bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving estimates for reliability and cost in microgrid investment planning models
Authors: Hanna Ryan , Disfani Vahid R. , Haghi Hamed Valizadeh , Victor David G. , Kleissl Jan
Published: July 2019

This paper develops a new microgrid investment planning model that determines cost-optimal investment and operation of distributed energy resources (DERs) in a microgrid. We formulate the problem in a bilevel framework, using particle swarm optimization to determine investment and the DER-CAM model (Distributed Energy Resources Customer Adoption Model) to determine operation. The model further uses sequential Monte Carlo simulation to explicitly simulate power outages and integrates time-varying customer damage functions to calculate interruption costs from outages. The model treats nonlinearities in reliability evaluation directly, where existing linear models make critical simplifying assumptions. It combines investment, operating, and interruption costs together in a single objective function, thereby treating reliability endogenously and finding the cost-optimal trade-off between cost and reliability—two competing objectives. In benchmarking against a version of the DER-CAM model that treats reliability through a constraint on minimum investment, our new model improves estimates of reliability (the loss of load expectation) by up to 600%, of the total system cost by 6%–18%, of the investment cost by 32%–50%, and of the economic benefit of investing 27%–47%. Improvements stem from large differences in investment of up to 56% for natural gas generators, solar photovoltaics, and battery energy storage.
Highly charged interface trap states in PbS1−x govern electro-thermal transport
Authors: Yazdani Sajad , Huan Tran Doan , Liu Yufei , Kashfi-Sadabad Raana , Montaño Raul David , He Jian , Pettes Michael Thompson
Published: July 2019

This work describes our discovery of the dominant role of highly charged interfaces on the electrothermal transport properties of PbS, along with a method to reduce the barrier potential for charge carriers by an order of magnitude. High temperature thermoelectrics such as PbS are inevitably exposed to elevated temperatures during postsynthesis treatment as well as operation. However, we observed that as the material was heated, large concentrations of sulfur vacancy (VS̈) sites were formed at temperatures as low as 266 °C. This loss of sulfur doped the PbS n-type and increased the carrier concentration, where these excess electrons were trapped and immobilized at interfacial defect sites in polycrystalline PbS with an abundance of grain boundaries. Sulfur deficient PbS0.81 exhibited a large barrier potential for charge carriers of 0.352 eV, whereas annealing the material under a sulfur-rich environment prevented VS̈ formation and lowered the barrier by an order of magnitude to 0.046 eV. Through ab initio calculations, the formation of VS̈ was found to be more favorable on the surface compared to the bulk of the material with a 1.72 times lower formation energy barrier. These observations underline the importance of controlling interface-vacancy effects in the preparation of bulk materials comprised of nanoscale constituents.
Scaling and spatial intermittency of thermal dissipation in turbulent convection
Authors: Bhattacharya Shashwat , Samtaney Ravi , Verma Mahendra K.
Published: July 2019

We derive scaling relations for the thermal dissipation rate in the bulk and in the boundary layers for moderate and large Prandtl number (Pr) convection. Using direct numerical simulations of Rayleigh-Bénard convection, we show that the thermal dissipation in the bulk is suppressed compared to passive scalar dissipation. The suppression is stronger for large Pr. We further show that the dissipation in the boundary layers dominates that in the bulk for both moderate and large Pr. The probability distribution functions of thermal dissipation rate, both in the bulk and in the boundary layers, are stretched exponential, similar to passive scalar dissipation.
Tuning of electronic and magnetic properties of multifunctional r-GO-ATA-Fe2O3-composites for magnetic resonance imaging (MRI) contrast agent
Authors: Idisi David O. , Oke J. A. , Sarma Sweety , Moloi S. J. , Ray Sekhar C. , Pong W. F. , Strydom André M.
Published: July 2019

We have synthesized r-GO-ATA-Fe2O3 nanocomposites and studied their microstructural and electromagnetic properties for future possible magnetic resonance imaging for biomedical application. X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption near edge spectroscopy were used to study the structural and electronic properties, while a superconducting quantum interface device magnetometer was used for investigating the magnetic behavior of the nanocomposites. The nanocomposites have been found to reduce the graphitic structure of GO due to the substitution of carbon/oxygen and/or iron nanoparticles. Conversely, the electrical conductivity of nanocomposites is found to be high due to the formation of Fe—C/Fe—O bonds in the structure of the nanocomposites. The composites also exhibit superparamagnetic features as observed from the M-H hysteresis loop with saturation magnetization of ≈0.1 emu/g at 1.8 K temperature. The results, in general, suggest possible applicability of r-GO/Fe2O3 nanocomposites as an effective multifunctional platform for magnetic resonance imaging in biomedical applications.
Splash formation and cavity dynamics of sphere entry through a viscous liquid resting on the water
Authors: Sun Tiezhi , Wang Heng , Zong Zhi , Zhang Guiyong , Wang An , Xu Chang
Published: July 2019

The splash formation and cavity dynamics during the entry of an object into a single-phase liquid system have been investigated considerably in the past, but only a few studies focus on such phenomena in a two-layer liquid system. In the current study, we present an experimental investigation of the entry of a falling sphere into a liquid system consisting of a deep pool of water and a thin layer of dimethicone resting on the water surface. To highlight and support the present findings, experiments of the same sphere entering water were performed and direct comparison were made. As anticipated, the upper-layer viscous liquid introduces a significant change in the splash formation and the differences in behavior are characterized by layered films and wave-like instability structures. In the experiments of the two-layer liquid system, observations show that the early sealing of the splash and the generation of a larger-scale splash fingers are strongly associated with large Froude number, Fr = V0(gD)-1/2 (where V0 is the impact velocity at the still free surface, g is the gravitational acceleration and D is the diameter of the sphere). In addition, the dimensionless cavity depth, the pinch-off depth and the pull-away cavity length behind the sphere are found to be in linear relationship with the Froude number for both water-entry cases and water-dimethicone-entry cases. One of the most interesting results is that the pinch-off time is almost independent of the Froude number. The highly viscous liquid in the upper layer is shown to be critical in determining the cavity dynamics.
Self-consistent charge embedding at very low cost, with application to symmetry-adapted perturbation theory
Authors: Liu Kuan-Yu , Carter-Fenk Kevin , Herbert John M.
Published: July 2019

Extended symmetry-adapted perturbation theory (XSAPT) uses a self-consistent charge embedding to capture many-body polarization, in conjunction with a pairwise-additive SAPT calculation of intermolecular interaction energies. The original implementation of XSAPT is based on charges that are fit to reproduce molecular electrostatic potentials, but this becomes a computational bottleneck in large systems. Charge embedding based on modified Hirshfeld atomic charges is reported here, which dramatically reduces the computational cost without compromising accuracy. Exemplary calculations are presented for supramolecular complexes such as C60@C60H28, a DNA intercalation complex, and a 323-atom model of a drug molecule bound to an enzyme active site. The proposed charge embedding should be useful in other fragment-based quantum chemistry methods as well.
River connectivity and fish migration considerations in the management of multiple stressors in South Africa
Authors: O'Brien Gordon C. , Ross Mathew , Hanzen Céline , Dlamini Vuyisile , Petersen Robin , Diedericks Gerhard J. , Burnett Matthew J.
Published: July 2019

People throughout the world depend on the services we derive from freshwater ecosystems. Human land-use activities often affect the quality, quantity and habitat of freshwater ecosystem, which need to be carefully managed to ensure their integrity and provision of services is sustainable. In South Africa, legislation has established resource-directed measures to attain a sustainable balance between the use and protection of water resources. These procedures have been implemented in most of South Africa’s nine water-management areas, resulting in new legislation to protect these resources. Unfortunately, very little protection has been afforded to river connectivity maintenance and fish migrations. For water storage and flow regulation for agriculture and other resource use activities, >610 formal dams and ~1430 gauging weirs have been constructed that act a partial or complete barriers to fish migration on river ecosystems. Only ~60 fish passage structures have been built, but many are not functional. River connectivity and fish migration management appears to be a shortcoming of the existing management approach for multiple stressors.
Anthelepis, a new genus for four mainly tropical species of Cyperaceae from Australia, New Caledonia and South-East Asia
Authors: Barrett Russell L. , Wilson Karen L. , Bruhl Jeremy J.
Published: July 2019

A new genus, Anthelepis R.L.Barrett, K.L.Wilson & J.J.Bruhl, is described for four Cyperaceae species from mainly tropical areas of South-East Asia, New Caledonia and Australia. The relationships of the three previously described species have been much-debated. In recent decades, they have most commonly been placed in either Schoenus L. or Tricostularia Nees ex Lehm., but molecular phylogenetic data have demonstrated that they are not closely related to either genus and a new generic name is required. The following three new combinations are made: Anthelepis guillauminii (Kük.) R.L.Barrett, K.L.Wilson & J.J.Bruhl (based on Schoenus guillauminii Kük.), A. paludosa (R.Br.) R.L.Barrett, K.L.Wilson & J.J.Bruhl (based on Chaetospora paludosa R.Br.) and A. undulata (Thwaites) R.L.Barrett, K.L.Wilson & J.J.Bruhl (based on Cladium undulatum Thwaites). One new species, Anthelepis clarksonii R.L.Barrett, K.L.Wilson & J.J.Bruhl, is described from northern Queensland, Australia, as distinct from A. undulata. Full descriptions, illustrations and a key to species are provided. All species are confirmed as having C3 anatomy.
How terpene content affects fuel flammability of wildland–urban interface vegetation
Authors: Romero Bastien , Fernandez Catherine , Lecareux Caroline , Ormeño Elena , Ganteaume Anne
Published: July 2019

Among plant characteristics promoting flammability, terpenes have received little attention, especially regarding the vegetation surrounding housing. Here, mono-, sesqui- and diterpenes were screened in live and dead leaves of ornamental species found in wildland–urban interfaces (WUIs) of south-eastern France. Terpene content and composition were compared among species and between fuel types. Their influence on flammability was assessed through several variables and compared with that of leaf thickness and moisture content. Six of the 17 species examined contained terpenes. Terpene diversity and content differed among species but not between fuel types. Mono-, sesqui- and diterpenes (especially the highly concentrated compounds) were involved to varying degrees in both leaf and litter flammability. Their effects could be opposite according to the flammability variable and the fuel type considered. Leaf sesquiterpene content and litter total terpene content had the strongest influence on maximum combustion temperature; the former also mainly drove leaf flaming duration. The other flammability variables were more strongly associated with either moisture content or leaf thickness. Our findings highlight the idea that fire management in the WUI must also acknowledge the potential for ornamental species containing terpenes, such as Pinus halepensis, to affect fire behaviour.
The use of contraceptive techniques in managed wild African lion (Panthera leo) populations to mimic open system cub recruitment
Authors: McEvoy Orla K. , Miller Susan M. , Beets Warren , Bodasing Tarik , Borrego Natalia , Burger André , Courtenay Brian , Ferreira Sam , Hanekom Cathariné , Hofmeyr Markus , Packer Craig , Robertson Dave , Stratford Ken , Slotow Rob , Parker Dan M.
Published: July 2019

Context
Managed wild lions (Panthera leo) are lions found in smaller (<1000 km2), fenced protected areas that hold a substantial portion of South Africa’s wild lion population. Because the natural population control mechanisms are compromised within these properties, managers must actively control population growth rates. Fecundity control is used by wildlife managers, but long-term, empirical data on the impact and consequences of such interventions in lions are lacking.

Aims
The aim of the present study was to assess the effectiveness of two methods of contraception (deslorelin implant and unilateral hysterectomy) in reducing cub recruitment of managed wild lions.

Methods
Survey data spanning 14 years from 94 managed wild lions on 19 protected areas were used to evaluate the effectiveness of deslorelin implant treatments and unilateral hysterectomies on population growth rates through mimicking open system cub recruitment.

Key results
Deslorelin implants were effective at increasing the age of first reproduction and lengthening inter-birth intervals. There was also an unexpected decrease in litter size. Behavioural side-effects were recorded in 40% of individuals: 19% pride fragmentation; 13% lack of receptiveness towards males; 8% other. The more successive deslorelin implants a lioness had, the more likely it was that weight gain was reported. Unilateral hysterectomy resulted in a decrease in litter size post-surgery, but this was not statistically significant. No behavioural or physiological side-effects were noted after unilateral hysterectomy.

Conclusions
Deslorelin treatment was more effective in reducing the reproductive output of managed wild lionesses than unilateral hysterectomy surgery. While more side-effects were associated with deslorelin implants than unilateral hysterectomies, a single deslorelin treatment is currently a good option for fecundity reduction. More research is required on unilateral hysterectomy surgery.

Implications
Neither deslorelin implants nor unilateral hysterectomies offer a ‘silver bullet’ solution for reducing rapid population growth in managed wild lions. Reproductive control should be integrated with other best-practice approaches.
The Mpemba effect in spin glasses is a persistent memory effect
Authors: Baity-Jesi Marco , Calore Enrico , Cruz Andres , Fernandez Luis Antonio , Gil-Narvión José Miguel , Gordillo-Guerrero Antonio , Iñiguez David , Lasanta Antonio , Maiorano Andrea , Marinari Enzo , Martin-Mayor Victor , Moreno-Gordo Javier , Muñoz Sudupe Antonio , Navarro Denis , Parisi Giorgio , Perez-Gaviro Sergio , Ricci-Tersenghi Federico , Ruiz-Lorenzo Juan Jesus , Schifano Sebastiano Fabio , Seoane Beatriz , Tarancón Alfonso , Tripiccione Raffaele , Yllanes David
Published: July 2019

Significance

The Mpemba effect, wherein an initially hotter system relaxes faster when quenched to lower temperatures than an initially cooler system, has attracted much attention. Paradoxically, its very existence is a hot topic. Using massive numerical simulations, we show unambiguously that the Mpemba effect is present in the archetypical model system for complex behavior, spin glasses. We find that the Mpemba effect in spin glasses is due to the aging dynamics of the internal energy, as controlled by the nonequilibrium spin-glass coherence length. Interestingly, the effect is not present when the system remains all of the time in the paramagnetic phase. Therefore, the Mpemba effect suggests itself as an effective probe for a glass transition, potentially useful for other glass-forming systems.
A genetic analysis of the Gibraltar Neanderthals
Authors: Bokelmann Lukas , Hajdinjak Mateja , Peyrégne Stéphane , Brace Selina , Essel Elena , de Filippo Cesare , Glocke Isabelle , Grote Steffi , Mafessoni Fabrizio , Nagel Sarah , Kelso Janet , Prüfer Kay , Vernot Benjamin , Barnes Ian , Pääbo Svante , Meyer Matthias , Stringer Chris
Published: July 2019

The Forbes’ Quarry and Devil’s Tower partial crania from Gibraltar are among the first Neanderthal remains ever found. Here, we show that small amounts of ancient DNA are preserved in the petrous bones of the 2 individuals despite unfavorable climatic conditions. However, the endogenous Neanderthal DNA is present among an overwhelming excess of recent human DNA. Using improved DNA library construction methods that enrich for DNA fragments carrying deaminated cytosine residues, we were able to sequence 70 and 0.4 megabase pairs (Mbp) nuclear DNA of the Forbes’ Quarry and Devil’s Tower specimens, respectively, as well as large parts of the mitochondrial genome of the Forbes’ Quarry individual. We confirm that the Forbes’ Quarry individual was a female and the Devil’s Tower individual a male. We also show that the Forbes’ Quarry individual is genetically more similar to the ∼120,000-y-old Neanderthals from Scladina Cave in Belgium (Scladina I-4A) and Hohlenstein-Stadel Cave in Germany, as well as to a ∼60,000- to 70,000-y-old Neanderthal from Russia (Mezmaiskaya 1), than to a ∼49,000-y-old Neanderthal from El Sidrón (El Sidrón 1253) in northern Spain and other younger Neanderthals from Europe and western Asia. This suggests that the Forbes’ Quarry fossil predates the latter Neanderthals. The preservation of archaic human DNA in the warm coastal climate of Gibraltar, close to the shores of Africa, raises hopes for the future recovery of archaic human DNA from regions in which climatic conditions are less than optimal for DNA preservation.
BCL-2 family protein BOK is a positive regulator of uridine metabolism in mammals
Authors: Srivastava Rahul , Cao Zhipeng , Nedeva Christina , Naim Samara , Bachmann Daniel , Rabachini Tatiana , Gangoda Lahiru , Shahi Sanjay , Glab Jason , Menassa Joseph , Osellame Laura , Nelson Tao , Fernandez-Marrero Yuniel , Brown Fiona , Wei Andrew , Ke Francine , O’Reilly Lorraine , Doerflinger Marcel , Allison Cody , Kueh Andrew , Ramsay Rob , Smith Brian J. , Mathivanan Suresh , Kaufmann Thomas , Puthalakath Hamsa
Published: July 2019

Significance

It is believed that the Bcl-2 family protein Bok has a redundant role similar to Bax and Bak in regulating apoptosis. We report that this protein interacts with the key enzyme involved in uridine biosynthesis, uridine monophosphate synthetase, and positively regulates uridine biosynthesis and chemoconversion of 5-fluorouracil (5-FU). Bok-deficient cell lines are resistant to 5-FU. Bok down-regulation is a key feature of cell lines and primary colorectal tumor tissues that are resistant to 5-FU. Our data also show that through its impact on nucleotide metabolism, Bok regulates p53 level and cellular proliferation. Our results have implications for developing Bok as a biomarker for 5-FU resistance and for the development of BOK mimetics for sensitizing 5-FU-resistant cancers.
Neural substrates of sexual arousal are not sex dependent
Authors: Mitricheva Ekaterina , Kimura Rui , Logothetis Nikos K. , Noori Hamid R.
Published: July 2019

Significance

Neuroimaging studies suggest differences in the underlying biology of sexual arousal associated with sex and sexual orientation, yet their findings are conflicting. Following a thorough statistical review of all significant neuroimaging studies, we offer strong quantitative evidence that the neuronal response to visual sexual stimuli, contrary to the widely accepted view, is independent of biological sex. Both men and women show increased activation in many cortical and subcortical brain regions thought to be involved in the response to visual sexual stimuli, while the limited sex differences that have been found and reported previously refer to subjective rating of the content.
Girls’ comparative advantage in reading can largely explain the gender gap in math-related fields
Authors: Breda Thomas , Napp Clotilde
Published: July 2019

Significance

Women remain strongly underrepresented in math-related fields. This phenomenon is problematic because it contributes to gender inequalities in the labor market and can reflect a loss of talent. The current state of the art is that students’ abilities are not able to explain gender differences in educational and career choices. Relying on the Programme for International Student Assessment (PISA) data, we show that female students who are good at math are much more likely than male students to be even better in reading. As a consequence, the difference between 15-y-old students’ math and reading abilities, which is likely to be determined by earlier socialization processes, can explain up to 80% of the gender gap in intentions to pursue math-studies and careers.
Marginados en la poesía burlesca colonial
Authors: Cabanillas Cárdenas Carlos F.
Published: July 2019

La poesía satírico burlesca de Juan del Valle y Caviedes (Porcuna, Jaén, 1645-Lima, 1698), fiel a la configuración
lírica de finales del siglo XVII, está muy ligada a la plaza pública y a las circunstancias y acontecimientos producidos en ella.
Por ello, el presente trabajo analiza en algunos textos de Caviedes la representación poética de los mulatos que habitaron la
ciudad de Lima en dicho periodo. Después de revisar las lecturas de Hill (2007) – que
estudia estos textos como “poemas de casta” – se presta particular atención a los modos de representación – y valoración – de este
grupo de sujetos marginales desde la perspectiva de un contemporáneo.
The Quantum Theory of Atoms in Molecules and the Interactive Conception of Chemical Bonding
Authors: Esser Stephen
Published: July 2019

Quantum physics is the foundation for chemistry, but the concept of chemical bonding is not easily reconciled with quantum mechanical models of molecular systems. The quantum theory of atoms in molecules, developed by Richard F. W. Bader and colleagues, seeks to define bonding using a topological analysis of the electron density distribution. The “bond paths” identified by the analysis are posited as indicators of a special pair-wise physical relationship between atoms. While elements of the theory remain subject to debate, I argue that the quantum theory of atoms in molecules embodies a distinctive interactive conception of bonding that is an attractive alternative to others previously discussed.
Why Replication Is Overrated
Authors: Feest Uljana
Published: July 2019

Current debates about the replication crisis in psychology take it for granted that direct replication is valuable, largely focusing on its role in uncovering questionable statistical practices. This article takes a broader look at the notion of replication in psychological experiments. It is argued that all experimentation/replication involves individuation judgments and that research in experimental psychology frequently turns on probing the adequacy of such judgments. In this vein, I highlight the ubiquity of conceptual and material questions in research, arguing that replication has its place but is not as central to psychological research as it is sometimes taken to be.
Occam’s Razor in Molecular and Systems Biology
Authors: Gross Fridolin
Published: July 2019

Occam’s razor refers to the idea that among competing explanations the simplest should be preferred. This principle has been understood and defended in different ways. Some systems biologists argue that traditional molecular biology is misguided because it relies on an unjustified application of Occam’s razor. I analyze which version of the principle is relevant in this context and ask whether the allegation stands up to scrutiny by looking at actual research. I defend the traditional approach by arguing that its use of Occam’s razor is innocuous and by showing that systems biology heavily relies on considerations of simplicity as well.
Spin determination by in-plane angular correlation analysis in various coordinate systems *
Authors: Yang Biao , Ye Yan-Lin , Lou Jian-Ling , Yang Xiao-Fei , Li Jing-Jing , Liu Yang , Liu Wei , Yu Han-Zhou
Published: July 2019

In the excitation of the resonant state followed by the sequential cluster-decay, the in-plane angular correlation method is usually employed to determine the spin of the mother nucleus. However, the correlation pattern exhibited in a two-dimensional angular-correlation spectrum depends on the selected coordinate system. In particular, the parity-symmetric and axial-symmetric processes should be presented in a way to enhance the correlation pattern, whereas the non-symmetric process should be plotted separately to reduce the background. In this study, three coordinate systems previously adopted for correlation patterns in the literature are described and compared to each other. The consistency among these systems is evaluated based on the experimental data analysis for the 10.29-MeV state in 18O. A spin-parity of 4+ is obtained for all three coordinate systems.
rotational bands in neutron-rich Mo, Ru, and Pd nuclei *
Authors: Dai A-Can , Xu Fu-Rong , Liang Wu-Yang
Published: July 2019

The collective rotations of the

configuration in neutron-rich Mo, Ru and Pd isotopes were systematically investigated by the configuration-constrained cranking shell model based on the Skyrme Hartree-Fock method with pairing treated by shell-model diagonalization. The calculations efficiently reproduce the experimental moments of inertia of both the ground-state and side bands. Rotational bands built on two-particle

configurations have been the subject of intense study. Possible configurations were assigned to the observed

bands in 102-106Mo, 108-112Ru and 112-114Pd. We predict the existence of the

bands in 108,110Mo. These results provide deep insights into the structure of neutron-rich nuclei, and provide useful information for future experiments.
Control problems for the stationary MHD equations under mixed boundary conditions
Authors: Alekseev Gennady , Brizitskii Roman
Published: July 2019

The optimal control problems for the stationary magnetohydrodynamic equations under inhomogeneous mixed boundary conditions for a magnetic field are considered. The role of control in control problems under study is played by normal component of the magnetic field on the part of the boundary. The existence of optimal solution is proved and optimality system for considered extremum problem is obtained.
Regularity of solutions to non-stationary Navier–Stokes equations
Authors: Amosova E V
Published: July 2019

This paper covers a non-stationary system of Navier–Stokes equations for incompressible fluids. A regularized problem is considered that factors in the velocity field being relaxed to a solenoidal field; this problem is used to prove the pressure function exists almost everywhere in the domain for the Hopf class solutions. The proposed regularization proves there exist more regular weak solutions to the initial problem that do not impose smallness restrictions on the input data. The theorem of uniqueness is proven for the 2D case.
Existence and large time behavior for generalized Kelvin-Voigt equations governing nonhomogeneous and incompressible fluids
Authors: Antontsev S N , de Oliveira H B , Khompysh Kh
Published: July 2019

Generalized Kelvin-Voigt equations governing nonhomogeneous and incompressible fluids are considered in this work. We assume that, in the momentum equation, the diffusion and relaxation terms are described by two distinct power-laws. Moreover, we assume that the momentum equation is perturbed by an extra term, which, depending on whether its signal is positive or negative, may account for the presence of a source or a sink within the system. For the associated initial-boundary value problem, we study the existence of weak solutions as well as the large time behavior of the solutions.
Hydraulic fracturing of cylindrical concrete bodies in a non-uniform stress field
Authors: Blinov V A , Legan M A
Published: July 2019

An experimental study of the hydraulic fracture of thick-walled cylinders with the application of a diametrical load was carried out on specimens in the form of cylinders with a central circular hole and a circular hole located at a distance of half the radius from the center of the cylinder at an angle of 45 degrees to the load application line. Specimens were made of concrete based on aluminous cement. Ultimate stresses in the material were determined for two types of stress state: under tension in bending conditions and under a compound stress state on the surface of the hole. The modeling of the fracturing process taking into account the inhomogeneity of the stress state near the hole was carried out using the boundary elements method (in the variant of the fictitious load method) and the gradient fracture criterion. Calculation results of the ultimate pressure were compared with experimental data. Experimental study showed scale effect in concrete specimens with stress concentrators.
Acoustic properties of overheated liquid with gas nuclei during temperature increasing
Authors: Agisheva U O , Galimzyanov M N , Vdovenko I I
Published: July 2019

The dynamics of weak harmonic disturbances in a superheated water-air bubble medium is studied when in addition to water vapor there is an inert gas (e.g. air) that does not participate in phase transitions. The maps of the stability zones of the considered systems are analyzed depending on the value of the liquid overheating on the “volume content - bubble radius” plane with an increase in the equilibrium pressure from 0.1 to 10 MPa. The effect of the initial pressure amplitude and the overheating (from hundredths to one degree) on the dispersion of harmonic waves as well as the dependence of the increment on the bubble radius for unstable systems are investigated.
Mathematical modeling and numerical analysis of reinforced composite beams
Authors: Golushko S , Buznik V , Nuzhny G
Published: July 2019

This paper is devoted to modeling the properties of composite materials and reinforced composite beams. Mathematical relations describing the nonlinear elastic three-point bending of isotropic and reinforced beams with account of different strength and stiffness behavior in tension and compression are obtained. An algorithm for numerical solution of corresponding boundary-value problems is proposed and implemented. Results of numerical analysis were compared to acquired data for polymer matrix and structural carbon fiber reinforced plastics.
Spatial flow around an obstacle of a mixture of compressible viscous fluids
Authors: Zhalnina A A , Kucher N A
Published: July 2019

We present results on the existence and uniqueness of a strong solution to the inhomogeneous boundary value problem for equations of motion of viscous compressible fluids mixture with three spatial variables.
Research on the impact of aluminium alloys forming technology on the resistance to fatigue
Authors: Zakharchenko K V , Kapustin V I , Larichkin A Yu , Raevskaya G A
Published: July 2019

The research is devoted to the evaluation of the impact of aluminium alloys processing by pressure in creep on the resistance to fatigue. Using the developed accelerated, non-destructive method, the kinetics of the total deformations response (longitudinal and transverse components) during deformation of the sample with increasing loading is considered. In the frames of this method, the limiting stresses are determined, a conservative estimate of the endurance limit for V95 and V-1461 aluminium alloys (analog 7475) (Al-Zn-Mg-Cu) and (analog 2099) (Al-Cu-Li-Zn), respectively, is obtained. Thick plates (40 mm) are molded on the UFP-1M equipment in creep, and surface control is carried out. More than 80% of the plate’s area is molded with a deviation of less than 1 mm from the nominal size. The microstructure of V-1461 alloy is studied before and after forming, and fatigue tests are performed on samples made of molded panels. Analysis of the research results showed that for the V95 and V-1461 alloys, the selected characteristics of the technological process of forming and heat treatment do not impair the fatigue properties of the studied alloys.
Solving a two-dimensional problem of heat wave initiation by a boundary condition specified on a movable manifold
Authors: Kazakov A L , Spevak L F , Nefedova O A
Published: July 2019

A boundary value problem for a nonlinear degenerate parabolic equation is considered for the case of two spatial variables. The boundary condition is specified on a movable manifold a time-varying closed line. A heat wave problem solution is constructed on the basis of the boundary element method. The numerical solution algorithm is based on the change of variables, when the roles of the required function and the radial coordinate of the polar system interchange. The BEM solution of the problem obtained in new symbols enables the zero front of the heat wave to be determined. The further solution of the problem with the known zero front yields a solution to the initial problem. The algorithm is implemented as a program. An exact (generalized self-similar) solution is constructed, whereby the program is tested.
Formation of a cavitation zone behind a rarefaction wave front in a shock-loaded thin layer of a multiphase liquid
Authors: Kedrinskiy V K , Zhuravleva E S
Published: July 2019

The evolution of bubble cavitation behind the front of a converging cylindrical rarefaction wave in distilled water containing micro inhomogeneities is investigated numerically within the framework IKvanW mathematical model. The dynamics of the cavitation zone state is considered in a one-dimensional formulation with cylindrical symmetry. A thin liquid layer bounded by the free surface is loaded by a shock wave generated by a piston coaxial the axis of symmetry. As a result of shock wave reflection from free surface, a rarefaction wave converging toward the axis of symmetry is formed. The influence of the initial size of microbubbles, gas phase concentration, and parameters of shock wave loading on the dynamics offormation of the cavitation zone and its growth in the course of rarefaction wave focusing is analyzed.
Modeling of supersonic gas flows in radial nozzles
Authors: Kiselev S P , Kiselev V P , Zaikovskii V N
Published: July 2019

In the present paper, we report on the results of a study of supersonic gas flows in a radial nozzle. The pressurized gas is supplied into a circular channel, from which it then flows into the gap between two parallel disks (radial nozzle). It is shown that the structure of the jet ejected into ambient space substantially depends on the friction force acting on the gas flow from the side of the disks. The force of friction leads to a considerable decrease of the velocity of the supersonic jet, which acquires a fan-shaped form instead of being barrel-shaped. The numerical results proved to be in good agreement with experimental data.
Mathematical modeling of the generation of acoustic waves in a two-channel system
Authors: Kravchenko A S , Zhilin A A
Published: July 2019

The purpose of this study is to determine the influence of the diameter of a subsonic conical nozzle on the generation of acoustic waves in a two-channel system. Three-dimensional numerical simulation of flow in the duct of an actual device was performed. A complete picture of the flow generated in the acoustic-convective drying system of the Institute of Theoretical and Applied Mechanics, SB RAS, was obtained. The results of the study show that to maintain the amplitude-frequency characteristics of the workflow with increasing diameter of the subsonic conical nozzle, it is necessary to reduce the settling chamber pressure. The numerically simulated amplitude-frequency characteristics of the acoustic flow generated in the working section of the drying system are in satisfactory agreement with the results of physical experiments.
Reconstruction of tsunami source by a part of wave time series
Authors: Lavrentiev M , Marchuk An , Kuzakov D
Published: July 2019

Determination of the initial water surface displacement at tsunami source is an essential part for most of tsunami warning systems. Every additional minute is important for safety measures in case of a near field event. We propose to determine initial sea surface displacement at tsunami source by processing only a part of a measured wave profile – time series. The measured wave profile is an input data for initial wave shape determination algorithm. As is established, even a part of wave profile is enough to determine the wave key parameters with an appropriate precision. This paper provides numerical experiments that allow to determine the length of the necessary part of the measured profile. The results will help decreasing total time spent on tsunami forecast.
The modelling of transportation process in porous media: transportation through channels
Authors: Maryshev B S , Klimenko L S
Published: July 2019

The paper is devoted to the study of solute transport through the channels. Since the fluid velocity in the present system is very heterogeneous, the transfer of solute particles has nontrivial properties. Particles of solute hold near the walls, which leads to the time lag of a large number of particles from the main mass flow. As a result, the transport process may become anomalous. Such flows are possible in a porous medium, where the anomalous transport is frequently observed and confirmed by numerous experiments. Usually, such transport is associated with sticking of particles on the pore walls. In the present paper, we had shown that the slow flow in a viscous boundary layer itself can be a reason for the anomalous transport.
On Hiemenz flow of Maxwell incompressible viscoelastic medium
Authors: Moshkin N P
Published: July 2019

Steady axisymmetric flow of a viscoelastic incompressible fluid near the critical point of the plane surface is considered. Model of Maxwellian fluid with upper convected derivative in the rheological constitutive law is used. Velocity and extra stresses field are discussed for various Weissenberg numbers. The subclass of solutions in a stationary case is completely described. The asymptotic solutions for small Weissenberg numbers are compared to the solutions of the complete nonlinear problem. It is found that the fluid elasticity decreases the boundary layer thickness.
On integration of the system of MHD equations modeling wave processes in a rotating liquid with arbitrary magnetic Reynolds number
Authors: Peregudin Sergey , Peregudina Elina , Kholodova Svetlana
Published: July 2019

The paper is concerned with the dynamics of large-scale wave processes in a rotating layer of inviscid conducting incompressible liquid of variable depth. The problem is modelled as a system of partial differential equations with necessary boundary conditions. With the help of auxiliary functions, the above system of partial differential magnetohydrodynamic equations is reduced to a single scalar partial differential equation. An exact analytic solution of the small perturbation problem is obtained. It is shown that if the external magnetic field is parallel to the axis of rotation of the layer, then the magnetic field decays for finite values of the magnetic Reynolds number.
Nonlocal integro-differential problems of multi-dimensional wave processes
Authors: Popov N S
Published: July 2019

Nonlocal boundary-value problems for one-dimensional parabolic second-order equations with integral conditions on the lateral boundary are considered in the articles by A.I. Kozhanov. Higher-dimensional integro–differential equations of higher order with integral conditions on the lateral boundary were not studied earlier. The existence and uniqueness theorems of regular solutions are proven. The method of regularization and the method of continuation in a parameter are employed to establish solvability. In the present article we study integro-differential equations with integral conditions on the lateral boundary and prove existence theorems for regular solutions.
Nonlinear systems’ equilibrium points: branching, blow-up and stability
Authors: Sidorov Nikolai , Sidorov Denis , Li Yong
Published: July 2019

This article considers the nonlinear dynamic model formulated as the system of differential and operator equations. This system is assumed to enjoy an equilibrium point. The Cauchy problem with the initial condition with respect to one of the desired functions is formulated. The second function controls the corresponding nonlinear dynamic process. The sufficient conditions of the global classical solution’s existence and stabilisation at infinity to the equilibrium point are formulated. The solution can be constructed by the method of successive approximations. If the conditions of the main theorem are not satisfied, then several solutions may exist. Some solutions can blow-up in a finite time, while others stabilise to an equilibrium point. The special case of considered dynamic models are differential-algebraic equations which model various nonlinear phenomena in circuit analysis, power systems, chemical processes and many other processes.
Movement of external load over free surface of fluid in the ice channel
Authors: Sturova I V , Tkacheva L A
Published: July 2019

The solution of a steady three-dimensional problem for the wave disturbances induced by a local pressure distribution moving with uniform speed on open water lead between two semi-infinite floating ice sheets (ice channel) is presented. This external load simulates an air-cushion vehicle (ACV). The problem is formulated within the linear hydroelastic theory. The fluid is assumed to be inviscid and incompressible and its motion is potential. The ice sheets are treated as viscoelastic thin plates. The solution of this problem is constructed using the Fourier transforms and the Wiener-Hopf technique. The displacements of free surface and ice sheets are determined as well as strains in ice and wave resistance acting on ACV at various speeds of its movement: subcritical and supercritical ones relative to the minimum phase velocity of flexural-gravity waves (FGW) in fluid under an ice cover. Special attention is paid to the characteristics of edge waves. It is shown that for some values of load speed, ice thickness and external pressure, ice fracture near the edge is possible.
Nonlinear self-adjointness and conservation laws for some equation systems of two-phase media
Authors: Fedorov V E
Published: July 2019

The T B Anderson — R Jackson system of equations with the Stokes regime of wrapping around is considered, which describes in the isothermal case the dynamics of a mixture of gas and fine solid particles, taking into account the difference in velocities and the presence of the own particle phase pressure. The system includes the equations for the conservation of mass and momentum, written for each phase and supplemented by equations of state. The aim of the paper is the search of conservation laws for the system by means of N Kh Ibragimov’s nonlinear self-adjointness method. For this purpose it was found a substitutions family, which corresponds to the nonlinear self-adjointness of equations of the T B Anderson — R Jackson system. Using this result and known symmetries of the equations system, the series of conservation laws were derived. It is noted that the analogous results are valid for the Kh A Rakhmatulin system of equations of a mixture dynamics with one pressure.
Representation of solutions of boundary value problems for nonlinear evolution equations by special series with recurrently calculated coefficients
Authors: Filimonov M Yu
Published: July 2019

One of the analytical methods of presenting solutions of nonlinear partial differential equations is the method of special series in powers of specially selected functions called basic functions. The coefficients of such series are found successively as solutions of linear differential equations. The basic functions can also contain arbitrary functions. By using such functional arbitrariness allows in some cases, to prove the global convergence of the corresponding constructed series, and also allows us to prove the solvability of the boundary value problem for the Korteweg-de Vries equation. In the paper for a nonlinear wave equation a theorem on the possibility of satisfying a given boundary condition using an arbitrary function contained in the basic function is proved.
On stability of radial collapse of cylindrical shell filled with viscous incompressible fluid
Authors: Fursova D A , Gubarev Yu G
Published: July 2019

We study nonlinear stability of radial collapse of a cylindrical shell filled with a viscous incompressible fluid homogeneous in density. We have made the following assumptions: 1) there is a vacuum inside the shell, 2) there is the layer of compressed polytropic gas outside the shell, the gas serves as a product of instant detonation and causes nonzero constant pressure on the outer surface of the shell, 3) there is a vacuum beyond the layer of gas. By the direct Lyapunov method, we state the absolute stability of radial collapse of the viscous cylindrical shell relative to finite disturbances of the same type of symmetry. Namely, we construct a Lyapunov function satisfying all conditions of the Lyapunov first theorem (stability theorem) regardless of radial collapse mode. Thus, we confirm the Trishin hypothesis and prove that cumulation of the fluid kinetic energy during the radial collapse of the cylindrical shell near its geometric axis never originates.
The least squares collocation method for the biharmonic equation in irregular and multiply-connected domains
Authors: Shapeev Vasily , Golushko Sergey , Bryndin Luka , Belyaev Vasily
Published: July 2019

This paper reports new h-and p-versions of the least squares collocation method of high-order accuracy proposed and implemented for solving boundary value problems for the biharmonic equation in irregular and multiply-connected domains. This paper shows that approximate solutions obtained by the least squares collocation method converge with high order and agree with analytical solutions of test problems with high degree of accuracy. There has been a comparison made for the results achieved in this study and results of other authors who used finite difference and spectral methods.
On the application of SPH to solid mechanics
Authors: Shutov Alexey , Klyuchantsev Vladislav
Published: July 2019

We analyze the applicability of the smooth particle hydrodynamics (SPH) to the solution of boundary value problems involving large deformation of solids. The main focus is set on such issues as the reduction of artificial edge effects by implementing corrected kernels and their gradients, accurate and efficient computation of the deformation gradient tensor, evaluation of the internal forces from the given stress field. For demonstration purposes, a hyperelastic body of neo-Hookean type and a visco-elastic body of Maxwell type are considered; the formulation of the Maxwell material is based on the approach of Simo and Miehe (1992). For the implementation of constitutive relations efficient and robust numerical schemes are used. A solution for a series of test problems is presented. The performance of the implemented algorithms is assessed by checking the preservation of the total energy of the system. As a result, a functional combination of SPH-techniques is identified, which is suitable for problems involving large strains, rotations and displacements coupled to inelastic material behaviour. The accuracy of the SPH-computations is assessed using nonlinear FEM as a benchmark.