Miracle-dz/UniFAR-FTUs huggingface dataset:
VIBRATION OF ARBITRARILY ORIENTED TWO-MEMBER OPEN FRAMES WITH TIP MASS

Abstract A generalized two-member open frame structure is modelled using Euler–Bernoulli beam theory. The generalization is approached in two ways: an arbitrary angle between the beams; and the attachment of a payload at the end of the second beam. The linearized equations of motion are derived using Hamilton's principle and the general frequency equation, mode shapes and orthogonality condition are presented along with some numerical examples.
A Parameter Sweep Experiment on Quasiperiodic Variations of a Polar Vortex due to Wave-Wave Interaction in a Spherical Barotropic Model

Abstract Weakly nonlinear aspects of a barotropically unstable polar vortex in a forced–dissipative system with a zonally asymmetric surface topography are investigated in order to obtain a deeper understanding of rather periodic variations of the winter circumpolar vortex in the Southern Hemisphere stratosphere that are characterized by the wave–wave interaction between the stationary planetary wave of zonal wavenumber 1 (denoted as Wave 1) and the eastward traveling Wave 2 as studied by Hio and Yoden in 2004. The authors use a spherical barotropic model with a forcing of zonally symmetric jet, dissipation, and sinusoidal surface topography. A parameter sweep experiment is performed by changing the amplitude of the surface topography, which forces the stationary Wave 1, and the width of the prescribed zonally symmetric jet, which controls the barotropic instability, to generate the traveling Wave 2. Several types of solutions from a time-independent solution to a nonperiodic irregular solution are obtain.
Automorphism orbits of finite groups

Abstract Let G be a finite group and let Aut(G) be its automorphism group. Then G is called a k-orbit group if G has k orbits (equivalence classes) under the action of Aut(G). (For g, hG, we have g ~ h if ga = h for some Aut(G). ) It is shown that if G is a k-orbit group, then kGp + 1, where p is the least prime dividing the order of G. The 3-orbit groups which are not of prime-power order are classified. It is shown that A5 is the only insoluble 4-orbit group, and a structure theorem is proved about soluble 4-orbit groups.
Volume displacement measurement via multi-wavelength digital holographic surface topography at the microscopic level

In this work multiwavelength digital holography, originally applied to calculate the volume displacement of various macroscopic topographic surface features, is now extended to the case of microscopic objects. Accurate measurements of volume displacement for macroscopic surface features has been achieved using long synthetic wavelengths up to several millimeters, generated via tunable IR laser sources. Microscopic volume measurements are performed via digital holographic microscopy using HeNe and Ar+ ion lasers to generate very short synthetic wavelengths. Practical methods of implementation are considered, including wavelength selection error and the geometric effects of both Michelson and Mach-Zehnder recording configurations on phase measurement. Results include comparisons to standard metrology tools, including 1D profilometry and white light interferometry.
Can trapped gravity waves be relevant for severe foehn windstorms? A case study

This study presents high-resolution numerical simulations of an Alpine south foehn case (14-16 November 2002) during which extremely strong surface winds occurred in several regions of the Alps. The specific focus is on a storm event in the upper Isar Valley in the Bavarian Alps, where gusts estimated to about 45 m s -1 caused substantial damage to buildings and vegetation. For this event, the simulations indicate that the extreme low-level wind speeds were related to a large-amplitude trapped gravity wave, contrasting previous findings that violent surface winds are usually related to vertically propagating gravity waves, especially in the presence of low-level wave breaking, or to shooting hydraulic flow. According to the model results, gravity waves were excited over the mountain ranges adjacent to the valley and propagated towards the valley axis due to their three-dimensional dispersion characteristics. Wave trapping was caused by a deep neutral layer in the upper troposphere. The low-level wind maximum formed beneath the wave trough, reflecting the dynamical structure of trapped waves for which wind and temperature perturbations are in phase. Comparison of the model results with surface wind measurements shows that the simulated flow evolution is consistent with reality except for a minor timing error. A sensitivity test in which the neutral layer was removed exhibits significantly weaker surface winds in the region of interest, suggesting that wave trapping made an important contribution to this windstorm event.
Modular group acting on real quadratic fields

Coset diagrams for the orbit of the modular group G = 〈x, y: x2 = y3 = 1〉 acting on real quadratic fields give some interesting information. By using these coset diagrams, we show that for a fixed value of n, a non-square positive integer, there are only a finite number of real quadratic irrational numbers of the form , where θ and its algebraic conjugate have different signs, and that part of the coset diagram containing such numbers forms a single circuit (closed path) and it is the only circuit in the orbit of θ.
Ensemble Kalman Filter Assimilation of HIWRAP Observations of Hurricane Karl (2010) from the Unmanned Global Hawk Aircraft

AbstractThis study utilizes an ensemble Kalman filter (EnKF) to assess the impact of assimilating observations of Hurricane Karl from the High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP). HIWRAP is a new Doppler radar on board the NASA Global Hawk unmanned airborne system, which has the benefit of a 24–26-h flight duration, or about 2–3 times that of a conventional aircraft. The first HIWRAP observations were taken during NASA’s Genesis and Rapid Intensification Processes (GRIP) experiment in 2010. Observations considered here are Doppler velocity (Vr) and Doppler-derived velocity–azimuth display (VAD) wind profiles (VWPs). Karl is the only hurricane to date for which HIWRAP data are available. Assimilation of either Vr or VWPs has a significant positive impact on the EnKF analyses and forecasts of Hurricane Karl. Analyses are able to accurately estimate Karl’s observed location, maximum intensity, size, precipitation distribution, and vertical structure. In addition, forecasts initialized f.
Mixed convection over a heated horizontal plane

Measurements of velocity and temperature fluctuations have been made in flows of air over a strongly heated horizontal surface in conditions of large negative Richardson number and approximating to horizontally homogeneous turbulent flow with constant shear stress and upwards flux of total heat. Within a layer that includes most of the total variation of mean temperature and velocity, the effect of the mean flow on the thermal structure is nearly confined to a change in the length scale which measures the thickness of the viscous-convective layer at the surface but which is also the length scale for the fully turbulent region. Measurements of the mean velocity and the mean-square fluctuation in the stream direction were made for a flow velocity of about 0·70 ms−1 and showed that the profiles of mean temperature and mean velocity are closely similar, implying proportionality at each height of the transfer coefficients for heat and for momentum. The ratio is estimated to be 1·4. The measurements were carried out in conditions such that the Monin-Obukhov length was in the range 8–60 mm and the maximum height of observation was 80 mm.
Closed-form expressions for the prediction of microcellular mobile radio propagation in urban environments

The paper derives two closed-form expressions for predicting microcellular mobile radio signal levels in urban street-grid environments. The results demonstrate that the two expressions are faster and more accurate than existing models and methods. Benefiting from physical optics and the conservation of energy, the two expressions are alternatives to available techniques such as ray tracing. The dielectric property (i.e., permittivity) of street buildings and other obstacles is essential to the ray tracing technique. However, there are no established, widely accepted techniques for selecting the permittivity in urban mobile environments, which varies in a wide range. Establishing a natural link between the received power after a street corner to the width of the street and the angle of incidence, our expressions show the possibility of making fast and accurate propagation predictions without having to use the permittivity.
Nondivergent simultaneous map building and localization using covariance intersection

The covariance intersection (CI) framework represents a generalization of the Kalman filter that permits filtering and estimation to be performed in the presence of unmodeled correlations. As described in previous papers, unmodeled correlations arise in virtually all real-world problems; but in many applications the correlations are so significant that they cannot be 'swept under the rug' simply by injecting extra stabilizing noise within a traditional Kalman filter. In this paper we briefly describe some of the properties of the CI algorithm and demonstrate their relevance to the notoriously difficult problem of simultaneous map building and localization for autonomous vehicles.
Nonlinear Interaction of a Small Cold Beam and a Plasma

Recently, a simple model was proposed for the nonlinear interaction of a low‐density monoenergetic electron beam and a relatively cold infinite homogeneous one‐dimensional plasma. The essential feature of this model is the observation that after several e‐foldings the bandwidth of the growing waves is so narrow that the electrons interact with a very nearly pure sinusoidal field. In terms of this single wave model, a properly scaled solution of the nonlinear beam‐plasma problem which depends analytically on all the basic parameters of the problem (i.e., plasma density, beam density, plasma thermal velocity, and beam drift velocity) is presented. This solution shows that the single wave grows exponentially at the linear growth rate until the beam electrons are trapped. At that time the wave amplitude stops growing and begins to oscillate about a mean value. During the trapping process the beam electrons are bunched in space and a power spectrum of the higher harmonics of the electric field is produced. Bot.
COHOMOLOGY GROUPS OF CIRCULAR UNITS

Let be a real abelian field of conductor f and (sub) = ∪(sub)n0(sub)n be its Z(sub)p-extension for an odd prime p such that plf(f). he aim of this paper is ot compute the cohomology groups of circular units. For m>n0, let G(sub)m,n be the Galois group Gal((sub)m/(sub)n) and C(sub)m be the group of circular units of (sub)m. Let l be the number of prime ideals of above p. Then, for mm>n0, we have (1) C(sub)m(sup)G(sub)m,n = C(sub)n, (2) H(sup)i(G(sub)m,n, C(sub)m) = (Z/p(sup)m-n Z)(sup)l-1 if i is even, (3) H(sup)i(G(sub)m,n, C(sub)m) = (Z/P(sup)m-n Z)(sup l) if i is odd (※Equations, See Full-text).
MOPA with kW average power and multi MW peak power: experimental results, theoretical modeling, and scaling limits

A Master-Oscillator-Power-Amplifier (MOPA) design combining rod and slab laser technology for high pulse energy, high average power and near diffraction limited beam quality for industrial use has been developed. To achieve the good beam quality at high average and high pulse power, an advanced birefringence compensation scheme, which ensures a high mode overlap while simultaneously minimizing the power densities on optical surfaces, has been developed and applied. The prototypes deliver an average power of up to 860 W with M2 < 2 or 1.3 kW with M2 < 12 at 10 kHz repetition rate and 5-16 ns pulse duration. At 1 kHz up to 420 mJ pulse energy can be achieved. The prototypes are fully computer controlled and can be operated from 0 to 100 % output power and from single shot to 10 kHz. They are currently operated for plasma generation in a laboratory surrounding and have run for more than one thousand hours without failure up to now. An analytical solution of the thermally induced refractive index profile in dependency of a radially symmetric pump light distribution including the effect of thermally induced birefringence, temperature dependency of the thermal conductivity and the second derivative of the refractive index with the temperature (d2n/dT2) has been derived. This allows a fast calculation of thermally induced aberrations without the use of FEA. Experimental results are compared to predictions from analytical and FEA modelling. Based on experimental and theoretical results, scaling limits of rod based MOPAs are predicted.
Residuals‐based tests for the null of no‐cointegration: an Analytical comparison

Abstract. This article studies the asymptotic distribution of five residuals‐based tests for the null of no‐cointegration under a local alternative when the tests are computed using both ordinary least squares (OLS) and generalized least squares (GLS)‐detrended variables. The local asymptotic power of the tests is shown to be a function of Brownian motion and Ornstein–Uhlenbeck processes, depending on a single nuisance parameter, which is determined by the correlation at frequency zero of the errors of the cointegration regression with the shocks to the right‐hand side variables. The tests are compared in terms of power in large and small samples. It is shown that, while no significant improvement can be achieved by using unit root tests other than the OLS detrended t‐test originally proposed by Engle and Granger (1987), the power of GLS residuals tests can be higher than the power of system tests for some values of the nuisance parameter.
Identification of Influential Cases in Structural Equation Models Using the Jackknife Method

Relatively little attention has been given to detecting influential cases (ICs) when estimating structural equation models (SEMs). Most techniques examine individual cases using covariance-based techniques such as the Mahalanobis distance, which examine the distributional characteristics of the cases but ignore the model. Cases identified using such model-free techniques are usually referred to as out-liers. In SEM, however, the model is of central importance. The characteristics of the model (number of latent variables, etc.) have an effect on which cases are influential. The authors propose applying the well-known jackknife procedure to detect model-based ICs, which may be influential with respect to overall fit, particular model parameters, or both. The procedure is illustrated by two studies—one using simulated data, the other empirical data.
Flapping Wing Aerodynamics: Progress and Challenges

It is the objective of this paper to review recent developments in the understanding and prediction of flapping-wing aerodynamics. To this end, several flapping-wing configurations are considered. First, the problem of single flapping wings is treated with special emphasis on the dependence of thrust, lift, and propulsive efficiency on flapping mode, amplitude, frequency, and wing shape. Second, the problem of hovering flight is studied for single flapping wings. Third, the aerodynamic phenomena and benefits produced by the flapping-wing interactions on tandem wings or biplane configurations are discussed. Such interactions occur on dragonflies or on a recently developed micro air vehicle. The currently available two- and three-dimensional inviscid and viscous flapping-wing flow solutions are presented. It is shown that the results are strongly dependent on flapping frequency, amplitude, and Reynolds number. These findings are substantiated by comparison with the available experimental data.
A Study of Microphysical Mechanisms for Correlation Patterns between Droplet Radius and Optical Thickness of Warm Clouds with a Spectral Bin Microphysics Cloud Model

Abstract This study investigates the correlation patterns between cloud droplet effective radius (CDR) and cloud optical thickness (COT) of warm clouds with a nonhydrostatic spectral bin microphysics cloud model. Numerical experiments are performed with the model to simulate low-level warm clouds. The results show a positive and negative correlation pattern between CDR and COT for nondrizzling and drizzling stages of cloud development, respectively, consistent with findings of previous observational studies. Only a positive correlation is simulated when the collection process is switched off in the experiment, whereas both the positive and negative correlations are reproduced in the simulation with collection as well as condensation processes. The positive and negative correlations can also be explained in terms of an evolution pattern of the size distribution function due to condensation and collection processes, respectively. Sensitivity experiments are also performed to examine how the CDR–COT correlat.
Modeling and optimization of floating raft systems in submarines under different objectives by using hybrid genetic algorithm

A systematic modeling and optimization method for analyzing typical floating raft systems in submarines is presented and optimization under different vibro-acoustic objectives is investigated. The Frequency Response Function-based (FRF-based) substructuring method and the coupled Finite Element/Boundary Element (FE/BE) method are employed to study vibration transmission from the vibrating machinery to the base structure as well as the vibro-acoustic behavior of the fluid- loaded cylindrical structure. The hybrid genetic algorithm (HGA) involving the FRF-based substructuring sensitivity analysis (SA) and the genetic algorithm (GA) is developed and applied to obtain the optimal values of stiffness of isolators under five objective functions at low frequencies. Optimization is carried out for two cases where the fluid–structure interaction is considered and neglected respectively. The modeling results demonstrate that the effect of fluid-loading reduces the driving point mobility of the connecting points on the base structure but has little influence on the isolation frequencies of the whole floating raft system. The optimized results are compared with those obtained by SA and GA. The results of SA show a regular trend of variation while those of GA show an irregular trend. Since GA is a stochastic optimization technique, the trend of variation in the results of HGA combines those of GA and SA. The optimized results demonstrate that HGA possesses the merits of SA and GA, and never gets trapped at a local optimum or goes into premature convergence. Compared with SA and GA, however, it requires more evaluation of objective functions in each iteration step and as a result is not computationally efficient.
Observer‐based non‐fragile control against measurement disturbances and controller perturbations for discrete systems with state delay

This paper investigates the observer‐based non‐fragile control problem for a class of discrete time delay systems with measurement disturbances and controller perturbations. A simultaneous state and disturbance estimation technique is developed by designing a state observer for a descriptor system obtained from the original system. Based on this observer, the design method of a non‐fragile controller is then formulated and the controller design problem is transformed to a convex optimization problem, which can be solved by a linear matrix inequality approach. In this design, the additive and multiplicative forms of uncertainties which perturb the gains of control and observer are both considered. The resultant non‐fragile observer‐based controller guarantees that the closed‐loop system is asymptotically stable and can tolerate measurement disturbances and a certain degree of controller parameter perturbation. A numerical example is given to illustrate the effectiveness of the proposed design method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Vector potential and magnetic field of current-carrying circular finite arc segment in analytical form. V. Polygon cross section

For pt.IV see ibid., vol.MAG-20, p.2145-50 (1984). Analytical expressions for the components of the vector potential and magnetic field of a circular-arc segment of a current-carrying conductor of polygonal cross section and arbitrary azimuthal length are derived. The expressions developed consists of known analytical functions such as Jacobian elliptic functions and complete and incomplete elliptic integrals of the first, second, and third kind, which permit the formulation of a time-saving efficient computation algorithm. An example of application is given. The case of a beam with polygonal cross-section carrying a longitudinal current is also examined. >
Ultralow-frequency magnetohydrodynamics in boundary-constrained geomagnetic flux coordinates

[1] A new method is described for constructing geomagnetic flux coordinates, constrained by magnetospheric and ionospheric boundary surfaces. The technique is especially useful for computing boundary value solutions in a geometry defined by a realistic, three-dimensional geomagnetic field with boundary conditions specified on surfaces oriented arbitrarily relative to the background magnetic field. An adaptable algorithm for calculating the metric tensor for a general class of geomagnetic flux coordinate systems is presented. Application to ultralow-frequency wave propagation in the magnetosphere is illustrated by solving the equations of linear, one-fluid magnetohydrodynamics for the driven field line resonance in a dipolar geomagnetic field bounded by a spherical ionosphere. A novel diagnostic for energy flow in the driven resonance problem shows that MHD wave power flows “radially” inward as a compressional wave from the boundary driver to the resonant flux surface, is diverted azimuthally at the resonant surface, and becomes field-aligned in the resonant surface by coupling to the magnetically guided Alfven wave at locations where the shear mode is in azimuthal phase quadrature with the compressional driver.
Real time measurements of strongly localized potential profile through Stark effects in the central core region of an inertial-electrostatic fusion device

Real time measurements of the electric fields were made in the central cathode core region of an inertial-electrostatic confinement fusion (IECF) device by the laser-induced fluorescence method by use of Stark effects. Preliminary results show double well potential formation with a slight concave at the center and also the existence of energetic electrons in the localized region near potential peaks.
Models of the longitudinal digital magnetic recording process in thin films

A review of the various mathematical models of the longitudinal recording process in thin-film recording media is given. One of the main focuses of the review is on the arctangent theories of recording, and these are discussed in terms of both their successes and their failures. More recent work shows an increasing trend towards determining the nature of the recorded distributions directly from the calculations. >