bluuebunny/crossref_metadata_2025 huggingface dataset:
Identifying QCD Transition Using Deep Learning
Authors: Zhou Kai , Pang Long-gang , Su Nan , Petersen Hannah , Stoecker Horst , Wang Xin-Nian
Published: February 2018

In this proceeding we review our recent work using supervised learning with a deep convolutional neural network (CNN) to identify the QCD equation of state (EoS) employed in hydrodynamic modeling of heavy-ion collisions given only final-state particle spectra ρ(pT, Ф). We showed that there is a traceable encoder of the dynamical information from phase structure (EoS) that survives the evolution and exists in the final snapshot, which enables the trained CNN to act as an effective “EoS-meter” in detecting the nature of the QCD transition.
Anisotropic flow of identified particles in Pb–Pb collisions at √SNN = 5.02 TeV
Authors: Bertens Redmer Alexander
Published: February 2018

Anisotropic flow is sensitive to the shear (η/s) and bulk (ζ/s) viscosity of the quark-gluon plasma created in heavy-ion collisions, as well as the initial state of such collisions and hadronization mechanisms. In these proceedings, elliptic (υ2) and higher harmonic (υ3, υ4) flow coefficients of π±, K±, p(p) and the ϕ-meson, are presented for Pb—Pb collisions at the highest-ever center-of-mass energy of [see formula in PDF] = 5.02 TeV. Comparisons to hydrodynamic calculations (IP-Glasma, MUSIC, UrQMD) are shown to constrain the initial conditions and viscosity of the medium.
Production of D0 meson in pp and PbPb Collisions at √SNN = 5.02 TeV with CMS
Authors: Lee Yen-Jie
Published: February 2018

Heavy flavour mesons are used as powerful tools for the study of the strongly interacting medium in heavy ion collisions as heavy quarks are sensitive to the transport properties of the medium. In these proceedings, D0 nuclear modification factors, comparing the yields in PbPb and pp collisions, and azimuthal anisotropies in PbPb collisions are reported. Prompt D0 mesons and their antiparticles have been measured with the CMS detector via the hadronic decay channels D0 → K−π+ and D0 → K+π− in PbPb and pp collisions at a centre-of-mass energy of 5.02 TeV. Nonprompt D0 from b quark decays are subtracted. The D0 results are compared to inclusive charged particles, non-prompt J/ψ mesons from b decays and B+ mesons in order to reveal possible meson mass dependence of the observables.
Correlation between heavy flavour production and multiplicity in pp and p-Pb collisions at high energy in the multi-pomeron exchange model
Authors: Feofilov Grigory , Kovalenko Vladimir , Puchkov Andrei
Published: February 2018

The multiplicity dependence of heavy flavour production in pp-collisions at LHC energies is studied in the framework of the multi-pomeron exchange model. The model is introducing the string-string interaction collectivity effects in pp collisions, which modifies multiplicity and transverse momenta, leading to the non-trivial mean pt vs. multiplicity (〈pt〉Nch − Nch). correlation. The string collectivity strength parameter is fixed by experimental data on multiplicity and transverse momentum correlation in a wide energy range (from ISR to LHC). The particles discrimination is implemented according to Schwinger mechanism taking into account the strong decays of hadron resonances. We demonstrate, that the faster-than-linear growth of the open charm production with the event charged particle multiplicity, observed in experimental pp high energy collisions, can be explained by the modification of the string tension due to the increasing overlap and interaction of quark-gluon strings. The model is extended for p-A interactions and the calculations for p-Pb collisions are performed.
Measurement of the D-meson nuclear modification factor and elliptic flow in Pb–Pb collisions at √SNN = 5.02 TeV with ALICE at
the LHC
Authors: Grosa Fabrizio
Published: February 2018

Heavy-flavour hadrons are recognised as a powerful probe for the characterisation of the deconfined medium created in heavy-ion collisions, the Quark-Gluon Plasma (QGP). The ALICE Collaboration measured the production of D0, D+, D*+ and [see formula in PDF] mesons in Pb–Pb collisions at [see formula in PDF] = 5.02 TeV. The measurement of the nuclear modification factor (RAA) provides a strong evidence of the in-medium parton energy loss. The comparison between the [see formula in PDF] and the non-strange D-meson RAA can help to study the hadronisation mechanism of the charm quark in the QGP. In mid-central collisions, the measurement of the D-meson elliptic flow v2 at low transverse momentum (pT) gives insight into the participation of the charm quark into the collective motion of the system, while at high pT it constrains the path-length dependence of the energy loss. The [see formula in PDF] v2, measured for the first time at the LHC, is found to be compatible to that of non-strange D mesons and positive with a significance of about 2.6 σ. The coupling of the charm quark to the light quarks in the underlying medium is further investigated for the first time with the application of the Event-Shape Engineering (ESE) technique to D-meson elliptic flow.
Low-mass dielectrons in pp, p–Pb and Pb–Pb collisions measured by the ALICE Experiment
Authors: Vorobyev Ivan
Published: February 2018

Dielectrons produced in ultra-relativistic heavy-ion collisions at the LHC provide a unique probe of the system evolution as they are unperturbed by final-state interactions. The dielectron continuum is extremely rich in physics sources: on top of ordinary Dalitz and resonance decays of pseudoscalar and vector mesons, thermal black-body radiation is of particular interest as it carries information about the temperature of the hot and dense system created in such collisions. The dielectron invariant-mass distribution is furthermore sensitive to medium modifications of the spectral function of short-lived vector mesons that are linked to the potential restoration of chiral symmetry at high temperatures. Correlated electron pairs from semi-leptonic charm and beauty decays provide complementary information about the heavy-quark energy loss.
Quarkonium measurements in heavy-ion collisions with the STAR experiment
Authors: Huang Xinjie
Published: February 2018

In these proceedings, we present the latest measurements of J/ψ and ϒ by the STAR experiment. The J/ψ and ϒ production measured in p+p collisions provide new baselines for similar measurements in Au+Au collisions, while the measurements in p+Au collisions can help quantify the cold nuclear matter effects. The J/ψ υ2 is measured in both U+U and Au+Au collisions to place constraints on the amount of J/ψ arising from recombination of deconfined charm and anti-charm pairs. Furthermore, the nuclear modification factors for ground and excited ϒ states as a function of transverse momentum and centrality are presented, and compared to those measured at the LHC as well as to theoretical calculations.
Coherent e+e- production at very low transverse momentum at STAR
Authors: Yang Chi
Published: February 2018

We report the measurements of e+e- pair production at very low e+e- pair transverse momentum (pT < 0.15 GeV/c) in Au+Au collisions at [see formula in PDF] = 200 GeV and U+U collisions at [see formula in PDF] = 193 GeV using the STAR detector at the Relativistic Heavy Ion Collider. In 60-80% centrality, significant excesses are observed with respect to hadronic cocktails in both Au+Au and U+U collisions. These excess yields can not be explained by a theoretical model calculation incorporating in-medium broadened ρ spectral function. Additionally, the [see formula in PDF] distribution for excess yield is shown and found to be exponential at very low pT.
J/ψ production in proton-lead collisions at 8 TeV with the LHCb detector
Authors: Okhrimenko Oleksandr
Published: February 2018

The production of J/ψ mesons is studied in proton-lead collisions at a centre-of-mass energy per nucleon pair [see formula in PDF] = 8.16 TeV with the LHCb detector. The double differential cross-sections of prompt and nonprompt J/ψ production are measured as functions of the J/ψ transverse momentum and rapidity. Nuclear modification factors are determined. The results are compared with different theoretical calculations.
Quarkonium production in pp and p-A collisions with ALICE at the LHC
Authors: Morreale Astrid
Published: February 2018

Quarkonia are mesons formed of either a charm and anti-charm quark pair (J/ψ, ψ(2S)) or a beauty and anti-beauty quark pair (ϒ(1S), (2S) and (3S)). We report on forward rapidity (2:5 < y < 4) J/ψ and ψ(2S) production measured in pp collisions at √s = 13 TeV, using data collected at the LHC in 2015. The results will be compared with similar measurements performed at √s = 2.76, 5.02, 7 and 8 TeV. They will be further compared to NRQCD and FONLL calculations, which describe prompt and non-prompt charmonium production respectively. Results of the J/ψ nuclear modification factor as a function of collision centrality in p–Pb collisions at [see formula in PDF] = 8.16 TeV, at forward and backward rapidities, will also be presented. These measurements will be compared with Run-1 (2009 – 2013) results as well as theoretical calculations and will be interpreted in terms of cold nuclear matter effects.
Heavy quark flow as better probes of QGP properties
Authors: Lin Zi-Wei , Li Hanlin , Wang Fuqiang
Published: February 2018

In earlier studies we have proposed that most parton v2 comes from the anisotropic escape of partons, not from the hydrodynamic flow, even for semi-central Au+Au collisions at [see formula in PDF] = 200 GeV. Here we study the flavor dependence of this escape mechanism with a multi-phase transport model. In contrast to naive expectations, we find that the charm v2 is much more sensitive to the hydrodynamic flow than the lighter quark v2, and the fraction of v2 from the escape mechanism decreases strongly with the quark mass for large collision systems. We also find that the light quark collective flow is essential for the charm quark v2. Our finding thus suggests that heavy quark flows are better probes of the quark-gluon-plasma properties than light quark flows.
Thermo-magnetic dependent couplings for quark matter
Authors: Timóteo V. S. , Farias R. L. S. , Avancini S. S. , Pinto M. B. , Tavares W. R.
Published: February 2018

In this work, we improve our model by adding the strange quark and the Polyakov loop. We then build a thermo-magnetic dependence for the G and K couplings of the SU(3) PNJL model by fitting lattice QCD calculations for the average and the difference of u and d quark condensates under a strong magnetic field.
Gravitational waves from binary compact star mergers in the context of strange matter
Authors: Hanauske Matthias , Yilmaz Zekiye Simay , Mitropoulos Christina , Rezzolla Luciano , Stöcker Horst
Published: February 2018

In this article we will focus on the appearance of the hadron-quark phase transition and the formation of strange matter in the interior region of the hypermassive neutron star and its conjunction with the spectral properties of the emitted gravitational waves (GWs). A strong hadron-quark phase transition might give rise to a mass-radius relation with a twin star shape and we will show in this article that a twin star collapse followed by a twin star oscillation is feasible. If such a twin star collapse would happen during the postmerger phase it will be imprinted in the GW-signal.
Multi-hop Fast Conflict Resolution Algorithm for Ad Hoc Networks
Authors: Wang Shengwei , Liu Jun , Cai Wei , Yin Minghao , Zhou Lingyun , Hao Hui
Published: February 2018

Media access control is an important technology in ad hoc networks. Based on the multi-hop Pseudo Bayesian (PB) algorithm and the single-hop Fast Conflict Resolution algorithm (FCR), in this paper, we propose a Multi-hop Fast Conflict Resolution (MFCR) algorithm for ad hoc networks. We make the detailed introduction of the theoretical model, the pseudo Bayesian analysis and the algorithm deign. MFCR employs a competition probability forecasting method, which is similar to the backoff counter used in FCR, combined with the handshake process used in PB to solve the utilization and the fairness problems of the time slot allocation. Simulations show that the MFCR has evident improvement in the network performance.
Neural Network-Based Receiver in Band-Limited Communication System with MPPSK Modulation
Authors: Wang Zixin , Meng Fan , Wu Lenan
Published: February 2018

As a type of the spectrally efficient modulation, the m-ary phase position shift keying (MPPSK) has been considered to meet the increasing spectrum requirement in the future wireless system. To limit the signal bandwidth and cancel the out-band interference the band-pass filters are used, which introduce the waveform distortion and inter-symbol interference (ISI). Therefore, a single hidden-layer neural network (NN)-based receiver is proposed to jointly equalize and demodulate the received signal. The impulse response of the system is static and the network parameters can be obtained after off-line training. The number of the hidden nodes is also determined through simulations. Simulation results show that the NN-based receiver works well in the communication system with different allocated bandwidths. By observing the modified confusion matrix, the false symbol decision is relevant to modulation index, waveform distortions and the ISI.
A Method for Detecting Large-scale Network Anomaly Behavior
Authors: Hu Huimin , Ma Wenping , Luo Wei
Published: February 2018

A clustering model identification method based on the statistics has been proposed to improve the ability to detect scale anomaly behavior of the traditional anomaly detection technology. By analyzing the distribution of the distance between each clustering objects and clustering center to identify anomaly behavior. It ensures scale abnormal behavior identification while keeping the processing mechanism of the traditional anomaly detection technology for isolation, and breaking through the limitation of the traditional anomaly detection method assumes that abnormal data is the isolation. In order to improve the precision of clustering, we correct the Euclidean distance with the entropy value method to weight the attribute of the data, it optimizes the similarity evaluating electric of the nearest neighbor clustering algorithm, and simulated. Experimental results show that the statistical method and the improved clustering method is more efficient and self-adaptive.
A IF Signal Precessing System Design Based on Software Radio Platform
Authors: Zhao Jing , Nie Hao , Yu Jing
Published: February 2018

Software radio is a definition of a design thought about how to implement flexible functions by using fixed hardware platform. Any platform based on this is characterized to be universal, standardized, modular, open and highly flexible. Due to some realistic reasons, a software radio platform is hard to be realized. So, most signal processing is operated after mixing. According to software radio requirements, a “FPGA+ADC+DAC” structure is designed. Compared with former processors, this module has broad application prospects with the small size, low power, configurable and programmable feathers. It has multifunction, such as generating IF signals, performing digital down conversion and realizing the synchronous demodulation and the other functions. This module also provides the extended host interface to communicate with upper computers. According to the practical test, take MSK signal for example, if the bit rate is 1Mb/s, bit error rate is lower than 10-6.
An Adaptive Contention Window Scheme for 802.11ah WLANs
Authors: Gao Renzheng , Lei Xiaoying , Hu Qiang
Published: February 2018

In order to cope with the rapid development of the Internet of things, IEEE working group has proposed a new wireless network technology, 802.11ah. IEEE 802.11ah operates at sub 1GHz band, and can provide long transmission range, wide coverage, while supporting more than 6,000 of station to be connected. In order to alleviate the high collision probability, 802.11ah MAC protocol involves in the RAW (restricted access window) mechanism combined with grouping mechanism. However, in 802.11ah WLAN (wireless local area network), most of the stations operate at sleep mode, and it is expected that at the start of a BI, the network suffers much higher collision probability than at the latter period of the BI. In order to improve these drawbacks, we propose an adaptive contention window scheme based on which an optimum contention window size is adapted at the start of the BI, and then gradually halved when the transmission completes successfully. Through conducting simulations, we prove that our proposed protocol can enhance the performance of 802.11ah WLAN.
An Improved Flooding Routing Protocol for Wireless Sensor Networks Based on Network-Coding
Authors: Tang Churan , Zhang Linghua
Published: February 2018

A central question in wireless sensor network research is how to reduce the consumption of the energy of the sensor nodes. Theoretically, the network coding technology proposed by Ahlswede et al (2000) can improve the network reliability and network throughput, increase the robustness and save energy. Based on the classic flooding routing protocol, the present study proposes a new flooding control protocol, i.e. NC-Flooding for wireless sensor networks. NC-Flooding protocol introduces five mechanisms to enhance the efficiency of wireless sensor networks. As shown by MATLAB simulation results, NC-Flooding protocol reduces the number of broadcasts of wireless sensor networks, increases the throughput of the network and increases the bandwidth utilization. We conclude that NC-Flooding protocol reduces data forwarding cost and node energy consumption and extends nodes’ life cycle, thus increasing network utilization.
Comparison of Three Different Styles of Submarine Sails on Electromagnetic Scattering under the Detection of Airborne Radar
Authors: Liu Ji , Huang Peilin , Zhao Yaodong , Ji Jinzu , Xue Fengli
Published: February 2018

This paper studies radar cross section of submarine sails on the water. Under the detection of the enemy’s airborne radar, considering the motion of the submarine, the sail model of radar pitch angle incidence range analysis is established. By using CATIA software, the 3D models of AKULA sail, SUBOFF sail and VICTOR sail are built. On the basis of the physical optics method and the equivalent currents method, the scattering characteristics of sails RCS(radar cross section) are simulated under X radar band. Through the microwave anechoic chamber test, this paper verifies the accuracy of the combination of the physical optics method and the equivalent electromagnetic flow method. The influence of the distance from the airborne radar to the sail on the pitch angle of the electromagnetic wave is discussed, with the elevation angle of the radar antenna varies. Then, we illustrate the characteristics of circumferential direction RCS of the sail under different pitch angles. Finally, the mean RCS of the sail at a given pitch angle is simulated. The results show that the AKULA sail is considerably superior to SUBOFF sail and VICTOR sail on stealth performance with the pitch angle less than 4° . But when the pitch angle exceeds 10°, the SUBOFF sail can be given priority.
The best marketing plan of photographing for money deduced by extensible mind mapping
Authors: Guo Bifeng , Fan Rui , Huang Chong-wen , Ma Fuyu , Li Zihao , Liu Qiubin , Liu Penghui , He Weitao
Published: February 2018

With the development of society and economy, there is a new way of marketing research by people’s taking photos of the respondents. They can get paid after finishing the survey tasks by taking photos. However, the contradictory problem is that, as for the project leader, the well pay makes him spend too much money while the poor pay causes low task completion rate. The solution to the problem is to put forward a way to find the best marketing plan of the project, which can both meet the demands of marketing research and reduce the budget. By means of Extenics in combination with extensible mind mapping, we find the best marketing plan for it.
Research on single carrier frequency domain equalization system based on FQPSK modulation
Authors: Zhang Meng , Bie Zhisong
Published: February 2018

Feher-patented quadrature phase shift keying (fqpsk) modulation is proposed for single-carrier frequency domain equalization (sc-fde). this paper puts forward a new method modulation called cc-bcd-fqpsk. the fqpsk signal is oversampled to make that the discrete fourier transform (dft)/ inverse dft (idft) processing of it can be applied for sc-fde. the methodology for maintaining waveform continuity with a cyclic prefix (cp) is presented. wrap-around viterbi algorithm (wava) is suggested for demodulation after equalization at the receiver. simulation results show that sc-fde system based on cc-bcd-fqpsk modulation has higher spectral efficiency than linear modulation qpsk and is an effective approach for eliminating isi and using nonlinear high power amplifier.
Research on AO/FO batch management technology in aircraft production
Authors: Yin Haijun , Wang Yuning , Shan Yingji
Published: February 2018

Based on the analysis of the characteristics and significance of AO/FO in the process of aircraft production, this paper analyzes the format rules of AO/FO batch management from the perspective of technology realization, and details the AO/FO The change of the query and the change status tracking, introduces the AO/FO single-stand status display in the batch management, increases the structure definition of the attribute table in the batch management, and designs the relevant algorithm to store and calculate the batch information. Finally, based on the above theory support AO/FO batch management system successfully used in the production of a machine.
An intelligent LED landscape lighting system
Authors: Zhang Lei , Fang Jie , Yu Ping
Published: February 2018

This paper introduces a kind of landscape lighting control system is composed of the monitoring center and intelligent controller. The intelligent controller realizes the control of the LED landscape lamp, and the monitoring center realizes the monitoring management of the system. The monitoring center and the intelligent controller communicate with each other through ZigBee net. This distributed LED landscape lighting system based on ZigBee network, can achieve the dimming, equipment monitoring, mode setting and fault alarm function, can effective management of landscape lighting system is composed of a large number of LED, solve the problems of large landscape lighting system lighting effects, monotonous monitoring management function is not perfect, the realization of LED landscape lighting system is difficult large scale problem.
Formal verification of dynamic hybrid systems: a NuSMV-based model checking approach
Authors: Xu Zhi , Zhong Deming , Li Weigang , Huang Hao , Sun And Yigang
Published: February 2018

Software security is an important and challenging research topic in developing dynamic hybrid embedded software systems. Ensuring the correct behavior of these systems is particularly difficult due to the interactions between the continuous subsystem and the discrete subsystem. Currently available security analysis methods for system risks have been limited, as they rely on manual inspections of the individual subsystems under simplifying assumptions. To improve this situation, a new approach is proposed that is based on the symbolic model checking tool NuSMV. A dual PID system is used as an example system, for which the logical part and the computational part of the system are modeled in a unified manner. Constraints are constructed on the controlled object, and a counter-example path is ultimately generated, indicating that the hybrid system can be analyzed by the model checking tool.
Research on wireless communication technology based on automatic logistics system of welder
Authors: Sun Xuan , Wang Zhi-yong , Ma Zhe-dong
Published: February 2018

In order to meet the requirements of high real-time and high stability of data transmission in automatic welding system, RTU data format and real-time communication mechanism are adopted in this system. In the automatic logistics system through the Ethernet and wireless WIFI technology will palletizer, stacker, AGV car organically together to complete the palletizer automatic crawling the goods, AGV car automatic delivery, stacking machine automatically out of the Dimensional warehouse. .
Experimental Determination of Rigid Body Properties: An Evaluation on the Use of Piezoelectric or MEMS Tri-Axial Accelerometers
Authors: Urgueira António , Venâncio Nuno , Riscado Pedro , Almeida Raquel , Silva Tiago
Published: February 2018

The development of new sensors that are available at more accessible prices may lead to the
spread of their use on common studies in structural dynamics. One of areas of interest is the experimental determination of rigid body properties that are mandatory when the vibration response is to be calculated at low frequency ranges. In this work, a comparison of the experimental determination of rigid body properties is carried out to evaluate the performance of the commonly used tri-axial piezoelectric accelerometers and their equivalent MEMS sensors. Although their prices are quite different, both sensors can measure the inertia restraint line that is related to the inertia properties of the tested object. An identification algorithm is applied to the frequency response functions obtained by using both sensors, leading to the estimation of the body mass value, as well as the three coordinates of the centre of mass and the six elements of the inertia tensor. An experimental example supports the use of the referred low-cost sensors.
The use of Classical Rolling Pendulum Bearings (CRPB) for vibration control of stay-cables
Authors: Papastergiou Georgia , Raftoyiannis Ioannis
Published: February 2018

Cables are efficient structural elements that are used in cable-stayed bridges, suspension bridges and other cable structures. A significant problem which arose from the praxis is the cables’ rain-wind induced vibrations as these cables are subjected to environmental excitations. Rain-wind induced stay-cable vibrations may occur at different cable eigenfrequencies. Large amplitude Rain-Wind-Induced-Vibrations (RWIV) of stay cables are a challenging problem in the design of cable-stayed bridges. Several methods, including aerodynamic or structural means, have been investigated in order to control the vibrations of bridge’s stay-cables. The present research focuses on the effectiveness of a movable anchorage system with a Classical Rolling Pendulum Bearing (CRPB) device. An analytical model of cable-damper system is developed based on the taut string representation of the cable. The gathered integral-differential equations are solved through the use of the Lagrange transformation. . Finally, a case study with realistic geometrical parameters is also presented to establish the validity of the proposed system.
Numerical analysis of non-linear vibrations of a fractionally damped cylindrical shell under the conditions of combinational internal resonance
Authors: Rossikhin Yury A. , Shitikova Marina V. , Ajarmah Basem
Published: February 2018

Non-linear damped vibrations of a cylindrical shell embedded into a fractional derivative medium are investigated for the case of the combinational internal resonance, resulting in modal interaction, using two different numerical methods with further comparison of the results obtained. The damping properties of the surrounding medium are described by the fractional derivative Kelvin-Voigt model utilizing the Riemann-Liouville fractional derivatives. Within the first method, the generalized displacements of a coupled set of nonlinear ordinary differential equations of the second order are estimated using numerical solution of nonlinear multi-term fractional differential equations by the procedure based on the reduction of the problem to a system of fractional differential equations. According to the second method, the amplitudes and phases of nonlinear vibrations are estimated from the governing nonlinear differential equations describing amplitude-and-phase modulations for the case of the combinational internal resonance. A good agreement in results is declared.
Exploiting nonlinearity in a flapping wing mechanism of a bio inspired micro air vehicle to enhance energy efficiency
Authors: Abolfathi Ali
Published: February 2018

In recent years, there was a great interest in developing flying drones with similar capabilities as flying insects. It is suggested that the flapping frequency of insects coincides with the resonance frequency of their flight mechanism to enhance the power consumptions. In this paper, the effect of nonlinearity in the flight mechanism on the power consumption is investigated. A simple nonlinear model of the insect flight mechanism is developed and normalised to study the effect of different parameters on its performance. Both bistable and hardening nonlinearity are considered. It is shown that for a harmonic loading, the bistable systems reach their peak power at lower frequencies when compared to the corresponding linear system. The maximum power factor of nonlinear oscillator would be lower than the liner one. It is also shown that the peak active power of the bistable system has a higher value than the linear system if the loading function is a pulse square signal.
A computational study on the influence of the delayed yielding phenomenon in magnetorheological oils on the steady state vibration and forces transmitted between the rotor and its frame
Authors: Zapoměl Jaroslav , Ferfecki Petr , Kozánek Jan
Published: February 2018

The theoretical analyses and practical experience show that only the damping effect adaptable to the current operating conditions makes it possible to achieve optimum performance of damping devices inserted in the supports of rotating machines. This is offered by magnetorheological squeeze film dampers. The magnetorheological oils are liquids sensitive to magnetic induction. Their response to the change of a magnetic field is not instantaneous, but it is a process called the delayed yielding. The research was focused on enhancement of the mathematical model of the magnetorheological squeeze film damper by considering the delayed yielding phenomenon and on its application for the study of the influence of the delayed yielding on the force transmission between the rotor and its stationary part. The results of the computational simulations show that rising value of the delayed yielding time constant that characterizes the delayed yielding process reduces the damping effect and efficiency of the magnetorheological damping devices.
Fluid nonlinearities effect on wake oscillator model performance
Authors: Kurushina Victoria , Pavlovskaia Ekaterina
Published: February 2018

Vortex-induced vibrations (VIV) need to be accounted for in the design of marine structures such as risers and umbilicals. If a resonance state of the slender structure develops due to its interaction with the surrounding fluid flow, the consequences can be severe resulting in the accelerated fatigue and structural damage. Wake oscillator models allow to estimate the fluid force acting on the structure without complex and time consuming CFD analysis of the fluid domain. However, contemporary models contain a number of empirical coeffcients which are required to be tuned using experimental data. This is often left for the future work with the opened question on how to calibrate a model for a wide range of cases and find out what is working and is not.

The current research is focused on the problem of the best choice of the fluid nonlinearities for the base wake oscillator model [1] in order to improve the accuracy of prediction for the cases with mass ratios around 6.0. The paper investigates six nonlinear damping types for two fluid equations of the base model. The calibration is conducted using the data by Stappenbelt and Lalji [2] for 2 degrees-of-freedom rigid structure for mass ratio 6.54. The conducted analysis shows that predicted in-line and cross-flow displacements are more accurate if modelled separately using different damping types than using only one version of the model. The borders of application for each found option in terms of mass ratio are discussed in this work, and appropriate recommendations are provided.
Normal form analysis of stator rub in rotating machinery
Authors: Shaw Alexander , Champneys Alan , Friswell Michael
Published: February 2018

This work considers analysis of sustained impacting cycles of rotating shafts with potentially many disks. The insight that this is an internal resonance phenomena makes this an ideal system to be studied with the method of normal forms. However, the presence of arbitrary non smooth nonlinearities due to impact and rub mean that the method must be extended by incorporating an Alternating Frequency/Time (AFT) step to capture nonlinear forces. The process results in an elegant formulation that can model a very wide variety of rotor systems and is demonstrated by comparing against simulation of a contacting overhung rotor.
Online adaptive semi-active vibration damping of slender structures subject to moving loads
Authors: Pisarski Dominik , Myśliński Andrzej
Published: February 2018

The paper deals with the adaptive optimal semi-active control of the slender vibrating structures subjected to the moving loads. The deflection of the structure is governed by Euler-Bernoulli beam equation approximated by the system of bilinear ordinary differential equations. The damping function of the structure support is chosen as the control function. The optimal control problem consists in finding such bang-bang control function to minimize the energy as well as the vibrations of the carrying structure. Although the switched optimal control is a very efficient tool in the reduction of structure vibrations it is very sensitive with respect to changes of the speed of the traveling load. This paper deals with the development of the adaptive descent type algorithm that enables the update of the optimal controls in real time based on the measured speed of the traveling load or structure’s state. The proposed algorithm uses reference optimal controls computed for the constant speeds and the set of functions describing the sensitivity of the system dynamics with respect to the measured parameters. Numerical computations are carried out for different speed scenarios of the moving load. The obtained numerical results indicate that the proposed adaptive controller can significantly outperform the reference optimal solutions.
Moving element analysis of high-speed rail system accounting for hanging sleepers
Authors: Dai Jian , Keng Ang Kok , Jiang Dongqi
Published: February 2018

It is very common in the ballasted track system that sleepers are not well supported by the ballast materials due to the uneven settlement of the ballast under repeated train passage. These unsupported track elements are often termed as hanging sleepers and they can lead to undesirable effects due to increased dynamic response of the train-track system, especially when the speed of the train is high. In this paper, we present a computation scheme in conjunction with the moving element method for the analysis of high-speed train-track dynamics accounting for hanging sleepers. The proposed computational scheme will be first verified by comparison with available analytical results. The dynamic response of a high-speed train traveling on a ballasted track considering unsupported sleepers is next investigated. Various factors affecting the response of the high-speed rail system including the speed of the train, the number of hanging sleepers and the pattern of the hanging sleepers will be examined and discussed.
A Reduced Model of a Thermo-Elastic Nonlinear Circular Plate
Authors: Warminska Anna , Manoach Emil , Warminski Jerzy
Published: February 2018

Nonlinear vibrations of a circular plate subjected to mechanical and thermal loadings are presented in the paper. A model of the plate is based on the extended Mindlin theory, taking into account nonlinear geometrical terms and acting heat uniformly distributed along the plate span. The dynamics of a coupled thermo-mechanical problem is reduced from a set of partial differential equations to ordinary differential equations. Considering oscillations around the first natural frequency just one mode reduction is proposed. The analysis shows that elevated temperature shifts the resonance curve and new post-buckling oscillations arise. Depending on initial conditions for the post-buckling state various scenarios of bifurcations take place and transient irregular oscillations may occur. The proposed one degree of freedom model shows a good agreement with response of the model based on three or five-modes reduction.
Synchronisation phenomenon in three blades rotor driven by regular or chaotic oscillations
Authors: Szmit Zofia , Warmiński Jerzy
Published: February 2018

The goal of the paper is to analysed the influence of the different types of excitation on the synchronisation phenomenon in case of the rotating system composed of a rigid hub and three flexible composite beams. In the model is assumed that two blades, due to structural differences, are de-tuned. Numerical calculation are divided on two parts, firstly the rotating system is exited by a torque given by regular harmonic function, than in the second part the torque is produced by chaotic Duffing oscillator. The synchronisation phenomenon between the beams is analysed both either for regular or chaotic motions. Partial differential equations of motion are solved numerically and resonance curves, time series and Poincaré maps are presented for selected excitation torques.
Static stability and load capacity of pyramidal trusses
Authors: Santana Murillo V. B. , Gonçalves Paulo B. , Silveira Ricardo A. M.
Published: February 2018

The analysis of pyramidal trusses has an immediate practical interest since these structures are currently used in many present-day civil constructions, either as main parts or a constitutive element. They can be used to represent tripod-like structures, cap of masts, tower cranes, big span roofs, and even a portion of a single-layer geodesic dome or of a generic-shaped reticulated shell. This paper examines the nonlinear static stability and load capacity for a simple class of space trusses in the shape of a regular pyramid. Joints located at the vertices of the base polygon are fixed while the joint at the apex is subjected to static loads acting in either the vertical direction, in the horizontal plane, or along a generic oblique direction. Despite their apparent simplicity, these structural systems exhibit a wide variety of post-critical responses, not exhausted by the classical snapping and bifurcation phenomena. In addition to regular primary and secondary branches, the equilibrium paths may include neutral branches, namely branches entirely composed of bifurcation or limit points. The analysis is conducted using the Finite Element Method together with a corotational formulation for the bars. The numerical results are validated in the elastic domain using the closed-form solutions found in literature.
Stochastic Bifurcation Analysis of an Elastically Mounted Flapping Airfoil
Authors: Bose Chandan , Sarkar Sunetra , Gupta Sayan
Published: February 2018

The present paper investigates the effects of noisy flow fluctuations on the fluid-structure interaction (FSI) behaviour of a span-wise flexible wing modelled as a two degree-of-freedom elastically mounted flapping airfoil. In the sterile flow conditions, the system undergoes a Hopf bifurcation as the free-stream velocity exceeds a critical limit resulting in a stable limit-cycle oscillation (LCO) from a fixed point response. On the other hand, the qualitative dynamics changes from a stochastic fixed point to a random LCO through an intermittent state in the presence of irregular flow fluctuations. The probability density function depicts the most probable system state in the phase space. A phenomenological bifurcation (P-bifurcation) analysis based on the transition in the topology associated with the structure of the joint probability density function (pdf) of the response variables has been carried out. The joint pdf corresponding to the stochastic fixed point possesses a Dirac delta function like structure with a sharp single peak around zero. As the mean flow speed crosses the critical value, the joint pdf bifurcates to a crater-like structure indicating the occurrence of a P-bifurcation. The intermittent state is characterized by the co-existence of the unimodal as well as the crater like structure.
Chatter identification in milling of Inconel 625 based on recurrence plot technique and Hilbert vibration decomposition
Authors: Lajmert Paweł , Rusinek Rafał , Kruszyński Bogdan
Published: February 2018

In the paper a cutting stability in the milling process of nickel based alloy Inconel 625 is analysed. This problem is often considered theoretically, but the theoretical finding do not always agree with experimental results. For this reason, the paper presents different methods for instability identification during real machining process. A stability lobe diagram is created based on data obtained in impact test of an end mill. Next, the cutting tests were conducted in which the axial cutting depth of cut was gradually increased in order to find a stability limit. Finally, based on the cutting force measurements the stability estimation problem is investigated using the recurrence plot technique and Hilbert vibration decomposition method.
Spectrum of Lyapunov exponents in non-smooth systems evaluated using orthogonal perturbation vectors
Authors: Balcerzak Marek , Dąbrowski Artur , Stefański Andrzej , Wojewoda Jerzy
Published: February 2018

This paper covers application of the novel method of Lyapunov exponents (LEs) spectrum estimation in non smooth mechanical systems. In the presented method, LEs are obtained from a Poincaré map. By analysing the map instead of the full trajectory, problems with transition of perturbations through discontinuities can be avoided. However, the explicit formula of the map is usually not known. Therefore, the Jacobi matrix of the map is estimated using small perturbations of the initial point. In such a manner, direct calculation of the Jacobi matrix can be avoided. The article provides a detailed description of the method accompanied by clear schemes. The algorithm of Jacobi matrix estimation is elaborated and an example is given. Efficiency of the method is confirmed by a numerical experiment. The mechanical oscillator with impact has been simulated. Bifurcation diagrams and Lyapunov exponents graphs have been generated. It has been shown that the method provides values of the whole Lyapunov exponents spectrum with high accuracy.
An inerter-based active vibration isolation system
Authors: Alujević Neven , Čakmak Damjan , Wolf Hinko , Jokić Marko
Published: February 2018

This paper presents a theoretical study on passive and active vibration isolation schemes using inerter elements in a two degree of freedom (DOF) mechanical system. The aim of the work is to discuss basic capabilities and limitations of the vibration control systems at hand using simple and physically transparent models. Broad frequency band dynamic excitation of the source DOF is assumed. The purpose of the isolator system is to prevent vibration transmission to the receiving DOF. The frequency averaged kinetic energy of the receiving mass is used as the metric for vibration isolation quality. It is shown that the use of inerter in the passive and active vibration isolation schemes considered enhances the isolation effect.
Influences of the Control on the Nonlinear Vibrations of a Variable Compression Ratio Mechanism
Authors: Mănescu Bogdan , Dragomir Ionuţ , Stănescu Nicolae–Doru
Published: February 2018

For the mechanism described in references the study of the nonlinear vibrations is performed considering a multibody approach for the elements of the mechanism and different laws of motion for the control element. A great attention is paid to the equilibrium of the motion. The influence of different parameters of control is highlighted in the paper. The results are numerically validated.
Optimal homotopy asymptotic method to large post-buckling deformation of MEMS
Authors: Herisanu Nicolae , Marinca Vasile
Published: February 2018

In the present paper, the post-buckling response of an axially stressed clamped-clamped actuator, modeled as a beam and subjected to a symmetric electrostatic field is analyzed. An analytical approximate method, namely the Optimal Homotopy Asymptotic Method (OHAM) is applied to the governing nonlinear integro-differential equation. The analytical results obtained through the proposed procedure show excellent agreement with numerical solution, proving the validity of the proposed procedure, which is simple and easy to use.
Vibro-acoustic and nonlinear analysis of cadavric femoral bone impaction in cavity preparations
Authors: Oberst Sebastian , Baetz Johanna , Campbell Graeme , Lampe Frank , Lai Joseph C.S. , Hoffmann Norbert , Morlock Michael
Published: February 2018

Owing to an ageing population, the impact of unhealthy lifestyle, or simply congenital or gender specific issues (dysplasia), degenerative bone and joint disease (osteoarthritis) at the hip pose an increasing problem in many countries. Osteoarthritis is painful and causes mobility restrictions; amelioration is often only achieved by replacing the complete hip joint in a total hip arthroplasty (THA). Despite significant orthopaedic progress related to THA, the success of the surgical process relies heavily on the judgement, experience, skills and techniques used of the surgeon. One common way of implanting the stem into the femur is press fitting uncemented stem designs into a prepared cavity. By using a range of compaction broaches, which are impacted into the femur, the cavity for the implant is formed. However, the surgeon decides whether to change the size of the broach, how hard and fast it is impacted or when to stop the excavation process, merely based on acoustic, haptic or visual cues which are subjective. It is known that non-ideal cavity preparations increase the risk of peri-prosthetic fractures especially in elderly people.

This study reports on a simulated hip replacement surgery on a cadaver and the analysis of impaction forces and the microphone signals during compaction. The recorded transient signals of impaction forces and acoustic pressures (≈ 80 μs - 2 ms) are statistically analysed for their trend, which shows increasing heteroscedasticity in the force-pressure relationship between broach sizes.

Tikhonov regularisation, as inverse deconvolution technique, is applied to calculate the acoustic transfer functions from the acoustic responses and their mechanical impacts. The extracted spectra highlight that system characteristics altered during the cavity preparation process: in the high-frequency range the number of resonances increased with impacts and broach size. By applying nonlinear time series analysis the system dynamics increase in complexity and demand for a larger minimum embedding dimension. The growing number of resonances with similar level of the transfer function indicates a higher propensity to dissipate energy over sound; the change in embedding dimension indicates a decrease in linearity. The spectral changes as well as the altered dimension requirements indicate either an improved coupling between the bone and the broach or the onset of micro-fractures caused by growing stress levels within the bone.