bluuebunny/crossref_metadata_2025 huggingface dataset:
High strength steel cold-formed hollow sections: implication of cross-section aspect ratio and slenderness characteristics on flexural behavior
Authors: Adib Shady , Misiunaite Ieva
Published: December 2019

Cold-formed tubular sections are widely applicated for a variety of structural solutions, primarily due to their
advantageous structural properties, inherent aesthetic characteristics and ease of prefabrication and mass production.
High strength steels (HSS) are attaining growing attention from structural engineers and researchers due to their potential
on the design of lightweight and more economic structures. In combination with cold-formed tubular sections HSS
might serve as improvement on structural efficiency as well as solution for structural problems when usage of normal
steel is limited due to insufficient strength. However, innovative structural solutions are often faced problems related
with absence of appropriate design procedures. In most of the design codes cross-section design is performed following
the traditional classification procedure based on the slenderness of the individual constituents without respect to their
interaction. Moreover, tubular sections are generally treated in the same manner without respect to their formation route,
embedding an elastic-perfectly plastic material model, without reference to the cold-formed sections increased strength
and reduced ductility over the flat material. This paper reports on the numerical study of cold-formed HSS tubular beams
deformation response, with a focus on the effect of cross-section constituent’s interaction and strength enhancement
influence on the cross-section slenderness. Finite element (FE) models were first developed and validated against existing test results. Upon validation against the experimental results, parametric studies were carried out to expand the
available flexural response data over a range of cross-section aspect ratio, cross-section slenderness and steel grades.
The obtained numerical results were used to assess the suitability of the current design codes cross-sections classification
for cold-formed HSS tubular beams.
Selection of structural system for wooden public building: Multiple criteria approach
Authors: Tupenaite Laura , Gecys Tomas , Kanapeckiene Loreta , Sajjadian Seyed Masoud , Naimaviciene Jurga
Published: December 2019

There has been a growing interest in the construction industry for using materials with lower environmental
impacts, in this context, stakeholders increasingly seeing wood as the natural and sustainable option for public buildings. Studies worldwide have already investigated modern structural systems for wooden construction. However, the
selection of alternative structural systems is rarely discussed, alternatives are seldom compared. To close a gap this
paper proposes a framework for selection of the structural system for a wooden public building based on a Simple
Additive Weighting (SAW) multiple criteria assessment method. The proposed methodology is applied for the case of
a public wooden building – shopping centre in Lithuania. Three structural systems (1) double tapered glued laminated
beams and columns, (2) laminated veneer lumber (LVL) trusses and columns and (3) single tapered glued laminated
beam and I type steel column are compared. The research allowed distinguishing the most efficient structural system
according to eight conflicting quantitative and qualitative criteria, which, in this case, contains double tapered glued
laminated beams and columns. Proposed assessment framework is relatively simple to apply, therefore can be successfully used in practice.
Stochastic modelling of fatigue crack growth
Authors: Omishore Abayomi
Published: December 2019

The article deals with the influence of the skewness of quasi-constant stress range on the fatigue resistance of
a steel bridge member subjected to multiple repeated loading. It is shown that it is necessary to know the statistical characteristics
and type of probability density function relatively accurately in the case of quasi-constant stress range, otherwise the estimation
of the fatigue resistance may be inaccurate. The fatigue resistance is studied using linear fracture mechanics. The random
characteristics of the steel member are simulated using the Latin Hypercube Sampling method. The results of experimental research
on calibration functions used in linear fracture mechanics are applied in this study. The calibration function for pure bending,
which is presented on an extended domain of relative crack length, is applied. Non-parametric rank-order correlation identifies
a strong influence of the quasi-constant stress range on the fatigue resistance. A detailed comparison of three variants of fatigue
resistance as output random variables is performed. The results show that the probabilistic assessment of reliability may be burdened
with greater or lesser epistemic uncertainty, which can distort the estimates of the remaining service life of the load bearing bridge member.
Spatial thin-walled reinforced concrete structures taking into account physical nonlinearity in SCAD software. Rod finite element
Authors: Fialko Sergiy , Karpilowskyi Viktor
Published: December 2019

This paper considers a spatial frame bar finite element for modeling reinforced concrete beams and
columns. Both concrete and reinforcement are described by the equations of the deformation theory of plasticity and
the theory of plastic flow. Degradation of concrete during cracking is modeled by the descending branch of the σ – ε
diagram (the deformation theory of plasticity), as well as the compression of the yield surface and its displacement in
the space of principal stresses (the plastic flow theory). The longitudinal reinforcement is considered discretely. It is
assumed that there is no reinforcement slipping in concrete. The paper provides the results of the studies that reveal
the causes of computational instability related to the presence of a descending branch of the σ – ε diagram for
concrete, and proposes ways to overcome it. The reliability of the obtained results is confirmed by comparing them
with the results of experimental studies performed by other researchers, as well as with the results of numerical
solutions obtained by the particle method. This paper also provides an example of the nonlinear analysis of the
fragment of a multi-storey building from the SCAD Soft collection of problems (www.scadsoft.com).
Shear resistance of clamped deck slabs assessed using design equations and FEM analysis
Authors: Vidaković Aleksandar , Halvonik Jaroslav
Published: December 2019

Reinforced concrete (RC) slabs without shear reinforcement are commonly used in the existing bridge
structures. An ability of RC slabs to distribute the concentrated loads due to the wheel pressure in transverse direction
is an important property for their verification. The aim of this paper is to investigate the effect of redistribution of
shear forces and bending moments on the load carrying capacity of RC slabs subjected to concentrated loads. Two
methods of the assessment are used: simplified analytical formulations and linear finite element analysis (LFEA). The
obtained results are consequently compared with the test results taken from three experimental campaigns. The analyses show big differences among the results obtained from the simplified analytical methods that are based on the design equations introduced in the relevant standards. Improved methods, such as LFEA combined with analytical
post-processing method, reflect the structural behaviour in a better way and provide more accurate load-bearing capacity prediction of the bridge deck slabs.
Initial investigation of the intrinsic geomechanical properties of soils in area of landslide Černá Pole
Authors: Faktorová Karolína , Chalmovský Juraj , Koudela Pavel , Míča Lumír
Published: December 2019

One of the most important type of Brno’s subsoil is Miocene’s clay. Mechanical properties of these clays
were already studied by various methods, authors, in several locations. These parameters, however, varies across the
locations and therefore new data are needed to further refineme them. The objective of the laboratory tests presented in
this paper was to determine shear strength and compressibility parameters on reconstituted samples, locality Černá Pole.
Stiffness parameters for primary loading and unloading – reloading were obtained from series of oedometer tests. Consolidated undrained triaxial tests were performed for evaluation of soil critical shear strength. Obtained results were
compared with another available data.
The influence of a column shape cross-section on the punching capacity
Authors: Sarvaicova Simona , Borzovic Viktor , Augustin Tomas
Published: December 2019

The article deals with non-linear modeling of slab-column connection which represents a fragment of flat
slab supported by a column and loaded up to the punching shear failure. The aim of this parametrical study is the analysis
of the length of reduced control perimeters in the case of columns with significantly elongated rectangular cross-section.
The non-linear analysis was performed in program Atena and calibrated by test results obtained from the laboratory
experiments carried out at Slovak University of Technology in Bratislava. The results of non-linear analysis are compared with the values of shear resistance calculated according to the current Eurocode 2 model; fib Model Code 2010
and model proposed for the second generation of Eurocode 2 based on the Critical shear crack theory. The reliability of
the models is evaluated by comparison of the results of numerical analyses and previously mentioned design models.
Numerical analysis of vertical stress distribution in the direct shear box devices
Authors: Medzvieckas Jurgis , Skuodis Šarūnas , Sližytė Danutė
Published: December 2019

When determining the soil strength parameters with direct shear box devices, the values of the parameters are
influenced by devices construction. In assessing this effect, it is necessary to know the magnitude of the vertical stresses
and the nature of the distribution in the shear plane. The soil shear resistance depends on the size of the vertical stresses
and the nature of the distribution in the shear plane. These factors depend on the interaction of the soil with the vertical
walls of the device, i.s. friction between the soil and the walls. At the beginning of the test, the vertical stresses on the
shear plane will be lower than the added pressure at the top of the sample, however the stresses increases due to dilation
during the test. Before the test ends, the stresses in the shear plane will be higher than at the top of the sample. The
article has presented the nature of the vertical stresses distribution on a horizontal plane when using direct shear box
device. The analysis was performed using the PLAXIS 3D software.
Multi-criteria assessment of pitched roof reconstruction technologies
Authors: Kuznecov Roman , Šaparauskas Jonas
Published: December 2019

The paper examines the technologies of reconstruction of sloping-pitched roofs, their application and eficiency. The analysis consist of the main characteristics of pitched roofs types, causes of their damages. The work also
analyzes roof defects, the main causes of these defects. There are described ways how to improve performance of roofs.
Three different reconstruction technologies are distinguished, which are compared between each other using multicriteria evaluation methods ARAS (additive ratio assessment) and COPRAS (Complex Proportional Assessment). After
performing a multi-criteria assessment, we found that the use of polyurethane foam is the best choice for roof reconstruction work.
Analysis of second-order effects of constructions behaviour
Authors: Venslavavičiūtė Raminta , Urbonas Kęstutis
Published: December 2019

This paper presents the importance of the second-order effects in behaviour of steel frame structures. EN
1993-1-1 were distinguished three main methods: taking / without taking into account second order effects depending
on the sensitivity of horizontal design effects and tolerance. Using these methods, the susceptibility of steel frame structures to second-order impacts is considered in accordance with EN 1993-1-1. The study was performed taking into
account also the rotational stiffness of the joints of the frame structure. In this way, trying to determine the effect of the
joint on the rotational rigidity makes the frame structure more sensitive to second order impacts. It is also considered a
semi-rigid joints effects the general frame-tailed P-Δ and the second row stress. This establishes the link between the
effects of the second-order and the semi-rigid joints in the overall (general) analysis. Frame-building sensitivity makes
it possible to compare and measure the importance of such dependencies.
The influence of the fireclay waste on the microstructure and the physico-mechanical properties of autoclaved aerated concrete
Authors: Šebestová Pavlína , Černý Vít , Drochytka Rostislav
Published: December 2019

Autoclaved aerated concrete is a building material with good thermal insulation properties, which it receives
through the pore structure. The production of autoclaved aerated concrete consists of two phases. In the first stage, a
porous structure is formed by the reaction of calcium hydroxide and aluminum powder to form hydrogen. In the second
stage, the lime and siliceous components react under hydrothermal conditions to form crystalline calcium hydrosilicates
which form a binder component in the material. In this paper, the degree of crystallization of calcium hydrosilicates is
studied depending on the quantity and fineness of the admixture of the fireclay waste. The effect of three different sizes
of the specific surface of the fireclay waste on the microstructure and physico-mechanical properties of the autoclaved
aerated concrete was monitored. At the same time, the influence of sand substitute for waste was monitored. The amount
of the substitute was 10%, 30% and 50%. Finally, the influence of the fireclay waste admixture on the autoclaved aerated
concrete porous structure was assessed. The microstructure was analyzed by X-ray diffraction. Based on the achieved
values, it can be said that the admixutre of fireclay waste has a positive effect on the crystallisation of calcium hydosilicate phases. Fireclay waste substitution is possible up to 50%. With a higher amount of substitution, the increasing
pressure of autoclaved aerated concrete compression is monitored.
Mechanical performance of biodegradable hemp shivs and corn starch-based biocomposite boards
Authors: Kremensas Arūnas , Kairytė Agnė Kairytė , Vaitkus Saulius , Vėjelis Sigitas , Balčiūnas Giedrius , Strąkowska Anna , Członka Sylwia
Published: December 2019

For the production of traditional building materials, excavated natural resources are used. The production
process of such materials requires high-energy demands, wherefore, high amounts of CO2 gases, which have a great
impact on climate change, are emitted. Only a small part of such materials is effectively recycled and reused. Generally,
they are transported to landfills, which rapidly expand and may pollute the soil, groundwater and air. Currently, a great
attention is paid to the production of novel building materials. The aim is to use as less excavated materials as possible
and replace them by natural renewable resources. Therefore, the recycling and utilisation at the end of life cycle of such
materials would be easier and generation of waste would reduce. This way, the efforts of switching to circular economy
are being put. One of the approaches – wider application of vegetable-based raw materials (cultivated and uncultivated
agricultural plants). The usage of fibre hemp shives (HS) as an aggregate and corn stach (CS) as a binding material
allows development of biocomposite boards (WPCs) which could contribute to the solution of the before mentioned
problems.
Bio-sourced materials combined with a polymer matrix offer an interesting alternative to traditional building materials.
To contribute to their wider acceptance and application, an investigation into the use of wood-polymer composite boards
is presented. In this study, biocomposite boards for the building industry are reported. WPCa are fabricated using a dry
incorporation method of corn starch and HS treatment with water at 100 °C. The amount of CS and the size of the HS
fraction are evaluated by means of compressive, bending and tensile strength, as well as microstructure. The results
show that the rational amount of CS, independently on HS fraction, is 10 wt.%. The obtained WPCs have compressive
stress at 10% of deformation in the range of (2.4–3.0) MPa, bending of (4.4–6.3) MPa and tensile strength of (0.23–
0.45) MPa. Additionally, the microstructural analysis shows that 10 wt.% of CS forms a sufficient amount of contact
zones that strengthen the final product. The obtained average density (~319–408 kg/m3) indicate that, according to European normative document EN 316, WPCs can be classified as softboards and used as self-bearing structural material
for building industry. Based on the requirements, WPCs can be applied in dry and humid conditions for the internal and
external uses without loading (EN 622-4, section 4.2) or as load-bearing boards in dry and humid conditions for instantaneous or short-term load duration (EN 622-4, section 4.3).
The global analysis of a structure on the basis of precast building
Authors: Grabiec-Mizera Teresa , Kaczmarczyk Michał , Kuczma Mieczysław
Published: December 2019

The aim of the paper is to present a global analysis of a precast, reinforced building structure. At the design
stage, information about structural behaviour of particular elements and the whole structure as well as its response to
applied loads are obtained. While solving the problem, the load-bearing elements and the type and deformability of
connections have to be defined. The latter is especially significant in the case of precast structure models. Calculations
according to the analytical method are going to be verified by the finite element method.
Bearing capacity and stiffness of pile group foundation
Authors: Norkus Arnoldas , Martinkus Vaidas
Published: December 2019

Pile group foundations are widely employed in geotechnical design. Bearing capacity increment/reduction of
pile group (PG) foundation in design practice often described via empirical efficiency factor (EF), a multiplier to sum
of single piles (SP) resistances, when they act isolated. The magnitude of EF depends on spacing of SP in PG, soil
parameters, configuration of piles, friction of soil-pile, etc. Proposed predictions for choosing the EF magnitude are
contradictory. The tests of displacement SP and PG tests conducted in laboratory conditions for 2 spacing cases, ground
stress-strain evolution of PG analyzed. The EF magnitude reproduced from tests results compared with proposed by
different authors predictions. The pronounced effect of installation sequence to displacement SP response measures,
when acting in PG estimated during the tests. From practical point, this phenomenon if ignored for certain connection
case of superstructure with PG cap and that of SP with PG cap may cause unexpected PG foundation movements,
subsequently resulting the additional stressing of superstructure and foundation. SP installation effect for displacement
PG foundation measures of ground response should be properly evaluated in design of constructional elements of superstructure and foundation.
The effect of glass powder on physical and mechanical properties of hardened cement paste
Authors: Barkauskas Kęstutis , Nagrockienė Džigita , Girnienė Ingrida
Published: December 2019

The article analyses the effect of finely crushed glass on the properties of hardened cement paste. Materials
used for the test: Portland cement CEM I 42.5 R, finely crushed glass (particle size ≤75 µm), and water. Seven
compositions of cement paste mixes with different amounts of crushed glass (0%, 5%, 10%, 15%, 20%, 25%, 30%)
added by weight of cement were designed. Compressive strength, density and ultrasonic pulse velocity of modified
hardened cement paste with different content of crushed glass were measured in the tests. The test results revealed the
increase of density, ultrasonic pulse velocity and compressive strength in specimens of hardened cement paste
containing 5% and higher percentage of crushed glass after 7, 28 and 56 days of hardening. Microstructure tests revealed
that crushed glass had an effect on the microstructure of hardened cement paste after 7 days of curing. X-ray analysis
revealed the effect of crushed glass on the physical composition of hardened cement paste hydration products. Hardened
cement paste containing 5% of crushed glass by weight of cement was found to have higher strength and density
compared to unmodified cement paste.
Development of an anchorage prototype for CFRP stress-ribbon systems using 3D printing technique
Authors: Gribniak Viktor , Arnautov Aleksandr K. , Rimkus Arvydas
Published: December 2019

Compared with other structure types, stress-ribbon systems are extremely simple though requiring massive
anchorage blocks because of very large tensile stresses induced in the ribbons. Such structural systems are efficient in
pedestrian bridges. A major drawback of these systems is related to corrosion of the steel ribbons. Unidirectional carbon
fibre reinforced polymer (CFRP) has a high potential for replacing steel in the ribbons because of lightweight, high
strength, and excellent resistance to corrosion and fatigue. Application of CFRP materials, however, faced serious problems due to construction of the anchorage joints. Thus, the anchorage system is the object of this research.
Adhesive bonding is a simplest technology for joining structural components made of CFRP composites with polymer
matrix. In the adhesion joints, the loads are transferred due to the shear effect. However, a relatively low inter-laminar
shear strength of CFRP decreases effectiveness of the gripping systems. Brittle failure of the bond is often consequence
of stress concentration. An innovative anchorage joint is proposed to control shear stresses by varying a local curvature
of the contact surface. A natural shape of Nautilus shell was chosen for the gripping system, whereas a 3D printing
technique was applied for the prototyping purpose. Mechanical behaviour of the anchorage prototypes made of printed
polymeric material was investigated experimentally.
Experimental research on load bearing capacity of adhesively jointed beech timber lamellas
Authors: Šuhajdová Eva , Novotný Miloslav , Pěnčík Jan , Šuhajda Karel
Published: December 2019

The aim of this work was to verify behavior of a beech timber finger-joint in local conditions in the Central
Europe. The samples were produced with a glued joint with the finger length of 23 mm according to standard ČSN EN
14 080. Commonly used polyurethane adhesive for production of engineered wood products in the Czech Republic was
used. The samples were loaded by destructive four-point bending tests according to standard ČSN EN 408, and the
achieved bending strength was statistically evaluated and compared with results of non-glued samples. The results
showed that bending strength of lamellas with a finger-joint reached about 65% of the strength of samples without
a joint, and the failure of lamellas occurred in most cases at the joint.
Shear failures in cantilevered reinforced concrete slab-strips without transverse reinforcement
Authors: Svarre Christian , Fisker Jakob , Hagsten Lars
Published: December 2019

Design of slabs without shear reinforcement is, in practice, based mainly on empirical codified methods,
derived on the basis of a large number of tests. However, the vast majority of these tests involves simply supported
beams, with substantial amounts of longitudinal reinforcement, subjected to three- or four point bending. This paper
presents the results of a significant experimental programme comprising eighteen simply supported – cantilevered slabstrips without stirrup reinforcement, and with a light amount of longitudinal reinforcement. Stirrups in the surrounding
parts founded a shear critical region located in the hogging region of the simple span. All beams failed in shear within
this shear critical region, the slenderness of which was fixed for all the beams. The influence of the concrete strength,
which is of special interest in relation to lightly reinforced members, was investigated by varying the concrete strength
systematically within the test series. The influence of the concrete strength and mix with respect to crack roughness was
further studied using a large number of concrete cores prepared with coloured epoxy. The cores were all extracted from
various zones containing critical and “non-critical” shear cracks. Photogrammetric measurements (digital image correlation) and optical fiber measurements were conducted in the shear critical region on all tested specimens, and detailed
analysis on the propagation and kinematics of critical cracks are presented.
Non-linear behavior of innovative steel cable-stayed bridge stiffening girder
Authors: Stragys Modestas
Published: December 2019

Until these days there are three very well-known structural forms in cable-stayed bridge construction: radial,
harp and fan. These three well-known and analyzed systems ensure the stability of the cable-stayed bridges in a variety
of conditions. In order to reduce the amount of materials various solutions are used. One way to reduce the cost of steel
may be a new, innovative structural form. A new cable-stayed bridge structure, which requires smaller quantities of
materials, is proposed in this Paper. New structural form is compared with traditional cable-stayed structures and the
conclusions, which reflect the advantages of this construction, are presented. Result of the analysis is evaluation of
innovative cable-stayed structure bending moments, axial forces, deflections and non-linear behavior compared with
traditional cable-stayed structure under the influence of both symmetric as asymmetric loads. Technical-economical
assessment is also proposed in the Paper. The Paper gives an overview of the differences between traditional and innovative design of cable-stayed bridges.
Moment redistribution in continuous prestressed concrete box girder with corrugated steel webs
Authors: Du Jin-Sheng , Ng Pui-Lam , Ma Xiang , Wang Jian
Published: December 2019

A fibre-finite-element model of continuous prestressed concrete (PC) composite box girder with corrugated steel webs is established with force-based elements using OpenSees. After the model is validated with existing experimental data, the effects of reinforcement index in upper and lower flanges, effective prestress and concrete strength on the moment redistribution behaviour is analysed. It is shown that increasing the reinforcement index in lower flange or effective prestress can increase the amount of bending moment redistribution, whereas increasing the concrete strength or reinforcement index in upper flange can decrease the amount of bending moment redistribution. By inspecting the sensitivity of parameters, it is found that the reinforcement index in lower flange has the most significant influence on the moment redistribution, followed by the concrete strength and then by the effective prestress, while the reinforcement index in upper flange has only little impact on the moment redistribution. The calculation results are compared with the existing formulas. Finally, a moment redistribution formula is proposed for continuous PC box girder with corrugated steel webs.
Calculating and estimating construction site plan preparation works and temporary objects, using virtual reality technology
Authors: Kontrimovičius Robertas , Ustinovičius Leonas , Vaišnoras Mantas
Published: December 2019

Aim of the article: to create a prototype of an information system of an optimized site plan using virtual reality
technology (VRT). The article consists of two parts. The first part: the review of the literary sources used; a comparative
analysis of the existing models of the construction site plans. Second part: the description of the prototype development
of the information system (the algorithm) using building information modeling (BIM), and VRT.
[C i](1–0) and [C i](2–1) in Resolved Local Galaxies*
Authors: Crocker Alison F. , Pellegrini Eric , Smith J.-D. T. , Draine Bruce T. , Wilson Christine D. , Wolfire Mark , Armus Lee , Brinks Elias , Dale Daniel A. , Groves Brent , Herrera-Camus Rodrigo , Hunt Leslie K. , Kennicutt Robert C. , Murphy Eric J. , Sandstrom Karin , Schinnerer Eva , Rigopoulou Dimitra , Rosolowsky Erik , Werf Paul van der
Published: December 2019

We present resolved [C i] line intensities of 18 nearby galaxies observed with the SPIRE FTS spectrometer on the Herschel Space Observatory. We use these data along with resolved CO line intensities from J
up = 1 to 7 to interpret what phase of the interstellar medium the [C i] lines trace within typical local galaxies. A tight, linear relation is found between the intensities of the CO(4–3) and [C i](2–1) lines; we hypothesize this is due to the similar upper level temperature of these two lines. We modeled the [C i] and CO line emission using large-velocity gradient models combined with an empirical template. According to this modeling, the [C i](1–0) line is clearly dominated by the low-excitation component. We determine [C i] to molecular mass conversion factors for both the [C i](1–0) and [C i](2–1) lines, with mean values of α
[C i](1−0) = 7.3 M
⊙ K−1 km−1 s pc−2 and α
[C i](2−1) = 34 M
⊙ K−1 km−1 s pc−2 with logarithmic root-mean-square spreads of 0.20 and 0.32 dex, respectively. The similar spread of

to

(derived using the CO(2–1) line) suggests that [C i](1–0) may be just as good a tracer of cold molecular gas as CO(2–1) in galaxies of this type. On the other hand, the wider spread of α
[C i](2−1) and the tight relation found between [C i](2–1) and CO(4–3) suggest that much of the [C i](2–1) emission may originate in warmer molecular gas.
Identifying TeV Source Candidates among Fermi-LAT Unclassified Blazars
Authors: Chiaro G. , Meyer M. , Mauro M. Di , Salvetti D. , Mura G. La , Thompson D. J.
Published: December 2019

Blazars, in particular the subclass of high synchrotron peaked active galactic nuclei are among the main targets for the present generation of Imaging Atmospheric Cerenkov Telescopes (IACTs), and they will remain of great importance for very high-energy γ-ray science in the era of the Cerenkov Telescope Array (CTA). Observations by IACTs, which have relatively small fields of view (∼few degrees), are limited by viewing conditions; therefore, it is important to select the most promising targets to increase the number of detections. The aim of this paper is to search for unclassified blazars among known γ-ray sources from the Fermi Large Area Telescope (LAT) third source catalog that are likely detectable with IACTs or CTA. We use an artificial neural network algorithm and updated analysis of Fermi-LAT data. We found 80 γ-ray source candidates, and for the highest-confidence candidates, we calculate their potential detectability with IACTs and CTA based on an extrapolation of their energy spectra. Follow-up observations of our source candidates could significantly increase the current TeV source population sample and ultimately confirm the efficiency of our algorithm to select TeV sources.
Exploring Plasma Heating in the Current Sheet Region in a Three-dimensional Coronal Mass Ejection Simulation
Authors: Reeves Katharine K. , Török Tibor , Mikić Zoran , Linker Jon , Murphy Nicholas A.
Published: December 2019

We simulate a coronal mass ejection using a three-dimensional magnetohydrodynamic code that includes coronal heating, thermal conduction, and radiative cooling in the energy equation. The magnetic flux distribution at 1 R

s
is produced by a localized subsurface dipole superimposed on a global dipole field, mimicking the presence of an active region within the global corona. Transverse electric fields are applied near the polarity inversion line to introduce a transverse magnetic field, followed by the imposition of a converging flow to form and destabilize a flux rope, producing an eruption. We examine the quantities responsible for plasma heating and cooling during the eruption, including thermal conduction, radiation, adiabatic effects, coronal heating, and ohmic heating. We find that ohmic heating is an important contributor to hot temperatures in the current sheet region early in the eruption, but in the late phase, adiabatic compression plays an important role in heating the plasma there. Thermal conduction also plays an important role in the transport of thermal energy away from the current sheet region throughout the reconnection process, producing a “thermal halo” and widening the region of high temperatures. We simulate emission from solar telescopes for this eruption and find that there is evidence for emission from heated plasma above the flare loops late in the eruption, when the adiabatic heating is the dominant heating term. These results provide an explanation for hot supra-arcade plasma sheets that are often observed in X-rays and extreme ultraviolet wavelengths during the decay phase of large flares.
Propagation of Scatter-free Solar Energetic Electrons in a Meandering Interplanetary Magnetic Field
Authors: Moradi Ashraf , Li Gang
Published: December 2019

We investigate energetic electron transport in a meandering interplanetary magnetic field under the scatter-free regime. The meandering magnetic field is adopted from the Giacalone model in which a single parameter V
rms is used to characterize how the interplanetary magnetic field deviates from the Parker field. The trajectories of energetic electrons are followed in this meandering field using test particle simulations. Ten thousand electrons are injected in the ecliptic plane and the path length distributions are obtained at distances 0.2, 0.5, 1.0, 2.0, and 3.0 au from the Sun for five different V
rms, 0.3, 0.6, 1.0, 1.5, 2.0, and 2.5 km s−1. By generating 10,000 different realizations of the meandering field line, we also obtain the path length distribution of the field lines. Our simulations show that the path length distributions of the electrons and that of the field lines are different and the difference increases with V
rms. When the V
rms approaches zero, the field lines approach the Parker field, and the differences between particle path lengths and field path lengths are small but nonzero due to the gradient and curvature drifts. The path lengths for 1 MeV electrons do not differ much from those for 100 MeV electrons. Our results of the distribution of electron path length can be compared to the observations of Zhao et al. to set constraints on V
rms. We also calculate both the longitudinal and latitudinal displacements from the source when electrons arrive at 1 au. This provides some basis for understanding simultaneous observations of impulsive events made at multiple spacecraft.
Spectral and Timing Properties of the Galactic X-Ray Transient Swift J1658.2–4242 Using Astrosat Observations
Authors: Jithesh V. , Maqbool Bari , Misra Ranjeev , T Athul. R. , Mall Gitika , James Marykutty
Published: December 2019

We present the X-ray timing and spectral analysis of the new Galactic X-ray transient Swift J1658.2–4242 observed with the Large Area X-ray Proportional Counter and Soft X-ray Telescope instruments on board Astrosat. We detect prominent C-type quasi-periodic oscillations (QPOs) of frequencies varying from ∼1.5 to ∼6.6 Hz along with distinct second harmonics and subharmonics. The QPO detected at ∼1.56 Hz drifts to a higher centroid frequency of ∼1.74 in the course of the observation, while the QPO detected at ∼6.6 Hz disappeared during hard flarings. The fractional rms at the QPO and the subharmonic frequencies increases with photon energy, while at the second harmonic frequencies the rms seems to be constant. In addition, we have observed soft time lag at QPO and subharmonic frequencies up to a timescale of ∼35 ms; however, at the second harmonic frequencies there is weak/zero time lag. We attempt spectral modeling of the broadband data in the 0.7–25 keV band using the doubly absorbed disk plus thermal Comptonization model. Based on the spectral and timing properties, we identified the source to be in the hard-intermediate state of black hole X-ray binaries. To quantitatively fit the energy- and frequency-dependent fractional rms and time lag, we use a single-zone fluctuation propagation model and discuss our results in the context of that model.
Spallation-altered Accreted Compositions for X-Ray Bursts: Impact on Ignition Conditions and Burst Ashes
Authors: Randhawa J. S. , Meisel Z. , Giuliani S. A. , Schatz H. , Meyer B. S. , Ebinger K. , Hood A. A. , Kanungo R.
Published: December 2019

Model predictions of X-ray burst ashes and light curves depend on the composition of the material accreted from the companion star, in particular the abundance of CNO elements. It has previously been pointed out that spallation in the atmosphere of the accreting neutron star can destroy heavy elements efficiently. In this work we study this spallation using a realistic reaction network that follows the complete spallation cascade and takes into account not only destruction, but also production of elements by the spallation of heavier species. We find an increased survival probability of heavier elements compared to previous studies, resulting in significantly higher CNO abundances. We provide resulting compositions as a function of accretion rate, and explore their impact on 1D multi-zone X-ray burst models. We find significant changes in the composition of the burst ashes, which will affect the thermal and compositional structure of accreted neutron star crusts.
Accelerated Expansion of the Universe in the Model with Nonuniform Pressure
Authors: Kopteva Elena , Bormotova Irina , Churilova Maria , Stuchlik Zdenek
Published: December 2019

We present the particular case of the Stephani solution for shear-free perfect fluid with uniform energy density and nonuniform pressure. Such models appeared as possible alternative to the consideration of the exotic forms of matter like dark energy that would cause the acceleration of universe expansion. These models are characterized by the spatial curvature, depending on time. We analyze the properties of the cosmological model obtained on the basis of exact solution of the Stephani class, and adapt it to the recent observational data. The spatial geometry of the model is investigated. We show that despite possible singularities, the model can describe the current stage of the universe’s evolution.
Expansion of Solar Coronal Hot Electrons in an Inhomogeneous Magnetic Field: 1D PIC Simulation
Authors: Sun Jicheng , Gao Xinliang , Ke Yangguang , Lu Quanming , Wang Xueyi , Wang Shui
Published: December 2019

The expansion of hot electrons in flaring magnetic loops is crucial to understanding the dynamics of solar flares. In this paper we investigate, for the first time, the transport of hot electrons in a magnetic mirror field based on a 1D particle-in-cell simulation model. The hot electrons with small pitch angles transport into the cold plasma, which leads to the generation of Langmuir waves in the cold plasma and ion acoustic waves in the hot plasma. The large pitch angle electrons can be confined by the magnetic mirror, resulting in the different evolution timescale between electron parallel and perpendicular temperatures. This will cause the formation of electron temperature anisotropy, which then generates the whistler waves near the interface between hot electrons and cold electrons. The whistler waves can scatter the large pitch angle electrons to smaller value through the cyclotron resonance, leading to electrons escaping from the hot region. These results indicate that the whistler waves may play an important role in the transport of electrons in flaring magnetic loops. The findings from this study provide some new insights to understand the electron dynamics of solar flares.
A 3D Dust Map Based on Gaia, Pan-STARRS 1, and 2MASS
Authors: Green Gregory M. , Schlafly Edward , Zucker Catherine , Speagle Joshua S. , Finkbeiner Douglas
Published: December 2019

We present a new three-dimensional map of dust reddening, based on Gaia parallaxes and stellar photometry from Pan-STARRS 1 and 2MASS. This map covers the sky north of a decl. of −30°, out to a distance of a few kiloparsecs. This new map contains three major improvements over our previous work. First, the inclusion of Gaia parallaxes dramatically improves distance estimates to nearby stars. Second, we incorporate a spatial prior that correlates the dust density across nearby sightlines. This produces a smoother map, with more isotropic clouds and smaller distance uncertainties, particularly to clouds within the nearest kiloparsec. Third, we infer the dust density with a distance resolution that is four times finer than in our previous work, to accommodate the improvements in signal-to-noise enabled by the other improvements. As part of this work, we infer the distances, reddenings, and types of 799 million stars. (Our 3D dust map can be accessed at doi:10.7910/DVN/2EJ9TX or through the Python package dustmaps, while our catalog of stellar parameters can be accessed at doi:10.7910/DVN/AV9GXO. More information about the map, as well as an interactive viewer, can be found at argonaut.skymaps.info.) We obtain typical reddening uncertainties that are ∼30% smaller than those reported in the Gaia DR2 catalog, reflecting the greater number of photometric passbands that enter into our analysis.
A Trio of Massive Black Holes Caught in the Act of Merging*
Authors: Liu Xin , Hou Meicun , Li Zhiyuan , Nyland Kristina , Guo Hengxiao , Kong Minzhi , Shen Yue , Wrobel Joan M. , Peng Sijia
Published: December 2019

We report the discovery of SDSS J0849+1114 as the first known triple Type 2 Seyfert nucleus. It represents three active black holes that are identified from new spatially resolved optical slit spectroscopy using the Dual Imaging Spectrograph on the 3.5 m telescope at the Apache Point Observatory. We also present new complementary observations including the Hubble Space Telescope Wide Field Camera 3 U- and Y-band imaging, Chandra Advanced CCD Imaging Spectrometer S-array X-ray 0.5–8 keV imaging spectroscopy, and NSF Karl G. Jansky Very Large Array radio 9.0 GHz imaging in its most extended A configuration. These comprehensive multiwavelength observations, when combined together, strongly suggest that all three nuclei are active galactic nuclei. While they are now still at kiloparsec-scale separations, where the host-galaxy gravitational potential dominates, the black holes may evolve into a bound triple system in ≲2 Gyr. These triple merger systems may explain the overly massive stellar cores that have been observed in some elliptical galaxies such as M87, which are expected to be unique gravitational wave sources. Similar systems may be more common in the early universe, when galaxy mergers are thought to have been more frequent.
The Nature of Ionized Gas in the Milky Way Galactic Fountain
Authors: Werk Jessica K. , Rubin K. H. R. , Bish H. V. , Prochaska J. X. , Zheng Y. , O’Meara J. M. , Lenz D. , Hummels C. , Deason A. J.
Published: December 2019

We address the spatial scale, ionization structure, mass, and metal content of gas at the Milky Way disk–halo interface detected as absorption in the foreground of seven closely spaced, high-latitude halo blue horizontal branch stars with heights z = 3–14 kpc. We detect transitions that trace multiple ionization states (e.g., Ca ii, Fe ii, Si iv, C iv) with column densities that remain constant with height from the disk, indicating that the gas most likely lies within z < 3.4 kpc. The intermediate ionization state gas traced by C iv and Si iv is strongly correlated over the full range of transverse separations probed by our sight lines, indicating large, coherent structures greater than 1 kpc in size. The low ionization state material traced by Ca ii and Fe ii does not exhibit a correlation with either N
H i
or transverse separation, implying cloudlets or clumpiness on scales less than 10 pc. We find that the observed ratio log(N
Si iv
/N
C iv
), with a median value of −0.69 ± 0.04, is sensitive to the total carbon content of the ionized gas under the assumption of either photoionization or collisional ionization. The only self-consistent solution for photoionized gas requires that Si be depleted onto dust by 0.35 dex relative to the solar Si/C ratio, similar to the level of Si depletion in DLAs and in the Milky Way interstellar medium. The allowed range of values for the areal mass infall rate of warm, ionized gas at the disk−halo interface is 0.0003 < dM
gas/dtdA [M
⊙ kpc−2 yr−1] <0.006. Our data support a physical scenario in which the Milky Way is fed by complex, multiphase processes at its disk−halo interface that involve kiloparsec-scale ionized envelopes or streams containing parsec-scale, cool clumps.
Distribution of two rare taxa of caddisflies (Trichoptera: Rhyacophilidae, Polycentropodidae) from the Republic of Kosovo
Authors: Ibrahimi Halil , Kuçi Ruzhdi , Bilalli Astrit , Musliu Milaim , Gashi Arben , Sinani Naman , Emërllahu Besnik
Published: December 2019

The knowledge about distribution, ecology and species composition of caddisflies of the Balkan Peninsula is still not complete. The ongoing investigations of the last years highlight this area as an important hotspot of caddisfly diversity. Polycentropus ierapetra slovenica has been considered a narrow range endemic of Slovenia and surrounding areas. Rhyacophila aurata, a species known from many parts of Europe, according to the current knowledge, is absent from a large part of the Balkan Peninsula.

In this paper, we present records of these two rare taxa of Trichoptera from the Republic of Kosovo with exact distribution data, based on sampling carried out randomly during 2014 and 2017. Polycentropus ierapetra slovenica was found in several streams in Bjeshkët e Nemuna Mountains and Karadak Mountains. Rhyacophila aurata was found during this investigation at a single locality in Bjeshkët e Nemuna Mountains.

The unexpected finding of these two taxa in Kosovo greatly enlarges their known distribution area and makes a contribution towards the better knowledge of distributional patterns of these rare taxa of caddisflies in this part of Europe.
First report of Rhabdochona acuminata (Nematoda, Rhabdochonidae) in Astyanax aff. fasciatus (Characiformes, Characidae) from Lake Guaíba, southern Brazil
Authors: Gallas Moisés , Calegaro-Marques Cláudia , Amato Suzana B.
Published: December 2019

Specimens of Rhabdochona (Rhabdochona) acuminata (Molin, 1860) were collected in Astyanax aff. fasciatus (Cuvier, 1819) from Lake Guaíba, municipalities of Guaíba (30°08.28'S, 51°18.53'W) and Barra do Ribeiro (30°17.11'S, 51°18.01'W), southern Brazil. In the present study, the prevalence of R. (R.) acuminata was low (1.43%) when compared to other studies performed withAstyanaxspp. from Brazil. The specimens of R. (R.) acuminata showed some morphological differences (mainly the deirids) that have not yet been reported for the species. This is the first report of R. (R.) acuminata from Lake Guaíba, filling a gap of occurrence of this nematode in South America.
Le terrorisme. Un défi pour la justice transitionnelle
Authors: Hubrecht Joël
Published: December 2019

Cette intervention explore les bases d'une justice transitionnelle pour le terrorisme qui serait élaborée collectivement à partir des besoins des victimes et des défis sociétaux qu'il pose. Elle inclurait un cadre symbolique de ré-affiliation (et non de réconciliation) pour des ex-djihadistes repentis et volontaires.