Miracle-dz/UniFAR-FTUs huggingface dataset:
Design of optimal midcourse guidance sliding-mode control for missiles with TVC

This work discusses a nonlinear midcourse missile controller with thrust vector control (TVC) inputs for the interception of a theater ballistic missile, including autopilot system and guidance system. First, a three degree-of-freedom (DOF) optimal midcourse guidance law is designed to minimize the control effort and the distance between the missile and the target. Then, converting the acceleration command from guidance law into attitude command, a quaternion-based sliding-mode attitude controller is proposed to track the attitude command and to cope with the effects from variations of missile's inertia, aerodynamic force, and wind gusts. The exponential stability of the overall system is thoroughly analyzed via Lyapunov stability theory. Extensive simulations are conducted to validate the effectiveness of the proposed guidance law and the associated TVC.
Direct numerical simulation of turbulent flow in a square duct

A direct numerical simulation of a fully developed, low-Reynolds-number turbulent flow in a square duct is presented. The numerical scheme employs a time-splitting method to integrate the three-dimensional, incompressible Navier-Stokes equations using spectral/high-order finite-difference discretization on a staggered mesh; the nonlinear terms are represented by fifth-order upwind-biased finite differences. The unsteady flow field was simulated at a Reynolds number of 600 based on the mean friction velocity and the duct width, using 96 × 101 × 101 grid points. Turbulence statistics from the fully developed turbulent field are compared with existing experimental and numerical square duct data, providing good qualitative agreement. Results from the present study furnish the details of the corner effects and near-wall effects in this complex turbulent flow field; also included is a detailed description of the terms in the Reynolds-averaged streamwise momentum and vorticity equations. Mechanisms responsible for the generation of the stress-driven secondary flow are studied by quadrant analysis and by analysing the instantaneous turbulence structures. It is demonstrated that the mean secondary flow pattern, the distorted isotachs and the anisotropic Reynolds stress distribution can be explained by the preferred location of an ejection structure near the corner and the interaction between bursts from the two intersecting walls. Corner effects are also manifested in the behaviour of the pressure-strain and velocity-pressure gradient correlations.
SPECIAL ISSUE OF ECONOMETRIC THEORY IN HONOR OF PAUL NEWBOLD: GUEST EDITORS’ INTRODUCTION

This special issue of Econometric Theory collects papers presented at a conference held at the University of Nottingham from September 21 to 22, 2007. This conference, the first to be run by the Granger Centre for Time Series Econometrics, was held to mark the contribution of Paul Newbold to both the University of Nottingham and the discipline of time series econometrics, following his retirement in 2006. The conference theme, reflecting a significant aspect of Paul’s research career, was Non-Stationary Time Series Econometrics. There were 45 conference delegates from around the globe who each contributed to this very stimulating and special event. Participants included present and former colleagues of Paul and a number of Paul’s Ph.D. students and co-authors, together with other researchers keen to join in the celebration of Paul’s contribution to their field. Despite ill health, Paul Newbold was also able to attend parts of the conference and chat with people about their work. Twenty papers were presented at the conference, 15 of which were in contributed sessions and five in keynote invited sessions. The keynote speakers at the conference were Peter Phillips (Yale University), Peter Robinson (London School of Economics), Bruce Hansen (University of Wisconsin—Madison), Pierre Perron (Boston University), and Graham Elliott (University of California, San Diego). The full conference program follows this introduction. Paul Newbold was born in England in 1945. In 1966 he obtained a B.Sc. in Economics at the London School of Economics before continuing to study for a Ph.D. in Statistics at the University of Wisconsin. He worked under the supervision
Transform coding of images using trellis coded quantization

Trellis-coded quantization (TCQ) is incorporated into a transform coding structure for encoding monochrome images. Both fixed-rate and entropy-constrained designs are considered. The fixed-rate TCQ-based systems provide gains in peak signal-to-noise ratio of up to 4.13 dB over scalar quantizer-based schemes, while the entropy-constrained TCQ-based systems provide gains of up to 6.39 dB. The subjective quality of the TCQ-based systems is substantially better than that of comparable scalar quantizer-based systems. The high-frequency background noise, fuzziness, and block artifacts produced by the scalar quantizer-based systems are virtually eliminated by the TCQ-based systems. <<ETX>>
Numerical signatures of non-self-adjointness in quantum Hamiltonians

Non-self-adjoint quantum mechanical operators do not necessarily possess eigenvalues. Finite N × N matrix representations of these operators, however, can be hermitian and therefore have a finite set of N real eigenvalues. Using the momentum operator, the kinetic energy operator, and the relativistic Hamiltonian of the Coulomb problem for the Klein–Gordon equation as examples, we examine analytically and also numerically the properties of the spectrum and eigenvectors in finite dimensional Hilbert spaces. We study the limit of N → ∞ for which some eigenvalues cease to exist as the corresponding operators are not self-adjoint.
Star formation in the southern dark cloud DC 287.1+02.4

Aims. We report the discovery of a group of 12 new infrared sources seen toward IRAS 10501-5630 and the southern dark globule DC 287.1+02.4. The globule appears as a round patch of extinction in optical images with a typical diameter of 5 arcmin. Methods. The sources are seen on K s and L' band images taken using SOFI at the NTT and ISAAC at the VLT. The globule was mapped in millimeter molecular transitions (CO(1–0), C 18 O(1–0), C 18 O(2–1), CS(2–1), HCN(1–0)) using the SEST telescope. Results. Millimeter-wave spectroscopy revealed a single dense core seen in C 18 O, CS, and HCN, extending about 2 arcmin. The infrared sources are likely to be embedded in the dense cloud core. The reddest of the new infrared sources, named here DC 287.1+02.4 IRS, is not detected shortward of 2 μ m, and it exhibits a very red $(K\! {\rm s} - L')$ colour. The location and colour of this source suggest that this is the near-infrared counterpart of IRAS 10501-5630. Red nebular emission with an elongated shape is also seen in the H and $K\! {\rm s}$ band images and could be due to scattered light originating in the embedded objects.
Technologies of fiber fusion and fused device fabrication for sensing applications

We review the technologies of fiber fusion and fused device fabrication for fiber sensing applications. Fiber interconnection and fused fiber components are integral parts in optical fiber sensing modules and systems. Dissimilar fibers need to be fused together with low loss and high strength to ensure long-term performance stability. Fused fiber components, such as fused couplers and polarization-maintaining (PM) components, are important for both coherent and incoherent detection. In addition, the latest advances in nano/micro-fiber device and multi-port signal combiners pose new challenges to the fiber fusion and fused component technologies. We describe fundamental optics, discuss fabrication techniques for these devices, and present some application examples.
Pocklington Equation via Circuit Theory

In this paper it is shown a circuit-theory approach for the integral equation for thin wire antennas, from which Pocklington’s equation can be deduced as a special case. In this way, when solving it via method of moments, impedance, current and voltage matrix acquire meaning [1]. It is shown that a thin wire can be considered as an infinite-port electric network, in which the goal consists in finding out the current in each port. The following approach is based on Aharoni’s theory [2].
Sample-size determination for two-sided b-expectation tolerance intervals for a normal distribution

In statistical practice, tolerance limits are constructed to contain a specified proportion of a population. When only sample data are available, the actual proportion contained in the interval is random and unknown but controlled by a statistical criterion. In this article, we consider some properties of two-sided β-expectation tolerance intervals for a normal distribution based on the sample mean and the sample standard deviation S computed from a random sample of size n. The tolerance interval is given by ± kS, where k = (l/n + l)½t and t is an appropriate quantile of a Student-t distribution. In repeated sampling, such intervals will, on the average, contain l0O0β% of the sampled distribution. These intervals provide a useful description of a population if the spread in the actual proportion contained in the interval is controlled or evaluated. We consider the effect that sample size has on the proportion of the population contained in the interval, using two different criteria for measuring the varia.
Near-field optical patterning on azo-hybrid sol–gel films

We report on the near-field optical patterning of photochromic sol–gel films with subwavelength resolution. The sample containing functionalized azobenzene species is locally illuminated in the visible absorption band of these photochromes through the aperture of a metallized tapered optical fiber. The surface topography imaged by in situ shear-force microscopy reveals that, due to repeated photoisomerization cycles of the azobenzene molecules, photoinduced matter migration occurs under the tip leading to the formation of a surface relief. The shape of this structure is characteristic of the electromagnetic field distribution and strongly depends on the tip-to-sample distance. In near-field illumination conditions, protrusions of lateral dimension as small as 60 nm (≈λ/10) are currently produced. When repeating this process, compact arrays of nanodots are optically inscribed.
Reverse time migration from topography

ABSTRACTMigration of seismic data from topography using methods based on finite-difference (FD) approximation to acoustic wave propagation commonly suffers from a number of imaging drawbacks due to the difficulty of applying FD stencils to irregular computational meshes. Altering the computational geometry from Cartesian to a topographic coordinate system conformal to the data acquisition surface can circumvent many of these issues. The coordinate transformation approach allows for acoustic wave propagation and the crosscorrelation and inverse-scattering imaging conditions to be posed and computed directly in topographic coordinates. Resulting reverse time migration (RTM) images may then be interpolated back to the Cartesian domain using the known inverse mapping. Orthogonal 2D topographic coordinates can be developed using known conformal mapping transforms and serve as the computational mesh for performing migration from topography. Impulse response tests demonstrate the accuracy of the 2D generalized a.
The absolute magnitudes of RR Lyrae stars and the age of the galactic globular cluster system

Evidence is adduced that many calibrations of the absolute luminosities of zero-age horizontal-branch RR Lyrae stars exhibit a dependence on metallicity. The primary unsolved problem is now why the various RR Lyrae absolute magnitude calibrations yield such different slope dependencies on metallicities. The ages of the globular clusters can, nevertheless, be determined independently of the calibration of RR Lyrae absolute luminosities, by relying on the main-sequence fits to directly ascertain bolometric magnitudes. 44 refs.
Influence of departures from LTE on oxygen abundance determination in the atmospheres of A-K stars

We have performed non-LTE calculations for O I with a multilevel model atom using currently available atomic data for a set of parameters corresponding to stars of spectral types from A to K. Departures from LTE lead to a strengthening of O I lines, and the difference between the non-LTE and LTE abundances (non-LTE correction) is negative. The non-LTE correction does not exceed 0.05 dex in absolute value for visible O I lines for main-sequence stars in the entire temperature range. For the infrared O I 7771 Å line, the non-LTE correction can reach −1.9 dex. The departures from LTE are enhanced with increasing temperature and decreasing surface gravity. We have derived the oxygen abundance for three A-type mainsequence stars with reliably determined parameters (Vega, Sirius, HD 32115). For each of the stars, allowance for the departures from LTE leads to a decrease in the difference between the abundances from infrared and visible lines, for example, for Vega from 1.17 dex in LTE to 0.14 dex when abandoning LTE. In the case of Procyon and the Sun, inelastic collisions with HI affect the statistical equilibrium of OI, and agreement between the abundances from different lines is achieved when using Drawin’s classical formalism. Based on the O I 6300, 6158, 7771-5, and 8446 Å lines of the solar spectrum, we have derived the mean oxygen abundance log ɛ = 8.74 ± 0.05 using a classical plane-parallel model solar atmosphere and log ɛ+3D = 8.78 ± 0.03 by applying the 3D corrections taken from the literature.
Parallel simulation of unsteady hovering rotor wakes

Numerical simulation using low diffusion schemes, for example free‐vortex or vorticity transport methods, and theoretical stability analyses have shown the wakes of rotors in hover to be unsteady. This has also been observed in experiments, although the instabilities are not always repeatable. Hovering rotor wake stability is considered here using a finite‐volume compressible CFD code. An implicit unsteady, multiblock, multigrid, upwind solver, and structured multiblock grid generator are presented, and applied to lifting rotors in hover. To allow the use of very fine meshes and, hence, better representation of the flow physics, a parallel version of the code has been developed, and parallel performance using upto 1024 CPUs is presented. A four‐bladed rotor is considered, and it is demonstrated that once the grid density is sufficient to capture enough turns of the tip vortices, hover exhibits oscillatory behaviour of the wake, even using a steady formulation. An unsteady simulation is then performed, and also shows an unsteady wake. Detailed analysis of the time‐accurate wake history shows that three dominant unsteady modes are captured, for this four‐bladed case, with frequencies of one, four, and eight times the rotational frequency. A comparison with theoretical stability analysis is also presented. Copyright © 2006 John Wiley & Sons, Ltd.
Optical Stark deceleration of nitric oxide and benzene molecules using optical lattices

We describe the deceleration of nitric oxide, benzene and xenon atoms in a molecular beam using one-dimensional pulsed optical lattices created by fields with intensities in the 1012 W cm−2 range. We show that for the same pulse duration and lattice intensity the velocity of the molecules can be controlled by tailoring the lattice velocity. By utilizing the time-dependent oscillatory motion of the molecules within the lattice, we demonstrate the deceleration of nitric oxide from an initial velocity of 400 m s−1 to a final velocity of 290 m s−1 in a single 5.8 ns pulse. Using higher intensities, we measure the deceleration of benzene molecules from 380 m s−1 to 191 m s−1, representing a 75% reduction in the kinetic energy within the lattice over the same duration.
Supernovae in luminous arcs

The giant luminous arcs seem to be images of galaxies distorted by foreground clusters acting as gravitational lenses, with galaxies close to the cusps of gravitational lens caustic. The part of a galaxy located inside a cusp has three images of itself within an arc. The arcs are very blue, so the galaxies may be in a stage of active star formation with supernovae exploding every few years. If a supernova goes off inside a cusp it will be observed thrice, at three positions. The apparent magnitudes of the supernovae images may be M(R) roughly 20-23. The arrival time differences between the images can be as short as a few weeks or even days, whereas for ordinary lenses on a cluster scale the differences can be decades to centuries. Simple relations between the ratios of the arrival time differences, magnifications, and image separations are predicted. 27 references.
Initial Experiments on the End-Point Control of a Flexible One-Link Robot

It has been known for some time (Gevarter 1970) that if a flexible structure is controlled by locating every sensor exactly at the actuator it will control, then stable operation is easy to achieve. Nearly all commercial robots are controlled in this way, for this reason. So are most flexible spacecraft. Conversely, when one attempts to control a flexible struc ture by applying control torques at one end that are based on a sensor at the other end, the problem of achieving stability is severe. Solving it is an essential step for better control in space: the space-shuttle arm is a cogent example. The next generation of industrial robots will also need such control capability, for they will need to be much lighter in weight (to achieve quick response with modest energy), and they will need to achieve greater precision by employing end-point sensing. A set of experiments has been constructed to demonstrate control strategies for a single-link, very flexible manipulator, where the position of one end is to be sensed and precisely positioned by torquing at the other end. The objective of this first set of experiments is to uncover and solve problems related to the control of very flexible manipulators where sen sors are not colocated with the actuator. The experimental arrangement described here is also a test bed for new designs for flexible-structure controllers, designs that use insensitive, reduced-order control and adaptive control methods, for example. This paper describes the experimental arrangement, model identification, control design, and first experimental results. Some interesting results are the following. First, good stability can be achieved for such noncolocated systems, and reponse can be achieved that is effectively three times faster than the first natural cantilever period of the system: but a good model of the system dynamics and rather sophisticated control algorithms are essential to doing so. Even then, the system will always be conditionally stable. In addition to the tip sensor, a colocated rate sensor and nearly colocated strain gauges have been found to be very useful for achieving good closed-loop performance, that is, high gain and high band width. Second, there is an ultimate physical limit to achiev able response time, namely, the time required for a wave to travel the length of the member. Well-designed controllers can approach this limit. Third, the use of end-point sensing makes less critical the elaborate dynamic conditioning of position-command signals— "model-following " differentia tors, feed-forward, and the like—such as are typically needed in present-generation robots that use "dead reckoning" in lieu of end-point sensing. With end-point sensing, feedback alone (suitably conditioned) is sufficient to whip the tip to the commanded position and hold it there precisely. Even more important, a shift in, for example, workpiece with respect to robot base, no longer produces an error.
Transient Interaction of Spherical Acoustic Waves and a Spherical Elastic Shell

and Bhatia and Nachbar [3]. All three papers deal with finite deformations in centrally loaded circular membranes; the first treats a linear elastic membrane loaded through a central circular plug, the second considers the load as a concentrated central force, and the last analyzes an elastic-plastic membrane loaded through a hemispherical indenter. For moderate rotations of the membrane, the solutions given in the three papers just cited and the authors' paper should show close agreement for the traction-free region of the membrane. Have the authors carried out any comparisons between their results and those given in references [1-3]?
Detection and separation of symbols connected to graphics in line drawings

Presents a technique for the detection and separation of symbols connected to graphics in line drawings. The approach is based on a special image representation, that the authors call graph representation. The graph representation is especially convenient for line-like images, since it decomposes the line structure into 'edges' and 'nodes', that formalise the intuitive notions of 'line' and 'crossing point between lines'. In this way, well-known algorithms from graph theory can be used. The graph is searched for characteristic sub-graphs, revealing the presence of symbols or noisy objects overlapping lines. Each symbol candidate is accurately processed, in order to make the area of its connection to lines as regular as possible. Actually, two different algorithms have been designed to perform this task: one for symbols crossing lines and the other for symbols only touching lines. Both of them are rotation invariant. <<ETX>>
COMPRESSIBLE FREE SHEAR LAYER WITH FINITE INITIAL THICKNESS

1) Experimental determination of the exponential coefficient in the growth law for a turbulent wake is very difficult, if not impossible. 2) If use is made of the theoretically predicted value of this coefficient, the existence of two distinct regions of growth (x 200) is shown by the experimental data. 3) Although the Slattery and Clay data indicate a scale effect for J-and \in. spheres, the authors \and J-in. sphere data indicate at most a much weaker scale effect. 4) It is important to fit the data with the proper algebraic expression of the theoretical growth law, i.e., r = bx + c. 5) If the effect of sphere deceleration is assumed to be described by a quasi-steady state transformation,:the coefficient 6 for the far wake is well predicted by the Lees-Hromas theory.
Design of One Degree of Freedom Closed Loop Spatial Chains Using Non-Circular Gears

This paper presents the design of one degree-of-freedom spatial mechanisms that use non-circular gears to constrain the motion. In a spatial body-guidance problem, representing the motion by systems of polynomial equations restricts the number of end-effector positions and orientations (end-effector poses) that can be used as inputs for mechanism design. An approach has been developed that takes any number of desired poses as guide points and develops a mechanism that approximately attains the desired poses over the course of its motion. A problem with implementing this design strategy is the inherent difficulty in accounting for orientation and position errors. The approach described here addresses this problem by defining a new error functional, calculated in the joint space domain. As the mechanisms being dealt with are single degree-of-freedom closed chains, the starting position is a crucial decision in the design process. The method outlines the choice of the starting position and details how this error term can be used along with optimization techniques on either the mechanism parameters or the non-circular gears. A numerical example is presented.Copyright © 2009 by ASME