bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrocochleography: New Uses for an Old Test and Normative Values
Authors: Ferraro John A. , Kileny Paul R. , Grasel Signe S.
Published: October 2019

Purpose

This article combines the results of 3 studies that were presented at the HeAL 2018 Conference in Lake Como, Italy, in June 2018. Each study involved electrocochleography (ECochG), a neurodiagnostic evaluation that has been used clinically for over 80 years but whose applications continue to expand. The 1st study describes recent research wherein ECochG was recorded from asymptomatic subjects who were siblings or offspring of patients with a confirmed diagnosis of Ménière's disease (MD). Our results provide evidence that ECochG may be helpful in not only diagnosing MD but also predicting it as well. Second, case studies are described where ECochG was important in both diagnosing superior semicircular canal dehiscence and monitoring the repair of this condition during surgery. Finally, although ECochG has been practiced clinically for over 8 decades, the protocols for recording, measuring, and interpreting the electrocochleogram continue to lack standardization among clinicians and scientists. We thus present normative data for some of these features based on noninvasive recordings made from the tympanic membrane from 100 normal hearing subjects.

Conclusions

Although the primary use of ECochG continues to be in the diagnosis of MD, we report on 2 additional clinical applications for this important test of inner ear/auditory nerve function. First, a preliminary study on a small sample of subjects indicates that ECochG may also be useful in predicting MD prior to the onset of symptoms in individuals who may be genetically predisposed to developing it. Second, through a series of case studies, we demonstrate how ECochG is used to help diagnose superior semicircular canal dehiscence and monitor the status of the inner ear during the surgical repair of this condition. Finally, normative values for clinically important components of the electrocochleogram based on tympanic membrane recordings have been established from a large sample of subjects.
Speech-Language Pathologists' Comfort Providing Intervention to Children With Traumatic Brain Injury: Results From a National Survey
Authors: Pelatti Christina Yeager , Bush Erin J. , Farquharson Kelly , Schneider-Cline Whitney , Harvey Judy , Carter Mary W.
Published: October 2019

Purpose

This exploratory study examined speech-language pathologists' (SLPs) clinical experience and work environment characteristics impacting comfort with providing intervention to children with traumatic brain injury (TBI).

Method

This study included 162 SLPs who responded to a national survey about their comfort providing intervention to children with TBI, clinical experience (i.e., years of experience treating children with TBI, TBI preprofessional training and professional development, and licensure/credentialing), and work environment (i.e., work setting, caseload size, geographic location).

Results

Findings from latent class analysis revealed 3 distinct groups of SLPs based on their comfort with providing services to children with TBI: those with low comfort, moderate comfort, and high comfort. Further analyses revealed statistically significant differences across the 3 groups in the areas of years of experience treating children with TBI, professional development, work setting, TBI caseload size, and geographic location.

Conclusions

Our findings reveal that most SLPs feel comfortable providing intervention to children with TBI; however, differences in characteristics across groups suggest that specific steps can be taken to ensure increased comfort for all SLPs working with this population. Practicing SLPs may increase their level of comfort through professional development and hands-on, mentored experience with TBI. Efforts such as these may influence the quality of service provision and expand the population of SLPs who feel comfortable treating children with TBI. Future research is needed to further examine how comfort and SLP characteristics directly impact the quality of speech and language intervention and long-term outcomes of children with TBI.
Going With the Flow: An Examination of Entrainment in Typically Developing Children
Authors: Wynn Camille J. , Borrie Stephanie A. , Pope Kiersten A.
Published: October 2019

Purpose

Conversational entrainment is the tendency for individuals to modify their behavior to more closely converge with the behavior of their communication partner and is an important aspect of successful interaction. Evidence of entrainment in adults is robust, yet research regarding its development in children is sparse. Here, we investigate the emergence of entrainment skills in typically developing children.

Method

Data were collected from a total of 50 typically developing children between the ages of 5 and 14 years. Children participated in a quasiconversational paradigm with a virtual interlocutor. Speech rate of the interlocutor was digitally manipulated to produce fast and slow speech rate conditions.

Results

Data from the fast and slow conditions were compared using linear mixed models. Results indicated that children, regardless of age, did not alter their speech to match the rate of the virtual interlocutor.

Conclusions

Findings suggest that entrainment in children may not be as robust as entrainment in adults and therefore not adequately captured with the current experimental paradigm. Modifications to the current paradigm will help identify a methodology sufficiently sensitive to capture the speech alignment phenomenon in children and provide much needed information regarding the typical stages of entrainment development.
DepthTiling: A novel way to increase visual SLAM performance in featureless environments
Authors: Altuntaş N. , Amasyalı M.F.
Published: October 2019

The common problem of visual simultaneous localisation and mapping systems is to suffer from featureless environments. It is possible for all environments to have such featureless situations; even though most of the mapped areas contain sufficient textures. This Letter brings a new approach using not only RGB values of the objects but also their positions in the map for feature extraction in order to decrease odometry loss in such situations. DepthTiling recolours RGB image using associated depth data. The experiments give promising results to increase the capability of visual odometry tracking. This study shows that it is possible to increase number of features using related depth data when RGB images are insufficient.
Efficient loose image content classifier
Authors: Zhang Huiqing , Sun Luyu , Gu Ke , Liu Yutao , Tang Lijuan
Published: October 2019

In this Letter, the authors put forward a loose classifier to determine whether the content of a given image belongs to screen content or natural scene. In the proposed classifier, they first extract 14 features by means of three typical histograms, the greyscale image histogram, local binary pattern histograms, and histograms of the oriented gradient, respectively. Then, in the second step, they try to build a non‐linear mapping, with stacking‐based integrated learners, from extracted features to the classification label. Experimental results prove that the effectiveness of their proposed method as compared with popular algorithms.
FRSIW filter
Authors: Huang Liwen , Cha Hao
Published: October 2019

A novel folded ridge substrate integrated waveguide (FRSIW) is proposed, and the design of a higher‐order‐mode bandpass filter in FRSIW technology is presented. The FRSIW is proposed by folding a typical RSIW. It has a size nearly half of the conventional RSIW while keeping a relatively wide single‐mode bandwidth. A higher‐order‐mode bandpass filter is designed and tested based on the TE201 mode in the FRSIW. The measured frequency responses show that the proposed FRSIW filter has good selectivity, low loss and compact size.
Blind watermark detection based on K‐S test in radio‐frequency signals
Authors: Xie Xu , Xu Zhengguang
Published: October 2019

Radio‐frequency (RF) watermarking is a new technology for physical layer authentication, whose carrier is not the traditional multimedia signals but the digital signals. In the available literature, the watermark detectors are based on the cooperative environment, where the parameters of the watermark signal are known to the receiver. In this Letter, a blind watermark detection scheme with Kolmogorov–Smirnov (K‐S) test is presented. The simulation results show that the proposed scheme is effective.
Data driven optimisation of small cell depolyment
Authors: Chen Bozhong , Zhang Zitian , Chu Xiaoli , Zhang Jie
Published: October 2019

Increasingly popular online social networks contribute to the massive growth in mobile traffic. The authors find that social network data, which is easier to obtain than carrier data, can be used to optimise the deployment of small base station (SBS). In this Letter, the authors propose a framework based on analysing social network data to identify and cluster mobile traffic hot‐spots by using the density‐based spatial clustering of applications with noise algorithm. By comparing the clustered hot‐spots with the existing macro base stations' locations, they identify where additional SBSs need to be deployed and show that such deployment can effectively improve the quality of service. The proposed simulation results show that the SBSs deployment around hot‐spot has relatively better user received signal power on mobile communication network than random SBS deployment following the normal distribution or the Poisson distribution.
Visualising ganglion cell layer based on image entropy optimisation for adaptive contrast enhancement
Authors: Han J.‐H. , Cha J.
Published: October 2019

Optical coherence tomography cannot easily be used for visual identification of the ganglion cell layer (GCL) for diagnosing retinal diseases owing to the extremely low image contrast between adjacent layers. To solve this problem, the authors used a limit‐clipping optimisation method along with the image entropy to enhance the image contrast of targeted layers. As a result, the GCL was successfully extracted using an intelligent tracking system without impacting the segmentation of other retinal layers and image morphology. The segmentation results were evaluated through comparisons with manual segmentation results provided by clinical experts. The results of this study should help realise simple and efficient discrimination of important retinal layers for the early diagnosis of glaucoma.
Efficient behaviour specification and bidirectional gated recurrent units‐based intrusion detection method for industrial control systems
Authors: Khan Izhar Ahmed , Pi Dechang , Yue Pan , Li Bentian , Khan Zaheer Ullah , Hussain Yasir , Nawaz Asif
Published: October 2019

Intrusion detection is a prevailing area of research for several years, and numerous intrusion detection systems have been proposed for industrial control systems (ICS). In recent ages, the attacks like seismic net, duqu and flame against ICS infrastructures have instigated great harm to nuclear infrastructures and precarious facilities in several nations. The authors outline an approach to detect intrusions/anomalies in ICS. A method is presented to detect intrusions in real‐time and automatically. The existing techniques are normally designed for open systems and protocols, that lacks adequate generalisation and resistance to acclimate to other networks, and they have either short detection rate or tall rate of false positive. This Letter presents a network packet contents behaviour and bidirectional Gated Recurrent Units‐based method to detect intrusions in a timely and efficient manner. The method has proven a robust method of classifying intrusions/anomalies in a proficient way. Through extensive evaluation on an actual huge scale dataset spawned from SCADA‐based gas pipeline network, the proposed method shows significant performance enhancement and outclasses the standard state‐of‐the‐art methods with 98.68% rate of accuracy. Moreover, it is also able to detect zero‐day (unseen) attacks.
Design and implementation of microstrip dual‐band filtering power divider using square‐loop resonator
Authors: Mirzaei M. , Sheikhi A.
Published: October 2019

This Letter presents a dual‐band filtering power divider (FPD) by employing square‐loop resonator loaded by open stubs. The even‐ and odd‐mode equivalent circuits of the proposed resonator are analysed and design equations are derived. For demonstration, the power divider (PD) is fabricated and measured. The simulated results of the PD not only show a good selectivity but also it does good isolation. Finally, the comparisons of the measured and simulated results of the dual‐band FPD are presented, which are in good agreement. The measured results show that the dual‐band FPD has better than −30/−36 dB isolation, −16.5/−18 dB return loss, and −3.9/−4.0 dB insertion loss at centre frequencies of 3.1 and 5.3 GHz, respectively.
Fast coherent integration method for moving target detection with random PRI variation
Authors: Zhu Weiqiang , Liu Zhiling , Xu Huajian
Published: October 2019

This Letter addresses the coherent integration problem for the moving target detection in a pulse repetition interval (PRI)‐staggered radar system. Due to the random sampling, the complex coupling effects between range and azimuth will severely degrade the target parameter estimation and coherent integration performance. To deal with this issue, a fast coherent integration detection method with random azimuth sampling is proposed, where range migration is firstly compensated by applying the range‐frequency reversal transform. Then, the random phase fluctuation caused by the staggered PRI can be efficiently removed by applying the non‐uniform FFT technique. Finally, a moving target can be well focused. Simulated results are provided to validate the effectiveness of the proposed algorithm.
Surface‐modification effect of MgO nanoparticles on the electrical properties of polypropylene nanocomposite
Authors: Hu Shixun , Zhou Yao , Yuan Chao , Wang Wei , Hu Jun , Li Qi , He Jinliang
Published: October 2019

Polypropylene (PP)‐based nanocomposite is a promising insulation material for recyclable high‐voltage direct current (HVDC) cables, where the coupling agent plays an important role. In this study, four silane coupling agents with different alkyl chain groups (methyl, propyl, octyl, and octadecyl) were used to surface‐modify magnesium oxide (MgO) nanoparticles. The surface‐modification effect on the electrical properties of PP/MgO nanocomposites was investigated. The results show that surface‐modified nanoparticles introduce quantities of deep traps, whose quantity increases as the alkyl chain length increases. The similar tendency also occurs on DC volume resistivity. All these nanocomposites show remarkable space charge suppression ability and improved DC breakdown strength. Among them, the nanocomposites with octyl‐modified MgO show the best electrical properties, which could be attributed to the introduction of a large quantity of deep traps. The work may give a reference for the selection of coupling agents in PP‐based nanocomposite insulation material for HVDC cable.
Mode transition induced by back‐breakdown of the gliding arc and its influence factors
Authors: Zhang Ruobing , Huang Haochen , Yang Tianshu
Published: October 2019

Gliding arc is a mostly used non‐equilibrium plasma generation method whose characteristic is affected by the back‐breakdown phenomenon. Mode transition induced by back‐breakdown of the gliding arc is studied in this work and effects of gas flow rate, applied voltage, electrode parameters on mode transition were studied. Experimental results show that there are two typical modes during the development of the gliding arc. Mode A comprises periodicitical development of the arc from the minimum gap breakdown to the longest extinguishment, while the arc in mode B continues to produce a back‐breakdown at the ends of the electrodes. As the flow rate descends, the gliding arc gradually changes from mode A to B. It is the decrease of the arc velocity caused by lower flow rate leads to the occurrence of back‐breakdown, which generates mode B. Smaller electrode opening angle, shorter length and wider minimum gap reduce the gliding speed, so that arc is more likely to enter mode B. As the applied voltage is increased, enhancing of the electric field strength on the breakdown path of the back‐breakdown and thickening of the arc's diameter allow the gliding arc to enter mode B at a higher arc speed.
Review about PD and breakdown induced by conductive particles in an insulating liquid
Authors: Pan Cheng , Tang Ju , Chen George , Zhang Yongze , Luo Xinyu
Published: October 2019

In insulating liquid, a conductive particle becomes charged through the interaction with a conductor exposed to an applied field. Then, it migrates in the action of both electric field and fluid and causes the enhancement of local field when it is in proximity of the conductor with opposite polarity. The enhancement will lead to partial discharge (PD) and may even ignite full gap breakdown in special cases. This study reviews comprehensive researches relevant to these topics. In the first place, several theoretical methods about how to obtain the charges held by a conductive particle with known potential are introduced, so are experimental methods. Then, forces acting on the charged particle in liquid are classified, and its migration characteristics, as well as influential factors, are described. Subsequently, PD and breakdown mechanisms of liquid initiated by conductive particles are presented. The latter involves two cases: electric‐field enhancement when the particle concentration is low and bridging phenomenon when it is high. At last, two important, but frequently ignored factors, i.e. dielectric barrier and oil flow, are highlighted, and the authors’ suggestions for future work are put forward.
Extra transient block for virtual synchronous machine with better performance
Authors: Pan Rongcai , Sun Peide
Published: October 2019

An extra transient block (ETB) for virtual synchronous machine (VSM) that is able to provide extra transient damping and adjust transient inertial to better stabilise the frequency of the VSM in a shorter time during transient period without altering the steady‐state performance is proposed in this study. The ETB uses extra parallel series lead‐lag blocks to get the transient frequency output to make the stability of the VSM less intensive to the parameter design of the virtual inertial and damping coefficient so that an easier parameter design method can be used. In other words, this method helps to solve the contradiction between dynamic response and stable performance, especially when the damping coefficient cannot be freely modified to increase damping for a large inertial value because of the mutual dependence between damping coefficient and droop coefficient caused by the use of inner reference frequency. Moreover, a simplified method for the parameter design of the ETB is proposed and the small‐signal model of the ETB‐based VSM is also derived. After that, the power coupling situation is analysed and comparisons with other control strategies are presented. Furthermore, time‐domain simulation results are demonstrated to verify the effectiveness of the proposed method.
TNEP of meshed HVDC grids: ‘AC’, ‘DC’ and convex formulations
Authors: Dave Jay , Ergun Hakan , An Ting , Lu Jingjing , Van Hertem Dirk
Published: October 2019

With the increased utilisation of high‐voltage direct current (HVDC) links in power systems, it is necessary to upgrade the traditional ac grid focused transmission network expansion planning (TNEP) problem to accommodate multiple HVDC links and even HVDC grids. This study proposes a non‐linear formulation for the TNEP problem of dc grids and derives two relaxations of the problem: the linear approximation, the second‐order cone convex relaxation as a branch flow model. The presented formulations allow both monopolar and bipolar configurations, and this as point‐to‐point connections and HVDC grids as expansion candidates. The three formulations are examined on various test cases and compared for their accuracy and computational speed.
Method to design saturated iron‐core fault current limiters
Authors: Baferani Mohamadreza Arab , Fahimi Navid , Shayegani Amir Abbas
Published: October 2019

Fault current limiter (FCL) is a kind of device with current‐dependent impedance that has low impedance in normal state of power system, and high impedance during fault condition. Among all classes of FCLs, the saturated iron‐core FCL (SICFCL) is practically the most favourable one nowadays. In this study, a numerical method for design and cost optimisation of SICFCLs is presented. It uses a set of constraints to ensure the desirable operation of the SICFCL based on its electrical and magnetic characteristics. For numerical calculations and optimisations, GAMS software has been used. Suitability of the method is approved by design, simulation and test of a 3500 VA prototype. Magnetic field distributions are simulated using COMSOL Multiphysics and performance of the designed SICFCL is evaluated in a power system hardware model. Simulation and experimental results show the satisfying agreement with predicted results by the proposed numerical method.
Coherent‐like integration for PD radar target detection based on short‐time Fourier transform
Authors: Zhang Xiao‐Wei , Zuo Lei , Yang Dong‐Dong , Guo Jian‐Xin
Published: October 2019

In the context of white complex Gaussian noise, this study presents one constant false‐alarm rate mono‐pulse detector for both the narrowband and wideband pulse‐Doppler (PD) radars. To this end, coherent‐like integration is proposed to improve the signal‐to‐noise ratios of one radar echo. The PD radar returned signals are first performed by stretch processing. Stretched signals are analysed by short‐time Fourier transform (STFT) in the time–frequency representation. Coherent‐like integration is then utilised to operate the two‐dimensional (2D) STFT matrix and the new 2D matrices after coherent‐like integration are decomposed to obtain singular values. Finally, the largest singular value, which is assumed to be corresponding to an isolated scatterer for narrowband PD radars (dominate scatterer for wideband PD radars) is selected as the test static to be compared with the detection threshold. Since the new detector is not highly sensitive to the target motion, it can solve the detection problem of the high‐speed manoeuvring target. Furthermore, the experiments based on raw data are conducted to illustrate the performance of the proposed detector.
Proposal of multiple access FMCW radar for inter‐radar interference avoidance
Authors: Kurosawa Mikihiro , Nozawa Takuya , Umehira Masahiro , Wang Xiaoyan , Takeda Shigeki , Kuroda Hiroshi
Published: October 2019

Inter‐radar interference will be a crucial problem when a number of frequency modulated continuous wave (FMCW) radars are densely deployed in future, since it can cause miss detection and false detection of the target due to wideband interference and narrowband interference. One of the approaches to solve this problem is to introduce a multiple access technique for automotive radars, e.g. carrier sense multiple access used in wireless LAN to avoid packet collision. This study proposes multiple access FMCW radar which can avoid both narrow‐band and wideband interference assuming all of the FMCW radars have the same design parameters. It also, proposes a carrier sense technique as a key technique for multiple access FMCW radar and evaluates the carrier sense performance by computer simulations.
Dynamic partial reconfiguration scheme for fault‐tolerant FFT processor based on FPGA
Authors: Wei Xin , Xie Yi Z , Xie Yu , Chen He
Published: October 2019

The fast Fourier transform FFT processor is an important part of the space real‐time signal processing system based on field programmable gate array (FPGA). Since occupying a large amount of logical resources and storage resources, FFT processor is more vulnerable to high‐energy particles in space, resulting in single event upset (SEU). This paper presents a novel FPGA scrubbing framework base on dynamic partial reconfiguration technique for a FFT processor to mitigate SEU. The proposed scheme is compared with the blind scrubbing, the reconfiguration time is reduced by 78%. Then, the resource utilisation is 61.5% less than triple modular redundancy scheme. This paper also presents a DPR controller for FFT processor, which is evaluated in terms of hardware resources and reconfiguration time. A comparison to the Xilinx PRC IP shows that multipath delay feedback FFT controller saves 38.6% resources.
Passive radar sparse imaging with transmitter and receiver position errors
Authors: Wang Tianyun , Liu Bing , Kang Kai , Wei Qiang , Liu Yong
Published: October 2019

Passive radar sparse imaging requires accurate known system observation matrix, but in practical applications there usually exists transmitter and receiver position errors, which would make radar observation matrix partially unknown, resulting in mismatch between echo measurements and observation matrix, thus seriously degrade the performances of traditional sparse imaging algorithms. Here, the passive radar imaging model under position errors of transceivers is established first. Then, an adaptive phase error correction imaging method based on Bayesian compressed sensing is presented, which can deal with transceivers position errors while reconstructing target image simultaneously. Simulation results verify the effectiveness of authors’ method.
Implementation architecture of signal processing in pulse Doppler radar system based on FPGA
Authors: Yang Ming , Yang Jing , Hou Yanan , Jin Cheng
Published: October 2019

A kind of high speed and parallel hardware architecture is proposed and designed for digital signal processing of high frequency Pulse Doppler radar here. The platform is based on one XC7K410T FPGA, two XC7K325T FPGAs, one TMS320C6678 DSP, and four sets of MT41J256M8 DDR3. The details of implementation including pulse compression, moving target detection and constant‐false‐alarm rate are described. The simulation results and resource consumption are presented to demonstrate the advantages of the proposed FPGA implementation architecture.
CIAPC algorithm forrandom frequency‐hopping radar
Authors: Lu Yi , Wang Ju
Published: October 2019

In random frequency‐hopping pulse–Doppler radar, the transmitted frequencies are randomly distributed in the given frequency bandwidth. As a result, this kind of radar has the advantage of anti‐jamming. However, because of the sidelobe level fluctuating randomly, the sidelobe of a large scatterer can mask the presence of nearby smaller scatterers. The adaptive pulse compression (APC) algorithm has been shown capable of effectively suppressing the range sidelobes, but the performance gain is diminished whenever the return signals have a low signal‐to‐noise ratio (SNR). Furthermore, moving targets with high speed bring about the range migration problem. To solve these problems, the coherent integration APC (CIAPC) algorithm is proposed. The simulation results indicate that in a low SNR scenario, the CIAPC algorithm can suppress the range sidelobes of large scatterers and can improve detection performance.
Coherent detection method for maneuvering target with complex motions
Authors: Sun Zhi , Li Xiaolong , Cui Guolong , Zhang Tianxian , Kong Lingjiang
Published: October 2019

In this study, a coherent detection method is proposed to solve the problems during the coherent integration (CI) process, including the range cell migration (RCM) and Doppler spread (DS) effects which are caused by the complex motions of the maneuvering target. Particularly, this method applies the third‐order keystone transform firstly, which could remove the third‐order RCM induced by the jerk motion. Then target's defined velocity can be estimated by performing the frequency‐shifting cross‐correlation function and scaled Fourier transform. Thereafter, utilising the estimated defined velocity to construct a velocity compensation function, which could correct the first‐order RCM (FRCM). Subsequently, the matched filtering process is performed to eliminate the second‐order RCM and DS effects. Finally, applying the Fourier transform with respect to the slow time to realise the CI.
Neural saliency algorithm guide bi‐directional visual perception style transfer
Authors: Zhu Chunbiao , Yan Wei , Cai Xing , Liu Shan , Li Thomas H. , Li Ge
Published: October 2019

The artistic style transfer of images aims to synthesise novel images by combining the content of one image with the style of another, which is a long‐standing research topic and already has been widely applied in real world. However, defining the aesthetic perception from the human visual system is a challenging problem. In this study, the authors propose a novel method for automatic visual perception style transfer. First, they render a novel saliency detection algorithm to automatically perceive the visual attention of an image. Then, different from conventional style transfer algorithm in which style transferring is applied uniformly across all image regions, the authors apply a saliency algorithm to guide the style transferring process, enabling different types of style transferring to occur in different regions. Extensive experiments show that the proposed saliency detection algorithm and the style transfer algorithm are superior in performance and efficiency.
Neighbourhood systems based attribute reduction in formal decision contexts
Authors: Zhang Xiaohe , Mi Jusheng , Li Meizheng , Liang Meishe
Published: October 2019

Attribute reduction of formal decision context mainly uses the relationship between two concept lattices generated by the condition and decision attributes to remove redundant condition attributes. By using decision attributes to observe the covering of objects, this study defines two types of consistent sets and reducts in a consistent formal decision context based on neighbourhood systems. Four types of reductions in inconsistent formal decision contexts are also studied. The methods to calculate all types of reductions are formulated by discernibility matrix. Finally, an approach to obtain the decision rules in consistent formal decision context is proposed.
Radiation thermo-chemical models of protoplanetary disks
Authors: Thi W. F. , Lesur G. , Woitke P. , Kamp I. , Rab Ch. , Carmona A.
Published: October 2019

Context. Disks around pre-main-sequence stars evolve over time by turbulent viscous spreading. The main contender to explain the strength of the turbulence is the magnetorotational instability model, whose efficiency depends on the disk ionization fraction.

Aims. Our aim is to compute self-consistently the chemistry including polycyclic aromatic hydrocarbon (PAH) charge chemistry, the grain charging, and an estimate of an effective value of the turbulence α parameter in order to find observational signatures of disk turbulence.

Methods. We introduced PAH and grain charging physics and their interplay with other gas-phase reactions in the physico-chemical code PRODIMO. Non-ideal magnetohydrodynamics effects such as ohmic and ambipolar diffusion are parametrized to derive an effective value for the turbulent parameter αeff. We explored the effects of turbulence heating and line broadening on CO isotopologue submillimeter lines.

Results. The spatial distribution of αeff depends on various unconstrained disk parameters such as the magnetic parameter βmag or the cosmic ray density distribution inside the protoplanetary disk s. The inner disk midplane shows the presence of the so-called dead zone where the turbulence is almost inexistent. The disk is heated mostly by thermal accommodation on dust grains in the dead zone, by viscous heating outside the dead zone up to a few hundred astronomical units, and by chemical heating in the outer disk. The CO rotational lines probe the warm molecular disk layers where the turbulence is at its maximum. However, the effect of turbulence on the CO line profiles is minimal and difficult to distinguish from the thermal broadening.

Conclusions. Viscous heating of the gas in the disk midplane outside the dead zone is efficient. The determination of α from CO rotational line observations alone is challenging.
Disc kinematics and stability in high-mass star formation
Authors: Ahmadi A. , Kuiper R. , Beuther H.
Published: October 2019

Context. In the disc-mediated accretion scenario for the formation of the most massive stars, high densities and high accretion rates could induce gravitational instabilities in the disc, forcing it to fragment and produce companion objects.

Aims. We investigate the effects of inclination and spatial resolution on the observable kinematics and stability of discs in high-mass star formation.

Methods. We studied a high-resolution 3D radiation-hydrodynamic simulation that leads to the fragmentation of a massive disc. Using RADMC-3D we produced 1.3 mm continuum and CH3CN line cubes at different inclinations. The model was set to different distances, and synthetic observations were created for ALMA at ~80 mas resolution and NOEMA at ~0.4′′.

Results. The synthetic ALMA observations resolve all fragments and their kinematics well. The synthetic NOEMA observations at 800 pc with linear resolution of ~300 au are able to resolve the fragments, while at 2000 pc with linear resolution of ~800 au only a single structure slightly elongated towards the brightest fragment is observed. The position–velocity (PV) plots show the differential rotation of material best in the edge-on views. A discontinuity is seen at a radius of ~250 au, corresponding to the position of the centrifugal barrier. As the observations become less resolved, the inner high-velocity components of the disc become blended with the envelope and the PV plots resemble rigid-body-like rotation. Protostellar mass estimates from PV plots of poorly resolved observations are therefore overestimated. We fit the emission of CH3CN (12K−11K) lines and produce maps of gas temperature with values in the range of 100–300 K. Studying the Toomre stability of the discs, we find low Q values below the critical value for stability against gravitational collapse at the positions of the fragments and in the arms connecting the fragments for the resolved observations. For the poorly resolved observations we find low Q values in the outskirts of the disc. Therefore, although we could not resolve any of the fragments, we are able to predict that the disc is unstable and fragmenting. This conclusion is valid regardless of our knowledge about the inclination of the disc.

Conclusions. These synthetic observations reveal the potential and limitations of studying discs in high-mass star formation with current (millimetre) interferometers. While the extremely high spatial resolution of ALMA reveals objects in extraordinary detail, rotational structures and instabilities within accretion discs can also be identified in poorly resolved observations.
The Araucaria project: High-precision orbital parallax and masses of eclipsing binaries from infrared interferometry
Authors: Gallenne A. , Pietrzyński G. , Graczyk D. , Pilecki B. , Storm J. , Nardetto N. , Taormina M. , Gieren W. , Tkachenko A. , Kervella P. , Mérand A. , Weber M.
Published: October 2019

Context. The precise determinations of stellar mass at ≲1% provide important constraints on stellar evolution models. Accurate parallax measurements can also serve as independent benchmarks for the next Gaia data release.

Aims. We measured the masses and distance of binary systems with a precision level better than 1% using a fully geometrical and empirical method.

Methods. We obtained the first interferometric observations for the eclipsing systems AI Phe, AL Dor, KW Hya, NN Del, ψ Cen and V4090 Sgr with the VLTI/PIONIER combiner, which we combined with radial velocity measurements to derive their three-dimensional orbit, masses, and distance.

Results. We determined very precise stellar masses for all systems, ranging in precision from 0.04% to 3.3%. We combined these measurements with the stellar effective temperature and linear radius to fit stellar isochrones models and determined the age of the systems. We also derived the distance to the systems with a precision level of 0.4%.

Conclusions. The comparison of theoretical models with stellar parameters shows that stellar models are still deficient in simultaneously fitting the stellar parameters (Teff, R and M) with this level of precision on individual masses. This stresses the importance of precisely measuring the stellar parameters to better calibrate stellar evolution models. The precision of our model-independent orbital parallaxes varies from 24 μas as to 70 μas and the parallaxes provide a unique opportunity to verify whether the future Gaia measurements have systematic errors.
Inferring the velocity of early massive stars from the abundances of extremely metal-poor stars
Authors: Choplin Arthur , Tominaga Nozomu , Ishigaki Miho N.
Published: October 2019

Context. The nature of the early generation of massive stars can be inferred by investigating the origin of the extremely metal-poor (EMP) stars, likely formed from the ejecta of one or a few previous massive stars.

Aims. We investigate the rotational properties of early massive stars by comparing the abundance patterns of EMP stars with massive stellar models including rotation.

Methods. Low metallicity 20 M⊙ massive stellar models with eight initial rotation rates between 0 and 70% of the critical velocity are computed. Explosions with strong fallback are assumed. The ejected material is considered to fit individually the abundance patterns of 272 EMP stars with −4 <  [Fe/H] <  −3.

Results. With increasing initial rotation, the [C/H], [N/H], [O/H], [Na/H], [Mg/H], and [Al/H] ratios in the massive star ejecta are gradually increased (up to ∼4 dex) while the 12C/13C ratio is decreased. Among the 272 EMP stars considered, ∼40 − 50% are consistent with our models. About 60 − 70% of the carbon-enhanced EMP star sample can be reproduced against ∼20 − 30% for the carbon-normal EMP star sample. The abundance patterns of carbon-enhanced EMP stars are preferentially reproduced with a material coming from mid to fast rotating massive stars. The overall velocity distribution derived from the best massive star models increases from no rotation to fast rotation. The maximum is reached for massive stars having initial equatorial velocities of ∼550 − 640 km s−1.

Conclusions. Although subject to significant uncertainties, these results suggest that the rotational mixing operating in between the H-burning shell and the He-burning core of early massive stars played an important role in the early chemical enrichment of the Universe. The comparison of the velocity distribution derived from the best massive star models with velocity distributions of nearby OB stars suggests that a greater number of massive fast rotators were present in the early Universe. This may have important consequences for reionization, the first supernovae, or integrated light from high redshift galaxies.
The low-frequency properties of FR 0 radio galaxies
Authors: Capetti A. , Baldi R. D. , Brienza M. , Morganti R. , Giovannini G.
Published: October 2019

Using the alternative data release of the TIFR GMRT Sky Survey (TGSS), we studied the low-frequency properties of FR 0 radio galaxies, the large population of compact radio sources associated with red massive early-type galaxies revealed by surveys at 1.4 GHz. We considered TGSS observations from FR0CAT, a sample formed by 104 FR 0s at z <  0.05: all but one of them are covered by the TGSS, and 43 of them are detected above a 5σ limit of 17.5 mJy. No extended emission has been detected around the FR 0s, corresponding to a luminosity limit of ≲4 × 1023 W Hz−1 over an area of 100 kpc × 100 kpc. All but eight FR 0s have a flat or inverted spectral shape (α <  0.5) between 150 MHz and 1.4 GHz: this spectral behavior confirms the general paucity of optically thin extended emission within the TGSS beam, as is expected for their compact 1.4 GHz morphology. Data at 5 GHz were used to build their radio spectra, which are also generally flat at higher frequencies. By focusing on a sub-sample of FR 0s with flux density > 50 mJy at 1.4 GHz, we found that ∼75% of them have a convex spectrum, but with a smaller curvature than the more powerful gigahertz peaked-spectrum sources (GPS). The typical FR 0s radio spectrum is better described by a gradual steepening toward high frequencies, rather than to a transition from an optically-thick to an optically-thin regime, possibly observed in only ∼15% of the sample.
Dusty phenomena in the vicinity of giant exoplanets
Authors: Arkhypov O. V. , Khodachenko M. L. , Hanslmeier A.
Published: October 2019

Context. Hitherto, searches for exoplanetary dust have focused on the tails of decaying rocky or approaching icy bodies only at short circumstellar distances. At the same time, dust has been detected in the upper atmospheric layers of hot jupiters, which are subject to intensive mass loss. The erosion and/or tidal decay of hypothetic moonlets might be another possible source of dust around giant gaseous exoplanets. Moreover, volcanic activity and exozodiacal dust background may additionally contribute to exoplanetary dusty environments.

Aims. In the present study, we look for photometric manifestations of dust around different kinds of exoplanets (mainly giants).

Methods. We used linear approximation of pre- and post-transit parts of the long-cadence transit light curves (TLCs) of 118 Kepler objects of interest after their preliminary whitening and phase-folding. We then determined the corresponding flux gradients G1 and G2, respectively. These gradients were defined before and after the transit border for two different time intervals: (a) from 0.03 to 0.16 days and (b) from 0.01 to 0.05 days, which correspond to the distant and adjoining regions near the transiting object, respectively. Statistical analysis of gradients G1 and G2 was used for detection of possible dust manifestation.

Results. It was found that gradients G1 and G2 in the distant region are clustered around zero, demonstrating the absence of artifacts generated during the light curve processing. However, in the adjoining region, 17 cases of hot jupiters show significantly negative gradients, G1, whereas the corresponding values of G2 remain around zero. The analysis of individual TLCs reveals the localized pre-transit decrease of flux, which systematically decreases G1. This effect was reproduced with the models using a stochastic obscuring precursor ahead of the planet.

Conclusions. Since only a few TLCs show the presence of such pre-transit anomalies with no analogous systematic effect in the post-transit phase, we conclude that the detected pre-transit obscuration is a real planet-related phenomenon. Such phenomena may be caused by dusty atmospheric outflows or background circumstellar dust compressed in front of the mass-losing exoplanet, the study of which requires dedicated physical modeling and numeric simulations. Of certain importance may be the retarding of exozodiacal dust relative to the planet by the Poynting-Robertson effect leading to dust accumulation in electrostatic or magnetic traps in front of the planet.
Improvement of energy indicators of conventional electric driving asynchronous motors of non-standard technological equipment at the enterprises for repair of railway rolling stock through the use of energy-saving motors
Authors: Bondar Оleh , Baliichuk Oleksii , Karzova Oksana , Krasnov Roman , Marenych Oksana , Ustimenko Dmytro
Published: October 2019

The purpose of this work is to study the utilization efficiency of electric driving energy-saving motors of non-standard technological equipment meant for repair of railway rolling stock, in terms of improvement of energy performance, i.e. improvement of efficiency factors and power factors, and decrease of power losses as compared with the most commonly used “conventional” asynchronous motors. There are two options for improvement of the energy performance of electric drives of non-standard technological equipment: replacement of a conventional motor with an energy-saving one similar in terms of nominal voltage, rotational speed, power, etc.; changeover of stator winding from “delta” to “star”. A special technique has been proposed to determine the effectiveness of this changeover in terms of improvement of energy indicators. Comparison of the real values of the energy indicators of conventional motors and energy-saving motors in the case under consideration is required to perform the technical and economic calculations when solving the problem of the expediency of replacement of conventional asynchronous motors with energy-saving motors in the abovementioned equipment.
Comparison of motor coach exhaust emissions in real operating conditions for different testing procedures
Authors: Gallas Dawid , Merkisz Jerzy , Andrzejewski Maciej , Tomaszewski Sylwin , Strzemkowski Jan , Kinter Stepan
Published: October 2019

The article discusses the results of applying real driving emissions (RDE) testing methods in measuring the exhaust emissions of a passenger rail vehicle. Portable Emissions Measuring Systems (PEMS) were used to measure the exhaust emissions from a motor coach in real operation, performed on a test track for selected drive cycle parameters. The road emission values of exhaust components have been calculated and compared to road vehicles and road exhaust emission limits based on the legal norms. The assessment was concluded with a comparison of the environmental cost, in terms of exhaust emissions, of transporting passengers using the tested rail vehicle relative to alternative road transport, based on measurements in real operating conditions.
Improving the safety of railway subgrade when it is strengthened using soil-cement elements
Authors: Krysan Vitalii , Krysan Volodymyr , Petrenko Volodymyr , Tiutkin Oleksii , Andrieiev Volodymyr
Published: October 2019

The article identifies the main parameters of the drilling-mixing technology, which is the most effective in fixing weak soil bases during the construction and restoration of transport, industrial and civil structures. The difference of the technology developed by the authors is that the strengthening process is carried out at low pressure (0.15 ... 0.25 MPa). The relevance of the research is that the proposed technology requires less cost with high rates of restoring the strength of soil foundations. To prove the high quality of the technology, laboratory studies were carried out to determine the optimal characteristics of the soil-cement element, as well as the proportions and composition of the fixing solution. The dependences of the strength of soil-cement elements in the air-dry condition with cement content from 7% to 23% with water-cement ratio in solution 1 / 0.3 and with cement content from 13% to 37.5% with water-cement ratio in solution 1/0,6. During the experimental-industrial studies of the author’s technology, the embankment was constructed with the soil-cement-reinforced elements for the access road approaches at one of the facilities in Kirovograd region, which ensured safety in the operation of a complex transport structure.