Miracle-dz/UniFAR-FTUs huggingface dataset:
On amphidromic points

Amphidromic points are isolated points at which the wave amplitude vanishes. We investigate the consequences of their existence in a wave field. For example, one method for solving the mild-slope equation (this models the propagation of water waves over a variable bathymetry) begins by writing the complex potential in terms of a real amplitude A and a real phase S, both of which are functions of position. We show that S is not continuous at amphidromic points, whereas its gradient is singular there. We also find local approximations for A and S. We discuss various differential equations governing A and S, with emphasis on their properties in the presence of amphidromic points, and find a new pair that is well behaved there. We discuss two simple examples for which the amphidromic points can be found explicitly. Finally, we show that our analysis can also be extended to Laplace’s tidal equations.
SU-GG-T-346: Impact of Post-Irradiation Time on the Accuracy of Dose Measurements for EBT-2 Model GAFCHROMIC(TM) Film

Purpose: A new EBT‐2 GAFCHROMIC™ model radiochromic film has been released recently with addition of a yellow marker dye within sensitive layer that enables correction of non‐uniformity of the active layer of the film. Performance of the EBT‐2 was compared with former EBT model in terms of absorption spectra. Since one of the major drawbacks of the current radiochromic film dosimetry protocols is the post‐irradiation waiting time, we studied the impact of post‐irradiation scanning time on the dose measurements accuracy if shorter times are to be adopted. Method and Materials: Post‐irradiation scanning times employed range from 3 minutes to 5 days and dose range extends from 0 to 6 Gy. Absorption spectra of film samples were measured using a Perkin Elmer Lambda 650 spectrophotometer over the spectral range from 400 nm to 800 nm. Changes in absorption spectra of the samples irradiated to various doses were determined as the net difference between measurement and control film pieces which accounts for changes due to environmental conditions. Results: Both film models experience similar dose change in net absorbance. However, the sensitivity of the latest EBT‐2 model GAFCHROMIC™ film is slightly lower than its predecessor. We show that for two post‐irradiation scanning times of 30 minutes and 24 hours the 1% dose error can be achieved if the scanning time window is less than ±5 minutes and ±2 hours, respectively. Conclusion: By comparing the resultant change in net absorbance between the latest EBT‐2 and previous EBT GAFCHROMIC™ film models we conclude that the addition of the yellow marker dye to the sensitive layer does not affect dosimetric properties of the latest film model. We also describe a procedure by which one can establish an acceptable time window around chosen post‐irradiation scanning time protocol that would provide an acceptable dose error for practical purposes.
ICT-enabled job crafting: How Business Unit Developers use Low-code Development Platforms to craft jobs

Recently, businesses are introducing low-code development platforms (LCDP) that enable employees with little to no development expertise to develop their own systems to improve their work. These so-called business unit developers (BUDs) possess necessary domain knowledge to understand how to use LCDPs to create useful (self-) services. Using job resource demand theory and the job crafting model, we conceptualize that BUDs use of LCDPs can be framed using the theoretical lens of job crafting. Job crafting stems from vocational psychology and provides well-researched positive consequences, such as wellbeing and meaningfulness. Thus, our research objective is to understand how BUDs can use LCDPs to job craft to gain access to positive job crafting consequences. We interviewed 17 experts across three organizations that employ an LDCP for chatbots. Our results suggest that job crafting is a suitable framework for understanding the effects of LCDP use.
Nonlinear H~ ¿ Flight Control of General Six-Degree-of-Freedom Motions

This paper investigates the application of nonlinear H,~) control theory to flight vehicles whose complete six degree-of-freedom lioiilinear equations of motion are considered directly without linearization. Nonlinear flight control modes such as velocity control, body-rate control, attitude control, and hovering control are designed in a unified framework such that the derived nonlinear H,. ,, control law is valid for arbitrary flight vehicles. The most difficult and challenging task involved in applying the nonlinear H,,, control theory is to solve the associated HamiltonJacobi partial differential inequality (HPDI). In this paper we show that the H.PD1 of flight control problems can be solved analytically with simple manipulations. A closed-form expression for the nonlinear H,n flight controller is derived from the solution ofH.PDI and shown to be in the simple structure of proportional feedback. The numerical simulations show that the derived nonlinear H,,, control law can ensure global and asymptotical stability of the closed loop system and have strong robustness against wind gusts with varying statistical characteristics.
Numerical and experimental detection of concentrated damage in a parabolic arch by measured frequency variations

The dynamics of a parabolic arch is studied in its undamaged and damaged states. The damage consists of a notch that reduces the height of the cross section at a given abscissa. A damage identification technique, based on the minimization of an objective function measuring the differences between numerical and experimental variations of natural frequencies for undamaged and damaged states, is used. The uniqueness of the solution in different damage configurations is investigated using pseudo-experimental data and the reliability of the identification procedure is assessed. The identification procedure is then applied to an experimental case, where frequencies are obtained by impulsive tests on a prototype arch. The minimum number of experimental data needed to identify damage parameters is defined and the sensitivity of the identification algorithm to different possible choices of sets of data is analyzed.
Internal waves in a continuously stratified atmosphere or ocean

A stably stratified shear flow has the velocity profile V(1 - e−y/h) and the density profile log(ρ/ρ) = σ(1 − e−y/h) in 0 < y < ∞ and is bounded by the rigid plane y = 0. It is proved that small disturbances with respect to this basic flow are stable for all wavelengths and Richardson numbers. The eigenvalues for neutral disturbances (internal gravity waves) are enumerated. The results are applicable to the atmosphere and to an infinitely deep ocean.
Existence theorems for a multivalued boundary value problem

Let F be a multifunction from [a, b] × ℝn × ℝn into ℝn, with non-empty closed convex values. In this paper we prove that, under suitable assumptions, the multivalued boundary value problem has at least one solution u ∈ W2, p([a, b], ℝn). Next we point out some particular cases.
Dualization of the internal model principle in compensator and observer theory with application to repetitive and learning control

This paper reconsiders the concepts of servo compensator and disturbance observer. Both concepts make use of an internal model representing general persistent disturbances. Although the use of such a model has been well recognized to be necessary within the servo compensator concept, its role has been less understood disturbance observers. In this paper necessary and sufficient conditions for proper use of both concepts will be derived by reformulating the servo compensator and disturbance observer problem in a general standard plant. Moreover, it is shown that a robust servo compensator, stabilized by an observer-based controller using output feedback, is dual to a disturbance observer in combination with state feedback and disturbance compensation. As an illustration, the presented theory is applied to the concepts of repetitive and learning control, which turn out to be dual concepts for accommodating arbitrary periodic signals.
Chemo-Mechanical Effects in Mortar Beams Subjected to Water Hydrolysis

Reliable predictions of the long-term behavior of concrete structures require both an accurate knowledge of the various degradation mechanisms that affect the structures over their lifetime and the use of simulation tools. Leaching due to aggressive water can be responsible for a loss of mechanical properties and stability of concrete structures. This paper focuses on coupled chemo-mechanical effects on concrete structures subjected to aggressive water inducing calcium leaching. Experimental investigations on mortar bending beams and their analysis are detailed. The response of leached mortar beams is deduced from these tests. It is found that the stiffness of mortar decreases, along with its strength, as the chemical attack progresses. The size effect on geometrically similar bending beams at various stages of degradation is studied experimentally. Due to leaching, the brittleness of the structures is increased and the fracture energy decreases.
Preliminary design optimization of stiffened panels using approximate analysis models

Preliminary sizing of structural components in the conceptual design phase of new aerospace vehicles requires a large number of structural optimizations. Use of detailed finite element models for global optimization of stiffened shell structures is not affordable. Designers have to compromise between the complexity in the structural analysis model (e.g. small models or linear analysis) and that of the optimization method (local versus global optimization). When designing new concepts where good initial designs are not available, global design optimization needs to be performed, and this is not currently possible with complex models. In this paper, we discuss the use of simple analysis methods for performing global optimization of stiffened shell structures. We demonstrate the efficiency of using approximate analysis models by using PANDA2 for a practical design trade‐study. Often approximate models are based on assumptions that are not satisfied throughout the design space. Hence, such models require constraints that will keep the designs in regions where the analysis assumptions are valid. We illustrate with examples situations where such design constraints result in sub‐optimal designs. We conclude that performing global optimization using approximate methods can permit a greater exploration of the design space than the use of local optimization with complex models. Copyright © 2003 John Wiley & Sons, Ltd.
Pitfalls in the Estimation of a Differenced Model

This article assesses the potential magnitude of the loss of estimation efficiency caused by the adoption of a differenced model when the disturbances of the original (levels) linear regression model follow either a stable (autoregressive) AR(1) process or a fixed start-up random-walk process (hence no filtering is necessary from the standpoint of estimation). The magnitude of the loss, which can be quite large, is found to be affected by both the form of the original model (homogeneous or nonhomogeneous) and the sign and magnitude of the autocorrelation coefficient of the AR(1) disturbance, as well as by the nature of the exogenous variable (smoothly trended or not).
The Effects of Digitization on Nonstationary Stochastic Signals with Applications to Pulsar Signal Baseband Recording

The process of digitizing a stochastic signal introduces systematic distortions into the resulting digitized data. Further processing of these data may result in the appearance of unwanted artifacts, especially when the input signal was generated by a nonstationary stochastic process. In this paper the magnitude of these distortions are calculated analytically and the results are applied to a specific example found in pulsar signal processing. A pulsar signal is an excellent example of a nonstationary stochastic process. When analyzing pulsar data, the effects of interstellar medium (ISM) dispersion must be removed by digitally filtering the received signal. The distortions introduced through the digitization process cause unwanted artifacts to appear in the final “dedispersed” signal. These artifacts are demonstrated using actual 2‐bit (4‐level) digitized data of the pulsar PSR B0833−45 (Vela). Techniques are introduced that simultaneously minimize these artifacts and maximize the signal‐to‐noise ratio of the digitized data. The distortion analysis and artifact removal techniques described in this paper hold for an arbitrary number of input digitization thresholds (i.e., number of bits). Also presented are tables of the optimum digitizer thresholds for both uniform and nonuniform input threshold digitizers.
Optimal guaranteed cost control of uncertain 2D discrete systems with both shift delays and input delays via memory state feedback

The problem of optimal guaranteed cost control for a class of 2D discrete uncertain systems under shift delays and input delays in a Fornasini–Marchesini (FM) second model setting via memory state feedback is considered in this paper. A linear matrix inequality (LMI)-based criterion for the existence of guaranteed cost controllers is established. Furthermore, a convex optimization problem with LMI constraints is formulated to design the optimal guaranteed cost controllers that minimize the upper bound of the closed-loop cost function. Illustrative examples are given to demonstrate the applicability of the proposed method.
Stability analysis of a double integrator swarm model related to position and velocity

In this paper, we propose a biologically inspired, continuous double integrator model based on individual Newton's law in an n-dimensional space. The double integrator model is related to positions and velocities of individuals. We discuss three cases of the attraction/repulsion functions, which are odd for the attractive force and repulsion force taking effect in opposite directions, and we obtain the swarm size and ultimate motions for cohesion in every case. Stability analysis and numerical simulations are also presented to demonstrate the effectiveness of our model.
Measurement of methane and carbon dioxide fluxes from peatland ecosystems by the conditional‐sampling technique

The conditional sampling method was used to measure methane (CH4) and carbon dioxide (CO2) fluxes from peatlands in northern Scotland. Preliminary data were obtained using a simple system. Subsequent automation made continuous nux-measurements possible. Observed CH4 fluxes were in the range -70 to +110 mu mol m(-2)h(-1) with a mean flux of 23 mu mol m(-2)h(-1). Peak photosynthetic CO2 fluxes were in the range -10 to -30 mmol m(-2) h(-1). Nocturnal respiration ranged from 0 to +10 mmol m(-2) h(-1). The conditional sampling observations showed reasonable agreement with measurements of flux by eddy-covariance, gradient and aircraft methods. Error analyses and laboratory tests were conducted to determine the precision of the flux-measurement system. The dominant error was associated with the determination of the mixing-ratio difference in conditionally-sampled updraught and downdraught air. The standard error of the difference for CH4 was typically 0.15 ng g(-1) (0.3 parts in 10(9) (p.p.b.))using a careful high-repetition sampling strategy with a modified gas chromatographic/flame ionization detector system. Under typical daytime atmospheric conditions this corresponded to a standard error in the flux measurement of 10 mu mol m(-2)h(-1), which is consistent with field observations. The empirical beta factor in the conditional sampling equation was found to be insensitive to changes in turbulence intensity and atmospheric stability. Simple upscaling models were used to estimate annual carbon-fluxes to Great Britain's peatlands of -0.5 Mt of carbon in the form of CO2 and 18 kt in the form of methane.
Impingementfreie Bewegung nach Hüft-TEP – wie realisieren?

Zusammenfassung Prothetisches Impingement und eine ungenügende Weichteilspannung stellen immer noch die Risikofaktoren dar, die in erster Linie für die Hüftgelenkluxation als eine der häufigsten Frühkomplikationen verantwortlich sind. Durch eine optimierte Komponentenausrichtung, optimiertes Prothesendesign und bestmögliche Rekonstruktion der individuellen Biomechanik kann das Risiko eines Impingements deutlich reduziert, wenn nicht gar ganz ausgeschaltet werden. Aufbauend auf Bewegungsanalysen zeigt diese Studie die Zusammenhänge zwischen der Komponentenausrichtung, dem Einfluss der Designparameter und dem erzielbaren Bewegungsspielraum auf und begründet damit das Konzept der „combined Safe-Zone“ (cSafe-Zone). Die maximale Größe dieser Zone liefert die optimalen Komponentenorientierungen für ein spezifisches Prothesensystem. Zwischen der Pfannenanteversion und der Schaftantetorsion besteht eine inverse lineare Beziehung. Größere Prothesenköpfe erlauben eine flachere Pfanneninklination, bei 28 mm empfiehlt sich eine Pfanneninklination von 40–45°, bei 32 mm von 38–42° und bei 36 mm von 35–40°. Anatomische Schäfte brauchen eine geringere Pfannenanteversion. Kurzschäfte weisen größere Variationen von CCD- und Antetorsionswinkel auf und verlangen die individuelle Anpassung der Pfannenorientierung. Die optimale Komponentenausrichtung muss für jedes Prothesensystem spezifisch ermittelt werden. Mithilfe eines computerbasierten oder dem vorgestellten mechanischen Navigations-Impaktierungssystem können die Zielvorgaben intraoperativ umgesetzt werden.
On the evolution of compression pulses in an exploding atmosphere: initial behaviour

The development in space and time of a plane initial disturbance to a spatially uniform exploding atmosphere is analysed on the assumption that the disturbance amplitude is comparable in magnitude with the inverse (dimensionless) activation energy of the explosion reaction. Particular attention is focused on the shock-fitting problem, which has features that distinguish it from its inert-atmosphere counterpart. Using the positive half of a sine wave to typify an isolated compression perturbation, it is found that the amplifying effect of the ambient reaction leads to very rapid shock wave development, which depends significantly on the spatial extent of the disturbance. The latter also influences the question of whether local explosion (local explosion is recognized here as a logarithmically unbounded growth of the disturbance amplitude; in other words as a local breakdown of the present approximations) occurs at the shock wave or some distance behind it. The subsequent evolution of these two states will no doubt be significantly different, but the answer to this speculation must await extension of the present theory to encompass the rapid events that ensue near the local explosion regions.
Fission yields in the symmetric region: Yields of the stable isotopes of tin and cadmium in the thermal neutron fission of /sup 235/U and /sup 239/Pu

The relative isotopic abundances of five isotopes of cadmium (111, 112, 113, 114, and 116) and eight isotopes of tin (117, 118, 119, 120, 121, 122, 124, and 126) have been measured in the thermal neutron fission of /sup 235/U and /sup 239/Pu. Samples of /sup 235/U and /sup 239/Pu were irradiated in a reactor; the elements were chemically separated and the isotopic abundances were mass spectrometrically determined. By suitably normalizing these relative yields, it has been possible to obtain the cumulative chain yields at 12 masses in the symmetric region of the mass distribution. These results indicate that there is a fine structure in the 113--115 mass region, especially in the fission of /sup 235/U. However, the mass distribution appears to be smooth between masses 116 and 126. The depression in the mass-yield curve around mass 115 may be related to the break around this mass number in the prompt neutron distribution as a function of mass. (AIP)
Stable Determination of X-Ray Transforms of Time Dependent Potentials from Partial Boundary Data

We consider compact smooth Riemmanian manifolds with boundary of dimension greater than or equal to two. For the initial-boundary value problem for the wave equation with a lower order term q(t, x), we can recover the X-ray transform of time dependent potentials q(t, x) from the dynamical Dirichlet-to-Neumann map in a stable way. We derive conditional Hölder stability estimates for the X-ray transform of q(t, x). The essential technique involved is the Gaussian beam Ansatz, and the proofs are done with the minimal assumptions on the geometry for the Ansatz to be well-defined.
Maximum-Likelihood Estimation of the Number-Flux Distribution of Radio Sources in the Presence of Noise and Confusion

The application of the method of maximum likelinood to the determination of the slope of the number- flux-density relationship is extended to include the presence of experimental errors in the flux-density measurements. It is shown that these experimental errors have a significant effect on the number counts at higher natios of flux density to error than is often recognized. The case of noise-limited fiux-density measurements is treated in some detail, and it is found that, provided the lower limit of a survey is chosen to be at least five times the rms noise, the enhancement in the source density as a function of fiux density can be readily calculated. For the case of significart confusion errors in the flux-density measurements the importance of a Monte Carlo approach is emphasized. Several methods that have been used previously are discussed and a number of shortcomings noted. (auth)
Spectroscopy of V711 Tauri (=HR 1099): fundamental properties and evidence for starspots

New orbital elements have been determined for the bright RS CVn-type system V711 Tau. The spectroscopic period has been refined to 2.83774 d + or - 0.00001 d. The eccentricity is determined to be 0.014 + or - 0.009, and the inclination of the system is 33 deg + or - 2 deg. The masses, radii, and equatorial rotational velocities for each component are stated.Evolutionary models suggest that mass transfer may begin in 70 to 80 million years. High SNR Reticon observations at red wavelengths show substantial differences in rotational velocity and line strength between the two components, as well as asymmetries in all absorption lines of the more massive, active, cooler star. These asymmetries are correlated with photometric variations and move across the line profiles with time. They are the result of starspot regions rotating in and out of view.
A Medium Survey of the Hard X-Ray Sky with the ASCA Gas Imaging Spectrometer: The (2-10 keV) Number Counts Relationship

In this paper, we report the first results of a medium survey program conducted in the 2-10 keV energy band using data from the GIS2 instrument onboard the ASCA satellite. We have selected from the ASCA public archive (as of 1996 February 14) 87 images suitable for this project. Sixty serendipitous X-ray sources with a signal-to-noise ratio greater than 3.5 were found. The 2-10 keV flux of the detected sources ranges from ~1.1 × 10-13 ergs cm-2 s-1 to ~4.1 × 10-12 ergs cm-2 s-1. Using this sample, we have extended the description of the 2-10 keV log N(>S)-log S to a flux limit of ~6.3 × 10-14 ergs cm-2 s-1 (the faintest detectable flux), i.e., about 2.7 orders of magnitude fainter than the Piccinotti et al. determination. The derived number-flux relationship is well described by a power-law model, N(>S) = K × S-α, with best-fit values α = 1.67 ± 0.18 and K = 2.85 × 10-21 deg-2. At the flux limit of the survey, about 27% of the cosmic X-ray background in the 2-10 keV energy band is resolved in discrete sources. A flattening of the number-flux relationship, within a factor of 10 from the flux limit of the present survey, is expected in order to avoid saturation. The implications of these results for models of the origin of the hard X-ray background are briefly discussed.