Miracle-dz/UniFAR-FTUs huggingface dataset:
Densities and porosities of meteoroids

Using a physical theory of meteors and on the basis of the results of double-station photographic observations of meteors in Dushanbe (Tajikistan), Kiev, and Odessa (Ukraine), the mean mineralogical and bulk densities of meteoroids belonging to nine meteoroid streams and sporadic background are determined. The mean mineralogical densities $\delta_{\rm m}$ of meteoroids range from 2.2 g cm -3 (Perseids) to 3.4 g cm -3 (Quadrantids, δ -Aquarids, and α -Capricornids). The meteoroid bulk densities δ , which were determined according to the theory of quasi-continuous fragmentation of meteoroids in the Earth's atmosphere, vary from 0.4 g cm -3 (Leonids) to 2.9 g cm -3 (Geminids). Using the relation between bulk density and mineralogical density the porosity of meteoroids was estimated. The Geminid meteoroids are found to have the lowest porosity, while the Leonid and Draconid meteoroids have the most porous structure (83%). These results confirm the porous-structure nature of meteoroids' parent bodies i.e. comets and asteroids.
Internal waves of permanent form in fluids of great depth

This paper presents a general theoretical treatment of a new class of long stationary waves with finite amplitude. As the property in common amongst physical systems capable of manifesting these waves, the density of the (incompressible) fluid varies only within a layer whose thickness h is much smaller than the total depth, and it is h rather than the total depth that must be considered as the fundamental scale against which wave amplitude and length are to be measured. Internal-wave motions supported by the oceanic thermocline appear to be the most promising field of practical application for the theory, although applications to atmospheric studies are also a possibility. The waves in question differ in important respects from long waves of more familiar kinds, and in § 1 their character is discussed on the basis of a comparison with solitary-wave and cnoidal-wave theories on customary lines, such as apply to internal waves in fluids of limited depth. A summary of some simple experiments is included at the end of § 1. Then, in § 2, the comparatively easy example of two-fluid systems is examined, again to illustrate principles and to prepare the way for the main analysis in § 3. This proceeds to a second stage of approximation in powers of wave amplitude, and its leading result is an equation (3·51) determining, for arbitrary specifications of the density distribution, the form of the streamlines in the layer of heterogeneous fluid. Periodic solutions of this equation are obtained, and their properties are discussed with regard to the interpretation of internal bores and wave-resistance phenomena. Solutions representing solitary waves are then obtained in the form \[ f(x) = a\lambda^2/(x^2+\lambda^2), \] where xis the horizontal co-ordinate and where aΛ = O(h2). (The latter relation between wave amplitude and length scale contrasts with the customary one, aΛ2 = O(h3)). The main analysis is developed with particular reference to systems in which the heterogeneous layer lies on a rigid horizontal bottom below an infinite expanse of homogeneous fluid; but in § 4 ways are given to apply the results to various other systems, including ones in which the heterogeneous layer is uppermost and is bounded by a free surface. Finally, in §5, three specific examples are treated: the density variation with depth is taken, respectively, to have a discontinuous, an exponential and a ‘tanh’ profile.
Spectroscopic Observation of the Planetary Nebula IC 4846

A high‐dispersion optical (3700–10100 Å) spectrum was secured with the Hamilton echelle spectrograph at the coudé focus of the 120 inch (3 m) Shane telescope at Lick Observatory, with the goal of deriving chemical abundances for the compact planetary nebula IC 4846. We also remeasured the UV spectra from the IUE archive. Diagnostics indicate that the entire planetary nebula may be represented by an electron density Nϵ≃9000 cm−3 and electron temperature Tϵ≃10,500 K. However, diagnostics seem to imply that the [O ii] and [S ii] zone electron temperatures are higher than the [O iii] radiating strata. The electron density of the [O ii] and [S ii] zone might be higher as well (for which Nϵ≃20,000 cm−3). The photoionization model, which represents most of the observed line intensities, seems to confirm this physical condition, although the actual situation may be much more complicated. On the basis of the semiempirical ionization correction method and the photoionization model calculation, we derived the chemical abundances in this planetary nebula. Our optical data were compared with the image‐tube scanner data from Aller & Czyzak. Apparently, there is a long‐term spectral line variation in IC 4846. Chemical abundances derived in the present study agree, within 30%, with those previously estimated in Aller & Czyzak, except for carbon; the C, N, O, and Ne ratios are lower than both the average planetary nebula and the solar abundance. IC 4846 is a metal‐deficient planetary nebula that may have evolved from a Population II progenitor.
Simulation of the Saturnian magnetospheric interaction with Titan

Flowing plasma interactions with small bodies in the solar system are frequently complicated by the significant size of the ion gyroradii relative to the scale size of the body and the interaction region. This situation often applies to both the flowing ion populations and the atmospheric pickup ions added to the flow in the vicinity of the body. Titan represents an important example of this type of system and is scheduled to be probed in some detail during the Cassini mission tour of Saturn. Initial results from global hybrid (particle ions, fluid electrons) numerical simulations of Saturn's magnetospheric plasma encountering Titan's ionosphere reveal the complexity of the interaction introduced by the ion kinetics. The scale of the interaction region is dominated by the heavy ion gyroradii of the ambient and pickup ions rather than the size of Titan and is found to depend on the mass loading of the magnetospheric flow encountering Titan. Comparison with data from the Voyager 1 flyby suggests that ion kinetics as well as the relative orientations of external plasma ram and pickup ion production regions affect what was observed.
Can such Long Time Steps Really be used in Dissipative Particle Dynamics Simulations?

Commonly used time steps in dissipative particle dynamics (DPD) simulations are too large and lead to systematic errors in the computed properties. The main source of errors is the inaccurate integration of the conservative force. This error can be reduced to some extent by constructing a smoother force without any abrupt change at the cut-off distance, but the improvement is marginal. Alternatively, we tried smooth forces that also lead to the same conclusion. It is possible to find combinations of parameters for the random and dissipative forces that make errors cancel, but the combinations will depend on the system's thermodynamic state and on the particular force model. The only safe procedure is to use small time steps, i.e. comparable with those used in MD simulations. Alternatively, an improved integration algorithm should be used for the conservative force.
Visibility Graph-based Cache Management for DRAM Buffer Inside Solid-state Drives

Most solid-state drives (SSDs) adopt an on-board Dynamic Random Access Memory (DRAM) to buffer the write data, which can significantly reduce the amount of write operations committed to the flash array of SSD if data exhibits locality in write operations. This article focuses on efficiently managing the small amount of DRAM cache inside SSDs. The basic idea is to employ the visibility graph technique to unify both temporal and spatial locality of references of I/O accesses, for directing cache management in SSDs. Specifically, we propose to adaptively generate the visibility graph of cached data pages and then support batch adjustment of adjacent or nearby (hot) cached data pages by referring to the connection situations in the visibility graph. In addition, we propose to evict the buffered data pages in batches by also referring to the connection situations, to maximize the internal flushing parallelism of SSD devices without worsening I/O congestion. The trace-driven simulation experiments show that our proposal can yield improvements on cache hits by between 0.8% and 19.8%, and the overall I/O latency by 25.6% on average, compared to state-of-the-art cache management schemes inside SSDs.
Isomorphism conjectures in algebraic $K$-theory

duff In this paper we are concerned with the four functors Y. , Y3 if, *, and *, which map from the category of topological spaces X to the category diff of Q-spectra. The functor 3*( ) (or ? if ( )) maps the space X to the Qspectrum of stable topological (or smooth) pseudoisotopies of X. (The spaces diff dif 3i(X), id9 (X), i > 0, are Hatcher's deloopings of 970(X), % Yd(X) (cf. [29])). The functor J*( ) maps a path-connected space X to the algebraic Ktheoretic S2-spectrum for the integral group ring Z7r1X. (The spaces X(X), i > 0, are the Gersten-Wagoner deloopings of Z%O(X); cf. [27, 52]. ) 5*(X) is also defined on a nonpath-connected space X to be () (X1), where {Xi: i e I} are the path components of X and iI (Xi) indicates the direct limit of all finite products of the {I (Xi): i E I}. If X is path connected then the functor *-' ( ) maps X to the L -surgery classifying spaces for oriented surgery problems with fundamental group r I1X identified by their fourfold periodicity k 90(X) = k+4j (X) (cf. [35, 39, 44, 47]). In addition, if X is not path connected then we set Y77(X) = tiEI5*fJ'(Xi), where {Xi: i E i} are the path components of X. Results obtained by the authors over the past five years (cf. [15-25] and, in particular, [19; 16, A.1, A.18]), together with many earlier results and conjectures which are reviewed in 1.6. 1-1.6. 6, suggest that, for any connected CWcomplex X and for 5* () denoting any of the above functors, the Q-spectrum *(X) should be computable in a simple way from the values taken by 9'*() on covering spaces of X, which have very simple fundamental groups. In more detail, we let 9'(X) denote the collection of all subgroups H c ir IX, which are either finite or virtually infinite cyclic. A group H is virtually infinite cyclic if there is a short exact sequence of groups 1 -+ Z -+ H -+ F -+ 1 with F equal to a finite group and Z equal to the infinite cyclic group. For each such group we let XH -+ X denote the covering space projection corresponding to H. Then the Q-spectrum 5? (X) should be computable in a simple way from the Q-spectra {5 (XH): H E 9 (X)}. The purpose of this paper is to formulate precisely a conjecture along these lines and to verify the conjecture for any X
Directional dependence of ultrasonic propagation in textured polycrystals

The theory of ultrasonic wave propagation in textured polycrystals presented previously [S. Hirsekorn, J. Acoust. Soc. Am. 77, 832–843 (1985)] for propagation and polarization parallel to symmetry axes of texture is generalized to calculate the directional‐dependent scattering coefficients and phase and group velocities of plane waves with arbitrary propagation and polarization direction as a function of frequency. The analytical calculations are carried out for cubic polycrystals with orthorhombic texture symmetry. Numerical evaluation is done for an austenitic weld metal. The results are compared to those of the frequency‐independent description of ultrasonic propagation.
Simulation of Secondary and Separated Flow in Diffusing S Ducts

The focus of this paper is on the numerical simulation of compressible flow in diffusing S-ducts; this flow is characterized by secondary flow as well as regions of boundary-layer separation. The S-duct geometry produces streamline curvature and an adverse pressure gradient resulting in these flow characteristics. Two S-duct geometries are employed in this investigation: one was used in an experimental study conducted at NASA John H. Glenn Research Center at Lewis Field in the early 1990s, and the other is a benchmark configuration proposed by AIAA Propulsion Aerodynamics Workshop to assess the accuracy and best practices of computational fluid dynamics solvers. The computational fluid dynamics flow solver ANSYS-FLUENT is employed in the investigation of compressible turbulent flow through the S duct. A second-order accurate, steady, density-based solver is employed in a finite-volume framework. The three-dimensional Reynolds-averaged Navier–Stokes equations are solved on a structured mesh with a number o.
TAM Constructs Predicting the Use of Mainstream Social Networking Sites by College Students in Kuwait

This study applies the model of technology acceptance (TAM) to examine the factors that explain the adoption and intensity of use of Facebook, Twitter, Instagram and Snapchat among a sample of college students in Kuwait. The three constructs that represented the predictor variables are perceived ease of use (PEOU), perceived usefulness (PU) and social influence (SI). Structural equation modelling was applied to analyse the impact and covariance of TAM constructs. Gender was used as a control variable to explain the variance in using Snapchat and Instagram. An 18-item questionnaire was developed and administered to a sample of 919 students at Kuwait University. The results show that Facebook and Twitter were male-dominated, whereas Instagram and Snapchat were female-dominated in the sample. TAM constructs invariably affect the adoption and intensity of using social networking sites. The use of Facebook and Snapchat is significantly explained by PU and PEOU, while the use of Twitter and Instagram is predicted by PEOU. PEOU was the only construct that explained the variance in the use of Twitter. SI was strongly correlated with PEOU and PU.
Quantum entanglement in polarization and space

One of the most intriguing concepts of quantum mechanics is quantum entanglement. Two physical systems are said to be entangled with respect to a certain variable, if their individual outcomes of the variable are undetermined before measurement, but strictly correlated. Measurement of the variable for only one system immediately determines the outcome for the other system, irrespective of the distance between the two systems. It is this strong correlation that provides a basis for perspective, powerful applications like quantum cryptography and quantum computation. The most studied entangled systems, often called EPR systems (after the pioneers Einstein, Podolsky and Rosen), are pairs of light particles or photon pairs. These photon pairs, usually generated via the optical process of a spontaneous parametric down-conversion, are, in principal, simultaneously entangled in three variables, being polarization (polarization entanglement), energy or time (time entanglement), and momentum or transverse space (spatial entanglement). The contents of this thesis cover new insights in the polarization and spatial entanglement of photons. We have investigated both the entanglement quality and the yield of entangled photons for different experimental geometries that are associated with the production and detection of the photons.
Joint image compression–encryption using discrete fractional transforms

Abstract Exchange of data in the form of text and image on internet is in fast progression and it is spawning new compression and encryption algorithms for bandwidth and security respectively. We have proposed a new kind of joint algorithm using discrete fractional transforms for compression–encryption of image. In this algorithm, the discrete fractional Fourier transform which is discrete version of fractional Fourier transform, is used to compress the images with variation of its parameter ‘α’ (order of transform). The compressed image is encrypted using discrete fractional cosine transform to provide security. The advantage of this method is its feasible implementation in practice, superior, robustness, security and sensitivity of keys, which has a good prospect and practicability in information security field. Results of computer simulations are presented to verify the validity of the proposed method such as mean square error (MSE) and peak signal to noise ratio between the original image and decrypted image. Sensitivity for right decryption key is proved with respect to MSE.
Low autocorrelation binary sequences: exact enumeration and optimization by evolutionary strategies

We investigate skew-symmetric sequences with chain lengths up to N = 71, giving a complete table of all merit factors F≥7 and their associated configurations. We also calculate the exact thermodynami-cal properties of shorter chains (N≤55). We then introduce an evolutionary strategy, describing the properties of our search algorithm and comparing our results to those of other heuristic methods such as simulated annealing. We find the highest merit factors ever reached for chains of length 81≤N≤201.
New Universal Extensional Rheometer for Polymer Melts. Measurements on a Polystyrene Sample

A new universal extensional rheometer, which makes it possible to investigate the elongational properties of polymer melts, is described. Measurements under a wide variety of constant stretching rates and constant tensile stresses can be undertaken and recoil and relaxation experiments can be performed on a small amount of material. The operation modes of the apparatus are demonstrated on a polystyrene sample. For this polystyrene the viscosity and the recoverable strain in the steady state of elongation were measured over more than three decades of the tensile stress. At small stresses the recoverable strain is proportional to the stress, i.e., the compliance is constant and the viscosity gives a constant value which is three times the zero‐shear viscosity. At higher stresses the recoverable strain seems to level off and the viscosity runs through a maximum which lies 30% above the stress‐independent value.
Thermal expansion of trigonal elements at low temperatures: As, Sb and Bi

Linear coefficients of thermal expansion have been measured from 2 to 30 K, 55 to 90 K, and at 283 K for single crystals of As, Sb and Bi inclined at various orientations to the symmetry axis. The principal coefficients alpha /sub /// and alpha perpendicular to and volume coefficient beta are reported, together with the Gruneisen parameters gamma , gamma /sub /// and gamma perpendicular to . The anisotropy of expansion is most marked for As and least for Bi: alpha is negative for As below about 150 K, for Sb below 20 K, but always positive for Bi. beta and hence gamma is positive for each: the limiting value is gamma 0=4.4+or-0.3 for As, 1.00+or-0.03 (Sb) and 1.9+or-0.1 (Bi). gamma (T) has a minimum at 8 to 10 K, a broad maximum between 20 and 40 K, and at room temperature approaches 1.5 for As and 1.0 for Sb and Bi.
This paper is included in the Proceedings of the 21st USENIX Conference on File and Storage Technologies.

Cloud object storage vendors are always in pursuit of better cost efﬁciency. Emerging Shingled Magnetic Recording (SMR) drives are becoming economically favorable in archival storage systems due to signiﬁcantly improved areal density. However, for standard-class object storage, previous studies and our preliminary exploration revealed that the existing SMR drive solutions can experience severe throughput variations due to garbage collection (GC). In this paper, we introduce SMR STORE , an SMR-based storage engine for standard-class object storage without compromising performance or durability. The key features of SMR STORE include directly implementing chunk store interfaces over SMR drives, using a complete log-structured design, and applying guided data placement to reduce GC for consistent performance. The evaluation shows that SMR-STORE delivers comparable performance as Ext4 on the Conventional Magnetic Recording (CMR) drives, and can be up to 2.16x faster than F2FS on SMR drives. By switching to SMR drives, we have decreased the total cost by up to 15% and provided performance on par with the prior system for customers. Currently, we have deployed SMR STORE in standard-class Alibaba Cloud Object Storage Service (OSS) to store hundreds of PBs of data. We plan to use SMR drives for all classes of OSS in the near future.
Magnetic shielding of walls from the unmagnetized ion beam in a Hall thruster

We demonstrate by numerical simulations and experiments that the unmagnetized ion beam formed in a Hall thruster can be controlled by an applied magnetic field in a manner that reduces by 2–3 orders of magnitude deleterious ion bombardment of the containing walls. The suppression of wall erosion in Hall thrusters to such low levels has remained elusive for decades.
Using visual scores and categorical data for genomic prediction of complex traits in breeding programs

Most genomic prediction methods are based on assumptions of normality due to their simplicity, robustness, and ease of implementation. However, in plant and animal breeding, target traits are often collected as categorical data, thus violating the normality assumption, which could affect the prediction of breeding values and the estimation of crucial genetic parameters. In this study, we examined the main challenges of categorical phenotypes in genomic prediction and genetic parameter estimation using mixed models, Bayesian approaches, and machine learning techniques. We evaluated these approaches using simulated and real breeding data sets. Our contribution in this study is a five-fold demonstration: (i) collecting data using an intermediate number of categories (1 to 3 and 1 to 5 scores) is the best strategy, even considering errors and subjectivity associated with visual scores; (ii) in the context of genomic prediction, Linear Mixed Models and Bayesian Linear Regression Models are robust to the normality violation, but marginal gains can be achieved when using Bayesian Ordinal Regression Models (BORM) and Random Forest Classification technique; (iii) genetic parameters are better estimated using BORM; (iv) our conclusions using simulated data are also applicable to real data in autotetraploid blueberry, which can guide breeders’ decisions; and (v) a comparison of continuous and categorical phenotype testing for complex traits with low heritability, found that investing in the evaluation of 600-1000 categorical data points with low error, when it is not feasible to collect continuous phenotypes, is a strategy for improving predictive abilities. Our findings suggest the best approaches for effectively using categorical traits to explore genetic information in breeding programs, and highlight the importance of investing in the training of evaluator teams and in high-quality phenotyping. Key message An approach for handling categorical data with potential errors and subjectivity in scores was evaluated in simulated and blueberry recurrent selection breeding schemes to assist breeders in their decision-making.