamic biosystems clearly limit what one can learn and validate about their structural interconnectivity (topology), even when collected kinetic output data are perfect (noise-free). As always, available access ports and other data limitations rule. For linear systems, exponential modes, visible and hidden, play an important role in understanding data limitations, embodied in what we call dynamical signatures in the data. We show here how to circumscribe and analyze modal response data in compartmentalizing model structures—so that modal analysis can be used constructively in systems biology mechanistic model building—for some nonlinear (NL) as well as linear biosystems. We do this by developing and exploiting the modal basis for dynamical signatures in hypothetical (perfect) input–output (I-O) data associated with a (mechanistic) structural model—one that includes inputs and outputs explicitly. The methodology establishes model dimensionality (size and complexity) from particular I-O datasets; helps select among multiple candidate models (model distinguishability); helps in designing new I-O experiments to extract “hidden” structure; and helps to simplify (reduce) models to their essentials. These modal analysis tools are introduced to NL enzyme-regulated and protein–protein interaction biosystems via nonlinear normal mode (NNM) and quasi-steady state approximation (QSSA) analyses and unified with linear models on invariant 2-dimensional manifolds in phase space, with properties similarly informative about their dominant dynamical properties. Some automation of these highly technical aspects of biomodeling is also introduced.

Development of human-touch smart armband for tele-haptic communication using a fabric-based soft pneumatic actuator

This study aimed to develop a human-touch smart armband that can transport emotional tactile stimuli to individuals in distant places. To simulate human touch stimuli, a soft pneumatic actuator (SPA) which we refer to in this study as “SPA touch,” of size 7 cm × 7 cm and thickness 0.3 cm was designed using fabric and silicone with nine touch points, which can be individually inflated and allocated within the actuator. The use of thermoplastic polyurethane-coated fabric as a backing material helps obtain one-side inflation toward the skin effectively. By controlling the position and duration time of the inflation of the nine touch points, three basic touch modes (“Touch,” “Double touch,” and “Drag”) and three emotional tactile gestures (“Patting,” “Hugging,” and “Caressing”) were programmed using Python. The evaluation of the operating performance of the basic touch modes and emotional tactile gestures showed that “SPA touch” could properly create and transmit touch stimulation remotely. The human-touch smart armband developed in the process of this study can be used for novel tele-haptic communication with individuals in distant places, such as nursing homes.

Simulation of binary collision of liquid drops using smoothed particle hydrodynamics with adaptive spatial resolution.

The binary collision of water drops in the air is studied by two-dimensional numerical simulation utilizing smoothed particle hydrodynamics with adaptive spatial resolution. The numerical method is validated by comparing the simulation with experiment. Three basic modes of equal-size drop collision are observed in numerical simulations at Weber number 3≤We≤120 and impact parameter 0≤x≤0.8, namely, reflexive separation, stretching separation, and coalescence collision. Based on the numerical results of different collision modes, the specific phenomena, evolution patterns, and physical principles are discussed. In particular, the detailed processes of the necking phenomenon and the propagation of surface wave in separation collision are obtained, corroborating the "end-pinching" theory proposed in the literature. At higher Weber numbers, the recoalescence of satellite drops is observed. The collision of unequal-size drops is also investigated. The effects of three dimensionless parameters, namely, drop diameter ratio, Weber number, and impact parameter are discussed. The physical mechanisms of some special phenomena are expressed in detail.