Position Of Barrier Research Articles

Impact of mixing and configurational entropies on the entropy-driven potential of mean force

Using classical density functional theory (cDFT) with the fundamental measure functional (FMF) approximation, we examine how the entropic force and its integration, the potential of mean force (PMF), between two hard walls in a polydisperse hard-body solvent vary with monomer size polydispersity (whether the solvent consists of spherical monomers or chain molecules formed by freely linked monomers) or the number of monomers in the chain solvent. Molecular dynamics simulations validate the FMF's accuracy in predicting density distributions for five- and seven-component hard sphere fluids in slit geometries, though improvements are possible at high packing fractions. The PMF calculations reveal that increasing monomer size polydispersity or the number of monomers in a chain molecule reduce entropic attraction strength at contact and lower the main potential barrier height. This reduction is due to the system's limited capacity to further increase entropy when both mixing and conformational entropies are already high. For monomer or dimer solvent, the main potential barrier position shows either monotonic or non-monotonic dependence on monomer size polydispersity, depending on bulk packing fractions, while the PMF range shortens with increasing monomer size polydispersity or chain molecule monomer number. These findings could inform the design of tunable materials.

Femtosecond laser ablation of nitrocellulose for spatio-temporal flow control in µPADs

Microfluidic paper-based analytical devices (μPADs) are gaining popularity due to their low cost and ease of use, but controlling fluid flow for more complex biochemical assays within these devices remains challenging. This study investigates femtosecond laser ablation of nitrocellulose (NC), a preferred material for µPADs, to create mechanically switchable barriers and flow controllers. We investigated NC ablation using single laser pulses and spatially overlapping pulses that generate lines. Single pulse ablation thresholds were determined for wavelengths of 1,030 nm, 515 nm and 343 nm. Line ablation characteristics were investigated as a function of the temporal and spatial pulse separation and laser wavelength. High aspect ratio grooves (up to 4.26) were achieved under specific conditions. These grooves can be used to define the spatial separation of the flow in separated microchannels or to form a barrier line perpendicular to the microchannel that can modulate the temporal behavior of the fluid flow. This barrier introduced an additional high flow resistance slowing down the flow or, if it was designed to cut through nitrocellulose at the entire depth, completely stopped the liquid flow. It was further shown that a barrier formed in this way could be switched by mechanically bending the µPAD at the barrier position. The femtosecond laser patterning method presented here provides precise spatio-temporal control not only for flow branching and multiplexing, but also for controlling flow speed and switching flow on and off within the same manufacturing process. Our results open up new possibilities for complex, multi-step assays on µPADs.

Safety-critical control of planar quadcopters under dynamic event-triggered mechanism

This paper aims to solve the problem of safety-critical control, i.e., safe flight of planar quadcopters in complex environments. By introducing input-to-state safe barrier function (ISSf-BF), the attitude, position, speed, and other key parameters of planar quadcopters are fully considered to realize safety-critical control. Also, a dynamic event-triggered mechanism (DETM) is constructed, and Zeno phenomenon is ruled out based on the constructed DETM. By monitoring the relative distance and speed changes between planar quadcopters and the boundary of the safe zone, the control action is triggered only when the control strategy needs to be adjusted, which effectively reduces the unnecessary waste of computation and communication resources. Finally, a series of simulation experiments are demonstrated to verify the feasibility of the proposed method.

Electrical discharge reproduction in rod-barrier-plane system

The present paper deals with new modeling to reproduce the electric discharge in the rod-plane air gap system with rubber insulating barrier under AC and impulse voltage. This model considers the randomness character of discharge evolution which is governed by the electric field. The discharges shape obtained by this model are compared with ones given by experimental tests. The established model reproduces correctly the forms of discharges obtained by experimental tests under AC voltage. It is found that the behavior of the electrical discharge depends not only on the dimension (thickness and width) of the insulating barriers but on its positions in the air gap as well. It is to highlight that the mode of applied voltage is of key importance barrier. Experimental investigation shows that the developed arc can evolve on 1 to 4 channels. The generated discharges in AC voltage distinguish by the formation of a multiple-channel arc. Whereas, the discharge under lightning impulse voltage found to progress in a single channel whatever the barrier position and dimensions. The model confirms that electric field is the most important factor in the behavior of the rod-insulating barrier-plane system submitted to high voltage.

Systematics of fusion of light nuclei

We have constructed the empirical formula for fusion barrier height (VB), fusion barrier position (RB), and inverted parabola (ħω) of light nuclei with atomic number in the range 2≤ZC≤10. This formula is obtained by studying the fusion barrier characteristics of 333 projectile target combinations. The values produced by the present formula are also compared with experiments. The present semi-empirical formula produces fusion barrier characteristics of light nuclei with the simple inputs of mass number (A) and atomic number (Z) of projectile targets. This semi-empirical formula can be utilized to calculate and interpret fusion barrier characteristics in light nuclear systems.

Conditioned adaptive barrier-based double integral super twisting SMC for trajectory tracking of a quadcopter and hardware in loop using IGWO algorithm

Researchers working in the field of unmanned aerial vehicles are observing rapid developments in the field, such as the use of quadrotors to grasp, manipulate, and transport objects. These advancements are made possible through sophisticated control systems, new types of actuation and sensing technologies, and a greater understanding of the aerodynamic effects and gyroscopic moment generated by the rotating blades of the quadrotor involved. Therefore, this research work proposes four novel optimized control laws, i.e., conditioned adaptive barrier-based double integral super twisting sliding mode controller (CABDIST-SMC), BF double integral SMC (BF-DISMC), BF integral SMC, and barrier function-based SMC control laws, for attitude, heading, position, and altitude trajectory tracking of the quadcopter. The non-linear model of the quadcopter is developed using the Lagrange formalism in MATLAB ODE-45 environment, including the gyroscopic moments and aerodynamic effects, and a Lyapunov stability analysis is performed to ensure the asymptotic stability of the system. A 3D-helical complex trajectory is employed to analyze the performance and consistency of the proposed optimized controllers. For performance comparison, the proposed four variants of the SMC are compared with three traditional control strategies, i.e., backstepping SMC, optimized adaptive SMC via particle swarm optimization algorithm, and improved adaptive SMC. These traditional control strategies have also been developed and tested in MATLAB-Simulink. All the controllers are optimized using the improved grey wolf optimization algorithm, and to determine the best control law, six performance indexes, i.e., mean absolute percentage error (MAPE), root mean square error (RMSE), integral square error (ISE), integral absolute error (IAE), integral time absolute error (ITAE), and integral time square error (ITSE) are used. A hardware-in-loop (HIL) test is also performed to validate the performance of the designed novel control law. The C2000 Delfino MCU F28379D launchpad is used for performing the HIL validation test. The simulated results showed that the performance of optimized CABDIST-SMC surpassed all other control laws for altitude, heading, position, and attitude trajectory tracking. It has achieved MAPE of 0.02%, RMSE of 3.9912e−5, ISE of 3.1859e−8, IAE of 7.9823e−4, ITAE of 0.0080, and ITSE of 3.1849e−7 in case of yaw angle control. The proposed control laws have successfully passed the HIL validation test, and real-time implementation of the proposed control laws indicates no significant variations compared to the simulated results.

Numerical simulation and validation of local wind environment of twin-box girder with wind barriers

Computational fluid dynamics (CFD) was used to reproduce wind fields around a twin-box girder. Wind tunnel tests and field measurements were conducted to verify the accuracy of the CFD results. Variations in wind speed at different heights and crosswind reduction effects with different barriers were also examined using CFD simulation; the barriers had significant reduction effects. The reduction effectiveness was closely related to the barrier height and position; porosity was also a crucial factor. The wind speed profiles of a twin-box girder and a single box girder were analysed to determine why the wind speeds above the downstream deck were lower than above the windward deck of the twin-box girder. The results show that the incoming flow leaked downward through the slotted parts of the bridge and formed regulation vortices. Wind speeds were lower above the downstream deck than above the upstream deck as a result of leakage effects. The gap width also influenced the wind environment around the bridge deck.

Multichannel hyperspherical model for Efimov physics with van der Waals interactions controlled by a Feshbach resonance

Here we present a four-channel model that incorporates a magnetically tunable Feshbach resonance in a system of three atoms that interact via pairwise van der Waals interactions. Our method is designed to model recent experiments where the tunability of the scattering length has been used to study three-body Efimov states, which appear in the limit of a diverging two-body scattering length. Using this model, we calculate three-body adiabatic and effective potential curves and study how the strength (or width) of the Feshbach resonance affects the three-body potential that is connected to the Efimov effect. We find that the position of the repulsive barrier, which has been used to explain the so-called van der Waals universality in broad resonances, is slightly shifted as the narrow resonance limit is approached and that this shift is correlated to the appearance of two avoided crossings in the adiabatic energy landscape. More importantly, the attractive well is markedly shifted upward in energy and is extremely shallow for the narrowest resonance. We argue that this behavior is connected to the breakdown of van der Waals universality for weak (narrow) resonances.

The study of angular momentum on the fusion of [formula omitted]Si+[formula omitted]Si, using SEDF in semiclassical extended Thomas-Fermi approach

The total fusion cross-sections are calculated for energies both above and below the potential barrier by using the properties of the interaction potential in Hill-Wheeler approximation for a positive Q-value system 1428Si+1428Si. The Coulomb and centrifugal parts of the potentials are added directly to the nuclear proximity potential to calculate the total interaction potential, where nuclear proximity potential is obtained in semiclassical extended Thomas-Fermi approach of Skyrme energy density formalism for Skyrme SIV parametrization. The angular momentum spectrum of total cross sections is obtained and calculated by using angular momentum dependent properties of the total interaction potential. The properties of total interaction potential, which are usually treated as independent of angular momentum, i.e. barrier height, barrier position and its width are calculated and found to depend sharply on the angular momentum value at a fixed center of mass energy. It effect the fusion cross-section sufficiently above the barrier energy. However at energies below the barrier energy the addition of large angular momentum values have negligible effects on fusion cross-section. Further, the maximum in fusion cross-section is observed at a particular value of angular momentum, which is not equal to the maximum value of angular momentum.

Probabilistic response analysis of nonlinear vibro-impact systems with two correlated Gaussian white noises

The response distributions of a dynamic system under the effect of correlation noise not only demonstrated a Gaussian symmetric distribution, but also exhibited a non-Gaussian skewed distribution. Thus, correlation noise can induce more complex dynamic phenomena in the response of a nonlinear system. The purpose of this study is to explore the stochastic response and bifurcation of nonlinear vibro-impact systems driven by correlated additive and multiplicative Gaussian white noises using the path integral (PI) method. First, we derived an equivalent correlated stochastic system without collision conditions in the new ancillary phase space using the non-smooth Ivanov transform method. We then used Novikov’s theorem to derive an effective Fokker–Planck–Kolmogorov equation for the equivalent correlated stochastic system. Second, we used PI technology, which combines the three-point Gauss–Legendre quadrature rule to solve the effective Fokker–Planck–Kolmogorov equation and obtained the probability density functions (PDFs) of the equivalent correlated stochastic system. Subsequently, we obtained the PDFs of the original vibro-impact stochastic system using the relationship between the initial state space and the new auxiliary phase space. Finally, the proposed method was used to investigate the transient and stationary responses of a Duffing-Van der Pol Vibro-impact system perturbed by additive and multiplicative random noises. In addition, this technique can also assess the effects of restitution coefficients and barrier position on stochastic P-bifurcation. The accuracy of this method was verified by comparing it with a Monte Carlo simulation.

Design and Performance Analysis of Three Phase Line Start Synchronous Reluctance Motor Using Finite Element Analysis

Three-phase Induction Motors (TPIM) are popular in industrial applications due to their numerous advantages. However, TPIM has comparatively lower efficiency than modern motor technologies like permanent magnet synchronous motor(PMSM), synchronous reluctance motor(SynRM), or switched reluctance motor(SRM). The expensive rare earth material and the inability of line starting operation discourage the replacement of TPIM with these modern energy-efficient motors. This research proposes a novel conversion of TPIM into Line Start SynRM (LS-SynRM) to cause a cost-effective and compatible performance solution. The proposed design modifications are carried out on the existing 0.5HP, TPIM rotor and analyzed using finite element (FE) software. The optimum barrier parameters such as barrier end width, barrier position, barrier width, and rib width have been determined through parametric analysis. The considerable effect of barrier dimensions on motor performance is evident from the analysis.

Метод обобщенного импеданса для расчета отражения и прохождения волны через многослойную структуру. Часть 2. Падение волны на прямоугольный барьер

On the basis of generalized impedance method the propagation of single-dimension wave in multi-layer structure which contains the rectangular-type barrier is investigated. The concept of single barrier as a slide which parameters are different from the parameters of all other slides of structure is introduced. It is investigated the variation of position of real negative single barrier along the length of structure. It is found that the entrance impedance along the length of structure is varied by periodic manner. It is found the analytical formulas which simulate the dependencies of real and imaginary parts of entrance media impedances from coordinate along the structure. It is found three basis regimes which correspond to different character of oscillations: regime №1 – precise periodicity, regime №2 – break periodicity, regime №3 – monotonous increasing. It is investigated the coefficient of reflection for all mentioned above cases. It is found that the reflection coefficient from barrier displacement is not depended. It is found the periodic character of changing of amplitude and phase of reflected wave and also reflection coefficient when the height of barrier is varied. For interpretation of observed dependencies it is proposed the model of resonance inside of barrier. It is investigated the special feature of wave propagation when the barrier has complex character. It is investigated the case when the real path of wave number of barrier medium is established constant but imaginary path of the same number is varied in wide boundaries. It is established that reflection coefficient started by zero when the imaginary part of wave number is equal to zero. When imaginary part of wave number increases the reflection coefficient smooth increases in limit goes to unit. The passing coefficient also smooth decreases but more quickly then reflection coefficient and in limit goes to zero. The absorb coefficient started by zero at first smooth increases and after reaching of maximum smooth decreases in limit goes to zero. It is investigated the case when real and imaginary paths of barrier medium wave number simultaneous increase in equally proportion. It is found that in this case on the smooth curves for coefficients ob reflection, passing and absorb it is putted the oscillations. The character of oscillations is explained in the frames of resonance model.

Awareness Regarding Occupational Hazards Among the Dental Students of a Medical College of Nepal

Introduction: Dental students, during their clinical and preclinical practices, are constantly exposed to a number of occupational hazards. Such exposures lead to various ailments and diseases. The study was done to assess the awareness regarding occupational hazards among dental students in College of Medical Sciences, Nepal. Methods: A questionnaire-based, descriptive cross-sectional study was conducted among the dental students from College of Medical Sciences, Nepal. Demographic details and awareness on different variables like bioaerosols, X-rays, blue light radiation, vibration, noise, posture, ergonomics, mercury vapour inhalation and percutaneous incidents, were assessed with the close-ended questions.Questionnaire was delivered to the participants in paper-printed forms. Data analysis was done using SPSS version 17. Chi-square tests were done to find the association between the variables to education and gender and the level of significance was set at p<0.05. Results: The mean knowledge score for the male students was higher than that for the female students and the difference was statistically significant (p<0.001). Fourth year students had the highest mean knowledge score (6.25±1.70) and second year students (2.71±2.43) had the lowest, and the scores were statistically significant (p<0.001). More than two-third of the students (72.8%) did not know that vibration causes peripheral neuropathy; more than three-fifth of them (61.7%) didn’t know that noise induced hearing loss is possible at dental settings and; about three-fifth of them (59.3%) did not know that X-ray hazards can be mitigated by barrier methods and position distance rule. Conclusion: The awareness regarding the radiation hazards, vibration hazards and noise induced hazards seem to be limited among the dental students. The study suggests introducing specific intervention programs like occupational safety seminars, trainings or workshops, for the dental students, before the commencement of their practical classes.

The Limit Tuning Effects Exerted by the Mechanically Induced Artificial Potential Barriers on the I-V Characteristics of Piezoelectric PN Junctions.

A mechanically induced artificial potential barrier (MIAPB) in piezoelectric semiconductor devices is set up under the action of a pair of tensile/compressive mechanical loadings. Three factors, namely, the barrier height, width and position, affect the nature and extent of interaction between the MIAPB and the contact barrier, and the tuning characteristics (generated under conditions of the artificial barrier) of the piezoelectric PN junctions were studied. The influence of these factors resulted in variations in the interaction intensities, superposition effects, carrier inversion degrees and carrier redistribution ranges. Subsequently, the limit tuning effects exerted by the tensile/compressive-mode MIAPB on the PN junctions were studied. The inconsistency between the left and right end of the tensile-mode MIAPB under conditions of the offset loading state proves that the maximum tuning effect is generated when both sides of the interface are symmetrically loaded. The range of carrier redistribution and the over-inversion of local carriers, affected by the width and height of MIAPB, result in a second competitive mechanism. The carrier redistribution range and the carrier inversion degree require that the compressive-mode MIAPB be sufficiently wide. The interaction intensities and the superposition effects, affected by the position and height of the MIAPB, contribute to the second competing mechanism. We logically clarify the relationship between multiple competition and find that the emergence of multiple competitive mechanisms proves the existence of the limit tuning effect of MIAPB on the I-V properties of PN junctions. The results reported herein provide a platform for understanding the mechanical tuning laws governing the functions of piezoelectric PN junctions and piezoelectric devices.

Propagation Speed of the Frontal Head Through Lock-Exchange Density Current in Cold Fresh Water: Simulations without the Effect of Back-reflected Waves

The behaviour of warm water discharged at 4\(^{\circ}\)C through lock-exchange in cold fresh water was investigated numerically, fixing lock volume at the centre of the domain. This investigation as presented here is practical and can also enhance policy making towards the protection of the aquatic ecosystems. Though, the aim of this study is to better fathom and as well, gain more insight into such ows. Our results have shown a speedy movement of the lock volume at the centre of the domain with a leading head at two front on the oor which resulted in a hat shape within the first few time frame. Fluid movement in the second phase is independent of the back reflected waves. We were able to identify two regimes of ow with a stepwise decreasing velocity in the second phase. Our results have shown that velocity with which the current travels with in the second regime is higher within the first time frame as compared to those with the effect of back reflected waves. One major factor that is responsible for decrease in the velocity here is mixing. Previous results have also shown that the front velocities in the collapsing phase are independent of lock volume. But this seem not to be the same here because fluid movement in the first phase (regime) is not totally independent of the lock volume and its position here, where density difference is as a result of temperature. However, our scaling power laws here in the second phase show some variations with previous studies where we have effect of back reflected waves. But results in the collapsing phase here are in strong agreement with those in the first phase of our previous simulations with small lock volume. Generally, the spreading behaviour here is dependent on lock volume, barrier position, density difference and Reynolds number.

A Numerical Study of the behaviour on Lock Volume Variations in Lock-Exchange Density Current in Cold Fresh Water

The behaviour of warm discharge through lock-exchange was investigated numerically, with the assumption that density was taken as a quadratic function of temperature. Simulations were conducted eleven different times varying barrier position. This work as presented here is practical and can also enhance policy making towards the protection of the aquatic ecosystems. Such behaviours are evident in lakes, especially in holomictic lakes and warm discharge from thermoelectric power generating plants. The sudden increase in water temperature after discharge may leads to ”thermal shock” killing aquatic life that has become acclimatised to living in a stable temperate environment. The aim of this investigation is to better fathom and as well, gain more insight into such flows. The results show that regimes of flow is dependent on the size of the lock volume. The general behaviours here are dependent on lock volume, density difference and Reynolds number. Effects of back reflected waves on the propagation speed was not significant for small lock volume simulations. A rapid collapsing behaviour of fluid was noticed for simulations with small lock volume, and the velocity decreases with increase in lock volume in this same phase. Propagation speed is not totally independent of the lock volume. Cabbeling was also key at the point where water masses meet, and as well the development of Kelvin-Helmholtz instabilities. Relations that describes the various regimes of flow are given in Table (1 - 11). Though, there are little variations in the scaling laws as compared to the earlier studied cases where density difference was by the means of salt water. Lastly, it will be interesting if measures can be taken to eliminate the effect of this back reflected waves in other to properly fathom the behaviour in thepropagation of the frontal speed after the slumping phase.

Distinguishing Majorana and Andreev bound states in a topological superconducting nanowire with a potential barrier

We propose a scheme to distinguish the Majorana bound states (MBSs) and the trivial Andreev bound states (ABSs) in a topological superconducting nanowire by applying a sharp local potential barrier on one part of the wire. The position and strength of the local potential barrier could be modulated by a gate voltage applied to the nanowire. It is found that a new pair of MBSs appear at both sides of the potential in the presence of the local potential barrier, as a manifestation of the topological nature. Differently, the local potential barrier does not induce extra ABSs. Such a difference can be traced back to the evolution of the conductance spectrum with the Zeeman field or the local potential strength. When modulating the local potential strength, the zero-bias conductance peak induced by MBSs can be split into two-, three-, or four-peak structures, while the zero-bias peak by ABSs is only split into two-peak form.

“Modeling of Saline Water Intrusion using MODFLOW in Una Coastal Aquifer of Gujarat, India.”

Abstract: Groundwater is the most valuable and extensively dispersed resource on the planet, and unlike any other mineral resource, it is replenished annually by meteoric precipitation. The present study would include simulation and modelling of the problem of seawater intrusion in the Una coastal area of Gujarat. The interrelationships of two miscible fluids in porous media have been widely explored both theoretically and experimentally. Because of the extreme salinity, many agricultural wells are no longer used. This high salinity is a sign of a process known as saltwater intrusion, which occurs mostly in coastal aquifers due to excessive pumping. Modelling software has also been utilized to analyze the behavior of groundwater flow models. Numerical models may simulate diverse groundwater scenarios and link them to groundwater management. To simulate seawater intrusion, MODFLOW-2005, a grid-based variable density-dependent flow model, is used. Water balance research reveals that rainwater recharge is the aquifer's primary input. To compute the water level in the area and estimate the position of the seawater intrusion barrier, the saltwater intrusion phenomena were simulated using the MODFLOW software combined with the SWI2 package. The model was used to visualize the salinity levels of the coastal aquifer's groundwater and their fluctuation over time and space from May 2004 to October 2014. The model was developed for a 10-year stress period with 100-time steps, which included a 5-year steady state and 5 years transient state stress period using the previous 10 years of pre-monsoon and postmonsoon data. This research would assist to describe Pumping's impact on groundwater levels and seawater intrusion was studied. Keywords: MODFLOW, Saltwater Intrusion, Modelling, Numerical Model, Coastal aquifer

Systematic study of fusion barrier characteristics within the relativistic mean-field formalism

Background: The nuclear interaction potential and hence the fusion barrier formed between the interacting nuclei are the keys to understanding the complex fusion process dynamics. Purpose: This work intends to explore the fusion barrier characteristics of different target-projectile combinations within the relativistic mean-field (RMF) formalism. Methods: The density distributions of interacting nuclei and the microscopic R3Y NN interaction are obtained from relativistic mean-field (RMF) formalism for non-linear NL1, NL3, TM1, and relativistic-Hartree-Bogoliubov (RHB) approach for DDME2 parameter sets. The fusion and/or capture cross-section for the different reaction systems is calculated using the well-known $\ell$-summed Wong model. Results: The barrier height and position of 24 heavy-ion reaction systems are obtained for different nuclear density distributions and effective NN interaction potentials. The comparison of fusion and/or capture cross-section obtained from the $\ell$-summed Wong model is made with the available experimental data. Conclusions: The phenomenological M3Y NN potential is observed to give higher barrier heights than the relativistic R3Y NN potential for all the reaction systems. The comparison of results obtained from different relativistic parameter sets shows that the densities from NL1 and TM1 parameter sets give the lowest and highest barrier heights for all the systems under study. We observed higher barrier heights and lower cross-sections for DDR3Y NN potential as compared to density-independent R3Y NN potentials obtained for considered non-linear NL1, NL3 and TM1 parameter sets. According to the present analysis, it is concluded that the NL1 and NL3 parameter sets provide comparatively better overlap with the experimental fusion and/or capture cross-section than the TM1 and DDME2 parameter sets.

A rare entity-lateral inflammatory follicular cyst

Sometimes, there is failure in tooth eruption not because of any physical barrier or abnormal position. The reason for the failure of tooth eruption in this current case is due to uncommon phenomenon. There was a swelling in the lower canine region bilaterally with impacted the 32,33,42 and 43. This case also shares a detailed CBCT report and microscopic features of the rare entity, the lateral inflammatory follicular cyst.