Classical Configuration Research Articles

Analysis and design of PEM fuel cell/photovoltaic system to supply a traffic/light signals in Ouargla city based on field experience

The idea of powering street traffic lights using stand-alone renewable systems has attracted much attention, in recent years. Classical configuration of photovoltaic (PV) cells connected to a battery bank is the most commonly employed approach in this regard. However, the low sunlight intensity in a lot of places around the globe, as well as the short-stage batteries autonomy, make this kind of systems technically less adequate. In this paper, and in order to improve the efficacy of the PV-based classical traffic lights, a hybrid system composed of a PV panel, battery, and a small PEM fuel cell is proposed. The goal is to develop a more reliable, efficient, and clean power supply that able to meet the load demands of the traffic lights during all the year. Ouargla region in Algeria (Latitude of 31°95′ N, Longitude of 5°24′E, and Altitude of 0.141 km above Mean Sea Level) is taken as a case study to be investigated. The influence of stack temperature on PEMFC I–V characteristics are also given and analyzed, furthermore, the proposed Whale Optimization Algorithm WOA is used to solve the parameters identification problems of the PEMFC electrochemical model. Comprehensive experiment results and analyses indicate that the proposed algorithm has good performance considering a two temperature samples (26 °C and 39 °C), in such a way, the lowest Mean Absolute Error reaches 0.0589 V and 0.1044 V respectively. Finally, an optimal computer program to design the system components is established and the results show that the optimum PV area, hydrogen generator number, and battery capacity for powering regular light signals are obtained to be 0.72 m2, one electrolyser of 60 l/h, and one battery of 80 Ah, respectively.

A novel dynamic compensation method for a contact probe based on Bayesian inversion

Undesired dynamic characteristics constitute a major source of dynamic measurement errors for contact probes and seriously restrict the improvement of measurement velocity and accuracy. However, the dynamic characteristics of probes are difficult to improve through structural enhancement. A novel dynamic compensation method based on Bayesian inversion was proposed to improve the dynamic performance of probe systems. On the basis of the dynamic model of probe systems, a Bayesian inversion model for dynamic compensation was derived and established. A Bayesian compensation model was developed for a self-developed contact probe. A recursive algorithm was also adopted to obtain the estimated state parameters that reflect the output values of dynamic compensation. The compensation effect was verified by simulation and experimental results. The overshoot of the probe system was reduced from 99.15% to 16.46%, and the settling time was shortened from 2.4825 s to 0.1452 s. The compensation effect of this method was better than that of the classical pole-zero configuration technique. The proposed method can effectively improve the time-domain tracking performance and broaden the frequency-domain measurement bandwidth of the probe system at the same time. The suggested approach is practical, effective, and can be widely used for dynamic system compensation.

A frequency response function-based optimization for metamaterial beams considering both location and mass distributions of local resonators

To date, phononic crystals/metamaterials normally adopt classical periodic configurations, and optimization strategies for them are based primarily on dispersion relations from a repeated unit cell. In this study, a frequency response function (FRF) based optimization scheme is presented for a locally resonant metamaterial beam that considers both the resonant frequencies and distribution locations of the resonators. Three optimization objectives involving (1) broadband, (2) multi-band, and (3) high-attenuation characteristics are exploited as study cases, and a single-objective genetic algorithm is used to determine the optimal solutions for the prescribed bandgap targets. The spectral element method is used as an analytic formulation to determine the metamaterial FRFs, and the finite element method is used to validate the effectiveness of the optimization strategy. The results reveal that these objective bandgap characteristics can be enabled without increasing the resonator mass following the proposed optimization procedure. This shows the potential of adjusting the locations and resonance frequencies of resonators in metamaterial beams beyond the widely accepted periodic structures. The most important finding of this study is that promising bandgap properties can be easily realized with only single-degree-of-freedom resonators instead of designing more complex ones or multi-resonators. This FRF-based optimization method can be considered as a simple but instructive strategy for optimal or inverse designs in metamaterials.

Rotating-Frame Overhauser Transfer via Long-Lived Coherences

Solution-state distance restraints for protein structure determination with Ångström-level resolution rely on through-space transfer of magnetization between nuclear spins. Such magnetization transfers, named Overhauser effects, occur via dipolar magnetic couplings. We demonstrate improvements in magnetization transfer using long-lived coherences (LLCs)—singlet-triplet superpositions that are antisymmetric with respect to spin-permutation within pairs of coupled magnetic nuclei—as the magnetization source. Magnetization transfers in the presence of radio-frequency irradiation, known as ‘rotating-frame’ Overhauser effects (ROEs), are predicted by theory to improve by the use of LLCs; calculations are matched by preliminary experiments herein. The LLC-ROE transfers were compared to the transmission of magnetization via classical transverse routes. Long-lived coherences accumulate magnetization on an external third proton, K, with transfer rates that depended on the tumbling regime. I,S →K transfers in the LLC configuration for (I,S) are anticipated to match, and then overcome, the same transfer rates in the classical configuration as the molecular rotational correlation times increase. Experimentally, we measured the LLC-ROE transfer in dipeptide AlaGly between aliphatic protons in different residues K = Ala − Hα and (I,S) = Gly − Hα1,2 over a distance dK,I,S = 2.3 Å. Based on spin dynamics calculations, we anticipate that, for such distances, a superior transfer of magnetization occurs using LLC-ROE compared to classical ROE at correlation times above τC=10 ns. The LLC-ROE effect shows potential for improving structural studies of large proteins and offering constraints of increased precision for high-affinity protein-ligand complexes in slow tumbling in the liquid state.

Model of the low temperature magnetic phases of gadolinium gallium garnet

The magnetic behaviour of gadolinium gallium garnet in an external magnetic field at zero temperature is considered. For high fields a classical spin model of the gadolinium ions predicts a spin configuration that is periodic at the level of the smallest repeating unit cell. The quantum version of the model is treated via a truncated Holstein–Primakoff transformation with axes defined by the classical spin configuration, and the magnon excitation bands are calculated. The model predicts a transition in the field range of 1.9–2.1 T, sensitive to the direction of the applied field, which is caused by one or more magnon modes becoming soft as the field is decreased. In general the soft modes occur at incommensurate wavevectors and therefore break the periodicity of the spin configuration below the transition. One exception occurs when the field aligns with one of the principle crystal axes, in which case periodicity of the spin configuration is found to be maintained on a larger crystallographic cubic cell even below the transition. This simple case is studied in more detail. Comparisons are drawn with existing experimental data, and further experimental tests of the model are suggested.

Chord failure resistance of 3D cut welded connections with CHS columns and through I‐beams

AbstractThis paper investigates the mechanical behaviour of a novel typology of steel beam‐to‐column connection made by welding circular hollow section (CHS) columns with through‐all double‐tee beams. Such connection represents an alternative to the classical configuration with the I‐beam simply welded to the external surface of the hollow profile for which Eurocode 3 part 1.8 provides specific design rules resulting from the “ring model” theory. The main features of connections with through‐all beams derive from a change of the resisting mechanism which leads to a significant increase of stiffness and resistance. Nevertheless, such a change of the mechanical behaviour, strictly affected by the different plasticity pattern, has not been embedded in the ring model theory, yet. Instead, experiments and finite element (FE) simulations have been carried out proving that the resistance exhibited by CHS to through‐all axially loaded plates is about 2‐3 times higher than resistance referred to CHS to branch plates. The last‐mentioned connections represent the basic components in order to assess the flexural strength of connections made by CHS and I‐beams. This means that doubling the resistance of connections with beam welded to the external surface of the column, as some studies have proposed, leads to a significant underestimation of the resistance.Within this framework, in this paper the flexural resistance of connections with CHS columns and through‐all I‐beams is assessed by developing experimental tests and analytical models aiming to propose a new design equation. Specifically, two cyclic ad two monotonic tests on real scale beam‐to‐column connections have been executed at the laboratory of the University of Salerno. Subsequently, finite element (FE) models have been calibrated and verified against the experimental results. Then, the developed FE models have been extended to perform parametric analyses to be used to verify the accuracy of a new theoretical approach able to predict the resistance of such a kind of connections. The theoretical approach has been developed basing on the upper‐bound theorem and exploiting the previous knowledge based on the so‐called ring model. The proposed formulation, when compared to the available experimental data and FE simulations, have proved to exhibit a high accuracy.

Dynamic Analysis of Two Parallel Rectangular Plates Coupled with Mechanical Links

The plate-type structures are classical configurations in many engineering applications. A comprehensive understanding of the structural dynamic mechanisms is of great significance. An analytical modeling approach is established and applied to investigate the dynamic characteristics of a plate system. The model encompasses two parallel elastically restrained rectangular plates coupled through mechanical links. The linear stiffness parameters are used to simulate various structural boundary conditions and mechanical links. The wave propagation of the plate structure is considered based on the improved Fourier series method. And the theoretical formulations for the dynamic performance of the plate system are obtained by employing the energy principle and Rayleigh–Ritz method. The stability and efficiency of the proposed model are firstly validated for the plate system with classical boundary conditions by comparing the results obtained from FEM software. Subsequently, the boundary restraining parameters are analyzed to figure out their effects on the modal characteristics of the plate system. In addition, the influence of mechanical link distributions on the forced response properties of the plate system is presented and discussed. Numerical results show that the importance of both the boundary conditions and the mechanical link distributions on the dynamic behavior of the plate system. The obtained results of the dynamic investigation and parametric analysis of the plate system can be useful for the further work of vibration and noise control technology of engineering applications.

Locally excited surface plasmon resonance for refractive index sensing with high sensitivity and high resolution.

An angle-interrogated surface plasmon resonance (SPR) sensor based on a prism-coupled configuration has been extensively applied in biomedicine, environment monitoring, and food safety. Yet, the low sensitivity and low spatial resolution impede its further development. In this Letter, we investigated objective-coupled locally excited SPR for refractive index (RI) sensing with high sensitivity and high resolution. Through theoretical analysis, the SPR angle was retrieved from back focal plane imaging, which was highly correlated to the RI of the surrounding medium. Experimentally, a RI sensitivity of 77.41° refractive index unit (RIU)-1 was achieved with a detection range of 0.068 RIU when using glucose solutions for the demonstration. Furthermore, we acquired the spatial resolution of the configuration being 290 nm, and the RI measurement to a polydimethylsiloxane droplet with high spatial resolution was implemented. As a result, compared with the classical prism-coupled configuration, the locally excited SPR provides a method to achieve RI sensing with high sensitivity and high resolution.

Positive energy warp drive from hidden geometric structures

Warp drives in Einstein’s general theory of relativity provide a unique mechanism for manned interstellar travel. It is well-known that the classical superluminal soliton spacetimes require negative energy densities, likely sourced by quantum processes of the uncertainty principle. It has even been claimed by few that negative energy densities are a requirement of superluminal motion. However, recent studies suggest this may not be the case. A general decomposition of the defining variables and the corresponding decomposition of the Eulerian energy are studied. A geometrical interpretation of the Eulerian energy is found, shedding new light on superluminal solitons generated by realistic energy distributions. With this new interpretation, it becomes a relatively simple matter to generate solitonic configurations, within a certain subclass, that respect the positive energy constraint. Using this newfound interpretation, a superluminal solitonic spacetime is presented that possesses positive semi-definite energy. A modest numerical analysis is carried out on a set of example configurations, finding total energy requirements four orders of magnitude smaller than the solar mass. Extraordinarily, the example configurations are generated by purely positive energy densities, a tremendous improvement on the classical configurations. The geometrical interpretation of the Eulerian energy thus opens new doors to generating realistic warp fields for laboratory study and potential future manned interstellar travel.

A CNN-based FBG demodulation method adopting the GAF-assisted ascending dimension of complicated signal

We introduce the convolutional neural network (CNN) to extract the effective information of some complex signals in the fiber sensing, and verify the feasibility in the specific process of fiber Bragg grating (FBG) demodulation. In the experiments, in order to eliminate the cross interference in the energized coil, classical double grating configuration is adopted to distinguish magnetic field and temperature. At the same time, the introduction of thermal induced chirp (TIC) phenomenon produces more wavelength components to achieve more precise demodulation. The signal received by oscilloscope presents complex waveform, and the traditional analytical solution cannot demodulate it precisely, while the deep learning capabilities of neural networks can be leveraged to solve this problem. The one-dimensional (1D) time-series signal is transformed into a two-dimensional (2D) image by using the Gramian angle field (GAF) method. On this basis, the data are augmented according to the characteristics of signal noise. Five classical neural network structures are used to process the data. The root mean square errors (RMSEs) of the demodulation results can achieve 0.3 °C and 17.1 Gs respectively, which are relatively high precision in terms of intensity demodulation. This method can be extended to demodulate 1D frequency domain signals and wavelength domain signals, rendering a demodulation scheme to process some complex signals in optical fiber sensing effectively.

Systematic Design of Wideband Bandpass Filters Based on Short-Circuited Stubs and λ/2 Transmission Lines

In this letter, a new technique to design wideband bandpass filters (BPFs) is proposed. It is based on the classical filter topology formed by shunt short-circuited stubs connected by transmission lines, where the λ/4 connecting lines are replaced by λ/2 lines. In this way, the connecting lines have a double functionality: to control the coupling between resonators and to add additional poles, increasing the filter order up to 2N-1, where N is the number of short-circuited stubs. In addition, their function as inverters is, theoretically, for all spectrum, avoiding the limitation of the λ/4 lines working as inverters or the coupled-line coupling mechanisms of classical configurations, which are of narrowband nature. Design equations are provided with up to N degrees of freedom, which allows for a proper selection of impedance values for the filter design. As a verification, a fifth-order BPF of fractional bandwidth 50% centered at 2.5 GHz and with a Chebyshev response is implemented, fullfiling the expections and validating, in this way, the proposed approach.

Configuration synthesis of nine-speed automatic transmissions based on structural decomposition

The configuration of nine-speed automatic transmission (AT) is one of the most important factors to determine its performance, and the pursuit of a better configuration of AT has always been the research focus. This paper proposes a new structural decomposition method, based on which the configuration synthesis of nine-speed AT with a cut-link is conducted by the combination of two independent planetary gear trains (PGT). Firstly, two different decomposition types are introduced, and the structure of nine-speed AT with four planetary gear sets (PGSs) and two degrees of freedom (DOF) is divided into two substructures with one-DOF. Secondly, all the topological graphs of substructures in the two decomposition types are obtained by screening in our atlas database. Thirdly, the layouts of shifting elements (SEs) are analyzed based on the lever method, and all the possible layouts of SEs are obtained. Finally, the substructures are combined according to the layouts of SEs to synthesize the configurations of nine-speed AT. As a result, 168 different configurations of AT are obtained including some classical and new configurations. Furthermore, the method can be extended to the synthesis of other multi-speed ATs.

High-resolution spectral analysis of long single-frequency pulses generated by a self-sweeping Yb-doped fiber laser

Continuous wave self-sweeping operation is demonstrated in a classical ring cavity configuration of Yb-doped fiber laser with a saturable absorber, which is usually used to obtain single-frequency lasing. Using heterodyne-based high-resolution spectral analysis we demonstrate that the laser generates a series of long (up to 1 ms) rectangular pulses consisting of single frequency radiation (the linewidth <0.7 MHz). At the same time, the lasing frequency changes between pulses regularly in a stepwise manner by one intermode beating frequency within a self-sweeping range of 100 pm. The effect of cavity configuration on pulse parameters (duration and chirp) is investigated. We also demonstrate that saturable absorbing mirrors design can be used to control the self-sweeping direction and value of the frequency jump.

A New Approach to the Rayleigh\u2013Taylor Instability

In this article we consider the inhomogeneous incompressible Euler equations describing two fluids with different constant densities under the influence of gravity as a differential inclusion. By considering the relaxation of the constitutive laws we formulate a general criterion for the existence of infinitely many weak solutions which reflect the turbulent mixing of the two fluids. Our criterion can be verified in the case that initially the fluids are at rest and separated by a flat interface with the heavier one being above the lighter one—the classical configuration giving rise to the Rayleigh–Taylor instability. We construct specific examples when the Atwood number is in the ultra high range, for which the zone in which the mixing occurs grows quadratically in time.

I ain’t afraid of no ghost

This paper criticizes the traditional philosophical account of the quantization of gauge theories and offers an alternative. On the received view, gauge theories resist quantization because they feature distinct mathematical representatives of the same physical state of affairs. This resistance is overcome by a sequence of ad hoc modifications, justified in part by reference to semiclassical electrodynamics. Among other things, these modifications introduce ”ghosts”: particles with unphysical properties which do not appear in asymptotic states and which are said to be purely a notational convenience. I argue that this sequence of modifications is unjustified and inadequate, making it a poor basis for the interpretation of ghosts. I then argue that gauge theories can be quantized by the same method as any other theory. On this account, ghosts are not purely notation: they are coordinates on the classical configuration space of the theory—specifically, on its gauge structure. This interpretation does not fall prey to the standard philosophical arguments against the significance of ghosts, due to Weingard. Weingard’s argumentative strategy, properly applied, in fact tells in favor of ghosts’ physical significance.

Bipolar Electrochemiluminescence Imaging: A Way to Investigate the Passivation of Silicon Surfaces.

This work depicts the original combination of electrochemiluminescence (ECL) and bipolar electrochemistry (BPE) to map in real-time the oxidation of silicon in microchannels. We fabricated model silicon-PDMS microfluidic chips, optionally containing a restriction, and monitored the evolution of the surface reactivity using ECL. BPE was used to remotely promote ECL at the silicon surface inside microfluidic channels. The effects of the fluidic design, the applied potential and the resistance of the channel (controlled by the fluidic configuration) on the silicon polarization and oxide formation were investigated. A potential difference down to 6 V was sufficient to induce ECL, which is two orders of magnitude less than in classical BPE configurations. Increasing the resistance of the channel led to an increase in the current passing through the silicon and boosted the intensity of ECL signals. Finally, the possibility of achieving electrochemical reactions at predetermined locations on the microfluidic chip was investigated using a patterning of the silicon oxide surface by etched micrometric squares. This ECL imaging approach opens exciting perspectives for the precise understanding and implementation of electrochemical functionalization on passivating materials. In addition, it may help the development and the design of fully integrated microfluidic biochips paving the way for development of original bioanalytical applications.

A Numerical Study of the Global Instability in Counter-Current Homogeneous Density Incompressible Round Jets

The paper focuses on a global instability phenomenon in counter-current round jets issuing from co-axial nozzles. Three different configurations that differ in a way of the counter flow generation are investigated. Besides typical configurations used in experimental and numerical research performed so far, in which suction applied in an annular nozzle is a driving force for the counterflow, a novel set-up is proposed where the annular nozzle is oriented in the opposite direction and placed above the main one. Such a configuration eliminates the suction of fluid from the main jet, which in previous research was found to have a destructive impact on the occurrence of the global flow instability. The research is performed using a large eddy simulation (LES) method and the computations are carried out applying a high-order numerical code, the accuracy of which has been proven in previous works and also in the present research through comparisons with available experimental data. The research is complemented by the linear stability analysis which supports the LES results and formulated conclusions. In agreement with a number of the previous works it has been shown that the global modes can be triggered only when the velocity ratio (I) between the main jet velocity and the velocity of the jet issuing from the annular nozzle is above a certain threshold level (I_{text {cr}}). It has been shown that in the classical configurations of the co-axial nozzles the range of Ige I_{text {cr}} for which the global instability phenomenon exists is very narrow and it disappears for larger velocity ratios. Reasons for that have been identified through detailed scrutiny of instantaneous flow pictures. In the new set-up of the nozzles the global instability persists for a significantly wider range of I. It has been shown that I_{text {cr}} depends on both the momentum thickness of the mixing layer formed between the counter-current streams and the applied configuration of the nozzles. The LES results univocally showed that the latter factor decides on the type of the instability mode (Mode I or Mode II) that emerges in the flow, as it directly influences on a length of the region where the counter-current streams are parallel allowing the growth of short or long wave disturbances characteristic for Mode I and Mode II, respectively.

Veno-Arterial-Venous ECMO in Severe Primary Lung Graft Dysfunction, a Retrospective Monocenter Study

Purpose Primary graft dysfunction (PGD) occurs in about 20-35% of lung transplantations (LT), with a mortality rate approaching 50% in grade 3 PGD. The treatment remains symptomatic with reports showing favorable survival rates when ECMO is used intra- and postoperatively. It exists two classical configurations, Veno-Venous (VV) and Veno-Arterial (VA) ECMO, with the former providing respiratory support, and the latter giving an additional hemodynamic one. The aim is to highlight the use and results of Veno-Arterial-Venous (VAV) ECMO in the management of Grade 3 PGD, as it combines the benefits of both types. Methods We performed a single-centre retrospective study based on our institutional database. In our VAV ECMO setting, the drainage cannula is placed in the femoral vein, while reinfusion cannulas are put in the femoral artery and the internal jugular vein. Flow is monitored using sensors, and regulated using a screw clamp on the reinfusion venous line. Our protocol is to wean the arterial cannula first when the patients become hemodynamically stable, then VV ECMO once respiratory support is longer required. Results Between April 2016, and April 2020, a total of 280 patients were transplanted at our center. 125 patients needed circulatory assistance intraoperatively. Of those, ECMO was maintained in 65 cases postoperatively (group 1). While 7 patients without intraoperative ECMO, required it during the postoperative 72 hours (group 2). VAV ECMO was used in a total of 8 patients, 6 belonging to group 1, and 2 to group 2. Median age was 40,8 [29,0-56,6] years All of the patients underwent bilateral LT with one patient having a combined liver transplantation as well. The indication of LT was cystic fibrosis in n=5, Idiopathic pulmonary fibrosis in n=2, and re-transplantation for chronic rejection in n=1. The arterial cannula was kept for a median of 5 [3-5] days, while total ECMO weaning was done at a median of 9 [6-17,25]. days. Median ventilation duration was 22 [8-29]. 2 patients died, while the other 6 patients are alive and well up to the date of the abstract. Conclusion VAV ECMO can safely be applied in case of severe refractory hypoxemia despite a VA ECMO in grade 3 PGD patients after LT. It provides a bridge to progressive weaning, with encouraging survival rates. However, more data is needed for further evaluation.

Improving the field homogeneity of fixed- and variable-diameter discrete Halbach magnet arrays for MRI via optimization of the angular magnetization distribution

The aim of this work was to maximize the homogeneity of fixed- or variable-diameter Halbach array of discrete magnets by optimizing the angular rotation of individual magnets within each ring of the array. Numerical simulations have been performed for magnet arrays with various length:radius ratios (L/R) using a dipole-approximation model. These simulations used an uninformed random-search algorithm, with the initial state corresponding to the classical Halbach dipole configuration. Two different classes of systems were studied, one with magnet rings of constant radius, and the other in which the radius of the rings was allowed to vary to increase the homogeneity. Simulation results showed that for a fixed-diameter array optimization of the angular orientation of individual magnets increased the homogeneity by ~17% for very short magnets, with the improvement dropping to ~5% for L/R values greater than ~3:1, where the homogeneity was measured over a region-of-interest equal to one-half the diameter of the magnet array. An empirical formula was derived which allows easy estimation of the required magnetization angles for any L/R. For a 23-ring variable diameter magnet with L/R of ~4:1 the optimization procedure produces an increase in homogeneity of ~18%.

Quantum correlations in -symmetric systems

We study the dynamics of correlations in a paradigmatic setup to observe -symmetric physics: a pair of coupled oscillators, one subject to a gain one to a loss. Starting from a coherent state, quantum correlations (QCs) are created, despite the system being driven only incoherently, and can survive indefinitely. Both total and QCs exhibit different scalings of their long-time behavior in the -broken/unbroken phase and at the exceptional point (EP). In particular, symmetry breaking is accompanied by non-zero stationary QCs. This is analytically shown and quantitatively explained in terms of entropy balance. The EP in particular stands out as the most classical configuration, as classical correlations diverge while QCs vanish.