Miracle-dz/UniFAR-FTUs huggingface dataset:
Infrared photometry of low-mass stars in Praesepe

ABSTRA C T We present follow-up infrared photometry for a sample of low-mass and very low-mass stars in the Praesepe open cluster. Our sample is selected from two sources: (i) 90 stars selected from the Hambly et al. photometric and proper-motion survey of Praesepe; (ii) 17 stars selected from the CCD imaging survey presented by Pinfield et al. We investigate cluster membership using infrared colour‐magnitude and colour‐colour diagrams. We find 81 likely and two possible members in the Hambly et al. sample, in line with predictions. Contamination in the Pinfield et al. sample is higher, and we find nine probable cluster members. We investigate the non-grey models of Baraffe et al., which are found to be in good agreement with the data. Multiplicity in Praesepe is also examined, and we find the multiple star fraction to be 0.51 from analysis of the I; I 2 K diagram. We investigate individual object masses, and find that the faintest candidate cluster members have masses close to the substellar limit.
A new estimator combining the ridge regression and the restricted least squares methods of estimation

It is well-known in the literature on multicollinearity that one of the major consequences of multicollinearity on the ordinary least squares estimator is that the estimator produces large sampling variances, which in turn might inappropriately lead to exclusion of otherwise significant coefficients from the model. To circumvent this problem, two accepted estimation procedures which are often suggested are the restricted least squares method and the ridge regression method. While the former leads to a reduction in the sampling variance of the estimator, the later ensures a smaller mean square error value for the estimator. In this paper we have proposed a new estimator which is based on a criterion that combines the ideas underlying these two estimators. The standard properties of this new estimator have been studied in the paper. It has also been shown that this estimator is superior to both the restricted least squares as well as the ordinary ridge regression estimators by the criterion of mean sauare e.
The Number of Classes in Chi-Squared Goodness-of-Fit Tests

Abstract The power of Pearson chi-squared and likelihood ratio goodness-of-fit tests based on different partitions is studied by considering families of densities “between” the null density and fixed alternative densities. For sample sizes n → ∞, local asymptotic theory with respect to the number of classes k is developed for such families. Simple sufficient and almost necessary conditions are derived under which it is asymptotically optimal to let k tend to infinity with n. A numerical study shows that the results of the asymptotic local theory for contamination families agree well with the actual power performance of the tests. For heavy-tailed alternatives, the tests have the best power when k is relatively large. Unbalanced partitions with some small classes in the tails perform surprisingly well, in particular when the alternatives have fairly heavy tails.
Boundary layers whose streamlines are closed

Certain two-dimensional, laminar bounday layers are considered whose streamlines are closed. The speed at the solid boundary is supposed uniform, the bounday outline being stationary, and the speed in the boundary layer is supposed to differ only slightly from that of the boundary. A formal solution is then obtained for the motion in the boundary layer. The analysis confirms that a closed boundary layer may exist and yields a condition needed to determine the inviscid motion. The condition is extracted in a simplified but approximate form and two examples of its use are given. A further class of closed boundary layers, namely those for which the pressure is uniform, is also considered. For this class the condition needed to determine the inviscid motion may be derived in a form both simple and exact.
THE LEGACY OF SCUPOL: 850 μm IMAGING POLARIMETRY FROM 1997 TO 2005

SCUPOL, the polarimeter for SCUBA on the James Clerk Maxwell Telescope, was the most prolific thermal imaging polarimeter built to date. Between 1997 and 2005, observations of 104 regions were made at 850 μm in the mapping mode. The instrument has produced ∼50 refereed journal publications, and that number is still growing. We have systematically re-reduced all imaging polarimetry made in the standard “jiggle-map” mode from the SCUBA archive (2800+ individual observations) to produce a catalog of SCUPOL images and tables. We present the results of our analysis with figures and data tables produced for all 83 regions where significant polarization was detected. In addition, the reduced data cubes and data tables can be accessed online. In many cases, the data included in this paper have been previously published elsewhere. However, this publication includes unpublished data sets, in whole or in part, toward 39 regions, including cores in ρ Ophiuchus, Orion's OMC-2 region, several young stellar objects, and the galaxy M87.
Numerical Simulations of the Vertical Structure of Quasi-Geostrophic Turbulence

Direct simulations of turbulent quasi-geostrophic flow on a βplane have been performed with an emphasis on three-dimensional resolution [128 × 128] in the horizontal and up to 6 vertical modes). The statistically equilibrated turbulence is forced by baroclinic instability of a mean shear, and dissipation occurs through friction in a bottom Ekman layer. Parameters which control the vertical structure of the variability and the energy partition between the vertical modes are identified. We verity Charney's prediction of three-dimensional isotropization of quasi-geostrophic flows in the case of a constant Brunt-Vaisala profile; for a variable Brunt- Vaisala however, their vertical scale is highly dependent on whether they appear in a forced turbulent flow or in freely evolving turbulence, the latter having a larger vertical scale.
Temperature dependence of the thermal conductivity of different forms of diamond

We present a systematic theoretical investigation of the thermal conductivity of naturally abundant, isotopically enriched, fast neutron irradiated single crystals of diamond, and chemical vapor deposited diamond films of different types over a large temperature range. Existing experimental data have been analyzed using Callaway’s theoretical model [Phys. Rev. 113, 1046 (1959)] for thermal conductivity based on an isotropic continuum phonon dispersion relation and using normal and umklapp phonon-phonon relaxation times derived from the application of time-dependent perturbation theory within an anharmonic continuum model. In contrast to existing theoretical studies of the thermal conductivity of diamond, our approach considers Gruneisen’s constant as the only (semi)adjustable parameter for anharmonic phonon interactions. This work quantifies the enhancement of the thermal conductivity of diamond with isotopic purity. This work also accounts for the dip in the thermal conductivity curve for hot filament ch.
Approximate maximum likelihood DOA estimation in multiplicative noise environments

We consider the problem of localizing a source by means of a uniform linear array of sensors when the received signal is corrupted by multiplicative noise. Since the exact maximum likelihood (ML) estimator is computationally intensive, two approximate solutions are proposed, originating from the analysis of the high and low signal to noise ratio (SNR) cases, respectively. First, starting with the no additive noise case, a very simple approximate ML (AML/sub 1/) estimator is derived. A theoretical expression for its asymptotic variance in the presence of additive noise is derived. It shows that the AML/sub 1/ estimator has a performance close to the Cramer-Rao bound (CRB) for moderate to high SNR. Next, the low SNR case is considered and the corresponding AML2 solution is derived. It is shown that the approximate ML criterion can be concentrated with respect to (w.r.t.) both the multiplicative and additive noise powers, leaving out a 2-D minimization problem instead of a 4-D problem required by the exact ML. Numerical results illustrate the performance of the estimators and confirm the validity of the theoretical analysis.
Interstellar pickup ions and quasi‐perpendicular shocks: Implications for the termination shock and interplanetary shocks

A new mechanism for the acceleration of pickup ions by repeated reflections from the electrostatic cross shock potential of a quasi-perpendicular shock is presented. The acceleration mechanism, multiply reflected ion (MRI) acceleration, offers a resolution to the issue of injecting pickup ions into an efficient particle energization scheme, and the injection efficiency for pickup ions is found to be inversely proportional to ion mass and proportional to charge. By studying the particle energy gain in the motional electric field (where a steady shock frame is assumed) the energized pickup ion spectrum can be computed. Extremely hard power law spectra (E −1.5 , for example) emerge from the upstream pickup ion distribution. The maximum energy that a reflected pickup ion can gain is found to be proportional to the square of the product of the Alfven speed and (r−1), where r is the shock compression ratio. For solar wind conditions at either interplanetary shocks or the termination shock the upper energy limit is typically in excess of 0.5 MeV. It is suggested here that MRI acceleration provides an efficient mechanism for injecting low-energy pickup ions into a subsequent acceleration process such as diffusive Fermi acceleration. Such a two-step acceleration scheme alleviates many of the difficulties which plague ion energization models at perpendicular shocks. The structure of a quasi-perpendicular shock modified by shock reflection of pickup ions is discussed in general terms. By way of application we present a detailed study of the MRI acceleration mechanism at the termination shock for a wide range of parameters and discuss the implications for the anomalous cosmic ray component. The acceleration of pickup ions by an interplanetary traveling shock is also discussed, and the observations made by Ulysses [Gloeckler et al., 1994] are addressed. The puzzling aspects of the Gloeckler et al. [1994] observations appear to be explained quite naturally by shock energization based on repeated pickup ion reflections. Observational tests of MRI acceleration may be possible by using pickup He + at either the terrestrial or Jovian bow shock or by using cometary ions at a cometary bow shock.
Improved bow shock models for Herbig-Haro objects - application to HH 2A-prime

An improved version of the bow shock theory previously applied to Herbig-Haro objects is presented. The modifications provide a more accurate calculation of the ionization state of material entering the bow shock. The revised preionization does not drastically affect the emission-line predictions for a 200 km/s bow shock model, though the effects will be more severe for slower shock velocities. The line profiles of the new models resemble the observed profiles somewhat more closely, and the relative emission-line intensities typically differ by 30 percent from those predicted by the older models. The models agree well with new IUE spectra and existing optical data for HH 2A-prime. 32 references.
The Mathematics of Computerized Tomography

The Mathematics of Computerized Tomography covers the relevant mathematical theory of the Radon transform and related transforms and also studies more practical questions such as stability, sampling, resolution, and accuracy. Quite a bit of attention is given to the derivation, analysis, and practical examination of reconstruction algorithm, for both standard problems and problems with incomplete data.
Non-linear free vibration analysis of laminated composite cylindrical/hyperboloid shell panels based on higher-order shear deformation theory using non-linear finite-element method

Abstract In this article, the non-linear free vibration analysis of the laminated composite shallow cylindrical/hyperboloid shell panels is attempted by taking geometric non-linearity in Green—Lagrange sense. A higher-order shear deformation theory is employed to model the shell panel flexure. A set of non-linear governing equations is derived using a variational approach. A non-linear finite-element model is proposed and applied to obtain discretized non-linear equations. Typical numerical examples have been solved using a direct iterative technique. Effects of lamination schemes, modular ratio, amplitude ratio, thickness ratio, and various boundary conditions on the frequency ratio (non-linear frequency to linear frequency) are examined in detail. The results are compared with those available in the literature. These show the importance and necessity of the Green—Lagrange-type non-linearity especially when the shell panel undergoes large deformation.
A SWIFTS operating in visible and near-infrared

SWIFTS (Stationary Wave Integrated Fourier Transform Spectrometer) is based on a very promising technology. It permits a drastic reduction of the size of spectrometers while conserving, even improving, their performances. We present the first attempt to realise a SWIFTS based on wave guides in glass operating in visible and near infra-red. Here, we present an original optical near-field detection in which nanowires of gold are used to directly sample the evanescent standing wave in the waveguide. With this first prototype we have been able to rebuild a spectrum with a resolution R=95.
Effect of Temperature Dependent Viscosity on Thermal Convection of Nanofluids: Steady Case

In this paper, the linear stability analysis of the thermal convection of a nanofluid layer heated from below with temperature-dependent viscosity for general boundary conditions is carried out. The principle of exchange of stabilities is shown to be valid for the problem, which means that instability sets in as stationary convection. The expressions for Rayleigh numbers with variable viscosities for each combination of rigid and dynamically free boundary conditions are derived using the Galerkin method. The values of critical wave numbers for different values of viscosity parameters, and consequently the critical Rayleigh numbers at which the onset of convection starts, are computed numerically. The effects of various parameters (namely, the viscosity variation parameter, Lewis number, and concentration Rayleigh number on the onset of stationary convection for each case of boundary combination) are computed numerically and depicted graphically. From the obtained results, it was found that the induction o.
Tautness for Alexander-Spanier cohomology.

Let F denote a contravariant functor from the category of topological spaces to the category of abelian groups. A subspace A of a topological space X is said to be taut with respect to F if the canonical map lim{F(U)}->F(A) is an isomorphism (the direct limit is taken over the family of all neighborhoods of A in X, the family being directed downward by inclusion). The subspace A is taut in X if it̂ is taut with respect to the Alexander-Spanier cohomology theory H for every dimension and every coefficient group (for notation and terminology dealing with H see [6]). This concept of tautness has proved to be important. In [6] and [7] it is shown that a closed subspace of a paracompact Hausdorff ^pace is taut, and this is used to deduce a strong excision property for H. This tautness property is also used in [6] to derive the continuity property for H. In [4] it is shown that an arbitrary subspace of a metric space is taut with respect to Cech cohomology, and this is used to obtain a general duality in spheres. Since the Cech cohomology is isomorphic to H [3], every subspace of a metric space is taut. In [2] it is shown that every neighborhood retract of X is taut in X, and this is used to prove a generalized homotopy property for compact spaces. In [1] tautness is considered for sheaf cohomology and used in proving the Vietoris-Begle mapping theorem. We shall prove a simple lemma which gives a sufficient condition for tautness. This sufficient condition is enough to establish tautness in all the various cases where it is known. Let % be a collection of subsets of X and A a subset of X. The star of A with respect to % denoted by st(A, °U), is defined to be the union of those elements of °U whose intersection with A is nonempty. An open covering of A in X is a collection °U of open sets of X such that A Cst(A, °U). The following seems to be the main fact underlying tautness (see [2] and [6]).
Optimal Signal Amplitude of Orthogonal Frequency-Division Multiplexing Systems in Dimmable Visible Light Communications

Visible light communications (VLC) using the intensity modulation of light-emitting diodes (LEDs) provides a new communication medium to overcome the shortage of radio spectrum, and allows reuse of LED lighting infrastructures. Orthogonal frequency-division multiplexing (OFDM) was introduced to VLC for its merits in mitigating the fading effects resulting from delay spread, and in avoiding low-frequency ambient interference. Noise and clipping are two major factors that degrade the performance of OFDM in VLC. A larger signal easily overcomes noise, but experiences impairment by clipping. Therefore, degradation due to clipping has a trade-off relationship with that due to noise, depending on the signal amplitude of OFDM. In this paper, the optimal signal amplitude in the trade-off is obtained by simulation when the dimming and LED intensity are given. The former indicates a user's requirement for lighting, and the latter represents the channel quality. The required LED intensity-to-noise ratio, as the channel quality that guarantees dimming as well as an adequate bit-error rate (BER), is also discussed.
The Importance of Iron Status for Young Children in Low- and Middle-Income Countries: A Narrative Review

Early childhood is characterised by high physiological iron demand to support processes including blood volume expansion, brain development and tissue growth. Iron is also required for other essential functions including the generation of effective immune responses. Adequate iron status is therefore a prerequisite for optimal child development, yet nutritional iron deficiency and inflammation-related iron restriction are widespread amongst young children in low- and middle-income countries (LMICs), meaning iron demands are frequently not met. Consequently, therapeutic iron interventions are commonly recommended. However, iron also influences infection pathogenesis: iron deficiency reduces the risk of malaria, while therapeutic iron may increase susceptibility to malaria, respiratory and gastrointestinal infections, besides reshaping the intestinal microbiome. This means caution should be employed in administering iron interventions to young children in LMIC settings with high infection burdens. In this narrative review, we first examine demand and supply of iron during early childhood, in relation to the molecular understanding of systemic iron control. We then evaluate the importance of iron for distinct aspects of physiology and development, particularly focusing on young LMIC children. We finally discuss the implications and potential for interventions aimed at improving iron status whilst minimising infection-related risks in such settings. Optimal iron intervention strategies will likely need to be individually or setting-specifically adapted according to iron deficiency, inflammation status and infection risk, while maximising iron bioavailability and considering the trade-offs between benefits and risks for different aspects of physiology. The effectiveness of alternative approaches not centred around nutritional iron interventions for children should also be thoroughly evaluated: these include direct targeting of common causes of infection/inflammation, and maternal iron administration during pregnancy.
Multi-step predictive control with TDBP method for pneumatic position servo system

This paper presents a new multi-step predictive controller based on neural networks and researches the adaptability of the predictive controller for a pneumatic position servo system which has some typical characteristics of non-linearity and time-varying. A diagonal recurrent neural network (DRNN) is used to predict the system output of the multi-step ahead directly. According to the intrinsic defects of a back-propagation (BP) algorithm that cannot update network weights incrementally, a new hybrid learning algorithm combining the temporal differences (TD) method with the BP algorithm to train the DRNN is put forward. A three-layer feedforward BP neural network is used as a non-linear rolling optimal controller to realize the optimization of control input of the next step according to a single-value predictive control algorithm to simplify computation. Simulation and experimental results indicate that the proposed predictive controller is suitable for real-time control of a pneumatic position servo system because of its characteristics of a simple algorithm, fast calculation of the control input and good tracking effects.
Sound generation and radiation from rotor tip-vortex pairing phenomenon

Sound generation and radiation from rotor tip-vortex pairing are calculated numerically. Wake geometries of a two-bladed rotor in axial flights are calculated using a time-marching free-wake method without a nonphysical model of the far wake. The acoustic field can be obtained using acoustic analogy. To show the accuracy of the flow calculation scheme, the tip-vortex geometries of the present calculation are compared with those done in the previous publication of a small-scaled rotor experiment. The accuracy of the vortex sound calculation scheme is validated by comparing its numerical and the analytic solution of circular vortex-ring interaction. The tip-vortex pairing consists of a turn of the tip-vortex from one blade rolling around the tip-vortex from the other blade. The tip-vortex pairing amplifies the noise and generates new dominant frequencies. The tip-vortex pairing noise has a quadrupole directivity pattern, and it is especially dominant in the direction of the rotation axis. The peak components of the noise spectrum represent the pairing period and an instability mode.
Modelling and compensating measurement errors caused by scattering in time-of-flight cameras

Recently, Range Imaging (RIM) cameras have become available that capture high resolution range images at video rate. Such cameras measure the distance from the scene for each pixel independently based upon a measured time of flight (TOF). Some cameras, such as the SwissRanger(tm) SR-3000, measure the TOF based on the phase shift of reflected light from a modulated light source. Such cameras are shown to be susceptible to severe distortions in the measured range due to light scattering within the lens and camera. Earlier work induced using a simplified Gaussian point spread function and inverse filtering to compensate for such distortions. In this work a method is proposed for how to identify and use generally shaped empirical models for the point spread function to get a more accurate compensation. The otherwise difficult inverse problem is solved by using the forward model iteratively, according to well established procedures from image restoration. Each iteration is done as a sequential process, starting with the brightest parts of the image and then moving sequentially to the least bright parts, with each step subtracting the estimated effects from the measurements. This approach gives a faster and more reliable compensation convergence. An average reduction of the error by more than 60% is demonstrated on real images. The computation load corresponds to one or two convolutions of the measured complex image with a real filter of the same size as the image.