Position Of Drop Research Articles

Coherent Quantum Network of Superconducting Qubits as a Highly Sensitive Detector of Microwave Photons for Searching of Galactic Axions

We propose a novel approach to detect a low power microwave signal with a frequency of the order of several GHz based on a coherent collective response of quantum states occurring in a superconducting qubits network (SQN). An SQN composes of a large number of superconducting qubits embedded in a low-dissipative superconducting resonator. Our theory predicts that an SQN interacting with the off-resonance microwave radiation, demonstrates the collective alternating current Stark effect that can be measured even in the limit of single photon counting. A design of the layout of three terminals SQN detectors containing 10 flux qubits weakly coupled to a low-dissipative R-resonator and T-transmission line was developed. The samples were fabricated by Al-based technology with Nb resonator. The SQN detector was tested in terms of microwave measurements of scattering parameters and two-tone spectroscopy. A substantial shift of the frequency position of the transmission coefficient drop induced by a second tone pump signal was observed, and this effect clearly manifests a nonlinear multiphoton interaction between the second-tone microwave pump signal and an array of qubits.

Stepping Closer to Pulsed Single Microwave Photon Detectors for Axions Search

Axions detection requires the ultimate sensitivity down to the single photon limit. In the microwave region this corresponds to energies in the yJ range. This extreme sensitivity has to be combined with an extremely low dark count rate, since the probability of axions conversion into microwave photons is supposed to be very low. To face this complicated task, we followed two promising approaches that both rely on the use of superconducting devices based on the Josephson effect. The first one is to use a single Josephson junction (JJ) as a switching detector (i.e. exploiting the superconducting to normal state transition in presence of microwave photons). We designed a device composed of a coplanar waveguide terminated on a current biased Josephson junction. We tested its efficiency to pulsed (pulse duration 10 ns) microwave signals, since this configuration is closer to an actual axions search experiment. We show how our device is able to reach detection capability of the order of 10 photons with frequency 8 GHz. The second approach is based on an intrinsically quantum device formed by two resonators coupled only via a superconducting qubit network (SQN). This approach relies on quantum nondemolition measurements of the resonator photons. We show that injecting RF power into the resonator, the frequency position of the resonant drop in the transmission coefficient (S21) can be modulated up to 4 MHz. We anticipate that, once optimized, both the devices have the potential to reach single photon sensitivity.

Ultrasonic Guided Waves for Liquid Water Localization in Fuel Cells: An Ex Situ Proof of Principle.

Water management is a key issue in the design and operation of proton exchange membrane fuel cells (PEMFCs). For an efficient and stable operation, the accumulation of liquid water inside the flow channels has to be prevented. Existing measurement methods for localizing water are limited in terms of the integration and application of measurements in operating PEMFC stacks. In this study, we present a measurement method for the localization of liquid water based on ultrasonic guided waves. Using a sparse sensing array of four piezoelectric wafer active sensors (PWAS), the measurement requires only minor changes in the PEMFC cell design. The measurement method is demonstrated with ex situ measurements for water drop localization on a single bipolar plate. The wave propagation of the guided waves and their interaction with water drops on different positions of the bipolar plate are investigated. The complex geometry of the bipolar plate leads to complex guided wave responses. Thus, physical modeling of the wave propagation and tomographic methods are not suitable for the localization of the water drops. Using machine learning methods, it is demonstrated that the position of a water drop can be obtained from the guided wave responses despite the complex geometry of the bipolar plate. Our results show standard deviations of 4.2 mm and 3.3 mm in the x and y coordinates, respectively. The measurement method shows high potential for in situ measurements in PEMFC stacks as well as for other applications that require deposit localization on geometrically complex waveguides.

Simulations of Helical Inflationary Magnetogenesis and Gravitational Waves

Abstract Using numerical simulations of helical inflationary magnetogenesis in a low reheating temperature scenario, we show that the magnetic energy spectrum is strongly peaked at a particular wavenumber that depends on the reheating temperature. Gravitational waves (GWs) are produced at frequencies between 3 nHz and 50 mHz for reheating temperatures between 150 MeV and 3 × 105 GeV, respectively. At and below the peak frequency, the stress spectrum is always found to be that of white noise. This implies a linear increase of GW energy per logarithmic wavenumber interval, instead of a cubic one. Both in the helical and nonhelical cases, the GW spectrum is followed by a sharp drop for frequencies above the respective peak frequency. In this magnetogenesis scenario, the presence of a helical term extends the peak of the GW spectrum and therefore also the position of the aforementioned drop toward larger frequencies compared to the case without helicity. This might make a difference in it being detectable with space interferometers. The efficiency of GW production is found to be almost the same as in the nonhelical case, and independent of the reheating temperature, provided the electromagnetic energy at the end of reheating is fixed to be a certain fraction of the radiation energy density. Also, contrary to the case without helicity, the electric energy is now less than the magnetic energy during reheating. The fractional circular polarization is found to be nearly 100% in a certain range below the peak frequency range.

Identification of the origin area of hematic spots on a crime scene: theoretical analysis

The aim of this work is to generate a theoretical physical analysis that could be used as a tool that facilitates the criminalistic function in its objective of clarifying the truth and helping to impart justice. One of the most studied fields of action in the criminal area is related to the scenes of a crime, in which, generally, there are evidences associated with hematic impressions. A drop of blood, in its way towards the ground, follows a trajectory that can be calculated through the laws of Physics, behaving like a body in a fluid. To the extent that this model is more detailed, the position of the blood drop can be described more precisely. A detailed analysis of the displacement in the air of a drop of blood, generated by a cutting wound, is presented. Results could be used to determine the spatial point of origin of a drop of blood from experimental measurements on the hematic impression in crime scene. The proper estimation of this position could be of great help at the moment of a criminal investigation since could serve as an additional evidence offering a clearer vision of the events that occurred, to the judge.

Research on Stator Main Insulation Temperature Field of Air-Cooled Turbo-Generator after Main Insulation Shelling

The stator main insulation is the key component of turbo-generator, which is related to the thermal aging of turbo-generator. It is vital to accurately judge the generator aging by calculating the temperature distribution under main insulation normal operation and fault operation. In this paper, taking a 150 MW air-cooled turbo-generator as an example, the temperature field of the main insulation was studied after the stator main insulation shelling. Based on the finite element method, the stator temperature field after the main insulation shelling was calculated. The main insulation position of maximum temperature drop and the temperature distribution of the stator main insulation along the circumference and the axial direction were analyzed. At the same time, with the shelling gap of main insulation increases, the temperature distribution between shelling gap δ = 0.5 mm and δ = 1.0 mm was compared. The results can provide a theory for fault monitoring and diagnostics of the large-scale turbine generator.

Simulation of liquid reaction and droplet formation on a moving micro-object by lattice Boltzmann method

This paper investigates condensation process and liquid reaction on a moving square shape micro-object by lattice Boltzmann method. Micro-object with a horizontal velocity toward the left side of the domain is considered. Both condensation and evaporation processes are included in the simulations for three cases. For first case, it is assumed that there is no liquid on micro-object walls at initial time and appearance of liquid is only due to the condensation. For second, and third cases, a drop is considered initially on upper, and back walls of the micro-object, respectively. The effects of initial position of drop and velocity of micro-object on liquid reaction and condensation process are investigated. It is found that for all values of micro-object velocity, the difference between three cases for liquid reaction parameter will be negligible over time. Moreover, the liquid reaction grows faster for high values of micro-object velocity.

Optimization for Cavitation Inception Performance of Pump-Turbine in Pump Mode Based on Genetic Algorithm

Cavitation is a negative factor of hydraulic machinery because of its undesirable effects on the operation stability and safety. For reversible pump-turbines, the improvement of cavitation inception performance in pump mode is very important due to the strict requirements. The geometry of blade leading edge is crucial for the local flow separation which affects the scale and position of pressure drop. Hence, the optimization of leading edge shape is helpful for the improvement of cavitation inception performance. Based on the genetic algorithm, optimization under multiple flow rate conditions was conducted by modifying the leading edge ellipse ratio and blade thickness on the front 20% meanline. By using CFD simulation, optimization was completed with obvious improvements on the cavitation inception performance. CFD results show that the pressure drop location had moved downstream with the increasement of the minimum pressure coefficient. Experimental verifications also got an obvious enhancement of cavitation inception performance. The stability and safety was improved by moving the cavitation inception curve out of the operating range. This optimization is proved applicable and effective for the engineering applications of reversible pump-turbines.

Nonequilibrium electron-vibration coupling and conductance fluctuations in a C60junction

We investigate chemical bond formation and conductance in a molecular C${}_{60}$ junction under finite bias voltage using first-principles calculations based on density functional theory and nonequilibrium Green's functions (DFT-NEGF). At the point of contact formation we identify a remarkably strong coupling between the C${}_{60}$ motion and the molecular electronic structure. This is only seen for positive sample bias, although the conductance itself is not strongly polarity dependent. The nonequilibrium effect is traced back to a sudden shift in the position of the voltage drop with a small C${}_{60}$ displacement. Combined with a vibrational heating mechanism we construct a model from our results that explain the polarity-dependent two-level conductance fluctuations observed in recent scanning tunneling microscopy (STM) experiments [N. N\'eel et al., Nano Lett. 11, 3593 (2011)]. These findings highlight the significance of nonequilibrium effects in chemical bond formation/breaking and in electron-vibration coupling in molecular electronics.

Equilibrium Position of a Buoyant Drop in Couette and Poiseuille Flows at Finite Reynolds Numbers

AbstractThe equilibrium position of a deformable drop in Couette and Poiseuille flows is investigated numerically by solving the full Navier-Stokes equations using a finite difference/front tracking method. The objective of this work is to study the motion of a non-neutrally buoyant drop in Couette and Poiseuille flows with different density ratios at finite Reynolds numbers. Couette flow: The equilibrium position of the lighter drops is higher than the heavier drops at each particle Reynolds number. Also, the equilibrium position height increases with increasing the Reynolds number at a fixed density ratio. At this equilibrium distance from the wall, the migration velocity is zero, while the velocity of the drop in the flow direction and rotational velocity of the drop is finite. It is observed that the equilibrium position is independent of the initial position of the drops and depends on the density ratio and the shear Reynolds number. Poiseuille flow: When the drop is slightly buoyant, it moves to an equilibrium position between the wall and the centerline. The equilibrium position is close to the centerline if the drop lags the fluid but close to the wall if the drop leads the fluid. As the Reynolds number increases, the equilibrium position of lighter drops moves slightly closer to the wall and the equilibrium position of heavier drops moves towards the centerline.

A simple approach to determine the equilibrium shape and position of sandwiched polymer droplets

AbstractThe thermodynamic shape and position of a polymer drop sandwiched between two polymer melt plates were predicted by simulating the change of the interfacial energy according to various shapes and position of the drop. The calculation results were in a precise coincidence with the experimental results exhibiting lens, spreading, and encapsulation. The simple formula and easy concept of the calculation can be useful to predict the morphology of immiscible ternary blends with the information of the interfacial tensions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2729–2738, 2007

Fast Penetration of Liquid Gallium in Polycrystalline Aluminum Films

From optical microscopic observations a small drop of liquid gallium placed on an aluminum thin film has been found to form arachnoid rises on the film surface. In addition, metallic luster was lost in a bigger region concentrically extending from the position of the gallium drop. These must have occurred because of the penetration of gallium atoms into the film. The speed of gallium webbing was measured to be 2.3 \\micron/s to 9.1 \\micron/s, depending on the film thickness, the temperature and the amount of gallium drop. On the other hand, the dull region extended at the speed of approximately 0.83 \\micron/s, insensitively to the above factors. The embrittlement of aluminum by liquid gallium can be associated with this fast penetration of liquid gallium.

A numerical study of the motion of drops in Poiseuille flow. Part 1. Lateral migration of one drop

The cross-stream migration of a deformable drop in two-dimensional Hagen–Poiseuille flow at finite Reynolds numbers is studied numerically. In the limit of a small Reynolds number (< 1), the motion of the drop depends strongly on the ratio of the viscosity of the drop fluid to the viscosity of the suspending fluid. For viscosity ratio 0.125 a drop moves toward the centre of the channel, while for ratio 1.0 it moves away from the centre until halted by wall repulsion. The rate of migration increases with the deformability of the drop. At higher Reynolds numbers (5–50), the drop either moves to an equilibrium lateral position about halfway between the centreline and the wall – according to the so-called Segre–Silberberg effect or it undergoes oscillatory motion. The steady-state position depends only weakly on the various physical parameters of the flow, but the length of the transient oscillations increases as the Reynolds number is raised, or the density of the drop is increased, or the viscosity of the drop is decreased. Once the Reynolds number is high enough, the oscillations appear to persist forever and no steady state is observed. The numerical results are in good agreement with experimental observations, especially for drops that reach a steady-state lateral position. Most of the simulations assume that the flow is two-dimensional. A few simulations of three-dimensional flows for a modest Reynolds number (Re = 10), and a small computational domain, confirm the behaviour seen in two dimensions. The equilibrium position of the three-dimensional drop is close to that predicted in the simulations of two-dimensional flow.

Plasma Confinement by Surface Magnetic Field

The mechanism of plasma confinement by a surface magnetic field configuration (surmac) is studied in a linear device. The end losses are reduced by bending the surmac coil so as to have a small aperture at the both ends. The penetrating length of a plasma into the magnetic wall is much shorter than the local ion gyroradius. A sharp potential dip was observed at the position of the density drop, and it is confirmed that the formation of the dip is essential for the plasma confinement. The particle loss across the magnetic wall is due to classical ambipolar diffusion, and the saturation at high magnetic field operation is explained by the end loss.

Drift of drops in density gradient columns

The rate of drift of drops of sodium chloride solution in density gradient columns composed of mixtures of bromobenzene and kerosine increases with concentration of solute and decreases with drop size. Size also affects position of drop, larger drops tending to come to rest at higher levels than smaller drops. Drift is greatest in columns whose components are dried over calcium chloride, is diminished in columns whose components are presaturated with water or sodium chloride solution, and is nearly eliminated in columns whose components are presaturated with potassium bromide solution. It is not affected significantly by presaturation of aqueous test samples with the mixtures of solvents used in the columns. Drift is also observed with test samples containing solutes other than sodium chloride. Further, it is greater in columns composed of bromobenzene and xylene than in those composed of bromobenzene and kerosine. The significance of these findings as they may affect error of measurement of density is pointed out. A new method for obtaining linearity in density gradient columns also is described.