Magnitude Fluctuation Research Articles

Comparative research of the effect of the unilateral vertical slope at tunnel portals on aerodynamic performances of trains

This study set out to explore the effect of a unilateral vertical slope terrain at tunnel portals on the aerodynamic performances and operating stability of a train through a single-track tunnel. Hence, the surrounding flow field and aerodynamic performances of the train traveling through a single-track tunnel with three different configurations of tunnel portal terrain were comparatively investigated using numerical simulations. These three tunnel cases were the tunnels without vertical slope at the entrance and exit, with unilateral vertical slope at the entrance, and with unilateral vertical slope at the exit. The key results revealed that the vortex characteristics around the tail car exhibited strong asymmetry as the tail car entered into the tunnel case with a unilateral vertical slope topography at the entrance, which was obviously different from those of the other two tunnel cases. On the contrary, the vortex characteristics around the tail car under the three tunnel cases exhibited a strong similarity as the tail car was exiting the tunnel. The existence of the unilateral vertical slope at the entrance led to Fy, Mx, and Mz with the greatest magnitude value and fluctuation intensity for the tail car moving into the tunnel. Compared to the tunnel without unilateral vertical slope, the peak-to-peak value of Fy, Mx, and Mz of the tail car increased by 175%, 191.2%, and 70.42%, respectively. Furthermore, a high-intensity main frequency region was observed from the spectral analysis result of Fy, Mx, and Mz between t = 5 and 11 s as the tail car moved into the tunnel. These findings contribute to a better understanding of the phenomenon that the tail car of a train experienced pronounced transverse vibrations as the train passed through a single-track tunnel.

Earthquakes time series visualization in cilacap earthquake zone using QGIS and USGS data sets

Cilacap region earthquakes often occur with more than 5 Richter Scale. With these seismic conditions, earthquake studies in the Cilacap region will always be needed. These studies usually only have output in form of map visualization spatially, however, they have not been compiled in a time series. This study attempts to include visualization of spatial data in the form of a time-series. The data visualization was presented in form of graphs and maps. Graphical visualization using line bar graph type by applying descriptive statistics tries to determine the earthquake’s magnitude fluctuation. The other visualization in form of Heatmap map analysis applying the Kernel Density method is interpolated earthquake magnitude spatial data. The data used in this research was retrieved from the USGS datasets between 1918 to 2021. The spatial boundaries were taken from -7.324 ˚S, 107.941˚E to -10.407˚S, 111.116˚E. The results of spatial data visualization using the heatmap techniques were then analyzed temporally using the Temporal function in the QGIS software. The results of temporal analysis within a year are then sequenced into a video which is displayed on the following link https://youtu.be/m3B7HkfI8qY. The descriptive statistical analysis shows that Earthquakes have magnitudes ranging from 3.3 to 7.58 with a mean of 4.58 and a mode of 4.4. Heatmap analysis shows the results of earthquake magnitude interpolation with high density, located in the south of Cilacap and south of Yogyakarta. Also, the spatiotemporal analysis results show that there is a change in location trends that have high earthquake magnitude density values

A Pareto–Poisson process model for intermittent debris flow surges developing from slope failures

Many debris flows originate from shallow slope failures over the source area of valley and move in form of successive surges. In order to understand the behavior of such failures, we conducted seven sets of experiments of rainfall-induced soil failures in a 4 × 8 m spot on a slope under different rainfall intensities ranging from 12 to 60 mm/h, according to the local rainfall conditions in the valley of Jiangjia Gully, and this work is based on the experimental data. It is found that the failures are realization of a Poisson process with failure volume satisfying the Pareto distribution, thus the failure process can be simulated using a combinative Pareto-Poisson process (PPP) model. The PPP model incorporates a Poisson process determining the failure time, and a Pareto distribution characterizing the fluctuation of failure volume. The developing course of a debris flow surge is reduced to the hierarchic evolution of the failures from their source to the mainstream, which amounts to a cascade thinning process of the Poisson sequence in the PPP model framework. Given the controlling parameters (i.e., the Poisson intensity, Pareto distribution parameters, and thinning ratio), the model is capable of predicting surge sequences that agree well with the monitored surges in terms of time interval, magnitude fluctuation, and probability distribution. This study represents the first attempt to formulate a stochastic framework for debris flows developing from source to mainstream, which applies to debris flows fed by discontinuous material supplies from shallow slope failures.

The Missing Satellite Problem outside of the Local Group. II. Statistical Properties of Satellites of Milky Way–like Galaxies

We present a new observation of satellite galaxies around seven Milky Way (MW)–like galaxies located outside of the Local Group (LG) using Subaru/Hyper Suprime-Cam imaging data to statistically address the missing satellite problem. We select satellite galaxy candidates using magnitude, surface brightness, Sérsic index, axial ratio, FWHM, and surface brightness fluctuation cuts, followed by visual screening of false positives such as optical ghosts of bright stars. We identify 51 secure dwarf satellite galaxies within the virial radius of nine host galaxies, two of which are drawn from the pilot observation presented in Paper I. We find that the average luminosity function of the satellite galaxies is consistent with that of the MW satellites, although the luminosity function of each host galaxy varies significantly. We observe an indication that more massive hosts tend to have a larger number of satellites. Physical properties of the satellites such as the size–luminosity relation are also consistent with the MW satellites. However, the spatial distribution is different; we find that the satellite galaxies outside of the LG show no sign of concentration or alignment, while that of the MW satellites is more concentrated around the host and exhibits a significant alignment. As we focus on relatively massive satellites with M V < −10, we do not expect that the observational incompleteness can be responsible here. This trend might represent a peculiarity of the MW satellites, and further work is needed to understand its origin.

Effect of Turbulence Inhibitors on Molten Steel Flow in 66-Ton T-Type Tundish with Large Impact Area

A multiphase numerical simulation of the steel-slag flow was established by using the volume of fluid (VOF) model to study the effect of different turbulence inhibitors on the improvement of the steel-slag flow in the tundish. The steel-slag interface fluctuation was studied by vorticity magnitude and transient fluctuation change. A prediction model of residence time distribution (RTD) curve was established based on mathematical simulation and the error of prediction model can be controlled below 6% by comparing with the hydraulic results. The results show that jet flow into the tundish generated very different flow patterns. Case 1 produced a double-roll flow pattern and case 2 produced a four-roll flow pattern in the impact area. The ratio of vorticity magnitude above 1.00 s−1 near the ladle shroud was 2.60% in case 1 and the ratio of vorticity magnitude above 1.00 s−1 near the ladle shroud was 13.15% in case 2, which indicates case 2 increased the possibility of slag entrainment via the upward flow mechanism and shear layer instability. Surface velocity fluctuations in case 2 were much more severe near the ladle shroud. The thickness of the slag layer was 60 mm, the interface fluctuation towards surface in case 2 was close to 20 mm. Meanwhile, case 1 involved very small volume-fraction contours near interface. The turbulence inhibitor with internal ripples (case 1) showed a better optimization effect and the results could provide a theoretical basis for the selection of a suitable turbulence inhibitor for the 66-ton T-type tundish.

As2Se3-Ge11.5As24Se64.5 based mid-infrared dual nano-slot optical waveguide with huge and wavelength tunable dispersion

An As2Se3-Ge11.5As24Se64.5 based dual nano-slot waveguide with huge chromatic dispersion at mid-infrared is proposed. The large chromatic dispersion at the target wavelength is achieved induced by resonance interaction. The characteristics of dispersion are investigated by employing the FDTD method. The simulation results indicate that by optimizing the geometrical parameters, the maximum dispersion of -3.48×105 ps·nm-1·km-1 over a full width at FWHM of 2 nm at 3000 nm has been attained. A flat and ultra-large dispersion of -3.48×105 ps·nm-1·km-1 from 2980 to 3010 nm is achieved by cascading the dual-slot waveguides. The relative dispersion magnitude fluctuation is less than 1.85%.

Turbulent statistics of flow fields using large eddy simulations in batch high shear mixers

Large eddy simulations (LES) have been carried out for the first time to characterize the flow and turbulent characteristics in three different batch high shear mixers (HSMs) at a constant rotor speed of 4000rpm. Three HSMs having different stator heads such as circular, square and inclined stator head with 6, 92 and 210 numbers of stator holes, respectively have been investigated. Dynamic Smagorinsky model with sliding mesh method is used for the sub-grid scale stresses at a Reynolds number of 52,000, to overcome the prediction of RANS models. Numerical methodology is validated, in terms of Power number with the available numerical and experimental studies and found in fairly good agreement. The velocity flow patterns and fluctuations at different planes are predicted and vortexes have been observed within the stator holes and bulk fluid. It is observed that velocity magnitude fluctuation is a function of rotor rotations and stator holes size, and fluctuations in one jets emerging from stator holes affect the fluctuations in other plane jets. Further, it is found that smaller the stator holes size, greater is the energy distribution and hence greater will be the drop size distribution in the mixer. Therefore, the inclined stator head HSM can be used for the uniform size distribution in application to de-agglomeration and dispersion. It is found that the energy spectrum of Kolmogorov is followed over the entire length scale for all HSMs and LES provided the richer flow and turbulent information as compared to RANS model.

On the Optimal Switch Functions for Fast FDTD Monochromatic Lightwave Generation

A smooth and monotone-increasing function is often applied to switch on a monochromatic lightwave source useful for modeling the coherent light interaction with optical and photonic structures by the finite-difference time-domain (FDTD) method. In this letter, the reasoning and guideline of the optimal switch functions for the fast generation of time-harmonic lightwaves in two or three periods were proposed and discussed based on the tradeoff between the higher order smoothness at the two connection points and the smaller average slope in the central segment of switch function in order to suppress the levels of high-frequency components of the impressed source that attribute to the initial transient magnitude deformation and fluctuation. Two candidates for the potentially optimal switch functions that satisfy the criteria are given, and numerical examples with FDTD simulations are presented to verify their superior performances over the conventional Hann function.

Is the dust-to-gas ratio constant in molecular clouds?

Abstract We perform numerical simulations of dusty, supersonic turbulence in molecular clouds. We model 0.1, 1 and 10 μm sized dust grains at an initial dust-to-gas mass ratio of 1:100, solving the equations of combined gas and dust dynamics where the dust is coupled to the gas through a drag term. We show that, for 0.1 and 1 μm grains, the dust-to-gas ratio deviates by typically 10–20 per cent from the mean, since the stopping time of the dust due to the gas drag is short compared to the dynamical time. Contrary to previous findings, we find no evidence for orders of magnitude fluctuation in the dust-to-gas ratio for ∼0.1 μm grains. Larger, 10 μm dust grains may have dust-to-gas ratios increased by up to an order of magnitude locally. Both small (0.1 μm) and large (≳1 μm) grains trace the large-scale morphology of the gas; however, we find evidence for ‘size-sorting’ of grains, where turbulence preferentially concentrates larger grains into dense regions. Size-sorting may help to explain observations of ‘coreshine’ from dark clouds and why extinction laws differ along lines of sight through molecular clouds in the Milky Way compared to the diffuse interstellar medium.

Cell capacitor sizing in multilevel converters: cases of the modular multilevel converter and alternate arm converter

Multilevel converters, such as the modular multilevel converter (MMC) or the alternate arm converter (AAC), rely on charged capacitors in their cells to generate their AC voltage waveform. Since the cell capacitors are physically large and occupy approximately half the cell volume, their capacitance must be kept minimal while limiting the voltage fluctuation caused by the current passing periodically through these capacitors. This study proposes a mathematical model which estimates the energy deviation for the stacks of both the MMC and the AAC during steady-state operation under any power factor and for AC voltage magnitude fluctuation of up to ±10%. The analysis is then used to calculate the minimum size for the cell capacitors in order to keep their voltage fluctuation within set boundaries for both topologies. The results show that the MMC requires 39 kJ/MVA of capacitive energy storage under sinusoidal modulation but this reduces with triplen injection modulation. The AAC has a lower requirement for storage in its cells of 11 kJ/MVA but the AAC has a six-pulse DC current ripple which requires a filter estimated to have a further 33% capacitive storage.

Effects of non-stationarity on the magnitude and sign scaling in the multi-scale vertical velocity increment

We study the scaling properties of multi-scale increment series from the stationary and non-stationary vertical velocity records by the detrended fluctuation analysis (DFA) and series decomposition methods, and show the impact of non-stationarity on the magnitude and sign scaling properties. Firstly, we show it is difficult to define a significant scaling range for stationary records themselves. Secondly, for increment series with lag one, the nonlinear correlation found in magnitude fluctuation (i.e. volatility fluctuation) is obvious for both cases. And over the smaller scale range, the linear correlation found usually in the sign series is the same for both cases. However, over the larger scale range, the difference is sharp and marked nonlinear correlation is also incorporated for the non-stationary sign series. Thirdly, with the lags in increment increasing, there exist two scaling ranges in both the magnitude and sign fluctuations. The nonlinear correlation in the magnitude series over both small and large scale ranges decreases with the lags increasing. For the sign series, the linear correlation is dominant over both small and large scale ranges for stationary case; however, the nonlinear correlation can be found over the large scale ranges for non-stationary case and will decrease with lags increasing. The nonlinear correlation found in the sign series over large-scale range is resulted from the modulation of the large scale structures found in the non-stationary data, which will incorporate parts of the magnitude information into the sign series.

Characteristics of Settlement and Assessment Methods of Engineered Structures under Certain High-Speed Railway Tracks in China

The assessment of settlement deformation of engineered structures under high-speed railway tracks is an important control link in high-speed railway line construction. This paper discusses characteristics of settlement deformation of sections of subgrade, bridges and tunnels, and analyzes the suitability of predictive methods in currently available technical codes and standards based on measured data of settlement deformation. Currently available assessment analysis methods have good applicability for subgrade sections but are not suitable for sections of bridges and tunnels. Suitable assessment analysis methods are proposed and have been successfully applied to settlement deformation of engineered structures under the tracks of high-speed railway lines. The methods suit the characteristics of “small magnitude and large fluctuation” changes of measured settlement deformations taking account of the construction process of the engineered project.

Conceptualizing Mass Media Effect

Scholars have generated evidence of a wide variety of mass media effects over almost 9 decades of research. Although each of these effects has been defined in a relatively clear manner, there has been much less conceptualizing about what constitutes a mass media effect in general. Rarely have scholars provided a formal definition of mass media effect, instead opting to provide a definition in either an ostensive or primitive manner. In this essay, a conceptualization of “mass media effect” at the most general level is synthesized from this previous definitional work. The proposed conceptualization posits 4 general kinds of mass media effects: gradual long-term change in magnitude, reinforcement, immediate shift, and short-term fluctuation change.

Investigation of StatComs With Capacitive Energy Storage for Reduction of Voltage Phase Jumps in Weak Networks

The voltage at the point of common coupling (PCC) in a weak network is very sensitive to load changes. A sudden change in active load will cause both a phase jump and a magnitude fluctuation in the bus voltage (voltage at the PCC), whereas reactive load changes mainly affect the voltage magnitude. With the addition of energy storage to a static synchronous compensator (STATCOM), it is possible to compensate for the active power change as well as providing reactive power support. In this paper effective active power compensation schemes are proposed. Simulation and experimental results verify the compensation schemes by showing that a STATCOM with energy storage can significantly reduce phase jumps and magnitude deviations of the bus voltage under load disturbances.

Determination of the lower natural frequencies of circular plates with mixed boundary conditions

The natural frequencies are obtained for elastic circular plates with mixed boundary conditions. The boundary conditions of the plate were combinations of clamped, simply supported, free, and guided. The natural frequencies are presented as a function of the angle over which the circumference of the plate is treated as one boundary and the remainder as another boundary condition. It was found that the axisymmetric modes exhibit continuous variation of the natural frequency from one pure condition to the other pure boundary condition, while the asymmetric modes show two branches of varying curvature and magnitude fluctuation, depending on the magnitude of the angles of mixed boundaries.

Magnetization and susceptibility of the two-spin Heisenberg model

To take the intra-site spin magnitude fluctuation into account, the usual one-spin per site Heisenberg Hamiltonian is extended to two interacting spins per site. We have studied the magnetization and susceptibility of the model Hamiltonian as function of temperature and coupling constants using the double-time Green's function method. In contrast to the one-spin per site Heisenberg Hamiltonian where the Curie constant depends only on the resultant saturated magnetic moment, our results show that Curie constant of the two-spin per site Heisenberg model depends rather on the individual moments. Thus, the Curie constant can have finite value even when the resultant saturated magnetic moment vanishes. The possible physical implication of our result is also discussed.