bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and photochemical response of Ru(ii)-coordinated double-decker silsesquioxane
Authors: Kucuk Asuman Celik , Matsui Jun , Miyashita Tokuji
Published: January 2018

A double-decker-silsesquioxane (DDSQ) based transition-metal-complex showed efficient energy-conversion owing to the assembling ability of the complexes in the DDSQ nano-building blocks.
Structural and impedance spectroscopy characteristics of BaCO3/BaSnO3/SnO2 nanocomposite: observation of a non-monotonic relaxation behavior
Authors: Salehizadeh S. A. , Chenari Hossein Mahmoudi , Shabani Mehdi , Ahangar Hossein Abbastabar , Zamiri Reza , Rebelo Avito , Kumar J. Suresh , Graça M. P. F. , Ferreira J. M. F.
Published: January 2018

A BaCO3/BaSnO3/SnO2 nanocomposite has been prepared using a co-precipitation method without adding any additives.
Static and dynamic electro-optical properties of liquid crystals mediated by ferroelectric polymer films
Authors: Garbovskiy Y. A. , Evans D. R. , Banerjee P. P. , Glushchenko A. V.
Published: January 2018

Liquid crystals (LC) can reveal the fractal dimension of multi-domain ferroelectric films (FF) while these films can control the switching time of FF–LC hybrids.
Dimeric cinchona ammonium salts with benzophenone linkers: enantioselective phase transfer catalysts for the synthesis of α-amino acids
Authors: Woo Seunga , Kim Yong-Gyun , Lim Baegeun , Oh Jiin , Lee Yeonji , Gwon Hyeri , Nahm Keepyung
Published: January 2018

Novel cinchona-alkaloid derived dimeric phase transfer catalysts (PTC) with benzophenone linkers and their α-alkylation of glycinate esters has been presented.
Facile synthesis of high-surface-area nanoporous carbon from biomass resources and its application in supercapacitors
Authors: Yao Yuechao , Zhang Qi , Liu Peng , Yu Liang , Huang Lin , Zeng Shao-Zhong , Liu Lijia , Zeng Xierong , Zou Jizhao
Published: January 2018

High-surface-area nanoporous carbon is obtained by direct pyrolysis of biomass resources without an activation process. An electrochemical test shows high capacitance.
Proinflammatory and osteolysis-inducing effects of 3D printing Ti6Al4V particles in vitro and in vivo
Authors: Li Cuidi , Jiang Chuan , Peng Mingzheng , Li Tao , Yang Zezheng , Liu Zhiyuan , Li Ning , Wang Chengtao , Dai Kerong , Wang Jinwu
Published: January 2018

Ti6Al4V printing particles have been recently used for fabricating orthopedic implants.
Eco-friendly polyethylene glycol (PEG-400): a green reaction medium for one-pot, four-component synthesis of novel asymmetrical bis-spirooxindole derivatives at room temperature
Authors: Hasaninejad Alireza , Beyrati Maryam
Published: January 2018

PEG-400 has been used for the synthesis of novel asymmetrical bis-spirooxindoles by the reaction of N-alkyl isatin, isatin derivatives, alkylmalonates and C–H activated carbonyl compounds in the presence of K2CO3 at room temperature.
Homogeneous and highly dispersed Ni–Ru on a silica support as an effective CO methanation catalyst
Authors: Liu Yi , Sheng Wei , Hou Zhanggui , Zhang Yi
Published: January 2018

The highly dispersed SiO2-supported nickel-based catalysts for CO methanation were prepared by an ethylene glycol (EG) modified wet-impregnation method.
Structure activity relationships in metal–organic framework catalysts for the continuous flow synthesis of propylene carbonate from CO2and propylene oxide
Authors: James Bryant R. , Boissonnault Jake A. , Wong-Foy Antek G. , Matzger Adam J. , Sanford Melanie S.
Published: January 2018

Studies of MOF catalysts under continuous flow have led to the discovery of a new catalyst for carbonation of propylene oxide.
Tunable seat belt behavior in nanocomposite interfaces inspired from bacterial adhesion pili
Authors: Dansuk Kerim C. , Keten Sinan
Published: January 2018

Chaperone-Usher pilus with catch bond adhesin—a bacterial biopolymer with the ability to attach to biotic/abiotic surfaces—can act as a “molecular seat belt” that has tunable cohesive strength and rate-responsive behavior.
Multifunctional NiTiO3nanocoating fabrication based on the dual-Kirkendall effect enabling a stable cathode/electrolyte interface for nickel-rich layered oxides
Authors: Xu Ming , Fei Linfeng , Zhu Si-Cong , Lu Wei , Lai Yanqing , Zhang Zhian , Lam Chi-Hang , Huang Haitao
Published: January 2018

A novel multifunctional NiTiO3nanocoating is fabricated based on the dual-Kirkendall effect, enabling high cyclability and rate capability for nickel-rich layered cathode material.
High performance Li–CO2 batteries with NiO–CNT cathodes
Authors: Zhang Xin , Wang Chengyi , Li Huanhuan , Wang Xin-Gai , Chen Ya-Nan , Xie Zhaojun , Zhou Zhen
Published: January 2018

A NiO/CNT composite was prepared by a solvothermal method. The composite was used as the air cathode for Li–CO2 batteries, and displayed great stability and high catalytic activity.
Anti-biofouling and antibacterial surfacesviaa multicomponent coating deposited from an up-scalable atmospheric-pressure plasma-assisted CVD process
Authors: Moreno-Couranjou Maryline , Mauchauffé Rodolphe , Bonot Sébastien , Detrembleur Christophe , Choquet Patrick
Published: January 2018

An efficient strategy was developed to produce dual anti-biofouling and antibacterial surfaces.
Facile construction of mechanically tough collagen fibers reinforced by chitin nanofibers as cell alignment templates
Authors: Huang Yao , Wang Yixiang , Chen Lingyun , Zhang Lina
Published: January 2018

Reconstituted collagen fibers with excellent mechanical performance were successfully fabricated with sodium alginate as coagulate and chitin nanofibers as reinforcing filler and applied as a fibroblast alignment templated scaffold.
Integration of antifouling and antibacterial properties in salt-responsive hydrogels with surface regeneration capacity
Authors: Zhang Dong , Fu Yanhong , Huang Lei , Zhang Yanxian , Ren Baiping , Zhong Mingqiang , Yang Jintao , Zheng Jie
Published: January 2018

A new design for a new multifunctional hydrogel that integrates antimicrobial, antifouling, and surface regeneration properties for antimicrobial applications.
Novel unsymmetrical squaraine-based small molecules for organic solar cells
Authors: Chen Yao , Wang Gang , Yang Lin , Wu Jianglin , Melkonyan Ferdinand S. , Huang Yan , Lu Zhiyun , Marks Tobin J. , Facchetti Antonio
Published: January 2018

New unsymmetrical squaraines for organic solar cells (OSCs) are synthesized without using highly toxic reagents. OSCs based on these squaraines exhibit an impressive open-circuit voltage of 0.92 V and power conversion efficiencies approaching 5%.
Thiacycle-fused benzo[1,2-b:4,5-b′]dithiophenes (BDTs): synthesis, packing, molecular orientation and semiconducting properties
Authors: Wang Chengyuan , Nakamura Hiroshi , Sugino Hiroyoshi , Takimiya Kazuo
Published: January 2018

Functionalization of benzo[1,2-b:4,5-b′]dithiophenes (BDTs) with thiacycles to selectively tune the packing, molecular orientation and semiconducting properties is systematically studied.
Low‐voltage ride‐through of a droop‐based three‐phase four‐wire grid‐connected microgrid
Authors: Sadeghkhani Iman , Hamedani Golshan Mohamad Esmail , Mehrizi‐Sani Ali , Guerrero Josep M.
Published: January 2018

The ability of riding through the grid disturbances can increase the integration of microgrids into the distribution system. Consequently, a grid‐connected microgrid should provide ancillary services such as low voltage ride‐through (LVRT) capability and reactive power support to sustain the power system operations during abnormal grid conditions. The objective of this paper is to propose an LVRT scheme that improves the power quality of the entire microgrid. The developed method is implemented as the controller of the interface voltage‐sourced converter (VSC) of a distributed energy resource and consists of primary and secondary control levels. The former includes the cascaded voltage and current control loops and the droop controller, while the latter controls the reactive power injection during the balanced/unbalanced voltage sags/swells. The proposed scheme is developed based on the independent control of each phase and does not require calculation of symmetrical components. Moreover, it can be employed in the VSC control systems with various reference frames and is effective for droop‐based grid‐connected microgrids with both single‐phase and three‐phase four‐wire configurations. The proposed strategy is implemented using the hierarchical control system and preserves the plug and play capability. Several case studies are presented to verify the effectiveness of the proposed strategy.
Non‐linear characteristics of an optically reconfigurable microwave switch
Authors: Pang Alexander W. , Bensmida Souheil , Gamlath Chris D. , Cryan Martin J.
Published: January 2018

A novel, high‐power optically controlled microwave switch is presented. The switch uses integrated illumination of a silicon superstate through a low‐loss glass substrate which reduces losses related to the plasma conductivity tail in the silicon. Numerical electromagnetic modelling is used to design the switch and good agreement between measured and simulated results has been achieved. The switch is then characterised using a two‐tone non‐linearity test at 2 GHz and a third‐order intercept point of +72 dBm is obtained with 10 W per tone.
Propagating wave in active region-loops, located over the solar disk observed by the Interface Region Imaging Spectrograph
Authors: Zhang B. , Hou Y. J. , Zhang J.
Published: January 2018

Aims. We aim to ascertain the physical parameters of a propagating wave over the solar disk detected by the Interface Region Imaging Spectrograph (IRIS).

Methods. Using imaging data from the IRIS and the Solar Dynamic Observatory (SDO), we tracked bright spots to determine the parameters of a propagating transverse wave in active region (AR) loops triggered by activation of a filament. Deriving the Doppler velocity of Si IV line from spectral observations of IRIS, we have determined the rotating directions of active region loops which are relevant to the wave.

Results. On 2015 December 19, a filament was located on the polarity inversion line of the NOAA AR 12470. The filament was activated and then caused a C1.1 two-ribbon flare. Between the flare ribbons, two rotation motions of a set of bright loops were observed to appear in turn with opposite directions. Following the end of the second rotation, a propagating wave and an associated transverse oscillation were detected in these bright loops. In 1400 Å channel, there was bright material flowing along the loops in a wave-like manner, with a period of ~128 s and a mean amplitude of ~880 km. For the transverse oscillation, we tracked a given loop and determine the transverse positions of the tracking loop in a limited longitudinal range. In both of 1400 Å and 171 Å channels, approximately four periods are distinguished during the transverse oscillation. The mean period of the oscillation is estimated as ~143 s and the displacement amplitude as between ~1370 km and ~690 km. We interpret these oscillations as a propagating kink wave and obtain its speed of ~1400 km s−1.

Conclusions. Our observations reveal that a flare associated with filament activation could trigger a kink propagating wave in active region loops over the solar disk.
Analysis of candidates for interacting galaxy clusters
Authors: Gonzalez Elizabeth Johana , de los Rios Martín , Oio Gabriel A. , Hernández Lang Daniel , Aguirre Tagliaferro Tania , Domínguez R. Mariano J. , Nilo Castellón José Luis , Cuevas L. Héctor , Valotto Carlos A.
Published: January 2018

Context. Merging galaxy clusters allow for the study of different mass components, dark and baryonic, separately. Also, their occurrence enables to test the ΛCDM scenario, which can be used to put constraints on the self-interacting cross-section of the dark-matter particle.

Aim. It is necessary to perform a homogeneous analysis of these systems. Hence, based on a recently presented sample of candidates for interacting galaxy clusters, we present the analysis of two of these cataloged systems.

Methods. In this work, the first of a series devoted to characterizing galaxy clusters in merger processes, we perform a weak lensing analysis of clusters A1204 and A2029/A2033 to derive the total masses of each identified interacting structure together with a dynamical study based on a two-body model. We also describe the gas and the mass distributions in the field through a lensing and an X-ray analysis. This is the first of a series of works which will analyze these type of system in order to characterize them.

Results. Neither merging cluster candidate shows evidence of having had a recent merger event. Nevertheless, there is dynamical evidence that these systems could be interacting or could interact in the future.

Conclusions. It is necessary to include more constraints in order to improve the methodology of classifying merging galaxy clusters. Characterization of these clusters is important in order to properly understand the nature of these systems and their connection with dynamical studies.
Laser contrast and other key parameters enhancing the laser conversion efficiency in ion acceleration regime
Authors: Torrisi Lorenzo
Published: January 2018

Measurements of ion acceleration in plasma produced by fs lasers at intensity of the order of 1018 W/cm2 have been performed in different European laboratories. The forward emission in target-normal-sheath-acceleration (TNSA) regime indicated that the maximum energy is a function of the laser parameters, of the irradiation conditions and of the target properties.In particular the laser intensity and contrast play an important role to maximize the ion acceleration enhancing the conversion efficiency. Also the use of suitable prepulses, focal distances and polarized laser light has important roles. Finally the target composition, surface, geometry and multilayered structure, permit to enhance the electric field driving the forward ion acceleration.Experimental measurements will be reported and discussed.
Ion energy distributions from laser-generated plasmas at two different intensities
Authors: Ceccio Giovanni , Torrisi Lorenzo , Okamura Masahiro , Kanesue Takeshi , Ikeda Shunsuke
Published: January 2018

Laser-generated non-equilibrium plasmas were analyzed at Brookhaven National Laboratory (NY, USA) and MIFT Messina University (Italy). Two laser intensities of 1012 W/cm2 and 109 W/cm2, have been employed to irradiate Al and Al with Au coating targets in high vacuum conditions. Ion energy distributions were obtained using electrostatic analyzers coupled with ion collectors. Time of flight measurements were performed by changing the laser irradiation conditions. The study was carried out to provide optimum keV ions injection into post acceleration systems. Possible applications will be presented.
Fabrication and characterization of porous opaque PMMA foils to be laser irradiated producing ion acceleration
Authors: Cutroneo Mariapompea
Published: January 2018

In this study, the effect of pore size in the opaque poly(methyl methacrylate) and its composition is investigated by optical measurements as well as Rutherford Backscattering Spectroscopy and Elastic Recoil Detection Analyses. The enhancement of the absorption coefficient induced by the presence of micrometric beads makes these porous thin foils high absorbent to IR radiation and suitable to be laser irradiated in order to generate a hot plasma rich in proton emission. The presented results indicate that the high optical transparency of PMMA foils can be strongly reduced by the presence of the micrometric acrylic beads and that the presence of high Z-metallic nanoparticles, such as gold, embedded in the polymer enhances the acceleration of emitted ions. The fabricated advanced targets have been irradiated by lasers at low intensity (Messina University) and at high intensity (PALS Research Infrastructure in Prague) generating plasma accelerating high proton yield and energy.
Emission of a low-power laser-induced vacuum discharge plasma in the EUV and SXR spectral ranges
Authors: Rupasov Alexander , Romanov Igor , Kologrivov Andrey , Paperny Viktor
Published: January 2018

X-ray spectral characteristics of a vacuum discharge plasma with the storage energy lower than 30 J initiated on an Al or a Fe cathode by a 1012 W/cm2 neodymium laser were studied in the 30 – 300 Å wavelength range. It is shown that both the spectral composition and intensity of radiation of a micropinch plasma produced in the cathode jet of the discharge are determined by parameters of the discharge and laser pulse. These parameters were optimized to achieve a regime in which a considerable part of radiation energy was concentrated in the long-wavelength band of the quasi-continuum (230 - 270 Å and 160 - 200 Å for Al and Fe, respectively), which makes this discharge a source of narrowband X-ray radiation.
Plasma Mirrors for Cleaning Laser Pulses from the Infrared to the Ultraviolet
Authors: Földes István B , Gilicze Barnabás , Kovács Zsolt , Szatmári Sándor
Published: January 2018

Ultrashort laser pulses are generally preceded by prepulses which - in case of high main pulse intensities - may generate preplasmas on solid surfaces, thus making the initial conditions for the interactions ambiguous. Infrared laser systems applied successfully, with high efficiency self-induced plasma mirrors for improving the contrast of the beam. Short wavelength laser beams however have a larger critical density in the plasma, and due to their deeper penetration the absorption is higher, the reflectivity, and the corresponding plasma mirror efficiency is lower. We show herewith that with carefully planned boundary conditions plasma mirrors can reach up to 70% efficiency even for KrF laser radiation. Our observations can be qualitatively explained by the classical Drude model. The high reflectivity allows the use of plasma mirrors even after the final amplification or before the last amplifier. Different arrangement proposals for its integration to our high power KrF laser system are given as well.
Plasma-laser ion discrimination by TOF technique applied to coupled SiC detectors.
Authors: Cavallaro Salvatore
Published: January 2018

The rate estimation of nuclear reactions induced in high intensity laser-target interaction (≥1016 W/cm2), is strongly depending on the neutron detection efficiency and ion charge discrimination, according to particles involved in exit open-channels. Ion discrimination is basically performed by means of analysis of pits observed on track detector, which is critically dependent on calibration and/or fast TOF devices based on SiC and diamond detectors. Last setup is used to determine the ion energy and to obtain a rough estimation of yields. However, for each TOF interval, the dependence of yield from the energy deposited in the detector sensitive region, introduces a distortion in the ion spectra. Moreover, if two ion species are present in the same spectrum, the discrimination of their contribution is not attainable. In this paper a new method is described which allows to discriminate the contribution of two ion species in the wide energy range of nuclear reactions induced in laser-target interactions. The method is based on charge response of two TOF-SiC detectors, of suitable thicknesses, placed in adjacent positions. In presence of two ion species, the response of the detectors, associated with different energy losses, can determine the ion specific contribution to each TOF interval.
On a ‘time’ reparametrization in relativistic electrodynamics with travelling waves
Authors: Fiore Gaetano
Published: January 2018

We briefly report on our method [23] of simplifying the equations of motion of charged particles in an electromagnetic (EM) field that is the sum of a plane travelling wave and a static part; it is based on changes of the dependent variables and the independent one (light-like coordinate ξ instead of time t). We sketch its application to a few cases of extreme laser-induced accelerations, both in vacuum and in plane problems at the vacuum-plasma interface, where we are able to reduce the system of the (Lorentz-Maxwell and continuity) partial differential equations into a family of decoupled systems of Hamilton equations in 1 dimension. Since Fourier analysis plays no role, the method can be applied to all kind of travelling waves, ranging from almost monochromatic to socalled “impulses”.
On the origin of negative target currents during laser ablation of polyethylene
Authors: Delle Side Domenico , Paola Caricato Anna , Krása Josef , Nassisi Vincenzo
Published: January 2018

The exposure of a target to a focused laser beam results in the occurrence of a time-varying current between the target itself and the grounded vacuum chamber. This current is composed by three distinct phases, namely the ignition phase, in which the laser pulse drives the electron emission, while electrons coming from the ground through the target holder balance the positive charge generated on the target. The active phase appears at post-pulse times and it is characterized by the presence of peaked structures in the time-resolved current, representing characteristics of the target composition. Lastly, the afterglow phase is determined by a current of electrons flowing from the target to the ground. During the active phase of the target current resulting from polymers ablation with an UV KrF laser, negative target current peaks are observed, whose origin is still unknown. We investigate the dependence of these current structures on the dimensions of the target, using ultra-high molecular weight polyethylene disks of different thickness.
Nanoparticles generated by laser in liquids as contrast medium and radiotherapy intensifiers
Authors: Restuccia Nancy , Torrisi Lorenzo
Published: January 2018

The synthesis of Au and Ag nanoparticles (NP) though laser ablation in liquids as a function the laser parameters is presented. Spherical NPs with diameter distribution within 1 and 100 nm were prepared by laser ablation in water. The nanoparticles characterization was performed using optical spectroscopy and electronic microscopy (SEM and TEM) measurements. Studies of the possible use of metallic nanoparticles as intensifier of diagnostics imaging contrast medium and absorbing dose from ionizing radiations in traditional radiotherapy and protontherapy are presented. Examples of in vitro (in tissue equivalent materials) and in vivo (in mice), were conducted thank to simulation programs permitting to evaluate the enhancement of efficiency in imaging and therapy as a function of the NPs concentrations and irradiation conditions.
Zinc oxide nanocolloids prepared by picosecond pulsed laser ablation in water at different temperatures
Authors: D’Urso Luisa , Spadaro Salvatore , Bonsignore Martina , Santangelo Saveria , Compagnini Giuseppe , Neri Fortunato , Fazio Enza
Published: January 2018

Zinc oxide with wide direct band gap and high exciton binding energy is one of the most promising materials for ultraviolet (UV) light-emitting devices. It further exhibits good performance in the degradation of non-biodegradable pollutants under UV irradiation. In this work, zinc oxide (ZnO) and zinc oxide/gold (ZnO/Au) nanocolloids are prepared by picosecond pulsed laser ablation (ps-PLA), using a Zn and Au metallic targets in water media at room temperature (RT) and 80°C. ZnO and Au nanoparticles (NPs) with size in the 10–50 nm range are obtained at RT, while ZnO nanorods (NRs) are formed when water is maintained at 80°C during the ps-PLA process. Au NPs, added to ZnO colloids after the ablation process, decorate ZnO NRs. The crystalline phase of all ZnO nanocolloids is wurtzite. Methylene blue dye is used to investigate the photo-catalytic activity of all the synthesised nanocolloids, under UV light irradiation.
Molybdenum oxide nanocolloids prepared by an external field-assisted laser ablation in water
Authors: Spadaro Salvatore , Bonsignore Martina , Fazio Enza , Cimino Francesco , Speciale Antonio , Trombetta Domenico , Barreca Francesco , Saija Antonina , Neri Fortunato
Published: January 2018

he synthesis of extremely stable molybdenum oxide nanocolloids by pulsed laser ablation was studied. This green technique ensures the formation of contaminant-free nanostructures and the absence of by-products. A focused picosecond pulsed laser beam was used to ablate a solid molybdenum target immersed in deionized water. Molybdenum oxide nearly spherical nanoparticles with dimensions within few nanometers (20-100 nm) are synthesized when the ablation processes were carried out, in water, at room temperature and 80°C. The application of an external electric field during the ablation process induces a nanostructures reorganization, as indicated by Scanning-Transmission Electron Microscopy images analysis. The ablation products were also characterized by some spectroscopic techniques: conventional UV-vis optical absorption, atomic absorption, dynamic light scattering, micro-Raman and X-ray photoelectron spectroscopies. Finally, NIH/3T3 mouse fibroblasts were used to evaluate cell viability by the sulforhodamine B assay
Research on Formation Mechanism of Dynamic Response and Residual Stress of Sheet Metal Induced by Laser Shock Wave
Authors: Feng Aixin , Cao Yupeng , Wang Heng , Zhang Zhengang
Published: January 2018

In order to reveal the quantitative control of the residual stress on the surface of metal materials, the relevant theoretical and experimental studies were carried out to investigate the dynamic response of metal thin plates and the formation mechanism of residual stress induced by laser shock wave. In this paper, the latest research trends on the surface residual stress of laser shock processing technology were elaborated. The main progress of laser shock wave propagation mechanism and dynamic response, laser shock, and surface residual stress were discussed. It is pointed out that the multi-scale characterization of laser and material, surface residual stress and microstructure change is a new hotspot in laser shock strengthening technology.
Gravitational Wave Polarizations in f (R) Gravity and Scalar-Tensor Theory
Authors: Gong Yungui , Hou Shaoqi
Published: January 2018

The detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory opens a new era to use gravitational waves to test alternative theories of gravity. We investigate the polarizations of gravitational waves in f (R) gravity and Horndeski theory, both containing scalar modes. These theories predict that in addition to the familiar + and × polarizations, there are transverse breathing and longitudinal polarizations excited by the massive scalar mode and the new polarization is a single mixed state. It would be very difficult to detect the longitudinal polarization by interferometers, while pulsar timing array may be the better tool to detect the longitudinal polarization.
Towards causal patch physics in dS/CFT
Authors: Neiman Yasha
Published: January 2018

This contribution is a status report on a research program aimed at obtaining quantum-gravitational physics inside a cosmological horizon through dS/CFT, i.e. through a holographic description at past/future infinity of de Sitter space. The program aims to bring together two main elements. The first is the observation by Anninos, Hartman and Strominger that Vasiliev’s higher-spin gravity provides a working model for dS/CFT in 3+1 dimensions. The second is the proposal by Parikh, Savonije and Verlinde that dS/CFT may prove more tractable if one works in so-called “elliptic” de Sitter space – a folded-in-half version of global de Sitter where antipodal points have been identified. We review some relevant progress concerning quantum field theory on elliptic de Sitter space, higher-spin gravity and its holographic duality with a free vector model. We present our reasons for optimism that the approach outlined here will lead to a full holographic description of quantum (higher-spin) gravity in the causal patch of a de Sitter observer.
Gravitational Collapse of Massless Fields in an Expanding Universe
Authors: Yoo Chul-Moon
Published: January 2018

Gravitational collapse of a massless scalar field with the periodic boundary condition in a cubic box is reported. This system can be regarded as a lattice universe model. The initial data is constructed for a Gaussian like profile of the scalar field taking the integrability condition associated with the periodic boundary condition into account. For a large initial amplitude, a black hole is formed after a certain period of time. While the scalar field spreads out in the whole region for a small initial amplitude. The difference of the late time expansion law of the lattice universe depending on the final fate of the gravitational collapse is discussed.
Experiments on Frequency Dependence of the Deflection of Light in Yang-Mills Gravity
Authors: Hao Yun , Zhu Yiyi , Hsu Jong-Ping
Published: January 2018

In Yang-Mills gravity based on flat space-time, the eikonal equation for a light ray is derived from the modified Maxwell’s wave equations in the geometric-optics limit. One obtains a Hamilton-Jacobi type equation, GLµv∂µΨ∂vΨ = 0 with an effective Riemannian metric tensor GLµv. According to Yang-Mills gravity, light rays (and macroscopic objects) move as if they were in an effective curved space-time with a metric tensor. The deflection angle of a light ray by the sun is about 1.53″ for experiments with optical frequencies ≈ 1014Hz. It is roughly 12% smaller than the usual value 1.75″. However, the experimental data in the past 100 years for the deflection of light by the sun in optical frequencies have uncertainties of (10-20)% due to large systematic errors. If one does not take the geometric-optics limit, one has the equation, GLµv[∂µΨ∂vΨcosΨ+ (∂µ∂vΨ)sinΨ] = 0, which suggests that the deflection angle could be frequency-dependent, according to Yang-Mills gravity. Nowadays, one has very accurate data in the radio frequencies ≈ 109Hz with uncertainties less than 0.1%. Thus, one can test this suggestion by using frequencies ≈ 1012 Hz, which could have a small uncertainty 0.1% due to the absence of systematic errors in the very long baseline interferometry.
Strong-field gravitational-wave emission in Schwarzschild and Kerr geometries: some general considerations
Authors: Rodríguez J.F. , Rueda J.A. , Ruffini R.
Published: January 2018

We have used the perturbations of the exact solutions of the Einstein equations to estimate the relativistic wave emission of a test particle orbiting around a black hole. We show how the hamiltonian equations of motion of a test particle augmented with the radiation-reaction force can establish a priori constraints on the possible phenomena occurring in the merger of compact objects. The dynamical evolution consists of a helicoidal sequence of quasi-circular orbits, induced by the radiation-reaction and the background spacetime. Near the innermost stable circular orbit the evolution is followed by a smooth transition and finally plunges geodesically into the black hole horizon. This analysis gives physical insight of the merger of two equal masses objects.
Hot Accretion onto Black Holes with Outflow
Authors: Park Myeong-Gu , Han Du-Hwan
Published: January 2018

Classic Bondi accretion flow can be generalized to rotating viscous accretion flow. Study of hot accretion flow onto black holes show that its physical charateristics change from Bondi-like for small gas angular momentum to disk-like for Keperian gas angular momentum. Especially, the mass accretion rate divided by the Bondi accretion rate is proportional to the viscosity parameter alpha and inversely proportional to the gas angular momentum divided by the Keplerian angular momentum at the Bondi radius for gas angular momentum comparable to the Keplerian value. The possible presence of outflow will increase the mass inflow rate at the Bondi radius but decrease the mass accretion rate across the black hole horizon by many orders of magnitude. This implies that the growth history of supermassive black holes and their coevolution with host galaxies will be dramatically changed when the accreted gas has angular momentum or develops an outflow.
Searches for magnetic monopoles with IceCube
Authors: Pollmann Anna
Published: January 2018

Particles that carry a magnetic monopole charge are proposed by various theories which go beyond the Standard Model of particle physics. The expected mass of magnetic monopoles varies depending on the theory describing its origin, generally the monopole mass far exceeds those which can be created at accelerators. Magnetic monopoles gain kinetic energy in large scale galactic magnetic fields and, depending on their mass, can obtain relativistic velocities.

IceCube is a high energy neutrino detector using the clear ice at the South Pole as a detection medium. As monopoles pass through this ice they produce optical light by a variety of mechanisms. With increasing velocity, they produce light by catalysis of baryon decay, luminescence in the ice associated with electronic excitations, indirect and direct Cherenkov light from the monopole track, and Cherenkov light from cascades induced by pair creation and photonuclear reactions. By searching for this light, current best limits for the monopole flux over a broad range of velocities was achieved using the IceCube detector. A review of these magnetic monopole searches is presented.
Higgs Portal Inflation with Fermionic Dark Matter
Authors: Aravind Aditya , Xiao Minglei , Yu Jiang-Hao
Published: January 2018

We discuss the inflationary model presented in [1], involving a gauge singlet scalar field and fermionic dark matter added to the standard model. Either the Higgs or the singlet scalar could play the role of the inflaton, and slow roll is realized through its non-minimal coupling to gravity. The effective scalar potential is stabilized by the mixing between the scalars as well as the coupling with the fermionic field. Mixing of the two scalars also provides a portal to dark matter. Constraints on the model come from perturbativity and stability, collider searches and dark matter constraints and impose a constraining relationship on the masses of dark matter and scalar fields. Inflationary predictions are generically consistent with current Planck data.
Non-minimal dark matter search in dark matter colliders
Authors: Shin Seodong
Published: January 2018

In the scenarios of dark matter (DM) with a non-minimal dark sector, we revisit a new detection strategy of observing two or three simultaneous signals from inelastic scattering of a boosted DM [1]. The relativistically incoming DM can scatter off inelastically to a heavier unstable dark sector particle which decays back in to the DM associated with visible Standard Model particles inside large volume neutrino detectors. The existence of the secondary procedure renders us to separate it from conventional neutrino scattering background. The relativistically incoming DM can come from the universe by the annihilation of heavy DM component in an inelastic boosted DM scenario or produced by the beam bombardments in fixed target experiments.
Wormholes in Einstein-Born-Infeld Gravity
Authors: Kim Jin Young , Park Mu-In
Published: January 2018

We introduce a new approach to construct wormholes without introducing exotic matters in Einstein-Born-Infeld gravity with a cosmological constant. Contary to the conventional approach, the throat is located at the place where the solutions can be joined smoothly. The metric and its derivatives are continuous so that the exotic matters are not needed there. The exoticity of the energy-momentum tensor is not essential to sustain the wormhole. We also present a method to check the stability of wormholes in the new approach.
Effect of DCT Image Compression on Eye Gaze Direction Detection
Authors: Dimililer Kamil , Kirsal Ever Yoney , Somturk Cansu , Ergun Fulden , Urun Guner , Kara Mehmet
Published: January 2018

The prediction of eye direction detection is the one of the popular research topic in human computer interaction area. This paper defines eye gaze detection by using Discrete Cosine Transform. Actually, determining the position of eyes is difficult to estimate the location of gaze which is more challenging. The database of the suggested research is organized as gaze directions of right, left and centre. The database is created with varied ages of images. In this paper, Discrete Cosine Transform has been applied to the image database and the effect of image compression is tested by using back propagation neural networks.
On attracting sets in artificial networks: cross activation
Authors: Sadyrbaev Felix
Published: January 2018

Mathematical models of artificial networks can be formulated in terms of dynamical systems describing the behaviour of a network over time. The interrelation between nodes (elements) of a network is encoded in the regulatory matrix. We consider a system of ordinary differential equations that describes in particular also genomic regulatory networks (GRN) and contains a sigmoidal function. The results are presented on attractors of such systems for a particular case of cross activation. The regulatory matrix is then of particular form consisting of unit entries everywhere except the main diagonal. We show that such a system can have not more than three critical points. At least n–1 eigenvalues corresponding to any of the critical points are negative. An example for a particular choice of sigmoidal function is considered.
Analysis of the susceptibility in a fluid system with Neumann – plus boundary conditions
Authors: Djondjorov Peter , Vassilev Vassil , Dantchev Daniel
Published: January 2018

The behaviour of the local and total susceptibilities of a fluid system bounded by different surfaces is studied in the framework of the Ginsburg-Landau Ising type model. The case of a plain geometry, Neumann-infinity boundary conditions under variations of the temperature and an external ordering field is considered. Exact analytic expressions for the order parameter, local and total susceptibilities in such a system are presented. They are used to analyse the phase behaviour of fluids confined in regions close to the bulk critical point of the respective infinite system.
Study of soccer ball flight trajectory
Authors: Javorova Juliana , Ivanov Anastas
Published: January 2018

In this paper the trajectories of a soccer ball for the most important kicks in the football game - a corner kick and a direct free kick are studied. The soccer ball is modelled as an ideal rigid hollow spherical body with six degrees of freedom, which performs a general motion in an immovable air environment with constant parameters. The ball 3D orientation is determined by the three Cardan angles. The aerodynamic forces and moments with which the air environment acts to the ball are taken into account. Two of the most dangerous areas of the football goal are defined. Differential equations which describe the motion of the soccer ball are solved numerically by MatLab-Simulink.
Dynamical behaviour of a compound elastic pendulum
Authors: Nikolov Svetoslav , Zaharieva Daniela
Published: January 2018

The aim of the paper is a comprehensive study of the compound elastic pendulum (CEP) with two degrees of freedom to point out the main complex (chaotic) dynamics that it can exhibit. The simplest way to find complex behavior in a nonintegrable Hamiltonian system is firstly to look for homoclinic (heteroclinic) orbit(s). Here, under suitable assumptions, we detect the existence of a homoclinic orbit of CEP and present the equation for it. Moreover, we show that for any value of the small parameter the system has a hyperbolic periodic orbit, whose invariant manifolds intersect themselves transversally.
Examination of the possibility of transborder pollution in the days with registered excee-dances of pollutant dust in the city of Ruse, Bulgaria
Authors: Stefanova Antoaneta , Zheleva Ivanka , Filipova Margarita , Tsvetkova Irina
Published: January 2018

The presented study of the PM10 concentrations in the atmosphere ground layer emitted from industrial sources in the Industrial zone in the city of Ruse in the days with exceedances for this pollutant is aimed to determining the possibility of cross-border BG-RO PM10 contamination. Climatic conditions measured in these days with PM10 exceedances in January 2017 are also taken into account in Jet Gauss model and in the Langrageo-statistical approach for describing the turbulent diffusion. The results show that the PM10 pollutant from the investigated sources in industrial zone in Ruse is reaching the territory of Republic of Romania with low concentrations and have no potential for impact on air quality in the cross-border area.
Statistical modeling of particle mater air pollutants in the city of Ruse, Bulgaria
Authors: Veleva Evelina , Zheleva Ivanka
Published: January 2018

This paper is devoted to examine the PM10 and PM2.5 pollution in Ruse region, Bulgaria. It is a continuation of our previous work [1] where we presented a statistical analysis and modelling of the level of PM10 air pollution in Ruse using data from one of two monitoring stations (station 2) in the city. Now in this paper we present statistical analysis of the level of PM10 pollutant on the basis of data from the another monitoring station (station 1). The measurements cover the period since 2015 up to now. The results from analysis and modelling of PM2.5 air pollutant are also presented and commented in the paper.
Study of the mechanical properties of single- layer and multi-layer metallic coatings with protective-decorative applications
Authors: Cherneva Sabina , Guergova Desislava , Iankov Roumen , Stoychev Dimitar
Published: January 2018

Single thin coating of matt nickel (Nimat), a mirror bright copper (Cubright), a mirror bright nickel (Nibright) and their combinations were electrochemically deposited on brass substrate with thickness 500 μm. The basic aim was electrodeposition of two-layer Cubright/Nimat and Nibright/Cubright systems, and three-layer Nibright Cubrigh/Nimat system, which are among the most widely applied protective and decorative systems in light and medium operating conditions of corrosion. The thicknesses of the obtained films varied from 1 μm to 3.25 μm. They were investigated via nanoindentation experiments, in order to characterize their basic physical and mechanical characteristics, related with their good adhesion and corrosion protective ability, as well as ensuring the integrity of the system “protective coating/substrate” to possible mechanical, dynamic and/or thermal stresses. As a result, load-displacement curves were obtained and indentation hardness and indentation modulus were calculated using the Oliver & Pharr approximation method. The dependence of the indentation modulus and the indentation hardness on the depth of the indentation, surface morphology and structure of the obtained coatings, their texture and surface roughness were investigated too. The obtained results showed that the three-layer Nibright/Cubright /Niimat/CuZn37 system has highest indentation modulus and indentation hardness, following by two-layer Nibright/Cubright system and single layer coatings.
Indentation hardness and modulus of electrochemically deposited triple protective-decorative Cu-Ni-Cr system
Authors: Datcheva Maria , Chalakova Gergana , Nikolov Antonio , Dimitrova Rayna , Iankov Roumen , Kamburov Valentin , Guergova Dessislava , Stoyanova Emilia , Stoychev Dimitar
Published: January 2018

With respect to the corrosion-protective and decorative characteristics of the Cu-Ni-Cr systems the advance of the technology resulted in products covering the required technical and economic norms and indicators. However, the knowledge about the mechanical characteristics such as elastic and plastic properties of the individual layers and the whole multilayered system is still sparse. The objective of this study is to obtain by means of nanoindentation experiments the mechanical characteristics of standard triple Cu-Ni-Cr coating system whose morphology, structure, texture, composition, and the copper-, nickel- and chrome-layer thickness are predefined. A series of nanoindentation tests in vertical direction to the layered coating and in the lateral direction (along a vertical cut) is analyzed to assess the changes of the mechanical properties of the investigated system in depth and along the layer as well as at layer-to-layer and layer-to-substrate interfaces.
Some considerations on modelling and homogenization of multiphase light alloys
Authors: Parashkevova Ludmila
Published: January 2018

The modelling strategies aimed to access the thermo-mechanical behavior of the up-to date light and superlight alloys should take into account characteristics of each particular manufacturing technology. In the present study the light alloys and materials of high porosity are regarded as multiphase composites for which the content of embedded phases is predominant. A new modification of differential effective medium theory is presented accounting for inclusion’s size effects. The applied approach is based on the size-sensitive dilute homogenization procedure with Cosserat material matrix. Numerical examples for elastic properties of a close cell foam materials with different Poisson’s ratio are presented and discussed.
Viscous flow around spherical particles in different arrangements
Authors: Kotsev Tsvetan
Published: January 2018

Viscous flow past two or more spherical particles in direction parallel or perpendicular to the line connecting the body centers is studied numerically at Reynolds number up to 200. The FEM is used to simulate the flow structure for different arrangements and diameters of the spheres. The drag and lift coefficients are calculated as functions of the flow velocity and the distance between the spheres. The results show the downstream spheres face a reduced drag compared to a single sphere and that the upstream one changes its drag coefficient according to the distance between the bodies. In the case of side by side arranged spheres, an effect of repulsion exists up to a certain separation distance and after that a weak pulling effect appears. A configuration of three (or more) spherical particles arranged in „V“ formation was examined where one body is set to be a leading and the others are located symmetrically up and down behind it. The flow characteristics are studied when the angle behind the leading sphere vary from 40° to 180°. This configuration supposes stronger interaction between the bodies due to the influence of the wakes behind the first sphere to the downstream ones and to the lift forces appeared.
Aerodynamic characteristics and flow field of delta wings with the canard
Authors: Mochizuki Saya , Yamada Gouji
Published: January 2018

Now, many kinds of explorations for outer planets have been proposed around the world. Among them Mars attracts much attention for future exploration. Orbiters and landers have been used for Mars exploration. Recently as a new exploration method, the usage of an airplane has been seriously considered and there are some development projects for Mars airplane. However, the airplane flying on the Earth atmosphere cannot fly on the Mars atmosphere, because atmospheric conditions are much different each other. Therefore, we focused on the usage of the airplane with unfolding wings for Mars exploration. These unfolding wings are designed as delta wings. However, delta wings do not have enough aerodynamics characteristics in a low speed region. In this study, to improve the aerodynamic characteristics of delta wings, we have proposed the usage of canard wings. The purpose of this study is to examine the effectiveness of canard wings to improve aerodynamic characteristics in a low speed region. CFD analysis is performed using four wing models with different canard shapes. The result shows that the usage of canards is effective to improve aerodynamic characteristics of delta wings in a low speed region. In addition, increasing lift coefficient is possible by changing the shape of canards.