bluuebunny/crossref_metadata_2025 huggingface dataset:
Non‐parametric statistics‐based predictor enabling online transient stability assessment
Authors: Liu Tingjian , Liu Youbo , Xu Lixiong , Liu Junyong , Mitra Joydeep , Tian Yuting
Published: October 2018

Online transient stability assessment (TSA) is of great necessity for fast awareness of transient instability caused by fault contingencies. In this paper, a non‐parametric statistics based scheme is proposed for response‐based online TSA. A critical clearing time‐based stability margin index is defined as the predictive output and 14 kinds of severity indicators are proposed as input features for the TSA predictor. With no prior knowledge of the correlation structure, the non‐parametric additive model is used as the basis of the predictor. To screen out the weakly correlated indicators and reduce the dimensionality of the input space, two‐stage feature selection is fulfilled by non‐parametric independence screening and group Lasso penalised regression successively. The predictor is then learnt by least‐squares regression in the reduced multi‐feature space. With phasor measurement unit measurements at generator buses, severity indicators can be computed in the real‐time and fast evaluation of post‐fault stability margin can be made by the offline‐trained predictor. The effectiveness of the proposed non‐parametric statistics based scheme is demonstrated in a modified New England 39‐bus system and a practical 756‐bus transmission system in China.
Preference‐based smart parking system in a university campus
Authors: Mohandes Mohamed , Deriche Mohamed , Abuelma'atti Muhammad T. , Tasadduq Noman
Published: October 2018

This study introduces the concept of space preferences to enhance the operation of recurrent‐users car parking systems. On campus, at KFUPM, several parking buildings are available for students, employees, and faculty. Still, substantial amount of time is wasted just looking for a suitable parking space. The authors propose to enrol all users together with their top ranked preferred parking spots and pedestrian exit of choice. Upon presentation of the user ID card, the system retrieves their preferences, matches them to the updated database of vacant spots, then directs the user to their topmost vacant parking spot. The system directs the user to the nearest parking building if no vacancy. Two options have been evaluated to detect parking vacancies: one is based on ultrasonic sensors and the second uses a set of cameras. The sensor‐based system was built around an Arduino platform paired with a wireless channel for communication. For the camera‐based system, the authors introduce a new set of features mixing both edge and texture information from the parking spot images. A performance analysis of both systems was carried showing that the sensor‐based implementation outperforms the camera‐based one for the authors’ specific application with an accuracy of 100 and 98%, respectively.
Modified PO–PO hybrid method for scattering of 2D ship model on the rough sea surface
Authors: Behdani Mahdi , Dehkhoda Parisa , Tavakoli Ahad , Zoofaghari Mohammad
Published: October 2018

The hybrid physical optics–physical optics (PO–PO) method was introduced in the previous works to compute the electromagnetic scattering from an object above a random rough surface. Here, first, the conventional PO–PO method is applied to find the scattering from a simple smooth two‐dimensional (2D) perfect electric conductor (PEC) object on a one‐dimensional (1D) rough PEC surface. Then, this method is modified to be used to calculate the scattering from a complex sharp‐cornered 2D PEC target on the 1D random rough PEC surface. In addition, here, the physical theory of diffraction is utilised to take into account the diffraction from the edges of the target. The accuracy and efficiency of the proposed method are validated by the method of moments.
Multi‐beam monopulse substrate integrated waveguide slot array antenna
Authors: Liu Yi , Yang Hu , Jin Zusheng , Zhu Jiang
Published: October 2018

A multi‐beam slot array antenna is proposed in the 10‐GHz band for a monopulse tracking system with resolution enhancement techniques. The antenna architecture combines a four‐subarray substrate integrated waveguide (SIW) slot antenna, a multi‐beam‐forming network of microstrip Rotman lens array, and a SIW comparator of four‐quadrant monopulse technique. A method to form difference patterns in both E‐plane and H‐plane for mutibeams is presented, and the method can improve the accuracy of angle detection for all beams. The key point of the method is to compensate the phase difference caused by the beam deflection between the two subarrays (quadrants) by constraining input delay lines of the Rotman lens array. To validate the proposed concepts, an antenna prototype is realized and measured. The experimental results demonstrate a scanning range of ±36° with −5 dB crossover level between two adjacent sum beams in the E‐plane. The corresponding difference patterns are generated in both E‐plane and H‐plane via the monopulse comparator. The multi‐beam monopulse system can achieve gains between 21.7 and 23.5 dBi for all sum beams at the center frequency of 10 GHz. This multi‐beam monopulse slot antenna can be applied in radars and communication systems requiring beam‐scanning capabilities and target tracking.
Review on low‐frequency ripple suppression methods for MMCs for medium‐voltage drive applications
Authors: Wang Ze , Chen Jimin , Liao Kaiwen , Xiong Jian , Zhang Kai
Published: October 2018

Advantages of the modular multilevel converter (MMC) such as modularity, scalability, fault‐tolerant ability, low device switching frequency, transformerless grid connection etc. have made it the most promising converter topology for medium‐to‐high‐voltage, high‐power applications. However, in MMC‐based medium‐voltage drives, the excessive fundamental‐frequency submodule capacitor voltage ripple at low speeds or start‐up poses a major technological challenge. A lot of low‐frequency ripple suppression methods have been proposed to address this problem. This study summarises the state of the art in this area and classifies these methods into three categories. The pros and cons of them are discussed. An in‐depth analysis of these methods from a practical viewpoint is given. Some future research trends are also discussed.
Engineering modelling of wind turbine applied in real‐time simulation with hardware‐in‐loop and optimising control
Authors: Tian Jun , Liu Jingbo , Shu Jun , Tang Jian , Yang Jiawei
Published: October 2018

In order to constantly improve the output characteristics of wind turbines, the HIL (Hardware Inthe Loop) experimental platform of wind turbines is built to optimize control.According to the product parameters of 1.5 MW direct‐drive PMSG (PermanentMagnet Synchronous wind Generator) of Dongfang Electric Corporation (DEC), thesimulation model of wind turbine is built in RTDS (Real Time Digital Simulator),and optimised by comparing with the wind speed–power curve of products, thesimulation model of wind turbine with engineering accuracy can be obtained. Baseon the engineering model and actual controller of products, the HIL experimentalplatform of wind turbines is built to optimise control. In the case ofunbalanced or asymmetrical grid voltage, in order to make the wind turbineoutput be stable, the DDSOGI‐PLL (direct Decoupling Double Second‐OrderGeneralized Integral Phase‐Locked Loop) is proposed to improve the performanceof PLL, the active/reactive current decoupling algorithm based on positive andnegative sequence voltage orientation respectively is proposed to eliminate thenegative sequence current to maintain a constant output power. The effectivenessof algorithm is verified by the HIL experimental platform, the active poweroutput of wind turbine remains constant, the grid‐connected adaptability of windturbines is improved significantly.
DC offset estimation‐based fault detection in transmission line during power swing using ensemble of decision tree
Authors: Shukla Sunil K. , Koley Ebha , Ghosh Subhojit
Published: October 2018

The nuisance tripping of distance relay during power swing has been identified as one of the major causes for power system blackouts. Avoiding the risk of maloperation of distance relay and hence improving resilience during power swing, demands the development of a scheme capable of generating blocking signal during power swing and detecting a fault occurring with power swing from the measurement of current signal. In this regard, a protection scheme based on the hybrid framework of an ensemble of the tree, least square, and Adaline algorithm to perform the task of fault detection/classification, zone identification, location estimation, and power swing detection is proposed. The proposed scheme is based on the online estimation of DC offset information along with the fundamental component of the current signal. The performance of the proposed scheme has been analysed for diverse power swing and fault scenarios for two‐machine system and Western System Coordinating Council 9‐bus system. The simulation results reflect the effectiveness of the developed scheme in terms of sensitivity and reliability. Furthermore, to authenticate the effectiveness of the proposed scheme for practical scenarios, implementation, and validation of the proposed scheme has been carried out in a real‐time environment using the OPAL‐RT digital simulator.
Influence of pressure on the properties of AlN deposited by DC reactive magnetron sputtering on Si (100) substrate
Authors: Li Tao , Han Jun , Xing Yanhui , Deng Xuguang , Li Junshuai , Zhang Li , Shi Fengfeng , Yu Lun , Sun Chi , Zhang Xiaodong , Zhang Baoshun
Published: October 2018

Preferred (002)‐oriented aluminium nitride (AlN) films by direct‐current (DC) magnetron sputtering on Si (100) substrate were prepared at various deposition pressure (0.12–0.5 Pa). The influence of pressure on the surface morphology, crystal structure and optical properties of AlN thin films was discussed the with the methods of X‐ray diffraction, atomic force microscopy and stress analyser, respectively. Optical properties were studied by ellipsometer and Fourier transform infrared spectrometer. It was observed that the AlN films tended to be preferred (002)‐oriented when the pressure was decreased and the value of full width at half maximum is 0.325° when the pressure was kept at 0.12 Pa. the tensile stress, refractive index, and the density of Al–N bonds decreased with increasing the sputtering pressure from 0.12 to 0.5 Pa. This work demonstrated the influence of sputtering pressure on the structural and optical properties of the AlN films deposited on Si (100) substrate, the gallium nitride epitaxial film on Si (100) substrate was expected to be realised using sputtered AlN as the buffer layer.
The intergalactic magnetic field probed by a giant radio galaxy
Authors: O’Sullivan S. P. , Machalski J. , Van Eck C. L. , Heald G. , Brüggen M. , Fynbo J. P. U. , Heintz K. E. , Lara-Lopez M. A. , Vacca V. , Hardcastle M. J. , Shimwell T. W. , Tasse C. , Vazza F. , Andernach H. , Birkinshaw M. , Haverkorn M. , Horellou C. , Williams W. L. , Harwood J. J. , Brunetti G. , Anderson J. M. , Mao S. A. , Nikiel-Wroczyński B. , Takahashi K. , Carretti E. , Vernstrom T. , van Weeren R. J. , Orrú E. , Morabito L. K. , Callingham J. R.
Published: October 2018

Cosmological simulations predict that an intergalactic magnetic field (IGMF) pervades the large scale structure (LSS) of the Universe. Measuring the IGMF is important to determine its origin (i.e. primordial or otherwise). Using data from the LOFAR Two Metre Sky Survey (LoTSS), we present the Faraday rotation measure (RM) and depolarisation properties of the giant radio galaxy J1235+5317, at a redshift ofz = 0.34 and 3.38 Mpc in size. We find a mean RM difference between the lobes of 2.5 ± 0.1 rad m−2, in addition to small scale RM variations of ∼0.1 rad m−2. From a catalogue of LSS filaments based on optical spectroscopic observations in the local universe, we find an excess of filaments intersecting the line of sight to only one of the lobes. Associating the entire RM difference to these LSS filaments leads to a gas density-weighted IGMF strength of ∼0.3μG. However, direct comparison with cosmological simulations of the RM contribution from LSS filaments gives a low probability (∼5%) for an RM contribution as large as 2.5 rad m−2, for the case of IGMF strengths of 10–50 nG. It is likely that variations in the RM from the Milky Way (on 11′ scales) contribute significantly to the mean RM difference, and a denser RM grid is required to better constrain this contribution. In general, this work demonstrates the potential of the LOFAR telescope to probe the weak signature of the IGMF. Future studies, with thousands of sources with high accuracy RMs from LoTSS, will enable more stringent constraints on the nature of the IGMF.
AthenaX-IFU synthetic observations of galaxy clusters to probe the chemical enrichment of the Universe
Authors: Cucchetti E. , Pointecouteau E. , Peille P. , Clerc N. , Rasia E. , Biffi V. , Borgani S. , Tornatore L. , Dolag K. , Roncarelli M. , Gaspari M. , Ettori S. , Bulbul E. , Dauser T. , Wilms J. , Pajot F. , Barret D.
Published: October 2018

Answers to the metal production of the Universe can be found in galaxy clusters, notably within their intra-cluster medium (ICM). The X-ray Integral Field Unit (X-IFU) on board the next-generation European X-ray observatoryAthena(2030s) will provide the necessary leap forward in spatially-resolved spectroscopy required to disentangle the intricate mechanisms responsible for this chemical enrichment. In this paper, we investigate the future capabilities of the X-IFU in probing the hot gas within galaxy clusters. From a test sample of four clusters extracted from cosmological hydrodynamical simulations, we present comprehensive synthetic observations of these clusters at different redshifts (up toz ≤ 2) and within the scaled radiusR500performed using the instrument simulator SIXTE. Through 100 ks exposures, we demonstrate that the X-IFU will provide spatially resolved mapping of the ICM physical properties with little to no biases (⪅5%) and well within statistical uncertainties. The detailed study of abundance profiles and abundance ratios withinR500also highlights the power of the X-IFU in providing constraints on the various enrichment models. From synthetic observations out toz = 2, we have also quantified its ability to track the chemical elements across cosmic time with excellent accuracy, and thereby to investigate the evolution of metal production mechanisms as well as the link to the stellar initial mass-function. Our study demonstrates the unprecedented capabilities of the X-IFU of unveiling the properties of the ICM but also stresses the data analysis challenges faced by future high-resolution X-ray missions such asAthena.
A Lagrangian model for dust evolution in protoplanetary disks: formation of wet and dry planetesimals at different stellar masses
Authors: Schoonenberg Djoeke , Ormel Chris W. , Krijt Sebastiaan
Published: October 2018

We introduce a new Lagrangian smooth-particle method to model the growth and drift of pebbles in protoplanetary disks. The Lagrangian nature of the model makes it especially suited to following characteristics of individual (groups of) particles, such as their composition. In this work we focus on the water content of solid particles. Planetesimal formation via streaming instability is taken into account, partly based on previous results on streaming instability outside the water snowline that were presented in a recent publication. We validated our model by reproducing earlier results from the literature and apply our model to steady-state viscous gas disks (with constant gas accretion rate) around stars with different masses. We also present various other models where we explore the effects of pebble accretion, the fragmentation velocity threshold, the global metallicity of the disk, and a time-dependent gas accretion rate. We find that planetesimals preferentially form in a local annulus outside the water snowline, at early times in the lifetime of the disk (≲105yr), when the pebble mass fluxes are high enough to trigger the streaming instability. During this first phase in the planet formation process, the snowline location hardly changes due to slow viscous evolution, and we conclude that assuming a constant gas accretion rate is justified in this first stage. The efficiency of converting the solids reservoir of the disk to planetesimals depends on the location of the water snowline. Cooler disks with a closer-in water snowline are more efficient at producing planetesimals than hotter disks where the water snowline is located further away from the star. Therefore, low-mass stars tend to form planetesimals more efficiently, but any correlation may be overshadowed by the spread in disk properties.
On overhead networks transfer from 10(6) kV to 20 kV
Authors: Mayorov Andrey , Osintsev Kirill , Shuntov Andrey
Published: October 2018

The expediency of preferential use of the rated voltage of 20 kV for the overhead networks of Russia is investigated. The feasibility study of the 20 kV voltage application areas based on the integrated parameters of the networks was performed. It is shown that due to the convergence of technical and economic characteristics of 10 and 20 kV equipment, 20 kV networks have more significant advantages in comparison with traditional 10 kV electrical installations.
Mining engineering system as an energy asset in industry 4.0
Authors: Radchenko Dmitriy , Bondarenko Alina
Published: October 2018

Mines now absorbing Industry 4.0 technologies face the challenges of production energy efficiency enhancement and energy safety improvement. Following the environmental standards involves the requirement of turning from diesel to electric drive of mining machinery and equipment. This significantly improves miners’ working environment in ore mines. At the same time, the share of energy consumption increases in the situation of low energy security of mines, particularly at peak loads. The article discusses the conditions, and proposes a scenario of mine energy supply system reliability enhancement. For this purpose, a mining engineering system is viewed as an energy asset, with identification of its expanding capabilities.
SAIFI reliability calculation for the distribution line
Authors: Bandurin Ivan , Khaimin Alexey
Published: October 2018

The article for the first time shows the method of calculating the SAIFI reliability index for the distribution line at the design stage. Formulas and examples of calculation of SAIFI indicators for distribution lines of different configurations are given.
Choosing of the FEC critical objects in model researches of energy security problems and its features
Authors: Beresneva Natalia , Pyatkova Natalia
Published: October 2018

The overall objective of the proposed work is to formulate the main provisions of the approach to the determination of critical objects for the fuel and energy complex within the framework of hierarchical system studies of the energy security problems for the country and its regions. This approach involves the use of a hierarchical system of models, presupposes a preliminary choice of critical objects for energy systems. The approach is focused on the analysis and evaluation of interrelated systems functioning when implementing threats to energy security (in the form of contingencies), requires the accounting for changes in the work of critical objects for industries. To assess the criticality of these objects for the energy complex as a whole, a criterion is proposed for the significance of objects by the most important model indicators.
This world is full of vibrations
Authors: Rao J. S.
Published: October 2018

Man ventured out of the caves nearly 15000 years ago and since then tried to explain earth vibrations as mythology. Naturally occurring earthquakes were observed and described over the last two thousand years. Though the Universe is nearly 14 billion years old and the trillions of celestial bodies are continuously colliding, sending gravitational waves passing energy to bodies like micro-earth that are responsible for tectonic plate movement on this macro-earth and earthquakes, the effects are recorded over two years ago. Ever since scientific revolution in 17th century machines became ubiquitous and their vibrations are felt in every day’s life. This paper summarizes these vibrations.
Helical buckling of thin rods: FE modelling
Authors: Kapitaniak Marcin , Vaziri Vahid , Wiercigroch Marian
Published: October 2018

In this paper, we utilize the Finite Element (FE) method to model twisting of long thin rods and capture the bifurcation scenarios leading to heli- cal buckling and various further post-buckling states. Since standard nonlinear beam elements do not account for nonlinearity in torsional mode, we derive a modiﬁed beam element, which allows to model complex torsional buckling bifurcation scenarios of a thin rod subjected to twisting load. A series of veri- ﬁcation tests (static analysis with load stepping) of the developed code are per- formed to determine critical torsional buckling loads for various helical buck- ling modes and compared with ABAQUS FE simulation.
Prediction of cutting tool vibration and surface roughness in hard turning of AISI52100 steel
Authors: Ambhore Nitin , Kamble Dinesh , Chinchanikar Satish
Published: October 2018

The changing behavior of vibration signals with varying cutting parameters (cutting speed, feed rate and depth of cut) for turning hardened AISI52100 steel has been studied and reported. The vibration response of cutting tool in all three mutually perpendicular directions, namely, in feed Vx, radial Vy and, tangential Vz directions have been captured by mounting piezoelectric tri-axial accelerometer close to the cutting tool. Experiments are planned and conducted as per Central composite rotatable design of Surface response methodology. The second order multiple regression models are developed to correlate cutting parameters with vibration acceleration and surface roughness. The coefficient of regression R2 for all models is found close to 0.92 which shows that the developed models are reliable and provide an excellent explanation between the cutting parameter and the vibration of cutting tool within limits. The analysis of the results revealed that cutting conditions are having prominent and mixed type effect on vibration signals. The acceleration amplitude Vx, Vy and Vz increases with increase in cutting speed, and depth of cut. The vibration amplitude Vx, Vy and Vz initially increases as feed increases and, with further increase in feed, the vibration amplitude decreases. The surface roughness is highly influenced by the feed rate followed by cutting speed whereas the depth of cut was found less significant. The fluctuation in frequency is observed in all directions. However, the band of frequency remains within a certain range. Within selected cutting parameter range, the maximum acceleration amplitude is observed in frequency band of 4 kHz - 16 kHz.
On reducing uncertainty on the Elliptical Plane modal identification method
Authors: Montalvão Diogo , Dupac Mihai , Amafabia Daerefa-a Mitsheal , David-West Opukuro , Haritos George
Published: October 2018

The Elliptical Plane has been recently introduced as a modal identification method that uses an alternative plot of the receptance. The method uses the dissipated energy per cycle of vibration as a starting point. For lightly damped systems with conveniently spaced modes, it produces quite accurate results, especially when compared to the well-known method of the inverse. When represented in the Elliptical Plane, the shape of the receptance is elliptical near resonant frequencies. The modal damping factor can be determined from the angle of the ellipse’s major axis with the horizontal axis, whereas the real and imaginary parts of the modal constants can be determined from numerical curve-fitting (as in the method of the circle - Nyquist plot). However, the lack of points that can be used near the resonance (due to limitations in the frequency resolution, and effects from other modes near each resonance) and the fact that measurements are polluted by noise, bring uncertainty to the numerical curve-fitting. This paper aims at providing the first steps on the improvement of the quality of the modal identification of the receptance in the Elliptical Plane. The method and results are discussed with a multiple degree-of-freedom numerical example.
Vibration analysis of footbridges: an overview of the current practice
Authors: De Luca Antonio , Bauer Michael , Pinto Marguerite , Malsch Elisabeth
Published: October 2018

The design of a footbridge is typically controlled by serviceability criteria. The dynamic forces induced by pedestrians may result in high-amplitude vibrations that the users may feel as uncomfortable, or unsafe. As a consequence of the several cases of footbridge vibration problems that occurred over the last two decades, research has been conducted to improve design criteria that account for pedestrian loading, traffic density, and comfort levels. To date, there are no accepted design guidelines in the United States to assess vibration levels in footbridges. This paper offers a general overview of the current practice for the vibration analysis of footbridges.
Experimental and computational dynamic analysis of the foam concrete as a sub-base layer of the pavement structure
Authors: Valaskova Veronika , Vlcek Jozef , Drusa Marian
Published: October 2018

Dynamic properties of the new materials represent the actual problem, which is solved at many departments in the world at this time. Foam concrete (FC) is a material that has wide application in the civil engineering structures. Currently, it's mainly used in the floor structures of the buildings but its usability can be much wider thanks to its specific properties. The foam concrete contains closed air pores, what achieves its low volume weight (density) and saving of material inputs. It's a building material with good mechanical properties and low thermal conductivity and at the same time with high-tech processing.

Nowadays, a research aimed at the application of the foam concrete in the pavement structures takes place at the University of Zilina. Foam concrete could be utilized as a sub-base layer at the road reconstructions, excavations or as a regular layer of the new constructed pavements.

The submitted paper is dedicated to the numerical simulation based on the Finite element method (FEM) in pursuance of the outputs of the experimental investigation of the dynamic effect on the pavement structure which contains the foam concrete layer. Obtained dynamic parameters will be a background for the pavement design using the foam concrete.
Experimental study in reduction of two phase flow induced vibration
Authors: Hossain Ismail , Velkin Vladimir I. , Shcheklein Sergei E.
Published: October 2018

Vibration in mechanical devices is one of the major problems in engineering field including power generated industry. In this study we focused on the method and possible equipment design availability in reduction of vibration level. A brief overview of the outcomings of pipeline vibrations is presented, the sources of vibrations are listed and possible solutions for eliminating vibrations are described. Devices for passive quenching of pressure pulsations in pipelines with a two-phase flow are considered. We presented the description of the experimental stand on the investigation of the influence of a two-phase flow on the vibration of sections of a pipeline under different flow patterns of a coolant, as well as the procedure for conducting an experiment to study the properties of developed and manufactured swirl models. An animated model was developed that reflects the relationship of swirl geometry with the reduction of the vibro-displacement of the pipeline as a result of passive action on a two-phase flow.
Influence of torsional stiffness on load sharing coefficient of a power split drive system
Authors: Jin Guanghu , Ren Wei , Zhu Rupeng
Published: October 2018

A dynamic model of power split transmission system with face gear and cylindrical gear is established. The factors including time-varying mesh stiffness, torsional stiffness, supporting stiffness, and clearance are considered in the model. The influence of the torsional stiffness of compound gear shaft on the load sharing coefficient is analyzed. The results show that the influence of the torsional stiffness of the compound gear shaft is obvious. Because the torsional stiffness of the output gear components is larger and the torsional stiffness of the input gear is smaller, so the input stage's deformation coordination ability is strong. Therefore, with the increase of the torsional stiffness of the compound gear shaft, the load sharing coefficient of the power input stages is improved, but the load sharing coefficient of the split torque stages and power confluence stages is worse. Hence, the torsional stiffness ratio of the transmission shaft should be rationally allocated under the condition that the torsional stiffness of the compound shaft is small.
Sensitivity analysis of smart rotor under to uncertainties
Authors: Koroishi Edson H. , Lara-Molina Fabian A. , Repinaldo Joana P.
Published: October 2018

This contribution encompasses the sensitivity analysis of flexible rotor with active vibration control subjected to uncertainties. The uncertain parameters consist of small variations that are modeled by using random variables and random fields. The structure response subjected to uncertain parameters is analyzed based on the stochastic modeling. Numerical simulations illustrate the structural response of the rotor and their sensitivity indices.
Parametric resonances of floating wind turbines blades under vertical wave excitation
Authors: Ikeda Takashi , Harata Yuji , Miyazawa Yugo , Ishida Yukio
Published: October 2018

The parametric resonances of the blades in floating offshore wind turbines are theoretically and experimentally investigated. In the theoretical analysis, each blade is pinned to a horizontal, rotating shaft and has a spring with rotational stiffness at the end. The blade is subjected to horizontal excitation which represents winds; the rotating shaft to vertical excitation which represents waves. The equation of motion for the blade inclination angle includes parametric excitation terms with three different frequencies, i.e., the rotational speed of the blade, and the sum of and difference between the rotational speed and wave excitation frequency. Numerical simulations are conducted for the corresponding linearized system, and it is found that unstable vibrations appear at several rotational speed ranges. An empirical approach is used to determine the regions where the unstable vibrations appear. Swept-sine tests are conducted to determine the frequency response curves for the nonlinear system and demonstrate that the parametric resonances appear at similar rotational speeds as those of the unstable regions. In experiments, parametric resonances were observed at the rotational speeds and wave excitation frequencies predicted by the theoretical analysis.
Fault detection based on instantaneous angular speed measurement and variational mode decomposition
Authors: Braut Sanjin , Žigulić Roberto , Skoblar Ante , Štimac Rončević Goranka
Published: October 2018

Rotating machinery encounter throughout their lifetime various problems. Among them, a rotor-stator rubbing problem is one of the most common. This paper proposes a procedure, which applies the instantaneous angular speed (IAS) measurement as a starting step for rotor-stator partial rub detection. There are various approaches regarding counting techniques and processing of signal. In this paper, an application of analog signals from toothed wheel encoder or zebra tape encoder is considered at low to moderate sampling rates. As the rubbing process is nonlinear, this paper is proposing a variational mode decomposition (VMD) as the second step of the detection procedure. The VMD is relatively new method with promising results especially interesting for machinery fault detection. Detection tool is tested on laboratory test rig at two different rotor operating conditions i.e. without rotor-stator rubbing and with light partial rotor-stator rub. Measurements were performed with non-contact eddy current displacement sensors pointed to toothed wheel encoder. Results are presented in the shape of rotor orbits, IAS signals, FFT spectra of IAS signals and VMD spectrograms. Developed fault detection procedure based on IAS measurement and VMD decomposition was successfully tested on laboratory test rig for no rubbing and light rotor to stator partial rub condition.
Effect of polycaprolactone nanofibers on the vibratory behaviour and the damage resistance of composite laminates
Authors: Garcia Cristobal , Trendafilova Irina , Zucchelli Andrea
Published: October 2018

Aircrafts, bridges, wind turbines and other civil structures made of composite materials are frequently subjected to vibrations, which are responsible for a considerable number of accidents. One of the methods to reduce the vibrations is the incorporation of nanofibers in the composite structures. The main purpose of this study is to investigate the effect of the inclusion of polycaprolactone nanofibers on the vibratory behaviour of composite laminates. For this purpose, the vibratory behaviour of nano composites (with nanofibers) and standard composites (without nanofibers) is investigated with the purpose of acquiring their natural frequencies and the damping ratio. The results indicated that the inclusion of polycaprolactone nanofibers in composites increased the damping ratio, however it did not change significantly the natural frequencies. Furthermore, the paper investigates the effect of polycaprolactone nanofibers on the damage resistance of glass fibre composites. For this purpose, a finite element model is used to simulate the damage caused by mechanical impact in standard and nano composites. The numerical simulations show that the interleaving with nanofibers increased the damage resistance considerably. This study contributes to the knowledge about the vibration behaviour and the damage resistance of composites interleaved with polycaprolactone nanofibers. It is demonstrated that the interleaving with polycaprolactone fibres can play an important role for reducing the vibrations and increasing their impact damage resistance in composite structures as aircrafts.
Dental implant placement in a patient with cystinosis. A case report
Authors: Bretaudeau Clara , Paredes Francesca Siu , Sergheraert Johan , Massa Luciana , Laurence Sébastien , Diebold Marie-Hélène , Lefèvre Benoît , Mauprivez Cédric
Published: October 2018

Introduction: Cystinosis is a rare genetic disease due to a defective transport of cystine out of the lysosomes, caused by a mutation of the gene encoding for the lysosomal carrier protein, the cystinosin. Cystine accumulation results in the formation of intracellular cystine cristals, that causes tissular and multi-organic lesions (kidney, eyes, endocrine glands). Observation: We report a rare case of a patient affected by infantile nephropathic cystinosis, who consulted for an implant placement in a single-tooth gap. Discussion: Accumulation of cystine leads to tissue damage, primarily in the kidney, the liver and the cornea, but other organs, such as the mouth, teeth and jaws may be also involved. The article aimed to present oral manifestations associated with this storage disease and to discuss how oral surgeon can evaluate and manage these patients despite the lack of a standardized protocol.
A Route to Highly Functionalized Stereospecific trans-Aminated Aurones from 3-Bromoflavones with Aniline and N-Phenylurea via a Domino Aza-Michael Ring Opening and Cyclization Reactions
Authors: Ahmed Naseem , Parveen Iram
Published: October 2018

A facile cascade reaction is reported via aza-Michael addition, ring opening, and cyclization between 3-bromoflavone and aniline derivatives or N-phenylurea in the presence of KOt-Bu and CuI in DMF under mild reaction conditions. Products were obtained as stereospecific trans-aminated aurones in good to excellent yields (61–83%). Our protocol is operationally successful with ease, avoids the requirement of additives and ligands, and offers broad substrate scope.
A Facile Synthesis of N-Boc-azocan-5-one
Authors: Vázquez Alfredo , Morales-Chamorro Maricela
Published: October 2018

The azacycloalkane 1-azocan-5-one is embedded in the structure of several products of natural origin displaying a variety of bioactivities. Two convenient and straightforward routes were developed to synthesize N-Boc-azocan-5-one from readily available raw materials featuring a ring-closing metathesis (RCM) reaction as the key step.
Heat dissipation performance of electric vehicle battery liquid cooling system with double-inlet and double-outlet channels
Authors: Xu Xiaoming , Fu Jiaqi , Ding Rongjun , Jin Huifen , Xiao Ye
Published: October 2018

Battery, as the main energy storage element, directly affects the performance of an electric vehicle. Battery thermal management research is required as the battery performance is obviously influenced by temperature. This article selects a liquid cooling system with double-inlet and double-outlet channels as a research object and studies heat dissipation performance at different ambient temperatures, coolant inflow, and charge-discharge rates of the battery. The results of the experiments indicate that with the increase in ambient temperature and charge-discharge rates, the temperature in the top of the cells increases more than in the bottom of cells, especially in the middle of the battery. Compared with coolant inflow, the charge-discharge rate of the battery is the main reason for the high temperature rise and difference. When the charge-discharge rate increases, the coolant inflow of the liquid cooling system should be strengthened a lot to balance the increased heat power of the battery itself. Then, the design reference of the battery liquid cooling system is offered.
Plasma afterglow circulation apparatus for decontamination of spacecraft equipment
Authors: Müller Meike , Shimizu Tetsuji , Binder Sylvia , Rettberg Petra , Zimmermann Julia L. , Morfill Gregor E. , Thomas Hubertus
Published: October 2018

A newly developed apparatus using cold atmospheric plasma (CAP) is presented, providing a useful alternative decontamination method for spacecraft equipment. The designed setup uses the plasma afterglow generated by a surface micro-discharge (SMD) technology and works with a circulating gas flow of ambient air at room temperature. Additionally, the apparatus allows the control of gas flow, plasma power and humidity, and offers O3 monitoring and a variable treatment volume. Within this study we examined the apparatus’ performance by evaluation of the inactivation efficacy of bacterial endospores Bacillus atrophaeus in different treatment volumes of 0.54 l, 1.8 l and 2.6 l. The experiments with Bacillus atrophaeus showed at least a 4.4 log reduction after the treatment times of 10, 20 and 30 min in the respective treatment chambers with a volume of 0.54 l, 1.8 l and 2.6 l. These results demonstrate that high sporicidal effects can be achieved with the newly developed apparatus, and that longer treatment times are needed for larger treatment volumes due to different filling rates of reactive components in different treatment volumes. Conclusively, these investigations illustrate the scalability of the designed apparatus up to 2.6 l for the afterglow treatment of samples with flat surfaces. The composition of the plasma afterglow was analysed by Fourier Transformation Infrared (FTIR) and UV absorption spectroscopy. The spectroscopic analyses identify O3, N2O, and HNO3 as predominant products of the CAP apparatus.
Semiclassical tunneling splittings for arbitrary vibrational states in multidimensional double wells
Authors: Kay Kenneth G.
Published: October 2018

A semiclassical theory developed in a previous paper [K. G. Kay, Phys. Rev. A 96, 042116 (2017)] is applied to calculate tunneling splittings for arbitrary vibrational states of model two-dimensional double-well systems. Cases in which the classical dynamics for the wells is chaotic, mixed, and regular are considered. A perturbative treatment, based on the condition of small tunneling amplitudes, is found to be sufficiently accurate for the cases studied and is applied for most of the calculations. Treatments that approximate certain imaginary-time trajectories in the classically forbidden region by linearization about a variety of judiciously selected reference trajectories yield good results for all systems treated. These calculations can be greatly simplified by approximating all imaginary-time trajectories as linearizations about a single reference trajectory. A simple way to determine optimal reference trajectories for this purpose is presented. It is found that their use yields splittings of satisfactory accuracy for the cases studied.
Photoelectron velocity map imaging spectroscopic and theoretical study of heteronuclear vanadium-nickel carbonyl anions VNi(CO)n− (n = 2-6)
Authors: Yuan Qinqin , Zhang Jumei , Zou Jinghan , Fan Hongjun , Jiang Ling , Xie Hua
Published: October 2018

Mass-selected heteronuclear vanadium-nickel carbonyl anions VNi(CO)n− (n = 2-6) were investigated by photoelectron velocity-map imaging spectroscopy and quantum chemical calculations to obtain their chemical bonding and intrinsic electronic structure in the gas phase. The calculated energies (adiabatic detachment energies)/vertical detachment energies (VDEs) match well with experimental values: 1.30/1.49, 1.66/1.95, 2.22/2.48, 2.70/2.89, and 2.95/3.15 eV. The VDE value of VNi(CO)n− increases with an increase of cluster size, implying that the negative electron is stabilized upon the bonding of CO molecules. VNi(CO)2− consists of one bridging carbonyl and one terminal carbonyl, whose feature is different from MNi(CO)2− (M = Sc, Y, La, and Ce) with the involvement of one side-on-bonded carbonyl and one terminal CO carbonyl. The building block composed of three bridging carbonyls is favored for VNi(CO)3−, the structure of which persists up to n = 6. The additional CO ligands are preferentially coordinated in the terminal mode to the Ni atom at n = 4 and then to the V atom at n = 5 and 6. The results obtained in this work would provide a molecular-level understanding about chemisorbed CO molecules on alloy surfaces/interfaces, which is important to understand CO molecule activation processes.
Effect of surface stress induced curvature on the eigenfrequencies of microcantilever plates
Authors: Ruz J. J. , Pini V. , Malvar O. , Kosaka P. M. , Calleja M. , Tamayo J.
Published: October 2018

Ultrasensitive physical, chemical and biological sensors have emerged in the last decade based on the measurement of the eigenfrequencies of micro- and nanosized cantilever plates. Surface stress is omnipresent in these devices due to a variety of factors such as the fabrication process, temperature variations and analyte adsorption. How surface stress influences on the eigenfrequencies of cantilever plates has remained as an unsolved question in physics that has raised a long debate since first experiments in 1975. Recent theoretical models have shed light on the role of the net surface stress. Still, there exists a discrepancy between theory and some experimental reports, affecting to the capability for quantification of these sensors. In this Letter, we present a theoretical framework that demonstrates that the cantilever bending due to differential surface stress between opposite faces of the cantilever, a neglected effect in classical beam theory, plays a relevant role in the stiffness and eigenfrequencies of cantilevers. We develop a new theoretical framework that provides analytical equations that accurately describe the effect of surface stress on the first three vibration modes of cantilevers. Our findings provide the final piece of the puzzle for solving this long-standing problem in physics.
Simulation of bioconvection in the suspension of second grade nanofluid containing nanoparticles and gyrotactic microorganisms
Authors: Zuhra Samina , Khan Noor Saeed , Shah Zahir , Islam Saeed , Bonyah Ebenezer
Published: October 2018

A time dependent symmetric flow with heat transmission of a second-grade fluid containing nanoparticles and gyrotactic microorganisms between two parallel plates in two dimensions is explored. Partial differential equations furnish the nonlinear ordinary differential equations due to the usage of relevant similarity transformations. Motion declines due to second grade fluid, energy elevates due to thermophoresis, concentration enhances due to Brownian motion and gyrotactic microorganisms profile elevates due to Peclet number. The unsteadiness parameter β has profound effect on the nanobioconvection flow within the plates. Optimal homotopy asymptotic method (OHAM) is followed to evaluate the transformed systems. Consistency and smoothness between the first and second orders of the optimal homotopy asymptotic method are revealed through graphs. Also, graphs are provided to manifest the impacts of each parameter.
What is it in Swedish?
Authors: Stoewer Kirsten
Published: October 2018

The present chapter investigates teacher-initiated translation requests as spontaneous vocabulary teaching during English mother tongue instruction in Sweden. The collection-based analysis draws on a corpus of 30 hours (11 weeks) of video-recordings of compulsory school-age students. The analysis shows how the teacher routinely draws on the local availability of two shared languages to accomplish a variety of actions: to check students’ comprehension of topicalised vocabulary; to engage the entire cohort; to perform medium repair; and to prompt student production of the target language. The findings may be of relevance for numerous types of bi- and multilingual settings, where language alternation serves to augment the teaching and learning of languages as well as other subject matter.
L1/L2 alternation practices in students’ task planning
Authors: Kunitz Silvia
Published: October 2018

This conversation analytic study explores the language alternation patterns enacted by students of Italian as a Foreign Language as they engage in planning a classroom presentation. The data consist of 13 planning sessions conducted by two groups of students enrolled in a third semester course and two groups of students enrolled in a sixth semester course at a US university. The analysis shows how the participants achieve a local interactional order (Cromdal 2005) where the alternation between the L1 and the L2 embodies the distinction between planning process (in L1-English) and planning product (in L2-Italian) and achieves the transition between such components of the planning activity. Overall, the study demonstrates that language alternation is a discursive skill that constitutes a resource for planning for students at different proficiency levels.
Making teacher talk comprehensible through language alternation practices
Authors: Filipi Anna
Published: October 2018

This study reports the ways in which students and their teacher co-manage the interactional problems resulting from a lack of understanding of the teacher’s instructions produced in the second language (L2) through language alternation practices. The study draws on data from two Italian as a Foreign Language lessons in an Australian high school involving students aged 13–14 at an A2 (CEFR) level of proficiency. Analysis shows: (1) how the teacher ascribed “expected” knowledge states to students as a class and to students as individuals; (2) how the teacher packaged her instructions multimodally and switched to students’ first language (L1) only as a last resort; and (3) how students availed themselves of serendipitous opportunities presented in the context to build their understanding of Italian as the medium of instruction in order to successfully answer the teacher’s questions or to follow instructions without having to admit that they did not know what was being asked of them.