Miracle-dz/UniFAR-FTUs huggingface dataset:
Heat Transfer on Internal Surfaces of a Duct Subjected to Impingement of a Jet Array with Varying Jet Hole-Size and Spacing

One significant issue concerning the impingement heat transfer with a jet array is related to the so-called "crossflow," where a local jet performance is influenced by the convection of the confluence from the impingement of the jet/jets placed upstream. As a result, the heat transfer coefficient may vary along the streamwise direction and creates more or less nonuniform cooling over the component, which is undesirable from both the performance and durability standpoints. Described in this paper is an experimental investigation of the heat transfer coefficient on surfaces impinged by an array of six inline circular jets with their diameters increased monotically along the streamwise direction. The local heat transfer distributions on both the target surface and jet-issuing plate are measured using a transient liquid crystal technique. By varying the jet hole-size in a systematic manner, the actual distribution of jet flow rate and momentum within a jet array may be optimally metered and controlled against crossftow. The effects on the heat transfer coefficient distribution due to variations of jet-to-target distance and interjet spacing are investigated. The varying-diameter results are compared with those from a corresponding array of uniform jet diameter.
Monitoring of long term behaviour of OH masers in semiregular variables: R Crt, W Hya and RT Vir ?

We present and interpret the results of a long-term OH variability study of three semiregular stars, one type a (SRa), W Hya, and two type b (SRb), R Crt and RT Vir. The 1665 and 1667 MHz OH masers of the three semiregulars were observed at intervals in the period 1982 January{1995 December using the Nan cay radio telescope, and we searched for 1612 MHz emission. The OH maser proles of the studied stars signicantly deviated from a standard double-peaked prole. The timescale of prole changes in the two SRb stars R Crt and RT Vir was as short as a month. The OH proles of the SRa star W Hya were much more stable but since November 1986 a very blue-shifted feature appeared at 1667 MHz. Our phase-lag measurements suggest that this feature comes from a detached OH shell of radius 3 10 16 cm. Faint 1612 MHz emission was found in W Hya only. Weak emission at velocities very close to the systemic velocity usually appeared during some intervals of high maser activity in R Crt and RT Vir and was almost always present in W Hya. For R Crt we estimated that this tangential emission disappeared when the kinetic temperature in the OH maser regions dropped below 150 200 K. For a few features, line narrowing and re-broadening were observed on timescales of 90 200 days. The linewidth was inversely proportional to the peak flux density, suggesting unsaturated amplication. Cyclic variations in the integrated flux density were observed in all the three stars. The OH variability curves were generally characterised by large amplitude (4 6 m ) variations over 400 800 days superimposed with 100 300-day variations of 0:2 2 m . Only the measured OH period of W Hya, of 362 7 days, was in agreement with the optical period. The two SRb stars exhibited multi-periodic OH variability including with two statistically signicant periods. The behaviour of their red- and blue-shifted emission was less correlated than in W Hya. The ratios of the flux densities at 1667 MHz to that at 1665 MHz in all the three stars were about 2 at epochs of high OH activity and usually increased during weak maser emission. Long term behaviour of the OH masers from W Hya resembled that of standard OH Miras, while that of R Crt and RT Vir suggested thin and clumpy envelopes where unsaturated emission was sustained in some clouds.
Speed of Sound in Distilled Water as a Function of Temperature and Pressure

An ultrasonic pulse type apparatus was used to measure the speed of sound in distilled water over the pressure range 14.7 to 14 000 psia and the temperature range 0.9 to 91.2°C. The temperature where the maximum sound speed occurs shifts to a higher temperature when the pressure is increased. At atmospheric pressure the computed maximum speed was 1555.36 m/sec and occurred at a temperature of 74.164°C. The isotherms of sound speed, plotted as a function of pressure, are concave upward below 20°C, concave downward above 20°C, and are approximately linear near 20°C for the pressure range of 14.7 to 14 000 psia. These curvatures have a maximum value of 1 part in 300 compared to the estimated accuracy of measurement which is 1 part in 10 000. The results are presented in tables and also in the form of a fourth degree equation fitted to the experimental data by the method of least squares.
Turbulent free-surface flow over a sill

An quasi-analytic method is presented for the calculation of free-surface flow over sills (e.g. dams under construction). Starting point is the set of shallow-water equations (SWE) valid for quasi-uniform flow. To make these equations also valid for flow over sills, adaptations to the SWE are proposed, introducing coefficients in the convection, pressure and friction terms. These terms are derived from analytical and numerical calculations with an experimental check.
THE MILLIMETER- AND SUBMILLIMETER-WAVE SPECTRUM OF SYMMETRIC MONO-DEUTERATED METHYL FORMATE (DCOOCH3)

Abstract The rotational-torsional spectrum of DCOOCH3, the symmetric, singly deuterated isotopomer of methyl formate, has been extended into the millimeter-wave and submillimeter-wave regions of the electromagnetic spectrum. A total of 885 lines belonging to the A and E torsional substates of the ground (νt = 0) torsional state has been measured through rotational quantum number J = 30 up to a frequency of 377 GHz. These lines have been added to 27 previously measured microwave lines and the combined data set was analyzed using a global internal axis method. A root-mean-square deviation of 85 kHz has been obtained by varying 31 rotation and internal rotation parameters. The newly measured spectra reported should be useful for interstellar searches for DCOOCH3, which has yet to be detected unambiguously in interstellar clouds despite the existence of copious numbers of observed transitions for methyl formate.
The Effect of Viscosity in Hypervelocity Impact Cratering

A numerical method, of second order in both time and space, for the solution of the time-dependent compressible Navier-Stoke equations is presented. Conditions for stability are discussed. The method has been applied to calculate an axisymmetric flow field produced by hypervelocity impact. Results are given for impacts of aluminum cylinders (having diameters of 0.16, 0.32, and 0.64 cm) into aluminum targets. Viscosities of zero and 104 poise were assumed. Both plates and semi-infinite targets are considered at an impact speed of 10 km/sec. It is concluded that viscous effects become increasingly important as projectile size diminishes and cannot be neglected during the initial stages of crater formation for projectiles smaller than 0.5 cm in diameter.
Cliff–Ramp Patterns and Kelvin–Helmholtz Billows in Stably Stratified Shear Flow in the Upper Troposphere: Analysis of Aircraft Measurements

Abstract Cliff–ramp patterns (CR) are a common feature of scalar turbulence, characterized by a sharp temperature increase (cliff) followed by a more gradual temperature decrease (ramp). Aircraft measurements obtained from NOAA best aircraft turbulence probes (BAT) were used to characterize and compare CR patterns observed under stably stratified conditions in the upper troposphere, a region for which there are few such studies. Experimental data were analyzed for three locations, one over Wales and two over southern Australia, the latter in correspondence with the Southern Hemisphere winter subtropical jet stream. Comparison of observed CR patterns with published direct numerical simulations (DNS) revealed that they were likely signatures of Kelvin–Helmholtz (KH) billows, with the ramps associated with the well-mixed billows and the cliffs marking the highly stretched braids. Strong correlation between potential temperature and horizontal velocity supported the KH link, though expected correlations with .
Perceived Level of Noise by Mark VII and Decibels (E)

The calculation procedure Mark VII gives the perceived level of loudness or noisiness in PLdB. It utilizes a set of frequency‐weighting contours based on an average of 25 experimental contours. The standard reference sound is defined as a 13‐oct band centered at 3150 Hz. The perceived magnitude (loudness or noisiness) grows as the 23 power of the sound pressure, so that perceived magnitude doubles with each increase of 9 dB. The summation formula for the total subjective magnitude remains St = Sm + F (∑S − Sm), but the value of F is made to vary as a function of level in order to reflect the nonlinear growth (in log‐log coordinates) of broad‐band noise. As a result of the new reference sound at 3150 Hz, perceived level in decibels (PLdB) is approximately 8 dB lower than the older loudness level in phons. Except for the nearly constant difference of 8 dB, Mark VI and Mark VII give closely similar results for typical broad‐band noises. The 8‐dB downward shift makes it possible for a sound level meter with a.
Using interacting multiple model particle filter to track airborne targets hidden in blind Doppler

In airborne tracking, the blind Doppler makes the target undetectable, resulting in tracking difficulties. In this paper, we studied most possible blind-Doppler cases and summed them up into two types: targets’ intentional tangential flying to radar and unintentional flying with large tangential speed. We proposed an interacting multiple model (IMM) particle filter which combines a constant velocity model and an acceleration model to handle maneuvering motions. We compared the IMM particle filter with a previous particle filter solution. Simulation results showed that the IMM particle filter outperforms the method in previous works in terms of tracking accuracy and continuity.
Lagrangian finite element method for the analysis of two‐dimensional sloshing problems

A new version of a numerical algorithm for the Lagrangian treatment of incompressible fluid flows with free surfaces is developed. The novel features of the present method are the adoptions of the Lagrangian finite element method and the velocity correction technique. The use of the velocity correction approach makes the computational scheme extremely simple in algorithmic structure. Hence, the present method is particularly attractive for large-scale problems. The techniques discussed here are applied to some two-dimensional sloshing problems, which may indicate the versatility and effectiveness of the present method.
Total Flux Density Variations in Extragalactic Radio Sources. II. Determining the Limiting Brightness Temperature for Synchrotron Sources

The maximum intrinsic brightness temperature Tb, lim for powerful synchrotron-emitting radio sources is usually assumed to be ≈1012 K, limited by the inverse Compton catastrophe. A lower value of ≈5×1010 K, based on the equipartition brightness temperature, has been suggested by Readhead on the basis of Tb, obs distributions derived from VLBI observations. We present two new methods for estimating Tb, lim in extragalactic radio sources by using total flux density variations. A reasonable estimate of the value of Tb, lim for a source can be obtained by comparing the Doppler boosting factors derived from total flux density variations at 22 and 37 GHz with traditional estimates based on the radio and synchrotron self-Compton (SSC) X-ray fluxes. Another independent estimate of Tb, lim is obtained by comparing the brightness temperatures derived from variability data with the values calculated from VLBI observations. Using several data sets, we find that both methods yield a value of ≤1011 K, in accordance with the equipartition brightness temperature limit proposed by Readhead.
Electronic structure of point defects in controlled self-doping of the TiO2 (110) surface: Combined photoemission spectroscopy and density functional theory study

Point defects in metal oxides such as TiO2 are key to their applications in numerous technologies. The investigation of thermally induced nonstoichiometry in TiO2 is complicated by the difficulties in preparing and determining a desired degree of nonstoichiometry. We study controlled self-doping of TiO2 by adsorption of 1/8 and 1/16 monolayer Ti at the (110) surface using a combination of experimental and computational approaches to unravel the details of the adsorption process and the oxidation state of Ti. Upon adsorption of Ti, x-ray and ultraviolet photoemission spectroscopy (XPS and UPS) show formation of reduced Ti. Comparison of pure density functional theory (DFT) with experiment shows that pure DFT provides an inconsistent description of the electronic structure. To surmount this difficulty, we apply DFT corrected for on-site Coulomb interaction (DFT+U) to describe reduced Ti ions. The optimal value of U is 3 eV, determined from comparison of the computed Ti 3d electronic density of states with the UPS data. DFT+U and UPS show the appearance of a Ti 3d adsorbate-induced state at 1.3 eV above the valence band and 1.0 eV below the conduction band. The computations show that the adsorbed Ti atom is oxidized to Ti2+ and a fivefold coordinated surface Ti atom is reduced to Ti3+, while the remaining electron is distributed among other surface Ti atoms. The UPS data are best fitted with reduced Ti2+ and Ti3+ ions. These results demonstrate that the complexity of doped metal oxides is best understood with a combination of experiment and appropriate computations.
Single-integral expressions for electron cyclotron damping, relativistically and with an arbitrary distribution function

The relativistic expressions for the dielectric-tensor elements can be expressed as a double integral over both parallel and perpendicular momenta. The anti-Hermitian (damping) parts can be integrated over a delta function for either one of these two momenta, leaving a single integral over the other momentum variable. We review these expressions for either integration option, and compare them with statements in the literature. We give the limits on the remaining integral explicitly, for all positive or negative values of the parallel refractive index, whose magnitude can be less or greater than one. This single-integral form can be applied to electron cyclotron harmonic damping for any distorted electron momentum distribution function. As an example, we recover the results for a Maxwellian distribution. We also provide approximate results when the distribution function can be taken as a Maxwellian only in the perpendicular-momentum direction. A computer program will be written for a distribution function subjected to distortion by both electron cyclotron and lower-hybrid waves.
Outgassing asymmetry of periodic comet Encke. I - Apparitions 1924-1984

A concept of a collimated flow of ejecta from a discrete source (vent) on the surface of a rotating cometary nucleus is applied to P/Encke, based on positional observations of its sunward fanlike coma at 13 apparitions between 1924 and 1984. The major results include a finding that the observations are consistent with an invariable position of the rotation pole during the 60 yr (yielding an obliquity of 70 deg), although this is not to be interpreted as an indication that the nucleus is not precessing. Two vents are identified on the nucleus surface: one on the northern hemisphere at a latitude of +55 deg, of an estimated sublimitation area of 0.4 sq km, which is active along the inbound leg of the comet's orbit until a few days preperihelion and again beginning several weeks postperihelion; the other on the southern hemisphere at -75 deg, of an estimated area of 0.6 sq km, whose activity prevails in the intervening time. There appears to be a significant difference between the two regions in terms of dust content in their emissions. 60 references.
Tensile properties of helical auxetic structures: A numerical study

This paper discusses a helical auxetic structure which has a diverse range of practical applications. The mechanical properties of the system can be determined by particular combinations of geometry and component material properties; finite element analysis is used to investigate the static behavior of these structures under tension. Modeling criteria are determined and design issues are discussed. A description of the different strain-dependent mechanical phases is provided. It is shown that the stiffnesses of the component fibers and the initial helical wrap angle are critical design parameters, and that strain-dependent changes in cross-section must be taken into consideration: we observe that the structures exhibit nonlinear behavior due to nonzero component Poisson’s ratios. Negative Poisson’s ratios for the helical structures as low as −5 are shown. While we focus here on the structure as a yarn our findings are, in principle, scaleable.
Upstream influence and Long's model in stratified flows

This paper describes an experimental study of a stratified fluid which is flowing over a smooth two-dimensional obstacle which induces no flow separation and in which effects of viscosity and diffusion are not important. The results are restricted to fluid of finite depth. Various properties of the flow field, in particular the criterion for the onset of gravitational instability in the lee-wave field, are measured and compared with the theoretical predictions of Long's model. The agreement is found to be generally poor, and the consequent inapplicability of Long's model is explained by the failure of Long's hypothesis of no upstream influence, which is demonstrably invalid when stationary lee waves are possible. The obstacle generates upstream motions with fluid velocities which appear to be of first order in the obstacle height. These motions have some of the character of shear fronts or columnar disturbance modes and have the same vertical structure as the corresponding lee-wave modes generated downstream. They result in a reduced fluid velocity upstream below the level of the top of the obstacle, together with a jet of increased fluid velocity above this level which pours down the lee side of the obstacle. This phenomenon becomes more pronounced as the number of modes is increased.
METHANOL IN THE STARLESS CORE, TAURUS MOLECULAR CLOUD-1

To explore the formation mechanisms of gas phase CH3OH in cold starless cores, we have conducted high spectral resolution observations toward the cyanopolyyne peak of Taurus Molecular Cloud-1 (TMC-1 CP) with the IRAM 30 m telescope, the Green Bank Telescope, and the Nobeyama 45 m telescope. The spectral lines of CH3OH toward TMC-1 CP are found to have a double-peaked profile separated by 0.5 km s−1. Since the double-peaked profile is observed for 13CH3OH, it is not due to optical depth and/or self-absorption effects. The spectral line profile of CH3OH is much different from those of C34S, C3S, and HC7N observed toward this source. The H2 densities of the emitting region of CH3OH for the blueshifted and redshifted components are derived to be (1.7 ± 0.5) × 104 cm−3 and (4.3 ± 1.2) × 104 cm−3, respectively. These densities are similar to or slightly lower than those found for the other molecules. These results suggest a chemical differentiation between CH3OH and the other molecules, which has indeed been confirmed by mapping observations of the CH3OH and C34S lines. These results are consistent with the general idea that CH3OH is formed on dust grains and is liberated into the gas phase by non-thermal desorption. The grain-surface origin of CH3OH is further confirmed by the CH3OH/13CH3OH ratio. Weak shocks caused by accreting diffuse gas to the TMC-1 filament, photoevaporation caused by cosmic-ray induced UV radiation, and the desorption of excess reaction energy in the formation of CH3OH on dust grains are discussed for the desorption mechanisms.
Factorization of Helmholtz Determinant Operator for Decomposable Bi-Anisotropic Media

Conditions for the most general bi-anisotropic media in which the electromagnetic field can be decomposed in two components with respect to two six-vectors were recently derived by these authors. In the present paper it is shown that the fourth-order Helmholtz determinant operator, which appears in the basic scalar Helmholtz equation for electromagnetic fields, can be expressed in factorized form as a product of two second-order operators. These two operators are shown to correspond to the decomposition of the field. Finally, because of the factorization, the scalar Green function corresponding to the Helmholtz determinant is shown to take a numerically tractable form in terms of two finite integrations.
Detecting and Correcting Scale Drift in Test Equating: An Illustration from a Large Scale Testing Program

The purpose of this study is to determine the extent of scale drift on a test that employs cut scores. It was essential to examine scale drift for this testing program because new forms in this testing program are often put on scale through a series of intermediate equatings (known as equating chains). This process may cause equating error to accumulate to a point when scale scores are rendered incomparable across two parallel chains or time periods. The study examined two conditions (i.e., parallel equating chains or a single long chain) to evaluate whether scale drift occurred for these conditions. Data from three tests that employed cut scores were used in this study. Results indicated that although there were some differences observed between the actual equating conversions derived via different equating chains, the effect of these differences on actual pass and fail status of test takers was not large. Recommendations on some alternatives to follow when a scale drift is observed are made and implications for future research are discussed.
Sierra Wave Project Revisited: 50 Years Later

Abstract The Sierra Wave Project was the first post–World War II (WWII) mountain meteorology field experiment in the United States designed to study mountain lee-wave phenomena. In its concept, design, organization, and execution, this Air Force–funded project served as an important predecessor of modern mesoscale field experiments proving clearly that mesoscale phenomena could be studied effectively by combining high-density ground-based and airborne observations. In this historical overview of the Sierra Wave Project, we set the scientific motivations for the experiment in their historical context, examine the coupling of the Air Force interests with the sport of soaring and the science of meteorology in this experiment, and evaluate the impact of the observational and theoretical programs of the Sierra Wave Project on the meteorological and aviation communities. We also provide a link to the related past investigations of mountain waves and an outlook for the future ones.
Analysis of physical ageing effects in iris biometrics

Physical ageing is an important issue for practical biometrics, since it is known that the associated physiological changes can impair performance for most modalities. Understanding the effects of ageing is necessary, therefore both to optimise attainable performance but also to understand how to manage biometric templates, especially as the time elapsed between enrolment and use increases. Many factors can affect the performance of an iris recognition system, and in this study the authors report an experimental investigation of the interrelationship between some characteristics which are particularly relevant in understanding how to manage the practical effects of ageing with respect to this modality. Moreover, template ageing will itself be affected by issues related to the biological age of a subject, and this is also explored here.