Static Fluctuations Research Articles

Comparison of entangling protocols in ABC-type spin chains

In this contribution we consider an advantageous building block with potential for various quantum applications: a device based on coupled spins capable of generating and sharing out an entangled pair of qubits. Our model device is a dimerized spin chain with three weakly coupled embedded sites (defects). Three different entangling protocols were proposed for this chain in [1] and [2], one producing a Cluster state building block and two generating a Bell state, depending on the initial state injection. Here we compare the robustness of such protocols as quantum entangling gates against different types of fabrication (static energy fluctuations) and operation (timing injection delays) errors.

Characterization of flow interactions in an axial fan stage

AbstractThe aim of this study is to characterize the steady and unsteady flows of a high‐speed axial fan stage and assess its aerodynamic performance parameters. The flow unsteadiness is related to the stator‐rotor interaction originated mainly by two mechanisms: the first is attributed to the potential effect and the second to the wake‐blade interaction and the mixing through the blades' passages. Such effects are dependent on the circumferential positions of blades and inter‐distance between stator and rotor, which could be alleviated by understanding these flow interactions. The pressure waves' main diametrical modes (two blades interacting with two vanes) and their sequences are predicted analytically. FFT analysis of the computed static pressure fluctuations at different monitor points allowed identifying the prevailing modes of interaction and their frequencies and sequence. The assessment of inter‐distance is an important step toward identifying the detrimental effects of axial interdistance on the aerodynamic performance. The closer the blade‐rows of this fan stage can be spaced, the more compact the cooling system of an automotive could be designed.

Design of Electronic Blood Pressure Testing System

With the continuous development of electronic technology, the previous traditional methods of blood pressure testing are far from meeting people’s requirements. Fortunately, the advent of electronic blood pressure meters has shown great convenience and potential. Against the backdrop, a new electric blood pressure testing system based on a CC3200 LaunchPad is proposed in this paper, which uses a pressure sensor to collect the information of static pressure and fluctuation of blood pressure, and then transmits the processed data to the software in PC. The software in PC analyzes the data by oscillometric method and Gaussian fitting method, and then the static pressure, systolic pressure and diastolic pressure are calculated and displayed. Test results show that the blood pressure testing efficiency is greatly improved by this system with its high accuracy and reliability, which can meet the requirement of the AAMI (Association for the Advancement of Medical Instrumentation) standard.

Experimental investigation of the dynamic cavitation behavior and wall static pressure characteristics through convergence-divergence venturis with various divergence angles

As a highly efficient and energy-saving cavitation method, Venturi cavitation is widely used in many industrial fields. This study synchronously investigated the cavity behavior and its corresponding wall static pressure characteristics in Venturi channels with various divergence angles to research the role of the divergence angle in cavity shape and the wall static pressure oscillation. Five rectangular Venturi channels with different divergence angles (4°, 6°, 8°, 10°, and 12°) were tested at the cavitation number (0.3–1.0). Based on the dynamic behaviour of gas–liquid interface, three cavity shedding types were identified: front shedding (I), central shedding (II) and tail shedding (III). A modified correlation for predicting average cavity length was proposed with the consideration of the effect of the divergence angle. Combined with the wall static pressure characteristics, as the divergence angle increased, the wall static pressure fluctuation in the Venturi became more intense. According to the wall static pressure oscillation characteristics, for the larger divergence angles (θ = 6°, 8°, 10° and 12°), the wall static pressure oscillation frequency was the same as the cavity shedding frequency and increased with the increase of the divergence angle. For smaller divergence angle (θ = 4°), no definite periodicity in pressure oscillation frequency could be observed.

Model tests of the evolutionary process and failure mechanism of a pile-reinforced landslide under two different reservoir conditions

Anti-slide piles are widely used for stabilizing landslides and a large number of landslide-piles systems were constituted in reservoir areas. How these landslide-piles systems evolve under reservoir effects is vital for the safe operation of dams. In this study, two reservoir conditions, namely condition of static water level and water level fluctuations, were considered for detailly exploring the influence of static and dynamic water pressure on a landslide-piles system in physical model tests. The pore water pressure, surface deformation and photographs of visual observations were obtained for comparatively analyzing the deformation characteristic and failure mechanism of landslide-piles models under the two conditions. The results show that the soil deformation and failure around the piles were similar in the two tests due to the same pile arrangements. However, retrogressive deformation and two soil collapses occurred in the landslide front area under water level fluctuations instead of slight deformation and shallow erosion under the static water level. The outward hydrodynamic pressure caused by reservoir drawdowns was the primary reason for the soil collapses in the landslide front area. The progressively intensified deformation around the piles which indirectly decreased the soil stability in the landslide front area was the secondary cause for the collapses. The Majiagou landslide-piles system in the field was identified as in the early period of the uniform deformation stage at present based on the field observations, monitoring data and the test results under water level fluctuations.

Clocking effect in a centrifugal pump with a vaned diffuser

The performance and service life of centrifugal pumps can be influenced by the clocking effect. In this study, 3D numerical calculations based on the k-omega shear stress transport model are conducted to investigate the clocking effect in a centrifugal pump. Time-averaged behavior and transient behavior are analyzed. Results show that the optimum diffuser installation angle in the centrifugal pump is [Formula: see text] due to the minimum total pressure loss and radial force acting on the impeller. Total pressure loss, particularly in the volute, is considerably influenced by the clocking effect. The difference in total pressure loss in the volute at different clocking positions is 2.75 m under the design flow rate. The large total pressure loss in the volute is primarily caused by the large total pressure gradient within the vicinity of the volute tongue. The radial force acting on the impeller is also considerably affected by the clocking effect. When the diffuser installation angle is [Formula: see text], flow rate fluctuations in the volute and impeller passage are minimal, and flow rate distribution in the diffuser passage is more uniform than those in other diffuser installation angles. Moreover, static pressure fluctuations in the impeller midsection and the diffuser inlet section are at the minimum value. These phenomena explain the minimum radial force acting on the impeller. The findings of this study can provide a useful reference for the design of centrifugal pumps.

Thermodynamics-Structure-Dynamics Correlations and Nonuniversal Effects in the Elastically Collective Activated Hopping Theory of Glass-Forming Liquids.

We employ the microscopic Elastically Collective Nonlinear Langevin Equation (ECNLE) theory of activated dynamics in combination with crystal-avoiding simulations to study four inter-related questions for metastable monodisperse hard sphere fluids. The first is how significantly improved integral equation theory structural input (Modified-Verlet (MV) closure) changes the dynamical predictions of ECNLE theory. The main consequence is a modest enhancement of the importance of the collective elastic barrier relative to its local cage contribution, which increases the alpha relaxation time and fragility relative to prior results based on the Percus-Yevick closure. Second, ECNLE-MV theory predictions for the alpha time and self-diffusion constant in the metastable regime are quantitatively compared to our new simulations. The small adjustment of a numerical prefactor that enters the collective elastic barrier leads to quantitative agreement over three decades. Third, using the more accurate MV structural input, ECNLE theory is shown to predict thermodynamics-structure-dynamics "correlations" based on various long and short wavelength scalar properties all related to static two-point collective density fluctuations. The logarithm of the alpha relaxation time scales as a power law with these scalar metrics with an exponent that is significantly lower in the less dense noncooperative activated regime compared to the very dense highly cooperative regime. However, the discovered correlation of activated relaxation with a thermodynamic property (dimensionless compressibility) is not causal in ECNLE theory, but rather reflects a strong connection between the local structural quantities that quantify kinetic constraints in the theory with the amplitude of long wavelength density fluctuations. Fourth, the consequences of chemically specific nonuniversalities associated with the onset condition and relative importance of collective elasticity are studied. The predicted thermodynamics-structure-dynamics correlations are found to be robust, albeit with nontrivial shifts of the onset condition.

Measurements of freestream density fluctuations in a hypersonic wind tunnel

Density disturbances in the freestream of the University of Southern Queensland’s Mach 6 wind tunnel ( $$\rho _{\infty } \approx {34\, \hbox {gm}^{-3}}$$ ) have been measured using a focused laser differential interferometer (FLDI). The direct contribution of the turbulent shear layer from the Mach 6 nozzle to the FLDI signal was largely eliminated by mechanically shielding the FLDI beams from these effects. This improvement significantly enhanced the low wavenumber FLDI spectra which allowed a von Kármán spectrum fit and demonstrated a $$-5/3$$ roll-off in the inertial subrange and enabled the identification of the integral length scale (28–29 mm). The normalised root-mean-square density fluctuations were found to change over the flow duration (typically between 0.4 and $$0.6\%$$ ) for the 1–250 kHz frequency range which corresponds to the wavenumber range of 6– 1600 $${\mathrm{m}}^{-1}$$ in this Mach 6 flow. Previous disturbance measurements using intrusive methods have identified a narrowband 3–4 kHz disturbance that is first measured in the core flow about 65 ms after the flow begins and remains until the flow terminates. The onset of this narrowband disturbance was previously correlated with transition-to-turbulence in the subsonic test gas supply to the nozzle. This correlation was investigated further herein, and the 3–4 kHz feature was inferred to be entropy mode disturbances by showing the departure of the FLDI measurements from Pitot pressure measurements. Through the comparison of FLDI and Pitot pressure data, Pitot pressure probes were demonstrated to produce a poor estimate of the static pressure fluctuations when non-isentropic disturbances are non-negligible.

Microscopic Theory of Dynamically Heterogeneous Activated Relaxation as the Origin of Decoupling of Segmental and Chain Relaxation in Supercooled Polymer Melts

We combine our force-based theory of activated segmental relaxation for glass-forming polymer melts, with our new formulation of how nm-scale effectively static structural fluctuations induce dynam...

Interactions between Moisture and Tropical Convection. Part II: The Convective Coupling of Equatorial Waves

AbstractThe exponential increase in precipitation with increasing column saturation fraction (CSF) is used to investigate the role of moisture in convective coupling. This simple empirical relationship between precipitation and CSF is shown to capture nearly all MJO-related variability in TRMM precipitation, ~80% of equatorial Rossby wave–related variability, and ~75% of east Pacific easterly wave–related variability. In contrast, this empirical relationship only captures roughly half of TRMM precipitation variability associated with Kelvin waves, African easterly waves, and mixed Rossby–gravity waves, suggesting coupling mechanisms other than moisture are playing leading roles in these phenomena. These latter phenomena have strong adiabatically forced vertical motions that could reduce static stability and convective inhibition while simultaneously moistening, creating a more favorable convective environment. Cross-spectra of precipitation and column-integrated dry static energy show enhanced coherence and an out-of-phase relationship in the Kelvin wave, mixed Rossby–gravity wave, and eastward inertio-gravity wave bands, supporting this narrative. The cooperative modulation of precipitation by moisture and temperature anomalies is shown to shorten the convective adjustment time scale (i.e., time scale by which moisture and precipitation are relaxed toward their “background” state) of these phenomena. Speeding the removal of moisture anomalies relative to that of temperature anomalies may allow the latter to assume a more important role in driving moist static energy fluctuations, helping promote the gravity wave character of these phenomena.

Two-dimensional O(n) Models with Defects of “Random Local Anisotropy” Type

The phase diagram of two-dimensional systems with continuous symmetry of the vector order parameter containing defects of the "random local anisotropy" type is investigated. In the case of a weakly anisotropic distribution of the easy anisotropy axes in the space of the order parameter, with decreasing temperature, a smooth transition takes place from the paramagnetic phase with dynamic fluctuations of the order parameter to the Imri-Ma phase with its static fluctuations. In the case when the anisotropic distribution of the easy axes induces a global anisotropy of the "easy axis" type that exceeds a critical value, the system goes into the Ising class of universality, and a phase transition to the ordered state occurs in it at a finite temperature.

Optical Absorption Spectrum of Small Graphene Fragments with Topological Defects

Energy spectra of small graphene fragments with and without topological defects (vacancies, nanopores and Stone–Wales defects) are obtained using the Hubbard model based on the approximation of static fluctuations. Modeling of optical absorption spectra is performed for both defect-free and defective small graphene fragments of the lattice. The analysis is given to optical absorption spectra changing with increasing number of vacancies. It is shown how the energy gap depends on the defect configuration and concentration.

Efficiency and stability of lump coal particles swirling flow pneumatic conveying system

To clear the swirling flow pneumatic conveying performance for blocky fuel particles, particularly for lump coal particles, a side inlet guide vane swirling generator was developed and employed to study the efficiency and stability of lump coal particles in swirling flow pneumatic conveying. In total, 32 pilot scale tests for different conditions, including different airflow rates, solid mass flow rates, and swirling intensities, were conducted in this paper. The efficiency and stability of lump coal particles in swirling flow pneumatic conveying are thoroughly discussed by considering the static pressure loss and pressure fluctuation standard deviation. The pressure characteristics for different conveying stages and frequency spectrum constituents of the static pressure are also discussed. The results show that the swirling flow has better energy preservation characteristics and conveying performance in proper conditions. Four main factors contribute to the static pressure fluctuation in three different frequency bands. The results also show that a low mean gas velocity with a medium swirling intensity and a high mean gas velocity with a weak swirling intensity can improve the conveying stability. The swirling flow is more stable at the front of the pipeline; meanwhile, the axial flow is better in the second half.

Long-range Order Induced by Random Fields in Two-dimensional O(n) Models, and the Imry–Ma State

The influence of defects of the "random local field" type with an anisotropic distribution of random fields on two-dimensional models with continuous symmetry of the vector order parameter is considered. In the case of weak anisotropy of random fields, with decreasing temperature there takes place a smooth transition from the paramagnetic phase with dynamic fluctuations of the order parameter to the Imry-Ma phase with static fluctuations caused by fluctuations of the random field of defects. In the case of strong anisotropy of random fields, defects lead to an effective decrease in the number of components of the order parameter and the appearance of a phase transition to an ordered state at finite temperature. It is shown that in the case of the defect-free two-dimensional X-Y model, the appearance of an arbitrarily weak anisotropy in the two-dimensional space of the order parameter completely eliminates the appearance of the Berezinsky-Kosterlitz-Thouless phase and gives rise to the phase with the long-range order.

Simulation of steady and unsteady flows through a small‐size Kaplan turbine

AbstractThe increasing demand for electric energy has pushed to rely on the microhydropower as one of the most cost‐effective technologies to improve the grid stability in rural localities. This article investigates the steady and unsteady flows in a complete small Kaplan turbine by means of the solver ANSYS‐CFX. Examination of the basic design parameters in terms of blade setting, vane opening, and interdistance has revealed the best operating parameters and the potentiality of performance improvement. Moreover, the Fast Fourier Transform of static pressure fluctuations recorded at different monitor points allowed analyzing the flow unsteadiness arising from the stator‐rotor interactions (RSI). The prevailing harmonics coinciding with the modes of RSI were determined and compared with the analytically predicted main diametrical modes and frequencies of the pressure waves. The found results in this category of low‐head small Kaplan turbine may serve in developing similar hydroturbines suitable for the microhydropower.

A collective elastic fluctuation mechanism for decoupling and stretched relaxation in glassy colloidal and molecular liquids.

We propose a microscopic theory for the decoupling of self-diffusion and structural relaxation in glass-forming liquids within the Elastically Collective Nonlinear Langevin Equation (ECNLE) activated dynamics framework. Our central hypothesis is that the heterogeneity relevant to this problem is static fluctuations of local density on the scale of 3-4 particle diameters and how this changes local packing correlations. These fluctuations modify the degree of dynamical cage expansion that mechanistically couples intracage large amplitude hopping and longer range collective elasticity in ECNLE theory. Decoupling only emerges in the deeply supercooled regime where the strongly temperature dependent elastic barrier becomes non-negligible relative to its noncooperative local analog. The theory makes predictions for various aspects of the decoupling phenomenon, including apparent fractional power law Stokes-Einstein behavior, that appear to be consistent with experiments and simulations on hard sphere fluids and molecular liquids. Of central importance is a microscopic connection between the barrier fluctuation variance and most probable barrier height. Sensible results are also obtained for the nonexponential stretching of a generic relaxation time correlation function and its temperature evolution. Nonuniversality can arise from the relative importance of the local and collective barriers (related to fragility) and the precise magnitude of the length scale that defines the transition from local cage to elastic physics. Comparison is made with a traplike model based on a Gaussian distribution of barriers.

Дальний порядок в двумерных O(n)-моделях, индуцированный случайными полями, и состояние Имри-Ма

A.A. Berzin, A.I. Morosov, and A.S. Sigov The influence of defects of the “random local field” type with an anisotropic distribution of random fields on two-dimensional models with continuous symmetry of the vector order parameter is considered. In the case of weak anisotropy of random fields, with decreasing temperature there takes place a smooth transition from the paramagnetic phase with dynamic fluctuations of the order parameter to the Imry-Ma phase with static fluctuations caused by fluctuations of the random field of defects. In the case of strong anisotropy of random fields, defects lead to an effective decrease in the number of components of the order parameter and the appearance of a phase transition to an ordered state at finite temperature.

Двумерные O(n)-модели с дефектами типа "случайная локальная анизотропия"

The phase diagram of two-dimensional systems with continuous symmetry of the vector order parameter containing defects of the “random local anisotropy” type is investigated. In the case of a weakly anisotropic distribution of the easy anisotropy axes in the space of the order parameter, with decreasing temperature, a smooth transition takes place from the paramagnetic phase with dynamic fluctuations of the order parameter to the Imri-Ma phase with its static fluctuations. In the case when the anisotropic distribution of the easy axes induces a global anisotropy of the “easy axis” type that exceeds a critical value, the system goes into the Ising class of universality, and a phase transition to the ordered state occurs in it at a finite temperature.

Numerical Examination on the Decay Characteristics of Static Pressure Fluctuation in the Developing Low Reynolds Number Grid-Generated Turbulence

Numerical Examination on the Decay Characteristics of Static Pressure Fluctuation in the Developing Low Reynolds Number Grid-Generated Turbulence

Электронное строение и оптическое поглощение фуллеренов как сильно коррелированных систем на примере молекулы C-=SUB=-96-=/SUB=-(C-=SUB=-2-=/SUB=-)

Taking into account the intrasite Coulomb interaction with the parameter U ~ 10 eV in the approximation of static fluctuations, the energy spectrum of the isomer N 181 (C2) of the C96 fullerene is calculated, based on which its optical absorption spectrum is modeled. The obtained curve of the optical absorption spectrum at a good qualitative level coincides with the experimental curve. The same curve obtained in the framework of the traditional model without taking into account the intranode Coulomb interaction differs significantly from the experimental curve. Keywords: fullerene, energy spectrum, optical absorption spectrum, π electron, Hubbard subband, optical transitions.