Double Phenomenon Research Articles

Influence of colored cross-correlated noise on stochastic resonance for an underdamped bistable system subjected to multiplicative and additive noises

The stochastic resonance (SR) behavior for an underdamped bistable system with colored cross-correlated noise between multiplicative and additive noise is investigated. The stationary probability density is obtained under the condition of the detailed balance. The expressions for the signal-to-noise ratios (SNRs) for two initial states is deduced by applying two-state theory under the adiabatic condition. The analysis result indicates that the SR phenomenon takes place when the SNRs vary with the coupling strength and the correlation time of the cross-correlated noise. Double SR phenomenon occurs on SNRs’ curves with the increase of the strength of the additive noise. One resonance peak exists when the SNRs change with the damping coefficient and with the intensity of the multiplicative noise.

An analysis of flow characteristics during ethanol natural evaporation in capillary tubes with varying diameters

For the design of the heat transfer system, heat transfer characteristics and flow state near the evaporation interface are crucial. This paper aims to experimentally investigate Marangoni convection and temperature distribution in thin films during natural ethanol evaporation in capillary tubes of varying diameters. In both horizontal and vertical views, the infrared camera and PIV are used to measure the flow pattern and interfacial temperature distribution of Marangoni convection. The quartz glass capillary has inner diameters of 0.3 mm, 0.5 mm, 0.7 mm, and 1 mm. As a result, the fluid in the capillary is less affected by gravity in the horizontal cross-section. Consequently, the temperature and the flow state exhibit a symmetrical phenomenon, and the lowest temperature value can be found near the capillary wall's angle. The interface from the center to the edges of the Marangoni macroscopic flow is characterized by two symmetrical, counter-rotating vortices. Due to the conflicting effects of gravity and surface tension, the vertical section exhibits both single and double vortices. Small inner diameters of capillaries are also less affected by gravity. As a result, as the capillary diameter decreases, the double vortex phenomenon gradually emerges, which is already apparent in tubes with an inner diameter of 0.3 mm.

Double resonance peak phenomenon and balance method of rotating machinery with flexible bearing support

A simplified dynamic model of the rotor-bearing-support system is established considering the influence of pedestal flexibility. The vibration characteristics of the system with a flexible pedestal are analyzed. There are two resonance peaks during the run-up process for this kind of system. It is generally thought that the stiffness difference in the vertical and the horizontal direction is the main cause of the double resonance peak phenomenon. The results of the paper show that the flexible pedestal support also causes the double resonance peak phenomenon. The shaft relative vibration cannot reflect the influence of rotor unbalances well near the resonance zone. In this case, the bearing vibration should be preferred in the balance test. The vibration phenomenon on an actual unit is analyzed as an example.

Asymmetric inter-layer interactions induce a double transition of information spreading

In recent years, a unique double transition phenomenon was observed under an asymmetric interaction in the epidemic model, where there are two transitions in the phase diagram of the spreading range versus the transmission probability. However, whether the asymmetric interactions exist and induce the double transition of information spreading is not very clear. Based on the global Twitter network communication data analysis, we found that besides the symmetric effects, there are also asymmetric interactions between different continents, indicated by the asymmetric weights of information exchange. To understand how the asymmetry affects the spreading behaviors, we proposed an information spreading model on a synthetic two-layered network and quantified the asymmetric interactions between regions by asymmetric inter-layer transmission probabilities. Interestingly, our results reveal a double transition under a strong inter-layer asymmetry in the phase diagram, which is derived from an asynchronous outbreak within the two layers. In addition, we discovered that depending on the strength of asymmetry, the second transition could alter from continuous to discontinuous. Finally, we developed a theory with asymmetric interactions to explain the numerical results thoroughly. The findings of this work may shed some light on comprehending the information’s secondary outbreaks in the real world.

Generalized transport analysis on mixed convection squeeze flow of a Casson fluid over an inclined stretching sheet with viscous dissipation and double stratification

The utility of squeezingly driven stretching movement of non-Newtonian liquid to enhance the mechanical efficiency of a industrial processes, such as, extraction crude oil, cooling process of nuclear reactors, food processes, electronic chips manufacturing, pollution of ground water, fabrication of plastic materials, etc., is diverse. This inspires us to describe the mathematical stimulation of squeezed fluid flow via stretchable inclined wall. The non-Newtonian Casson fluid model is utilized here. The investigation related to heat and mass transport is pursued under the Cattaneo-Christov theory. Additionally, viscous dissipation and double stratification phenomena are also incorporated in the analysis of heat and mass transport. The governing equations are transformed under the appropriate variables. The convergent analytical solutions are acquired through homotopic technique. To notice the remarkable impacts of notable parameters on flow fields and skin friction coefficient, graphs have been plotted in two-dimensional axes. The values used for involved parameters are λh=Pr=λc=Sq=1.2,δ=ε=ε1=0.1,Gh=Gc=0.3,α=π/4,Re=0.2,β=1.0. The results depict that the dissipative effect increments the temperature distribution. Casson fluid parameter has decrementing impact in velocity field near the plates while opposite trend is witnessed apart from the plates. The current analysis incorporates numerous industrial and technological processes including pharmaceutical, petroleum related industries, marine engineering, nuclear up and down processes, etc.

Experimental and Numerical Investigation of the Added Resistance in Regular Head Waves for the DTC Hull

Reducing the added resistance in waves has become a crucial aspect of today’s ship design. The added resistance in waves is traditionally considered proportional to the square of wave height. However, this assumption is believed to be only partly valid, and further investigations are required. In the present study, experimental tests and numerical simulations were carried out to determine the added resistance in regular head waves of the DTC hull (the scale factor is 135). The numerical analysis was performed with SHIPFLOW 7.01, and the experimental campaign was carried out in the ETSIN-UPM towing tank. The investigation revealed that the added resistance in waves was not proportional to the square of the wave height, and a better correlation was obtained by changing the power of the wave weight to 1.75. Furthermore, an unexpected double resonance phenomenon on the added resistance was found at a Froude number of 0.13. The study also revealed an acceptable agreement between the numerical simulations and the experiments, except for the double resonance phenomenon.

School Leadership in Argentina during the COVID-19 Pandemic: Emotions, Tensions and Policy Challenges for the Future

ABSTRACT This paper reviews the professional situation of school principals during COVID-19 in Argentina, where one of the longest school closures in the world was maintained. It analyzes the existence of burnout, concerns, constraints and needs of 252 principals at the end of the 2020 school year. The results indicate that there is a double phenomenon of Emotional Exhaustion and Personal Accomplishment, while tensions with regulations and working conditions are evidenced. We found a leadership open to the context, with greater autonomy and a strong emotional commitment, with implications and challenges for the post-pandemic future.

Newton-GMRES-Method for the Scritinization of electric double layer and surface roughness on EHL line contact problem

The electric double layer phenomenon exists on the solid interface under the water-liquid condition. The water molecules are ionized and adhered in the interface forming the sturn layer is a diffused layer in which molecules can move with the movement of bulk of molecules. Because of these two characteristics, the boundary layer of water molecules is called the electric double layer. The aim of present study is to explore the impact of two fraction surfaces of electric double layer (EDL) on a thin water lubricating film on an elastohydrodynamic lubrication (EHL) line contact problem with a sinusoidal surface roughness. The governing modified Reynolds and film thickness equations are based on mathematical model of electro-viscosity of asymmetrical electrical double layer is analyzed numerically. The viscosity-pressure relation of water and theoretical evaluation pertaining to the effect of electric double layer on film-thickness and pressure distribution of EHL with water film of line contact problem is discussed in detail. The effect of zeta potential on film thickness and pressure is determined using Newton’s-GMRES method with Daubechies D6 wavelet as a pre-conditioner. The results predict that, EDL has less impact on pressure distribution and significant impact on film thickness. The obtained results are compared with results of Dowson and Higginson which are comparable.

Modeling of modified Eyring–Powell nanofluid flow subject to thermal-solutal stratification phenomenon

Population growth and rapid industrialization have led to many serious problems such as change in climate, fossil fuel shortages, crisis of energy, and environmental issues, which have become the primary risks for the survival of human being on this planet, to overcome these problems researchers take keen interest in nanofluid because they have a higher thermal conductivity than conventional base fluids, and thus can serve as an effective heat transfer medium. In present article, the impact of magnetized flow for modified Eyring–Powell fluid under thermophoretic and Brownian movements aspects is examined. Double stratification phenomenon for heat/mass transportation analyses is introduced. Some suitable similarity transformations are exploited to achieve the non-linear ODEs. The acquired ODEs are resolved numerically by using bvp4c technique. Moreover, physical elucidation for dimensionless variable's is presented. Velocity of modified Eyring–Powell nanofluid has opposite behaviors versus magnetic parameter and fluid parameter. Augmented values of radiation parameter, thermophoresis, thermal Biot number, and magnetic parameters intensify the temperature of nanofluid. More specifically, concentration of nanofluid dwindles against larger solutal Biot number and Brownian moment parameter. Transportation rate of heat intesifies for larger [Formula: see text].

Modeling the Double Peak Phenomenon in Drug Absorption Kinetics: The Case of Amisulpride

An interesting issue observed in some drugs is the “double peak phenomenon” (DPP). In DPP, the concentration-time (C-t) profile does not follow the usual shape but climbs to a peak and then begins to degrade before rising again to a second peak. Such a phenomenon is observed in the case of amisulpride, which is a second-generation antipsychotic. The aim of this study was to develop a model for the description of double peaks in amisulpride after oral administration. Amisulpride plasma C-t data were obtained from a 2 × 2 crossover bioequivalence study in 24 healthy adult subjects. A nonlinear mixed-effects modeling approach was applied in order to perform the analysis. Participants’ characteristics, such as demographics (e.g., body weight, gender, etc.), have also been investigated. A model for describing the double peak phenomenon was successfully developed. Simulations were run using this model to investigate the impact of significant covariates and recommend appropriate dosage regimens. For comparison purposes and to investigate the suitability of our developed model for describing the double peak phenomenon, modeling of previously published population pharmacokinetic models was also applied to the C-t data of this study.

Abstract Number ‐ 54: First Fully Automated Robotic Transcranial Doppler Optimization of Cerebral Blood Flow During Cardiac Revascularization Surgery

Introduction Current technologies including EEG and near infrared pulse oximetry for non‐invasive monitoring of cerebral blood flow during cardiac surgery have proven inadequate for perioperative stroke risk mitigation. Cerebral arterial flow velocity is an excellent indicator of cerebral blood flow making transcranial doppler ultrasound (TCD) an excellent alternative technology for operating room continuous cerebral monitoring. To date, TCD utilization in the operating room has been limited due to frequent movement‐related loss of signal requiring nearly continuous manual probe readjustment. The recent development of fully autonomous robotic TCD (aTCD) has overcome these technical limitations, opening the door for real‐time continuous noninvasive cerebral blood flow monitoring with simultaneous emboli detection. Methods A 47‐year‐old female patient was found to have preoperative complete occlusion of the proximal brachiocephalic artery producing a double cerebral steal phenomenon with retrograde flow in the right internal carotid and vertebral arteries into the subclavian. A preoperative aTCD study disclosed baseline markedly diminished blood flow in the right middle cerebral artery (MCA) fed exclusively by small‐diameter collaterals via the circle of Willis.Intraoperatively, robotic aTCD was used to continuously monitor blood flow in the bilateral MCAs and perform emboli detection. In response to movement‐related signal loss, the robotic aTCD autonomously adjusted the probe position to maintain continuous MCA insonation. Results Shortly after intubation, a small drop in mean arterial pressure led to a near‐total loss of cerebral perfusion to the entire right hemisphere. This perfusion decrease was detected by aTCD, triggering the anesthesiologist to rapidly correct blood pressure to ensure adequate cerebral perfusion as confirmed by the robotic system. The patient was then placed on bypass pump with deployment of a temporary Y‐graft from the pump to the subclavian artery distal to the vertebral branch point and to the aorta to temporarily reverse the double cerebral steal. Coronary bypass was then performed, throughout which cerebral flow velocities were monitored continuously with aTCD and maintained in the safe cerebral perfusion range by adjusting pump pressures. Following a three‐vessel coronary bypass graft, permanent brachiocephalic artery bypass grafts were placed from the proximal aorta to the right subclavian and the proximal common carotid artery.Postoperative aTCD disclosed correction of the previously diminished blood flow detected in the right MCA preoperatively. Brain MRI postoperatively confirmed the absence of acute stroke. Conclusions This case represents the first use of robotic aTCD for real time continuous cerebral blood flow monitoring and optimization during complex cardiac surgery. Our experience suggests that aTCD may improve patient outcomes, particularly during high‐risk cardiac surgical and interventional procedures. Further studies of this promising technology are now needed.

Soil-building resonance effect in the urban area of Villa d’Agri (Southern Italy)

This study aims to evaluate the possible occurrence during seismic shaking of interaction effects between the shallow subsoil and the overlying buildings of the Villa d’Agri town (Southern Italy). From the geological and building heritage points of view, the investigated area represents a typical town along the Apennines chain and therefore the obtained results could be easily exported to similar urban areas. A total of 239 single-station seismic ambient noise measurements were thus performed, 154 on the urban soils and 85 within buildings. Both subsets of measurements were planned to cover the main outcropping lithologies and building typologies. By means of the Horizontal-to-Vertical Noise Spectral Ratio technique, isofrequency and isoamplitude maps have been reconstructed for the whole area. The results evaluated on the 65 tested buildings allowed to infer the empirical relationship between the first vibrational period, T(s), and their height, H(m). Using this relationship and available information on the height of each building, the first vibrational frequency was estimated for 659 buildings belonging to the urban area of Villa d'Agri. Finally, in order to assess the possible occurrence of the double resonance phenomenon, we compared the main frequency of each building with that interpolated for the underlying foundation soil. The results show that the probability of being affected by the double resonance effect is very high only for a couple of buildings, high for about 16% of the buildings, moderate for the 23% and practically null for most buildings (60%).

Investigation on double shock in vibration response of the gear pair with spalling defects

As an important component, the gear pair is frequently used in the mechanical transmission. If there is a localized spalling defect on the gear pair, the double shock phenomenon in the vibration response can be observed. In order to reveal the mechanism, an 8DOFs dynamic model for the gear pair is established, the symmetric and asymmetric rectangular spalling defects are considered, the torsional deformation is introduced. Meanwhile, the change law of the double shock during the defect expansion is explored. From the results, the double shock is caused by multiple changes in meshing stiffness, the amplitude and distribution range are closely related to the defect sizes. When the localized defect is extended along the length and depth directions, the amplitude of the double shock is significantly increased. If the defect area is asymmetric along the center plane, the torsional deformation of the gear pair will be generated. Then, the meshing stiffness is reduced, and the double shock becomes more obvious. Finally, through the finite element method and the experiment, the established model is confirmed.

Determination of the Dominating Coalescence Pathways in Double Emulsion Formulations by Use of Microfluidic Emulsions

In water-in-oil-in-water (W1/O/W2) double emulsions several irreversible instability phenomena lead to changes. Besides diffusive processes, coalescence of droplets is the main cause of structural changes. In double emulsions, inner droplets can coalesce with each other (W1–W1 coalescence), inner droplets can be released via coalescence (W1–W2 coalescence) and oil droplets can coalesce with each other (O–O coalescence). Which of the coalescence pathways contributes most to the failure of the double emulsion structure cannot be determined by common measurement techniques. With monodisperse double emulsions produced with microfluidic techniques, each coalescence path can be observed and quantified simultaneously. By comparing the occurrence of all possible coalescence events, different hydrophilic surfactants in combination with PGPR are evaluated and discussed with regard to their applicability in double emulsion formulations. When variating the hydrophilic surfactant, the stability against all three coalescence mechanisms changes. This shows that measuring only one of the coalescence mechanisms is not sufficient to describe the stability of a double emulsion. While some surfactants are able to stabilize against all three possible coalescence mechanisms, some display mainly one of the coalescence mechanisms or in some cases all three mechanisms are observed simultaneously.

Size-dependent vibrations of bi-directional functionally graded porous beams under moving loads incorporating thickness effect

This article analyzes the forced and free vibrations of bi-directional functionally graded (BDFG) porous nanobeams under moving loads by considering the thickness effect based on the nonlocal strain gradient theory (NSGT). It is assumed that the material properties of the system are graded across the transverse and axial directions according to power and exponential laws, respectively. Various porosity models, including even, uneven, and asymmetric porosity distribution patterns, are considered to model the porosity effects. The dynamic equation of the system is derived by implementing the physical neutral surface concept. Analytical and numerical approaches are adopted to acquire the vibration response of the system. Mathematical closed-form expressions are provided for various dynamic phenomena, such as two types of cancelation, two types of resonance, maximum resonance, cancelation disappearance, and resonance disappearance. In addition, for the first time in this article, it is demonstrated that BDFG porous nanobeams under moving loads are prone to experience the double cancelation phenomenon. Several comparison studies with published data are conducted to validate the results. Also, comprehensive parametric studies are carried out to elucidate the impacts of system parameters such as thickness power index, axial gradient parameter, scale parameter ratio, axial force, porosity coefficient, and porosity distribution pattern on the dynamic magnification factor, critical load speed, and maximum free-response. The outcomes established that by considering the thickness effect, the stiffening behavior of the system is amplified depending on the slenderness ratio. Also, it is concluded that, among the considered porous models, the critical load speed for the system with an even porosity distribution is more dependent on the thickness power index.

Identification of wind turbine gearbox weak compound fault based on optimal empirical wavelet transform

A double modulation phenomenon is found in wind turbine gearbox compound fault signals, consisting of a resonance modulation frequency band and an asymmetric modulation frequency band. The modal aliasing and the double modulation phenomena make it difficult to use empirical wavelet transform to obtain the spectral components in the meshing modulation regions. Our main contribution is to establish an optimal empirical wavelet transform (OEWT) framework for weak feature extraction of compound faults, which incorporates the optimal velocity synchronous linear chirplet transform (OVSLCT) and the simulated annealing (SA) algorithm to obtain the optimal parameters of the filter bank. The frequency boundary of the fault component is obtained through OVSLCT rather than the extreme value of the spectrum. A filter transition band width optimization scheme is proposed in which the optimal transition band width of the filter bank in EWT is optimized by the SA algorithm. Compared with the original EWT and variational mode decomposition, OEWT can better obtain the compound fault characteristic frequency and solve the mode aliasing problem.

Analysis of Interpolating Regression Models and the Double Descent Phenomenon

A regression model with more parameters than data points in the training data is overparametrized and has the capability to interpolate the training data. Based on the classical bias-variance tradeoff expressions, It is commonly assumed that models which interpolate noisy training data are poor to generalize. In some cases, this is not true. The best models obtained are overparametrized and the testing error exhibits the double descent behavior as the model order increases. In this contribution, we provide some analysis to explain the double descent phenomenon, first reported in the machine learning literature. We focus on interpolating models derived from the minimum norm solution to the classical least-squares problem and also briefly discuss model fitting using ridge regression. We derive a result based on the behavior of the smallest singular value of the regression matrix that explains the peak location and the double descent shape of the testing error as a function of model order.

Longitudinal Evolution of Storm-Enhanced Densities: A Case Study

Due to the limitations on observational data, most storm-enhanced density (SED) studies have focused on the North American sector. The complete picture of the longitudinal evolution of SEDs is still not clear. In this study, we investigated the dynamic evolution of SEDs from the European sector to the North American sector during a geomagnetic storm that occurred on the 15 July 2012, the main phase of which lasted nearly 30 h, maintaining the stable interplanetary magnetic field (IMF) and solar wind input conditions. Multiple data sets were analyzed, including convection data from the Super Dual Auroral Radar Network (SuperDARN), total electron contents (TECs) from the Madrigal database, plasma data from the Millstone Hill incoherent scatter radar (MHISR), solar wind and geomagnetic indices from OMNIWeb, and regional auroral electrojet indices from SuperMAG. The observations showed that the positions of SEDs shifted from local noon over the European sector towards dusk over the American sector and simultaneously moved to lower latitudes. The peak values of SED TECs were found to be greater in the European sector and to decrease with universal time. A double SED phenomenon appeared in the North American sector, which is the first of its kind to be reported. Further analysis showed that the temporal and spatial changes in the SEDs were associated with the eastward auroral electrojet.

Influence of chemisorption on the double hysteresis phenomenon during reactive sputtering

Process curves that are obtained during reactive magnetron sputtering can exhibit a double S-shape, also termed a double hysteresis. A previous study mainly focused on the relationship between the double shape behavior and the reaction kinetics of implanted reactive ions, although chemisorption also defines the target condition. As a follow-up study, the influence of chemisorption on double hysteresis is computationally studied by high-throughput calculations using a state-of-the-art model for reactive sputtering. The analysis reveals that the magnitude of the double hysteresis is a conserved quantity for the chemisorption driven reactions at the substrate level. At the target level, a balance between compound formation by direct reactive ion implantation and chemisorption is established. A minimal condition for double hysteresis is derived and process conditions are identified for which the double hysteresis can be measured for target materials prone to strong chemisorption of the reactive gas. The condition can assist to further explore the close interplay between chemisorption and implantation during reactive sputtering.

The Double Capsule Phenomenon in a Case Series and its Relationship with the Macro-Textured Breast Implant.

Silicone breast augmentation remains one of the most common aesthetic surgery procedures, and 2022 marks the 60th anniversary of the first case. Recent studies suggest a link between double capsule (DC) formation and macro-textured devices. Between 2010 and 2015, 268 aesthetic patients underwent bilateral mammary prosthesis exchange for indications including PIP exchange, adverse capsular contracture and ultrasonographic evidence of rupture. All surgery, in the form of implant exchange and capsulectomy, was undertaken by the senior author using standard techniques. A retrospective review was undertaken, and data analysed with descriptive statistics and Fisher's exact and Mann-Whitney U tests. Of 268 patients identified, 40 (14.9%) showed some degree of capsular duplication and bilateral involvement was marginally more common (52.5%). Two macroscopic patterns of duplication were observed: complete and subtotal. Complete DCs correlated with a clinical triad of extreme firmness, mobility and minimal-to-no pain. Whilst a wide range of manufacturers was represented, macro-textured devices were associated with the highest DC prevalence (58.3% vs. 5.6%) (Fisher's exact test p < 0.00001). Patients with DC had been implanted for less than half the time, median 52 versus. 120 months (p = 0.0003) of those without. An elevated prevalence of duplicate capsules in macro-textured prostheses is reconfirmed in addition to a novel symptom constellation that may assist with clinical diagnosis. Our study reinforces the aetiopathogenic influence of the elastomer in DC formation and reports DC for the first time in non-macrotextured implants. Single-surgeon cohort of 268 consecutive patients with 532 implants Statistically significant association of macro-textured devices with DC Statistically significant reduced duration of implantation of macro-textured devices First report of DC in non-macro-textured devices LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .