bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigating Social Presence in Audio and Text Online Interaction for Language Learning
Authors: Wu Ligao 
Published: February 2021

Abstract
This study aimed at comparing the level of social presence generated in a voice-based chat room and a text-based forum when learners tried to build personal relationships and form an online community for learning on an online language course in China. A mixed-method approach was taken for the study, drawing on data from questionnaires to find out about student perception of social presence, and postings of text messages and audio messages in the communication of the student learning process to search for students’ projected social presence in terms of affective, interactive and cohesive features. Interviews were also conducted to supplement additional information with the hope of forming a complete picture of social presence in the reality of an online learning environment. The text-based forum and the voice-based chat room were found to have a different impact on student social presence. In terms of student perception, most of them were more likely to get to know peers in the text-based forum and thus developed a sense of community in their learning process of the online course. Yet they believed that the voice-based chat room had the advantage of helping them with course learning. In the actual interaction, the voice-based chat room was more interactive although the text-based forum was more affective and cohesive. But in terms of the affective category, the problem with the existing framework in literature was that there were no prosodic features included. Therefore, in future more research is needed to probe for the relationship between prosodic sound features and social presence, and the present theoretic framework must be extended. In interviews, students explained that in the voice-based chat room prosodic features led to higher peer awareness, which further reinforced this need.
A Study of Localization of Task-Based Language Teaching in China
Authors: Liu Chunyan , Guo Rui 
Published: February 2021

Abstract
In view of a series of challenges since Task-Based Language Teaching (TBLT) was introduced into China, we interviewed 14 front-line teachers in primary and secondary schools about their viewpoints and classroom strategies of TBLT. The results show teachers’ willingness to use TBLT. They adopt flexible teaching procedures, apply TBLT creatively, and explore task-based language assessment. The authors argue for inclusive non-doctrinaire approaches to TBLT, and propose to construct localized TBLT theory and practice with Chinese characteristics.
Universal central extensions of gauge algebras and groups
Authors: Janssens Bas , Wockel Christoph 
Published: February 2021

Abstract.

We show that the canonical central extension of the group of sections
of a Lie group bundle over a compact manifold, constructed by Neeb and Wockel (2009), is universal.
In doing so, we prove universality of the corresponding central
extension of Lie algebras in a slightly more general setting.
Descente galoisienne sur le groupe de Brauer
Authors: Colliot-Thélène Jean-Louis , Skorobogatov Alexei N. 
Published: February 2021

Abstract.

Soit X une variété projective et lisse sur un corps k de
caractéristique zéro.
Le groupe de Brauer de X s'envoie dans les invariants,
sous le groupe de Galois absolu de k, du groupe de Brauer de la même
variété considérée sur une clôture algébrique de k.
Nous montrons que le quotient est fini. Sous des hypothèses supplémentaires,
par exemple sur un corps de nombres, nous donnons des estimations sur
l'ordre de ce quotient. L'accouplement d'intersection entre les groupes de diviseurs et de 1-cycles modulo
équivalence numérique joue ici un rôle important.
For a smooth and projective variety X over a field k
of characteristic zero we prove the finiteness of the
cokernel of the natural map from the Brauer group of X to the
Galois-invariant subgroup of the Brauer group of the same
variety over an algebraic closure of k. Under further conditions,
e.g., over a number field, we give estimates for
the order of this cokernel. We
emphasise the rôle played by the exponent of the discriminant
groups of the intersection pairing between the groups of divisors
and curves modulo numerical equivalence.
Stokes factors and multilogarithms
Authors: Bridgeland Tom , Toledano Laredo Valerio 
Published: February 2021

Abstract.

Let G be a complex, affine algebraic group and
a meromorphic connection on the trivial G-bundle over
, with a pole of order 2 at zero and a pole of order
1 at infinity. We show that the map taking the residue
of at zero to the corresponding Stokes factors is
given by an explicit, universal Lie series whose coefficients
are multilogarithms. Using a non-commutative analogue
of the compositional inversion of formal power series, we
show that the same holds for the inverse of , and that
the corresponding Lie series coincides with the generating
function for counting invariants in abelian categories constructed
by D. Joyce.
The production of less harmful and less toxic sparklers in an experiment for school students
Authors: Scheid Michael , Rusan Magdalena , Klapötke Thomas M. , Schwarzer Stefan 
Published: February 2021

AbstractIn this article, a new and simple way of producing sparklers is presented as a school experiment. These sparklers are more environmentally friendly and less health threatening than sparklers produced with existing preparation methods. The problem of conventional sparklers is the toxicity of barium nitrate, which is used as the oxidizer. The substitution of this oxidizer with strontium nitrate and also the reduction of the weight proportion makes the new mixture less dangerous and less toxic. Various tests for the categorization of high-energetic materials show that the newly developed sparklers are not classified as explosives. Furthermore, the tests demonstrate that the newly developed sparklers are not as dangerous as commercial sparklers. Due to their lower health risk, these new sparklers are well suited for use in school education. In addition, expenditure for this experiment is low and integrating it into the upper secondary level curriculum is easy. Sparklers are an impressive example of redox reactions from everyday life. The experiment is a best-practice application for chemistry education, incorporating current results of chemistry research.
Optimization of a Piezoelectric Bending Actuator for a Tactile Virtual Reality Display
Authors: Hofmann Viktor , Twiefel Jens 
Published: February 2021

Abstract
The excitation of mechanoreceptors in the finger with different frequencies and intensities generates a tactile impression. For the experience of a complete surface many distributed sources are needed in the tactile display. For these local stimulations of the finger several piezoelectric bending actuators will be arranged in an array perpendicular to the skin. The challenge in the system design is to transfer high dynamic shear forces to the skin at required frequencies together with a compact display design. In order to estimate the dynamic behavior of the bending actuators a transfer matrix method model based on the Timoshenko beam theory is derived. Beside the outer geometric values, the layered structure of the actuator is included in the model. In addition the influence of the load on the actuator’s tip in lateral and in normal direction as well as on the rotational degree of freedom is taken into account. Using the analytical approach, a parametric study is carried out to find an optimized actuator design for the display. For the validation, the modeled beam is compared with experimental data.
Pcf and abelian groups
Authors: Shelah Saharon 
Published: February 2021

Abstract.
We deal with some pcf (possible cofinality theory) investigations
mostly motivated by questions in abelian group theory. We concentrate
on applications to test problems but we expect the combinatorics will
have reasonably wide applications. The main test problem is the
“trivial dual conjecture” which says that there is a quite free abelian
group with trivial dual. The “quite free” stands
for “-free” for a suitable cardinal , the first open case is
. We almost always answer it positively, that is, prove
the existence of -free abelian groups
with trivial dual, i.e., with no non-trivial homomorphisms to the integers. Combinatorially, we prove that “almost
always” there are which are
quite free and have a relevant black box. The qualification “almost always”
means except when we have strong restrictions on cardinal
arithmetic, in fact restrictions which hold “everywhere”. The nicest combinatorial result is probably the so-called
“Black Box Trichotomy Theorem” proved in ZFC. Also we may replace abelian groups by R-modules. Part of our
motivation (in dealing with modules) is that in some sense the improvement
over earlier results becomes clearer in this context.
On the Durrmeyer-Type Modification of Some Discrete Approximation Operators
Authors: Pych-Taberska Paulina 
Published: February 2021

Abstract
In [Kratz and Stadtmüller, J. Approximation Theory 54: 326-337, 1988], for continuous functions f from the domain of certain discrete operators Ln
the inequalities are proved concerning the modulus of continuity of Lnf. Here we present analogues of the results obtained for the Durrmeyer-type modification of Ln
. Moreover, we give the estimates of the rate of convergence of in Hölder-type norms
Fractional Type Operators in Weighted Generalized Hölder Spaces
Authors: Samko S. G. , Mussalaeva Z. U. 
Published: February 2021

Abstract
Weighted Zygmund type estimates are obtained for the continuity modulus of some convolution type integrals. In the case of fractional integrals this is strengthened to a result on isomorphism between certain weighted generalized Hölder type spaces.
Sequential Convergence in Topological Vector Spaces
Authors: Katsaras A. K. , Benekas V. 
Published: February 2021

Abstract
For a given linear topology τ, on a vector space E, the finest linear topology having the same τ convergent sequences, and the finest linear topology on E having the same τ precompact sets, are investigated. Also, the sequentially bornological spaces and the sequentially barreled spaces are introduced and some of their properties are studied.
On the Convergence and Summability of Series with Respect to Block-Orthonormal Systems
Authors: Nadibaidze G. 
Published: February 2021

Abstract
Statements connected with the so-called block-orthonormalized systems are given. The convergence and summability almost everywhere by the (c, 1) method with respect to such systems are considered. In particular, the well-known theorems of Menshov-Rademacher and Kacmarz on the convergence and (c,1)-summability almost everywhere of orthogonal series are generalized.
Test for Disconjugacy of a Differential Inclusion of Neutral Type
Authors: Haščák A. 
Published: February 2021

Abstract
Generalizations of the disconjugacy for a differential inclusion of neutral type are given. The relation between these generalizations and the existence of solutions of multipoint boundary value problems is discussed and the tests for disconjugacy are established. These tests are applicable to the linear differential equations of neutral type, too.
Obstructions to the Section Problem in a Fibration with a Weak Formal Base
Authors: Saneblidze S. 
Published: February 2021

Abstract
For a class of Serre fibrations with a weak formal base X (or with a degenerated A
∞-algebra structure on the integral cohomology H*(X)), obstructions are defined by means of spherical twisting cochains of ξ. In particular, for a given section sn
: Xn
→ E on n-skeleton of X, the problem of avoiding the (n+1)th obstruction o(sn
) ∈ H

n+1(X; π
n
(F)) to the existence of a section on X

n+1 reduces to solving a system of linear equations with respect to cohomology elements of the groups Hi
(X; π
i
(F)), i < n. Homotopy classification theorems for sections as well as for weak formal maps are given, too.
Non-Abelian Cohomology with Coefficients in Crossed Bimodules
Authors: Inassaridze H. 
Published: February 2021

Abstract
When the coefficients are crossed bimodules, Guin's non-abelian cohomology [Guin, C. R. Acad. Sci. Paris 301: 337–340, 1985], [Guin, J. Pure Appl. Algebra 50: 109–137, 1988] is extended in dimensions 1 and 2, and a nine-term exact cohomology sequence is obtained.
On a Singular Two-Point Boundary Value Problem for the Nonlinear mth-Order Differential Equation with Deviating Arguments
Authors: Půža B. 
Published: February 2021

Abstract
Sufficient conditions of solvability and unique solvability of the boundary value problem

u
(m)(t) = f(t, u(τ
11(t)), . . . , u(τ
1k
(t)), . . . , u
(m–1)(τ

m1(t)), . . .
. . . , u
(m–1)(τ

mk
(t))), u(t) = 0, for t ∉ [a, b],

u
(i–1)(a) = 0 (i = 1, . . . , m – 1), u
(m–1)(b) = 0,
are established, where τ

ij
: [a, b] → R (i = 1, . . . , m; j = 1, . . . , k) are measurable functions and the vector function f : ]a, b[×Rkmn
→ Rn
is measurable in the first and continuous in the last kmn arguments; moreover, this function may have nonintegrable singularities with respect to the first argument.
On Some Multidimensional Versions of A Characteristic Problem for Second-Order Degenerating Hyperbolic Equations
Authors: Kharibegashvili S. 
Published: February 2021

Abstract
Some multidimensional versions of a characteristic problem for second-order degenerating hyperbolic equations are considered. Using the technique of functional spaces with a negative norm, the correctness of these problems in the Sobolev weighted spaces are proved.
The Contact Problem for an Elastic Orthotropic Plate Supported by Periodically Located Bars of Equal Resistance
Authors: Gogolauri L. 
Published: February 2021

Abstract
The contact problem of the plane theory of elasticity is studied for an elastic orthotropic half-plane supported by periodically located (infinitely many) stringers of equal resistance. Using the methods of the theory of a complex variable, the problem is reduced to the Keldysh–Sedov type problem for a circle. The solution of the problem is constructed.
On Three-Dimensional Dynamic Problems of Generalized Thermoelasticity
Authors: Burchuladze T. , Burchuladze D. 
Published: February 2021

Abstract
Lord–Shulman's system of partial differential equations of generalized thermoelasticity [Green and Lindsay, J. Elasticity 2: 1–7, 1972] is considered, in which the finite velocity of heat propagation is taken into account by introducing a relaxation time constant. General aspects of the theory of boundary value and initial-boundary value problems and representation of solutions by series and quadratures are considered using the method of a potential.
The Tensor Category of Linear Maps and Leibniz Algebras
Authors: Loday J. L. , Pirashvili T. 
Published: February 2021

Abstract
We equip the category of linear maps of vector spaces with a tensor product which makes it suitable for various constructions related to Leibniz algebras. In particular, a Leibniz algebra becomes a Lie object in and the universal enveloping algebra functor UL from Leibniz algebras to associative algebras factors through the category of cocommutative Hopf algebras in . This enables us to prove a Milnor–Moore type theorem for Leibniz algebras.
The Dependence of Solution Uniqueness Classes of Boundary Value Problems for General Parabolic Systems on the Geometry of an Unbounded Domain
Authors: Gagnidze A. 
Published: February 2021

Abstract
General boundary value problems are considered for general parabolic (in the Douglas–Nirenberg–Solonnikov sense) systems. The dependence of solution uniqueness classes of these problems on the geometry of a nonbounded domain is established.
On Convergence of Series of Random Elements via Maximal Moment Relations with Applications to Martingale Convergence and to Convergence of Series with p-Orthogonal Summands
Authors: Rosalsky Andrew , Volodin Andrei I. 
Published: February 2021

Abstract
The rate of convergence for an almost surely convergent series of Banach space valued random elements is studied in this paper. As special cases of the main result, known results are obtained for a sequence of independent random elements in a Rademacher type p Banach space, and new results are obtained for a martingale difference sequence of random elements in a martingale type p Banach space and for a p-orthogonal sequence of random elements in a Rademacher type p Banach space. The current work generalizes, simplifies, and unifies some of the recent results of Nam and Rosalsky [Teor. Īmovīr. ta Mat. Statist. 52: 120–131, 1995] and Rosalsky and Rosenblatt [Bull. Inst. Math. Acad. Sinica 11: 185–208, 1983, Nonlinear Anal. 30: 4237–4248, 1997].
Suspension and Loop Objects and Representability of Tracks
Authors: Baues H.-J. , Jibladze M. 
Published: February 2021

Abstract
In the general setting of groupoid enriched categories, notions of suspender and looper of a map are introduced, formalizing a generalization of the classical homotopy-theoretic notions of suspension and loop space. The formalism enables subtle analysis of these constructs. In particular, it is shown that the suspender of a principal coaction splits as a coproduct. This result leads to the notion of theories with suspension and to the cohomological classification of certain groupoid enriched categories.
Geometry of Modulus Spaces
Authors: Khalil R. , Hussein D. , Amin W. 
Published: February 2021

Abstract
Let ϕ be a modulus function, i.e., continuous strictly increasing function on [0, ∞), such that ϕ(0) = 0, ϕ(1) = 1, and ϕ(𝑥+𝑦) ≤ ϕ(𝑥)+ϕ(𝑦) for all 𝑥, 𝑦 in [0, ∞). It is the object of this paper to characterize, for any Banach space 𝑋, extreme points, exposed points, and smooth points of the unit ball of the metric linear space ℓ
ϕ
(𝑋), the space of all sequences (𝑥𝑛), 𝑥𝑛 ∈ 𝑋, 𝑛 = 1, 2, . . . , for which ∑ϕ(‖𝑥𝑛‖) < ∞. Further, extreme, exposed, and smooth points of the unit ball of the space of bounded linear operators on ℓ𝑝, 0 < 𝑝 < 1, are characterized.
Periodic Points and Chaotic-Like Dynamics of Planar Maps Associated to Nonlinear Hill's Equations with Indefinite Weight
Authors: Papini Duccio , Zanolin Fabio 
Published: February 2021

Abstract
We prove some results about the existence of fixed points, periodic points and chaotic-like dynamics for a class of planar maps which satisfy a suitable property of “arc expansion” type. We also outline some applications to the nonlinear Hill's equations with indefinite weight.
Mackey Continuity of Characteristic Functionals
Authors: Kwapień S. , Tarieladze V. 
Published: February 2021

Abstract
Problems of the Mackey-continuity of characteristic functionals and the localization of linear kernels of Radon probability measures in locally convex spaces are investigated. First the class of spaces is described, for which the continuity takes place. Then it is shown that in a non-complete sigmacompact inner product space, as well as in a non-complete sigma-compact metizable nuclear space, there may exist a Radon probability measure having a non-continuous characteristic functional in the Mackey topology and a linear kernel not contained in the initial space. Similar problems for moment forms and higher order kernels are also touched upon. Finally, a new proof of the result due to Chr. Borell is given, which asserts that any Gaussian Radon measure on an arbitrary Hausdorff locally convex space has the Mackey-continuous characteristic functional.
Relative Inversion and Embeddings
Authors: Dupré Maurice J. , Glazebrook James F. 
Published: February 2021

Abstract
Commencing from a monoidal semigroup 𝐴, we consider the geometry of the space 𝑊(𝐴) of pseudoregular elements. When 𝐴 is a Banachable algebra we show that there exist certain subspaces of 𝑊(𝐴) that can be realized as submanifolds of 𝐴. The space 𝑊(𝐴) contains certain subspaces constituting the Stiefel manifolds of framings for 𝐴. We establish several embedding results for such subspaces, where the relevant maps induce embeddings of associated Grassmann manifolds.
Explicit Solutions of the Basic Boundary Value Problems of Statics of the Elastic Mixture Theory for an Annulus
Authors: Basheleishvili M. 
Published: February 2021

Abstract
Using the complex representation formulae of regular solutions of equations of statics of the theory of elastic mixtures, we construct the explicit solutions of the Dirichlet and Neumann type boundary value problems for an annulus in the form of absolutely and uniformly convergent series.
On the Existence and Uniqueness of a Solution to a Stochastic Differential Equation in a Banach Space
Authors: Mamporia B. 
Published: February 2021

Abstarct
A sufficient condition is given for the existence of a solution to a stochastic differential equation in an arbitrary Banach space. The method is based on the concept of covariance operator and a special construction of the Itô stochastic integral in an arbitrary Banach space.
General Existence Principle for Singular BVPs and Its Application
Authors: Rachůnková Irena , Staněk Svatoslav 
Published: February 2021

Abstract
We present a general existence principle which can be used for a large class of singular boundary value problems of the form

where 𝑓 satisfies the local Carathéodory conditions on [0, 𝑇] × 𝐷, a set 𝐷 ⊂ is not closed, 𝑓 has singularities in its phase variables on the boundary ∂𝐷 of 𝐷, and 𝑆 is a closed subset in 𝐶𝑛–1([0, 𝑇]). The proof is based on the regularization and sequential techniques. An application of the general existence principle to singular conjugate (𝑝, 𝑛–𝑝) BVPs is also given.
Investigation of the First and the Second Exterior Plane Boundary Value Problems of Steady State Oscillations in the Linear Theory of Elastic Mixtures
Authors: Svanadze K. 
Published: February 2021

Abstract
Displacement vectors are represented by combinations of special potentials; singular integral equations of the normal type with zero index are obtained for the first and the second boundary value problem of steady oscillations in the theory of elastic mixtures. It is proved that in the case of positive frequencies the corresponding homogeneous singular integral equations have only a trivial solution.
Connectedness of a Fine Topology and Localization in Bitopological Spaces
Authors: Dvalishvili B. 
Published: February 2021

Abstract
The paper, consisting of four sections, of which Section 0 is auxiliary, is devoted to some principal questions of the theory of bitoplogical spaces. In Section 1, the 𝑝 -extremally disconnected, (𝑖, 𝑗)-strongly extremally disconnected and (𝑖, 𝑗)-nodec spaces are studied by means of the localization at a point. In Section 2, the (𝑖, 𝑗)-pseudoscattered, (𝑖, 𝑗)-ndscattered, 𝑝 -ultradisconnected and (𝑖, 𝑗)-Moscow spaces are introduced, their interrelations and their relations with the 𝑝 -extremally disconnected spaces are investigated, in particular, when one of the topologies is finer than the other. Section 3 is concerned with the problem of existence of a finer connected topology on a connected topological space and so, it is related to the concept of a maximal connected space.
More on Descent Theory for Schemes
Authors: Mesablishvili B. 
Published: February 2021

Abstract
In this paper we continue the investigation of some aspects of descent theory for schemes that was begun in [Mesablishvili, Appl. Categ. Structures]. Let 𝐒𝐂𝐇 be a category of schemes. We show that quasi-compact pure morphisms of schemes are effective descent morphisms with respect to 𝐒𝐂𝐇-indexed categories given by (i) quasi-coherent modules of finite type, (ii) flat quasi-coherent modules, (iii) flat quasi-coherent modules of finite type, (iv) locally projective quasicoherent modules of finite type. Moreover, we prove that a quasi-compact morphism of schemes is pure precisely when it is a stable regular epimorphism in 𝐒𝐂𝐇. Finally, we present an alternative characterization of pure morphisms of schemes.